CN1836290A - Probe for an atomic force microscope - Google Patents

Abstract

A probe (22) for an atomic force microscope is adapted such that, as a sample (14) is scanned, it experiences a biasing force Fdirect urging the probe towards the sample. This improves probe tracking of the sample surface and faster scans are possible. This is achieved by either including a biasing element (24, 50), which is responsive to an externally applied force, on the probe (22) and / or reducing the quality factor of a supporting beam. The biasing element may, for example, be a magnet (24) or an electrically-conducting element (50). The quality factor may be reduced by coating the beam with a mechanical-energy dissipating material.

Description

Atomic Force Microscopy Probe

technical field

The present invention relates to the field of atomic force microscopy, probes used in such microscopes, and methods of operating such microscopes. In particular, it concerns atomic force microscopy that does not utilize conventional feedback control of probe height.

Background technique

The atomic force microscope (AFM) or scanning force microscope (SFM) was invented in 1986 by Binnig, Quate and Gerber. Like all other scanning probe microscopes, AFM is based on the principle of mechanically scanning nanoprobes over the sample surface in order to obtain an "interaction map" of the sample. The interaction force in this case is only the molecular interaction between the sample and the tip of the sharp probe to which the cantilever spring is attached. When the probe tip comes into close proximity with the sample, the cantilever bends in response to the interaction force. Images were collected by scanning the sample relative to the probe and measuring cantilever deflection as a function of lateral position. Optical lever techniques are commonly used to measure this bending. Because the cantilever obeys Hooke's law for small displacements, the interaction force between the tip and the sample can be derived.

AFMs are typically operated in one of two modes. In constant force mode, feedback allows the positioning of the piezoelectric actuator to move the sample (or probe) up or down in response to any change in the detected interaction force. In this way, the interaction forces can be kept relatively stable and a fairly reliable topographical image of the sample can be obtained. Optionally the AFM can be operated in constant altitude mode. There is little or no adjustment to the vertical height of the sample or probe during scanning. In this context, adjustment of the vertical height means imposing a transition on the actuator attached to the cantilever probe or on the sample itself. Thus, the probe tip also has freedom to move up or down when the degree of cantilever bending is changed. In constant-height mode, it is not possible to distinguish between changes in the topography of the sample and changes in the interaction force, since either or both will cause the cantilever spring to bend.

In addition to these different feedback mechanisms, image contrast is typically achieved in one of three different ways. In contact mode, the tip and sample remain in close contact while scanning is performed, ie the repulsive mechanism that maintains molecular interactions. In tapping mode, the actuator drives the boom in a "tapping" motion at its resonant frequency. Thus, the probe tip only touches the surface during a very small portion of its oscillation (tapping) cycle. This significantly shortened contact time means that the lateral force on the sample is greatly reduced and therefore the probe is less destructive to the sample when scanning. It is therefore widely used for imaging sensitive biological samples. Typically a feedback mechanism is used to keep the oscillation amplitude constant. In non-contact operation, the cantilever is oscillated at a distance above the sample at which molecular interaction forces are no longer repulsive. But this mode of operation is very difficult to implement in practice.

New advances in probe microscopy have resulted in much faster data collection times. With faster scanning techniques, such as that described in PCT Patent Application Publication No. WO 02/063368, limited probe responsivity is increasingly becoming the limiting factor in image collection time. Probes cannot respond instantaneously to changes in sample characteristics, so for example there is an inherent time delay between the probe encountering a sample surface area of increasing height and the system reacting to it. This shortcoming applies to the constant-force and constant-altitude modes of AFM operation. It is less severe in constant height mode, so for fast scanning techniques constant height mode is the preferred mode of operation, but it is still enough to unduly limit the scan speed of current generation fast scanning probe microscopes.

In constant force AFM mode, an electronic feedback mechanism is typically utilized in order to keep the average interaction force constant. As the scan progresses, if the interaction force changes (e.g., caused by a change in sample height), this is first observed by a change in the probe response detected by the detection electronics, generating an error (e.g., set point minus deflection ) and use a feedback loop to minimize error by adjusting the probe or sample position. The feedback loop has a time constant associated with it that imposes a limit on the ultimate speed at which a complete image can be collected.

This problem is not so restrictive if operating in constant altitude mode, where electronic feedback is generally not utilized to the extent used in constant force AFM. But for the interaction force to be measured accurately, the probe tip should track the contours of the sample surface as closely as possible. This is ensured by utilizing the reaction force induced when the cantilever is bent by the sample surface. That is, when scanning high regions of the sample surface, the cantilever bends upward more and more, and the energy stored in the spring increases. When the height is dropped, the restoring force pushes the cantilever back towards its equilibrium (flat) position, thereby maintaining contact with the surface. But if the scanning speed is too fast, the probe will not be able to track the surface, but will be thrown forcefully over any bumps on the surface and may start to resonate or "resonate". This in turn causes oscillations in the imaging interaction force. Similarly, when the height is dropped, the restoring force may not be strong enough to ensure that the probe tip remains in contact with the surface, and information around the surface in that image area will be lost.

WO 02/063368 mentioned above describes a scanning probe microscope in which the sample or probe is mounted on a resonator and by driving the resonator at or close to the resonant frequency the sample can be scanned relative to the probe. The resonator will typically have a resonant frequency of a few tens of kHz similar to that of the probe. The typical time interval between pixels is thus shorter than 1/ _fr , where _fr is the resonance frequency of the probe. On the other hand, the time taken to respond to a change in topography of the sample surface (τ _res ) is based on the effective mass of the probe and the spring constant of the cantilever. If τ _res > f _r , then obviously the interaction force cannot be measured accurately from one pixel to another.

Recognizing that there is a need to provide improved probe responsivity to sample topography fluctuations or to changes in interaction forces in order to allow image artifacts such as those caused by probe resonance or poor tracking of surfaces before they begin to degrade image quality, Perform AFM microscopy methods at faster scan speeds.

Contents of the invention

The present invention provides a probe for atomic force microscopy or for use in nanolithography comprising a force sensing element attached to a probe tip having a tip radius of 100 nm or less, characterized in that the probe is modified such that When subjected to an applied force, the biasing force pushes either or both the probe tip and sample toward each other by a magnitude greater than the restoring force caused by the displacement of the probe tip when probing the sample.

Having appreciated the scope of the present invention, it is useful to consider the forces involved in prior art atomic force microscopy when a typical cantilever probe comes into contact with a sample surface. This is therefore now explained with reference to FIG. 1 .

In FIG. 1 , a sample 1 scanned by the probe of an atomic force microscope (AFM) is shown. The probe comprises a substrate 2 from which protrudes a cantilever 3 having a sharp probing nanotip 4 with a tip radius of 100 nm or less mounted at the end remote from the substrate 2 . In preparation for scanning, a downward force (F _external ) is applied to the probe via its mounting to the AFM at the probe substrate end 2, moving the probe tip 4 into contact with the sample 1 . In order to maintain contact during scanning, the force F _external is greater than that required to just bring the tip 4 into contact with the sample 1 . As a result the cantilever 3 bends upwards from its rest position 5 when scanning the sample.

In the simplified model, it can be considered that the cantilever 3 obeys Hooke's law for small displacements. Thus when a force is applied to the sample, if the bending is such that the tip 4 is moved a vertical distance x from its rest position, and the cantilever spring constant is k, then the restoring force exerted by the cantilever is kx. The downward force exerted by the tip 4 to keep it tracking the surface is therefore proportional to kx.

Apparently, the responsivity of the probe tip 4 and thus the resolution of the AFM technique depends on the magnitude of the force kx exerted by the cantilever 3 on the sample 1 . The greater the force between the probe and the surface, the greater the responsiveness to surface changes. This suggests that a high spring constant k is desirable, especially if fast sweeps are to be made. On the other hand, the greater the force, the more likely the probe will damage the sample. Therefore, prior art AFM cantilever probes must make a fundamental trade-off between probe responsivity and the possibility of damaging the sample.

But the probe according to the invention is modified so that when scanning the sample it is subjected to a biasing force which is significantly greater than the restoring force kx exerted by the probe on the sample. This allows it to better track the sample surface and faster scans are possible. As will be seen in more detail later, the need for the present invention to exceed the restoring force with a biasing force is achieved by including a biasing element on the probe that is responsive to an applied force and/or reducing the spring constant of the cantilever beam.

Unlike conventional AFM where image collection may take more than 30 seconds, with the present invention millisecond imaging of the sample is possible. For example, a tip speed of 22.4 cms ^-1 allows imaging a 4.4 x 4.4 micron area in 14.3 ms and a 1.5 x 1.5 micron area in 8.3 ms at 128 x 128 pixels. Furthermore, even at this speed, images with better resolution than 10 nm laterally and 1 nm vertically can be obtained with soft polymer surfaces.

In one embodiment of the invention, the biasing element may be, for example, a magnetic element responsive to an applied magnetic force, or a conductive element connected to one end of a power supply to allow a voltage potential to be induced between the probe and the sample. In both cases, the polarity of the biasing force (magnetic or electrostatic) is such that it pushes the probe and sample towards each other. Furthermore, the magnitude of the biasing force applied to the probe is independent of its degree of deflection. Thus, because the probe beam has a very low spring constant, the bending/deflection restoring force is very small compared to the biasing force, so the tip-to-surface force is virtually deflection independent.

Prior art AFM probes have been specially fabricated so as to respond to external biasing forces. For example, EP 872707 describes a cantilever probe comprising piezoelectric elements. A control signal is sent to the piezoelectric element in order to push the probe upwards away from the sample such that the suction force is overcome. Similarly, US 5,515,719 describes a probe comprising magnetic particles which, in response to a solenoid-controlled magnetic field, pull the probe away from the sample surface. As before, the focus of this patent is to prevent probes from being attracted to the sample surface and causing damage.

The cantilever probe disclosed in Patent Application Publication No. WO 99/06793 also includes a magnetic element. However, the magnetic field in this scheme is used to control the probe-sample distance and is varied according to the desired isolation. This is in contrast to the magnetic field scheme used in the present invention. During scanning, the force provided to the tip is constant in this example only for the purpose of accelerating the tip's return to the sample surface if contact is lost. Another system including a probe responsive to an adjustable magnetic field is described in US Patent No. 5,670,712. The field amplitude is controlled by a feedback loop set up to maintain the cantilever deflection at a constant level. And this is in contrast to AFM probes according to the present invention which inherently allow varying degrees of deflection. Without this freedom of movement, it is impossible to follow the contours of the sample surface and measure the interaction forces, which defeats the whole purpose of the invention.

In an alternative approach, the cantilever beam is designed to have a low quality (or Q) factor. This increases the rate at which mechanical energy is dissipated compared to high Q factor beams. If a probe placed on such a beam is knocked away from the surface during scanning, any resulting mechanical oscillations are dampened and the probe will snap back to track the sample surface. In one embodiment, the Q-factor of the cantilever beam is reduced by applying a coating to the beam that is suitable for dissipating energy that would otherwise be mechanically stored in the beam through excitation of one or more oscillatory modes. Thus, the Q-factor of the supported beam is reduced for one or more of its modes of oscillation compared to an equivalent uncoated beam. The coating is preferably an energy absorbing material, such as a polymer film, applied to at least one side of the probe.

Apparently, sample tracking by the probe of the present invention is best achieved if it is modified to be externally guided and have a low Q-factor. But in some environments, only one of these characteristics is required. When the probe is brought into the vicinity of the sample, it is believed that a capillary neck will form connecting the two. In particular, it has been found that the biasing force induced by the capillary neck forms the dominant restoring force if the Q-factor of the probe is sufficiently low. Similarly, the Q-factor of the beam does not need to be as low if a stronger biasing force is applied. It is considered in this example that dissipation of mechanical energy may also occur via interaction of the probe with the sample surface.

AFM cantilevers with coatings are disclosed in the prior art, although none are coated with a material suitable for damping mechanical oscillations. US 5,515,719 mentioned above discloses a magnetic coating through which force can be applied to the cantilever. US 6,118,124 and US 6,330,824 both describe coated cantilevers for detecting radiation. The coating is thus affected by the radiation, and the intensity of the radiation is measured by a quantitative change in the properties of the cantilever. This is in contrast to the coating material of the present invention, which is not affected by incident radiation but absorbs mechanical energy.

In an alternative aspect, the invention provides an atomic force microscope for imaging a sample based on the interaction forces between the sample and the probe, the microscope comprising an arrangement to provide a relative scanning motion between the probe and the sample surface and enabling the sample and the probes are in close enough proximity to the actuation means to establish a detectable interaction between them; and

a probe detection mechanism arranged to measure deflection and/or displacement of the probe;

It is characterized in that the microscope comprises the above-mentioned probe.

Optionally, the microscope is characterized in that it comprises a force (F _direct ) arranged such that in operation a force (F direct ) is exerted on either or both _of the sample or the probe or between the sample and the probe Means are generated to control the force (F _direct ) such that the probe is pushed towards the sample and vice versa.

In yet another aspect, the present invention provides a method of collecting image data from a scanned region of a sample having nanofeatures, wherein the method comprises the steps of:

(a) moving the probe into close proximity to the sample such that an interaction force is allowed to be established between the probe and the sample, wherein the probe comprises a support beam having a tip with a tip radius of 100 nm or less;

(b) causing a force (F _direct ) to be established between the sample and the probe such that the probe is pushed towards the sample and vice versa;

(c) scanning the probe across the surface of the sample or the sample below the probe while providing relative motion between the probe and the surface such that the scan lines are arranged to cover the scan area;

(d) measuring probe deflection and/or displacement; and

(e) processing the measurements obtained in step (d) in order to extract information relating to the nanostructure of the sample.

Description of drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

Figure 1 is a graphical illustration of the forces involved when a suspended probe comes into contact with a sample surface in a prior art atomic force microscope.

Figure 2 shows a schematic implementation of an atomic force microscope comprising a probe according to a first embodiment of the invention.

Figure 3 shows a schematic implementation of an atomic force microscope comprising a probe according to a second embodiment of the invention.

Figure 4 shows a schematic implementation of an atomic force microscope comprising a probe according to a third embodiment of the invention.

Figure 5 shows a schematic implementation of an atomic force microscope comprising a probe according to a fourth embodiment of the invention.

Figure 6 shows a schematic implementation of an atomic force microscope comprising a probe according to a fifth embodiment of the invention.

Figure 7 shows a schematic implementation of an atomic force microscope comprising a probe according to a sixth embodiment of the invention.

Figure 8 is a graphical illustration of the forces involved when the probe is in contact with the sample surface in the AFM of Figures 2-7.

Figures 9a and 9d are AFM images of two isolated surface regions of a crystalline polyethylene oxide (PEO) sample generated using probes according to the invention.

Figures 9b, 9c, 9e and 9f are conventional AFM images of the same surface area as Figures 9a and 9d.

Figure 10 illustrates an example of a predetermined cantilever design for a probe of the present invention.

Figures 11 and 12 illustrate the formation of a region with a low and controlled spring constant in a predetermined cantilever.

Detailed ways

Referring to Figure 2 there is shown a schematic implementation of an AFM, indicated generally at 10, using a first embodiment of a probe constructed in accordance with an aspect of the present invention. The illustrated AFM apparatus 10 includes a plate 12 adapted to carry a sample 14 and mounted on one arm of a tuning fork 16 . The tuning fork 16 is connected to a piezoelectric transducer 18 and a coarse drive 20 . A piezoelectric transducer 18 is used to drive the sample 14 (along with the plate 12 and tuning fork 16) in three dimensions x, y and z. It is common in the art to take the z-axis of the Cartesian coordinate system to be perpendicular to the plane occupied by the sample 14 . That is, the interaction force depends not only on the xy position of the probe 22 above the sample 14 (imaged pixel), but also on its height above. A tuning fork control (not shown) is arranged to apply a sinusoidal voltage to the tuning fork 16 to excite resonant or near-resonant vibrations in the xy plane. Optionally, plate 12 and tuning fork 16 may be supported on a vibration isolation table 32 to isolate vibrations of tuning fork 16 from the rest of the microscope. However, at the image frequencies considered for microscopes using this probe, external noise is less of an issue than at lower image frequencies, so the vibration isolation table can be dispensed with. Probe 22 is a low-mass AFM probe that induces interaction forces between probe tip 22a and the sample surface during scanning. The probe detection mechanism 28 is arranged to measure the displacement of the probe tip 22a or the bending of the beam 22b supporting the tip indicative of the strength of the interaction force. Data collected by probe detection mechanism 28 is analyzed and output to display 30 .

Typically, prior art cantilever probes are made of silicon or silicon nitride, which makes it easy to fabricate them using well-established silicon microfabrication techniques. However, unlike prior art cantilever probes, the probe 22 according to the present invention has a polymer coating 22c applied to the support beam 22b of the probe. As will be explained in more detail subsequently, this coating 22c serves to dissipate energy that would otherwise be stored mechanically in the probe through the excitation of an oscillatory mode, thereby making a difference for one of its vibrational modes compared to the same beam without the coating 22 present. or more to reduce the Q-factor of the braced beam.

In acquiring an image using device 10 , coarse drive device 20 is first used to bring sample 14 into contact with probe 22 . Slender height and initial start position adjustments are made with piezoelectric actuator 18 while probe detection mechanism 28 measures probe deflection as a result of probe 22 and sample 14 interaction forces. Once the measured curvature reaches the desired level, the surface of the sample under the probe 22 is scanned. As the sample 14 beneath the probe 22 is scanned, the tuning fork 16 is positioned so as to vibrate in and out of the plane of the graph (y-axis). This causes the platform on which the sample is mounted to oscillate. Simultaneously, piezoelectric actuator 18 mobilizes sample 14 in the vertical (x) direction. The sample oscillations have considerable amplitudes on the order of a few micrometers. During the scan, the probe detection mechanism 28 continuously takes readings, which may be based on optical lever technology as is standard in the art: probe deflection is measured using laser light reflected from the probe. The output signal of the probe detection mechanism 28 is provided directly to the processor and display 30 .

As mentioned above, the probe 22 shown in Figure 2 differs from the prior art in that it is coated with a polymeric material 22c. Coating 22c can be on one or both sides, as long as the material itself is suitable for dissipating energy that would otherwise be stored in the probe.

The Q factor is a dimensionless quantity that can be used to quantify the dissipation (or damping) of an oscillator. It has the properties:

Q = energy stored in the oscillator / energy dissipated per radian

Strongly damped systems, where the stored energy is quickly dissipated, have a low Q, while lightly damped systems have a high Q. Oscillators made of Si and SiN materials do not have much internal loss, as a result most commercially available AFM cantilevers will have a high Q, typically on the order of 5-500 in air. Furthermore, it is advantageous for the cantilever to have a high Q if designed for use in tapping mode. In this mode, the cantilever is driven at resonance and the interaction force is measured over a number of oscillation cycles. The high Q acts as a mechanical filter by minimizing energy loss over the oscillation period.

A mechanical oscillator has many resonant modes of oscillation, and the quality factor of each of these modes can differ depending on the frequency-dependent material properties and the shape of the oscillator. When referring to a Q-factor here, we mean the Q-factor of a probe for any of these modes, or the Q-factor of a set of modes.

But in the context of the present invention, it is desirable to use probes with low Q in high speed atomic force microscopy. If the probe has a high Q, it will take a long time to respond to changes, and if given a stimulus such as that provided by sweeping high topography on the sample surface, it will resonate in a combination of resonant modes. The present probe is designed to have a low Q by virtue of its coating 22c. Ideally, the Q factor is low enough that any excited oscillations are tightly damped. The use of a low quality factor means that little energy can be stored in the probe's support beam, so the probe does not "resonate" for long when struck, for example when scanning over high regions of the sample surface. This allows for faster return to the sample surface and thus better tracking during scanning.

The coating on the probe serves to dissipate mechanical energy that would otherwise be stored in the probe. A probe with a coating will store less mechanical energy than a probe without a coating, and the motion of a coated probe at a specific time will correspond to that specific time compared to when no coating is present. The surface below the probe tip at time is more closely associated.

Depending on the sample being imaged and the scan speed chosen, it may be that modes higher than the first or fundamental mode are most likely to be excited during imaging. In this case, the coating is chosen to ensure that the Q-factor of this mode is significantly reduced. By adjusting the energy absorbing and dissipating properties of the coating, it is possible to reduce or eliminate the oscillations of the probe most likely to impede image quality, while minimizing changes in probe mass.

A number of polymeric materials can be used to provide coating 22c, and the timing of particular selection will be apparent to those skilled in the art. The material is chosen according to its viscoelastic properties: it must be elastic enough to maintain its shape as the cantilever-coated membrane, while at the same time performing its task of dissipating mechanical energy. The dissipation of mechanical energy occurs primarily through viscous mechanisms that depend on the coefficient of friction of the polymer chain and its environment at the molecular level. An ideal coating is a rubber with a low cross-link density just enough to keep the coating cohesive. The cross-links can be chemical like conventional rubber, or physical like thermoplastic elastomers. It has been found that the majority of the components coated on both sides of the AFM support beam are amorphous rubber masses with a glass transition temperature below room temperature and the minority are amorphous polymers with a glass transition temperature above room temperature The copolymer material significantly improves its tracking ability when used at room temperature. Copolymers are applied by solution casting. That is, drops of a polymer-containing solution are placed on the support beam at elevated temperature in order to drive off the solvent. Other thermoplastic elastomers may also be used. It has been found that this approach allows the probe to track the sample surface even at resonant oscillation speeds such as those described in WO 02/063368.

Considerations regarding the polymeric material employed and the method of application somewhat limit the options available. The basic idea is to coat the support beam with an energy absorbing material that ideally does not unduly affect other properties of the probe, such as mass, tip shape, etc. Casting of support beams with the above copolymer solutions has been found to be accompanied by acceptable mass gain but enhanced energy dissipation. However, other coating methods can be used. These include: "dragging" charged polymers onto support beams in an electrolytic cell; chemically labeling polymers (e.g. with thiol groups) and using it to interact with support beam materials or metal coatings on support beams ( A reaction such as gold in the case of thiol chemistry) attaches the polymer to the support beam.

As mentioned previously, polymer coatings on AFM cantilevers are known. But such prior art coating materials are chosen according to their chemical nature in order to allow detection of incident radiation. That is, the material must have chemical bonds that preferentially absorb energy at specific frequencies. Such a material would not be suitable for mechanical energy dissipation with an efficiency suitable for use with high speed microscopy.

Applying the coating 22c to both sides of a supposedly small-sized support beam is actually somewhat easier to accomplish than to only one side. However, the side of the support beam closer to the sample is preferably left uncoated. One-sided coating is sufficient to reduce the mechanical energy stored in the probe and reduce the likelihood of any coating material contaminating the sample when the probe comes into contact.

Ideally, the polymeric material used for coating 22c will have a peak in its energy loss spectrum at the temperature at which the probe is expected to be used and in the frequency range of the main resonant mode of the support beam. Typically, it should therefore be a rubbery polymer. Alternatively, copolymers or other compounds with a high fraction of rubbery polymers may also be used.

The energy dissipation of the polymer coating can be increased if applied to the transverse gap in the cantilever. That is, if a thin polymer membrane bridges the holes in the cantilever, the membrane will serve both to dissipate energy internally and to increase the interaction area with the surrounding fluid medium, such as air. The viscous energy dissipation is thus increased through this approach while minimizing the spring constant of the cantilever.

Figure 3 shows a schematic implementation of an AFM, indicated generally at 10, using a second embodiment of a probe constructed in accordance with the present invention. The AFM device 10 is very similar to that shown in Figure 2, and components common to both systems are similarly labeled. As before, the plate 12 carrying the sample 14 is mounted on one arm of a tuning fork 16 driven in resonant or near-resonant vibration in the xy plane. The sample 14 (together with the plate 12 and tuning fork 16) is scanned in the three dimensions x, y, and z, and the induced interaction forces are not only dependent on the xy position of the probe 22 above the sample 14 (imaged pixels), but also depends on its height above. The cantilever assembly of probe 22 is coated with a polymer film on both sides and shaped so as to have a low spring constant of less than 1 NM-1. Unlike the cantilever shown in Figure 2, however, the probe 22 according to this embodiment of the invention additionally has a magnetic element 24 (a ball shown in Figure 3) mounted above the tip 22a. Also, a magnet 26 is included in the AFM, for example below the plate 12 , to provide a magnetic field strong enough to exert a force on the magnetic beads 24 . The force can be via a magnetic moment applied to the probe or through a magnetic field gradient. As with the device 10 shown in FIG. 2 , the probe detection mechanism 18 is arranged to measure the bending of the probe 22 . Data collected by probe detection mechanism 28 is analyzed and output to display 30 .

When using device 10 to acquire images, the contact mechanisms and scanning techniques to establish interaction forces are substantially the same as described with respect to device 10 of FIG. 2 . But once the desired level of interaction force is established and thus the bending of the probe's support beam 22b, the magnet 26, which is absent in the device 10 of Fig. 2, is switched on and a magnetic field B is generated in the vicinity of the probe tip 22a. Magnetic beads 24 interact with this magnetic field, directing the magnetic field such that the resulting magnetic force attracts magnetic beads 24 downward toward sample 14 . The probe tip 22a thus remains in contact with the sample 14 by this magnetic guiding action. When the magnetic field B is switched on, the sample surface is oscillated (to tune the resonant frequency of the tuning fork-sample stage) and scanned under the probe 22, and the output signal is processed as before.

Figures 4 to 7 show a schematic implementation of an alternative AFM, indicated generally at 10, using further embodiments of probes constructed in accordance with the present invention. In each case, the AFM device 10 is very similar to that shown in Figures 2 and 3, and components common to all devices are similarly labeled. Sample 14 is mounted on plate 12 as before. Unlike the embodiments shown in FIGS. 2 and 3 , in FIGS. 4 , 5 , 6 and 7 , the probe 22 is mounted on one fork arm of the tuning fork 16 , and the proximity control and thickness positioning of the probe relative to the sample is controlled by the converter. 18 , 20 are controlled as piezoelectric transducers, which control the movement of the probe 22 and tuning fork 16 instead of the plate 12 . This protocol allows scanning the probe over the sample using the resonant scanning method instead of scanning the sample under the fixed probe. With respect to FIG. 4 the resonator 16 and probe 22 are scanned in the x-axis using the x-y-z transducer 18, while in FIGS. /Control of the relative motion of the sample. In this way, the sample can be scanned in two axes while the probe is stationary, or the probe can be scanned in two axes while the sample is stationary, or one or the other of the probe or sample can be scanned in one axis while passing through the other. Movement of one provides scanning on the other axis. In the case of FIG. 7, control of the relative probe/sample scanning motion is provided by a transducer 70 connected to the resonator 16 and probe 22, and because such accuracy of the starting scan position is not available in all cases Required, so omit the fine position control. This highlights the additional advantage of the very fast scan speeds obtainable using the described invention in combination with the resonant scan method. The image velocity is higher than the usual frequency of mechanical noise and higher than the motion instabilities typically present in process positioning methods. Therefore, it is possible to dispense with the normally necessary high-precision piezoelectric transducers.

In FIGS. 4 , 5 and 7 , probe tip 22a is subjected to a force that pushes tip 22a toward sample 14 . In the example of FIG. 4 , the force is attractive and is produced by a bias voltage applied between probe tip 22a and plate 12 . Thus, the probe tip 22a and the plate 12 are connected in series across the terminals of the power supply 60 . In order to establish the required attractive force between the probe tip 22a and the plate 12, the probe is provided with a conductive coating 50 in addition to the damping coating 22c, so as to ensure that the probe has a low Q-factor. In the case of Figure 6, the sample 14 and probe tip 22a are placed in a sealed viscous environment 80, such as a liquid environment. In this embodiment, the power source 60 is connected across the conductive coating 50 and a second plate 90 placed below the sample plate 12 outside the viscous environment. By immersing the probe in a liquid (which would be desirable in the case of biological samples), the damping coating 22c can be omitted from the probe, since exposure of the probe to a liquid environment results in a probe with a low Q close to 1 factor.

In order to appreciate the essential features of the invention, it is useful to look at a graphical representation of the forces involved in performing a scan. This is illustrated in Figure 8, which shows the same setup as Figure 1, and similar components are similarly labeled. Referring to FIG. 8 , there is shown a sample 1 scanned with the probe of an atomic force microscope (AFM) according to the present invention. The probe comprises a substrate 2 from which protrudes a support beam 3 having a sharp probing tip 4 mounted at the end remote from the substrate 2 . In preparation for scanning, a downward force (F _external ) is applied to the probe via its mounting to the AFM at the probe substrate end 2, moving the probe tip 4 into contact with the sample 1 . In order to maintain contact during scanning, the force F _external is greater than that required to just bring the tip 4 into contact with the sample 1 . As a result, the support beam 3 bends upwards from its rest position 5 due to the presence of F _direct when scanning the sample. As before, a force proportional to kx is generated as a result of the bending of the support beam and directs the probe tip 4 downwards towards the sample surface.

If a probe designed according to the invention deviates from the sample surface, for example by encountering a raised portion, two factors contribute to bringing it back into contact. This allows better tracking of the surface to be obtained even at high scan speeds. First, as seen most clearly in the embodiments shown in FIGS. 3-7 , the second force F _direct used to accelerate the probe closer to the sample can be adjusted so as to reduce the amount of time it takes the probe to return to contact with the surface. time is reduced to a minimum. This force, essentially independent of the topography, serves to reduce the response time of the probe. Second, the probe is coated with an energy absorbing material (or submerged in a liquid), which reduces the mechanical energy stored in the probe, and thus reduces the impact of the aforementioned shocks on its motion, ensuring that it quickly acquires a stable contact with the surface state. The total restoring force holding the probe to the surface now depends on:

F _direct +kx

Ideally, the additional force F _direct is greater than the cantilever bending force kx. Also, its amplitude should be large enough so that if the probe loses contact it makes contact with the surface within about one pixel.

In the embodiment shown in Figure 3, the additional force F _direct is a magnetic force provided by applying a magnetic field to the probe tip comprising a magnetic element such as a bead or a magnetic coating. It is therefore clear that the positioning of the magnet in the AFM is not critical, it just has to be arranged so that there is a downward component of force that pulls the probe tip 4 towards the sample 1 . In a subsequent embodiment, the additional force F _direct is an electrostatic force.

In the embodiment shown in Fig. 2, the additional force F _direct still benefits the tracking performance of the probe, but its origin is finer. When the probe and sample are brought into close proximity, it is generally believed that a capillary neck is formed connecting the two. This capillary neck is thought to result from fluid liquefied around the probe-sample contact that is unavoidably present in the sample environment when imaging in air. In normal operation, it was found that the guiding force F _direct generated by the capillary neck is sufficiently large that it quickly forms a dominant restoring force on the low-Q probe, ie F _direct > kx. This is especially true for hydrophilic surfaces. By choosing a probe with a hydrophilic surface, such as silicon nitride, it is possible to ensure the formation of a capillary neck between the probe and the sample.

Regardless of the origin of the additional guiding force F _direct , the low Q of the probe allows the stored energy to be quickly dissipated when the support beam straightens and the contact of the probe to the sample surface is restored by the action of the guiding force F _direct . Thus, the tracking of the probe to the sample surface is achieved through a mechanical feedback loop that is faster than prior art tracking mechanisms that rely on the cantilever bending force kx.

In the microscope described here, the probe tip responds at a frequency significantly higher than its first oscillation mode. Thus, there is no longer a simple relationship between the bending of the probe and its vertical position, since now the degree of bending will depend on how long it has been in that vertical position. Thus, images obtained using methods based on reflection of laser light from the back of the probe to discrete photodiodes will not correspond to the topography of the surface, but to a combination of topography and gradients. In order to obtain an image that does correspond to the topography, the displacement of the probe can be monitored, for example using interferometric measurements. For example, a fiber optic interferometer can be used to monitor the position of the probe end relative to the fiber, or a Wollaston prism-based interferometer can be used to monitor the position of the probe end relative to another point, or an interference microscope can be used to monitor the position of the probe end, where In this case the light intensity at the position in the field of view of the microscope corresponding to the tip of the probe will vary depending on its vertical position. Whichever method is used, it is now possible to obtain images corresponding to surface topography, especially for metrology.

To help achieve F _direct >kx, the probe should further be designed with a relatively low spring constant. Typically this should be less than 1 Nm ^-1 , which can be achieved by using an appropriately shaped probe. In the present invention, the cantilever deflection is only useful to define the position in space where the probe is located, ie the interaction forces between the probe and the sample, allowing images to be collected.

In one prototype probe design, the cantilever has a typical spring constant of 0.01 to 0.06 Nm ⁻¹ . The acceptable range depends on the height of the features to be imaged. For features 50nm high, the prototype probe will exert a restoring force of 0.5nN to 3nN. The guiding force applied to the tip is estimated to be on the order of 1–100 nN, resulting from a combination of forces originating from the capillary neck and electrostatic forces such as those generated by the setup shown in Figs. 4, 5 and 7. The magnitude of the electrostatic force can be controlled to optimize the image. This is set so that for the fastest desired response and thus maximum tip velocity, the highest force possible is supplied to the tip, which does not damage or break the surface under study.

The ability to utilize the guided restoring force F _direct in sample tracking as opposed to relying on cantilever forces represents a significant improvement over the prior art. By providing a probe with a reduced ability to store mechanical energy, the main force acting on the probe is the directing force F _direct , and the force due to the immediate bending of the probe against the surface, and the directing force F _direct is the dominant force. This applies regardless of whether the guiding force is by means of a "natural" force generated by the capillary neck, or an additional external force such as that applied via a magnetic bead. In either case, the restoring force has a magnitude that is substantially independent of probe position. In contrast, the magnitude of the prior art restoring force kx depends on the displacement x of the cantilever from its rest position. High restoring forces are thus generated at particularly high positions on the sample. If the restoring force is allowed to vary in this way, it is very difficult to consistently ensure that the sample is not damaged. The recovery mechanism implemented in accordance with the present invention has a magnitude that is largely independent of sample height.

As stated, it is not essential that the applied force is magnetic, although preferably it is a force whose magnitude does not depend on the height of the sample. It is necessary that there is a net force towards the surface such that any force from the oscillatory modes present in the probe does not cause the probe to leave the surface. Therefore, the larger the directing force F _direct , the less stringent the expected requirements on energy absorption and dissipation through the coating. In this regard, while it is possible to implement the invention with a low-Q cantilever relying only on the capillary neck as a source of F _direct , it is preferable to also apply an external force independent of deflection. As illustrated in the embodiments described herein, probes subjected to electrostatic or magnetic forces are more controllable and provide more options for forming the highest quality images.

Figures 9a-9f clearly illustrate the improved performance of the probes of the present invention over conventional AFM devices. Figures 9a, 9b and 9c are all images of the same surface area, and similar maps 9d, 9e and 9f are images of another surface area. In all cases, the scale bar represents 1 micron and the material on which the surface was imaged was crystalline polyethylene oxide (PEO) mounted on a glass substrate. Figures 9a and 9d are images generated using the probe of the present invention, while Figures 9b and 9e are images generated using conventional AFM monitoring changes in probe height, and Figures 9c and 9f are images generated using conventional AFM monitoring deflection changes . To generate the images of Figures 9a and 9d, a Veeco Dimension 3100 ^™ AFM with a Nanoscope ^™ IV controller was used together with a commercially available cantilever coated with a thin polymer film. Samples were mounted on a microresonant scanner consisting of a quartz crystal resonator and a 5 micron piezoelectric stack (P-802 and E-505, PhysikInstrument, Germany). To collect the data for Figures 9a and 9d, a resonant scan controller from Infinitesima Ltd. was used.

Figures 9a and 9d consist of 128x128 pixel arrays over a period of only 14.3 ms, with probe tip velocities of 22.4 cms ^-1 and 16.8 cms ^-1 near the center of each image, respectively.

Thus with the present invention, images of regions of a few microns can be generated within milliseconds, unlike conventional AFMs where image collection can take upwards of 30 seconds. While the illustrated embodiment can be operated with scanning tip velocities identical to those currently used by conventional AFM microscopes, the embodiment allows for tip velocities above 0.1 ^cms , and depending on the flatness of the sample surface, over 50.0 cms can be obtained ^{. 1} tip speed. For example, a 4.4 x 4.4 micron area can be imaged in 14.3 ms and a 1.5 x 1.5 micron area can be imaged in 8.3 ms with a tip speed of 22.4 cms ⁻¹ . Furthermore, even at this speed, images with better than 10 nm lateral and 1 nm vertical resolution can be obtained with soft polymer surfaces.

It has further been observed that at these probe tip velocities the sample appears to be less susceptible to damage than at lower velocities. When the probe tip spends less time at each point, the sample is subject to less deformation and is therefore less likely to reach the point where it begins to deform plastically. Using the present invention, the surface of a sample can be subjected to a shear rate of about 10 ⁸ ms ^-1 , which is the rate at which many polymers, for example, exhibit glass properties. In general, it has been found that higher frequencies are likely to lower the viscoelastic fluid below the glass transition temperature, thus changing the surface properties of the probe that appear to cause less damage to the coupon.

The probes of the present invention are chosen to have a low Q, ideally so that any induced oscillations are strongly damped. As described here, the most preferred embodiment, and one that relies on the natural restoring forces generated by the capillary necks to be sufficiently effective to allow improved tracking, consists in coating one or both sides of the probe's support beam with an energy absorbing material such as a polymer film. side. An alternative way to ensure low Q is through judicious choice of probe shape, especially if large magnetic forces (or other additional forces) are applied. Another alternative provides a low Q-factor simply by submerging the probe into a viscous/liquid environment during scanning. Yet another option is to electrically alter the properties of the support beam of the probe, for example where the support beam is formed of or includes an electrically responsive material capable of providing a lower effective Q factor.

Support beams, probe tips, and any additional components such as magnetic beads are ideally of low mass. For a given restoring force, this naturally increases the acceleration of the tip returning to the surface, thus better allowing the probe to track the surface.

The support beams may have a predetermined design such that a desired response is promoted. That is, minimizing direction-dependent restoring forces that arise as a result of bending when the probe tracks the sample, and damping the oscillatory response (low Q-factor) if the probe is off the surface. Although often referred to here as a cantilever design, this is simply because of the use of a modified prior art AFM to this new purpose. Prior art AFM utilizes cantilever probes. Essential to the invention is that the probe tip must have a definable lateral position (x,y plane) relative to the sample and free movement in the z direction. A prior art AFM cantilever probe can easily perform this function, but it does not represent the only solution.

Returning to the embodiment of the support beam including the probe tip, Fig. 10 illustrates various possible design features that appear to be more sophisticated from the above, which facilitate reducing restoring forces and lowering the Q-factor. The polymer coatings described here can be used in conjunction with each design to further tune the response. Figure 10(c) shows a more conventional beam shape, while Figures 10(a) and (b) depict alternative possibilities. In each design, regions 1 to 4 are highlighted, and each region is designed to have specific properties. Each of figures (a) to (c) illustrates one or more support beams extending forwardly from the substrate.

Area 1 is the pivot point in all cases. That is, the cantilever beam swings in an arc around this region. Region 1 thus has a very low spring constant (ideally <0.01 Nm ⁻¹ ) along the z-axis, and a very high spring constant in the x,y plane. In this way, the lateral position of the tip is specified relative to the substrate position, but also allows free movement perpendicular to the sample surface for small deflections.

Region 2 forms the basic beam structure. It should be stiff and have a high fundamental resonance frequency.

Region 3 is the curved region connecting the beam and tip regions, which allows the tip to move up and down. The spring constant of this region is chosen such that the resonant frequency of the tip is higher than the response time of the probe, i.e. larger than the bandwidth of the mechanical feedback loop. This area should also be polymer coated to provide damping in the air. But if imaging in a liquid, the need for a coating is largely overcome due to the energy-dissipative nature of the liquid environment.

Region 4 is the tip region. The probe tip is adhered to, or forms part of, its lower surface. The area must be large enough that its position can be determined by a position detection system, essentially larger than a few microns in lateral dimension for optical levers and other far-field optical systems.

In embodiments where an externally directed force is applied to the probe to push it toward the surface, elements responsive to this force may be placed on the tip region 4, the beam region 2, or both. But preferably, it is placed on the tip.

Figures 11 and 12 illustrate examples of low and controlled spring constants in forming beams. Essentially as shown in Figure 11, this involves forming holes in the support beams at desired locations. The design shown in Figures 11(b) and (c) provides increased lateral stability compared to Figure 11(a). The hole shape can be varied, for example as shown in Figure 12, in order to control the properties of the polymer coating. That is, curved, square, or other shaped holes differently affect the way the polymer coating forms on the beam surface, which in turn affects the damping properties of the cantilever.

An advantage of providing a predetermined design of the probe support beam is that it allows separating the different requirements for oscillation damping and reducing deflection related restoring forces. In particular, it can be designed such that only the main mode is excited when high regions of the sample surface are encountered. Thus, in contrast to the multimode requirement of prior art cantilever beams, it is only necessary to ensure that the beam has a low Q-factor with respect to the mode, for example by its coating.

It should be noted that the arrangements shown in Figures 2 to 7 are illustrations of example AFMs only. There are many different AFM implementations in which the invention can be practiced, all of which omit the conventional feedback control of probe height as a fundamental method of acquiring images. For example, mounting on a resonator such as a tuning fork is not necessary. This scheme is used in these embodiments only to illustrate the applicability of the invention to fast scanning techniques using resonant oscillations. It also applies to slower scanning methods. Probe 22 can optionally be oscillated instead of sample 14 . Using this alternative embodiment, it is conceivable that the imaging beam is wide enough to include the fast scan axis where optical techniques are used to monitor probe displacement.

Probe deflection/displacement can be measured by methods other than optical lever technology. Alternative techniques known in the art include interferometric measurements and piezoelectrically coated probes, as well as detection of thermal changes in the radiant output of heated probes. Due to the frequency at which the probe responds, the frequency at which the probe deflection data represents both topography and spatial features of the sample surface, is simply extracted from the probe deflection data by monitoring the deflection/displacement of the probe using interferometric measurements Surface topography data is possible. Also, while the use of piezoelectric actuators for sample plate/probe movement is preferred, other actuators including, for example, thermal expansion of levers are contemplated.

Although the control of the probe's Q-factor has been described in terms of providing an energy-absorbing coating to the probe's support beam, other means for controlling the probe's Q-factor can be envisioned, including electrical control.

In order to image a surface area larger than the probe's scanning area, separate, sequential images of different, often adjacent, areas can be generated and then combined to form an image over this large area. Stepper motors or other actuators can be used to move the probe and/or sample plate between discrete images prior to fine positional adjustments for each individual image. The individual scan areas are ideally selected and overlapped such that visual confirmation of the alignment of the individual images is possible.

If a tuning fork 16 is used, it may be one of a variety of commercially available tuning forks, or be of a predetermined design to provide the desired frequency of oscillation. A suitable example is a quartz crystal tuning fork with a resonant frequency of 32kHz. A tuning fork is well suited for this application when it is designed with highly anisotropic mechanical properties. Its resonances are thus independent and can be excited individually, so only the one (or those) within the plane of the sample. Importantly, the tuning fork 16 can be resonated in one direction and scanned in the other without coupling between modes. Steady rapid movement of the sample 14 is thus permitted while the sample 14 is being probed by the probe 22 . A similarly convenient optional mechanical resonator with well-separated lateral and vertical resonances can be used in place of the tuning fork.

The present invention is not limited to pure AFM operation, although a vigorous interaction between the probe and the sample surface is required. But this mode of operation can also be combined with microscope components designed to monitor other interactions or indications of interactions between the probe and the sample. Examples of other interactions may include optical, capacitive, magnetic, shear, or thermal interactions. Other indications include oscillation amplitude, tapping or shear force, capacitance or induced current. These different modes of operation of a general probe microscope are described, for example, in UK Patent Application No. 0310344.7.

The interaction of probes with the sample surface utilized in AFM also makes it possible to deliberately "write" information onto the sample by influencing the properties of the surface. This technique is called nanolithography, and AFM is widely used for this purpose. For example, regions of the metal layer of the sample wafer can be oxidized by applying a voltage to the conductive cantilever. Another example using two-photon absorption and polymerization of photoresists is in Xiaobo Yin et al., "Near-field two-photon nanolithography using non-porous optical probes" in Appl. Phys, Lett. 81 (193663 (2002) described in ". In both examples, the very small probe size allows information to be written at very high densities. The AFM and cantilever probes of the present invention can also be adapted for use in nanolithography. Through the present invention The ability to improve surface tracking offers the possibility not only of faster write times than previously obtained, but also of increased image resolution, i.e. write density. To make it more suitable for use in nanolithography, the probe tip can be Conductive, it can be metallized to increase its optical interaction with the surface, or it can be coated with selected molecular species for use in dip pen etch printing applications.

Claims (33)

1. one kind for the probe (22) that uses in atomic force microscope or the nano-photoetching art, this probe comprises the power sensing element (3) that is connected to the probe tip (4) with 100nm or littler needle type radius, it is characterized in that this probe comprises biasing element (24,50), biasing element is in response to pushing each other compelling force to irrelevant any or both with probe tip (4) and sample of being used for of deflection basically.

2. according to the probe (22) of claim 1, it is characterized in that biasing element comprises in response to the magnetic element that adds magnetic force (24).

3. according to the probe of claim 2, it is characterized in that magnetic element (24) is installed in power sensing element (3) and goes up adjacent with most advanced and sophisticated (4).

4. according to the probe (22) of claim 1, it is characterized in that biasing element comprises conducting element (50), conducting element (50) is suitable for being connected to a terminal of the power supply (60) that is used for applying voltage potential between probe (22) and print.

5. according to any probe (22) of aforementioned claim, it is characterized in that providing biasing element and probe tip (4) adjacent.

6. one kind for the probe (22) that uses in atomic force microscope or the nano-photoetching art, this probe comprises the power sensing element (3) that is connected to the probe tip (4) with 100nm or littler needle type radius, it is characterized in that this probe is suitable for when being subjected to compelling force, the bigger amplitude of the restoring force that bias force is caused by the displacement of probe tip during with the ratio detection sample is pushed any or both of probe tip (4) and sample each other to.

7. according to any probe (22) of aforementioned claim, it is characterized in that power sensing element (3) has low quality factor for one or more vibration modes of power sensing element (3).

8. according to the probe (22) of claim 7, it is characterized in that power sensing element (3) comprises being adapted to pass through to excite one or more vibration modes and the damping element (22c) of dissipation energy, otherwise energy will mechanically be stored in the power sensing element.

9. probe according to Claim 8 (22) is characterized in that damping element (22c) comprises the coating of mechanical energy absorbing material at least one side of power sensing element (3).

10. according to the probe (22) of claim 9, it is characterized in that energy absorbing material is a polymer film.

11., it is characterized in that polymer film is that amorphous rubber and minority are that the multipolymer of crystal or glass ingredient forms by most components according to the probe (22) of claim 10.

12., it is characterized in that the power sensing element is coated with polymkeric substance by solution-cast according to the probe (22) of claim 10 or 11.

13. probe according to Claim 8 (22) is characterized in that providing damping element (22c) by the zone (zone 3) of the power sensing element (3) with controlled spring constant.

14. one kind be used for per sample and probe (22) between the atomic force microscope (10) of interaction force imaging sample, this microscope (10) comprising:

What the relative scanning that arranging provides between probe (22) and the sample surfaces was moved also can make sample and probe (22) closely approaching enough to set up detectable interactional drive unit (16,18,20,70) between them; And

Arrange the deflection of measuring probe (22) and/or the probe in detecting mechanism (28) of displacement;

It is characterized in that microscope (10) comprises the probe (22) according to any of claim 1 to 13.

15., it is characterized in that also comprising the syntonic oscillator that is used between probe (22) and sample, causing relative oscillating movement that is mechanically connected to probe (22) or sample stage according to the atomic force microscope of claim 14.

16. one kind be used for per sample and probe (22) between the atomic force microscope (10) of interaction force imaging sample, this microscope (10) comprising:

What the relative scanning that arranging provides between probe (22) and the sample surfaces was moved also can make sample and probe (22) closely approaching enough to set up detectable interactional drive unit (16,18,20,70) between them; And

Arrange the deflection of measuring probe (22) and/or the probe in detecting mechanism (28) of displacement;

It is characterized in that microscope (10) comprises that being arranged any or both that make in operation at sample and probe (22) goes up or apply power (F between sample and probe (22) _Direct) power (F _Direct) generation device (24,26; 50,60), this power (F _Direct) direction for making probe (22) be pushed to sample or sample is pushed to probe.

17., it is characterized in that power (F according to the microscope of claim 16 _Direct) have basically and the irrelevant amplitude of the degree of deflection of probe (22).

18. according to the microscope of claim 17, it is characterized in that probe (22) has spring constant k, and select probe (22) character and compelling force (F _Direct), make at least in predetermined time scale compelling force (F _Direct) greater than the restoring force kx that provides by the deflection x of probe (22) when scanning samples when surface.

19., it is characterized in that probe (22) has less than 1Nm according to the microscope of claim 18 ^-1Spring constant k.

20. any the microscope according to claim 16 to 19 is characterized in that power (F _Direct) generation device comprises magnet (26) and be contained in magnetic element (24) in the probe (22).

21. any the microscope according to claim 16 to 19 is characterized in that power (F _Direct) generation device comprises be used for applying the device (50,60) that attracts bias voltage between probe tip (4) and sample.

22., it is characterized in that power (F according to the microscope of claim 16 _Direct) generation device comprises and impel between probe (22) and sample the sample environment that forms narrow capillary segment that narrow capillary segment provides described compelling force (F _Direct).

23., it is characterized in that power (F according to the microscope of claim 22 _Direct) generation device also comprises water-wetted surface on described probe (22).

24. any the microscope according to claim 16 to 23 is characterized in that probe (22) has low quality factor.

25., it is characterized in that also being included in during the microscope work probe (22) and sample be immersed in device (80) in the liquid according to the microscope of claim 24.

26. microscope according to claim 24, the power sensing element (3) that it is characterized in that probe (22) comprises being adapted to pass through and excites one or more vibration modes and the damping element (22c) of dissipation energy, otherwise energy will mechanically be stored in the power sensing element (3).

27., it is characterized in that damping element comprises polymeric material coating (22c) at least one side of power sensing element (3) according to the microscope of claim 26.

28. any the atomic force microscope according to claim 16 to 27 is characterized in that also comprising the syntonic oscillator that is used for causing relative oscillating movement between probe (22) and sample that is mechanically connected to probe (22) or sample stage.

29. a method of collecting view data from the sample scanning area with nanofeature, wherein the method comprising the steps of:

(a) will comprise having needle type radius to be that the probe (22) of the power sensing element (3) at 100nm or littler tip (4) moves to sample closely approaching, and make to allow between probe (22) and sample, to set up interaction force;

(b) make between sample and probe (22) and to set up basically and the irrelevant power (F of deflection _Direct), make that promotion probe (22) is shifted to sample (14) or vice versa;

(c) sample of leap sample surfaces scan-probe (22) or probe (22) below provides the relative motion between probe (22) and the sample surfaces simultaneously, makes the layout of sweep trace cover scanning area;

(d) deflection and/or the displacement of measuring probe (22); And

(e) handle the measured value of obtaining in step (d), so that extract the information relevant with the nanostructured of sample.

30., it is characterized in that also being included in during the step (c) and to dissipate by the excited vibrational pattern otherwise will be stored in energy in the power sensing element (3) according to the method for claim 29.

31., it is characterized in that providing probe (22) in the step (c) and the relative motion between the sample surfaces by syntonic oscillator according to the method for claim 29 or 30.

32. one kind write information to scanning probe microscopy (10) on the sample by the interaction between sample and the AFM cantilever probe (22), this microscope comprises:

Layout provides that the relative scanning between probe (22) and the sample surfaces is moved and can make closely approaching drive unit (16,18,20,70) of sample and probe (22); And

Arrange typically to change off and on than the short time scale of a sweep trace interaction strength between probe and the sample, make the probe of character of the sample surfaces that changes the probe location place off and on write mechanism,

It is characterized in that microscope (10) comprises being arranged to make in operation at any of sample and probe (22) or the power (F that both go up or apply substantially and deflection has nothing to do between sample and probe (22) _Direct) power (F _Direct) generation device (24,26; 50,60), this power (F _Direct) direction push probe (22) to sample or vice versa for making.

33., it is characterized in that providing relative motion between probe (22) and the sample surfaces by syntonic oscillator according to the microscope of claim 32.

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