JP2003288738A - Recording medium, information recording method and information reading method - Google Patents

Abstract

(57) [Problem] A magneto-optical recording medium or an optical recording medium is a recording medium capable of recording information at a high recording density, but requires relatively high power when recording information. Becomes SOLUTION: A semiconductor nanocrystal having a neutral defect or a negatively charged defect on the surface and having a size where the density of the wave function of electrons in an excited state increases on the surface is used as a recording material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a recording medium capable of recording information by irradiation of light, an information recording method for recording information on the recording medium by irradiation of light, and reading information from the recording medium by irradiation of light. The present invention relates to a method of reading out information and a recording material capable of recording information by irradiation of light.

[0002]

2. Description of the Related Art Today, various kinds of information such as character information, image information, voice information, musical sound information, etc. are converted into electric signals, optical signals, etc. and transmitted. Recording media such as magnetic recording media, semiconductor memories, magneto-optical recording media, and optical recording media are used to record such information at high density.

Among these recording media, magneto-optical recording media and optical recording media have higher recording density than other recording media, and therefore their applications are expanding.

Information is recorded on the magneto-optical recording medium by locally reversing the magnetization of the magneto-optical recording layer. In the case of a rewritable optical recording medium, information is recorded on the optical recording medium by locally causing a phase transition between amorphous and crystal in the recording film.

In order to locally reverse the magnetization of the magneto-optical recording layer, the magneto-optical recording layer is locally irradiated with laser light to raise the temperature of the region to near the Curie temperature, and in this state, external It is necessary to apply a magnetic field.

In order to cause a phase transition in the recording film, it is necessary to locally irradiate the recording film with laser light to melt the region.

In both the magneto-optical recording medium and the rewritable optical recording medium, laser light with a relatively large power is required for recording information, so that the power consumption is relatively high.

[0008]

OBJECT OF THE INVENTION It is an object of the present invention to provide a new recording medium.

Another object of the present invention is to provide a new information recording method.

Still another object of the present invention is to provide a new information reading method.

Still another object of the present invention is to provide a new recording material.

[0012]

According to one aspect of the present invention, the surface has neutral defects or negatively charged defects, and the magnitude of the wave function density of excited state electrons is increased on the surface. Provided is a recording medium having a recording layer containing the semiconductor nanocrystals.

According to another aspect of the present invention, (A) a semiconductor having a neutral defect or a negatively charged defect on the surface thereof and having a magnitude such that the wave function density of electrons in an excited state increases on the surface. Information recording including the steps of preparing a recording medium having a recording layer containing nanocrystals, and (B) irradiating the recording medium with writing light or an electron beam having an energy not lower than the band gap of the semiconductor nanocrystals. A method is provided.

According to still another aspect of the present invention, (A) the surface has neutral defects or negatively charged defects, and
A recording layer comprising a semiconductor nanocrystal having a size in which the density of the wave function of electrons in the excited state increases on the surface, and a step of preparing a recording medium having information recorded in the recording layer,
(B) A first read light having an energy that resonates with the energy level of the neutral defect or a second read light having an energy that resonates with the energy level of the negatively charged defect is applied to the recording medium. Detecting the presence or absence of the first read light or the second read light that has been irradiated and transmitted through the recording medium, or the first read light or the second read light reflected by the recording layer. According to the present invention, there is provided a method for reading information including the step of reading the information.

According to still another aspect of the present invention, a semiconductor nanocrystal having a neutral defect or a negatively charged defect on the surface and having a size such that the density of the wave function of excited state electrons increases on the surface. A recording material including is provided.

The present inventors have found that in a semiconductor nanocrystal having a neutral defect on the surface and having a size in which the density of the wave function of electrons in an excited state increases on the surface, the neutral defect is a negatively charged defect. It was found that the transition can be made reversibly.

As used herein, the term "neutral defect" means a defect in which the surface level is occupied by one electron, and the "negatively charged defect" means that the surface level is It means a defect occupied by two electrons.

By utilizing the above transition, a binary signal can be recorded in the semiconductor nanocrystal. A recording medium can be constructed using semiconductor nanocrystals as a storage material.

[0019]

FIG. 1 schematically shows the cross-sectional structure of a recording medium according to an embodiment. The recording medium 10 shown in FIG.
It has a substrate 1 and a recording layer 5 arranged on the substrate 1.

The substrate 1 is made of, for example, an inorganic material such as silica glass, quartz, sapphire, or silicon, or a plastic such as an acrylic resin, and is transparent to read light described later.

The recording layer 5 contains, as a recording material, a large number of silicon nanocrystals 5a having neutral defects on the surface. These silicon nanocrystals 5a are distributed over the entire thickness direction of the recording layer 5.

The silicon nanocrystal 5a has a size such that the density of the wave function of electrons in the excited state increases on the surface. If the particle size is approximately 2.5 nm or less, the probability that electrons generated by being excited by light having an energy of a band gap or more and generated in the crystal will be present on the surface of the silicon nanocrystal is high.

In this case, the excited electron e and the neutral defect D
¹⁰ meV to 1e when ⁰ and ⁰ are separately present on the surface of the silicon nanocrystal and are bonded to each other to form a negatively charged defect (hereinafter referred to as “negative defect”) D ⁻ .
Since the energy becomes lower by about V, it becomes stable. If this reaction is described by a chemical reaction formula, D ⁰ + e → D ⁻ + ΔE
(ΔE indicates surplus energy).

[0024] From the above reaction formula, negative defects externally D ^-
It is understood that the negative defect D ⁻ can be converted to the neutral defect D ⁰ by applying energy of ΔE or more to the infrared defect in the form of infrared light.

Therefore, from the neutral defect D ⁰ to the negative defect D
It is possible to reversibly control the transition to ⁻ and the transition from the negative defect D ⁻ to the neutral defect D ⁰ . A binary signal can be recorded on the recording layer 5.

The recording layer 5 containing the above-mentioned silicon nanocrystals 5a can be produced, for example, by the following methods (i) to (iii). (i) Annealing is performed after implanting silicon ions into the glass substrate surface. (ii) High frequency (R
F) After depositing silicon on the glass substrate by sputtering, anneal. (iii) The silicon substrate is electrochemically etched.

FIG. 2 schematically shows an apparatus capable of producing the recording layer 5 or the silicon nanocrystal film as a base thereof according to the method (iii).

The illustrated device 20 includes a p-type silicon substrate 12
A stage 13 that holds the aluminum electrode 14 provided on the back surface of the p-type silicon substrate 12,
The electrolytic cell 15 whose bottom is closed by the p-type silicon substrate 12 held by the supporting member 16, the support member 16 for closely contacting the stage 13 to the bottom of the electrolytic tank 15, and the p-type silicon that is arranged so as to surround the support member 16. It has a constant temperature bath 17 for keeping the temperature around the substrate 12 constant, and a platinum mesh electrode 18 immersed in the electrolysis bath 15.

The plane orientation of the p-type silicon substrate 12 is (10
0), and its specific resistance is, for example, about 1 to 10 Ωcm. The electrolytic bath 15 contains a predetermined electrolytic solution 20, for example, a mixed solution of hydrofluoric acid (HF: H ₂ O = 1: 1) and ethanol mixed at a volume ratio of 1: 1.

The aluminum electrode 14 and the platinum mesh electrode 18 are energized from a current source 22 while maintaining the liquid temperature of the electrolytic solution 20 around the p-type silicon substrate 12 at approximately 0 to 40 ° C., for example, 20 mA / cm 2. 10 under the current density of ²
The p-type silicon substrate 12 is electrochemically etched for 100 minutes. The symbol A in the figure indicates an ammeter.

By this etching, silicon nanocrystals are deposited on the surface of the p-type silicon substrate 12. It is possible to obtain the recording layer 5 or the silicon nanocrystal film serving as the base thereof.

By appropriately selecting the thickness and size of the p-type silicon substrate 12, the p-type silicon substrate having the silicon nanocrystals deposited on the surface as described above can be used as it is as a recording medium. . In addition, the silicon nanocrystals deposited in layers on the surface of the p-type silicon substrate 12 are removed by, for example, electrolytic polishing, and the silicon nanocrystal film is formed into a desired size and shape as necessary, and then the silicon nanocrystals are formed. The recording medium can be obtained by using the film as it is or by fixing it on a predetermined substrate.

In place of the p-type silicon substrate 12, n
It is also possible to use a mold silicon substrate. In this case, it is preferable to use the lamp 24 together in order to promote the generation of holes. In addition, regardless of whether a p-type or n-type silicon substrate is used, a spacer 26 may be provided between the silicon substrate and the bottom surface of the electrolytic cell 15 as needed.
Are placed.

A silicon nanocrystal film obtained by depositing a layer of silicon nanocrystals on a p-type silicon substrate by the method described above and peeling the layer from the p-type silicon substrate was evaluated by the X-ray small angle scattering method.

As a result, the average particle size of the silicon nanocrystals in this silicon nanocrystal film was 2.24 nm, and many silicon nanocrystal surfaces were terminated by hydrogen atoms H. However, some surfaces of silicon nanocrystals had neutral defects that were not terminated by hydrogen atoms H.

FIG. 3 shows the analysis result of this silicon nanocrystal film by electron spin resonance (hereinafter abbreviated as “ESR”) method.

From the intensity of the ESR signal shown in the figure, it is recognized that the silicon nanocrystal film has neutral defects of about 1 × 10 ¹⁵ / cm ³ .

The analysis by the ESR method was carried out by an X-band spectrometer (JEOL Ltd.) with a microwave power of 1 mW.
Manufactured by JES-FELX) under the conditions of a measurement temperature of 300K, a vacuum degree of 10 ^-6 Torr (about 1.33 × 10 ^-4 Pa), and a magnetic field modulation width of 2.5 G (2.5 × 100 μT). ,
Calibration of the neutral defect density by ESR was performed using a Mn standard sample.

FIG. 4 shows the results of analysis by the ESR method performed on the silicon nanocrystal film after irradiating the silicon nanocrystal film with an argon (Ar) laser having a wavelength of 514.5 nm and an intensity of 200 mW / cm ² for 30 minutes. Indicates.

From the intensity of the ESR signal shown in the figure, the density of neutral defects in this silicon nanocrystal film is almost 0 (zero).
Is recognized as By irradiation with an argon laser,
It is recognized that the neutral defects in the silicon nanocrystal film have almost disappeared.

FIG. 5 shows the ESR performed on the silicon nanocrystal film after the conductor was brought into contact with the silicon nanocrystal film in which the density of neutral defects was made almost zero by irradiation with an argon (Ar) laser. The analysis results by the method are shown.

From the intensity of the ESR signal shown in the same figure, it is recognized that the density of neutral defects in this silicon nanocrystal film has returned to the density before the argon (Ar) laser irradiation. It is recognized that neutral defects were formed again in the silicon nanocrystal film by the contact with the conductor.

From the analysis results shown in FIGS. 4 to 5, it is understood that the density of neutral defects in the silicon nanocrystal film can be reversibly controlled.

In order to investigate how this reversible change in neutral defect density occurs, the energy of the light with which the silicon nanocrystal film is irradiated and the intensity of the ESR signal obtained from this silicon nanocrystal film The relationship was measured.
Results are shown in FIG.

As is clear from FIG. 6, when the energy of the irradiation light is less than 1.4 eV, the intensity of the ESR signal hardly changes. In other words, the density of neutral defects hardly changes. The energy of 1.4 eV almost corresponds to the band gap of silicon nanocrystals at 20 ° C. The intensity of the ESR signal changes greatly as the energy of the irradiation light is increased to more than 1.4 eV.

From these results, the reversible change of the neutral defect density in the silicon nanocrystal film is not caused by the irreversible structural change, but from the neutral defect D ⁰ to the negative defect D ^−.
It is considered that this is due to the reversible transition between the negative defect D ⁻ and the neutral defect D ⁰ .

FIG. 7 shows the neutral defect D described above.⁰ And negative defects
D^- The transition between and is shown schematically. As shown in Figure 7 (A)
Sea urchin, neutral defect D⁰ To eliminate or reduce
Almost no hydrogen on the surface of the silicon nanocrystal SNC that has not been subjected to
It is terminated by the atom H, but by the hydrogen atom H
Unterminated neutral defect D⁰ Also exists. This silico
The energy above the band gap of the nanocrystal SNC
When the light L1 having a light is emitted, as shown in FIG.
In addition, the electrons in the silicon nanocrystal SNC are excited by photoexcitation.
e is generated. As shown in FIG. 7C, this electron e
Is a neutral defect D⁰Captured by. That is, the neutral defect D⁰ 
Is a negative defect D^- Transition to. Neutral defect D ⁰ Is a negative defect D
^- When the transition to the
Resonance does not occur and the ESR signal disappears.

On the other hand, as shown in FIG. 7 (D), the silicon nanocrystal SNC in which the neutral defect D ⁰ is changed to the negative defect D ⁻ .
When the conductor C is brought into contact with the electron C, the electron e captured by the negative defect D ⁻ moves to the conductor C. As a result, the negative defect D ⁻ transits to the neutral defect D ⁰ and returns to the state shown in FIG. 7 (A). Since the neutral defect D ⁰ having unpaired electrons occurs again, the ESR signal is recovered.

By the way, in order for the electrons generated in the silicon nanocrystal SNC to be captured by the neutral defects D ⁰ , the density of the wave function of the excited electron on the surface of the silicon nanocrystal SNC must be higher than a certain level. I have to. If the particle size of the silicon nanocrystal SNC is made smaller than approximately 2.5 nm, the density of the wave function of the excited state electron on the surface of the silicon nanocrystal SNC becomes large, and the electron e generated in the silicon nanocrystal SNC e Are captured by the neutral defect D ⁰ (T. Uda, M. Hirao, J. Phys. So
c. Jpn, vol. 63, pp. 97-106 (1994)).

The generation of electrons in the silicon nanocrystal SNC occurs not only by photoexcitation but also by irradiation with an electron beam having a predetermined energy.

The transition from the neutral defect D ⁰ to the negative defect D ⁻ described above will be examined as follows using an energy band diagram.

FIG. 8 shows the energy level SD ⁰ of the neutral defect D ⁰ (hereinafter referred to as “neutral defect level SD ⁰ ”) and the negative defect D ⁰ in the band gap BG of the silicon nanocrystal.
^- of the energy level SD - ^(hereinafter referred to as "negative defect level SD
^- ". ) And are shown schematically.

As shown in the figure, the neutral defect level SD ⁰ is located almost at the center of the band gap BG, and its energy level (hereinafter referred to as “neutral defect level SD ⁰ ”) is
It is located about 0.7 to 0.8 eV above the valence band VB. On the other hand, the negative defect level SD ⁻ is the neutral defect level SD
^It is located approximately in the center between ⁰ and the conduction band CB, and has a valence band V
It is located about 1.0 to 1.2 eV above B.

When the silicon nanocrystals are photoexcited,
Alternatively, the total energy when excited by an electron beam becomes stable when the electrons generated by this excitation are trapped by the neutral defects D ^{0 as} compared with the electrons existing in the conduction band CB as conduction electrons, and are stable.

Therefore, when a silicon nanocrystal is excited,
As shown in FIG. 7, the transition from the neutral defect D ⁰ to the negative defect D ⁻ occurs. Reference numeral VB in FIG. 8 indicates a valence band.

The existence of the negative defect D ⁻ means that the negative defect level SD
^- the resonating light transmission with energy, opaque, i.e., negative defect level SD ^- red with an energy of about 0.3~0.4eV corresponding to the difference between the neutral defect level SD ⁰ It can be detected by utilizing the transmission and non-transmission of external light. The neutral defect D ⁰ is detected by measuring the intensity of the ESR signal, and in addition to the detection of the light having energy resonating with the neutral defect level SD ⁰ , that is, 0.
It is also possible to detect by utilizing transmission or non-transmission of infrared light of about 7 to 0.8 eV.

FIGS. 9A to 9D show silicon nanocrystals SNC1 to SNC in spatially different positions.
4 schematically shows a method of writing information to the No. 4 and a method of reading information from these silicon nanocrystals SNC1 to SNC4. Among the elements shown in the figure, those common to the elements shown in FIG. 7 are designated by the same reference numerals as those used in FIG. 7, and the description thereof will be omitted.

Silicon nanocrystal SNC shown in FIG. 9 (A)
In the silicon nanocrystal SNC3 shown in FIG. 1 and FIG. 9C, the neutral defect D ^{0 on} its surface is changed to the negative defect D ⁻ by irradiation with the light L1 (see FIG. 7). The silicon nanocrystal SNC2 shown in FIG. 9 (B) and the silicon nanocrystal SNC4 shown in FIG. 9 (D) are not irradiated with the light L1 and have neutral defects D ^{0 on} their surfaces.

Light L2 having energy resonating with the negative defect level SD ⁻ is supplied to the silicon nanocrystals SNC1 to SNC4.
When the irradiation is performed on the silicon nanocrystals SNC1 and SNC3, the light L2 is absorbed by the negative defects D ⁻ , and therefore the photodetector LD does not detect the light L2 and outputs a signal S0 indicating the result. On the other hand, silicon nanocrystals SNC2, SNC4
Then, the light L2 is not absorbed and the silicon nanocrystal SN
Since it passes through C2 and SNC4, the photodetector LD detects the light L2 and outputs a signal S1 representing the result.

Therefore, when the light L2 is sequentially applied from the silicon nanocrystal SNC1 to the silicon nanocrystal SNC4, the photodetector LD alternately outputs the signal S0 and the signal S1.

As is clear from these descriptions, by selectively irradiating the silicon nanocrystals SNC1 to SNC4 with the light L1, these silicon nanocrystals SNC1 to SNC1 are selectively irradiated.
Information can be written to SNC4. Further, by sequentially irradiating the silicon nanocrystals SNC1 to SNC4 with the light L2, these silicon nanocrystals SNC1 to SNC are
The information recorded in 4 can be read.

10A to 10D show silicon nanocrystals SNC1 to S in spatially different positions.
The other reading method of the information written in NC4 is shown roughly. Among the elements shown in the figure, the elements common to the elements shown in FIG. 9 are denoted by the same reference numerals as those used in FIG. 9, and the description thereof will be omitted.

Of the silicon nanocrystals SNC1 to SNC4 shown in FIGS. 10A to 10D, in the silicon nanocrystals SNC1 and SNC3, the neutral defect D ⁰ becomes a negative defect D ⁻ by irradiation with the light L1. It is transitioning. On the other hand, the silicon nanocrystals SNC2 and SNC4 are not irradiated with the light L1, and the surface thereof has the neutral defect D ⁰ .

The light L3 having energy resonating with the neutral defect level SD ⁰ is supplied to the silicon nanocrystals SNC1 to SNC4.
When the light is irradiated onto the silicon nanocrystals SNC1 and SNC3, the light L3 is not absorbed and the silicon nanocrystals SNC are not absorbed.
1, the photodetector LD transmits the light L because it passes through SNC3.
3 is detected and a signal S1 representing the result is output. On the other hand, in the silicon nanocrystals SNC2 and SNC4, light L
3 is absorbed by the neutral defect D ⁰ , the photodetector LD
Does not detect the light L3 and outputs a signal S0 representing the result.

Therefore, when the light L3 is sequentially irradiated from the silicon nanocrystal SNC1 to the silicon nanocrystal SNC4, the photodetector LD alternately outputs the signal S1 and the signal S0.

As is clear from these explanations, the light L1
The information recorded in these silicon nanocrystals SNC1 to SNC4 can be read by sequentially irradiating the silicon nanocrystals SNC1 to SNC4 on which information has been written by selective irradiation with the light L3.

In any of the methods shown in FIGS. 9 and 10, the signals S0 and S1 output from the photodetector LD are changed to 2 signals.
It can be used as a value signal. Specifically, using the above-mentioned silicon nanocrystal film as a recording layer, for example, light L
By irradiating the silicon nanocrystal film (recording material) with 1 so that the irradiation position changes temporally and intermittently,
Information can be recorded on the recording layer. Also, the light L
2 or the light L3 is scanned on the recording layer on which information is recorded, and the presence or absence of the light L2 or the light L3 passing through the recording layer is continuously detected to read the information recorded on this recording material. be able to.

Instead of the light L1, an electron beam having an energy larger than the band gap of the silicon nanocrystal can be used.

In principle, one silicon nanocrystal has one
Since bit information can be recorded, information can be recorded under a high recording density of 10 ¹³ bits / cm ² or more.

[0070] In practice, for example, it becomes possible to record one bit of information in the area having a diameter of about 20nm by using the technique of the near-field light, 10 ^11-bit / c
Information can be recorded under a recording density of about m ² . This recording density is about 10 ⁹ bytes / cm ² (10
Gigabyte / (inch) ² )) about 100 times.

The transition from the neutral defect D ⁰ to the negative defect D ⁻ can be caused by light having lower energy than that required for writing information on the conventional optical recording medium. Further, the energy of light necessary for detecting the neutral defect D ⁰ or the negative defect D ⁻ , that is, the energy of light that resonates with the neutral defect level SD ⁰ or the negative defect level SD ⁻ ,
It is lower than the energy of light required for reading the information recorded on the conventional optical recording medium. Therefore, the power required for recording or reproducing information can be reduced.

Using the method described above, a recording device for recording information on the recording layer 5 shown in FIG. 1, a reproducing device for reproducing information recorded on the recording layer 5, or a recording device for recording information on the recording layer 5 is used. A recording / reproducing device for recording and reproducing the information recorded in the recording layer 5 can be manufactured.

Hereinafter, examples of an information recording / reproducing apparatus will be given to record information on the recording layer 5 shown in FIG. 1, read information recorded on the recording layer 5, and record on the recording layer 5. The erasing of the recorded information will be specifically described.

FIG. 11 schematically shows the structure of the recording / reproducing apparatus 200 according to the first embodiment. Among the constituent elements shown in the figure, those common to the constituent elements shown in FIG. 1 are designated by the same reference numerals as those used in FIG. 1, and the description thereof will be omitted.

The illustrated recording / reproducing apparatus 200 is an apparatus for recording or reproducing information while rotating the recording medium 120 mounted in the recording medium mounting section 130 together with the recording medium mounting section 130.

The recording medium 120 includes a substrate 1, a recording layer 5 arranged on one side of the substrate 1, and a protective layer 11 covering the recording layer 5.
5 and the recording medium mounting portion 1 is provided at the central portion in plan view.
A through hole 117 that fits in 30 is formed.

The recording layer 5 contains a large number of silicon nanocrystals 5a having neutral defects on the surface, and the substrate 1 and the protective layer 11 are included.
Both 5 are transparent to the readout light described below. The protective layer 115 is also transparent to the writing light described below. The protective layer 115 has one opening 115a formed therein.

The recording medium mounting portion 130 on which the recording medium 120 is mounted is fixed to the tip of the drive shaft 135 of the motor 133 and rotates in a predetermined direction together with the drive shaft 135. The recording medium 120 mounted in the recording medium mounting unit 130 is rotationally driven together with the recording medium mounting unit 130 as described above.

The recording medium 120, which is being rotationally driven, is prevented from floating by the clamper 137. The clamper 137 is
The drive mechanism (not shown) can reciprocate in the direction indicated by arrow A in the figure, that is, in the longitudinal direction of the drive shaft 135.

Recording medium 120 being rotated (recording layer 5)
In order to write information to the recording / reproducing apparatus 200, the recording / reproducing apparatus 200 includes a writing light source 140, a beam splitter BS, and a first focusing lens C.
It has an L1 and a recording signal generation unit 145.

The writing light source 140 is composed of, for example, a laser oscillator that oscillates a blue laser beam, and outputs a predetermined writing light L _W , that is, an energy equal to or more than the band gap of the above-mentioned silicon nanocrystal having a neutral defect on the surface. The writing light L _W which it has is emitted. This writing light L _W is
The first focusing lens CL1 is transmitted through the beam splitter BS.
After being collected by the light source, the light is incident on the recording medium 120. The beam splitter BS and the first focusing lens CL1 are an optical system for recording information on the recording medium 120 (hereinafter, referred to as an optical system).
It is called "recording optical system". ).

When recording information on the recording medium 120, the oscillating operation of the writing light source 140 is performed by the recording signal generator 1.
While being controlled by 45, the writing light source 140, the beam splitter BS, and the first focusing lens CL1 are driven by a drive mechanism (not shown) such as arrow B in FIG.
Integrally reciprocates in the direction indicated by (the radial direction of the recording medium 120). The recording signal generation unit 145 uses the recording medium 120.
A control signal for controlling the oscillation operation of the writing light source 140 is generated according to the information to be written into.

In order to read the information recorded on the recording medium 120 (recording layer 5), the recording / reproducing apparatus 200 includes the reading light source 150, the second focusing lens CL2, the photodetector 160, and the reproduction signal generator 165. Have.

The reading light source 150 is composed of, for example, a laser oscillator that oscillates infrared laser light, and has a predetermined reading light L _R , that is, the light L2 shown in FIG.
The light L3 shown in 0 is emitted. Specifically, the wavelength is 1.
Infrared light of about 5 μm or about 3.0 μm is emitted.

This read light L _R is reflected by the beam splitter B.
Is reflected by S and enters the first focusing lens CL1,
The light is condensed by the first focusing lens CL1 and enters the recording medium 120.

Readout light L _R incident on the recording medium 120
Is absorbed by the recording medium 120 (recording layer 5) or penetrates the recording medium 120 (recording layer 5). The read light L _R transmitted through the recording medium 120 is the second focusing lens CL.
It is collected by 2 and enters the photodetector 160. The beam splitter BS, the first focusing lens CL1 and the second focusing lens CL2 form an optical system (hereinafter, referred to as “reproducing optical system”) for reading the information recorded on the recording medium 120.

As already described with reference to FIG. 9 or FIG. 10, the photodetector 160 generates a predetermined signal according to the presence / absence of detection of the read light L _R , and this signal is sent to the reproduction signal generator 165. Supply.

The reproduction signal generating section 165 includes a photodetector 160.
A signal S corresponding to the information recorded on the recording medium 120 is generated and output based on the signal supplied from the recording medium 120.

When reading information from the recording medium 120, the reading light source 150, the beam splitter BS, and the first
The focusing lens CL1, the second focusing lens CL2, and the photodetector 160 integrally reciprocate in the direction indicated by arrow B in the figure by a drive mechanism (not shown). The reading light source 150 emits the reading light L _R continuously instead of intermittently.

The recording / reproducing apparatus 200 has an erasing head 170 which can reciprocate in the direction of arrow A by a drive mechanism (not shown). The erasing head 170 has a convex portion 170a formed of an inorganic conductor or an organic conductor having a height equal to or larger than the thickness of the protective layer 115 on the recording layer 5. The information recorded in the recording layer 5 can be erased by bringing the tip of the convex portion 170a into contact with the recording layer 5 through the through hole 15a.

As already described with reference to FIGS. 9 and 10, recording of information on the recording layer 5 and reading of information recorded on the recording layer 5 can be performed under low power consumption.

Therefore, also in the recording / reproducing apparatus 200, it is possible to record and read information with low power consumption.

Next, a recording / reproducing apparatus according to the second embodiment will be described.

FIG. 12 shows a recording / reproducing apparatus 2 according to this embodiment.
10 is shown schematically. The illustrated recording / reproducing device 210 is
(i) a point without a clamper 137, (ii) a point with a near-field optical probe EP in place of the first focusing lens CL1,
And (iii) instead of the erasing head 170, the erasing head 1
The recording / reproducing apparatus 200 shown in FIG.
Different from

The structure of the recording / reproducing device 210 is the same as the above (i).
Except for the difference (iii), the configuration is the same as that of the recording / reproducing apparatus 200 shown in FIG. Among the constituent elements shown in FIG. 12, those common to the constituent elements shown in FIG. 1 or 11 are designated by the same reference numerals as those used in FIG. 1 or FIG. .

The near-field optical probe EP of the recording / reproducing device 210 produces near-field light at its tip (on the recording medium 10 side). In order to record information on the recording medium using the near-field light or read the information recorded on the recording medium, the tip of the near-field optical probe EP is separated from the surface of the recording layer 5 by a distance of about 10 to 20 nm. It is necessary to get closer to. Therefore, as the recording medium handled by the recording / reproducing apparatus 210, the recording medium 10 in which the surface of the recording layer 5 is exposed.
Is preferred.

Since the recording medium 10 having the exposed recording layer 5 is used, the shape of the erasing head 175 can be made simpler than that of the erasing head 170 shown in FIG. The erasing head 175 has, for example, a rod shape.

The clamper can be omitted as shown or can be used. When the clamper is used, it is preferable that the clamper and the substrate 1 are not in contact with each other, but the contact between the clamper and the recording layer 5. For example, the recording medium 10 may be attached to the recording medium mounting unit 130.
The surface of the substrate 1 may be exposed around the through hole formed in the central portion of the recording medium 10 in plan view for mounting, and the exposed surface may be in contact with the clamper.

The recording / reproducing apparatus 210 described above has the same effect as the recording / reproducing apparatus 200 according to the first embodiment.
Further, since the information is recorded on the recording medium 10 by using the near-field light, the information can be recorded under a recording density higher than that of the recording / reproducing apparatus 200 according to the first embodiment. Of course, information recorded under such a high recording density can be read.

The reading light L transmitted through the recording medium 10
Instead of detecting the presence or absence of _{R with} the photodetector 160, the presence or absence of the reading light L _R reflected on the surface of the recording layer 5 is detected with the photodetector 160.
It can also be configured to detect at.

In any case, in order to stably hold the information recorded on the recording medium 10 (recording layer 5), the above-described negative defect D ⁻ to neutral defect D ⁰ is undesirably changed. Recording medium 10 (recording layer 5) so that transition does not occur
It is preferable that recording of information on the recording medium and reading of information from the recording medium 10 (recording layer 5) are performed in a vacuum.

Next, a recording / reproducing apparatus according to the third embodiment will be described.

FIG. 13 shows a recording / reproducing apparatus 2 according to this embodiment.
20 is shown schematically. The illustrated recording / reproducing device 220 is
(i) A point having an electron beam source 180 instead of the writing light source 140, (ii) A point having an infrared light reflecting mirror M having a through hole P1 formed in the central portion instead of the beam splitter BS, (iii)
In place of the near-field optical probe EP, a point having a focusing lens CL3 having a through hole P2 along the optical axis direction formed in the central portion, (iv) between the infrared light reflecting mirror M and the focusing lens CL3. The recording / reproducing apparatus shown in FIG. 12 in that the electronic lens EL is provided, and (v) recording of information to the recording medium 10 and reading of information from the recording medium 10 are performed in the vacuum container 190. Different from 210.

The structure of the recording / reproducing apparatus 220 is from (i) to
The recording / reproducing apparatus 2 shown in FIG. 12 except for the difference (v).
The configuration is the same as that of 10. Of the constituent elements shown in FIG. 13, those common to the constituent elements shown in FIG. 12 are designated by the same reference numerals as those used in FIG. 12, and description thereof will be omitted.

Electron beam source 18 of recording / reproducing apparatus 220
0 is configured by, for example, an electron gun, and emits an electron beam having a predetermined energy, that is, an electron beam E _W having an energy equal to or higher than the band gap of the above-described silicon nanocrystal having a neutral defect on the surface.

This electron beam E _W enters the electron lens EL through the through hole P1 formed in the infrared light reflecting mirror M,
Here, after being converged to a desired diameter, it enters the recording layer 5 through the through hole P2 formed in the focusing lens CL3.

The vacuum container 190 has a window 190a transparent to infrared light so that the read light L _R emitted from the read light source 150 arranged outside the vacuum container 190 can enter the infrared light reflecting mirror M. Have. The read light L _R passes through the window 190a and enters the infrared light reflecting mirror M, and the infrared light reflecting mirror M
Is reflected by and passes through the electron lens EL, then
The recording medium 10 after being converged by the focusing lens CL3
It enters the (recording layer 5).

The recording / reproducing device 220 having the above-mentioned configuration.
Then, the spot diameter of the electron beam E _W on the recording layer 5 is set to the read light L _R on the recording layer 5 with relatively low power consumption.
The spot diameter can be made almost the same as or smaller than the spot diameter. Similar to the recording / reproducing apparatus 200 according to the first embodiment described above, it is possible to record and read information with low power consumption.

When the near-field optical probe EP (see FIG. 12) is used instead of the condenser lens CL3, the above-mentioned second
It is possible to obtain a recording / reproducing device having the same effect as the recording / reproducing device 210 according to the embodiment.

Next, a recording / reproducing apparatus according to the fourth embodiment will be described.

FIG. 14 shows a recording / reproducing apparatus 2 according to this embodiment.
30 is shown schematically. Among the constituent elements shown in the figure, those common to the constituent elements shown in FIG.
The same reference numerals as those used in No. 3 are attached and the description thereof is omitted.

The reading light source 150A in the illustrated recording / reproducing apparatus 230 is composed of a surface light source that emits a predetermined reading light (infrared light having a wavelength of about 1.5 μm or 3.0 μm). The emitter array 18 functioning as an electron beam source is provided on the emission surface of infrared light from the reading light source 150A.
0A, the recording layer 5, the electrical insulating film IF, the matrix type transparent electrode 178, and the photodetector 160A are arranged in this order.

The emitter array 180A has, for example, a silicon substrate 181, and a large number of electron emitters 182 formed on one surface of the silicon substrate 181 in a row or in a plurality of rows. One electron emitter 18
2 corresponds to the recording area of the 1-bit signal in the recording layer 5.

Each of the electron emitters 182 is, for example, a hollow body having a truncated cone shape in a side view, and has openings at its upper end (electron emission end) and lower end. Emitter array 1
The reading light applied to 80A passes through the inside of the electron emitter 182 and enters the electrical insulating film IF.

The recording layer 5 is a silicon nanocrystal layer (silicon nanocrystal 5a (see FIG. 1) formed on a silicon substrate.
including. 2) is subsequently removed from the silicon substrate to obtain a silicon nanocrystal film. The electrical insulating film IF is transparent to the reading light and is made of, for example, silicon oxide.

The matrix-type transparent electrode 178 has a large number of transparent electrodes 178a which are transparent to the reading light and are arranged in a line or in a plurality of lines in a state that each transparent electrode 178a can be controlled independently of the other transparent electrodes 178a. It is configured by One transparent electrode 178a corresponds to the recording area of the 1-bit signal in the recording layer 5.

The matrix type transparent electrode 178 constitutes a means for writing information to the recording layer 5 together with the emitter array 180A. Transparent electrode 178a and silicon substrate 18
When a predetermined voltage is applied between the transparent electrode 17 and
8a from the electron emitter 182 corresponding to the transparent electrode 1
Electrons are emitted toward 78a. By this electron,
The aforementioned transition, that is, the transition from the neutral defect D ⁰ to the negative defect D ⁻ can be caused in the recording region corresponding to the electron emitter 182 that has emitted electrons. By controlling which transparent electrode 178a the voltage is applied to by the recording signal generation unit 145, the recording layer 5
It is possible to record desired information in.

The matrix type transparent electrode 178 is
An erasing head is configured with the silicon substrate 181. When a bias voltage reverse to that at the time of writing is applied between the transparent electrode 178a and the silicon substrate 181, this transparent electrode 17
A transition from the negative defect D ⁻ to the neutral defect D ⁰ can be caused in the above-mentioned recording area corresponding to 8a. Information recorded in the recording layer 5 can be selectively erased by controlling which transparent electrode 178a the bias voltage is applied to by the erase signal generator 95.

The photodetector 160A arranged on the matrix-type transparent electrode 178 is a surface-type photodetector, and the presence or absence of read light transmitted through the recording layer 5, the electrically insulating film IF, and the matrix-type transparent electrode 178. Is detected using, for example, a large number of light receiving elements or photoelectric conversion elements, and a signal S representing the result is output. The light receiving element or the photoelectric conversion element is arranged corresponding to each one-bit signal recording area in the recording layer 5.

The recording / reproducing apparatus 230 having the above-mentioned configuration
Then, the voltage applied between the silicon substrate 181 and the matrix-type transparent electrode 178 (transparent electrode 178a) at the time of writing information can be made relatively low. Further, the voltage applied between the silicon substrate 181 and the matrix-type transparent electrode 178 (transparent electrode 178a) at the time of reading information can be made relatively low. Similar to the recording / reproducing apparatus 200 according to the first embodiment described above, it is possible to record and read information with low power consumption.

If necessary, the reading light source 150
A laminated body composed of A, the emitter array 180A, the recording layer 5, the electrical insulating film IF, the matrix type transparent electrode 178, and the photodetector 160A may be covered with a resin.

The recording medium, the method of recording information on the recording medium and the apparatus therefor, and the method of reading information from the recording medium and the apparatus therefor have been described above, but the present invention is described above. However, the present invention is not limited to this example.

For example, the nanocrystals used as the recording material are semiconductor nanocrystals, which have neutral defects or negatively charged defects on the surface, and the density of the wave function of electrons in the excited state increases on the surface. It is not limited to silicon nanocrystals as long as it has a size. It is expected that nanocrystals of indirect transition type semiconductors other than silicon, such as diamond nanocrystals and germanium nanocrystals, can be used as a recording material, like the above-mentioned silicon nanocrystals. Further, it is considered that a substance in which amorphous silicon and the above-mentioned silicon nanocrystal are mixed is also usable as the recording material.

The structure of the recording optical system in the recording apparatus and the reproducing optical system in the reproducing apparatus are as follows.
It can be appropriately changed according to the performance and the like.

It will be apparent to those skilled in the art that other various changes, improvements, combinations and the like are possible.

[0126]

As described above, according to the present invention,
A new recording material, a recording medium, and an information recording method capable of recording a large amount of information with low power consumption are provided. Further, a new recording material, recording medium and information reading method capable of reading a large amount of information with low power consumption are provided. It becomes easy to obtain a recording device, a reproducing device, or a recording / reproducing device with low power consumption per unit information amount.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a recording medium according to an example.

FIG. 2 is a schematic view showing an example of an apparatus capable of producing silicon nanocrystals by electrochemically etching a silicon substrate.

FIG. 3 is a graph showing an analysis result of a silicon nanocrystal film by an ESR method.

FIG. 4 is a graph showing an ESR analysis result of the silicon nanocrystal film obtained by irradiating the silicon nanocrystal film obtained with the analysis result shown in FIG. 3 with an argon (Ar) laser.

FIG. 5 is a graph showing an analysis result by an ESR method performed on the silicon nanocrystal film obtained by bringing a conductor into contact with the silicon nanocrystal film obtained by the analysis result shown in FIG.

FIG. 6 is a graph showing the relationship between the energy of light applied to a silicon nanocrystal film and the intensity of an ESR signal obtained from this silicon nanocrystal film.

FIG. 7 is a schematic diagram showing a transition between a neutral defect D ⁰ and a negative defect D ⁻ which is expected to occur in a silicon nanocrystal film.

FIG. 8: Neutrality within the band gap of silicon nanocrystals
Defect D⁰ Energy level SD ⁰ And the negative defect D^-D
Energy level SD^- It is a schematic diagram showing.

9 (A) to 9 (D) show a method of writing information to silicon nanocrystals spatially different from each other and a method of reading information from these silicon nanocrystals. It is a schematic diagram.

10 (A) to 10 (D) are schematic views showing another method of reading information written in silicon nanocrystals at spatially different positions.

FIG. 11 is a schematic diagram showing a configuration of a recording / reproducing apparatus according to a first embodiment.

FIG. 12 is a schematic diagram showing a configuration of a recording / reproducing apparatus according to a second embodiment.

FIG. 13 is a schematic diagram showing the structure of a recording / reproducing apparatus according to a third embodiment.

FIG. 14 is a schematic diagram showing the structure of a recording / reproducing apparatus according to a fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 5 ... Recording layer, 5a, SNC ... Silicon nanocrystals having neutral defects on the surface, 10, 120 ... Recording medium, 115 ... Protective layer, 140 ... Writing light source, 1
50 ... Read-out light source, 160, 160A ... Photodetector,
180 ... Electron beam source, 180A ... Emitter array, 2
00, 210, 220, 230 ... Recording / reproducing apparatus, D ⁰
... neutral defects, D ^- ... negative defects, L _W ... write light,
_LR ... Readout light.

Claims (20)

[Claims] 1. A recording medium provided with a recording layer having a semiconductor nanocrystal having a surface having a neutral defect or a negatively charged defect and having a size in which a density of a wave function of an excited electron increases on the surface. . 2. The recording medium according to claim 1, further comprising a substrate, and the recording layer formed on the substrate. 3. The first light, which has energy that resonates with the energy level of the neutral defect, or second light, which has energy that resonates with the energy level of the negatively charged defect, in the substrate. A transparent material having a transparency to the surface.
The recording medium described in. 4. An electrically insulating protective layer that covers the recording layer, the electrically insulating protective layer being transparent to a third light having an energy equal to or larger than a band gap of the semiconductor nanocrystal. The recording medium according to claim 3, further comprising: and having transparency to the first light or the second light. 5. The recording medium according to claim 4, wherein the electrically insulating protective layer has an opening that exposes a part of the recording layer. 6. The recording medium according to claim 1, wherein the semiconductor nanocrystal is a silicon nanocrystal. 7. A recording layer comprising (A) a semiconductor nanocrystal having a neutral defect or a negatively charged defect on the surface thereof and having a size such that the density of the wave function of an excited electron increases on the surface. An information recording method comprising: a step of preparing a recording medium described above; and (B) a step of irradiating the recording medium with writing light or an electron beam having an energy not lower than the band gap of the semiconductor nanocrystal. 8. The recording medium further comprises a substrate,
The information recording method according to claim 7, wherein the recording layer is formed on the substrate. 9. The recording medium further includes an electrically insulating protective layer covering the recording layer, and the electrically insulating protective layer is transparent to the writing light. Information recording method described in. 10. The information recording method according to claim 9, wherein the electrically insulating protective layer has an opening that exposes a part of the recording layer. 11. The information recording method according to claim 7, wherein the semiconductor nanocrystal is a silicon nanocrystal. 12. The information recording method according to claim 7, wherein the recording medium is arranged in a vacuum container. 13. A recording layer comprising (A) a semiconductor nanocrystal having a neutral defect or a negatively charged defect on the surface thereof and having a size such that the density of a wave function of an excited electron increases on the surface. A step of preparing a recording medium having information recorded in the recording layer, and (B) a first reading light having energy resonating with an energy level of the neutral defect,
Or irradiating the recording medium with a second reading light having energy that resonates with the energy level of the negatively charged defect, and the first reading light or the second reading light transmitted through the recording medium; Or a step of reading the information by detecting the presence or absence of the first reading light or the second reading light reflected by the recording layer. 14. The recording medium further has a substrate, and the recording layer is formed on the substrate.
The information reading method described in. 15. The substrate is transparent to the first read light or the second read light.
4. The information reading method described in 4. 16. The recording medium further includes an electrically insulating protective layer that covers the recording layer, and the electrically insulating protective layer protects against the first read light or the second read light. The information reading method according to any one of claims 13 to 15, which has transparency. 17. The information reading method according to claim 16, wherein the electrically insulating protective layer has an opening that exposes a part of the recording layer. 18. The information reading method according to claim 13, wherein the semiconductor nanocrystal is a silicon nanocrystal. 19. The information reading method according to claim 13, wherein the recording medium is arranged in a vacuum container. 20. A recording material comprising a semiconductor nanocrystal having a neutral defect or a negatively charged defect on the surface thereof and having a size such that the density of the wave function of an excited state electron increases on the surface.