JP2014066586A - Method for preparing analysis sample and analysis method using the analysis sample - Google Patents

Abstract

An object of the present invention is to provide an analysis sample preparation method and an analysis method thereof capable of suppressing an electrification phenomenon and performing an accurate analysis in Auger electron spectroscopy analysis using an insulating powder sample as an analysis target.
An analytical sample preparation method for performing elemental analysis of insulating powder by Auger electron spectroscopy, wherein the insulating powder and a conductive additive are mixed, and the mixture obtained by mixing is mixed with metal. An analysis cross section is formed by filling a powder holder made of the product and processing the cross section of the mixture.
[Selection] Figure 3

Description

  The present invention relates to an analysis sample preparation method for performing elemental analysis of an insulating powder sample by Auger electron spectroscopy and an analysis method thereof.

  Auger electron spectroscopy (AES) is an analysis method in which a sample surface is irradiated with an electron beam and the kinetic energy of Auger electrons emitted from the sample surface is detected.

  When an atom is irradiated with an electron beam, a hole is generated in the inner shell of the atom due to the irradiation of the electron beam, and an electron transits to the inner shell hole from the level of the outer shell. At this time, energy corresponding to the difference between the inner shell and the outer shell is given to another electron in the outer shell, and the given electron jumps out of the atom. This jumped-out electron is called Auger electron.

Specifically, these phenomena will be explained using oxygen as an example. When an oxygen atom is irradiated with an electron beam, vacancies are generated in the K shell, which is the inner shell of the oxygen atoms, and the outer L shell is formed in the K shell vacancies. The electrons will transition. At this time, the energy of the difference between the K shell and the L shell is given to another electron of the L shell, and the electron jumps out of the atom as an Auger electron (denoted as “O _KLL Auger electron”).

  Since the kinetic energy value of Auger electrons is unique to each element, element information contained in the sample can be acquired by Auger electron spectroscopy that detects the kinetic energy of Auger electrons. In addition, since this Auger electron spectroscopic analysis method is an analysis method based on the above-described principle, the element to be analyzed is an element having an atomic number larger than that of Li.

  This Auger electron spectroscopy is more effective for the analysis of light elements compared to spectroscopic methods using fluorescent X-rays and characteristic X-rays because the generation efficiency of Auger electrons is higher for light elements. is there. The Auger electron spectroscopy is an analysis method characterized in that element information on the outermost surface of the sample can be acquired because the escape depth of the Auger electrons is several nm from the sample surface. Furthermore, in Auger electron spectroscopy, a thermionic emission or field emission electron beam gun is used as the electron beam source, and the electron beam can be converged by a magnetic lens, so that analysis of a local region of about sub-μm is possible. Is possible.

  By the way, the cross-sectional portion of the sample can be analyzed by using the above-described Auger electron spectroscopy and various cross-section processing techniques in combination.

  However, Auger electron spectroscopy uses the electron beam as a probe, so that there is a problem that a charging phenomenon occurs when the sample is insulative. Electrons irradiated to the sample flow out of the system through a metal sample holder when the sample is a conductive material, but when the sample is insulative, it is generated by irradiation of electrons or electron beams on the sample surface. Secondary electrons accumulate and the sample surface is negatively charged. In particular, if you want to analyze the cross-section of a powder in an insulating powder sample, the conventional method is to embed the sample in a resin and perform cross-section processing using a cross-section polisher or polishing. Then, since the sample is not only insulative, but also the surrounding resin is insulative, excess electrons in the measurement region do not escape outside the measurement region, making it very difficult to suppress the charging phenomenon.

  When such a charging phenomenon occurs, the work function changes as a result, and the peak energy value of Auger electrons shifts to a higher energy side than the true value. Such peak shifts can lead to erroneous results when identifying elements.

  As a method of suppressing the charging phenomenon as described above, a method of irradiating low-energy Ar ions using an Ar ion gun to remove excess electrons (for example, see Non-Patent Document 1), or tilting a sample. Thus, a method of increasing the amount of secondary electrons emitted by making the incident angle of the electron beam shallow to make it difficult for electrons to accumulate on the sample surface (see, for example, Non-Patent Document 2) has been taken. In addition, a method has been proposed in which a conductive thin film of about several nm is formed on the sample surface to allow electrons to escape outside the sample (see, for example, Patent Document 1). Furthermore, when the sample is bulk, a method is generally employed in which a mask is taken so as to surround the measurement site with a metal plate and electrons are allowed to escape from the system.

  However, in the method of irradiating Ar ions or the method of tilting the sample, a sufficient charge eliminating effect is often not obtained when the conductivity of the sample is extremely low. In addition, the method of forming a conductive thin film of about several nm on the sample surface has a problem that information on the conductive thin film interferes with information on the target element because the Auger electron detection depth is several nm. Furthermore, the method of masking with a metal plate can be applied to a flat bulk sample, but it is sufficient for a sample with large irregularities, a powder sample, or a powder sample embedded in a resin and subjected to cross-section processing. It is difficult to obtain the effect.

Japanese Patent No. 2994606

JEOL News Vol.42,2010 Yuji Nagasawa SCAN TECH 2000 Proceedings, 14 (2000) JEOL Applied Surface Science, Vol. 133, 213-220,1998

  Therefore, the present invention has been proposed in view of such circumstances, and in the Auger electron spectroscopic analysis with an insulating powder sample as an analysis object, an analysis that enables accurate analysis by suppressing the charging phenomenon. Sample preparation methods and analysis methods are provided.

  As a result of intensive studies in order to solve the above-mentioned problems, the present inventor efficiently causes excess electrons in the measurement region to escape from the sample by allowing a conductive additive to exist around the insulating powder. It has been found that charging can be eliminated, and the present invention has been completed.

  That is, the analytical sample preparation method according to the present invention is a method for preparing an analytical sample for performing elemental analysis of an insulating powder by Auger electron spectroscopy, and the insulating powder and a conductive additive are mixed. The analysis section is formed by filling the mixture obtained by the mixing into a metal powder holder and subjecting the mixture to cross-section processing.

  Here, it is preferable to use graphite powder or metal powder as the conductive assistant.

  Moreover, in the said mixing, it is preferable that the volume ratio of the said conductive support agent with respect to the said insulating powder shall be 1 / 10-9 / 10 on the volume reference | standard before mixing.

  Moreover, it is preferable to perform the said cross-section process by a cross section polisher.

  Moreover, the analysis method according to the present invention is an analysis method for performing elemental analysis of insulating powder by Auger electron spectroscopy, and obtained by mixing the insulating powder and a conductive additive. The mixture is filled in a metal powder holder, and the analysis is performed using the analysis sample obtained by forming an analysis section by performing cross-section processing on the mixture.

  According to the analytical sample preparation method of the present invention, when an insulating powder sample is analyzed by Auger electron spectroscopy, the charging phenomenon caused by secondary electrons generated by electron beam irradiation is easily and effectively suppressed. An analytical sample that can be used. Further, according to the analysis method using this analysis sample, the charging phenomenon can be suppressed, so that element information can be obtained accurately and element analysis can be performed with high accuracy.

It is a schematic diagram which shows an example of a powder holder. It is a schematic diagram which shows a state when a powder holder is filled with the mixture of insulating powder and a conductive support agent. It is a schematic diagram of the analytical sample obtained by carrying out cross-sectional processing of the mixture of the insulating powder with which the powder holder was filled, and the conductive support agent. It is a schematic diagram which shows the state which mounted and fixed the analysis sample to the sample holder of an Auger electron spectroscopy analyzer. 2 is an Auger electron spectrum of Example 1. 2 is an Auger electron spectrum of Comparative Example 1.

Hereinafter, a specific embodiment of an analysis sample preparation method used in the Auger electron spectroscopy analysis method according to the present invention and an analysis method using the analysis sample prepared by the method (hereinafter referred to as “this embodiment”). Will be described in detail in the following order with reference to the drawings.
1. 1. Preparation method of analytical sample used for Auger electron spectroscopy 2. Analysis method by Auger electron spectroscopy Example

<1. Preparation of analytical sample for use in Auger electron spectroscopy>
The analytical sample preparation method according to the present embodiment is an analytical sample preparation method for performing elemental analysis of a sample by Auger electron spectroscopy, and is an insulating and powder sample (hereinafter referred to as “insulating powder”). Is a sample preparation method for analysis.

  Specifically, in this analytical sample preparation method, the insulating powder to be analyzed and the conductive additive are mixed, the mixture obtained by mixing is filled in a metal powder holder, and the cross-section processing is performed on the mixture. The analysis cross section is formed by performing the above.

  According to this analytical sample preparation method, charging phenomenon caused by secondary electrons generated by electron beam irradiation in Auger electron spectroscopic analysis can be easily and effectively suppressed (eliminated), and accurate elemental information is acquired. Thus, it is possible to obtain an analysis sample that enables highly accurate elemental analysis.

(Mixing of insulating powder and conductive aid)
In the analytical sample preparation method according to the present embodiment, first, an insulating powder that is a sample to be analyzed and a conductive additive are mixed. That is, by mixing a conductive additive with the insulating powder, the conductive material is present around the insulating powder.

  In this way, by mixing the insulating powder and the conductive additive, secondary electrons generated by irradiating the insulating sample with the electron beam can be released via the conductive additive, Generation of the charging phenomenon can be suppressed.

  Although it will not specifically limit as a conductive support agent if it has electroconductivity, For example, a graphite powder, a metal powder, etc. can be used. However, it is preferable that the insulating powder is made of a substance composed of an element different from the element to be analyzed.

  Moreover, it is preferable that a conductive support agent is a fine powder, and it is preferable that the average particle diameter is 1 micrometer or less. In this way, by using a fine conductive assistant having an average particle size of 1 μm or less, the insulating powder and the conductive assistant can be effectively contacted to obtain a more effective charge elimination effect. . When the average particle size of the conductive auxiliary agent is 1 μm or more, the contact area with the insulating powder as the sample becomes small, and there is a possibility that sufficient effect of eliminating the charge cannot be obtained.

  The mixing ratio of the insulating powder and the conductive auxiliary agent is not particularly limited, but is mixed so that the volume ratio of the conductive auxiliary agent to the insulating powder is 1/10 to 9/10 based on the volume before mixing. It is preferable. If the volume ratio of the conductive additive to the insulating powder is less than 1/10, there is a possibility that sufficient effect of eliminating the charge cannot be obtained. On the other hand, if the volume ratio exceeds 9/10, the insulating powder becomes conductive after the cross-section processing. There is a possibility of being buried in the auxiliary agent and not being exposed on the surface.

  Further, the mixing method of the insulating powder and the conductive additive is not particularly limited, and a well-known mixing method can be applied. Among them, it is preferable to use a method in which an insulating powder as a sample is placed in a vial of an appropriate size, covered, and mixed using a vortex mixer. Thereby, insulating powder and a conductive support agent can be mixed more uniformly, and the generated secondary electron can be efficiently escaped via a conductive support agent. Further, when mixing by this method, in order to remove the influence of contamination during mixing as much as possible, the material of the vial is preferably glass and the material of the lid is preferably Teflon.

(Filling into powder holder)
When the insulating powder and the conductive additive are mixed in this manner, the mixture obtained by the mixing is then filled in the powder holder. This powder holder is made of metal.

  In this way, by filling and fixing the mixture containing the insulating powder to be analyzed in the powder holder, it is possible to place and fix the powder holder together with the analyzer. Analysis by Auger electron spectroscopy can be performed. In addition, by using a metal holder as the powder holder, secondary electrons generated by electron beam irradiation can be released out of the system through the metal powder holder, and the charging phenomenon can be suppressed more effectively. can do.

  Specifically, as the powder holder for filling the mixture, one having a shape shown in a schematic diagram in FIG. 1 can be used. 1A is a perspective view of the powder holder 10 shown as an example, and FIG. 1B is a vertical cross-sectional view passing through the powder filling portion 11 of the powder holder 10.

  If the powder holder 10 is a metal thing, the kind will not be specifically limited.

  Moreover, the shape of the powder filling part 11 of the powder holder 10 is not particularly limited, but may be a circular shape as shown in FIG. Further, the diameter and depth of the hole of the powder filling portion 11 are not particularly limited, and can be appropriately set according to the amount of the sample.

  FIG. 2 is a schematic view showing a state when the powder holder 10 is filled with a mixture 22 obtained by mixing the insulating powder 20 and the conductive additive 21. 2A is a perspective view of a state in which the mixture 22 is filled in the powder holder 10, and FIG. 2B is a vertical sectional view through the mixture 22 filled in the powder filling unit 11.

(Cross section processing (formation of analysis section))
When the powder holder is filled with the mixture of the insulating powder and the conductive additive as described above, the cross section is processed for the mixture, and the analysis cross section that becomes the irradiation surface of the electron beam by Auger electron spectroscopy analysis To form an analysis sample.

  The cross-section processing method applied to the mixture is not particularly limited, but is preferably performed by a cross section polisher.

  The cross section polisher method (CP method) is a method of creating a cross section by bringing a shielding plate into close contact with a sample and scraping a portion protruding from the shielding plate by sputtering with argon ions. According to this cross section polisher, a finer mirror finish can be achieved and analysis accuracy can be improved. In particular, different materials of insulating powder and conductive additive are mixed as in this embodiment. It is preferable in that the cross-section processing can be effectively performed on the existing mixture.

  FIG. 3 is a schematic view of an analytical sample 30 obtained by cross-sectional processing of the mixture 22 of the insulating powder 20 and the conductive additive 21 filled in the powder holder 10. 3A is a perspective view of the analysis sample 30, and FIG. 3B is a vertical cross-sectional view passing through the mixture 22 subjected to cross-section processing.

  As described above, in the analytical sample preparation method according to the present embodiment, the conductive powder is mixed with the insulating powder to be analyzed, and the resulting mixture is filled into a metal powder holder. Then, by performing cross-section processing on the mixture, an analysis cross section is formed to obtain an analysis sample.

  According to the analysis sample prepared by such a method, even if the analysis target is an insulating material and a powder sample, the charging phenomenon caused by the secondary electrons caused by the electron beam irradiation is suppressed (eliminated). be able to. Moreover, in this analysis sample, since the insulating powder and the conductive auxiliary agent are filled in the metal powder holder, excess secondary electrons can be efficiently released out of the measurement region, and more effectively. Generation of the charging phenomenon can be suppressed.

  In addition, according to such a preparation method, laborious and precise adjustments such as a conventional method of irradiating low-energy Ar ions or a method of tilting a sample to make it difficult for secondary electrons to accumulate are performed. It is not necessary to prepare an analytical sample that can suppress the charging phenomenon with a simple operation. Further, unlike the conventional method in which a conductive thin film is formed on the sample surface, the information on the analysis element is not disturbed, so that the element information can be obtained accurately and with high accuracy.

<2. Analysis method by Auger electron spectroscopy>
Next, an analysis method using Auger electron spectroscopy will be described. The analysis method using Auger electron spectroscopy according to this embodiment is characterized in that the analysis sample prepared as described above is used. That is, the analysis powder is formed by mixing the insulating powder to be analyzed and the conductive additive, filling the resulting mixture into a metal powder holder, and performing cross-section processing on the mixture. Elemental analysis is performed using the analysis sample obtained in this way.

  In this analysis method, first, an analysis sample 30 as shown in FIG. 3 is placed and fixed on a metal sample holder attached to the Auger electron spectroscopy analyzer. FIG. 4 is a schematic diagram showing a state in which the analysis sample 30 is placed and fixed on the sample holder 13 of the Auger electron spectroscopy analyzer. As shown in FIG. 4, when mounting and fixing on the sample holder 13, the analysis sample 30 is fixed to the metal sample holder 13 using a conductive adhesive 12 such as a conductive tape.

  When the analysis sample 30 is placed and fixed in this way, the electron beam is then irradiated to the mixture 22 composed of the insulating powder 21 and the conductive additive 22 that has been cross-sectional processed by the Auger electron spectroscopy analyzer. Perform elemental analysis. In addition, it does not specifically limit as an analysis condition of Auger electron spectroscopy analysis, According to a sample to be analyzed, it can set suitably.

  In the analysis method according to the present embodiment, Auger electron spectroscopic analysis is performed using the analysis sample prepared as described above, so that the occurrence of a charging phenomenon in the measurement region can be suppressed. The shift of peak energy based on the phenomenon can be prevented. According to such an analysis method, accurate elemental information can be effectively obtained for the elements contained in the insulating powder sample, and highly accurate elemental analysis can be performed.

<3. Example>
Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[Example 1]
(Preparation of analysis sample)
Insulating metal oxide powder having a known composition having an average particle diameter of about 20 μm and acetylene black serving as a conductive assistant were collected at a volume ratio of 1: 1. As acetylene black, Denka Black powder (average particle size 35 nm, bulk density 0.04 g / ml, specific surface area 68 m ² / g) manufactured by Denki Kagaku Kogyo Co., Ltd. was used.

  Next, the metal oxide powder and acetylene black were put into a glass vial with a capacity of 2 ml, and mixed using a vortex mixer. The mixed mixture is filled in a metal powder holder (sample filling part diameter 1 mmφ) attached to a cross-section sample preparation device (JEOL SM-09010) manufactured by JEOL Ltd., and the cross-section processing of the mixture is performed using the device. An analysis cross section was formed and used as an analysis sample. The cross-section processing was performed for 12 hours under the conditions of an Ar ion acceleration voltage of 5 kV, a current of 90 μA, and an inclination angle of 2 °.

(Auger electron spectroscopy analysis and analysis results)
The prepared analysis sample was placed and fixed on a metal sample holder attached to an Auger electron spectroscopy analyzer (JEOL JAMP-9500F) manufactured by JEOL Ltd., and Auger analysis was performed. At the time of mounting and fixing, the powder holder constituting the analysis sample was fixed to the sample holder using a conductive double-sided tape. As analysis conditions, an electron beam acceleration voltage of 10 kV, an irradiation current of 5.0 × 10 ⁻⁹ A, an electron beam incident angle of 30 °, and a range of 30 to 2000 eV was scanned in 1 eV steps to detect Auger electrons. .

  FIG. 5 is an Auger electron spectrum showing the analysis result. The peak of oxygen was detected in the energy value described in Non-Patent Document 3, and it was confirmed that analysis was possible without the influence of charging.

[Comparative Example 1]
The same insulating metal oxide powder as used in Example 1 was embedded in an epoxy resin, and then a cross-section was processed using a microtome (REICHERT ULTRACUT S manufactured by Leica Corporation) to obtain an analysis sample. Then, Auger analysis was performed using the analysis sample with the same apparatus and analysis conditions as in Example 1.

  FIG. 6 is an Auger electron spectrum showing the analysis result. As shown in the spectrum diagram, it can be seen that the oxygen peak is shifted to the high energy side of 20 eV. In addition, it can be seen that the slope of descending right-handed shoulders from secondary electrons appearing from 0 to 200 eV in the spectrum diagram of FIG. 5 shifts to the higher energy side and forms a peak near 100 eV.

  This is because a charging phenomenon caused by secondary electrons generated by irradiating an insulating metal oxide powder with an electron beam occurs, and the work function by Auger analysis is changed by the charging phenomenon. It is thought that it has shifted.

  DESCRIPTION OF SYMBOLS 10 Powder holder, 11 Powder filling part, 12 (Conductive) adhesive, 13 Sample holder, 20 Insulating powder, 21 Conductive auxiliary agent, 22 Mixture, 30 Analytical sample

Claims (5)

A method for preparing an analytical sample for performing elemental analysis of an insulating powder by Auger electron spectroscopy,
The insulating powder and the conductive additive are mixed, the mixture obtained by the mixing is filled in a metal powder holder, and an analysis cross section is formed by performing cross-section processing on the mixture. Analytical sample preparation method.   The analytical sample preparation method according to claim 1, wherein graphite powder or metal powder is used as the conductive assistant.   2. The analytical sample preparation method according to claim 1, wherein in the mixing, a volume ratio of the conductive additive to the insulating powder is set to 1/10 to 9/10 on a volume basis before mixing.   The analytical sample preparation method according to claim 1, wherein the cross-section processing is performed by a cross section polisher. An analysis method for performing elemental analysis of insulating powder by Auger electron spectroscopy,
It is obtained by mixing the insulating powder and the conductive additive, filling the mixture obtained by the mixing into a metal powder holder, and processing the cross section of the mixture to form an analysis cross section. The analysis method characterized by performing elemental analysis using the analyzed sample.

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