JP2846520B2 - How to measure the particle size or average particle size of ultrafine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the particle size or the average particle size of ultrafine particles present in a very small area, for example, 10 μm or less.

[0002]

2. Description of the Related Art Ultrafine particles of semiconductors and metals exhibit strong optical nonlinearity, and thus have attracted attention as new optical or electronic materials, and have been studied in many ways. It is known that the properties of the ultrafine particles are related to the quantum size effect, and is characterized by being very sensitive to the particle size of the ultrafine particles. Therefore, it is very important in this study to measure the particle size or average particle size of the ultrafine particles. As a method for measuring the particle diameter or the average particle diameter of the ultrafine particles, the following two methods are conventionally used. One is a method using a transmission electron microscope. This method
After thinning the ultra-fine particle sample whose particle size is to be measured to about 10 nm, a large number of ultra-fine particles can be directly observed using a transmission electron microscope or photographed on a silver halide film, and the size of each ultra-fine particle can be reduced. This is a method of measuring the diameter and obtaining the particle diameter or the average particle diameter (hereinafter, referred to as a direct observation method). The second is a method using X-rays. The outline of this method is as follows. The diffraction pattern obtained when a large crystal is exposed to X-rays consists of thin rings or small spots. On the other hand, the diffraction pattern obtained from the ultrafine particles consists of a wide ring. It is known that the half width B representing this spread is represented by the following equation with respect to the particle diameter D of the ultrafine particles. B = 0.9λ / D / cos θ where λ is the wavelength of the X-ray and θ is the Bragg angle. By using this equation, the average particle size of the ultrafine particles can be determined from the half-width of the X-ray diffraction line (hereinafter, referred to as the half-width method). By the way, when ultrafine particles are applied as a new optical or electronic device, the structure of the device is on the order of μm. Therefore, for example, 10 μm
It is necessary to measure the particle size or the average particle size of the ultrafine particles existing in the minute region as described below.

[0003]

However, in the above-described direct observation method, the single particle size of specific ultrafine particles existing in a minute region of about 10 μm or less can be measured, but the average particle size is measured. However, there is a problem that it takes a very long time because the particle size must be measured for each of a large number of ultrafine particles of about several hundred to 1,000.
Also, when measuring either single particle size or average particle size,
Since the form of the sample to be measured is limited, it is necessary to make the sample to be measured thin to about 10 nm through which the electron beam passes.
There is a problem that it takes much time to prepare an observation sample. On the other hand, in the half width method, a specific about 10 μm
Since it is impossible to selectively apply X-rays to the following minute regions, there is a problem that this measurement method cannot be applied. Therefore, an object of the present invention is to provide a novel method capable of easily measuring the particle size or the average particle size of ultrafine particles existing in a minute region of, for example, 10 μm or less.

[0004]

The object of the present invention is achieved by the following inventions. That is, the present invention provides a method for irradiating a small region of a sample of ultrafine particles with an electron beam, measuring an electron energy loss spectrum with an electron energy analyzer, and generating plasmon generated in the ultrafine particles of the sample from the energy of the loss peak of the spectrum. After obtaining the energy, based on the correlation existing between the particle size of the ultrafine particles and the plasmon energy generated in the ultrafine particles, the particle size or average particle size of the ultrafine particles of the sample is obtained from the plasmon energy obtained earlier. This is a method for measuring the particle diameter or average particle diameter of ultrafine particles, which is characterized by calculating the diameter.

[0005]

The method for measuring the particle size or average particle size of the ultrafine particles of the present invention is characterized by the fact that the plasmon energy generated in the ultrafine particles changes according to the particle size, which was found as a result of intensive studies by the inventors. To use. That is, if the energy of the plasmon is measured using electron energy loss spectroscopy, the particle size or average particle size of the ultrafine particles can be easily obtained from the energy.

[0006]

Next, preferred embodiments will be described.
The present invention will be described in more detail. First, the measurement principle of the method for measuring the particle size or average particle size of the ultrafine particles of the present invention will be described below. As a result of the inventor's diligent research, as shown in FIG. 1, the plasmon energy generated in the ultrafine particles is affected by the quantum size effect when the particle diameter is reduced, and is lower than the plasmon energy generated in a large crystal. Also became larger. Further, as a result of conducting detailed research, the present inventor has found that the following equation (1) is established between the plasmon energy E and the particle diameter d of the ultrafine particles. E (d) = E ₀ (1 + h ² π ² / mEgd ² ) (1) where E ₀ is the plasmon energy observed in a large crystal, Eg is the band gap, m is the effective mass of electrons, and h is Planck. It is a value obtained by dividing the constant by 2π. Therefore, if the plasmon energy in the ultrafine particles is measured, the single particle size of the ultrafine particles can be calculated from the above equation. Further, if the plasmon energy of a plurality of ultrafine particles having a particle size distribution is measured, the average particle size of the plurality of ultrafine particles can be obtained.

The above plasmon energy can be obtained by measuring an electron energy loss spectrum as described below. That is, when an electron energy loss spectrum is measured in a state where an electron beam is applied to a minute region of a sample of ultrafine particles, a loss peak is found when the energy of plasmon corresponding to the average particle diameter of the ultrafine particles present in the minute region coincides. Appears. Therefore, if the electron energy loss spectrum is measured, the plasmon energy corresponding to the peak position of the energy loss spectrum is obtained. If the plasmon energy is obtained in this manner, the average particle size of the ultrafine particles existing in the minute region can be obtained from the relationship of the above equation (1). In the method for measuring the particle diameter of ultrafine particles or the average particle diameter according to the present invention, the minute region irradiated with an electron beam can be suitably used when it is 10 μm or less. Also, by narrowing down the electron beam and measuring the electron energy loss spectrum of a single ultrafine particle in the same manner and determining the plasmon energy, the particle diameter of the single particle can be determined.

The plasmon energy measuring device required in the method of the present invention is only an electron beam source and an electron energy analyzing device using an electric or magnetic field, so that it can be easily combined with any other vacuum vessel. It is possible.
Examples of the ultrafine particle material whose particle diameter or average particle diameter can be measured by the method of the present invention include semiconductor materials such as C, Si, and Ge and alloys thereof, such as Si-O, Sn-O, and Ti-O. Oxides, nitrides such as Si-N, Ti-N, BN, Si-
The present invention can be applied to all semiconductor and insulator materials such as carbides such as C and WC. Among them, the method of the present invention is preferably applied to Si-based ultrafine particles.

[0009]

Next, the present invention will be described in more detail with reference to examples of the present invention. Example 1 FIG. 2 shows electron energy loss spectra of two types of Si ultrafine particles prepared under different conditions by a microwave plasma method. The spectrum is an electron energy loss spectrum obtained in a minute region of 0.5 μm using an electron energy loss spectrometer attached to a transmission electron microscope. Comparing FIG. 1 with the position of the loss peak due to plasmon excitation seen in this spectrum,
The average particle size as shown in Table 1 is obtained for each material. For the same Si ultrafine particles as above, the average particle size is determined by a conventional direct observation method and compared with the above results.
As shown in Table 1, good agreement is shown, and it is understood that the average particle size obtained by the method of the present invention has the same accuracy as that of the conventional direct observation method.

[0010]

[Table 1]

Example 2 FIG. 3 shows silicon ultra-fine particles deposited on a 1-inch Si wafer by a microwave plasma method from a minute portion (3 μm) on the wafer using a cylindrical mirror type electron energy analyzer. It is the obtained electron energy loss spectrum. However, this spectrum is drawn in the form of a second derivative in order to clearly indicate the peak position.
In this spectrum, as in Example 1, a loss peak due to plasmon excitation was observed, and the average particle size of the Si ultrafine particles was determined from this peak position. or,
The average particle size of the same Si ultrafine particles was measured using the half-value width method by irradiating a wide area on the wafer with X-rays. This shows that the average particle size obtained by the method of the present invention has the same accuracy as that of the half width method conventionally used.

[0012]

As described above, according to the method for measuring the particle size or average particle size of the ultrafine particles of the present invention, the particle size or average particle size of the ultrafine particles existing in a minute region of, for example, 10 μm or less can be measured by an electron beam. It can be easily measured simply by using a source and an electron energy analyzer.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between plasmon energy generated in ultrafine particles and a particle size.

FIG. 2 shows electron energy loss spectra of two types of Si ultrafine particles prepared under different conditions by a microwave plasma method.

FIG. 3 is an electron energy obtained from a microscopic portion (3 μm) of Si ultrafine particles deposited on a Si wafer by a microwave plasma method, measured using a cylindrical mirror type electron energy analyzer. It is a loss spectrum.

Claims (4)

(57) [Claims] 1. A plasmon generated in an ultrafine particle of a sample by irradiating an electron beam to a minute region of the ultrafine particle sample, measuring an electron energy loss spectrum by an electron energy analyzer, and using energy of a loss peak of the spectrum. After obtaining the energy, based on the correlation existing between the particle size of the ultrafine particles and the plasmon energy generated in the ultrafine particles, the particle size or average particle size of the ultrafine particles of the sample is obtained from the plasmon energy obtained earlier. A method for measuring the particle diameter or average particle diameter of ultrafine particles, comprising calculating the diameter. 2. The method for measuring the particle size or average particle size of ultrafine particles according to claim 1, wherein the electron beam is applied to a minute region having a size of 10 μm or less. 3. The particle size or average particle size of the ultrafine particles according to claim 1, wherein the electron beam is narrowed down to irradiate a single ultrafine particle of a sample, and the particle size of the single ultrafine particle is measured. Measurement method. 4. The method according to claim 1, wherein the sample is made of ultrafine Si particles.