JPH04343054A - Photoelectron spectral device - Google Patents

Abstract

PURPOSE:To obtain a photoelectron spectral device which can capture a distribution image of a photoelectron with a target energy two-dimensionally and with a simple method. CONSTITUTION:An X-ray source 2 is placed in a vacuum chamber 1 and X rays are applied to a specimen 15. Also, a fluorescent screen 5 is placed in the vacuum chamber 1. Furthermore, a barrier electrode 6 which allows only a photoelectron with an energy exceeding a photoelectron energy according to an application voltage to be selectively transmitted is placed between the specimen 15 and the fluorescent screen 5. Also, while a first and a second application voltages are applied to the barrier electrode 6 by an image processing device 12 and a computer 13 for control, a photoelectron image data is taken through the fluorescent screen 5, a view port 10, and a TV camera 11, and then a difference between the photoelectron image data by the first application voltage and that by the second application voltage is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectron spectrometer, and more particularly to a photoelectron spectrometer that captures information regarding the structure of a sample surface as a two-dimensional image for each element.

0002

[Prior Art] Conventionally, Academic Monthly Report, Vol. 43,No.
．． 9 (September 1990), a method for capturing the structure of a sample surface using an X-ray photoelectron spectrometer is presented. However, in order to obtain the necessary information, it is necessary to perform measurements while rotating and tilting the analysis sample, which requires an enormous amount of measurement time. On the other hand, JP-A-61-26
By using the optical system shown in Japanese Patent No. 4241, it becomes possible to two-dimensionally measure the distribution of photoelectrons of a certain energy. That is, the grid electrodes constitute a high-pass filter, the grid electrodes constitute a low-pass filter, and these two types of grid electrodes constitute a band-pass filter.

0003

[Problem to be Solved by the Invention] However, this optical system is complicated because the low-pass filter is composed of a grid and the high-pass filter is composed of a grid, and it is extremely difficult to assemble it while suppressing image distortion. It is. An object of the present invention is to provide a photoelectron spectroscopy device that can two-dimensionally capture a distribution image of photoelectrons having a desired energy using a simple method.

0004

[Means for Solving the Problems] The present invention provides an excitation source for exciting photoelectrons from a sample, an imager for converting the photoelectrons from the sample into a two-dimensional image by the excitation source, and a combination of the sample and the imager. A barrier electrode is arranged between the barrier electrode and selectively allows photoelectrons having photoelectron energy equal to or higher than the applied voltage to pass through, and photoelectron image data is obtained by an imager with first and second applied voltages being applied to the barrier electrode. A photoelectron spectrometer is provided with a photoelectron spectroscopy device comprising a data acquisition means for taking in the data, and a difference processing means for taking a difference between the photoelectron image data at the first applied voltage and the photoelectron image data at the second applied voltage by the data acquisition means. This is a summary.

[0005]

[Operation] Photoelectron image data is captured by the image pickup device while the first and second applied voltages are applied to the barrier electrodes by the data acquisition means. Then, the difference processing means calculates the difference between the photoelectron image data at the first applied voltage and the photoelectron image data at the second applied voltage by the data acquisition means. As a result, one electrode constitutes a high-pass filter, and two
By image processing the photoelectron image data, it is possible to perform spectroscopy with a predetermined photoelectron energy width.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an X-ray photoelectron spectrometer. The X-ray photoelectron spectrometer is provided with a vacuum chamber 1, and this vacuum chamber 1 has an ultra-high vacuum evacuation system. An X-ray source 2 is disposed inside the vacuum chamber 1, and the X-ray source 2 accelerates thermionic electrons emitted from a filament 3 heated by electricity using an electric field to target a target (usually A
X-rays are generated by colliding with L and Mg). These X-rays include characteristic X-rays and continuous X-rays, but in this example, the characteristic X-rays are
Only the lines are taken out.

[0007] Also, an X-ray spectrometer 4 is disposed within the vacuum chamber 1, and the X-ray spectrometer 4 uses an X-ray spectroscopy crystal such as LiF. Then, the X-rays from the X-ray source 2 are focused by the X-ray spectrometer 4, and the X-rays are made monochromatic and irradiated onto the sample 15 placed in the vacuum chamber 1. Note that this X-ray spectrometer 4 has a working distance of several centimeters for a normal X-ray source, and if the X-ray source is used as it is, it will obstruct the field of view of the fluorescent screen 5 described later, so an X-ray spectrometer with a longer working distance is required. It is used.

Further, a fluorescent screen 5 is arranged on the side wall of the vacuum chamber 1, and the screen 5 allows the X-rays to pass through the sample 15.
When the surface of the atom is irradiated, photoelectrons with energy unique to the surface atoms are emitted, and the image of these photoelectrons can be seen. Further, a barrier electrode 6 is arranged between the sample 15 and the fluorescent screen 5, and a voltage generator 7 is connected to the barrier electrode 6. Voltage generator 7 generates a voltage to be applied to barrier electrode 6. The barrier electrode 6 allows only photoelectrons from the sample 15 having energy higher than the potential set by the voltage generator 7 to pass through. In this embodiment, the barrier electrode 6 is made of a metal mesh so that photoelectrons can easily pass therethrough, and its shape is a hemisphere centered on the portion of the sample 15 that is irradiated with X-rays. Note that the barrier electrode 6 may have a flat shape.

Further, an accelerating electrode 8 is arranged between the barrier electrode 6 and the fluorescent screen 5, and an accelerating power source 9 is connected to the accelerating electrode 8. The acceleration power source 9 is a power source for accelerating photoelectrons that have passed through the barrier electrode 6 using an electric field to make the fluorescent screen 5 glow. The acceleration electrode 8 is the barrier electrode 6.
Photoelectrons with energy higher than the potential pass through the barrier electrode 6 and reach the accelerating electrode 8, but since these photoelectrons do not have enough energy to make the fluorescent screen 5 glow, a voltage is applied between the accelerating electrode 8 and the fluorescent screen 5. This gives the photoelectrons enough energy to make the fluorescent screen 5 glow. The accelerating electrode 8 is made of a metal mesh so that photoelectrons can easily pass therethrough, and its shape is a hemisphere centered on the portion of the sample 15 that is irradiated with X-rays. Note that the accelerating electrode 8 may have a flat shape.

A view port 10 is arranged on the back side of the fluorescent screen 5, and a TV camera 11 is arranged opposite to the view port 10 outside the vacuum chamber 1. The photoelectrons passing through the barrier electrode 6 are accelerated by the electric field and collide with the fluorescent screen 5, thereby exciting the fluorescent agent and emitting light. A photoelectron image appearing on the fluorescent screen 5 through the view port 10 is captured by the TV camera 11. Note that since X-rays are generated within the vacuum chamber 1, the viewport 10 is made of a material that can block X-rays.

An image processing device 12 is connected to the TV camera 11 . The image processing device 12 has a built-in first frame memory MF1 and a second frame memory MF2, and each of the frame memories MF1 and MF2 has a large number of data storage areas, and each storage area is used for the TV camera 11. This corresponds to each coordinate on the screen. Further, a CRT 14 is connected to the image processing device 12.

The control computer 13 controls the voltage generator 7 to adjust the voltage applied to the barrier electrode 6, and also controls the image processing device 12 to capture the photoelectron image by the TV camera 11, store the photoelectron image data, and It is designed to perform calculations, etc. In this embodiment, the fluorescent screen 5, view port 10, and TV camera 11 constitute an image pickup device, and the image processing device 12 and control computer 13 constitute data acquisition means and difference processing means. .

Next, the operation of the X-ray photoelectron spectrometer constructed as described above will be explained. Figure 2 shows the control computer 13.
shows a flowchart executed by Here, photoelectrons generated by normal X-rays have a distribution as shown in FIG. Here, peaks (a), (b), and (c) are unique to the elements. Then, let the energy of the photoelectrons to be measured be E1, E2, E3, and the resolution (bandwidth)
Let be dE.

First, the sample 15 to be measured is set in the vacuum chamber 1, and the inside of the vacuum chamber 1 is heated to 10-8P.
Create an ultra-high vacuum of about a. Then, in step 100, the control computer 13 sets the voltage applied to the barrier electrode 6 to E1 - (1/2) dE. Thereafter, the sample is irradiated from the X-ray source 2 through the X-ray spectrometer 4. The irradiated X-rays excites the inner shell electrons of atoms constituting the sample 15 to become photoelectrons, which are emitted into vacuum. Here, a voltage generator 7 is used for the barrier electrode 6 to generate a voltage E1 - (1/2) dE
When E1 −(1
/2) Only photoelectrons with energy greater than dE reach the accelerating electrode 8.

The photoelectrons that have arrived are accelerated by the voltage applied between the accelerating electrode 8 and the fluorescent screen 5, and collide with the fluorescent screen 5, causing fluorescence excitation at that location. In this way, as shown in Figure 4, if you look at the entire screen, E
A photoelectron image drawn by photoelectrons with energy of 1 - (1/2) dE or more can be obtained. In step 101, the control computer 13 stores this image in the first frame memory MF1 of the image processing device 12 through the TV camera 11.

Next, the control computer 13 changes the voltage applied to the barrier electrode 6 to E1 + (1/2) in step 102.
)dE. As a result, as shown in Figure 5, E1 +
A photoelectron image drawn by photoelectrons with energy greater than (1/2) dE can be obtained. In step 103, the control computer 13 stores the photoelectronic image appearing on the fluorescent screen in the second frame memory MF2 of the image processing device 12.

Then, in step 104, the control computer 13 performs differential processing on the photoelectron image data in the first frame memory MF1 and the second frame memory MF2. As a result, as shown in FIG. 6, a photoelectron image drawn by photoelectrons having an energy of E1 is obtained as a resolution dE. Thereafter, in step 105, the control computer 13 causes the CRT 14 to display the photoelectron image obtained after the differential processing.

When the spectroscopic processing of peak (a) in FIG. 3 is completed in this way, peaks (b) and (c) are
We will also do this. As described above, in this embodiment, a barrier electrode 6 is arranged between the sample 15 and the fluorescent screen 5 to selectively pass only photoelectrons having photoelectron energy equal to or higher than the applied voltage. The computer 13 captures photoelectron image data while applying the first and second applied voltages to the barrier electrode 6, and calculates the difference between the photoelectron image data at the first applied voltage and the photoelectron image data at the second applied voltage. I decided to take it. As a result, by configuring a high-pass filter with one electrode and image processing the two photoelectron image data, it is possible to perform spectroscopy in a predetermined photoelectron energy width, creating a two-dimensional distribution image of photoelectrons with the desired energy. This means that it can be captured using a simple method.

Note that the present invention is not limited to the above embodiments; for example, in the above embodiments, X-rays were used as the excitation source and inner shell electrons were used as the signal; Information about the surface atomic structure can also be obtained using Auger electrons. Further, in the above embodiment, a fluorescent screen and an accelerating electrode were used to visualize the photoelectron image, but a multi-channel plate may be used for visualization.

[0020]

[Effects of the Invention] As detailed above, according to the present invention,
It has an excellent effect of simplifying the spectroscopic optical system when performing two-dimensional measurements.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an X-ray photoelectron spectrometer according to an example.

FIG. 2 is a diagram showing a flowchart.

FIG. 3 is a diagram showing the energy distribution of photoelectrons.

FIG. 4 is a diagram showing the energy distribution of photoelectrons.

FIG. 5 is a diagram showing the energy distribution of photoelectrons.

FIG. 6 is a diagram showing the energy distribution of photoelectrons.

[Explanation of symbols]

2 X-ray source 5 Fluorescent screen 6 constituting the image pickup device Barrier electrode 10 Viewport 11 constituting the image pickup device TV camera 12 constituting the image pickup device Image processing device 13 constituting the data acquisition means and differential processing means Control computer 15 constituting the difference processing means Sample

Claims (1)

[Claims] 1. An excitation source for exciting photoelectrons from a sample, an imager for converting the photoelectrons from the sample into a two-dimensional image by the excitation source, and an imager disposed between the sample and the imager, and an applied voltage. a barrier electrode that selectively passes only photoelectrons having a photoelectron energy equal to or higher than the photoelectron energy corresponding to the photoelectron energy; Photoelectron image data at the first applied voltage by the data acquisition means and the second
1. A photoelectron spectroscopy apparatus comprising: a difference processing means for calculating a difference between the photoelectron image data and the photoelectron image data at an applied voltage of .