JPH01175159A - Charged particle energy analyzer - Google Patents

Abstract

PURPOSE:To dissolve the disturbance of the electric field at end edges of electrodes by covering the opening face of the end edge sections of semi-spherical concentric double electrodes with a resistance film and feeding a current in the direction of the electrode radius. CONSTITUTION:A ceramic substrate 3 is fitted so as to close the opening between semi-spherical concentric double electrodes 1 and 2, a conductor film 4 is formed on the surface on the side toward the space between the electrodes, and the film 4 is made of a resistance film. A conducting layer 41 is formed facing flanges 11 and 21 on the inner periphery and the outer periphery of the film 4. When the voltage is applied across the electrodes 1 and 2, a current flows in the direction of the electrode radius, and the desired potential gradient is obtained. The above resistance layer is made thick in proportion to the distance from the center of the electrodes 1 and 2, thus the potential in the resistance film is changed in reverse proportion to the distance from the center. On the other hand, the potential across the electrodes 1 and 2 is in reverse proportion to the distance from the center. When both inner and outer edges of the resistance film and the edges of the electrodes 1 and 2 are connected, the potential at each point of the resistance film becomes the same potential as the correct potential across the double electrodes 1 and 2. The disturbance of the electric field at end edges of the electrodes is dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an electrostatic energy analyzer using spherical electrodes.

B. Prior Art A method using concentric double spherical electrodes is generally used to analyze charged particle beams based on their kinetic energy.

This type of energy analyzer uses hemispherical concentric double electrodes, and charged particles are formed between the electrodes in an electric field whose direction is the radial direction of the spherical electrode and whose strength is inversely proportional to the square of the distance from the center of the sphere. Energy is sorted by the movement of the As mentioned above, this type of energy analyzer performs energy analysis by the action of an electric field that is inversely proportional to the square of the distance radially from the center, but since the electrode is hemispherical, near the edge of the electrode (where the electric field is The lines of force bend outward and the motion of charged particles is disturbed.In order to prevent this, conventionally a number of conductor rings G were placed concentrically between the edges of the inner and outer hemispherical electrodes 1.2, as shown in Figure 2. These are connected to appropriate positions in the middle of the voltage dividing resistor R, so that each ring has the same potential as the correct potential between the double electrodes at that position, so that disturbances in the electric field at the edges of the electrodes are avoided. This prevents it from reaching deep inside the body.

C1 Problem to be solved by the invention In the conventional method of using several rings to prevent disturbance of the electric field at the edge of the double hemispherical electrode, only the positions of the rings are kept at the correct potential. , the influence of external space enters between the rings, and the nearby electric field is disturbed in a wavy shape as shown in Figure 3. Due to such disturbances in the electric field, the charged particle beam is scattered when it enters between the electrodes and when it exits, reducing the resolution of the energy spectrum and increasing the background.

Therefore, it is an object of the present invention to completely correct the disturbance of the electric field at the edge of the electrode in a hemispherical concentric dual electrode energy analyzer.

21. Means for solving the problem The opening between the edges of the inner and outer electrodes was covered with a resistive film to allow current to flow in the radial direction of the electrodes.

The electric field strength formed between the two concentric spherical electrodes is inversely proportional to the square of the distance from the center, and therefore the potential between the electrodes changes inversely to the distance from the center. A resistive film whose thickness is proportional to the distance from the center is oriented at one point or -
When flowing a radial current that diverges from a point, the current density in the circumferential direction is inversely proportional to the distance from the center, so the potential inside the resistive film changes inversely to the distance from the center. , if both the inner and outer edges of the resistive film are connected to the edges of the inner and outer electrodes and made to have the same potential as each electrode, the potential at each point on the resistive film will naturally become the same potential as the correct potential between the double electrodes, and the voltage will increase. The electric field disturbances at the extreme edges are completely eliminated.

Embodiment FIG. 1 shows an embodiment of the present invention. 1 and 2 are hemispherical concentric double electrodes, and 3 is a ceramic substrate attached to close the opening between the inner and outer hemispherical electrodes, and a conductive thin film 4 is formed on the surface facing the interelectrode space. , this thin film is a resistive film. A flange 11 extends from the edge of the inner electrode 1 in a direction toward the spherical center, and a flange 21 extends outward from the edge of the outer electrode 2. A comparatively thick conductive layer 41 of silver or copper is formed in a ring shape on the inner and outer circumferences of the conductor film 4 at the portions facing the flanges 11.21, respectively, and seven flange 11.21 are formed on this layer. The electrodes 1 and 2 and the ceramic substrate 3 are connected by a clamp member 5 so as to be in pressure contact with each other. With this structure, when a voltage is applied between the picture electrodes 1 and 2, a current naturally flows in the conductor layer 4 in the radial direction, forming a desired potential gradient. Reference numeral 6 denotes an entrance aperture for the charged particle beam, which is a slit in the circumferential direction in the ceramic substrate 3, and a charged particle exit aperture also has the same shape. On both sides of the entrance slit 6, parallel to the entrance slit, there are portions where the conductor film 4 is not formed, as shown by a. When there is no such dummy slit, the electric current is interrupted by the slit 6, and a potential difference appears between the two edges of the slit.However, by providing the dummy slit a, the potential difference between the two edges of the slit 6 is reduced. Since this eliminates the problem, the entrance slit can be made larger. Note that the entrance/exit aperture may be a circular small hole. The conductor film 4 acts as a resistive film, but if the resistance is too high, the influence of resistance change due to adhesion of contaminants will be large, and the incidence of charged particles scattered due to collision with residual gas in the interelectrode space, etc. Since the effect of potential disturbance due to current becomes large, it is desirable that a current of about 10 to 100 mA flow with respect to an interelectrode voltage of 100 V.

The conductor film is formed by a metal vapor deposition method. By arranging the evaporation source so that it can be deposited to a uniform thickness and performing the deposition while rotating an appropriately shaped shielding plate coaxially with the substrate, the thickness increases in proportion to the distance from the center. A layer of conductive film can be formed.

Effects According to the present invention, disturbances in the electric field at the edge of the electrode are completely eliminated, so that the effects of improved resolution and background reduction in charged particle energy analysis can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a main part of an embodiment of the present invention, FIG. 2 is a perspective view of a main part of a conventional example, and FIG. 3 is a diagram showing disturbance of an electric field in a conventional example. 1.2... Hemispherical concentric double electrode, 3... Ceramic substrate, 4... Conductor film, 5... Clamp, 6 Charged particle beam incidence aperture. Agent Patent Attorney Kosuke Agata

Claims (1)

[Claims] The edge opening of the hemispherical concentric double electrode is covered with a resistive layer whose thickness increases in proportion to the distance from the center, and the inner and outer edges of this resistive layer are connected to the edges of the double electrode, respectively. A charged particle energy analyzer characterized in that: