JPS5878362A - Charged-particle energy analyzer - Google Patents

Abstract

PURPOSE:To correct the difference in the selecting energy level which is caused according to the value of theta by preparing a conductor surface, which constitutes a low-pass filter, from a resistance layer, giving an electric-potential gradient along the surface of the resistance layer, and decreasing the electric-potential difference between a part of the resistance layer and a facing grid as said part comes apart from the center of the resistance layer. CONSTITUTION:Since the incidence angle upon a low-pass filter is 1/2 of the emission angle of electrons (or ions) discharged from a sample (S), the incidence angle becomes large as it comes apart from the center of the surface of a resistance film 2. Therefore, in the figure, the angle (theta) is larger than the angle (theta'). A lead wire 3 is made to penetrate the center of an insulating body 1, and connected to the center point of the resistance film 2. An electric-potential difference is given between the lead wire 3, and conductor rings 4 connected to the outermost periphery of the film 2. The film 2 is provided with an electric potential gradient sloping up from the periphery to the center of the film 2. When the angle of the outermost periphery of the film 2 seen from the position of the sample (S) is supposed to be (2thetao), the incidence angle at the outermost periphery of the film 2 is (thetao). When the electric potentials of the center and the outermost periphery of the film 2, respectively, are supposed to be (Vo) and (V) with reference to that of a grid (G1), the influence of the slant incidence is compensated when the relationship of V=Vocos thetao is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a low-pass filter that reflects charged particles with a kinetic energy lower than the above value and a kinetic energy higher than another energy value slightly lower than the above-mentioned value. A charged particle energy analyzer, etc. that is configured to select charged particles having kinetic energy contained within a narrow energy range centered on the energy value formed by combining an i-pass filter with an i-pass filter that passes through the charged particles. Regarding the off-pass 0-pass filter.

The above-described charged particle energy analyzer has a configuration similar to that shown in FIG. 1, for example. M is a metal spherical surface centered at 0, and a spherical grid G1 also centered at 0 is placed in front of it, and M and G constitute a 1 and t low-pass filter. G2 and G3 are also concentric spherical grids centered on 0, and 02 and G3 constitute a bypass filter. Grid Gl
, G2 are at the same potential, and considering electrons as charged particles, M and G3 are at a lower potential than the grids Gl and G2, respectively. Place an electron source S near the 0 point. This is, for example, a sample excited with X-rays, in which case the illustrated device will perform an energy analysis of the X-ray photoelectrons emanating from the sample. Among the electrons emitted from S, those with kinetic energy higher than the energy of the component collide with the metal surface M, but electrons with kinetic energy lower than that energy are reflected by the metal surface M, and S Once focused on the opposite side, the electrons enter the surface of grid G2, and further electrons with energy lower than this value are reflected by G3, and only electrons with energy higher than that are reflected by grid G3. pass through. Only electrons having energy contained within a narrow width around the energy thus formed are taken out to the right side of grid G3.

Now let's consider the effect of a low-pass filter. Figure 2 is an enlarged view of a part of the low-pass filter, and the charged particles reflected by the low-pass filter are θ with respect to the normal N to the metal surface M.
It enters at an angle of θ and is reflected at an angle of θ. This angle of incidence 2
The reflection angle θ is a small value when the 8 points are close to 0 in FIG. 1, and can be considered to be approximately the same both near the center on M and on the outer periphery of M. However, for various purposes, there are cases where the 8 points are moved away from the 0 point and brought closer to the metal surface so that the reflected charged particles are nearly parallel, or when the metal surface M is made an ellipsoid and the 8 points and the reflected particles are focused. When a point is located at its focal point, the above-mentioned angle of incidence and angle of reflection θ differ depending on the location on the metal surface M. Now, the charged particles are connected to the metal surface M and the grid G.
It is not the velocity V of the charged particle that determines whether it is reflected between the charged particle and l, but the component v1 of the velocity V in the normal direction to the plane M, and vl-v cosθ≠v(1-θ2/2 ), so when θ changes from 0 to a considerably large value depending on the location on plane M, the term θ2/2 cannot be ignored,
Even if the particles have the same energy, that is, the same V, those in the direction where θ is small are not reflected, and those in the direction where θ is small are reflected, resulting in a decrease in energy resolution.

The present invention has been made with the object of preventing the energy resolution from decreasing due to the above-mentioned causes when the angle of incidence and reflection of a low-pass filter differs depending on the location. In the present invention, the conductive surface constituting the low-pass filter is formed with a resistive layer, a potential gradient is applied along the surface, and the incident reflection angle θ is
The present invention provides a low-pass filter that corrects the difference in the sorting energy level caused by the magnitude of θ by reducing the potential difference between the opposing grid and the grid at locations where θ is small.

The present invention will be explained below with reference to Examples.

FIG. 3 shows an embodiment of the present invention. Reference numeral 1 denotes an insulator supporting the conductor surface, which has a concave spherical surface centered at 0, and has a resistive coating 2 formed on its surface, and this coating corresponds to M shown in FIG.

G1 is a spherical grid centered at O and corresponds to 01 in FIG. A sample S of an electron source (or ion source) is placed at a position that is 1/2 the radius of curvature of the coating 2 . With this configuration, electrons emitted from the sample S and reflected by the low-pass filter become parallel. The energy distribution of electrons emitted from the sample S depends on the inclination of the electron emission direction with respect to the normal to the sample surface, and the electrons reflected by the low-pass filter are passed through a planar... When detected, a concentric pattern is obtained, and from this pattern the distribution of electron energy in the radiation direction can be determined. With such a device configuration, the angle of incidence and reflection of the low-pass filter is 1/2 of the angle of emission of electrons (or ions) from the sample S.
Therefore, the outer circumference of the surface of the resistive coating 2 is larger. That is, in the figure, θ>G1. A lead wire 3 is passed through the center of the insulator 1 and connected to the center point of the resistive coating 2, creating a potential difference of ΔV between the outer periphery of the resistive coating 2 and the connected conductor ring 4. A potential gradient is formed in the resistive coating 2 from the outer periphery toward the center. If the angle at which the outer periphery of the resistive coating 2 is viewed from the position of the sample S is 2θ0, then the incident/reflection angle at this outer periphery is θO. The potential at the center of the resistive film 2 is VO with respect to the potential of the grid G1.
Assuming that the potential at the outer periphery is ■, then if ■=Vocosθ0, the influence of oblique incidence can be compensated. Of course, in this case, if the resistive film 2 is uniform, the potential gradient along the film 2 will be gentle at the outer periphery and steeper toward the center, and complete compensation will occur only at the outer periphery and at some radius along the way. Compensation is approximate at .

Figure 4 shows an embodiment suitable for more complete compensation, in which conductor rings R1 to R5 are laid on the concave spherical surface of the insulator 1, the surfaces of these rings are finished flush with the concave surface of the insulator, and a resistor is placed on top of the conductor rings R1 to R5. A coating 2 is formed on the rings R1 to R4 with lead wires l! 1 to /4 are connected, and the angle of each ring and the outer periphery of the resistive coating 2 as seen from the sample S is 201 to 2θ5,
A potential of (a) cos θ1 to Vo cos θ5 is applied to each ring.

Figure 5 shows a configuration in which the low-pass filter is an ellipsoid of revolution, the charged particle source S is located at one focal point, and the reflected charged particles are concentrated at the other focal point.In this case, the charged particle low-pass filter The angle of incidence and reflection is greatest in the central band of the filter (the band extends perpendicular to the plane of the figure). In this embodiment, the same potential band on the surface of the resistive film 20 is not a concentric circle as in the embodiments shown in FIGS. The conductors a, a', b, etc. that are connected to the membrane 2 extend in a direction perpendicular to the plane of the drawing, and a predetermined voltage is applied to each of them.

In each example, p, p', etc. are the cicada anti-film 2 and the grid G1.
This is a protective ring that prevents disturbance of the electric field at the edge of the

The resistive coating 2 may be formed by a coating method or a vapor deposition method,
It is also possible to control the film thickness distribution and make the potential gradient distribution along the film surface appropriate using the configuration shown in FIG.

The charged particle energy analyzer of the present invention has the above-described configuration, and can be used without deteriorating energy resolution when the incident angle of charged particles varies depending on the location.
It becomes possible to realize the purpose of its usage.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an example of a charged particle energy analyzer, Fig. 2 is a partially enlarged view of a low-pass filter, Fig. 3 is a side sectional view of an embodiment of the present invention, and Fig. 4 is a side view showing an example of a charged particle energy analyzer. FIG. 5 is a side sectional view of still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Insulator, 2... Resistance coating, 3... Lead wire, S... Sample, G1... Grid. Agent Patent Attorney Kosuke Agata

Claims (1)

[Claims] By applying an appropriate voltage between a conductive surface and a grid stretched in front of the conductive surface, charged particles having a kinetic energy lower than the energy level of the charged particles incident on the conductive surface are reflected, thereby energizing the charged particles. 1. A charged particle energy analyzer characterized in that the conductor surface is formed of a resistive film and a potential gradient is provided along the surface.