VARIABLE REDUCTION RATIO SPHERICAL ABERRATION CORRECTION ELECTROSTATIC LENS, WIDE ANGLE ENERGY ANALYZER, AND TWO-DIMENSIONAL ELECTRON SPECTROMETER
|Posted date||Jan 30, 2020|
|International application number||2019JP018418|
|International publication number||WO 2019216348|
|Date of international filing||May 8, 2019|
|Date of international publication||Nov 14, 2019|
|Title||VARIABLE REDUCTION RATIO SPHERICAL ABERRATION CORRECTION ELECTROSTATIC LENS, WIDE ANGLE ENERGY ANALYZER, AND TWO-DIMENSIONAL ELECTRON SPECTROMETER|
|Abstract||Provided is a compact two-dimensional electron spectrometer that is capable of variably adjusting the reduction ratio across a wide range, and performing simultaneous measurements of the two-dimensional emission angle distribution measurement of high energy resolution across a wide solid angle of acquisition. The two-dimensional electron spectrometer is configured from: a variable reduction ratio spherical aberration correction electrostatic lens; a cylindrical mirror type energy analyzer or a wide angle energy analyzer; and a projection lens. The variable reduction ratio spherical aberration correction electrostatic lens is configured from: an electrostatic lens that consists of an axially symmetrical spherical mesh having a concave shape with respect to a point source, and one or a plurality of axially symmetrical electrodes, and that adjusts the spherical aberration of charged particles generated from the point source; and an axially symmetrical deceleration field generating electrode that is placed coaxially with the electrostatic lens, wherein the mesh shape, and the potential and placement of the electrode are adjusted so that the charged particles generated from the point source converge at the lens exit using the electrostatic lens, the deceleration field generating electrode is provided in front of the convergence point, and broad control of the reduction ratio of charged particles can be done by adjusting the applied potential.|
|Outline of related art and contending technology||
Is an electron spectrometer, the energy distribution of electrons emitted from the sample, by measuring the angular emission distribution, and the surface of the sample in the depth direction of the elemental composition and a chemical-bonding state, the energy band structure and further, the atomic arrangement and a device capable of detailed analysis of the structure, performance up to this point, the efficiency of the, in pursuit of the convenience of a variety of forms of apparatus have been developed. In an electron spectrometer, an incident portion of the energy analyzer lens is referred to as the input to the electrostatic lens is often used, the electrostatic lens, electrons emitted from the sample are captured as much as possible, and reduces the electron is incident from the analyzer, the energy resolution can be improved. Conventional electrostatic lens, by the spherical aberration, a large opening angle of the beam focused to one point is difficult, the capture angle is limited to about ±20° was, by using the spherical mesh and thereby increase the sensitivity, the capture angle is improved to about ±30 ° (see Patent Document 1). In addition, the spherical aberration correction action of the non-spherical mesh is applied, a plurality of electrodes to create an electric field to the optimum, the spherical mesh can be wider than the capture angle of the spherical aberration correction electrostatic lens has been known (Patent Document 2, 3, see Non-Patent Document 1).
Disclosed in Patent Document 3 using an electrostatic lens, the charged particles coming from one point to take a large acceptance angle, it is possible to converge on the deceleration of the vehicle becomes possible. Fig. 27 to, a conventional deceleration type electrostatic lens of the spherical aberration correction according to the first embodiment. In this case, the acceptance angle is set to ±50°. And the lens 0 the second electrode-third electrode (EL0-EL4) 4 and is configured, the first electrode 0 is provided with a mesh or an ellipsoid of revolution. (EL0) The first electrode 0 is set to the ground potential, the electrode 1 the first-second (EL1-EL4) to the electrode 4, the convergence speed of the charged particles to a suitable negative or positive voltage is applied. More specifically, having a negative charge in the case of particles, a suitable negative voltage to the second 1 electrode-electrode 4 is applied to the first (EL1-EL4), with a positive charge in the case of particles, the first electrode 1 an appropriate positive voltage-is applied to the first electrode 4 (EL1-EL4). These generated by applying voltage to the convergence state of the electric field of the deceleration type, shown by the equipotential lines in the figure.
Deceleration type electrostatic lens is spherical aberration correction, as well as general electrostatic lens, an axially symmetrical electrode, the equipotential surface of the electrostatic equipotential lines around the center axis of the lens is rotated in the plane of rotation. Normal deceleration type electrostatic lens in the spherical aberration correction, the convergence of the deceleration type is a substantial electric field in the distribution range, as shown in Fig. 27, the mesh electrode (Mesh) from the inner diameter of the electrostatic lens and an area having a degree of spread. A wide range of angles of incidence of the charged particles, pass through the mesh electrode and in the inward direction perpendicular to the equipotential surface with a force, the speed of which is bent with a monotonic, converging point of exit of the electrostatic lens. Ε Ek is the kinetic energy of charged particles at this time (0 1 ε<<) becomes. Here, Ek is the kinetic energy at the entrance of the electrostatic lens, the kinetic energy Ek of ε is at the outlet of the ratio (hereinafter, referred to as the reduction ratio of ε). In the present specification, the reduction ratio is high means that the smaller the value of ε is, the reduction ratio is low when the value of ε is large. Fig. 27 showing the spherical aberration correction electrostatic lens in the deceleration type, the first reduction ratio (EL4) ε is applied to the electrode 4 is determined by the voltage. (EL4) The first electrode 4 of 1KeV with respect to the electrons is applied to the source voltage of-794V, deceleration type electrostatic lens of the spherical aberration correction is the reduction ratio ε, (1000-794) /1000=and 1/5 approximately. Fig. 27 showing the spherical aberration correction electrostatic lens in the deceleration type, it is possible to change the reduction ratio ε is, in this case, the convergence property is remarkably reduced, the charged particles over a wide range of angles of incidence is difficult to converge the problem.
On the other hand, the properties of the material and function of the atomic arrangement structure or band structure is analyzed in detail from a microscopic viewpoint, high energy analyzer having a resolution is required. This is, the difference between the binding energy of electrons is less than or equal to about 1eV even slightly, such as the structure and the atomic arrangement of the different band structure and consequently microscopic structure, there is a possibility that a great influence on the properties in some cases. The difference between the binding energy of electrons or less than about 1eV different atom, to clearly distinguish the electronic structure to be measured, at least about 0.1-0.3eV in absolute resolution is required.
0.1eV In order to obtain the absolute resolution of the relative resolution is obtained by the analyzer, the kinetic energy in the case of 100eV, and 1/1000, in the case of a 1KeV kinetic energy, becomes 1/10000. X-ray photoelectron diffraction (XPD: X-ray Photoelectron Diffraction) or light in the electron holography, the angular distribution of light by measuring the release of electrons, the atomic arrangement around a specific atom structure of the information can be obtained, therefore the light emission of electrons a few hundred eV or more energy needs to be set. Such in a low energy region, in order to achieve high energy resolution, electrons emitted from the sample prior to the energy input to the selection unit, it is necessary to reduce the kinetic energy thereof. Here, the energy selection unit, the motion trajectory of a charged particle or distributed in accordance with the energy, of the aperture or slit by the insertion of the selection of a specific energy of charged particles according to the present invention.
In an electron spectrometer is the most prevalent of the electrostatic hemispherical energy analyzer of (CHA; Concentric Hemispherical Analyzer) of the present invention. In the case of a CHA, the two semi-sphere of radius 2 is different from the electrostatic hemispherical energy corresponding to the selection unit. In general, by increasing the size of the energy selector is possible to improve the energy resolution is possible, manufacturing cost, maintenance costs, and in view of convenience, the apparatus size cannot be too large. Therefore, various system components including the CHA in the energy analyzer, the relative resolution of the selected energy, corresponding to the energy analyzer from a relatively small size of about 1/1000 to 1/200 remains. The advantages of a CHA, high energy resolution can be easily achieved in the state, on the other hand, the angular emission distribution of the measurement efficiency is very low, a more sophisticated analysis is a large obstacle is pointed out a problem.
In this way, the action of the energy selector only it is difficult to obtain a high energy resolution. Therefore, in the CHA, a combination of an electrostatic hemispherical portion and the deceleration by the input lens is performed. 1/200-1/1000 The relative resolution of the energy selector in the analyzer, the kinetic energy of charged particles by a factor of 1/10 as long, the incident energy (analysis of the kinetic energy of the charged particle beam is incident) of the possible resolution 1/2000-1/10000. Δ E may be an absolute resolution, the resolution r relative to the denomination of the energy, the reduction ratio ε, using the incident energy Ek, represented by Δ E=r ε Ek. Ε is the required reduction ratio, calculated from the equation to determine an absolute resolution. XPD and Ek is the kinetic energy suitable for electron holography light is approximately 500eV-1000eV. Ek=1keV In, 0.1eV in order to achieve the absolute resolution, from the formula Δ E=r ε Ek, the reduction ratio of the necessary about 1/10-1/50. The reduction ratio is as high 1/50, high energy resolution and the size of the analyzer becomes necessary when attempting to realize and thereby. In addition, in a low energy region higher than 1000eV, less than or equal to about 0.1eV when attempting to achieve a resolution of, a higher speed reduction ratio is required.
In general, a high reduction ratio is set, high energy resolution can be expected on the other hand, the low reduction ratio and detection sensitivity is greatly reduced compared to the case where there is a possibility of those. Therefore, low energy resolution there is no problem in measurement of the reduction ratio is set low, high energy resolution necessary to measure only at a high reduction ratio, the reduction ratio is preferably varied widely.
|Scope of claims||
|IPC(International Patent Classification)||
Contact Information for " VARIABLE REDUCTION RATIO SPHERICAL ABERRATION CORRECTION ELECTROSTATIC LENS, WIDE ANGLE ENERGY ANALYZER, AND TWO-DIMENSIONAL ELECTRON SPECTROMETER "
- Nara Institute Science and Technology Cooperative Research Division
- URL: http://www.naist.jp/sankan/index_en.html
- Address: 8916-5,Takayama-cho,Ikoma-shi,Nara , 630-0192
- Fax: 81-743-72-5194