RU2448389C2 - Electrostatic energy analyser with angular resolution - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: axial-symmetric energy analyser of box type realises the circuit of angular dependencies measurement in the entire range of polar and azimuthal angles with the help of a position sensitive detector. The electron-optical circuit of the energy analyser provides for angular focusing of the fourth order near the central trajectory with an initial polar angle of 90°. Focusing of the fourth order is a criterion of high quality of an energy analyser, since in this case a conflict consisting in simultaneous requirement of high values of illumination and resolution capability compared to the case of focusing with lower orders is considerably weakened. The analyser with energy and angular resolution built in accordance with a proposed circuit may provide for relative energy resolution of less than 0.1% and angular resolution of less than 0.5 degrees, which more than by a factor increases consumer and operational parameters of instruments of such type at considerably more simple configuration of electrodes.

EFFECT: improved analytical, operational and consumer properties of electronic spectrometers with angular resolution used for research of objects of micro- and nanoelectronics by methods of electronic spectroscopy.

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Description

The invention relates to the field of energy analysis of charged particle flows excited by primary, for example, synchrotron radiation from a solid surface and can be used to improve the analytical, operational and consumer properties of angular resolution electronic spectrometers used to study micro- and nanoelectronic objects by electron spectroscopy .

To detect charged particles with characteristic energies, it is necessary to isolate particles that are in a narrow range of energies ΔЕ, for which use devices called energy analyzers.

к его поверхности.Known [1] is an electrostatic energy analyzer of charged secondary particle flows, providing second-order focusing near a trajectory with an initial angle of 90 ° and consisting of two steps - spherical and cylindrical. Collector registration of secondary particles with a certain kinetic energy is achieved by placing a hole diaphragm at the focal point and applying corresponding potentials to the outer sphere and outer cylinder. Registration of polar angles of emission of secondary electrons in the entire range of -90 ÷ + 90 ° is achieved by using a position-sensitive recording device as a collector. Registration of azimuthal angles in the entire range 0 ÷ 360 ° is achieved by sequential rotation of the test sample around the normal

to its surface.

The disadvantages of the known device include the complexity of the design, consisting of two steps, and a low (second) order of angular focusing.

Closest to the proposed one is an electrostatic analyzer [2] of charged particle energies, containing coaxially located external and internal toroids, end cone-shaped grounded electrodes with cuts made for them to pass electrons, a cone-shaped system for focusing and transporting particles to a receiver, a particle receiver based on positional a sensitive detector with a diaphragm located in front of it and a potential scanner connected to the toroids.

The disadvantages of this analyzer are the complex toroidal configuration of the electrodes, the need to use a focusing system and transport the electron beam to the axis of symmetry, and the low (second) order of angular focusing near the central path with an initial angle of 90 °.

The technical task of the invention is to improve the operational parameters of the analyzers - energy and angular resolutions, while simplifying the design.

The solution to this problem is achieved by the fact that the electrostatic energy analyzer with angular resolution contains two coaxially located electrodes, one of which is connected to the scanner, and the other is grounded; the electrodes are made of cylindrical shape, one of them is external, and the other is internal, and the external electrode connected to the scan unit by its ends is mechanically and electrically connected respectively to the introduced two coaxially arranged ring electrodes.

позволяет исследовать распределение фотоэлектронов, энергия которых соответствует энергии настройки по полярному углу φ в диапазоне -90÷+90° и по азимутальному углу θ в диапазоне 0÷360°.Figure 1 shows a diagram of the study of angular dependencies. A point source located on the Z axis of the electrostatic analyzer emits a fan-shaped stream of charged particles, the average plane of which is perpendicular to the Z axis (α = 90 °). After passing through the electrostatic field, this stream forms an image displayed on a position-sensitive detector (PSD). The coordinates of the image points depend on the energy of the flow due to the dispersion properties of the analyzer and the polar angle φ of departure of each electron from the sample. The analyzer’s diaphragm “cuts” electrons from the output stream in a certain band of initial energies. "Instant" analysis of the output stream at the polar angle φ using the PSD during sequential rotation of the probed sample around the normal

allows you to study the distribution of photoelectrons, whose energy corresponds to the tuning energy for the polar angle φ in the range -90 ÷ + 90 ° and for the azimuthal angle θ in the range 0 ÷ 360 °.

Figure 2 presents the electron-optical circuit of the analyzer. The electrostatic analyzer of energies and initial angles of movement of charged particles consists of an inner cylindrical electrode 1 with an input 2 and an output 3 ring slots on the side surface, an external cylindrical electrode 4, mechanically and electrically connected with the middle 5 and the far 6 with respect to the input slot 2 ring-shaped electrodes , the diaphragm 7, the particle receiver 8 and the electrostatic screen 13. The analyzer also contains a scanner 9 connected to the external cylinder 4.

The radius of the outer cylinder is (2.000 ± 0.001) a, the length of the cylinders (1.68 ± 0.01) a, the smaller radius of the far ring electrode (1.38 ± 0.01) a, the radius of the diaphragm (0.0020 ± 0.0001) a, the distance between the diaphragm plane and the surface facing the analyzer of the near ring-shaped electrode (1.48 ± 0.01) a, the distance between the particle source and the surface of the near ring-shaped electrode (0.24 ± 0.01) a, facing the analyzer, where, a is the radius of the inner cylinder.

The analyzer works as follows. A deflecting potential V relative to the inner cylinder 1 with a polarity coinciding with the polarity of the analyzed particles is supplied to the outer cylinder 4 from the scanner. The inner cylinder 1 and the shield 13 are grounded. The stream of secondary electrons 10 knocked out of sample 11, having overcome the free drift due to the initial energy through the input slot 2, enters the region of the analyzing field created by the potentials on the electrodes 1, 4, 5, and 6. The charged particles deflected by the field leave the analyzing field through output slot 3, pass through the limiting aperture 7 and enter receiver 8. The analyzer has a band pass function, i.e. only particles with a certain energy interval get to the input of receiver 8. Moreover, the deflecting field of the analyzer provides the fourth order of angular focusing, which leads to a tenfold decrease in the passband compared to the case of the second order of focusing. By varying the voltage supplied to the outer cylinder 4, we can obtain the entire energy spectrum of the secondary particles emitted by sample 11. By fixing the angular coordinate φ using a position-sensitive recording device, we can study the angular dependences of the analyzed particle flux in the full range of angles from -90 to 90 ° . The sequential rotation of the sample around the normal vector 12 to its surface allows us to measure the dependence of the intensity of the recorded signal in the entire range of polar and azimuthal angles.

Thus, the proposed analyzer by changing the electrode configuration and, consequently, increasing the focusing order allows to obtain a higher resolution in energy and angles than the prototype, and with a much simpler configuration of the electrodes.

Claims (1)

An angular resolution electrostatic energy analyzer containing two coaxially arranged electrodes, one of which is connected to a scan unit, characterized in that the electrodes are cylindrical in shape, one of them is external and the other is internal, and the external electrode connected to the scan unit mechanically with its ends and is electrically connected respectively to the inserted two ring electrodes.

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