Electronic two-dimensional spin detector and application thereof

Abstract

The invention discloses an electron two-dimensional spin detector and application thereof. The electron two-dimensional spin detector comprises a high-transmittance metal net, an electron spin screening film, an electron multiplier and an electron detector which are sequentially arranged in the electron movement direction. Magnetizing devices are arranged around the electron spin screening film in the circumferential direction in an array mode, and positive and negative polarization in multiple directions is achieved. The high-transmittance metal net, the electron spin screening film and the electron multiplier are respectively connected with a voltage source, the voltage is changed, and the voltage difference between the high-transmittance metal net and the electron spin screening film is changed. The electron two-dimensional spin detector designed by the invention is simple in structure, does not need a complex process of coating or surface treatment, can directly detect two-dimensional spin electrons, can be combined with a hemispherical energy analyzer, a time-flight electron energy analyzer and other electron energy analyzers, and meets more measurement scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electron spin detection, and in particular to an electron two-dimensional spin detector and application thereof. BACKGROUND

[0002] Spin-resolved electron spectroscopy (such as spin-ARPES) needs to synchronously analyze the energy, momentum and spin triple information of electrons. A traditional scheme adopts a discrete design: a hemispherical energy analyzer (HDA) screens the electron kinetic energy (Delta E / E~0.1%), and a spin detector (such as a VLEED or Mott detector) needs an additional optical relay system to transfer the electron beam, resulting in low efficiency (FOM<10 -6 ) and inability to two-dimensional imaging. In recent years, the ferromagnetic micro-channel plate (FM-MCP) technology integrates spin filtering (Sherman function S=0.6) and electron amplification (gain x 10³), supports two-dimensional spin imaging (micron resolution), but has not been directly coupled with the HDA.

[0003] All the spin detectors of photoelectron spectroscopy currently are based on reflection measurement. There are the following problems: 1. When not two-dimensional measurement, only one-dimensional data acquisition efficiency is extremely low.

[0004] 2. When two-dimensional measurement, a surface reflection structure is often used; the quality requirement for a reflection crystal, such as Ir metal or Fe2O3 film, is very high; this leads to a very complex device and extremely great use difficulty.

[0005] Therefore, an electron spin detector is needed to improve the acquisition efficiency while realizing a simple device structure and facilitating operation. SUMMARY

[0006] In order to solve the problems in the prior art, the present application provides an electron two-dimensional spin detector and application thereof, which can directly detect two-dimensional spin electrons and can be combined with various types of electron energy analyzers, and has good application prospect.

[0007] The technical scheme adopted by the present application is as follows: An electron two-dimensional spin detector comprises: a high-transmittance metal mesh, an electron spin screening film, an electron multiplier and an electron detector which are sequentially arranged along the electron motion direction; A magnetization device is arranged in a circumferential array around the electron spin screening film to realize positive and negative polarization in multiple directions; The high-transmittance metal mesh, the electron spin screening film and the electron multiplier are respectively connected to a voltage source to change the voltage and change the voltage difference between the high-transmittance metal mesh and the electron spin screening film.

[0008] Further, the electron multiplier adopts a micro-channel plate electron multiplier, which is composed of two stacked micro-channel plate electron multipliers.

[0009] Further, the electron detector adopts a DLD detector or an optical detector composed of a fluorescent screen and a phase.

[0010] Further, the electron spin screening film adopts a Co / Pt superlattice film.

[0011] Further, the magnetization device is composed of multiple groups of coils arranged in pairs.

[0012] A time-of-flight electron energy-spin analyzer, which combines the above-described electron two-dimensional spin detector with a time-of-flight electron energy analyzer, performs non-spin polarization measurement and spin polarization measurement.

[0013] A hemispherical electron energy-spin analyzer, which combines the above-described electron two-dimensional spin detector with a hemispherical electron energy analyzer, switches between conventional measurement and spin resolution measurement by controlling the kinetic energy of electrons passing through the electron spin screening film through a control voltage.

[0014] Advantages of the present application: 1. The electron two-dimensional spin detector designed in the present application adopts a transmission type spin screening film to screen electron spins, instead of a reflection type, which can directly detect two-dimensional spin electrons, and has a simple structure without the need for complex film plating or surface treatment processes.

[0015] 2. The electron two-dimensional spin detector designed in the present application can also be combined with a hemispherical energy analyzer, a time-of-flight electron energy analyzer, and other electron energy analyzers to realize new measurements, switch between conventional measurement and spin measurement, have multiple modes, and expand the measurement dimensions and application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a structural schematic diagram of an electron two-dimensional spin detector of the present application.

[0017] Figure 2 is a distribution schematic diagram of an electron spin screening film and a magnetization device.

[0018] Figure 3 is a time-of-flight electron energy-spin analyzer.

[0019] Figure 4 is a hemispherical electron energy-spin analyzer.

[0020] In the figure, 1, electron beam, 2, high-transmittance metal mesh, 3, electron spin screening film, 4, magnetization device, 5, electron multiplier, 6, electron detector, 7, 8, 9, all are conducting wires, 10, two-dimensional spin detector, 11, time-of-flight electron energy analyzer, 12, hemispherical electron energy analyzer. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. EXAMPLE

[0022] In combination with the drawings Figure 1 and 2 , the present application designs an electron two-dimensional spin detector, which comprises: high-transmittance metal mesh 2, electron spin screening film 3, electron multiplier 5, and electron detector 6 arranged in sequence along the direction of electron movement, magnetization device 4 arranged in a circumferential array around the electron spin screening film 3, and the magnetization device 4 can realize positive and negative polarization in X, Y, or Z directions.

[0023] In the present example, the electron beam generating device is arranged towards the high-transmittance metal mesh 2, and the electron beam 1 generated thereby passes through the high-transmittance metal mesh 2, electron spin screening film 3, electron multiplier 5, and electron detector 6 in sequence. The electron beam 1 can be each type of electron from an electron gun, photoelectron, etc.

[0024] In the present example, the high-transmittance metal mesh 2 is connected with a voltage source through conducting wire 7, and the kinetic energy of the electrons passing through the high-transmittance metal mesh 2 is regulated or screened.

[0025] In the present example, the electron spin screening film 3 is connected with a voltage source through conducting wire 8, and a voltage is applied to the front surface of the electron spin screening film 3; the electron spin screening film 3 is a thin film structure with electron spin gating, and can screen the spin, and is preferably a Co / Pt superlattice thin film.

[0026] In the present example, the magnetization device 4 is composed of coils arranged in pairs, for example, 4a and 4c in the figure constitute a group of coils, which can realize polarization in +Y and -Y directions. 4b and 4d constitute another group of coils, which can realize polarization in +X and -X directions; Z is not shown in the figure, and the layout can be analogously arranged.

[0027] In this embodiment, an electron multiplier 5 is arranged behind the electron spin filtering film 3, the electron multiplier 5 is connected with a voltage source through a wire 9, and a voltage is applied to the back surface of the electron multiplier 5; the electron multiplier 5 can increase the number of single electrons by orders of magnitude. For example, a microchannel plate electron multiplier (MCP) can be used to simultaneously amplify a two-dimensional incident electron beam. The electron multiplier 5 is composed of two stacked MCPs.

[0028] In this embodiment, an electron detector 6 is arranged behind the electron multiplier 5, and the multiplied electrons are directly measured by the electron detector 6. The electron detector 6 can be a DLD detector or an optical detector composed of a fluorescent screen and a camera.

[0029] In this embodiment, by controlling the voltage difference between the high-transparency metal mesh 2 and the electron spin filtering film 3, the electron energy of the electrons incident to the electron spin filtering film 3 can be controlled.

[0030] For a Co / Pt superlattice film, the highest spin polarization efficiency of the electrons is in the range of 0 to 2 eV, and the spin polarization efficiency is very low when the electron kinetic energy is greater than 10 eV, and the electron transmission efficiency is very high. Embodiment

[0031] The time-of-flight electron energy analyzer 11 can use a conventional electron lens system, which can control the flight of electrons in the lens system according to the requirements of the trajectory. Therefore, based on the two-dimensional spin detector 10 designed in Embodiment 1, the two-dimensional spin detector 10 is combined with the time-of-flight electron energy analyzer 11 to form a time-of-flight electron energy-spin analyzer, as shown in Figure 3

[0032] For conventional non-spin polarization measurement, the drift energy of the drift end of the time-of-flight electron energy analyzer 11 is usually 30 eV. In this case, by using the voltage difference (deceleration voltage -15 V) between the high-transparency metal mesh 2 and the electron spin filtering film 3 in the two-dimensional spin detector 10, the electrons pass through the electron spin filtering film 3 with a kinetic energy of 15 eV. At this time, because the spin polarization efficiency is very low, there is no spin resolution. At the same time, at this time, the transmission efficiency is very high, and there is basically no loss of the number of electrons. Then the electrons are amplified by the electron multiplier 5 and measured by the electron detector 6. Thus, the energy information of the electrons, or multi-dimensional data such as energy and angle, can be obtained.

[0033] ​For spin polarization measurements, the electron spin screening film 3 is first polarized in the +Z direction. The drift kinetic energy at the drift end of the time-of-flight electron energy analyzer 11 is typically 30 eV. In this case, a deceleration voltage of -28V can be set between the high-transmittance metal mesh 2 and the electron spin screening film 3, allowing electrons to pass through the electron spin screening film 3 with a kinetic energy of 2 eV. At this point, the +Z direction spin has higher transmittance, while other electrons have lower transmittance. Then, the electron spin screening film 3 is first polarized in the -Z direction, and the same measurements are performed as described above to obtain valid polarization data. Example

[0034] By combining the aforementioned two-dimensional spin detector 10 with the hemispherical electron energy analyzer 12, a hemispherical electron energy-spin analyzer is formed, such as... Figure 4 As shown.

[0035] The hemispherical electron energy analyzer 12 has a fixed transmission energy, such as 2eV, 5eV, 10eV, 20eV, etc., which is the electron kinetic energy of the high-transmittance metal mesh 2.

[0036] By adjusting the electron spin screening film voltage 3, the kinetic energy of electrons passing through the electron spin screening film 3 can be controlled, allowing switching between conventional measurement and spin-resolved measurement. During conventional measurement, a high voltage is applied between the high-transparency metal mesh 2 and the electron spin screening film 3 through wires 7 and 8 to accelerate electrons; during spin measurement, a voltage of 2V is applied. Example

[0037] By combining a spin-polarized electron gun with a two-dimensional spin detector 10, the polarization performance of the spin-polarized electron gun can be characterized.

[0038] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A two-dimensional electron spin detector, characterized in that, include: A high-transparency metal mesh (2), an electron spin screening film (3), an electron multiplier (5), and an electron detector (6) are sequentially arranged along the direction of electron movement. Magnetizing devices (4) are arranged in a circumferential array around the electron spin screening film (3) to achieve positive and negative polarization in multiple directions; The high-transparency metal mesh (2), the electron spin screening film (3), and the electron multiplier (5) are connected to voltage sources respectively. Changing the voltage changes the voltage difference between the high-transparency metal mesh (2) and the electron spin screening film (3).

2. The two-dimensional electron spin detector according to claim 1, characterized in that, The electron multiplier (5) is a microchannel plate electron multiplier, which is composed of two stacked microchannel plate electron multipliers.

3. The two-dimensional electron spin detector according to claim 1, characterized in that, The electronic detector (6) adopts a DLD detector or an optical detector consisting of a fluorescent screen and a camera.

4. The two-dimensional electron spin detector according to claim 1, characterized in that, The electron spin screening thin film (3) adopts a Co / Pt superlattice thin film.

5. The two-dimensional electron spin detector according to claim 1, characterized in that, The magnetization device (4) consists of multiple sets of coils arranged in pairs opposite each other.

6. A time-flight electron energy-spin analyzer, characterized in that, The two-dimensional spin detector of claim 1 is combined with a time-flying electron energy analyzer (11) to perform non-spin polarization measurement and spin polarization measurement.

7. A hemispherical electron energy-spin analyzer, characterized in that, By combining the two-dimensional electron spin detector of claim 1 with a hemispherical electron energy analyzer (12), the kinetic energy of electrons passing through the electron spin screening film (3) is controlled by controlling the voltage, and switching between conventional measurement and spin-resolved measurement is performed.

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