JP2015045653A - Analyzer for particulate spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analyzer that enables improvement in energy resolution in a particulate spectrometry, for example, photoelectron spectrometry and the like.SOLUTION: A method is for determining at least one parameter about a charged particle discharged from a particle discharge sample 11, for example, a parameter about an energy of the particle, a start direction thereof, a start position thereof or a spin thereof, and the method comprises the steps of: guiding a beam of a charged particle to an entrance of a measurement area with a lens system 13; and detecting a position of the particle which is an index of the at least one parameter within the measurement area. The method further comprises a step of causing the particle beam to be deflected at least two times in the same coordinate direction before the particle beam is incident to the measurement area. Thereby, both of a position of the particle beam at an entrance 8 of a measurement area 3 and a direction thereof can be controlled so as to remove a necessity of a physical operation of the sample 11.

Description

  The present invention relates to a method and analysis device for analyzing, for example, the energy, start direction and start position of charged particles emitted from a particle emission sample, and particle spectroscopy comprising such an analysis device. Regarding the total. In particular, the present invention relates to a method and analyzer for use in a hemispherical deflection photoelectron spectrometer.

  A conventional hemispherical deflector type photoelectron spectrometer is shown in FIG. In the hemispherical deflector-type photoelectron spectrometer 1, the central component is the measurement region 3, and the energy of electrons is analyzed in the measurement region 3. The measurement region 3 is formed from two concentric hemispheres 5. The two concentric hemispheres 5 are placed on the base plate 7 and an electrostatic field is applied between the two concentric hemispheres 5. Electrons enter the measurement region 3 through the inlet 8, and the electrons that enter the region between the hemispheres 5 in a direction near the base plate 7 are deflected by the electrostatic field. Those electrons having a kinetic energy within a certain range defined by the deflection field will travel through the semicircle and then reach the detection device 9. In a typical apparatus, the electrons are common in a substantially straight line from the electron source (typically the sample 11 emitting electrons after excitation by photons, electrons, or other particles) to the hemispherical entrance 8. It is transported by an electrostatic lens system 13 comprising a plurality of lenses L1 to L3 having an optical axis 15.

In the following description, a Cartesian coordinate system is used in which the z-axis of the coordinate system is along the optical axis 15 of the lens system 13 (in most cases, a rotationally symmetric axis). The hemisphere is symmetric about the (y, z) plane. The direction of the electron trajectory is described by the angle θ _x of the electron trajectory relative to the (y, z) plane and the angle θ _y of the electron trajectory relative to the (x, z) plane.

  The lens system 13 and the detection device 9 will only receive electrons emitted in a limited area perpendicular to the lens axis 15 and within a limited angular range. Furthermore, the electron source must be arranged within a narrow range in the z direction in order to achieve the best properties (in terms of sensitivity and resolution). For this reason, it is necessary to place the sample on the manipulator 17 that enables both translation and rotation in all coordinate directions, that is, six degrees of freedom.

  In many applications, such as Angle Resolved Photoelectron Spectroscopy (ALPES), for complete measurements, detection of all solid angles across a 30 ° conical aperture from a well-aligned sample is required. Cost. Depending on the sample and the excitation / kinetic energy, the required angular range can vary. The request for angular resolution also varies with the application, but typically ranges from 1 ° to less than 0.1 °. In energy resolution, the desired range is from 0.5 eV to 0.5 meV depending on the application. In order to achieve high resolution measurements, the analyzer must have sufficient angular and energy resolution, but the hemispherical analyzer emits within a limited angular range perpendicular to the lens axis 15. Since only the generated electrons are received, the sample manipulator 17 must have very high precision operation and repeatability. The manipulator 17 is required to precisely rotate and tilt the sample to build a complete data set of 30 ° solid angle.

The energy dispersion of electrons emitted from the sample depends on the thermal spread given by ΔE = 3.5 × k _B [eV / K] × T [K]. Here, ΔE is energy dispersion in eV units, k _B is Boltzmann's constant, and T is temperature in Kelvin units. Therefore, in order to achieve the desired energy resolution, it is essential that the sample 11 can be cooled to a very low temperature. For example, to obtain a spread of less than 1 meV, a sample temperature of at most 3K is required.

  The hemisphere 5 disperses electrons relative to the energy of the electrons along the y direction in the detector plane (which coincides with the plane of the entrance 8 of the measurement region 3 in the hemispherical analyzer). In the x direction, the position in the detector plane is a direct image of the x coordinate in the plane of the entrance 8 of the hemisphere 5. The entrance 8 of the hemisphere 5 is formed as a narrow slit in the x direction and is hereinafter referred to as the entrance slit in the measurement region or simply the entrance slit. If electrons can enter the hemisphere 5 through the narrow entrance slit 8, the two-dimensional detection device 9 will simultaneously provide information on energy dispersion and information on the distribution along the entrance slit 8. The two-dimensional detection device 9 typically includes a multi-channel electron-multiplier plate (MCP) 19. The multichannel electron multiplier is placed in the same plane as the entrance slit 8 of the hemisphere 5 and generates a measurable electrical signal at the location of the incoming electrons. Thus, the position of the incoming electrons can be optically recorded by a phosphorous screen and video camera 21, or as an electrical pulse on a delay line or resistive anode detector, for example. You can also Alternatively, some of the energy-selected electrons may be further analyzed after leaving the hemispherical region through the exit hole 23 leading to the spin detector 25, particularly with respect to the spin of the electrons. In a kind of spin detector, the electrons leaving the hemisphere 5 in a direction close to the (negative) z direction consist of a first lens system, a 90 ° deflector and a second lens system on the target. After passing through the array, the distribution of scattered electrons is measured. Some devices are mounted with deflectors and make an angle of 90 ° to each other (ie, one bends in the (y, z) plane and one is parallel to the (x, z) plane. There are two such spin detectors. These inlet apertures are located in the hemispherical (y, z) symmetry plane and at different radial (y) positions on each side of the MCP detector.

Due to the electric field applied between the hemispheres 5, electrons of a certain kinetic energy, called path energy (E _p ), will collide with the center of the MCP detector 19, and the range called the energy window is MCP. Fall within the sensitivity region of Energy Dispersive (dy / dE) is inversely proportional to _{E p,} whereas the energy window is directly proportional to _{E p.} Therefore, to achieve an appropriate compromise between energy resolution and information rate, it is usually necessary to adjust the kinetic energy E _k of the emitted electrons to the appropriate path energy. is there. This energy adjustment is performed by the lens system 13. The lens system 13 consists of a series of lens elements L1 to L3 in the form of concentric electrodes (cylinder, truncated cone, aperture, etc.) arranged along the optical axis 15. The lens elements L1 to L3 are each connected to a voltage source. In addition to adjusting the energy (acceleration or deceleration), the lens system 13 also allows the sample to be placed at a convenient distance from the hemisphere 5, and most importantly in the current context, the lens system 13 Thus, the distribution of electrons in the plane of the hemispherical entrance slit 8 can be controlled. Acceleration or deceleration is directly controlled by the potential difference between the sample 11 and the hemispherical inlet 8, while other lens voltages are used to control the electron distribution. The lens system 13 can be operated in two different modes, called imaging mode and angular resolution mode (angle mode), respectively. In the imaging mode, there is a point-to-point correspondence between the emission point (to the first order) and the (x, y) position in the plane of the entrance slit 8 and the take-off angle from the sample 11 It does not depend on (take-off angle). Therefore, the entrance slit 8 has the same shape as the entrance slit, and sorts electrons emitted from the sample region having a size determined by the magnification of the lens. That is, the region is usually in a narrow range in the y direction. In the angle mode, the lens voltage is instead the same point in the plane 26 of the entrance slit 8 as shown in FIG. 2 where the electrons emitted at the same angle (θ _x , θ _y ) with respect to the lens axis. Prepare to be focused to (x, y). In FIG. 2, the y-axis and z-axis are arbitrary units and are shown on different scales. Here, the final position does not depend on the starting position up to the linear expression and is therefore fairly uncritical. Thus, electrons received in the entrance slit 8 have their take-off angles in the y direction within a narrow range, which range is determined by the entrance slit width and angular dispersion (dy / dθ _y ), while x Different extraction angles in the direction are distributed along the entrance slit 8. However, the angular dispersion is equal in the x and y directions due to the rotational symmetry of the lens system (dx / dθ _x = dy / dθ _y ). Both magnification in imaging mode and angular dispersion in angle mode are arbitrarily chosen by adjusting the lens voltage according to a pre-calculated function, and remain constant over a wide range of (E _k / E _p ). It is possible.

  The energy resolution of the hemisphere 5 at a given path energy is both the width of the entrance slit 8 and the angular spread of the electron beam in the radial direction when the electrons are incident on the hemisphere (ie, the spread of dy / dz). to be influenced. For each size of the entrance slit 8, there is a corresponding angular spread, and the corresponding angular spread gives an optimal combination of intensity and resolution. For a narrow entrance slit, ie high energy resolution, the corresponding angular spread is very small, typically 1-2 °. This angular spread is determined by combining the entrance slit 8 with another slit 27 (hereinafter referred to as an opening slit) as shown in FIG. There is some distance in front of the opening slit 27. In the direction along the entrance slit ((x, z) plane) there is no such angle limitation from resolution requirements. However, the outgoing angle after the hemisphere with respect to the central (y, z) plane is the same as the incident angle (dx / dz) with respect to this central (y, z) plane (the central plane in FIG. 1). The direction of the electrons intended to reach the entrance hole of the spin detector from the inner orbit and another in-plane orbit must be very close to the z-direction.

  In order to compensate for the unevenness of the emission point of the sample 11 to be emitted with respect to the optical axis 15 of the lens system 13, one deflector that normally operates in the x direction and one deflector that operates in the y direction are provided in the lens system. Incorporated. The x deflector and the y deflector may be placed behind each other along the lens axis 15, but the x deflector and the y deflector have a single deflector package 29 consisting of four electrodes. It is more often incorporated in Each of the x and y deflectors covers an azimuth angle close to 90 ° (see FIG. 1).

  In the following, some problems of the prior art particle spectrometer will be discussed with reference to FIG. For convenience, the discussion will mainly refer to the angle resolution operation mode (angle operation mode) of the lens system 13. However, it should be understood that much of the discussion applies equally well to mapping in imaging mode.

  The requirements for efficient cooling to cryogenic temperatures include that the sample 11 needs to be in very good thermal contact with the refrigerant and must also be effectively shielded from thermal radiation. This requirement is incompatible with placing on the manipulator 17 with sufficient flexibility to cover the entire angular range. Moving the sample 11 mechanically also poses a risk that the emission region or the visible region will change with respect to the analyzer of the spectrometer, so that the spectra acquired at different angles are inadvertently different from sample to sample. It is also acquired from the part.

  To some extent, using the x and / or y deflectors described above, the electrons were fired off-axis (in the imaging mode) or in a direction not along the optical axis 15 of the lens system 13 (in the angle mode). It is possible to avoid moving the sample 11 by guiding the electrons to the center of the entrance slit 8. The method disclosed in Japanese Patent Application Laid-Open No. 58-200344 provides one variation of this theme. However, the trajectory that reaches the center of the entrance slit 8 with this technique will generally be angled with respect to the optical axis 15, so the practical applicability of any such approach is very high. It is limited to. Thus, due to deflection in the y-direction (across the slit), their trajectories will be hindered by the combination of the angled aperture slit 27 and the entrance slit 8 or will result in an unacceptable loss of energy resolution. . In the x direction (along the slit), only trajectories within a relatively small initial angular range will fall within the angular range allowed for the spin detector system. If it is intended to make use of the entire distribution along the entrance slit 8, there is generally the further problem that the angular scale is severely distorted even for very small deflections.

Furthermore, the achievable angular resolution depends on the angular dispersion of the lens system 13. This is most clearly seen in the y direction, where the resolution is not better than the entrance slit width divided by the angular dispersion. From this point of view, it is often desirable to be able to operate with great dispersion. On the other hand, the range of θ _{x that} can be observed is limited by the smaller one of (length of entrance slit of hemisphere) / (angle dispersion) and acceptance of the lens front aperture. Therefore, as the dispersion increases, the limit due to the length of the hemispherical entrance slit becomes too severe, and the observable range of θ _x may be much smaller than the acceptance of the lens.

Japanese Patent Laid-Open No. 58-200344

  It is an object of the present invention to solve, or at least alleviate, one or more of the problems described above.

  In particular, it is an object of the present invention to improve energy resolution in particle spectroscopic measurements, such as photoelectron spectroscopic measurements.

This and other objectives are achieved by a method for determining at least one parameter for charged particles emitted from a particle emission sample. One parameter relates to, for example, the energy of the charged particle, the starting direction, the starting position, or the spin.
The method is
Forming a particle beam of the charged particles and transporting the particles between the particle emitting sample and the entrance of the measurement region by a lens system having a substantially straight optical axis;
Deflecting the particle beam in at least a first coordinate direction orthogonal to the optical axis of the lens system before the particle beam is incident on the measurement region;
Detecting the position of the charged particle in the measurement region, the position being an indicator of at least one of the parameters.

  Further, the method comprises the step of deflecting the particle beam at least twice in the same first coordinate direction before the particle beam is incident on the measurement region.

  By deflecting the particle beam twice in the same coordinate direction between the particle emission sample and the entrance of the measurement region, both the position and direction of the particle beam at the entrance of the measurement region can be controlled.

  Preferably, prior to the particle beam entering the measurement area, the particle beam is deflected at least twice in each of two coordinate directions orthogonal to the optical axis of the lens system. This assumes that a three-dimensional Cartesian coordinate system with the z-axis along the optical axis of the lens system, the particle beam is preferably viewed from the particle point of view at least twice in each of the x and y directions. It means that it is deflected upstream the entrance of the measurement region. To satisfy the four conditions (position and direction in two orthogonal directions), at least two degrees of freedom are required in each direction.

  The method allows a predetermined part of the angular distribution of the particles forming the particle beam to pass through the entrance of the measurement area. Preferably, the deflection of the particle beam is controlled so that the predetermined part of the angular distribution of the particles passes through the entrance of the measurement area in a direction substantially parallel to the optical axis of the lens system. In order to analyze any part of the angular distribution of the particle beam (not just the part along the x or y axis of the Cartesian coordinate system described above), the deflection of the particle beam is performed before the particle beam is incident on the measurement chamber. In addition, it may have to be performed twice in each of the x-axis and y-axis directions.

In one embodiment of the invention, the first and at least second directions are controlled, and the predetermined portion of the angular distribution of particles is in a predetermined starting direction (θ _x0 , θ _y0 ) or within a predetermined range Only particles released from the sample in the starting direction are included.

  The method allows particles emitted in a direction not parallel to the optical axis of the lens system to be incident on the entrance of the measurement area in a direction substantially parallel to the lens axis, so that the sample surface is The criterion that the emission angle relative to the normal and must be oriented to have a desired emission angle parallel to the lens axis is eliminated, and by eliminating the criterion, the test sample (in turn) the need to move the test sample) to achieve this orientation is reduced. The present invention thus discloses a new type of particle beam manipulation. This new type of particle beam manipulation, to some extent, eliminates the need for physical manipulation of the test sample.

  In particular, the proposed particle beam manipulation reduces the need for tilting and rotating the test sample in the x and y directions of the three-dimensional Cartesian coordinate system described above.

  Since the need for complex manipulator mobility is reduced, a manipulator can be used that allows cooling directly to the test sample. As mentioned above, this manipulator allows for more efficient cooling of the test sample, which in turn allows for improved energy resolution of the measurements obtained by the spectroscopic analyzer. Brought about. By reducing the need for complex manipulator mobility, the test sample can be attached directly to the cold plate and the test sample can be cooled to about 2K. When cooling to about 2K is possible, an energy resolution of about 0.7 meV is obtained as a result of using a narrow bandwidth excitation source with the spectroscopic analyzer according to the invention.

  In addition to the advantage of improved energy resolution while maintaining angular resolution, a particle spectrometer with an analyzer capable of performing the method described above allows for complex operation of a test sample such as a 6-axis manipulator. It can be manufactured at a lower cost than a spectrometer having a manipulator.

  Furthermore, the complex operation of the test sample in such a prior art spectrometer makes it difficult to continuously irradiate the precisely defined area of the test sample, and thus the precisely defined area of the test sample. Make it difficult to analyze. The present invention eliminates the need for complex operation of the test sample, thereby facilitating the irradiation of the test sample to a precisely defined target area and the analysis of the precisely defined target area of the test sample. In particular, the sample position can be kept unchanged during a series of long measurements that often cover all directions within a solid angle that is large enough to obtain all physically relevant information. is there.

  In the measurement region, charged particles are deflected by an electrostatic field, and the position of the deflected particles is detected by a detection device. Depending on the measurement area, the entrance of the measurement area, and the design of the detection device, various particle-related parameters such as particle energy, starting direction, or starting position can be determined from the detected position. Preferably, the detection includes detection of particle positions in two dimensions. One of the particle positions in two dimensions substantially represents the energy of the particle, and the other represents the spatial distribution of the particles along a straight line in the incidence plane of the measurement region. Since the spatial distribution of the particles along a straight line in the plane of incidence (typically in the length direction of the slit-type entrance) provides information on the starting direction and starting position of the particles, It is possible to simultaneously determine both the energy and the starting direction or starting position of the particle.

  However, another result of the ability to control both the position and direction of the particle beam at the entrance to the measurement region is that a larger angular range is obtained compared to a single deflection of the beam in each coordinate direction. It is a point that can be detected. In addition, larger angular ranges can be examined while maintaining intensity and resolution (energy and angle). The use of two deflections in the same coordinate direction controls both the position and direction of the particle beam at the entrance to the measurement area, and provides an angular range within a solid angle substantially determined by the acceptance angle of the front aperture of the lens, Allows examination without moving the sample. This is virtually impossible with a single set of deflectors.

  The invention also provides an analytical device for determining at least one parameter relating to charged particles emitted from a particle emission sample, the analytical device being able to carry out the method described above. For this purpose, the analysis device comprises a measurement region having an inlet that allows charged particles to be incident on the measurement region, and a detection device for detecting the position of the charged particles in the measurement region. The position of the particles is an indicator of at least one of the above parameters. Furthermore, the analysis device comprises a lens system having a substantially straight optical axis, the lens system being operable to form a particle beam of charged particles emitted from the sample, the inlet of the sample and the measurement area described above Transport particles to and from. The analyzer includes a first deflector for deflecting the particle beam in at least a first coordinate direction orthogonal to the optical axis of the lens system before the particle beam is incident on the measurement region, and the particle beam is incident on the measurement region. And further comprising at least a second deflector operable to deflect the particle beam at least twice in the same first coordinate direction.

  Preferably, at least the second deflector is arranged downstream of the first deflector and spaced from the first deflector along the optical axis of the lens system. As can be seen from the above discussion, the combined effect of the first and at least the second deflector is to control which part of the beam is incident on the measurement region and in which direction. This control allows a selected portion of the beam to be incident on the measurement region along the direction of the lens axis (ie, the optical axis of the lens system).

  The deflection device is preferably integrated in the lens system of the analyzer. This means that the lens system and the deflection device form an integral part. The integration of the deflection device and the lens system allows a compact design of the analyzer and reduces the number of separate parts in the analyzer. However, the deflection device can also be arranged upstream or downstream of the lens system of the analyzer, can be arranged between two lenses of the lens system, or at least two deflectors It is also possible to be arranged at different positions with respect to the lens system.

  For the reasons discussed above, the deflection device preferably allows the particle beam to travel in a coordinate direction perpendicular to the optical axis of the lens system, i.e. the x-direction and y-direction, before it passes through the entrance of the measurement area. It is operable to deflect twice in each direction.

  For this purpose, the deflection device can comprise, for example, four deflectors, two of the four deflectors being operable to deflect the particle beam in the x direction and two of which are particle It is operable to deflect the beam in the y direction.

  In a preferred embodiment of the invention, the deflecting device comprises two deflector packages, each deflector package being operable to deflect the particle beam in both the x and y directions. For this purpose, each deflector package can comprise two electrode pairs, which are two orthogonal components of the electric field when a voltage is applied between each pair of electrodes. Is operable to generate The four electrodes of each deflector package are preferably arranged in an essentially quadrupolar symmetry form.

  The analysis device further comprises a control unit for controlling the deflection of the particle beam by applying a controlled voltage to the electrodes of the deflection device.

  The control unit can be configured to determine a specific starting direction of particles emitted from the sample. The emitted particles are incident on the measurement area along the optical axis of the lens system by applying a deflection voltage according to a pre-calculated function.

In one application, the voltage will be scanned in such a way that a series of start angles θ _y in the y direction are continuously recorded by the measurement system. For each θ _y , the range of angles θ _x in the x direction limited by the slit length at the entrance of the measurement area is recorded, so that each energy in the window defined by the detector system A two-dimensional map of the angular distribution for is obtained. During such angular scanning, the deflection in the x direction will typically be kept constant, resulting in a map over a rectangular region in (θ _x , θ _y ). When the lens is operated with high angular dispersion, it is possible to combine such multiple scans with different deflections in the x-direction to obtain a complete map over the entire acceptance angle of the front aperture of the lens. It is also possible to scan the acceleration voltage or the deceleration voltage between the sample and the measurement area in order to cover an energy range larger than the detector energy window. This application example can be used for, for example, Angle Resolved Photoelectron Spectroscopy (ARPES), but is not limited thereto.

In another application, the deflector voltage is such that particles emitted within a narrow solid angle around one selected direction (θ _x0 , θ _y0 ) _enter the measurement region along the optical axis of the lens. As will be set by the control unit, after energy analysis, particles in a narrow energy range with this particular initial direction can enter the spin detector.

  In both cases, the control unit changes the lens voltage and the deflector electrode voltage according to a pre-calculated function in order to maintain the focusing and dispersion characteristics of the lens and to provide the necessary deflection angle. I will let you.

  In a further embodiment of the invention, a quadrupolar symmetric voltage is superimposed on the deflector voltage in at least one deflector package. Such a voltage allows focusing in one plane and defocusing in an orthogonal plane, and such voltage can be applied to reduce distortion in the angle map. Can do.

  As briefly discussed above, the detection device of the analyzer is typically arranged to detect the position of the charged particle after further deflection of the charged particle within the measurement region. Since the magnitude of the particle deflection depends on the kinetic energy of the particle, the detection position of the particle in a specific direction is an index of the energy of the particle. Also as mentioned above, the detection device preferably has a position in two dimensions of the charged particles in the measurement region in order to determine both the energy of the charged particles in the measurement region and the starting direction or start position. Can be detected. For this purpose, the detection device can comprise, for example, a multi-channel electron multiplier (MCP). Multi-channel electron multipliers generate measurable electrical signals at the incoming particle locations. Thus, the position of the incoming particles can be recorded optically with a phosphorus screen and video camera, or as an electrical pulse on a delay line or resistive anode detector, for example.

  The analytical device is preferably used in a hemispherical deflector type particle spectrometer such as a hemispherical photoelectron spectrometer as described in the background section. Therefore, in this case, the measurement region can comprise two concentric hemispheres that are symmetric with respect to the (y, z) plane of the coordinate system described above. The hemisphere can rest on the base plate and have an electrostatic field applied between the two hemispheres. Particles incident on the region between the hemispheres in a direction nearly perpendicular to the base plate are deflected by the field, and electrons with kinetic energy within a certain range defined by the deflection field traveled through the semicircle. Later, the detection device is reached. In this embodiment, the entrance to the measurement area, i.e. the entrance to the hemisphere, is typically a slit along the x-direction, which allows the detection device to detect in two dimensions. It is possible to simultaneously provide information on the energy distribution and information on the distribution along the entrance slit. Information on the distribution along the entrance slit serves as an index for both the start direction and the start position of the particles according to the operation mode of the lens apparatus.

  In an improved embodiment of the invention, the analytical device comprises a spin detector. In prior art spin detectors, only electrons incident on the spin detector within a narrow angular range around the axis of the lens at the entrance of the spin detector are allowed. In prior art spectrometers this means that the electrons must also jump out of the sample parallel to the direction of the spectrometer's lens axis. However, another advantage of the proposed electron beam manipulation principle instead of or in addition to the test sample is that spin detection of electrons emitted from the sample in any direction within the acceptance of the lens system It can be carried to enter the spin detector along the direction of the lens at the entrance of the device. The present invention also provides a particle spectrometer comprising an analyzer as described above, such as a photoelectron spectrometer. In a preferred embodiment, the particle spectrometer is a hemispherical deflector type photoelectron spectrometer, as described above in the background section.

  The present invention will become more fully understood from the detailed description given below and the accompanying drawings given solely by way of illustration. In the different drawings, the same reference signs refer to the same elements.

It is a figure which shows the hemispherical deflector type photoelectron spectrometer by a prior art. It is a figure which shows the track | orbit of the particle | grains which passed through the lens system of the photoelectron spectrometer shown by FIG. It is a figure which shows the entrance slit of the measurement area | region of an opening slit and the photoelectron spectrometer shown by FIG. FIG. 3 shows a hemispherical deflector-type photoelectron spectrometer according to one exemplary embodiment of the present invention. 2 is an end view of two deflector packages of an analyzer according to one exemplary embodiment of the invention. FIG. 2 is an end view of two deflector packages of an analyzer according to one exemplary embodiment of the invention. FIG. FIG. 3 shows a portion of an analyzer according to an exemplary embodiment of the present invention. FIG. 6 illustrates an exemplary method in which a deflector voltage can be applied to the electrodes of the deflector package shown in FIGS. 5A and 5B. FIG. 3 shows the trajectory of particles through the lens system of the analyzer according to the invention when no deflector potential is applied. FIG. 6 shows the trajectory of particles through the lens system of the analyzer according to the invention when a deflector potential is applied. FIG. 3 shows how selected portions of the angular distribution of emitted particles can be deflected according to the principles of the present invention.

  FIG. 4 illustrates a particle spectrometer 30 according to an exemplary embodiment of the present invention. In addition to the differences described below, the components and functionality of the particle spectrometer 30 are similar to those of the prior art hemispherical deflector type photoelectron spectroscopy described with reference to FIGS. It is identical to a total of 1 components and functionality. The components shown in FIG. 4 that correspond to the components shown in FIGS. 1-3 are given the same reference numerals and further description thereof is omitted.

  Accordingly, the particle spectrometer 30 is a hemispherical deflector-type photoelectron spectrometer equipped with an analysis device adapted for analyzing the energy of the charged particles emitted from the particle emission sample 11 and the starting direction or starting position. is there.

  As can be seen in FIG. 4, the analysis device includes a deflection device 31 comprising a first deflector package 29 and a second deflector package 29 '. Each of the first deflector package 29 and the second deflector package 29 'is devised and designed as the single deflector package 29 of FIG. 1 described in the background art section.

Referring simultaneously to FIGS. 5A and 5B, which illustrate end views of the first deflector package 29 and the second deflector package 29 ′, respectively, this indicates that each of the first and second deflector packages has four electrodes. 33A to 33D and 33A ′ to 33D ′, which means that each of the electrodes covers an azimuth angle close to 90 °. Two opposing electrodes in each deflector package form electrode pairs 33A / 33C, 33B / 33D, 33A '/ 33C', 33B '/ 33D'. These electrode pairs can be operated to generate an electric field between the electrodes by applying deflector voltages V _x and V _y , so that the charged particles passing between the electrodes of the deflector package are deflected in one coordinate direction. It is possible to operate. Thus, each such electrode pair forms a deflector for deflecting charged particles in one coordinate direction.

  Assuming a three-dimensional Cartesian coordinate system in which the z-axis of the coordinate system is along the optical axis 15 of the lens system 13 and the hemisphere 5 is symmetric about the (y, z) plane, each deflector package 29, 29 ′. One electrode pair 33A / 33C, 33A ′ / 33C ′ is arranged to deflect charged particles in the x direction, and the other electrode pair 33B / 33D, 33B ′ / of each deflector package 29, 29 ′. 33D ′ is arranged to deflect the charged particles in the y direction. An electrode pair arranged to deflect charged particles in the x direction will hereinafter sometimes be referred to as an x deflector, and an electrode pair arranged to deflect charged particles in the y direction will be As a y deflector.

  FIG. 6 shows a more detailed view of a portion of the analyzer, as illustrated in FIG. 6, the deflection applied to the electrodes 33A-33D, 33A′-33D ′ of the deflector packages 29, 29 ′. The device voltage is controlled by the control unit 35. The same control unit 35 can also be configured to control the lens voltage applied to the plurality of concentric electrodes that make up the lenses L1-L3 of the lens system 13.

The sign and absolute value of the deflector voltages V _x and V _y applied between the respective electrode pairs 33A / 33C, 33B / 33D, 33A ′ / 33C ′, 33B ′ / 33D ′ of the deflecting device 31 are the control unit. 35 independently controlled. As illustrated in FIGS. 5A and 5B, the deflector voltage of the x deflector 33A / 33C in the first deflector package 29 is denoted as V _x1 and the x deflector 33A in the second deflector package 29 ′. The deflector voltage of '/ 33C' is represented as V _x2 . Similarly, the deflector voltages of the y deflectors 33B / 33D and 33B ′ / 33D ′ in the first and second deflector packages are expressed as V _y1 and V _y2 , respectively.

Thus, the deflector electrodes 33A-33D, 33A'-33D 'in each deflector package 29, 29' are applied between one pair of opposing electrodes 33A / 33C, 33A '/ 33C'. the voltage [Delta] V _x brought deflection only in the x-direction, orthogonal pairs 33B / 33D, 33B '/ 33D ' voltage [Delta] V _y applied between are arranged to provide deflection only in the y direction. Thus, any required deflection (Δx ′, Δy ′) can be achieved by applying a combination of voltages for deflection in the x and y directions. Therefore, the output direction from the deflector region, that is, the charged particles are deflected by any combination of the incident angles of the charged particles entering the lens system 13 by an appropriate combination of voltages applied to the deflector electrodes. The direction of the charged particles when passing through the last deflector 31 is parallel to the lens axis 15 and the emission of the charged particles from the deflector region along the lens axis 15 is achieved simultaneously. Is possible. This means that the trajectory in this particular direction is substantially unchanged by the part of the lens system 13 that is located after the deflector 31 (ie downstream of the deflector as viewed from the particle point of view). .

As illustrated in FIG. 7, a quadrupolar symmetric voltage V _q can be superimposed on the deflector voltages V _x , V _y applied to the electrodes of the deflector package. Although FIG. 7 shows only the first deflector package 29, the quadrupole symmetric voltage V _q is applied to the deflector in either or both of the first deflector package 29 and the second deflector package 29 ′. It should be understood that it can be superimposed on the voltage. These superimposed voltages _Vq are also controlled by the control unit 35 to achieve focusing in one plane and defocusing in an orthogonal plane, thereby reducing distortion in the angle map. To reduce.

8A and 8B show the case where the deflector potentials ΔV _x and ΔV _y are not applied to the first and second deflector packages 29 and 29 ′ during the angle operation mode of the lens system 13 and when they are applied. Lens system 13 for different starting directions of charged particles from particle emitting sample 11 (located in the illustrated coordinate system at z = 0 and having a small width around y = 0). FIG. 6 shows projections in the (y, z) plane of several trajectories passing through. The vertical axis of the figure shows the y coordinate of the three-dimensional coordinate system discussed previously, and the horizontal axis is the distance from the sample in the z direction of the same coordinate system, that is, the distance from the sample along the optical axis 15 of the lens system 13. Indicates. The axes are in arbitrary units and are drawn on different scales. The trajectory indicated by the solid line is the trajectory of the particles emitted from the sample 11 with an extraction angle of 0 ° with respect to the optical axis 15 of the lens system, while the trajectory indicated by the dashed line and the dashed line is the extraction angle of 4 ° and The corresponding trajectory of 8 °.

FIG. 8A illustrates the trajectory when the lens system 13 is operated in the angle mode when no deflector potential is applied to the deflector packages 29, 29 ′. The particles emitted on the lens axis 15 will be guided to the center of the plane 26 of the entrance slit 8 by the lens system under the influence of different lenses L1-L3 (see FIGS. 4-6). Particles emitted at other angles (θ _x , θ _y ) with respect to the lens axis will be focused at other defined positions on the entrance slit plane 26.

FIG. 8B illustrates the trajectory when the lens system 13 is operated in the angle mode when the deflector potentials V _x and V _y are applied. In this exemplary embodiment, the deflector voltage applied to the electrodes 33A-33D, 33A′-33D ′ of the deflector packages 29, 29 ′ is a part of the angular distribution of the particles, ie the lens axis 15. The part containing the particles emitted at the extraction angle of 8 ° is controlled to be guided to the center of the plane of the entrance slit 8, and the particles enter the measurement region 3 in the direction of the lens axis 15. Particles emitted at other angles (θ _x , θ _y ) with respect to the lens axis will be focused at other defined locations on the entrance slit plane.

  In this exemplary embodiment, the first deflector package 29 bends the particle trajectory “down” so that the selected trajectory gradually approaches the lens axis 15, while the second deflector package 29. 'Bend in the opposite direction. Trajectories starting in the other direction will exit the lens system at positions that are all offset by substantially the same amount while maintaining substantially the same dispersion as if they were not deflected.

FIGS. 9A-9C are also described herein where selected portions A, B of the angular distribution of emitted particles are whatever the extraction angles θ _x , θ _y from the sample 11. Using the inventive concept, it is illustrated how a selected part can be deflected to enter the entrance 8 of the measurement region 3 in a direction substantially parallel to the optical axis 15 of the lens apparatus. 9A and 9B illustrate the angular distribution of the particle beam, which is represented by reference numeral 39. FIG. 9C also shows these angular distributions drawn on the hemispherical entrance plane 26 after deflection of the particle beam.

9A and 9C together illustrate the desired deflection of part A of the particle beam angular distribution, and FIGS. 9B and 9C illustrate both the desired deflection of part B of the particle beam angular distribution. Part A and part B contain particles selected for analysis in the measurement region 3, for example with respect to particle energy, starting direction, starting position or spin. In accordance with the example illustrated in FIG. 8B, two deflections in a single coordinate direction (y-direction) can be obtained by selecting any selected portion A of the angular distribution within the strip defined by the vertical dashed line in FIG. 9A. Is sufficient to enter the measurement area in a direction substantially parallel to the lens axis 15. On the other hand, two deflections in each of two coordinate directions orthogonal to the lens axis 15 (ie, the x and y directions) are arbitrarily selected for the angular distribution in the strip limited by the vertical dashed line in FIG. 9B. It is necessary for the part B to be incident on the measurement region in a direction substantially parallel to the lens axis. Arbitrary selected portions of the angular distribution between the vertical dashed lines in FIG. 9B, with the center of that portion being (θ _x , θ _y ), the trajectory with a fixed start direction θ _x ≠ 0 is x = 0 and If the voltage V _x is set so as to exit at dx / dz = 0, and the voltage V _y is changed so that the continuous direction θ _y exits at y = 0 and dy / dz = 0, the measurement region It is possible to make it enter.

  Referring again to FIG. 6, the first deflector package 29 and the second deflector package 29 ′ are deflectors in which charged particles are on the path between the particle emission sample 11 and the entrance 8 of the measurement region 3. Concentrically arranged at some distance around the optical axis 15 of the lens system 13 to pass between the electrode pairs 33A / 33C, 33B / 33D, 33A '/ 33C', 33B '/ 33D' of the package Only separated. Because different applications may require different combinations of individual lens elements L1, L2, L3, the number of lens elements in the lens device 13 and / or the entire lens device 13 may be used for another application. The length of the length (including the integrated deflection device 31) can be substantially changed. Preferably, all the deflectors of the deflecting device 31 are arranged in the lens element L2, but are located closer to the end of the lens element L2 than the radius of one lens element from the end of the lens element L2. Should not do. Furthermore, the distance between the first deflector package 29 and the second deflector package 29 ′ should preferably be at least the radius of the lens element L2, and the deflector package is within the lens element L2. Be placed. Thus, if the first deflector package 29 and the second deflector package 29 ′ are located within the same lens element L2 having the radius of the lens element, the first deflector package 29 is preferably The second deflector package 29 'is preferably located at a distance of at least one lens element radius from the starting end of the lens element L2, and the second deflector package 29' is preferably located between the first deflector package 29 and the end of the lens element L2. They are located at least one lens element radius away from both. This not only gives the charged particles time to change their direction before the charged particles enter the next deflector, but also the electrostatic potential crosstalks between the first and second deflector packages. It is also to avoid doing.

  Furthermore, the deflectors 33A / 33C, 33B / 33D, 33A '/ 33C', 33B '/ 33D' of the deflection device 31 are preferably provided in the region including the deflector electrode and the gap between the electrodes. Is arranged with respect to the lens elements L1 to L3 of the lens device 13 so that there is substantially no electric field other than that generated by. For this purpose, as illustrated in FIGS. 5A and 5B, the deflector electrodes 33A-33D, 33A′-33D ′ are preferably arranged in cylindrical tubes 41, 41 ′, The potentials of the deflector electrodes 33A to 33D and 33A ′ to 33D ′ are referred to the potentials of the cylindrical tubes 41 and 41 ′ (with their electrical potentials referred to the potential of this tube). Thus, in a preferred embodiment in which the deflection device 31 comprises two deflector packages 29, 29 ', each of the deflector packages 29, 29' comprising four electrodes 33A-33D, 33A'-33D ' The electrodes of the deflector package form a cylindrical region with quadruple rotational symmetry so as to form a substantially cylindrical deflector package, the cylindrical deflector package being the outer cylindrical tube 41, 41 '.

  In the exemplary embodiment shown in the drawing, it is integrated into the lens system 13, but the deflectors 33A / 33C, 33B / 33D, 33A '/ 33C', 33B '/ 33D' of the deflection device 31 are integrated into the lens system. It is to be understood that other arrangements in relation to the individual lens elements L1-L3 of the lens system 13 and the lens system 13 are possible. For example, the deflecting device 31 and all deflectors of the deflecting device 31 may be arranged in an “upstream position” between the sample 11 and the starting end of the lens system 13, or the outlet of the lens system 13 and the hemisphere 5. It is also possible to arrange it at a “downstream position” between the entrance slit 8. As long as such an arrangement further separates the deflection and lens movements, such an arrangement may be advantageous in some situations. For example, because of a system that is dedicated to observation in one unidirectional direction at a time (eg, a system dedicated to spin detection), the upstream position of the deflecting device 31 has a wider angular range than the integrated solution. Enable. However, increasing the distance between the sample 11 and the lens device 13 will lead to an undesired decrease in the acceptance angle for normal applications. At a position downstream of the deflecting device 31, increasing the distance between the last active lens element L3 and the entrance slit 8 of the measurement region 3 will reduce the dispersion and energy range flexibility.

  Therefore, in a preferred embodiment of the present invention, the deflectors 33A / 33C, 33B / 33D, 33A ′ / 33C ′, 33B ′ / 33D ′ of the deflecting device 31 have at least one lens for the first deflection of the particle beam. It is arranged with respect to the individual lens elements L1 to L3 of the lens arrangement 13 so that it acts on the particle beam before and at least one lens acts on the particle beam after the last deflection of the particle beam. Also, all deflectors of the deflection device 31 are preferably arranged in the same lens element L2 of the lens system 13. This means that all deflectors of the deflection device are surrounded by the same potential. This is in that it facilitates the control of the deflector voltage and the lens voltage which are necessary for the desired part of the angular distribution of the particle beam to pass through the entrance 8 of the measurement region 3 parallel to the lens axis 15. It is advantageous.

  As discussed above, in the preferred design, the deflector electrode is shaped like a cylindrical portion packed in two deflector packages 29, 29 'having quadruple rotational symmetry, The two deflector packages are identical in both cross section and length. However, it should be understood that none of these features are essential for the operation of the analyzer, flat or other shaped electrodes are conceivable, eg to reduce angular pattern distortion Can have the advantage. A configuration having 8 (or 4n) electrodes in at least one package is also possible. Mirror symmetry with respect to the (x, z) and (y, z) planes is highly desirable from a practical point of view, but is not strictly necessary.

  The invention is not limited to the embodiments described above, but may be varied within the scope of the appended claims.

DESCRIPTION OF SYMBOLS 1 Photoelectron spectrometer 3 Measurement area | region 5 Hemisphere 7 Base board 8 Incidence slit 9 Detection apparatus 11 Particle emission sample 13 Lens system 15 Optical axis 17 Manipulator 19 MCP detector 21 Video camera 23 Outlet part 25 Spin detector 26 Entrance slit plane 27 Aperture slit 29 First deflector package 29 'Second deflector package 30 Particle spectrometer 31 Deflector 33A-33D, 33A'-33D' Deflector electrode 35 Control unit 39 Particle beam 41, 41 'Tube

Claims (18)

A method for determining at least one parameter for charged particles emitted from a particle emission sample (11), comprising:
Between the particle emitting sample (11) and the entrance (8) of the measurement region (3) by a lens system (13) that forms a particle beam of the charged particles and has a substantially straight optical axis (15). Transporting the particles;
Deflecting the particle beam in at least a first coordinate direction (x, y) orthogonal to the optical axis of the lens system before the particle beam is incident on the measurement region;
Detecting the position of the charged particles in the measurement region, wherein the position is an indicator of at least one of the parameters,
The step of detecting the position of the charged particle includes detection of a position in two dimensions, one of the positions in the two dimensions being an indicator of the energy of the particle, and the position of the position in the two dimensions. The other is an indicator of the starting direction of the particles,
A method comprising deflecting the particle beam at least twice in the same first coordinate direction (x, y) before the particle beam enters the measurement region. The first deflection of the particle beam is realized by a first deflector (33A / 33C, 33B / 33D), and at least a second deflection of the particle beam is at least a second deflector (33A ′ / 33C). ', 33B' / 33D '), wherein the second deflector is arranged along the optical axis (15) of the lens system (13) downstream of the first deflector. The method of claim 1, wherein the method is spaced apart from the vessel.   The particle beam has a second coordinate direction orthogonal to the first coordinate direction (x) and the optical axis (15) of the lens system (13) before the particle beam enters the measurement region (3). 3. A method according to claim 1 or 2, wherein (y) is also deflected at least twice.   All the deflection of the particle beam takes place in the lens system (13), at least one lens (L1) acts on the particles before the first deflection of the particle beam, and at least one lens (L3) The method according to claim 1, wherein the method acts on the particles after the last deflection of the particle beam. At least one deflection of the particle beam is achieved by a deflector package (29), which comprises four electrodes (33A-33D) arranged in an essentially quadrupolar symmetry, The four electrodes (33A to 33D) form two electrode pairs (33A / 33C, 33B / 33D), and the two electrode pairs (33A / 33C, 33B / 33D) have respective coordinate directions (x, y). )
Applying a first deflector voltage (V _x ) between one of the two electrode pairs (33A / 33C) of the deflector package (29);
Applying a second deflector voltage (V _y ) between the other (33B / 33D) of the two electrode pairs of the deflector package (29);
Applying a voltage (± V _q ) of quadrupolar symmetry to the electrodes (33A to 33D) of the deflector package (29) and superimposing the voltage on the deflector voltages (V _x , V _y ), The method according to any one of claims 1 to 4.   Predetermined portions (A, B) of the angular distribution (39) of the particles forming the particle beam control the deflection of the particle beam so as to pass through the inlet (8) of the measurement region (3). The method according to claim 1, further comprising the step of:   The predetermined portion (A, B) of the angular distribution of the particles is substantially parallel to the entrance (8) of the measurement region (3) with the optical axis (15) of the lens system (13). The method of claim 6, further comprising controlling the deflection of the particle beam to pass in a direction. The at least one parameter is
Energy of the charged particles,
The starting direction of the charged particles,
The starting position of the charged particles, and the spin of the charged particles,
The method according to claim 1, which relates to at least one of the above. A hemispherical deflector-type photoelectron spectrometer for analyzing the particle emission sample (11) by determining at least one parameter relating to charged particles emitted from the particle emission sample (11),
A measurement region (3) having an inlet (8) allowing the particles to enter the measurement region;
A lens system (13) for forming a particle beam of the charged particles and transporting the particles between the particle emission sample and the inlet of the measurement region, wherein the lens system (15) is substantially in a straight optical axis (15). A lens system (13) having
A first deflector for deflecting the particle beam in at least a first coordinate direction (x, y) orthogonal to the optical axis of the lens system before the particle beam is incident on the measurement region (3) A deflection device (31) comprising (33A / 33C, 33B / 33D);
A detection device (9) for detecting the position of the charged particles in the measurement region, the position being an indicator of the at least one parameter;
The detection device (9) is configured to determine the position of the charged particle in two dimensions, one of the positions in the two dimensions being an indicator of the energy of the particle, The other of the positions is an indicator of the starting direction of the particles,
The deflecting device (31) is at least first for deflecting the particle beam at least twice in the same first coordinate direction (x, y) before the particle beam enters the measurement region (3). A hemispherical deflector-type photoelectron spectrometer, further comprising two deflectors (33A ′ / 33C ′, 33B ′ / 33D ′).   The second deflector (33A ′ / 33C ′, 33B ′ / 33D ′) is disposed downstream of the first deflector (33A / 33C, 33B / 33D) and the optical axis of the lens system (13). The hemispherical deflector-type photoelectron spectrometer according to claim 9, wherein the hemispherical deflector-type photoelectron spectrometer is spaced apart from the first deflector along (15).   The deflecting device (31) has a second coordinate orthogonal to the first coordinate direction (x) and the optical axis (15) of the lens system (13) before the particle beam is incident on the measurement region (3). 11. A hemispherical deflector-type photoelectron spectrometer according to claim 9 or 10, which is operable to deflect the particle beam at least twice in the direction (y).   The deflecting device (31) comprises at least one deflector package (29) comprising four electrodes (33A-33D) arranged in an essentially quadrupolar symmetry form, the said deflector package (29) The four electrodes (33A to 33D) form two electrode pairs (33A / 33C, 33B / 33D), and the two electrode pairs (33A / 33C, 33B / 33D) have the first coordinate direction (x) and The hemispherical deflector-type photoelectron spectrometer according to claim 11, which serves as a deflector in each of the second coordinate directions (y).   The hemispherical deflector-type photoelectron spectrometer according to claim 12, further comprising a control unit (35) configured to apply individual voltages to each of the electrodes (33A-33D).   At least one lens element (L1) of the lens system is located upstream of all the deflectors (33A / 33C, 33B / 33D, 33A ′ / 33C ′, 33B ′ / 33D ′) of the deflection device, The deflection device (31) and the lens system (13) are arranged such that at least one other lens element (L3) of the system is located downstream of all deflectors of the deflection device. A hemispherical deflector-type photoelectron spectrometer according to any one of 9 to 13.   All the deflectors (33A / 33C, 33B / 33D, 33A ′ / 33C ′, 33B ′ / 33D ′) of the deflecting device (31) are arranged in the same lens element (L2) of the lens device (13). The hemispherical deflector-type photoelectron spectrometer according to any one of claims 9 to 14.   The hemispherical deflector-type photoelectron spectrometer according to any one of claims 9 to 15, wherein the deflection device (31) forms an integral part of the lens system (13).   The deflection device (31) is arranged such that a predetermined part (A, B) of the angular distribution (39) of the particles forming the particle beam passes through the inlet (8) of the measurement region (3). The hemispherical deflector-type photoelectron spectrometer according to any one of claims 9 to 16, further comprising a control unit (35) operable to deflect the particle beam.   The control unit (35) is configured such that the predetermined portion (A, B) of the angular distribution (39) of the particles passes the entrance (8) of the measurement region (3) to the lens system (13). 18. A hemispherical deflector type according to claim 17, wherein the deflecting device (31) is operable to deflect the particle beam so as to pass in a direction substantially parallel to the optical axis (15). Photoelectron spectrometer.

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