Device and method for transferring electrons from a sample to an energy analyzer and electron spectrometer device

Abstract

The present invention provides an electron imaging device for electron transfer from an electron optical axis of a sample emitting electrons to an energy analyzer device, comprising a first lens group, a second lens group and a deflector device, which deflects electrons in an exit plane of the electron imaging device along a deflection direction perpendicular to the electron optical axis, the first lens group forms a first reciprocal plane in the first lens group, forms a first Gaussian plane between the first lens group and the second lens group, generates a first momentum distribution image of electron momentum distribution in the first reciprocal plane, generates a first Gaussian image of the sample in the first Gaussian plane, the second lens group forms a second reciprocal plane on the analyzer side of the second lens group, generates a second momentum distribution image of electron momentum distribution in the second reciprocal plane, and the first lens group is capable of generating a first Gaussian image with a sufficiently small size so that the second momentum distribution image is a parallel image. An electron energy spectrometer device, an electron transfer method and an electron energy spectrometer method are also described.

Description

Technical Field

[0001] The present invention relates to an electron imaging device and an electron transfer method for transferring electrons from a sample to an energy analyzer device, in particular an energy analyzer device for momentum and energy resolution detection of electrons, such as photoelectrons. The present invention also relates to an electron spectrometer device provided with the electron imaging device and an electron spectroscopy method. The application of the present invention lies in the electron spectroscopy analysis of a sample. Background Art

[0002] In this specification, reference is made to the following prior art documents which illustrate the technical background of the present invention:

[0003] [1] B.Wannberg in "Nucl.Instrum.Meth.A" 601 (2009) 182;

[0004] [2] EP 2 823 504 B1;

[0005] [3] US 9 997 346 B1;

[0006] [4] EP 2 851 933 B1;

[0007] [5] SE 539 849 C2;

[0008] [6]DE 10 2005 045 622 B4;

[0009] [7]DE 10 2013 005 173 B4;

[0010] [8] EP 1 559 126 B9;

[0011] [9]DE 10 2014 019408 B4; and

[0012]

[10] M.Patt et al. in "Review of Scientific Instruments" 85, 113704 (2014).

[0013] The use of a transfer optical system with an electron optical lens is generally known for transferring and focusing electrons from a solid sample to an energy analyzer, in particular for the measurement of photoelectrons and Auger electrons. Various types of energy analyzers and associated transfer optical systems are known. A group of methods in which electrons emitted from a sample are detected with angular resolution is known as the ARPES (angular-resolved photo-electron spectroscopy) method (see, for example, [1]). In the ARPES method, the emission angle of the electrons when they are emitted from the sample relative to a reference axis, such as the surface normal of the sample surface, is of particular interest. Although high angular resolution has been achieved in the past, this is only within a relatively limited angular range. For example, a high resolution of 0.1° within an angular range of approximately + / -7° and a reduced resolution of 0.5° within a range of approximately + / -15° have been achieved to date.

[0014] A hemispherical analyzer assembled from two concentric hemispherical electrodes is typically used as an energy analyzer in conventional angular imaging using the ARPES method. Depending on the voltage between the hemispherical electrodes, only particles in a specific energy band (e.g., an energy interval with a width of 10% of the pass energy of the hemispherical analyzer) are allowed to pass through the hemispherical analyzer. Imaging of the angular distribution of electrons on the entrance plane of the energy analyzer is provided for energy and angle-resolved measurements. An angular distribution image of electrons from the sample is generated on the entrance plane of the energy analyzer in real space (in a polar coordinate system). Since the slit diaphragm is arranged as an entrance slit in the entrance plane of the hemispherical analyzer, the hemispherical analyzer is able to determine the angular distribution of a first angular coordinate (e.g., along the y direction) along the extension of the entrance slit. In order to also determine the angular distribution along a second coordinate (e.g., x) perpendicular to the first angular coordinate, the arrangement structure of two deflectors [2] or one deflector [3] in the transfer lens sequentially scans (scanning motion) the angular distribution image perpendicular to the extension of the entrance slit and the electron-optical axis.

[0015] Conventional transfer optics for angle-resolved measurements of electrons have a major disadvantage that the electron beam enters the energy analyzer at a significant divergence angle of typically greater than 10° relative to the electron optical axis (e.g., z-axis) at the exit of the transfer optics and / or at the entrance plane of the energy analyzer. Figure 7As shown (prior art, cited from [2], using the example of trajectories of a small number of electron partial beams from a sample 1' with different emission angles in the yz plane (see also [1] and [3])). It leads to imaging errors in the energy analyzer and requires a lot of post-processing work to calculate the energy and angular distribution of the electrons. In addition, conventional transfer optical systems do not have a sufficiently well-focused and concentrated positional spatial image of the sample source point from which the electrons are emitted (see, for example, [1]).

[0016] The divergence angle is particularly disadvantageous when acquiring the angular distribution along the second angular coordinate, wherein the second angular coordinate is scanned sequentially with the help of one or two deflectors 20A', 20B' in the transfer optical system (see [1], [2], [3], [4] and [5]). In the case where the scanning movement of the diverging beam is perpendicular to the extension of the entrance slit, the beam divergence angle from the entrance plane combined with the aberrations caused by the beam deflection by the deflectors produces a combined error.

[0017] In spin-resolved electron spectroscopy (see [6]), where an imaging spin filter with a spin filter crystal is arranged at the exit of the energy analyzer, the beam divergence angle in the entrance plane is also disadvantageous. The beam divergence angle along the entrance slit in the entrance plane leads to a significant beam divergence in the form of astigmatism in the exit plane, which makes it impossible to form a well-focused image of the exit beam on the spin filter crystal.

[0018] In summary, for electron angle-resolved spectroscopy using energy analyzers, especially hemispherical analyzers, the high angular divergence of the electron beam at the end of a conventional transfer optical system has considerable disadvantages. These disadvantages limit the angular interval that can be detected and are more significant when a scanning motion is used to capture the second angular coordinate and when an imaging spin filter is used.

[0019] References [7], [8], [9] and

[10] describe further transfer optical systems intended for momentum microscopy and comprising an amplified beam path, in which a Gaussian image (real space image) and a momentum distribution image (momentum space image) are present. However, these transfer optical systems are not designed for a scanning motion of the momentum distribution image extending perpendicularly to the entrance slit of the energy analyzer. Furthermore, all these techniques are based on the use of a cathode lens in which the electrons are accelerated into the transfer optical system with the aid of a strong electrostatic extraction field. However, the strong extraction field interferes when examining non-planar surfaces (such as can occur after sample splitting in UHV), microstructures (such as semiconductor components) or crystallites with a three-dimensional structure (a common test subject for new quantum materials). Summary of the invention

[0020] The object of the present invention is to improve an electron imaging device, an electron transfer method, an electron spectrometer device and / or an electron spectroscopy method in order to avoid the disadvantages of conventional techniques. The object is in particular to minimize or even eliminate imaging errors caused by divergence, to obtain better angular resolution, to achieve detection at larger angular intervals and / or to simplify spin-resolved electron spectroscopy.

[0021] These objects are correspondingly achieved by the electron imaging device, electron transfer method, electron spectrometer device and electron spectroscopic method according to the present invention.Preferred embodiments and applications of the present invention are described below.

[0022] According to a first general aspect of the present invention, the above-mentioned object is achieved by an electronic imaging device, which is configured for electron transfer from an electron emitting sample to an energy analyzer device along an electron optical axis. The electron transfer includes the transfer and imaging of emitted electrons (also called electron beams) from an entrance plane to an exit plane of the electronic imaging device, wherein the entrance plane is arranged on the surface of the sample facing the electronic imaging device, and the exit plane is arranged on the back of the electronic imaging device facing the energy analyzer, and therefore they are also respectively referred to as the sample side entrance plane and the analyzer side exit plane. The electron optical axis is preferably a continuous straight axis extending perpendicular to the entrance plane and the exit plane, but alternatively, it may have an angled route whose sections are straight lines.

[0023] The electronic imaging device comprises a first lens group on the sample side, a second lens group on the analyzer side and a deflector device, the deflector device being configured to electrically and / or magnetically deflect electrons in a deflection direction perpendicular to the electron optical axis in an exit plane of the electronic imaging device. Each of the first lens group and the second lens group comprises at least two electron optical lenses. The first lens group and the second lens group and the deflector device are each connected to a control circuit for providing an operating voltage, wherein the control circuit can be a separate component or connected to a common control device.

[0024] According to the present invention, the first lens group is configured to be able to form a first reciprocal plane within the first lens group, and to form a first Gaussian plane between the first lens group and the second lens group, so as to generate a first momentum distribution image of the momentum distribution of electrons from the sample in the first reciprocal plane, and to generate a first Gaussian image of the sample, in particular the irradiated sample source point, in the first Gaussian plane. The reciprocal plane is an imaging plane in which a reciprocal image (also called a momentum image or a Fourier image) exists. Therefore, the first reciprocal image, which is referred to as the momentum distribution image here, is focused in the first reciprocal plane. The momentum distribution image is an image of the momentum distribution of electrons, wherein the transverse momentum of the electrons increases as the distance of the partial beam of the momentum distribution image from the electron optical axis increases. The control circuit of the first lens group is configured to be able to apply an appropriately adjusted control voltage to the first lens group for electron optical imaging of the first reciprocal plane and the first Gaussian plane.

[0025] Furthermore, according to the present invention, the second lens group is configured to be able to form a second reciprocal plane on the analyzer side of the second lens group, and to be able to generate a second momentum distribution image of the momentum distribution of electrons from the sample in the second reciprocal plane. The control circuit of the second lens group is configured to be able to apply a properly adjusted control voltage to the second lens group for electron optical imaging of the second reciprocal plane.

[0026] Furthermore, according to the present invention, the first lens group is configured to generate a first Gaussian image having a sufficiently small size (extension of the image perpendicular to the optical axis) while making the second momentum distribution image generated by the second lens group a parallel image.

[0027] The deflector device preferably acts on a Gaussian plane of the electronic imaging device, for example the first Gaussian plane or another Gaussian plane (see below), so that the deflection of the electrons advantageously affects the parallel displacement of the partial beams forming parallel images in the second reciprocal plane without changing the angle between the partial beams perpendicular to the optical axis.

[0028] The term "parallel image" (or: substantially parallel angular image or momentum distribution image with substantially parallel partial beams) hereinafter refers to a momentum distribution image whose partial beams are parallel to the electron optical axis when passing through the second reciprocal plane and / or have such a minimum divergence angle: for the desired energy-resolved measurement of the electrons, the aberrations in the energy analyzer device (especially the imaging errors caused by the divergence angle) are negligibly small, and in particular do not cause any significant impairment of the energy spectrum characteristics (energy resolution, momentum resolution) of the energy analyzer device. The parallel image is composed of partial beams aligned perpendicularly or virtually perpendicularly to the second reciprocal plane. The partial beams enter the energy analyzer device as parallel beams. The substantially perpendicularly aligned partial beams extend within the angular range of electrons emitted from the sample to be detected in the subsequent energy analysis of the energy analyzer.

[0029] The control circuit of the first lens group is configured to generate a control voltage of the first lens group so that the first Gaussian image has a desired size. The geometric structure of the electron optical lens of the first lens group is preferably configured to generate a minimum possible Gaussian image of the source point of the electrons on the sample in the first Gaussian plane. For example, the optimization of the geometric structure of the electron optical lens is performed by numerical simulation.

[0030] The parallel image (parallel momentum distribution image in the exit plane) preferably has an angular deviation (divergence angle) of its partial beams of less than 0.4°, in particular preferably less than 0.2°. In simulations, the angular deviation has been shown to be sufficiently small (see below). Figure 2 ), without affecting subsequent imaging in the energy analyzer equipment.

[0031] According to another advantageous embodiment of the invention, the first lens group is configured to be able to generate a first Gaussian image having an extension of less than 1 mm, in particular less than 0.5 mm, perpendicular to the electron optical axis. For these size ranges, typical measurement tasks occurring in practice and in typical configurations of electron optical systems, a parallel momentum distribution image is advantageously obtained with sufficiently small angular deviations.

[0032] The control circuit of the deflector device is configured for scanning deflection of the momentum distribution image in a second reciprocal plane perpendicular to the electron optical axis. Thus, the electrons in the exit plane of the electronic imaging device undergo a scanning motion in a direction deviating from the extension of the entrance slit (also called slit or slit aperture) of the energy analyzer device, preferably in a direction perpendicular to the extension of the entrance slit. The configuration of the first lens group and the second lens group and the deflector device or the corresponding associated control circuit is adjusted based on calculations using electron optical imaging equations known per se and the geometrical dimensions of the electronic imaging device.

[0033] According to the second general aspect of the present invention, the above-mentioned object is achieved by an electron spectrometer device, which includes a sampler for holding a sample, an electronic imaging device according to the first general aspect of the present invention or an embodiment thereof, and an energy analyzer device. According to the present invention, the electronic imaging device is configured for the transfer and imaging of electrons emitted from the sample along the electron optical axis to the energy analyzer device, and for the scanning movement of the momentum distribution image perpendicular to the electron optical axis and along a deflection direction extending away from the entrance slit of the energy analyzer device, preferably along a deflection direction extending perpendicular to the entrance slit. The electronic imaging device is configured so that the momentum distribution image of the electrons emitted from the sample source point is generated as a parallel image in the entrance plane of the energy analyzer device.

[0034] The energy analyzer device is generally an electron optical imaging device configured for angular or momentum resolved detection of angular or momentum distribution imaging along at least one direction perpendicular to the electron optical axis. The energy analyzer device preferably includes a hemispherical analyzer (hemispherical electron energy analyzer). By using a hemispherical analyzer with an entrance slit, the angular distribution along the entrance slit direction and along the second offset direction can be determined by scanning movement of the momentum distribution image with the aid of a deflector device. As an alternative to using a hemispherical analyzer, the energy analyzer device may include other types of analyzers, such as a cylindrical analyzer or a 127° analyzer.

[0035] According to the third general aspect of the present invention, the above-mentioned object is achieved by an electron transfer method, wherein electrons are transferred from a sample along an electron optical axis to an energy analyzer device through an electronic imaging device. The sample preferably includes a solid sample, whose surface is exposed for irradiation with excitation light and emission to the electronic imaging device. Electrons emitted from a source point (the incident surface of the excitation light beam) are sequentially transferred through a first lens group on the sample side, a deflector device, and a second lens group on the analyzer side, wherein the electrons are deflected by the deflector device in an exit plane of the electronic imaging device along a deflection direction perpendicular to the electron optical axis and deviating from the extension of the entrance slit of the energy analyzer device, preferably along a deflection direction perpendicular to the extension of the entrance slit. According to the present invention, the first lens group forms a first reciprocal plane within the first lens group and a first Gaussian plane between the first lens group and the second lens group, a first momentum distribution image of the momentum distribution of electrons from the sample is generated in the first reciprocal plane, and a first Gaussian image of the source point is generated in the first Gaussian plane. In addition, the second lens group forms a second reciprocal plane on the analyzer side of the second lens group, and forms a second momentum distribution image of the momentum distribution of electrons from the sample in the second reciprocal plane. The first lens group generates a first Gaussian image with a sufficiently small size so that the second momentum distribution image generated by the second lens group is a parallel image. The electron transfer method is preferably performed by an electronic imaging device according to the first general aspect of the present invention or an embodiment thereof.

[0036] According to a fourth general aspect of the present invention, the above object is achieved by an electron spectroscopy method (a method for detecting the energy and momentum distribution of electrons that have been emitted from a sample), the method comprising: irradiating the sample and emitting electrons from the sample, transferring the emitted electrons to an energy analyzer device by an electron transfer method according to the third general aspect of the present invention or an embodiment thereof, and performing momentum and energy resolved detection of the electrons by the energy analyzer device. The electron spectroscopy method is preferably performed by an electronic imaging device according to the second general aspect of the present invention or an embodiment thereof.

[0037] The present invention advantageously provides an apparatus and method for substantially improving beam transfer of electrons emitted from a solid sample, preferably in a field-free environment, wherein the electrons are analyzed in an energy analyzer device according to their energy and momentum distribution. By generating a momentum distribution image as a parallel image, imaging errors that accompany the generation of angular images in real space in conventional electronic imaging devices are avoided. Since a suitably small Gaussian image of the area illuminated by the excitation source (sample source point) is positioned on the front focal plane of the second lens group, the momentum distribution image focused on the plane of the entrance slit of the energy analyzer device is generated from parallel partial beams in the rear reciprocal plane of this lens group, and all electrons enter the energy analyzer device substantially parallel to the electron optical axis. As a result, the angular deviation at the entrance of the energy analyzer device is reduced by 1 to 2 orders of magnitude compared to conventional methods. The first Gaussian image is generated by means of the first lens group, which preferably minimizes aberrations by means of an appropriate geometric structure.

[0038] Therefore, an important advantage of the present invention is that it can capture electrons emitted from the sample over a very large angular range. ‖ The relationship between the image angle α is proportional to the root of the energy: k ‖ ~sinα√E kin , so at lower kinetic energies (e.g., equal to or less than 5 electron volts under laser excitation), the angular spacing may be greater than + / - 30°, which greatly improves the efficiency of the energy analyzer. Particular advantages of the present invention also come from scanning the second momentum coordinate to measure the two-dimensional momentum distribution and the use of an imaging spin filter. By positioning the deflector device in the focus of the first Gaussian image and the second lens group, a parallel displacement of the momentum distribution image can be achieved in the entrance plane of the energy analyzer device, preferably using a single deflector unit, wherein the parallelism of the beam is maintained.

[0039] The aberrations of the combination of the lens group and the deflector device can be advantageously reduced to the minimum value theoretically possible, because the image reciprocal to the desired momentum distribution image (i.e. the first Gaussian image of the source point on the sample) is so small that the encoding of the momentum distribution image is defined with extremely high accuracy as a trajectory in this small Gaussian image. This feature distinguishes the present invention from all conventional beam transfer systems, in particular those according to [1, 2, 3, 4 and 5].

[0040] The inventors have found that the concept implemented in an electron microscope using the technique according to the invention, in particular the creation of a predetermined, well-focused real space image and a reciprocal image in a predetermined imaging plane using the optical image transformation theorem, not only serves to reduce aberrations in the electron energy spectrum in the electron optical system, but also provides an additional substantial advantage: since the first Gaussian image can be displaced along the electron optical axis by means of the first lens group, the tilt angles of the individual partial beams of the momentum distribution image can be minimized without losing the beam position at the entrance plane of the energy analyzer device. This allows the deflection technique to be used for scanning the second momentum direction, in particular the direction perpendicular to the entrance slit, even under high delay conditions (ratio of the initial kinetic energy of the electrons when they are emitted from the sample to the kinetic energy when they enter the energy analyzer device). The preferred embodiment of the second lens group in the form of a zoom lens (a lens configured for adjusting the image magnification and preferably comprising five or more lens elements) makes it possible to, in particular, vary the image size and the electron energy of the momentum image at the exit of the electron imaging device over a wide range, thereby adapting the momentum image size and energy to the desired conditions (energy resolution, momentum resolution) of the energy analyzer.

[0041] Creating a parallel image in the entrance plane of the energy analyser device also advantageously simplifies spin-resolved electron spectroscopy, since image errors on the spin filter crystal at the exit of the energy analyser are reduced or completely avoided.

[0042] Another particularly important advantage of the present invention is that the deflection of the momentum distribution image is simplified. Therefore, in a preferred embodiment of the present invention, it is proposed that the deflector device only acts on a single plane perpendicular to the electron optical axis. When the electron is transferred along the electron optical axis, the deflector device is actuated once when the electron passes through the space between the first lens group and the second lens group. This is advantageous in avoiding conventional, complex double deflectors, such as the deflector according to [2], without having to accept imaging errors. Particularly preferably, the deflection plane of the deflector device coincides with the first Gaussian plane (or another Gaussian plane, see below), so that an accurate parallel displacement of the momentum distribution image in the second reciprocal plane can be promoted by driving the deflector device. This completely avoids any additional beam tilt, such as the additional beam tilt described in [3] and [5].

[0043] Deflection in a single plane has the additional advantage that the deflector arrangement can have a particularly simple structure, for example a deflector element with a pair of electrically and / or magnetically acting deflector elements, a quadrupole arrangement or an octopole arrangement. In the case of electrical deflection, the deflector element comprises a deflection electrode, in the case of magnetic deflection, the deflector element comprises a deflection coil. The octopole arrangement advantageously allows a rotation of the deflection direction around the electron optical axis, so that the deflector arrangement can additionally rotate the direction of the displacement of the momentum distribution image relative to the alignment of the entrance slit of the energy analyser device, in this way, for example, any undesired image rotation caused by stray magnetic fields is compensated.

[0044] According to another advantageous embodiment of the electronic imaging device (hereinafter also referred to as the first embodiment), the second reciprocal plane is simultaneously the exit plane of the electronic imaging device, wherein the slit aperture forming the entrance slit of the energy analyzer device is arranged in the second reciprocal plane. This embodiment offers the advantages of direct adjustment of the parallel image upon entry into the energy analyzer device and a relatively compact structure.

[0045] According to an alternative embodiment of the electronic imaging device, it has at least one third lens group located between the second lens group and the energy analyzer device, the at least one third lens group being arranged on the analyzer side of the second lens group, i.e., in the overall arrangement structure of the electronic spectrometer device. The at least one third lens group forms a second Gaussian plane within the at least one third lens group and a third reciprocal plane on the analyzer side of the at least one third lens group, so that a second Gaussian image of the sample is created by the at least one third lens group in the second Gaussian plane, and a third momentum distribution image of the momentum distribution of electrons from the sample is created in the third reciprocal plane. The third reciprocal plane is the exit plane of the electronic imaging device and the entrance plane of the energy analyzer device, and the third momentum distribution image generated by the at least one third lens group is a parallel image. Even in the case of these alternative embodiments of the invention, a scanning motion of the momentum distribution image is provided, which affects the corresponding deflection of the momentum distribution image in the third reciprocal plane. The at least one third lens group is provided with a control circuit, which is configured to be able to apply a properly adjusted control voltage to the at least one third lens group for electron optical shaping of the third reciprocal plane and the second Gaussian plane. Arranging the at least one third lens group has the particular advantage that the beam energy in the parallel momentum distribution image can be varied in the entrance plane of the energy analyser device over a range of, for example, two orders of magnitude, thereby allowing an optimal resolution and transmission setting of the energy analyser device.

[0046] The slit diaphragm can be arranged in a second reciprocal plane in front of the third lens group to form an entrance slit of the energy analyzer device (hereinafter referred to as the second embodiment). In this case, the slit diaphragm is not directly located on the entrance plane of the energy analyzer device, but is located on a second reciprocal plane conjugate to the entrance plane in front of the third lens group that generates the parallel momentum distribution image, thereby generating a real image of the slit diaphragm covered by the parallel momentum distribution image on the entrance plane of the analyzer. In this arrangement structure, electrons can advantageously pass through the entrance slit with greater energy, which improves subsequent imaging in the energy analyzer device. Since the slit diaphragm is arranged in the second reciprocal plane, the slit diaphragm can be imaged as a real image in the entrance plane of the energy analyzer device, so that the effective slit diaphragm width in the entrance plane and the energy of the electrons can be changed electro-optically, while the physical slit diaphragm width is fixed.

[0047] Alternatively, the slit diaphragm forming the entrance slit of the energy analyzer device can be arranged in the third reciprocal plane and forms the entrance slit of the energy analyzer device, wherein, in this case, no slit diaphragm is arranged in the second reciprocal plane (hereinafter also referred to as the third embodiment). The third embodiment provides the particular advantage of being able to use an energy analyzer of conventional design, i.e. with an integrated entrance slit.

[0048] According to further variant embodiments of the present invention, a fourth lens group or further lens groups may be provided, each lens group being constructed like the third lens group and providing further Gaussian planes and reciprocal planes.

[0049] Advantageously, there are various options for positioning the deflector device. In particular, in the first, second and third embodiments of the invention, the deflector device can be arranged between the first lens group and the second lens group and in the first Gaussian plane. Alternatively, in the second and third embodiments of the invention, the deflector device can be arranged at the third lens group and in the second Gaussian plane. According to a further alternative, the deflector device can be arranged in another Gaussian plane in the fourth lens group or in a further lens group.

[0050] Another important difference with respect to the electron optical concept of an electron momentum microscope is achieved by an advantageous embodiment of the invention in which the foremost electron optical lens element of the sample side of the first lens group is configured to be able to have the same electrical potential as the sample. Advantageously, this allows the area around the sample to remain field-free, thereby also enabling the examination of samples with highly three-dimensional structures or crystallites without any significant field distortion due to the three-dimensional shape that would impair the momentum resolution.

[0051] For the displacement of the momentum distribution image in the second reciprocal plane, the deflector device particularly preferably acts on the first Gaussian plane. The arrangement structure located in the first Gaussian plane means that the deflector device generates a changing deflector field, which acts in a narrow range symmetrically around the first Gaussian plane. This embodiment has the following advantages: the entire electron beam is deflected particularly effectively, wherein the parallelism of the momentum image at the exit of the imaging device is maintained. Alternatively, when the third lens group is provided, a single deflector device can be arranged in the second Gaussian plane and act on the electrons in the second Gaussian image, wherein the parallelism of the momentum image is also maintained at the exit of the deflected imaging device.

[0052] According to another advantageous embodiment of the invention, it is proposed that the rearmost electron-optical lens on the analyzer side of the second lens group forms a field-free space in the region of the second reciprocal plane. Alternatively or additionally, it is proposed in the second or third embodiment that the third lens group has boundary elements at its ends, which are configured to be able to form a field-free space near both sides of the third lens group. This embodiment prevents any electrostatic feeding of electric fields that leads to a deflection of the electron path and thus to a distortion of the momentum image. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further details and advantages of the present invention are described below with reference to the accompanying drawings. The accompanying drawings show:

[0054] Figure 1 : A schematic diagram of a first embodiment of an electronic imaging device according to the present invention;

[0055] Figure 2 : Further illustration of the Gaussian images generated when the sample is excited by various excitation sources;

[0056] Figure 3 : A schematic diagram of a second embodiment of an electronic imaging device according to the present invention;

[0057] Figure 4 : A schematic diagram of a third embodiment of an electronic imaging device according to the present invention;

[0058] Figure 5 : Schematic diagrams of different variants of the deflector device;

[0059] Figure 6 : A schematic diagram of an embodiment of an electron spectrometer device according to the present invention;

[0060] Figure 7 : Beam trajectory diagram of a conventional transfer optical system (cited from [2]). DETAILED DESCRIPTION

[0061] The invention is described below with exemplary reference to an electron imaging device in combination with a hemispherical analyzer. The invention is not limited to the use of a hemispherical analyzer, but can also be performed with other types of energy analyzer devices. The details of exciting the sample and recording the energy distribution of the electrons emitted from the sample with a hemispherical analyzer are not described, because these are themselves known from conventional technology. The illustrations of the electron optical components in the accompanying drawings are schematic diagrams. Details such as the arrangement of the electron optical components in a vacuum space or the formation of electron optical lenses by spaced lens elements are not shown. Typically, for example, the electron optical lenses and the associated control circuits may be substantially the same as those known from conventional transfer optical systems.

[0062] Reference Figure 1 The drawings are described with reference to the relevant spatial directions shown in the figure, which in the position space include the z direction along the electron optical axis and the x and y directions perpendicular to this direction, wherein the slit aperture 201 in the entrance plane of the energy analyzer 200 (see also Figure 6 ) extends in the y direction. Therefore, the direction of the slit aperture defines the momentum coordinate k y The direction and the momentum coordinate k perpendicular to it x direction.

[0063] Figure 1 A first embodiment of an electronic imaging device 100 according to the present invention is shown in the form of an electron optical system, which is used to transfer and laterally shift a parallel momentum distribution image based on an electron optical cylinder having multiple lens groups 10, 30 and a field-free drift path 22 in which a deflector device 20 is arranged. Figure 1 A shows the structure of the electronic imaging device 100, Figure 1 B shows the simulated beam path of the real optics with the deflector arrangement 20 closed, Figure 1 C shows the Figure 1 B Simulated beam path of the same lens arrangement, but with the deflector device 20 activated by applying a suitable voltage to the deflector electrodes 21. Figure 1 B, Figure C and Figure 2 , Figure 3 and Figure 4 In all representations of the electron trajectories in the figures, the radial coordinates are radially magnified to show the details of the individual beams more clearly. The lens groups 10, 30 and the deflector device 20 are connected to a control device 50, which comprises a control circuit for energizing the electrodes of the electron optical lenses or assemblies 10, 20 and 30. The electronic imaging device 100 is arranged on a sample holder 101, the distance between the surface of the sample 1 and the front cover electrode 11 of the first lens group 10 being, for example, 15 mm, so that the sample 1 is located in the object plane of the first lens group 10. The length of the slit stop 201 is, for example, 20 mm to 40 mm and its width is, for example, 50 μm to 2 mm.

[0064] In particular, according to Figure 1 The first lens group 10 of A comprises a front cover electrode 11, a focusing electrode 12 and an adapter lens 13. In order to create a field-free space between the sample 1 and the first lens group 10, the sample holder 101 can be electrically connected to the front cover electrode 11 so that both components are at the same potential. The second lens group 30 comprises a plurality of lens elements 31, preferably forming a zoom lens, and a boundary element 32 for creating a field-free space between the last lens element and the slit stop 201 of the energy analyzer device 200. To this end, the boundary element 32 and the slit stop 201 are electrically connected to each other.

[0065] For example, a cylindrical element is provided to form a field-free drift path 22 between the first lens group 10 and the second lens group 30, the length of the cylindrical element being such that any feed to adjacent lens groups is reduced and there is no longer any significant electric field, which would cause electron trajectories in the region of the Gaussian image to deflect at the deflector device when the deflector device is closed.

[0066] For example, the deflector device 20 comprises an octupole arrangement of deflection electrodes 21, or alternatively comprises a further electrode arrangement (see Figure 5 ). The deflector arrangement 20 is preferably a single deflector, ie the electron is deflected only once when it passes through the first Gaussian plane on its path along the electron optical axis OA between the sample and the second reciprocal plane.

[0067] When the sample 1 is excited by light (see also Figure 2 ), a collection of electrons 2 are emitted from the sample ( Figure 1 B), wherein the electron 2 is imaged by the first lens group 10 to reach a predetermined emission angle of, for example, + / -15° along the electron optical axis OA. Figure 1 B, the first lens group 10 generates a reciprocal image of the sample source point that emits electrons 2 in the first reciprocal plane RP1 and generates a first Gaussian image of the sample source point in the first Gaussian plane GP1 which is the back focal plane of the first lens group 10. The second reciprocal image (the momentum distribution image with parallel partial beams) is imaged onto the entrance slit of the energy analyzer device 200 by the second lens group 30. Therefore, it is ensured that all electrons enter the energy analyzer device 200 as parallel partial beams with a very small angular deviation. The first lens group 10 is controlled so that the intersection of the first Gaussian plane GP1 and the electron optical axis OA is located in the deflection plane of the deflector device 20, in particular, at the center of the deflector device 20. Centering the Gaussian image on the deflector device 20 allows precise parallel displacement of the momentum distribution image with parallel partial beams generated by the second lens group 30 in the second reciprocal plane RP2. As shown Figure 1 By applying suitable voltages to the deflector device 20, a parallel displacement of the momentum distribution image in the second reciprocal plane RP2 is possible without additional beam tilting, as shown in FIG.

[0068] Figure 1 C shows the effect of the deflector device 20 acting on the first Gaussian plane GP1 to provide an optimized lens geometry and practical measurement conditions (angular spacing of + / -15°, kinetic energy of 16 eV about the sample, which is suitable for a conventional vacuum ultraviolet laboratory light source). In the example shown, the momentum distribution image on the analyzer side in the second reciprocal plane RP2 is parallel-displaced by the momentum radius R at the power of the deflection device 20 set by the voltage on the deflection electrode 21. At the parallel displacement, the parallelism and the diameter 2R of the momentum distribution image are preserved. Therefore, by continuously changing the deflection force of the deflector device 20 by means of the control circuit (control device 50), a two-dimensional momentum image can be completely scanned.

[0069] Figure 2 The example of the case where electrons 2 are generated using different excitation sources (not shown) is shown. Figure 1 B shows the trajectory of the electron beam 2, where Figure 2 A shows the excitation by a beam of synchrotron radiation or laser, Figure 2 B shows the excitation by a focused vacuum UV excitation source, Figure 2 C shows excitation by an unfocused vacuum UV excitation source.

[0070] The angle θ specifies the emission angle of the electrons from the sample relative to the electron optical axis OA, and the angle α is the (half) opening angle of the beam of the momentum distribution image in the second reciprocal plane RP2 corresponding to a specific emission angle. This opening angle α of the partial beam (in Figure 2 It is barely visible in the detail of A, but Figure 2 The size of the electron source region (clearly visible in the detail image of C) is determined by the size of the electron source area on the sample surface and therefore by the profile of the excitation beam and its angle of incidence on the sample.

[0071] Practical calculations were performed using a trajectory simulation program (SIMION 8.0) for a practical embodiment of the electronic imaging device 100 according to the invention, wherein three Figure 2 . The distance along the axial coordinate z between the surface of the sample 1 and the momentum distribution image in the second reciprocal plane RP2 is 462 mm. The electron optical lens is aberration-minimized, in this case a reduced image of the source area on the sample is arranged in the Gaussian plane GP1 with a magnification factor M=0.6. Other magnification factors, even magnification factors M greater than 1, are also possible in the present invention.

[0072] Simulations for an angular acceptance range of θ=15° gave the following parameters: In all three cases the momentum distribution image in the second reciprocal plane RP2 has a radius R of 4.3 mm. The tilts of the central rays of the beam (=deviation from a parallel beam) are all less than 0.09°, which, as expected, does not depend on the size of the source region.

[0073] For excitation by synchrotron radiation or laser sources ( Figure 2 A), assuming that the conventional size of the beam on the sample is 50 μm. Due to the large angular range of θ=15°, the first Gaussian image in the first Gaussian plane GP1 is widened by the spherical aberration of the first lens group 10 and has a radius of r~40 μm. The partial beam in the plane RP2 has an opening angle α of less than or equal to 0.16°. For example, this value is almost better than the conventional one such as Figure 7 The corresponding value of the angular divergence in the transfer lens system shown is two orders of magnitude smaller.

[0074] Focused vacuum UV light source ( Figure 2 B) with a conventional spot size of 200 μm. In this case, the first Gaussian image in the first Gaussian plane GP1 has a radius of 80 μm, and the beam opening angle, ie the angular divergence produced in the momentum image in the plane RP2, is α less than or equal to 0.2°.

[0075] For unfocused vacuum UV laboratory light sources ( Figure 2 C) The excitation beam has a regular diameter of, for example, 0.5 mm, which in the first Gaussian plane GP1 produces a first Gaussian image with a radius r = 155 μm. Here, the opening angle of the beam in the plane RP2 is α ~ 0.35°. Figure 2 The detail of C is radially magnified to make small angles clearly visible. In this case, the momentum distribution image in the second reciprocal plane RP2 is also sharply focused, and the electrons enter the energy analyzer device 200 as a parallel beam with minimal divergence.

[0076] Figure 3 A preferred variation of the second embodiment of the electronic imaging device 100 according to the present invention is shown, wherein Figure 1Components 10, 20 and 30 and their components are provided as shown. Different from the first embodiment, a third lens group 40 is additionally provided, which generates a second Gaussian image in the second Gaussian plane GP2 on the analyzer side, behind the slit aperture 201, and generates a third momentum distribution image with parallel partial beams in the third reciprocal plane RP3. The third reciprocal plane RP3 is the entrance plane of the energy analyzer device 200 so that the electrons 2 enter the energy analyzer device 200 as parallel beams. The third lens group 40 includes an electron optical lens element 42 forming a zoom lens. The lens element 42 and the associated control circuit (not shown) are configured so that the lateral magnification of the electron energy and the momentum distribution image in the reciprocal plane RP3 is variable to optimize the energy and / or momentum resolution of the energy analyzer device 200. At the end of the zoom lens including the lens element 42, boundary elements 41 and 43 are provided, which are arranged to be able to create a field-free space at the end of the zoom lens and to minimize any feed-in of the electric field from the region of the slit diaphragm 201 and the entrance of the energy analyzer device 200 at the third reciprocal plane RP3. In this embodiment, there is an image of the slit diaphragm 201 in the entrance plane of the energy analyzer device 200, but there is no physical slit, i.e. no physical slit diaphragm.

[0077] Figure 4 A preferred variant of the third embodiment of the electronic imaging device 100 according to the invention is shown, in which a third lens group 40 with a lens element 42 and boundary elements 41, 43 is also provided. However, in the case of the third embodiment, the slit aperture 201 is arranged in the third reciprocal plane RP3 of the entrance of the energy analyzer device 200. In this case, the third lens group 40 comprises a lens element 42 forming a zoom lens, which allows to vary the electron energy and the lateral magnification of the momentum distribution image in the third reciprocal plane RP3 within a wide range in order to optimize the energy and momentum resolution of the energy analyzer device 200. In this case, a conventional energy analyzer with an integral entrance slit can be used.

[0078] Figure 5 20 that may be provided in various embodiments. Figure 5 The deflector device 20 of A comprises at least two electrodes 21 (referred to as a parallel plate deflector), or according to Figure 5 B, the deflector device 20 comprises four electrodes 21 in one plane (called xy deflector), or according to Figure 5 C, the deflector device 20 comprises eight electrodes 21 in one plane (called an octupole arrangement or an octupole deflector). Figure 5The embodiment of C is particularly advantageous because, by means of appropriate voltages on the eight electrodes 21, deflection can be effected in any plane so that the deflection plane is aligned exactly in the x direction, that is to say exactly perpendicular to the direction of the entrance slit 201, as shown in FIG. Figure 1 B and 1C. In addition, the octupole arrangement enables correction of undesired image rotations due to longitudinal stray magnetic fields that may occur during the scanning process.

[0079] Figure 6 is a schematic diagram of an embodiment of an electronic spectrometer device 300, the electronic spectrometer device 300 includes, for example, Figure 1 , Figure 3 or Figure 4 The electron imaging device 100 of any of the figures and the energy analyzer device 200 in the form of a hemispherical analyzer having an electron detector 202. When the electron energy spectrum method is implemented, the electrons emitted from the sample 1 on the sample holder 101 are transferred to the energy analyzer device 200 along the electron optical axis OA through the electron imaging device 100. The energy and momentum distribution of the electrons are recorded by capturing the momentum distribution image of the electrons along the first momentum coordinate along the slit aperture 201 and by stepwise shifting the momentum distribution image perpendicular to the slit aperture 201, so that the complete two-dimensional momentum distribution can be recorded.

[0080] The features of the invention disclosed in the above description and the drawings are important for realizing the invention individually or in combination or in subcombination in its various embodiments.

[0081] Reference numerals list

[0082] 100 Electronic imaging equipment

[0083] 101 Sample Holder

[0084] 200 Energy Analyzer Equipment

[0085] 201 Slit aperture

[0086] 202 Electronic Detector

[0087] 300 Electron Spectrometer Equipment

[0088] 1 Sample

[0089] 2 Electronics

[0090] 10 The first lens group

[0091] 11 Front cover electrode

[0092] 12 Focusing Electrode

[0093] 13 Adapter lens

[0094] 20 Deflector device

[0095] 21 Deflector element

[0096] 22 Drift tube

[0097] 30 Second lens group

[0098] 31 Lens elements

[0099] 32 Boundary elements

[0100] 40 The third lens group

[0101] 41 Boundary elements

[0102] 42 Zoom lens

[0103] 43 Boundary Elements

[0104] 50 Control device

[0105] RP1 First reciprocal plane (momentum image plane)

[0106] GP1 First Gaussian plane (plane of real space image)

[0107] RP2 Second reciprocal plane

[0108] GP2 Second Gaussian plane

[0109] RP3 Third reciprocal plane

[0110] OA optical axis

[0111] θ Emission angle relative to OA

[0112] α beam opening angle

[0113] R is the radius of the momentum distribution image.

[0114] r is the radius of the Gaussian image

[0115] x,y,z coordinates

[0116] k x ,k y ,k z Momentum coordinates

Claims

1. An electron imaging device (100) configured for electron transfer from a sample (1) emitting electrons (2) to an energy analyzer device (200) along an electron optical axis (OA), and comprising a first lens group (10) on the sample side and a second lens group (30) on the analyzer side and a deflector device (20) configured to be able to deflect electrons (2) in an exit plane of the electron imaging device (100) along a deflection direction perpendicular to the electron optical axis (OA), characterized in that: - the first lens group (10) provides a first reciprocal plane (RP1) within the first lens group (10), provides a first Gaussian plane between the first lens group and the second lens group (10, 30), and is configured to be able to generate a first momentum distribution image of the momentum distribution of electrons (2) from the sample (1) in the first reciprocal plane (RP1), and to generate a first Gaussian image of the sample (1) in the first Gaussian plane (GP1), - the second lens group (30) provides a second reciprocal plane (RP2) on the analyzer side of the second lens group (30), and is configured to be able to generate a second momentum distribution image of the momentum distribution of electrons (2) from the sample (1) in the second reciprocal plane (RP2), wherein, - the first lens group (10) is configured to be able to generate a first Gaussian image having a small size, so that the second momentum distribution image generated by the second lens group (30) is a parallel image, - The deflector device (20) acts on the first Gaussian plane (GP1) or another Gaussian plane so that the deflection of the electrons (2) causes a parallel displacement of the partial beams forming the parallel image in the second reciprocal plane (RP2) without changing the angle between the partial beams perpendicular to the electron optical axis (OA).

2. The electronic imaging device according to claim 1, wherein: The deflector device (20) is configured such that the deflector device (20) acts on a single plane perpendicular to the optical axis (OA).

3. An electronic imaging device according to claim 1 or 2, wherein: The deflector device (20) comprises a pair of electrically and / or magnetically acting deflector elements (21), four deflector elements (21) in a quadrupole arrangement on one plane or eight deflector elements (21) in an octupole arrangement on one plane.

4. The electronic imaging device according to claim 1 or 2, wherein: - the second reciprocal plane (RP2) is the exit plane of the electronic imaging device (100), - the slit aperture (201) is arranged in the second reciprocal plane (RP2) forming the entrance slit of the energy analyzer device (200).

5. The electronic imaging device according to claim 1 or 2, further comprising: - at least one third lens group (40), which is arranged on the analyzer side of the second lens group (30) and forms a second Gaussian plane (GP2) in the at least one third lens group (40), forms a third reciprocal plane (RP3) on the analyzer side of the at least one third lens group (40), and is configured to be able to generate a second Gaussian image of the sample (1) in the second Gaussian plane (GP2) and generate a third momentum distribution image of the momentum distribution of electrons (2) from the sample (1) in the third reciprocal plane (RP3), wherein, - the third reciprocal plane (RP3) is an exit plane of the electronic imaging device (100), and - the third momentum distribution image generated by the at least one third lens group (40) is a parallel image.

6. The electronic imaging device according to claim 5, wherein: A slit diaphragm (201) is arranged in the second reciprocal plane (RP2), said slit diaphragm (201) forming an entrance slit of the energy analyzer device (200) by imaging into the entrance plane of the energy analyzer device (200).

7. The electronic imaging device according to claim 5, wherein: - a slit aperture (201) is arranged in the third reciprocal plane (RP3) forming an entrance slit of the energy analyzer device (200), wherein, - no slit aperture is arranged in the second reciprocal plane (RP2).

8. The electronic imaging device according to claim 1 or 2, wherein: The deflector device (20) is arranged between the first lens group and the second lens group (10, 30) and is located in the first Gaussian plane (GP1).

9. An electronic imaging device according to claim 5, wherein: The deflector device (20) is arranged at the third lens group (40) and is located in the second Gaussian plane (GP2).

10. The electronic imaging device according to claim 1 or 2, wherein: - the first lens group (10) is configured to generate a first Gaussian image having an extension of less than 1 mm perpendicular to the electron optical axis (OA), and / or - the first lens group and the second lens group (10, 30) are configured to form parallel images, the angular deviation of the partial beams of the parallel images being less than 0.4°.

11. The electronic imaging device according to claim 1 or 2, wherein: The foremost sample-side electron optical element (11) of the first lens group (10) is configured to be able to have the same electrical potential as the sample (1) in order to generate a field-free region in front of the sample.

12. The electronic imaging device according to claim 1 or 2, wherein: The deflector means (20) are coupled to control means (50) configured for scanning deflection of the electrons (2) in an exit plane of the electronic imaging device while maintaining a parallel image.

13. The electronic imaging device according to claim 10, wherein: The extension of the first Gaussian image is less than 0.5 mm.

14. The electronic imaging device according to claim 10, wherein: The angular deviation is less than 0.2°.

15. An electron spectrometer device (300), comprising: - a sample holder (101) configured to hold a sample (1), - an electronic imaging device (100) according to any one of claims 1 to 14, - an energy analyzer device (200), wherein: The electron imaging device (100) is configured for electron transfer of electrons emitted from the sample (1) along an electron optical axis (OA) to an energy analyzer device (200).

16. The electron spectrometer device according to claim 15, wherein: - The energy analyzer device (200) comprises a hemispherical analyzer.

17. An electron transfer method, wherein: Electrons (2) from a sample (1) are transferred from an electron imaging device along an electron optical axis (OA) to an energy analyzer device (200), wherein the electrons (2) sequentially pass through a first lens group (10) on the sample side and a second lens group (30) on the analyzer side and the electrons (2) are deflected by a deflector device (20) in a deflection direction perpendicular to the electron optical axis (OA) in an exit plane of the electron imaging device (100), characterized in that: - the first lens group (10) forms a first reciprocal plane (RP1) within the first lens group (10), a first Gaussian plane (GP1) is formed between the first lens group and the second lens group (30), and A first momentum distribution image of the momentum distribution of electrons (2) from a sample (1) is generated in a first reciprocal plane (RP1), and a first Gaussian image of the sample (1) is generated in a first Gaussian plane (GP1). - a second lens group (30) forms a second reciprocal plane (RP2) on the analyzer side of the second lens group (30), and a second momentum distribution image of the momentum distribution of electrons (2) from the sample (1) is generated in the second reciprocal plane (RP2), wherein - the first lens group (10) generates a first Gaussian image with a small size, so that the second momentum distribution image generated by the second lens group (30) is a parallel image, - wherein the deflector device (20) acts on the first Gaussian plane (GP1) or another Gaussian plane, so that the deflection of the electrons (2) causes a parallel displacement of the partial beams forming the parallel image in the second reciprocal plane (RP2) without changing the angle between the partial beams perpendicular to the electron optical axis (OA).

18. The electron transfer method according to claim 17, wherein: The deflector device (20) is configured such that the deflector device (20) acts in a single plane perpendicular to the optical axis (OA).

19. The electron transfer method according to any one of claims 17 to 18, wherein: - the second reciprocal plane is the exit plane of the electronic imaging device, - the slit aperture (201) forming the entrance slit of the energy analyzer device (200) is arranged in the second reciprocal plane.

20. The electron transfer method according to any one of claims 17 to 18, wherein: - at least one third lens group (40) arranged on the analyzer side of the second lens group (30) forms a second Gaussian plane (GP2) in the at least one third lens group (40), forms a third reciprocal plane (RP3) on the analyzer side of the at least one third lens group (40), and generates a second Gaussian image of the sample (1) in the second Gaussian plane (GP2), and generates a third momentum distribution image of the momentum distribution of electrons (2) from the sample (1) in the third reciprocal plane (RP3), wherein, - the third reciprocal plane (RP3) is an exit plane of the electronic imaging device (100), and - the third momentum distribution image generated by the at least one third lens group (40) is a parallel image.

21. The electron transfer method according to claim 20, wherein: A slit diaphragm (201) is arranged in the second reciprocal plane (RP2), said slit diaphragm (201) forming an entrance slit of the energy analyzer device (200) by imaging into the entrance plane of the energy analyzer device (200).

22. The electron transfer method according to claim 20, wherein: - a slit aperture (201) is arranged in the third reciprocal plane (RP3) forming an entrance slit of the energy analyzer device (200), wherein, - no slit aperture is arranged in the second reciprocal plane (RP2).

23. The electron transfer method according to claim 17 or 18, wherein: - The deflector device (20) is arranged in a first Gaussian plane (GP1).

24. The electron transfer method according to claim 20, wherein: The deflector device (20) is arranged at the at least one third lens group (40) and is located in the second Gaussian plane (GP2).

25. The electron transfer method according to claim 17 or 18, wherein: - the first lens group (10) generates a first Gaussian image having an extension perpendicular to the electron optical axis (OA) of less than 1 mm, and / or - the first lens group and the second lens group (30) are configured to form parallel images, the angular deviation of the partial beams of the parallel images being less than 0.4°.

26. The electron transfer method according to claim 17 or 18, wherein: The foremost sample-side electron optical element (11) of the first lens group (10) has the same electrical potential as the sample (1) in order to generate a field-free region in the region of the sample.

27. The electron transfer method according to claim 17 or 18, wherein: - The electrons (2) in the exit plane of the electron imaging device (100) are deflected to produce a scanning motion of the momentum distribution image while maintaining a parallel image.

28. The electron transfer method according to claim 25, wherein: The extension of the first Gaussian image is less than 0.5 mm.

29. The electron transfer method according to claim 25, wherein: The angular deviation is less than 0.2°.

30. An electron spectroscopy method, comprising the following steps: - irradiating the sample (1) and emitting electrons from the sample (1), - transferring the emitted electrons (2) to an energy analyzer device (200) by an electron transfer method according to any one of claims 17 to 29, and - energy-resolved detection of the electrons (2) by the energy analyzer device (200).

31. The electron spectroscopy method according to claim 30, wherein: - The energy analyzer device (200) comprises a hemispherical analyzer.

Images