X-RAY APPARATUS, ELECTRON EMISSION DEVICE AND MANUFACTURING METHOD

Abstract

In an embodiment an X-ray apparatus includes at least one of an X-ray source configured for generating X-rays or an X-ray detector configured for detecting X-rays, a housing in which the at least one of the X-ray source or the X-ray detector is located, the housing having an opening and a window covering the opening, wherein the window is configured to be passed by the X-rays, wherein the window comprises a transmission layer, and wherein the transmission layer is a carbon layer of glassy carbon.

Claims

1. An X-ray apparatus comprising: at least one of an X-ray source configured for generating X-rays or an X-ray detector configured for detecting X-rays; a housing in which the at least one of the X-ray source or the X-ray detector is located, the housing comprises an opening; and a window covering the opening, wherein the window is configured to be passed by the X-rays, wherein the window comprises a transmission layer, and wherein the transmission layer is a carbon layer of glassy carbon.

2. The X-ray apparatus according to claim 1, wherein a thickness of the carbon layer is at least 50 nm and at most 50 m.

3. The X-ray apparatus according to claim 1, wherein the transmission layer is self-supporting and consists of the carbon layer at least in a central portion of the window layer.

4. The X-ray apparatus according to claim 1, wherein the window layer comprises a supporting structure which is a grid structure or a bar structure.

5. The X-ray apparatus according to claim 1, wherein a ratio of a mean diameter of the carbon layer and a thickness of the carbon layer is at least 10 and at most 107.

6. The X-ray apparatus according to claim 1, wherein the glassy carbon is an amorphous material.

7. The X-ray apparatus according to claim 6, wherein, seen in top view and by transmission electron microscopy, the carbon layer comprises filaments with a length-to-width ratio of at least 10.

8. An electron emission device comprising: an electrically conductive base layer; an intermediate layer directly on the base layer, wherein the intermediate layer is of a material having a band gap leading to a higher energy of a conduction band edge of the intermediate layer compared to the base layer, and wherein a breakdown voltage of the intermediate layer exceeds a work function of the gate layer divided by the elementary charge; and an electrically conductive gate layer directly on a side of the intermediate layer remote from the base layer, wherein the gate layer is a carbon layer of glassy carbon, and wherein the electron emission device is configured to emit electrons through the gate layer upon applying a voltage between the base layer and the gate layer.

9. The electron emission device according to claim 8, wherein a thickness of the carbon layer is at least one monolayer and is at most 20 nm, and wherein the band gap of the intermediate layer is at least 4 eV.

10. The electron emission device according to claim 8, wherein the glassy carbon is an amorphous material.

11. The electron emission device according to claim 10, wherein, seen in top view and by transmission electron microscopy, the carbon layer comprises filaments with a length-to-width ratio of at least 10.

12. The electron emission device according to claim 8, wherein the base layer is also of glassy carbon.

13. The electron emission device according to claim 12, wherein the intermediate layer is of hexagonal boron nitride.

14. The electron emission device according to claim 8, further comprising a first electric contact structure, wherein the first electric contact structure comprises at least one of a grid structure or a bar structure extending across the gate layer and directly located at the gate layer, wherein a thickness of the first electric contact structure exceeds a thickness of the carbon layer by at least a factor of 102, and wherein the first electric contact structure is of glassy carbon as well.

15. The electron emission device according to claim 8, wherein the gate layer has a specific electric conductivity of at least 103 S/m.

16. The electron emission device according to claim 8, wherein the electron emission device is configured for a bending radius of 1 cm or less.

17. A manufacturing method for a carbon layer comprising: applying an organic raw material onto a substrate, the raw material being applied as a liquid; solidifying the raw material so that a raw material layer is formed; and pyrolizing the raw material layer at a temperature of at least 400 C. and of at most 2000 C. so that a carbon layer of glassy carbon is formed, wherein the carbon layer is a transmission layer in a window covering an opening in a housing of an X-ray apparatus that comprises at least one of an X-ray source configured for generating X-rays or an X-ray detector configured for detecting X-rays, or the carbon layer is a gate layer directly located on an intermediate layer of a material having a band gap leading to a higher energy of a conduction band edge of the intermediate layer compared to the base layer, and a breakdown voltage of the intermediate layer exceeds a work function of the gate layer divided by the elementary charge directly on an electrically conductive base layer in an electron emission device configured to emit electrons through the gate layer upon applying a voltage between the base layer and the gate layer.

18. The method according to claim 17, wherein the substrate is the intermediate layer.

19. The method according to claim 17, wherein the substrate is an auxiliary carrier or a starting material for a frame or a supporting structure, and wherein the method further comprises: removing the substrate partially or completely from the carbon layer.

20. The method according to claim 17, further comprising structuring the raw material layer so that a shape of the carbon layer is determined prior to pyrolizing the raw material layer, wherein the raw-material is a photo-resist or a photo-sensitive lacquer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] FIGS. 1 and 2 are schematic sectional views of exemplary embodiments of X-ray apparatuses described herein;

[0086] FIGS. 3 and 4 are schematic sectional views of exemplary embodiments of windows for X-ray apparatuses described herein;

[0087] FIG. 5 is a schematic top view of the window of FIG. 4;

[0088] FIG. 6 is a schematic sectional view of an exemplary embodiment of a window for X-ray apparatuses described herein;

[0089] FIG. 7 is a schematic top view of the window of FIG. 6;

[0090] FIGS. 8 and 9 are schematic top views of exemplary embodiments of windows for X-ray apparatuses described herein;

[0091] FIGS. 10 and 11 are schematic sectional views of exemplary embodiments of X-ray apparatuses described herein;

[0092] FIGS. 12 to 14 are schematic sectional views of exemplary embodiments of electron emission devices described herein;

[0093] FIG. 15 is a sectional view of an interface between a gate layer and in insulation layer of a modified electron emission device;

[0094] FIG. 16 is a representation of electrical data of an exemplary embodiment of an electron emission device described herein;

[0095] FIG. 17 is a schematic top view of an exemplary embodiment of a carbon layer for X-ray apparatuses and electron emission devices described herein;

[0096] FIG. 18 is a schematic block diagram of an exemplary embodiment of a manufacturing method for X-ray apparatuses and electron emission devices described herein;

[0097] FIGS. 19 to 21 are schematic sectional views of method steps of an exemplary embodiment of a manufacturing method for X-ray apparatuses and electron emission devices described herein; and

[0098] FIG. 22 is a schematic sectional view of an exemplary embodiment of a window for X-ray apparatuses described herein; and

[0099] FIGS. 23 and 24 are schematic top views of exemplary embodiments of gate layers for electron emission devices described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0100] FIGS. 1 and 2 illustrate exemplary embodiments X-ray apparatuses 1 configured as an X-ray source 21. The X-ray source comprises a housing 3 in which an electron source 210 is placed. For example, the electron source 210 is a heated wire. However, the electron source 210 may also be an electron emission device 10 as described, for example, in connection with FIGS. 12 to 16.

[0101] The electron source 210 may be mounted on a base plate 32 of the housing 3 and may be surrounded by a tube 31 of the housing 3. At a side of the tube 31 remote from the electron source 210, there is an opening 33.

[0102] The opening 33 is closed by a window 4. Between the electron source 210 and the window 4 or the tube 31 next to the window 4, by means of electrodes, not shown, a suitable electric field is applied to accelerate electrons from the electron source 210 towards a target 35. For example, the target 35 is a layer of a target material, like a metal. When the accelerated electrons hit the target 35, subsequently X-rays are produced. As an option, electron optics 34 can be provided in the housing 3.

[0103] The window 4 seals an interior of the housing 3. The interior is, for example, an evacuated space 30. Thus, the window 4 needs to be sufficiently mechanically stable to bear a pressure difference of around 1 bar between the interior and an exterior of the housing, and has to be translucent for the produced X-rays. Optionally, the window 4 needs to carry the target 35 as well.

[0104] According to FIG. 1, the target 35 is located on a side of the window 4 facing the electron source 210. The electrons are straightly accelerated on the target 35 and, thus, on the window 4. Contrary to that, in FIG. 2 the window 4 is a side window on a lateral side of the tube 31, and the target 35 is a separate component. Hence, in FIG. 2 the window 4 is not or not significantly hit by the electrons.

[0105] The window 4 comprises glassy carbon, GC. Especially, that part of the window 4 that mechanically carries the window is of GC. In other words, without the GC the window 4 would not be mechanically stable in the intended use of the X-ray apparatus 21.

[0106] Although the apparatus 1 is referred to as an X-ray apparatus, as in all other embodiments the same concept can be applied not only for an X-ray source, but also for particle sources, for example, of electrons or protons, and may also be extended to other apparatuses like XUV or UV sources. However, in each case the window 4 comprising or consisting of the carbon layer 5 made of GC is present.

[0107] In FIGS. 3 to 9, some examples of windows 4 are shown. In each case, the window 4 comprises a transmission layer 43 made of GC so that the transmission layer 43 is a carbon layer 5.

[0108] According to FIG. 3, the window 4 can consist of the transmission layer 43. However, as an option, in addition there can be the target 35 as a further layer on the transmission layer 43 so that an exterior face 40 of the window 4 is of the transmission layer 43 and an interior face 41 is of the target 35. Further, it is possible that at least one adhesive layer, not shown, is located between the target 35 and the transmission layer 43. Such a layer for the target 35 and such an adhesive layer can be present in all the other examples of the window 4 as well.

[0109] Such a window 4, that is, the transmission layer 43 and the optional target 35, may directly be mounted on the opening 33 to close the housing 3.

[0110] In FIGS. 4 and 5 it is shown that the window 4 further comprises a frame 45. The frame 45 completely surrounds a central portion 44 of the transmission layer 43. Thus, the central portion 44 is free of the frame 45. Seen in cross-section and at each lateral face of the window, the frame 45 may be of L-shape. Seen in top view, the frame 45 may be annular. The transmission layer 43 may be located on an inner side of the frame 45 so that the exterior face 40 is next to the frame 45.

[0111] For example, the central portion 44 refers to a middle-most area having at least 20% of an overall area content of the transmission layer 43, seen in top view of the exterior face 40. For example, the transmission layer 43 is circular or elliptic or square of polygonal, seen in top view.

[0112] Such a window 4 may be mounted to the housing 3 by means of the frame 45 so that the transmission layer 43 may be distant from the housing 3 due to the frame 45 and possibly due to the target 35.

[0113] In the embodiment of FIGS. 6 and 7, the frame 45 is located on the interior face 41. It is possible that the transmission layer 43 and the frame 45 terminate flush with each other in a longitudinal direction. Hence, the frame 45 and the transmission layer 43 may have the same shape and/or may have congruent outer edges, seen in top view.

[0114] The windows 4 shown in FIGS. 8 and 9 additionally comprise a supporting structure 42. The supporting structure 42 is located on at least one of the interior face 41 or the exterior face 40. The supporting structure 42 can also be of GC, or the supporting structure 42 is of a different material compared with the transmission layer 43. The supporting structure 42 and the transmission layer 43 can be in direct contact with each other or there is an adhesion layer in-between. Such at least one adhesion layer, not shown in the drawings, may alternatively or additionally also be used to assemble the frame 45 and/or the target 35, if present.

[0115] According to FIG. 8, the supporting structure 42 is made of one or of a plurality of bars that may run in parallel with each other. Contrary to that, in FIG. 9 it is shown that the supporting structure 42 forms a grid, seen in top view. Said grid may be a regular pattern, for example, a square, rectangular or hexagonal pattern.

[0116] Such a supporting structure 42 can be present in all the other examples of the window 4 as well. Further, as stated above, all the windows 4 may comprise the target 35 and alternatively or additionally the at least one adhesive layer. These windows 4 having the carbon layer 5 can be used for all the examples of the X-ray apparatus. Furthermore, as stated above, the optional supporting structure 42 can be attached by using an adhesive layer as well.

[0117] The X-ray apparatus 1 of FIG. 10 comprises an X-ray detector 22 and is therefore for detecting X-rays. Alternatively, the apparatus may serve as a detector for gamma rays or particles like electrons or protons.

[0118] The X-ray detector 22 is, for example, a silicon drift detector. The window 4 is located in the opening 33 in the housing 3. As also possible for the apparatuses of FIGS. 1 and 2, the window 4 may terminate flush with the housing 3 at least one of the exterior side 40 or the interior side 41.

[0119] Otherwise, the same as to FIGS. 1 to 9 may also apply to FIG. 10, and vice versa.

[0120] In FIG. 11 an X-ray apparatus 1 is shown that comprises both the X-ray source 21 and the X-ray detector 22, for example, configured as explained in connection with FIGS. 1, 2 and/or 10. As an option, the X-ray apparatus 1 may further comprise at least one of a display 24, a control unit 25 and an energy source 26, like a battery. By way of example, the X-ray apparatus 1 may be a hand-held apparatus used for material analysis.

[0121] In FIGS. 12 to 14, another application for the carbon layer 5 is illustrated. The carbon layer 5 is used, at least, as a gate layer 13 in an electron emission device 10 which is configured as a GIS structure. The GIS structure further comprises an electrically conductive base layer 11, like a carrier, an electrically insulating intermediate layer 12 directly thereon and the carbon layer 5, that is, the gate layer 13, directly on the intermediate layer 12.

[0122] In a GIS structure, field emission allows electrons to tunnel into the conduction band of the intermediate layer 12 when a voltage is applied between the base layer 11 and the gate layer 13. If there is a sufficient voltage drop and low scattering probability, these hot electrons can be emitted through the gate layer 13 into a space above the gate layer 13. An energy that can be achieved by the electrons is limited by the dielectric strength and/or by the lifetime of the intermediate layer 12. As the voltage increases, for a given thickness of the intermediate layer 12, the tunneling current increases and consequently the stress increases and thus the lifetime decreases. To a certain extent, the thickness of the intermediate layer 22 can be increased to reduce the tunnel current at a given voltage, but in doing so, stray effects increase, decreasing efficiency. Similarly, the maximum charge transported by the tunneling process before a breakdown can decrease with increasing thickness.

[0123] An energy range for the emitted electrons of, for example, up to 50 eV is possible. In this type of electron emitter, the actual tunnel barrier is the interface between the intermediate layer 12 and the base layer 11, which is thus not exposed to the influence of an environment of the device 10. This principle thus works not only in vacuum but also at atmospheric pressure around the device 10 as well as in liquids, making an evacuated package superfluous. Since the electron energy can be adjusted in a certain range, via the voltage as well as for a constant electric field via the thickness of the intermediate layer 12, an electron source with variable electron energy can thus be realized. However, this electron source can also be used inside of the described x-ray source as an electron emitting element.

[0124] In order to achieve the lowest possible scattering in the gate layer 13 and at the interface to the intermediate layer 12, the gate layer 13 should be made as thin as possible on the one hand. On the other hand, the gate layer 13 should have a small energy difference of the conduction band edge to the conduction band edge of the intermediate layer 12 in order to minimize quantum mechanical reflection and should be sufficiently electrically conductive. The gate layer 13 realized by the carbon layer 5 of GC allows such a layer to be efficiently produced.

[0125] For example, the intermediate layer 12 is made of silicon dioxide, since the achievable high oxide quality as well as the relatively precisely adjustable thickness allow a high current density and thus service life. Especially in combination with a silicon carrier as the base layer 11, established manufacturing processes are also available. In addition, the intermediate layer 12 can be of hexagonal boron nitride, or hBN for short. Since the thickness can also be very well controlled by various fabrication methods, hBN is an interesting option for the intermediate layer 12. The high-k dielectrics used in CMOS technology can also be considered for the intermediate layer 12. Especially fabrication methods like atomic layer deposition, ALD, are able to achieve very homogeneous layers with a relatively high quality.

[0126] Silicon dioxide for the intermediate layer 12 can be generated, for example, thermally, in particular wet, dry, at room temperature or in an oxidation furnace, or by chemical vapor deposition, CVD, or by vapor deposition. hBN or BN can be generated, for example, by plasma-enhanced CVD and annealing, pulsed CVD, Pulsed Laser deposition, Low Pressure CVD, cathalytic growth and transfer. High-k dielectrics such as Al.sub.2O.sub.3 or HfO can be produced by evaporation, sputtering, ALD, CVD, pulsed CVD, plasma-enhanced CVD or Pulsed Laser deposition. For example, the intermediate layer 12 has a dielectric strength of 0.1 V/nm to 500 V/nm.

[0127] With silicon as the material for the base layer 11, also referred to as carrier electrode or substrate electrode, common methods from the CMOS industry are available and scalable, reproducible manufacturing is achievable. By varying the doping, the electrical properties can be influenced and even a voltage drop at the gate electrode can be compensated for by a suitable doping profile. Silicon also offers the possibility of integrating further functionality on a chip.

[0128] Furthermore, for the base layer 11 Highly Oriented Pyrolitic Graphite, or HOPG for short, is possible as a highly conductive, flexible material. Sapphire, hBN, silicon carbide or even a metal or metal film are also possible for the base layer 11. As an option, the electrically conductive base layer 11 can be applied on a non-conductive carrier layer for mechanical stability, not shown.

[0129] The base layer 11 can thus be silicon, with a possible doping of either p or n and a doping level of to ++, with P, As, Sb, B, Al, Ga and/or In as possible dopants. Furthermore, HOPG and graphite foils as well as sapphire wafers, possibly with a carbon layer, and SiC, possibly with a carbon layer, too, can also be used, as well as metal films.

[0130] For example, a thickness of the base layer 11 is at least one monolayer and/or at most 5 mm. The base layer 11 may be mechanically rigid or flexible. For example, a specific electrical conductivity of the base layer 11 is between 10.sup.1 S/m and 10.sup.9 S/m, inclusive.

[0131] It is possible that a first electric contact structure 14 is applied directly on the carbon layer 5, see FIG. 12, or also between the carbon layer 5 and the intermediate layer 12. For example, the first electric contact structure 14 can be a metallic structure. However, the first electric contact structure 14 also be made of GC, however, with a thickness of, for example, at least 0.1 m and, thus, by far thicker than the gate layer 13.

[0132] As a further option, on top of the gate layer 13 and optionally on top of the first electric contact structure 14, there can be a protection layer 63, the protection layer 63 protects the device 10 from environmental influences. However, GC has a high robustness against environmental influences so that such a protection layer 63 may be omitted, especially if the first electric contact structure 14 is made of GC as well. In other words, the carbon layer 5 and, thus, the GC itself may act as a protection layer. However, in oxygen an additional material may be needed or may be practical. An additional protection layer, not shown, may also be present on a side of the base layer 11 facing away from the gate layer 13, for example.

[0133] It is possible that the carbon layer 5 is provided with a bar structure or a grid structure and/or with a frame to improve current distribution across the gate layer 13. Hence, the gate layer 13 can be provided with an electrically conductive structure, possibly made of GC, and configured as disclosed in connection with FIG. 8 or 9, for example.

[0134] Otherwise, the same as to FIGS. 1 to 11 may also apply to FIG. 12, and vice versa.

[0135] In FIG. 13 it is illustrated that the base layer 11 is a carbon layer 5, too, and is thus also can be made of GC or another carbon based material. Hence, the device 10 can be mechanically flexible. If the base layer 11 is comparably thin, for example, having a thickness of at most 1 mm or of at most 0.1 mm, as an option there can be a second electric contact structure 19. The second electric contact structure 19 can be a metallic structure or can also be made of GC. Other than shown, the second electric contact structure 19 may also be a continuous layer of constant thickness.

[0136] Otherwise, the same as to FIG. 12 may also apply to FIG. 13, and vice versa.

[0137] The electron emission device of FIG. 14 further comprises an insulation layer 16 and a control electrode 17. For the insulation layer 16, the same applies as for the intermediate layer 12. For the control electrode 17, the same as for the gate layer 13 may apply.

[0138] In this case, the potential set on the control electrode adjusts the energy of the emitted electrons, in particular, according to the following equation:

[00001]${\stackrel{\_}{E}}_e=V_{\mathrm{SESE}}*e-{\stackrel{\_}{E}}_{\mathrm{verl}\text{.2}}-W_A;$

where .sub.e is the average energy of the emitted electrons, V.sub.SESE the applied potential difference between the carrier and the energy control electrode 17 of the GIS, e the elementary charge, .sub.verl.2 the average energy loss due to scattering in the GIS structure 12, 13, 16, 17, and W.sub.A the work function of the control electrode 17. That is, the additional stack 16, 17 increases the average energy loss, but the total energy can then be adjusted independently of the emission current by the additional potential provided by means of the control electrode 17.

[0139] To electrically contact the control electrode 17, as an option there is the third electric contact structure 18 which may be placed on top of the control electrode 17 and on top of the first electric contact structure 14. The third electric contact structure 18 can be made of GC as is possible for the first electric contact structure 14. Both the gate layer 13 and the control electrode 17 may be carbon layers made of GC.

[0140] Otherwise, the same as to FIGS. 12 and 13 may also apply to FIG. 14, and vice versa.

[0141] In FIG. 15, a modified electron emission device 10 is illustrated. Instead of the gate layer made of GC, there is a gate layer 13 made of graphene which exhibits better electric conductivity and which may be made thinner. However, due to the increased temperature required to apply graphene, a roughening 15 can occur at an interface between the intermediate layer 12, for example, made of silicon dioxide, and the gate layer 13. This roughening 15 can lead to an increased electron scattering at the interface and/or a non-uniform current distribution, hence a lower areal efficiency. By having the carbon layer 5 of GC, a smoother interface can be achieved.

[0142] Concerning FIG. 16, a GIS structure 10 with an oxide thickness of 13 nm of the intermediate layer 12 was produced, in which the gate layer 13 as the electrode was made of glassy carbon. For this purpose, the photoresist AZ-nLof 2070 from MicroChemicals was diluted to 5 wt. % with the diluent AZ EBR and was spin-coated at a rotation speed of 6000 rpm to achieve a target thickness of 5 nm to 20 nm. After subsequent exposure and development, the layer was annealed in an oven at 900 C. and at 1.1 mbar with 200 sccm flowrate of argon for 1 h. FIG. 16 shows a voltage sweep of the gate voltage Vg at the gate layer 13 of such a component wherein a current strength I through the gate layer 13 and a current of an opposite anode receiving the emitted electrodes are plotted as well as a resulting electron emission efficiency E. Despite the relatively simple process, an electron emission efficiency E of about 25% is achieved.

[0143] In FIG. 17, the microstructure of the GC is schematically shown. Thus, the carbon layer 5 comprises a plurality of filaments 54. These filaments 54 are relatively long and can be slung and weaved into each other. For example, because of this structure, the carbon layer 5 can have a relatively large mechanical strength.

[0144] FIG. 18 shows a block diagram of a method to produce the carbon layer 5, either used as the transmission layer 43 or as the gate layer 13.

[0145] In a method step S1, a substrate 50 is provided. The substrate 50 is either the final component the carbon layer 5 is desired to be on, or the substrate 50 is a temporal auxiliary substrate.

[0146] In method step S2, an organic raw material 51 is applied onto the substrate 50, see also FIG. 19. The raw material 51 is applied as a liquid. For example, the raw material is a photo-sensitive material.

[0147] Then, in method step S3, the raw material 51 is solidified so that a raw material layer 52 is formed. The solidifying is or comprises, for example, radiation hardening using radiation like UV or thermal hardening.

[0148] In optional method step S4, the raw material layer 52 is structured to have the shape of the final carbon layer, see also FIG. 20. This is either done directly, for example, by a photo-based technique like hardening and removing superfluous material after an irradiation step, if the raw material layer 52 is photo-sensitive, or this is done indirectly by applying a photo-sensitive material, like a photo-resist, on the raw material layer 52 and structuring the latter, for example, lithographically.

[0149] Hence, for example, after the lithographic structuring an additional hardening is carried out or the hardening is only done after structuring.

[0150] Subsequently, see method step S5, the raw material layer 52 is pyrolized so that the GC and, thus, the carbon layer 5 is created. This may be done, for example, at any temperature between 400 C. and 2000 C.

[0151] If the substrate 50 is just an auxiliary carrier and is not present in the finished component, as shown in FIG. 21, the carbon layer 5 may be transferred to a final carrier, like a frame 45, and an electrical or mechanical support structure 42, compare FIGS. 3 to 9, may be applied to the carbon layer 5. Otherwise, the carbon layer 5 may directly be formed on the intermediate layer 12, for example.

[0152] Otherwise, the same as to FIGS. 1 to 14 and 17 may also apply to FIGS. 18 to 21, and vice versa.

[0153] Thus, an example of the manufacturing method may be summarized as follows; these aspects may individually or in any combination apply to all other embodiments: [0154] A photosensitive lacquer, like AZ-nLof 2070, can be diluted between 1% and 100% percent by weight using a thinner, like AZ EBR. The diluted lacquer is then spin-coated onto a substrate with a spin coater at a rotation frequency between 500 rpm and 10000 rpm, for example. Depending on the chosen parameters, like dilution and rotation speed, a resulting resist thickness between 1 nm and 10 m can be produced.

[0155] The substrate with the spun-on photoresist can then be structured by lithography, like photo structuring or electron beam structuring. Subsequently, the resist is pyrolized in an oven at temperatures between 500 C. and 2000 C., for example. The resulting resist film thickness after lithography is then determined. The resulting film thickness after pyrolysis is between half and one-twentieth of the thickness before pyrolysis and, thus, between a monolayer and 10 m, for example. This process is easily scalable and industrially suitable thanks to well-known processes such as rotational coating or lithography. As a developer, for example, AZ 2026 MIF may be used.

[0156] In FIG. 22, another example of the window 4 is illustrated. In this case, the protection layer 63 is present at a side of the carbon layer 5 remote from the target 35, for example. A further protection layer, not shown, may be applied on the target 35 as well. Such protection layers can also be present in all other embodiments of the X-ray apparatus 1.

[0157] As an additional option it is illustrated in FIG. 22 that there is a first adhesion layer 61 located directly between the carbon layer 5 and the target 35, for example. Alternatively or additionally, there is a second adhesion layer 62 directly between the target 35 and the frame 45 or the supporting structure 42 or otherwise directly between the carbon layer 5 and the frame 45 or the supporting structure 42. Such adhesion layers 61, 62 can also be present in all other embodiments of the X-ray apparatus 1.

[0158] In FIGS. 23 and 24, further embodiments of the gate layer 13 are illustrated. In this embodiments, the gate layer 13 is not of continuous, hole-free fashion, as in FIGS. 12 to 14, for example, but has pores or holes 55.

[0159] In FIG. 23 it is shown that the pores or holes 55 are arranged irregularly and may also have a size distribution. Such pores or holes 55 can be produced, for example, by rapidly heating the raw material layer 52 or the liquid raw material 51 so that pores and/or holes may result. For example, a heating rate is then at least 20 K/min. A diameter of these pores or holes 55 may be relatively small and may range, for example, from at least 1 nm to at most 1 m or to at most 0.1 m or to at most 0.01 m.

[0160] According to FIG. 24, the pores or holes 55 are arranged in a regular fashion, for example, in a rectangular or hexagonal grid. Such pores or holes 55 can be produced, for example, by means of nanoimprint or electron beam structuring. A diameter of these pores 55 may range, for example, from at least 0.001 m or at least 0.01 m to at most 1 m or to at most 0.1 m.

[0161] By means of such pores or holes 55, a transmittance of the gate layer 13 for electrons can be increased.

[0162] The application of the liquid raw material is also possible with other known methods such as spray coating or dip coating, for example. The specific properties of the carbon layer 5, like an electric conductivity, can be varied and adjusted depending on the pyrolysis temperature, the precursor used and the duration of the pyrolysis, for example.

[0163] The components shown in the figures follow, unless indicated otherwise, exemplarily in the specified sequence directly one on top of the other. Components which are not in contact in the figures are exemplarily spaced apart from one another. If lines are drawn parallel to one another, the corresponding surfaces may be oriented in parallel with one another. Likewise, unless indicated otherwise, the positions of the drawn components relative to one another are correctly reproduced in the figures.

[0164] The invention described here is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.