Composite electrode for nickel oxide-based device as well as preparation and application of composite electrode

Abstract

The invention relates to the technical field of semiconductor material preparation, in particular to a composite electrode for a nickel oxide-based device and preparation and application of the composite electrode. The composite electrode for the nickel oxide-based device provided by the invention comprises a nickel oxide base, a lithium-doped nickel oxide intermediate layer and a metal electrode layer which are deposited on the upper surface of a substrate and are vertically stacked from bottom to top, wherein the lithium-doped nickel oxide intermediate layer and the metal electrode layer are deposited on the upper surface of the nickel oxide substrate in a shape like a Chinese character'hui '. According to the invention, the intermediate layer has low resistivity and high hole concentration, so that the interface barrier is reduced, the carrier injection efficiency is improved, and stable and low-resistance ohmic contact between metal and nickel oxide is realized. By optimizing the electrode structure and material parameters, the conductivity and the thermal stability of the device are remarkably improved, and the method is suitable for various NiO-based application scenes such as photoelectric detection, gas-sensitive sensing and transparent electronic devices and has a wide industrialization prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor material preparation, and particularly to a composite electrode for nickel oxide-based devices, its preparation and application. Background Art

[0002] Nickel oxide (NiO) is an important transition metal oxide and has been widely studied due to its unique physical and chemical properties. As a thermodynamically stable p-type semiconductor material, NiO has a relatively large band gap (about 3.6 - 4.0 eV), good thermal stability and chemical stability, which makes it show broad application prospects in many fields such as materials science, energy, and environment. In recent years, with the continuous in-depth research of functional materials, the potential applications of NiO in gas sensors, catalysis, electrochromics, energy storage, and magnetic materials have also attracted increasing attention and become one of the hot materials in basic research and application development.

[0003] In the research of metal-semiconductor contact structures and device design, the control of contact resistance is one of the core factors determining device performance. A high contact resistance not only reduces the current transmission efficiency but also causes device heating and increased energy loss, and in severe cases, it can lead to device function degradation or even failure. Therefore, achieving a low contact resistance and a stable and reliable ohmic contact interface has become the key to improving the overall performance of devices. For NiO, due to its low intrinsic carrier concentration, it is difficult for conventional metals to form an ideal ohmic contact on its surface and is prone to show Schottky behavior, which limits the further improvement of device electrical performance. In addition, traditional metal electrodes may undergo interfacial reactions, structural degradation, or peeling during long-term operation or in high-temperature environments, affecting device stability.

[0004] Therefore, it is crucial to provide a technical solution that can solve the above technical problems. Summary of the Invention

[0005] To address the problems of low electrical conductivity (high contact resistance) and interface mismatch (difficulty in forming Ohmic contact) during the contact process between traditional electrode structures and NiO materials, the object of the present invention is to provide a composite electrode for nickel oxide-based devices and its preparation and application. The composite electrode for nickel oxide-based devices provided by the present invention includes a nickel oxide substrate, a lithium-doped nickel oxide intermediate layer, and a metal electrode layer that are vertically stacked from bottom to top on the upper surface of the substrate; among them, the lithium-doped nickel oxide intermediate layer and the metal electrode layer are deposited on the upper surface of the nickel oxide substrate in a "hui" character shape. In the present invention, the intermediate layer has a low resistivity and a high hole concentration, which helps to reduce the interface barrier and improve the carrier injection efficiency (low contact resistance), and achieve stable (stable electrical properties) and low-resistance Ohmic contact (excellent interface compatibility) between the metal and nickel oxide. The intermediate layer is deposited by radio frequency magnetron sputtering, and the metal electrode is formed by electron beam evaporation. It has the advantages of mild process (room temperature), no need for high-temperature annealing, and strong adaptability (applicable to various substrate materials and integration processes), and has good scalability and process compatibility. By optimizing the electrode structure and material parameters, the present invention significantly improves the electrical conductivity and thermal stability of the device, is applicable to various NiO-based application scenarios such as photodetection, gas sensing, and transparent electronic devices, and has broad industrialization prospects.

[0006] The object of the present invention can be achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a composite electrode for nickel oxide-based devices, including a nickel oxide substrate, a lithium-doped nickel oxide intermediate layer, and a metal electrode layer that are vertically stacked from bottom to top on the upper surface of the substrate;

[0008] Among them, the lithium-doped nickel oxide intermediate layer and the metal electrode layer are deposited on the upper surface of the nickel oxide substrate in a "hui" character shape;

[0009] The resistivity of the lithium-doped nickel oxide intermediate layer is less than 1 Ω·cm, and the hole concentration is greater than 10 17 cm -3 .

[0010] In an embodiment of the present invention, the thickness of the nickel oxide substrate is 300 - 600 nm.

[0011] In an embodiment of the present invention, in the lithium-doped nickel oxide intermediate layer, the doping amount of lithium is 0.1 - 10 at.%.

[0012] The thickness of the lithium-doped nickel oxide intermediate layer is 5 - 200 nm.

[0013] In an embodiment of the present invention, the material of the metal electrode layer is selected from one or two of nickel, chromium, titanium, or gold with a purity of 99% - 99.9999%;

[0014] The thickness of the metal electrode layer is 5 to 200 nm.

[0015] The present invention introduces a lithium-doped low-resistance NiO (Li:NiO) interlayer between the nickel oxide substrate and the metal electrode layer. This interlayer can effectively increase the interfacial carrier concentration and reduce the barrier height, thereby promoting the formation of a high-quality and thermally stable ohmic contact between NiO and the metal electrode, providing a reliable electrode solution for constructing high-performance NiO-based devices.

[0016] The second object of the present invention is to provide a method for preparing a composite electrode for a nickel oxide-based device, comprising the following steps:

[0017] (S1) Using the nickel oxide thin film pre-deposited on the substrate as the base material, after post-treatment, a baffle is placed at the center of the nickel oxide thin film, and the lithium-doped nickel oxide interlayer is deposited.

[0018] (S2) After step (S1) is completed, after post-treatment, a metal electrode layer is deposited on the upper surface of the lithium-doped nickel oxide interlayer to prepare a composite electrode for a nickel oxide-based device.

[0019] In one embodiment of the present invention, in step (S1), the post-treatment is to remove organic impurities and particle contamination on the surface of the base material. The base material is sequentially placed in acetone, methanol, and deionized water for cleaning. After cleaning, high-purity nitrogen gas is used to thoroughly dry the base material to ensure its surface is clean and dry.

[0020] The area of the baffle is 1 mm * 1 mm / 1 cm * 1 cm nickel oxide substrate.

[0021] In one embodiment of the present invention, in step (S1), the deposition of the lithium-doped nickel oxide interlayer is a room-temperature magnetron sputtering technique.

[0022] In step (S2), the deposition is an electron beam evaporation deposition technique.

[0023] In one embodiment of the present invention, during the room-temperature magnetron sputtering process, the working atmosphere is high-purity argon, the working pressure is 0.4 to 0.8 Pa, the radio frequency power is 40 to 80 W, and the base material rotates at a rate of 1 to 5 rad / min.

[0024] In one embodiment of the present invention, during the electron beam evaporation deposition process, the electron beam acceleration voltage is 9 to 12 keV, the power is 38 to 43%, and the metal growth rate is

[0025] The third object of the present invention is to provide an application of the composite electrode for a nickel oxide-based device in the preparation of electronic devices.

[0026] In one embodiment of the present invention, the composite structure is reasonably designed, and the types of the metal layer and the intermediate layer materials are rich and the selection is flexible. It not only ensures the electrical conductivity but also has good chemical stability and thermal stability, and is applicable to the preparation of electronic devices in a variety of application scenarios.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Excellent ohmic contact performance: By introducing a low-resistance doped NiO intermediate layer, the present invention effectively reduces the contact resistance between the metal and NiO, realizes stable and efficient ohmic contact, and improves the overall electrical transport efficiency of the device.

[0029] (2) Strong process compatibility and mild preparation conditions: The intermediate layer is prepared by room-temperature magnetron sputtering. The process conditions are mild, without high-temperature annealing, applicable to a variety of substrate materials and integration processes, and have good scalability and process compatibility.

[0030] (3) Stable structure and flexible material selection: The composite structure is reasonably designed, and the types of the metal layer and the intermediate layer materials are rich and the selection is flexible. It not only ensures the electrical conductivity but also has good chemical stability and thermal stability, and is applicable to the preparation of electronic devices in a variety of application scenarios. Description of the Drawings

[0031] Figure 1 Schematic diagram of the composite electrode for the nickel oxide-based device described in Example 1; (a) Cross-sectional view; (b) Top view;

[0032] Figure 2 Schematic diagram of the composite electrode prepared in Comparative Example 1;

[0033] Figure 3 Current-voltage (I-V) characteristic curve graph of different structure NiO / Au contact interfaces;

[0034] Figure 4 Current-voltage (I-V) characteristic curve graph of different structure NiO / Ni-Cr contact interfaces;

[0035] Figure 5 Current-voltage (I-V) characteristic curve graph of different structure NiO / Ti-Cr contact interfaces;

[0036] Reference numerals in the figures: 1, Substrate; 2, Nickel oxide substrate; 3, Lithium-doped nickel oxide intermediate layer; 4, Metal electrode layer. Detailed Embodiments

[0037] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0038] In the following examples and comparative examples, the preparation method of depositing a NiO thin film with a thickness of 450 nm on a borosilicate glass substrate in advance is specifically as follows:

[0039] (1) Select a borosilicate glass with a thickness of 0.5 mm as the substrate for growing the NiO bottom layer (length * width is 2 cm * 2 cm). To remove organic impurities and particle contamination on the substrate surface, place it in acetone, methanol, and deionized water in sequence for ultrasonic cleaning, with each step lasting 5 minutes; after cleaning, use high-purity nitrogen to thoroughly dry the substrate to ensure its surface is clean and dry; then quickly transfer the treated substrate into the cavity of a high-vacuum sputtering system, and turn on the mechanical pump and molecular pump in sequence for pumping to gradually make the background vacuum of the system reach 10 -4 ~10 -5 Pa, and prepare to enter the NiO bottom layer deposition process.

[0040] (2) In a high-vacuum environment, deposit the NiO bottom layer on the substrate surface in step (1) by radio frequency magnetron sputtering technology. The target used is a NiO ceramic target, which is prepared by the co-sintering method to ensure uniform component distribution. During the deposition process, the substrate is maintained at room temperature (without external heating), the working atmosphere is a mixed gas of high-purity argon and high-purity oxygen, the argon-oxygen ratio is 7:3, the flow rate is stable, the working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure a stable and uniform thin film growth process. To further improve the thickness uniformity of the film layer, the sample tray rotates continuously at a rate of 5 rad / min during the deposition process; use a film thickness monitoring system to perform real-time feedback control on the thin film growth process to ensure that the thickness of the bottom layer is stable at about 450 nm; after deposition, introduce high-purity nitrogen into the cavity to relieve the vacuum, then take out the sample and naturally cool it to room temperature to obtain the NiO bottom layer deposited on the glass substrate surface; the obtained NiO bottom layer has a resistivity of about 700 Ω·cm and a carrier concentration of 3.05×10 16 cm -3 ; the surface is flat, providing a basis for forming good contact with the Li-doped NiO intermediate layer.

[0041] Unless otherwise specified, the reagents are all commercially available reagents, and the detection means and methods used are all conventional detection means and methods in the art.

[0042] Example 1

[0043] This example provides a composite electrode for a nickel oxide-based device, such as Figure 1As shown, it includes a nickel oxide substrate 2 deposited on the upper surface of a substrate 1, a lithium-doped nickel oxide intermediate layer 3, and a metal electrode layer 4 that are vertically stacked from bottom to top; among them, the lithium-doped nickel oxide intermediate layer 3 and the metal electrode layer 4 are deposited in a "hui" character shape on the upper surface of the nickel oxide substrate 2; among them, the resistivity of the lithium-doped nickel oxide intermediate layer 3 is less than 1 Ω·cm, and the hole concentration is greater than 10 17 cm -3 ; the thickness of the nickel oxide substrate 2 is 300 - 600 nm; in the lithium-doped nickel oxide intermediate layer 3, the doping amount of lithium is 0.1 - 10 at.%; the thickness of the lithium-doped nickel oxide intermediate layer 3 is 5 - 200 nm; the material of the metal electrode layer 4 is selected from one or two of nickel, chromium, titanium, or gold with a purity of 99% - 99.9999%; the thickness of the metal electrode layer 4 is 5 - 200 nm.

[0044] Example 2

[0045] This example provides a preparation method for a composite electrode for a nickel oxide-based device.

[0046] The overall structure of the composite electrode for the nickel oxide-based device provided in this example includes, from bottom to top in sequence, a nickel oxide substrate, a NiO intermediate layer with a Li doping concentration of 2 at.%, and a metal electrode layer (Au), presenting a typical vertical stacking form.

[0047] The specific preparation process is as follows:

[0048] (S1) Material cleaning and pretreatment

[0049] Select a NiO thin film with a thickness of 450 nm deposited on a borosilicate glass substrate in advance as the electrode substrate material (length * width is 2 cm * 2 cm). To remove surface organic impurities and particle contamination, place the sample in acetone, methanol, and deionized water for ultrasonic cleaning in sequence, with each step lasting 5 minutes; after cleaning, use high-purity nitrogen to thoroughly dry the sample to ensure its surface is clean and dry; then quickly transfer the treated NiO thin film into the cavity of a high-vacuum sputtering system, and turn on the mechanical pump and molecular pump in sequence for pumping to gradually bring the background vacuum of the system to 10 -4 ~10 -5 Pa, and prepare to enter the intermediate layer deposition process.

[0050] (S2) Growth of a low-resistance Li-doped NiO intermediate layer

[0051] In a high-vacuum environment, a NiO thin film doped with Li element is deposited on the surface of the NiO thin film in step (S1) as an intermediate layer by radio frequency magnetron sputtering technology. The target used is a Li:NiO ceramic target with a Li doping concentration of 2 at.%, which is prepared by the co-sintering method to ensure uniform distribution of the doping components. During the deposition process, a baffle with a length * width of 2 mm * 2 mm is placed at the center position of the upper surface of the NiO thin film. The substrate is maintained at room temperature (without external heating). The working atmosphere is high-purity argon with a stable flow rate. The working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure a stable and uniform thin film growth process.

[0052] To further improve the thickness uniformity of the film layer, the sample tray continuously rotates at a rate of 5 rad / min during the deposition process; a film thickness monitoring system is used to perform real-time feedback control on the thin film growth process to ensure that the thickness of the intermediate layer is stable at about 100 nm; after the deposition is completed, high-purity nitrogen is introduced into the cavity to relieve the vacuum, and then the sample is taken out and naturally cooled to room temperature to obtain a low-resistance Li-doped NiO intermediate layer deposited on the upper surface of the NiO thin film;

[0053] The Li-doped NiO intermediate layer (marked as Li:NiO intermediate layer) obtained in this embodiment exhibits good electrical conductivity, with a resistivity of about 0.74 Ω·cm and a carrier concentration reaching 3.72×10 18 cm -3 , having the electrical basis for constructing an ohmic contact.

[0054] (S3) Deposition of the metal electrode layer (Au):

[0055] On the upper surface of the prepared Li:NiO intermediate layer, a metal electrode layer is further deposited by electron beam evaporation technology. The selected metal is high-purity gold (Au) with a purity as high as 99.999% to ensure excellent electrical conductivity and chemical stability of the electrode layer.

[0056] The electron beam evaporation process is carried out in a high-vacuum cavity. The electron beam acceleration voltage is set at 9.7 keV, and the power is adjusted to 39.6%. A film thickness gauge is used to perform real-time control on the metal growth rate, which is stable at around, and the deposition temperature is maintained at room temperature; finally, the thickness of the metal electrode layer is about 100 nm, with a flat surface and good adhesion. After the deposition is completed, the sample is taken out of the vacuum cavity, and a composite electrode for nickel oxide-based devices with structural integrity, clear interfaces, and excellent ohmic contact characteristics can be obtained, providing a reliable basis for subsequent device performance testing and integrated applications.

[0057] In this embodiment, the current-voltage (I-V) characteristic curve of the NiO / Au contact interface is as Figure 3 shown.

[0058] Example 3

[0059] This example provides a method for preparing a composite electrode for a nickel oxide-based device.

[0060] The overall structure of the composite electrode for the nickel oxide-based device provided in this example sequentially includes a nickel oxide substrate, a NiO intermediate layer with a Li doping concentration of 4 at.%, and a metal electrode layer (Au) from bottom to top, showing a typical vertical stacking form.

[0061] The specific preparation process is as follows:

[0062] (S1) Material cleaning and pretreatment

[0063] Select a NiO thin film with a thickness of 450 nm deposited on a borosilicate glass substrate in advance as the electrode substrate material (length * width is 2 cm * 2 cm). To remove surface organic impurities and particle contamination, the sample is successively placed in acetone, methanol, and deionized water for ultrasonic cleaning, with each step lasting for 5 minutes; after cleaning, the sample is thoroughly dried with high-purity nitrogen to ensure its surface is clean and dry; then the treated NiO thin film is quickly transferred into the chamber of a high-vacuum sputtering system, and the mechanical pump and molecular pump are successively turned on for pumping, so that the background vacuum of the system gradually reaches 10 -4 ~10 -5 Pa, and it is ready to enter the intermediate layer deposition process.

[0064] (S2) Growth of a low-resistance Li-doped NiO intermediate layer

[0065] In a high-vacuum environment, a NiO thin film doped with Li element is deposited on the surface of the NiO thin film in step (S1) as the intermediate layer by radio frequency magnetron sputtering technology. The target used is a Li:NiO ceramic target with a Li doping concentration of 4 at.%, which is prepared by a co-sintering method to ensure uniform distribution of the doping components. During the deposition process, a baffle with a length * width of 2 mm * 2 mm is placed at the center position on the upper surface of the NiO thin film, the substrate is maintained at room temperature (without external heating), the working atmosphere is high-purity argon, the flow rate is stable, the working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure stable and uniform film growth.

[0066] To further improve the thickness uniformity of the film layer, the sample tray continuously rotates at a rate of 5 rad / min during the deposition process; a film thickness monitoring system is used to perform real-time feedback control on the film growth process to ensure that the thickness of the intermediate layer is stable at about 100 nm; after deposition, high-purity nitrogen is introduced into the chamber to relieve the vacuum, and then the sample is taken out and naturally cooled to room temperature to obtain a low-resistance Li-doped NiO intermediate layer deposited on the upper surface of the NiO thin film;

[0067] The Li-doped NiO intermediate layer obtained in this embodiment (labeled as the Li:NiO intermediate layer) exhibits good electrical conductivity, with a resistivity of approximately 0.081 Ω·cm and a carrier concentration reaching 9.33×10 19 cm -3 , possessing the electrical basis for constructing an ohmic contact.

[0068] (S3) Deposition of the metal electrode layer (Au):

[0069] On the upper surface of the prepared Li:NiO intermediate layer, a metal electrode layer is further deposited through electron beam evaporation technology. The selected metal is high-purity gold (Au) with a purity as high as 99.999% to ensure excellent electrical conductivity and chemical stability of the electrode layer.

[0070] The electron beam evaporation process is carried out in a high-vacuum chamber. The electron beam acceleration voltage is set to 9.7 keV and the power is adjusted to 39.6%. A film thickness gauge is used to control the metal growth rate in real time, which is stable at around, and the deposition temperature is maintained at room temperature; finally, the thickness of the metal electrode layer is approximately 100 nm, with a flat surface and good adhesion. After the deposition is completed, the sample is taken out of the vacuum chamber, and a composite electrode for nickel oxide-based devices with structural integrity, clear interfaces, and excellent ohmic contact characteristics can be obtained, providing a reliable basis for subsequent device performance testing and integrated applications.

[0071] In this embodiment, the current-voltage (I-V) characteristic curve of the NiO / Au contact interface is as shown in Figure 3 the figure.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing a composite electrode.

[0074] In this comparative example, the schematic diagram of the composite electrode is as shown in Figure 2 the figure, including a nickel oxide substrate 2 deposited on the upper surface of the substrate 1 and vertically stacked from bottom to top, and a metal electrode layer 4; wherein, the metal electrode layer 4 is deposited in a "hui" shape on the upper surface of the nickel oxide substrate 2;

[0075] Specifically, compared with Example 2, this comparative example is the same as Example 2 except that it does not contain a NiO intermediate layer with a Li doping concentration of 2 at.%.

[0076] In this comparative example, the current-voltage (I-V) characteristic curve of the NiO / Au contact interface is as shown in Figure 3 the figure.

[0077] By Figure 3It can be found that the NiO / Au contact (Comparative Example 1, black curve) exhibits obvious non-linear behavior, especially showing a certain bending trend in the low-voltage region, indicating that it is a non-ideal Ohmic contact with a large contact resistance or a slight potential barrier at the interface. After introducing 2% Li-doped NiO as the intermediate layer (Example 2, blue curve), the curve significantly tends to be linear, indicating that the injection efficiency of carriers is improved, the contact resistance decreases, and the contact characteristics are improved. Further increasing the Li doping concentration to 4% (Example 3, red curve), the I-V curve is almost an ideal linear relationship, indicating that a good Ohmic contact has been formed between NiO and Au at this time. This is attributed to the appropriate concentration of Li-doped NiO intermediate layer that increases the carrier concentration and conductivity of NiO, while improving the interface energy band alignment and effectively reducing the contact resistance.

[0078] Example 4

[0079] This example provides a preparation method for a composite electrode for a nickel oxide-based device.

[0080] The overall structure of the composite electrode for the nickel oxide-based device provided in this example sequentially includes a nickel oxide substrate, a NiO intermediate layer with a Li doping concentration of 2 at.%, and a metal electrode layer (Ni / Cr) from bottom to top, showing a typical vertical stacking form.

[0081] The specific preparation process is as follows:

[0082] (S1) Material cleaning and pretreatment

[0083] Select a pre-deposited NiO thin film with a thickness of 450 nm on a borosilicate glass substrate as the electrode substrate material (length * width is 2 cm * 2 cm). To remove surface organic impurities and particle contamination, the sample is sequentially ultrasonically cleaned in acetone, methanol, and deionized water for 5 minutes each; after cleaning, the sample is thoroughly dried with high-purity nitrogen to ensure its surface is clean and dry; then the treated NiO thin film is quickly transferred into the cavity of a high-vacuum sputtering system, and the mechanical pump and molecular pump are sequentially turned on for pumping to gradually bring the system background vacuum to 10 -4 ~10 -5 Pa, and it is ready to enter the intermediate layer deposition process.

[0084] (S2) Growth of a low-resistance Li-doped NiO intermediate layer

[0085] In a high-vacuum environment, a NiO thin film doped with Li element is deposited on the surface of the NiO thin film in step (S1) as an intermediate layer by radio frequency magnetron sputtering technology. The target used is a Li:NiO ceramic target with a Li doping concentration of 2 at.%, which is prepared by a co-sintering method to ensure uniform distribution of the doping components. During the deposition process, a baffle with a length * width of 2 mm * 2 mm is placed at the center position on the upper surface of the NiO thin film. The substrate is maintained at room temperature (without external heating), and the working atmosphere is high-purity argon with a stable flow rate. The working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure a stable and uniform thin film growth process.

[0086] To further improve the thickness uniformity of the film layer, the sample tray continuously rotates at a rate of 5 rad / min during the deposition process; a film thickness monitoring system is used to perform real-time feedback control on the thin film growth process to ensure that the thickness of the intermediate layer is stable at about 100 nm; after the deposition is completed, high-purity nitrogen is introduced into the cavity to relieve the vacuum, and then the sample is taken out and naturally cooled to room temperature to obtain a low-resistance Li-doped NiO intermediate layer deposited on the upper surface of the NiO thin film;

[0087] The Li-doped NiO intermediate layer (marked as Li:NiO intermediate layer) obtained in this embodiment exhibits good electrical conductivity, with a resistivity of about 0.74 Ω·cm and a carrier concentration reaching 3.72×10 18 cm -3 , having the electrical basis for constructing an ohmic contact.

[0088] (S3) Deposition of the metal electrode layer (Ni / Cr):

[0089] On the upper surface of the prepared Li:NiO intermediate layer, a metal electrode layer is further deposited by electron beam evaporation technology. The selected metals are high-purity nickel (Ni) and chromium (Cr), with purities as high as 99.999% to ensure excellent electrical conductivity and chemical stability of the electrode layer.

[0090] The electron beam evaporation process is carried out in a high-vacuum chamber. First, metal Ni is prepared, and the electron beam acceleration voltage is set at 9.7 keV and the power is adjusted to 41%. After the Ni crucible cools down, metal Cr is continued to be prepared, and the electron beam acceleration voltage is set at 9.7 keV and the power is adjusted to 38%. The whole process uses a crystal oscillator monitoring system to perform real-time control on the metal growth rate, which is stable at Around, the deposition temperature was maintained at room temperature. Finally, the thickness of the metal electrode layer was about 100 nm (the thickness of the Ni layer was 70 nm, and the thickness of the Cr layer was 30 nm), with a flat surface and good adhesion. After the deposition was completed, the sample was taken out of the vacuum chamber, and a composite electrode for nickel oxide-based devices with structural integrity, clear interfaces, and excellent ohmic contact characteristics could be obtained, providing a reliable basis for subsequent device performance testing and integrated applications.

[0091] In this embodiment, the current-voltage (I-V) characteristic curve of the NiO / Ni-Cr contact interface is as Figure 4 shown.

[0092] Example 5

[0093] This embodiment provides a preparation method for a composite electrode for nickel oxide-based devices.

[0094] The overall structure of the composite electrode for nickel oxide-based devices provided in this embodiment sequentially includes a nickel oxide substrate, a NiO intermediate layer with a Li doping concentration of 4 at.%, and a metal electrode layer (Ni / Cr) from bottom to top, showing a typical vertical stacking form.

[0095] The specific preparation process is as follows:

[0096] (S1) Material cleaning and pretreatment

[0097] Select a NiO thin film with a pre-deposited thickness of 450 nm on a borosilicate glass substrate as the electrode substrate material (length * width is 2 cm * 2 cm). To remove surface organic impurities and particle contamination, the sample was successively placed in acetone, methanol, and deionized water for ultrasonic cleaning, with each step lasting 5 minutes; after cleaning, the sample was thoroughly dried with high-purity nitrogen to ensure its surface was clean and dry; then the treated NiO thin film was quickly transferred into the chamber of a high-vacuum sputtering system, and the mechanical pump and molecular pump were successively turned on for pumping to gradually bring the system background vacuum to 10 -4 ~10 -5 Pa, and preparation for the intermediate layer deposition process was carried out.

[0098] (S2) Growth of a low-resistance Li-doped NiO intermediate layer

[0099] In a high-vacuum environment, a NiO thin film doped with Li element is deposited on the surface of the NiO thin film in step (S1) as an intermediate layer by radio frequency magnetron sputtering technology. The target used is a Li:NiO ceramic target with a Li doping concentration of 4 at.%, which is prepared by a co-sintering method to ensure uniform distribution of the doping components. During the deposition process, a baffle with a length * width of 2 mm * 2 mm is placed at the center position on the upper surface of the NiO thin film. The substrate is maintained at room temperature (without external heating). The working atmosphere is high-purity argon with a stable flow rate. The working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure a stable and uniform thin film growth process.

[0100] To further improve the thickness uniformity of the film layer, the sample tray continuously rotates at a rate of 5 rad / min during the deposition process; a film thickness monitoring system is used to conduct real-time feedback control on the thin film growth process to ensure that the thickness of the intermediate layer is stable at about 100 nm; after the deposition is completed, high-purity nitrogen is introduced into the cavity to relieve the vacuum, and then the sample is taken out and naturally cooled to room temperature to obtain a low-resistance Li-doped NiO intermediate layer deposited on the upper surface of the NiO thin film;

[0101] The Li-doped NiO intermediate layer (marked as Li:NiO intermediate layer) obtained in this embodiment exhibits good electrical conductivity, with a resistivity of about 0.081 Ω·cm and a carrier concentration reaching 9.33×10 19 cm -3 , having the electrical basis for constructing an ohmic contact.

[0102] (S3) Deposition of the metal electrode layer (Ni / Cr):

[0103] On the upper surface of the prepared Li:NiO intermediate layer, a metal electrode layer is further deposited by electron beam evaporation technology. The selected metals are high-purity nickel (Ni) and chromium (Cr), both with a purity as high as 99.999% to ensure excellent electrical conductivity and chemical stability of the electrode layer.

[0104] The electron beam evaporation process is carried out in a high-vacuum cavity. First, metal Ni is prepared, with the electron beam acceleration voltage set at 9.7 keV and the power adjusted to 41%. After the Ni crucible cools down, metal Cr is prepared, with the electron beam acceleration voltage set at 9.7 keV and the power adjusted to 38%. The crystal oscillator monitoring system is used throughout the process to conduct real-time control on the metal growth rate, which is stable at Around, the deposition temperature was maintained at room temperature. Finally, the thickness of the metal electrode layer was about 100 nm (the thickness of the Ti layer was 70 nm, and the thickness of the Cr layer was 30 nm), with a flat surface and good adhesion. After the deposition was completed, the sample was taken out of the vacuum chamber, and a composite electrode for nickel oxide-based devices with structural integrity, clear interfaces, and excellent ohmic contact characteristics could be obtained, providing a reliable basis for subsequent device performance testing and integrated applications.

[0105] In this embodiment, the current-voltage (I-V) characteristic curve of the NiO / Ni-Cr contact interface is as follows Figure 4 shown.

[0106] Comparative Example 2

[0107] This comparative example provides a method for preparing a composite electrode.

[0108] Compared with Example 4, this comparative example is the same as Example 4 except that it does not contain a NiO intermediate layer with a Li doping concentration of 2 at.%.

[0109] In this comparative example, the current-voltage (I-V) characteristic curve of the NiO / Ni-Cr contact interface is as follows Figure 4 shown.

[0110] By Figure 4 It can be found that when undoped NiO is in direct contact with the metal electrode (Comparative Example 2, black curve), the I-V curve shows obvious non-linear characteristics, indicating that there is a high contact resistance or a slight potential barrier is formed at the contact, belonging to non-ideal ohmic contact. After introducing a 2% Li-doped NiO intermediate layer between NiO and the metal (Example 4, blue curve), the I-V curve significantly tends to be linear, indicating that the carrier transport efficiency is improved, the contact resistance is reduced, and the contact behavior is improved; further increasing the doping concentration to 4% (Example 5, red curve), the curve approaches ideal linearity, and the current response is significantly enhanced, indicating that a good ohmic contact has been formed at the interface. This shows that an appropriately concentrated Li-doped NiO intermediate layer helps to regulate the carrier concentration and energy band structure of NiO, and improve the electrical properties of the metal / semiconductor interface.

[0111] Example 6

[0112] This example provides a method for preparing a composite electrode for nickel oxide-based devices.

[0113] The overall structure of the composite electrode for nickel oxide-based devices provided in this example includes, from bottom to top in sequence, a nickel oxide substrate, a NiO intermediate layer with a Li doping concentration of 2 at.%, and a metal electrode layer (Ti / Cr), showing a typical vertical stacked form.

[0114] The specific preparation process is as follows:

[0115] (S1) Material cleaning and pretreatment

[0116] Select a NiO thin film with a thickness of 450 nm deposited on a borosilicate glass substrate in advance as the electrode substrate material (length * width is 2 cm * 2 cm). To remove surface organic impurities and particulate contamination, the sample is ultrasonically cleaned in acetone, methanol, and deionized water in sequence, with each step lasting for 5 minutes; after cleaning, the sample is thoroughly dried with high-purity nitrogen to ensure its surface is clean and dry; then the treated NiO thin film is quickly transferred into the chamber of a high-vacuum sputtering system, and the mechanical pump and molecular pump are turned on in sequence for pumping to gradually bring the system background vacuum to 10 -4 ~10 -5 Pa, and prepare to enter the intermediate layer deposition process.

[0117] (S2) Growth of low-resistance Li-doped NiO intermediate layer

[0118] In a high-vacuum environment, a NiO thin film doped with Li element is deposited on the surface of the NiO thin film in step (S1) as the intermediate layer by radio frequency magnetron sputtering technology. The target used is a Li:NiO ceramic target with a Li doping concentration of 2 at.%, which is prepared by the co-sintering method to ensure uniform distribution of the doping components. During the deposition process, a baffle with a length * width of 2 mm * 2 mm is placed at the center position on the upper surface of the NiO thin film, the substrate is maintained at room temperature (without external heating), the working atmosphere is high-purity argon, the flow rate is stable, the working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure stable and uniform film growth.

[0119] To further improve the thickness uniformity of the film layer, the sample tray rotates continuously at a rate of 5 rad / min during the deposition; a film thickness monitoring system is used to conduct real-time feedback control on the film growth process to ensure that the thickness of the intermediate layer is stable at about 100 nm; after deposition, high-purity nitrogen is introduced into the chamber to relieve the vacuum, and then the sample is taken out and naturally cooled to room temperature to obtain a low-resistance Li-doped NiO intermediate layer deposited on the upper surface of the NiO thin film;

[0120] The Li-doped NiO intermediate layer (marked as Li:NiO intermediate layer) obtained in this embodiment exhibits good electrical conductivity, with a resistivity of about 0.74 Ω·cm and a carrier concentration reaching 3.72×10 18 cm -3 , having the electrical basis for constructing an ohmic contact.

[0121] (S3) Deposition of metal electrode layer (Ti / Cr):

[0122] On the upper surface of the prepared Li:NiO intermediate layer, a metal electrode layer is further deposited by electron beam evaporation technology. The selected metals are high-purity titanium (Ti) and chromium (Cr), both with a purity as high as 99.999%, to ensure that the electrode layer has excellent electrical conductivity and chemical stability.

[0123] The electron beam evaporation process is carried out in a high-vacuum chamber. First, metal Ti is prepared. The electron beam acceleration voltage is set to 9.7 keV, and the power is adjusted to 39.7%. After the Ni crucible cools down, metal Cr is prepared. The electron beam acceleration voltage is set to 9.7 keV, and the power is adjusted to 38%. The crystal oscillator monitoring system is used throughout the process to control the metal growth rate in real time, which is stable at around, and the deposition temperature is maintained at room temperature. Finally, the thickness of the metal electrode layer is about 100 nm (the Ti layer thickness is 70 nm, and the Cr layer thickness is 30 nm), with a flat surface and good adhesion. After the deposition is completed, the sample is taken out of the vacuum chamber, and a composite electrode for nickel oxide-based devices with structural integrity, clear interfaces, and excellent ohmic contact characteristics can be obtained, providing a reliable basis for subsequent device performance testing and integrated applications.

[0124] In this embodiment, the current-voltage (I-V) characteristic curve of the NiO / Ti-Cr contact interface is as shown in Figure 5 shown.

[0125] Example 7

[0126] This embodiment provides a method for preparing a composite electrode for nickel oxide-based devices.

[0127] The overall structure of the composite electrode for nickel oxide-based devices provided in this embodiment includes, from bottom to top, a nickel oxide substrate, a NiO intermediate layer with a Li doping concentration of 4 at.%, and a metal electrode layer (Ti / Cr), showing a typical vertical stacking form.

[0128] The specific preparation process is as follows:

[0129] (S1) Material cleaning and pretreatment

[0130] Select a NiO thin film with a thickness of 450 nm deposited on a borosilicate glass substrate in advance as the electrode substrate material (length * width is 2 cm * 2 cm). To remove surface organic impurities and particle contamination, the sample is successively placed in acetone, methanol, and deionized water for ultrasonic cleaning, each step lasting for 5 minutes; after cleaning, the sample is thoroughly dried with high-purity nitrogen to ensure its surface is clean and dry; then the treated NiO thin film is quickly transferred into the chamber of a high-vacuum sputtering system, and the mechanical pump and molecular pump are successively turned on for pumping, so that the background vacuum of the system gradually reaches 10 -4 ~10 -5 Pa, and it is ready to enter the intermediate layer deposition process.

[0131] (S2) Growth of Low-Resistance Li-Doped NiO Intermediate Layer

[0132] In a high-vacuum environment, a NiO thin film doped with Li element is deposited on the surface of the NiO thin film in step (S1) as an intermediate layer by radio frequency magnetron sputtering technology. The target used is a Li:NiO ceramic target with a Li doping concentration of 4 at.%, which is prepared by the co-sintering method to ensure uniform distribution of the doping components. During the deposition process, a baffle with a length * width of 2 mm * 2 mm is placed at the center position of the upper surface of the NiO thin film. The substrate is maintained at room temperature (without external heating). The working atmosphere is high-purity argon with a stable flow rate. The working pressure is controlled at 0.4 Pa, and the radio frequency power is set at 80 W to ensure a stable and uniform thin film growth process.

[0133] To further improve the thickness uniformity of the film layer, the sample tray rotates continuously at a rate of 5 rad / min during the deposition process; a film thickness monitoring system is used to conduct real-time feedback control on the thin film growth process to ensure that the thickness of the intermediate layer is stable at about 100 nm; after the deposition is completed, high-purity nitrogen is introduced into the cavity to relieve the vacuum, and then the sample is taken out and naturally cooled to room temperature to obtain a low-resistance Li-doped NiO intermediate layer deposited on the upper surface of the NiO thin film;

[0134] The Li-doped NiO intermediate layer (marked as Li:NiO intermediate layer) obtained in this embodiment exhibits good electrical conductivity, with a resistivity of about 0.081 Ω·cm and a carrier concentration reaching 9.33×10 19 cm -3 , having the electrical basis for constructing an ohmic contact.

[0135] (S3) Deposition of Metal Electrode Layer (Ti / Cr):

[0136] On the upper surface of the prepared Li:NiO intermediate layer, a metal electrode layer is further deposited by electron beam evaporation technology. The selected metals are high-purity titanium (Ti) and chromium (Cr), with purities as high as 99.999% to ensure excellent electrical conductivity and chemical stability of the electrode layer.

[0137] The electron beam evaporation process is carried out in a high-vacuum cavity. First, metal Ti is prepared, and the electron beam acceleration voltage is set at 9.7 keV and the power is adjusted to 39.7%. After the Ni crucible cools down, metal Cr is prepared. The electron beam acceleration voltage is set at 9.7 keV and the power is adjusted to 38%. The crystal oscillator monitoring system is used throughout the process to conduct real-time control on the metal growth rate, which is stable at Around, the deposition temperature was maintained at room temperature. Finally, the thickness of the metal electrode layer was approximately 100 nm (the thickness of the Ti layer was 70 nm, and the thickness of the Cr layer was 30 nm), with a flat surface and good adhesion. After the deposition was completed, the sample was taken out of the vacuum chamber, and a composite electrode for nickel oxide-based devices with structural integrity, clear interfaces, and excellent ohmic contact characteristics could be obtained, providing a reliable basis for subsequent device performance testing and integrated applications.

[0138] In this embodiment, the current-voltage (I-V) characteristic curve of the NiO / Ti-Cr contact interface is as Figure 5 shown.

[0139] Comparative Example 3

[0140] This comparative example provides a method for preparing a composite electrode.

[0141] Compared with Example 6, this comparative example is the same as Example 6 except that it does not contain a NiO intermediate layer with a Li doping concentration of 2 at.%.

[0142] In this comparative example, the current-voltage (I-V) characteristic curve of the NiO / Ti-Cr contact interface is as Figure 5 shown.

[0143] Through Figure 5 it can be found that the contact between undoped NiO and Ti-Cr (Comparative Example 3, black curve) shows a relatively small current, indicating that there is a serious barrier effect or extremely high contact resistance at the contact, and the curve is relatively curved. When a 2% Li-doped NiO intermediate layer (Example 5, red curve) is introduced at the interface, the I-V curve is slightly improved and the current response increases, indicating that the carrier injection efficiency has been improved to some extent, but an ideal ohmic contact has still not been formed. After further increasing the Li doping concentration to 4% (Example 6, blue curve), the I-V curve becomes significantly linear and the current value increases significantly, indicating that a good ohmic contact has been achieved at the interface. This result shows that an NiO intermediate layer with an appropriate concentration of Li doping can effectively regulate the conductance characteristics and interface energy band structure of NiO, thereby improving the metal-semiconductor contact performance.

[0144] Generally speaking, after adding the Li-doped NiO intermediate layer, the ohmic contact between NiO and different metals has been significantly optimized. And the intermediate layer with a 4% doping concentration optimizes the ohmic contact more significantly than the 2% doping concentration. It can be judged that adding the Li-doped NiO intermediate layer is an effective strategy for regulating the metal / NiO contact characteristics.

[0145] In summary, a composite electrode for a nickel oxide-based device provided by the present invention adopts a combination form of an intermediate layer - metal electrode layer, and is integrally composed of a NiO substrate, a Li-doped NiO intermediate layer, and a metal electrode layer stacked in sequence. By introducing a Li:NiO intermediate layer with a high hole concentration and a low resistivity between NiO and the metal electrode, the interface barrier is effectively reduced, the current injection efficiency is improved, stable and efficient ohmic contact is achieved, which helps to improve the overall performance of the device and the reliability of long-term operation. The present invention has significant advantages in solving the problem of electrode contact of NiO materials and has broad application prospects in the fields of optoelectronic devices, transparent electronic devices, gas sensors, etc.

[0146] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the interpretation of the present invention should be within the protection scope of the present invention.

Claims

1. A composite electrode for a nickel oxide-based device, characterized in that, It includes a nickel oxide substrate deposited on the upper surface of a substrate, a lithium-doped nickel oxide intermediate layer, and a metal electrode layer that are vertically stacked from bottom to top; Among them, the lithium-doped nickel oxide intermediate layer and the metal electrode layer are deposited on the upper surface of the nickel oxide substrate in a "return" shape; The resistivity of the lithium-doped nickel oxide intermediate layer is less than 1 Ω·cm, and the hole concentration is greater than 10 17 cm -3 .

2. The composite electrode for a nickel oxide-based device according to claim 1, wherein The thickness of the nickel oxide substrate is 300 - 600 nm.

3. The composite electrode for a nickel oxide-based device according to claim 1, characterized in that, In the lithium-doped nickel oxide intermediate layer, the doping amount of lithium is 0.1 - 10 at.%. The thickness of the lithium-doped nickel oxide intermediate layer is 5 - 200 nm.

4. A composite electrode for a nickel oxide-based device according to claim 1, wherein, The material of the metal electrode layer is selected from one or two of nickel, chromium, titanium or gold with a purity of 99% - 99.9999%; The thickness of the metal electrode layer is 5 - 200 nm.

5. A method for preparing a composite electrode for a nickel oxide-based device according to any one of claims 1 to 4, characterized in that, It includes the following steps: (S1) Use the nickel oxide thin film pre-deposited on the substrate as the substrate material. After post-treatment, place a baffle at the center of the nickel oxide thin film, and deposit the lithium-doped nickel oxide intermediate layer; (S2) After step (S1) is completed, deposit the metal electrode layer on the upper surface of the lithium-doped nickel oxide intermediate layer after post-treatment to prepare a composite electrode for nickel oxide-based devices.

6. The preparation method of a composite electrode for a nickel oxide-based device according to claim 5, characterized in that, In step (S1), the post-treatment is to remove organic impurities and particle contamination on the surface of the substrate material. Place the substrate material in acetone, methanol, and deionized water for cleaning in sequence. After cleaning, use high-purity nitrogen to thoroughly dry the substrate material to ensure its surface is clean and dry; The area of the baffle is 1 mm * 1 mm / 1 cm * 1 cm of the nickel oxide substrate.

7. The preparation method of a composite electrode for a nickel oxide-based device according to claim 5, characterized in that, In step (S1), the deposition of the lithium-doped nickel oxide intermediate layer is a room-temperature magnetron sputtering technique; In step (S2), the deposition is an electron beam evaporation deposition technique.

8. The preparation method of a composite electrode for a nickel oxide-based device according to claim 7, characterized in that, During the room-temperature magnetron sputtering process, the working atmosphere is high-purity argon, the working pressure is 0.4 - 0.8 Pa, the radio frequency power is 40 - 80 W, and the substrate material rotates at a rate of 1 - 5 rad / min.

9. The preparation method of a composite electrode for a nickel oxide-based device according to claim 7, characterized in that, During the electron beam evaporation deposition process, the electron beam acceleration voltage is 9 - 12 keV, the power is 38 - 43%, and the metal growth rate is 10. Application of a composite electrode for nickel oxide-based devices as described in any one of claims 1 - 4 in the preparation of electronic devices.

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