ZnS thin film photoelectric device with persistent photoconductivity effect and preparation method thereof

Abstract

The application relates to the technical field of semiconductor photoelectric devices, in particular to a ZnS thin film photoelectric device with a sustained photoconductive effect and a preparation method thereof. A Pt / ZnS / ITO three-layer structure is constructed, a required pattern is obtained by using photoetching in a preparation process, thin film deposition is completed by combining a magnetron sputtering coating process and an electron beam evaporation coating process, finally, corresponding products are put into a reaction chamber of CVD for reaction and annealing treatment to obtain final products. The device has a significant resistance change under ultraviolet light irradiation, still maintains a conductive state after photoelectric response, shows a sustained photoconductive characteristic, has strong sustained light response performance and light signal retention capacity, and is suitable for the fields of optical storage and memory type photoelectronic devices. In addition, the device has excellent response capacity to ultraviolet light and is suitable for the field of ultraviolet light detection. The problems of a complex ZnS photoelectric device structure, insufficient interface contact performance and weak sustained light response capacity are solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device technology, specifically to a ZnS thin-film optoelectronic device with continuous photoconductivity and its preparation method. Background Technology

[0002] ZnS is a typical group II-VI wide-bandgap semiconductor material, possessing a large bandgap, high transmittance, and good chemical stability, making it promising for applications in ultraviolet light detection, optoelectronic devices, and photoresponse. With the development of thin film deposition technology, ZnS thin films, with their relatively simple fabrication process, low cost, and ease of large-area deposition, have gradually become one of the important materials for optoelectronic device research.

[0003] Currently, ZnS thin-film optoelectronic devices are mainly fabricated using methods such as magnetron sputtering, evaporation deposition, and chemical deposition. Although existing ZnS-based optoelectronic devices can produce a certain photoresponse under ultraviolet light irradiation, they still suffer from problems such as complex device structure, insufficient interfacial contact performance, and weak sustained response capability.

[0004] Furthermore, in existing ZnS thin-film optoelectronic devices, photogenerated carriers tend to recombine easily after illumination ceases, resulting in a short recovery time for the device's conductivity to return to its initial state, thus limiting its sustained photoresponse performance. Sustained photoconductivity refers to the phenomenon where the conductivity state of a semiconductor material remains unchanged for a certain period after illumination ceases. This effect has potential applications in optical storage (such as optical memory and optical write memory cells), optical detection (such as photoconductivity detectors, ultraviolet detectors, and ultraviolet sensors), and memory-type optoelectronic devices (such as optical memory devices, photoresponse memristors, and photosynaptic devices). Summary of the Invention

[0005] The purpose of this invention is to provide a ZnS thin film optoelectronic device with continuous photoconductivity and its fabrication method. By constructing a Pt / ZnS / ITO three-layer structure and combining it with an annealing process, the photoresponse stability of the ZnS thin film and the conductivity of the device are improved, thus solving the problems of complex structure, insufficient interfacial contact performance and weak continuous photoresponse capability of existing ZnS optoelectronic devices.

[0006] To achieve the above objectives, the present invention provides a method for fabricating a ZnS thin-film optoelectronic device with a sustained photoconductivity effect, comprising the following steps:

[0007] Step 1: Use a smooth, rigid thin-film material as the device substrate;

[0008] Step 2: Perform photolithography on the substrate surface to obtain the underlying Pt electrode pattern;

[0009] Step 3: Deposit a Pt metal thin film on the substrate surface with electrode patterns using metal or oxide thin film deposition technology;

[0010] Step 4: Perform photolithography again on the surface of the Pt metal thin film to obtain the ZnS pattern of the intermediate active layer;

[0011] Step 5: Deposit a ZnS thin film on the surface of the ZnS patterned intermediate active layer using metal or oxide thin film deposition technology to obtain a patterned Pt / ZnS structure;

[0012] Step 6: Perform photolithography again on the patterned Pt / ZnS structure surface to obtain the top ITO electrode pattern;

[0013] Step 7: Deposit an ITO thin film on the surface of the top ITO electrode pattern using metal or oxide thin film deposition technology to obtain a patterned Pt / ZnS / ITO structure;

[0014] Step 8: Place the patterned Pt / ZnS / ITO structure into the CVD reaction chamber, introduce carrier gas at a certain flow rate, heat to the corresponding temperature, maintain constant temperature for a certain period of time, and after heating is finished, allow it to cool naturally to room temperature, turn off the carrier gas, and complete the annealing.

[0015] Optionally, the rigid sheet material includes silicon oxide sheets, quartz glass sheets, and ceramic sheets, wherein the oxide layer thickness of the silicon oxide sheet is 100-300 nm.

[0016] Optionally, the photolithography technology used in the preparation process employs AZ5214 photoresist, AZ300 developer, and a URE-2000 / 35L ultraviolet depth lithography machine.

[0017] Optionally, the thin film in the metal or oxide thin film deposition technology includes magnetron sputtering deposition, thermal evaporation deposition, and electron beam evaporation deposition; the depositable metals are Pt, Pb, Au, Ti, Al, and Cu; and the depositable oxides are ITO, ZnO, and CuO.

[0018] Optionally, the carrier gas in step 8 is a mixture of hydrogen and argon, with the ratio of argon to hydrogen ranging from 97:3 to 5. The annealing temperature is 290℃ to 330℃, the heating rate is 5 to 10℃ / min, and the annealing time is 20 to 40 min.

[0019] This invention also proposes a ZnS thin-film optoelectronic device with a continuous photoconductivity effect, which is fabricated using the method described above. It adopts a three-layer structure of Pt / ZnS / ITO, with a substrate, a bottom Pt electrode pattern, a middle active ZnS pattern, and a top ITO electrode pattern arranged sequentially from bottom to top.

[0020] This invention provides a ZnS thin-film optoelectronic device with sustained photoconductivity and its fabrication method. A Pt / ZnS / ITO three-layer structure is constructed. During fabrication, photolithography is used to obtain the desired pattern, followed by magnetron sputtering and electron beam evaporation deposition to complete the thin film deposition. Finally, the device is placed in a CVD reaction chamber for reaction and annealing to obtain the final product. The device exhibits significant resistance changes under ultraviolet light irradiation and retains its conductive state after the light irradiation stops, demonstrating sustained photoconductivity. It also exhibits strong sustained photoresponse performance and optical signal retention, making it suitable for fields such as optical storage and memory-type optoelectronic devices. Furthermore, the device demonstrates excellent ultraviolet light response, making it suitable for ultraviolet light detection. This invention solves the problems of complex structure, insufficient interfacial contact performance, and weak sustained photoresponse capability in existing ZnS optoelectronic devices. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of a method for fabricating a ZnS thin-film optoelectronic device with a continuous photoconductivity effect according to the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of a ZnS thin-film optoelectronic device with continuous photoconductivity in a specific embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the light illumination experiment results in a specific embodiment of the present invention. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] Please see Figure 1 This invention provides a method for fabricating a ZnS thin-film optoelectronic device with a sustained photoconductivity effect, comprising the following steps:

[0027] S1: A smooth, rigid sheet material is used as the device substrate;

[0028] S2: Photolithography is performed on the substrate surface to obtain the underlying Pt electrode pattern;

[0029] S3: A Pt metal thin film is deposited on the surface of a substrate with an electrode pattern using metal or oxide thin film deposition technology;

[0030] S4: Photolithography is performed again on the surface of the Pt metal thin film to obtain the ZnS pattern of the intermediate active layer;

[0031] S5: A ZnS thin film is deposited on the surface of the ZnS patterned intermediate active layer using metal or oxide thin film deposition technology to obtain a patterned Pt / ZnS structure.

[0032] S6: Perform photolithography again on the patterned Pt / ZnS structure surface to obtain the top ITO electrode pattern;

[0033] S7: An ITO thin film is deposited on the structural surface of the top ITO electrode pattern using metal or oxide thin film deposition technology to obtain a patterned Pt / ZnS / ITO structure;

[0034] S8: Place the patterned Pt / ZnS / ITO structure into the CVD reaction chamber, introduce carrier gas at a certain flow rate, heat to the corresponding temperature, maintain constant temperature for a certain time, and after heating is finished, allow it to cool naturally to room temperature, turn off the carrier gas, and complete the annealing.

[0035] The rigid sheet material includes silicon oxide sheets, quartz glass sheets, and ceramic sheets, wherein the oxide layer thickness of the silicon oxide sheet is 100-300 nm.

[0036] The photolithography process used in the fabrication process employed AZ5214 photoresist, AZ300 developer, and a URE-2000 / 35L ultraviolet depth lithography machine.

[0037] The thin films in the metal or oxide thin film deposition technology include magnetron sputtering deposition, thermal evaporation deposition, and electron beam evaporation deposition; the depositable metals are Pt, Pb, Au, Ti, Al, and Cu; and the depositable oxides are ITO, ZnO, and CuO.

[0038] The carrier gas in step 8 is a mixture of hydrogen and argon, with the ratio of argon to hydrogen ranging from 97:3 to 5. The annealing temperature is 290℃ to 330℃, the heating rate is 5℃ to 10℃ / min, and the annealing time is 20 to 40 min.

[0039] The following description, in conjunction with specific embodiments and execution steps, provides further details:

[0040] In this embodiment, the rigid sheet material mentioned in step S1 is a silicon oxide sheet with an oxide layer thickness of 100~300 nm.

[0041] The Pt electrode pattern in step S2 is a square region of 3000 µm in size, with an electrode 200 µm wide extending to the right.

[0042] The metal or oxide thin film deposition technology mentioned in step S3 is a DC magnetron sputtering sputtering coating process with a working pressure of 0.4-0.6 Pa, a sputtering power of 97 W, a sputtering time of 240 s, and finally a Pt thin film with a thickness of 70-100 nm is deposited.

[0043] In step S4, the ZnS pattern is a square region of 3020µm in size, covering the Pt square region.

[0044] The metal or oxide thin film deposition technology described in step S5 is an electron beam evaporation coating process with a working pressure of 6.6 x 10⁻⁴ Pa, an evaporation power of 1800 W, an evaporation time of 1200 s, and finally a ZnS thin film with a thickness of 100-150 nm is deposited.

[0045] In step S6, the ITO electrode pattern is a square region of 1990 µm, covering the ZnS square region, with an electrode of 200 µm width extending upwards.

[0046] The metal or oxide thin film deposition technology described in step S7 is a DC magnetron sputtering sputtering coating process with a working pressure of 0.4-0.6 Pa, a sputtering power of 100 W, a sputtering time of 240 s, and finally an ITO thin film with a thickness of 50-80 nm is deposited.

[0047] The following explanation is based on specific process steps:

[0048] 1. Photolithography

[0049] The photolithography technique used in the fabrication process includes the following steps:

[0050] Step 1.1: Take a piece of silicon dioxide as a substrate;

[0051] Step 1.2: Place the silicon oxide wafer in a spin coater, add negative photoresist evenly on the silicon oxide wafer, set the rotation speed and time, so that the negative photoresist is evenly coated on the silicon oxide wafer;

[0052] Step 1.3: The silicon oxide wafer with a layer of negative photoresist is then heated on a hot plate and exposed in a photolithography machine;

[0053] Step 1.4: Place the silicon dioxide on a heating plate and heat it for a general exposure. After exposure, place the silicon dioxide wafer into the developer. After development, rinse it with deionized water 4-5 times to remove any developer residue.

[0054] Step 1.5: After thin film deposition, perform overlay etching, spin-coat negative photoresist, heat, use the display screen to find the corresponding position, and expose;

[0055] Step 1.6: Place the silicon dioxide on a hot plate and heat it once for general exposure. Then develop the above structure with developer and wash it with deionized water 4-5 times to remove developer residue.

[0056] Wherein, the thickness of the substrate oxide layer described in step 1.1 is 300 nm;

[0057] The photoresist used in steps 1.2 and 1.5 is AZ5214. The spin coater speed is set as follows: low speed 450r / min, 10 s rotation, high speed 4000r / min, 40 s rotation. The thickness of the photoresist after spin coating is approximately 1.4 µm.

[0058] In steps 1.3 and 1.5, the heating time is 90 seconds, the heating temperature is 105℃, and the exposure time is 4 seconds for the URE-2000 / 35L ultraviolet depth lithography machine.

[0059] The heating time for steps 1.4 and 1.6 is 120 seconds, the heating temperature is 120℃, and the developer for the URE-2000 / 35L UV depth lithography machine is AZ300, which requires 40-50 seconds of development.

[0060] 2. Metal or oxide deposition technology

[0061] Includes the following steps:

[0062] Step 2.1: Load the photolithographically lithographically completed sample and target into the metal / oxide coating machine;

[0063] Step 2.2: Configure the deposition environment required for the target material to achieve a high vacuum within the chamber;

[0064] Step 2.3: Introduce a certain flow rate of argon / oxygen as a carrier gas for deposition;

[0065] Step 2.4: Deposit thin films of different thicknesses under a specific working pressure, according to a certain power and time;

[0066] Step 2.5: After deposition is complete, turn off the machine and remove the sample;

[0067] Step 2.6: Immerse the deposited sample in acetone and sonicate to dissolve the photoresist and remove the film deposited outside the pattern. Then rinse with deionized water 4-5 times to remove acetone residue.

[0068] The metal / oxide coating machine mentioned in step 2.1 is a TRP-450 high vacuum three-target magnetron coating system and a VEB500 high vacuum electron beam and thermal evaporation coating system;

[0069] The high vacuum mentioned in step 2.2 is an ionization unit of 6.6 x 10⁻⁶. -4 ~5x10 -4 Pa;

[0070] The reaction carrier gas mentioned in step 2.3 is argon gas with a flow rate of 18-20 sccm during Pt deposition, and a mixture of argon and oxygen gas with an argon flow rate of 18-20 sccm and an oxygen flow rate of 0.1-0.3 sccm during ITO deposition.

[0071] Step 2.4: For Pt deposition, DC magnetron sputtering was used with a working pressure of 0.4-0.6 Pa, a power of 97 W, and a time of 240 s, resulting in a Pt electrode with a thickness of 70-100 nm. For ZnS deposition, electron beam evaporation was used with a working pressure of 6.6 x 10⁻⁶. -4 A ZnS thin film with a thickness of 100-150 nm was deposited by evaporation at a pressure of 0.4-0.6 Pa, a sputtering power of 1800 W, and an evaporation time of 1200 s. For ITO deposition, DC magnetron sputtering was used with a working pressure of 0.4-0.6 Pa, a sputtering power of 100 W, and a sputtering time of 240 s, resulting in an ITO electrode with a thickness of 50-80 nm.

[0072] 3. CVD Operation Procedures and Process Parameters

[0073] Step 3.1: Open the quartz tube of the CVD tube furnace;

[0074] Step 3.2: Prepare a quartz boat and clean it with anhydrous alcohol;

[0075] Step 3.3: Place the prepared components into the quartz boat and then into the quartz tube, and seal the quartz tube.

[0076] Step 3.4: Start the machine pump to create a vacuum inside the quartz tube, then open the gas valve to make the ratio of argon to hydrogen between 97:3 and 5.

[0077] Step 3.5: Set the heating rate to 5~10℃ / min, press the heating button, heat to between 290℃~330℃, and maintain for 20~40 min;

[0078] Step 3.6: After annealing is completed, open the CVD tube furnace shroud to cool down, while maintaining the same proportion of carrier gas. After cooling to room temperature, open the quartz tube and take out the device placed in the quartz boat.

[0079] For further details, please refer to Figure 2 The present invention also proposes a ZnS thin film optoelectronic device with continuous photoconductivity effect, which is prepared using the method for preparing the ZnS thin film optoelectronic device with continuous photoconductivity effect. It adopts a three-layer structure of Pt / ZnS / ITO, and from bottom to top, a substrate, a bottom Pt electrode pattern, a middle active layer ZnS pattern, and a top ITO electrode pattern are arranged sequentially. Specifically, it includes a silicon oxide wafer 100, a Pt metal thin film 200, a ZnS thin film 300, and an ITO thin film 400.

[0080] In this embodiment, the device performance was also tested experimentally, as detailed in the diagram below. Figure 3 As shown.

[0081] In summary, the present invention has the following beneficial effects:

[0082] 1. This invention adopts a Pt / ZnS / ITO three-layer structure, with a clear structural hierarchy of the device. The thin film deposition is completed by combining magnetron sputtering and electron beam evaporation processes. The preparation process is simple and controllable, and is suitable for the large-scale preparation and integration of thin film optoelectronic devices.

[0083] 2. The device exhibits a significant change in resistance under ultraviolet light irradiation and retains its conductive state after photoelectric response even after the light irradiation stops, demonstrating continuous photoconductivity. It also exhibits strong continuous photoresponse performance and optical signal retention capability, making it suitable for fields such as optical storage and memory-type optoelectronic devices. Furthermore, the device has excellent response capability to ultraviolet light, making it suitable for ultraviolet light detection.

[0084] 3. After annealing, the ZnS thin film exhibits good crystallinity and the interfacial contact performance of the ITO transparent conductive electrode. The device has low resistance, stable conductivity and photoresponse performance, and great potential for practical applications.

[0085] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for fabricating a ZnS thin-film optoelectronic device with continuous photoconductivity, characterized in that, Includes the following steps: Step 1: Use a smooth, rigid thin-film material as the device substrate; Step 2: Perform photolithography on the substrate surface to obtain the underlying Pt electrode pattern; Step 3: Deposit a Pt metal thin film on the substrate surface with electrode patterns using metal or oxide thin film deposition technology; Step 4: Perform photolithography again on the surface of the Pt metal thin film to obtain the ZnS pattern of the intermediate active layer; Step 5: Deposit a ZnS thin film on the surface of the ZnS patterned intermediate active layer using metal or oxide thin film deposition technology to obtain a patterned Pt / ZnS structure; Step 6: Perform photolithography again on the patterned Pt / ZnS structure surface to obtain the top ITO electrode pattern; Step 7: Deposit an ITO thin film on the surface of the top ITO electrode pattern using metal or oxide thin film deposition technology to obtain a patterned Pt / ZnS / ITO structure; Step 8: Place the patterned Pt / ZnS / ITO structure into the CVD reaction chamber, introduce carrier gas at a certain flow rate, heat to the corresponding temperature, maintain constant temperature for a certain period of time, and after heating is finished, allow it to cool naturally to room temperature, turn off the carrier gas, and complete the annealing.

2. The method for fabricating a ZnS thin-film optoelectronic device with sustained photoconductivity as described in claim 1, characterized in that, The rigid sheet material includes silicon oxide sheets, quartz glass sheets, and ceramic sheets, wherein the oxide layer thickness of the silicon oxide sheet is 100-300 nm.

3. The method for fabricating a ZnS thin-film optoelectronic device with continuous photoconductivity as described in claim 2, characterized in that, The photolithography process used in the fabrication process employed AZ5214 photoresist, AZ300 developer, and a URE-2000 / 35L ultraviolet depth lithography machine.

4. The method for fabricating a ZnS thin-film optoelectronic device with sustained photoconductivity as described in claim 3, characterized in that, The thin films in the metal or oxide thin film deposition technology include magnetron sputtering deposition, thermal evaporation deposition, and electron beam evaporation deposition; the depositable metals are Pt, Pb, Au, Ti, Al, or Cu; and the depositable oxides are ITO, ZnO, or CuO.

5. The method for fabricating a ZnS thin-film optoelectronic device with sustained photoconductivity as described in claim 4, characterized in that, The carrier gas in step 8 is a mixture of hydrogen and argon, with the ratio of argon to hydrogen ranging from 97:3 to 5. The annealing temperature is 290℃ to 330℃, the heating rate is 5℃ to 10℃ / min, and the annealing time is 20 to 40 min.

6. A ZnS thin-film optoelectronic device with continuous photoconductivity, fabricated using the method for fabricating a ZnS thin-film optoelectronic device with continuous photoconductivity as described in any one of claims 1 to 5, characterized in that, It adopts a three-layer structure of Pt / ZnS / ITO, with the substrate, bottom layer Pt electrode pattern, middle active layer ZnS pattern and top layer ITO electrode pattern arranged from bottom to top.

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