A lead selenide room temperature mid-wave infrared detector and a preparation method and application thereof

Abstract

The application discloses a preparation method of a lead selenide room-temperature mid-wave infrared detector, which comprises the following steps: (1) adopting a magnetron sputtering technology, and depositing a lead selenide film layer on a substrate by using oxygen as a reaction gas; (2) placing the lead selenide film in a horizontal tube furnace to realize high-temperature oxidation in pure oxygen at normal pressure; and (3) placing the lead selenide film in a vertical tube furnace to realize high-temperature iodization in an environment at normal pressure. The lead selenide film is prepared by the magnetron sputtering technology, compared with chemical bath deposition, the film quality is effectively improved, large-area and high-uniformity film preparation is realized, the magnetron sputtering film is subjected to high-temperature "oxidation-iodization" treatment, the magnetron sputtering film has excellent light response to infrared light, the sensitization technology is specific, clear and good in repeatability, the sensitized lead selenide film layer and a top electrode are combined to form a photoconductive type detector, and the device has a room-temperature device specific detectivity of 7.6*10 9 Jones@4.3 mu m, and excellent performance.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a lead selenide room temperature mid-wave infrared detector, its preparation method, and its application. Background Technology

[0002] As is well known, in addition to visible light, all objects spontaneously radiate infrared light according to Planck's law. Infrared detection technology can convert these invisible infrared radiation signals into electrical signals according to certain rules, thereby obtaining the rich optical information contained in the infrared radiation of the target object. Infrared detection technology is extremely important, and in the military field it can be used for infrared aiming, reconnaissance, red-light sensing, and guidance; in the civilian field it can be used for food damage detection, autonomous driving, atmospheric monitoring, and facial recognition. The next generation of infrared detection technology is developing along the Swap3 concept, and improving the operating temperature of the detector and reducing the cooling requirements have become key to achieving miniaturization, low power consumption, and low cost of detection systems. Against this backdrop, polycrystalline PbSe materials, due to their ability to operate at room temperature, are widely used in 1-5μm spectral detection.

[0003] The room-temperature infrared detection properties of PbSe materials were discovered in the 1930s. Currently, the mainstream preparation method for this material is chemical bath deposition (CBD). The deposited film still requires sensitization to achieve a high response to infrared light. However, this preparation and sensitization technique still has the following problems:

[0004] (1) Thin films prepared using CBD technology have problems such as low stability, uniformity, low yield, and poor compatibility with substrates, making large-scale manufacturing impossible;

[0005] (2) There is no unified understanding of the sensitization mechanism and technology of thin films, which makes it difficult to reproduce and improve the detection performance of devices. Summary of the Invention

[0006] In response to the problems raised in the background art, this invention proposes a lead selenide room temperature mid-wave infrared detector, its preparation method and application, aiming to effectively improve the thin film deposition quality and obtain a high-performance lead selenide room temperature mid-wave infrared detector.

[0007] In a first aspect, this application provides a method for fabricating a lead selenide room-temperature mid-wave infrared detector, comprising the following steps:

[0008] (1) A lead selenide thin film layer was deposited on the substrate using magnetron sputtering technology with oxygen as the reaction gas.

[0009] (2) The lead selenide film obtained in step (1) is placed in a horizontal tube furnace and treated at 250-350℃ for 30-60 minutes to achieve high-temperature oxidation in a normal pressure pure oxygen atmosphere;

[0010] (3) The lead selenide film obtained in step (2) is placed in a vertical tube furnace and treated at 350-400℃ for 10-30 minutes. Iodine vapor at 20-30℃ is introduced with oxygen as a carrier to achieve high-temperature iodization under normal pressure.

[0011] Preferably, step (1) employs magnetron sputtering technology, using oxygen as the reactant gas, to deposit a lead selenide thin film layer on the substrate, specifically including:

[0012] a) Place the substrate in the magnetron sputtering chamber and adjust the chamber pressure to 10. -3 -10 -4 Pa;

[0013] b) Introduce argon gas into the chamber as a sputtering gas and adjust the pressure inside the chamber to 0.5-2 Pa;

[0014] c) A lead selenide target is sputtered using radio frequency technology to form a lead selenide thin film on the substrate surface;

[0015] d) Introduce oxygen as a reaction gas into the chamber, with an oxygen content of 1%-5%, so that oxygen element is incorporated into the membrane.

[0016] Preferably, the thickness of the lead selenide thin film deposited by magnetron sputtering in step (1) is 650-750 nm.

[0017] Preferably, the deposition rate of magnetron sputtering in step (1) is 0.2-0.5 nm / s, so as to form columnar crystals with a horizontal dimension of 30-80 nm.

[0018] Preferably, the heating rate in steps (2) and (3) is 10-20℃ / min.

[0019] Preferably, in step (3), during the iodination treatment, the oxygen flow rate is 50-100 sccm, and the iodine vapor concentration is the equilibrium concentration at 20-30℃ under saturated vapor pressure.

[0020] Preferably, step (3) further includes: closing the iodine inlet and outlet channels after iodization and evacuating to a vacuum of ≤10. 2 Pa removes residual sublimed iodine, and then oxygen is introduced to restore normal pressure.

[0021] Secondly, this application provides a lead selenide room temperature mid-wave infrared detector prepared and sensitized by magnetron sputtering, comprising: a substrate, a lead selenide thin film layer prepared by any one of claims 1-7 and disposed on the substrate, and a top electrode formed on the surface of the lead selenide thin film layer, forming a photoconductive detector structure. A back reflection structure is introduced on the back side of the substrate to reflect the infrared light transmitted out of the device and reflect it back into the device, thereby further improving the infrared light utilization rate.

[0022] Preferably, the substrate is sapphire, the lead selenide thin film layer has an absorption cutoff wavelength of 4.3 μm and a thickness of 500-1000 nm, the top electrode is an Au electrode with a thickness of 50-120 nm, and the back reflection structure is an Ag mirror structure with a thickness of 10-100 nm.

[0023] Thirdly, this application provides an application of a lead selenide room temperature mid-wave infrared detector in infrared detection or thermal imaging in the 3-5μm band.

[0024] The beneficial effects of this invention are as follows: (1) This invention prepares lead selenide thin films using magnetron sputtering technology, which can effectively improve film quality and achieve large-area, highly uniform film preparation compared to chemical bath deposition; (2) This invention performs high-temperature "oxidation-iodization" treatment on magnetron sputtered films, enabling them to have excellent photoresponse to infrared light. This sensitization technique is specific, clear, and reproducible, providing a clear sensitization path for magnetron sputtered films; (3) This invention constructs a photoconductive detector by combining the sensitized lead selenide thin film layer with the top electrode. The device has a specific detectivity of 7.6 × 10⁻⁶ at room temperature in the mid-infrared band. 9 Jones@4.3μm exhibits excellent performance. Attached Figure Description

[0025] 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.

[0026] Figure 1 This is a schematic flowchart of an embodiment of the method for fabricating a lead selenide room temperature mid-wave infrared detector according to the present invention (showing the complete process of magnetron sputtering deposition (S11), high-temperature oxidation (S12), and high-temperature iodization (S13) to obtain an active thin film layer).

[0027] Figure 2 This is a schematic flowchart of another embodiment of the method for fabricating a lead selenide room temperature mid-wave infrared detector according to the present invention (showing the fabrication of the substrate (S21), top electrode (S22), and back reflection structure (S23) excluding the active thin film layer, to obtain the complete process of obtaining a photoconductive device);

[0028] Figure 3 This is a large-area thin film deposition and its microstructure diagram of an embodiment of a lead selenide room temperature mid-wave infrared detector disclosed in this invention.

[0029] Figure 4This is a schematic diagram of the device structure of an embodiment of a lead selenide room temperature mid-wave infrared detector disclosed in this invention;

[0030] The structure consists of: 1. Back reflection structure, 2. Substrate, 3. Lead selenide active layer, and 4. Top electrode.

[0031] Figure 5 This is a detection performance diagram of an embodiment of a lead selenide room temperature mid-wave infrared detector disclosed in this invention;

[0032] Figure 6 This invention relates to the application of the lead selenide room temperature mid-wave infrared detector prepared in the field of thermal imaging. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Please see Figure 1 , Figure 1 This is a schematic flowchart of an embodiment of the magnetron sputtering preparation and sensitization method for a lead selenide room temperature mid-wave infrared detector (magnetron sputtering preparation and sensitization method) of the present invention. The method includes the following steps:

[0035] Step S11: Deposit a lead selenide thin film layer on the substrate using magnetron sputtering technology;

[0036] Step S12: Place the lead selenide film obtained in step S11 in a horizontal tube furnace and oxidize it at high temperature in a pure oxygen atmosphere at atmospheric pressure.

[0037] Step S13: Place the oxidized lead selenide film in a vertical tube furnace, and introduce sublimated iodine vapor with oxygen as a carrier to iodize at high temperature under normal pressure.

[0038] Please combine Figure 2 , Figure 2 This is a schematic flowchart of another embodiment of the method for fabricating a lead selenide mid-wave infrared detector according to the present invention (magnetron sputtering preparation and sensitization method), compared to... Figure 1 The embodiment shown, Figure 2 The illustrated embodiment further includes the following steps before step S11:

[0039] Step S21: Provide a substrate.

[0040] The substrate is used to support the various layers of the infrared detector. The substrate can be any of glass, silicon wafer, quartz wafer or sapphire wafer. In this embodiment, the substrate is sapphire with dimensions of length × width × thickness = 10mm × 10mm × 0.5mm. The surface is ultrasonically cleaned with deionized water and ethanol.

[0041] After preparing the substrate, a lead selenide thin film layer is further prepared on the substrate (see details). Figure 1 (Step S11).

[0042] Step S11: Perform magnetron sputtering of lead selenide thin film on sapphire substrate.

[0043] The substrate was placed in the magnetron sputtering chamber, and the chamber pressure was evacuated to 5 × 10⁻⁶. -4 Pa high vacuum state.

[0044] Argon gas was introduced into the chamber as the sputtering gas, with an argon gas inlet flow rate of 30 sccm, and the chamber pressure was adjusted to 1 Pa.

[0045] Lead selenide targets were sputtered using radio frequency technology to form a lead selenide thin film on the substrate surface. Specifically, the lead selenide active layer deposited by magnetron sputtering was 700 nm thick, and the microstructure consisted of columnar crystals with a horizontal dimension of 50 nm.

[0046] Meanwhile, oxygen is introduced into the chamber as a reaction gas. In this embodiment, the oxygen inlet flow rate is 0.8 sccm.

[0047] After the magnetron sputtered lead selenide layer is prepared, a high-temperature sensitization treatment is performed. For details, please refer to [link to relevant documentation]. Figure 1 Steps S12 and S13:

[0048] Step S12: The obtained lead selenide film is placed in a horizontal tube furnace and oxidized at high temperature in a pure oxygen atmosphere at atmospheric pressure.

[0049] Specifically, the lead selenide film is placed in a horizontal tube furnace, the vacuum inside the tube furnace is evacuated to 5 Pa, then the evacuation is stopped, and oxygen is introduced to restore atmospheric pressure. The evacuation and oxygen introduction operations are repeated three times to achieve a pure oxygen atmosphere in the tube furnace chamber. Oxygen is continuously introduced at a flow rate of 40 sccm at the front end of the tube furnace chamber, and the gas outlet is opened at the rear end to maintain atmospheric pressure inside the chamber.

[0050] The furnace chamber of the tube furnace is heated at a slow heating rate until the high-temperature oxidation temperature is reached. In one embodiment, the slow heating rate is set to 10°C / min. Heating is stopped when 300°C is reached, and thin film oxidation is performed at this temperature. The high-temperature oxidation time is 60 minutes. After the oxidation time is reached, heating of the tube furnace is stopped, and the furnace is allowed to cool naturally to room temperature.

[0051] Step S13: The oxidized lead selenide film is placed in a vertical tube furnace, and sublimated iodine vapor is introduced with oxygen as a carrier to iodize at high temperature under normal pressure.

[0052] Specifically, the oxidized lead selenide film is placed in a vertical tube furnace, and the vacuuming and oxygen-introducing operations are repeated three times to achieve a pure oxygen atmosphere in the vertical tube furnace chamber. Then, oxygen is continuously introduced into the front end of the vertical tube furnace chamber at a flow rate of 10 sccm, and the gas outlet channel is opened at the rear end to maintain atmospheric pressure in the chamber.

[0053] The tubular furnace chamber is heated at a slow rate until the high-temperature iodization temperature is reached. In one embodiment, the slow heating rate is set to 10°C / min, and heating is stopped when 400°C is reached, at which temperature thin-film iodization is performed.

[0054] Close the pure oxygen inlet channel and open the sublimated iodine inlet channel with oxygen as the carrier gas at a flow rate of 80 sccm for iodization for 23 minutes. The sublimated iodine concentration used is the saturated vapor concentration, and the iodine temperature is 25℃.

[0055] After iodization is completed, the iodine inlet and outlet channels are closed, and the vacuum inside the vertical tube furnace is evacuated to 100 Pa using a mechanical pump. After the vacuum treatment, the sublimed iodine inside the tube furnace is completely removed, and the reaction between the lead selenide film and iodine stops. Then, oxygen is introduced to restore the pressure to atmospheric pressure, and the furnace is allowed to cool naturally to room temperature.

[0056] Please continue reading Figure 2 After completing the high-temperature sensitization treatment through step S13, step S22 is performed: a top electrode is prepared on the side of the lead selenide film away from the substrate.

[0057] In one embodiment, an Au film is deposited on the lead selenide film layer by thermal evaporation deposition to form a top electrode with a thickness of 60 nm, forming a 3 mm × 0.3 mm photosensitive area.

[0058] Step S23: Prepare a back reflection structure on the back of the substrate.

[0059] In one embodiment, an Ag thin film with a thickness of 50 nm is prepared by magnetron sputtering deposition and added to the back side of the substrate.

[0060] Please see Figure 3 , Figure 3 This invention provides a large-area thin film deposition and its microstructure of a lead selenide room-temperature mid-wave infrared detector (fabricated by magnetron sputtering). The thin film is deposited on a glass substrate with an area of ​​approximately 10 × 10 cm². 2This method enables the fabrication of large-area (≥4-inch wafer-level) thin films. The microstructure at the four corners and center of the film is characterized, revealing columnar crystals with a horizontal dimension of 50 nm. The morphology and thickness exhibit good consistency, achieving highly uniform thin film fabrication.

[0061] Please see Figure 4 , Figure 4 This is a schematic diagram of a lead selenide room temperature mid-wave infrared detector (a lead selenide mid-wave infrared detector prepared and sensitized by magnetron sputtering) provided in this application. The infrared detector includes: a back reflection structure 1, a substrate 2, a lead selenide active layer 3 prepared by magnetron sputtering and sensitized by "oxidation-iodization" synergistic process, and a top electrode 4. The substrate 2 and the top electrode 4 are located on opposite sides of the lead selenide active layer 3, and the back reflection structure 1 is located on the back of the substrate 2.

[0062] Specifically, the lead selenide room-temperature mid-wave infrared detector disclosed in this application comprises, from bottom to top: a back reflection structure 1, a substrate 2, a lead selenide active layer 3, and a top electrode 4. The substrate 2 is sapphire, the lead selenide active layer 3 has an absorption cutoff wavelength of 4.3 μm and a thickness of 700 nm, the top electrode 4 is an Au electrode with a thickness of 100 nm, and the back reflection structure 1 is an Ag mirror structure with a thickness of 100 nm. The lead selenide active layer 3, prepared and sensitized by magnetron sputtering, and the top electrode 4 constitute a photoconductive infrared detector device. After high-temperature sensitization, the carrier lifetime of the lead selenide active layer 3 is greatly extended, resulting in a photoconductive device with low dark current and high optical response. When mid-wave infrared light is incident on the device, the lead selenide active layer 3 absorbs the infrared light and converts infrared photons into photogenerated carriers. The top electrode 4 is used to collect charge carriers in the active layer and conduct current under the applied bias voltage. The back reflection structure 1 is used to reflect the infrared light transmitted out of the device and reflect it back into the device, further improving the utilization rate of infrared light.

[0063] Please see Figure 5 , Figure 5 This is a performance schematic diagram of a lead selenide room temperature mid-wave infrared detector provided in this application. Figure 5 A represents the spectral response of the lead selenide mid-wave infrared detector, with a cutoff wavelength of 4.3 μm. Figure 5 B represents the light-dark current-voltage characteristic curve of the lead selenide mid-wave infrared detector. Under a bias voltage of 10V, the light-dark current ratio of the device is 38.4% under the illumination of an LED light source with a power of 0.95mW and a center wavelength of 1550nm, and the light-dark current ratio is 81.6% under the illumination of a blackbody light source with a power of 2.25mW and a temperature of 400℃. Figure 5 C represents the noise power density of the lead selenide mid-wave infrared detector as a function of frequency. At a bias voltage of 10V, the noise power density of the device at 1000Hz is 3.12 × 10⁻⁶. -14 A / Hz1 / 2 Therefore, the specific detectivity of the infrared detector at the 1550nm band is calculated to be 7.3 × 10⁻⁶. 9 Jones achieved a specific detectivity of 5.8 × 10⁻⁶ under blackbody illumination at 400°C. 9 Jones; Figure 5 D represents the specific detectivity spectrum of the device, and the specific detectivity of the device exceeds 10 over a wide spectral range. 10 Jones, with a detectivity of 7.6 × 10⁻⁶ at the cutoff wavelength. 10 Jones@4.3μm.

[0064] Please see Figure 6 , Figure 6 This invention relates to the application of the lead selenide room-temperature mid-wave infrared detector prepared in the field of thermal imaging. For example... Figure 6 As shown in A, for a size of 2×2cm 2 Imaging a high-temperature ceramic sheet with a core temperature of 350℃, the mid-infrared image of the ceramic sheet is clearly visible in complete darkness. When part of the ceramic sheet is blocked with transparent glass, the glass hardly obstructs the image in visible light, but the glass blockage is clearly visible in the mid-infrared image. Mid-infrared imaging can also detect the temperature distribution of high-temperature objects, such as... Figure 6 As shown in Figure B, the visible light image cannot identify the temperature distribution of the soldering iron. In contrast, the mid-infrared image clearly shows that the tip of the soldering iron is the brightest, corresponding to the highest temperature, while the tail is the weakest, corresponding to the lowest temperature.

[0065] In summary, this invention prepares lead selenide thin films using magnetron sputtering technology, which, compared to chemical bath deposition, can effectively improve film quality and achieve large-area, highly uniform film preparation; (2) this invention performs high-temperature "oxidation-iodization" treatment on the magnetron sputtered thin film, enabling the magnetron sputtered thin film to have excellent photoresponse to infrared light. This sensitization technique is specific, clear, and reproducible, providing a clear sensitization path for magnetron sputtered thin films; (3) this invention constructs a photoconductive detector by combining the sensitized lead selenide thin film layer with the top electrode. The device has a specific detectivity of 7.6 × 10⁻⁶ at room temperature in the mid-infrared band. 9 Jones@4.3μm exhibits excellent performance.

[0066] 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 lead selenide room-temperature mid-wave infrared detector, characterized in that: Includes the following steps: (1) A lead selenide thin film layer was deposited on the substrate using magnetron sputtering technology with oxygen as the reactant gas; (2) The lead selenide film obtained in step (1) is placed in a horizontal tube furnace and treated at 250-350 °C for 30-60 min to achieve high-temperature oxidation in a pure oxygen atmosphere at normal pressure. (3) The lead selenide film obtained in step (2) is placed in a vertical tube furnace and treated at 350-400 °C for 10-30 min. Iodine vapor is introduced at 20-30 °C using oxygen as a carrier to achieve high-temperature iodization under normal pressure. Step (1) employs magnetron sputtering technology, using oxygen as the reactant gas, to deposit a lead selenide thin film layer on the substrate, specifically including: a) Place the substrate in the magnetron sputtering chamber and adjust the chamber pressure to 10. -³ -10 -4 Pa; b) Introduce argon gas into the chamber as a sputtering gas and adjust the pressure inside the chamber to 0.5-2 Pa; c) A lead selenide target is sputtered using radio frequency technology to form a lead selenide thin film on the substrate surface; d) Introduce oxygen as a reactant gas into the chamber, with an oxygen content of 1%-5%, so that oxygen element is incorporated into the membrane.

2. The method for fabricating a lead selenide room-temperature mid-wave infrared detector as described in claim 1, characterized in that: In step (1), the thickness of the lead selenide thin film deposited by magnetron sputtering is 650-750 nm.

3. The method for preparing a lead selenide room temperature mid-wave infrared detector as described in claim 1, characterized in that: In step (1), the deposition rate of magnetron sputtering is 0.2-0.5 nm / s to form columnar crystals with a horizontal dimension of 30-80 nm.

4. The method for fabricating a lead selenide room-temperature mid-wave infrared detector as described in claim 1, characterized in that: The heating rate in steps (2) and (3) is 10-20 °C / min.

5. The method for fabricating a lead selenide room-temperature mid-wave infrared detector as described in claim 1, characterized in that: During the iodization treatment in step (3), the oxygen flow rate is 50-100 sccm, and the iodine vapor concentration is the equilibrium concentration at 20-30 ℃ under saturated vapor pressure.

6. The method for fabricating a lead selenide room-temperature mid-wave infrared detector as described in claim 1, characterized in that: Step (3) also includes: closing the iodine inlet and outlet channels after iodization and evacuating to a vacuum of ≤10. 2 Pa removes residual sublimed iodine, and then oxygen is introduced to restore normal pressure.

7. A lead selenide room temperature mid-wave infrared detector, characterized in that: The device includes a substrate, a lead selenide thin film layer prepared by any one of claims 1-6 and disposed on the substrate, and a top electrode formed on the surface of the lead selenide thin film layer, forming a photoconductive detector structure. A back reflection structure is introduced on the back side of the substrate to reflect the infrared light transmitted out of the device and reflect it back into the device, thereby further improving the infrared light utilization rate.

8. The lead selenide room temperature mid-wave infrared detector as described in claim 7, characterized in that: The substrate is sapphire, the lead selenide thin film layer has an absorption cutoff wavelength of 4.3 μm and a thickness of 500-1000 nm, the top electrode is an Au electrode with a thickness of 50-120 nm, and the back reflection structure is an Ag mirror structure with a thickness of 10-100 nm.

9. The lead selenide room temperature mid-wave infrared detector prepared by the method of any one of claims 1-6, or the lead selenide room temperature mid-wave infrared detector as described in any one of claims 7-8, is used in infrared detection or thermal imaging in the 3-5μm band.

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