Lead selenide room-temperature medium-wave infrared detector and preparation method and application thereof

Abstract

The invention relates to a preparation method of a lead selenide room-temperature medium-wave infrared detector, which comprises the following steps of: (1) depositing a lead selenide film layer on a substrate by adopting a magnetron sputtering technology and taking oxygen as reaction gas; (2) placing the lead selenide film in a horizontal tube furnace, and realizing high-temperature oxidation in normal-pressure pure oxygen; and (3) putting the lead selenide film into a vertical tube furnace, and realizing high-temperature iodination in a normal-pressure environment. The lead selenide thin film is prepared through the magnetron sputtering technology, compared with chemical bath deposition, the quality of the thin film is effectively improved, and large-area and high-uniformity thin film preparation is achieved; the magnetron sputtering film is subjected to high-temperature oxidation-iodination treatment, the magnetron sputtering film has excellent photoresponse to infrared light, and the sensitization technology is specific and clear and good in repeatability; the sensitized lead selenide thin film layer and the top electrode form the photoconductive detector, the specific detection rate of the device is 7.6 * 10 < 9 > Jones at 4.3 microns at the room temperature of a medium-wave infrared band, and the performance is excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and in particular relates to a lead selenide room-temperature medium-wave infrared detector and a preparation method and application thereof. Background Art

[0002] As we all know, 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 target's infrared radiation. Infrared detection technology is extremely important. In the military, it can be used for infrared targeting, reconnaissance, infrared 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 based on the Swap3 concept. Raising the detector's operating temperature and reducing cooling requirements have become key to achieving miniaturization, low power consumption, and low cost of detection systems. In this context, polycrystalline PbSe materials, due to their ability to operate at room temperature, are widely used for 1-5μm spectral detection.

[0003] The room-temperature infrared detection properties of PbSe materials have been discovered since the 1930s. To date, the mainstream preparation method for this material is chemical bath deposition (CBD). The deposited film also needs to be sensitized to achieve high response to infrared light. However, this preparation and sensitization technology 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 currently 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 technology, the present invention proposes a lead selenide room-temperature medium-wave infrared detector and its preparation method and application, aiming to effectively improve the quality of thin film deposition and obtain a high-performance lead selenide room-temperature medium-wave infrared detector.

[0007] In a first aspect, the present application provides a method for preparing a room-temperature medium-wave infrared detector of lead selenide, comprising the following steps:

[0008] (1) Using magnetron sputtering technology and oxygen as the reaction gas, a lead selenide thin film layer is deposited on the substrate;

[0009] (2) placing the lead selenide film obtained in step (1) in a horizontal tube furnace for treatment at 250-350° C. for 30-60 min, and performing high-temperature oxidation in a pure oxygen atmosphere at normal pressure;

[0010] (3) placing the lead selenide film obtained in step (2) in a vertical tube furnace for treatment at 350-400° C. for 10-30 min, introducing 20-30° C. sublimated iodine vapor using oxygen as a carrier, and achieving high-temperature iodination under normal pressure.

[0011] Preferably, in step (1), magnetron sputtering technology is used, oxygen is used as a reaction gas, and a lead selenide thin film layer is deposited on the substrate, specifically comprising:

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

[0013] b) Introducing argon into the chamber as sputtering gas and adjusting the pressure in the chamber to 0.5-2 Pa;

[0014] c) sputtering a lead selenide target using a radio frequency process to form a lead selenide film on the surface of the substrate;

[0015] d) Oxygen is introduced into the chamber as a reaction gas, with the oxygen accounting for 1%-5%, so that the oxygen element is doped into the film.

[0016] Preferably, the thickness of the lead selenide thin film layer deposited by magnetron sputtering technology 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 size of 30-80 nm.

[0018] Preferably, the heating rates in step (2) and step (3) are both 10-20°C / min.

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

[0020] Preferably, the step (3) further comprises: closing the iodine inlet and outlet channels after the iodination is completed, and evacuating the iodine to a temperature of ≤10 2 Pa to remove the remaining sublimated iodine, and then oxygen is passed through to restore normal pressure.

[0021] In the second aspect, the present application provides a room-temperature medium-wave infrared detector of lead selenide prepared and sensitized by magnetron sputtering, comprising: a substrate, a lead selenide thin film layer prepared by the method described in any one of claims 1 to 7 and arranged on the substrate, and a top electrode formed on the surface of the lead selenide thin film layer, constituting a photoconductive detector structure. A back reflection structure is introduced on the back side of the substrate to reflect infrared light transmitted out of the device and reflect it back into the device, thereby further improving the utilization efficiency of infrared light.

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

[0023] In a third aspect, the present application provides an application of a lead selenide room-temperature medium-wave infrared detector in 3-5 μm band infrared detection or thermal imaging.

[0024] The beneficial effects of the present invention are as follows: (1) The present invention prepares lead selenide thin films by magnetron sputtering technology, which can effectively improve the film quality compared with chemical bath deposition and realize the preparation of large-area, highly uniform thin films; (2) The present invention performs high-temperature "oxidation-iodination" treatment on the magnetron sputtering thin film, so that the magnetron sputtering thin film has excellent light response to infrared light. The sensitization technology is specific and clear with good repeatability, and provides a clear sensitization path for the magnetron sputtering thin film; (3) The present invention constructs a photoconductive detector by combining the sensitized lead selenide thin film layer with the top electrode, and the device has a specific detection rate of 7.6×10 9 Jones@4.3μm, excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic flow chart of an embodiment of a method for preparing a room-temperature mid-wave infrared detector of lead selenide according to the present invention (showing the complete process of magnetron sputtering deposition (S11), high-temperature oxidation (S12), and high-temperature iodination (S13) to obtain an active thin film layer);

[0027] Figure 2 A schematic flow chart of another embodiment of a method for preparing a room-temperature mid-wave infrared detector of lead selenide according to the present invention (showing the preparation of a substrate ( S21 ), a top electrode ( S22 ), and a back reflection structure ( S23 ) excluding an active thin film layer, to obtain a complete process for a light-conducting device);

[0028] Figure 3 A diagram showing the large-area thin film deposition and microscopic morphology of an embodiment of a lead selenide room-temperature medium-wave infrared detector disclosed in the present invention;

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

[0030] Among them: 1. back reflection structure, 2. substrate, 3. lead selenide active layer, 4. top electrode.

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

[0032] Figure 6 The invention discloses an application of the room-temperature medium-wave infrared detector of lead selenide prepared by the present invention in the field of thermal imaging. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] See Figure 1 , Figure 1 The present invention is a flow chart of an embodiment of a method for preparing and sensitizing a lead selenide room-temperature medium-wave infrared detector by magnetron sputtering (magnetron sputtering preparation and sensitization method), which includes the following steps:

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

[0036] Step S12: placing the lead selenide film obtained in step S11 in a horizontal tube furnace and oxidizing it at high temperature in a pure oxygen atmosphere at normal pressure;

[0037] Step S13: placing the oxidized lead selenide film in a vertical tube furnace, introducing sublimated iodine vapor with oxygen as a carrier, and performing high-temperature iodination under normal pressure.

[0038] Please combine Figure 2 , Figure 2 This is a flow chart of another embodiment of a method for preparing a lead selenide medium-wave infrared detector (magnetron sputtering preparation and sensitization method) of the present invention. Figure 1 The embodiment shown, Figure 2 The embodiment shown further includes, before step S11:

[0039] Step S21: providing a substrate.

[0040] The substrate is used to support the various layers of the infrared detector. The substrate can be any one 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 Figure 1 Step S11).

[0042] Step S11: performing magnetron sputtering on a sapphire substrate to form a lead selenide thin film.

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

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

[0045] Radio frequency technology is used to sputter a lead selenide target to form a lead selenide thin film on the substrate surface. Specifically, the lead selenide active layer deposited by magnetron sputtering technology has a thickness of 700nm and a microscopic morphology of columnar crystals with a horizontal dimension of 50nm.

[0046] At the same time, oxygen is introduced into the chamber as a reaction gas. In the embodiment of the present application, the oxygen inlet flow rate is 0.8 sccm.

[0047] After the magnetron sputtering lead selenide layer is prepared, a high temperature sensitization treatment is performed. For details, see Figure 1 Step S12 and step 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 normal pressure.

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

[0050] 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. The temperature is stopped when it reaches 300°C, and thin film oxidation is performed at this temperature. The high-temperature oxidation time is 60 minutes. After the oxidation time is reached, the tube furnace is stopped from being heated and the temperature is naturally cooled to room temperature.

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

[0052] Specifically, the oxidized lead selenide film was placed in a vertical tube furnace, and the vacuum and oxygen supply operations were repeated three times until the vertical tube furnace chamber reached a pure oxygen atmosphere. Subsequently, oxygen was continuously introduced at a flow rate of 10 seem at the front end of the vertical tube furnace chamber, and the exhaust channel was opened at the rear end to maintain the strong chamber at atmospheric pressure.

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

[0054] The pure oxygen inlet was closed, and the sublimed iodine inlet was opened with oxygen as the carrier gas at a flow rate of 80 sccm. The iodine concentration used was saturated vapor concentration, and the iodine temperature was 25°C.

[0055] After iodination is completed, the iodine inlet and outlet channels are closed, and the vertical tube furnace is vacuumed to 100Pa by a mechanical pump. After vacuum treatment, the sublimated iodine in the tube furnace is completely removed, and the reaction between the lead selenide film and iodine stops. Then oxygen is passed through to restore the pressure to atmospheric pressure, and the temperature is naturally lowered to room temperature.

[0056] Please continue to see Figure 2 After the high temperature sensitization treatment is completed in 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, a Au thin film is deposited on the lead selenide thin film layer by thermal evaporation to form a top electrode. The top electrode thickness is 60 nm, forming a photosensitive area of ​​3 mm×0.3 mm.

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

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

[0060] See Figure 3 , Figure 3 This is a large-area thin film deposition and microscopic structure diagram of a room-temperature medium-wave infrared detector of lead selenide (magnetron sputtering preparation scheme) provided by the present invention. The film is deposited on a glass substrate with an area of ​​about 10×10 cm 2, enabling large-area (≥4-inch wafer-level) thin film production. Characterization of the microstructure at the four corners and center of the film revealed columnar crystals with a horizontal size of 50nm. The morphology and thickness were consistent, achieving highly uniform film production.

[0061] See Figure 4 , Figure 4 This is a schematic diagram of the structure of a room-temperature lead selenide medium-wave infrared detector (a lead selenide medium-wave infrared detector prepared and sensitized by magnetron sputtering) provided in this application. The infrared detector comprises a back reflection structure 1, a substrate 2, a lead selenide active layer 3 prepared by magnetron sputtering and synergistically sensitized by oxidation-iodination, and a top electrode 4. The substrate 2 and top electrode 4 are located on either side of the lead selenide active layer 3, and the back reflection structure 1 is located behind the substrate 2.

[0062] Specifically, the 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 a Ag mirror structure with a thickness of 100 nm. The lead selenide active layer 3 and the top electrode 4, prepared and sensitized by magnetron sputtering, form a photoconductive infrared detection device. After high-temperature sensitization, the lead selenide active layer 3 significantly extends the carrier lifetime, resulting in a photoconductive device with low dark current and high photoresponse. When mid-wave infrared light is incident on the device, the lead selenide active layer 3 absorbs the infrared light and converts the infrared photons into photogenerated carriers. The top electrode 4 is used to collect carriers in the active layer and conduct current under the condition of applying 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] See Figure 5 , Figure 5 This is a performance diagram of a lead selenide room-temperature medium-wave infrared detector provided in this application. Figure 5 A is the spectral response of the lead selenide medium-wave infrared detector, and the detector response cutoff wavelength is 4.3μm; Figure 5 B is the light-to-dark current-voltage characteristic curve of the lead selenide medium-wave infrared detector. Under a bias of 10V, the light-to-dark current ratio of the device is 38.4% when illuminated by a 0.95mW LED light source with a central wavelength of 1550nm. The light-to-dark current ratio is 81.6% when illuminated by a blackbody light source with a power of 2.25mW and a temperature of 400℃. Figure 5 C is the noise power density curve of the lead selenide medium-wave infrared detector as a function of frequency. Under a bias voltage of 10V, the noise power density of the device at 1000Hz is 3.12×10 -14 A / Hz1 / 2 , the calculated specific detectivity of the infrared detector at 1550nm is 7.3×10 9 Jones, the specific detectivity under the blackbody light source at a temperature of 400°C is 5.8×10 9 Jones; Figure 5 D is the device’s specific detectivity spectrum, which exceeds 10 in a wide spectral range. 10 Jones, the specific detectivity at the cutoff wavelength is 7.6×10 10 Jones@4.3μm.

[0064] See Figure 6 , Figure 6 The invention is the application of the lead selenide room temperature medium wave infrared detector in the field of thermal imaging. Figure 6 As shown in A, the size is 2×2cm 2 , a high-temperature ceramic piece with a center temperature of 350℃ is imaged. In a completely dark environment with the naked eye, the medium-wave infrared image of the ceramic piece is clearly presented. When part of the ceramic piece is covered with transparent glass, the glass piece hardly blocks the imaging of the ceramic piece in the visible light picture, but it can be seen in the medium-wave infrared image that the ceramic piece is blocked by the glass. Medium-wave infrared can also detect the temperature distribution of high-temperature objects, such as Figure 6 As shown in B, the visible light image cannot identify the temperature distribution of the soldering iron. In contrast, in the mid-infrared image, it can be clearly seen that the tip of the soldering iron has the strongest brightness, corresponding to the highest temperature, and the tail has the weakest brightness, corresponding to the lowest temperature.

[0065] In summary, the present invention prepares lead selenide thin films by magnetron sputtering technology, which can effectively improve the film quality compared with chemical bath deposition and realize the preparation of large-area, highly uniform thin films; (2) The present invention performs high-temperature "oxidation-iodination" treatment on the magnetron sputtering film, so that the magnetron sputtering film has excellent light response to infrared light. The sensitization technology is specific and clear with good repeatability, providing a clear sensitization path for the magnetron sputtering film; (3) The present invention constructs a photoconductive detector by combining the sensitized lead selenide thin film layer with the top electrode, and the device has a specific detection rate of 7.6×10 9 Jones@4.3μm, excellent performance.

[0066] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment 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 preparing a room-temperature medium-wave infrared detector of lead selenide, characterized in that: The following steps are involved: (1) Using magnetron sputtering technology and oxygen as the reaction gas, a lead selenide thin film layer is deposited on the substrate; (2) placing the lead selenide film obtained in step (1) in a horizontal tube furnace for treatment at 250-350° C. for 30-60 min, and performing high-temperature oxidation in a pure oxygen atmosphere at normal pressure; (3) placing the lead selenide film obtained in step (2) in a vertical tube furnace for treatment at 350-400° C. for 10-30 min, introducing 20-30° C. sublimated iodine vapor using oxygen as a carrier, and achieving high-temperature iodination under normal pressure.

2. The method for preparing a room-temperature medium-wave infrared detector of lead selenide according to claim 1, characterized in that: In the step (1), magnetron sputtering technology is used, oxygen is used as a reaction gas, and a lead selenide thin film layer is deposited on the substrate, specifically comprising: a) Place the substrate in the magnetron sputtering chamber and adjust the pressure in the chamber to 10 -3 -10 -4 Pa; b) Introducing argon into the chamber as sputtering gas and adjusting the pressure in the chamber to 0.5-2 Pa; c) sputtering a lead selenide target using a radio frequency process to form a lead selenide film on the surface of the substrate; d) Oxygen is introduced into the chamber as a reaction gas, with the oxygen accounting for 1%-5%, so that the oxygen element is doped into the film.

3. The method for preparing a room temperature medium-wave infrared detector of lead selenide according to claim 1, characterized in that: The thickness of the lead selenide thin film layer deposited by magnetron sputtering technology in step (1) is 650-750nm.

4. The method for preparing a room-temperature medium-wave infrared detector of lead selenide according to claim 1, wherein: 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 size of 30-80 nm.

5. The method for preparing a room-temperature medium-wave infrared detector of lead selenide according to claim 1, characterized in that: The heating rates in step (2) and step (3) are both 10-20°C / min.

6. The method for preparing a room-temperature medium-wave infrared detector of lead selenide according to claim 1, characterized in that: During the iodination treatment in step (3), the oxygen flow rate is 50-100 sccm, and the iodine vapor concentration is an equilibrium concentration of 20-30° C. under saturated vapor pressure.

7. The method for preparing a room-temperature medium-wave infrared detector of lead selenide according to claim 1, characterized in that: The step (3) further comprises: closing the iodine inlet and outlet channels after the iodination is completed, and evacuating the iodine inlet and outlet channels to a vacuum of ≤10 2 Pa to remove the remaining sublimated iodine, and then oxygen is passed through to restore normal pressure.

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

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

10. Use of the lead selenide room temperature medium-wave infrared detector according to any one of claims 1 to 9 in 3-5 μm band infrared detection or thermal imaging.

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