Fabrication method of lead selenide photosensitive thin film and integrable photoconductive sensor

Abstract

This invention provides a method for preparing a lead selenide photosensitive thin film, comprising the following steps: using soluble lead salt, strong alkali, selenium source, and soluble halide salt as raw materials, a halogen-doped lead selenide thin film is deposited on a substrate using a chemical bath method to obtain a lead salt thin film substrate; the halogen-doped lead selenide thin film is chemically oxidized using an oxidizing agent solution to obtain an oxide thin film substrate, wherein the oxidizing agent solution is an H2O2 solution or a K2S2O8 solution; the oxide thin film substrate is sensitized using a halogen mixed gas to form a lead selenide photosensitive thin film on the substrate; wherein the halogen mixed gas is a mixture of halogen gas and N2 or O2. The lead selenide photosensitive thin film prepared by the above method can improve its photoelectric sensitivity, fast response speed, and high resolution, and effectively extend its service life. In addition, this invention also provides a method for preparing an integrable photoconductive sensor using the above lead selenide photosensitive thin film.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic sensor technology, specifically relating to a lead selenide photosensitive thin film and a method for preparing an integrable photoconductive sensor. Background Technology

[0002] Photoelectric sensors are semiconductor devices that convert optical information into electrical information. They possess numerous advantages such as high precision, high resolution, high reliability, and fast response speed, and are widely used in control and detection fields. Lead selenide (PbSe), a traditional group IV-VI semiconductor material, is a narrow-band semiconductor material with a NaCl structure. Its bandgap is 0.27 eV at room temperature and can be reduced to 0.17 eV at absolute zero. PbSe has a large exciton Bohr radius (46 nm) and a high dielectric constant, giving it strong absorption and response in the 1-5 μm infrared spectral band.

[0003] In the supply of optoelectronic sensor products, European, American, and Japanese manufacturers dominate the market, while domestic optoelectronic sensors lag behind in both technology and manufacturing. Lead selenide thin films are typically prepared using physical methods such as molecular beam epitaxy, vacuum evaporation, laser flash evaporation, and magnetron sputtering. These methods require expensive coating equipment, resulting in high costs. Electrochemical deposition of lead selenide thin films is relatively cheaper, but its disadvantage lies in the requirement for a conductive substrate, limiting its applicability. Chinese patent CN200910054457.X mainly discloses a process for preparing nanoscale lead telluride (PbTe) particles using chemical solution deposition, but this similar chemical solution process cannot obtain PbSe thin films with mid-infrared photoconductive properties. Summary of the Invention

[0004] In view of this, it is indeed necessary for the present invention to provide a method for preparing a lead selenide photosensitive thin film and an integrable photoconductive sensor to solve the above problems.

[0005] Therefore, the present invention provides a method for preparing a lead selenide photosensitive thin film, comprising the following steps:

[0006] Preparation of lead salt thin film substrate: Using soluble lead salt, strong alkali, selenium source and soluble halide salt as raw materials, halogen-doped lead selenide thin film is deposited on the substrate by chemical bath method to obtain lead salt thin film substrate.

[0007] Oxidation treatment: The halogen-doped lead selenide film is chemically oxidized using an oxidizing agent solution to obtain an oxide film substrate; wherein the oxidizing agent solution is an H2O2 solution or a K2S2O8 solution;

[0008] High-temperature sensitization treatment: The oxide film substrate is sensitized by a halogen mixed gas to form a lead selenide photosensitive film on the substrate; wherein, the halogen mixed gas is a mixture of halogen gas and N2 or O2.

[0009] In the step of preparing the lead salt thin film substrate, the halogen-doped lead selenide thin film is mainly formed in an alkaline environment. The main formation process of the halogen-doped lead selenide thin film is as follows: in an alkaline environment, lead ions form lead hydroxide precipitate, which then dissolves in excess alkaline solution to generate leadite products. Therefore, when the alkaline environment is weak, there is more lead hydroxide deposit; when the alkaline environment is strong, the lead hydroxide deposit is completely dissolved. Subsequently, the selenium source solution and the soluble halide salt are added, and both react with the lead ions in the solution to form the doped lead selenide thin film.

[0010] In addition, the addition of the soluble halide salt introduces halogen dopants into the lead selenide film. The doping of halogen elements prolongs the induction period of the lead selenide film, promotes the growth of PbSe microcrystals, increases the PbSe grain size, and enhances the photocurrent and sensitivity of the lead selenide film. Therefore, the doping concentration of the soluble halide salt will affect the final responsivity.

[0011] Therefore, preferably, the molar ratio of the soluble lead salt, strong alkali, selenium source, and soluble halide is 1:5-15:0.5-3.5:0.1-1. The soluble lead salt can be lead nitrate, lead acetate, or lead chloride, etc. The strong alkali can be sodium hydroxide or potassium hydroxide, etc. The soluble halide can be potassium chloride, sodium chloride, potassium bromide, or sodium bromide, etc. The selenium source is selenium dioxide, sodium selenosulfate, sodium selenite, or potassium selenite.

[0012] Based on the above preparation method, the steps for preparing the lead salt thin film substrate include:

[0013] Preparation of selenium source solution: Selenium powder and sodium sulfite were placed in a 300ml container at a molar ratio of 0.5-3.5:3-15, and deionized water was added. The mixture was heated at 60℃-90℃ with stirring for 8-12 h, and then filtered to obtain the selenium source solution.

[0014] Preparation of deposition solution: First, the soluble lead salt is added to a strong alkaline solution and heated in a water bath at 20℃~50℃, and stirred at 300~500 rpm until the reaction is complete; then the selenium source solution and the soluble halide salt are added in sequence and stirred evenly to obtain a colorless and transparent deposition solution;

[0015] Depositing lead selenide thin film: The deposition solution is placed in a water bath at 50℃~80℃, the substrate is suspended in the middle and lower part of the deposition solution, and the mixture is stirred for 3~7 h to deposit the halogen-doped lead selenide thin film on the substrate to obtain the lead salt thin film substrate.

[0016] In the step of preparing the selenium source solution, if there is too little sodium sulfite, the selenium powder cannot be completely dissolved, resulting in impurities; if there is too much sodium sulfite, more impurity ions will be introduced. Therefore, preferably, the molar ratio of selenium powder to sodium sulfite is 0.5-3.5:3-15. At the same time, the reaction time and temperature of the two will also affect whether the reaction is complete.

[0017] The deposition temperature of the halogen-doped lead selenide affects the deposition rate and film quality. If the deposition temperature is low, the deposition rate is slow; if the deposition temperature is high, the deposition rate is fast, the film adhesion is poor, and the deposition quality is relatively poor. Therefore, the deposition temperature of the halogen-doped lead selenide is preferably 50℃~80℃.

[0018] Based on the above preparation method, the method further includes a step of cleaning the substrate before the step of preparing the lead salt thin film substrate. The substrate is immersed in chromic acid cleaning solution for 4-6 hours to completely remove organic and inorganic contaminants, taken out and rinsed with deionized water, and then placed in beakers containing ethanol and deionized water in sequence and sonicated for 10-30 minutes each. It is then dried with nitrogen gas to obtain a clean substrate.

[0019] Based on the above preparation method, the oxidation treatment step includes: using a concentration of 1×10 -3 ~1×10 -2 The halogen-doped lead selenide film is chemically oxidized with the oxidant solution at a concentration of mol / L for 10–60 min, causing the surface layer of the halogen-doped lead selenide film to be oxidized to form PbO and PbO. x Se (1-x) A mixture of PbO and PbSexO1-x is used, with x being 0.1 to 0.5, to form a lead selenide oxide thin film on the substrate, thus obtaining the oxide thin film substrate. During this oxidation process, PbSe exposed on the outer surface of the lead selenide thin film is oxidized to a mixture of PbO and PbSexO1-x, forming a heterojunction on the surface of the lead selenide thin film. This oxidized heterojunction creates conditions for trapping minority carriers and separating majority carriers, which is beneficial for improving the photoelectric responsivity of lead selenide. This oxidation process only changes the chemical state of the surface layer of the lead selenide thin film, thereby causing changes in the photoelectric properties of the thin film, thus extending the photoelectric response lifetime of the lead selenide thin film material.

[0020] Based on the above, the high-temperature sensitization treatment step includes: placing the oxide film substrate in an annealing furnace at 250℃~500℃, introducing the halogen mixed gas for sensitization treatment for 20~90 min, and forming the lead selenide photosensitive film on the substrate; wherein, the volume ratio of halogen gas to N2 or O2 in the halogen mixed gas is 0.1 : 10~2 : 1.

[0021] The high-temperature sensitization process takes place in the halogen mixture gas and forms lead halide (PbX2) and various PbSe. a X b O c The complex facilitates the recrystallization of the film on the oxide film substrate formed after oxidation treatment, and also facilitates the controllable incorporation of oxygen into the PbSe lattice, while reducing the Se content in the upper part of the PbSe film. Preferably, the halogen is I2.

[0022] During the high-temperature sensitization process, if the halogen mixed gas is introduced for too long or at too high a flow rate, the sensitized film will become thinner, resulting in poor photoconductivity. If the sensitization temperature is too high, the selenium in the lead selenide film will volatilize, causing the lead selenide film to thin and potentially leading to the formation of lead halide, which also degrades photoconductivity. If the sensitization temperature is too low, the sensitization reaction cannot proceed.

[0023] The present invention also provides a method for fabricating an integrated photoconductive sensor, comprising the following steps: firstly, depositing the lead selenide photosensitive film on the substrate using the above method to obtain a sensitized film substrate; then, sequentially performing passivation, photolithography, physical processing, electrode fabrication, and encapsulation on the sensitized film substrate to obtain an integrated photoconductive sensor.

[0024] Based on the above, the steps for obtaining the integrated photoconductive sensor include: first, depositing a passivation protective layer with a thickness of 50-400 nm on the sensitized thin film substrate to obtain a semi-finished sensor element; then, processing the semi-finished sensor element using a photolithography machine and a mask until the desired integrated sensor element pattern of 50-2000 μm is developed on the semi-finished sensor element; next, etching the developed sensor element pattern on the semi-finished sensor element using an etching machine to obtain the desired sensor element pattern; then, depositing electrodes on the desired sensor element pattern to obtain the sensor element; cutting the sensor element to the required size, placing it in a matching housing, such as TO, surface mount, or array packaging, binding wires, and packaging to obtain the integrated photoconductive sensor.

[0025] The passivation protective layer is a silicon dioxide layer, an aluminum oxide layer, a magnesium fluoride layer, an arsenic sulfide layer, or a zinc selenide layer, and can be formed by methods such as magnetron sputtering or electron beam evaporation.

[0026] Therefore, compared with the prior art, the method for preparing the lead selenide photosensitive film provided by this invention includes the steps of preparing a lead salt film substrate, oxidation treatment, and high-temperature sensitization treatment. This allows the lead selenide film, serving as the sensitive film, to undergo halogen doping treatment, oxidation treatment, and high-temperature sensitization treatment with a mixed halogen gas in sequence, thereby improving its photoelectric sensitivity, fast response speed, and high resolution, and effectively extending the service life of the lead selenide sensitive film. Furthermore, the method for preparing an integrable photoconductive sensor provided by this invention mainly involves synthesizing the lead selenide film via a chemical bath method, while simultaneously preparing the sensitive film through halogen doping, oxidation, and high-temperature sensitization treatments. Based on this sensitive film, the sensor element can be integrated using semiconductor MEMS technology, making it more suitable for mass production and low-cost manufacturing.

[0027] Therefore, the method for preparing the lead selenide photosensitive film and the integrable photoconductive sensor provided by the present invention is simple and easy to implement, has universality, and can quickly and effectively prepare integrable, miniaturized photoconductive sensors with high sensitivity, fast response speed, high resolution, and high reliability. Attached Figure Description

[0028] Figure 1 This is a graph showing the relationship between different molar ratios of selenium and lead elements and the resistance of the lead selenide film in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0029] Figure 2 This is a graph showing the relationship between different molar ratios of selenium and lead elements and the resistance change rate of the lead selenide film in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0030] Figure 3 This is a graph showing the relationship between bromine doping concentration and the dark resistance of bromine-doped lead selenide film in the preparation method of lead selenide photosensitive film provided in this embodiment of the invention.

[0031] Figure 4 This is a graph showing the relationship between the bromine doping concentration and the rate of change of resistance of the bromine-doped lead selenide film in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0032] Figure 5 This is an SEM image of the undoped bromine-containing lead selenide film synthesized in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0033] Figure 6 This is an SEM image of the bromine-doped lead selenide film synthesized in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0034] Figure 7 This is the XRD pattern of the lead selenide film synthesized in the preparation method of the lead selenide photosensitive film provided in the embodiment of the present invention before and after bromine doping.

[0035] Figure 8 This is a spectral response curve of a bromine-doped lead selenide film and an undoped lead selenide film synthesized in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0036] Figure 9 This is an SEM image of the lead selenide oxide film formed after oxidation treatment in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention.

[0037] Figure 10 This is an XRD pattern of lead selenide oxide film before its formation in the preparation method of lead selenide photosensitive film provided in this embodiment of the invention.

[0038] Figure 11 This is an XRD pattern of the lead selenide oxide film after its formation in the preparation method of the lead selenide photosensitive film provided in this embodiment of the invention.

[0039] Figure 12 This is a graph showing the effect of sensitization temperature on the dark resistance of the lead selenide photosensitive film in the preparation method of the lead selenide photosensitive film provided in this embodiment of the invention.

[0040] Figure 13 This is a graph showing the effect of sensitization temperature on the resistivity change rate of the lead selenide photosensitive film in the preparation method of the lead selenide photosensitive film provided in this embodiment of the invention.

[0041] Figure 14 This is an SEM image of the lead selenide photosensitive film formed after high-temperature sensitization treatment in the preparation method of the lead selenide photosensitive film provided in the embodiment of the present invention.

[0042] Figure 15 This is a graph showing the photoelectric response curve of the lead selenide photosensitive film formed after high-temperature sensitization treatment in the preparation method of the lead selenide photosensitive film provided in the embodiments of the present invention. Detailed Implementation

[0043] The technical solution of the present invention will be further described in detail below through specific embodiments. The technical terms or scientific and technological terms used herein should have the ordinary meaning understood by those skilled in the art.

[0044] This invention provides a method for preparing a lead selenide photosensitive thin film, comprising the steps of preparing a lead salt thin film substrate, oxidation treatment, and high-temperature sensitization treatment. Specifically, the preparation method includes:

[0045] Cleaning the substrate: Immerse the substrate in chromic acid cleaning solution for 5 hours to completely remove organic and inorganic contaminants. Remove it and rinse it with deionized water. Then, place it in beakers containing ethanol and deionized water in sequence and sonicate for 20 minutes each. Dry it with nitrogen to obtain a clean substrate and place it in a drying oven for later use.

[0046] Preparation of lead salt thin film substrate: Using soluble lead salt, strong alkali, selenium source and soluble halide salt as raw materials, halogen-doped lead selenide thin film is deposited on the clean substrate by chemical bath method to obtain lead salt thin film substrate.

[0047] Oxidation treatment: The halogen-doped lead selenide film is chemically oxidized using an oxidizing agent solution, causing the PbSe on the surface of the halogen-doped lead selenide film to be oxidized into PbO and PbSe. x O 1-x A mixture of these components is used to form a lead selenide oxide thin film on the substrate, thereby obtaining an oxide thin film substrate; wherein the oxidant solution is an H2O2 solution or a K2S2O8 solution;

[0048] High-temperature sensitization treatment: The oxide film substrate is sensitized using a halogen X2 mixed gas, resulting in the formation of lead halide (PbX2) and various PbSe on the surface of the lead selenide oxide film. a X b O c and PbSe d An OX composite is used to form a lead selenide photosensitive film on the substrate to obtain a sensitized film substrate; wherein the halogen mixed gas is a mixture of halogen X2 and N2 or O2.

[0049] Lead selenide photosensitive films are mainly used as sensitive films in photoconductive sensors. The main factors affecting the photoconductive performance of the sensitive film are the molar ratio of selenium and lead in the raw materials, the doping concentration of soluble halide salts, oxidation treatment, and high-temperature sensitization treatment. The following is a detailed analysis of the effects of these factors on the performance of the sensitive film.

[0050] I. Effect of the molar ratio of selenium to lead on lead selenide thin films

[0051] Experimental conditions: The light and dark resistance of lead salt thin film substrates prepared by the following chemical bath synthesis method were measured under pulsed infrared light source conditions. The test results are as follows: Figures 1-2 As shown.

[0052] The specific preparation steps for synthesizing lead selenide thin films using the chemical bath method are as follows:

[0053] Preparation of selenium source solution: Selenium powder and sodium sulfite were placed in a container at a molar ratio of 1:2 and 300 ml of deionized water was added. The mixture was heated at 70℃~80℃ with stirring for 6 h. Unreacted selenium powder and selenate were removed by filtration to obtain a selenium source solution with sodium selenosulfate as the main component.

[0054] Preparation of the deposition solution: First, add 1 mol / L lead nitrate solution to 5 mol / L sodium hydroxide solution, heat in a 40°C water bath, and stir at 400 rpm until the reaction is complete; then add 0.1 mol / L potassium bromide solution and the selenium source solution sequentially, and stir until homogeneous to obtain a colorless and transparent deposition solution. The molar ratio of lead nitrate, sodium hydroxide, and potassium bromide added in this step is 1:8:0.8, and the molar ratio of selenium source to lead nitrate is 1.5:1, 1.6:1, 1.7:1, 2:1, 3:1, 3.5:1, and 4:1, respectively.

[0055] Preparation of lead selenide thin film substrate: The deposition solution is placed in a 65°C water bath, and the clean substrate is suspended in the lower part of the deposition solution. Stirring and deposition are carried out for 3-6 hours to form a bromine-doped lead selenide thin film, thus obtaining a lead salt thin film substrate.

[0056] from Figures 1-2 It can be seen that as the molar ratio of Se:Pb increases, the resistance and resistance change rate peak when the ratio is 1.7:1; when the molar ratio increases to 2:1, the resistance and resistance change rate decrease; as the molar ratio continues to increase, the resistance change rate continues to increase until the molar ratio reaches 3.5:1, at which point the resistance change rate reaches 7.2%; when the molar ratio increases further, it will be impossible to form a bromine-doped lead selenide film.

[0057] II. The Influence of Bromine Doping on the Photoelectric Properties of Lead Selenide Thin Films

[0058] Experimental conditions: These experimental conditions are basically the same as those in "I. Effect of the molar ratio of selenium and lead on lead selenide thin films," with the main difference being that in the synthesis of bromine-doped lead selenide thin films, the molar ratio of lead nitrate, sodium hydroxide, and selenium source is 1:8:3.5, and the molar ratios of KBr and lead nitrate are 0.1:1, 0.4:1, 0.8:1, and 1:1, respectively. Experimental results are as follows: Figures 3-4 As shown.

[0059] from Figures 3-4 As can be seen, with the increase of the molar ratio of KBr to lead nitrate, the rate of change of resistance increases, but at the same time, the dark resistance also increases.

[0060] SEM, XRD, and photoresponse tests were performed on bromine-doped lead selenide films synthesized with a KBr to lead nitrate molar ratio of 0.8:1 and those synthesized without KBr, respectively. The test results are as follows: Figures 5-7 As shown. From Figure 7 As can be seen, doping did not affect the main peak of lead selenide, achieving small-element doping; from Figure 8As can be seen, the spectral response intensity of the undoped sample is much weaker than that of the doped sample.

[0061] Therefore, bromine doping can lengthen the induction period of lead selenide films. Compared with lead selenide films synthesized without bromine doping, bromine-doped lead selenide films have increased photocurrent and photoelectric sensitivity.

[0062] III. Effects of Oxidation Treatment on Lead Selenide Films

[0063] Experimental conditions: First, prepare lead salt film substrates according to the "Experimental Conditions" in "I. Effect of Molar Ratio of Selenium and Lead on Lead Selenide Thin Films" mentioned above, with the molar ratio of lead nitrate, sodium hydroxide, selenium source, and KBr being 1:8:3.5:0.8; then use 5×10 -3 The bromine-doped lead selenide film formed on the lead salt film substrate was chemically oxidized with a mol / L H2O2 solution for 30 min, causing the surface of the bromine-doped lead selenide film to be oxidized, forming a layer as shown in the figure. Figure 9 The lead selenide oxide thin film shown is used to prepare an oxide thin film substrate.

[0064] Using an EDS energy dispersive spectroscopy analyzer to respectively Figure 7 The bromine-doped lead selenide film shown and Figure 9 Elemental composition analysis of the lead selenide oxide thin film shown is as follows: Figure 10 As shown.

[0065] contrast Figure 5 and Figure 9 It can be seen that the SEM surface morphology of the thin film on the substrate changed after oxidation treatment. From... Figure 10 and Figure 11 The comparison shows that the oxygen content of the bromine-doped lead selenide film increases significantly after chemical oxidation treatment. This is mainly because the PbSe on the surface of the bromine-doped lead selenide film on the substrate is oxidized into PbO and PbSe. x O 1-x A mixture of these components forms a heterojunction on the surface of the bromine-doped lead selenide film.

[0066] IV. Effects of High-Temperature Sensitization Treatment on Lead Selenide Films

[0067] Experimental conditions: First, an oxide film substrate was prepared according to the "Experimental conditions" in "III. Effect of Oxidation Treatment on Lead Selenide Film" mentioned above; then, the oxide film substrate was placed in an annealing furnace at sensitization temperatures of 250℃, 300℃, 350℃, 400℃, 450℃, and 500℃, respectively, and a N2 mixed gas containing I2 was introduced for sensitization treatment for 60 min, thereby forming the corresponding lead selenide photosensitive film on the substrate, thus obtaining the sensitized film substrate; wherein, the volume ratio of I2 to N2 in the mixed gas was 0.1:1.

[0068] The light and dark resistance of the lead selenide photosensitive film were measured under pulsed infrared light source conditions, and the test results are as follows: Figure 12 and Figure 13 As shown. From Figure 12 and Figure 13 It can be seen that the dark resistance increases with increasing temperature. This may be because if the sensitization temperature is too high, selenium volatilizes, the lead selenide photosensitive film thins down, and lead halide is formed, which deteriorates the photoconductivity of the film; if the sensitization temperature is too low, the sensitization reaction cannot proceed.

[0069] The lead selenide photosensitive film prepared at a sensitization temperature of 350℃ is as follows: Figure 14 As shown, a light-dark test was performed on the lead selenide photosensitive film, and the test results are as follows. Figure 15 As shown. Figure 15 It can be seen that the sensitivity and response speed of the lead selenide film after high-temperature sensitization treatment are significantly increased. This indicates that iodine helps the lead selenide film to recrystallize and facilitates the controllable incorporation of oxygen into the PbSe lattice, thereby improving photoelectric sensitivity.

[0070] Example 1

[0071] Please see Figure 1 This embodiment provides a method for fabricating an integrable photoconductive sensor, including:

[0072] First, refer to the "Experimental Conditions" in "IV. Effect of High Temperature Sensitization Treatment on Lead Selenide Thin Films" above to prepare a sensitized thin film substrate with a sensitization temperature of 350℃;

[0073] The integrated photoconductive sensor is fabricated by sequentially passivating, patterning, patterning, electrode fabrication, and encapsulation of the sensitized thin film substrate. The specific steps are as follows:

[0074] The passivation protective layer was prepared by magnetron sputtering to deposit a 250 nm thick silicon dioxide passivation protective layer on the sensitized thin film substrate, thus obtaining a semi-finished sensitive element.

[0075] To form the integrated sensor pattern, a photolithography machine is first used in conjunction with a photomask to process the semi-finished sensor until the desired integrated sensor pattern is developed. Then, an etching machine is used to etch the pattern developed on the semi-finished sensor at a power of 400 W using Ar / O2 / Br2. Finally, a photoresist remover is used to remove the photoresist to obtain the desired sensor pattern.

[0076] Electrode fabrication and packaging are carried out using magnetron sputtering. Gold electrodes are deposited under the action of an aligned mask. The prepared sensing element is cut into the required size, such as 50×50 μm, 1×1 mm, and 10×10 mm, placed into a matching housing, wired, and packaged to obtain the sensor.

[0077] This embodiment provides a method for fabricating an integrable photoconductive sensor. This method is basically the same as the method provided in Embodiment 1, with the main difference being:

[0078] In the step of preparing the lead salt thin film substrate, the molar ratio of selenium powder to sodium sulfite is 1:4, and the volume ratio of the lead nitrate solution, sodium hydroxide solution, hydrogen bromide solution and selenium source solution is 1:3:0.5:5.

[0079] In the oxidation treatment step, 6×10 -3 The thin film was chemically oxidized by reacting it with mol / L K2S2O8 solution for 45 min to obtain an oxidized thin film substrate.

[0080] In the high-temperature sensitization treatment step, the sensitization temperature is 250°C, the volume ratio of I2 to N2 in the halogen-containing gas is 2:1, and the sensitization time is 30 min.

[0081] In the step of fabricating the integrable sensor, a 150 nm thick aluminum oxide passivation protective layer is deposited on the sensitized thin film substrate using magnetron sputtering to obtain a semi-finished sensor.

[0082] Example 3

[0083] This embodiment provides a method for fabricating an integrable photoconductive sensor. This method is basically the same as the method provided in Embodiment 1, with the main difference being:

[0084] In the step of preparing the lead salt thin film substrate, the molar ratio of selenium powder to sodium sulfite is 1:5, and the volume ratio of the lead nitrate solution, sodium hydroxide solution, potassium bromide solution and selenium source solution is 1:5:1:10.

[0085] In the oxidation treatment step, 1×10 -2The thin film was chemically oxidized by reacting it with mol / L H2O2 solution for 30 min to obtain an oxidized thin film substrate;

[0086] In the high-temperature sensitization treatment step, the sensitization temperature is 300°C, the volume ratio of I2 to N2 in the halogen-containing gas is 1:10, and the sensitization time is 90 min.

[0087] In the step of fabricating the integrable sensor, a 200 nm thick MgF2 passivation protective layer is deposited on the sensitized thin film substrate using magnetron sputtering to obtain a semi-finished sensing element. Therefore, the fabrication method of the integrable photoconductive sensor provided by this invention can reduce the size of the sensing element from the millimeter level to the micrometer or even nanometer level, making the application of photoconductivity more easily modularized, miniaturized, electronic, and fully automated, and possessing characteristics such as high sensitivity, fast response speed, high resolution, and high reliability. Furthermore, the fabrication method provided by this invention has the advantages of being simple, easy to implement, having a high yield, and being suitable for large-scale production.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for preparing a lead selenide photosensitive thin film, comprising the following steps: Preparation of lead salt thin film substrates: Using soluble lead salts, strong alkalis, selenium sources, and soluble halide salts as raw materials, halogen-doped lead selenide thin films are deposited on a substrate using a chemical bath method to obtain lead salt thin film substrates; wherein, The molar ratio of the soluble lead salt, strong alkali, selenium source and soluble halide is 1:5-15:0.5-3.5:0.1-1, and the soluble halide is potassium chloride, sodium chloride, potassium bromide or sodium bromide; Oxidation treatment: using a concentration of 1×10 -3 ~1×10 -2 The halogen-doped lead selenide film was chemically oxidized with a mol / L oxidant solution for 10–60 min, causing the surface of the halogen-doped lead selenide film to be oxidized to form PbO and PbO. x Se (1-x) A mixture of [agents] is used, and x is 0.1 to 0.5, thereby forming a lead selenide oxide thin film on the substrate to obtain an oxide thin film substrate; wherein the oxidant solution is an H2O2 solution or a K2S2O8 solution; High-temperature sensitization treatment: The oxide film substrate is placed in an annealing furnace at 250℃~500℃ and sensitized with a halogen mixed gas for 20~90 min to form a lead selenide photosensitive film on the substrate; wherein the halogen mixed gas is a mixture of halogen gas and N2 or O2, and the volume ratio of halogen gas to N2 or O2 is 0.1 : 10~2 :

1.

2. The method for preparing lead selenide photosensitive thin film according to claim 1, characterized in that, The soluble lead salt is lead nitrate, lead acetate, or lead chloride; the selenium source is selenium dioxide, sodium selenosulfate, sodium selenite, or potassium selenite.

3. The method for preparing lead selenide photosensitive thin film according to claim 1, characterized in that, The steps for preparing the lead salt thin film substrate include: Preparation of selenium source solution: Selenium powder and sodium sulfite were placed in a 300 ml container at a molar ratio of 0.5-3.5:3-15, and deionized water was added. The mixture was heated at 60℃-90℃ with stirring for 8-12 h, and then filtered to obtain the selenium source solution. Preparation of deposition solution: First, the soluble lead salt is added to a strong alkaline solution and heated in a water bath at 20℃~50℃, and stirred at 300~500 rpm until the reaction is complete; then the selenium source solution and the soluble halide salt are added in sequence and stirred evenly to obtain a colorless and transparent deposition solution; Depositing lead selenide thin film: The deposition solution is placed in a water bath at 50℃~80℃, the substrate is suspended in the middle and lower part of the deposition solution, and the mixture is stirred for 3~7 h to deposit the halogen-doped lead selenide thin film on the substrate to obtain the lead salt thin film substrate.

4. The method for preparing the lead selenide photosensitive thin film according to any one of claims 1 to 3, characterized in that, The method also includes a step of cleaning the substrate before the step of preparing the lead salt thin film substrate. The substrate is immersed in chromic acid cleaning solution for 4 to 6 hours to completely remove organic and inorganic contaminants. After being taken out and rinsed with deionized water, it is then placed in beakers containing ethanol and deionized water and sonicated for 10 to 30 minutes each. After being dried with nitrogen, a clean substrate is obtained.

5. A method for fabricating an integrable photoconductive sensor, comprising the following steps: Preparation of lead salt thin film substrates: Using soluble lead salts, strong alkalis, selenium sources, and soluble halide salts as raw materials, halogen-doped lead selenide thin films are deposited on a substrate using a chemical bath method to obtain lead salt thin film substrates; wherein, The molar ratio of the soluble lead salt, strong alkali, selenium source and soluble halide is 1:5-15:0.5-3.5:0.1-1, and the soluble halide is potassium chloride, sodium chloride, potassium bromide or sodium bromide; Oxidation treatment: using a concentration of 1×10 -3 ~1×10 -2 The halogen-doped lead selenide film was chemically oxidized with a mol / L oxidant solution for 10–60 min, causing the surface of the halogen-doped lead selenide film to be oxidized to form PbO and PbO. x Se (1-x) A mixture of [agents] is used, and x is 0.1 to 0.5, thereby forming a lead selenide oxide thin film on the substrate to obtain an oxide thin film substrate; wherein the oxidant solution is an H2O2 solution or a K2S2O8 solution; High-temperature sensitization treatment: The oxide film substrate is placed in an annealing furnace at 250℃~500℃ and sensitized for 20~90 min by introducing a halogen mixed gas to form a lead selenide photosensitive film on the substrate, thus obtaining a sensitized film substrate; wherein the halogen mixed gas is a mixture of halogen gas and N2 or O2, and the volume ratio of halogen gas to N2 or O2 is 0.1 : 10~2 : 1; An integrated photoconductive sensor is obtained by sequentially performing passivation, photolithography, physical processing, electrode fabrication, and packaging on the sensitized thin film substrate.

6. The method for fabricating an integrable photoconductive sensor according to claim 5, characterized in that: The steps for obtaining the integrated photoconductive sensor include: first, depositing a passivation protective layer with a thickness of 50–400 nm on the sensitized thin film substrate to obtain a semi-finished sensor element; then, processing the semi-finished sensor element using a photolithography machine and a mask until the required integrated sensor element pattern of 50–2000 μm is developed on the semi-finished sensor element; next, etching the developed sensor element pattern on the semi-finished sensor element using an etching machine to obtain the required sensor element pattern; then, depositing electrodes on the required sensor element pattern to obtain the sensor element; cutting the sensor element to the required size, placing it in a matching housing, binding wires, and encapsulating it to obtain the integrated photoconductive sensor.

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