Method for preparing single crystal lead sulfide film by chemical liquid phase deposition method

Abstract

The invention discloses a method for preparing a single crystal lead sulfide film through a chemical liquid phase deposition method. The method comprises the following steps that S1, a layer of amorphous lead sulfide film is deposited on a substrate through a thermal evaporation method; s2, annealing the amorphous lead sulfide thin film in a nitrogen atmosphere at the temperature of 250-350 DEG C for 5-15 minutes for pre-crystallization to obtain a lead sulfide seed layer; s3, preparing a lead source precursor solution and a sulfur source precursor solution required by chemical liquid phase deposition; s4, placing the lead sulfide seed layer in a growth container added with a lead source precursor solution, then adding a sulfur source precursor solution into the growth container, mixing and reacting, placing the growth container in a vibration isolation system for film growth, and finally obtaining the lead sulfide film. The method provided by the embodiment of the invention is simple in process, low in cost, compact in grain structure, single in crystal orientation and high in mobility.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and particularly relates to a method for preparing single-crystalline lead sulfide thin films by chemical liquid deposition. Background Art

[0002] Lead sulfide is an important narrow-bandgap semiconductor material for infrared detection. At 300K, its bandgap width is 0.41eV. Therefore, its intrinsic absorption cut-off wavelength at room temperature can reach 3μm. And it has a relatively large exciton Bohr radius (18nm) and a low Auger recombination coefficient. These properties have made lead sulfide semiconductor thin films receive extensive attention and research since the last century and have been widely used in many aspects such as security monitoring, infrared remote sensing, infrared guidance, and infrared tracking, showing good application prospects.

[0003] Traditional methods for preparing lead sulfide thin films usually include molecular beam epitaxy, physical vapor deposition, magnetron sputtering, chemical liquid deposition, etc. Compared with other preparation methods, chemical liquid deposition is more suitable for industrialization because of its low preparation cost, high yield, easy integration at low temperature, and simple preparation equipment, so it has received extensive research.

[0004] However, most of the lead sulfide thin films prepared by chemical liquid deposition at present are polycrystals with complex grain packing, and their grains are not dense enough, with many crystallization orientations, a relatively high free carrier concentration, and a relatively low mobility. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing single-crystalline lead sulfide thin films by chemical liquid deposition in order to solve various deficiencies existing in the preparation of lead sulfide thin films by existing chemical liquid deposition.

[0006] To solve the above technical problem, an embodiment of the present invention provides a method for preparing single-crystalline lead sulfide thin films by chemical liquid deposition, including the following steps:

[0007] S1: Depositing an amorphous lead sulfide thin film on a substrate by thermal evaporation;

[0008] S2: Annealing the amorphous lead sulfide thin film in a nitrogen atmosphere at 250°C to 350°C for 5 minutes to 15 minutes for pre-crystallization to obtain a lead sulfide seed layer;

[0009] S3: Preparing a lead source precursor solution and a sulfur source precursor solution required for chemical liquid deposition;

[0010] S4: Placing the lead sulfide seed layer in a growth container containing the lead source precursor solution, then adding the sulfur source precursor solution to the growth container, mixing and reacting, and placing the growth container in a vibration isolation system for film growth to finally obtain the lead sulfide thin film.

[0011] Preferably, in the step S3, the method for preparing the lead source precursor solution includes:

[0012] Quickly add an alkaline substance to a first solution containing a lead source to obtain a second solution, and filter to obtain the lead source precursor solution;

[0013] The lead source includes one or more combinations of lead nitrate and lead acetate;

[0014] The alkaline substance includes one or more combinations of sodium hydroxide and potassium hydroxide.

[0015] Preferably, the content of the alkaline substance is 0.1 mol to 0.15 mol.

[0016] Preferably, in the step S3, the molar ratio of the lead source precursor solution to the sulfur source precursor solution is 1:0.4 to 1:0.5.

[0017] Preferably, in the step S3, the sulfur source in the sulfur source precursor solution is thiourea, and the concentration is 1 mol / L to 2 mol / L.

[0018] Preferably, in the step S1, the conditions of the thermal evaporation method are: the evaporation current is 60 A to 80 A; the evaporation pressure is < 10 -4 Pa; the thickness of the amorphous lead sulfide thin film is 4 nm to 6 nm.

[0019] Preferably, in the step S4, the noise of the active vibration isolation system is 10 -10 ~10 -9 g / Hz 1 / 2 , the ambient temperature is a constant 20 °C, and the ambient humidity is a constant 50% RH.

[0020] Preferably, the step S1 is specifically:

[0021] Pretreat the substrate;

[0022] Put the pretreated substrate into a thermal evaporation chamber, and deposit an amorphous lead sulfide thin film by evaporation;

[0023] Among them, the pretreatment is specifically: successively perform ultrasonic cleaning for 20 min with dishwashing liquid, deionized water, acetone, isopropanol, and ethanol, dry, and place the substrate in an ultraviolet ozone or plasma cleaner for 5 - 10 min.

[0024] Preferably, the substrate includes one or more combinations of silicon wafers, quartz glass, fluorine-doped tin oxide glass, and indium-doped tin oxide glass.

[0025] An embodiment of the present invention also provides a single-crystal lead sulfide thin film, which is prepared by the method for preparing a single-crystal lead sulfide thin film using the above chemical liquid deposition method.

[0026] Implementing the embodiments of the present invention has the following beneficial effects:

[0027] (1) In the embodiments of the present invention, a chemical liquid phase method is used to prepare a single-crystal lead sulfide thin film. By using a substrate to evaporate a lead sulfide seed layer and performing high-temperature annealing, substrate pre-crystallization is achieved, and the vibration influence of the growth environment is reduced to achieve steady-state growth. Thus, the problems that most lead sulfide thin films are polycrystals with complex grain stacking, their grains are not dense enough, there are many crystallization orientations, the free carrier concentration is high, and the mobility is low are solved, and the preparation of high-quality lead sulfide thin films is realized, laying a foundation for the preparation of lead sulfide infrared photoconductive devices and photodiode devices. In addition, the process of the embodiments of the present invention is simple and the cost is low. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a flowchart of a method for preparing a single-crystal lead sulfide thin film by a chemical liquid deposition method provided by an embodiment of the present invention;

[0030] Figure 2 It is an XRD pattern of a lead sulfide thin film generated by an embodiment of the present invention;

[0031] Figure 3 It is a surface SEM image generated by an embodiment of the present invention;

[0032] Figure 4 It is a cross-sectional SEM image generated by an embodiment of the present invention;

[0033] Figure 5 It is a vibration noise diagram of an active vibration isolation system provided by an embodiment of the present invention. Detailed Embodiments

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0035] See Figure 1 , the embodiment of the present invention also provides a method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition includes the following steps:

[0036] S1: Deposit an amorphous lead sulfide thin film on a substrate by thermal evaporation;

[0037] S2: Anneal the amorphous lead sulfide thin film in a nitrogen atmosphere at 250°C to 350°C for 5 min to 15 min for pre-crystallization to obtain a lead sulfide seed layer;

[0038] S3: Prepare a lead source precursor solution and a sulfur source precursor solution required for chemical liquid deposition;

[0039] S4: Place the lead sulfide seed layer in a growth container containing the lead source precursor solution, then add the sulfur source precursor solution to the growth container, mix and react, and place the growth container in a vibration isolation system for thin film growth to obtain the lead sulfide thin film.

[0040] In the step S1, the conditions of the thermal evaporation method are:

[0041] The evaporation current is 60 A to 80 A;

[0042] The evaporation pressure is < 10 -4 Pa;

[0043] The thickness of the amorphous lead sulfide thin film is 4 nm to 6 nm.

[0044] The thermal evaporation is carried out in a thermal evaporation chamber, and lead sulfide powder is evaporated onto the substrate by thermal evaporation to form an amorphous lead sulfide thin film.

[0045] The substrate includes one or a combination of a silicon wafer, quartz glass, fluorine-doped tin oxide glass, and indium-doped tin oxide glass.

[0046] The step S1 is specifically:

[0047] Pre-treat the substrate;

[0048] Put the pre-treated substrate into the thermal evaporation chamber and deposit an amorphous lead sulfide thin film by evaporation;

[0049] Among them, the pre-treatment is specifically: successively perform ultrasonic cleaning for 20 min with dishwashing liquid, deionized water, acetone, isopropanol, and ethanol, dry, and place the substrate in an ultraviolet ozone or plasma cleaner for treatment for 5 - 10 min.

[0050] In the step S3, the preparation method of the lead source precursor solution includes:

[0051] Quickly add an alkaline substance to a first solution containing a lead source to obtain a second solution, and filter to obtain the lead source precursor solution.

[0052] Among them, the lead source includes one or more combinations of lead nitrate and lead acetate. The alkaline substance includes one or more combinations of sodium hydroxide and potassium hydroxide. The sulfur source in the sulfur source precursor solution is thiourea.

[0053] The content of the alkaline substance is 0.1 mol to 0.15 mol. The thiourea concentration is 1 mol / L to 2 mol / L. The molar ratio of the lead source precursor solution to the sulfur source precursor solution is 1:0.4 to 1:0.5.

[0054] In the step S4, the noise of the active vibration isolation system is 10 -10 ~10 -9 g / Hz 1 / 2 , the ambient temperature is a constant 20 °C, and the ambient humidity is a constant 50% RH. The active vibration isolation system is used to reduce the vibration noise of the thin film growth environment, reduce the environmental vibration noise by two orders of magnitude, and reduce the homogeneous nucleation and crystallization process in the solution caused by environmental disturbances. The finally formed lead sulfide thin film has a thickness of 500 nm - 1000 nm.

[0055] The single-crystal lead sulfide thin film prepared by the method of preparing a single-crystal lead sulfide thin film by chemical liquid deposition uses a substrate to evaporate a lead sulfide seed layer and perform high-temperature annealing to achieve substrate pre-crystallization, and reduce the vibration influence of the growth environment to achieve steady-state growth. Thus, it solves the problems that most lead sulfide thin films are polycrystals with complex grain stacking, their grains are not dense enough, there are many crystallization orientations, the free carrier concentration is high, and the mobility is low, etc. It realizes the preparation of high-quality lead sulfide thin films, laying a foundation for the preparation of lead sulfide infrared photoconductive devices and photodiode devices. In addition, this method has a simple process, low cost, and can achieve large-scale industrial production.

[0056] The present invention also provides a single-crystal lead sulfide thin film, which is prepared by the method of preparing a single-crystal lead sulfide thin film by the above chemical liquid deposition method. The single-crystal lead sulfide thin film has the advantages of dense grains, few holes, single orientation, low carrier concentration, and high mobility, and is a high-quality lead sulfide thin film.

[0057] The embodiment of the present invention also provides a specific method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition, including the following steps:

[0058] S11: Sequentially perform ultrasonic cleaning for 20 min with dishwashing liquid, deionized water, acetone, isopropanol, and ethanol, dry, and place the substrate in an ultraviolet ozone or plasma cleaner for 5 - 10 min;

[0059] S12: Place the processed substrate into the thermal evaporation chamber and deposit an amorphous lead sulfide thin film through evaporation; wherein, the evaporation current of the thermal evaporation is 70 A; the evaporation pressure of the thermal evaporation is <10-4 Pa; the thickness of the amorphous lead sulfide thin film is 5 nm;

[0060] S13: Anneal the amorphous lead sulfide thin film in a nitrogen atmosphere at 300 °C for 10 min for pre-crystallization to obtain a lead sulfide seed layer;

[0061] S14: Prepare the lead source precursor solution and the sulfur source precursor solution required for chemical liquid phase deposition; wherein, the molar ratio of the lead source precursor solution to the sulfur source precursor solution is 1:0.45; the lead source is lead nitrate and the sulfur source is thiourea.

[0062] S15: Place the lead sulfide seed layer in a growth container containing the lead source precursor solution, then add the sulfur source precursor solution to the growth container, mix and react, place the growth container in a vibration isolation system for thin film growth to obtain the lead sulfide thin film. Use an active vibration isolation system to control the vibration noise in the growth container to be 1-2 orders of magnitude lower than the laboratory environment.

[0063] See Figures 2 - 4 , Figures 2 - 4 is the single crystal lead sulfide thin film generated by the method for preparing a single crystal lead sulfide thin film by the above-described chemical liquid phase deposition method. Wherein, the Figure 2 is the XRD pattern of the single crystal lead sulfide thin film. The Figure 3 is the SEM pattern of the surface of the single crystal lead sulfide thin film. The Figure 4 is the cross-sectional SEM pattern of the single crystal lead sulfide thin film.

[0064] Table 1

[0065] <![CDATA[Carrier concentration (cm -3 )]]> <![CDATA[Mobility (cm 2 / Vs)]]> <![CDATA[8.8928×10 14 > 465.84

[0066] The said Table 1 is the carrier concentration and mobility data of the single crystal lead sulfide thin film. From the Figures 2 - 4 and Table 1, it can be seen that the single crystal lead sulfide thin film has the advantages of dense grains, few holes, single orientation, low carrier concentration, high mobility, etc., and is a high-quality lead sulfide thin film. The method for preparing a single crystal lead sulfide thin film by the chemical liquid phase deposition method can prepare a high-quality lead sulfide thin film, laying a foundation for the preparation of lead sulfide infrared photoconductive devices and photodiode devices.

[0067] See Figure 5 , Figure 5 is the vibration noise comparison diagram of the ground vibration under normal conditions and the ground vibration at the same position after using the active vibration isolation system. Through Figure 5It can be seen that the active vibration isolation system can reduce the vibration noise effect of ground vibration by 1-2 orders of magnitude. When the active vibration isolation system is used, the vibration noise in the growth container can be kept within -10 ~10 -9 g / Hz 1 / 2 , reducing the vibration influence on the growth environment and achieving steady-state growth.

[0068] In summary, the embodiment of the present invention provides a method for preparing a single-crystal lead sulfide thin film by chemical liquid-phase deposition. By using substrate evaporation to obtain an amorphous lead sulfide thin film and performing high-temperature annealing to achieve substrate pre-crystallization, and reducing the vibration influence on the growth environment to achieve steady-state growth. Its process flow is simple and the technology is stable, overcoming the problem that high-quality (dense grains, few holes, single orientation, low carrier concentration, high mobility) lead sulfide thin films cannot be obtained at the present stage, realizing the preparation of high-quality lead sulfide thin films, and laying a foundation for the preparation of lead sulfide infrared photoconductive devices and photodiode devices.

[0069] The above-disclosed is only a preferred embodiment of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition, characterized in that: The following steps are involved: S1: depositing an amorphous lead sulfide thin film on a substrate by thermal evaporation; S2: annealing the amorphous lead sulfide film at 250° C. to 350° C. for 5 min to 15 min in a nitrogen atmosphere for pre-crystallization to obtain a lead sulfide seed layer; S3: preparing the lead source precursor solution and the sulfur source precursor solution required for chemical liquid deposition; S4: placing the lead sulfide seed layer in a growth container with a lead source precursor solution added thereto, then adding a sulfur source precursor solution into the growth container, mixing and reacting, placing the growth container in a vibration isolation system for thin film growth, and obtaining the lead sulfide thin film.

2. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: In step S3, the method for preparing the lead source precursor solution comprises: Rapidly adding an alkaline substance into the first solution containing the lead source to obtain a second solution, and filtering to obtain the lead source precursor solution; The lead source includes: one or more combinations of lead nitrate and lead acetate; The alkaline substance includes: one or more combinations of sodium hydroxide and potassium hydroxide.

3. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 2, characterized in that: The content of the alkaline substance is 0.1 mol to 0.15 mol.

4. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: In the step S3, the molar ratio of the lead source precursor solution to the sulfur source precursor solution is 1:0.4 to 1:0.

5.

5. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: In the step S3, the sulfur source in the sulfur source precursor solution is thiourea, and the concentration is 1 mol / L to 2 mol / L.

6. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: In step S1, the thermal evaporation method conditions are: evaporation current is 60A to 80A; evaporation pressure is <10 -4 Pa; the thickness of the amorphous lead sulfide film is 4nm to 6nm.

7. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: In step S4, the noise of the active vibration isolation system is 10 -10 ~10 -9 g / Hz 1 / 2 , the ambient temperature is constant at 20°C, and the ambient humidity is constant at 50% RH.

8. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: The step S1 is specifically as follows: Pre-treating the substrate; The pretreated substrate is placed in a thermal evaporation chamber to deposit an amorphous lead sulfide film by evaporation; The pretreatment specifically includes: using detergent, deionized water, acetone, isopropanol, and ethanol to perform ultrasonic cleaning for 20 minutes, drying, and placing the substrate in an ultraviolet ozone or plasma cleaning machine for 5-10 minutes.

9. The method for preparing a single-crystal lead sulfide thin film by chemical liquid deposition according to claim 1, characterized in that: The substrate comprises: one or more combinations of silicon wafer, quartz glass, fluorine-doped tin oxide glass, and indium-doped tin oxide glass.

10. A single crystal lead sulfide thin film, characterized in that: The single crystal lead sulfide film is prepared by using any one of the chemical liquid deposition methods described in claims 1-9 to prepare a single crystal lead sulfide film.

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