Van der Waals photoelectric detector, preparation method and application thereof, and non-dispersive infrared gas sensor

Abstract

The invention relates to the technical field of non-dispersive infrared gas sensors, in particular to a Van der Waals photoelectric detector, a preparation method and application thereof and a non-dispersive infrared gas sensor. The invention provides a Van der Waals photoelectric detector. The Van der Waals photoelectric detector comprises a substrate layer, a heterojunction layer and a double-end metal electrode layer, the heterojunction layer is of a heterojunction structure formed by partially embedding a first Van der Waals material layer into the bottom of a second Van der Waals material layer, the whole bottom of the first Van der Waals material layer is in contact with the upper surface of the substrate layer, and part of the bottom of the second Van der Waals material layer is in contact with the upper surface of the substrate layer; the double-end metal electrode layer comprises a first metal electrode and a second metal electrode, the first metal electrode is located on the surface of the first Van der Waals material layer, and the second metal electrode is located on the surface of the second Van der Waals material layer. The Van der Waals photoelectric detector has extremely low interface defects and relatively low thermal noise.

Description

Technical Field

[0001] The present invention relates to the technical field of non-dispersive infrared gas sensors, and in particular to a van der Waals photoelectric detector, a preparation method and application thereof, and a non-dispersive infrared gas sensor. Background Art

[0002] The safety and health of the air environment is not only related to economic development, but also to human survival and health. It is an important global issue. Controllable monitoring of the air environment is of great significance to security, environmental protection, industrial applications, scientific research and technological development. Among gas sensors, non-dispersive infrared gas sensors are based on the principle of gas infrared absorption and have the advantages of non-contact monitoring, high sensitivity and strong selectivity.

[0003] The infrared photodetectors used in traditional non-dispersive gas sensors mostly use narrow bandgap semiconductor materials, so the thermal noise of the devices is large at room temperature; the defective contact between multiple materials causes the composite noise of the materials to be large. These problems cause the noise of traditional non-dispersive gas sensor systems to remain high at room temperature, making it difficult for the sensors to identify and detect weak gases. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a van der Waals photodetector and a preparation method and application thereof, and a non-dispersive infrared gas sensor. The van der Waals photodetector has extremely low interface defects and low thermal noise.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a van der Waals photodetector, comprising a substrate layer, a heterojunction layer and a double-terminal metal electrode layer stacked in sequence; The heterojunction layer is a heterojunction structure formed by partially embedding a first van der Waals material layer into a bottom portion of a second van der Waals material layer, and the entire bottom portion of the first van der Waals material layer contacts the upper surface of the base layer, and a portion of the bottom portion of the second van der Waals material layer contacts the upper surface of the base layer; The double-terminal metal electrode layer includes a first metal electrode and a second metal electrode, wherein the first metal electrode is located on a surface of the first van der Waals material layer, and the second metal electrode is located on a surface of the second van der Waals material layer.

[0006] Preferably, the materials of the first van der Waals material layer and the second van der Waals material layer are independently one or more of molybdenum disulfide, bismuth tin oxide and black phosphorus, and the materials of the first van der Waals material layer and the second van der Waals material layer are different.

[0007] Preferably, the material of the first van der Waals material layer is molybdenum disulfide and / or bismuth tin oxide, and the material of the second van der Waals material layer is black phosphorus; Or the material of the first van der Waals material layer is black phosphorus, and the material of the second van der Waals material layer is molybdenum disulfide and / or bismuth tin oxide.

[0008] Preferably, the material of the first van der Waals material layer is molybdenum disulfide, and the material of the second van der Waals material layer is black phosphorus; or the material of the first van der Waals material layer is black phosphorus, and the material of the second van der Waals material layer is molybdenum disulfide.

[0009] Preferably, the first metal electrode and the second metal electrode both include a chromium layer and a gold layer stacked in sequence.

[0010] The present invention also provides a method for preparing the van der Waals photodetector described in the above technical solution, comprising the following steps: A first van der Waals material layer and a second van der Waals material layer are sequentially transferred onto the surface of the substrate layer by a mechanical transfer method, wherein the entire bottom of the first van der Waals material layer contacts the upper surface of the substrate layer, and the second van der Waals material layer partially covers the first van der Waals material layer, and a portion of the bottom contacts the upper surface of the substrate layer, to obtain a heterojunction layer; A first metal electrode is evaporated on the surface of the first van der Waals material layer in the heterojunction layer, and a second metal electrode is evaporated on the surface of the second van der Waals material layer in the heterojunction layer to obtain the van der Waals photodetector.

[0011] The present invention also provides the use of the van der Waals photoelectric detector described in the above technical solution or the van der Waals photoelectric detector prepared by the preparation method described in the above technical solution in a non-dispersive infrared gas sensor.

[0012] The present invention also provides a non-dispersive infrared gas sensor, comprising a tungsten lamp light source, a chopper, a gas chamber, a van der Waals photodetector, a signal processing circuit and a display, which are arranged in sequence; The chopper is arranged between the light outlet of the tungsten lamp light source and the air chamber; The van der Waals photodetector is used to receive the light emitted by the tungsten lamp light source through the gas chamber; The van der Waals photodetector is electrically connected to the signal processing circuit and the display in sequence; The van der Waals photodetector is the van der Waals photodetector described in the above technical solution or a van der Waals photodetector prepared by the preparation method described in the above technical solution.

[0013] Preferably, the air chamber comprises an air inlet, an air outlet, an air chamber inner cavity and a light-transmitting window; The air inlet is located at the top of the air chamber, and the air outlet is located at the bottom of the air chamber; The light-transmitting windows are located on two opposite sides of the air chamber.

[0014] Preferably, the signal processing circuit includes a light source driving circuit and an analog-to-digital conversion circuit; The circuit substrate of the signal processing circuit is of STC series.

[0015] The present invention provides a van der Waals photodetector, comprising a base layer, a heterojunction layer and a double-terminal metal electrode layer stacked in sequence; the heterojunction layer is a first van der Waals material layer partially embedded in the bottom of a second van der Waals material layer to form a heterojunction structure, and the entire bottom of the first van der Waals material layer contacts the upper surface of the base layer, and part of the bottom of the second van der Waals material layer contacts the upper surface of the base layer; the double-terminal metal electrode layer comprises a first metal electrode and a second metal electrode, the first metal electrode is located on the surface of the first van der Waals material layer, and the second metal electrode is located on the surface of the second van der Waals material layer. The van der Waals photodetector of the present invention utilizes the advantages of van der Waals materials with few surface defects and low thermal noise at room temperature to effectively reduce the system noise of non-dispersive infrared gas sensors, improve the recognition and detection capabilities of non-dispersive infrared gas sensors for weak gases, reveal the mechanism of suppressing background noise by photoacoustic-electric coupling dual-degree-of-freedom phase regulation, and reveal the action law of photoelectric conversion coherent superposition to enhance the signal-to-background ratio of narrow-spectrum radiation targets. By building a heterostructure, the built-in electric field spontaneously formed by the contact between the electron semiconductor and the hole semiconductor can be used to further promote the separation of photogenerated carriers. This structural design allows the van der Waals photodetector to operate under zero bias, further reducing system noise and improving the ability to resolve gases. Therefore, the van der Waals photodetector described in the present invention has extremely low interface defects and low thermal noise, which makes the van der Waals photodetector exhibit superior performance at room temperature, improving the detection and identification capabilities of non-dispersive infrared gas sensors for weak gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The van der Waals photodetector of the present invention, wherein 1 is a substrate layer, 2 is a first van der Waals material layer, 3 is a second van der Waals material layer, and 4 is a double-terminal metal electrode layer; Figure 2 Schematic diagram of the working principle of the non-dispersive infrared gas sensor of the present invention, wherein 5 is a tungsten lamp light source, 6 is a chopper, 7 is a gas chamber, 8 is a van der Waals photodetector, 9 is a signal processing circuit, and 10 is a display; Figure 3Schematic diagram of the structure of the air chamber in the non-dispersive infrared gas sensor of the present invention, wherein 11 is the air inlet, 12 is the air outlet, 13 is the inner cavity of the air chamber, and 14 is the light-transmitting window; Figure 4 The system noise level of the van der Waals photodetector described in Example 1 and the system noise level of the traditional detector (a), the signal intensity change curve of the non-dispersive infrared gas sensor described in Example 1 at different methane concentrations (b), and the fitting curve of methane gas concentration and the signal intensity of the non-dispersive infrared gas sensor (c). DETAILED DESCRIPTION

[0017] like Figure 1 As shown, the present invention provides a van der Waals photodetector, comprising a substrate layer 1, a heterojunction layer and a double-terminal metal electrode layer 4 which are stacked in sequence; The heterojunction layer is a heterojunction structure formed by partially embedding the first van der Waals material layer 2 into the bottom of the second van der Waals material layer 3, and the entire bottom of the first van der Waals material layer 2 is in contact with the upper surface of the base layer 1, and part of the bottom of the second van der Waals material layer 3 is in contact with the upper surface of the base layer 1; The double-terminal metal electrode layer 4 includes a first metal electrode and a second metal electrode. The first metal electrode is located on the surface of the first van der Waals material layer 2 , and the second metal electrode is located on the surface of the second van der Waals material layer 3 .

[0018] The present invention has no special limitation on the base layer 1, and any base layer 1 known to those skilled in the art can be used. In an embodiment of the present invention, the base layer 1 may include a silicon layer with a thickness of 15 mm and a silicon oxide layer with a thickness of 300 nm stacked in sequence.

[0019] In the present invention, the heterojunction layer is a heterojunction structure formed by partially embedding the first van der Waals material layer 2 in the bottom of the second van der Waals material layer 3, and the entire bottom of the first van der Waals material layer 2 is in contact with the upper surface of the base layer 1, and part of the bottom of the second van der Waals material layer 3 is in contact with the upper surface of the base layer 1. In the present invention, the partial embedding is preferably that 3 / 4 of the first van der Waals material layer 2 is embedded in the second van der Waals material layer 3. In the present invention, the materials of the first van der Waals material layer 2 and the second van der Waals material layer 3 are independently preferably one or more of molybdenum disulfide, bismuth tin oxide and black phosphorus, and the materials of the first van der Waals material layer 2 and the second van der Waals material layer 3 are different; more preferably, the material of the first van der Waals material layer 2 is molybdenum disulfide and / or bismuth tin oxide, and the material of the second van der Waals material layer 3 is black phosphorus; or the material of the first van der Waals material layer 2 is black phosphorus, and the material of the second van der Waals material layer 3 is molybdenum disulfide and / or bismuth tin oxide; most preferably, the material of the first van der Waals material layer 2 is molybdenum disulfide, and the material of the second van der Waals material layer 3 is black phosphorus; or the material of the first van der Waals material layer 2 is black phosphorus, and the material of the second van der Waals material layer 3 is molybdenum disulfide. In the present invention, the thickness of the first van der Waals material layer 2 is preferably 10-50 nm, more preferably 25-35 nm; the thickness of the second van der Waals material layer 3 is preferably 30-70 nm, more preferably 45-55 nm. The present invention does not have any special limitation on the planar dimensions of the first van der Waals material layer 2 and the second van der Waals material layer 3, and the planar dimensions known to those skilled in the art can be adopted. In an embodiment of the present invention, the planar dimensions of the first van der Waals material layer 2 and the second van der Waals material layer 3 can both be 40 μm×40 μm.

[0020] In the present invention, the first metal electrode and the second metal electrode preferably both include a chromium layer and a gold layer stacked in sequence; the thickness of the chromium layer is preferably 5 to 25 nm independently, more preferably 15 nm; the thickness of the gold layer is preferably 35 to 75 nm independently, more preferably 45 nm. In an embodiment of the present invention, the thickness of the chromium layer may be 15 nm, and the thickness of the gold layer may be 45 nm. The present invention does not have any special restrictions on the planar dimensions of the first metal electrode and the second metal electrode, and the planar dimensions familiar to those skilled in the art may be used. In an embodiment of the present invention, the planar dimensions of the first metal electrode and the second metal electrode may both be 10 μm × 20 μm.

[0021] The present invention also provides a method for preparing the van der Waals photodetector described in the above technical solution, comprising the following steps: A first van der Waals material layer 2 and a second van der Waals material layer 3 are sequentially transferred onto the surface of a substrate layer 1 by a mechanical transfer method, wherein the entire bottom of the first van der Waals material layer 2 is in contact with the upper surface of the substrate layer 1, and the second van der Waals material layer 3 partially covers the first van der Waals material layer 2, and a portion of the bottom is in contact with the upper surface of the substrate layer 1, to obtain a heterojunction layer; The first metal electrode is evaporated on the surface of the first van der Waals material layer 2 in the heterojunction layer, and the second metal electrode is evaporated on the surface of the second van der Waals material layer 3 in the heterojunction layer to obtain the van der Waals photodetector.

[0022] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0023] The present invention adopts a mechanical transfer method to sequentially transfer a first van der Waals material layer 2 and a second van der Waals material layer 3 onto the surface of a substrate layer 1, wherein the entire bottom of the first van der Waals material layer 2 contacts the upper surface of the substrate layer 1, and the second van der Waals material layer 3 partially covers the first van der Waals material layer 2, and a portion of the bottom contacts the upper surface of the substrate layer 1, thereby obtaining a heterojunction layer.

[0024] In the present invention, the specific process of the mechanical transfer is preferably: the first van der Waals material layer 2 is prepared on the surface of the base layer 1 by a mechanical peeling method, and then the base layer 1 with the first van der Waals material layer 2 attached is placed on the base of the transfer platform, and the first van der Waals material layer 2 is found using a transfer platform microscope, and with the assistance of the transfer platform, the second van der Waals material layer 3 is transferred to the upper surface of the first van der Waals material layer 2.

[0025] After obtaining the heterojunction layer, the present invention evaporates a first metal electrode on the surface of the first van der Waals material layer 2 in the heterojunction layer, and evaporates a second metal electrode on the surface of the second van der Waals material layer 3 in the heterojunction layer to obtain the van der Waals photodetector.

[0026] In the present invention, the process of preparing the first metal electrode and the second metal electrode preferably includes sequentially performing spin coating of photoresist, photolithography, development, evaporation and removal of the photoresist.

[0027] In the present invention, the spin coating of the photoresist preferably includes: placing the prepared base layer 1 containing the heterojunction layer on the rotating vacuum table of the coating machine, vacuum adsorbing the substrate, dripping industrial A5 PMMA solution on the surface of the base layer 1 containing the heterojunction layer with a rubber-tipped dropper, and curing after spin coating. In the present invention, the spin coating preferably includes the first spin coating and the second spin coating performed in sequence; the rotation speed of the first spin coating is preferably 500 rpm, and the time is preferably 5s; the rotation speed of the second spin coating is preferably 3000 rpm, and the time is preferably 30s. In the present invention, the curing temperature is preferably 150°C, and the time is preferably 5min.

[0028] In the present invention, the photolithography process preferably includes: placing the base layer 1 obtained after spin coating on an electron beam lithography platform, finding a clear target sample image that needs to be photolithographic under an electronic photograph, adjusting the coordinates and angles, exposing the designed electrode area with an electron beam, and finally taking it out of the electron cavity.

[0029] In the present invention, the development process is preferably: placing the base layer 1 obtained after the photolithography in a developer, performing static development, then taking it out with tweezers, and placing it in isopropanol for fixing. In the present invention, the developer preferably includes isopropanol, methanol and deionized water in a volume ratio of 7:2:1. In the present invention, the static development time is preferably 45s; the fixing time is preferably 1min.

[0030] In the present invention, the evaporation process is preferably as follows: attaching the developed base layer 1 to the top of the thermal evaporation chamber and closing the chamber door; opening the vacuum air pump and the pipe valve, and after reaching a high vacuum, turning on the thermal evaporation current, heating the metal chromium, turning on the film thickness meter, and observing the thickness of the chromium layer obtained by evaporation in real time, and after the thickness of the chromium layer reaches 15nm, turning off the current; then turning on the gold current, heating the gold, turning on the film thickness meter, and observing the thickness of the gold layer obtained by evaporation in real time, and after the thickness of the gold layer reaches 45nm, turning off the current, breaking the vacuum, and taking the obtained sample out of the chamber.

[0031] In the present invention, the process of removing the photoresist is preferably as follows: placing the substrate layer 1 obtained by evaporation in a stripping container filled with acetone solution and soaking it for 10 minutes to dissolve the photoresist, taking out the sample with tweezers, and gently blowing it dry with a nitrogen chamber.

[0032] The present invention also provides the use of the van der Waals photoelectric detector described in the above technical solution or the van der Waals photoelectric detector prepared by the preparation method described in the above technical solution in a non-dispersive infrared gas sensor.

[0033] like Figure 2As shown, the present invention also provides a non-dispersive infrared gas sensor, comprising a tungsten lamp light source 5, a chopper 6, a gas chamber 7, a van der Waals photodetector 8, a signal processing circuit 9 and a display 10 arranged in sequence; The chopper 6 is arranged between the light outlet of the tungsten lamp light source 5 and the gas chamber 7; The van der Waals photodetector 8 is used to receive the light emitted by the tungsten lamp light source 5 through the gas chamber 7; The van der Waals photodetector 8 is electrically connected to the signal processing circuit 9 and the display 10 in sequence; The van der Waals photodetector 8 is the van der Waals photodetector described in the above technical solution or a van der Waals photodetector prepared by the preparation method described in the above technical solution.

[0034] The present invention has no special limitation on the tungsten lamp light source 5, and any tungsten lamp light source 5 known to those skilled in the art can be used. In the embodiment of the present invention, the tungsten lamp light source 5 can be a model of the Solebo HEP3965-Broadband Infrared Tungsten Filament Lamp, which outputs an optical power of 39mW at a voltage of 1.5V.

[0035] The present invention has no special limitation on the chopper 6, and those skilled in the art may adopt any chopper. In the embodiment of the present invention, the chopper 6 may be Model-300CD, and the operating frequency of the chopper 6 of Model-300CD may be 233 Hz.

[0036] In the present invention, the air chamber 7 preferably includes an air inlet 11, an air outlet 12, an air chamber inner cavity 13 and a light-transmitting window 14; the air inlet 11 is preferably located at the top of the air chamber 7, and the air outlet 12 is located at the bottom of the air chamber 7; the light-transmitting window 14 is preferably located at two opposite sides of the air chamber 7 (such as Figure 3 As shown). In the present invention, the light-transmitting window 14 is preferably a light-transmitting glass window. The present invention does not have any special limitation on the size of the air chamber 7, and the size familiar to those skilled in the art can be adopted. In an embodiment of the present invention, the air chamber 7 can be a hollow alloy tube shell with a length of 80 cm and a width of 40 cm. The present invention does not have any special limitation on the air inlet 11 and the air outlet 12, and the size familiar to those skilled in the art can be adopted. In an embodiment of the present invention, the air inlet 11 and the air outlet 12 can both be metal tube openings with a radius of 6 mm. In an embodiment of the present invention, the light-transmitting window 14 can be a double-polished glass sheet with a diameter of 2.5 cm and a thickness of 0.5 cm.

[0037] The present invention does not have any special limitation on the size of the van der Waals photodetector 8, and any size known to those skilled in the art may be adopted. In an embodiment of the present invention, the size of the van der Waals photodetector 8 may be 40 μm×40 μm.

[0038] In the present invention, the signal processing circuit 9 preferably includes a light source driving circuit and an analog-to-digital conversion circuit, and the circuit substrate of the signal processing circuit 9 is preferably an STC series.

[0039] The present invention has no special limitation on the display 10 , and any method known to those skilled in the art may be adopted. In the embodiment of the present invention, the display 10 may be a digital display screen.

[0040] In the present invention, the method for using the non-dispersive infrared gas sensor preferably includes: Turn on the main power of the system to make the tungsten lamp light source 5, the chopper 6 and the signal processing circuit 9 work normally, place the van der Waals photodetector 8 at the rear end of the gas chamber 7, and connect the van der Waals photodetector 8 to the signal processing circuit 9 through a data line; Adjust the positions of the tungsten light source 5 and the van der Waals photodetector 8 so that the light emitted by the tungsten light source 5 passes through the inner cavity of the gas chamber 7 and then irradiates the surface of the van der Waals photodetector 8, so that the van der Waals photodetector 8 generates a signal; The target gas to be measured is introduced into the gas chamber 7 from the gas inlet 11 of the gas chamber 7, and the excess tail gas of the cycle is discharged from the gas outlet 12, so that the concentration of the gas to be measured in the gas chamber 7 is stabilized; The signal of the van der Waals photodetector 8 is calculated by the signal processing circuit 9 and then displayed on the display 10. By reading the data on the display 10, the concentration value of the target gas can be obtained.

[0041] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1 The structure of van der Waals photodetector: It comprises a base layer 1 stacked in sequence: a silicon layer with a thickness of 0.5 mm and a silicon oxide layer with a thickness of 300 nm stacked in sequence; Heterojunction layer: 3 / 4 of a molybdenum disulfide layer with a size of 40 μm×40 μm is embedded in the bottom of a black phosphorus layer with a size of 40 μm×40 μm to form a heterojunction structure, and the entire bottom of the molybdenum disulfide layer is in contact with the upper surface of the base layer 1, and the bottom of a portion of the black phosphorus layer that is not embedded in the molybdenum disulfide layer is in contact with the upper surface of the base layer 1; and a double-terminal metal electrode layer 4, comprising a first metal electrode and a second metal electrode, wherein the first metal electrode is located on the surface of the molybdenum disulfide layer, and the second metal electrode is located on the surface of the black phosphorus layer; the first metal electrode and the second metal electrode each comprise a chromium layer with a thickness of 15 nm and a plane size of 10 μm×20 μm and a gold layer with a thickness of 45 nm and a plane size of 10 μm×20 μm, which are stacked in sequence; Preparation process of van der Waals photodetector: The molybdenum disulfide layer is prepared on the surface of the base layer 1 by a mechanical stripping method, and then the base layer 1 with the molybdenum disulfide layer attached is placed on the base of the transfer platform, the molybdenum disulfide layer is found by using a transfer platform microscope, and with the assistance of the transfer platform, the black phosphorus layer is transferred to the upper surface of the molybdenum disulfide layer to cover about 30 μm, thereby obtaining the base layer 1 containing the heterojunction layer; The prepared substrate layer 1 containing the heterojunction layer is placed on the rotating vacuum table of the coating machine, the substrate is vacuum-adsorbed, and the industrial A5 PMMA solution is dripped onto the surface of the substrate layer 1 containing the heterojunction layer with a rubber-tipped dropper, and then spin-coated (first at a speed of 500 rpm for 5 seconds, and then at a speed of 3000 rpm for 30 seconds), and then cured (temperature of 150°C for 5 minutes); The substrate layer 1 obtained after spin coating is placed on an electron beam lithography platform, a clear target sample image to be lithographically processed is found under the electron photograph, and the coordinates and angles are adjusted, the designed electrode area is exposed with an electron beam, and finally taken out from the electron cavity; The base layer 1 obtained after the photolithography is placed in a developer (isopropanol, methanol and deionized water in a volume ratio of 7:2:1) and allowed to stand for 45 seconds for development. The base layer 1 is then taken out with tweezers and placed in isopropanol for fixing for 1 minute. The base layer 1 obtained by the development is attached to the top of the thermal evaporation chamber, and the chamber door is closed; the vacuum air pump and the pipe valve are turned on, and after reaching a high vacuum, the thermal evaporation current is turned on, the metal chromium is heated, the film thickness meter is turned on, and the thickness of the chromium layer obtained by evaporation is observed in real time. After the thickness of the chromium layer reaches 15nm, the current is turned off; then the gold current is turned on, the gold is heated, the film thickness meter is turned on, and the thickness of the gold layer obtained by evaporation is observed in real time. After the thickness of the gold layer reaches 45nm, the current is turned off, the vacuum is broken, and the obtained sample is taken out of the chamber; The base layer 1 obtained by evaporation is placed in a stripping container filled with acetone solution and soaked for 10 minutes to dissolve the photoresist, and then the sample is taken out with tweezers and gently blown dry with a nitrogen chamber to obtain the van der Waals photodetector; Non-dispersive infrared gas sensor based on the above van der Waals photodetector: It includes a model of Sorebo HEP3965-broadband infrared tungsten lamp (with an output light power of 39mW at a voltage of 1.5V, a model of Medel-300CD chopper (with an operating frequency of 233Hz), a hollow alloy tube shell with a length of 80cm and a width of 40cm (a metal tube mouth with a radius of 6mm is provided on the top of the tube shell as an air inlet 11, and a metal tube mouth with a radius of 6mm is provided on the bottom of the tube shell as an air outlet, and double-polished glass sheets with a diameter of 2.5cm and a thickness of 0.5cm are provided at both ends as light-transmitting glass windows) as an air chamber 7, a van der Waals photodetector 8 (with a size of 40μm×40μm), a model processing circuit composed of a light source driving circuit and an analog-to-digital conversion circuit (the circuit substrate is STC series) and a digital display screen as a display 10; the van der Waals photodetector 8 is used to receive the light emitted by the tungsten lamp light source 5 through the air chamber 7; the van der Waals photodetector 8 is electrically connected to the signal processing circuit 9 and the display 10 in sequence.

[0043] Method for using the non-dispersive infrared gas sensor based on the van der Waals photodetector 8: Turn on the main power of the system to make the tungsten lamp light source 5, the chopper 6 and the signal processing circuit 9 work normally, place the van der Waals photodetector 8 at the rear end of the gas chamber 7, and connect the van der Waals photodetector 8 to the signal processing circuit 9 through a data line; Adjust the positions of the tungsten light source 5 and the van der Waals photodetector 8 so that the light emitted by the tungsten light source 5 passes through the inner cavity of the gas chamber 7 and then irradiates the surface of the van der Waals photodetector 8, so that the van der Waals photodetector 8 generates a signal; The methane gas is introduced into the air chamber 7 from the air inlet 11 of the air chamber 7, and the excess tail gas of the cycle is discharged from the air outlet 12, so that the concentration of the methane gas in the air chamber 7 is stabilized; The signal of the van der Waals photodetector 8 is calculated by the signal processing circuit 9 and then displayed on the display 10. By reading the data on the display 10, the concentration value of the target gas can be obtained.

[0044] Figure 4 In the figure, a is the system noise level of the van der Waals photodetector and the traditional detector (Hamamatsu P10090-11), b is the signal intensity variation curve of the non-dispersive infrared gas sensor under different methane concentrations, and c is the fitting curve of methane gas concentration and signal intensity of the non-dispersive infrared gas sensor. Figure 4It can be seen that the van der Waals photoelectric detection device can significantly reduce the noise level of the non-dispersive infrared gas sensor at room temperature, and improve the recognition and detection capabilities of the non-dispersive infrared gas sensor for weak gases.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A van der Waals photodetector, characterized in that: It includes a base layer, a heterojunction layer and a double-terminal metal electrode layer which are stacked in sequence; The heterojunction layer is a heterojunction structure formed by partially embedding a first van der Waals material layer into a bottom portion of a second van der Waals material layer, and the entire bottom portion of the first van der Waals material layer contacts the upper surface of the base layer, and a portion of the bottom portion of the second van der Waals material layer contacts the upper surface of the base layer; The double-terminal metal electrode layer includes a first metal electrode and a second metal electrode, wherein the first metal electrode is located on a surface of the first van der Waals material layer, and the second metal electrode is located on a surface of the second van der Waals material layer.

2. The van der Waals photodetector according to claim 1, wherein: The materials of the first van der Waals material layer and the second van der Waals material layer are independently one or more of molybdenum disulfide, bismuth tin oxide and black phosphorus, and the materials of the first van der Waals material layer and the second van der Waals material layer are different.

3. The van der Waals photodetector according to claim 2, characterized in that: The material of the first van der Waals material layer is molybdenum disulfide and / or bismuth tin oxide, and the material of the second van der Waals material layer is black phosphorus; Or the material of the first van der Waals material layer is black phosphorus, and the material of the second van der Waals material layer is molybdenum disulfide and / or bismuth tin oxide.

4. The van der Waals photodetector according to claim 3, characterized in that The material of the first van der Waals material layer is molybdenum disulfide, and the material of the second van der Waals material layer is black phosphorus; or the material of the first van der Waals material layer is black phosphorus, and the material of the second van der Waals material layer is molybdenum disulfide.

5. The van der Waals photodetector according to claim 1, wherein: The first metal electrode and the second metal electrode each include a chromium layer and a gold layer stacked in sequence.

6. The method for preparing the van der Waals photodetector according to any one of claims 1 to 5, characterized in that: The following steps are involved: A first van der Waals material layer and a second van der Waals material layer are sequentially transferred onto the surface of the substrate layer by a mechanical transfer method, wherein the entire bottom of the first van der Waals material layer contacts the upper surface of the substrate layer, and the second van der Waals material layer partially covers the first van der Waals material layer, and a portion of the bottom contacts the upper surface of the substrate layer, to obtain a heterojunction layer; A first metal electrode is evaporated on the surface of the first van der Waals material layer in the heterojunction layer, and a second metal electrode is evaporated on the surface of the second van der Waals material layer in the heterojunction layer to obtain the van der Waals photodetector.

7. Use of the van der Waals photodetector according to any one of claims 1 to 5 or the van der Waals photodetector prepared by the preparation method according to claim 6 in a non-dispersive infrared gas sensor.

8. A non-dispersive infrared gas sensor, characterized in that: It includes a tungsten light source, a chopper, a gas chamber, a van der Waals photodetector, a signal processing circuit and a display which are arranged in sequence; The chopper is arranged between the light outlet of the tungsten lamp light source and the air chamber; The van der Waals photodetector is used to receive the light emitted by the tungsten lamp light source through the gas chamber; The van der Waals photodetector is electrically connected to the signal processing circuit and the display in sequence; The van der Waals photodetector is the van der Waals photodetector described in any one of claims 1 to 5 or a van der Waals photodetector prepared by the preparation method described in claim 6.

9. The non-dispersive infrared gas sensor according to claim 8, characterized in that: The air chamber comprises an air inlet, an air outlet, an air chamber cavity and a light-transmitting window; The air inlet is located at the top of the air chamber, and the air outlet is located at the bottom of the air chamber; The light-transmitting windows are located on two opposite sides of the air chamber.

10. The non-dispersive infrared gas sensor according to claim 8, characterized in that: The signal processing circuit includes a light source driving circuit and an analog-to-digital conversion circuit; The circuit substrate of the signal processing circuit is of STC series.

Images