Monoatomic layer modified crystalline silicon nanowire gas sensor and preparation method thereof
By modifying the metal single atomic layer on the surface of crystalline silicon nanowires to form M/SiNWs, the problems of long response time and poor selectivity of traditional gas-sensitive sensors are solved, and a gas-sensitive sensor with high sensitivity and fast response are realized, which can effectively identify and detect complex gas mixtures.
Patent Information
- Application Number
- CN202411934529.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-04-11
AI Technical Summary
Traditional gas-sensitive sensors have problems with long response time and poor selectivity, making it difficult to efficiently identify and detect complex gas mixtures.
The metal single atom layer modification strategy is adopted to grow precious metal single atoms in situ on the surface of the crystalline silicon nanowire to form M/SiNWs. Through the redox reaction between the gas to be detected and the metal M, the resistance value of the crystalline silicon nanowire is changed, thereby realizing the identification and detection of gas.
It achieves high sensitivity, fast response time and good selectivity, can effectively identify and detect complex gas mixtures, significantly improving the performance of gas-sensitive sensors.
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Figure CN119804593A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor materials and gas sensors, and in particular to a single atomic layer modified crystalline silicon nanowire gas sensor and a preparation method thereof. Background Art
[0002] With the development of Internet of Things technology, gas sensors are moving towards smaller size and lower power consumption to facilitate integration into various smart devices. The sensitive materials or sensitive layers in gas sensors are crucial to achieving efficient molecular detection. In order to solve the problems of long response time and poor selectivity in traditional gas sensors, nanomaterials of different dimensions such as zero-dimensional nanoparticles, one-dimensional nanowires / tubes, and two-dimensional nanofilms are used to optimize the physical and chemical properties of the sensor. The nanoscale structure increases the surface active sites and improves the interaction with the target gas molecules, thereby enhancing the performance of the sensor.
[0003] Silicon nanowires (SiNWs) materials show broad application prospects due to their high specific surface area and unique optoelectronic properties. Silicon nanowires are attractive for label-free, real-time and sensitive detection of various gases and can be used in gas sensing (Mehdi Akbari-Saatlu, et al. Silicon Nanowires for Gas Sensing: A Review. Nanomaterials (Basel), 2020, 6; 10(11): 2215, doi: 10.3390 / nano10112215.).
[0004] Based on the innovative self-assembled in-plane solidliquid-solid (IPSLS) growth mode, positionable integrated crystalline silicon nanowire arrays are prepared on a variety of substrates (wafers, glass and flexible polymers) for the application of integrated SiNWs in various functional devices. Reference (Yang Chunsheng, et al. High-Performance Field-Effect Sensing of Ammonia Based on High-Density and Ultrathin SiliconNanowire Channels. ACS Sens., 2024, 22; 9(11): 6284-6291, doi: 10.1021 / acssensors.4c02426.) discloses the application of reliably integrated SiNWs in field effect transistor FET type gas sensors to achieve highly sensitive detection of gases such as ammonia at room temperature, which can further explore potential applications in the field of wearable or portable electronic products.
[0005] Starting from material design, the present invention adopts a metal single atomic layer modification strategy to in-situ grow noble metal single atoms on the surface of silicon nanowires in the sensitive layer, thereby improving the gas sensing properties. By developing a gas sensor based on SiNWs, effective identification of complex gas mixtures and qualitative and quantitative analysis and detection capabilities can be achieved. Summary of the invention
[0006] In order to solve the above technical problems, the present invention provides a single atomic layer modified crystalline silicon nanowire gas sensor, which has high sensitivity, fast response time and good selectivity.
[0007] A single atomic layer modified crystalline silicon nanowire gas sensor comprises a gate electrode, a source electrode and a drain electrode, wherein a channel layer is provided between the source electrode and the drain electrode, the channel layer is M / SiNWs, and the M is metal Pt, Pd, Au, Rh or Ru.
[0008] In the present invention, starting from material design, a metal single atomic layer modification strategy is adopted to in-situ grow noble metal single atoms M on the surface of crystalline silicon nanowires to obtain M / SiNWs. When the gas to be detected comes into contact with the metal M on the surface, an oxidation-reduction reaction occurs, which in turn causes a change in the resistance of the crystalline silicon nanowires. By detecting the change in resistance value, the type and concentration of the gas to be detected can be determined.
[0009] Preferably, the element proportion of M in the channel layer is 0.1-0.5 wt %.
[0010] In the present invention, when the element ratio of M in the channel layer is within the above range, it can better undergo redox reaction with the gas to be tested, so that the M-modified crystalline silicon nanowire gas sensor can quickly respond to gas testing.
[0011] The present invention also provides a method for preparing the above-mentioned single-atom-layer modified crystalline silicon nanowire gas sensor. The method prepares M / SiNWs by modifying a single atom M on the surface of a crystalline silicon nanowire, and prepares it into a single-atom-layer modified crystalline silicon nanowire gas sensor. The preparation method is easy to operate.
[0012] A method for preparing a single-atom modified crystalline silicon nanowire gas sensor comprises the following steps:
[0013] (1) Preparing crystalline silicon nanowires by chemical vapor deposition;
[0014] (2) immersing the crystalline silicon nanowires in a metal M precursor solution, and using plasma treatment or annealing treatment to prepare a single-atom M modification layer on the surface of the crystalline silicon nanowires to obtain M / SiNWs;
[0015] (3) The M / SiNWs obtained in step (2) are used to prepare a single atomic layer modified crystalline silicon nanowire gas sensor using a photolithography and magnetron sputtering system.
[0016] The present invention, by modifying single atoms M on the surface of crystalline silicon nanowires, utilizes the maximum atomic utilization and unique electronic and chemical properties of the anchored single atom sites to promote gas adsorption, improve selectivity and enhance electron transmission, thereby enhancing the detection sensitivity and selectivity of the sensor to the target gas, while having the advantages of chemical and physical stability and low cost.
[0017] Preferably, the concentration of the metal M precursor solution is 0.1 to 1 M, and the immersion time is 1 to 6 hours.
[0018] Preferably, the plasma treatment step is: subjecting the immersed crystalline silicon nanowires to reduction treatment in a plasma treatment device, followed by annealing in an inert atmosphere to form a single-atom M modification layer on the surface of the crystalline silicon nanowires to obtain M / SiNWs.
[0019] In the present invention, high-energy particles of plasma are used to promote the reduction of metal M precursors (such as metal salts, metal organic compounds, etc.) into metal M atoms, and then subsequent annealing treatment is performed to optimize the distribution and uniformity of single atoms on crystalline silicon nanowires.
[0020] Further preferably, the plasma is a reducing gas, such as hydrogen.
[0021] Further preferably, the set power of the plasma processing equipment is 30-100 W, and the processing time is 10-50 min.
[0022] In the present invention, when the power and processing time are controlled within the above ranges, the reduction degree of the metal M precursor solution to metal M can be better, the size of the metal M on the crystalline silicon nanowires can be adjusted, and M / SiNWs can be better prepared.
[0023] More preferably, the inert atmosphere is a nitrogen or argon atmosphere, the annealing treatment is performed at a temperature of 200 to 300° C. for a time of 1 to 3 hours.
[0024] When the annealing temperature and time are within the above ranges, the metal M particles are less likely to agglomerate.
[0025] Preferably, the annealing step is: placing the soaked crystalline silicon nanowires directly in a hydrogen atmosphere for annealing to form a single-atom M modification layer on the surface of the crystalline silicon nanowires to obtain M / SiNWs.
[0026] The metal M precursor solution is directly reduced to metal M by hydrogen treatment for in-situ reduction. The size of the metal M particles can be controlled by controlling the reduction temperature and hydrogen concentration.
[0027] Preferably, the annealing treatment is performed at 200-300°C for 1-3 hours.
[0028] Preferably, in step (1), the method for preparing crystalline silicon nanowires by chemical vapor deposition comprises the following steps:
[0029] S1. Depositing a SiO2 buffer layer on the substrate material by chemical vapor deposition;
[0030] S2. Preparation of growth steps on the surface of the SiO2 buffer layer by photolithography and ICP etching process, wherein the etching depth cannot exceed the thickness of the SiO2 buffer layer;
[0031] S3. At one end of the growth step, a strip-shaped catalytic metal layer is locally deposited perpendicular to the growth step direction by photolithography and thermal evaporation processes, the temperature is raised to above the melting point of the catalytic metal layer, and a reducing gas plasma is introduced for treatment, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball;
[0032] S4. lowering the temperature to below the melting point of the catalytic metal pellets to deposit an a-Si:H precursor layer;
[0033] S5. In a vacuum or inert gas protected environment, the temperature is raised to above the melting point of the catalytic metal balls, so that the catalytic metal balls are re-melted, absorbing the a-Si:H precursor layer at the front end and depositing crystalline silicon nanowires at the rear end. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown parallel to the growth steps are obtained.
[0034] Crystalline silicon nanowires of different sizes are prepared on the substrate based on the in-plane solidliquid-solid (IPSLS) growth mode. Their unique morphological characteristics allow for a variety of structural designs and are easy to bend and stretch to meet the needs of different application scenarios. They also have good chemical stability and can operate stably for a long time under harsh working conditions, providing possibilities for sensing and monitoring in extreme environments.
[0035] Preferably, in step S1, the temperature of the chemical vapor deposition SiO2 buffer layer is 150-360°C.
[0036] Preferably, in step S1, the thickness of the SiO2 buffer layer is 200-300 nm.
[0037] Preferably, in step S3, the strip-shaped catalytic metal layer is metal Au, In, Sn, Bi or Ga.
[0038] Preferably, in step S3, the length of the strip-shaped catalytic metal layer is 3-10 μm, and the width is 10-20 nm.
[0039] In the present invention, by controlling the size of the strip-shaped catalytic metal layer, catalytic metal balls of different sizes are obtained, thereby preparing crystalline silicon nanowires of different sizes.
[0040] Preferably, in step (3), the M / SiNWs are first passivated, and an HF solution is used to remove the oxide layer on the surface of the M / SiNWs.
[0041] More preferably, the concentration of the HF solution is 1-10%.
[0042] Compared with the prior art, the present invention has the following beneficial effects:
[0043] (1) The single-atom-layer modified crystalline silicon nanowire gas sensor of the present invention adopts a metal single-atom-layer modification strategy to in-situ grow noble metal single atoms M on the surface of the crystalline silicon nanowires to obtain M / SiNWs. When the gas to be detected comes into contact with the metal M on the surface, an oxidation-reduction reaction occurs, which in turn causes a change in the resistance of the crystalline silicon nanowires. By detecting the change in the resistance value, the type and concentration of the gas to be detected are determined. It exhibits good performance when detecting NH3 gas, with a faster response time and higher sensitivity.
[0044] (2) The present invention uses the IPSLS growth mode to prepare crystalline silicon nanowires on a substrate, and adopts a plasma treatment method or a wet chemical treatment method to grow a single atomic layer on the surface of the crystalline silicon nanowire to obtain a single atomic layer modified crystalline silicon nanowire gas sensor. The preparation method is easy to operate, and by optimizing the single atom modification process, the gas sensitive performance of the sensor is improved, and it is further used in environmental monitoring, food health, industrial safety and other fields. BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Figure 1 Schematic diagram of the structure of a single atomic layer modified crystalline silicon nanowire gas sensor, wherein 1 is the crystalline silicon nanowire, 2 is the source, 3 is the drain, and 4 is the gate electrode.
[0046] Figure 2 The scanning electron microscope and EDS spectra of Pt / SiNWs prepared in Example 1, wherein a is a scanning electron microscope image, b is an elemental energy spectrum, and c and d are EDS-mapping spectra of Si and Pt, respectively.
[0047] Figure 3This is a graph showing the current responsiveness of the Pt-modified crystalline silicon nanowire gas sensor prepared in Example 1 to ammonia gas of different concentrations at room temperature.
[0048] Figure 4 These are the scanning electron microscope and EDS spectra of Ru / SiNWs prepared in Example 8, a and b are the scanning electron microscope images of Ru / SiNWs, and c and d are the EDS-mapping spectra of Si and Ru, respectively. DETAILED DESCRIPTION
[0049] The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited to the following examples.
[0050] The raw materials used in the present invention are all commercially available.
[0051] Example 1
[0052] (1) A high-purity silicon wafer is selected as the substrate material, and the chemical vapor deposition (CVD) system is heated to 150°C to preferentially grow a 200 nm thick SiO2 buffer layer on the substrate;
[0053] (2) using photolithography and ICP etching techniques to prepare growth steps on the surface of the SiO2 buffer layer with an etching depth of 100 nm;
[0054] (3) using photolithography, thermal evaporation and other equipment, locally depositing a 3 μm wide and 10 nm thick strip-shaped catalytic metal indium layer on one side of the step perpendicular to the growth step direction, then heating to 300° C., introducing H2 plasma to treat the strip-shaped catalytic metal indium layer for 3 min, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball, and the oxide layer on the surface of the catalytic metal ball is removed;
[0055] (4) When the temperature is lowered to below 100° C., an a-Si:H precursor layer is deposited;
[0056] (5) Evacuate the CVD system to 10 -3 Pa, the temperature is raised to 200°C, so that the catalytic metal ball melts, and absorbs silicon atoms of the a-Si:H precursor layer at its front end. When the silicon atoms reach saturation, crystalline silicon nanowires will be deposited at the rear end. The CVD system is cooled to 100°C, and the residual a-Si:H precursor layer is removed by H2 plasma etching. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown in parallel with the growth steps are obtained;
[0057] (6) Using a plasma treatment method, 15 mL of chloroplatinic acid (H2PtCl6·6H2O, 0.1M) was used as a metal Pt source, and the crystalline silicon nanowires were immersed in the above metal Pt source solution, left to stand for 2 hours, and the excess metal solution was removed with deionized water, and then placed in a plasma treatment device, and reduced with hydrogen, with a power setting of 50 W and a treatment time of 20 minutes. Subsequently, annealing was performed in a nitrogen atmosphere at a temperature of 200°C for 2 hours to form a stable single-atom platinum modification layer, and Pt / SiNWs were obtained for the preparation of crystalline silicon nanowire gas sensors;
[0058] (7) The Pt / SiNWs were passivated at room temperature, the source / drain regions were masked by photolithography, the oxide layer on the surface of the Pt / SiNWs was removed by using a 5% HF solution, a Pt / Au electrode was deposited by a magnetron sputtering system, the photoresist was stripped off, and Al metal was prepared as a gate electrode by photolithography, magnetron sputtering, etc., and finally a Pt-modified crystalline silicon nanowire gas sensor was obtained. The schematic diagram of its structure is shown in FIG. Figure 1 shown.
[0059] Figure 1 Schematic diagram of the structure of a crystalline silicon nanowire gas sensor modified with a single atomic layer, wherein 1 is a crystalline silicon nanowire, 2 is a source, 3 is a drain, and 4 is a gate electrode. The Pt / SiNWs prepared in Example 1 is located between the source and the drain as a channel layer, the gate electrode is arranged below the source, the drain and the channel layer, and the Pt modified layer is located on the surface of the crystalline silicon nanowire.
[0060] Elemental Analysis: Figure 2 is the scanning electron microscope and EDS spectrum of Pt / SiNWs prepared in Example 1, a is the scanning electron microscope image of Pt / SiNWs, Figure 2 As shown in b, the element proportion of Si is 99.8wt%, the element proportion of Pt is 0.2wt%, c and d are the EDS-mapping spectra of Si and Pt, respectively, indicating that Pt / SiNWs were successfully prepared.
[0061] Responsiveness analysis of gas sensors:
[0062] The prepared Pt-modified crystalline silicon nanowire gas sensor is placed in a self-made gas-sensitive test platform system and connected to an external source meter to test the gas-sensitive performance. First, the sensor response changes of different NH3 gas concentrations (5ppm to 20ppm) are tested at room temperature. The sensitivity of the sensor can be calculated based on the stable current value exposed to NH3 and air. As the NH3 concentration increases, the current response of the sensor to NH3 is obvious.
[0063] Figure 3Figure 1 is a graph showing the current response of the Pt-modified crystalline silicon nanowire gas sensor prepared in Example 1 to different concentrations of ammonia gas at room temperature, wherein all tests were conducted at room temperature 25°C, using dry high-purity air as the background carrier gas, at V DS is -0.1V, V BG The prepared Pt-modified crystalline silicon nanowire gas sensor was exposed to NH3 atmospheres with different concentrations ranging from 5 to 20 ppm to test the current response changes and corresponding sensing characteristics, where |I DS | is the stable current value exposed to NH3. The results show that the current in the channel decreases with the introduction of NH3 gas. By controlling the gate voltage, as the ammonia gas concentration increases from 5ppm to 20ppm, the response current also decreases accordingly, indicating that the adsorption of ammonia molecules will hinder the carrier transmission channel and cause the current to decrease. Especially when the ammonia concentration is 20ppm, the change in the response current reaches about 1 order of magnitude. The above results show that Pt-modified crystalline silicon nanowire gas sensors can promote the adsorption of gas molecules and enhance electron transmission, thereby enhancing the sensor's detection sensitivity and selectivity for the target gas and significantly enhancing the gas sensing performance.
[0064] Example 2
[0065] (1) A high-purity silicon wafer is selected as the substrate material, and the chemical vapor deposition (CVD) system is heated to 200°C to preferentially grow a 300nm thick SiO2 buffer layer on the substrate;
[0066] (2) using photolithography and ICP etching techniques to prepare growth steps on the surface of the SiO2 buffer layer with an etching depth of 100 nm;
[0067] (3) using photolithography, thermal evaporation and other equipment, locally depositing a 5 μm wide and 15 nm thick strip-shaped catalytic metal indium layer on one side of the step perpendicular to the growth step direction, then heating to 300° C., introducing H2 plasma to treat the strip-shaped catalytic metal indium layer for 8 min, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball, and the oxide layer on the surface of the catalytic metal ball is removed;
[0068] (4) When the temperature is lowered to below 100° C., an a-Si:H precursor layer is deposited;
[0069] (5) Evacuate the CVD system to 10 -3Pa, the temperature is raised to 200°C, so that the catalytic metal ball melts, and absorbs silicon atoms of the a-Si:H precursor layer at its front end. When the silicon atoms reach saturation, crystalline silicon nanowires will be deposited at the rear end. The CVD system is cooled to 100°C, and the residual a-Si:H precursor layer is removed by H2 plasma etching. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown in parallel with the growth steps are obtained;
[0070] (6) Using a plasma treatment method, 10 mL of chloroplatinic acid (H2PtCl6·6H2O, 0.2 M) was used as a metal Pt source, and the crystalline silicon nanowires were immersed in the above metal Pt source solution, left to stand for 3 hours, and the excess metal solution was removed with deionized water, and then placed in a plasma treatment device, and reduced with hydrogen, with a power setting of 80 W and a treatment time of 10 minutes. Subsequently, annealing was performed in a nitrogen atmosphere at a temperature of 200 ° C for 2 hours to form a stable single-atom platinum modification layer, and Pt / SiNWs were obtained for the preparation of crystalline silicon nanowire gas sensors;
[0071] (7) The Pt / SiNWs were passivated at room temperature, the source / drain regions were masked by photolithography, the oxide layer on the surface of the Pt / SiNWs was removed by using a 5% HF solution, a Pt / Au electrode was deposited by a magnetron sputtering system, the photoresist was stripped off, and Al metal was prepared as a gate electrode by photolithography, magnetron sputtering, etc., to finally obtain a Pt-modified crystalline silicon nanowire gas sensor.
[0072] Example 3
[0073] (1) A high-purity silicon wafer is selected as the substrate material, and the chemical vapor deposition (CVD) system is heated to 250°C to preferentially grow a 300nm thick SiO2 buffer layer on the substrate;
[0074] (2) using photolithography and ICP etching techniques to prepare growth steps on the surface of the SiO2 buffer layer with an etching depth of 100 nm;
[0075] (3) using photolithography, thermal evaporation and other equipment, locally depositing a 5 μm wide and 15 nm thick strip-shaped catalytic metal indium layer on one side of the step perpendicular to the growth step direction, then heating to 360° C., introducing H2 plasma to treat the strip-shaped catalytic metal indium layer for 8 min, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball, and the oxide layer on the surface of the catalytic metal ball is removed;
[0076] (4) When the temperature is lowered to below 100° C., an a-Si:H precursor layer is deposited;
[0077] (5) Evacuate the CVD system to 10 -3Pa, the temperature is raised to 250°C, so that the catalytic metal ball melts, and absorbs silicon atoms in the a-Si:H precursor layer at its front end. When the silicon atoms reach saturation, crystalline silicon nanowires will be deposited at the rear end. The CVD system is cooled to 150°C, and the residual a-Si:H precursor layer is removed by H2 plasma etching. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown in parallel with the growth steps are obtained;
[0078] (6) Using a plasma treatment method, 10 mL of chloroplatinic acid (H2PtCl6·6H2O, 0.3 M) was used as a metal Pt source, and the crystalline silicon nanowires were immersed in the above metal Pt source solution, left to stand for 3 hours, and the excess metal solution was removed with deionized water, and then placed in a plasma treatment device, and reduced with hydrogen, with a power setting of 80 W and a treatment time of 10 minutes. Subsequently, annealing was performed in a nitrogen atmosphere at a temperature of 200 ° C for 2 hours to form a stable single-atom platinum modification layer, and Pt / SiNWs were obtained for the preparation of crystalline silicon nanowire gas sensors;
[0079] (7) The Pt / SiNWs were passivated at room temperature, the source / drain regions were masked by photolithography, the oxide layer on the surface of the Pt / SiNWs was removed by using a 5% HF solution, a Pt / Au electrode was deposited by a magnetron sputtering system, the photoresist was stripped off, and Al metal was prepared as a gate electrode by photolithography, magnetron sputtering, etc., to finally obtain a Pt-modified crystalline silicon nanowire gas sensor.
[0080] Example 4
[0081] (1) A high-purity silicon wafer is selected as the substrate material, and the chemical vapor deposition (CVD) system is heated to 360°C to preferentially grow a 300nm thick SiO2 buffer layer on the substrate;
[0082] (2) using photolithography and ICP etching techniques to prepare growth steps on the surface of the SiO2 buffer layer with an etching depth of 100 nm;
[0083] (3) using photolithography, thermal evaporation and other equipment, locally depositing a 10 μm wide and 20 nm thick strip-shaped catalytic metal indium layer on one side of the step perpendicular to the growth step direction, then heating to 360° C., introducing H2 plasma to treat the strip-shaped catalytic metal indium layer for 10 min, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball, and the oxide layer on the surface of the catalytic metal ball is removed;
[0084] (4) When the temperature is lowered to below 100° C., an a-Si:H precursor layer is deposited;
[0085] (5) Evacuate the CVD system to 10 -3Pa, the temperature is raised to 300°C, so that the catalytic metal ball melts, and absorbs silicon atoms in the a-Si:H precursor layer at its front end. When the silicon atoms reach saturation, crystalline silicon nanowires will be deposited at the rear end. The CVD system is cooled to 150°C, and the residual a-Si:H precursor layer is removed by H2 plasma etching. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown in parallel with the growth steps are obtained;
[0086] (6) Using a plasma treatment method, 10 mL of chloroplatinic acid (H2PtCl6·6H2O, 0.5 M) was used as a metal Pt source, and the crystalline silicon nanowires were immersed in the above metal Pt source solution, left to stand for 2 hours, and the excess metal solution was removed with deionized water, and then placed in a plasma treatment device, and reduced with hydrogen, with a power setting of 80 W and a treatment time of 10 minutes. Subsequently, annealing was performed in a nitrogen atmosphere at a temperature of 200 ° C for 2 hours to form a stable single-atom platinum modification layer, and Pt / SiNWs were obtained for the preparation of crystalline silicon nanowire gas sensors;
[0087] (7) The Pt / SiNWs were passivated at room temperature, the source / drain regions were masked by photolithography, the oxide layer on the surface of the Pt / SiNWs was removed by using a 5% HF solution, a Pt / Au electrode was deposited by a magnetron sputtering system, the photoresist was stripped off, and Al metal was prepared as a gate electrode by photolithography, magnetron sputtering, etc., to finally obtain a Pt-modified crystalline silicon nanowire gas sensor.
[0088] Example 5
[0089] (1) A high-purity silicon wafer is selected as the substrate material, and the chemical vapor deposition (CVD) system is heated to 250°C to preferentially grow a 300nm thick SiO2 buffer layer on the substrate;
[0090] (2) using photolithography and ICP etching techniques to prepare growth steps on the surface of the SiO2 buffer layer with an etching depth of 100 nm;
[0091] (3) using photolithography, thermal evaporation and other equipment, locally depositing a 5 μm wide and 15 nm thick strip-shaped catalytic metal indium layer on one side of the step perpendicular to the growth step direction, then heating to 360° C., introducing H2 plasma to treat the strip-shaped catalytic metal indium layer for 8 min, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball, and the oxide layer on the surface of the catalytic metal ball is removed;
[0092] (4) When the temperature is lowered to below 100° C., an a-Si:H precursor layer is deposited;
[0093] (5) Evacuate the CVD system to 10 -3Pa, the temperature is raised to 250°C, so that the catalytic metal ball melts, and absorbs silicon atoms in the a-Si:H precursor layer at its front end. When the silicon atoms reach saturation, crystalline silicon nanowires will be deposited at the rear end. The CVD system is cooled to 150°C, and the residual a-Si:H precursor layer is removed by H2 plasma etching. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown in parallel with the growth steps are obtained;
[0094] (6) Using a plasma treatment method, the crystalline silicon nanowires were immersed in 15 mL of chloroplatinic acid (H2PtCl6·6H2O, 0.1 M) solution, left at room temperature for 2 h, washed with deionized water to remove excess chloroplatinic acid, and then annealed in a hydrogen atmosphere at 300 °C for 1 h to form a stable single-atom platinum modification layer to obtain Pt / SiNWs, which were used for the preparation of crystalline silicon nanowire gas sensors;
[0095] (7) The Pt / SiNWs were passivated at room temperature, the source / drain regions were masked by photolithography, the oxide layer on the surface of the Pt / SiNWs was removed by using a 5% HF solution, a Pt / Au electrode was deposited by a magnetron sputtering system, the photoresist was stripped off, and Al metal was prepared as a gate electrode by photolithography, magnetron sputtering, etc., to finally obtain a Pt-modified crystalline silicon nanowire gas sensor.
[0096] Example 6
[0097] The preparation method is the same as that of Example 5, except that the metal precursor solution used is 15 mL of palladium chloride (PdCl2, 0.1 M) solution.
[0098] Example 7
[0099] The preparation method is the same as that of Example 5, except that the metal precursor solution used is 15 mL of chloroauric acid (HAuCl4, 0.1 M) solution.
[0100] Example 8
[0101] The preparation method is the same as that of Example 5, except that the metal precursor solution used is 15 mL of ruthenium trichloride (RuCl3, 0.1 M) solution.
[0102] Figure 4 The scanning electron microscope and EDS spectra of Ru / SiNWs prepared in Example 8, a and b are scanning electron microscope images of Ru / SiNWs, respectively, and c and d are EDS-mapping spectra of Si and Ru, respectively, indicating that Ru / SiNWs were successfully prepared.
[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A single atomic layer modified crystalline silicon nanowire gas sensor, comprising a gate electrode, a source electrode and a drain electrode, characterized in that: A channel layer is provided between the source and the drain, and the channel layer is M / SiNWs, where M is metal Pt, Pd, Au, Rh or Ru.
2. The single atomic layer modified crystalline silicon nanowire gas sensor according to claim 1, characterized in that: The M element accounts for 0.1-0.5 wt % in the channel layer.
3. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 1 or 2, characterized in that: The following steps are involved: (1) Preparing crystalline silicon nanowires by chemical vapor deposition; (2) immersing the crystalline silicon nanowires in a metal M precursor solution, and using plasma treatment or annealing treatment to prepare a single-atom M modification layer on the surface of the crystalline silicon nanowires to obtain M / SiNWs; (3) The M / SiNWs obtained in step (2) are used to prepare a single atomic layer modified crystalline silicon nanowire gas sensor using a photolithography and magnetron sputtering system.
4. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 3, characterized in that: The concentration of the metal M precursor solution is 0.1-1M, and the immersion time is 1-6 hours.
5. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 3, characterized in that: The plasma treatment step is: reducing the soaked crystalline silicon nanowires in a plasma treatment device, and then annealing them in an inert atmosphere to form a single-atom M modification layer on the surface of the crystalline silicon nanowires to obtain M / SiNWs.
6. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 5, characterized in that: The set power of the plasma treatment equipment is 30-100W, and the treatment time is 10-50min.
7. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 3, characterized in that: The annealing treatment step is: directly placing the soaked crystalline silicon nanowires in a hydrogen atmosphere for annealing, forming a single-atom M modification layer on the surface of the crystalline silicon nanowires, and obtaining M / SiNWs.
8. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 3, characterized in that: In step (1), the method for preparing crystalline silicon nanowires by chemical vapor deposition comprises the following steps: S1. Depositing a SiO2 buffer layer on the substrate material by chemical vapor deposition; S2. Preparation of growth steps on the surface of the SiO2 buffer layer by photolithography and ICP etching process, wherein the etching depth cannot exceed the thickness of the SiO2 buffer layer; S3. At one end of the growth step, a strip-shaped catalytic metal layer is locally deposited perpendicular to the growth step direction by photolithography and thermal evaporation processes, the temperature is raised to above the melting point of the catalytic metal layer, and a reducing gas plasma is introduced for treatment, so that the strip-shaped catalytic metal layer covering one end of the growth step is transformed into an independent catalytic metal ball; S4. lowering the temperature to below the melting point of the catalytic metal pellets to deposit an a-Si:H precursor layer; S5. In a vacuum or inert gas protected environment, the temperature is raised to above the melting point of the catalytic metal balls, so that the catalytic metal balls are re-melted, absorbing the a-Si:H precursor layer at the front end and precipitating crystalline silicon nanowires at the rear end. The crystalline silicon nanowires grow in parallel with the growth steps, and finally the crystalline silicon nanowires grown parallel to the growth steps are obtained.
9. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 8, characterized in that: In step S3, the strip-shaped catalytic metal layer is metal Au, In, Sn, Bi or Ga.
10. The method for preparing a single atomic layer modified crystalline silicon nanowire gas sensor according to claim 8, characterized in that: In step S3, the length of the strip-shaped catalytic metal layer is 3-10 μm, and the width is 10-20 nm.