CN112557456A - Silicon nanowire-based gas sensor element, preparation method thereof and application thereof in acetone detection - Google Patents

Silicon nanowire-based gas sensor element, preparation method thereof and application thereof in acetone detection Download PDF

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CN112557456A
CN112557456A CN201910913552.4A CN201910913552A CN112557456A CN 112557456 A CN112557456 A CN 112557456A CN 201910913552 A CN201910913552 A CN 201910913552A CN 112557456 A CN112557456 A CN 112557456A
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hydrofluoric acid
silicon
silicon wafer
soaking
concentration
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CN112557456B (en
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秦玉香
藏俊生
闻棕择
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Tianjin University
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    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
    • G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y15/00—Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
    • C23C14/165—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon by cathodic sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/08—Etching
    • C30B33/10—Etching in solutions or melts

Abstract

The invention discloses a silicon nanowire-based gas sensor element, a preparation method thereof and application thereof in acetone detection, wherein a double-modification structure of nano Ag and APTES is introduced on the surface of a silicon nanowire, namely, the modification of the silicon nanowire is realized by utilizing a metal Ag byproduct generated by reaction in the process of forming the silicon nanowire by chemical etching, APTES interacts with the silicon nanowire in an ethanol solution, and the effective adhesion of an amino functional group of the APTES is formed on the surface of the nanowire, so that the surface adsorption capacity of the silicon nanowire on organic acetone molecules is greatly enhanced, and the sensitivity response of the silicon nanowire sensor to acetone is remarkably improved. The element of the invention has accurate recognition effect on 1ppm and 2ppm acetone at room temperature and 80% relative humidity, and is expected to be applied to detection and diagnosis of early diabetes.

Description

Silicon nanowire-based gas sensor element, preparation method thereof and application thereof in acetone detection
Technical Field
The invention belongs to the technical field of gas detection, and particularly discloses an ordered porous silicon nanowire-based gas sensor element based on double modification of nano silver (Ag) and 3-Aminopropyltriethoxysilane (APTES), wherein the sensor element has high sensitivity and ultra-fast response characteristics to acetone gas in a room-temperature and high-humidity environment.
Background
With the continuous development of global economy, the living standard of people is continuously improved. However, an unexpected disease afflicts the world, especially in the developed world-diabetes. Diabetes is a chronic long-term disease, and brings endless pain to patients. Medical analysis has indicated that diabetes can be divided into three categories, with 5-10% of patients suffering from type I diabetes and 90-95% of patients suffering from type II diabetes and Gestational Diabetes Mellitus (GDM). In 2014, 4.42 billion adults worldwide have diabetes. However, according to the study report of the world health organization, the number of patients is still increasing, and the number is estimated to be approximately 5.52 hundred million by 2030. Currently, various invasive methods are mostly used for clinical detection of diabetes, but the invasive methods easily cause discomfort of patients and risk of infection of other diseases, and special instruments and laboratory personnel are usually required, so that the invasive methods for detecting diabetes are expensive and are not favorable for timely diagnosis and accurate diagnosis of patients at early stage. According to pathological investigations and studies, once the body develops a condition, the patient's exhaled breath carries specific gas components, such as acetone, which is characteristic of diabetes. However, the humidity of exhaled breath from the human body is very high, often with a relative humidity above 80%. Studies have reported that Acetone in the Exhaled Breath of normal persons is less than 1ppm, and that Acetone in the Exhaled Breath of diseased persons is generally higher than 1.8ppm (MEMS-Based Acetone Vapor Sensor for Non-Invasive Screening of Diabetes, IEEE SENSOR JOURNAL, VOL.18, NO.23, DECEMBER 1,2018; A Review of Biosensors for Non-Invasive Diabetes Monitoring and Screening in Human exposed Break, Received Oberber 24,2018, Received December 6,2018, date of publication December 17,2018, date of current version January 16,2019, Digital Object entry 10.1109/ACCESS.2018.2887066). Therefore, the development of a portable acetone sensor with normal temperature and high humidity resistance is very necessary for the early diagnosis of diabetes patients.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a nano Ag-APTES double-modified ordered porous silicon nanowire-based gas sensor element which can be used for quickly detecting acetone at room temperature and high humidity and is modified by nano Ag-APTES, a preparation method and application thereof. The technical scheme of the invention obviously improves the sensitivity, response speed, detection limit and other gas sensitivity performances of the silicon nanowire array-based gas sensor working in a room-temperature high-humidity environment, realizes the high relative humidity sensitivity and ultra-fast room-temperature response of the sensor to acetone gas, and is expected to be applied to the medical field to realize the early detection and diagnosis of diabetes.
The technical purpose of the invention is realized by the following technical scheme.
A silicon nanowire-based gas sensor element and a preparation method thereof are carried out according to the following steps:
step 1, etching a silicon wafer to obtain a silicon nanowire array;
placing the silicon wafer in a hydrofluoric acid aqueous solution for soaking treatment, then placing the silicon wafer in a mixed aqueous solution of silver nitrate and hydrofluoric acid for soaking treatment, and finally placing the silicon wafer in a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid for soaking treatment to obtain an etched silicon nanowire array; in a hydrofluoric acid aqueous solution, the concentration of hydrofluoric acid is 1-2M, and the soaking treatment time is 1-2 min; soaking in a mixed aqueous solution of silver nitrate and hydrofluoric acid for 1-2 min, wherein the concentration of the hydrofluoric acid is 4-6M, the concentration of the silver nitrate is 0.003-0.005M; in a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid, the concentration of the hydrofluoric acid is 4-6M, and the concentration of the hydrogen peroxide is 0.4-1M, preferably 0.5-0.8M;
in the step 1, the soaking temperature is 20-30 ℃.
In the step 1, the time for soaking treatment (i.e. etching) in the mixed aqueous solution of hydrogen peroxide and hydrofluoric acid is 30-90 min, and the length of the nanowire increases with the increase of the etching time.
In the step 1, the total volume of the mixed aqueous solution of silver nitrate and hydrofluoric acid is 100ml, the concentration of the hydrofluoric acid is 4-6M, the concentration of the silver nitrate is 0.003-0.005M, and the soaking time is 1-2 min.
In the step 1, the total volume of the mixed aqueous solution of hydrogen peroxide and hydrofluoric acid is 100ml, the concentration of the hydrofluoric acid is 4-6M, and the concentration of the hydrogen peroxide is 0.4-1M.
Step 2, carrying out nano silver modification treatment on the silicon nanowire array obtained by etching in the step 1;
according to the accumulation of experiments before the applicant and the subject group of the inventor, the complete removal of the nano silver particles needs to be soaked in concentrated nitric acid for 5-10 min; in order to obtain the purpose of taking out part of the nano silver and reserving part of the nano silver, the silicon wafer etched in the step 1 is soaked by concentrated nitric acid to remove part of nano silver particles, and the soaking time is 30-90 seconds;
in the step 2, the concentrated nitric acid used is 50-70% by mass.
In the step 2, the soaking temperature is 20-30 ℃ and the soaking time is 40-80 s.
Step 3, carrying out APTES modification treatment on the silicon nanowire array treated in the step 2
Placing the silicon wafer treated in the step 2 in 3-aminopropyltriethoxysilane (APTES, H)2NCH2CH2CH2Si(OC2H5)3) The anhydrous ethanol solution is treated to enable hydroxyl on the surface of the silicon wafer to react with 3-aminopropyltriethoxysilane to generate a silicon-oxygen bond, so that amino of the 3-aminopropyltriethoxysilane is grafted to the surface of the silicon wafer to obtain a silicon nanowire array doubly modified by nano-silver and 3-aminopropyltriethoxysilane;
in step 3, performing second-step modification on the silicon wafer by using 3-Aminopropyltriethoxysilane (APTES), obtaining a roughened surface structure, forming a rough silicon nanowire array based on APTES and Ag nanoparticle modification and having high active gas adsorption performance, then sequentially cleaning by using ethanol, acetone, ethanol and isopropanol, and finally drying in a vacuum drying oven.
In step 3, the volume percentage of 3-aminopropyltriethoxysilane in the anhydrous ethanol solution of 3-aminopropyltriethoxysilane is 5-25%, preferably 10-20%, the reaction temperature is 50-70 ℃, preferably 60-70 ℃, and the reaction time is 5-60 min, preferably 20-40 min.
And 3, fully drying the silicon wafer treated in the step 2, and then placing the silicon wafer into an infrared box for 4-10min for treatment.
Step 4, preparing sensor electrode
Arranging platinum-plated interdigital electrodes on the surface of the silicon wafer obtained in the step 3 to form ohmic contact between the electrodes and the nano wires on the surface of the silicon wafer
In step 4, a vacuum magnetron sputtering method is adopted, the preparation of the platinum-plated interdigital electrode is carried out by means of a hard template, the sputtering target material is metal platinum with the mass purity of 99.95 percent, the sputtering gas is argon with the mass purity of 99.999 percent, and the bulk vacuum degree is 4.0 multiplied by 10-4Pa, sputtering time 4-6 min.
In step 4, the thickness of the electrode is 160-240 nm.
In the technical scheme of the invention, the silicon wafer is a monocrystalline silicon wafer, the thickness is 300-500 mu m, the resistivity is 10-15 omega cm, and the crystal orientation is <100> +/-0.5 degrees.
In the technical scheme of the invention, before silicon nanowire etching is carried out, a silicon wafer is placed into a mixed solution of concentrated sulfuric acid and hydrogen peroxide for soaking for 30-50min, then taken out, then placed into a mixed solution of hydrofluoric acid and deionized water for soaking for 5-10min, then taken out, finally ultrasonically cleaned for 5-10min in an acetone solvent, absolute ethyl alcohol and deionized water in sequence, and placed in a vacuum drying oven for complete drying, wherein the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 3:1, the volume ratio of hydrofluoric acid to deionized water is 1: 1.
the invention discloses a porous silicon nanowire ordered array gas sensor based on double modification of nano Ag and APTES, which has high sensitivity and ultra-fast response characteristics to acetone gas in a room temperature and high humidity environment. The specific content of the invention is as follows: while preparing the porous silicon nanowire array by adopting a metal-assisted chemical etching method, forming nano Ag nano particle modification on the surface of the nanowire based on proper process treatment, and then introducing amino functional groups on the surface of the nanowire by utilizing an ethanol solution of APTES to realize secondary APTES modification and modification on the surface of the silicon nanowire. Before preparing the nano-wires, the clean silicon wafer is soaked by hydrofluoric acid to obtain the silicon wafer with hydrophobic surface, and the nano-wires with aggregated top ends can be formed in the preparation process. The noble metal nano-particle modification can reduce the adhesion of water molecules on the surface of the silicon nanowire, remarkably improve the humidity interference resistance of the silicon-based gas sensor, and simultaneously, the catalytic action of the modified nano-Ag particles can improve the adsorption, reaction and desorption of acetone gas on the surface of the silicon nanowire, improve the dynamic response rate of a device and improve the sensitivity of the sensor to the acetone gas to a certain extent; APTES is a short-chain organic matter carrying amino, and after nano silicon is modified, the surface adsorption capacity of the silicon nano wire on organic acetone molecules can be greatly enhanced, so that the sensitivity response of the silicon nano wire sensor to acetone is remarkably improved. The nano Ag-APTES double modified silicon nanowire can realize accurate discrimination of 1ppm and 2ppm acetone under the environment humidity of 80%, so that the aim of early diagnosis of diabetic conditions can be realized.
Compared with the prior art, the invention provides a nano Ag-APTES double-modified ordered porous silicon nanowire-based gas sensor element and a preparation method thereof, the element has the characteristic of quick response to trace acetone gas with the concentration as low as 200ppb at room temperature and 35% relative humidity, has accurate identification effect on 1ppm and 2ppm acetone at room temperature and 80% relative humidity, and is expected to be applied to detection and diagnosis of early diabetes; meanwhile, the sensitive element has the advantages of simple preparation process, high compatibility with silicon microelectronic process, high process repeatability, low cost and the like.
Drawings
Fig. 1 is an SEM photograph of smooth silicon nanowires used in the present invention.
FIG. 2 is an SEM photograph of a nano Ag-APTES double modified silicon nanowire in the invention.
Fig. 3 is a photograph of a contact angle test of smooth silicon nanowires in the present invention.
FIG. 4 is a photograph of a contact angle test of a nano Ag-APTES double modified silicon nanowire according to the present invention.
FIG. 5 is a graph of the results of the dynamic response of nano Ag-APTES double modified silicon nano-wires to acetone at 35% relative humidity.
FIG. 6 is a graph of the results of the dynamic response of nano Ag-APTES double modified silicon nano-wires to acetone at 80% relative humidity.
FIG. 7 is a Fourier infrared spectrum of a nano Ag-APTES double modified silicon nanowire array according to the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining specific examples, and all the raw materials used in the examples of the invention adopt commercially available chemical pure reagents, as shown in the following table.
Figure BDA0002215408270000051
Example 1
(1) Cleaning of monocrystalline <100> P-type silicon wafers
Soaking a silicon wafer with the size of 2 x 2cm in a mixed solution of concentrated sulfuric acid and hydrogen peroxide with the volume ratio of 3:1 for 40min to remove metal impurities on the surface, and then soaking in an HF solution and deionized water with the volume ratio of 1:1 for 10min to remove SiO generated on the surface2Finally, ultrasonic cleaning is carried out in acetone solvent, absolute ethyl alcohol and deionized water respectively for 10min in sequence, oil stains and organic impurities on the surface are removed, and the product is placed in a vacuum drying oven to be dried thoroughly.
(2) Preparing chemical etching solution
Placing 1M hydrofluoric acid in a polytetrafluoroethylene beaker, and standing for later use.
Taking hydrofluoric acid (evenly dispersed in water) in a polytetrafluoroethylene beaker, weighing AgNO3Dissolving in the hydrofluoric acid, standing for 5min to obtain AgNO3Fully dissolving, and then adding deionized water to 100ml, wherein the concentration of hydrofluoric acid is 5M, and the concentration of silver nitrate is 0.0035M.
Hydrofluoric acid (evenly dispersed in water) is taken out to be placed in a polytetrafluoroethylene beaker, then hydrogen peroxide and the hydrofluoric acid are taken out to be mixed and placed still, and then deionized water is added to reach 100ml, the concentration of the hydrofluoric acid is 5M, and the concentration of the hydrogen peroxide is 0.8M.
(3) Catalytic etching preparation of silicon nanowire array
Putting the silicon wafer completely cleaned in the step (1) into the 1M hydrofluoric acid solution in the step (2) for 1min, then taking out and washing with deionized water, and then putting in the solution to fully dissolve AgNO3Taking out the silicon wafer from the hydrofluoric acid solution for 1min, and finally putting the silicon wafer into a mixed solution of hydrogen peroxide and hydrofluoric acid, wherein the etching time is controlled to be 60min, and the etching temperature is 30 ℃.
(4) Nano Ag modifying treatment
And (4) putting the silicon nanowire sample coated with the Ag on the surface obtained in the step (3) into a concentrated nitric acid solution with the mass fraction of 60% to remove the Ag coating on the outer surface of the nanowire array, and controlling the standing time to be 60 s.
(5) APTES modification treatment
And (3) fully drying the Ag nano particle modified silicon nanowire obtained in the step (4), putting the dried Ag nano particle modified silicon nanowire into an infrared box for 5min, then putting the dried Ag nano particle modified silicon nanowire into an APTES ethanol solution with the volume fraction of 20%, heating the solution in a water bath at 60 ℃ for 5min, and carrying out second-step modification to obtain a surface roughened structure. Sequentially cleaning with ethanol, acetone, ethanol and isopropanol, and drying in a vacuum drying oven. The step completes double modification of the silicon nanowire, and forms a rough silicon nanowire array based on APTES and Ag nanoparticle modification and having high active gas adsorption performance.
(6) Preparation of electrodes
And (4) plating a platinum interdigital electrode on the surface of the double-modified silicon nanowire ordered array obtained in the step (5) by using a vacuum magnetron sputtering method and a hard template so as to form ohmic contact between the electrode and the silicon wafer surface nanowire. The metal platinum is used as a sputtering target material, argon is used as working gas, the sputtering time is 6min, and the thickness of the formed electrode is 200 nm. Thus, the double-modified silicon nanowire array device is obtained.
Example 2
The present embodiment is different from embodiment 1 in that: in the step (5), the dried Ag nanoparticle modified nanowire is placed in an ethanol solution of APTES with the volume fraction of 20% and heated for 15min in a water bath at 60 ℃.
Example 3
The present embodiment is different from embodiment 1 in that: in the step (5), the dried Ag nano particle modified nano wire is placed in an ethanol solution of APTES with the volume fraction of 10% and heated for 30min in water bath at 70 ℃.
Example 4
The present embodiment is different from embodiment 1 in that: in the step (5), the dried Ag nano particle modified nano wire is placed in an ethanol solution of APTES with the volume fraction of 25% and heated for 20min in water bath at 60 ℃.
Example 5
The present embodiment is different from embodiment 1 in that: in the step (5), the dried Ag nanoparticle modified nanowire is placed in an ethanol solution of APTES with the volume fraction of 25% and heated for 40min in a water bath at 70 ℃.
As shown in the attached figures 1 and 2, SEM pictures of the silicon nanowire modified by double modification of smooth silicon nanowire and nano Ag-APTES show that Ag nanoparticles are scattered on the surface of the nanowire, and the surface of the nanowire also presents rough and porous shapes. As shown in figure 7, the Fourier infrared spectrogram of the nano Ag-APTES double modified silicon nanowire array in the invention has a value of about 1000 as the peak value of Si-O, which indicates that the substrate material is silicon-based; the peak data near 1400 shows a C-N bond, indicating that the sample contains C, N organics; and the peaks near 1600 and 3000 represent N-H bonds, further indicate that the organic substance APTES exists in the sample, which indicates that the APTES and the silicon nanowire form a good composite structure, and the amino functional group of the APTES exists on the surface of the nanowire.
A contact angle test is carried out by using a Definuo/DEFNUO digital contact angle measuring instrument (model: ZR-SDJ-S1), and as shown in attached figures 3 and 4, the smooth silicon nanowire shows hydrophilicity (62-67 degrees) and shows hydrophobicity (140-155 degrees) after being modified by Ag-APTES double modification.
The technical scheme of the invention realizes the double modification of the nano Ag-APTES of the silicon nano wires by a relatively simple process flow, and obviously improves the active gas adsorption capacity and the humidity interference resistance of the silicon nano wire ordered array, thereby obviously improving the sensitivity, the response speed, the detection limit and other room temperature gas sensitivity of the silicon nano wire array-based gas sensor, and realizing the high humidity sensitivity and the ultra-fast room temperature response of the sensor to ppb level trace acetone gas. As shown in fig. 5, at room temperature and a relative humidity of 35%, the response sensitivities of the double modified silicon nanowire sensing element prepared by the invention to acetone of 200ppb, 500ppb, 1ppm, 2ppm, 3ppm and 4ppm are respectively: 1.06, 1.26, 1.56, 1.70, 1.82 and 1.865, can achieve instantaneous response, and the response time is 1-3 s; as shown in FIG. 6, the response sensitivity of the device of the present invention to 1ppm, 2ppm, 4ppm, and 5ppm acetone at room temperature and 80% relative humidity is: 1.06, 1.14, 1.28 and 1.37, and the response time is 3-20 s.
Compared with the prior art, the invention has the innovativeness that: firstly, a new technology of modifying a silicon nanowire by double modification of nano Ag and APTES is introduced, and the double modification effect enables the silicon nanowire ordered array gas sensor to have high relative humidity sensitivity and ultra-fast room temperature response characteristic to acetone; secondly, the chemical etching preparation of the silicon nanowire array and the modification of the nano Ag on the surface of the nanowire are realized in one step, namely, the modification of the silicon nanowire is realized by utilizing a metal Ag byproduct generated by reaction in the process of forming the silicon nanowire by chemical etching. The modification process of the nano Ag particles on the surface of the silicon nanowire has the obvious advantages of simple process and economy, the Ag nano particle modification can reduce the adhesion of water molecules on the surface of the silicon nanowire, the humidity interference resistance of the silicon-based gas sensor is obviously improved, and meanwhile, the modified nano Ag particles have a catalytic action, can improve the adsorption, reaction and desorption of acetone gas on the surface of the silicon nanowire, improve the dynamic response rate of a device and improve the sensitivity of the sensor to the acetone gas to a certain extent; thirdly, APTES interacts with the silicon nanowire in the ethanol solution to form effective adhesion of an amino functional group of the APTES on the surface of the nanowire, so that the surface adsorption capacity of the silicon nanowire on organic acetone molecules is greatly enhanced, and the sensitivity response of the silicon nanowire sensor to acetone is remarkably improved. The silicon nanowire-based gas sensor element or the silicon nanowire array obtained by the method is applied to the detection of acetone (gas), is suitable for the detection of acetone gas under the conditions of room temperature and relative humidity of 80 percent, can realize the identification of acetone with the concentration of 1ppm and 2ppm, and judges whether the human body has diabetes symptoms or not by detecting the content of the acetone in the exhaled air of the human body.
The preparation of the gas sensor element of the invention can be achieved by adjusting the process parameters according to the invention, and tests show substantially the same performance as the invention. The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims (10)

1. A silicon nanowire-based gas sensor element, characterized by being performed according to the following steps:
step 1, etching a silicon wafer to obtain a silicon nanowire array;
placing the silicon wafer in a hydrofluoric acid aqueous solution for soaking treatment, then placing the silicon wafer in a mixed aqueous solution of silver nitrate and hydrofluoric acid for soaking treatment, and finally placing the silicon wafer in a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid for soaking treatment to obtain an etched silicon nanowire array; in a hydrofluoric acid aqueous solution, the concentration of hydrofluoric acid is 1-2M, and the soaking treatment time is 1-2 min; soaking in a mixed aqueous solution of silver nitrate and hydrofluoric acid for 1-2 min, wherein the concentration of the hydrofluoric acid is 4-6M, the concentration of the silver nitrate is 0.003-0.005M; in a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid, the concentration of the hydrofluoric acid is 4-6M, and the concentration of the hydrogen peroxide is 0.4-1M, preferably 0.5-0.8M;
step 2, carrying out nano silver modification treatment on the silicon nanowire array obtained by etching in the step 1; soaking the silicon wafer etched in the step 1 by using concentrated nitric acid to remove part of nano silver particles, wherein the soaking time is 30-90 seconds;
step 3, carrying out APTES modification treatment on the silicon nanowire array treated in the step 2
Placing the silicon wafer treated in the step 2 in an absolute ethanol solution of 3-aminopropyltriethoxysilane for treatment, so that hydroxyl on the surface of the silicon wafer and the 3-aminopropyltriethoxysilane react to generate a silicon-oxygen bond, and grafting amino of the 3-aminopropyltriethoxysilane to the surface of the silicon wafer to obtain a silicon nanowire array doubly modified by nano silver and the 3-aminopropyltriethoxysilane;
and 4, preparing a sensor electrode, and arranging a platinum-plated interdigital electrode on the surface of the silicon wafer obtained in the step 3 to form ohmic contact between the electrode and the surface nanowire of the silicon wafer.
2. The gas sensor element according to claim 1, wherein the silicon wafer is a single crystal silicon wafer having a thickness of 300 to 500 μm, a resistivity of 10 to 15 Ω · cm, and a crystal orientation of <100> ± 0.5 °.
3. The silicon nanowire-based gas sensor element according to claim 1, wherein in step 1, the immersion treatment temperature is 20 to 30 degrees celsius at room temperature; the time for soaking treatment (namely etching) in the mixed aqueous solution of hydrogen peroxide and hydrofluoric acid is 30-90 min, and the length of the nanowire is increased along with the increase of the etching time; the total volume of the mixed aqueous solution of silver nitrate and hydrofluoric acid is 100ml, the concentration of the hydrofluoric acid is 4-6M, the concentration of the silver nitrate is 0.003-0.005M, and the soaking time is 1-2 min; the total volume of the mixed aqueous solution of hydrogen peroxide and hydrofluoric acid is 100ml, the concentration of the hydrofluoric acid is 4-6M, and the concentration of the hydrogen peroxide is 0.4-1M.
4. The silicon nanowire-based gas sensor element according to claim 1, wherein in step 2, the concentrated nitric acid used is 50 to 70 mass% concentrated nitric acid, the soaking temperature is 20 to 30 degrees celsius at room temperature, and the soaking time is 40 to 80 s; in step 3, the volume percentage of 3-aminopropyltriethoxysilane in the anhydrous ethanol solution of 3-aminopropyltriethoxysilane is 5-25%, preferably 10-20%, the reaction temperature is 50-70 ℃, preferably 60-70 ℃, and the reaction time is 5-60 min, preferably 20-40 min.
5. The silicon nanowire-based gas sensor element as claimed in claim 1, wherein in step 4, the preparation of the platinum-plated interdigital electrode is performed by a vacuum magnetron sputtering method via a hard template, the sputtering target material is platinum metal with a mass purity of 99.95%, the sputtering gas is argon with a mass purity of 99.999%, and the bulk vacuum degree is 4.0 x 10-4Pa, sputtering time is 4-6 min; the thickness of the electrode is 160-240 nm.
6. A method for manufacturing a silicon nanowire-based gas sensor element is characterized by comprising the following steps:
step 1, etching a silicon wafer to obtain a silicon nanowire array;
placing the silicon wafer in a hydrofluoric acid aqueous solution for soaking treatment, then placing the silicon wafer in a mixed aqueous solution of silver nitrate and hydrofluoric acid for soaking treatment, and finally placing the silicon wafer in a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid for soaking treatment to obtain an etched silicon nanowire array; in a hydrofluoric acid aqueous solution, the concentration of hydrofluoric acid is 1-2M, and the soaking treatment time is 1-2 min; soaking in a mixed aqueous solution of silver nitrate and hydrofluoric acid for 1-2 min, wherein the concentration of the hydrofluoric acid is 4-6M, the concentration of the silver nitrate is 0.003-0.005M; in a mixed aqueous solution of hydrogen peroxide and hydrofluoric acid, the concentration of the hydrofluoric acid is 4-6M, and the concentration of the hydrogen peroxide is 0.4-1M, preferably 0.5-0.8M;
step 2, carrying out nano silver modification treatment on the silicon nanowire array obtained by etching in the step 1; soaking the silicon wafer etched in the step 1 by using concentrated nitric acid to remove part of nano silver particles, wherein the soaking time is 30-90 seconds;
step 3, carrying out APTES modification treatment on the silicon nanowire array treated in the step 2
Placing the silicon wafer treated in the step 2 in an absolute ethanol solution of 3-aminopropyltriethoxysilane for treatment, so that hydroxyl on the surface of the silicon wafer and the 3-aminopropyltriethoxysilane react to generate a silicon-oxygen bond, and grafting amino of the 3-aminopropyltriethoxysilane to the surface of the silicon wafer to obtain a silicon nanowire array doubly modified by nano silver and the 3-aminopropyltriethoxysilane;
and 4, preparing a sensor electrode, and arranging a platinum-plated interdigital electrode on the surface of the silicon wafer obtained in the step 3 to form ohmic contact between the electrode and the surface nanowire of the silicon wafer.
7. The method for manufacturing a silicon nanowire-based gas sensor element according to claim 6, wherein in the step 1, the immersion treatment temperature is 20 to 30 degrees celsius at room temperature; the time for soaking treatment (namely etching) in the mixed aqueous solution of hydrogen peroxide and hydrofluoric acid is 30-90 min, and the length of the nanowire is increased along with the increase of the etching time; the total volume of the mixed aqueous solution of silver nitrate and hydrofluoric acid is 100ml, the concentration of the hydrofluoric acid is 4-6M, the concentration of the silver nitrate is 0.003-0.005M, and the soaking time is 1-2 min; the total volume of the mixed aqueous solution of hydrogen peroxide and hydrofluoric acid is 100ml, the concentration of the hydrofluoric acid is 4-6M, and the concentration of the hydrogen peroxide is 0.4-1M.
8. The method for manufacturing a silicon nanowire-based gas sensor element according to claim 6, wherein in the step 2, the concentrated nitric acid is 50 to 70 mass%, the soaking temperature is 20 to 30 degrees celsius at room temperature, and the soaking time is 40 to 80 seconds; in step 3, the volume percentage of 3-aminopropyltriethoxysilane in the anhydrous ethanol solution of 3-aminopropyltriethoxysilane is 5-25%, preferably 10-20%, the reaction temperature is 50-70 ℃, preferably 60-70 ℃, and the reaction time is 5-60 min, preferably 20-40 min.
9. The method according to claim 6, wherein in step 4, the Pt-plated interdigital electrode is formed by a hard template using a vacuum magnetron sputtering method, the sputtering target is Pt with a purity of 99.95%, the sputtering gas is Ar with a purity of 99.999%, and the bulk is trueThe void degree is 4.0 multiplied by 10-4Pa, sputtering time is 4-6 min; the thickness of the electrode is 160-240 nm.
10. Use of a silicon nanowire-based gas sensor element according to one of claims 1 to 5 for the detection of acetone gas, characterized in that 1ppm and 2ppm of acetone are recognized precisely at room temperature and 80% relative humidity.
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