Vanadium dioxide nanowire sensor capable of being greatly tuned as well as preparation method and application of vanadium dioxide nanowire sensor

Abstract

The invention discloses a vanadium dioxide nanowire sensor capable of being greatly tuned and a preparation method and application thereof. The vanadium dioxide nanowire sensor comprises a substrate, electrodes, vanadium dioxide nanowires, a fixed end, a power supply end, a voltmeter and a sensitive layer, wherein the electrodes, the vanadium dioxide nanowires, the fixed end and the power supply end are located on the substrate, and the sensitive layer is located on a resonator. The two fixed ends are positioned on the two electrodes of the source electrode and the drain electrode and are connected with the two ends of the vanadium dioxide nanowire; the two electrodes of the source electrode and the drain electrode are positioned on the substrate, are connected with the vanadium dioxide nanowires and the two fixed ends, and support and fix one vanadium dioxide nanowire; the power supply end is connected with the electrode of the source electrode, and the vanadium dioxide nanowire is subjected to phase change by changing the circuit voltage, so that the resonant frequency of the nanowire is changed. An electric loop is formed on the vanadium dioxide nanowire, potential difference is formed at the two ends of the nanowire, and the vanadium dioxide nanowire is gradually subjected to phase change through Joule heating, so that the resonant frequency of the nanowire is changed, the sensitivity of the nanowire is improved, and meanwhile gas molecules can be detected through the laid sensitive layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanowire resonant sensors, and in particular relates to a vanadium dioxide nanowire sensor that can be tuned to a large extent, and a preparation method and application thereof. Background Art

[0002] Resonant gas sensors have broad application prospects in the fields of biochemical reaction monitoring and environmental monitoring due to their high sensitivity and high selectivity. Among them, ultra-sensitive detection technology for biochemical reactions is crucial for mass spectrometry, atomic physics, and a wide range of clinical and environmental applications, including disease diagnosis, drug discovery, pathogen detection in food, environmental toxin detection, and bioprocess control. Due to the lack of accuracy in detecting very low concentrations of biochemical molecules, the realization of single-molecule detection technology for biochemical reactions remains a key challenge in many application areas.

[0003] Nanowire resonators have many advantages. They are small in size, high in frequency, and high in quality factor. They are very suitable for use in high-frequency precision measurement and sensors. Among them, resonant mass sensors can be used to reveal the interaction forces between tiny masses and biochemical reaction kinetics information, which is one of the most important uses of micro-nano sensors based on mechanics. One-dimensional nanowire resonant mass sensors have a small equivalent mass and a high resonant frequency, so their sensitivity is generally high. They are mainly used for the measurement of small masses, and can be used to reveal the interaction forces between small masses and biochemical reaction kinetics information, and can be used as a potential atomic or molecular scale kinetic detection.

[0004] As the accuracy requirements for biochemical reaction detection increase, higher requirements are placed on the sensitivity of resonant sensors. Resonators have also evolved from the micrometer scale to the nanometer scale to continuously improve the resonant frequency to meet the sensitivity measurement requirements of the sensor. However, the current resonator sensitivity has not yet reached the accuracy of biochemical reactions. At the same time, existing resonator technologies, such as resonators based on piezoelectric materials, usually require a higher driving voltage to produce sufficient mechanical vibrations, which limits their application in low-power devices. In addition, the resonant frequencies of many resonators are currently fixed and difficult to adjust according to actual needs, limiting their scope of application. Therefore, there is an urgent need for a nanowire resonator that uses a new driving method and can be tuned to a large extent to break the limitations of existing nanowire resonators.

[0005] We learned that vanadium dioxide nanowires are a typical phase change material, which undergoes a phase change from semiconductor to metal when the temperature rises to 68°C. During the phase change, the resistance of vanadium dioxide nanowires will decrease by several orders of magnitude, accompanied by a significant increase in the axial force of the nanowires, and then the resonant frequency will increase by 33%, thereby increasing the sensitivity of the sensor by 33%. At the same time, vanadium dioxide nanowires can use electrostatic excitation and resistance detection methods, which have low power consumption and simpler detection circuits. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a vanadium dioxide nanowire sensor that can be tuned to a large extent. The structure thereof comprises:

[0009] Base silicon wafer;

[0010] The vanadium dioxide nanowire is located on the base silicon wafer and contacts the metal electrodes at both ends;

[0011] The metal electrodes include a source electrode, a drain electrode and a gate electrode. The source electrode and the drain electrode are used to provide support and fixation for the vanadium dioxide nanowires and are also responsible for connecting with an external circuit to realize the input of an excitation signal and the output of a response signal.

[0012] A gate is located below the vanadium dioxide nanowire and is not connected to the vanadium dioxide nanowire, and is used to apply a bias electrostatic force to the vanadium dioxide nanowire;

[0013] The fixed end includes a first fixed end and a second fixed end, and the first fixed end and the second fixed end fix the vanadium dioxide nanowire on the electrode;

[0014] The power supply end includes an AC power supply and a DC power supply, the AC power supply is connected to the source electrode, and the DC power supply is connected to the gate electrode;

[0015] The voltmeter is connected to the first fixed end and the second fixed end through a wire to form a parallel connection with the nanowire, and is used to detect the change of the voltage of the vanadium dioxide nanowire;

[0016] The sensitive layer is arranged at the midpoint of the vanadium dioxide nanowire, and different sensitive materials can be replaced to detect different gas molecules.

[0017] Another object of the present invention is to provide a method for preparing a vanadium dioxide nanowire sensor that can be tuned to a large extent.

[0018] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0019] The surface-polished and oxidized silicon wafer is activated and then sequentially cleaned, dehydrated and subjected to surface film-forming treatment to obtain a pre-treated base silicon wafer;

[0020] A layer of polymethyl methacrylate (PMMA) photoresist is uniformly coated on the surface of the base silicon wafer, and a first photoresist layer is formed by pre-baking;

[0021] The first photoresist layer is exposed on a photolithography machine using a first mask, and then the base silicon wafer is subjected to development, dry etching and other processes to form a groove with a depth of 1-5 μm and a width of 4-7 μm on the base silicon wafer as the gate of the sensor;

[0022] Coating a layer of PMMA on the etched base silicon wafer to form a second photoresist layer;

[0023] Using a second mask to expose the second photoresist layer on a photolithography machine, and then continuing to develop the base silicon wafer to reserve a position for the electrode;

[0024] Sputtering metal onto the electrode region of the photolithographic substrate silicon wafer by magnetron sputtering, and removing excess photoresist and excess metal on the photoresist to form a source, a drain and a gate;

[0025] The synthesis of vanadium dioxide nanowires is carried out by placing 0.2 g of commercial vanadium dioxide powder with a purity of 99% in a quartz boat and then placing it in the center of a horizontal tube furnace; an unpolished (rough) quartz substrate is placed 5 mm above the bottom of the quartz boat to obtain a higher vapor density and deposition temperature; the furnace tube is first evacuated to a basic gas pressure of 1.33 Pa and then purged with argon (Ar); then, the temperature is increased at a rate of 15°C / min and maintained at a target temperature of 700°C-800°C for 5-6 hours; during the whole process, the gas pressure is maintained at 1333 Pa; after the reaction is completed, the unpolished (rough) quartz substrate on which the vanadium dioxide nanowires are grown is taken out after the tube furnace is cooled to room temperature;

[0026] A tungsten probe is used to transfer the vanadium dioxide nanowire grown on a quartz substrate, ensuring that both ends of the vanadium dioxide nanowire are placed on the source and drain electrodes and are perpendicular to the gate.

[0027] The vanadium dioxide nanowires with a diameter of 180-240 nm, a length of 5-8 μm, and an aspect ratio of 28-33 are used as resonant beams;

[0028] Platinum (Pt) is deposited on both ends of the vanadium dioxide nanowire using a focused ion beam (FIB) technique to form two rectangular platinum metal blocks to smoothly fix the vanadium dioxide nanowire to form a first fixed end and a second fixed end;

[0029] A layer of PMMA photoresist with a thickness of about 200 nm is firstly spin-coated on the surface of the fixed vanadium dioxide nanowire, and then the midpoint of the vanadium dioxide nanowire is exposed at the midpoint under a scanning electron microscope, and then a sensitive layer is vapor-deposited, and a lift-off process is used to obtain a vanadium dioxide nanowire sensor with a midpoint-coated sensitive layer;

[0030] Then, an AC power source is connected to the source electrode with a wire, a DC power source is connected to the gate electrode, and a voltmeter is connected to the first fixed end and the second fixed end to obtain a vanadium dioxide nanowire sensor that can be tuned to a large extent.

[0031] As a preferred solution of the method for preparing the vanadium dioxide nanowire sensor with large tunability described in the present invention, the activation temperature of the silicon wafer activation is 500-700K, and the activation time is 20-40min.

[0032] As a preferred solution of the method for preparing the greatly tunable vanadium dioxide nanowire sensor of the present invention, the pre-baking treatment is performed at a temperature of 373-383 K and for a time of 50-60 s.

[0033] As a preferred solution of the method for preparing the vanadium dioxide nanowire sensor that can be tuned to a large extent according to the present invention, the method for preparing the vanadium dioxide nanowire adopts a chemical vapor deposition method.

[0034] As a preferred solution of the preparation method of the greatly tunable vanadium dioxide nanowire sensor described in the present invention, the vanadium dioxide nanowire is transferred by first peeling the vanadium dioxide nanowire from the quartz substrate with a tungsten probe, then applying a voltage of 5V to adsorb the vanadium dioxide nanowire for transfer, placing the vanadium dioxide nanowire on the source and drain perpendicular to the gate, then turning off the additional voltage to release the vanadium dioxide nanowire, and finally completing the transfer.

[0035] As a preferred embodiment of the method for preparing the vanadium dioxide nanowire sensor which can be tuned greatly according to the present invention, the metal material of the sputtered metal includes gold, silver or copper, and the speed during the sputtering process is The vacuum degree is less than 1×10 -2 Pa.

[0036] As a preferred solution of the method for preparing the greatly tunable vanadium dioxide nanowire sensor of the present invention, the thickness of the source electrode, the drain electrode and the gate electrode is 400-600 nm.

[0037] As a preferred solution of the method for preparing the tunable vanadium dioxide nanowire sensor of the present invention, the photoresist is AZ5214 photoresist, and the exposure dose is 3.6m-4.0mW / cm 2 , the developing time is 60-100 seconds.

[0038] As a preferred solution of the method for preparing the greatly tunable vanadium dioxide nanowire sensor of the present invention, the first fixed end and the second fixed end are formed by depositing metal Pt using FIB technology, and are rectangular blocks with a length of 2 microns, a width of 200 nanometers, and a thickness of 200 nanometers.

[0039] As a preferred solution of the method for preparing the highly tunable vanadium dioxide nanowire sensor of the present invention, the sensitive layer 111 can be replaced with different materials, such as copper phthalocyanine, platinum, and tin oxide, for detecting different gas molecules.

[0040] As a preferred solution of the method for preparing the greatly tunable vanadium dioxide nanowire sensor of the present invention, the resonant frequency f of the vanadium dioxide nanowire 102 is 27.1 MHz at the temperature T=295K, and is 36 MHz at the temperature T=360K.

[0041] As a preferred solution of the method for preparing the greatly tunable vanadium dioxide nanowire sensor of the present invention, the sensitive layer is coated at the midpoint of the vanadium dioxide nanowire.

[0042] Another object of the present invention is to provide a vanadium dioxide nanowire sensor that can be tuned to a large extent for use in constructing an ultra-high sensitivity sensor.

[0043] The invention discloses a vanadium dioxide nanowire sensor which can be tuned greatly. The sensor comprises a substrate and electrodes on the substrate, a vanadium dioxide nanowire, a fixed end and a power end, a voltmeter and a sensitive layer on a resonator; two fixed ends are located on two electrodes of a source and a drain, connected to two ends of the vanadium dioxide nanowire and used to fix a vanadium dioxide nanowire; two electrodes of the source and the drain are located on the substrate, connected to the vanadium dioxide nanowire and the two fixed ends, and support a vanadium dioxide nanowire, forming a current path with the vanadium dioxide nanowire, and another electrode is located on the gate and connected to a power end for applying an electrostatic bias force to make the vanadium dioxide nanowire vibrate; another power end is connected to the electrode of the source, provides a working voltage for the sensor, and can make the vanadium dioxide nanowire undergo a phase change by changing the circuit voltage, thereby changing the resonant frequency of the nanowire and improving its sensitivity; a voltmeter is connected in parallel to detect the change of the voltage of the nanowire; and a sensitive layer is laid on the vanadium dioxide nanowire to detect gas molecules. The vanadium dioxide nanowire sensor disclosed in the present invention can be tuned greatly. By forming an electric circuit on the vanadium dioxide nanowire, a potential difference is formed at both ends of the nanowire. By Joule heating, the vanadium dioxide nanowire gradually undergoes a phase change, thereby changing its resonant frequency and improving its sensitivity. At the same time, gas molecules can be detected through the laid sensitive layer. The present invention has simple driving, low driving voltage, wide tuning range, and high sensitivity. It has shown a wide range of application prospects in many fields such as quality detection, mechanical detection, displacement detection, and gas molecule detection.

[0044] Beneficial effects of the present invention:

[0045] (1) High sensitivity: The nanowire sensor of the present invention can cause the vanadium dioxide nanowire to undergo a phase change by changing the voltage. During the phase change, the resistance of the vanadium dioxide nanowire will decrease by several orders of magnitude, accompanied by a significant increase in the axial force of the nanowire, thereby changing its resonant frequency and increasing its sensitivity by 33%.

[0046] (2) Wide detection range: The nanowire sensor of the present invention can change its resonant frequency and sensitivity to different gases by changing the voltage so that the vanadium dioxide nanowires work in the insulating phase and the metallic phase respectively, thereby having a wider detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0048] Figure 1This is a flow chart of a highly tunable vanadium dioxide nanowire sensor prepared in Example 1 of the present invention.

[0049] Figure 2 This is a schematic structural plan view of the greatly tunable vanadium dioxide nanowire sensor prepared in Example 1 of the present invention.

[0050] Figure 3 This is a schematic three-dimensional structural diagram of the highly tunable vanadium dioxide nanowire sensor prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0051] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0052] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0053] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0054] Unless otherwise specified, the raw materials used in the present invention are all commercially available in the art.

[0055] The processes involved in the present invention are all conventional processes in the art unless otherwise specified.

[0056] Example 1

[0057] Reference Figure 1 This embodiment provides a method for preparing a vanadium dioxide nanowire sensor that can be tuned to a large extent, specifically:

[0058] Step 1) Substrate pretreatment:

[0059] A silicon wafer with a polished and oxidized surface is used as the substrate material, and an activation treatment is performed at 500K for 20 minutes to ensure good electrical insulation. Subsequently, cleaning, dehydration and surface film formation treatment are performed in sequence to enhance the adhesion between the silicon wafer and the photoresist, thereby obtaining a pretreated substrate 100.

[0060] Step 2) Photoresist coating and gate preparation:

[0061] A layer of PMMA photoresist is uniformly coated on the surface of the pre-treated substrate 100, and pre-baked at 373K for 50 seconds to form a first photoresist layer 101;

[0062] The first photoresist layer 101 is exposed on a photolithography machine using a first mask, and then the substrate 100 is subjected to development, dry etching, debonding and other processes to form a groove with a depth of 1-5 μm and a width of 4-7 μm on the quartz wafer as the gate of the sensor.

[0063] The photoresist in this step is AZ5214 photoresist, and the exposure dose is 3.8W / cm 2 , the developing time is 100 seconds. Step 3) Metal electrode sputtering and stripping:

[0064] A layer of PMMA is coated on the etched substrate 100 to form a second photoresist layer;

[0065] The second photoresist layer is exposed on a photolithography machine using a second mask, and then the substrate 100 is developed to reserve positions for electrodes;

[0066] Metal is sputtered onto the electrode region of the substrate 100 after photolithography by magnetron sputtering. The metal material is gold with good conductivity and oxidation resistance. Acetone is used to remove excess photoresist and excess metal layer on the photoresist to form a source 103, a drain 104 and a gate 105.

[0067] In this step, the thickness of the source 103, the drain 104 and the gate 105 is 400 nm, and the speed during magnetron sputtering is controlled at The vacuum degree used is less than 1×10 – 2 Pa to ensure the continuity and conductivity of the electrodes.

[0068] Step 4) Preparation of vanadium dioxide nanowires:

[0069] Preparation of vanadium dioxide nanowires. Before preparing vanadium dioxide nanowires using vapor deposition technology, the quartz boat and the unpolished (rough) quartz substrate must be cleaned according to standard electronic cleaning operations, mainly including acetone ultrasound, alcohol ultrasound, isopropanol ultrasound and distilled water ultrasound for 5 minutes each, and then blown dry with nitrogen (N2).

[0070] 0.2 g of commercial vanadium dioxide powder with a purity of 99% was placed in a quartz boat and then placed in the center of a horizontal tube furnace; an unpolished (rough) quartz substrate was placed 5 mm above the reaction source to obtain a higher vapor density and deposition temperature.

[0071] First, the furnace tube is evacuated to a basic gas pressure of 1.33 Pa, and then purged with argon for multiple times; then, the temperature is increased at a rate of 15°C / min and maintained at a target temperature of 700°C for 5 hours; during the entire process, the gas pressure is maintained at 1333 Pa and the argon rate is 50 sccm; after the reaction is completed, the tube furnace is cooled to room temperature and then the unpolished (rough) quartz substrate on which the vanadium dioxide nanowires 102 are grown is taken out.

[0072] Step 5) Transfer and fixation of vanadium dioxide nanowires:

[0073] After the preparation in step 4), the vanadium dioxide nanowire 102 is initially embedded in a quartz substrate. A tungsten probe is used to first peel the vanadium dioxide nanowire 102 from the quartz substrate, and then a voltage of 5V is applied to adsorb the vanadium dioxide nanowire 102 for transfer. The vanadium dioxide nanowire 102 is placed on the source 103 and the drain 104 perpendicular to the gate 105, and then the additional voltage is turned off to release the vanadium dioxide nanowire 102, and finally the transfer is completed.

[0074] The vanadium dioxide nanowire 102 grown on the quartz substrate is transferred using a tungsten probe to ensure that both ends of the vanadium dioxide nanowire 102 are placed on the source 103 and the drain 104 and are perpendicular to the gate 105; the vanadium dioxide nanowire is in a free state and the residual strain is released by overcoming the adhesion between the nanowire and the electrode.

[0075] Then, metal Pt is deposited on the interface between the vanadium dioxide nanowire 102 and the electrode using FIB technology, and two rectangular Pt blocks are deposited on both sides of the vanadium dioxide nanowire 102 on the electrode to smoothly fix the vanadium dioxide nanowire 102 to form a first fixed end 106 and a second fixed end 107.

[0076] Specifically, in this step, the metal blocks deposited by the FIB technology at the first fixed end 106 and the second fixed end 107 are rectangular blocks with a length of 2 micrometers, a width of 200 nanometers, and a thickness of 200 nanometers.

[0077] Step 6) Preparation of sensitive layer:

[0078] The surface of the fixed vanadium dioxide nanowire 102 obtained in step 5) is first spin-coated with a layer of PMMA photoresist of about 200 nm, and then the midpoint of the vanadium dioxide nanowire 102 is point-exposed under a scanning electron microscope, and then the sensitive layer 111 is vapor-deposited, and a lift-off process is used to obtain a vanadium dioxide nanowire sensor having a point-coated sensitive layer 111.

[0079] Step 7) Circuit connection:

[0080] Then, an AC power source 108 is connected to the source electrode 103 by a wire, a DC power source 109 is connected to the gate electrode 105, and a voltmeter 110 is connected to the first fixed end 106 and the second fixed end 107 to obtain a vanadium dioxide nanowire sensor that can be tuned to a large extent.

[0081] The vanadium dioxide nanowire sensor that can be tuned to a large extent prepared according to this embodiment has performance characteristics such as excellent sensitivity and a wide detection range, and can be widely used in the field of gas detection. At the same time, the present invention also has the characteristics of being able to be tuned to a large extent, being able to be initialized, and being able to replace different sensitive layers.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that the first fixed end and the second fixed end of different thicknesses are made for the vanadium dioxide nanowire of the same size by the FIB method to obtain the vanadium dioxide nanowire sensor of this comparative example. Under the same test environment, the vanadium dioxide nanowire sensor is subjected to an open-loop test, and five groups of experimental data are read respectively, and the average value is taken. The results are shown in Table 1.

[0084] Table 1

[0085] Thickness of deposited metal Quality Factor Example 1 200nm 1366 Comparative Example 1 100nm 1145

[0086] It can be seen from Table 1 that the average overall quality factor of the vanadium dioxide nanowire sensor with a fixed end of 200 nm deposited by the FIB method in Example 1 of the present invention is 1366, while the average overall quality factor of the vanadium dioxide nanowire sensor with a fixed end of 100 nm deposited by the FIB method is 1145. Obviously, the thickness of the metal deposited by the FIB method cannot be too thin, which is conducive to improving the resonance characteristics of the resonator and is more conducive to the detection of the resonator.

[0087] The average overall quality factor of the vanadium dioxide nanowire sensor with a fixed end having a thickness of 200 nm deposited by the FIB method in Example 1 of the present invention is 1366, while the average overall quality factor of the vanadium dioxide nanowire sensor with a fixed end having a thickness of 100 nm deposited by the FIB method is 1145. Obviously, the fixed end with a thickness of 200 nm has better clamping of the resonant beam, and has lower clamping loss during resonance, which is beneficial to improving the resonant characteristics of the resonator and the sensitivity of the resonator.

[0088] Example 2

[0089] The difference between this embodiment and embodiment 1 is that:

[0090] Adjust the type of metal material to be sputtered to silver and the sputtering speed to

[0091] The treatment temperature of the pre-baking treatment is 383K and the time is 60s;

[0092] The photoresist exposure dose is 3.6mW / cm 2 , the developing time is 60 seconds;

[0093] The target temperature in the preparation of vanadium dioxide nanowires was 800°C, the holding time was 6 hours, and the argon rate was 100 sccm.

[0094] The remaining steps and processes are all based on Example 1 to obtain the vanadium dioxide nanowire sensor of this embodiment. An open-loop test is performed on the sensor, and the result is equivalent to that of Example 1.

[0095] Example 3

[0096] The difference between this embodiment and embodiment 1 is that:

[0097] Adjust the type of metal material to be sputtered to silver and the sputtering speed to

[0098] The treatment temperature of the pre-baking treatment is 378K and the time is 55s;

[0099] The photoresist exposure dose is 4.0mW / cm 2 , the developing time is 80 seconds;

[0100] The target temperature in the preparation of vanadium dioxide nanowires was 750°C, the holding time was 5.5 hours, and the argon rate was 75 sccm.

[0101] The remaining steps and processes are all based on Example 1 to obtain the vanadium dioxide nanowire sensor of this embodiment. An open-loop test is performed on the sensor, and the result is equivalent to that of Example 1.

[0102] Comparative Example 2

[0103] The difference between this comparative example and Example 1 is that in step 6) of Example 1, the portion of the vanadium dioxide nanowire 102 to be deposited with the sensitive layer 111 is changed from the midpoint of the vanadium dioxide nanowire to the entire vanadium dioxide nanowire, and the remaining steps and processes are all referred to Example 1 to obtain the vanadium dioxide nanowire sensor of this comparative example.

[0104] Under the same test environment, an open-loop test was performed on the zinc oxide nanowire resonator. Five sets of experimental data were read and the average value was taken. The results are shown in Table 2.

[0105] Table 2

[0106] Sensitive layer location Resonant frequency Example 1 midpoint 36MHz Comparative Example 2 overall 30MHz

[0107] As can be seen from Table 2, the average overall resonant frequency of the vanadium dioxide nanowire sensor in Example 1 of the present invention, in which the sensitive layer is deposited at the midpoint of the vanadium dioxide nanowire, is 36 MHz, while the average overall resonant frequency of the vanadium dioxide nanowire sensor in which the sensitive layer is deposited on the entire vanadium dioxide nanowire is 30 MHz. Obviously, depositing the sensitive layer at the midpoint of the vanadium dioxide nanowire is beneficial to improving the resonant frequency and sensitivity of the resonator, and is more conducive to the detection of the resonator. The average overall resonant frequency of the vanadium dioxide nanowire sensor in Example 1 of the present invention, in which the sensitive layer is deposited at the midpoint of the vanadium dioxide nanowire, is 36 MHz, while the average overall resonant frequency of the vanadium dioxide nanowire sensor in which the sensitive layer is deposited on the entire vanadium dioxide nanowire is 30 MHz. Obviously, depositing the sensitive layer at the midpoint of the vanadium dioxide nanowire makes the adsorption position uniform for the gas molecules, which is beneficial to improving the measurement accuracy of the resonator and improving the sensitivity of the resonator.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 1 is that the operating temperature of the vanadium dioxide nanowire resonator in Example 1 is adjusted to obtain the vanadium dioxide nanowire sensor of this comparative example.

[0110] Under the same test environment, the vanadium dioxide nanowire sensor was subjected to an open-loop test. Five sets of experimental data were read and the average value was taken. The results are shown in Table 3.

[0111] Table 3

[0112] Operating temperature Resonant frequency Example 1 360K 36MHz Comparative Example 1 295K 27.1MHz

[0113] It can be seen from Table 3 that when the operating temperature of the vanadium dioxide nanowire resonator in Example 1 of the present invention is 360K, the average value of the overall resonant frequency of the vanadium dioxide nanowire sensor is 36MHz, while when the operating temperature of the vanadium dioxide nanowire resonator is 295K, the average value of the overall resonant frequency of the vanadium dioxide nanowire sensor is 36MHz. Obviously, when the operating temperature of the vanadium dioxide nanowire resonator is 360K, it is beneficial to increase the resonant frequency of the resonator, thereby improving the sensitivity of the sensor.

[0114] When the working temperature of the vanadium dioxide nanowire resonator in Example 1 of the present invention is 360K, the average value of the overall resonant frequency of the vanadium dioxide nanowire sensor is 36MHz, while when the working temperature of the vanadium dioxide nanowire resonator is 295K, the average value of the overall resonant frequency of the vanadium dioxide nanowire sensor is 36MHz. Obviously, when the working temperature of the vanadium oxide nanowire resonator is 360K, the axial force of the nanowire is greatly improved compared with that at 295K, which is conducive to improving the resonant frequency of the resonator, thereby improving the sensitivity of the sensor.

[0115] In summary, the present invention uses vanadium dioxide nanowires to utilize their phase change characteristics from insulating phase to metallic phase to improve the sensitivity of the sensor and expand its detection range. In addition, by depositing the sensitive layer at the midpoint of the vanadium dioxide nanowire to unify its adsorption position, the sensitivity of the sensor can also be improved. The above optimizations are all conducive to improving the performance of the sensor.

[0116] In addition to the above-mentioned optimization measures, the manufacturing method of the present invention can also be appropriately adjusted to adapt to different application scenarios and needs. For example, different electrode materials and sensitive layers can be selected according to actual needs to reduce the manufacturing cost of the resonator and change the performance indicators of the sensor such as the detection gas. Electrode materials can be selected from metals such as copper, aluminum, and nickel to reduce the manufacturing cost of the resonator. The sensitive layer can be selected from sensitive materials such as copper phthalocyanine, platinum, and tin oxide to detect gases such as ethanol, oxygen, and methane.

[0117] It can be seen that the method for making the tunable vanadium dioxide nanowire sensor of the present invention has the characteristics of flexibility and adjustability, and can be optimized and adjusted according to actual needs to meet different application scenarios and needs. The resonator prepared by the method of the present invention has excellent performance characteristics such as sensitivity and stability, and can be widely used in gas detection and other fields, providing strong support for research and development in related fields.

[0118] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A highly tunable vanadium dioxide nanowire sensor, characterized in that: include, A base silicon wafer (100); The vanadium dioxide nanowire (102) is located above the base silicon wafer (100) and is in contact with metal electrodes at both ends; The metal electrode includes a source electrode (103), a drain electrode (104) and a gate electrode (105). The source electrode (103) and the drain electrode (104) are used to support and fix the vanadium dioxide nanowire (102) and are also responsible for connecting with an external circuit to realize the input of an excitation signal and the output of a response signal respectively. A gate (105), located below the vanadium dioxide nanowire (102), not connected to the vanadium dioxide nanowire (102), and used to apply a bias electrostatic force to the vanadium dioxide nanowire (102); The fixed end includes a first fixed end (106) and a second fixed end (107), and the first fixed end (106) and the second fixed end (107) fix the vanadium dioxide nanowire (102) on the electrode; The power supply end includes an AC power supply (108) and a DC power supply (109), the AC power supply (108) is connected to the source (103), and the DC power supply (109) is connected to the gate (105); The voltmeter (110) is connected to the first fixed end (106) and the second fixed end (107) via a wire to form a parallel connection with the nanowire, and is used to detect the change in the voltage of the vanadium dioxide nanowire (102); The sensitive layer (111) is arranged at the midpoint of the vanadium dioxide nanowire (102) and is used to detect different gas molecules.

2. A method for preparing a highly tunable vanadium dioxide nanowire sensor as claimed in claim 1, characterized in that: include, After the surface of the polished and oxidized silicon wafer is activated, it is sequentially cleaned, dehydrated and subjected to surface film forming treatment to obtain a pre-treated base silicon wafer (100); A layer of polymethyl methacrylate photoresist is uniformly coated on the surface of a base silicon wafer (100), and a first photoresist layer (101) is formed by pre-baking. The first photoresist layer (101) is exposed on a photolithography machine using a first mask, and then a base silicon wafer (100) is subjected to development, dry etching and other processes to form a groove with a depth of 1-5 μm and a width of 4-7 μm on the base silicon wafer, and metal is deposited inside the groove as a gate of the sensor; Coating a layer of PMMA on the etched base silicon wafer (100) to form a second photoresist layer; Using a second mask to expose the second photoresist layer on a photolithography machine, and then continuing to develop the base silicon wafer (100) to reserve a position for the electrode; Depositing metal on the electrode region of the photolithographic base silicon wafer (100) through a lift-off process to form a source electrode (103), a drain electrode (104) and a gate electrode (105); The synthesis of vanadium dioxide nanowires (102) is carried out by placing 0.2 g of commercial vanadium dioxide powder with a purity of 99% in a quartz boat and then placing it in the center of a horizontal tube furnace; an unpolished quartz substrate is placed 5 mm above the bottom of the quartz boat to obtain a higher vapor density and deposition temperature; the furnace tube is first evacuated to a basic gas pressure of 1.33 Pa and then purged with argon; then, the temperature is increased at a rate of 15°C / min and maintained at a target temperature of 700°C-800°C for 5-6 hours; during the whole process, the gas pressure is maintained at 1333 Pa; after the reaction is completed, the tube furnace is cooled to room temperature and then the unpolished quartz substrate on which the vanadium dioxide nanowires (102) are grown is taken out; Using a tungsten probe to transfer the vanadium dioxide nanowire (102) grown on a quartz substrate, ensuring that both ends of the vanadium dioxide nanowire (102) are placed on the source electrode (103) and the drain electrode (104) perpendicular to the gate electrode (105); The vanadium dioxide nanowire (102) has a diameter of 180-240 nm, a length of 5-8 μm, and an aspect ratio of 28-33 and is used as a resonant beam; Platinum is deposited on both ends of the vanadium dioxide nanowire (102) using a focused ion beam technique to form two rectangular platinum metal blocks as a first fixed end (106) and a second fixed end (107) to smoothly fix the vanadium dioxide nanowire (102); Firstly, a layer of polymethyl methacrylate photoresist with a thickness of about 200 nm is spin-coated on the surface of the fixed vanadium dioxide nanowire (102), then the midpoint of the vanadium dioxide nanowire (102) is exposed at the midpoint under a scanning electron microscope, then a sensitive layer (111) is vapor-deposited, and a vanadium dioxide nanowire sensor having the midpoint-coated sensitive layer (111) is obtained by a lift-off process; Then, an AC power source (108) is connected to the source electrode (103) with a wire, a DC power source (109) is connected to the gate electrode (105), and a voltmeter (110) is connected to the first fixed end (106) and the second fixed end (107) to obtain a vanadium dioxide nanowire sensor that can be tuned to a large extent.

3. The method for preparing a vanadium dioxide nanowire resonator capable of being tuned to a large extent as claimed in claim 2, characterized in that: The activation temperature of the silicon wafer activation is 500-700K, and the activation time is 20-40min; the treatment temperature of the pre-baking treatment is 373-383K, and the time is 50-60s.

4. The method for preparing the highly tunable vanadium dioxide nanowire sensor according to claim 2, characterized in that: The preparation method of the vanadium dioxide nanowire (102) adopts a chemical vapor deposition method.

5. The method for preparing the highly tunable vanadium dioxide nanowire sensor according to claim 2, characterized in that: The transfer of the vanadium dioxide nanowire (102) is performed by first peeling the vanadium dioxide nanowire (102) from the quartz substrate using a tungsten probe, then applying a voltage of 5V to adsorb the vanadium dioxide nanowire (102) for transfer, placing the vanadium dioxide nanowire (102) on the source (103) and the drain (104) perpendicular to the gate (105), then turning off the additional voltage to release the vanadium dioxide nanowire (102), and finally completing the transfer.

6. The method for preparing a tunable vanadium dioxide nanowire sensor according to claim 2, characterized in that: The metal material of the magnetron sputtering metal includes gold, silver or copper, and the speed during the sputtering process is The vacuum degree is less than 1×10 – 2 Pa.

7. The method for preparing a tunable vanadium dioxide nanowire sensor according to claim 2, characterized in that: The photoresist is AZ5214 photoresist, and the exposure dose is 3.6m-4.0mW / cm 2 , the developing time is 60-100 seconds.

8. The method for preparing a tunable vanadium dioxide nanowire sensor according to claim 2, characterized in that: The first fixed end (106) and the second fixed end (107) are formed by depositing metal Pt using a focused ion beam technique, and have a length of 2 μm, a width of 200 nm, and a thickness of 200 nm.

9. The method for preparing a tunable vanadium dioxide nanowire sensor according to claim 2, characterized in that: The resonant frequency f of the vanadium dioxide nanowire (102) is 27.1 MHz at a temperature of T=295K, and is greatly tuned to 36 MHz at a temperature of T=360K.

10. Use of a vanadium dioxide nanowire sensor that can be tuned greatly and prepared by the preparation method according to any one of claims 2 to 19 in constructing an ultra-high sensitivity sensor.

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