Preparation method of low-concentration phosphorus-doped VO2 thermosensitive film for cable infrared temperature measurement

Abstract

The invention relates to a preparation method of a low-concentration phosphorus-doped VO2 thermosensitive film for cable infrared temperature measurement. The preparation method comprises the following steps: mixing vanadium pentoxide and oxalic acid, dissolving in deionized water, and heating in an oil bath to obtain a vanadyl oxalate solution; dissolving sodium hypophosphite in the vanadyl oxalate solution to obtain a mixed solution; enabling solute in the mixed solution to grow on the surface of the double-parabolic sapphire substrate by adopting a high-temperature hydrothermal method to form a modified thermosensitive film; washing the modified thermosensitive film with deionized water, and blow-drying; spin-coating one surface of the modified thermosensitive film with a hydrogen peroxide solution to obtain a sample; post-annealing treatment on the sample is completed, and the low-concentration phosphorus-doped VO2 modified thermosensitive film is obtained. The method has the beneficial effects that the surface roughness is reduced; the linear temperature measurement range is widened; temperature measurement is more sensitive; and the application range is wider.

Description

Technical Field

[0001] The invention relates to the field of modified preparation of thermosensitive layer materials of infrared temperature sensor chips, in particular to a method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables. Background Art

[0002] Vanadium oxide is a transition metal oxide with the special property of reversible phase transition from low-temperature insulating state to high-temperature metallic state, and it has multiple valence forms and phase structures. Compared with vanadium oxides of other valence states, the insulating-metal phase transition temperature of vanadium dioxide is closer to room temperature (about 340K), and during the phase transition, it is accompanied by sudden changes in optical and electrical properties such as infrared transmittance, sheet resistance, and conductivity. Therefore, based on this important characteristic, vanadium oxide has been widely used in many key fields in recent years, such as infrared detector photosensitive layer thin film, color-changing glass and intelligent temperature control coating manufacturing, and two-terminal and three-terminal electronic switch research and development.

[0003] The requirements for the phase transition process of vanadium dioxide in various application scenarios are often different. When vanadium dioxide is used as a material for indoor photochromic glass, its critical phase transition temperature is expected to be near room temperature; however, when vanadium dioxide is used as a thermosensitive film for infrared temperature monitoring of power equipment components such as cables or electrical materials, it is expected to have a wider range of linear temperature resistance changes while ensuring test sensitivity, that is, the phase transition process is delayed or even eliminated; in addition, it is also expected to have high detection response performance and low noise power consumption under specific band light pulses. Therefore, the regulation of the phase transition process and photocurrent response characteristics of vanadium dioxide is of key significance to improving its application value and achieving more significant application effects.

[0004] External physical environment induction such as thermal field, electric field and stress field, as well as chemical modification methods such as doping, vacancy introduction and ion implantation can all regulate the phase transition process of vanadium oxide. Among them, doping modification is the most widely used and most effective chemical induction method, which mainly regulates the dⅡ orbital splitting gap of tetravalent vanadium ions and the band structure of vanadium dioxide by introducing high- and low-valent cations or anions, thereby increasing or decreasing the phase transition temperature of the material to a certain extent.

[0005] In addition, the doping method can also improve the temperature resistivity TCR of vanadium dioxide, making it more effectively used in thermosensitive thin film layer materials. The current research on doping and modification of vanadium dioxide mainly has the following problems: First, the selection of doping ions is not very innovative, mainly focusing on metal cations such as tungsten ions, niobium ions, aluminum ions, and halogen anions such as fluoride ions; second, the current low-concentration doping modification method cannot achieve phase transition elimination and significant improvement in detection response performance, and can only regulate the phase transition critical temperature and light response to a certain extent, which will limit the application of vanadium dioxide and its modified materials in cable infrared temperature measurement. Therefore, there is still a lot of room for innovation and development in the doping and modification research of vanadium dioxide. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems and design a method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables. The specific design scheme is:

[0007] A method for preparing low-concentration phosphorus-doped VO2 thermosensitive film for cable infrared temperature measurement.

[0008] Step 1: Dissolve vanadium pentoxide and oxalic acid in deionized water and heat in an oil bath to obtain a vanadium oxalate solution containing a high concentration of vanadium;

[0009] Step 2: dissolving sodium hypophosphite as a phosphorus doping source in the vanadyl oxalate solution to obtain a mixed solution;

[0010] Step 3: using a high temperature hydrothermal method to allow the solute in the mixed solution to fully grow on the surface of the double-polished sapphire substrate to form a modified thermosensitive film;

[0011] Step 4: After the hydrothermal reaction is completed, the sapphire substrate is taken out, and the residual mixed solution on the modified thermosensitive film is washed with deionized water and blown dry;

[0012] Step 5, spin-coating a hydrogen peroxide solution on one side of the modified thermosensitive film to dissolve and remove the side with poor film formation, thereby obtaining a sample;

[0013] Step 6: Use a tubular annealing furnace to complete the post-annealing treatment of the sample, and finally obtain a uniform and dense blue-black low-concentration phosphorus-doped VO2 modified thermosensitive film grown on a sapphire substrate.

[0014] In the step 1, the oil bath heating temperature is 80° C. and the oil bath time is 2 h.

[0015] In step 2, the molar ratio of phosphorus atoms to vanadium atoms in the vanadium pentoxide raw material is 1 part:20 parts, that is, the doping ratio is 5 at %.

[0016] In step 2, the stirring method includes using a temperature-controlled magnetic stirrer to continuously stir the doped vanadium oxalate mixed solution at a constant temperature of 50° C. for 1 hour.

[0017] In step 3, 40 ml of the mixed solution was transferred into the mixture and the mixture was sealed and placed in a forced air oven for hydrothermal reaction at 230° C. for 4 h.

[0018] In step six, the sample is annealed in a tubular annealing furnace under the conditions of 5 kPa argon atmosphere, 400° C. annealing temperature, 25.3° C. / min heating rate, and 60 s annealing time.

[0019] The molar ratio of vanadium pentoxide to oxalic acid in the vanadium oxalate solution is 1 part:3.5 parts, and the vanadium concentration is 27.4 mmol / L.

[0020] The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables obtained by the above technical solution of the present invention has the following beneficial effects:

[0021] 1. Low concentration of phosphorus doping inhibits the growth of vanadium dioxide crystals, reduces the grain size and thus reduces the surface roughness;

[0022] 2. After low-concentration phosphorus doping, the bandgap width of vanadium dioxide increases, the phenomenon of transition from insulating phase to metallic phase is eliminated, and the linear temperature measurement range becomes wider;

[0023] 3. After low-concentration phosphorus doping, the temperature resistance coefficient of the modified thermistor film is greatly improved, the resistance change reversibility during the heating and cooling process is good, and it has a more suitable square resistance value and higher conductivity, which can realize infrared temperature measurement of cables more accurately and sensitively, and timely monitor the occurrence of cable overheating defects and faults;

[0024] 4. The low-concentration phosphorus-doped thermosensitive film has better detection performance and stronger anti-noise interference ability. It can sensitively perceive changes in external infrared radiation, respond to weak infrared light signals in real time under the background of noise, and realize infrared temperature measurement of cables efficiently and accurately.

[0025] 5 After low-concentration phosphorus doping, a localized electronic state is generated near the conduction band of the vanadium dioxide crystal, that is, the impurity energy level contributed by the phosphorus doping source. This change triggers the synaptic plasticity function of the modified thermosensitive film under the action of near-infrared light pulses, and has the potential to be applied to neuromorphic photoelectric detection devices, and the scope of application has been broadened to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a basic method and a schematic diagram of the process for preparing the low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to the present invention;

[0027] Figure 2It is a diagram showing the energy band structure and the corresponding bandgap width change caused by low-concentration phosphorus doping according to the present invention;

[0028] Figure 3 This is a diagram showing changes in the X-ray diffraction angle position and peak value of vanadium dioxide caused by low-concentration phosphorus doping according to the present invention;

[0029] Figure 4 This is a diagram showing the changes in crystal morphology and grain size caused by low-concentration phosphorus doping under a scanning electron microscope according to the present invention;

[0030] Figure 5 It is a temperature-resistance curve diagram of the low-concentration phosphorus-doped VO2 thermosensitive film of the present invention in the process of heating and cooling from 20 to 90°C;

[0031] Figure 6 It is a characteristic curve diagram of infrared light response and net photocurrent modulation of the low-concentration phosphorus-doped VO2 thermosensitive film of the present invention;

[0032] Figure 7 It is the infrared switch characteristic curve diagram of the low-concentration phosphorus-doped VO2 thermosensitive film of the present invention;

[0033] Figure 8 It is the neuromorphic photocurrent response curve of the low-concentration phosphorus-doped VO2 thermosensitive film of the present invention, that is, the synaptic plasticity function diagram. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0035] like Figure 1As shown, a method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables is shown. First, vanadium pentoxide and oxalic acid are mixed and dissolved in deionized water and heated in an oil bath at 80°C for 2 hours to obtain a deep blue vanadium oxalate solution containing a high concentration of vanadium. Then, sodium hypophosphite is dissolved in the vanadium oxalate solution as a phosphorus doping source. The doped vanadium oxalate mixed solution is continuously stirred at a constant temperature of 50°C for 1 hour using a temperature-controlled magnetic stirrer. A double-polished sapphire substrate with a crystal orientation of

[001] is vertically placed at the bottom of the inner substrate of a reactor. 40m l The mixed solution was transferred into it and the seal was tightened and placed in a blast oven. The hydrothermal reaction was carried out at 230℃ for 4h to ensure that the solute grew vertically on both sides of the substrate. After the reaction was completed and cooled to room temperature, the reactor was opened and the substrate was taken out. The residual liquid on the surface of the modified thermosensitive film grown on both sides of the substrate was carefully cleaned with deionized water, and then blown dry with low-pressure nitrogen. Then, the hydrogen peroxide solution was fully spin-coated to dissolve and remove the side with poor film formation. The sample was annealed in a tubular annealing furnace under the conditions of 5kPa argon atmosphere, 400℃ annealing temperature, 25.3℃ / min heating rate and 60s annealing time. Finally, a uniform and dense blue-black low-concentration phosphorus-doped VO2 modified thermosensitive film grown on a sapphire substrate was obtained.

[0036] The molar ratio of vanadium pentoxide to oxalic acid in the vanadium oxalate solution is 1 part:3.5 parts, and the vanadium concentration is 27.4 mmol / L.

[0037] The molar ratio of phosphorus atoms to vanadium atoms in the vanadium pentoxide raw material is 1 part:20 parts, that is, the doping ratio is 5at%.

[0038] Example 1

[0039] The sodium hypophosphite added to the vanadyl oxalate solution has the characteristic of high-temperature decomposition. The phosphine gas produced by its decomposition realizes the phosphating modification of vanadium dioxide under a hydrothermal environment. The corresponding trivalent phosphorus ions replace the vanadium atoms in the crystal, which can achieve significant regulation of the crystal structure, phase change process and detection response performance.

[0040] Starting from five aspects, including reducing the surface roughness of the film, widening the linear temperature measurement range, improving the electrical properties of the film, improving the photoelectric detection performance and power consumption of the film, and broadening the application functions and fields, it is proposed to introduce low-concentration phosphorus doping to modify the vanadium dioxide film. The trivalent phosphorus ions occupy the vanadium atomic positions inside the crystal, which increases the band gap width of vanadium dioxide and increases the energy required for free electrons to jump from the valence band to the conduction band. At the same time, localized electronic states are generated near the conduction band, that is, the impurity energy levels contributed by the phosphorus doping source, such as Figure 2 As shown, it is beneficial to eliminate the phase transition process of the thin film material and improve its photoelectric detection performance.

[0041] Example 2

[0042] In terms of reducing the surface roughness of the film, the introduction of trivalent phosphorus ions reduces the lattice parameters and the diffraction peak of vanadium oxide shifts toward the direction of high diffraction angles, such as Figure 3 The crystal morphology changes from large-sized nanosheets to small-sized raspberry-like shapes, as shown in Figure 4 As shown, the surface roughness of the prepared modified vanadium oxide thermosensitive film is reduced, and the density and uniformity are improved.

[0043] Example 3

[0044] In terms of widening the linear temperature measurement range, from the perspective of crystal structure changes, the introduction of phosphorus ions will shorten the VV bonds in the crystal, and a higher temperature is required for the crystal structure to return to its original state, resulting in the elimination of the phase change phenomenon of vanadium dioxide. From the perspective of the band structure, the occupation of phosphorus ions increases the band gap width of vanadium dioxide, increases the energy required for free electrons to jump from the valence band to the conduction band, suppresses the phase change process, and broadens the linear part of the temperature-resistance curve, such as Figure 5 As shown, accurate cable infrared temperature measurement can be achieved in a wider temperature range.

[0045] Example 4

[0046] In terms of improving the electrical properties of the film, the doping effect of phosphorus ions makes the modified thermosensitive film have an extremely high temperature resistivity TCR (about 4.60% / K), and the reversibility of the film resistance change during the temperature rise and fall process of 20-90℃ is strong, and the hysteresis width is extremely small. The film has a moderate room temperature square resistance value of about 16.21kΩ; it has a high conductivity of about 41.67×10-3(Ω·cm)-1.

[0047] Example 5

[0048] In terms of improving the photoelectric detection performance and anti-noise interference ability of the film, the doping effect of phosphorus ions enables the modified thermosensitive film to produce strong photocurrent changes at all infrared light powers, such as Figure 6 As shown; it has a fast rise time (0.25s), extremely high photoresponsivity (52.8μA / W), normalized detection rate (3.79×1010W-1), external quantum efficiency (61.53%) and extremely low noise equivalent power (2.64×10-11W), such as Figure 7 As shown, it can sensitively respond to changes in near-infrared light and accurately realize infrared temperature measurement of cables with high responsiveness, high detection rate and strong anti-noise interference mode.

[0049] Example 6

[0050] In terms of broadening the application functions and fields, the doping effect of phosphorus ions introduces impurity energy levels into the band gap, and some photogenerated carriers are temporarily captured and stored by this energy level during the transition to the conduction band; under the action of the light pulse in the next stage, in addition to the transition of the newly generated photogenerated carriers, the captured carriers in the previous stage are also excited in large quantities to further transition to the conduction band, which is manifested as a continuous increase in the accumulation of conductivity and leakage current under the action of multiple infrared light pulses, thereby triggering the synaptic plasticity enhancement function of the modified thermosensitive film under the action of near-infrared light pulses, such as Figure 8 As shown, in addition to cable infrared temperature measurement, it can play an excellent role and effect in neuromorphic optoelectronic devices.

[0051] The above technical solutions only reflect the preferred technical solutions of the technical solutions of the present invention. Some changes that may be made to certain parts thereof by technicians in this technical field all reflect the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables, characterized in that: Step 1: Dissolve vanadium pentoxide and oxalic acid in deionized water and heat in an oil bath to obtain a vanadium oxalate solution; Step 2, dissolving sodium hypophosphite in the vanadyl oxalate solution to obtain a mixed solution; Step 3: using a high temperature hydrothermal method to make the solute in the mixed solution grow on the surface of a double-polished sapphire substrate to form a modified thermosensitive film; Step 4, washing the modified thermosensitive film with deionized water and drying it; Step 5, spin coating a hydrogen peroxide solution on one side of the modified thermosensitive film to obtain a sample; Step six: complete the post-annealing treatment of the sample to obtain a low-concentration phosphorus-doped VO2 modified thermosensitive film.

2. The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to claim 1, characterized in that: In the step 1, the oil bath heating temperature is 80° C. and the oil bath time is 2 h.

3. The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to claim 1, characterized in that: In step 2, the molar ratio of phosphorus atoms to vanadium atoms in the vanadium pentoxide raw material is 1 part:20 parts.

4. The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to claim 1, characterized in that: In step 2, the stirring method includes using a temperature-controlled magnetic stirrer to continuously stir the doped vanadium oxalate mixed solution at a constant temperature of 50° C. for 1 hour.

5. The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to claim 1, characterized in that: In step 3, 40 ml of the mixed solution was transferred into the mixture and the mixture was sealed and placed in a forced air oven for hydrothermal reaction at 230° C. for 4 h.

6. The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to claim 1, characterized in that: In step six, the sample is annealed in a tubular annealing furnace under the conditions of 5 kPa argon atmosphere, 400° C. annealing temperature, 25.3° C. / min heating rate, and 60 s annealing time.

7. The method for preparing a low-concentration phosphorus-doped VO2 thermosensitive film for infrared temperature measurement of cables according to claim 1, characterized in that: The molar ratio of vanadium pentoxide to oxalic acid in the vanadium oxalate solution is 1 part:3.5 parts, and the vanadium concentration is 27.4 mmol / L.

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