CN101265036A - A low-temperature deposition method of vanadium dioxide thin film on glass - Google Patents

Abstract

The invention utilizes the crystal heterogeneous epitaxy growth principle, and provides a low-temperature preparation method for the deposition of the vanadium dioxide film on a glass substrate without damaging the quality (thermochromic property) of the vanadium dioxide film. Taking glass as the substrate, the following steps are sequentially included: 1) cleaning and processing the glass substrate; 2) depositing a layer of silicon dioxide diffusion barrier layer on the glass substrate; Depositing a zinc oxide seed crystal layer; 4) finally depositing a vanadium dioxide thermochromic film layer on the zinc oxide seed crystal layer. The zinc oxide seed crystal layer adopted in the present invention has a low crystallization temperature and a good match between the lattice constant and the vanadium dioxide, and is especially suitable for the heteroepitaxial growth of the vanadium dioxide thin film, thereby effectively reducing the deposition temperature of the vanadium dioxide thin film, simplifying the The preparation process of vanadium dioxide smart glass reduces costs, saves energy consumption, and greatly reduces the difficulty of the industrialization process of vanadium dioxide smart glass.

Description

A low-temperature deposition method of vanadium dioxide thin film on glass

technical field

The invention belongs to the technical field of building energy saving among high-efficiency energy-saving and consumption-reducing technologies, and in particular relates to a low-temperature deposition method of a vanadium dioxide film on a glass substrate.

technical background

According to statistics, my country's building energy consumption has reached 30% of the total social energy consumption. With the expansion of my country's urbanization scale, the advancement of urban construction, and the improvement of people's living standards, building energy consumption will increase year by year. In 1996, my country's construction consumed 330 million tons of standard coal annually, accounting for 24% of the total energy consumption. By 2001, it had reached 376 million tons, accounting for 27.6% of the total consumption, with an annual growth rate of 5/1000. According to forecasts, my country's building energy consumption will climb to more than 35% in a relatively short period of time in the future. The current domestic energy shortage situation will face severe challenges. In recent years, frequent power cuts in South China and North China have sounded the alarm for us. At present, building energy conservation has become a major issue of common concern to all countries in the world, and it is an important guarantee for the sustainable development of the economy and society, especially the rapid growth of my country's economy.

The energy saving of windows is the first problem that must be considered in building energy saving. Among the four major enclosure components of a building (doors and windows, walls, roof and ground), the thermal insulation performance of doors and windows is the worst, and it is one of the main factors affecting the indoor thermal environment and building energy efficiency. In terms of components, the energy consumption of doors and windows is about 4 times that of the wall, 5 times that of the roof, and more than 20 times that of the ground, accounting for more than 50% of the energy consumption of the building envelope.

Western developed countries have carried out building energy conservation work since the 1970s, and have achieved outstanding results so far. The energy-saving technology of windows has also made considerable progress, and energy-saving windows are showing a multi-functional and high-tech development trend. People's functional requirements for doors and windows range from simple light transmission, wind protection, and rain protection to energy saving, comfort, and flexible adjustment of lighting, etc., and technically from the use of ordinary flat glass to the use of hollow heat insulation technology (hollow glass) and various High-performance thermal insulation film technology (heat reflective glass, etc.). At present, developed countries have begun to develop the next generation of "intelligent" energy-saving glass windows, referred to as smart glass, which can change the amount of sunlight penetrating into the room according to environmental conditions or people's will to achieve maximum energy saving.

Smart glass can be realized in many ways. These smart glasses mainly rely on the film deposited on the window glass, which changes the optical properties of the film under the excitation of some physical factors (such as light, electricity or heat), so as to realize the adjustment of solar radiation. The change of the optical properties of the film is called discoloration. The discoloration mechanism can be divided into electrochromic (electrically sensitive), thermochromic (heat sensitive), gasochromic (gas sensitive) and photochromic (light sensitive) and so on. Smart glasses based on these discoloration mechanisms can all adjust to varying degrees of sunlight, but each has its own advantages and disadvantages. For example, electrochromism can continuously change from high transmittance to low transmittance, and the switching efficiency is high, but the manufacturing process is complex and requires power supply voltage, and the system cost is high. Currently, it is only used in small-scale high-end automotive glass. ; Photochromism can simply change the optical properties (such as sunglasses) through light, but it is not applicable to the production process of float glass at present. If the organic plastic layer plays the role of color change, the durability of the material is another problem; Color-changing energy-saving glass is a hot spot in current research. This energy-saving window can realize color change through hydrogen and argon mixed gas. The biggest advantage is that it can be combined with solar hydrogen production technology. On the other hand, the high gas The tightness requirements greatly limit its application; for thermochromism, several products have been developed on the market, such as ink, pigment, safety equipment, temperature indicator, etc. In terms of smart glass, some companies have developed The thermosensitive polymer has certain effect, but the durability of the polymer is still a difficult problem to be overcome.

Vanadium dioxide (VO ₂ ) is a typical thermochromic phase change material with a bulk phase transition temperature of 68°C. Below this temperature, it is semiconducting and moderately transparent; when it is higher than 68°C, it is metallic and highly reflective to infrared. Importantly, its phase transition temperature can be lowered to near room temperature by doping with high-valence metals. The research on applying vanadium dioxide to energy-saving windows started as early as the early 1970s, but there are still many technical problems to be solved. At the same time, in the preparation process, the high deposition temperature of _VO2 (generally higher than 500°C) will be a serious obstacle to the industrialization of this kind of smart glass. On the one hand, high temperature will lead to high power consumption and increase the cost of preparation. On the other hand, it also puts forward more requirements on the preparation system, which increases the difficulty of industrialization. Therefore, reducing the deposition temperature of _VO2 is an important problem to be solved in the industrialization process of this kind of smart glass. This patent proposes a low-temperature deposition method of vanadium dioxide thin film according to the film-forming mechanism and thermodynamic principle of _VO2 thin film. After searching the published patent documents and scientific research literature, no relevant content was found.

Contents of the invention

The invention utilizes the crystal heterogeneous epitaxy growth principle, and provides a low-temperature preparation method for the deposition of the vanadium dioxide film on a glass substrate without damaging the quality (thermochromic property) of the vanadium dioxide film.

The present invention comprises the following steps in turn: 1) glass substrate cleaning and treatment; 2) on the glass substrate, first deposit a layer of silicon dioxide diffusion barrier layer; 3) deposit a layer of oxide on the silicon dioxide diffusion barrier layer Zinc seed crystal layer; 4) Finally, a vanadium dioxide thermochromic thin film layer is deposited on the zinc oxide seed crystal layer.

The silicon dioxide diffusion barrier layer can prevent impurity ions in the glass substrate from diffusing into the zinc oxide seed crystal layer and the vanadium dioxide thermochromic thin film layer under high temperature conditions (higher than 200 ° C), forming uncontrollable ion doping impurity, which will eventually lead to the deterioration of the film quality of the thermochromic layer and affect the thermochromic performance of vanadium dioxide. Silicon dioxide is the most preferred material for the diffusion barrier layer. Silica has the advantages of being stable at high temperature, easy to form a film, and low cost.

There are two reasons for using zinc oxide as the seed layer: one is that zinc oxide can form a polycrystalline film at low temperature or even room temperature, and the film grows preferentially along the (001) direction on the glass substrate; the other is that The lattice constant of the zinc oxide can be well matched with the vanadium dioxide rutile, and the lattice mismatch is less than 6.8%, which meets the heterogeneous epitaxial growth conditions. Therefore, even at a lower deposition temperature, due to the template effect of zinc oxide, the vanadium dioxide film can still grow normally. This is very beneficial to reducing the deposition temperature of the vanadium dioxide thin film and reducing the production cost.

In the preparation steps of each film layer, the method of magnetron sputtering is used to prepare multi-layer films. The preparation system parameters are as follows: the background vacuum pressure of the magnetron sputtering system is less than 8×10 ^-3 Pa; Or DC sputtering method; the total pressure of the working gas is kept at 0.2-1.5Pa during sputtering.

The detailed description of each step is as follows:

1) Glass substrate cleaning and treatment: After the glass substrate is cleaned and before the film deposition, the glass substrate is heated to 200-500°C, and this temperature is kept constant during the film preparation process.

2) Preparation of the diffusion barrier layer: a silicon target or a silicon dioxide ceramic target can be used as the cathode sputtering material. When a silicon target is used, the sputtering method is preferably radio frequency sputtering. When the sputtering chamber is fed with Ar gas, it is also fed with O ₂ gas (purity higher than 99.9%), and the partial pressure ratio or flow rate of O ₂ gas and Ar gas The ratio is 0.1-0.4:1; when a silicon dioxide ceramic target is used, the sputtering method is preferably non-reactive radio frequency sputtering, and the sputtering working gas is Ar gas.

3) Preparation of zinc oxide seed crystal layer: it can be prepared in two ways. One is to use zinc oxide ceramic target as the cathode sputtering material, and the sputtering method is preferably radio frequency sputtering; the working gas is Ar gas. Another way is to use a metal zinc target, the sputtering power supply is preferably DC sputtering, the working gas is a mixed gas of Ar gas and _O2 , and the partial pressure ratio or flow rate ratio of _O2 gas to Ar gas is 0.1 to 0.4: 1.

4) Preparation of vanadium dioxide thermochromic layer: There are also many ways to select the target material, including the use of metal vanadium target, vanadium dioxide target and vanadium pentoxide ceramic target. If vanadium pentoxide ceramic target is used, direct current sputtering can be used to deposit in a mixed atmosphere of Ar gas and H ₂ gas, the percentage of H ₂ gas and Ar mixture H ₂ /(Ar+H ₂ )=2%～ 8%. ; If a metal vanadium target or a vanadium dioxide target is used as the sputtering target material, the sputtering method can be direct current or radio frequency, preferably radio frequency, and an appropriate amount of high-purity O ₂ gas, the partial pressure ratio or flow rate ratio of O ₂ gas to Ar gas is 0.03-0.3:1.

The thickness requirements of each film layer are as follows: the thickness of the diffusion barrier layer is 50-100 nanometers, the thickness of the zinc oxide seed layer is 10-200 nanometers, and the thickness of the vanadium dioxide thermochromic layer is 20-200 nanometers.

The zinc oxide seed crystal layer adopted in the present invention has a low crystallization temperature and a good match between the lattice constant and the vanadium dioxide, and is especially suitable for the heteroepitaxial growth of the vanadium dioxide thin film, thereby effectively reducing the deposition temperature of the vanadium dioxide thin film, simplifying the The preparation process of vanadium dioxide smart glass reduces costs, saves energy consumption, and greatly reduces the difficulty of the industrialization process of vanadium dioxide smart glass.

Detailed ways

The content of the present invention will be further described below in conjunction with the examples, but the scope of protection of the present invention is not limited to the following examples, and any technical solutions that are equivalent to the content of the present invention all belong to the scope of protection of this patent.

Example 1

The multilayer film was prepared by magnetron sputtering, and the magnetron sputtering system included a transition chamber and a main sputtering chamber (45 cm in diameter). The main sputtering chamber is connected with a molecular diffusion pump, and the ultimate vacuum is 2.0×10 ^-6 Pa. The sputtering chamber has three target positions for three different 2-inch diameter targets. Each target position is inclined upward at an angle of 30°, and can be co-sputtered upwards in a confocal manner or sputtered upwards in a three-target independent manner. The sample stage can be heated up to over 600°C and can keep rotating continuously during the sputtering process.

In the experiment, the substrate was float glass. The substrate was ultrasonically cleaned in anhydrous alcohol and acetone for 5 minutes, then dried with nitrogen, fixed on the sample stage and placed in a transitional vacuum chamber for vacuuming. After 10 minutes, transfer to the sputtering vacuum chamber via a magnetic transfer rod. Turn on the substrate heating system, heat the float glass sheet to 400°C and keep it constant.

The first is the preparation of the silica diffusion barrier layer. The preparation conditions are as follows: adopt silicon dioxide ceramic target, the working atmosphere is high-purity Ar gas (purity: 99.9995%), inject in the sputtering chamber with the flow velocity of 30sccm and make the sputtering chamber working pressure keep as 0.6Pa; RF power Set to 150W, sputtering for 160 minutes. At this time, the thickness of the _SiO2 film layer deposited on the glass substrate is about 90nm.

Next is the preparation of the zinc oxide seed layer. The preparation conditions are as follows: use ZnO ceramic target material, the working atmosphere is high-purity Ar gas (purity: 99.9995%), inject it into the sputtering chamber with a flow rate of 30 sccm and keep the working pressure of the sputtering chamber at 0.6Pa; radio frequency sputtering The power was set at 30W, and the sputtering was performed for 20 minutes. At this time, the thickness of the ZnO film layer deposited on the glass substrate is about 50 nm.

The last is the preparation of vanadium dioxide thermochromatography. The preparation conditions are as follows: a metal vanadium target (target purity 99.9%) is used for reactive deposition in a mixed gas of Ar gas (flow rate: 30 sccm) and O _gas (flow rate: 2.1 sccm), the radio frequency power is set to 160W, and sputtering 90 minutes. VO ₂ film thickness is about 85nm.

X-ray diffraction results show that: VO ₂ thin film grows on ZnO in a heteroepitaxial manner, and the (020) plane of VO ₂ grows on the (002) plane of ZnO. The electrical test results show that the phase transition temperature of _VO2 thin film occurs around 65°C, and the magnitude _of resistance change before and after the phase transition is about 100 times.

Example 2

The vacuum deposition system and substrate cleaning and installation process are the same as those in Embodiment 1. Before thin film sputtering, the glass substrate was heated to 300 °C and kept constant.

Preparation of silica diffusion barrier layer. Silicon is used as the cathode sputtering material, radio frequency sputtering, and the sputtering power is set to 100W. When the sputtering chamber is fed with Ar gas, O ₂ gas (purity higher than 99.9%) is also fed into the sputtering chamber. The flow rate of Ar gas is 30 sccm, and the flow rate of O ₂ gas is 7.5 sccm. After sputtering for 20 minutes, the thickness of the deposited SiO ₂ film is about 60nm.

Preparation of ZnO seed layer. The preparation conditions are as follows: metal zinc is used as the target material (purity: 99.9%), and the working atmosphere is a mixed gas of high-purity Ar gas (purity: 99.9995%) and high-purity _O2 gas (purity: 99.9%). Ar gas was injected into the sputtering chamber at a flow rate of 30 sccm and the working pressure of the sputtering chamber was maintained at 0.6 Pa; the flow rate of _O2 gas was 6.5 sccm. The DC sputtering power was set to 120W, and the sputtering was performed for 30 minutes. At this time, the thickness of the ZnO film deposited on the glass substrate is about 120 nm.

The last is the preparation of vanadium dioxide thermochromatography. The preparation conditions are as follows: use vanadium pentoxide ceramics as the sputtering target (purity 99.5%), pass in a mixed gas of Ar gas and H ₂ gas [mixing ratio H ₂ /(Ar+H ₂ )=5%], The flow rate is 30 sccm, DC sputtering, the sputtering power is set at 120W, and the sputtering is performed for 60 minutes. VO ₂ film thickness is about 140nm.

The results of X-ray diffraction showed that the (020) plane of VO ₂ film grew along the (002) plane of ZnO. The electrical test results show that the phase transition temperature of VO ₂ thin film occurs around 65°C, the surface resistance changes about 100 times, and the phase transition performance is close to that of VO ₂ thin film prepared under normal conditions (deposition temperature higher than 500°C).

Example 3

The vacuum deposition system and substrate cleaning and installation process are the same as those in Embodiment 1.

Before thin film sputtering, the float glass substrate was heated to 250 °C and kept constant.

The preparation of the silicon dioxide diffusion barrier layer is exactly the same as in Example 1.

The preparation of the zinc oxide seed layer was the same as in Example 2, and the sputtering was performed for 50 minutes. At this time, the thickness of the ZnO film deposited on the glass substrate is about 200nm.

The last is the preparation of vanadium dioxide thermochromatography. The preparation conditions are as follows: using vanadium dioxide as a sputtering target (purity 99.5%), reactive deposition is carried out in a mixed gas of Ar gas (flow rate 30 sccm) and O ₂ gas (flow rate 1.5 sccm). The RF power was set to 100W, and the sputtering was performed for 100 minutes, and the thickness of the VO ₂ film was about 35nm.

X-ray diffraction results and electrical test results are the same as in Example 2.

Example 4

The vacuum deposition system and substrate cleaning and installation process are the same as those in Embodiment 1.

Before thin film sputtering, the float glass substrate was heated to 200°C and kept constant.

The preparation conditions of the _SiO2 diffusion barrier layer are the same as in Example 1. After sputtering for 90 minutes, the thickness of the deposited _SiO2 film is about 50nm.

The preparation of the ZnO seed layer is the same as in Example 2. After sputtering for 5 minutes, the thickness of the ZnO film deposited on the glass substrate is about 20 nm.

The last is the preparation of VO2 thermochromatography. The preparation conditions are the same as in Example 2. After sputtering for 80 minutes, the thickness of the VO2 film is about 180nm.

X-ray diffraction results and electrical test results are the same as in Example 2.

Claims (9)

1. a low-temperature deposition method of vanadium dioxide thin film on glass, with glass as substrate, it is characterized in that comprising the following steps successively: 1) cleaning and processing of glass substrate; 2) on glass substrate, first deposit a 3) depositing a zinc oxide seed crystal layer on the silicon dioxide diffusion barrier layer; 4) finally depositing a vanadium dioxide thermochromic thin film layer on the zinc oxide seed crystal layer. 2. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 1, it is characterized in that the thickness of silicon dioxide diffusion barrier layer is 50～100 nanometers, the thickness of zinc oxide seed crystal layer is 10～200 nanometers , the thickness of the vanadium dioxide thermochromic layer is 20-200 nanometers. 3. The low-temperature deposition method of vanadium dioxide film on glass according to claim 1, characterized in that after the glass substrate is cleaned in step 1), before film deposition, the glass substrate is heated to 200～500°C, And keep this temperature constant during the film preparation process. 4. according to claim 1 or 2 described vanadium dioxide film on the low-temperature deposition method on glass, it is characterized in that step 2) and step 3), step 4) all adopt the method for magnetron sputtering to prepare multilayer film , The background vacuum pressure of the magnetron sputtering system is less than 8×10 ^-3 Pa, the sputtering power supply adopts radio frequency or intermediate frequency or DC sputtering mode, and the total pressure of the working gas during sputtering is kept at 0.2-1.5Pa. 5. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 4, it is characterized in that the preparation of step 2) diffusion barrier layer adopts silicon as cathode sputtering material, and sputtering mode is radio frequency sputtering, working gas The mixed gas of high-purity O ₂ gas and Ar gas is adopted, and the partial pressure ratio or flow rate ratio of O ₂ gas and Ar gas is 0.1-0.4:1. 6. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 4, it is characterized in that the preparation of step 3) zinc oxide seed crystal layer adopts zinc oxide ceramic target as cathode sputtering material, and sputtering mode is radio frequency For sputtering, the working gas is high-purity Ar gas. 7. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 4, it is characterized in that the preparation of step 3) zinc oxide seed crystal layer adopts metal zinc target as cathode sputtering material, and sputtering power supply is DC sputtering The working gas is a mixed gas of high-purity Ar gas and O ₂ , and the partial pressure ratio or flow rate ratio of O ₂ gas and Ar gas is 0.1-0.4:1. 8. the low temperature deposition method of vanadium dioxide thin film on glass according to claim 4, it is characterized in that the preparation of step 4) vanadium dioxide thermochromic film layer adopts metal vanadium target or vanadium dioxide target as cathode sputtering material , The sputtering method is radio frequency sputtering; the working gas is a mixed gas of high-purity Ar gas and O ₂ , and the partial pressure ratio or flow rate ratio of O ₂ gas and Ar gas is 0.03-0.3:1. 9. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 4, it is characterized in that step 4) the preparation of vanadium dioxide thermochromic thin film layer adopts metal vanadium target as cathode sputtering material, and sputtering power supply is For DC sputtering, the working gas is a mixed gas of high-purity Ar gas and O ₂ , and the partial pressure ratio or flow rate ratio of O ₂ gas and Ar gas is 0.1-0.4:1.