CN101280413A - A low-temperature deposition method of vanadium dioxide thin film on glass - Google Patents

Abstract

The invention provides a low-temperature deposition method of a vanadium dioxide thin film on a glass substrate by utilizing the template induction principle of crystal growth. Taking glass as the substrate, the following steps are sequentially included: (a) cleaning and pretreatment of the glass substrate; (b) preparing a silicon dioxide diffusion barrier layer; (c) preparing a metal oxide buffer layer; (d) preparing a silicon dioxide Vanadium thermochromatography. The metal oxide buffer layer material used in the present invention is transparent in the visible light region, has a low crystallization temperature, and can match the crystal form with vanadium dioxide well, and can produce template induction during the growth process of the vanadium dioxide film, thereby greatly reducing the amount of vanadium dioxide film deposition temperature. Simplify the preparation process of vanadium dioxide smart glass, reduce costs, save energy consumption, and greatly reduce 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 building enclosure components (doors and windows, walls, roof and ground), doors and windows have the worst thermal insulation performance, which is one of the main factors affecting the indoor thermal environment and building energy saving. 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 inks, pigments, safety equipment, temperature indicators, 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 object of the present invention is to provide a low-temperature deposition method of vanadium dioxide film on a glass substrate by utilizing the principle of template induction of crystal growth.

The present invention comprises the following steps in turn: (a) cleaning and pretreatment of the glass substrate; (b) preparing a silicon dioxide diffusion barrier layer; (c) preparing a metal oxide buffer layer; (d) preparing a vanadium dioxide thermochromic layer .

The silicon dioxide diffusion barrier layer can prevent impurity ions in the glass substrate from diffusing into the metal oxide buffer layer and the vanadium dioxide thermochromic thin film layer under high temperature conditions (higher than 200 ° C), forming an uncontrollable ion-doped 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.

The metal oxide buffer layer is a semiconductor material that is transparent in the visible light region, has a low crystallization temperature, and has a crystal form that can well match vanadium dioxide, preferably tin oxide (SnO ₂ ) and indium oxide (In ₂ O ₃ ). One of them, or a mixture of them doped in a certain proportion, such as ITO (mass ratio SnO ₂ :In ₂ O ₃ =1:9). These buffer layer materials can form polycrystals at about 300°C, and the crystal phase is a cubic phase, which can be well matched with the crystal form of vanadium dioxide (cubic phase at high temperature). Under the induction of underlying SnO ₂ , In ₂ O ₃ , or ITO polycrystalline films, vanadium dioxide films can grow normally even at lower deposition temperatures. This will be beneficial to reduce the deposition temperature of the vanadium dioxide film.

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 10 ^-2 Pa; Sputtering mode; the total pressure of the working gas is kept at 0.2-1.5Pa during sputtering.

The details of each step are as follows:

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

b) Preparation of silicon dioxide diffusion barrier layer: silicon target or silicon dioxide ceramic target can be used as 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.

c) Preparation of the metal oxide buffer layer: it can be prepared in two ways. One is to use tin oxide or indium oxide (or a mixture of the two, such as ITO) ceramic target as the cathode sputtering material. The sputtering method can be DC sputtering, which can be directly deposited in an Ar gas atmosphere. Another way is to use one of the metal tin target, metal indium target, and tin-indium alloy target. The sputtering power supply can be DC or radio frequency sputtering, preferably radio frequency sputtering; the working gas is filled with Ar gas, O ₂ must also be charged, and the partial pressure ratio or flow rate ratio of O ₂ gas to Ar gas is 0.1-0.5:1.

d) Preparation of vanadium dioxide thermochromic layer: There are many ways to select the target material, including metal vanadium target, vanadium dioxide target and vanadium pentoxide ceramic target. If vanadium pentoxide ceramic target is used, DC sputtering can be used, the working gas is a mixed gas 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 DC or radio frequency, preferably radio frequency, and an appropriate amount of Ar gas must also be introduced during the sputtering process. 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 metal oxide buffer layer is 10-200 nanometers, and the thickness of the vanadium dioxide thermochromic layer is 20-250 nanometers.

The metal oxide buffer layer material used in the present invention is transparent in the visible light region, has a low crystallization temperature, and can match the crystal form with vanadium dioxide well, and can produce template induction during the growth process of the vanadium dioxide film, thereby greatly reducing the amount of vanadium dioxide film deposition temperature. Simplify the preparation process of vanadium dioxide smart glass, reduce costs, save energy consumption, and greatly reduce 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

Multilayer thin films were prepared by magnetron sputtering. The magnetron sputtering system consists of 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 diffusion barrier layer silicon dioxide. The preparation conditions are as follows: use a silicon dioxide ceramic target material, the working atmosphere is high-purity Ar gas (purity: 99.9995%), inject it into the sputtering chamber at a flow rate of 30 sccm and keep the working pressure of the sputtering chamber at 0.6Pa; The power was set to 150W, and the sputtering was performed 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 metal oxide buffer layer. The preparation conditions are as follows: use the ITO ceramic target material, the working atmosphere is high-purity Ar gas (purity: 99.9995%), inject it into the sputtering chamber at a flow rate of 30 sccm and keep the working pressure of the sputtering chamber at 0.6Pa; DC sputtering The power was set at 30W, and sputtering was performed for 40 minutes. At this time, the thickness of the ITO film layer deposited on the glass substrate is about 120 nm.

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

The results of electrical tests show that the phase transition temperature of the _VO2 thin film prepared at 400 °C occurs near 65 °C, the thermochromic properties of the film are good, and the resistance change before and after the phase transition exceeds 100 times, which is different from that prepared at 500 °C. VO ₂ thermochromic film equivalent.

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 float glass substrate was heated to 350 °C and kept constant.

Preparation of Diffusion Barrier Silica. 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 metal oxide buffer layers. The preparation conditions are as follows: use a tin oxide ceramic target material, the working atmosphere is high-purity Ar gas (purity: 99.9995%), inject it into the sputtering chamber at a flow rate of 30 sccm and keep the working pressure of the sputtering chamber at 0.6Pa; Set to 120W and sputter for 60 minutes. At this time, the thickness of the SnO ₂ film deposited on the glass substrate is about 80nm.

Preparation of vanadium dioxide by thermochromatography. The preparation conditions are as follows: use vanadium pentoxide ceramics as the sputtering target (purity 99.5%), feed a mixed gas of Ar gas and H ₂ gas [mixing ratio H ₂ /(Ar+H ₂ )=5%], flow rate 30 sccm, direct current sputtering, sputtering power set to 120W, sputtering for 80 minutes. VO ₂ film thickness is about 180nm.

The results of electrical tests show that the phase transition temperature of this _VO2 thin film prepared at 350 °C occurs around 65 °C. The thermochromic performance of the film is good, and the resistance change before and after the phase transition exceeds 100 times.

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 280 °C and kept constant.

The preparation of silicon dioxide as a diffusion barrier layer is the same as in Example 1. After sputtering for 85 minutes, the thickness of the deposited SiO ₂ film is about 50nm.

Preparation of metal oxide buffer layers. The preparation conditions are as follows: use an indium oxide ceramic target material, the working atmosphere is high-purity Ar gas (purity: 99.9995%), inject it into the sputtering chamber at a flow rate of 30 sccm and keep the working pressure of the sputtering chamber at 0.6Pa; Set to 50W and sputter for 10 minutes. At this time, the thickness of the In ₂ O ₃ film deposited on the glass substrate is about 30 nm.

Preparation of vanadium dioxide by thermochromatography. Vanadium dioxide was used as a sputtering target (purity 99.5%), and reactive deposition was 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, sputtering was performed for 200 minutes, and the thickness of the VO ₂ film was about 70nm.

The results of electrical tests show that the phase transition temperature of VO ₂ film occurs around 65℃. The thermochromic performance of the film is good, and the resistance change before and after the phase transition exceeds 100 times.

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 250 °C and kept constant.

The preparation of silicon dioxide as a diffusion barrier layer is the same as in Example 1. After sputtering for 85 minutes, the thickness of the deposited SiO ₂ film is about 50nm.

Preparation of metal oxide buffer layers. The preparation conditions were as follows: Reactive deposition was carried out in a mixed gas of Ar gas (flow rate 30 sccm) and O ₂ gas (flow rate 4.3 sccm) using a metal tin target. The RF power was set to 100W, and the sputtering was performed for 50 minutes. At this time, the thickness of the SnO ₂ film deposited on the glass substrate was about 160nm.

The preparation of thermochromatographic vanadium dioxide is the same as in Example 3. After sputtering for 200 minutes, the thickness of the VO ₂ film is about 70nm.

The results of electrical tests show that the phase transition temperature of the VO ₂ thin film occurs around 65°C, the resistance before and after the phase transition changes more than 100 times, and the thermochromic properties of the VO ₂ thin film are good.

Example 5

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 of silicon dioxide as a diffusion barrier layer is the same as in Example 1. After sputtering for 170 minutes, the thickness of the deposited SiO ₂ film is about 100nm.

Preparation of metal oxide buffer layers. The preparation conditions are as follows: a tin-indium alloy target is used, and tin accounts for 8 wt% (consistent with the metal component in the ITO ceramic target). Reactive deposition was performed in a mixed gas of Ar gas (flow rate 30 sccm) and O ₂ gas (flow rate 3.2 sccm). The radio frequency power was set to 80W, and the sputtering was performed for 30 minutes. At this time, the thickness of the tin oxide and indium oxide mixture film (ITO film) deposited on the glass substrate was about 80 nm.

The preparation of thermochromatographic vanadium dioxide is the same as in Example 3. After sputtering for 100 minutes, the thickness of the VO ₂ film is about 35nm.

The results of electrical tests show that the phase transition temperature of VO ₂ thin film occurs around 65°C, the resistance change before and after the phase transition is close to 100 times, and the thermochromic performance of VO ₂ thin film is good.

Claims (10)

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: (a) cleaning and pretreatment of glass substrate; (b) preparation of silicon dioxide diffusion Barrier layer; (c) preparing a metal oxide buffer layer, the metal oxide buffer layer is a semiconductor material that is transparent in the visible light region, has a low crystallization temperature, and has a crystal form that can match vanadium dioxide; (d) prepares a vanadium dioxide thermochromic layer . 2. The low-temperature deposition method of vanadium dioxide thin film on glass according to claim 1, characterized in that: the metal oxide layer buffer layer material is one of the following: tin oxide, indium oxide, and tin oxide and indium oxide mixture. 3. The low-temperature deposition method of vanadium dioxide thin film on glass according to claim 2, characterized in that: the mass ratio of the mixture of tin oxide and indium oxide is tin oxide:indium oxide=1:9. 4. according to claim 1 or 2 or 3 described vanadium dioxide film on the low-temperature deposition method on glass, it is characterized in that: the thickness of silicon dioxide diffusion barrier layer is 50～100 nanometers, the thickness of metal oxide buffer layer film The thickness is 10-200 nanometers, and the thickness of the vanadium dioxide thermochromic layer is 20-250 nanometers. 5. The low-temperature deposition method of vanadium dioxide thin film on glass according to claim 1, characterized in that after the glass substrate is cleaned in step a), before the thin film deposition, the glass substrate is heated to 200～500°C, And keep this temperature constant during the film preparation process. 6. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 1 is characterized in that in step b) and step c), step d) all adopts the method for magnetron sputtering to prepare multilayer thin film, magnetic The background vacuum pressure of the controlled sputtering system is less than 10 ^-2 Pa; the sputtering power supply adopts radio frequency, intermediate frequency or DC sputtering; the total pressure of the vacuum chamber is kept at 0.2-1.5Pa during sputtering. 7. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 6 is characterized in that in step b) the preparation of silicon dioxide diffusion barrier layer adopts silicon target or silicon dioxide ceramic target as cathode sputtering Material. 8. the low temperature deposition method of vanadium dioxide thin film on glass according to claim 6, it is characterized in that in step c) the preparation of metal oxide buffer layer adopts one of following as cathode sputtering material: tin oxide or oxide Indium or a mixture of both ceramic targets. 9. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 6, it is characterized in that in step c) the preparation of metal oxide buffer layer adopts one of following as cathode sputtering material: metal tin target, Metal indium target, tin indium alloy target. 10. the low-temperature deposition method of vanadium dioxide thin film on glass according to claim 6 is characterized in that in step d), the preparation of vanadium dioxide thermochromic layer adopts one of following as cathode sputtering material: vanadium target, Vanadium dioxide target, vanadium pentoxide ceramic target.