Principle of Reactive Magnetron Sputtering
Magnetic sputtering is widely used in industrial coating (Yang & Yu 7). The main reason for the increased demand of the magnetron sputtering is due to the rising demand for functional films (Zhao et al. 3397). According to Nyberg et al. (106) and Raniero et al. (172), the magnetron sputtering outperforms films made by deposition of physical vapor process. The main feature of reactive magnetron sputtering is that it has a reduced rate of deposition of compounds that result from a reactive mode (Sicha et al. 3793). The principle applied in reactive magnetron sputtering entails the process of sputtering gas ions from plasma and transferring to a target surface for deposition (Aubry et al. 7709). The mechanism of sputtering entails stepping up of gas ions out of the plasma and moved to a target (Chaiyankun & Pichet 580). The target consists of the materials that are supposed to be deposited (Noguchi et al. 43). The materials are detached from the target and then deposited on a substrate that is located in the vicinity. The mechanism of the sputtering takes place on a closed recipient in which before the deposition begins, the recipient is pumped down a vacuum pressure (Okimura 286). The stepping up of the ions can be achieved by application of bias-voltage of ±100V to the substrate.
Effect of Sputtering Parameters on Quality of Ti02 Thin Film Page
The sputtering parameters affect the quality of TiO2 thin film page (Turkevyeh et al. 2387). According to Can et al. (744), the deposition of the film depends on the substrate temperature, the pressure applied, the duration of deposition, and the sputtering power applied. For instance, the chamber pressure affects the size of the hysteresis. Increased pumping speed increases the volume of the chamber and decreases the size of the hysteresis loop (Doong et al. 192, Noguchi et al. 41 & Zhang et al. 192). The increased yield of TiO2 increases the rate of transition from oxide to the metallic mode; hence, decreasing the size of the hysteresis (Heft & Pfuch 2852).
Pulse DC also affects the deposition (Musil et al. 103). Kolouch et al. (350) carried an experiment in which transparent films of TiO2 were made by use of reactive magnetron. A mixture of Ar +O2 and pulsed DC with an equipped Ti (99.5) of 25mm in diameter was used. The magnetron was subjected to a pulsed DC accompanied by power supply of 5kw. An increase in pulsed DC resulted in increased deposition in the sputtering (Kolouch et al. 359). The experiment pointed that the chemical effect of the gas mixture and pulsed DC determines the final quality of the film (Vancoppenolle et al. 943). Gases such as nitrogen are fed to the closed chamber with the argon gas. The chemical reaction results in formation of nitridic or oxidic films. Ions are accelerated to the target surface and the sputter material using a pulsed DC (Vancoppenolle et al. 944).
Growing Crystalline TiO2 thin Film in Low Temperature
Crystalline TiO2 has different polymorphs, which include anatase, rutile and brookite (Zhang et al. 328). There are different methods used to grow the crystalline TiO2 (Belkind et al. 163). In order to grow crystalline TiO2 at low temperatures, the deposition of TiO2 is placed on substrates that are not heated (Kadlec 729). According Magnus et al. (4) voltage of 400 V and sputtering DC current varies from 0.5 to 1.00 provide suitable conditions for the process of developing the thin film. The crystallinity of the thin film depends on the sputtering current used (Zhao et al. 3395). The time of deposition does not affect the crystallization of the thin film. For example, the crystalline of the thin film of the anatase increases as the current increases (Li & Miyaka 3662).
In the standard thin filmmaking, temperatures above 300 °C are required in the deposition phase and the post-treatment in order to form TiO2 thin films (Liao 7258). However, recent studies have presented a shift in which low temperature is used in the reactive magnetron (Musil & Kadlec 729). For instance, TiO2 films can be grown at room temperature using reactive radio frequency. Kadlec (729) conducted an experiment to produce nanocrystalline TiO2 using low temperatures. The substrates used included plane slides of glass that had the right surface roughness. In addition, DCRMS system was used to deposit TiO2 films (Kadlec 731). The growth of the film involved placing the TiO2 deposits at room temperature (Kerdiles & Rizk 603). The deposits of TiO2 were radiated at 300 W in which a wavelength ranging from 250 to 200 nm was applied. The duration of deposition varied for the different processes of thin TiO2 filmmaking.
The deposition of nanocrystalline TiO2 at room temperature resulted to a high transmittance luminous (Kadlec 729). The film also had high photocatalytic activity of TiO2. The film structure was investigated to ascertain its quality. According to Liao (7258), growth of film requires temperatures above 300°C. Zhang et al. (84) noted that time variation does not affect the crystalline structure. For instance, the crystalline structure was found to be strongly correlated to the sputtering current (Kadleck, 730). At room temperature, the films were of high quality.
The experiment was conducted using different sputtering current and varying deposition time. In all experiments, room temperature was maintained. TiO2 thin films were produced in all deposition time conditions. Size of the grain ranged from 10-30 nm. In the case of different sputtering currents, the size significantly increased with increase in the sputtering current (Wu & Chung (1595). Therefore, the deposition time and temperature do not have effect on the crystal growth. Thus, films of TiO2 can be developed by the use of direct current pulse in which magnetron sputtering is carried at room temperature (Baroch et al. 108).
Conclusion
In conclusion, Ranga (1077) noted that magnetic sputtering is widely used in many industrial coating. The reactive magnetic sputtering has become a process of choice due to the quality thin films it produces at low temperature. In addition, the increased demand of the magnetron sputtering is due to increased demand for functional films. The use of low temperature in the growth of the film presents an alternative of cost reduction.
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