Titanium dioxide (TiO<sub>2</sub>) thin films were grown on SiO2 substrates by DC magnetron sputtering combine with thermal oxidation. A series O<sub>2</sub>:Ar ratio from 0:50 to 25:25 and a set of post thermal oxidation at 380~550 oC were tested respectively. The transmittance of titanium dioxide thin films changed with the sputtering parameters and thermal oxidation process in the range. The experiment results showed that reactive gas concentration, sputtering power, sputtering time, film thickness, oxidation temperature and oxidation time had great influence on optical properties of the titanium dioxide thin films. Finally a typical O2:Ar ratio of 20:30~25:25 and a sputtering time of 5 min were selected as the optimized experimental conditions. The optical parameters include: ultraviolet absorption, visible transmittance and the absorption band gaps of the titanium dioxide samples are about 100%, 85% and 4.15 eV.
Zinc oxide thin films with Ag dopant (ZnO:Ag) were prepared on n-type silicon and quartz substrates by co-sputtering and post annealing. The ZnO:Ag thin films were measured by means of ultraviolet-visible spectrophotometer, fluorescence spectrophotometer, Hall Effect and I-V experiment. Optical measurement results show that the average transmittance of ZnO:Ag thin films in the wavelength range of 200~850 nm decrease with the increase of Ag content. The Hall effect measurement results show that the corresponding hole concentration of the ZnO:Ag film is 1.29×10<sup>21</sup> cm<sup>-3</sup> . This reveals that the ZnO:Ag film is really p-type behavior. The sensitivity of p-ZnO:Ag/n-Si heterojunction structure is 0.1985. The devices based on p-type ZnO:Ag thin films have a good ultraviolet light (360 nm) sensitive properties.
VO<sub>2</sub> thin films were prepared on ZnO buffer layers by DC magnetron sputtering at room temperature using vanadium target and post annealing at 400 °C. The ZnO buffer layers with different thickness deposited on glass substrates by magnetron sputtering have a high visible and near infrared optical transmittance. The electrical resistivity and the phase transition properties of the VO<sub>2</sub>/ZnO composite thin films in terms of temperature were investigated. The results showed that the resistivity variation of VO<sub>2</sub> thin film with ZnO buffer layer deposited for 35 min was 16 KΩ-cm. The VO<sub>2</sub>/ZnO composite thin films exhibit a reversible semiconductor-metal phase transition at 48 °C.
The Nb-doped VO<sub>2</sub> thin films were successfully prepared on the glass substrates by ion beam co-sputtering at room temperature and post annealing under the air condition. The effects of the preparation processing and Nb doping on the thermal hysteresis loop and phase transition temperature of the VO<sub>2</sub> thin films were analyzed by resistancetemperature measurement. The results show that Nb doping significantly changes the surface morphologies of VO<sub>2</sub> thin films, and Nb-doped VO<sub>2</sub> thin films exhibit VO<sub>2</sub>(002) preferred orientation growth with greatly improved crystallinity and orientation. Compared with pure VO<sub>2</sub>, the phase transition temperature of Nb-doped VO<sub>2</sub> thin films drops to 40 ºC, and the width of thermal hysteresis loop narrows to 8 ºC. It is demonstrated that Nb-doped VO<sub>2</sub> thin films prepared by ion beam co-sputtered at room temperature have an obvious thermal sensitive effect, and keep a good characteristic from metal to semiconductor phase transition.
Proc. SPIE. 8418, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Smart Structures, Micro- and Nano-Optical Devices, and Systems
VO<sub>2</sub> thin films were prepared on soda-lime glass substrates by DC magnetron sputtering at room temperature using vanadium target and post annealing in air. X-ray diffraction and FTIR spectroscopy analyses showed that the films obtained at the optimized parameters have high VO<sub>2</sub> (011) orientation. Both low temperature deposition and post annealing method were beneficial to grow the nano-films with pure VO<sub>2</sub> phase-structure and composition. Metalinsulator transition properties of the VO<sub>2</sub> films in terms of infrared transmittance, transmittance variation and film thickness were investigated under varying annealing temperature. Results showed that infrared transmittance variation and transition temperature of the nano-films were significantly improved and reduced respectively. Therefore, this study was able to develop practical low-cost preparation methods for high-performance intelligent energy-saving thin films.