Titanium Dioxide-Based Optoelectronic Devices

Titanium dioxide (TiO2) is an indirect bandgap semiconductor. Because of its unique properties in physics, chemistry, optics etc., TiO2 has been studied extensively for the applications in photocatalysis, solar cells and sensors, etc. In this thesis, by summarizing the study of titanium oxide film and related devices, titanium oxide-related optoelectronic devices were studied, and the main results are listed below:1. The TiO2 films were prepared on glass substrates in an atomic layer deposition (ALD) technique. Then a metal-insulator-semiconductor-insulator-metal (MISIM) structured ultraviolet photodetector was prepared on the films. Meanwhile, a metal-semiconductor-metal (MSM) structured photodetector was also fabricated under the same conditions for comparison. The responsivity of the MISIM structured photodetector is effectively improved compared with the MSM structured photodetector. It is shown that the improvement can be attributed to the carrier multiplication process occurred in the insulator layer under high electric field. The results may open a door for high performance titanium dioxide based photodetectors.2. An n-TiO2/n-Si isotype heterojunction has been fabricated by depositing TiO2 thin films onto n-Si substrates in an atomic layer deposition technique. Obvious photovoltaic behaviors have been observed in this isotype heterojunction. The open circuit voltage and short circuit current can reach 123 mV and 20μA/cm2, respectively, and the conversion efficiency is about 0.00051%. The photovoltaic behaviors found in the titanium-based isotype heterojunction have not reported before, and this work may provide a possible route to simple and cheap photovoltaic devices.