Pulsed Laser Preparation Of Nano-titanium Dioxide Thin Films And Their Optical And Electrical Properties

Titanium oxide is widely investigated and employed as a functional material in a number of applications such as pigments, gas sensing, photovoltaics, photocatalytic and photo-electrochromic devices and self-cleaning surfaces. The bulk material of titanium and titanium oxide does not easily exhibit photoluminescence (PL) signal at room temperature, which limits the application of titanium oxide in photo electronic integration, but nano-sized titanium oxide can have PL signals resulting from electric transitions related to surface states. Vertical pulsed laser deposition (VPLD) was utilized here to prepare titanium oxide nanoparticles and nanofilms on glass substrates and titanium targets. Laser-induced forward transfer (LIFT) was also adopted to prepare titanium oxide nanofilms on titanium target at ambient temperature and atmospheric pressure. The influence of various method, laser output power, ambient gas during film formation on morphology and fluorescence characteristics of the films was investigated. The changes in the morphology, structure and chemical composition of the layers were studied by SEM, XRD and Raman spectroscopy. Strong variations in structure with preparation method and ambient gas are observed. In argon, porous films of mutually agglomerated titanium oxide nanoparticles are obtained. By VPLD in air, a compact network of hyperbranched TiOx nanowires(TiOxHBNWs) on Ti target is observed. While by LIFT, the films consist of a network of hyperbranched nanowires. In oxygen, porous films are made up of mutually agglomerated titanium oxide nanoparticles and nanowires. XRD and Raman measurements revealed that the films obtained via pulsed laser are made up of diversified titanium oxide. When excited by radiation of 385 nm wavelength, it is found that all samples which have photoluminescence characteristic exhibit the characteristic emission peak at about 440 nm. Nano-titanium oxide films prepared through LIFT in air ambient and VPLD in oxygen ambient with output power of 12.9W exhibited strong fluorescence emission intensity which can be employed to prepare photoluminescence materials. The films prepared via LIFT in oxygen ambient were directly applied to photoelectric cells. Photocurrent response of the cells showed that the films have potential applications to solar cells.