Sputtering pressure dependent photocatalytic properties of TiO2 thin films T. Takahashi, K. Prabakar, T, Nezuka, T. Yamazaki, T. Nakashima, Y. Kubota, A. Fujishima J. Vac. Sci. Technol. A, 24(4), 1161-1165 (2006). published in July