Study of Modified Optical Properties of TiO2/Au/TiO2 multilayered thin films by chemical vapor deposition

Abstract

Wide band gap semiconductors have efficient UV absorption and very low absorption in the visible spectrum. The surface plasmon resonance (SPR) phenomenon of gold is used to change the optical properties of TiO2 in this study. In this study metal sandwiched planar (TiO2/Au/TiO2) structures were studied using a variety of optical techniques, including spectroscopic ellipsometry, UV/Vis absorption, and photoluminescence spectroscopy (PL). UV/Vis spectroscopy of TiO2/Au/TiO2 unfolded the presence of two broad bands in the visible range that were not present in TiO2 thin film. This was attributed to improved interband and plasmon resonance oscillations of Au in a dielectric environment. Photoluminescence spectroscopy revealed three types of luminescent centers in TiO2 around 351nm, 520nm and in the IR range. PL also revealed the introduction of near band gap edge defects as well as a rounded peak in composite films. UV/Vis spectroscopy revealed enhanced absorption in the visible region for composite films compared to a simple absorption spectrum for TiO2 only. 1nm thickness showed a drastic amount of absorption intensity compared to any other thickness. With the increase in the thickness of gold, this absorption intensity can be observed to be decreasing. In composite films with thickness of Au to be 5nm, 10nm and 20nm surface plasmon resonance modes are observed around 730nm, 670nm and 620nm respectively showing a shift in SPR modes towards smaller wavelength.

Wide band gap semiconductors have efficient UV absorption and very low absorption in the visible spectrum. The surface plasmon resonance (SPR) phenomenon of gold is used to change the optical properties of TiO2 in this study. In this study metal sandwiched planar (TiO2/Au/TiO2) structures were studied using a variety of optical techniques, including spectroscopic ellipsometry, UV/Vis absorption, and photoluminescence spectroscopy (PL). UV/Vis spectroscopy of TiO2/Au/TiO2 unfolded the presence of two broad bands in the visible range that were not present in TiO2 thin film. This was attributed to improved interband and plasmon resonance oscillations of Au in a dielectric environment. Photoluminescence spectroscopy revealed three types of luminescent centers in TiO2 around 351nm, 520nm and in the IR range. PL also revealed the introduction of near band gap edge defects as well as a rounded peak in composite films. UV/Vis spectroscopy revealed enhanced absorption in the visible region for composite films compared to a simple absorption spectrum for TiO2 only. 1nm thickness showed a drastic amount of absorption intensity compared to any other thickness. With the increase in the thickness of gold, this absorption intensity can be observed to be decreasing. In composite films with thickness of Au to be 5nm, 10nm and 20nm surface plasmon resonance modes are observed around 730nm, 670nm and 620nm respectively showing a shift in SPR modes towards smaller wavelength.