Formation of Nb2O5 matrix and Vis-NIR absorption in Nb-Ge-O thin film
Research Institute for Electromagnetic Materials, Sendai, 982-0807, Japan
Nanoscale Research Letters 2012, 7:341 doi:10.1186/1556-276X-7-341Published: 25 June 2012
This paper investigates the crystal structure and optical absorption of Ge-doped Nb-oxide (Nb-Ge-O) thin films prepared by RF sputtering. A wide-gap material, Nb2O5, is selectively produced as a matrix to disperse Ge nanocrystals through compositional optimization with Ge chip numbers and oxygen ratio in argon. The optical-absorption spectra are obviously shifted to visible (vis) and near-infrared (NIR) regions, suggesting that a composite thin film with Ge nanocrystals dispersed in Nb2O5 matrix exhibits quantum-size effects. Accordingly, the two valuable characteristics of the Nb2O5 matrix and the vis-NIR absorption are found to be retained simultaneously in Nb-Ge-O thin films.