Optical properties of nanocrystalline ytterbia dopedc zirconia thin films

Abstract

Thin films of Zr(1-x)Yb(x)O(2-y) where x ranges from 0 to 0.3 have been coated onto quartz substrates using an inorganic sol-gel approach at low temperature. The films were fully crystalline and continuous as deposited, with a fluorite structure. On heating over 900°C, films with less than 16% doping had a tetragonal structure whilst those above retained a cubic structure. Crystallite size measurements indicated that the films were nanocrystalline, the size decreasing as a function of increasing dopant concentration. The films are transparent in the region 500 to 1500 nm with very low optical losses. The film refractive index seems relatively independent of the dopant concentration. The optical band gap is dependent on the dopant concentration and is in the range 5.6 to 5.7 eV. There is an increase in refractive index and decrease in optical absorption with increase in annealing temperature from 600°C to 1050°C.