Effect of annealing on Ge-doped SiO2 thin films

Thermal annealing effects on optical and structural properties of Ge-doped SiO2 thin films prepared by the chemical vapor deposition and flame hydroly sis deposition methods were investigated. The thin film prepared by the for mer method showed inhomogeneous Ge distribution, and Ge oxygen-deficient ce nters were observed. When it was thermally annealed at temperatures higher than 800 degrees C, the Ge distribution became uniform. The concentration o f oxygen deficient centers was found to decrease with the thermal annealing in an O-2 atmosphere, while it increased with the thermal annealing at 100 0 degrees C in N-2. This suggests that improvement of the film quality can be achieved by thermal annealing. On the other hand, neither inhomogeneity of Ge distribution nor the appearance of oxygen deficient centers was obser ved in the film prepared by the latter method, and its film quality was sca rcely affected by the thermal annealing. (C) 1999 American Institute of Phy sics. [S0021-8979(99)02621-3].