A study of solid phase reactions at the Ge-GeO2 interface

The sublimation of GeO molecules formed by the solid phase reaction between a-Ge and a-GeO₂ films (Ge+GeO₂=2GeO↑) was studied using vacuum microbalance. The c-Si/Ge/GeO₂, c-Si/GeO₂ /Ge, c-Ge/GeO₂ and c-Si/GeO/GeO₂ structures, fabricated by the ion-plasma deposition were annealed in the temperature range of 650-725°C. The diffusion of GeO molecules through the amorphous GeO ₂ and Ge films was investigated. The calculated activation energy indicated that the sublimated molecules were (GeO)₂ dimers. Dimeric (GeO)₂ molecules were formed directly in the reaction zone at the Ge/GeO₂ interface and after diffusion through the overlayer they were sublimated without decomposition. The sublimation rate of (GeO)₂ was influenced by the degree of crystallinity of the Ge film. The Arrhenius expressions were obtained for calculation of diffusivities and permeability. Examination of the diffusion and permeation data suggests, that the process of diffusion through the GeO₂ or Ge films limits the evaporation rate of (GeO)₂