Metastable phase ofGeOx

Optical and electron diffraction data for sufaces of Si${\mathrm{O}}_2$, Ge${\mathrm{O}}_2$, and partially oxidized Si are reviewed. It is concluded that an intermediate phase $\mathrm{Ge}{\mathrm{O}}_x$ can be formed at the surface of Ge${\mathrm{O}}_2$, and that this phase may be a metastable crystalline film. Patches of an amorphous film of nearly the same composition may be found on partially oxidized Ge surfaces, in analogy with patches of similar material on partially oxidized Si surfaces, as observed in electron-diffraction energy-loss experiments.