Ion beam studies of Ge diffusion in Al2O3Al2O3

Rutherford backscattering spectroscopy (RBS) has been used in combination with X-ray photoemission spectroscopy (XPS) to investigate Ge diffusion in Al2O3Al2O3 (0001) samples. Ge was implanted in c-plane α-Al2O3α-Al2O3 (0001) at 80 keV to a fluence of 1×1016cm-2 at room temperature followed by thermal annealing in the 30–180 min range at 1200 °C in a N2N2 environment. RBS results indicate that implantation-induced damage does not fully amorphize the substrate, while incurred defects are partially annealed after 1 h accompanied by Ge phase crystallization. XPS data confirms the existence of GeO2GeO2 and GeO. There is a decrease in the Ge content compared to the as-implanted sample, attributed to GeO desorption, which is evident after 30 min and by 180 min 15% of the original Ge concentration remains. Integrated intensity of the Ge peak in aligned geometry is much lower compared to random geometry with a bimodal distribution of Ge evident in both spectra indicating Ge substitutional incorporation and the formation of a distinct Ge layer. XPS data shows a peak thought to be associated with the distinct Ge layer at ≈1216.5 eV, which is a lower binding energy than a Ge reference peak. The lower binding energy is thought to result from a net positive electron density in the substrate due to excess Al atoms in the peak defect-region.