Electron stimulated reduction of sapphire studied by electron energy loss and Auger spectroscopies

Electron irradiation may change the surface composition of solids by electron stimulated processes. In the present work the effect of 1 keV electron irradiation on the near surface composition of sapphire was studied. The use of the whole range of the electron spectrum produced by 1 keV primary electrons has provided a detailed picture of the variation with depth and electron dose of the surface and near surface of electron irradiated alpha-Al2O3(1000). Electron irradiation doses were in the range of 0.7 C/cm(2) to 26 C/cm(2). After a dose of about 1 C/cm(2) sufficiently large clusters of aluminum were produced to allow the generation of the AI(LVV) 67 eV Auger peak, while after about 8 C/cm(2) the collective excitation surface and bulk plasmons were generated. An equilibrium in the composition of the first nanometer depth of the surface is reached after a dose of about 6 C/cm(2), with similar to 50% of the aluminum in alumina being reduced to the metallic form. After a dose of about 13 C/cm(2), the composition of the first 2 nm reaches equilibrium, while deeper alumina continues to be reduced.