Chemical reaction via hydroxyl groups at the titanium/α-Al2O3(0 0 0 1) interface

The growth of a titanium thin film on the α-Al2O3(0 0 0 1) surface occurs in two steps. In the first stage, titanium is oxidised via a chemical reaction with the surface oxygen species which are characterised by a shift of 1.5 eV of the O 1s level. These species involve removable OH groups ((5±2)×1014/cm2 at saturation) and—likely—residual OH groups ((3±1.5)×1014/cm2, minimum value). At higher titanium coverage, the titanium film becomes metallic.