UV-laser-induced oxidation kinetics of c-Ge: transient reflectivity study

UV-laser-induced oxidation of crystalline Ge (c-Ge) is analyzed by means of real-time optical measurements. Irradiations are performed in a controlled oxygen atmosphere with laser fluences above the melting threshold. The melt duration determined from the reflectivity transients depends strongly on the oxygen pressure and on the number of laser pulses. The reflectivity of the material tends to decrease as the number of pulses is increased. The results indicate that the irradiation induces the growth of a surface oxide layer at a non-constant rate. The optical coupling between the oxide layer and the bulk material underneath at the irradiation wavelength explains the results and is found responsible for an enhancement of the oxide growth rate. © 1992.