REAL-TIME OPTICAL DIAGNOSTICS DURING PULSED UV LASER-INDUCED SURFACE CLEANING AND OXIDATION

Ultraviolet (UV) laser pulses are used to irradiate c-Ge and c-Sb both in vacuum and in an oxygen pressure while a HeNe laser beam is used to record the real time reflectivity (RTR) transients. It will be shown that the removal of the native oxide and therefore surface cleaning is produced when irradiating in vacuum while an oxidation process occurs when irradiating in an oxygen environment. The optical coupling between the growing oxide layer with the bulk material underneath is responsible of the high sensitivity of the RTR measurements to the presence or transformation of small thickness oxide layers at the surface. The RTR transients can be used to optically control pulse-to-pulse the laser energy density in order to induce surface oxidation at a constant rate and to minimize material losses during the oxidation process.