Photoablation in amorphous dielectric films

Irradiation of amorphous SiO2 films using 248 nm laser light at energy densities up to 600mJ/cm2 results progressively in defect creation then ablation. In SiOx the films are immediately ablated. It is reasoned that energetic conduction electrons pumped from mid-gap defect states then accelerated in the photon field lead to impact ionization then defect creation via photolysis. When defect densities are large (as intrinsically the case in SiOx) the material is thermally desorbed by heat generated by the relaxing electrons