Laser-induced Etching of Chlorinated Silicon Surfaces

Abstract

Measurements of excitation spectra of photoetching of chlorinated Si(111)7×7 surfaces stimulated by ultraviolet nanosecond pulse laser light revealed that there are two distinct spectral peaks, one (α-peak) being located near 290nm and another (β-peak) at 245 nm. The α-peak exhibits a strong supralinear dependence on light intensity above laser fluence of∼100mJ/cm² pulse, while the β-peak grows linearly with light intensity. The red shift of the α-peak with increasing intensity coincides with the shift of laser abration, which strongly suggests that the origin of the α-peak photoetching is thermal etching enhanced by surface heating due to interband transition in the substrate. The dependence on polarization of the incident light suggests that the β-peak photoetching originates in excitation of hot carriers in the substrate which are captured resonantly by the anti-bonding states of the adsorbate chlorides resulting in destabilization of the molecules.