Influence of nanosecond laser irradiation on optical properties of surface layers of CdTe crystals

The effect of surface laser processing on the optical properties and structure of the surface region of (111) oriented CdTe single crystals have been studied by multiple-angle-of-incidence single-wavelength ellipsometry. The measurements were performed both on Cd and Te surfaces of CdTe(111) crystals and morphology was monitored by AFM. CdTe crystals were subjected to various treatments including chemical and laser etching. The ellipsometric parameters Δ and Ψ were obtained at several light incidence angles and data were interpreted based on the model of an absorbing surface layer located on an absorbing substrate. Surface roughness was taken into account and the surface layer was considered as an equivalent film with flat boundaries and effective optical parameters. The refraction n and absorption k indexes, and thickness d of the modified surface layer were calculated and features of nanosecond laser irradiation on CdTe(111) polar surfaces were discussed.