Laser-Induced Modification of the Surface State and Optical Properties of CdTe Crystals

Abstract

Optical properties and surface state of semiconductor CdTe crystals subjected to irradiation with nanosecond laser pulses were studied. Ellipsometric parameters Δ and Ψ were measured on two opposite surfaces of (111) oriented CdTe wafers before. The samples were subjected to polishing chemical etching and laser irradiation with energy densities lower and higher than the melting threshold of CdTe. The morphology and structure of CdTe crystals were monitored before and after treatments. Irradiation formed a thin modified surface layer on the both sides of CdTe crystals (Cd- and Te-terminated) with the similar optical constants n and k, respectively. However, the effective thicknesses of such modified layers differed and depended on the chemical and laser treatment conditions and also on the faces of CdTe(111) crystals.

Characterization of the surfaces of CdTe(111) single crystals after laser processing

“…A confirmation of this assumption is the data about laser-induced formation of a low resistivity Te film on the CdTe surface under irradiation ruby laser pulses 6 . After removing this modified layer with chemical etching, the optical properties of the irradiated CdTe samples (No 13,14) tend to be restored and only slightly differ from the properties of the chemically etched samples before laser irradiation.…”

“…In order to monitor the surface state and properties of CdTe crystals under different surface treatments, the ellipsometry technique has been used [11][12][13][14] . Ellipsometry has many advantages (simple experimental setup, high sensitivity, nondestructive action) that make it an attractive instrument for investigations [15][16][17] .…”

Detection of the Nanostructures in ZnO Thin Films by Using Optical Methods

“…The Beattie's method is used for measuring ellipsometric parameters of the films [4]. The optical constants of the films are calculated using the model of semi-infinite medium.…”