Grazing incidence X-ray diffraction and reflectometry are used to characterize chemically treated cadmium telluride single crystal (c-CdTe) surfaces, amorphous silicon (a-Si) thin films and amorphous oxygenated cadmium telluride( a-CdTe : O) thin layers. In the case of CdTe single crystal surface treated with an oxidizing agent (a solution of BQ in CH₃OH), the superficial layer was found to be less dense than its support with a profound alteration of CdTe in the volume. After rinsing in KOH solution, the properties of single crystalline CdTe are obtained. In the case of a-Si thin layers, we show that the simulation of the reflectometry curves enables not only the determination of the layer thickness but also the detection of an ultra-thin superficial oxide layer. Finally, in the case of a-CdTe: O films it is found that the oxygen contents of the surface increases with increased exposure time. Also, this exposure leads to an increase of the oxide thickness and a net decrease in the surface roughness.