Rutherford backscattering spectroscopy analysis of the growth quality of chemical bath deposited PbSe thin films

Abstract

This research focuses on the study of the growth quality, by means of the chemical profile analysis, of good structural and morphological quality chemical bath deposited PbSe thin films on glass substrates (SiO2) by Rutherford Backscattering Spectroscopy (RBS). RBS results with other complementary techniques like XRD and SEM were contrasted. Thin films by using different NaOH concentrations during the growth process were synthesized. XRD studies showed the films polycrystalline nature and their good structural quality. Pure structural effects of amorphous SiO2 and PbSe face-cubic-centered structure were observed. SEM imaging analysis revealed the good morphological growth quality of the PbSe films, observing well-defined films dimensions (thickness), a clear film-to-substrate transition at the interface and good microstructural homogeneity. According to XRD and SEM results, RBS experiments contrasted with theoretical simulations evidenced the good growth quality of the PbSe films. A good agreement between experimental data and theoretical modelling by assuming a simple film/substrate structure with a perfectly defined interface and negligible film roughness for the PbSe/SiO2 samples was achieved. RBS experimental-theoretical analysis reveal the non-stoichiometric nature of the PbSe films, being consequent with preliminary EDS based chemical studies. In particular, a predominance of Se with respect to Pb (considering the atomic concentration) in all samples was observed, suggesting a possible p-type conductivity. By stopping power analysis, thin films thicknesses between 141 and 296 [nm] were also estimated, being comparable to those obtained from SEM imaging analysis of the samples cross-sections. General results show that some aspects (chemical profile of the structure and interfaces quality) related to the growth quality of the chemical bath deposited PbSe thin films, studied by RBS experiments, are considerably intercorrelated to those analyzed by other techniques like XRD and SEM. This suggests RBS method as a suitable technique for a complete and rigorous analysis of thin films growth quality.