Surface stoichiometry analysis by AES, EELS spectroscopy and AFM microscopy in UHV atmosphere of SnO2 thin film

Abstract

SnO2 thin films are materials with surfaces sensitive to the processes of elaboration, synthesis and post-synthesis treatments for different technology applications. The main objective of the present work is to investigate three samples issued from spray pyrolysis method elaborated at different temperatures of substrate 300 °C, 340 °C and 380 °C, with the precursor Bu2SnAc2 (dybutil tin diacitate) and submitted to three repeated heatings at 300 °C and then to a treatment by Argon ions bombardment in an Ultra-High Vacuum Chamber (UHV). We found that the carbon has escaped by diffusion in depth to surface during the both heating effects for two samples, unlike to the sample of 300 °C temperature of substrate carries the elevated rate of oxygen on the surface. These increases have been detected by both complementary methods of Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS) analysis techniques, which are able to follow the stoichiometric change of oxygen. Furthermore, the bombardment by Argon beam has caused desorption of carbon and oxygen atoms from the surfaces. A third heating was carried out for two purposes, first to restore the surfaces which have been perturbed by the bombardment effect and second to cause the modification of surfaces stoichiometry. The method to confirm this observation is the AES and EELS signatures change of tin and oxygen of SnO2 thin films, which have been incurred electronic and structural modifications related to the treatments and the electrical charges. The latter was due to the surface morphology of samples approved by Atomic Force Microscopy (AFM) analysis. Through these treatments the stability of the surface has been recognized.