Particle induced X-ray emission spectroscopic (PIXE) and surface morphological (AFM) studies on electron beam evaporated WO 3 thin films

Abstract

The present work is concerned with tungsten oxide (WO₃) thin films, which feature strongly in electrochromic applications. The films were deposited on glass substrates and fluorine doped tin oxide (FTO) coated glass substrates by the electron beam evaporation technique using a WO₃ target. The elemental analysis of the films was performed by particle induced X-ray emission (PIXE) spectroscopy, and the surface morphology of the films was studied using atomic force microscopy (AFM). To the best of our knowledge, this is the first time that PIXE has been used for the analysis of elements present in electron beam evaporated WO₃ films. In this study, PIXE was applied to confirm the presence of constituent element in the films. Atomic force microscopic studies revealed that the deposited WO₃ films are homogeneous, crack-free surfaces with uniform spherical nanograins. These characterisation studies were carried out for the films prepared on different substrates, and at different deposition temperatures and annealing temperatures. The increase in cluster size with increasing substrate temperature can be explained by the increased diffusion kinetics of the neighbouring particles and/or clusters in the film, causing them to coalesce to form a dense surface coating. This would provide a better understanding of the electrochemical behaviour of the films.