SnO₂ thin films prepared by ion beam induced CVD. Preparation and characterization

Abstract
Tin dioxide thin films have been prepared by Ion Beam Induced Chemical Vapour Deposition [IBICVD]. The films, with a SnO₂ stoichiometry as determined by XPS, are compact and homogeneous as revealed by SEM/TEM. Preparation was carried out on different substrates at 300 K [i.e. room temperature] or 673 K. Small differences were detected in the granular structure at these two different temperatures. In the two cases the films were partially crystalline and depicted the cassiterite structure of SnO₂. Small crystallographic domains between 30 and 50 Å and a preferential growth of certain planes are deduced from the analysis of the X-ray diagrams. The UV-vis spectra are characterised by a oscillatory absorption behaviour typical of thin films deposited on a transparent substrate with a different refraction index. The value of this optical parameter at λ = 420 ± 20 for films with d ≥ 2000 Å was about 1.9, very close to the value of bulk SnO₂. A selective deposition of the SnO₂ films has been also intended by using a mask between the accelerated ion beam used by IBICVD and the substrate.