Investigations on the CuI thin films production by pulsed laser deposition

Abstract

CuI thin films were deposited by pulsed laser deposition (PLD) in various Ar atmospheres. Control over the morphology, structure and defect nature of the deposited films was attempted by in-situ plasma diagnostics. The deposited films presented stoichiometric crystallinity on the full range of experimental condition with no residual oxidation, as per XRD and XPS measurements. Band gap tailoring was achieved by controlling the plasma ion kinetic energy with optimum conditions being defined by Cu and I ionic groups with kinetic energies surpassing 200 eV. Variation in Ar pressure allowed control over the nature of vacancies from VI + Cui to predominantly VCu. In situ plasma measurements revealed that the addition of Ar leads to the preferentially scattering of the Cu ions in the plasma which subsequently leads Cu ions energy losses. This energetic imbalance in the plasma is reflected in the disappearance of interstitial Cui vacancies and the increase in VCu. The generation of Cui vacancies was achieved in high temperature plasma and low plasma potential (Te > 20 eV and Vp < 8 V) conditions. The increase in plasma potential balances the accelerations during expansion and maintaining a high average temperature at the substrate inducing crystallinity even above 5 Pa or Ar.