Structural and optical properties of II-VI semiconductor thin films deposited by laser ablation

Experimental results on the structural and optical properties of CdSxSe1-x films deposited by pulsed laser ablation technique are reviewed. Technical details of the laser ablation process and deposition apparatus are illustrated. The influence of growth parameters on the physical properties of deposited films is discussed. The more critical growth parameters result to be the energy density of the laser pulse, which is strongly related to the crystalline grain dimensions, and the substrate temperature, which dramatically influences the preferential orientation of the polycrystalline films. The asymmetric lineshape of the LO phonon structure in micro-Raman spectra and the large contribution of the acoustic phonons to the thermal gap shrinkage in absorption and photoluminescence measurements are related to the alloy disorder. The disorder causes also the localization of excitons and a strong enhancement of the radiative efficiency. Band gap narrowing and band tails are observed in the absorption spectra when heavy doping occur.