Rotary target method to prepare thin films of CdS/SiO2 by pulsed laser deposition

Abstract

Thin films of CdS-doped SiO2 glass were prepared by using the conventional pulsed laser deposition (PLD) technique. The laser target consisted of a specially constructed rotary wheel which provided easy control of the exposure-area ratio to expose alternately the two materials to the laser beam. The physical target assembly avoided the potential complications inherent in chemically mixed targets such as in the sol-gel method. Time-of-flight (TOF) spectra confirmed the existence of the SiO2 and CdS components in the thin-film samples so produced. X-ray diffraction (XRD) and atomic force microscopy (AFM) results showed the different sizes and structures of the as-deposited and annealed films. The wurtzite phase of CdS was found in the 600 °C-annealed sample, while the as-deposited film showed a cubic-hexagonal mixed structure. In the corresponding PL (photoluminescence) spectra, a red shift of the CdS band edge emission was found, which may be a result of the interaction between the CdS nanocrystallite and SiO2 at their interface.