Optical characterizations of ZnO thin films on Si (100) substrates deposited by pulsed laser deposition

ZnO thin films were deposited on Si (100) substrates at different temperatures (100similar to600 degreesC) in the pulsed laser deposition (PLD) system. Micro-Raman, spectroscopic ellipsometry (SE), and spectrometry techniques were used to characterize the thin films. Raman spectra of the thin films revealed the E-2 modes at around 99 and 436 cm(-1), which indicates that the wurtzite structure is easily formed in the thin films. As a function of growth temperature, greater tensile stress is induced at lower growth temperature. The Sellmeier relation was used to simulate SE data (Delta and Psi). The refractive indices and thicknesses of the thin films were extracted by the simulation. The refractive indices of the thin films deposited at temperatures higher than 300 degreesC show normal dispersion behavior in the wavelength range concerned. However, the refractive indices of the thin films deposited at 200 degreesC deviate from the normal values. ZnO thin films deposited at room temperature were annealed in a PLD chamber and a rapid thermal annealing system, respectively. The annealing effects on the luminescent properties were observed. It was found that the optical properties of ZnO thin films deposited at room temperature could be greatly improved by a post-annealing process.