Vanadium dioxide (VO2) films were grown on c-and m-plane sapphire substrates by pulsed laser deposition (PLD) technique with VO2ceramic target. The VO2films with preferred growth orientation and uniform dense distribution have been achieved on both substrates, as confirmed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The terahertz (THz) transmission properties of VO2thin films were studied by terahertz time-domain spectroscopy (THz-TDS). The results indicate that the THz transmission properties of VO2films are strongly influenced by the sapphire substrate orientation, suggesting that VO2films are ideal material candidates for THz modulation.
ABSTRACTUsing pulsed laser deposition, Bi4Ti3O12 thin films were grown on (0001) and (1102) surfaces of Al2O3. Substrate temperature from 700 to 800 °C and oxygen pressure from 50 to 1000 mtorr were varied, and their effects on Bi4Ti3O12 film growth behavior was investigated. Only for a narrow range of deposition parameters, can highly oriented Bi4Ti3O12(104) films be grown on Al2O3(0001). Further, epitaxial BTO(004) films can be grown on Al2O3(1102). The growth behavior of preferential BTO film orientations can be explained in terms of atomic arrangements in the Bi4Ti3O12 and the Al2O3 planes.
Abstract:Gallium nitride thin films were grown by pulsed laser deposition. Subsequently, post-growth annealing of the samples was performed at 400, and 600 oC in the nitrogen atmosphere. Surface morphology of the as-grown and annealed samples was performed by atomic force microscopy, surface roughness of the films improved after annealing. Chemical analysis of the samples was performed using x-ray photon spectroscopy, stoichiometric Gallium nitride thin films were obtained for the samples annealed at 600 oC. Optical measurements of the samples were performed to investigate the effect of annealing on the band gap and optical constants the films.
Influence of Oxygen Pressure on Growth of Si-Doped β-(AlxGa1 − x)2O3 Thin Films on c-Sapphire Substrates by Pulsed Laser Deposition