Analysis Of Structural And Luminescent Properties Of ZnO Thin Films Grown By PLD

ZnO is a semiconductor material with wide direct band gap of 3.37eV and a large exciton binding energy of 60meV at room temperature. It can realize stimulated UV emission at RT and full-screen display,and so ZnO attracts as much attention as GaN in opoelectronics reseach field. ZnO films can be used to fabricate transparency electrode, cell battery window, surface acoustic wave device and light-emitting diode etc. ZnO can also be used to fabricated UV light emitting and UV laser devices, which is very important for the improvement of memory density and optical information access speed. There are many growth methods to prepare ZnO thin films such as magnetron sputtering, sol-gel, spay pyrolysis, and molecular beam epitaxy, pulsed laser deposition, metal organic chemical vapor deposition, atomic layer epitaxy and so on. Pulsed laser deposition is a newly developed film growth technique. In this technique, high density laser ablates the target and produces ZnO plume depositing on heated substrate in high vacuum background. In this paper, ZnO films were prepared on Si(OOl) substrate and the effects of various substrate temperatures, annealing temperatures and oxygen pressures on the properties of ZnO thin films are discussed.The thin films were examined by XRD,AFM, SEM, PL. Some results are following as:1. The structural properties and optical properties of ZnO films are importantly influenced by substrate temperature during films deposition. As substrate temperature increases from 500℃ to 600℃, XRD shows that the intensity of (002) peaks increases and FWHM decreases from 0.259° to 0.198° ,which shows the crystallinity of obtained films is improved. AFM shows that the grain size is bigger at 600℃. Meantimes, PL shows that the ultraviolet peak positioning at 380nm is stronger and the ratio between the intensity of ultraviolet peak and that of visible peak is bigger at 600℃.2. As-grown ZnO films were annealed at different temperature for 1h in air. The as-grown films possessed c-axis orientation,which is enhanced after the annealing p rocess; With increasing annealing temperature from 600℃ to 750℃, the c-axis tensile stress become smaller and then turn to compressive stress. At 650℃, the films has smaller tensile stress(-1. 7 × 10~8N/m~2) and the grain size of the film is bigger ,which results in a much rougher surface.The investigation of PL is the the ratio between the intensity of ultraviolet peak and that of deep-level peak is biggest and is around 6.8 at 650℃, which indicate that the transition between conduction...