ZnO is a wide and direct band semiconductor. It has a large fundamental band gap of 3.37 eV

which makes it a promising material for use in ultraviolet light-emitting and laser diodes. Moreover

ZnO possesses a large exciton binding energy (60 meV)

which is much larger than that of GaN (25 meV) as well as the thermal excitation energy at room temperature

and can ensure an efficient exciton emission at room temperature. ZnO thin film can be fabricated by various methods such as pulse laser deposition

chemical or physical vapor deposition and molecular beam epitaxy.But pulse laser deposition has many advantage.ZnO thin films were prepared using a pulsed laser deposition (PLD) technique on Si (001) substrates.All samples were grown at the same substrate temperature and different oxygen partial pressure.After growing the samples

the influence of ambient oxygen pressure

ranging from 10 to 100 Pa

on the structural and optical properties of ZnO films was investigated systematically by XRD

SEMand PL.X-ray diffraction patterns indicate all films have (002) preferred orientation.But the experiment results indicated that as the oxygen pressure increases from 10 Pa to 100 Pa during the thin film deposition

the FWHMof (002) diffraction peaks becomg larger from 0.19° to 0.43°.We suppose this is because that at higher O

2

pressure the kinetics of Zn and Oatoms are degraded by collisions with the ambient gas. These atoms have no sufficient energy to move to the plan of (002)

so the crystallinity of the samples degrades.But the photoluminescence intensity of ultra-violet (UV) luminescence increases as the oxygen pressure increases.This is probably because the stoichiometry of oxygen-deficient ZnO film is improved by increasing oxygen pressure. At high oxygen pressure atmosphere

ZnO films bnough oxygen to absorb

so the stoichiometry of oxygen-deficient ZnO film is improved. Comparing XRDresults

it is concluded that the UV luminescence intensity strongly depended on the stoichiometry in the ZnO film rather than the micro-structural quality of the crystal.SEM resultes indicate that ambient oxygen pressure has an effect on the morphology of the samples.