Over the past few years

wide and direct band gap semiconductors have been intensively studied for their application as blue and ultraviolet light emitters. As a wide gap semiconductor

ZnO has a wide band gap of 3.37 eV and a large binding energy of 60 meV. Therefore

ZnO is considered as one of the most promising candidates for short wavelength optoelectronics devices

and it is very important to conduct further studies of the properties of ZnO thin films.An un-doped zinc oxide thin film was prepared by radio frequency (RF) reactive co-sputtering on silicon (100) substrate. Sputtering target was metal zinc (99.99%)

the sputtering gas is a mixture gas of argon (99.97%) and oxygen (99.95%)

the partial pressure ratio of oxygen is 0.4. The structure

surfaces (morphology) and PL spectra of the sample were characterized by X-ray diffractometer

atomic force microscopy(AFM) and fluorescent spectrophotometer

respectively. The X-ray diffraction patterns indicated that the film has highly c-axis orientation and low biaxial compressive stress (2.8×10

8

N/m

2

)

the 2θ angle of (002) diffraction peak is 34.48° and the full width at half maximum is 0.306°. The grain size of the sample is about 50 nm. A strong blue emission peak and a weak violet emission peak located at 434 nm and at 414 nm are observed in the photoluminescence (PL) spectrum when exited with 325 nm wavelength (He-Cd) at room temperature. The full width at half maximum of blue emission peak is only 50 meV. We assigned that the violet (emission) and blue photoluminescence peaks originate from Zn vacancy and Zn interstitial defects

respectively.