Recently

there has been an increasing interest in ZnO due to its electrical

optical and piezoele-ctric properties making suitable for many applications such as light emitting diodes

photodetectors

surface acoustic waves device and so on. SAW filters with working frequency higher than 1 GHz will be widely applied in the intending wireless communication

whereas higher resonant frequencies (superior to 2.5 GHz) tend to push the limits of conventional photolithography. ZnO/diamond structure as SAW substrates offers an attractive means for relaxation of the lithographic criteria since ZnO has excellent piezoelectricity while diamond has the highest elastic and stiff coefficient and highest sound velocity. The use of ZnO based on diamond as SAW substrates offers an attractive means for relaxation of the lithographic criteria since diamond has the highest stiff coefficient and sound velocity. SAW devices have been reported based on ZnO/diamond/Si layered structures with a diamond layer of 10~100 μm deposited by chemical vapor deposition (CVD) technique. However the silicon substrate restricts the heat dissipation performance of the diamond films. In regard of actual applications

a ZnO/diamond layered structure without a silicon substrate can make full use of the outstanding thermal

elastic

and sound velocity characteristics of diamond while avoiding restriction of heat dispassion due to additional silicon substrates. High quality ZnO films are currently the foundation of device preparation and the variation of deposition technological parameters is an important factor to obtain ZnO films with high quality.In this paper

ZnO thin films have been prepared on the smooth nucleation surfaces of freestanding CVD thick diamond films by reactive radio-frequency magnetron sputtering. With the variation of O

2

/Ar

the growth and optical properties of the ZnO films are characterized experimentally by X-ray diffraction

room temperature photoluminescence spectra

and electron probe microanalysis and Hall measurements. The results indicate that the ZnO film deposited with a O

2

/Ar ratio of 1 is of

c

-preferred orientation and high resistivity and has the best optical property.