ZnO epitaxial films with and without Au buffer layer were grown on Si(001) substrates by a home-made chemical vapor deposition(CVD) technique.The Au buffer layer was evaporated in a physical vapor deposition(PVD) equipment

and its thickness was about 300 nm.After that

the Au/Si(001) template was transferred to a home-made CVD system to grow ZnO epilayer.Zn and Oprecursors were element zinc(5N) and deionized water vapour respectively

and high-purity nitrogen gas(5N) was employed as a carrier gas.The reactor pressure was at atmospheric pressure.A 1 μm-thick ZnO buffer layer was firstly deposited on the Au/Si(001) template at 650℃

and annealed in situ at 800℃ for 10 min.Then the main layer was grown at 800℃ for 3 min.The thickness of ZnO main epilayer was about 6 μm.The crystal properties of the ZnO films are studied by X-ray diffraction(XRD) equipment.The ZnO film directly grown on Si(001) substrate is apparently polycrystalline.Besides the diffraction peaks of ZnO (002) and(004)

there are many other peaks like ZnO (102)

(103) etc.For the ZnO film with an Au buffer layer

the crystal quality is improved a lot.Although it is still polycrystalline

the ZnO film with an Au buffer layer is highly c-axis oriented.Optical microscope is used to observe the surface morphologies of the ZnO films.The size of the grains and smoothness of surface of the ZnO film with an Au buffer layer are much better than that of the opposite one.The optical pro-perties of ZnO films are examined by means of photoluminescence(PL) spectra excited by a 325 nm He-Cd laser at room temperature.There are the excitonic related near band edge(NBE) emission peaks in the ultraviolet region in both of samples.While the deep-level emission(DLE)

which is usually defect-related

is difficult to observe in the spectra of both samples

which indicates that the two films have good optical qualities.It is interesting that the intensity of NEB peak of the ZnO film with an Au buffer layer is weaker than the one without Au buffer layer.The main reasons could be:(1)The intensity of NEB peak is related to the crystal quality of every single grains.For the ZnO film directly grown on Si(001) substrate

the crystal quality of the single grains may be better than the opposite one;(2)The confinement of the carriers is favor to the photoluminescence of the films.For the ZnO film without Au buffer layer

there are more grains to confine the carriers

so the intensity of NEB peak is much stronger;(3)The surface of the ZnO film without Au buffer layer is more rough

so the picking-up light efficiency is much higher

then the light is much easier to give out.Further studies are in progress to investigate this phenomenon.