ZnO film has attracted more and more interest since its UV lasing was reported on "Science" (1997). A lot of sources

such as Xe lamp

YAG:Nd laser and cathode ray

have been used as the excitation sources to investigate the luminescence of ZnO thin film. In the present work

synchrotron radiation light (VUV) of HASYLAB in Hamburg

Germany was applied to study the UV luminescence of ZnO thin film. The UV luminescence of ZnO thin film on Si substrate at different temperatures (7～300K) were observed using synchrotron radiation light (195nm) as excitation source. Its emission spectra include three different band peaking at 380

369.5

290nm

respectively. Each of the three bands has different decay time and different temperature dependence

but they all have the same excitation spectra. The strong excitation band is in VUV range (100～200nm) instead of near UV range. Combining the calculated results of ZnO electronic structure and experimental data

we suppose that the VUV excitation (6～10eV) can be attributed to the excitation of electrons in the lower valance band of ZnO

which mainly consists of Zn3d states with bound energy from 4.0～6.5eV. The origin of the three different UV emission bands was also discussed. 369.5nm emission is from free exciton recombination

and 380 nm broad band is related to the inter band transition

while 290nm emission may be corresponding to the recombination of the electron in the secondary energy well of the conduction band with the hole in the valance band

or may be come from structural defects.