Recently

ZnO film has attracted much interest because of its huge potential commercial application in ultraviolet (UV) laser since its optically pumped UV lasing was found at room temperature

and the photoluminescence (PL) properties of ZnO films have been studied widely.Some early works indicate that the peak excitation of the UV band should be in the vacuum ultraviolet (VUV) region and the intensity of Xe lamp is not enough to excite them.In the present work

a detailed study on the PL properties of ZnO film deposited on Si substrates by reactive DC sputtering was carried out with a synchrotron radiation (SR) light source for the first time to our knowledge. The excitation and emission spectra were measured at HASYLAB

DESY at Hamburg

Germany.The excitation spectra show a strong excitation band around 195nm related to 390nm emission band.Under SR vacuum ultraviolet excitation

a new emission band peaked at 290nm was found for the first time

besides the ultraviolet emission band (390nm) and green band (520nm). Since the energy of 290nm emission photon is larger than the band gap energy of ZnO (3.2eV)

it does not originate from the band gap radiative recombination or intrinsic defects

as well as impurities.The excitation spectra of the two emission bands are very similar to each other

which also prove that the 290nm emission originates from ZnO film itself.In addition

it seems also not come from the Si substrate

because the VUV light is strongly absorbed by ZnO film (0.2μm) and can not reach the substrate. In conclusion

the newly found emission band peaked at 290nm indicates that there are some structures in the conduct band of ZnO film.The excitation spectra show that the strong excitation bands are in VUV region (photon energy higher than 6eV)

but almost no excitation in the lower energy region.The strange behaviors in the PL properties of ZnO film may be one of the reasons that few report is found in the past

and also imply that more detailed experimental as well as theoretical studies should be carried out in the future.