The surface and internal structure states of commercially available ZnS powder

twice heated powder and the ZnS:Er

3+

thin film material prepared by evaporating with two boats

are measured by using X-ray diffraction(XRD)

X-ray photoelectron spectroscopy(XPS)and electroluminescence brightness measurement techniques.The information of the relation between the microstructure and the concentration of luminescent centers in the film was obtained.The experimental results show that the deposited polycrystalline films have a trend of preferential orientation.It was found that the high brightness of the devices may be attributed to the deposition growth of crystallites oriented in the(311)

(400)directions and the existence of a higher population of erbium in trivalent charge state in these planes.This phenomenon may be explained that the energy needed for Er

3+

ion to substitute for Zn

2+

ion is less in higher index planes such as(311)

(400)than in other planes.This provides a favorable condition for the formation of luminescence center.In addition

the electroluminescence brightness-increases-with increasing the size of polycrystalline grains in the higher index planes.