No abstract

ZnS:Mn thin film electroluminescent devices having doubly-stacked insulating layers have been developed. The insulating layer consists of electron-beam evaporated Ta2O5, and rf-magnetron sputtered SiO2 stacked layers. It is concluded that the thick semi-insulating Ta2O5 films (1000 nm) deposited on both sides of the ZnS:Mn active layer act as a carrier injctor for electroluminescence and the thin insulating SiO2 films (80 nm) inserted between the electrodes and Ta2O5 films act as a carrier limiter. The breakdown voltage margin defined by (V bd-V th)/V th was improved from 15% to more than 80% by introducing thick semi-insulating Ta2O5 films.

Effect of stacking layers on the microwave dielectric properties of the (Li 0:5 Sm 0:5 )TiO 3 /CaTiO 3 (LSTO/CTO) thin films prepared by the metalorganic solution deposition technique (MOSD) was investigated. The dielectric constant (K), dielectric loss (tan ) and temperature coefficient of dielectric constant (TCK) of CaTiO 3 films measured at 6 GHz were 160, 0.003 and À1340 ppm/ C, respectively. In contrast, the (Li 0:5 Sm 0:5 )TiO 3 films showed K of 35, tan of 0.001 and TCK of þ320 ppm/ C. As the thickness of CTO layer in the LSTO/CTO films increased, K increased and TCK changed from positive values to negative values by dielectric mixing rule. Especially, LSTO(200 nm)/CTO(200 nm) films exhibited TCK of þ10 ppm/ C, indicating temperature stability. The tan of LSTO/CTO films increased with increasing the thickness of CTO layer. This result was attributed to the fact that the stresses were induced by the higher thermal-expansion coefficient of CTO than that of LSTO. Also, as compared with LSTO(200 nm)/CTO(200 nm) film, the K and TCK of LSTO(100 nm)/CTO(200 nm)/ LSTO(100 nm) film were not changed, but the dielectric loss increased. This result indicated that the dielectric loss was affected by the number of interfaces between CTO and LSTO layers.

The effects of annealing on sputtered ZnS:Tb, F thin films is investigated by electron probe microanalysis, secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. It is shown that the annealing decreases the F/Tb atomic ratio from 4 to 1, due to the release of F atoms. It is concluded that many of the F ions not contributing to the formation of luminescent centers with Tb ions exist in as-sputtered film and that efficient Tb-F complex centers are formed by annealing at over 400°C. Luminance is enhanced by increasing the Tb-F complex centers and decreasing the hot-electron scattering centers of the F ions.

No abstract