Dielectric properties, electronic conductivity and Li+ion motion in LiPON thin films

International audienceVol. 253, pp. doi: (Dec. 2013

Auger and x‐ray photoemission spectroscopy study on Cs2Te photocathodes

Thin films of Cs2Te have been produced and analyzed by Auger depth profiling and x-ray photoemission spectroscopy (XPS). The formation of the photoemissive material passes through different phases, each of them has been characterized by XPS and by its total yield in the spectral region 3.5-5 eV. Copper and molybdenum substrates have been considered. While Mo behaves to all practical purposes like an ideal support for Cs2Te, strong diffusion from the substrate material into the photoemissive film has been observed on photocathodes fabricated on Cu, The ruggedness of the photocathodes has been tested by exposing them to a few hundred Langmuirs of different gases, namely O-2, CO2, CO, N-2, and CH4. The last three have no effect on the photocathode lifetime, while a substantial reduction of the quantum efficiency has been observed after the exposure to oxygen. The main reason for this is the formation of a thick cesium oxide layer at the surface of the photocathode. However, the oxygen pollution can be partially recovered by the combined effect of heating the photocathode at 230 degrees C and illuminating the poisoned material with the 4.9 eV radiation. No rejuvenation has been observed under the effect of the temperature or the radiation alone

Influence of sputtering conditions on ionic conductivity of LiPON thin films

LiPON films were deposited using radio-frequency magnetron sputtering in a pure N2 gas atmosphere. The influence of rf power, N2 pressure, target–substrate distance and target density on thin film composition and ionic conductivity has been studied. Impedance measurements performed between 25 and 80 °C have indicated that ionic conductivity increases with nitrogen incorporation into the glass structure. An increase in the deposition rate with the target density has also been observed

Development, operation and analysis of bialkali antimonide photocathodes for high-brightness photo-injectors

Different methods for the preparation of K-Cs-Sb photocathodes, suitable for electron sources in RF guns, are described in detail. The resulting material has been characterized by Auger depth profiling technique, and by its spectral response in the 250-600 nm range, as well. The results of lifetime experiments under operational and ''laboratory'' conditions are presented. The role of CO2 in reducing the operational lifetime of the photocathodes and that of O-2 in improving the long-wavelength response are investigated