Bakar Ismail

Electrical conductivity measurements in evaporated tin sulphide thin films

Tin sulphide (SnS) has been evaporated on to substrates maintained at fixed temperatures in the range 50-300°C. X-ray diffraction measurements have shown that the films deposited at the lower substrate temperatures are non-stoichiometric, containing higher sulphides of tin, but that those deposited at 300°C consist essentially only of SnS. Film conductivity increased in the range 0·5-20 Sm-1 as the substrate temperature during deposition increased from 50°C to 250°C, this effect being attributed to the changing film composition. Films deposited at 50°C and 150°C showed thermally activated conductivity at temperatures above 220-250 K, with activation energies EB; of 0·12 eV and 014eV, respectively. At lower temperatures both conductivity and activation energy were considerably lower, consistent with hopping via localized states. The conductivity is modified after prolonged cooling to 160K, although the mechanism of this process is not understood

Effect of Pressing Force on the Physical Properties of CaMgTiO3 Ceramic Prepared by HEBM

CaMgTiO3 ceramics were synthesized by using the high energy ball-milling method (HEBM) at different pressing forces. The raw materials were ball milled for 20 hours and sintered at 1000°C. Ceramics surfaces morphologies and particle sizes were measured using SEM analysis. Archimedes’ method was adapted to obtain their densities and porosities. It was found that pressing forces influenced both morphologies and particle sizes. As pressing forces increased, the particle sizes decreased as shown in SEM observation. However, the particle sizes increased at 200 kN due to agglomerated grain growth. The densities were almost constant with increasing of pressing forces while porosities were reduced.

ZnO Thin Film Ga s Sensor for CO

ZnO thin films were deposited onto corning glass substrates by rf magnetron sputtering system using ZnO targets. Films were deposited under rf power of 80 W at various deposition time. The distance between the target and substrate was held at 45 cm. A mixed Ar and O2 gas was introduced into the chamber at 4×10−2 Torr. The structure of the deposited ZnO films was investigated by Scanning electron miscroscopy. The gas sensing properties were evaluated at various operation temperatures by measuring the changes of resistance of the sensor in air and in CO gas respectively using the gas sensing characterization system. The grain size was increased as the film thickness was increased during deposition. The sensor with 233 nm film thickness exhibited the highest sensitivity for CO gas.