H₂S gas sensing properties of BST ((Ba_0.67Sr_0.33)TiO₃) thick films are reported here for the first time. BST ceramic powder was prepared by mechanochemical process. Thick films of BST were prepared by screen-printing technique. The sensing performance of the films was tested for various gases. The films were surface customized by dipping them into aqueous solutions of CuCl₂ and CrO₃ for various intervals of time. These surface modified BST films showed improved sensitivity to H₂S gas (100 ppm) than pure BST film. Chromium oxide was observed to be a better activator than copper oxide in H₂S gas sensing. The effect of microstructure and amount of activators on H₂S gas sensing were discussed. The sensitivity, selectivity, stability, response and recovery time of the sensor were measured and presented.

Thin films of copper indium diselenide (CIS) were prepared by chemical bath deposition technique onto glass substrate at temperature, 60°C. The studies on composition, morphology, optical absorption, electrical conductivity and structure of the films were carried out and discussed. Characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX) and absorption spectroscopy. The results are discussed and interpreted.

Barium strontium titanate ((Ba_0.87Sr_0.13)TiO₃–BST) ceramic powder was prepared by mechanochemical process. The thick films of different thicknesses of BST were prepared by screen-printing technique and gas-sensing performance of these films was tested for various gases. The films showed highest response and selectivity to ammonia gas. The effect of film thickness on gas response was also studied. As prepared BST thick films were surface modified by dipping them into an aqueous solution of titanium chloride (TiCl₃) for different intervals of time. Surface modification shifted response to H₂S gas suppressing the responses to ammonia and other gases. The surface modification, using dipping process, altered the adsorbate–adsorbent interactions, which gave the unusual sensitivity and selectivity effect. Sensitivity, selectivity, thermal stability, response and recovery time of the sensor were measured and presented.

Polycrystalline thin films of copper indium sulphoselenide [CuIn(S,Se)₂] were deposited on glass substrate by chemical bath deposition technique. The deposition parameters such as pH, temperature and time were optimized. A set of films having different elemental compositions was prepared by varying Cu/In ratio from 1.87–12.15. The films were characterized by X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDAX). The chemical composition of the CuIn(S,Se)₂ was found to be nonstoichiometric. The d.c. conductivities of the films were studied below and near room temperature. The thermo-electric power of the films was also measured and type of semiconductivity was ascertained.

Stoichiometric and nonstoichiometric powders of cadmium indium oxide were derived from calcination of cadmium indium sulphide prepared by flux method. The materials were confirmed by XRD. Thick films of above prepared powders were prepared on glass substrates using screen printing technique. The thick films were characterized by SEM and EDAX. The electrical conductivity of CdIn₂O₄ thick films was calculated. The gas sensing performance of stoichiometric thick films of CdIn₂O₄ was tested for various gases. The films showed good response to LPG.

The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al₂O₃ (1 wt%) doped ZnO were observed to be highly sensitive to ethanol vapours at 300°C. Aluminium oxide grains dispersed around ZnO grains would result into the barrier height among the grains. Upon exposure of ethanol vapours, the barrier height would decrease greatly leading to drastic increase in conductance. It is reported that the surface misfits, calcination temperature and operating temperature can affect the microstructure and gas sensing performance of the sensor. The efforts are, therefore, made to create surface misfits by doping Al₂O₃ into zinc oxide and to study the sensing performance. The quick response and fast recovery are the main features of this sensor. The effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of ethanol vapours were studied and discussed.

Stoichiometric and nonstoichiometric thin films of copper selenide have been prepared by chemical bath deposition technique at temperature below 60°C on glass substrate. The effect of nonstoichiometry on the optical, electrical and structural properties of the film was studied. The bandgap energy was observed to increase with the increase in at % of copper in composition. The grain size was also observed to increase with the decrease of at % of copper in composition. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), absorption spectroscopy, and AFM. The results are discussed and interpreted.

Thin films of copper bismuth diselenide were prepared by chemical bath deposition technique onto glass substrate below 60°C. The deposition parameters such as time, temperature of deposition and pH of the solution, were optimized. The set of films having different elemental compositions was prepared by varying Cu/Bi ratio from 0.13–1.74. Studies on structure, composition, morphology, optical absorption and electrical conductivity of the films were carried out and discussed. Characterization includes X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX), absorption spectroscopy, and electrical conductivity. The results are discussed and interpreted.