Bi-2(S1-x, Se-x)(3) thin film composites: synthesis and properties

Chemical synthesis of the bismuth sulphoselenide (Bi-2(S1-x,Se-x)(3)) compo site thin films is presented in this paper for the first time. The composit es were obtained onto the plane microscopic amorphous glasses by a simple e lectroless solution growth process. The different preparation conditions an d parameters (temperature, time, solution composition and pH etc) were fina lized in the initial stages of the work and the reaction kinetics and growt h mechanism have been discussed in brief. The contents of Bi and Se in the bath and in the film were determined by the spectrophotometric and atomic a bsorption spectrophotometric techniques. The X-ray diffraction analysis sho wed that the composites are microcrystalline in nature and are mixed ternar y chalcogens of the general formula Bi-2(S1-x, Se-x)(3). The optical studie s revealed that the films are highly absorptive with a band to band type tr ansitions and the energy gap decreased, typically, from 1.9 eV for Bi2S3 to 0.97eV for Bi2Se3. The electrical conductivity and thermoelectric power me asurements showed increase in the conductivity with increased Se-content (x ) in the film and n-type conduction of the samples, respectively. The therm o power is of the order of muV/K.