Studies on chemically deposited nanocrystalline Bi2S3 thin films

Nanocrystalline thin films of Bi2S3 of different thicknesses were deposited from solutions containing bismuth nitrate, ethylenediamine tetraacetic acid (EDTA), and thioacetamide maintained at a bath temperature of 6 degrees C. These films were prepared for different deposition time periods. Uniform thin films having thicknesses up to 437 nm were obtained on the glass substrates. Characterization of the films was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption, electrical resistivity, and thermoemf techniques. These studies reveal that Bi2S3 films consist of nanocrystalline grains. Average grain size was calculated using Scherrer's formula. With an increase in grain size of Bi2S3 crystallites from 6.85 to 33.86 nm, a shift of 0.46 eV in the optical bandgap energy E-g, and a decrease in electrical resistivity from 2.4043 x 10(6) to 0.7250 x 10(6) ohm-cm were observed. The n-type electrical conductivity of the Bi2S3 films was observed from thermoemf studies. (C) 2000 Elsevier Science Ltd. All rights reserved.