Nanocrystalline stoichiometric [Mo(S1-xSex)(2)] thin films were deposited by using arrested precipitation technique (APT) developed in our laboratory. The precursors used for this are namely, molybdenum triethanolamine complex, thioacetamide and sodium selenosulphite; and various preparative conditions are finalised at the initial stages of deposition. Formation of [Mo(S1-xSex)(2)] semiconducting thin films are confirmed by studying growth mechanism, optical and electrical properties. X-ray diffraction analysis showed that the composites are nanocrystalline being mixed ternary chalcogenides of the general formula [Mo(S1-xSex)(2)]. The optical studies revealed that the films are highly absorptive (alpha x 10(4) cm(-1)) with a band-to-band direct type of transitions and the energy gap decreased typically from 1.86 eV for pure MoS2 down to 1.42 eV for MoSe2. The thermoelectrical power measurement shows negative polarity for the generated voltage across the two ends of semiconductor thin films. This indicate that the [Mo(S1-xSex)(2)] thin film samples show n-type conduction. (C) 2003 Elsevier B.V. All rights reserved.