Influence of the preparation conditions on the properties of CuInS2 films deposited by one-stage RF reactive sputtering

We investigated systematically the influence of the sputter parameters, such as substrate temperature, H2S flow, and sputter power on the structural, optical, and electrical properties of the sputtered CuInS2 films, to optimize the parameters for the one-stage growth of CuInS2 films by radio frequency (R-F) reactive sputtering. When the H2S flow during sputtering is too low, there are mainly Cu-In secondary phases coexisting in the films. With a RF power of 200 W and a H2S flow in the range of 20-30 sccm (standard cubic centimeter per minute), high quality films with good adhesion can be sputtered on bare float glass at a substrate temperature of 400 degreesC or above. A higher substrate temperature (500 degreesC) resulted in bigger grain sizes of the films. Moreover, the films sputtered at 500 degreesC showed a sharper absorption edge than those sputtered at 400 degreesC, and the corresponding band gap shifted from approximately 1.27 to 1.44 eV. Mo- or ZnO-coatings of the substrates can help to reduce the substrate temperature to 200 degreesC, and work effectively as a barrier to prevent Na diffusion from the substrates into the sputtered CuInS2 layers. (C) 2003 Elsevier Science B.V. All rights reserved.