Deposition of c⊥-oriented tungsten disulfide (WS 2) films by reactive DC magnetron sputtering from a W-target in Ar/H 2S

Abstract

The layered type compound WS 2 (tungstenite) which exhibits an energy bandgap of 1.8 eV and a very high absorption coefficient above 10 5 cm −1 has been proposed as a potential absorber materials for thin film solar cells. In the present paper DC reactive magnetron sputtering from a metallic W-target has been investigated as a low temperature deposition method for WS 2-films with a preferential c ⊥-orientation. The sputtering was performed in an Ar H 2 S-atmosphere , which allows a simple control of the sulphur partial pressure in the discharge. The structural and electrical properties have been evaluated as a function of the deposition parameters: substrate temperature, amount of the reactive gas in the discharge atmosphere, sputtering pressure and the kind of substrate material used. Films have been deposited onto different substrates (glass, quartz, glassy carbon, highly oriented pyrolytic graphite) in order to apply different characterization methods (X-ray diffraction, Rutherford-backscattering, scanning electron microscopy, electrical measurements) and to use substrates which are suitable as a back contact. The conditions for the desired layer growth with the van der Waals-planes parallel to the substrate surface are reported.