Reactive magnetron sputtering of highly (001)-textured WS2−x films: Influence of Ne+, Ar+ and Xe+ ion bombardment on the film growth

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2006-02, Vol.203 (3), p.497-503
• Main Authors: Ellmer, K., Seeger, S., Sieber, I., Bohne, W., Röhrich, J., Strub, E., Mientus, R.
• Format: Article
• Language: English
• Subjects: 61.10.Eq; 61.80.Jh; 68.55.Jk; 81.05.Hd; 81.15.Cd
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.200521363

Layer‐type van der Waals semiconductor WS2−x films were grown by radio frequency reactive magnetron sputtering from a metallic tungsten target onto oxidized silicon substrates. The sputtering atmosphere consisted of 75% hydrogen sulfide and 25% neon, argon or xenon. The substrate voltage and hence the energy of the ions bombarding the growing film, was varied from about 20 V (floating potential) to −80 V. By in situ energy‐dispersive X‐ray diffraction the growth of the films was monitored and by elastic recoil detection analysis the film composition was measured. It was found that with xenon in the sputtering atmosphere a substrate voltage of −20 V is sufficient to suppress the crystalline film growth, while for argon as the sputtering rare gas this occurs only at −80 V. The disturbed film growth is accompanied by a sulfur loss of the growing WS2−x films down to x  = 1.1 for sputtering in Ar + H2S at a substrate potential of −60 V. The results are tentatively explained by the different momentum transfers to sulfur atoms, which is highest for argon ions. It has also to be taken into account that the low‐energy xenon bombardment is a many‐body cascade process with a much higher local energy density compared to argon and neon bombardment and leading to a higher defect density and a supression of the crystalline growth. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)