Brunken, S.; Mientus, R,; Seeger, S.; Ellmer, K.: The mechanism of nickel sulfide induced rapid crystallization of highly textured tungsten disulfide (WS2) thin films: An in situ real-time diffraction study. Journal of Applied Physics 103 (2008), p. 063501/1-6
10.1063/1.2875679
Open Access Version (available 01.06.2008)
Abstract:
Highly (001) textured tungsten disulphide (WS2 ) thin films have been grown by nickel-sulphide induced rapid crystallization of amorphous sulphur-rich tungsten sulphide (WS3+x ) films. The rapid crystallization was monitored by real-time in situ energy dispersive X-ray diffraction (EDXRD). Provided that a thin nickel film is deposited prior to the deposition of WS3+x , the films crystallize very fast ( > 20 nm/s). The crystallization starts at a temperature of about 650 °C, i.e. slightly above the Ni-S eutectic temperature of 637 °C. After crystallization iso- lated hexagonal NiSx crystallites are located on the surface of the WS2 layer, which was proved by scanning and transmission electron microscopy. These results lead to the model that the rapid crystallization occurs by liquid-phase crystal growth from NiSx droplets floating on top of the crystallized WS2 films. These nickel-sulphide induced crystallized WS2 layers exhibit a pronounced (001) orientation with crystallite sizes up to 3 ?m diameter.