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Highly (001) textured tungsten disulphide (WS2) thin films are grown by rapid nickel-induced crystallization of amorphous reactive sputtered sulphur-rich tungsten sulphide (WS3+x). The rapid crystallization is monitored by real-time in-situ energy dispersive X-ray diffraction (EDXRD). Provided that a thin nickel film is deposited prior the deposition of WS3+x the films crystallize very fast ( about 20 nm/s) . The crystallization starts at about 650 °C, in the range of the Ni-S eutectic temperature of 637 °C. After crystallization isolated hexagonal NiS - crystallites are located on the surface of the WS2-layer, which is proved by scanning electron microscopy and transmission electron microscopy. This together with the crystallization temperature leads to the model that the rapid crystallization occurs from liquid NiSx droplets, which solve WSx, oversaturate, release WS2 and floating on the top of the crystallizing volume to the top of the layer. These nickel-induced crystallized WS2-layers exhibit a pronounced (001) orientation with large crystallites up to 3 μm. They show photoactivity and high hole mobilities (about 50 cm2/Vs). Combined with the high absorption coefficient of 105 cm-1 and a direct band gap of 1.8 eV these properties make such films suitable for absorber layers in thin film solar cells. Rapid Crystallization is possible on oxidized silicon as well as on conductive films, which can serve as back contact in thin film solar cells. |