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  Brunken, S.; Wollgarten, M.; Ellmer, K.: Analysis of the early stages of the rapid, nickel-assisted crystallization of WS₂ films. Journal of Applied Physics 120 (2016), p. 165307/1-4

10.1063/1.4966166

Abstract:
The nickel-sulfide-assisted rapid crystallization process was investigated in detail, and the understanding of the process of crystallization was improved. We found that nickel-sulfide-assisted crystal growth of WS2 films starts at the temperatures already below the eutectic temperature, leading to films with metallic behavior. This metallic behavior is due to a nickel-containing phase at the grain boundaries of the WS2-crystallites. Only annealing temperatures above the Ni-S-eutectic temperature lead to highly (001) textured WS2 films due to recrystallization induced by liquid nickel sulfide droplets. In these films, the WS2 crystallites have lateral sizes of several micrometers. Across the film NiSx crystallites are distributed. They are isolated from each other and generally exhibit a connection to the substrate surface.