EFFECT OF HUMIDITY ON SPREAD NBS2 FILMS

Highly orientated films of the transition metal dichalcogenides 2H-MoS2, 2H-WS2, 2H-TaS2and 3R-NbS2have been prepared using a suspension of the powders in water. The layered material is collected at the water/organic interface by shaking the suspension with a water-immiscible organic liquid. The films are spread spontaneously over a wet substrate using the Marangoni effect. The electrical resistance of spread films of NbS2increased on exposure to humidity, contrary to conventional behaviour. Rapid, reversible incorporation of water into the spacing between the basal planes of the layered platelets and at platelet edges is believed to be the cause of this curious effect. The response of the other dichalcogenide films to humidity was not significant. © 1990 IOP Publishing Ltd.