Encapsulated and hollow closed-cage structures of WS2 and MoS2 prepared bylaser ablation at 450-1050 degrees C

Encapsulated and hollow closed-cage onion-like structures of WS2 and MoS2 w ere prepared by laser ablation of the corresponding layered structures in a rgon atmosphere at four varied temperatures. A detailed study for WS2 indic ates that only metal-filled onion-like structures are produced at temperatu res T less than or equal to 650 degreesC, whereas a mixture of metal-filled and hollow structures are produced at T greater than or equal to 850 degre esC. The encapsulated metal is identified to be predominantly the metastabl e beta phase of tungsten. Very short tube-like or elongated polyhedral stru ctures are also obtained at high temperatures. (C) 2001 Published by Elsevi er Science B.V.