Bulk synthesis of long nanotubes of transition metal chalcogenides

Abstract

Nanotubes of transition metal chalcogenides as long as 0.2-20 microns or more, perfect in shape and of high crystallinity, are synthesized from a transition metal material, e.g. the transition metal itself or a substance comprising a transition metal such as an oxide, water vapor and a H 2 X gas or H 2 gas and X vapor, wherein X is S, Se or Te, by a two-step or three-step method. The transition metal chalcogenide is preferably WS 2 or WSe 2 . Tips for scanning probe microscopy can be prepared from said long transition metal chalcogenide nanotubes.

What is claimed is:  
     
         1 . A method for preparation of tips for scanning probe microscopy which comprises: 
 a) transferring adhesive from carbon tape to a microfabricated Si tip; and    b) pulling off bundles of a transition metal chalcogenide nanotubes with said tip from a mat of long nanotubes prepared on a different area of the tape,    wherein said long nanotubes have a size of 0.2-20 μm or greater, and are obtained by bulk synthesis of long nanotubes of transition metal chalcogenides from a transition metal material, water vapor and H 2 X gas or H 2  gas and X vapor, wherein X is S, Se or Te and synthesis, comprising: 
 a) either heating a transition metal material in the presence of water vapor in a vacuum apparatus or electron beam evaporating a transition metal material in the presence of water vapor, at a preselected pressure, to obtain nanoparticles of the transition metal oxide as long as 0.3 microns; and  
 b) annealing the transition metal oxide nanoparticles obtained in step (a) in a mild reducing atmosphere with a H 2 X gas or H 2  gas and X vapor, wherein X is S, Se or Te, at a suitable temperature, thus obtaining said long nanotubes of the transition metal chalcogenide, said nanotubes.  
   
     
     
         2 . A method according to  claim 1 , wherein said transition metal chalcogenide is WS 2  and/or WSe 2 .