Improved chemical vapor transport growth of transition metal   dichalcogenides
  In the crystal growth of transition metal dichalcogenides by the Chemical Vapor Transport method (CVT), the choice of the transport agent plays a key role. We have investigated the effect of various chemical elements and compounds on the growth of TiSe2, MoSe2, TaS2 and TaSe2 and found that pure I2 is the most suitable for growing TiSe2, whereas transition metal chlorides perform best with Mo- and Ta- chalcogenides. The use of TaCl5 as a transport agent in the CVT process allows to selectively growth either polymorph of TaS2 and TaSe2 and the optimum growth conditions are reported. Moreover, by using TaCl5 and tuning the temperature and the halogen starting ratio, it was possible to grow whiskers of the compounds TaS2, TaSe2, TaTe2, TaS3 and TaSe3. 
Alberto Ubaldini and Enrico Giannini
cond-mat.mtrl-sci