Chemical vapour transport of molybdenum and tungsten diselenides by various transport agents

In order to obtain, by the chemical vapour transport (CVT) process, MoSe2 and WSe2 single crystals in maximal dimensions for photoelectrochemical studies of these materials, various transport agents have been used: Se, Br2, I2, SeCl4 and TeCl4. The nature and quantity of the transport agent alter the dimensions and the morphology of the obtained single crystals and also the semiconductivity type. Maximal dimensions have been obtained with TeCl4 and especially SeCl4 as transporting agents. They are very efficient in spite of silica attack problems, due to adsorbed water in the tetrachlorides.