Abstract
Transition-metal dichalcogenides is constituted by transition metal and chalcogenide elements. The two dimensional monolayer material is able to be stable in nature. Depending on the selection of the metal, these materials may exhibit insulator, semiconducting, or metallic properties. It attracts much attention in recent years. This thesis discusses the growth of WSe2 and NbSe2. Initially, we construct the equipment (i.e. furnace) by self. We will then describe WSe2 monolayer and large-scale of WSe2 which is 5 centimeters in diameter. It proves the LPCVD could deposit large-scale WSe2. On the other hand, we use selenization of transition metal oxide to form Nb-doped WSe2. We hope to upgrade the value in this application. In devices, the maximum current of monolayer WSe2 reaches 12 nA/µm and on/off current ratio is 10^4 to 10^6. the best subthreshold swing is up to 96 mV/dec. It is very suitable for logic circuit design. On the other hand, the doping concentration of Nb-doped WSe2 is below 5%. The current and mobility are larger. It only exhibits an on/off current ratio of 1.1 and subthreshold swing of 12.77 V/dec. It appears to be metallic.