Composition and temperature-dependent phase transition in miscible Mo1-x Wx Te2 single crystals

Abstract

Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1-x Wx Te2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1-x Wx Te2. Simultaneously the electrical property gradually evolves from semiconductor to semimetal behavior. Temperature-dependent Raman spectroscopy proves that temperature also can induce the structural phase transition from β to Td phase in Mo1-x Wx Te2 crystals. Based on aforementioned characterizations, we map out the temperature and composition dependent phase diagram of Mo1-x Wx Te2 system. In addition, a series of electrical parameters, such as carrier type, carrier concentration and mobility, have also been presented. This work offers a scheme to accurately control structural phase in Mo1-x Wx Te2 system, which can be used to explore type-II Weyl semimetal, as well as temperature/composition controlled topological phase transition therein.