Transition from Schottky-to-Ohmic contacts in 1T VSe2-based van der Waals heterojunctions: Stacking and strain effects

•The contact type and mechanism in 1T VSe2-based transition-metal dihalogenated vertical heterostructures have been investigated.•Ohmic contact is only found in the VSe2-multilayer MoSSe junctions.•Ohmic contact can be achieved when VSe2-based metal-semiconductor junctions are subjected to a tensile stress.