High unsaturated room-temperature magnetoresistance in phase-engineered Mo x W 1−x Te 2+δ ultrathin films

Highly stable ultrathin films of large unsaturated room-temperature magnetoresistance (MR) are essential for the next-generation real-time magnetoelectric devices. A large-area, transfer-free, highly crystalline, and phase-engineered ultrathin film of T d -Mo 0.27 W 0.71 Te 2.02 or 2H- & T d -Mo 0.22 W 0.89 Te 1.89 on a hexagonal boron nitride (h-BN) substrate was synthesized using an atmospheric-pressure chemical vapor deposition (APCVD) method. The T d -Mo 0.27 W 0.71 Te 2.02 with average mobility of 725 cm 2 V −1 s −1 possesses non-saturating MR of 18% at 5 K and 11% at room temperature. Quantum correction to the magnetotransport study suggests the existence of a weak anti-localization effect dominated by the electron–electron interaction to render the non-saturating linear MR in a wide temperature range. Moreover, the spin–orbit interaction in T d -Mo 0.27 W 0.71 Te 2.02 was found valid till an applied field of 0.05 T with an interaction length of 18 nm at 300 K. In this alloy system, the weak localization effect was evidenced unprecedentedly by the Te-deficient 2H- & T d -Mo 0.22 W 0.89 Te 1.89 thin film with unusual co-existence of two crystal phases, which exhibit a suppressed MR caused by the recurring inelastic scattering with a reduced phase coherence length. This work explores the production of phase-engineered large-area Weyl semi-metallic 2D materials for the realization of magnetoelectrics in the near future.