Low-resistivity Ohmic contacts of Ti/Al on few-layered 1T'-MoTe/2H-MoTe heterojunctions grown by chemical vapor deposition.

This study explores the phase-controlled growth of few-layered 2H-MoTe, 1T'-MoTe, and 2H-/1T'-MoTe heterostructures and their impacts on metal contact properties. Cold-wall chemical vapor deposition (CW-CVD) with varying growth rates of MoO and reaction temperatures with Te vapors enabled the growth of continuous thin films of either 1T'-MoTe or 2H-MoTe phases on two-inch sapphire substrates. This methodology facilitates the meticulous optimization of chemical vapor deposition (CVD) parameters, enabling the realization of phase-controlled growth of few-layered MoTe thin films and their subsequent heterostructures. The study further investigates the influence of a 1T'-MoTe intermediate layer on the electrical properties of metal contacts on few-layered 2H-MoTe. Bi-layer Ti/Al contacts directly deposited on 2H-MoTe exhibited Schottky behavior, indicating inefficient carrier transport. However, introducing a few-layered 1T'-MoTe intermediate layer between the metal and 2H-MoTe layers improved the contact characteristics significantly. The resulting Al/Ti/1T'-MoTe/2H-MoTe contact scheme demonstrates Ohmic behavior with a specific contact resistance of around 1.7 × 10 Ω cm. This substantial improvement is attributed to the high carrier concentration of the 1T'-MoTe intermediate layer which could be attributed tentatively to the increased tunneling events across the van der Waals gap and enhancing carrier transport between the metal and 2H-MoTe.