Large-area and few-layered 1T'-MoTe2thin films grown by cold-wall chemical vapor deposition.

ABSTRACT

This study employs cold-wall chemical vapor deposition to achieve the growth of MoTe2thin films on 4-inch sapphire substrates. A two-step growth process is utilized, incorporating MoO3and Te powder sources under low-pressure conditions to synthesize MoTe2. The resultant MoTe2thin films exhibit a dominant 1T' phase, as evidenced by a prominent Raman peak at 161 cm-1. This preferential 1T' phase formation is attributed to controlled manipulation of the second-step growth temperature, essentially the reaction stage between Te vapor and the pre-deposited MoOxlayer. Under these optimized growth conditions, the thickness of the continuous 1T'-MoTe2films can be precisely tailored within the range of 3.5-5.7 nm (equivalent to 5-8 layers), as determined by atomic force microscopy depth profiling. Hall-effect measurements unveil a typical hole concentration and mobility of 0.2 cm2Vs-1and 7.9 × 1021cm-3, respectively, for the synthesized few-layered 1T'-MoTe2films. Furthermore, Ti/Al bilayer metal contacts deposited on the few-layered 1T'-MoTe2films exhibit low specific contact resistances of approximately 1.0 × 10-4Ω cm2estimated by the transfer length model. This finding suggests a viable approach for achieving low ohmic contact resistance using the 1T'-MoTe2intermediate layer between metallic electrodes and two-dimensional semiconductors.