Hexagonal MoTe with Amorphous BN Passivation Layer for Improved Oxidation Resistance and Endurance of 2D Field Effect Transistors.

Environmental and thermal stability of two-dimensional (2D) transition metal dichalcogenides (TMDs) remains a fundamental challenge towards enabling robust electronic devices. Few-layer 2H-MoTe with an amorphous boron nitride (a-BN) covering layer was synthesized as a channel for back-gated field effect transistors (FET) and compared to uncovered MoTe. A systematic approach was taken to understand the effects of heat treatment in air on the performance of FET devices. Atmospheric oxygen was shown to negatively affect uncoated MoTe devices while BN-covered FETs showed considerably enhanced chemical and electronic characteristic stability. Uncapped MoTe FET devices, which were heated in air for one minute, showed a polarity switch from n- to p-type at 150 °C, while BN-MoTe devices switched only after 200 °C of heat treatment. Time-dependent experiments at 100 °C showed that uncapped MoTe samples exhibited the polarity switch after 15 min of heat treatment while the BN-capped device maintained its n-type conductivity for the maximum 60 min duration of the experiment. X-ray photoelectron spectroscopy (XPS) analysis suggests that oxygen incorporation into MoTe was the primary doping mechanism for the polarity switch. This work demonstrates the effectiveness of an a-BN capping layer in preserving few-layer MoTe material quality and controlling its conductivity type at elevated temperatures in an atmospheric environment.