Hexagonal MoTe₂ with Amorphous BN Passivation Layer for Improved Oxidation Resistance and Endurance of 2D Field...

Environmental and thermal stability of two-dimensional (2D) transition metal dichalcogenides (TMDs) remains a fundamental challenge towards enabling robust electronic devices. Few-layer 2H-MoTe₂ 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 MoTe₂. 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 MoTe₂ devices while BN-covered FETs showed considerably enhanced chemical and electronic characteristic stability. Uncapped MoTe₂ FET devices, which were heated in air for one minute, showed a polarity switch from n- to p-type at 150 °C, while BN-MoTe₂ devices switched only after 200 °C of heat treatment. Time-dependent experiments at 100 °C showed that uncapped MoTe₂ 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 MoTe₂ was the primary doping mechanism for the polarity switch. This work demonstrates the effectiveness of an a-BN capping layer in preserving few-layer MoTe₂ material quality and controlling its conductivity type at elevated temperatures in an atmospheric environment.