Abstract
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.
Highlights
Recent advances in the field of 2D materials have focused on molecular-thin, TMDs as semiconductor counterparts to graphene in the use of nanoscale electronics[1,2,3,4,5]
An exploration of a non-oxide based and environmentally stable dielectric material to be used in conjunction with TMD field effect transistors (FET) devices, or other 2D materials such as graphene and black phosphorus, and would benefit the wider usage of such materials
Formation of Te vacancy sites and the potential for atmospheric oxygen to form substitutional dopants were of critical attention in the performed study. We find this BN capping layer to be an effective barrier layer, which protects the 2D TMD material from detrimental chemical oxidation, and significantly reduces the rate of field effect mobility and on/off ratio degradation of FET devices as compared to the uncapped sample
Summary
Received: 25 January 2018 Accepted: 18 May 2018 Published: xx xx xxxx of 2D Field Effect Transistors. The charge carrier quantum confinement, high mobility, and reduced interaction with adjusted layers due to a lack of dangling surface bonds has initiated an extensive number of studies regarding monolayer TMDs for electrical and optoelectronic devices In this respect, field effect transistors made of 2D MoTe2 have been demonstrated to exhibit p-type[11,12], n-type[13], and ambipolar[14] behavior. Formation of Te vacancy sites and the potential for atmospheric oxygen to form substitutional dopants were of critical attention in the performed study We find this BN capping layer to be an effective barrier layer, which protects the 2D TMD material from detrimental chemical oxidation, and significantly reduces the rate of field effect mobility and on/off ratio degradation of FET devices as compared to the uncapped sample
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