[TuP3F] F. Low dimensional materials and structures

[TuP3F-04] Effects of Substrate Interactions on the Electrical Properties of hBN-Capped Monolayer MoTe₂ FETs

〇Takuto Ono¹, Kenji Watanabe², Takashi Taniguchi², Yusuke Hoshi¹ (1. Tokyo City University (Japan), 2. NIMS (Japan))

This study investigates the influence of substrate interactions on the electrical characteristics of hBN-capped monolayer (1L) MoTe₂ field-effect transistors (FETs) for gas-sensing applications. Monolayer MoTe₂ FETs were fabricated on SiO₂/Si substrates using a silver-assisted exfoliation technique, with graphite source/drain electrodes and an hBN capping layer. Transfer characteristics were measured under high vacuum as well as oxygen and nitrogen gas atmospheres. Even under high-vacuum conditions, clear hysteresis was observed during wide-range gate-voltage sweeps, indicating the presence of deep trap states. By limiting the gate-voltage sweep to either the p-type or n-type operation regime, the hysteresis was significantly reduced. Under O₂ exposure, a gradual positive threshold voltage shift was observed only in the n-type regime, while the p-type regime remained nearly unchanged. Similar behavior was also observed under inert N₂ gas, suggesting that the threshold voltage shift is not directly caused by gas adsorption. Instead, the results indicate that electrical stress and trap sites associated with mobile charges and defects in the SiO₂ substrate play a dominant role. These findings highlight the importance of minimizing substrate interactions, for example, by inserting atomically flat dielectric layers such as hBN, for reliable gas-sensing performance in TMD-based devices.