High-Performance Monolayer MoS_2 Field-Effect Transistors on Cyclic Olefin Copolymer-Passivated SiO_2 Gate Dielectric

摘要

Trap states of the semiconductor/gate dielectric interface give rise to a pronouncedsubthreshold behavior in field-effect transistors (FETs) diminishingand masking intrinsic properties of 2D materials. To reduce the well-knowndetrimental effect of SiO_2 surface traps, this work spin-coated an ultrathin(≈5 nm) cyclic olefin copolymer (COC) layer onto the oxide and this hydrophobiclayer acts as a surface passivator. The chemical resistance of COCallows to fabricate monolayer MoS_2 FETs on SiO_2 by standard cleanroom processes.This way, the interface trap density is lowered and stabilized almostfivefold, to around 5 × 10~(11) cm~(?2) eV~(?1), which enables low-voltage FETs evenon 300 nm thick SiO_2. In addition to this superior electrical performance, thephotoresponsivity of the MoS_2 devices on passivated oxide is also enhancedby four orders of magnitude compared to nonpassivated MoS_2 FETs. Underthese conditions, negative photoconductivity and a photoresponsivity of3 × 10~7 A W~(?1) is observed which is a new highest value for MoS_2. These findingsindicate that the ultrathin COC passivation of the gate dielectric enablesto probe exciting properties of the atomically thin 2D semiconductor, ratherthan interface trap dominated effects.