Nature of Electrically Induced Defects in CVD-grown Monolayer MoS2

Abstract We find that defects are also introduced by prolonged operation of single crystal CVD-grown monolayer MoS2 FETs which hinder the overall performance. These defects result in threshold voltage instabilities, enhanced channel conductance, improved screening of charged impurity scattering sites and better thermal management in MoS2 transistors. It turns out that long-term electrical stress (LTES) results in a piezoelectric response in MoS2 which leads to permanent change in the material’s molecular configuration. This change in the molecular structure of MoS2 is, in fact, weakening of Mo-S bonds. Such a deviation from the original crystal structure results in suppressed hopping transport within the channel while increasing free electron concentration and hence reduction in channel potential without increasing sulfur vacancy concentration. It is also found that these defects result in enhanced thermal dissipation capability of MoS2 transistors. These results are particularly important from a fundamental perspective because they unveil a unique self-adaptive piezoelectric response in MoS2 against long-term high-field transport which eventually modifies its electrical and thermal transport properties. This is an entirely new property of single crystal CVD-grown monolayer MoS2 which has remained unidentified. It triggers a need to reconsider supply voltage requirements of MoS2-based CMOS circuits for low-power logic applications.