Electric-Field Sensor Based on Multilayer-MoS₂/Multilayer-Graphene Heterostructure with Built-In Tensile Strain

We report a highly sensitive electric field (E-field) sensor based on a multilayer MoS₂/multilayer graphene (ML-MoS₂/MLG) heterostructure with built-in tensile strain. The MLG functions as a bottom source-drain contact, thereby enhancing the charge injection into the ML-MoS₂ channel. The unique device geometry further induces tensile strain in the ML-MoS₂ channel by bending it over the MLG edge, which improves the carrier mobility through reduced electron-phonon scattering. As a result, the ML-MoS₂/MLG device achieves an average carrier mobility of 75.7 cm² V^-1 s^-1, with values up to ∼108 cm² V^-1 s^-1 at room temperature, significantly exceeding that of conventional metal-contacted MoS₂ devices. Upon exposure to external E-fields, the device exhibits polarity-dependent variations in the drain current arising from field-induced carrier transfer between the ML-MoS₂ channel and trap states at the SiO₂/channel interface. The E-field sensitivity, defined as the relative change in drain current, increases linearly with the E-field magnitude. Owing to the enhanced charge injection and improved carrier mobility, the ML-MoS₂/MLG device demonstrates superior E-field sensing performance, achieving a sensitivity around three times that of metal-contacted MoS₂ devices. Notably, the minimum detectable E-field reaches ∼100 V/m, highlighting its potential for atmospheric E-field monitoring toward lightning detection applications.