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Register a new userBlack Phosphorus Nanoelectromechanical Resonators Vibrating at Very High Frequencies
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We report on experimental demonstration of a new type of nanoelectromechanical resonators based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200nm down to ~20nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting promises for moveable and vibratory devices, and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus.
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The discovery of graphene triggered a rapid rise of unexplored two-dimensional materials and heterostructures having optoelectronic and photonics properties that can be tailored on the nanoscale. Among these materials, black phosphorus (BP) has attracted a remarkable interest thanks to many favorable properties, such as high carrier mobility, in-plane anisotropy, the possibility to alter its transport via electrical gating and direct band-gap, that can be tuned by thickness from 0.3 eV (bulk crystalline) to 1.7 eV (single atomic layer). When integrated in a microscopic field effect transistor (FET), a few-layer BP flake can detect Terahertz (THz) frequency radiation. Remarkably, the in-plane crystalline anisotropy can be exploited to tailor the mechanisms that dominate the photoresponse; a BP-based field effect transistor can be engineered to act as a plasma-wave rectifier, a thermoelectric sensor or a thermal bolometer. Here we present a review on recent research on BP detectors operating from 0.26 THz to 3.4 THz with particular emphasis on the underlying physical mechanisms and the future challenges that are yet to be addressed for making BP the active core of stable and reliable optical and electronic technologies.
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