Ultrathin Single-Crystalline Boron Nanosheets for Enhanced Electro-Optical Performances

Large-scale single-crystalline ultrathin boron nanosheets (UBNSs, ≈10 nm) are fabricated through an effective vapor-solid process via thermal decomposition of diborane. The UBNSs have obvious advantages over thicker boron nanomaterials in many aspects. Specifically, the UBNSs demonstrate excellent field emission performances with a low turn-on field, E_to, of 3.60 V μm^-1 and a good stability. Further, the dependence of (turn-on field) E_to/(threshold field) E_thr and effective work function, Φ_e, on temperature is investigated and the possible mechanism of temperature-dependent field emission phenomenon has been discussed. Moreover, electronic transport in a single UBNS reveals it to be an intrinsic p-type semiconductor behavior with carrier mobility about 1.26 × 10^-1 cm² V^-1 s^-1, which is the best data in reported works. Interestingly, a multiconductive mechanism coexisting phenomenon has been explored based on the study of temperature-dependent conductivity behavior of the UBNSs. Besides, the photodetector device fabricated from single-crystalline UBNS demonstrates good sensitivity, reliable stability, and fast response, obviously superior to other reported boron nanomaterials. Such superior electronic-optical performances are originated from the high quality of single crystal and large specific surface area of the UBNSs, suggesting the potential applications of the UBNSs in field-emitters, interconnects, integrated circuits, and optoelectronic devices.