Mechanical exfoliation and electrical characterization of a one-dimensional Nb₂Se₉ atomic crystal

A novel semiconductor 1D nanomaterial, Nb₂Se₉, was synthesized on a bulk scale via simple vapor transport reaction between niobium and selenium. Needle-like single crystal Nb₂Se₉ contains numerous single Nb₂Se₉ chains linked by van der Waals interactions, and we confirmed that a bundle of chains can be easily separated by mechanical cleavage. The exfoliated Nb₂Se₉ flakes exhibit a quasi-two-dimensional layered structure, and the number of layers can be controlled using the repeated-peeling method. The work function varied depending on the thickness of the Nb₂Se₉ flakes as determined by scanning Kelvin probe microscopy. Moreover, we first implemented a field effect transistor (FET) based on nanoscale Nb₂Se₉ flakes and verified that it has p-type semiconductor characteristics. This novel 1D material can form a new family of 2D materials and is expected to play important roles in future nano-electronic devices.