  We report the realization of field-effect transistors (FETs) made with
chemically- synthesized layered two dimensional (2D) crystal semiconductor WS2.
The 2D Schottky-barrier FETs demonstrate ambipolar behavior and a high (~105x)
on/off current ratio at room temperature with current saturation. The behavior
is attributed to the presence of an energy bandgap in the 2D crystal material.
The FETs show clear photo response to visible light. The promising electronic
and optical characteristics of the devices combined with the layered 2D crystal
flexibility make WS2 attractive for future electronic and optical devices.

Mesoscale and Nanoscale Physics;Materials Science