  In recent years, two-dimensional (2D) layered semiconductors have received
much attention for their potential in next-generation electronics and
optoelectronics. Wide-bandgap 2D semiconductors are especially important in
blue and ultraviolet wavelength region, while there are very few 2D materials
in this region. Here, monolayer \b{eta}-type zirconium nitride chloride
(\b{eta}-ZrNCl) is isolated for the first time, which is an air-stable layered
material with a bandgap of ~3.0 eV in bulk. Systematical investigation of
layer-dependent Raman scattering of ZrNCl from monolayer, bilayer, to bulk
reveals a blue shift of its out-of-plane A1g peak at ~189 cm-1. Importantly,
this A1g peak is absent in monolayer, suggesting that it is a fingerprint to
quickly identify monolayer and for the thickness determination of 2D ZrNCl. The
back-gate field-effect transistor based on few-layer ZrNCl shows a high on/off
ratio of 108. These results suggest the potential of 2D \b{eta}-ZrNCl for
electronic applications.
