Anomalous Heavy Doping In Chemical-Vapor-Deposited Titanium Trisulfide Nanostructures

Nanoscale transition-metal trichalcogenides such as TiS3 have shown great potential for both fundamental studies and application developments, yet their bottom-up synthesis strategy is to be realized. Here we explored the chemical vapor deposition (CVD) synthesis of TiS3, whose lattice anisotropy has enabled the preferential growth along the b axis, resulting in rectangular nanosheets or nanoribbons with aspect ratios tunable by the growth temperature. The obtained nanostructures, while maintaining the spectroscopic and structural characteristics as that of pristine semiconducting TiS3, exhibit high conductivities and ultralow carrier activation barriers, promising as nanoscale conductors. Our experimental and calculation results suggest that the existence of S-2(2-) vacancies in the CVD-grown TiS3 is responsible for the heavy n-type doping up to a degenerate level. Moreover, the semiconducting property is predicted to be recovered by passivating the S-2(2-) vacancies with oxygen atoms from ambient. This work hence portends the tantalizing possibility of constructing nanoscale electronics with defect-engineered trichalcogenide semiconductors.