Realization of vertical metal semiconductor heterostructures via solution phase epitaxy.

The creation of crystal phase heterostructures of transition metal chalcogenides, e.g., the 1T/2H heterostructures, has led to the formation of metal/semiconductor junctions with low potential barriers. Very differently, post-transition metal chalcogenides are semiconductors regardless of their phases. Herein, we report, based on experimental and simulation results, that alloying between 1T-SnS and 1T-WS induces a charge redistribution in Sn and W to realize metallic SnWS nanosheets. These nanosheets are epitaxially deposited on surfaces of semiconducting SnS nanoplates to form vertical heterostructures. The ohmic-like contact formed at the SnWS/SnS heterointerface affords rapid transport of charge carriers, and allows for the fabrication of fast photodetectors. Such facile charge transfer, combined with a high surface affinity for acetone molecules, further enables their use as highly selective 100 ppb level acetone sensors. Our work suggests that combining compositional and structural control in solution-phase epitaxy holds promises for solution-processible thin-film optoelectronics and sensors.