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 2 and 1T-WS 2 induces a charge redistribution in Sn and W to realize metallic Sn 0.5 W 0.5 S 2 nanosheets. These nanosheets are epitaxially deposited on surfaces of semiconducting SnS 2 nanoplates to form vertical heterostructures. The ohmic-like contact formed at the Sn 0.5 W 0.5 S 2 /SnS 2 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. Controlling the composition and crystal phase of layered heterostructures is important. Here, the authors report the liquid-phase epitaxial growth of Sn 0.5 W 0.5 S 2 nanosheets with 83% metallic phase on SnS 2 nanoplates, which are used as 100 ppb level chemiresistive gas sensors at room temperature.