摘要
Monolayer molybdenum disulfide (MoS <sub>2</sub> ) has become a promising building block in optoelectronics for its high photosensitivity. However, sulfur vacancies and other defects significantly affect the electrical and optoelectronic properties of monolayer MoS <sub>2</sub> devices. Here, highly crystalline molybdenum diselenide (MoSe <sub>2</sub> ) monolayers have been successfully synthesized by the chemical vapor deposition (CVD) method. Low-temperature photoluminescence comparison for MoS <sub>2</sub> and MoSe <sub>2</sub> monolayers reveals that the MoSe <sub>2</sub> monolayer shows a much weaker bound exciton peak; hence, the phototransistor based on MoSe <sub>2</sub> presents a much faster response time (<25 ms) than the corresponding 30 s for the CVD MoS <sub>2</sub> monolayer at room temperature in ambient conditions. The images obtained from transmission electron microscopy indicate that the MoSe exhibits fewer defects than MoS <sub>2</sub> . This work provides the fundamental understanding for the differences in optoelectronic behaviors between MoSe <sub>2</sub> and MoS <sub>2</sub> and is useful for guiding future designs in 2D material-based optoelectronic devices. © 2014 American Chemical Society.