Ternary metal-oxy-chalcogenides are emerging as next-generation layered semiconductors beyond binary metal-chalcogenides (i.e., MoS 2 ). Among ternary metal-oxy-chalcogenides, especially Bi 2 O 2 Se has been demonstrated in field-effect transistors and photodetectors, exhibiting ultrahigh performance with robust air stability. The growth method for Bi 2 O 2 Se that has been reported so far is a powder sublimation based chemical vapor deposition. The first step for pursuing the practical application of Bi 2 O 2 Se as a semiconductor material is developing a gas-phase growth process. Here, we report a cracking metal−organic chemical vapor deposition (c-MOCVD) for the gas-phase growth of Bi 2 O 2 Se. The resulting Bi 2 O 2 Se films at very low growth temperature (∼300 °C) show single-crystalline quality. By taking advantage of the gas-phase growth, the precise phase control was demonstrated by modulating the partial pressure of each precursor. In addition, c-MOCVD-grown Bi 2 O 2 Se exhibits outstanding electrical and optoelectronic performance at room temperature without passivation, including maximum electron mobility of 127 cm 2 /(V•s) and photoresponsivity of 45134 A/W.
Charge doping to Mott insulators is critical to realize hightemperature superconductivity, quantum spin liquid state, and Majorana fermion, which would contribute to quantum computation. Mott insulators also have a great potential for optoelectronic applications; however, they showed insufficient photoresponse in previous reports. To enhance the photoresponse of Mott insulators, charge doping is a promising strategy since it leads to effective modification of electronic structure near the Fermi level. Intercalation, which is the ion insertion into the van der Waals gap of layered materials, is an effective charge-doping method without defect generation. Herein, we showed significant enhancement of optoelectronic properties of a layered Mott insulator, α-RuCl 3 , through electron doping by organic cation intercalation. The electron-doping results in substantial electronic structure change, leading to the bandgap shrinkage from 1.2 eV to 0.7 eV. Due to localized excessive electrons in RuCl 3 , distinct density of states is generated in the valence band, leading to the optical absorption change rather than metallic transition even in substantial doping concentration. The stable near-infrared photodetector using electronic modulated RuCl 3 showed 50 times higher photoresponsivity and 3 times faster response time compared to those of pristine RuCl 3 , which contributes to overcoming the disadvantage of a Mott insulator as a promising optoelectronic device and expanding the material libraries.
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