Single-Atom Vacancy Doping in Two-Dimensional Transition Metal Dichalcogenides

Abstract

ConspectusFaced with the growing quests of higher-performance chips, developing new channel semiconductors immune to short channel effects has become a realistic option for continuing Moore’s Law. With outstanding gate electrostatic capacitance, stable chemical properties, and suitable bandgap, two-dimensional (2D) transition metal dichalcogenides (TMDCs) are considered as potential candidates for next-generation channel materials. However, the practical applications of 2D TMDCs are severely limited by stable, precise, and controllable doping technologies, due to their ultrathin body and dangling bond-free surface. Compared to three-dimensional semiconductors, donors in 2D semiconductors need larger ionization energy which can be attributed to the reduced screening of Coulomb interaction and the larger bandgap induced by quantum confinement. Limited by the ultrathin body of 2D TMDCs and the strong film–substrate charge transfer, typical silicon-based substitutional doping technology encounters some headache difficulties in 2D TMDCs and hardly achieves high-concentration doping. The other two doping technologies also cannot take on this task either; local gate electrostatic doping cannot leave the aid of the external electric field. And surface charge transfer doping of molecule adsorbents behaves unstably (e.g., thermal desorption) or ineffectively modifies the original electronic structure. Fortunately, single-atom vacancies can effectively and precisely adjust the carrier concentration of 2D TMDCs and significantly enhance their conductivity. Therefore, clarifying the work rules and function mechanism of single-atom vacancy doping in 2D TMDCs is beneficial in creating a brand-new optimization strategy of electrical properties and overcoming the technical obstacles of the “lab-to-fab” transition for their practical applications in high-performance electronics and optoelectronics.In this Account, we summarize the state-of-the-art progress in single-atom vacancy doping in 2D TMDCs and highlight the applications in optoelectronic and electronic devices. First, the common defects and the density-largest-defect type in 2D TMDCs are demonstrated through experimental characterizations. Second, the healing and manufacturing strategies of chalcogen vacancies in 2D TMDCs are systematically summarized. Third, we clarify the doping mechanism of single-atom vacancies in 2D TMDCs and its regulation of the electrical properties including carrier concentration and carrier mobility. Fourth, the correlations between chalcogen vacancies in 2D TMDCs and the optical signals from Raman and photoluminescence spectroscopies are established, which will help to quickly and nondestructively evaluate the chalcogen vacancy concentration. Fifth, the current applications of single-atom vacancy doping of 2D TMDCs materials are reviewed, including complementary metal–oxide semiconductor (CMOS) logic inverters, homojunctions, Schottky diodes, and photovoltaic devices. Finally, the potential challenges and future development trends of single-atom vacancy doping for next-generation electronic and optoelectronic devices are pointed out. Overall, this Account guides on controllable and precise doping technologies for researchers in these fields from materials, electronics, and optoelectronics to promote the practical applications of 2D TMDCs.