Ying Zhang, Chang Liu, Huiting Wang, Guichen Teng, Yilu Qin, Wencheng Niu, Shuimei Ding, Binmin Wu, Shuaiqin Wu, Yan Chen, Ni Yang, Tie Lin, Hong Shen, Xiangjian Meng, Yuan Liu, Xuming Zou, Xudong Wang, Lei Liao, Junhao Chu, Lain-Jong Li, Jianlu Wang
Metal contacts remain one of the key bottlenecks in two-dimensional (2D) semiconductor electronics. We developed an atomic-scale step-by-step evaporation method to directly grow single-crystal metals on monolayer semiconductors with clean interfaces. This method accesses a distinct growth-kinetic window that suppresses secondary nucleation and promotes lateral coalescence, enabling van der Waals epitaxy of diverse metals-including bismuth, silver, indium, gold, and palladium-on molybdenum disulfide (MoS2) and tungsten diselenide (WSe2). The single-crystal metals support ultrathin conduction, provide spatially uniform work functions, and exhibit improved thermal robustness. As contacts, they show minimal Fermi-level pinning, approaching the Schottky-Mott limit. With bismuth and palladium contacts, monolayer MoS2 and WSe2 transistors achieved ultralow n- and p-type contact resistances of 36 and 145 ohm-micrometers, respectively, and short-channel currents both above 1.1 milliampere per micrometer.