Xing-Yue Wang, Hui Zhang, Zi-Lin Ruan, Zhen-Liang Hao, Xiao-Tian Yang, Jin-Ming Cai, Jian-Chen Lu. Research progress of monolayer two-dimensional atomic crystal materials grown by molecular beam epitaxy in ultra-high vacuum conditions [J]. Acta Physica Sinica, 2020, 69(11): 118101-1