  Ultrathin semiconductors present various novel electronic properties. The
first experimental realized two-dimensional (2D) material is graphene.
Searching 2D materials with heavy elements bring the attention to Si, Ge and
Sn. 2D buckled Si-based silicene was realized by molecular beam epitaxy (MBE)
growth1,2. Ge-based germanene was realized by mechanical exfoliation3. Sn-based
stanene has its unique properties. Stanene and its derivatives can be 2D
topological insulators (TI) with a very large band gap as proposed by
first-principles calculations4, or can support enhanced thermoelectric
performance5, topological superconductivity6 and the near-room-temperature
quantum anomalous Hall (QAH) effect7. For the first time, in this work, we
report a successful fabrication of 2D stanene by MBE. The atomic and electronic
structures were determined by scanning tunneling microscopy (STM) and
angle-resolved photoemission spectroscopy (ARPES) in combination with
first-principles calculations. This work will stimulate the experimental study
and exploring the future application of stanene.
