Planar Silicene: A New Silicon Allotrope Epitaxially Grown by Segregation

Abstract 2D sheets of graphene‐like silicon, namely planar silicene, are synthesized. This new silicon allotrope is prepared on Au(111) thin films grown on a Si(111) substrate in the process of surface segregation. Owing to its almost perfectly flat geometry it shares the atomic structure with graphene rather than with low‐buckled silicene. Scanning tunneling microscopy measurements clearly display an atomically resolved planar silicene honeycomb lattice. Ab initio density functional theory calculations fully support the experimental findings and predict a pure sp² atomic configuration of Si atoms. The present work is the first experimental evidence of epitaxial planar silicene.