  The band modulation of the silicene and graphene quantum dots is investigated
by a first-principles method. This study includes the ordinary silicene and
graphene quantum dots and the embedded quantum dots in the hydrogenated
silicene and graphene. The shapes and sizes of quantum dots are recognized as
important factors for the electronic properties. We studied several types of
quantum dots: triangular, parallelogram, rectangular, hexagonal dots. It
demonstrates the energy gap of the quantum dot can be tuned by the dot size,
the larger of the dot the smaller the energy gap. Moreover, the shapes affect
the magnetism of the quantum dots. The triangular dot exhibits as magnetic
semiconductor; the parallelogram dot shows antiferromagnetic characteristics;
while the hexagonal dot is non-magnetic. Control the size and shape of a
silicene or graphene quantum dot can manipulate its magnetism and electronic
properties.
