Journal Club do Departamento de Física dos Materiais e Mecânica

Black phosphorus consists of stacked layers of phosphorene, a
two-dimensional semiconductor with promising device characteristics.
We report the realization of a widely tunable band gap in few-layer
black phosphorus doped with potassium using an in situ surface doping
technique. Through band structure measurements and calculations, we
demonstrate that a vertical electric field from dopants modulates the
band gap, owing to the giant Stark effect, and tunes the material from
a moderate-gap semiconductor to a band-inverted semimetal. At the
critical field of this band inversion, the material becomes a Dirac
semimetal with anisotropic dispersion, linear in armchair and
quadratic in zigzag directions. The tunable band structure of black
phosphorus may allow great flexibility in design and optimization of
electronic and optoelectronic devices.