  In this review article, we discuss the synthesis, properties, and novel
device applications of low-symmetry 2D materials, including black phosphorus
and its arsenic alloys, compounds with black-phosphorus like structure such as
the monochalcogenides of group IV elements like Ge and Sn, as well as the class
of low-symmetry transition metal dichalcogenide (TMDC) materials such as
rhenium disulfide (ReS2) and rhenium diselenide (ReSe2). Their unique physical
properties resulting from the low symmetry in-plane crystal structure and the
prospects of their application in nanoelectronics and nanophotonics, as well as
piezoelectric devices and thermoelectrics are discussed.
