  A few-layer black phosphorene has recently gained significant interest in the
scientific community. In this paper, we consider several polymorphs of
phosphorene nanoribbons (PNRs) and employ deformation potential theory within
the effective mass approximation together with density functional theory to
investigate their structural, mechanical and electronic properties. The results
show that stability of PNRs strongly depends on the direction along which they
can be cut from 2D counterpart. PNRs also exhibit a wide range of line
stiffness ranging from 6x10^10 eV/m to 18x10^11 eV/m which has little
dependence on the edge passivation. Likewise, the calculated electronic
properties of PNRs display them to be either narrow-gap semiconductor (Eg < 1
eV) or wide-gap semiconductor (Eg > 1 eV). The carrier mobility of PNRs is
found to be comparable to that of the black phosphorene. Some of the PNRs show
n-type (p-type) semiconducting character owing to their higher electron (hole)
mobility. Passivation of the edges leads to n-type <-> p-type transition in
many of the PNRs considered. The predicted novel characteristics of PNRs with a
wide range of mechanical and electronic properties make PNRs to be potentially
suitable for the use in nanoscale devices.
