We
study the anisotropic electronic properties of two-dimensional
(2D) SnS, an analogue of phosphorene, grown by physical vapor transport.
With transmission electron microscopy and polarized Raman spectroscopy,
we identify the zigzag and armchair directions of the as-grown 2D
crystals. The 2D SnS field-effect transistors with a cross-Hall-bar
structure are fabricated. They show heavily hole-doped (∼1019 cm–3) conductivity with strong in-plane
anisotropy. At room temperature, the mobility along the zigzag direction
exceeds 20 cm2 V–1 s–1, which can be up to 1.7 times that in the armchair direction. This
strong anisotropy is then explained by the effective mass ratio along
the two directions and agrees well with previous theoretical predictions.
Temperature-dependent carrier density determined the acceptor energy
level to be ∼45 meV above the valence band maximum. This value
matches a calculated defect level of 42 meV for Sn vacancies, indicating
that Sn deficiency is the main cause of the p-type conductivity.