  We report structural, physical properties and electronic structure of van der
Waals (vdW) crystal VI3. Detailed analysis reveals that VI3 exhibits a
structural transition from monoclinic C2/m to rhombohedral R-3 at Ts ~ 79 K,
similar to CrX3 (X = Cl, Br, I). Below Ts, a long-range ferromagnetic (FM)
transition emerges at Tc ~ 50 K. The local moment of V in VI3 is close to the
high-spin state V3+ ion (S = 1). Theoretical calculation suggests that VI3 may
be a Mott insulator with the band gap of about 0.84 eV. In addition, VI3 has a
relative small interlayer binding energy and can be exfoliated easily down to
few layers experimentally. Therefore, VI3 is a candidate of two-dimensional FM
semiconductor. It also provides a novel platform to explore 2D magnetism and
vdW heterostructures in S = 1 system.
