An exfoliable transition metal chalcogenide semiconductor NbSe2I2

As the field of exfoliated van der Waals electronics grows to include complex heterostructures, the variety of available in-plane symmetries and geometries becomes increasingly valuable. In this work, we present an efficient chemical vapor transport synthesis of NbSe2I2 with triclinic space group P-1. This material contains Nb–Nb dimers and an inplane crystallographic angle γ = 61.3◦. We show that NbSe2I2 can be exfoliated down to few-layer and mono-layer structures and used Raman spectroscopy to test the preservation of crystal structure of exfoliated thin films. The crystal structure was verified by singlecrystal and powder X-ray diffraction. Density functional theory calculations show triclinic NbSe2I2 to be a semiconductor with a band gap of around 1 eV, with similar band structure features for bulk and mono-layer crystals. The physical properties of NbSe2I2 have been characterized by transport, thermal, optical, and magnetic measurements, demonstrating triclinic NbSe2I2 to be a diamagnetic semiconductor that does not exhibit any phase transformation below room temperature.