Atomically Precise PdSe 2 Pentagonal Nanoribbons.

We report atomically precise pentagonal PdSe nanoribbons (PNRs) fabricated on a pristine PdSe substrate with a hybrid method of top-down and bottom-up processes. The PNRs form a uniform array of dimer structure with a width of 2.4 nm and length of more than 200 nm. In situ four-probe scanning tunneling microscopy (STM) reveals metallic behavior of PNRs with ballistic transport for at least 20 nm in length. Density functional theory (DFT) calculations produce a semiconducting density of states (LDOS) of isolated PNRs and find that the band gap narrows and disappears quickly once considering coupling between PNR stacking layers or interaction with the PdSe substrate. The coupling of PNRs is further corroborated by Raman spectroscopy and field-effect transistor measurements. The facile method of fabricating atomically precise PNRs offers an air-stable functional material for dimensional control.