Comparing study of picene thin films on SnSe and Au(1 1 1) surfaces

Picene, as one representative of polycyclic hydrocarbons, represents an appealing application in hydrocarbon superconductors. Here, using scanning tunneling microscopy and spectroscopy combined with density functional theory calculations, we investigated the structural and electronic properties of picene thin films on p-type SnSe and Au(1 1 1) surfaces. For both substrates, at low coverage, the molecules present a flat-lying geometry, while at high coverage, the molecules exhibit alternating flat-lying and tilt-standing configurations. The diffusion of the molecules on SnSe and the splitting of lowest unoccupied molecular orbital state on Au(1 1 1) indicate that SnSe surface has a weaker interaction with the adsorbed molecules compared to other metallic substrate. Therefore, based on our study on structural and electronic properties, we conclude that a semiconductor substrate can maintain the intrinsic properties of picene films. The study of picene on different substrates may pave a way to unveil the structural and electronic properties of hydrocarbon superconductors on substrates.