Underpotential-Assisted Electrodeposition of Highly Crystalline and Smooth Thin Film of Bismuth

In this work, the electrodeposition of smooth bismuth thin films was investigated. Bismuth is known for its peculiar magnetic, thermal and electrical properties but the deposition of a uniform and flat film, which are features required for its application in electronic devices, is not trivial. We investigated the morphology of Bi film electrodeposited at increasing overpotential on a monocrystalline silver electrode. We found that the presence of an underpotential deposition (UPD) layer, previously deposited on the surface, drives the overpotential deposition to a smoother growth. The samples were investigated by means of different techniques: atomic force microscopy (AFM) and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDS) to study the morphology, X-ray photoemission spectroscopy (XPS) to assess the composition and X-ray diffraction spectroscopy (XRD) to check the crystallinity. We also found an unexpected form birefringence behaviour, which has been preliminary investigated with cross polarized light microscopy (CPL).