Electrodeposition of Germanene from Aqueous Solution, pH 9.0

Abstract

The group IV elements including C, Si, Ge and Sn have all shown to form 2D allotropes that have drastically different properties from their bulk component. Following the discovery of graphene and silicene, the study of germanene has garnered increasing interest and has raised many questions pertaining to its exact structure, properties and formation. A number of theoretical calculations have proposed structures for germanene with varying bond distances and degree of buckling. Some experimental works suggest that germanene could be deposited via molecular beam epitaxy (MBE) using germanium wafer as source. This study proposes an alternative route of forming germanene via electrodeposition 1. Electrochemical scanning tunneling microscopy (EC-STM), and in situ surface-enhanced micro Raman (SERS) are used as means to gather information on the deposition process of Ge on Au(111). The optimal condition to grow a single atomic layer of Ge was selected based on atomic resolution images from EC-STM. Various phases of Ge were observed, detailing the transition from a precursor stage to complete honeycomb rings of germanene. The nucleation process started with growth of some small Ge domains, followed by a lateral expansion through the edges. After forming the second layer, the surface became passivated as expected for an insulating gap of a 2D bulk material. Current efforts are being directed toward forming a thicker germanene film using our previously developed methodology called Ge-Te bait-and-switch electrochemical ALD cycle 2-4. The approach involves using Te as a capping layer and as a basal support to allow Ge to form new layer. This work is supported by the National Science Foundation.