Direct Experimental Observation of Facet‐Dependent SERS of Cu2O Polyhedra

Abstract Semiconductor‐based surface enhanced Raman scattering (SERS) has attracted great attention due to its excellent spectral reproducibility, high uniformity, and good anti‐interference ability. However, its relatively low SERS sensitivity still hinders its further developments in both performance and applications. Since the SERS is a peculiar surface effect, investigating the facet‐dependent SERS activity of semiconductor nanostructures is crucial to boost their SERS signals. Although the semiconductor facet‐dependent SERS effect is predicted via numerical calculations, convincing experimental evidence is scarce due to complicated and undefined surface conditions. In this work, three facet‐defined (100, 110, and 111 facets) Cu 2 O microcrystals (MCs) with clear surface atomic configuration are utilized to investigate the facet‐dependent SERS effect. The results from the Kelvin probe force microscopy measurements on single Cu 2 O polyhedron, demonstrate that the facet‐dependent work function plays a crucial role in the interfacial charge transfer process. Comparing with the 110 and 111 facets, the 100 facet possesses the lowest electronic work function, which enables more efficient interfacial charge transfer. The simulation results further confirm that the 100‐facets can transfer the most electrons from Cu 2 O MCs to molecules due to its lowest facet work function, resulting in the largest increment of the molecular polarization.