Visible-frequency plasmonic enhancement at the edge of graphene/h-BN heterostructures on silicon substrate

• Published in: Carbon (New York) 2024-02, Vol.219, p.118836, Article 118836
• Main Authors: Kuliček, Jaroslav, Yamada, Takatoshi, Taniguchi, Takashi, Rezek, Bohuslav
• Format: Article
• Language: English
• Subjects: Boron nitride; Graphene; Nanostructures; Plasmons; Raman; Surface potential
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2024.118836

Heterostructures of graphene and hexagonal boron nitride (G/h-BN) have been widely studied for controlling and utilizing graphene electronic properties. Here we characterize specific optical and electronic properties of G/h-BN heterostructures made of a high-quality single layer chemical vapor deposition (CVD) graphene laid over h-BN flakes, with focus on plasmonic effects. We compare the G/h-BN properties on Si and SiO2 substrates by micro-Raman spectroscopy mapping, Kelvin probe force microscopy, optical and atomic force microscopy. We observe highly enhanced Raman intensity (up to 280 %) from Si as well as graphene along the G/h-BN edge. It is attributed to localized concentration of electrons in graphene and suitable perpendicular orientation of plasmonic vibrations at the edge. The plasmonic Raman enhancement occurs under a visible light excitation (532 nm) and the effect can be tuned by the h-BN flake thickness (10–150 nm). The enhancement is specific to G/h-BN/Si structures, on G/h-BN/SiO2 structures the Raman signal is suppressed while I2D/IG ratio is increased. Vice versa, change of surface potential under visible light illumination (photovoltage) is on G/h-BN/Si negligible (within 10 mV) compared to the G/h-BN/SiO2 structures. These results open new prospects for broad utilization of localized visible plasmonic effects in graphene. [Display omitted]