Phonon anharmonicities in 7-armchair graphene nanoribbons

Graphene nanoribbons (GNRs) provide a potential alternative to overcome the shortcoming of gapless graphene and have been applied into next-generation nanoelectronic devices like FETs. The phonon anharmonicities in functional materials usually play a key role in the device performance. Here, temperature dependent Raman scattering measurements on high quality 7-armchair GNRs (7-AGNRs) on Au(111) synthesized by on-surface method were conducted in the temperature range from 80 to 520 K. The frequency of optical phonon G mode (collective acoustic phonon RBLM mode) linearly (nonlinearly) downshifts with temperature. The first-order temperature coefficient of G mode of 7-AGNR is calculated to be -0.026 cm-1K-1, almost twice that of freestanding graphene of -0.015 cm-1K-1 and half of that of CVD grown single layer graphene on Cu foils of -0.056 cm-1K-1. For RBLM, the anharmonicity is much weaker and attributed to the intrinsic quartic-phonon decay processes rather than the cubic-phonon ones. Our findings make a first step to the thermal properties of atomically precise GNRs. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Graphene nanoribbons (GNRs) are a potential alternative to graphene with gaps, and have been used in next-generation nanoelectronic devices. Research has found that temperature affects the frequency of G mode and RBLM, and the temperature coefficient of 7-AGNR is relatively high.