Strong asymmetric charge carrier dependence in inelastic electron tunneling spectroscopy of graphene phonons

Published

June 16, 2015

Author(s)

Donat F. Natterer, Yue Y. Zhao, Jonathan E. Wyrick, Yang-Hao Chan, Wen-Ying Ruan, Mei-Yin Chou, Kenji Watanabe, Takashi Taniguchi, Nikolai B. Zhitenev, Joseph A. Stroscio

Abstract

The observation of phonons in graphene by inelastic electron tunneling spectroscopy has been met with limited success in previous measurements arising from weak signals and other spectral features which inhibit a clear distinction between phonons and miscellaneous excitations. Utilizing a back-gated graphene device that allows adjusting the global charge carrier density, we introduce an averaging method where individual tunneling spectra at varying charge carrier density are combined into one representative spectrum. This method improves the signal for inelastic transitions while it suppresses dispersive spectral features. We thereby map the total graphene phonon density of states, in good agreement with density functional calculations. Unexpectedly, an abrupt change in the phonon intensity is observed when the graphene charge carrier type is switched through a variation of the back-gate electrode potential. This sudden variation in phonon intensity is asymmetric in the carrier type, depending on the sign of the tunneling bias.

Citation

Physical Review Letters

Volume

114

Issue

24

Pub Type

Journals

Download Paper

https://doi.org/10.1103/PhysRevLett.114.245502

Keywords

graphene, phonons, scanning tunneling microscopy, scanning tunneling spectroscopy

Citation

Natterer, D. , Zhao, Y. , Wyrick, J. , Chan, Y. , Ruan, W. , Chou, M. , Watanabe, K. , Taniguchi, T. , Zhitenev, N. and Stroscio, J. (2015), Strong asymmetric charge carrier dependence in inelastic electron tunneling spectroscopy of graphene phonons, Physical Review Letters, [online], https://doi.org/10.1103/PhysRevLett.114.245502 (Accessed December 26, 2024)