Giant modulation of the electronic band gap of carbon nanotubes by dielectric screening

Lee Aspitarte,Massimo Rontani,Andrea Bertoni,Marvin Ostermann,Joshua O Island,Daniel R Mcculley,Gary A Steele,Ethan D Minot

doi:10.1038/s41598-017-09372-1

Lee Aspitarte, Massimo Rontani + Show 6 more

Open Access

https://doi.org/10.1038/s41598-017-09372-1

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Abstract

Carbon nanotubes (CNTs) are a promising material for high-performance electronics beyond silicon. But unlike silicon, the nature of the transport band gap in CNTs is not fully understood. The transport gap in CNTs is predicted to be strongly driven by electron-electron (e-e) interactions and correlations, even at room temperature. Here, we use dielectric liquids to screen e-e interactions in individual suspended ultra-clean CNTs. Using multiple techniques, the transport gap is measured as dielectric screening is increased. Changing the dielectric environment from air to isopropanol, we observe a 25% reduction in the transport gap of semiconducting CNTs, and a 32% reduction in the band gap of narrow-gap CNTs. Additional measurements are reported in dielectric oils. Our results elucidate the nature of the transport gap in CNTs, and show that dielectric environment offers a mechanism for significant control over the transport band gap.

Highlights

Carbon nanotubes (CNTs) are a promising platform to move integrated-circuit technology beyond the current limits of silicon[1–3]
There are critical open questions regarding the nature of the transport band gap in CNTs, and in particular the role that electron-electron (e-e) interactions may play in determining this band gap
Beyond this low-energy physics typically observed at cryogenic temperatures, theoretical models suggest that e-e interactions play a significant role in nanotube electronic properties even at room temperature

Summary

Introduction

Carbon nanotubes (CNTs) are a promising platform to move integrated-circuit technology beyond the current limits of silicon[1–3]. In quantum transport experiments[4], e-e interactions lead to phenomenon such as Luttinger liquid physics[5, 6] and Wigner crystal formation in CNTs7, 8, and may explain anomalous spin-orbit coupling in CNTs9, and anomalous band gaps in nominally-metallic CNTs10 Beyond this low-energy physics typically observed at cryogenic temperatures, theoretical models suggest that e-e interactions play a significant role in nanotube electronic properties even at room temperature. A theoretical framework for understanding the influence of dielectric environment on the transport gap of semiconducting CNTs was first developed by Ando[11]. This framework begins with the non-interacting model for CNT band structure[4], in which the “bare” transport gap of semiconducting CNTs is given by. While Ando’s theory describing Eg in semiconducting CNTs has been corroborated by additional theoretical work[18–25], experimental verification of the relationship between Eg and dielectric environment has remained lacking

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