External condition-induced interfacial charge transfer in single-walled carbon nanotube/graphene van der Waals heterostructures

Single-walled carbon nanotube (SWCNT)/graphene van der Waals (vdW) heterostructures have shown great potential for use in high-performance carbon-based heterojunction nanodevices owing to their strong interfacial coupling effects and unique physical and chemical properties. However, the interfacial charge transfer process and related influencing factors, which are crucial in determining device performance, have not been adequately investigated. Herein, we systematically investigate the interfacial charge transfer between SWCNTs and graphene using Raman spectroscopy under different external conditions, including bias voltage, temperature, and atmosphere. Our results indicate that electrons are transferred from SWCNTs to graphene when the applied voltage deviates from the neutral point voltage of -4 V. Under various atmospheric and temperature conditions, the built-in electric field induces the transfer of electrons from SWCNTs to graphene. Under humid conditions, electrons are injected into both the SWCNTs and graphene from H2O molecules, while in an NO2 atmosphere holes and electrons are injected into graphene and SWCNTs, respectively, from the NO2 molecules. Our study not only provides an important basis for understanding the interfacial charge transfer between SWCNTs and graphene, but also provides guidance for designing high-performance all-carbon vdW heterostructure nanodevices. The external conditions interfacial charge transfer in SWCNT/graphene van der Waals heterostructures was systematically investigated by Raman spectroscopy and the mechanism was deduced by the trend of changes in Raman characteristic peaks.