Effect of ribbon width on electrical transport properties of graphene nanoribbons

Kyuhyun Bang,Kangmi Kim,Hanbyeol Jang,Myungwoo Son,Sang-Soo Chee,Kwang Hyeon Baik,Moon-Ho Ham,Jae-Min Myoung,Byoung Hun Lee

doi:10.1186/s40580-018-0139-0

Abstract

There has been growing interest in developing nanoelectronic devices based on graphene because of its superior electrical properties. In particular, patterning graphene into a nanoribbon can open a bandgap that can be tuned by changing the ribbon width, imparting semiconducting properties. In this study, we report the effect of ribbon width on electrical transport properties of graphene nanoribbons (GNRs). Monolayer graphene sheets and Si nanowires (NWs) were prepared by chemical vapor deposition and a combination of nanosphere lithography and metal-assisted electroless etching from a Si wafer, respectively. Back-gated GNR field-effect transistors were fabricated on a heavily p-doped Si substrate coated with a 300 nm-thick SiO2 layer, by O2 reactive ion etching of graphene sheets using etch masks based on Si NWs aligned on the graphene between the two electrodes by a dielectrophoresis method. This resulted in GNRs with various widths in a highly controllable manner, where the on/off current ratio was inversely proportional to ribbon width. The field-effect mobility decreased with decreasing GNR widths due to carrier scattering at the GNR edges. These results demonstrate the formation of a bandgap in GNRs due to enhanced carrier confinement in the transverse direction and edge effects when the GNR width is reduced.

Highlights

Over the past decade, graphene has emerged as a promising candidate for application in future nanoelectronics due to its excellent material properties such as high carrier mobility, excellent mechanical flexibility, high thermal conductivity, and high optical transparency [1,2,3,4,5,6,7]
The bandgap energy increased with increasing on/off current ratio by narrowing the width of the graphene nanoribbons (GNRs). These results demonstrate that the opening of the bandgap in GNRs is due to the enhanced carrier confinement in the transverse direction and the edge effect when the GNR width is reduced
The GNRs were prepared from chemical vapor deposition (CVD)-grown graphene sheets by using etch masks based on Si NWs synthesized from Si substrates by a combination of nanosphere lithography and metalassisted chemical etching, and aligned between two electrodes by an electric-field-assisted alignment method, producing GNR field-effect transistor (FET)

Summary

Introduction

Graphene has emerged as a promising candidate for application in future nanoelectronics due to its excellent material properties such as high carrier mobility, excellent mechanical flexibility, high thermal conductivity, and high optical transparency [1,2,3,4,5,6,7]. Graphene is regarded as an outstanding channel material because of its electron mobility as high as 200,000 cm V−1 s−1 [8]. In spite of the superior properties of graphene, there are several challenges to be overcome for practical applications in electronic devices. Bang et al Nano Convergence (2018) 5:7 transport properties of GNRs. Si NWs, fabricated by a combination of polystyrene (PS) nanosphere lithography and metal-assisted electroless etching, were used as etch masks to fabricate a nanoribbon structure by exposing graphene to oxygen plasma. The ribbon widths of the GNRs were controlled by the diameters of the Si NWs, and the electrical transport properties of these GNRs with different ribbon widths were investigated

Experimental

Results and discussion

Conclusions