Abstract
Abstract2D materials have unique structural and electronic properties with potential for transformative device applications. However, such devices are usually bespoke structures made by sequential deposition of exfoliated 2D layers. There is a need for scalable manufacturing techniques capable of producing high‐quality large‐area devices comprising multiple 2D materials. Additive manufacturing with inks containing 2D material flakes is a promising solution. Inkjet‐printed devices incorporating 2D materials have been demonstrated, however there is a need for greater understanding of quantum transport phenomena as well as their structural properties. Experimental and theoretical studies of inkjet‐printed graphene structures are presented. Detailed electrical and structural characterization is reported and explained by comparison with transport modeling that include inter‐flake quantum tunneling transport and percolation dynamics. The results reveal that the electrical properties are strongly influenced by the flakes packing fraction and by complex meandering electron trajectories, which traverse several printed layers. Controlling these trajectories is essential for printing high‐quality devices that exploit the properties of 2D materials. Inkjet‐printed graphene is used to make a field effect transistor and Ohmic contacts on an InSe phototransistor. This is the first time that inkjet‐printed graphene has successfully replaced single layer graphene as a contact material for 2D metal chalcogenides.
Highlights
The discovery and isolation of single layer graphene (SLG) has opened new regimes of fundamental science and enabled transformative change in the architectures and performance of electronic devices.[1]
Large-area graphene layers have been produced by chemical vapor deposition (CVD) and molecular beam epitaxy (MBE),[2] their electronic properties are inferior to those measured for highquality mechanically exfoliated SLG.[3,4]
Micro Raman spectroscopy was used to investigate the impact of annealing temperature, Tann, on the quality of printed graphene samples
Summary
The discovery and isolation of single layer graphene (SLG) has opened new regimes of fundamental science and enabled transformative change in the architectures and performance of electronic devices.[1]. The transport properties of other 3D printed graphene devices, such as graphene/hBN FETs,[8] have been analyzed by adapting an approach first developed for SLG devices,[4] where the charge carrier concentration and fieldeffect mobility are determined from the gate voltage dependence of the conductivity. We report experimental and theoretical studies of electron transport in 3D-printed graphene and hBN/graphene structures, which elucidate the inter-flake electron and hole percolation dynamics across multiple printed layers and determine the macroscopic electrical properties. Our results show that controlling the inter-flake electron trajectories is vital for printing devices that exploit the unique characteristics of mechanically exfoliated 2D materials. To explain the dependence of conductivity on layer thickness we develop a Monte Carlo model for electron transport in inkjetprinted random graphene networks. Our results provide new insights into electron transport in 3D-printed heterostructures based on 2D materials, which could inform strategies for their implementation in future gene rations of additively manufactured device architectures
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