The Fabrication of Large-Area, Uniform Graphene Nanomeshes for High-Speed, Room-Temperature Direct Terahertz Detection

Nanoscale Research Letters, Jul 2018

In recent years, graphene nanomesh (GNM), a material with high flexibility and tunable electronic properties, has attracted considerable attention from researchers due to its wide applications in the fields of nanoscience and nanotechnology. Herein, we have processed large-area, uniform arrays of rectangular graphene nanomesh (r-GNM) and circular graphene nanomesh (c-GNM) with different neck widths by electron beam lithography (EBL). The electronic properties of those high-quality GNM samples have been characterized systematically. Electrical measurements illustrated that top-gated field effect transistors with different neck widths of the GNM possessed different Ion/Ioff ratios. In particular, the devices based on r-GNM with a neck width of 30 nm were found to possess the largest Ion/Ioff ratio of ~ 100, and the band gap of the r-GNM was estimated to be 0.23 eV, which, to the best of authors’ knowledge, is the highest value for graphene ribbons or a GNM with a neck width under 30 nm. Furthermore, the terahertz response of large-area r-GNM devices based on the photoconductive effect was estimated to be 10 mA/W at room temperature. We also explored the practical application of terahertz imaging, showing that the devices can be used in a feasible setting with a response time < 20 ms; this enables accurate and fast imaging of macroscopic samples.

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The Fabrication of Large-Area, Uniform Graphene Nanomeshes for High-Speed, Room-Temperature Direct Terahertz Detection

Yuan et al. Nanoscale Research Letters The Fabrication of Large-Area, Uniform Graphene Nanomeshes for High-Speed, Room-Temperature Direct Terahertz Detection Weiqing Yuan 0 1 Min Li 0 1 Zhongquan Wen 0 1 Yanling Sun 2 Desheng Ruan 0 1 Zhihai Zhang 0 1 Gang Chen 0 1 Yang Gao 3 0 College of Optoelectronic Engineering, Key Laboratory of Optoelectronic Technology and Systems, Ministry of Education, Chongqing University , Chongqing 400044 , People's Republic of China 1 College of Optoelectronic Engineering, Key Laboratory of Optoelectronic Technology and Systems, Ministry of Education, Chongqing University , Chongqing 400044 , People's Republic of China 2 School of Electronic Information Engineering, Yangtze Normal University , Fuling 408100 , People's Republic of China 3 Institute of Electronic Engineering, China Academy of Engineering Physics , Mianyang 621900 , People's Republic of China In recent years, graphene nanomesh (GNM), a material with high flexibility and tunable electronic properties, has attracted considerable attention from researchers due to its wide applications in the fields of nanoscience and nanotechnology. Herein, we have processed large-area, uniform arrays of rectangular graphene nanomesh (r-GNM) and circular graphene nanomesh (c-GNM) with different neck widths by electron beam lithography (EBL). The electronic properties of those high-quality GNM samples have been characterized systematically. Electrical measurements illustrated that top-gated field effect transistors with different neck widths of the GNM possessed different Ion/Ioff ratios. In particular, the devices based on r-GNM with a neck width of 30 nm were found to possess the largest Ion/Ioff ratio of ~ 100, and the band gap of the r-GNM was estimated to be 0.23 eV, which, to the best of authors' knowledge, is the highest value for graphene ribbons or a GNM with a neck width under 30 nm. Furthermore, the terahertz response of large-area r-GNM devices based on the photoconductive effect was estimated to be 10 mA/W at room temperature. We also explored the practical application of terahertz imaging, showing that the devices can be used in a feasible setting with a response time < 20 ms; this enables accurate and fast imaging of macroscopic samples. Graphene nanomesh; Electron beam lithography; Terahertz detection Background Graphene, a single layer of an sp2-hybridized carbon film, has drawn great attention in the last few years, as it possesses unique optoelectronic properties, such as high carrier mobility, zero band gap, and frequency-independent absorption. These properties facilitate its potential applications in the field of nanoelectronics, nanocomposites, chemical sensors, biosensors, and photodetectors [ 1?6 ]. However, the zero energy gap of graphene limits its applications in electronic and photonic devices. Consequently, it is highly desirable to open the energy gap of graphene and in turn improve the Ion/Ioff ratio [7]. It is universally acknowledged that the band gap of graphene can be tuned by various methods, including application of an electric (or magnetic) field to the bilayered graphene [ 8, 9 ], chemical doping [10], application of strain [ 11 ], and reshaping of the nanostructure of graphene [ 12?14 ]. For example, in 2017, Cheng et al. introduced the chemically regulative graphene with incorporated heteroatoms into the honeycomb lattice and demonstrated microstructure-tailored nanosheets (e.g., 0D quantum dots, 1D nanoribbons, and 2D nanomeshes), which enlarged the band gap and induced special chemical and physical properties of graphene, further presenting promising applications in actuators and power generators [ 15 ]. However, among all the methods that tuned the band gap of graphene, reshaping the nanostructure of graphene is currently the most convenient way [ 16 ], as it minimizes the inherent electronic properties of graphene [ 17 ]. The properties of graphene are reshaped when it is scaled to nanostructures, such as a graphene nanoribbon (GNR) [ 18?20 ], graphene nanoring, and graphene nanomesh [ 21?24 ]. Sun et al. proposed a simple method to open a comparable band gap in graphene by narrowing it down into a GNR and employed it in FETs, achieving large Ion/Ioff ratios of ~ 47 and ~ 105 at room temperature and 5.4 K, respectively [12]. However, the fabrication of long, narrow GNRs is difficult, which will be an obstacle in the application of nanoelectronic devices. Graphene nanomesh (GNM), a simpler nanostructure to fabricate, can open up a band gap in large graphene sheets, and the FETs based on GNMs can support currents nearly 100 times greater than individual GNR devices [ 25 ]. In 2017, Yang et al. utilized a mesoporous silica (meso-SiO2) template for the preparation of GNM FETs with improved on/off ratios, constructing highly sensitive biosensors for selective detection of human epidermal growth factor receptor 2. This further proved that it is an effective method to tai (...truncated)


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Weiqing Yuan, Min Li, Zhongquan Wen, Yanling Sun, Desheng Ruan, Zhihai Zhang, Gang Chen, Yang Gao. The Fabrication of Large-Area, Uniform Graphene Nanomeshes for High-Speed, Room-Temperature Direct Terahertz Detection, Nanoscale Research Letters, 2018, pp. 190, Volume 13, Issue 1, DOI: 10.1186/s11671-018-2602-6