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)