Research

Jump to: Review

13 pages, 5853 KiB

Open AccessArticle

Extraction of Graphene’s RF Impedance through Thru-Reflect-Line Calibration

by Ivo Colmiais, Vitor Silva, Jérôme Borme, Pedro Alpuim and Paulo M. Mendes

Micromachines 2023, 14(1), 215; https://0-doi-org.brum.beds.ac.uk/10.3390/mi14010215 - 14 Jan 2023

Viewed by 1119

Graphene has unique properties that can be exploited for radiofrequency applications. Its characterization is key for the development of new graphene devices, circuits, and systems. Due to the two-dimensional nature of graphene, there are challenges in the methodology to extract relevant characteristics that [...] Read more.

Graphene has unique properties that can be exploited for radiofrequency applications. Its characterization is key for the development of new graphene devices, circuits, and systems. Due to the two-dimensional nature of graphene, there are challenges in the methodology to extract relevant characteristics that are necessary for device design. In this work, the Thru-Reflect-Line (TRL) calibration was evaluated as a solution to extract graphene’s electrical characteristics from 1 GHz to 65 GHz, where the calibration structures’ requirements were analyzed. It was demonstrated that thick metallic contacts, a low-loss substrate, and a short and thin contact are necessary to characterize graphene. Furthermore, since graphene’s properties are dependent on the polarization voltage applied, a backgate has to be included so that graphene can be characterized for different chemical potentials. Such characterization is mandatory for the design of graphene RF electronics and can be used to extract characteristics such as graphene’s resistance, quantum capacitance, and kinetic inductance. Finally, the proposed structure was characterized, and graphene’s resistance and quantum capacitance were extracted. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Figure 1

10 pages, 3999 KiB

Open AccessArticle

CVD-Grown 2D Nonlayered NiSe as a Broadband Photodetector

by Fang Liang, Liangliang Zhan, Tianyu Guo, Xing Wu and Junhao Chu

Micromachines 2021, 12(9), 1066; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12091066 - 01 Sep 2021

Cited by 3 | Viewed by 2613

Abstract

Two-dimensional (2D) materials have expansive application prospects in electronics and optoelectronics devices due to their unique physical and chemical properties. 2D layered materials are easy to prepare due to the layered crystal structure and the interlayer van der Waals combination. However, the 2D [...] Read more.

Two-dimensional (2D) materials have expansive application prospects in electronics and optoelectronics devices due to their unique physical and chemical properties. 2D layered materials are easy to prepare due to the layered crystal structure and the interlayer van der Waals combination. However, the 2D nonlayered materials are difficult to prepare due to the nonlayered crystal structure and the combination of interlayer isotropic chemical bonds, resulting in limited research on 2D nonlayered materials with broad characteristics. Here, a 2D nonlayered NiSe material has been synthesized by a chemical vapor deposition method. The atomic force microscopy study shows that the grown NiSe with a thin thickness. Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy results demonstrate the uniformity and high quality of NiSe flakes. The NiSe based photodetector realizes the laser response to 830 nm and 10.6 μm and the maximum responsivity is ~6.96 A/W at room temperature. This work lays the foundation for the preparation of 2D nonlayered materials and expands the application of 2D nonlayered materials in optoelectronics fields. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Figure 1

12 pages, 3660 KiB

Open AccessArticle

ZnS Quantum Dot Based Acetone Sensor for Monitoring Health-Hazardous Gases in Indoor/Outdoor Environment

by Rajneesh Kumar Mishra, Gyu-Jin Choi, Hyeon-Jong Choi and Jin-Seog Gwag

Micromachines 2021, 12(6), 598; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12060598 - 22 May 2021

Cited by 15 | Viewed by 2881

Abstract

This study reports the ZnS quantum dots (QDs) synthesis by a hot-injection method for acetone gas sensing applications. The prepared ZnS QDs were characterized by X-ray diffraction (XRD) and transmission electron microscopy analysis. The XRD result confirms the successful formation of the wurtzite [...] Read more.

This study reports the ZnS quantum dots (QDs) synthesis by a hot-injection method for acetone gas sensing applications. The prepared ZnS QDs were characterized by X-ray diffraction (XRD) and transmission electron microscopy analysis. The XRD result confirms the successful formation of the wurtzite phase of ZnS, with a size of ~5 nm. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and fast Fourier transform (FFT) images reveal the synthesis of agglomerated ZnS QDs with different sizes, with lattice spacing (0.31 nm) corresponding to (111) lattice plane. The ZnS QDs sensor reveals a high sensitivity (92.4%) and fast response and recovery time (5.5 s and 6.7 s, respectively) for 100 ppm acetone at 175 °C. In addition, the ZnS QDs sensor elucidates high acetone selectivity of 91.1% as compared with other intrusive gases such as ammonia (16.0%), toluene (21.1%), ethanol (26.3%), butanol (11.2%), formaldehyde (9.6%), isopropanol (22.3%), and benzene (18.7%) for 100 ppm acetone concentration at 175 °C. Furthermore, it depicts outstanding stability (89.1%) during thirty days, with five day intervals, for 100 ppm at an operating temperature of 175 °C. In addition, the ZnS QDs acetone sensor elucidates a theoretical detection limit of ~1.2 ppm at 175 °C. Therefore, ZnS QDs can be a promising and quick traceable sensor nanomaterial for acetone sensing applications. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Graphical abstract

10 pages, 2468 KiB

Open AccessArticle

High-Performance CVD Bilayer MoS₂ Radio Frequency Transistors and Gigahertz Mixers for Flexible Nanoelectronics

by Qingguo Gao, Chongfu Zhang, Kaiqiang Yang, Xinjian Pan, Zhi Zhang, Jianjun Yang, Zichuan Yi, Feng Chi and Liming Liu

Micromachines 2021, 12(4), 451; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12040451 - 16 Apr 2021

Cited by 11 | Viewed by 3086

Abstract

Two-dimensional (2D) MoS₂ have attracted tremendous attention due to their potential applications in future flexible high-frequency electronics. Bilayer MoS₂ exhibits the advantages of carrier mobility when compared with monolayer mobility, thus making the former more suitable for use in future flexible [...] Read more.

Two-dimensional (2D) MoS₂ have attracted tremendous attention due to their potential applications in future flexible high-frequency electronics. Bilayer MoS₂ exhibits the advantages of carrier mobility when compared with monolayer mobility, thus making the former more suitable for use in future flexible high-frequency electronics. However, there are fewer systematical studies of chemical vapor deposition (CVD) bilayer MoS₂ radiofrequency (RF) transistors on flexible polyimide substrates. In this work, CVD bilayer MoS₂ RF transistors on flexible substrates with different gate lengths and gigahertz flexible frequency mixers were constructed and systematically studied. The extrinsic cutoff frequency (f_T) and maximum oscillation frequency (f_max) increased with reducing gate lengths. From transistors with a gate length of 0.3 μm, we demonstrated an extrinsic f_T of 4 GHz and f_max of 10 GHz. Furthermore, statistical analysis of 14 flexible MoS₂ RF transistors is presented in this work. The study of a flexible mixer demonstrates the dependence of conversion gain versus gate voltage, LO power and input signal frequency. These results present the potential of CVD bilayer MoS₂ for future flexible high-frequency electronics. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Figure 1

11 pages, 3326 KiB

Open AccessArticle

Effect of the Pressure of Reaction Gases on the Growth of Single-Crystal Graphene on the Inner Surfaces of Copper Pockets

by Kaiqiang Yang, Jianlong Liu, Ruirui Jiang, Yubin Gong, Baoqing Zeng, Zichuan Yi, Qingguo Gao, Jianjun Yang, Feng Chi and Liming Liu

Micromachines 2020, 11(12), 1101; https://0-doi-org.brum.beds.ac.uk/10.3390/mi11121101 - 14 Dec 2020

Cited by 4 | Viewed by 1860

Abstract

Single-crystal graphene has attracted much attention due to its excellent electrical properties in recent years, and many growth methods have been proposed, including the copper pockets method. In the copper pockets method, a piece of copper foil is folded into a pocket and [...] Read more.

Single-crystal graphene has attracted much attention due to its excellent electrical properties in recent years, and many growth methods have been proposed, including the copper pockets method. In the copper pockets method, a piece of copper foil is folded into a pocket and put into a chemical vapor deposition (CVD) system for the growth of graphene. The dynamic balance of evaporation and deposition of copper on the inner surfaces of the copper pockets avoids high surface roughness caused by the evaporation of copper in open space, such as the outer surfaces of copper pockets. Much lower partial pressure of methane in the copper pockets and lower surface roughness reduce the nucleation density of graphene and increase the size of single-crystal graphene. It is found that the growth pressure is closely related to the size of single-crystal graphene prepared by the copper pockets method; the higher the growth pressure, the larger the size of single-crystal graphene. It is also found that the growth pressure has an effect on the inner surface roughness of the copper pockets, but the effect is not significant. The main factor affecting the size of the single-crystal graphene is the change in the volume of the copper pockets caused by the change in the growth pressure, and the volume of the copper pockets determines the content of methane in the copper pockets. According to the above law, the size of single-crystal graphene prepared by the copper pockets method can be enlarged by increasing the growth pressure. The size of single-crystal graphene can be enlarged in a wide range as the growth pressure can be increased in a wide range. In our experiments, when the growth pressure reached 450 Pa, single-crystal graphene with a diameter of 450

μ m

was prepared. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Figure 1

9 pages, 4418 KiB

Open AccessArticle

Fabrication of Screen Printing-Based AgNWs Flexible Transparent Conductive Film with High Stability

by Jianjun Yang, Wei Zeng, Yaxin Li, Zichuan Yi and Guofu Zhou

Micromachines 2020, 11(12), 1027; https://0-doi-org.brum.beds.ac.uk/10.3390/mi11121027 - 24 Nov 2020

Cited by 3 | Viewed by 2039

Abstract

Flexible transparent conductive thin films (TCFs) prepared from Silver nanowires (AgNWs) have attractive features of low cost, flexibility, and solution-processed, but the usual manufacturing methods could still be hard to be scaled up. In addition, large-scale/large-area fabrication process with industrialized potential is strongly [...] Read more.

Flexible transparent conductive thin films (TCFs) prepared from Silver nanowires (AgNWs) have attractive features of low cost, flexibility, and solution-processed, but the usual manufacturing methods could still be hard to be scaled up. In addition, large-scale/large-area fabrication process with industrialized potential is strongly needed. In this paper, the flexible TCFs with high stability are obtained via using screen printing method to print the AgNWs inks on a flexible and transparent substrate. The micro-structure of the AgNWs patterns is investigated by optical microscope and scanning electron microscope. Furthermore, the sheet resistance, light transmittance, and film thickness of the AgNWs patterns prepared under different conditions are characterized to explore the influence of different factors on its optical and electrical properties. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Figure 1

Review

Jump to: Research

26 pages, 6755 KiB

Open AccessReview

All-Optical Modulation Technology Based on 2D Layered Materials

by Hongyan Yang, Yunzheng Wang, Zian Cheak Tiu, Sin Jin Tan, Libo Yuan and Han Zhang

Micromachines 2022, 13(1), 92; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13010092 - 07 Jan 2022

Cited by 21 | Viewed by 4526

Abstract

In the advancement of photonics technologies, all-optical systems are highly demanded in ultrafast photonics, signal processing, optical sensing and optical communication systems. All-optical devices are the core elements to realize the next generation of photonics integration system and optical interconnection. Thus, the exploration [...] Read more.

In the advancement of photonics technologies, all-optical systems are highly demanded in ultrafast photonics, signal processing, optical sensing and optical communication systems. All-optical devices are the core elements to realize the next generation of photonics integration system and optical interconnection. Thus, the exploration of new optoelectronics materials that exhibit different optical properties is a highlighted research direction. The emerging two-dimensional (2D) materials such as graphene, black phosphorus (BP), transition metal dichalcogenides (TMDs) and MXene have proved great potential in the evolution of photonics technologies. The optical properties of 2D materials comprising the energy bandgap, third-order nonlinearity, nonlinear absorption and thermo-optics coefficient can be tailored for different optical applications. Over the past decade, the explorations of 2D materials in photonics applications have extended to all-optical modulators, all-optical switches, an all-optical wavelength converter, covering the visible, near-infrared and Terahertz wavelength range. Herein, we review different types of 2D materials, their fabrication processes and optical properties. In addition, we also summarize the recent advances of all-optical modulation based on 2D materials. Finally, we conclude on the perspectives on and challenges of the future development of the 2D material-based all-optical devices. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures

Figure 1

18 pages, 3820 KiB

Open AccessReview

2D Electronics Based on Graphene Field Effect Transistors: Tutorial for Modelling and Simulation

by Bassem Jmai, Vitor Silva and Paulo M. Mendes

Micromachines 2021, 12(8), 979; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12080979 - 18 Aug 2021

Cited by 11 | Viewed by 6887

Abstract

This paper provides modeling and simulation insights into field-effect transistors based on graphene (GFET), focusing on the devices’ architecture with regards to the position of the gate (top-gated graphene transistors, back-gated graphene transistors, and top-/back-gated graphene transistors), substrate (silicon, silicon carbide, and quartz/glass), [...] Read more.

This paper provides modeling and simulation insights into field-effect transistors based on graphene (GFET), focusing on the devices’ architecture with regards to the position of the gate (top-gated graphene transistors, back-gated graphene transistors, and top-/back-gated graphene transistors), substrate (silicon, silicon carbide, and quartz/glass), and the graphene growth (CVD, CVD on SiC, and mechanical exfoliation). These aspects are explored and discussed in order to facilitate the selection of the appropriate topology for system-level design, based on the most common topologies. Since most of the GFET models reported in the literature are complex and hard to understand, a model of a GFET was implemented and made available in MATLAB, Verilog in Cadence, and VHDL-AMS in Simplorer—useful tools for circuit designers with different backgrounds. A tutorial is presented, enabling the researchers to easily implement the model to predict the performance of their devices. In short, this paper aims to provide the initial knowledge and tools for researchers willing to use GFETs in their designs at the system level, who are looking to implement an initial setup that allows the inclusion of the performance of GFETs. Full article

(This article belongs to the Special Issue Electronic Devices and Circuits Based on 2D Materials)

► Show Figures