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Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (15 November 2019) | Viewed by 26903

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Special Issue Editor

Prof. Dr. Jie Sun

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Guest Editor

Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, and College of Physics and Information Engineering, Fuzhou University, Fuzhou 210000, China
Interests: semiconductor materials/devices, especially GaN micro-LED displays and other devices based on GaAs and InP; 2D materials/devices, especially MOCVD growth and integration with III-Vs

Special Issue Information

Dear Colleagues,

Graphene and other two-dimensional (2D) materials have been one of the hottest research areas in the past decade. Giant projects, e.g., the EU Graphene Flagship led by Chalmers, have been launched. Today, commercial graphene products are readily available. However, most of them are graphene-based powders, paints, and composites. They are exciting, but one should not forget that the original motivation of Geim et al. to explore graphene was to study its field effect, hoping it would play a key role in post-silicon electronics. After all, nanoelectronics and optoelectronics are the main thread for 2D materials. That is the field where scientists tell the public 2D materials could replace, or at least complement the dominant role of Si in electronics.

Graphene’s carrier mobility is one of the highest among all materials, making it promising in high speed electronics. The lack of bandgap makes the transistor on–off ratio, as well as current saturation, hard to improve. However, MoS₂, phosphorene, etc., possess large enough bandgaps. 2D insulators, such as h-BN, are also available. Therefore, the combination of 2D semiconductors, conductors and insulators is very valuable in post-silicon electronics. In addition, 2D materials are promising in optoelectronics, both for active elements, such as light emitting substances, and for passive elements, such as transparent electrodes. Generally speaking, the advantages of using 2D materials in nanoelectronics and optoelectronics include their ultra-small thickness, mechanical flexibility, sustainability, large varieties of material combinations, and most importantly, their outstanding optical and electrical properties. One thing worth mentioning is that, taking graphene as an example, it is not hard to find materials competing well with graphene in terms of mobility, electrical and thermal conductivity, transmittance, flexibility, etc.; nevertheless, it seems impossible to find something that combines all these properties in one single material—I believe that this is the fascinating part of graphene.

It is my pleasure to invite you to submit manuscripts to this Special Issue. Full papers, communications and reviews on experimental and theoretical studies of atomically-thin 2D materials in nanoelectronics and optoelectronics are all welcome.

Prof. Jie Sun
Guest Editor

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Keywords

Graphene
2D materials
semiconductors
nanoelectronics
optoelectronics

Published Papers (7 papers)

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Research

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11 pages, 4338 KiB

Open AccessArticle

High Quality Graphene Thin Films Synthesized by Glow Discharge Method in A Chemical Vapor Deposition System Using Solid Carbon Source

by Le Wang, Jie Sun, Weiling Guo, Yibo Dong, Yiyang Xie, Fangzhu Xiong, Zaifa Du, Longfei Li, Jun Deng and Chen Xu

Materials 2020, 13(9), 2026; https://doi.org/10.3390/ma13092026 - 26 Apr 2020

Cited by 1 | Viewed by 2420

Abstract

Arc discharge is traditionally used to synthesize randomly arranged graphene flakes. In this paper, we substantially modify it into a glow discharge method so that the discharge current is much more reduced. The H₂ and/or Ar plasma etching of the graphitic electrode (used to ignite the plasma) is hence much gentler, rendering it possible to grow graphene in thin film format. During the growth at a few mbar, there is no external carbon gas precursor introduced. The carbon atoms and/or carbon containing particles as a result of the plasma etching are emitted in the chamber, some of which undergo gas phase scattering and deposit onto the metallic catalyst substrates (Cu-Ni alloy thin films or Cu foils) as graphene sheets. It is found that high quality monolayer graphene can be synthesized on Cu foil at 900 °C. On Cu-Ni, under the same growth condition, somewhat more bilayer regions are observed. It is observed that the material quality is almost indifferent to the gas ratios, which makes the optimization of the deposition process relatively easy. Detailed study on the deposition procedure and the material characterization have been carried out. This work reveals the possibility of producing thin film graphene by a gas discharge based process, not only from fundamental point of view, but it also provides an alternative technique other than standard chemical vapor deposition to synthesize graphene that is compatible with the semiconductor planar process. As the process uses solid graphite as a source material that is rich in the crust, it is a facile and relatively cheap method to obtain high quality graphene thin films in this respect. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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9 pages, 3548 KiB

Open AccessArticle

Properties of Undoped Few-Layer Graphene-Based Transparent Heaters

by Yong Zhang, Hao Liu, Longwang Tan, Yan Zhang, Kjell Jeppson, Bin Wei and Johan Liu

Materials 2020, 13(1), 104; https://doi.org/10.3390/ma13010104 - 24 Dec 2019

Cited by 19 | Viewed by 2823

Abstract

In many applications like sensors, displays, and defoggers, there is a need for transparent and efficient heater elements produced at low cost. For this reason, we evaluated the performance of graphene-based heaters with from one to five layers of graphene on flexible and transparent polyethylene terephthalate (PET) substrates in terms of their electrothermal properties like heating/cooling rates and steady-state temperatures as a function of the input power density. We found that the heating/cooling rates followed an exponential time dependence with a time constant of just below 6 s for monolayer heaters. From the relationship between the steady-state temperatures and the input power density, a convective heat-transfer coefficient of 60 W·m⁻²·°C⁻¹ was found, indicating a performance much better than that of many other types of heaters like metal thin-film-based heaters and carbon nanotube-based heaters. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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12 pages, 6965 KiB

Open AccessArticle

Transfer-Free Graphene-Like Thin Films on GaN LED Epiwafers Grown by PECVD Using an Ultrathin Pt Catalyst for Transparent Electrode Applications

by Fangzhu Xiong, Weiling Guo, Shiwei Feng, Xuan Li, Zaifa Du, Le Wang, Jun Deng and Jie Sun

Materials 2019, 12(21), 3533; https://doi.org/10.3390/ma12213533 - 28 Oct 2019

Cited by 8 | Viewed by 2784

Abstract

In this work, we grew transfer-free graphene-like thin films (GLTFs) directly on gallium nitride (GaN)/sapphire light-emitting diode (LED) substrates. Their electrical, optical and thermal properties were studied for transparent electrode applications. Ultrathin platinum (2 nm) was used as the catalyst in the plasma-enhanced chemical vapor deposition (PECVD). The growth parameters were adjusted such that the high temperature exposure of GaN wafers was reduced to its minimum (deposition temperature as low as 600 °C) to ensure the intactness of GaN epilayers. In a comparison study of the Pt-GLTF GaN LED devices and Pt-only LED devices, the former was found to be superior in most aspects, including surface sheet resistance, power consumption, and temperature distribution, but not in optical transmission. This confirmed that the as-developed GLTF-based transparent electrodes had good current spreading, current injection and thermal spreading functionalities. Most importantly, the technique presented herein does not involve any material transfer, rendering a scalable, controllable, reproducible and semiconductor industry-compatible solution for transparent electrodes in GaN-based optoelectronic devices. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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8 pages, 2245 KiB

Open AccessArticle

Monolithic Integrated Device of GaN Micro-LED with Graphene Transparent Electrode and Graphene Active-Matrix Driving Transistor

by Yafei Fu, Jie Sun, Zaifa Du, Weiling Guo, Chunli Yan, Fangzhu Xiong, Le Wang, Yibo Dong, Chen Xu, Jun Deng, Tailiang Guo and Qun Yan

Materials 2019, 12(3), 428; https://doi.org/10.3390/ma12030428 - 30 Jan 2019

Cited by 18 | Viewed by 6265

Abstract

Micro-light-emitting diodes (micro-LEDs) are the key to next-generation display technology. However, since the driving circuits are typically composed of Si devices, numerous micro-LED pixels must be transferred from their GaN substrate to bond with the Si field-effect transistors (FETs). This process is called massive transfer, which is arguably the largest obstacle preventing the commercialization of micro-LEDs. We combined GaN devices with emerging graphene transistors and for the first-time designed, fabricated, and measured a monolithic integrated device composed of a GaN micro-LED and a graphene FET connected in series. The p-electrode of the micro-LED was connected to the source of the driving transistor. The FET was used to tune the work current in the micro-LED. Meanwhile, the transparent electrode of the micro-LED was also made of graphene. The operation of the device was demonstrated in room temperature conditions. This research opens the gateway to a new field where other two-dimensional (2D) materials can be used as FET channel materials to further improve transfer properties. The 2D materials can in principle be grown directly onto GaN, which is reproducible and scalable. Also, considering the outstanding properties and versatility of 2D materials, it is possible to envision fully transparent micro-LED displays with transfer-free active matrices (AM), alongside an efficient thermal management solution. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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9 pages, 1665 KiB

Open AccessArticle

Direct van der Waals Epitaxy of Crack-Free AlN Thin Film on Epitaxial WS₂

by Yue Yin, Fang Ren, Yunyu Wang, Zhiqiang Liu, Jinping Ao, Meng Liang, Tongbo Wei, Guodong Yuan, Haiyan Ou, Jianchang Yan, Xiaoyan Yi, Junxi Wang and Jinmin Li

Materials 2018, 11(12), 2464; https://doi.org/10.3390/ma11122464 - 4 Dec 2018

Cited by 18 | Viewed by 3698

Abstract

Van der Waals epitaxy (vdWE) has drawn continuous attention, as it is unlimited by lattice-mismatch between epitaxial layers and substrates. Previous reports on the vdWE of III-nitride thin film were mainly based on two-dimensional (2D) materials by plasma pretreatment or pre-doping of other hexagonal materials. However, it is still a huge challenge for single-crystalline thin film on 2D materials without any other extra treatment or interlayer. Here, we grew high-quality single-crystalline AlN thin film on sapphire substrate with an intrinsic WS₂ overlayer (WS₂/sapphire) by metal-organic chemical vapor deposition, which had surface roughness and defect density similar to that grown on conventional sapphire substrates. Moreover, an AlGaN-based deep ultraviolet light emitting diode structure on WS₂/sapphire was demonstrated. The electroluminescence (EL) performance exhibited strong emissions with a single peak at 283 nm. The wavelength of the single peak only showed a faint peak-position shift with increasing current to 80 mA, which further indicated the high quality and low stress of the AlN thin film. This work provides a promising solution for further deep-ultraviolet (DUV) light emitting electrodes (LEDs) development on 2D materials, as well as other unconventional substrates. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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10 pages, 4582 KiB

Open AccessArticle

Direct Growth of AlGaN Nanorod LEDs on Graphene-Covered Si

by Fang Ren, Yue Yin, Yunyu Wang, Zhiqiang Liu, Meng Liang, Haiyan Ou, Jinping Ao, Tongbo Wei, Jianchang Yan, Guodong Yuan, Xiaoyan Yi, Junxi Wang, Jinmin Li, Dheeraj Dasa and Helge Weman

Materials 2018, 11(12), 2372; https://doi.org/10.3390/ma11122372 - 26 Nov 2018

Cited by 16 | Viewed by 5288

Abstract

High density of defects and stress owing to the lattice and thermal mismatch between nitride materials and heterogeneous substrates have always been important problems and limit the development of nitride materials. In this paper, AlGaN light-emitting diodes (LEDs) were grown directly on a single-layer graphene-covered Si (111) substrate by metal organic chemical vapor deposition (MOCVD) without a metal catalyst. The nanorods was nucleated by AlGaN nucleation islands with a 35% Al composition, and included n-AlGaN, 6 period of AlGaN multiple quantum wells (MQWs), and p-AlGaN. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) showed that the nanorods were vertically aligned and had an accordant orientation along the [0001] direction. The structure of AlGaN nanorod LEDs was investigated by scanning transmission electron microscopy (STEM). Raman measurements of graphene before and after MOCVD growth revealed the graphene could withstand the high temperature and ammonia atmosphere in MOCVD. Photoluminescence (PL) and cathodoluminescence (CL) characterized an emission at ~325 nm and demonstrated the low defects density in AlGaN nanorod LEDs. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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Review

Jump to: Research

15 pages, 6283 KiB

Open AccessReview

Thermal Characterization of Low-Dimensional Materials by Resistance Thermometers

by Yifeng Fu, Guofeng Cui and Kjell Jeppson

Materials 2019, 12(11), 1740; https://doi.org/10.3390/ma12111740 - 29 May 2019

Cited by 8 | Viewed by 3060

Abstract

The design, fabrication, and use of a hotspot-producing and temperature-sensing resistance thermometer for evaluating the thermal properties of low-dimensional materials are described in this paper. The materials that are characterized include one-dimensional (1D) carbon nanotubes, and two-dimensional (2D) graphene and boron nitride films. The excellent thermal performance of these materials shows great potential for cooling electronic devices and systems such as in three-dimensional (3D) integrated chip-stacks, power amplifiers, and light-emitting diodes. The thermometers are designed to be serpentine-shaped platinum resistors serving both as hotspots and temperature sensors. By using these thermometers, the thermal performance of the abovementioned emerging low-dimensional materials was evaluated with high accuracy. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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