石墨烯及石墨烯场效应管的辐照效应研究进展

石墨烯由于高迁移率、高导热性、柔韧性好和机械强度高等优异性能使其成为构筑新型纳米电子器件的重要材料,已成为电子信息、生物医学、显示等领域的研究热点。当石墨烯材料及其电子器件放置于含有辐照因素的场景中时,会因为与高能光子和带电粒子等相互作用而改变晶格结构或积累电荷,使石墨烯材料及电子器件的性能发生变化。本文主要综述了典型辐照因素对石墨烯及器件的主要效应及研究进展,旨在总结不同辐照在石墨烯及其电子器件中引发的物理效应,归纳其微观-宏观性质变化,为加深石墨烯材料及器件的辐照效应的理解,推动其在辐照场景中的实际应用奠定基础。     

从石墨烯开关看电子在石墨烯中的奇异行为

与固态器件相比,真空电子器件的最大特点是电子在真空中的运动速率远大于在固体中的运动速率.然而,石墨烯的问世使这种现象发生了变化.现已发现,石墨烯中的电子不仅运动速率远高于传统半导体中的电子,而且存在各种奇特行为,使石墨烯的研究和应用备受关注.本文首先对普通晶体管材料和石墨烯中的电子行为进行比较,然后介绍石墨烯p-n结的特性和石墨烯逻辑开关的一些应用研究进展.     

石墨烯在散热及热管理中的应用

由于其优异的机械、光学、电子和热性能,石墨烯引起了全球科技界和工业界的高度关注。其中,石墨烯极高的横向热导率使石墨烯成为电子和光子器件热管理的理想材料。本文介绍石墨烯在电子热管理中的应用,特别关注其产业化方面的进展。本文首先介绍石墨烯的制备和热学性能,然后介绍石墨烯散热片在电子器件热管理中的应用,最后,介绍石墨烯在散热和热管理领域中的机遇、挑战和未来趋势。     

电流增益截止频率为40GHz的柔性衬底石墨烯FET

<正>石墨烯自问世以来,因其优异的性能已在电子领域取得了显著的成果,成为全球研究的热点。兼具高电子迁移率以及优良机械韧性的优点,石墨烯同柔性衬底的结合有望突破柔性电子高频化的技术瓶颈,推进柔性电子的应用进程。南京电子器件研究所在柔性衬底PEN(聚萘二甲酸乙二醇酯)上成功制备了高性能的石墨烯FET器件。该器件可在外力作用下发生较大幅度的形变[见图1(a)左上角]。在0.5 V漏压下,源漏间电阻为1800Ω·μm,电流密度为0.3 A/mm。小信号特性测结果显示,器件具有优良的频率性能。图1(b)为以OPEN-SHORT法除去PAD寄生电阻、电容后的频率性能,最大电流增益截止频率f_T和最大功率增益截止频率f_(max)分别达到41.4 GHz和17.7 GHz。     

石墨烯基电子学研究进展

综述了石墨烯晶体的能带结构和独特的电子性质,如双极性电场效应、单双层石墨烯效应、衬底效应、石墨烯纳米带(GNR)带隙等特殊效应的研究现状。介绍了石墨剥落技术、外延生长和化学气相淀积(CVD)等石墨烯材料的制备以及表征方法。列举了石墨烯在电子、显示、太阳电池、传感器和氢存储等方面的应用,如在石墨烯场效应管、石墨烯纳米带场效应管(SET)、石墨烯单电子晶体管、石墨烯金属晶体管、石墨烯基纳米电子机械系统(NEMS)、石墨烯分子开关以及石墨烯基高电子迁移率晶体管(HEMT)制备方面的应用。人们已经研究出不同栅长的n/p型顶栅石墨烯场效应管(GFET),并采用标准的S参数直接表征器件的高频性能。理论和实验表明,所有石墨烯纳米带场效应管(GNRFET)在室温下工作的前提是GNR的带宽尺寸小于10nm,并具有半导体场效应管的性能。     

GaN HEMT器件封装技术研究进展

GaN高电子迁移率晶体管(HEMT)器件由于其宽禁带材料的独特性能,相比硅功率器件具有击穿场强高、导通电阻低、转换速度快等优势,在智能家电、交直流转换器、光伏逆变器以及电动汽车等领域有着广泛的应用前景。但GaN HEMT器件的高功率密度和高频工作特性,给器件封装带来了极大挑战,要使其出色性能得以充分发挥,其封装结构、材料、工艺等起着至关重要的作用。介绍了GaN HEMT及其组成的功率模块的典型封装结构,并对国内外在寄生电感、热管理等封装关键技术问题的研究现状,以及高导热二维材料石墨烯在GaN HEMT器件热管理中的应用进行了综述。     

高频石墨烯场效应晶体管研制

<正>石墨烯具有高电子迁移率和高热导率等优良特性,在毫米波、亚毫米波乃至太赫兹器件、超级计算机等方面具有广阔应用前景。然而石墨烯是二维结构,受衬底、栅界面的影响较体材料更为敏感,因而高性能的石墨烯FET器件的研制也成为一个极具挑战性的课题。南京电子器件研究所通过氢插入等工艺用SiC热解法制备出高质量的石墨烯薄膜,材枓霍尔迁移率达2000 cm2/(V·s)。在此基础上,开发了可降低栅介质散射作用的A1自氧化缓冲工艺,同时以自对准和T栅(150 nm栅脚,400 nm栅帽)减小器件的寄生效应,研制出了高性能石墨烯场效应     

石墨烯异质结及其光电器件的研究进展

石墨烯是具有高迁移率、高热导率、高比表面积、高透过率及良好的机械强度等特性的二维材料,在光电子器件领域被广泛用作透明电极及电荷传输层等。但由于石墨烯是零带隙材料,为半金属性,限制了其在半导体光电子器件领域的应用。为更加切合半导体产业应用的要求,构建异质结已经成为相关领域实现应用的重要途径。国际上已有较多团队开展了石墨烯异质结相关研究,目前已有较多报道。本文从石墨烯的性质出发,讲述了石墨烯异质结的发展历程,制备方法,并从材料制备与器件结构的角度总结了基于石墨烯异质结光电子器件的研究进展。最后,对石墨烯异质结在光电子器件领域的发展进行了展望。     

石墨烯合成及其光电特性

石墨烯因具有高迁移率和光透明性使其在光电子学方面受到了广泛关注,其独特的光学和电子性质的结合可以得到充分利用。最近的一些研究成果显示了石墨烯在光电子学方面的兴起,从太阳能电池和发光器件到触摸屏、光电探测器和超快激光器等应用。本文综述了这一快速发展领域的最新进展。     

基于石墨烯的太赫兹光电功能器件研究进展

作为一种新型光电材料,石墨烯独特的能带结构和电子输运特性,使其与太赫兹科学有着密切的内在关系：石墨烯内部的等离子体振荡频率在太赫兹频段;人为调谐石墨烯的禁带宽度在0~0.3 eV时,正好覆盖太赫兹频段;光电导率的外部可控性等,这些特点使得石墨烯有望成为太赫兹频段新一代高性能设备研制的基础。最近的研究显示,石墨烯在太赫兹波产生、调控、检测等光电功能器件的研制中取得了很好的成果。重点介绍了基于石墨烯的太赫兹光电功能器件,包括太赫兹源器件、可控调控器件及检测器研究的最新进展,并对这一快速发展的研究领域进行了展望。     

FeCl3‐Based Few‐Layer Graphene Intercalation Compounds: Single Linear Dispersion Electronic Band Structure and Strong Charge Transfer Doping

Graphene has attracted much attention since its first discovery in 2004. Various approaches have been proposed to control its physical and electronic properties. Here, it is reported that graphene‐based intercalation is an efficient method to modify the electronic properties of few‐layer graphene (FLG). FeCl₃ intercalated FLGs are successfully prepared by the two‐zone vapor transport method. This is the first report on full intercalation for graphene samples. The features of the Raman G peak of such FLG intercalation compounds (FLGIC) are in good agreement with their full intercalation structures. The FLGICs present single Lorentzian 2D peaks, similar to that of single‐layer graphene, indicating the loss of electronic coupling between adjacent graphene layers. First principle calculations further reveal that the band structure of FLGIC is similar to single‐layer graphene but with a strong doping effect due to the charge transfer from graphene to FeCl₃. The successful fabrication of FLGIC opens a new way to modify properties of FLG for fundamental studies and future applications.     

具有双周期势的石墨烯超晶格电子带隙和传输特性的研究

运用传输矩阵理论,研究了双周期势石墨烯超晶格(GSL)的电子带隙和传输特性。结果表明,这种准周期结构存在一个新的狄拉克点,并且它的位置恰好位于零平均波数带隙处;与传统的布拉格带隙相比,这种带隙的位置对晶格常数和入射角度的变化不敏感。讨论了入射角度对电子在双周期势中传输特性的影响,预言了双周期势中可控的电子传输过程,定量分析了允带宽度与周期总数目的幂指数关系。     

Integration of Stiff Graphene and Tough Silk for the Design and Fabrication of Versatile Electronic Materials

The production of structural and functional materials with enhanced mechanical properties through the integration of soft and hard components is a common approach to Nature's material design. However, directly mimicking these optimized design routes in the lab for practical applications remains challenging. For example, graphene and silk are two materials with complementary mechanical properties that feature ultrahigh stiffness and toughness, respectively. Yet, no simple and controllable approach is developed to homogeneously integrate these two components into functional composites, mainly due to the hydrophobicity and chemical inertness of graphene. In this study, well‐dispersed and highly stable graphene/silk fibroin (SF) suspension systems are developed, which are suitable for processing to fabricate polymorphic materials, such as films, fibers, and coatings. The obtained graphene/SF nanocomposites maintain the electronic advantages of graphene, and they also allow tailorable mechanical performance to form including ultrahigh stretchable (with a strain to failure to 611 ± 85%), or high strength (339 MPa) and high stiffness (7.4 GPa) material systems. More remarkably, the electrical resistances of these graphene/SF materials are sensitive to material deformation, body movement, as well as humidity and chemical environmental changes. These unique features promise their utility as wearable sensors, smart textiles, intelligent skins, and human–machine interfaces.     

一种新型半导体材料的电子结构和光学特性：石墨烯一氧化物：

本文首次基于密度泛函理论研究了石墨烯一氧化物一种新型半导体材料的电子结构和光学特性。计算表明石墨烯一氧化物是直接带隙为0.95ev的半导体。通过绘制态密度和分波态密度研究了该材料的能带结构。除此之外,本文给出了该材料的光学特性,这对于材料在光电子器件的潜在应用有着一定的意义。     

Extraordinary Macroscale Wear Resistance of One Atom Thick Graphene Layer

During the last few years, graphene's unusual friction and wear properties have been demonstrated at nano to micro scales but its industrial tribological potential has not been fully realized. The macroscopic wear resistance of one atom thick graphene coating is reported by subjecting it to pin‐on‐disc type wear testing against most commonly used steel against steel tribo‐pair. It is shown that when tested in hydrogen, a single layer of graphene on steel can last for 6400 sliding cycles, while few‐layer graphene (3–4 layers) lasts for 47 000 cycles. Furthermore, these graphene layers are shown to completely cease wear despite the severe sliding conditions including high contact pressures (≈0.5 GPa) observed typically in macroscale wear tests. The computational simulations show that the extraordinary wear performance originates from hydrogen passivation of the dangling bonds in a ruptured graphene, leading to significant stability and longer lifetime of the graphene protection layer. Also, the electronic properties of these graphene sheets are theoretically evaluated and the improved wear resistance is demonstrated to preserve the electronic properties of graphene and to have significant potential for flexible electronics. The findings demonstrate that tuning the atomistic scale chemical interactions holds the promise of realizing extraordinary tribological properties of monolayer graphene coatings.     

Ultrafast Laser Pulses Enable One‐Step Graphene Patterning on Woods and Leaves for Green Electronics

Fast, simple, cost‐efficient, eco‐friendly, and design‐flexible patterning of high‐quality graphene from abundant natural resources is of immense interest for the mass production of next‐generation graphene‐based green electronics. Most electronic components have been manufactured by repetitive photolithography processes involving a large number of masks, photoresists, and toxic etchants; resulting in slow, complex, expensive, less‐flexible, and often corrosive electronics manufacturing processes to date. Here, a one‐step formation and patterning of highly conductive graphene on natural woods and leaves by programmable irradiation of ultrafast high‐photon‐energy laser pulses in ambient air is presented. Direct photoconversion of woods and leaves into graphene is realized at a low temperature by intense ultrafast light pulses with controlled fluences. Green graphene electronic components of electrical interconnects, flexible temperature sensors, and energy‐storing pseudocapacitors are fabricated from woods and leaves. This direct graphene synthesis is a breakthrough toward biocompatible, biodegradable, and eco‐friendlily manufactured green electronics for the sustainable earth.     

Modification of CuPc/graphene interfacial electronic structure with F16CuPc

The electronic structure between organic and solid electrode is a crucial issue in obtaining high-performance organic-based electronic devices (e.g. organic photovoltaic and organic light-emitting diode). In this communication we report that the electronic properties of phthalocyanine CuPc/graphene interface can be modified by sequential deposition of hexadecafluorophthalocyaninatocopper (F₁₆CuPc) on the CuPc/graphene interface due to the interactions of F₁₆CuPc with graphene. This method can be used to alter the energy barrier heights between graphene Dirac point and organic’s highest occupied molecular orbital and lowest unoccupied molecular orbital at the organic/graphene interface by simple deposition of another electron acceptor or donor layer on this interface.     

Band Gap Opening of Doped Graphene Stone Wales Defects: Simulation Study

Semiconductors - We implemented density functional theory to investigate the electronic properties of doped graphene Stone Wales defects. We found that the band gap of nitrogen doped graphene with...     

Thermodynamic properties of graphene nanoribbons under zero and quantizing magnetic fields

The thermodynamic properties of graphene nanoribbons under zero and finite magnetic fields have been investigated. We have obtained qualitative and quantitative results of the free energy and the magnetic susceptibility in graphene nanoribbons. The electronic states in the tight-binding approximation were used to calculate the thermal and magnetic properties. In the case of a finite magnetic field, the Harper equation was solved for the electronic state for various wavevectors. The magnetic field and temperature dependence of the magnetic susceptibility over a wide field and temperature range are presented.