空间整形飞秒激光图案化加工氧化石墨烯

氧化石墨烯(GO)是结构中含有部分含氧官能团的石墨烯衍生物,通过加热、化学反应和激光诱导等方法,该材料可以被还原。激光辐照可以诱导一定区域内的GO发生还原反应,具有灵活、区域选择性良好、无需特殊环境等优点。提出了一种基于空间整形的飞秒激光图案化加工GO的方法,即空间整形激光辐照法,分别采用空间整形激光辐照法和激光逐点扫描法在GO上加工图案,并对加工结果进行表征和对比,分析了辐照时间、激光通量等参数对加工结果的影响。结果表明空间整形激光辐照法可以图案化加工GO并使加工区域的GO被还原,从而提高图案化加工效率,且该方法具有良好的可重复性和图案灵活性,在制备GO基底的微电路、微器件方面具有应用潜力。     

基于飞秒激光还原氧化石墨烯的SiC纳米线接头电学增强

纳米线连接为高性能微纳器件的组装和应用提供了技术手段,但现有的连接方式对于能量输入的空间精度和外部环境要求较高,其工艺窗口较窄。为改善这一问题,以氧化石墨烯(GO)作为中间连接层的纳米线连接方式,通过干法转移制备了碳化硅(SiC)纳米线-氧化石墨烯(GO)薄膜-SiC纳米线的结构,并通过飞秒激光辐照还原氧化石墨烯,降低了SiC和GO之间的势垒,通过层内导电与层间导电的方式形成了更宽的载流子通道,从而显著提升了电流水平。此外生成的还原氧化石墨烯(rGO)纳米膜对SiC纳米线的接头形成了包裹与保护作用,从而使接头部分具有更好的抗辐照和热传导性能,提升了器件的稳定性与使用寿命。最后,利用飞秒激光还原GO薄膜实现了SiC纳米线网络的电性能提升,制备了具有良好响应度和较快响应速度的紫外光传感器及透明柔性导电薄膜等器件。     

高导电三维打印石墨烯墨水的制备与性能研究

当前利用三维打印技术(3DP)制备石墨烯器件时,通常采用的化学还原法由于常使用剧毒的强还原剂,生产过程危险性大,污染性强。相较而言,热还原法制作工艺简单,参数可控性强,更适合用于通过3DP技术制备高导电集成电路器件。采用还原氧化法来制备石墨烯,通过Hummers法氧化石墨单质合成氧化石墨烯(GO),以GO作为基底材料,加入一定比例的黏结剂、分散剂等添加剂来配制可用于3DP的GO墨水。选择3DP中简单可控的直写成型(DIW)工艺来打印导电线路,并将导线置于氩气环境下的管式炉中,分别在200,500和800℃的温度中进行烧结还原,经过800℃热还原的还原氧化石墨烯(rGO),其方阻可降低至200 mΩ/以下。试验测试分析表明,配制的GO墨水可用于三维打印导电线路,且经烧结热还原后得到高电导率的rGO电子器件。     

基于石墨烯复合薄膜的平面微电感

石墨烯由于其独特的组成结构,具有极其优异的电学性能,基于石墨烯薄膜的电子器件越来越受到研究者的关注。通过将石墨烯与微型导电线圈结合,探究石墨烯对线圈微电感性能的影响。滴涂石墨烯并通过三组对比实验确定石墨烯薄膜的干燥方式(-5℃冷干干燥、室温真空干燥和室温自然干燥)。结果显示,室温真空干燥形成的石墨烯薄膜更为连续均匀、薄膜厚度小且电阻率更低。进一步实验得到,45℃为室温真空干燥方式的较佳干燥温度。采用微电子机械系统(MEMS)工艺制备三种不同材料的微型导电线圈(铜导线、石墨烯/铜复合导线、石墨烯导线)。对三种线圈的电学参数进行测试,发现石墨烯/铜复合导电线圈的电感性能有较大提高。     

非晶IGZO透明导电薄膜的L-MBE制备

报道了一种利用等离子辅助激光分子束外延技术(L-MBE)在石英衬底上制备IGZO透明导电薄膜的新工艺.该工艺在超高真空中进行,可以有效避免杂质和污染,提高薄膜的纯度和光学、电学性能.通过优化生长时的气体离化功率,在300W射频功率下,得到光学电学性能优良的非晶态IGZO透明导电薄膜,其可见光范围内透过率超过80%,其室温电子迁移率高达16.14cm2v-1s-1,明显优于目前薄膜晶体管(TFT)中常用的非晶硅和有机物材料.测试结果表明,采用此工艺制备的非晶态IGZO透明导电薄膜,具有优良的光学、电学特性,能代替非晶硅和有机物,提高TFT-LCD的性能,实现真正的全透明、高亮度及柔性显示.     

聚3,4-乙撑二氧噻吩(PEDOT)-氧化石墨烯复合电极在有机发光二极管中的应用

通过将氧化石墨烯(Graphene Oxide,GO)与十二烷基苯磺酸钠(Sodium Dodecyl Benzene Sulfonate,SDBS)作为填料混入聚3,4-乙撑二氧噻吩∶聚苯乙烯磺酸(PEDOT∶PSS)溶液中制备了高透光率和低方块电阻的透明导电薄膜.当氧化石墨烯与PEDOT∶PSS质量比为0.02％时,薄膜获得了最佳的导电率,电阻为85 Ω/口,在550 nm的光波长下透光率为87％.采用不同掺杂比例的薄膜作为电极制备了有机发光二极管(OLED)器件,相比于常用的ITO电极,复合薄膜作为阳极更有利于空穴的注入和传输,所制备的器件能够得到更优的性能.这些结果表明PEDOT∶PSS和氧化石墨烯复合电极有望取代柔性OLED器件中的ITO阳极.     

脉冲激光沉积法制备ITO薄膜及性质研究

本文采用脉冲激光沉积法(PLD)制备了ITO导电薄膜,并对其形貌、光学性质和电学性质进行了研究.结果表明,使用PLD方法制备的ITO导电薄膜在可见光区的平均透光率约为80%,方块电阻在100～200Ω/□之间.当衬底温度控制在300℃,氧压控制在1.33Pa时,可以得到具有较高透光率和电导率的ITO导电薄膜.     

激光刻蚀对Ag/FTO/AZO薄膜光学和电学性能的影响

采用不同能量密度的激光对制备的Ag/FTO/AZO多层薄膜进行光栅结构刻蚀,分析激光刻蚀后薄膜的表面形貌、光学性能和电学性能的变化,并确定薄膜获得最佳性能时的激光能量密度。结果表明,以一定的激光能量密度对薄膜进行光栅结构刻蚀处理,不仅能有效提高薄膜的抗反射能力,还能产生附加退火作用,促使薄膜晶粒生长,减少晶界面积,从而减少晶界的光子和载流子的散射损失,提高载流子的迁移率,最终提高薄膜的透过率,优化薄膜的导电性能,实现薄膜的光学性能和电学性能的优化。     

激光制备液态金属基柔性电子及其应用

随着科技的发展,柔性电子器件在医疗健康、柔性机器人以及人机交互领域中的应用越来越广泛。柔性电子器件的关键在于柔性电极材料,传统柔性电极材料如结构化的金属薄膜、金属纳米颗粒/线以及导电聚合物等存在高延展性与高导电性无法同时满足的问题。镓基液态金属作为一种室温下呈现液态的金属材料,具备金属高导电性的同时也具有无限延展性,是一种理想的柔性电极材料,是近年来的研究热点。对液态金属进行图案化处理是制备液态金属基柔性电子器件的必要环节。重点介绍了以浸润性调控的方法实现液态金属图案化的工艺。激光作为一种精密加工方式,被常用来制备各种功能表面,同时也是调控液体浸润性的主要手段之一。结合激光的高精密加工能力与液态金属优异的电学性能,能够实现高分辨率、多功能以及高集成度的液态金属电子器件制备。综述了近年来国内外在激光制备液态金属柔性电子器件方面的主要工作,并展望了未来激光制备高性能液态金属电子器件的前景。     

飞秒激光直写制备内嵌微透镜、能源器件及生物传感器的研究进展

飞秒激光具有超短脉宽和极高峰值强度,已广泛应用于精细加工与微纳制造领域。目前,激光直写技术用于柔性器件的制备受到极大的关注。综述了激光直写技术的四个研究方向:1)激光直写微透镜用于广角成像;2)激光制备纳米金/还原氧化石墨烯微超级电容器;3)聚酰亚胺基体上多层超级电容器的制备;4)电容生物传感器的激光制备。同时介绍了本课题组开展的相关研究工作,可为激光直写制备微纳结构器件的研究与应用及未来发展方向提供参考。     

Confocal Microscopy for In Situ Multi-Modal Characterization and Patterning of Laser-Reduced Graphene Oxide (Adv. Funct. Mater. 30/2023)

Graphene oxide (GO) films can be readily prepared at wafer scale, then reduced to form graphene-based conductive circuits relevant to a range of practical device applications. Among a variety of reduction methods, laser processing has emerged as an important technique for localized reduction and patterning of GO films. In this study, the novel use of confocal microscopy is demonstrated for high-resolution characterization, in situ laser reduction, and versatile patterning of GO films. Multi-modal imaging and real-time tracking are performed with 405 and 488 nm lasers, enabling large-area direct observation of the reduction progress. Using image analysis to cluster flake types, the different stages of reduction can be attributed to thermal transfer and accumulation. Delicate control of the reduction process over multiple length scales is illustrated using millimeter-scale stitched patterns, micropatterning of single flakes, and direct writing conductive 2D wires with sub-micrometer resolution (530 nm). The general applicability of the technique is shown, allowing fabrication of both conductive reduced graphene oxide (rGO) films (sheet resistance: 2.5 kOhm sq⁻¹) and 3D microscale architectures. This simple and mask-free method provides a valuable tool for well-controlled and scalable fabrication of reduced GO structures using compact low-power lasers (< 5 mW), with simultaneous in situ monitoring and quality control.     

Bioinspired Fabrication of Superhydrophobic Graphene Films by Two‐Beam Laser Interference

Reported here is a bioinspired fabrication of superhydrophobic graphene surfaces by means of two‐beam laser interference (TBLI) treatment of graphene oxide (GO) films. Microscale grating‐like structures with tunable periods and additional nanoscale roughness are readily created on graphene films due to laser induced ablation effect. Synchronously, abundant hydrophilic oxygen‐containing groups (OCGs) on GO sheets can be drastically removed after TBLI treatment, which lower its surface energy significantly. The synergistic effect of micro‐nanostructuring and the OCGs removal endows the resultant graphene films with unique superhydrophobicity. Additionally, dual TBLI treatment with 90° rotation is implemented to fabricate superhydrophobic graphene films with two‐dimensional grating‐like structures that can effectively avoid the anisotropic hydrophobicity originated from the grooved structures. Moreover, the superhydrophobic graphene films become conductive due to the laser reduction effect. Unique optical characteristics including transmission diffraction and brilliant structural color are also observed due to the presence of periodic microstructures. As a mask‐free, chemical‐free, and cost‐effective method, the TBLI processing of GO may open up a new way to biomimetic graphene surfaces, and thus hold great promise for the development of novel graphene‐based microdevices.     

Flexible Organic Photovoltaic Cells with In Situ Nonthermal Photoreduction of Spin‐Coated Graphene Oxide Electrodes

The first reduction methodology, compatible with flexible, temperature‐sensitive substrates, for the production of reduced spin‐coated graphene oxide (GO) electrodes is reported. It is based on the use of a laser beam for the in situ, non‐thermal, reduction of spin‐coated GO films on flexible substrates over a large area. The photoreduction process is one‐step, facile, and is rapidly carried out at room temperature in air without affecting the integrity of the graphene lattice or the flexibility of the underlying substrate. Conductive graphene films with a sheet resistance of as low as 700 Ω sq^?1 and transmittance of 44% can be obtained, much higher than can be achieved for flexible layers reduced by chemical means. As a proof of concept of our technique, laser‐reduced GO (LrGO) films are utilized as transparent electrodes in flexible, bulk heterojunction, organic photovoltaic (OPV) devices, replacing the traditional ITO. The devices displayed a power‐conversion efficiency of 1.1%, which is the highest reported so far for OPV device incorporating reduced GO as the transparent electrode. The in situ non‐thermal photoreduction of spin‐coated GO films creates a new way to produce flexible functional graphene electrodes for a variety of electronic applications in a process that carries substantial promise for industrial implementation.     

Electrical Conductivity and Ferromagnetism in a Reduced Graphene–Metal Oxide Hybrid

The rare coexistence of ferromagnetism and electrical conductivity is observed in the reduced graphene oxide–metal oxide hybrids, rGO‐Co, rGO‐Ni, and rGO‐Fe, using chemical reduction with hydrazine or ultraviolet photoirradiation of the graphene oxide–metal complexes, GO‐Co, GO‐Ni, and GO‐Fe. The starting and final materials are characterized by X‐ray photoelectron spectroscopy, transmission electron microscopy (TEM), elemental analysis, Mössbauer spectroscopy, and Raman spectroscopy. In contrast to graphene, where the electrical conductivity and magnetic properties are controlled by carrier (electron or hole) doping, those of graphene oxide can be controlled by complexation with Co²⁺, Ni²⁺, and Fe³⁺ cations through the strong electrostatic affinity of negatively charged graphene oxide towards metal cations. The presence of ferromagnetism and electrical conductivity in these hybrids can promote significant applications including magnetic switching and data storage.     

Highly Stable Graphene‐Based Multilayer Films Immobilized via Covalent Bonds and Their Applications in Organic Field‐Effect Transistors

Highly stable graphene oxide (GO)‐based multilayered ultrathin films can be covalently immobilized on solid supports through a covalent‐based method. It is demonstrated that when (3‐aminopropyl) trimethoxysilane (APTMS), which works as a covalent cross‐linking agent, and GO nanosheets are assembled in an layer‐by‐layer (LBL) manner, GO nanosheets can be covalently grafted on the solid substrate successfully to produce uniform multilayered (APTMS/GO)N films over large‐area surfaces. Compared with conventional noncovalent LBL films constructed by electrostatic interactions, those assembled using this covalent‐based method display much higher stability and reproducibility. Upon thermal annealing‐induced reduction of the covalent (APTMS/GO)N films, the obtained reduced GO (RGO) films, (APTMS/RGO)N, preserve their basic structural characteristics. It is also shown that the as‐prepared covalent (APTMS/RGO)N multilayer films can be used as highly stable source/drain electrodes in organic field‐effect transistors (OFETs). When the number of bilayers of the (APTMS/RGO)N film exceeds 2 (ca. 2.7 nm), the OFETs based on (APTMS/RGO)N electrodes display much better electrical performance than devices based on 40 nm Au electrodes. The covalent protocol proposed may open up new opportunities for the construction of graphene‐based ultrathin films with excellent stability and reproducibility, which are desired for practical applications that require withstanding of multistep post‐production processes.     

π‐Conjugated Molecules Crosslinked Graphene‐Based Ultrathin Films and Their Tunable Performances in Organic Nanoelectronics

Graphene‐based ultrathin films with tunable performances, controlled thickness, and high stability are crucial for their uses. The currently existing protocols, however, could hardly simultaneously meet these requirements. Using amino‐substituted π‐conjugated compounds, including 1,4‐diaminobenzene (DABNH2), benzidine (BZDNH2), and 5,10,15,20‐tetrakis (4‐aminophenyl)‐21H,23H‐porphine (TPPNH2), as cross‐linkages, a new protocol through which graphene oxide (GO) nanosheets can be anchored on solid supports with a high stability and controlled thickness via a layer‐by‐layer method is presented. A thermal annealing leads to the reduction of the films, and the qualities of the samples can be inherited by the as‐produced reduced GO films (RGO). When RGO films are integrated as source/drain electrodes in OFETs, tunable performances can be realized. The devices based on the BZDNH2‐crosslinked RGO electrodes exhibit similar electrical behaviors as those based on the non‐π‐conjugated compound crosslinked electrodes, while improved performances can be gained when those crosslinked by DABNH2 are used. The performances can be further improved when RGO films crosslinked by TPPNH2 are employed. This work likely paves a new avenue for graphene‐based films of tunable performances, controlled thickness, and high stability.     

Highly Conductive Nanocomposites with Three‐Dimensional,Compactly Interconnected Graphene Networks via a Self‐Assembly Process

Polymer‐based materials with high electrical conductivity are of considerable interest because of their wide range of applications. The construction of a 3D, compactly interconnected graphene network can offer a huge increase in the electrical conductivity of polymer composites. However, it is still a great challenge to achieve desirable 3D architectures in the polymer matrix. Here, highly conductive polymer nanocomposites with 3D compactly interconnected graphene networks are obtained using a self‐assembly process. Polystyrene (PS) and ethylene vinyl acetate (EVA) are used as polymer matrixes. The obtained PS composite film with 4.8 vol% graphene shows a high electrical conductivity of 1083.3 S/m, which is superior to that of the graphene composite prepared by a solvent mixing method. The electrical conductivity of the composites is closely related to the compact contact between graphene sheets in the 3D structures and the high reduction level of graphene sheets. The obtained EVA composite films with the 3D graphene structure not only show high electrical conductivity but also exhibit high flexibility. Importantly, the method to fabricate 3D graphene structures in polymer matrix is facile, green, low‐cost, and scalable, providing a universal route for the rational design and engineering of highly conductive polymer composites.     

Multilayer Hybrid Films Consisting of Alternating Graphene and Titania Nanosheets with Ultrafast Electron Transfer and Photoconversion Properties

Alternating graphene (G) and titania (Ti_0.91O₂) multilayered nanosheets are fabricated using layer‐by‐layer electrostatic deposition followed by UV irradiation. Successful assemblies of graphene oxide (GO) and titania nanosheets in sequence with polyethylenimine as a linker is confirmed by UV–vis absorption and X‐ray diffraction. Photocatalytic reduction of GO into G can be achieved upon UV irradiation. Ultrafast photocatalytic electron transfer between the titania and graphene is demonstrated using femtosecond transient absorption spectroscopy. Efficient exciton dissociation at the interfaces coupled with cross‐surface charge percolation allows efficient photocurrent conversion in the multilayered Ti_0.91O₂/G films.