电弧法制备石墨烯材料的表征与评价

针对一种电弧法制备的石墨烯材料,通过X射线光电子能谱、拉曼光谱、红外光谱和扫描电镜分析等方法进行了表征与评价。结果表明:石墨烯中C元素含量为89.77%,O元素和N元素含量分别为3.03%和7.21%;通过拉曼光谱中G峰和2D峰的位置确定石墨烯样品以多层石墨烯为主;红外光谱显示石墨烯样品吸附了水分子;显微结构观察确定了石墨烯片层结构的层数及尺寸。根据实验方法总结了一套石墨烯的测试表征方案,为石墨烯在复合材料中的推广应用提供了评价依据。     

温度对堆叠双层石墨烯层间耦合的影响

将不同层数堆叠和化学气相沉积法（CVD）生长的石墨烯在室温下进行拉曼光谱表征分析其层间耦合状态,并分析了不同温度下堆叠和CVD生长的双层石墨烯温度对其层间耦合的影响。研究结果表明:室温下CVD生长双层石墨烯和堆叠双层石墨烯的层间耦合状态截然不同;在25～250 ℃范围内,层间没有耦合作用或存在弱耦合作用的堆叠双层石墨烯的G峰峰位温度系数小于存在电子耦合的CVD生长双层石墨烯;超过250 ℃后,堆叠双层石墨烯G峰峰位温度系数变为正值,层与层之间可能产生了耦合,性质发生改变;在25～400 ℃ 范围内两种材料的2D峰半峰宽和G峰/2D峰强度比变化趋势几乎相同,但堆叠双层石墨烯波动大,对温度更敏感。     

三嗪对CVD石墨烯n型掺杂的研究

以化学气相沉积(CVD)制备的单层石墨烯为原料, 小分子三嗪为掺杂剂, 采用吸附掺杂的方式, 在低温下对石墨烯实现n型掺杂。利用拉曼光谱(Raman)、X射线光电子能谱分析(XPS)、原子力显微镜(AFM)、紫外分光光度计(UV)和霍尔效应测试仪(Hall)对样品的形貌、结构及电学性能进行表征。结果表明: 该方法简单安全, 能够对石墨烯实现均匀的n型掺杂, 掺杂石墨烯的透光率达到95%。掺杂后石墨烯的特征峰G峰和2D峰向高波数移动。掺杂180 min后, 载流子浓度达到4×10¹²/cm², 接近掺杂前的载流子浓度, 掺杂后的石墨烯在450℃的退火温度下具有可逆能力, 其表面电阻在300℃以下具有较好的稳定性。     

Mn掺杂ZnO纳米线的拉曼散射和光致发光特性

研究了不同Mn掺杂含量的ZnO纳米线在室温条件下的拉曼散射和光致发光性能,发现Mn掺杂入ZnO后引入了部分应力,在其拉曼光谱中表现出拉曼峰的位置发生偏移,Mn的掺杂含量越高,峰偏移得越明显.Mn的掺杂对ZnO纳米线的发光性能也有影响,尽管掺杂后仍保持有较为明显的紫外发光峰,但是,随着Mn含量的增加,紫外发光峰的强度降低,并且半峰宽逐渐增大.此外,Mn的掺杂明显地改变了ZnO紫外发光峰的位置.     

微机械法制备石墨烯和二硫化钼及对其拉曼光谱的特性分析

本文详细介绍了石墨烯和MoS2的性能,如能带结构,载流子迁移率,相应的物理、化学、机械性能等。特别是多层到单层的变化情况,相应的物理、化学、机械性能等,以及能带变化在其光学反射率、荧光光谱、拉曼光谱上的反映。我们用微机械力法制备了100um线度的石墨烯和10um的MoS2,并使用拉曼光谱作为手段鉴别石墨烯的层数,从石墨烯的G峰和2D峰的劈裂可以看出石墨烯晶格中的光子和声子的相互作用,对此现象我们做了数据处理、拟合和理论分析。且使用拉曼光谱测量了MoS2单层、少量层、多层之间的变化,分析了其内在物理机制。     

微机械法制备石墨烯和二硫化钼及对其拉曼光谱的特性分析

本文详细介绍了石墨烯和MoS2的性能，如能带结构，载流子迁移率，相应的物理、化学、机械性能等。特别是多层到单层的变化情况，相应的物理、化学、机械性能等，以及能带变化在其光学反射率、荧光光谱、拉曼光谱上的反映。我们用微机械力法制备了100um线度的石墨烯和10um的MoS2，并使用拉曼光谱作为手段鉴别石墨烯的层数，从石墨烯的G峰和2D峰的劈裂可以看出石墨烯晶格中的光子和声子的相互作用，对此现象我们做了数据处理、拟合和理论分析。鼠使用拉曼光谱测量了MoS2单层、少量层、多层之间的变化，分析了其内在物理机制。     

原料尺寸对氧化石墨与石墨烯性能的影响

采用改进的Hummers法对不同尺寸的天然石墨进行氧化处理,水合肼还原获得石墨烯。利用红外光谱(FTIR)、拉曼光谱(Raman)、X射线衍射(XRD)等对天然石墨、氧化石墨和石墨烯的化学结构、光谱学及结晶性进行表征。结果表明:天然石墨被充分氧化为氧化石墨,氧化石墨被还原为完美的石墨烯;天然石墨尺寸越小,氧化程度越大,氧化石墨的层间距越大;氧化石墨的D峰和G峰的强度比ID/IG与天然石墨尺寸大小成正比;与同尺寸的氧化石墨相比,石墨烯的ID/IG值比氧化石墨的大,说明石墨烯中sp2杂化碳层平面的平均尺寸小于氧化石墨的平均尺寸,新生成的石墨化区域被一些缺陷分割成尺寸更小的sp2杂化区域。     

化学气相沉积法制备大面积石墨烯及其光谱学表征

化学气相沉积（CVD）法是近年来发展起来的制备石墨烯的新方法。该方法产物具有生长面积大、质量高等优点,逐渐成为制备石墨烯的主要方法。用CVD法在常压下通过全面优化实验参量,以镍箔为基底制备了大面积少数层和单层石墨烯,用拉曼光谱,场发射扫描电子显微镜（SEM）和原子力显微镜（AFM）手段表征,通过分析常压下不同温度、不同载气成分比等实验参数,最终获得制备高质量、大面积、少数层石墨烯的最佳参量,用双共振理论解释少数层和单层石墨烯的拉曼光谱中2D峰强度随石墨烯层数变化而变化的原理。CVD法制备的石墨烯具有面积大、低成本、可测量性强、可用于大批量生产的优点,为工业用途石墨烯的制备提供了有效途径。     

拉曼光谱在石墨烯聚合物纳米复合材料中的应用EI北大核心CSCD

拉曼光谱不仅能够用于确定石墨烯的物理性质、缺陷程度及层数等,也逐渐发展成为研究石墨烯聚合物复合材料重要的分析表征工具。石墨烯拉曼特征峰可用于对复合材料中石墨烯进行二维及三维的拉曼成像,从而获得石墨烯的分散状态。石墨烯拉曼特征峰的位移能够灵敏地反映石墨烯的形变程度,从而定量地评估复合材料中石墨烯与聚合物分子之间的相互作用、计算石墨烯的有效杨氏模量以及确定石墨烯的空间取向。本文综述了拉曼光谱在石墨烯聚合物复合材料领域的应用研究,介绍了拉曼光谱技术在石墨烯聚合物复合材料领域的最新研究进展,如石墨烯复合材料的微观变形机理、石墨烯与聚合物基体之间的应力转移效率、影响材料性能的关键性因素等。石墨烯聚合物复合材料的拉曼光谱研究目前仍以模型化复合材料为主要研究对象,而且聚合物基体的荧光效应也会在一定程度上限制拉曼光谱的应用。针对于此,可适当提高激发光的功率而产生一些非线性效应,以大幅增大拉曼光强度,从而使拉曼光谱技术在石墨烯聚合物复合材料领域中得到更广泛的应用。     

La掺杂SrBi4Ti4O15结构影响研究

通过对La不同掺杂比例SBT的XRD、拉曼光谱测试表明La掺杂对铋层状结构材料SBT的结构没有破坏.随掺杂量增加La取代不同位置,SBT拉曼光谱中270cm-1峰和550cm-1峰先宽化然后逐渐锐化,314cm-1肩峰锐化,870cm-1峰没有太大的变化.La掺杂进入类钙钛矿层对邻近TiO6八面体振动影响更大.     

Modification of the structural and electrical properties of graphene layers by Pt adsorbates

The properties of graphene are strongly affected by metal adsorbates and clusters on graphene. Here, we study the effect of a thin layer of platinum (Pt) metal on exfoliated single, bi- and trilayer graphene and on chemical vapor deposition-grown single-layer graphene by using Raman spectroscopy and transport measurements. The Raman spectra and transport measurements show that Pt affects the structure as well as the electronic properties of graphene. The shift of peak frequencies, intensities and widths of the Raman bands were analyzed after the deposition of Pt with different thicknesses (1, 3, 5 nm) on the graphene. The shifts in the G and 2D peak positions of the Raman spectra indicate the n-type doping effect by the Pt metal. The doping effect was also confirmed by gate-voltage dependent resistivity measurements. The doping effect by the Pt metal is stable under ambient conditions, and the doping intensity increases with the increasing Pt deposition without inducing a severe degradation of the charge carrier mobility.     

Synthesis and characterization of electrochemically-reduced graphene

Graphene has superior electrical conductivity than graphite and other allotropes of carbon because of its high surface area and chemical tolerance. Electrochemically processed graphene sheets were obtained through the reduction of graphene oxide from hydrazine hydrate. The prepared samples were heated to different temperatures such as 673 and 873 K. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM), Raman spectra and conductivity measurements were made for as-prepared and heat-treated graphene samples. XRD pattern of graphene shows a sharp and intensive peak centred at a diffraction angle (2θ) of 26·350. FTIR spectra of as-prepared and heated graphene were used to confirm the oxidation of graphite. TEM results indicated that the defect density and number of layers of graphene sheets were varied with heating temperature. The hexagonal sheet morphology and purity of as-prepared and heat treated samples were confirmed by SEM–EDX and Raman spectroscopy. The conductivity measurements revealed that the conductivity of graphene was decreased with an increase in heating temperature. The present study explains that graphene with enhanced functional properties can be achieved from the as-prepared sample.     

Determining the number of layers in graphene films synthesized by filtered cathodic vacuum arc technique

We have synthesized graphene film by the filtered cathodic vacuum arc (FCVA) technique and determined the number of layers in graphene films by various techniques. Amorphous carbon (a-C) films of different thicknesses (1, 2, 3, 6, 10 and 18 nm) were synthesized by the FCVA technique on Si/SiO₂/Ni substrate and then annealed in vacuum at 800°C and cooled down to room temperature naturally to obtain graphene. Prepared graphene films were transferred on different substrates and characterized by the Raman spectroscopy, UV-VIS-NIR spectroscopy, high-resolution transmission electron microscopy (HRTEM), optical microscopy, atomic force microscopy (AFM) and sheet resistance to determine the number of layers present in the graphene films. Raman spectra of the prepared graphene films exhibit that there is red shift in the position of D, G and 2 D peak. The value of I_2D/I_G varied from 0.18 to 0.51, I_D/I_G varied from 0.82 to 1.02 and full width at half maximum of 2 D peak varied from 101.2 to 128.0 cm^?1, for different thicknesses of graphene films, respectively. The value of transmittance decreases from 97 to 63.7% and that of sheet resistance increases from 460 to 1400 Ω/square with the increase in the thickness of the prepared graphene film. The HRTEM and AFM study revealed that the graphene synthesis from 1 nm thick a-C film possesses a single layer structure.     

Probing the nature of defects in graphene by Raman spectroscopy

Raman spectroscopy is able to probe disorder in graphene through defect-activated peaks. It is of great interest to link these features to the nature of disorder. Here we present a detailed analysis of the Raman spectra of graphene containing different type of defects. We found that the intensity ratio of the D and D' peak is maximum (～13) for sp(3)-defects, it decreases for vacancy-like defects (～7), and it reaches a minimum for boundaries in graphite (～3.5). This makes Raman Spectroscopy a powerful tool to fully characterize graphene.     

Optoelectronic properties of graphene thin films prepared by thermal reduction of graphene oxide

Graphene thin films have been prepared by thermal reduction of graphene oxide. Raising the reduction temperature results in a red-shift of the G peak in Raman spectra. The reduction temperature turns out to strongly affect the morphology of the prepared graphene film. Photoluminescence (PL) results show that the band gap of graphene can be tuned by varying the reduction temperature. The thermal reduction process has been optimized in an effort to minimize the formation of wrinkles/folds on the graphene surface leading to enhanced PL and Raman peak intensities and reduced electrical sheet resistance.     

Hysteresis I–V nature of mechanically exfoliated graphene FET

Graphene is an attractive material for device applications due to its excellent electrical and mechanical properties. The mechanical exfoliation is an attractive method to fabricate graphene devices using mono and multilayer graphene flakes. As the graphene is very sensitive to atmosphere the occurrence of hysteresis and p-doping is common. This paper reports electrical characterization and hysteresis effect of graphene field effect transistor (FET) fabricated using mechanically exfoliated graphene flakes. Raman spectra and atomic force microscopy techniques have been used to examine the quality and thickness of the exfoliated graphene. This fabricated graphene FET has shown hysteresis nature with p-type doping. The possible reason for the observed hysteresis and p-doping has been explained.     

Direct growth of graphene/hexagonal boron nitride stacked layers

Graphene (G) and atomic layers of hexagonal boron nitride (h-BN) are complementary two-dimensional materials, structurally very similar but with vastly different electronic properties. Recent studies indicate that h-BN atomic layers would be excellent dielectric layers to complement graphene electronics. Graphene on h-BN has been realized via peeling of layers from bulk material to create G/h-BN stacks. Considering that both these layers can be independently grown via chemical vapor deposition (CVD) of their precursors on metal substrates, it is feasible that these can be sequentially grown on substrates to create the G/h-BN stacked layers useful for applications. Here we demonstrate the direct CVD growth of h-BN on highly oriented pyrolytic graphite and on mechanically exfoliated graphene, as well as the large area growth of G/h-BN stacks, consisting of few layers of graphene and h-BN, via a two-step CVD process. The G/h-BN film is uniform and continuous and could be transferred onto different substrates for further characterization and device fabrication.     

Graphene synthesis by thermal chemical vapor deposition using solid precursor

We report single layer to few layer graphene on polycrystalline nickel by chemical vapor deposition at ambient pressure using solid precursor, camphor. Investigating at a wide range of temperature, it was observed that 870 °C is better for the deposition of single layer graphene on nickel substrate. The percentage of single layer on the substrate reduced significantly with decreasing the deposition temperature. The full width half maximum of the synthesized single layer graphene was 21 cm^?1 and Raman intensity ratio of 2D to G peak was almost nine. The film was transferred to insulating substrate and measured transmittance was 85 %. Raman spectroscopy, Raman mapping, SEM and UV–visible spectrometer measurement were performed for characterization.     

爆炸法合成石墨烯

以石墨氧化物为前躯体,采用爆炸法合成石墨烯.利用XRD,SEM,XPS,TEM,SAED和Raman等测试手段对石墨烯的形貌,成份和结构进行表征.结果表明,石墨氧化物在爆炸产生的热量和冲击波的作用下发生完全剥离并被还原成石墨烯.新合成的石墨烯呈透明褶皱状,含有2层～5层石墨层,并具有较好的晶体结构.

Abstract：

Graphene nanosheets were synthesized using graphite oxide as a precursor by detonation. The composition,and structure of graphene nanosheets were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,scanning and transmission electron microscopy,selected area electron diffraction,and Raman spectroscopy. Results indicated that the as-prepared material was transparent and wrinkled,and comprised 2-5 graphenes with a highly crystalline structrue. The exfoliation and reduction of graphite oxide to graphene nanosheets was induced by the self-generated thermal energy and shockwave of detonation.