【作者】 高银军；

【导师】 王冠中；

【作者基本信息】 中国科学技术大学 ， 凝聚态物理， 2009， 硕士

【摘要】 Graphene是由单层碳原子组成的碳二维材料。自从04年Novoselov小组在成功制备了大面积Graphene后,其研究工作迅速开展。Graphene之所以受到广泛关注,主要是由于其具有特殊的电学输运性质和独特的量子效应。与Graphene相关的研究工作,主要集中在:制备和表征、电学性质测量、量子效应的研究以及用Graphene制备电子器件等。而在这些研究领域中,Graphene制备和表征是所有研究的基础。本论文工作,以Graphene制备和表征为主,着重于以下两个方面: 1,Graphene的制备和表征。以机械剥离法为主,通过不同手段制备层数不同的Graphene。对比了不同制备方法的特点,找到有效制备Graphene的方法。利用光学显微镜、Raman光谱,对Graphene进行表征,研究了不同层数的Graphene在光学下和Raman光谱中的特征,确定了单层和双层Graphene。另外,在Graphene的研究中,经常会使用SEM对Graphene进行定位和操作,这需要事先对Graphene进行表征。为方便SEM在graphene研究中的应用,我们首次尝试了利用SEM对Graphene进行表征:通过改变SEM成像时电子的加速电压,得到不同加速电压下Graphene的SEM图像。根据衬度差异来确定Graphene的层数,实现Graphene在SEM下的更精细表征。2,对于Graphene在真空退火下的Raman光谱进行了研究。真空下退火是实现Graphene表面清洁的有效方法,但Graphene在退火后,结构上是否能够保持一致性,文献中一直没有这方面的讨论。我们借助于Raman光谱在Graphene结构研究方面的优势,研究Graphene在不同退火温度下的光谱特征,从而推断其结构在退火后的变化。我们发现:随着退火温度的升高,Graphene的G峰和2D峰逐渐蓝移,温度越高,移动越大。同时,峰的半高宽逐渐增大。另外,2D峰与G峰的相对强度随退火温度升高逐渐减小。我们认为,在退火下,Graphene结构会出现更多的褶皱,褶皱一方面使得Graphene中出现更多缺陷,使得峰展宽以及相对强度的减小;另一方面,Graphene中会出现多余的压应力,导致G峰和2D峰的蓝移。单层Graphene在退火后的结构变化,有助于理解Graphene的热力学稳定性,也有助于更快的使Graphene投入应用。更多还原

【Abstract】 Graphene, which consists of only one plain layer of atoms arranged in a honeycomb lattice, is a special 2-dimensial material. Since 2004, a group of physicists from Manchester University, led by Novoselov, used a very different approach to obtain graphene and lead a revolution in the field. After that, the research on graphene grows rapidly, making graphene a focus of attention in the scientific research. What make graphene so attractive is: the special electrical transport properties and the unique quantum effect. At present, research on graphene is mainly in four aspects: 1, preparation and characterization of graphene; 2, special electrical transport properties; 3, novel quantum effects; 4, fabrication of electronic devices. For all of these works, preparation and characterization, aim to obtain graphene layers with high quality and large size by a proper method, are the basis of other graphene reaerches.The work in this thesis concentrates on fabrication and characterization of graphene layers, which mainly foucs on:1. Preparation and characterizztion of graphene layers by mechanical exfoliation. On the principle of mechanical exfoliating, we use different methods to obtain graphene layers from HOPG. We analyse the difference in the optical images and Raman spectra of single- and multi-layer graphene and identify them. We also use scanning electron microspecopy (SEM) to characterize graphene according to the contrast of single-layer graphene flakes in SEM image, in order to find a way to indentify single- and multilayer graphene under SEM.2. Investigation of the Raman property of single layer graphene after annealing at different temperature in vacuum. Annealing at several hundreds of Celsius in vacuum has been shown to remove contamination left on the graphene. However, it is not clear whether the annealing influences the structure of graphene. From the annealing temperature dependent of Raman spectra, we find blue-shift and broadening of both the G-band and the 2D-band, and decreasing of their relative intensity I2D/IG wih the annealing temperature. We suggeste that graphene is more crumpled after annealing, which is responsible for the changes in its Raman spectra.更多还原