Epitaxial graphene on SiC: modification of structural and electron transport properties by substrate pretreatment
Epitaxial graphene on SiC: modification of structural and electron transport properties by substrate pretreatment
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DOI：
10.1088/0953-8984/27/18/185303
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发表时间：
2015-05-13
影响因子：
2.7
通讯作者：
Schumacher, Hans W.
中科院分区：
文献类型：
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作者：
Kruskopf, Mattias;Pierz, Klaus;Schumacher, Hans W.
外延石墨烯层的电输运性能与SiC表面形貌有关。在这项研究中，我们通过原子力显微镜和拉曼测量表明，当不同的预处理程序应用于近轴6H-SiC（0001）衬底时，外延石墨烯层的表面形态和结构发生了显著变化。结果表明，在石墨烯生长过程中，经常使用的基板氢蚀刻是导致不良的高宏观步长演变的原因。采用一种新的方法：在氩气环境下对SiC表面进行高温调理，得到了一种更有利的亚纳米级阶梯石墨烯层。这一结果可以用调节过程后观察到的石墨烯缓冲层域来解释，该缓冲层域抑制了石墨烯的大阶聚束和阶流生长。在纳米探针输运实验中获得了较小的外部电阻各向异性，在低温磁输运测量中获得了出色的霍尔电阻量子化，证明了优越的电子质量。量子霍尔电阻与标称值（von Klitzing常数的一半）在4.5x10（-9）的标准偏差范围内一致，这使该方法有资格用于制造电量子标准。
The electrical transport properties of epitaxial graphene layers are correlated with the SiC surface morphology. In this study we show by atomic force microscopy and Raman measurements that the surface morphology and the structure of the epitaxial graphene layers change significantly when different pretreatment procedures are applied to nearly on-axis 6H-SiC(0001) substrates. It turns out that the often used hydrogen etching of the substrate is responsible for undesirable high macro-steps evolving during graphene growth. A more advantageous type of sub-nanometer stepped graphene layers is obtained with a new method: a high-temperature conditioning of the SiC surface in argon atmosphere. The results can be explained by the observed graphene buffer layer domains after the conditioning process which suppress giant step bunching and graphene step flow growth. The superior electronic quality is demonstrated by a less extrinsic resistance anisotropy obtained in nano-probe transport experiments and by the excellent quantization of the Hall resistance in low-temperature magneto-transport measurements. The quantum Hall resistance agrees with the nominal value (half of the von Klitzing constant) within a standard deviation of 4.5x10(-9) which qualifies this method for the fabrication of electrical quantum standards.