Revealing the Crystalline Integrity of Wafer-Scale Graphene on SiO2/Si: An Azimuthal RHEED Approach.
Revealing the Crystalline Integrity of Wafer-Scale Graphene on SiO2/Si: An Azimuthal RHEED Approach.
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DOI：
10.1021/acsami.7b01370
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发表时间：
2017-06
影响因子：
9.5
通讯作者：
Zonghuan Lu;Xin Sun;Yu Xiang;Morris Washington;Gwo-Ching Wang;T. Lu
中科院分区：
文献类型：
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作者：
Zonghuan Lu;Xin Sun;Yu Xiang;Morris Washington;Gwo-Ching Wang;T. Lu
当石墨烯在导电衬底上时，通常通过低能电子衍射（LEED）方法确定石墨烯的对称性，但是由于充电效应，LEED不能处理转移到SiO2/Si衬底上的石墨烯。虽然透射电子显微镜可以在后转移的石墨烯上产生电子衍射，但这种方法过于局部化。在本文中，我们采用方位角反射高能电子衍射（RHEED）方法来构建倒易空间映射，并确定转移前后晶片尺寸石墨烯的对称性。本文采用溅射法在蓝宝石（0001）和尖晶石（111）衬底上制备了单晶Cu（111）薄膜。然后用低压化学气相沉积法在单晶Cu（111）薄膜上外延生长石墨烯。利用方位角RHEED的倒易空间映射证实了在Cu（111）薄膜上生长的石墨烯是单晶的，无论是单层还是多层结构。虽然在蓝宝石（0001）上生长的Cu（111）薄膜偶尔可能包含60°面内旋转孪生，但倒易空间映射显示，顶部生长的石墨烯的面内取向不受影响。所提出的用于检查后转移的石墨烯片的晶体完整性的方法是实现石墨烯作为制造电子和光电器件的平台的重要步骤。
The symmetry of graphene is usually determined by a low-energy electron diffraction (LEED) method when the graphene is on the conductive substrates, but LEED cannot handle graphene transferred to SiO2/Si substrates due to the charging effect. While transmission electron microscopy can generate electron diffraction on post-transferred graphene, this method is too localized. Herein, we employed an azimuthal reflection high-energy electron diffraction (RHEED) method to construct the reciprocal space mapping and determine the symmetry of wafer-size graphene both pre- and post-transfer. In this work, single-crystalline Cu(111) films were prepared on sapphire(0001) and spinel(111) substrates with sputtering. Then the graphene was epitaxially grown on single-crystalline Cu(111) films with a low pressure chemical vapor deposition. The reciprocal space mapping using azimuthal RHEED confirmed that the graphene grown on Cu(111) films was single-crystalline, no matter the form of the monolayer or multilayer structure. While the Cu(111) film grown on sapphire(0001) may occasionally consist of 60° in-plane rotational twinning, the reciprocal space mapping revealed that the in-plane orientation of graphene grown atop was not affected. The proposed method for checking the crystalline integrity of the post-transferred graphene sheets is an important step in the realization of the graphene as a platform to fabricate electronic and optoelectronic devices.