arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1811.09830cond-mat.mes-hallcond-mat.mtrl-sciphysics.ins-det
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扭曲双层石墨烯中莫尔结构的透射电镜研究

Moire structures in twisted bilayer graphene studied by transmission electron microscopy

Tatiana Latychevskaia, Conrad Escher, Hans-Werner Fink

摘要:

我们研究了独立扭曲双层石墨烯(TBG)中莫尔结构的成像,通过透射电子显微镜(TEM)在衍射和同轴伽柏全息模式下进行。在80 - 300 keV的典型TEM电子能量下获得的TBG的电子衍射图案显示出由各个层上的衍射引起的衍射峰。然而,在这样的衍射图案中没有观察到与莫尔结构的周期性相关的散射角处的衍射峰。我们表明,衍射莫尔结构可以创建强烈的衍射峰,如果探测电子的能量很低,在几十eV的范围内。示出了用236 eV的低能量电子获得的TBG的实验衍射图案,其表现出归因于莫尔结构周期性的峰。在全息模式下,透射通过样品并在远场中测量的波的强度可以根据原子排列(例如AA或AB堆叠)而增强或减小。因此,远场中强度的降低不一定与样品内部的一些吸收有关,而可以仅仅是特定原子排列的结果。我们相信,我们的发现对于利用石墨烯作为电子成像的支撑物非常重要。

英文摘要:

We investigate imaging of moire structures in free-standing twisted bilayer graphene (TBG) carried out by transmission electron microscopy (TEM) in diffraction and in-line Gabor holography modes. Electron diffraction patterns of TBG acquired at typical TEM electron energies of 80 - 300 keV exhibit the diffraction peaks caused by diffraction on individual layers. However, diffraction peaks at the scattering angles related to the periodicity of the moire structure have not been observed in such diffraction patterns. We show that diffraction on moire structure can create intense diffraction peaks if the energy of the probing electrons is very low, in the range of a few tens of eV. Experimental diffraction patterns of TBG acquired with low-energy electrons of 236 eV exhibiting peaks attributed to the moire structure periodicity are shown. In holography mode, the intensity of the wave transmitted through the sample and measured in the far-field can be enhanced or decreased depending on the atomic arrangement, as for example AA or AB stacking. Thus, a decrease of intensity in the far-field must not necessarily be associated with some absorption inside the sample but can simply be a result of a particular atomic arrangement. We believe that our findings can be important for exploiting graphene as a support in electron imaging.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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