少数层石墨炔的电子结构和光学性质的理论计算研究

Considering the electronic structures with Dirac corn is very important for graphyne material, we focus the fators which may alter the Dirac cone's existence and its shape. Previous studies of graphene materials have shown the interlayer interaction have a great effect on their electronic structures, especilly the Dirac cone's existence and its shape. In this project, we will apply the vdW - DFT method to calculate the electronic structure of multilayer graphynes (layer number1~10 or more), then we will compare their electronic structures with those of bulk graphynes with the same stacking sequence, defining the critical layer number between the quasi-two-dimensional (2-D) few-layer graphynes and three dimensional (3-D) bulk graphynes. On this basis, we further analyze the low-energy electronic structures of quasi 2-D few-layer graphynes, revealing the effects of the interlayer interaction on their low-energy electronic structures, especially the existence of Dirac cone or its shape. By calculating the low-energy Infrared (IR) absorption spectra of the few-layer graphynes, we will make an analysis of the characteristic absorption structures of the few-layer graphynes with different stacking number and stacking sequence respectively. The characteristic structures in the spectra will supply a theoretically powerful guider for the future experiments to identify the stacking number and stacking sequence of the few-layer graphynes. Finally, we will study how to control the low-energy electronic structures of few-layer graphynes by the external circumstance, and explore the possible fields of application. All aspects mentioned above have not been studied systematically at home and abroad yet, thus this project will promote the researches in these aspects.

鉴于Dirac锥的电子结构在石墨炔材料中的重要性，我们必须关注那些可能影响Dirac锥存在或形状的因素。以往对石墨烯的研究表明层间相互作会影响到Dirac锥存在或形状。因此在本项目中，我们将采用vdW-DFT方法，首先研究不同的层间相互作用（堆积层数和堆积方式）下的多层石墨炔（1～10层或更多）的电子结构，界定出准二维少数层石墨炔和三维体态石墨炔之间的临界层数。在此基础上，进一步分析少数层石墨炔在费米面附近的低能电子结构，揭示层间相互作用对其低能电子结构的影响，尤其是对Dirac锥的存在或形状的影响。进而通过计算少数层石墨炔的低能红外光学吸收谱，分析不同堆积层数和堆积方式的少数层石墨炔的特征结构，为将来在实验上鉴定它们提供理论依据。最后我们会研究如何利用外界环境调控少数层石墨炔的低能电子结构，探究它们的可能应用。这几方面在国际国内还尚待研究，本项目的工作将有力地推进这方面的研究

本项目原计划研究少数层石墨炔的层间相互作用对其电子结构影响,并通过研究其低能红外光学吸收谱,在不同堆积层数和堆积方式下的特征结构, 从而为将来在实验上鉴定它们提供理论依据. 但考虑到二维石墨炔的结构很多都还没有在实验上制备出来, 而实验上已经成功制备出二维的黑磷单层, 这种新的二维材料的发现带来了新的研究热点. 为了更好和实验比较,本项目的研究对象从石墨炔转为二维黑磷,但研究目标不变,仍然是研究这类层状材料的层间相互作用对其电子性质的影响,并通过光学手段或者电学手段鉴定出它们的层数或者堆积方式. 实验上对少数层黑磷的电输运性质研究结果表明,少数层黑磷的输运带隙随着层数增加而逐渐减小,这给我们提供了通过增加堆积层数来调控少数层黑磷的电输运特性的方法, 也提供了通过测量其输运带隙来鉴定其层数的方法. 然而,层间相互作用不仅会影响少数层黑磷电子能带隙, 还有很能影响其整个的能带结构. 而这些应该也可以在其输运性质上有所反映. 因此我们的理论计算继续探究了少数层黑磷的层间相互作用,对例如I-V曲线和微分电导的影响。我们的目标是通过对不同层数的少数层黑磷的这些输运性质的研究，能够为未来实验上制备，鉴定它们的层数提供更多的电学测量手段。单层，双层，三层的黑磷在与Cu(111)面以top-contact 相互连接时，可从它们的电流电压曲线上，以电流值的大小来区分不同的层数。更为有效的途径是从它们的微分电导图上，不同层数的黑磷，它们的微分电导曲线差异比起它们的电流电压曲线更为明显。它们的微分电导曲线上峰值的位置和幅度都可以作为鉴定它们的依据。