石墨烯超晶格之負微分電阻特性

Negative Differential Resistance in Graphene Superlattices

許仕傲(Shih-Ao Hsu)

指導教授 ： 薛文証

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.10999

摘要

本論文主旨為研究扶手椅型石墨烯奈米帶超晶格的電流-電壓特性。首先以緊束縛法求得純質石墨烯的電子能帶結構，計算有限層數超晶格的穿透率。再由穿透率推算出超平整石墨烯奈米帶的電流-電壓特性，並且評估出現負微分電阻區域之峰谷比。在設定的模型參數下，源汲極偏壓0.1V附近出現負微分電阻。本論文分別評估溫度、接面誘導的能隙、超晶格的周期數以及超晶格的層寬對負微分電阻的影響。降低溫度有助於提高元件的峰谷比。提高接面誘導的能隙也會提高峰谷比，但是影響不大。增加超晶格的週期數將會使共振能階對穿透率的影響更加明顯，在特定條件下也會提高峰谷比。此外，在模型評估的寬度參數中，適當地設計層寬可以得到最佳的性能。

關鍵字

石墨烯奈米帶 ； 緊束縛法 ； 轉移矩陣 ； 超晶格 ； 負微分電阻 ； 峰谷比

並列摘要

The main purpose of this thesis is to investigate the current properties of armchair graphene nanoribbon superlattices. By tight-binding method, the low-energy electronic bands of the pristine graphene is obtained. The transfer-matrix method is used to calculate the transmission of finite superlattices. Combining the Dirac Hamiltonian with Landauer-Büttiker Formalism, the current of ultrasmooth graphene nanoribbons and the peak-to-valley current ratio (PVR) are evaluated. In this model, it’s found that negative differential resistance (NDR) effect occurs in the vicinity of source-to-drain voltage, 0.1V. The PVR increases with decreasing of the temperature. Increasing the substrate-induced band gaps will slightly increase PVR as well. For certain conditions, increasing the numbers of cells will enhance the resonant spikes, therefore increasing PVR. Moreover, the largest PVR can be achieved when the layer width is properly designed.

並列關鍵字

graphene nanoribbon ； tight-binding method ； transfer matrix ； superlattice ； negative differential resistance ； peak to valley ratio

參考文獻

[1] K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, "Two-dimensional atomic crystals," Proc. Natl. Acad. Sci. U.S.A. 102, 10451-10453 (2005).

[2] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, "Electric field effect in atomically thin carbon films," Science 306, 666-669 (2004).

[3] L. Esaki and R. Tsu, "Superlattice and negative differential conductivity in semiconductors," IBM J. Res. Dev. 14, 61-65 (1970).

[4] C.-H. Park, L. Yang, Y.-W. Son, M. L. Cohen, and S. G. Louie, "Anisotropic behaviours of massless Dirac fermions in graphene under periodic potentials," Nature Phys. 4, 213-217 (2008).

[5] M. I. Katsnelson, K. S. Novoselov, and A. K. Geim, "Chiral tunnelling and the Klein paradox in graphene," Nature Phys. 2, 620-625 (2006).