Lee Hsun Lecture Series
Topic: First-principles modeling to explore new functional low-dimensional materials
Speaker: Dr. Mina Yoon
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory,
Oak Ridge, TN, U.S.A.
Time: 10:00-11:30, (Tues.) Oct.17th, 2017
Venue: Room 468, Lee Hsun Building, IMR CAS
Abstract:
The recent discovery of graphene, the thinnest known material in nature, has triggered exploration of other types of ultrathin materials. Ultrathin two-dimensional (2D) materials are a promising new class of materials that exhibits numerous exotic properties. Structural heterogeneities, such as localized defects, alloys, and lateral and 2D interfaces, are inevitable in 2D materials. Our recent studies [1-15] demonstrated that they can be interesting key parameters to engineer 2D materials properties. Our studied 2D materials include organic semiconductors and graphene and beyond graphene materials. For a given chemical composition, structural phases of 2D materials can be distinctive and strongly deviated from their 3D counterpart. In this case, they cannot simply be treated as resembles of their parental 3D structures. Moreover, seemingly nonreachable phases in 3D may become possible in 2D form. Two-dimensional alloying turns out to be an efficient way to control the overall materials properties [1-3]. It can be served as a tool to obtain desired materials properties. By combining global structural prediction and first-principles calculations, we have identified a couple of new 2D chemical compounds that have comparable or even lower formation enthalpies than their known allotropes. I will discuss how localized defects and alloys can play as an unexpected mean to engineer band gap properties. Lateral heterogenetieis [4-6] in combination with strain can efficiently tune optoelectronic properties of some of transition metal dichalcogenides. 2D heterogeneities [7-15] can be utilized to control morphologies of low-D materials as well as their overall electronic and phonon transport properties by their stacking order and interfaces. We further report new thermodynamically stable low-dimensional (1D and 2D) electrides by using first-principles approaches [16,17]. The method was applied to binary compounds consisting of alkaline-earth elements as cations and group VA, VIA, or VIIA nonmetal elements as anions, and further extended to <~100K materials in databases. We demonstrated a new avenue to discover new electrides and provide new design principles, which will significantly boost the discovery of this new class of material with great technical application.
References
1. B. Huang, M. Yoon, B. Sumpter, S.-H. Wei, and F. Liu, Phys. Rev. Lett. 115, 126806 (2015).
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6. J. Lee, J. Huang, B.G. Sumpter, M. Yoon, 2D Mat. 4, 021016 (2017).
7. Z. Yan, L. Chen, M. Yoon, S. Kumar, Nanoscale 8, 4037 (2016).
8. C. Park, J. Ryou, S. Hong, B. Sumpter, G. Kim, M. Yoon, Phys. Rev. Lett. 115, 015502 (2015).
9. W. Ming, Z. Wang, M. Zhou, M. Yoon, and Feng Liu, Nano Lett. 16, 404 (2016).
10. S. Wagner, B. Huang, C. Park, J. Feng, M. Yoon, P. Zhang, Phys. Rev. Lett. 115, 096101 (2015).
11. X. Li et al., ACS Nano 9, 8078 (2015).
12. X. Li et al., Ang. Chem. 54, 1 (2015).
13. C. Park et al., Phys. Rev. B 90, 125432 (2014).
14. K. Xiao et al., J. Am. Chem. Soc. 135, 3680 (2013)
15. K. Xiao, M. Yoon, A. J. Rondinone, E.A. Payzant, and D.B. Geohegan, J. Am. Chem. Phys. 135, 14353 (2012).
16. Two-dimensional electrides predicted by global structure optimization, W. Ming, M. Yoon, M.-H. Du, F. Liu, K. Lee, and S. W. Kim, J. Am. Chem. Soc. 138, 15336 (2016).
17. New electrides based on one-dimensional building blocks, Changwon Park, Sung Wng Kim, Mina Yoon (2017, Phys. Rev. Lett. Under review).
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