COLUMN: 나노소재기술개발 - 세계가 주목하는 차세대 신물질 그래핀

홍석륜,Hong, Seok-Ryun 한국과학기술단체총연합회 2014 과학과 기술 Vol.538 No.-

세계로, 미래로 나아가는 회원 중심 한국물리학회

홍석륜(Suk Lyun HONG) 한국물리학회 2023 물리학과 첨단기술 Vol.32 No.1·2

First-principles study of carbon atoms adsorbed on MgO(100) related to graphene growth

류정아,홍석륜 한국물리학회 2013 Current Applied Physics Vol.13 No.2

We have performed density functional theory calculations to understand the initial growth of graphene by studying the adsorption of carbon atoms on the oxide substrates such as magnesium oxide. For adsorption behaviors of carbon atoms on the MgO(100) surface, their adsorption geometries and binding energies are calculated. The binding of a carbon atom is the most stable at the on-top oxygen site on MgO(100). Such strong CeO binding is analyzed by examining the projected density of states. Then, we also increase the number of carbon atoms on MgO(100) to investigate their adsorption behaviors. Due to strong binding between carbon atoms, adsorbed carbon atoms form chain-like or graphene-like structures on the surface. Combined with relatively strong CeO binding, this result may explain the graphene growth on MgO(100) observed in available experiments.

니켈 표면 및 (110) 면과 (100) 면이 만나는 부분에서 탄소의 퍼짐에 대한 이론적 연구

신영한,홍석륜 한국진공학회 2003 한국진공학회 학술발표회초록집 Vol.- No.-

Ab initio Calculations with van der Waals Corrections: Benzene-benzene Intermolecular Case and Graphite

박진우,유병덕,홍석륜 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1

For the benzene-benzene intermolecular case and graphite, we have performed ab initio density functional theory (DFT) calculations with van der Waals corrections. We use two DFT methods: the Vienna ab initio simulation package (VASP) and the Fritz Haber Institute ab initio molecular simulations package (FHI-aims). For the van der Waals description, we adopt Grimme’s DFT-D2 approach in VASP while the Tkatchenko-Scheffler (TS) scheme is used in FHI-aims. First, we calculate the equilibrium distance between the in-plane benzene-dimer molecules by using the two methods. The equilibrium intermolecular distance obtained using the DFT-D2 scheme of Grimme is shorter than that obtained using the TS scheme. The equilibrium structural parameters of graphite are calculated by varying the lattice parameters a and c simultaneously and are compared with previous results.

금속클러스터 M_(13)의 구조

성동철,박노정,홍석륜 한국물리학회 2011 새물리 Vol.61 No.3

We have performed density functional theory (DFT) calculations to find the low-energy structure of various types of small metal clusters. We investigated the electronic structure of M13 clusters consisting of Al, Au, and transition metal atoms, such as Pd, Pt and Ti. Icosahedron and cuboctahedron consisting of 13 atoms are minimal cluster shapes of closed atomic shells. As a result,we found low-energy structures for several metal clusters. For the cases of Al and Ti clusters, the icosahedron structure has the lowest energy. On the other hand, gold clusters are flake-like, and Pd and Pt clusters have a cage shape for their low-energy structures. Finally, we calculated the magnetic moments of the transition metal clusters. 이 논문에서는 다양한 종류의 금속 클러스터에 대한 안정된 구조를 찾기위하여 제일원리 밀도범함수 이론을 이용한 연구를 수행하였다. 먼저우리는 13개의 원자로 이루어진 알루미늄과 금, 그리고 팔라듐, 백금,타이타늄과 같은 전이금속에 대한 전자구조를 조사하였다. 정십이면체(icosahedron)와 육팔면체(cuboctahedron)은 가장 작은 수의닫힌 원자껍질을 가지는 구조이다. 우리는 이 구조를 기본으로 금속원자13개로 이루어진 클러스터의 안정된 구조를 얻기 위해서 클러스터의모양을 여러 형태로 바꿔서 계산을 하였다. 그 결과, 알루미늄과타이타늄은 정십이면체 구조가 가장 안정된 구조이고, 팔라듐과 백금은새장(cage) 구조, 금은 박편(flake) 구조가 가장 안정된 구조임을 알게되었다. 마지막으로 각 금속클러스터의 구조에 따른 자기모멘트(magnetic moment)를 계산하였다.

Van der Waals density functional theory study for bulk solids with BCC, FCC, and diamond structures

박진우,유병덕,홍석륜 한국물리학회 2015 Current Applied Physics Vol.15 No.8

Proper inclusion of van der Waals (vdW) interactions in theoretical simulations based on standard density functional theory (DFT) is crucial to describe the physics and chemistry of systems such as organic and layered materials. Many encouraging approaches have been proposed to combine vdW interactions with standard approximate DFT calculations. Despite many vdW studies, there is no consensus on the reliability of vdW methods. To help further development of vdW methods, we have assessed various vdW functionals through the calculation of structural properties at equilibrium, such as lattice constants, bulk moduli, and cohesive energies, for bulk solids, including alkali, alkali-earth, and transition metals, with BCC, FCC, and diamond structures as the ground state structure. These results provide important information for the vdW-related materials research, which is essential for designing and optimizing materials systems for desired physical and chemical properties.

Polar oxide substrates for graphene growth: A first-principles investigation of graphene on MgO(111)

민경아,Jinwoo Park,류정아,홍석륜,손알로이시우스 한국물리학회 2013 Current Applied Physics Vol.13 No.5

Given the recent excitement over the truly two-dimensional carbon “super” material e graphene, there is now much effort and focus on the various possibilities of engineering the band gap of graphene for its device applications. One possible and promising route will be to grow graphene directly on some nonmetallic substrates. In this paper, we address the atomic and electronic structure of various graphene structures on the polar MgO(111) using first-principles density-functional theory (DFT) calculations. We find that graphene generally interacts strongly with the O-terminated polar oxide surface, forming strong chemical bonds, inferred from both energetics and detailed density-of-states analysis. We compare our theoretical findings with available experimental results, offering a possible direction for future band gap engineering of graphene on such oxide substrates.

Atomic and Electronic Structures of the Ni-induced Phases on Si(111): Scanning Tunneling Microscopy and Spectroscopy Study

심형준,이근섭,김도환,홍석륜,김세훈 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.6

The atomic and electronic structures of Ni-induced phases formed on a Si(111) surface were investigated using scanning tunneling microscopy (STM) and spectroscopy (STS). STM images show the presence of two kinds of the ring clusters ('1x1'-RCs and √19-RCs) which are related to the known '1x1' and √19×√19 phases, respectively. In addition, a new ordered structure having a √7×√7 periodicity with a considerable domain size was also observed to form on the surface. Islands of the √7×√7 structure embedded in the surface of the √19×√19 structure are found to be made by regular packing of the '1x1'-RCs. High-resolution, dual-bias STM images reveal unprecedented atomistic details of both the ring clusters forming the ordered √19×√19 and √7×√7 structures. STS data indicate that the local √7×√7 phase is semiconducting with a gap of about 1 eV. The √19×√19 structure is either metallic or semiconducting with a gap smaller than 0.2 eV. The peaks in the (dI/dV)/(I/V) curves were attributed to the density of the states expected from the existing atomic models of the two ordered structures.

Electronic structure of graphene/Y2C heterostructure and related doping effect

최창규,김정환,최형규,차장환,홍석륜 한국물리학회 2021 Current Applied Physics Vol.28 No.-

Until now, many attempts have been made to dope graphene in various ways, but each method turned out to have pros and cons. In this study, to overcome the limitations of doping methods, yttrium hypocarbide (Y2C) is investigated as one prospective material to dope graphene, using density functional theory calculations. In monolayer Y2C, the anionic electrons localized away from Y atomic layers are confirmed to contribute to occupied states near the Fermi level. Next, we investigate the electronic structure of graphene in heterojunction with Y2C. Anionic electrons of Y2C occupy the empty states of graphene in graphene/Y2C heterostructure, which makes the Dirac cone of graphene located at about 1.7 eV below the Fermi level. Such charge transfer of anionic electrons to graphene and the flatness of electric cloud of anionic electrons leads to evenly n-doped graphene in graphene/Y2C heterostructure. This suggests that Y2C is a good candidate to dope graphene.