탄소 나노튜브의 길이변화에 따른 물리적 특성에 관한 이론적 연구

문원하,변기량,황호정 중앙대학교 기술과학연구소 2001 기술과학연구소 논문집 Vol.31 No.-

본 연구에서는 나노 단위의 소자개발을 위하여 (6, 6) 탄소 나노튜브의 유한길이에 따른 물리적 특성에 관해 알아보았다. 먼저 브레너 전위식을 이용하여 모자가 씌워진 탄소 나노튜브의 최적화된 구조를 얻어내었다. 그후 탄소 나노튜브의 최적화된 구조를 가지고 TBMD 시뮬레이션을 수행하였다. TBMD 결과, 에너지 밴드갭은 길이에 따라 반비례하는 것을 알 수 있으며 특히 길이가 20 이하인 경우 탄소와 탄소간의 나타나는 π 결합의 영향으로 인하여 길이에 따라 에너지 밴드갭이 민감한 변화를 보이며 진동함을 알 수 있다. 여기서 (6, 6) 탄소 나노튜브의 에너지 배드갭은 0.3∼2.5 eV 정도임을 알 수 있다. The electronic properties of Carbon Nanotube(CNT) are currently the focus of considerable interest. In this paper, the electronic properties of finite length effect in CNT for carbon nano-scale device is presented. To Calculate the electronic properties of CNT, Empirical potential method (the extended Brenner potential for C-Si-H) for carbon and Tight Binding molecular dynamic (TBMD) simulation are used. As a result of study, we have known that the value of the band gap decreases with increasing the length of the tube. The energy band gap of (6,6) armchair CNT have the ranges between 0.3 eV and 2.5 eV. Also, our result are in agreements with the result of the other computational techniques.

Monte Carlo 시뮬레이션을 이용한 이온 주입시의 점결함 분포의 계산

손명식,이준하,변기량,황호정 중앙대학교 기술과학연구소 1995 기술과학연구소 논문집 Vol.25 No.-

이온 주입시의 점결함 분포를 간접적으로 계산하기 위해 단결정 실리콘에서의 3차원 이온 주입 시뮬레이터인 TRICSI (TRansport Ions in Crystal Slilicon) Monte Carlo 코드를 확장하여 Boron 이온 주입시의 에너지와 dose에 따른 불순물(particle) 및 점결함 분포(point defect)를 계산하였다. 결함 분포는 Modified Kinchin-Pease equation을 단결정 실리콘에 적용하여 displacement damage에 의해 발생한 Frenkel Pair(vacancy-interstitial)분포를 계산하였으며 이온 주입시의 웨이퍼 온도에 의한 Frenkel Pair 소멸 효과는 고려하지 않았다. 계산 결과는 3차원 각면으로의 2차원 투영 불순물 농도로 표현하고 주입된 dose와 에너지에 다른 마스크 주입시의 에너지 및 dose 의존성 도펀트 분포와 이에 따른 damage 분포를 이해하는 데 중요한 정보가 될 것으로 기대된다. We extended our ion implantation simulator, TRICSI (TRansport lons in Crystal Slilicon) Monte Carlo(MC) code, and indirectly calculated particle and its generating point defect distributions depending on energy and dose during boron implantation into <100> single0crystal silicon. The point defect distribution of Frenkel Pair(vacancy-interstitial) was abtained by applying the modified Kinchin-Pease equation, which usually uses in MC simulation in amorphous target, to MC simulation in crystalline silicon. We did not considered the annihilation of Frenkel Pairs due to wafer temperature. The calculated results were projected onto each free-dimensional plane, presented as two-dimensional concentration profile on it. The particle concentration profile was presented with typical open mask structure. We expect that these results help understand the dopant and its generating damage distributions depending on energy and dose during boron implantation.

Atomistic Simulation of Hypothetical Silicon Nanotubes under Tension

Ki Ryang Byun,Jeong Won Kang,Ho Jung Hwang 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.5

The responses of hypothetical silicon nanotubes under axial tensile forces have been investigated using an atomistic simulation based on the Terso potential. A tension, proportional to the deformation within Hooke's law, eventually led to a breaking of the silicon nanotubes. As the diameter of silicon nanotubes increased, the ultimate strength linearly increased. However, the force per atom at the breaking of silicon nanotubes was almost constant irrespective of the diameter of the silicon nanotubes. The behaviors of the elastic energy of silicon nanotubes with strain were similar with those of carbon nanotubes and the responses of silicon nanotubes under axial tension were similar with those of carbon nanotubes under axial tension, except for quantitative values, because the structure of silicon nanotubes used in this study was identical with that of carbon nanotubes. The eective strain energy constant of the silicon nanotubes was less than half of that of carbon nanotubes, and the stiness of the silicon nanotubes was much lower than that of carbon nanotubes, and these implied diculty with the formation and application of silicon nanotubes. When the parameters of silicon nanotubes are properly chosen (Young's modulus, eective strain constant, diameter, lattice constant, and strains), the maximum strains, ultimate strengths, and elastic energy at which the breaking events of silicon nanotubes occur could be estimated by using the equations in this work.? ?

질화붕소 나노피포드에 기반한 나노분자 메모리 시스템에 관한 연구

변기량(Ki Ryang Byun),강정원(Jeong Won Kang),최원영(Won Young Choi),황호정(Ho Jung Hwang) 한국진공학회(ASCT) 2005 Applied Science and Convergence Technology Vol.14 No.1

분자 위치제어 메모리 시스템에 대하여 고전적인 분자동역학을 이용하여 결합에너지 및 다양한 외부전기장의 형태에 따른 셔틀 풀러렌 동작에 관하여 연구하였다. 단일 나노피포드 형(single-nanopeapod type)은 질화붕소 나노튜브(boron-nitride nanotube) 속에 세 개의 엔도풀러렌(endo-fullerene)과 양쪽 끝에 구리 전극이 채워져 있는 구조를 갖고 있는 구조를 갖고 있다. 결론적으로, 분자동역학 시뮬레이션 결과로부터 이 나노메모리 시스템은 비휘발성임을 알 수 있었다. 안정적인 bit 변화를 위해서는 단일 나노피포드 형은 0.1eV/Å 외부전기장이 필요로 함을 알 수 있었다. Bucky shuttle memory systems were investigated by the classical molecular dynamics(MD) simulations. Energetics and operating response of the shuttle-memory-elements were examined by MD simulations of the C_(60) shuttle in the nanomemory systems under various external force fields. Single-nanopeapod type was consisting of three fullerenes encapsulated in (l0, 10) boron-nitride nanotube and filled Cu electrode. Studied systems could be applied to nonvolatile memory. MD simulation results showed that the stable bit flops could be achieved from the external force fields of 0.1 eV/Å for single-nanopeapod type.

A nanoscale field effect data storage of bipolar endo-fullerenesshuttle device

황호정,Ki Ryang Byun,Ju Yul Lee,Jeong Won Kang 한국물리학회 2005 Current Applied Physics Vol.5 No.6

We investigated the internal dynamics of an electro-uid shuttle memory element, consisting of K+@C 60 and F. @C 60 encapsu-lated in a C640 nanocapsule. Energetics and operating responses of bipolarendo-fullerenes shuttle memory device, (K+@C 60F. @C 60)@C 640, were examined by classical molecular dynamics simulations under the external force flelds..

Nanomechanical Properties of a Suspended Ultrathin Carbon Nanoribbon

강정원,Ki Ryang Byun,황호정,이준하,Hoong Joo Lee,Oh-Keun Kwon 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1

A carbon nanoribbon was investigated using atomistic simulations based on the Tersoff-Brenner potential function. The nanoribbon obtained from a compressed (5, 5) carbon nanotube had a cross-sectional binocular telescope structure composed of both sp2 and sp3 bonds. One carbon atom per ten carbon atoms had an sp3 bond. For the optimized structures, the residual forces on the nanoribbon were three-orders of magnitude higher than that on the nanotube, and the lattice constant of the nanoribbon was 0.0624 °A higher than that of the nanotube along the tube axis. The Young’s modulus of the nanoribbon was the same as that of the nanotube whereas the critical strain of the nanoribbon was significantly lower than that of the nanotube because the residual stresses on the nanoribbon were much higher than those on the nanotube. The tensile force curve vs. the strain of the nanotube was slightly higher than that of the nanoribbon.

Nanoscale Data Storage Device of Metallofullerene Peapods

Jeong Won Kang,황호정,Ki Ryang Byun 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2

We studied the energetics and the operations of nonvolatile nano-memory elements based on metallofullerene peapods by using classical molecular dynamics simulations. The system proposed in this work was composed of two carbon nanotubes and metallofullerenes. In classical molecular dynamics simulations, the open ends of two (10, 10) carbon nanotubes were face to face with a separation of 8 A, and the metallofullerenes shuttled between two carbon nanotubes under alternatively applied force elds. When the metallofullerenes were encapsulated in the carbon nanotubes, the electronic properties of the metallofullerene peapods were dierent from those of the carbon nanotubes. Therefore, these changes could be detected by a current ow change; then, the bit classications could be done by using metallofullerene shuttle between two carbon nanotubes under applied force elds. Since the metallofullerenes encapsulated in the carbon nanotubes can hardly escape from the carbon nanotubes without external force elds, the proposed system can operate a non-volatile memory device.

Model schematics of carbon-nanotube-based-nanomechanical-tuner using piezoelectric strain

Won Kang, Jeong,Kim, Ki-Sub,Ryang Byun, Ki,Kang, Eu-Seok,Lee, Junha,Kuen Kwon, Oh,Gyu Choi, Young,Hwang, Ho Jung Elsevier 2010 Physica E, Low-dimensional systems & nanostructure Vol.42 No.7

<P><B>Abstract</B></P><P>Model schematics of a carbon-nanotube-based frequency tuner are presented and their vibration frequencies are analyzed by theoretical approaches such as classical molecular dynamics simulations and the continuum model equation. Outertube’s position displacement by a piezoelectric strain of a piezoelectric material induces the change of the vibrating carbon nanotube length. The desired frequencies are achieved by manipulating the electric potential applied to the piezoelectric material.</P>

Molecular Dynamics Simulations of Nanomemory Element Based on Boron Nitride Nanotube-to-peapod Transition

황호정,Jeong Won Kang,Ki Ryang Byun 한국전기전자재료학회 2004 Transactions on Electrical and Electronic Material Vol.5 No.6

We investigated a nonvolatile nanomemory element based on boron nitride nanopeapods using molecular dynamics simulations. The studied system was composed of two boron-nitride nanotubes filled Cu electrodes and fully ionized endo-fullerenes. The two boron-nitride nanotubes were placed face to face and the endo-fullerenes came and went between the two boron-nitride nanotubes under alternatively applied force fields. Since the endo-fullerenes encapsulated in the boron-nitride nanotubes hardly escape from the boron-nitride nanotubes, the studied system can be considered to be a nonvolatile memory device. The minimum potential energies of the memory element were found near the fullerenes attached copper electrodes and the activation energy barrier was 3.579 eV. Several switching processes were investigated for external force fields using molecular dynamics simulations. The bit flips were achieved from the external force field of above 3.0 eV/ Å.

비균형적인 앉은자세 교정을 위한 힘-감지 저항센서 이용 연구

변상필(Sang Pil Byun),장인혁(In Hyuk Jang),박기혁(Ki Hyuk Park),손량희(Ryang Hee Sohn),이원구(Won Gu Lee) 한국산업융합학회 2014 한국산업융합학회 논문집 Vol.17 No.4

In this study, we present a method for correcting unbalanced sitting posture alignment to its optimal position, by designing a chair equipped with pressure sensor. With increasement in sedentary work, such as office work or study, people are now spending more time in chair. To accommodate sedentary life styles, many chairs are being designed for a comfortable sitting condition. However, without awareness and efforts for correct sitting posture, it may not be possible to achieve such condition. When the weight is not distributed evenly while sitting, it may cause various diseases such as scoliosis and a herniated disc. Being inspired by such facts, we have progressed basic researches to maintain the correct sitting posture. To demonstrate the proof-of-concept validation, we installed a series of sensors to a chair and then measured the changes in pressure distribution in various postures. The results show that this approach can be potentially helpful for understanding how fundamental problems due to unbalanced sitting posture can be corrected and maintained properly.