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4시부터 2층 라운지세미나실에 다과를 준비하오니 많은 참석 부탁드립니다
1. 제 목: On-Film Formation of Bi Nanowires with Extraordinary Electron Mobility
2. 연 사: 이 우 영 교수(연세대 금속시스템 공학과)
3. 일 시: 2008년 11월 7일(금) 오후4:30
4. 장 소: 물리학과세미나실(31355호실)
5. 초 록: The search for new growth methods for one-dimensional (1D) structures with nanometer
diameters, such as nanowires, continues to be of central importance in nanoscience and
nanotechnology, since they have great potentials for understanding their unusual quantum properties
and for use in nanoscale devices. In particular, bismuth (Bi) nanowires have been of great
significance in nanophysics to both theorists and experimentalists, as Bi is known to be a Group V
semimetallic element that exhibits unusual transport properties due to its highly anisotropic Fermi
surface. Single-crystalline Bi nanowires have motivated many researchers to investigate novel quasi-
one-dimensional phenomena such as the wire-boundary scattering effect and quantum confinement
effects due to their electron effective mass (~0.001 me), which is the smallest of all known materials.
Moreover, single-crystalline Bi nanowires are expected to usher in new class of thermometric devices
with high thermoelectric figure-of-merit (ZT) values. Here, a novel stress-induced method to grow
semimetallic Bi nanowires along with an analysis of their transport properties is presented. Single
crystalline Bi nanowires were found to grow on as-sputtered films after thermal annealing at 270 ˚C.
This was facilitated by relaxation of stress between the film and the thermally oxidized Si substrate that
originated from a mismatch of the thermal expansion. The diameter-tunable Bi nanowires can be
produced by controlling the mean grain size of the film, which is dependent upon the thickness of the
film. Four-terminal devices based on individual Bi nanowires were found to exhibit Shubnikov-de Haas
oscillation (SdH) as well as very large transverse and longitudinal ordinary magnetoresistance (OMR),
indicating high-quality, single crystalline Bi nanowires. Unusual transport properties, including a
mobility value of 76,900 cm2/Vs and a mean free path of 1.35 μm in a 120-nm Bi nanowire, were
observed at room temperature.
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