Seung-Baek Lee

Ultraviolet-visible absorption measurements of high purity and well separated carbon onion samples are reported. The results show that, after purification, absorption features from carbon onions match well with the interstellar UV spectrum. The measurements show that the absorption peak position remains constant at 4.55+/-0.1 microm(-1), and the width varies from 1.2-1.6 microm(-1), a key feature of the interstellar spectrum. The similarities between the experimental and observed absorption spec

We have investigated the electrochemical gating characteristics of hole transport in aligned single-walled carbon nanotube (SWCNT) network thin film transistors (TFT). SWCNT thin films were aligned between source and drain electrodes by using dielectrophoresis. An electric field applied between 1 mM NaCl solution and the SWCNT actively controlled the hole transport in a p-type TFT. This may be due to the applied electric field polarizing the ions creating an electrical double layer on the SWCNT

We have investigated the perpendicular magnetic anisotropy of [CoSiB t(CoSiB)/Pt t(Pt)](n) multilayers as a function of the CoSiB and the Pt thicknesses and the number of repetition of the CoSiB/Pt bilayers. The coercivity (H(c)) and the saturation magnetization (M(s)) of the amorphous ferromagnetic material Co(75)Si(15)B(10) were taken to be 1.6 Oe and 407 emu/cm(3), respectively. The H(c) in [CoSiB t(CoSiB)/Pt 14 angstrom](5) multilayers increases with increasing t(CoSiB) to reach a maximum at

We report on the fabrication of multiwalled carbon nanotube (MWCNT) bridges using poly-methylmethacrylate (PMMA) suspended dispersion. This method makes it possible to suspend nanotubes between metal electrodes, without any chemical etching of the substrate, and to remove unwanted nanotubes from the substrate. Using a spacer layer of PMMA with a known thickness, it is also possible to control the suspended height of the MWCNT bridges. The electrical measurement results on suspended MWCNT bridges

We have investigated the perpendicular magnetic anisotropy of [CoSiB t CoSiB/Pt t Pt]n multilayers as a function of the CoSiB and the Pt thicknesses and the number of repetition of the CoSiB/Pt bilayers. The coercivity (Hc) and the saturation magnetization (Ms)of the amorphous ferromagnetic material Co75 Si15 B10 were taken to be 1.6 Oe and 407 emu/cm3, respectively. The Hc in [CoSiB t CoSiB /Pt 14 Å]5 multilayers increases with increasing t CoSiB to reach a maximum at t CoSiB = 3 Å and then dec

In high-strength bolted joints, it is known that the corrosion of base material causes the reduction of slip resistance. In this article, tensile tests on slip-critical joints utilizing Zn/Al metal spraying corrosion resistance method, which can prevent corrosion and meet the required mechanical characteristics of bolted joints, were carried out. In addition, slip coefficient and surface roughness were calculated. The key parameters of specimens were surface finishing condition and thickness of

We fabricated a magnetic field sensor made of an InAs quantum-well. Various numbers of magnetic particles were located on the sensor and the stray field generated by the magnetic particles was detected using micro-Hall magnetometry at room temperature. A numerical calculation carried out for this device successfully explained the experimental results and a useful equation relating the signal of the device and the number of particles was deduced.

The role of thermal oxidation before acid treatment and post high-temperature vacuum annealing of single walled carbon nanotube (SWCNTs) was studied by scanning electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analyses and Raman spectroscopy. An efficient procedure is developed for the purification of SWCNTs with minimal damage to the walls and minimal modification in the length of the tubes. SWCNTs are employed in this study, are synthesized by arc-discha

We report on a novel tactile pressure sensor structure that transfers the vertical pressure applied to the sample’s surface to lateral strain in the carbon-nanotube thin film embedded in an elastomer by using a “wavy” structured substrate contact surface. When pressure was applied to the poly(dimethylsiloxane) (PDMS) surface, it was transferred to a carbon-nanotube thin film (CNTF) underneath, where it stretched to conform to the wavy substrate surface. This resulted in an elongation, or lateral

최적화된 량의 황화수소 첨가 가스를 이용하여 실리콘 기판위에 증착된 Fe/Al 박막위에 촉매 화학 기상 증착법을 사용하여 직경이 얇은 다중층 탄소나노튜브가 수직 정렬되어 합성되었다. 주사전자현미경 관측 이미지에서 합성된 탄소나노튜브는 상대적으로 일정한 길이를 가지고 기판에 수직으로 정렬되었다. 투과전자현미경 관측에서 합성된 탄소나노튜브는 10nm 이내의 작은 외경을 가졌고 촉매가 거의 없었다. 평균 튜브의 벽 수는 약 다섯 개이다. 수직 정렬된 직경이 얇은 다중층 탄소나노튜브의 성장 메카니즘이 제시되었다. 수직 정렬된 직경이 얇은 다중층 탄소나노튜브는 <TEX>$0.1\;{\mu}A/cm^2$</TEX>의 전류밀도에서 약 <TEX>$1.1\;V/{\mu}m$</TEX> 낮은 턴-온 전계를 나타내었고 <TEX>$2.7\;V/{\mu}m$</TEX>의 전계에서 약 <TEX>$2.5\;mA/cm^2$</TEX>의 전류밀도를 얻었다. 게다가, 수직 정렬된 직경이 얇은 다중층 탄소나노튜브는

We examine ultrafast nonlinear birefringence of femtosecond optical pulses propagating through a semiconductor optical amplifier whose active element is composed of InAs/InP quantum dots at about 1.55 $\mu$m. The polarization-sensitive carrier dynamics in quantum dots are modeled for nonlinear gain bleaching that is employed for nonlinear birefringence for all-optical-wavelength converters. It is revealed that quantum dots support ultrafast nonlinear gain bleaching for ultrafast birefringence us

We have succeeded in synthesizing vertically aligned thin multi-walled carbon nanotubes (VA thin-MWCNTs) by a catalytic chemical vapor deposition (CCVD) method onto Fe/Al thin film deposited on a Si wafers using an optimum amount of hydrogen sulfide (H2S) additive. Scanning electron microscope (SEM) images revealed that the as-synthesized CNT arrays were vertically well-oriented perpendicular to the substrate with relatively uniform length. Transmission electron microscope (TEM) observations ind

We report on the toxic-gas-sensing characteristics of density-controlled carbon-nanotube-network (NTN) thin-film devices prepared on exible poly-dimethylsiloxane (PDMS) substrates. The devices were prepared by directly curing PDMS on selective vacuum-filtered NTN surfaces. The roomtemperature NH3 gas-sensing characteristics showed that for a 9-mm-channel-length device, a 40-s exposure to 10-ppm NH3 resulted in a 17 % decrease in conductance. Comparing devices with uniform square resistances and