• Journal of Powder Materials
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• v.15 no.6
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• pp.482-488
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• 2008

The indentation technique has been one of the most commonly used techniques for the measurement of the mechanical properties of materials due to its experimental ease and speed. Recently, the scope of indentation has been enlarged down to the nanometer range through the development of instrumentations capable of continuously measuring load and displacement. In addition to testing hardness, the elastic modulus of submicron area could be measured from an indentation load-displacement (P-h) curve. In this study, the hardness values of the constituent phases in Ti($C_{0.7}N_{0.3}$)-NbC-Ni cermets were evaluated by nanoindentation. SEM observation of the indented surface was indispensable in order to separate the hardness of each constituent phase since the Ti($C_{0.7}N_{0.3}$)-based cermets have relatively inhomogeneous microstructure. The measured values of hardness using nanoindentation were ${\sim}20$ GPa for hard phase and ${\sim}10$ GPa for binder phase. The effect of NbC addition on hardness was not obvious in this work.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.159-167
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• 2005

Quantization effects (QEs), which manifests when the device dimensions are comparable to the de Brogile wavelength, are becoming common physical phenomena in the present micro-/nanometer technology era. While most novel devices take advantage of QEs to achieve fast switching speed, miniature size and extremely small power consumption, the mainstream CMOS devices (with the exception of EEPROMs) are generally suffering in performance from these effects. In this paper, an analytical model accounting for the QEs and poly-depletion effects (PDEs) at the silicon (Si)/dielectric interface describing the capacitance-voltage (C-V) and current-voltage (I-V) characteristics of MOS devices with thin oxides is developed. It is also applicable to multi-layer gate-stack structures, since a general procedure is used for calculating the quantum inversion charge density. Using this inversion charge density, device characteristics are obtained. Also solutions for C-V can be quickly obtained without computational burden of solving over a physical grid. We conclude with comparison of the results obtained with our model and those obtained by self-consistent solution of the $Schr{\ddot{o}}dinger$ and Poisson equations and simulations reported previously in the literature. A good agreement was observed between them.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.117-123
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• 2004

A 30 nm $In_{0.7}GaAs$ High Electron Mobility Transistor (HEMT) with triple-gate has been successfully fabricated using the $SiO_2/SiN_x$ sidewall process and BCB planarization. The sidewall gate process was used to obtain finer lines, and the width of the initial line could be lessened to half by this process. To fill the Schottky metal effectively to a narrow gate line after applying the developed sidewall process, the sputtered tungsten (W) metal was utilized instead of conventional e-beam evaporated metal. To reduce the parasitic capacitance through dielectric layers and the gate metal resistance ($R_g$), the etchedback BCB with a low dielectric constant was used as the supporting layer of a wide gate head, which also offered extremely low Rg of 1.7 Ohm for a total gate width ($W_g$) of 2x100m. The fabricated 30nm $In_{0.7}GaAs$ HEMTs showed $V_{th}$of -0.4V, $G_{m,max}$ of 1.7S/mm, and $f_T$ of 421GHz. These results indicate that InGaAs nano-HEMT with excellent device performance could be successfully fabricated through a reproducible and damage-free sidewall process without the aid of state-of-the-art lithography equipment. We also believe that the developed process will be directly applicable to the fabrication of deep sub-50nm InGaAs HEMTs if the initial line length can be reduced to below 50nm order.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2923-2928
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• 2010

This study examined the synthesis of the crystal structure of bis(2,2'-bipyridine)nitrato zinc (II) nitrate, $[Zn(bipy)_2(NO_3)]^+NO_3^-$ using a microwave treatment at 300 W and 60 Hz for the application to dye-sensitized solar cells. The simulated complex structure of the complex was optimized with the density functional theory calculations for the UV-vis spectrum of the ground state using Gaussian 03 at the B3LYP/LANL2DZ level. The structure of the acquired complex was expected a penta-coordination with four nitrogen atoms of bipyridine and the oxygen bond of the $NO_3^-$ ion. The reflectance UV-vis absorption spectra exhibited two absorptions (L-L transfers) that were assigned to the transfers from the ligand ($\sigma$, $\pi$) of $NO_3$ to the ligand ($\sigma^*$, $\pi^*$) of pyridine at around 200 - 350 nm, and from the non-bonding orbital (n) of O in $NO_3$ to the p-orbital of pyridine at around 450 - 550 nm, respectively. The photoelectric efficiency was approximately 0.397% in the dye-sensitized solar cells with the nanometer-sized $TiO_2$ at an open-circuit voltage (Voc) of 0.39 V, a short-circuit current density (Jsc) of $1.79\;mA/cm^2$, and an incident light intensity of $100\;mW/cm^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.132-132
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• 2008

Silicon carbide (SiC) is an attractive material for high-power, high-temperature, and high-frequency applications. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, the surface potential and topography distributions SiC with different doping levels were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip and a metal defined electrical contacts of Au onto SiC. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the Au deposited on SiC surface was higher than that of original SiC surface. The dependence of the surface potential on the doping levels in SiC, as well as the variation of surface potential with respect to the schottky barrier height has been investigated. The results confirm the concept of the work function and the barrier heights of metal/SiC structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1147-1156
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• 2011

A contact-type area-varying capacitive displacement sensor, or CLECDiS, can measure displacements over millimeter ranges with nanometer resolution. However, a small changes in the contact condition due to the surface profile or friction, which are inherent characteristics of contact-type sensors, lead to significant distortion of the output signal. Therefore, ensuring reliable contact conditions during CLECDiS measurements is the most important area to be improved in their actual use. Herein, in order to design an instrument for ensuring reliable contact conditions, the contact condition is analyzed by characterizing the signal distortion, observing the pressure distribution between the contacting surfaces, and measuring the motional errors of the sensor using a laser Doppler vibrometer (LDV). The manufactured instrument enables a CLECDiS to be used in an ultraprecise positioning system with improved reliability.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.2
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• pp.95-103
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• 2011

This paper proposes a 6b 1.2 GS/s 47.8 mW 0.17 $mm^2$ 65 nm CMOS ADC for high-rate wireless personal area network systems. The proposed ADC employs a source follower-free flash architecture with a wide input range of 1.0 $V_{p-p}$ at a 1.2 V supply voltage to minimize power consumption and high comparator offset effects in a nanometer CMOS technology. The track-and-hold circuits without source followers, the differential difference amplifiers with active loads in pre-amps, and the output averaging layout scheme properly handle a wide-range input signal with low distortion. The interpolation scheme halves the required number of pre-amps while three-stage cascaded latches implement a skew-free GS/s operation. The two-step bubble correction logic removes a maximum of three consecutive bubble code errors. The prototype ADC in a 65 nm CMOS demonstrates a measured DNL and INL within 0.77 LSB and 0.98 LSB, respectively. The ADC shows a maximum SNDR of 33.2 dB and a maximum SFDR of 44.7 dB at 1.2 GS/s. The ADC with an active die area of 0.17 $mm^2$ consumes 47.8 mW at 1.2 V and 1.2 GS/s.

• Clean Technology
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• v.18 no.4
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• pp.355-359
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• 2012

For effectively photochemical hydrogen production, Ti ions (0.01, 0.10, 0.50 mol%) impregnated $WO_3$ ($Ti/WO_3$) nanometer sized particles were prepared using a impregnation method as a photocatalyst. The characteristics of the synthesized $Ti/WO_3$ photocatalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectra (PL), atomic force microscope (AFM), and electrostatic force microscope (EFM). The evolution of $H_2$ from methanol/water (1/1) photo-splitting over $Ti/WO_3$ photocatalysts was enhanced compared to those over pure $TiO_2$ and $WO_3$ photocatalysts; 3.02 mL of $H_2$ gas was evolved after 8 h when 0.5 g of a 0.10 mol% $Ti/WO_3$ catalyst was used.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.24.2-24.2
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• 2009

Nanostuctures such as nanodot and nanowire have been extensively studied as building blocks for nanoscale devices. However, the direct growth of the nanostuctures at the desired position is one of the most important requirements for realization of the practical devices with high integrity. Self-assembled nanotemplate is one of viable methods to produce highly-ordered nanostructures because it exhibits the highly ordered nanometer-sized pattern without resorting to lithography techniques. And selective epitaxial growth (SEG) can be a proper method for nanostructure fabrication because selective growth on the patterned openings obtained from nanotemplate can be a proper direction to achieve high level of control and reproducibility of nanostructucture fabrication. Especially, SiGe has led to the development of semiconductor devices in which the band structure is varied by the composition and strain distribution, and nanostructures of SiGe has represented new class of devices such nanowire metal-oxide-semiconductor field-effect transistors and photovoltaics. So, in this study, various shaped SiGe nanostructures were selectively grown on Si substrate through ultrahigh vacuum chemical vapor deposition (UHV-CVD) of SiGe on the hexagonally arranged Si openings obtained using nanotemplates. We adopted two types of nanotemplates in this study; anodic aluminum oxide (AAO) and diblock copolymer of PS-b-PMMA. Well ordered and various shaped nanostructure of SiGe, nanodots and nanowire, were fabricated on Si openings by combining SEG of SiGe to self-assembled nanotemplates. Nanostructure fabrication method adopted in this study will open up the easy way to produce the integrated nanoelectronic device arrays using the well ordered nano-building blocks obtained from the combination of SEG and self-assembled nanotemplates.

• Polymer(Korea)
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• v.36 no.4
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• pp.536-541
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• 2012

The effects of silica content were studied on UV curing characteristics and defect formations in imprinted patterns of hundreads nanometer size for the photo-curable imprinting composites with silica particles. An increase in elasticity and a decrease in shrinkage were observed with an increase in silica content in the imprinting resin which was UV cured at room temperature. However, the patterned nano-pillars were stuck together with neighboring nano-pillars if the amount of silica is more than 7 wt%. This can be ascribed to the increased viscosity of imperfectly cured resin due to the obstruction of the photo-reaction by silica particles. Addition of silica to the imprinting resin is useful in enhancing the strength of the cured resin although it is difficult to get good imprinted patterns for the resin with more than 7 wt% of silica due to the reduction of photo-reaction conversion.