• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.302-302
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• 2011

Fabrications of metal-organic hybrid networks attracted much attention due to possible applications in gas storages, heterogeneous catalyses, information storages, and opto-electronic devices. One way to construct three-dimensional hybrid structures is to make the arrays of planar or linear metal-organic hybrid structures which are linked through electrostatic interactions. As a model study, we fabricated the arrays of one-dimensional hybrid chains and investigated inter-chain interactions between adjacent hybrid chains using scanning tunneling microscopy (STM) and spectroscopy (STS) on Ag(111). Brominated anthracene molecules were used to grow the arrays of hybrid chains on Ag(111). We proposed atomic models for the observed structures. Linear chains are made of repetition of Ag-anthracene units. Br atoms are attached to anthracene molecules through Br-H structures which mediate inter-chain interactions. Two different apparent heights were observed in anthracene molecules. Molecules having a Br-H connection look brighter than those with two connections due to electronic effect. When a chain is laterally manipulated with STM tip, Br atoms move together with the chain implying that Br-H inter-chain interactions are quite strong.

• 반도체디스플레이기술학회지
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• 제22권2호
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• pp.87-95
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• 2023

TiO₂ thin films were grown using the Atomic Layer Deposition (ALD) and their structural and electrical properties were investigated. The crystal structure, dielectric constant, and surface roughness of the TiO₂ thin films grown by the ALD deposition method were studied. The grown TiO₂ thin films showed an anatase crystal structure, and their properties varied with temperature. In particular, the properties of the TiO₂ thin films were confirmed by changing the process temperature. The electrical properties of Metal-Insulator-Silicon (MIS) capacitor structures were analyzed using a probe station. The performance improvement of capacitors using TiO₂ as a dielectric was confirmed by measuring capacitance through Capacitance-Voltage (C-V) curves.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.33-33
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• 2009

Silicon nano-structures have great potential in bionic sensor applications. Atomic force microscopy (AFM) anodic oxidation have many advantages for the nanostructure fabrication, such as simple process in atmosphere at room temperature, compatibility with conventional Si process. In this work, we fabricated simple FET structures with channel width W~ 10nm (nanowire) and $1{\mu}m$ (nano-ribbon) on ~10, 20 and 100nm-thinned silicon-on-insulator (SOI) wafers in order to investigate the surface effect on the transport characteristics of nano-channel. For further quantitative analysis, we carried out the 2D numerical simulations to investigate the effect of channel surface states on the carrier distribution behavior inside the channel. The simulated 2D cross-sectional structures of fabricated devices had channel heights of H ~ 10, 20, and 100nm, widths of L ~ $1{\mu}m$ and 10nm respectively, where we simultaneously varied the channel surface charge density from $1{\times}10^{-9}$ to $1{\times}10^{-7}C/cm2$. It has been shown that the side-wall charge of nanowire channel mainly affect the I-V characteristics and this was confirmed by the 2D numerical simulations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.83-83
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• 2008

Metal-oxide-silicon-on-insulator (MOSOI) structures were fabricated to study the effect caused by reactive ion etching (RIE) and sacrificial oxidation process on silicon-on-insulator (SOI) layer. The MOSOI capacitors with an etch-damaged SOI layer were characterized by capacitance-voltage (C-V) measurements and compared to the sacrificial oxidation treated samples and the reference samples without etching treatment. The measured C-V curves were compared to the numerical results from 2-dimensional (2-D) simulations. The measurements revealed that the profile of C-V curves significantly changes depending on the SOI surface condition of the MOSOI capacitors. The shift in the measured C-V curves, due to the difference of the fixed oxide charge ($Q_f$), together with the numerical simulation analysis and atomic force microscopy (AFM) analysis, allowed extracting the fixed oxide charges ($Q_f$) in the structures as well as 2-D carrier distribution profiles.

• The Journal of the Acoustical Society of Korea
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• 제15권1E호
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• pp.5-19
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• 1996

This paper proposes a loose part monitoring system (LPMS) design with a signal processing method based on fuzzy logic. Considering fuzzy characteristics of metallic impact waveform due to not only interferences from various types of noises in an operating nuclear power plant but also complex wave propagation paths within a monitored mechanical structure, the proposed LPMS design incorporates the comprehensive relation among impact signal features in the fuzzy rule bases for the purposes of alarm discrimination and impact diagnosis improvement. The impact signal features for the fuzzy rule bases include the rising time, the falling time, and the peak voltage values of the impact signal envelopes. Fuzzy inference results based on the fuzzy membership values of these impact signal features determine the confidence level data for each signal feature. The total integrated confidence level data is used for alarm discrimination and impact diagnosis purposes. Through the perpormance test of the proposed LPMS with mock-up structures and instrumentation facility, test results show that the system is effective in diagnosis of the loose part impact event(i.e., the evaluation of possible impacted area and degree of impact magnitude) as well as in suppressing false alarm generation.

• EDISON SW 활용 경진대회 논문집
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• 제6회(2017년)
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• pp.457-462
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• 2017

A linear carbon chain with pure sp hybridization has been intensively studied for the application of its intrinsic electrical properties to electronic devices. Owing to the high chemical reactivity derived from its unsaturated bond, encapsulation by carbon nanotubes (CNT) is provided as a promising method to stabilize the geometry of the linear carbon chain. Although the influence of CNT on the carbon chain has extensively been studied in terms of both electronic structure and geometries, the electron transport properties has not been discussed yet. In this regard, we provide the systematic atomic-scale analyses of the properties of the linear carbon chain within CNT based on a computational approach combining density-functional theory (DFT) and matrix green function (MGF) method. Based on the DFT calculations, the influence of CNT on electronic structures of the linear carbon chain is provided as well as its electrical origin. Via MGF calculations, we also identify the electron transport properties of the carbon chain - CNT complex.

• 한국재료학회지
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• 제17권5호
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• pp.250-255
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• 2007

The alloying effects on the electronic structures of Zinc are investigated using the relativistic $DV-X{\alpha}molecular$ orbital method in order to obtain useful information for alloy design. A new parameter which is the d obital energy level(Md) and the bonder order(Bo) of alloying elements in Zinc was introduced and used for prediction of the mechanical properties. The Md correlated with the atomic radius and the electronegativity of elements. The Bo is a measure of the strength of the covalent bond between M and X atoms. First-principles calculations of electronic structures were performed with a series of models composed of a MZn18 cluster and the electronic states were calculated by the discrete variational- $X{\alpha}method$ by using the program code SCAT. The central Zinc atom(M) in the cluster was replaced by various alloying elements. In this study energy level structures of pure Zinc and alloyed Zinc were calculated. From calculated results of energy level structures in MZn18 cluster, We found Md and Bo values for various elements of Zn. In this work, Md and Bo values correlated to the tensile strength for the Zn. These results will give some guide to design of zinc based alloys for high temperature applications and it is possible the excellent alloys design.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.425.1-425.1
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• 2014

Thermal transport in nanomaterials is not only scientifically interesting but also technological important for various future electronic, bio, and energy device applications. Among the various computation approaches to investigate lattice thermal transport phenomena in nanoscale, the atomistic nonequilibrium Green's function approach based on first-principles density functional theory calculations appeared as a promising method given the continued miniaturization of devices and the difficulty of developing classical force constants for novel nanoscale interfaces. Among the nanometerials, carbon atomic chains, namely the cumulene (all-doulble bonds, ${\cdots}C=C=C=C{\cdots}$) and polyyne (alternation of single and triple bonds, ${\cdots}C{\equiv}C-C{\equiv}C{\cdots}$) can be considered as the extream cases of interconnction materials for nanodevices. After the discovery and realization of carbon atomic chains, their electronic transport properties have been widely studied. For the thermal transport properties, however, there have been few literatures for this simple linear chain system. In this work, we first report on the development of a non-equilibrium Green's function theory-based computational tool for atomistic thermal transport calculations of nanojunctions. Using the developed tool, we investigated phonon dispersion and transmission properties of polyethylene (${\cdots}CH2-CH2-CH2-CH2{\cdots}$) and polyene (${\cdots}CH-CH-CH-CH{\cdots}$) structures as well as the cumulene and polyyne. The resulting phonon dispersion from polyethylene and polyene showed agreement with previous results. Compared to the cumulene, the gap was found near the ${\Gamma}$ point of the phonon dispersion of polyyne as the prediction of Peierls distortion, and this feature was reflected in the phonon transmission of polyyne. We also investigated the range of interatomic force interactions with increase in the size of the simulation system to check the convergence criteria. Compared to polyethylene and polyene, polyyne and cumulene showed spatially long-ranged force interactions. This is reflected on the differences in phonon transport caused by the delicate differences in electronic structure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.79-80
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• 2009

The local oxidation using an atomic force microscopy (AFM) is useful for Si-base fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC poly types, 4H-SiC is the most attractive poly type due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, $0.01{\sim}0.025\;{\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50%. The height of the fabricated oxide pattern ($1{\sim}3\;nm$) on SiC is similar to that of typically obtained on Si ($10^{15}{\sim}10^{17}\;cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. Whereas the simulated electric field on Si surface is constant ($5\;{\times}\;10^7\;V/m$), the electric field on SiC surface increases with increasing the doping concentration from ${\sim}10^{15}$ to ${\sim}10^{17}\;cm^{-3}$. We demonstrated that a specific electric field ($4\;{\times}\;10^7\;V/m$) and a doping concentration (${\sim}10^{17}\;cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.

• 한국전기전자재료학회논문지
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• 제17권11호
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• pp.1218-1223
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• 2004

Porous silicon materials have been shown to have bright prospects for applications in light emitting, solar cell, as well as light- and chemical-sensing devices. In this report, structures of porous silicon prepared by anodic etching in HF-based solution with various etching times were studied in detail by Atomic Force Microscopy and Small Angle X -ray Scattering technique using the high energy beam line at Pohang Light Source in Korea. The results showed the coexistence of the various pores with nanometer and submicrometer scales. For nanameter size pores, the mixed ones with two different shapes were identified: the larger ones in cylindrical shape and the smaller ones in spherical shape. Volume fractions of the cylindrical and the spherical pores were about equal and remained unchanged at all etching times investigated. On the whole uniform values of the specific surface area and of the size parameters of the pores were observed except for the larger specific surface area for the sample with the short etching time. The results implies that etching process causes the inner surfaces to become smoother while new pores are being generated. In all SAXS data at large Q vectors, Porod slope of -4 was observed, which supports the fact that the pores have smooth surfaces.