• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.362-362
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• 2014

Atomic layer deposition (ALD) can be regarded as a special variation of the chemical vapor deposition method for reducing film thickness. ALD is based on sequential self-limiting reactions from the gas phase to produce thin films and over-layers in the nanometer scale with perfect conformality and process controllability. These characteristics make ALD an important film deposition technique for nanoelectronics. Tantalum pentoxide ($Ta_2O_5$) has a number of applications in optics and electronics due to its superior properties, such as thermal and chemical stability, high refractive index (>2.0), low absorption in near-UV to IR regions, and high-k. In particular, the dielectric constant of amorphous $Ta_2O_5$ is typically close to 25. Accordingly, $Ta_2O_5$ has been extensively studied in various electronics such as metal oxide semiconductor field-effect transistors (FET), organic FET, dynamic random access memories (RAM), resistance RAM, etc. In this experiment, the variations of chemical and interfacial state during the growth of $Ta_2O_5$ films on the Si substrate by ALD was investigated using in-situ synchrotron radiation photoemission spectroscopy. A newly synthesized liquid precursor $Ta(N^tBu)(dmamp)_2$ Me was used as the metal precursor, with Ar as a purging gas and $H_2O$ as the oxidant source. The core-level spectra of Si 2p, Ta 4f, and O 1s revealed that Ta suboxide and Si dioxide were formed at the initial stages of $Ta_2O_5$ growth. However, the Ta suboxide states almost disappeared as the ALD cycles progressed. Consequently, the $Ta^{5+}$ state, which corresponds with the stoichiometric $Ta_2O_5$, only appeared after 4.0 cycles. Additionally, tantalum silicide was not detected at the interfacial states between $Ta_2O_5$ and Si. The measured valence band offset value between $Ta_2O_5$ and the Si substrate was 3.08 eV after 2.5 cycles.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.221.1-221.1
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• 2015

The vapor-liquid-solid (VLS) method, where the "liquid" catalytic droplets collecting atoms from vapor precursors build the solid crystal layers via supersaturation, is a ubiquitous technique to synthesize 1-dimensional nanoscale materials. However, the lack of fundamental understanding of chemical information governing the process inhibits the rational route to the structural programming. By combining the in situ or operando IR spectroscopy with post-growth high resolution electron microscopy, we show the strong correlation between the surface chemical species concentration and nanowire structures. More specifically, the critical role of surface adsorbed hydrogen, generated from the decomposition of Si2H6 precursor on the interplay between nanowire / kinking and the defect propagation is demonstrated. Our results show that adsorbed hydrogen atoms are responsible for selecting -oriented growth and indicate that a twin boundary imparts structural coherence. The twin boundary, only continuous at / kinks, reduces the symmetry of the trijunction and limits the number of degenerate directions available to the nanowire. These findings constitute a general approach for rationally engineering kinking superstructures and also provide important insight into the role of surface chemical bonding during VLS synthesis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1211-1214
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• 2003

The film is prepared by electron cyclotron resonance chemical vapor deposition (ECRCVD) employing CH$_4$ and H$_2$ gases. It is deposited by the control of microwave plasma power, gas flow ratio, deposition pressure, and In-situ thermal treatment temperature. The structure of a-C:H (hydrogenated amorphous carbon) thin film is analysed by FT-IR spectroscopy. The fraction sp$^3$ versus sp$^2$ bonding is very important to clear up the surface and interrace of a-C:H film properties such as nano-scale friction behavior. The sp$^3$ versus sp$^2$ bonding of a-C:H thin film is dependent on the deposition conditions, therefore. nano-scale friction behavior is dependent on the deposition conditions.

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.995-1002
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• 1993

The thermal decomposition of trimethylaluminum (TMA) with ammonia has been investigated by in-situ Fourier transform infrared spectroscopy. The spectroscopic reaction cell, which permits heating interna lly up to 1100$^{\circ}C$, consists of stainless-steel hexagonal-port chamber containing two NaCl windows installed in parallel. In this work, the stoichiometric reaction between TMA and $NH_3$ is found to be completed immediately after mixing. FTIR spectra observed in the range of temperature 25∼1100$^{\circ}C$ show that TMA and TMA : $NH_3$ adduct decompose into methane as a predominant product around 500$^{\circ}C$. The assignments of the IR bands due to the gaseous TMA, $NH_3$ and TMA : $NH_3$ adduct are attempted on the basis of the published data. Furthermore, the decomposition of TMA can be described as a first-order reaction. Kinetic data about the decompositon of TMA and TMA : $NH_3$adduct will also be discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.251-251
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• 2013

고 유전 박막을 이용하여 초고집적 DRAM용 캐패시터를 만들고자 하는 연구가 전세계 메모리 반도체 산업계에 걸쳐 활발히 이루어지고 있다. 본 연구는 High-k의 precursor인 Tetrakis (EthylMethylAmino) Zirconium) TEMAZ와 새로운 전구체인 Tris (dimethylamino) cyclopentadienyl Zirconium) CpZr (DMA)3의 열 안정성과 증착 특성을 비교하였다. in-situ Fourier tramsform infrared spectroscopy (FTIR)을 통해 long-term 열안정성을 확인하였다. 증착과 동시에 자체개발한 FTIR-cell을 이용하여 Gas phase를 실시간으로 확인하였다. 증착 sample은SEM과 AFM을 통해 박막 특성 비교를 하였다.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2351-2357
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• 2011

Three new metal-organic copper(II) complexes, $[Cu(H_2PZTC)_2]_n{\cdot}2nH_2O$ (1), $[Cu(HPZTC){\cdot}2H_2O]_n{\cdot}2nH_2O$ (2), and $Cu_2[(PZHD)(OH)(H_2O)_2]_n$ (3) ($H_3PZTC$ = pyrazine-2,3,5-tricarboxylic acid, $PZHD^{3-}$ = 2-hydroxypyrazine-3,5-dicarboxylate), have been synthesized from $Cu(II)/H_3PZTC$ system under different synthetic conditions, and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. In complexes 1 and 2, $H_3PZTC$ ligands loose one and two protons, which were transformed into $H_2PZTC^-$ anion and $HPZTC^{2-}$ dianion under different preparation condition, respectively. Furthermore, two ligands coordinate with Cu(II) cations in different modes, leading to the formation of the different chain structures. In complex 3, $H_3PZTC$ ligand was converted into a new ligand-PZHD by in situ decarboxylation and hydroxylation under a higher pH value than that for complexes 1 and 2. PZHD ligands link the Cu(II) cations to form a 2D layer structure. These results demonstrate that the preparation conditions, including pH value and reaction temperature etc, play an important role in the construction of complexes based on $H_3PZTC$ ligand.

• Macromolecular Research
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• v.15 no.4
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• pp.343-347
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• 2007

Novel composite membranes, which delivered high separation performance for propylene/propane mixtures, were developed by coating inert poly(ethylene-co-propylene) rubber (EPR) onto a porous polyester substrate, followed by the physical distribution of $AgBF_4$. Scanning electron microscopy-wavelength dispersive spectrometer (SEM-WDS) revealed that silver salts were uniformly distributed in the EPR layer. The physical dispersion of the silver salts in the inert polymer matrix, without specific interaction, was characterized by FT-IR and FT-Raman spectroscopy. The high separation performance was presumed to stem from the in-situ dissolution of crystalline silver ionic aggregates into free silver ions, which acted as an active propylene carrier within a propylene environment, leading to facilitated propylene transport through the membranes. The membranes were functional at all silver loading levels, exhibiting an unusually low threshold carrier concentration (less than 0.06 of silver weight fraction). The separation properties of these membranes, i.e. the mixed gas selectivity of propylene/propane ${\sim}55$ and mixed gas permeance ${\sim}7$ GPU, were stable for several days.

• Journal of Microbiology and Biotechnology
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• v.31 no.10
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• pp.1366-1372
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• 2021

Bacterial nanocellulose (BNC) is a biocompatible material with a lot of potential. To make BNC commercially feasible, improvements in its production and surface qualities must be made. Here, we investigated the in situ fermentation and generation of BNC by addition of different cellulosic substrates such as Avicel and carboxymethylcellulose (CMC) and using Komagataeibacter sp. SFCB22-18. The addition of cellulosic substrates improved BNC production by a maximum of about 5 times and slightly modified its structural properties. The morphological and structural properties of BNC were investigated by using Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy and X-ray diffraction. Furthermore, a type-A cellulose-binding protein derived from Clostridium thermocellum, CtCBD3, was used in a novel biological analytic approach to measure the surface crystallinity of the BNC. Because Avicel and CMC may adhere to microfibrils during BNC synthesis or crystallization, cellulose-binding protein could be a useful tool for identifying the crystalline properties of BNC with high sensitivity.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.148-155
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• 2018

To get a better understanding of the effect of physicochemical properties and microstructure on $SO_2$ absorption behavior of DESs with different molar ratios of EmimCl and EG (from 2:1 to 1:2), densities (${\rho}$), viscosities (${\eta}$), speeds of sound (u), refractive indices ($n_D$), and thermal decomposition temperatures ($T_d$) of EmimCl-EG DESs were measured and used to obtain the other derived properties, such as thermal expansion coefficient (${\alpha}_p$) and activation energy for viscous flow ($E_{\eta}$). Moreover, FT-IR spectra and in situ variable-temperature NMR spectroscopy were employed to study the microstructures of DESs. Based on physicochemical and spectroscopic properties, the influence of the concentrations of EmimCl on the interactions in DESs was explored to be associated with their $SO_2$ absorption behavior. The results show that the interactions between $Emim^+$ and $Cl^-$ of EmimCl is gradually weakening with increasing the concentration of EG in DESs by forming of hydrogen bond interaction of $O-H{\cdots}Cl^-$, resulting in a decrease of ${\rho}$, ${\eta}$, u, $n_D$, and $T_d$ of DESs, and hindering the charge-transfer interaction of $SO_2$ with $Cl^-$ and deceasing $SO_2$ capture capacity. Moreover, the $SO_2$ absorption capacity of DESs is proportional to their ${\rho}$ and $E_{\eta}$, respectively.

• Korean Journal of Materials Research
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• v.8 no.4
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• pp.345-353
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• 1998

Metal organic chemical vapor deposition (MOCVD) of copper using three Cu( I ) precursors. (hfac)Cu (VTMS) (hfac= hexafluoroacetylacetonate, VTMS= vinyltrimethylsilane), (hfac)Cu(VTMOS) (VTMOS= vinyltri¬methoxysilane) and (hfac)Cu(A TMS) (A TMS= allyltrimethylsilane) was studied. The thermal stability and the gase¬ous phase reaction mechanism of Cu( I ) precursors were identified using $^1H$-, $^I3C$-NMR and Fourier transform infra¬red spectroscopy. It was found out that thermal stability of liquid phase (hfac)Cu(VTMS) and (hfac)Cu(VTMOS) were better than that of (hfac)Cu(A TMS) using FT - NMR. From in-situ FT - IR experiments, the disproportion reaction of Cu(hfac). the decomposition reaction of Cu(hfac), and cracking of free hfac ligand were observed. Also the effect of gaseous phase reaction on the deposition rates and film properties was investigated. The minimum temperature that deposition of copper films from (hfac)Cu(A TMS) was as low as 60$^{\circ}$C and such a low deposition temperature compared with those of other Cu( I ) precursors is believed to be related with weaken Cu- A TMS bond.