• 한국재료학회지
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• 제18권10호
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• pp.515-520
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• 2008

We fabricated 10 nm-$TiO_2$ thin films for DSSC (dye sensitized solar cell) electrode application using ALD (atomic layer deposition) method at the low temperatures of $150^{\circ}\;and\;250^{\circ}$. We characterized the crosssectional microstructure, phase, chemical binding energy, and absorption of the $TiO_2$ using TEM, HRXRD, XPS, and UV-VIS-NIR, respectively. TEM analysis showed a 10 nm-thick flat and uniform $TiO_2$ thin film regardless of the deposition temperatures. Through XPS analysis, it was found that the stoichiometric $TiO_2$ phase was formed and confirmed by measuring main characteristic peaks of Ti $2p^1$, Ti $2p^3$, and O 1s indicating the binding energy status. Through UV-VIS-NIR analysis, ALD-$TiO_2$ thin films were found to have a band gap of 3.4 eV resulting in the absorption edges at 360 nm, while the conventional $TiO_2$ films had a band gap of 3.0 eV (rutile)${\sim}$3.2 eV (anatase) with the absorption edges at 380 nm and 410 nm. Our results implied that the newly proposed nano-thick $TiO_2$ film using an ALD process at $150^{\circ}$ had almost the same properties as thsose of film at $250^{\circ}$. Therefore, we confirmed that the ALD-processed $TiO_2$ thin film with nano-thickness formed at low temperatures might be suitable for the electrode process of flexible devices.

• Nano
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• 제13권10호
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• pp.1850124.1-1850124.12
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• 2018

$TiO_2$ films were deposited from oxygen/titanium tetraisopropoxide (TTIP) plasmas at low temperature by Helicon-PECVD at floating potential ($V_f$) or substrate self-bias of -50 V. The influence of titanium precursor partial pressure on the morphology, nanostructure and optical properties was investigated. Low titanium partial pressure ([TTIP] < 0.013 Pa) was applied by controlling the TTIP flow rate which is introduced by its own vapor pressure, whereas higher titanium partial pressure was formed through increasing the flow rate by using a carrier gas (CG). Then the precursor partial pressures [TTIP+CG] = 0:027 Pa and 0.093 Pa were obtained. At $V_f$, all the films exhibit a columnar structure, but the degree of inhomogeneity is decreased with the precursor partial pressure. Phase transformation from anatase ([TTIP] < 0.013 Pa) to amorphous ([TTIP+CG] = 0:093 Pa) has been evidenced since the $O^+_2$ ion to neutral flux ratio in the plasma was decreased and more carbon contained in the film. However, in the case of -50 V, the related growth rate for different precursor partial pressures is slightly (~15%) decreased. The columnar morphology at [TTIP] < 0.013 Pa has been changed into a granular structure, but still homogeneous columns are observed for [TTIP+CG] = 0:027 Pa and 0.093 Pa. Rutile phase has been generated at [TTIP] < 0:013 Pa. Ellipsometry measurements were performed on the films deposited at -50 V; results show that the precursor addition from low to high levels leads to a decrease in refractive index.

• 멤브레인
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• 제29권3호
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• pp.183-189
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• 2019

양친성 PCZ-r-PEG 랜덤 공중합체를 기반으로 한 수열합성법을 통해 자가조립된 메조기공 이산화티타늄 마이크로 스피어를 합성하였다. 중합된 PCZ-r-PEG는 푸리에 변환 적외분광법(fourier transform infrared spectroscopy, FT-IR), 핵자기공명(nuclear magnetic resonance, NMR), 젤 투과 크로마토그래피(gel permeation chromatography, GPC) 그리고 투과전자 현미경(transmission electron microscopy, TEM)을 통해 그 특성이 분석되었다. 다공성 이산화티타늄 입자는 PCZ-r-PEG, 글루코스(glucose), 물을 테트라히드로푸란(tetrahydrofuran, THF) 용액에 분산시킨 뒤 $150^{\circ}C$, 12시간 동안 반응시켰다. 다공성 이산화티타늄 입자의 구조와 결정성 분석을 위해 주사전자현미경(scanning electron microscopy, SEM)과 엑스선 회절(X-ray diffraction, XRD)이 사용되었다.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2283-2289
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• 2018

$TiO_2$ microspheres were successfully synthesised by simple solution phase method by using various amount of titanium butoxide as precursor. The prepared $TiO_2$ were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance absorption spectra (UV-DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XRD analysis revealed that the as-synthesized $TiO_2$ microsphere poses an anatase phase. The photocatalytic degradation experiments were carried out with three different dyes, such as methylene blue, brilliant black, reactive red-120 for four hours under UV light irradiation. The results show that $TiO_2$ morphology had great influence on photocatalytic degradation of organic dyes. The experimental results of dye mineralization indicated the concentration was reduced by a high portion of up to 99% within 4 hours. On the basis of various characterization of the photocatalysts, the reactions involved to explain the photocatalytic activity enhancement due to the concentration of titanium butoxide and morphology include a better separation of photogenerated charge carriers and improved oxygen reduction inducing a higher extent of degradation of aromatics.

• 대한금속재료학회지
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• 제49권8호
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• pp.596-600
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• 2011

Thermal degradation behavior of a $WO_3-TiO_2$ monolithic catalyst was investigated in terms of structural, morphological, and physico-chemical analyses. The catalyst with 4 wt.% $WO_3$ contents were prepared by a wet-impregnation method, and a durability test of the catalysts were performed in a temperature range between $400^{\circ}C$ and $800^{\circ}C$ for 3 h. An increase of thermal stress decreased the specific surface area, which was caused by grain growth and agglomeration of the catalyst particles. The phase transition from anatase to rutile occurred at around $800^{\circ}C$ and a decrease in the Brønsted acid sites was confirmed by structural analysis and physico-chemical analysis. A change in Brønsted acidity can affect to the catalytic efficiency; therefore, the thermal degradation behavior of the $WO_3-TiO_2$ catalyst could be explained by the transition to a stable rutile phase of $TiO_2$ and the decrease of specific surface area in the SCR catalyst.

• 한국재료학회지
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• 제32권9호
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• pp.384-390
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• 2022

A spin coating process for RRAM, which is a TiN/TiO₂/FTO structure based on a PTC sol solution, was developed in this laboratory, a method which enables low-temperature and eco-friendly manufacturing. The RRAM corresponds to an OxRAM that operates through the formation and extinction of conductive filaments. Heat treatment was selected as a method of controlling oxygen vacancy (V_O), a major factor of the conductive filament. It was carried out at 100 ℃ under moisture removal conditions and at 300 ℃ and 500 ℃ for excellent phase stability. XRD analysis confirmed the anatase phase in the thin film increased as the heat treatment increased, and the Ti³⁺ and OH- groups were observed to decrease in the XPS analysis. In the I-V analysis, the device at 100 ℃ showed a low primary SET voltage of 5.1 V and a high ON/OFF ratio of 10⁴. The double-logarithmic plot of the I-V curve confirmed the device at 100 ℃ required a low operating voltage. As a result, the 100 ℃ heat treatment conditions were suitable for the low voltage driving and high ON/OFF ratio of TiN/TiO₂/FTO RRAM devices and these results suggest that the operating voltage and ON/OFF ratio required for OxRAM devices used in various fields under specific heat treatment conditions can be compromised.

• 한국재료학회지
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• 제34권6호
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• pp.283-290
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• 2024

The aggressive scaling of dynamic random-access memory capacitors has increased the need to maintain high capacitance despite the limited physical thickness of electrodes and dielectrics. This makes it essential to use high-k dielectric materials. TiO₂ has a large dielectric constant, ranging from 30~75 in the anatase phase to 90~170 in rutile phase. However, it has significant leakage current due to low energy barriers for electron conduction, which is a critical drawback. Suppressing the leakage current while scaling to achieve an equivalent oxide thickness (EOT) below 0.5 nm is necessary to control the influence of interlayers on capacitor performance. For this, Pt and Ru, with their high work function, can be used instead of a conventional TiN substrate to increase the Schottky barrier height. Additionally, forming rutile-TiO₂ on RuO₂ with excellent lattice compatibility by epitaxial growth can minimize leakage current. Furthermore, plasma-enhanced atomic layer deposition (PEALD) can be used to deposit a uniform thin film with high density and low defects at low temperatures, to reduce the impact of interfacial reactions on electrical properties at high temperatures. In this study, TiO₂ was deposited using PEALD, using substrates of Pt and Ru treated with rapid thermal annealing at 500 and 600 ℃, to compare structural, chemical, and electrical characteristics with reference to a TiN substrate. As a result, leakage current was suppressed to around 10^-6 A/cm² at 1 V, and an EOT at the 0.5 nm level was achieved.

• 한국지반환경공학회 논문집
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• 제17권2호
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• pp.5-11
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• 2016

다층벽탄소나노튜브(MWCNT)와 titanium(IV) butoxide(TNB) 그리고 silver nitrate($AgNO_3$)를 이용하여 졸-겔법으로 $MWCNT-TiO_2$ 복합체와 $Ag-MWCNT-TiO_2$ 복합체를 제조하였다. 복합체에서의 Ag의 분산 및 구조를 주사전자현미경(SEM)과 투과전자현미경(FE-TEM)으로 관찰하였다. X선 회절 분석기(XRD)를 이용하여 복합체의 패턴을 보았을 때 anatase 결정구조를 확인할 수 있었다. 에너지 분광 분석기(EDX)로 원소성분을 분석한 결과 주요 원소인 C, Ti, O 그리고 Ag가 확인되었다. $TiO_2$ 입자는 MWCNT에 균일하게 분산되었고, Ag 입자는 튜브 표면에 고정되었다. 또한 UV 조사 시간에 따른 메틸렌블루의 분해를 통하여 광촉매 활성평가를 하였다. $Ag-MWCNT-TiO_2$ 복합체는 $MWCNT-TiO_2$ 복합체보다 높은 광분해능을 보였다. Ag의 높은 전도성이 $MWCNT-TiO_2$ 복합체의 광활성을 향상 시킨다는 결과를 나타냈다.

• 한국지반환경공학회 논문집
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• 제11권1호
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• pp.5-11
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• 2010

본 연구에서는 에어로졸 증착법을 사용하여 광촉매 $TiO_2$ 박막을 제조하기 위하여 원심분리기의 회전속도, vibration milling 시간에 의한 입경 변화 등과 같은 운전인자의 영향을 검토하였고, 제조된 고정화 $TiO_2$ 광촉매 박막의 경우와 $TiO_2$ 광촉매 분말을 부유 상태로 존재시킨 경우와의 막투과 특성의 변화를 실험적으로 비교검토 하였다. 원심분리기의 회전속도 1000-3000rpm 에서 얻어진 $TiO_2$ 분말은 저온 분사 성형법(aerosol deposition, AD)으로 $TiO_2$ 박막을 제조하는데 있어서 nozzle powder 막힘 현상과 같은 문제점을 나타내었다. 한편, vibrating milling에 의해 제어된 $TiO_2$ 분말의 평균입경 크기는 vibrating milling 2시간 후 약 420nm로 AD법을 이용한 입자의 증착에 효과적인 것으로 나타났다. XRD 분석 결과, 광촉매에 효과적인 아나타제 상을 잘 유지하고 있는 것으로 나타났으며, 이러한 결과로부터 vibrating milling은 $TiO_2$ 분말을 제어하는데 있어 적절한 전처리 공정임을 확인할 수 있었다. 제조된 $TiO_2$ 박막의 여과 특성으로 $TiO_2$ 분말을 분리막의 표면에 고정화 한 경우가 부유 상태일 경우보다 더 높은 막투과 유속을 나타내었다.

• 한국광물학회지
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• 제21권3호
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• pp.247-259
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• 2008

카올리나이트(kaolinite) 분말의 티타니아(Titania, $TiO_2$) 포팅을 위한 출발물질로서 인도네시아산 카올리나이트와 티타늄-아이소프로폭사이드(titanium isopropoxidc, TIP)가 사용되었으며, 실험은 졸-겔법(sol-gel method)으로 수행되었다. 또한 강매로서 에탄올이, 가수분해 반응을 위해 물이 사용되었으며 촉매로서 염산을 첨가하였다. 카올리나이트 분말의 소성여부에 따른 영향을 검토하기 위해 카올리나이트와 메타카올리나이트(metakaolinite)를 대상으로 각각 실험하였으며, 반응 혼합물의 몰비, 교반시간, 숙성시간, 결정화 시간과 온도의 변화에 따른 티타니아 결정도를 검토하였다. 실험조건 TIP 0.1 몰(mol), 물 0.15 몰, 염산 0.005 몰, 에탄을 100 ml, 카올리나이트 50 g, 교반 4시간, 숙성 24시간, 결정화온도 $1050^{\circ}C$, 결정화 2시간에서 가장 높은 아나타제 결정도 17.61%를 나타냈다. 결정화온도의 변화에 따른 아나타제 결정도 분석결과, 카올리나이트와 메타카올리나이트 분말에 코팅된 티타니아는 $1050^{\circ}C$와 $1200^{\circ}C$에서 각각 37.61%, 17.39%로 최고의 결정도가 관찰되었다. 즉, 카올리나이트 분말에 코팅된 티타니아가 메타카올리나이트에 비해 더 낮은 온도에서 더 높은 결정도를 나타냈다.