http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Ferroelectric (Bi4)Thin Films forMetal-Ferroelectric-Insulator-Semiconductor (MFIS) Structures
Taekjib Choi,Youngsung Kim,Jaichan Lee 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.1
We propose ferroelectric (Bi3:25,La0:75)Ti3O12 (BLT) thin lms for metal-ferroelectric-insulatorsemiconductor (MFIS) structures. The BLT thin lms were prepared on SiO2/Si (100) and yttriastabilized zirconia (YSZ) buered SiO2/Si (100) substrates using pulsed laser deposition (PLD). The BLT thin lms tended to grow with a c-axis preferred orientation with increasing substrate temperature above 540 C. Transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) revealed that there was no inter-diusion at the interface of the BLT thin lms grown at temperatures as low as 620 C. The MFIS structure exhibited a capacitance-voltage (C-V) hysteresis (memory window) due to ferroelectric polarization. The asymmetric behaviors of the C-V and the leakage current (I-V) characteristics are discussed in terms of both electron injection from Si and the ferroelectric polarization eect.
Jung, Chulho,Choi, Taekjib,Phan, Bach Thang,Lee, Jaichan Gordon and Breach Science Publishers 2007 Integrated ferroelectrics Vol.90 No.1
<P> The resistive switching of 0.2% Cr-doped SrTiO3 (Cr-STO) thin films grown on (La0.5, Sr0.5)CoO3/SrTiO3 (LSCO/STO) substrate have been investigated. The structure in a metal-insulator-metal (MIM) i.e., Pt/Cr-STO/LSCO, shows hysteretic and asymmetric behaviors in current-voltage (I-V) characteristics. The current-voltage characteristics are attributed to the resistive switching of Cr-STO thin films between high resistance state (HRS) and low resistance state (LRS) by applying pulsed or dc bias voltage stress. The current and voltage ramp sweeps in the I-V measurement reveal that threshold current is required to induce the resistive switching from HRS to LRS in the negative voltage region.</P>
Large Resistive Switching in Ferroelectric BiFeO<sub>3</sub> Nano‐Island Based Switchable Diodes
Hong, Sahwan,Choi, Taekjib,Jeon, Ji Hoon,Kim, Yunseok,Lee, Hosang,Joo, Ho‐,Young,Hwang, Inrok,Kim, Jin‐,Soo,Kang, Sung‐,Oong,Kalinin, Sergei V.,Park, Bae Ho WILEY‐VCH Verlag 2013 Advanced Materials Vol.25 No.16
<P><B>Comparison between piezoelectric force microscopy images and current‐voltage data</B> consecutively obtained using conductive atomic force microscopy below transition voltages for a highly oriented ferroelectric BiFeO<SUB>3</SUB> nano‐island confirms that ferroelectric polarization reversal induces transitions of forward‐direction, and thus down‐ and up‐polarization is accompanied by positive‐ and negative‐forward diode‐like behavior, respectively.</P>
Study of Graphene-based 2D-Heterostructure Device Fabricated by All-Dry Transfer Process
Tien, Dung Hoang,Park, Jun-Young,Kim, Ki Buem,Lee, Naesung,Choi, Taekjib,Kim, Philip,Taniguchi, Takashi,Watanabe, Kenji,Seo, Yongho American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.5
<P>We developed a technique for transferring graphene and hexagonal boron nitride (hBN) in dry conditions for fabrication of van der Waals heterostructures. The graphene layer was encapsulated between two hBN layers so that it was kept intact during fabrication of the device. For comparison, we also. fabricated the devices containing graphene on SiO2/Si wafer and graphene on hBN. Electrical properties of the devices were investigated at room temperature. The mobility of the graphene on SiO2 devices and graphene on hBN devices were 15 000 and 37 000 cm(2) V-1 s(-1), respectively, while the mobility of the sandwich structure device reached the highest value of similar to 1.00 000 cm(2) V-1 s(-1), at room temperature. The electrical measurements of the samples were carried out in air and vacuum environments. We found that the electrical properties of the encapsulated graphene devices remained at a similar level both in a vacuum and in air, whereas the properties of the graphene without encapsulation were influenced by the external environment.</P>
Dynamic mechanical control of local vacancies in NiO thin films
Seol, Daehee,Yang, Sang Mo,Jesse, Stephen,Choi, Minseok,Hwang, Inrok,Choi, Taekjib,Park, Bae Ho,Kalinin, Sergei V,Kim, Yunseok IOP 2018 Nanotechnology Vol.29 No.27
<P>The manipulation of local ionic behavior via external stimuli in oxide systems is of great interest because it can help in directly tuning material properties. Among external stimuli, mechanical force has attracted intriguing attention as novel stimulus for ionic modulation. Even though effectiveness of mechanical force on local ionic modulation has been validated in terms of static effect, its real-time i.e., dynamic, behavior under an application of the force is barely investigated in spite of its crucial impact on device performance such as force or pressure sensors. In this study, we explore dynamic ionic behavior modulated by mechanical force in NiO thin films using electrochemical strain microscopy (ESM). Ionically mediated ESM hysteresis loops were significantly varied under an application of mechanical force. Based on these results, we were able to investigate relative relationship between the force and voltage effects on ionic motion and, further, control effectively ionic behavior through combination of mechanical and electrical stimuli. Our results can provide comprehensive information on the effect of mechanical forces on ionic dynamics in ionic systems.</P>
Lee, Heejin,Joo, Ho-yong,Yoon, Chulmin,Lee, Joonbong,Lee, Hojin,Choi, Jinsik,Park, Baeho,Choi, Taekjib Elsevier 2017 Current Applied Physics Vol.17 No.5
<P>Ferroelectric based heterostructures have shown great promises in solar water splitting due to unique photoelectrochemical (PEC) properties including polarization-induced charge separation and tunable electrochemical surface reaction. A highly ordered ferroelectric BiFeO3/TiO2 nanotube (TNT) heterostructures were fabricated by anodic oxidation and pulsed laser deposition. The microscopic morphology, optical, and PEC properties of nanostructures were characterized. The BiFeO3/TNT photoelectrode is photoactive under visible light illumination, which exhibits higher photocurrent from greater water oxidation, compared with the pure TNT photoelectrode. The coating thickness of BiFeO3 strongly affected the photoelectrochemical properties. The enhanced PEC performance could be attributed to the effective charge separation and the favorable band bending for water oxidation, originating from ferroelectric polarization-related internal field. (C) 2017 Elsevier B.V. All rights reserved.</P>
강유전체 BiFeO<sub>3</sub>가 증착된 TiO<sub>2</sub> 전극을 이용한 염료감응형 태양전지의 효율 향상
주호용,홍수봉,이호상,전지훈,박배호,홍성철,최택집,Joo, Ho-Yong,Hong, Su Bong,Lee, Hosang,Jeon, Ji Hoon,Park, Bae Ho,Hong, Sung Chul,Choi, Taekjib 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.3
Dye-sensitized solar cells (DSSCs) based on titanium dioxide ($TiO_2$) have been extensively studied because of their promising low-cost alternatives to conventional semiconductor based solar cells. DSSCs consist of molecular dye at the interface between a liquid electrolyte and a mesoporous wide-bandgap semiconductor oxide. Most efforts for high conversion efficiencies have focused on dye and liquid electrolytes. However, interface engineering between dye and electrode is also important to reduce recombination and improve efficiency. In this work, for interface engineering, we deposited semiconducting ferroelectric $BiFeO_3$ with bandgap of 2.8 eV on $TiO_2$ nanoparticles and nanotubes. Photovoltaic properties of DSSCs were characterized as a function of thickness of $BiFeO_3$. We showed that ferroelectric $BiFeO_3$-coated $TiO_2$ electrodes enable to increase overall efficiency of DSSCs, which was associated with efficient electron transport due to internal electric field originating from electric polarization. It was suggested that engineering the dye-$TiO_2$ interface using ferroelectric materials as inorganic modifiers can be key parameter for enhanced photovoltaic performance of the cell.
Lee, Sang A,Oh, Seokjae,Hwang, Jae-Yeol,Choi, Minseok,Youn, Chulmin,Kim, Ji Woong,Chang, Seo Hyoung,Woo, Sungmin,Bae, Jong-Seong,Park, Sungkyun,Kim, Young-Min,Lee, Suyoun,Choi, Taekjib,Kim, Sung Wng,C The Royal Society of Chemistry 2017 ENERGY AND ENVIRONMENTAL SCIENCE Vol.10 No.4
<P>Transition metal oxides have been extensively studied and utilized as efficient catalysts. However, the strongly correlated behavior which often results in intriguing emergent phenomena in these materials has been mostly overlooked in understanding the electrochemical activities. Here, we demonstrate a close correlation between the phase transitions and oxygen evolution reaction (OER) in strongly correlated SrRuO3. By systematically introducing Ru-O vacancies into the single-crystalline SrRuO3epitaxial thin films, we induced a phase transition in crystalline symmetry which resulted in the corresponding modification of the electronic structure. The modified electronic structure significantly affects the electrochemical activities, so a 30% decrease in the overpotential for the OER activity was achieved. Our study suggests that a substantial enhancement in the OER activity can be realized even within single material systems, by rational design and engineering of their crystal and electronic structures.</P>