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"Solution"

Humidity monitoring of exhaled breath has emerged as a vital approach for noninvasive respiratory health assessment, underscoring the need for sensitive and reliable humidity sensors. Despite its high conductivity and hydrophilic functional groups, reduced graphene oxide (rGO) often undergoes irreversible moisture adsorption and gradual oxidation by residual water, resulting in sensitivity degradation and long-term instability during cycling. In this study, a montmorillonite/reduced graphene oxide (MMT/rGO) composite is developed as a room-temperature humidity-sensing material, exhibiting an optimized response of 115%, more than 14 times higher than that of pristine rGO. This superior performance originates from the synergistic interaction between the reversible MMT swelling and the conductive rGO network near the electrical percolation transition, which ensures excellent stability and repeatability under repeated humidity cycles. These findings suggest that the MMT/rGO composite provides a cost-effective and biocompatible platform for next-generation wearable humidity sensors capable of continuous respiratory monitoring.
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Fabrication and Characterization of Piezoelectric Porous Sponge Using Sugar Cubes
Yebin Lee, Hyunseung Kim, Tauk Eom, Chang Kyu Jeong
J Electr Electron Mater 2025;38(4):366-375.   Published online July 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.4.3
Porous polymeric structures with piezoelectric properties have attracted considerable attention in the fields of biomaterials and tissue engineering due to their ability to convert mechanical stimuli into electrical signals. However, conventional fabrication methods for porous structures often face limitations in controlling pore architecture, maintaining structural uniformity, and achieving process reproducibility, in addition to requiring complex processing conditions. To address these issues, we propose a facile and reproducible fabrication method for porous poly (vinylidene fluoride) (PVDF) piezoelectric sponges using molded sugar cubes as sacrificial pore templates. By adjusting the particle size of the sugar templates, the pore size and distribution of the sponges could be effectively controlled, and a uniform open-pore network was achieved. The fabricated sponges were evaluated with a focus on pore morphology, mechanical behavior, and piezoelectric performance depending on the sugar particle size, and these evaluations confirmed the structural properties and functional efficacy. This study presents a simple and reproducible fabrication strategy along with a quantitative analysis method for porous structures, which is expected to enhance process accessibility and practical applicability in the development of piezoelectric polymer-based biomaterial platforms.
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Electrical Characteristics of Solution-Based TiO₂ Resistive Switch
Jae Mo Yun, Ha Na Kang, Jin Tae Park, Soon Joo Yoon, Yoon Kyeung Lee
J Electr Electron Mater 2025;38(3):330-335.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.14
The solution-based fabrication process for resistive random-access memory (ReRAM) offers several advantages over conventional vapor deposition processes, including simplicity, cost-effectiveness, and high versatility for coating complex structures over large areas. In this study, a TiO₂-based ReRAM device was fabricated using a solution process with Pt top and P++-Si bottom electrodes. The synthesized TiO₂ films contain a residual Cl element as revealed by X-ray photoelectron spectroscopy (XPS). Reversible volatile resistance switching was observed due to the formation of conductive Ti-O-Ti networks in the TiO₂ layer. Post-annealing led to an increase in the threshold voltage (Vth). Asymmetric Current-Voltage characteristics was observed due to the different in the work functions of the electrodes. Additionally, the influence of compliance current settings on filament formation and hysteresis behavior was systematically investigated. The results demonstrated that higher compliance currents enhanced the hysteresis width for both positive and negative voltage bias conditions.
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Solution-Processed Indium-Gallium Oxide Thin-Film Transistors for Power Electronic Applications
Se-hyun Kim, Jeong Min Lee, Daniel Kofi Azati, Min-kyu Kim, Yujin Jung, Kang-jun Baeg
J Electr Electron Mater 2024;37(4):400-406.   Published online July 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.4.6
Next-generation wide-bandgap semiconductors such as SiC, GaN, and Ga2O3 are being considered as potential replacements for current silicon-based power devices due to their high mobility, larger size, and production of high-quality wafers at a moderate cost. In this study, we investigate the gradual modulation of chemical composition in multi-stacked metal oxide semiconductor thin films to enhance the performance and bias stability of thin-film transistors (TFTs). It demonstrates that adjusting the Ga ratio in the indium gallium oxide (IGO) semiconductor allows for precise control over the threshold voltage and enhances device stability. Moreover, employing multiple deposition techniques addresses the inherent limitations of solution-processed amorphous oxide semiconductor TFTs by mitigating porosity induced by solvent evaporation. It is anticipated that solution-processed indium gallium oxide (IGO) semiconductors, with a Ga ratio exceeding 50%, can be utilized in the production of oxide semiconductors with wide band gaps. These materials hold promise for power electronic applications necessitating high voltage and current capabilities.
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Hybrid Energy Storage Mechanism Through Solid Solution Chemistry for Advanced Secondary Batteries
Sion Ha, Kyeong-ho Kim
J Electr Electron Mater 2024;37(1):11-25.   Published online January 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.1.2
Lithium-ion batteries (LIBs) have attracted great attention as the common power source in energy storage fields of large-scale applications such as electrical vehicles (EVs), industries, power plants, and grid-scale energy storage systems (ESSs). Insertion, alloying, and conversion reactions are the main electrochemical energy storage mechanisms in LIBs, which determine their electrochemical properties and performances. The electrochemical reaction mechanisms are determined by several factors including crystal structure, components, and composition of electrode materials. This article reviews a new strategy to compensate for the intrinsic shortcomings of each reaction mechanism by introducing the material systems to form a single compound with different types of reaction mechanisms and to allow the simultaneous hybrid electrochemical reaction of two different mechanisms in a single solid solution phase.
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Development of an Oraganic-Inorganic Hybrid Coating Solution for Improvement in Flame Retardant Properties of Wallpapers
Gyu Jin Jeong, Tae Wook Kang, Jin Ho Kim, Bong Man Kim, Eun Kyung Seo, Byungseo Bae, Sun Woog Kim
J Electr Electron Mater 2022;35(2):178-183.   Published online March 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.2.11
For enhancing the flame-retardant properties of wallpapers, we developed an organic-inorganic hybrid solution with ZrSiO4 as a functional ceramic powder, coated on non-woven fabric using dip coating, spray coating, and slot-die coating methods. Their flame retardant properties were characterized by a 45° combustion tester, which is manufactured according to the flame-retardant performance standard (KOFEIS 1001 and KS F 2819). In organic-inorganic hybrid solution, with increasing the concentration of acid-catalyst (acetic acid), the precipitation of ZrSiO4 powders increased, and the flame retardant properties decreased. The highest flame retardant result was obtained for the solution adding 5 wt% acetic acid. The optimization of the coating method and coating number resulted in the most excellent flame-retardant properties being obtained for the non-woven fabric coated for 5 or 7 times by dip coating method, and their flame-retardant properties corresponded to class 2 flame-retardant performance of wallpapers.
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A Brief Review on 2-Dimensional Dielectric Nanosheets
Haena Yim, Ji-won Choi
J Electr Electron Mater 2022;35(1):1-10.   Published online January 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.1.1
Two-dimensional materials have shown a great promise for the next-generation electronic materials due to their unique optical, physical, and chemical properties that are distinct from their bulk counterparts. Their atomic-level thickness, the feature for flexible tenability, and exposed huge surface allow various approaches for high-performance nanoscale devices. Especially, this review highlights the recent progress on two-dimensional dielectric nanosheets, which are obtained by cheap and mass-producible solution-based exfoliation process, accompanied by the preparation methods, various deposition methods, and the characteristics of devices using a dielectric nanosheet thin films. We also present a perspective on the advantages offered by this two-dimensional dielectric nanosheets for the upcoming future nanoelectonics.
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Investigation of Transparent Electrodes for Solution-Processed Organic Solar Cells
Sumin Lee, Moon Hee Kang
J Electr Electron Mater 2021;34(2):115-120.   Published online March 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.2.6
In this study, composite transparent electrodes were fabricated either from a conductive polymer poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) or silver nanowire (AgNW). Three transparent electrodes such as PEDOT:PSS, PEDOT:PSS and AgNW mixture, and AgNW were fabricated. As for a transparent electrode, measured sheet resistance values were 89.6, 60.6 and 28.6 Ω/sq, and the transmittance values were 80.2, 82.0 and 83.8% while surface roughness (Rq) values were 4.1, 8.1, 20.4 nm for PEDOT:PSS, PEDOT:PSS and AgNW mixture, and AgNW, respectively. To verify the overall performance of these composite electrodes, we applied these electrodes to the top electrode of the solution-processed organic solar cells (OSCs). PEDOT:PSS provided the best performance with a fill factor (FF) of 51.2% and a photoconversion efficiency (PCE) of 2.2%, while traditional metal top electrode OSC provided FF of 60.5% and PCE of 3.1%.
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A Study on Characteristics of Liquid-Crystal Based Cell for Smart Window
Byung-gyu Park, Sun-keum Kim, Seung-woo Lee, Soon-yeol So, Jin Lee
J Electr Electron Mater 2020;33(4):271-275.   Published online July 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.4.4
Smart windows are used as windows and doors to determine the cooling and heating efficiency of a building. They have characteristics that can increase the energy efficiency of a building, which leads to energy savings. In addition, smart windows can control the amount of light transmitted from the external environment of a building to the interior of a building according to the needs of the user. In this study, a 297×210 mm2 liquid crystal cell capable of controlling light transmittance was fabricated using a liquid crystal device as an optical shutter. The effect of driving voltage on the transmittance and the effect of the thermal environment on the driving stability were analyzed. We confirmed the applicability of using smart windows as exterior building materials.
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Evaluation of Electrical Properties of IZO Thin-Film with UV Post-Annealing Treatment Time
Jae-yun Lee, Han-sang Kim, Sung-jin Kim
J Electr Electron Mater 2020;33(2):93-98.   Published online March 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.2.3
We investigated the effect of a post-annealing process using ultraviolet (UV) light on the electrical properties of solution-processed InZnO (IZO) thin-film transistors (TFTs). UV light was irradiated on IZO TFTs for different time periods of 0s, 30s, and 90s. We measured transfer and retention stability curves to evaluate the performance of the fabricated TFTs. In addition, we measured height, amplitude, and phase AFM images to analyze changes in the surface and morphology of the devices. AFM measurements were performed by setting the drive amplitude of the cantilever tip to 47.9 mV in tapping mode, then dividing the device surface into 500 nm × 500 nm. In the case of IZO TFT irradiated with UV for 30s, the electron mobility and Ion/Ioff ratio were improved, the threshold voltage was reduced by approximately 2 V, and the subthreshold swing also decreased form 1.34 V/dec to 1.11 V/dec.
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Fabrication of Multi-Fin-Gate GaN HEMTs Using Honeycomb Shaped Nano-Channel
Jeong Jin Kim, Jong Won Lim, Dong Min Kang, Sung Bum Bae, Ho Young Cha, Jeon Wook Yang, Hyeong Seok Lee
J Electr Electron Mater 2020;33(1):16-20.   Published online January 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.1.4
In this study, a patterning method using self-aligned nanostructures was introduced to fabricate GaN-based fin-gate HEMTs with normally-off operation, as opposed to high-cost, low-productivity e-beam lithography. The honeycomb-shaped fin-gate channel width is approximately 40~50 nm, which is manufactured with a fine width using a proposed method to obtain sufficient fringing field effect. As a result, the threshold voltage of the fabricated device is 0.6 V, and the maximum normalized drain current and transconductance of Gm are 136.4 mA/mm and 99.4 mS/mm, respectively. The fabricated devices exhibit a smaller sub-threshold swing and higher Gm peak compared to conventional planar devices, due to the fin structure of the honeycomb channel.
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Effect of Residual Droplet on the Solution-Grown SiC Single Crystals
Minh-tan Ha, Yun-ji Shin, Si-young Bae, Yong-jae Yoo, Seong-min Jeong
J Electr Electron Mater 2019;32(6):516-521.   Published online November 1, 2019
The top seeded solution growth (TSSG) method is an alternative technique to grow high-quality SiC crystals that has been actively studied for the last two decades. However, the TSSG method has different issues that need to be resolved when compared to the commercial SiC crystal growing method, i.e., physical vapor transport (PVT). A particular issue of the TSSG method of results from the presence of liquid droplets on the grown crystal that can remain even after crystal growth; this induces residual stress on the crystal surface. Hence, the residual droplet causes several unwanted effects on the crystal such as the initiation of micro-cracks, micro-pipes, and polytype inclusions. Therefore, this study investigated the formation of the residual droplet through multiphysics simulations and lead to the development of a liquid droplet removal method. As a result, we found that although residual liquid droplets significantly apply residual stress on the grown crystal, these could be vaporized by adopting thermal annealing processes after the relevant crystal growing steps.
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Homogeneous Alignment Characteristics of Liquid Crystal Molecules on Solution-Derived Lanthanum Zinc Oxide Film with Ion-Beam Irradiation
Byeong-yun Oh
J Electr Electron Mater 2019;32(5):382-386.   Published online September 1, 2019
The alignment characteristics of liquid crystal (LC) molecules on a solution-derived lanthanum zinc oxide (LZO) film under ion-beam irradiation were demonstrated. Using the solution process, an LZO film was fabricated on the glass substrate and cured at 100℃. Afterwards, ion-beam irradiation was performed following the LC alignment method. Using this film, an LC cell was fabricated and the characteristics of the LC alignment were verified. Cross polarizing microscopy and the crystal rotation method were used to investigate the alignment state of the LC molecules on the LZO films. Furthermore, field emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to explore the effect of the ion-beam irradiation on the LZO film. Through these, it was confirmed that the ion-beam irradiation induced surface modification, which demonstrated anisotropic physical and chemical surface characteristics. Due to this, uniform LC alignment was achieved. Finally, the residual DC and anchoring energy of the LC cell based on the LZO films were measured using a capacitance-voltage curve.
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Structural and Electrical Properties of BiFeO3 Thin Films by Eu and V Co-Doping
Sung-keun Chang, Youn-jang Kim
J Electr Electron Mater 2019;32(3):229-233.   Published online May 1, 2019
Pure BiFeO3 (BFO) and (Eu, V) co-doped Bi0.9Eu0.1Fe0.975V0.025O3+δ (BEFVO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by chemical solution deposition. The effects of co-doping were observed by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The electrical properties of the BEFVO thin film were improved as compared to those of the pure BFO thin film. The remnant polarization (2Pr) of the BEFVO thin film was approximately 26 μC/cm2 at a maximum electric field of 1,190 kV/cm with a frequency of 1 kHz. The leakage current density of the co-doped BEFVO thin film (4.81×10-5 A/cm2 at 100 kV/cm) was two orders of magnitude lower than of that of the pure BFO thin film.
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Fully Solution-Processed Green Organic Light-Emitting Diodes Using the Optimized Electron Transport Layers
Joo Won Han, Yong Hyun Kim
J Electr Electron Mater 2018;31(7):486-489.   Published online November 1, 2018
Solution-processed organic light-emitting diodes (OLEDs) have the advantages of low cost, fast fabrication, and large-area devices. However, most studies on solution-processed OLEDs have mainly focused on solution-processable hole transporting materials or emissive materials. Here, we report fully solution-processed green OLEDs including hole/electron transport layers and emissive layers. The electrical and optical properties of OLEDs based on solution-processed TPBi (2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) as the electron transport layer were investigated with respect to the spin speed and the number of layers. The performance of OLEDs with solution-processed TPBi exhibits a power efficiency of 9.4 lm/W. We believe that the solution-processed electron transport layers can contribute to the development of efficient fully solution-processed multilayered OLEDs.
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Synthesis and Characterization of Rod-Shaped Ni-Zn Ferrite Particles
Seung-yeop Chun, Jin-ah Hwang, Myoung-pyo Chun
J Electr Electron Mater 2018;31(5):300-306.   Published online July 1, 2018
The rod-shaped Ni0.5Zn0.5Fe2O4 particles were synthesized via a topotactic reaction, in which goethite (α-FeOOH) particles are the main constituents. The phases, microstructures and magnetic properties of these particles were studied using XRD, FE-SEM and VSM. The precursor solution consisted of NiSO4·xH2O, ZnSO4·xH2O, goethite and D.I. water werereacted at four different temperatures (50, 70, 90, 100℃) to generate four differently precipitated particles respectively. During the co-precipitation reaction, the pH of the solution was maintained at 8.0 using NaOH. The particles coprecipitated and calcined at a temperature of 700℃, exhibited a rod-shape similar to its original goethite, which means that the shape of Ni-Zn ferrite particles can be topotactically controlled by the goethite. The particles synthesized at 70 and 90℃ have a saturation magnetization of 29 and 35 emu/g respectively; representing better values than the ones synthesized at the 50 and 100℃, in which some second phases such as Fe2O3 were observed.
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The Effects of Lithium-Incorporated on N-ZTO/P-SiC Heterojunction Diodes by Using a Solution Process
Hyun-soo Lee, Sung-joon Park, Jae-in An, Seulki Cho, Sang-mo Koo
J Electr Electron Mater 2018;31(4):203-207.   Published online May 1, 2018
In this work, we investigate the effects of lithium doping on the electric performance of solution-processed n-type zinc tin oxide (ZTO)/p-type silicon carbide (SiC) heterojunction diode structures. The proper amount of lithium doping not only affects the carrier concentration and interface quality but also influences the temperature sensitivity of the series resistance and activation energy. We confirmed that the device characteristics vary with lithium doping at concentrations of 0, 10, and 20 wt%. In particular, the highest rectification ratio of 1.89×107 and the lowest trap density of 4.829×1,022 cm-2 were observed at 20 wt% of lithium doping. Devices at this doping level showed the best characteristics. As the temperature was increased, the series resistance value decreased. Additionally, the activation energy was observed to change with respect to the component acting on the trap. We have demonstrated that lithium doping is an effective way to obtain a higher performance ZTO-based diode.
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Structural and Electrical Properties of Bi0.9A0.1Fe0.975Zn0.025O3-δ (A=Eu, Dy) BiFeO3 Thin Films by Chemical Solution Deposition
Youn-jang Kim, Jin-won Kim, Sung-keun Chang
J Electr Electron Mater 2018;31(4):226-230.   Published online May 1, 2018
Pure BiFeO3 (BFO) and codoped Bi0.9A0.1Fe0.975Zn0.025O3-δ (A=Eu, Dy) thin films were prepared on Pt(111)/ Ti/SiO2/Si(100) substrates by chemical solution deposition. The remnant polarizations (2Pr) of the Bi0.9Eu0.1Fe0.975Zn0.025O3-δ (BEFZO) and Bi0.9Dy0.1Fe0.975Zn0.025O3-δ (BDFZO) thin films were about 36 and 26 μC/cm2 at the maximum electric fields of 900 and 917 kV/cm, respectively, at 1 kHz. The codoped BEFZO and BDFZO thin films showed improved electrical properties, and leakage current densities of 3.68 and 1.21×10-6 A/cm2, respectively, which were three orders of magnitude lower than that of the pure BFO film, at 100 kV/cm.
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Study on Solution Processed Indium Zinc Oxide TFTs Using by Femtosecond Laser Annealing Technology
Han-sang Kim, Sung-jin Kim
J Electr Electron Mater 2018;31(1):50-54.   Published online January 1, 2018
In this study, a femtosecond laser pre-annealing technology based on indium zinc oxide (IZO) thin-film transistors (TFTs) was investigated. We demonstrated a stable pre-annealing process to analyze the change in the surface structures of thin-films, and we improved the electrical performance. Furthermore, static and dynamic electrical characteristics of IZO TFTs with n-channel inverters were observed. To investigate the static and dynamic responses of our solution-processed IZO TFTs, simple resistor-load-type inverters were fabricated by connecting a 1-MΩ resistor. The femtosecond laser pre-annealing process based on IZO TFTs showed good performance: a field-effect mobility of 3.75 cm2/Vs, an Ion/Ioff ratio of 1.8×105, a threshold voltage of 1.13 V, and a subthreshold swing of 1.21 V/dec. Our IZO-TFT-based N-MOS inverter performed well at operating voltage, and therefore, is a good candidate for advanced logic circuits and display backplane.
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Optical Property and Surface Morphology Control by Randomly Patterned Etching
Sung Soo Kim, Jeong Woo Lee, Bup Ju Jeon
J Electr Electron Mater 2017;30(12):800-805.   Published online December 1, 2017
Randomly patterned and wet chemical etching processes were used to treat anti-glare of display cover glasses. The surface and optical properties of grain size and surface morphology controlled by randomly patterned etching and wet chemical solution etching were investigated. The surface morphology and roughness of the etched samples were examined using a spectrophotometer and a portable surface roughness (Ra) measuring instrument, respectively. The gloss caused by reflection from the glass surface was measured at 60° using a gloss meter. The surface of the sample etched by the doctor-blade process was more uniform than that obtained from a screen pattern etching process at gel state etching process of the first step. The surface roughness obtained from the randomly patterned etching process depended greatly on the mesh size, which in turn affected the grain size and pattern formation. The surface morphology and gloss obtained by the etching process in the second step depended primarily on the mesh size of the gel state etching process of the first step. In our experimental range, the gloss increased on decreasing the grain size at a lower mesh size for the first step process and for longer reaction times for the second step process.
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Microstructural and Electrical Properties of Bi0.9A0.1Fe0.975V0.025O3+α(A=Nd, Tb) Thin Films by Chemical Solution Deposition Method
Sung-keun Chang, Youn-jang Kim
J Electr Electron Mater 2017;30(10):646-650.   Published online October 1, 2017
We have evaluated the ferroelectric and electrical properties of pure BiFeO3 (BFO) and Bi0.9A0.1Fe0.975V0.025O3+α(A=Nd, Tb) thin films on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. The remnant polarization (2Pr) of the Bi0.9Tb0.1Fe0.975V0.025O3+α (BTFVO) thin film was approximately 65 μC/㎠, with a maximum applied electric field of 950 kV/cm and a frequency of 10 kHz, where as that of the Bi0.9Nd0.1Fe0.975V0.025O3+α (BNFVO) thin film was approximately 37 μC/㎠ with a maximum applied electric field of 910 kV/cm. The leakage current density of the co-doped BNFVO thin film was four orders of magnitude lower than that of the pure BFO thin film, at 2.75×10-7 A/㎠ with an applied electric field of 100 kV/cm. The grain size and uniformity of the co-doped BNFVO and BTFVO thin films were improved, in comparison to the pure BFO thin film, through structural modificationsdue to the co-doping with Nd and Tb.
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Improvement in Electrical Characteristics of Solution-Processed In-Zn-O Thin-Film Transistors Using a Soft Baking Process
Han-sang Kim, Sung-jin Kim
J Electr Electron Mater 2017;30(9):566-571.   Published online September 1, 2017
A soft baking process was used to enhance the electrical characteristics of solution-processed indium-zincoxide (IZO) thin-film transistors (TFTs). We demonstrate a stable soft baking process using a hot plate in air to maintain the electrical stability and improve the electrical performance of IZO TFTs. These oxide transistors exhibited good electrical performance; a field-effect mobility of 7.9 cm2/Vs, threshold voltage of 1.4 V, sub-threshold slope of 0.5 V/dec, and a current on/off ratio of 2.9×107 were measured. To investigate the static response of our solutionprocessed IZO TFTs, simple resistor load type inverters were fabricated by connecting a resistor (5 or 10 MΩ). Our IZO TFTs, which were manufactured using the soft baking process at a baking temperature of 120℃, performed well at the operating voltage, and are therefore a good candidate for use in advanced logic circuits and transparent display backplanes.
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Effect of Thin-Film Thickness on Electrical Performance of Indium-Zinc-Oxide Transistors Fabricated by Solution Process
Han-sang Kim, Dong-gu Kyung, Sung-jin Kim
J Electr Electron Mater 2017;30(8):469-473.   Published online August 1, 2017
We investigated the effect of different thin-film thicknesses (25, 30, and 40 nm) on the electrical performance of solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs). The structural properties of the IZO thin films were investigated by atomic force microscopy (AFM). AFM images revealed that the IZO thin films with thicknesses of 25 and 40 nm exhibit an uneven distribution of grains, which deforms the thin film and degrades the performance of the IZO TFT. Further, the IZO thin film with a thickness of 30 nm exhibits a homogeneous and smooth surface with a low RMS roughness of 1.88 nm. The IZO TFTs with the 30-nm-thick IZO film exhibit excellent results, with a field-effect mobility of 3.0(±0.2) cm2/Vs, high Ion/Ioff ratio of 1.1×107, threshold voltage of 0.4(±0.1) V, and subthreshold swing of 0.7(±0.01) V/dec. The optimization of oxide semiconductor thickness through analysis of the surface morphologies can thus contribute to the development of oxide TFT manufacturing technology.
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A Study on the Material Characteristics of the NiO/ZnO Ultraviolet Sensor Based on Solution Process
Seong-cheol Moon, Ji-seon Lee, Kyeong-jae No, Seong-ju Yang, Seong-eui Lee
J Electr Electron Mater 2017;30(8):508-513.   Published online August 1, 2017
Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.
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Sintering and Optical Properties of ZnS Nanoparticles Sintered by Spark Plasma Sintering
Chang-il Kim, You-bi Kim, Seo-yeong Yeo, Youn-woo Hong, Ji-sun Yun, Woon-ik Park, Young-hun Jeong, Jeong-ho Cho, Jong-hoo Paika
J Electr Electron Mater 2017;30(6):349-355.   Published online June 1, 2017
Zinc sulphide (ZnS) nanoparticles were fabricated by hydrothermal synthesis at 180℃ for 12 h. Two kinds of ZnS powder (hydrothermal synthesized ZnS and commercial ZnS) were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) for phase and microstructure, respectively. The XRD patterns showed that all ZnS nanoparticles have a sphalerite (cubic) structure. The nanoparticles of two different ZnS powders were sintered by spark plasma sintering. The sintered ZnS were analyzed by XRD, SEM, and FT-IR. We found that the transmittance of the infrared region is highly dependent on the density and crystal structure of sintered ZnS and the purity of the starting ZnS powder.
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Regular Paper : Fabrication of PMMA-HfOx Organic-Inorganic Hybrid Resistive Switching Memory
Il Jin Baek, Won Ju Cho
J Electr Electron Mater 2016;29(3):135-140.   Published online March 1, 2016
In this study, we developed the solution-processed PMMA-HfOx hybrid ReRAM devices to overcome the respective drawbacks of organic and inorganic materials. The performances of PMMA-HfOx hybrid ReRAM were compared to those of PMMA- and HfOx-based ReRAMs. Bipolar resistive switching behavior was observed from these ReRAMs. The PMMA-HfOx hybrid ReRAMs showed a larger operation voltage margin and memory window than PMMA-based and HfOx-based ReRAMs. The reliability and electrical instability of ReRAMs were remarkably improved by blending the HfOx into PMMA. An Ohmic conduction path was commonly generated in the LRS (low resistance state). In HRS (high resistance state), the PMMA-based ReRAM showed SCLC (space charge limited conduction). the PMMA-HfOx hybrid ReRAM and HfOx-based ReRAM revealed the Pool-Frenkel conduction. As aresult of flexibility test, serious defects were generated in HfOx film deposited on PI (polyimide) substrate. On the other hand, the PMMA and PMMA-HfOx films showed an excellent flexibility without defect generation.
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Effects of Soft Baking Temperature on the Properties of Solution Processed Zn-Sn-O Thin-Film Transistors
Jae Won Lee, Won Ju Choa
J Electr Electron Mater 2016;29(1):6-10.   Published online January 1, 2016
In this study, the effects of soft baking temperature on the solution derived ZTO (Zn-Sn-O) TFTs (thin-film transistors) as a In-free oxide semiconductor were investigated. In spite of the same hard baking at high temperature(600℃), the electrical properties of ZTO TFT was greatly changed by a small difference in soft baking temperature(180~250℃). The performance of TFT was deteriorated as the soft baking temperature increased. Therefore, it is important to remove the water-related defects well as organic impurities from the ZTO films during soft baking for fabrication of solution-derived high performance of TFTs.
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Nano and Oxide Electronics : Regular Paper ; Physical and Chemical Properties of (Sr,Mg)FeO3-y System Heat-treated in N2
Eumseok Lee
J Electr Electron Mater 2015;28(10):642-647.   Published online October 1, 2015
The perovskite solid solutions of the Sr1-xMgxFe3+ 1-τFe4+ τO3-y system (x=0.0, 0.1, 0.2, and 0.3) were synthesized in N2 at 1,150℃. X-ray powder diffraction study assured that all the four samples had cubic symmetries(SM-0: 3.865 Å, SM-1: 3.849 Å, SM-2: 3.833 Å, and SM-3: 3.820 Å) and that the lattice volumes decreased steadily from 57.7 Å3 to 55.7 Å3 with x values. The nonstoichiometric chemical formulas were determined by Mohr salt analysis and with the increase of x values the amounts of Fe4+ ion and oxygen were decreased simultaneously. Thermal analysis showed that SM-0 started to lose its oxygen at 450℃ and SM-1, Sm-2, and SM-3 began to lose their oxygen at around 350~400℃. SM-0 showed almost reversible weight change in the cooling process. All the samples exhibited semiconducting behaviors in the temperature range of 10~400℃. Conductivities of the 4 samples were decreased in the order of SM-0, SM-1, SM-2, and SM-3 at constant temperature. The activation energies of the conductions were in the range of 0.176 eV~0.244 eV.
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Light Source and Application Technology : Optical Properties Control by Surface Treatment on Display Cover Glass
Sung Soo Kim, Jai Suk Hwang, Bup Ju Jeon
J Electr Electron Mater 2015;28(9):607-614.   Published online September 1, 2015
To provide the clear images from the direct light on electrical board and display devices, anti glare treatment of display cover glass is needed. In this study, the effects of surface treatment temperature, concentration, and etching solution coating thickness of the gel phase on optical elements control such as gloss, haze of reflected light and transmittance, were investigated. Cover glasses were treated at different coating thickness and additive concentration. The optical properties were examined using spectrophotometer, gloss and haze meter. The surface morphology and roughness were measured by the optical microscope and Ra measuring instrument. The etching rate and surface morphologies were dramatically affected by the concentration of acid additive in the viscous gel because of re-crystallization of components in the etching solution, hydrogel formation and coagulant after coating on glass substrate. In our experimental range, cover glass which is surface-treated with various optical properties as well as the morphology uniformity was obtained; in particular, optical properties could be controlled by etching solution coating thickness of the gel phase and the concentration of additive. The gloss was depended on the surface roughness and it showed the linear relationship between optical transmittance and haze of reflected light, respectively.
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Effects of Annealing on Solution Processed n-ZTO/p-SiC Heterojunction
Sang Mo Koo, Young Seok Jeong
J Electr Electron Mater 2015;28(8):481-485.   Published online August 1, 2015
We investigated the effects of annealing on the electrical and thermal properties of ZTO/4H-SiC heterojunction diodes. A ZTO thin film layer was grown on p-type 4H-SiC substrate by using solution process. The ZTO/SiC heterojunction structures annealed at 500℃ show that Ion/Ioff increases from ~5.13×107 to ~1.11×109 owing to the increased electron concentration of ZTO layer as confirmed by capacitance-voltage characteristics. In addition, the electrical characterization of ZTO/SiC heterojunction has been carried out in the temperature range of 300∼500 K. When the measurement temperature increased from 300 K to 500 K, the reverse current variation of annealed device is higher than as-grown device, which is related to barrier height in the ZTO/SiC interface. It is shown that annealing process is possible to control the electrical characteristics of ZTO/SiC heterojunction diode.
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