Search results for: Cheul-Ro Lee

Items from 1 to 20 out of 88 results

article

New Charge Carrier Transport‐Assisting Paths in Ultra‐Long GaN Microwire UV Photodetector

Dae‐Young Um, Bagavath Chandran, Ji‐Yeon Kim, Jeong‐Kyun Oh, more

Advanced Functional Materials > 33 > 40 > n/a - n/a

GaN‐based materials are the hottest research topic in UV photodetectors (PDs) because of their low operating voltage, small volume, long lifetime, high‐temperature resistance, and low energy consumption. However, there are still fundamental issues to be overcome, and the most important issue is to get a photoconductive gain. In this paper, the following new approaches are provided to innovatively...

article

Conformable, Thin, and Dry Electrode for Electrocardiography Using Composite of Silver Nanowires and Polyvinyl Butyral

Su Bin Choi, Min Suk Oh, Chul Jong Han, Jae-Wook Kang, more

Electronic Materials Letters > 2019 > 15 > 3 > 267-277

Development of a thin and dry electrode for electrocardiography (ECG) is essential in order to prevent skin irritation, allergic reactions from electrolytic gel, and motion artifacts caused by relative motion between the electrodes and the skin. In this study, we have developed a composite electrode made from Ag nanowires (AgNWs) and polyvinyl butyral (PVB), prepared by inverted layer processing (ILP)...

article

Revisiting the thickness reduction approach for near-foldable capacitive touch sensors based on a single layer of Ag nanowire-polymer composite structure

Kwang-Seok Kim, Sun Ok Kim, Chul Jong Han, Dae Up Kim, more

Composites Science and Technology > 2018 > 165 > C > 58-65

Although a percolated network of silver nanowires (AgNWs) is considered the most promising flexible transparent electrode because of its high conductivity, high transmittance, excellent flexibility, and facile patternability, it has encountered a serious delay in its application to most optoelectronic devices. Here, we analyzed the reasons and tried to resolve the current issues to achieve near-foldable...

article

1.4 µm-Thick Transparent Radio Frequency Transmission Lines Based on Instant Fusion of Polyethylene Terephthalate Through Surface of Ag Nanowires

Sang-Woo Kim, Kwang-Seok Kim, Myeongkoo Park, Wansoo Nah, more

Electronic Materials Letters > 2018 > 14 > 5 > 599-609

Though a percolated network of silver nanowires (AgNWs) has been considered the most promising flexible transparent electrode because of it high conductivity, high transmittance, and excellent flexibility, fabrication of AgNW-based transmission lines designed to conduct high frequency signals has been scarcely reported. The fabrication and performance of extremely thin (1.4 µm thick) and low lossy...

article

Growth and characterization of n-AlGaN 1-D structures with varying Al composition using u-GaN seeds

San Kang, Uddipta Chatterjee, Dae-Young Um, In Seok Seo, more

Journal of Crystal Growth > 2017 > 480 > C > 108-114

Like all the ternary alloys in III-nitride materials family, aluminum gallium nitride (AlGaN) has unique band gap tuning property which enables the alloy to be suitable for many opto-electronic applications. The direct band gap of AlGaN can be tuned from 3.4 to 6.2 eV by changing the composition. In this article, the growth of ternary n-AlGaN micro and nano structures on Si (1 1 1) substrate is demonstrated...

article

III-nitride nanowires for solar light harvesting: A review

U. Chatterjee, Ji-Hyeon Park, Dae-Young Um, Cheul-Ro Lee

Renewable and Sustainable Energy Reviews > 2017 > 79 > C > 1002-1015

The world needs economical and sustainable alternate energy sources to combat the irreversible phenomenon like global warming. Solar photovoltaic technology, which converts sunlight directly to electricity, is the most potential candidate for alternate energy source. On the other hand, increasing global pollution due to energy emission compels the worldwide researcher community to deliberate over...

article

Dependence of Internal Crystal Structures of InAs Nanowires on Electrical Characteristics of Field Effect Transistors

Sangmoon Han, Ilgyu Choi, Kwanjae Lee, Cheul-Ro Lee, more

Journal of Electronic Materials > 2018 > 47 > 2 > 944-948

We report on the dependence of internal crystal structures on the electrical properties of a catalyst-free and undoped InAs nanowire (NW) formed on a Si(111) substrate by metal–organic chemical vapor deposition. Cross-sectional transmission electron microscopy images, obtained from four different positions of a single InAs NW, indicated that the wurtzite (WZ) structure with stacking faults was observed...

article

Zr doping effect with low-cost solid-state reaction method to synthesize submicron Li4Ti5O12 anode material

Inseok Seo, Cheul-Ro Lee, Jae-Kwang Kim

Journal of Physics and Chemistry of Solids > 2017 > 108 > C > 25-29

To improve the electrochemical properties, fine Zr-doping Li₄Ti₅O₁₂ anode materials for rechargeable lithium batteries with a uniform particle size distribution were synthesized by a modified solid-state reaction using fine Li₂CO₃ and TiO₂ (anatase) powders as precursors with a Li:Ti molar ratio of 4:5. The use of fine Li₂CO₃ and TiO₂ (anatase) powders as precursors prevented the formation of ZrO₂...

article

Improvement of device performances, including electrostatic discharge characteristics, of InGaN/GaN light-emitting diodes by using a Si-doped graded superlattice

Kwanjae Lee, Cheul-Ro Lee, Haeng-Keun Ahn, Jin Soo Kim, more

Journal of the Korean Physical Society > 2017 > 70 > 11 > 1001-1006

We report the influences of a Si-doped graded-superlattice (SiGSL) on the structural, optical, and electrical properties of InGaN/GaN light-emitting diodes (LEDs). For comparison, LEDs fabricated on an undoped graded superlattice (unGSL-LED) and conventional LEDs without the superlattice (C-LED) were prepared. The dependences of the carrier behaviors on the surface inhomogeneity and the defect/dislocation...

chapter

Flower-like light distribution inside InGaN-based light-emitting diodes operated in spectral range from violet to red

Kwanjae Lee, Sangmun Han, Cheul-Ro Lee, Jin Soo Kim, more

2017 75th Annual Device Research Conference (DRC) > 1 - 2

2017 75th Device Research Conference (DRC)

Nowadays, phosphor-based light-emitting diodes (LEDs) with InGaN/GaN quantum wells (QWs) are commonly used for white light sources [1]. However, degradation of phosphor material during long-term optical pumping is inevitable, resulting that output efficiency and color-rendering index of white LEDs are significantly reduced. Therefore, a phosphor-free white LED realized by directly mixing three primary...

article

From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes

Dae‐Yoon Kim, Suyong Shin, Won‐Jin Yoon, Yu‐Jin Choi, more

Advanced Functional Materials > 27 > 18 > n/a - n/a

For the demonstration of remote‐controllable actuators, a dendronized polymer (denpol) is newly designed and successfully synthesized by ring‐opening metathesis polymerization of azobenzene‐based macromonomers. The incorporation of azobenzene mesogens into the denpols helps to construct finely tuned hierarchical superstructures with anisotropic physical properties and reversible photoisomerization...

article

Light Switches: From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes (Adv. Funct. Mater. 18/2017)

Dae‐Yoon Kim, Suyong Shin, Won‐Jin Yoon, Yu‐Jin Choi, more

Advanced Functional Materials > 27 > 18 > n/a - n/a

In article number 1606294, Tae‐Lim Choi, Kwang‐Un Jeong, and co‐workers synthesize a new azobenzene‐based norbonene chromophore for remotecontrollable actuators. Photoreversible actuation experiments and diffraction results indicate a direct relationship between chemical structures, hierarchical superstructures, and their corresponding photomechanical behaviors.

article

Influences of graded superlattice on the electrostatic discharge characteristics of green InGaN/GaN light-emitting diodes

Kwanjae Lee, Cheul-Ro Lee, Tae-Hoon Chung, Jinyoung Park, more

Journal of Crystal Growth > 2017 > 464 > C > 138-142

In this paper, the influence of a Si-doped graded superlattice (SiGSL) on the electrostatic discharge (ESD) characteristics of green InGaN/GaN light-emitting diodes (LEDs) is discussed. To investigate the effects of Si doping to the superlattice, green LEDs were also fabricated on undoped graded superlattice (unGSL). Furthermore, a conventional green InGaN/GaN LED without the superlattice (C-LED),...

article

Efficiency enhancement of CIGS compound solar cell fabricated using homomorphic thin Cr2O3 diffusion barrier formed on stainless steel substrate

Jae-Kwan Sim, Seung-Kyu Lee, Jin-Soo Kim, Kwang-Un Jeong, more

Applied Surface Science > 2016 > 389 > C > 645-650

It is known that the efficiency of flexible Cu(In,Ga)Se₂ (CIGS) solar cells fabricated on stainless-steel (STS) substrates deteriorates due to iron (Fe) and Cr impurities diffusing into the CIGS absorber layer. To overcome this problem, a nanoscale homomorphic chromium oxide layer was formed as a diffusion barrier by thermal oxidation on the surface of STS substrates for 1min at 600°C in oxygen atmosphere...

article

Electrophoretic deposition of CdZnS-ZnS QDs on InGaN/GaN MQW pillar structure

Sudarsan Raj, Taek-Soo Jang, Woo-Min Lee, Sang-Yeob Oh, more

Superlattices and Microstructures > 2016 > 100 > C > 1193-1197

In this study, CdZnS-ZnS quantum dots (QDs) films were fabricated on InGaN/GaN multi-quantum well (MQW) pillar structure by electrophoretic deposition demonstrated for the first time. The as synthesized QDs have particle size 5–8 nm and emission peak at 425 nm. The QDs are loaded both on the top as well as on the side wall of the InGaN/GaN MQW pillar structure. It showed a uniform coating having gradually...

article

Emission characteristics of shape-engineered InAs/InAlGaAs quantum dots subjected to thermal treatments

Hamin Lee, Cheul-Ro Lee, Haeng-Keun Ahn, Jin Soo Kim, more

Journal of the Korean Physical Society > 2016 > 69 > 1 > 85-90

We indirectly evaluated the inter-diffusion behaviors of group-III elements at the interface between shape-engineered (SE)-InAs/In_0.52Al_0.24Ga_0.24As quantum dots (QDs) and In_0.52Al_0.24Ga_0.24As (InAlGaAs) barriers by investigating the optical properties. Rapid thermal annealing (RTA) was carried out for five stacks of SE-InAs/InAlGaAs QDs separated by an InAlGaAs spacer under temperatures ranging from...

article

Effects of growth temperatures on the characteristics of n-GaN nanorods–graphene hybrid structures

San Kang, Arjun Mandal, Ji-Hyeon Park, Dae-Young Um, more

Journal of Alloys and Compounds > 2015 > 644 > C > 808-813

The effects of different growth temperatures of n-GaN nanorods (NRs) on the material and electrical properties of n-GaN NRs–graphene hybrid device structures are being demonstrated for the first time. A high quality graphene transfer method was applied for transferring the graphene layer on Si (111) substrate and n-GaN NRs were synthesized on the graphene layer on Si using a metal organic chemical...

article

Se interlayer in CIGS absorption layer for solar cell devices

Seung-Kyu Lee, Jae-Kwan Sim, N.J. Suthan Kissinger, Il-Seok Song, more

Journal of Alloys and Compounds > 2015 > 633 > C > 31-36

A CIGS absorber layer with high gallium contents in the space-charge region can reduce the carrier recombination and improve the open circuit voltage V_oc. Therefore, controlling Ga grading on top of CIGS thin film solar cells is the main objective of this experiment. To reduce Selenium (Se) vacancy, it is important that the diffusion of Ga elements into Se vacancy between Mo back contact and CIGS...

article

Periodic variation in the electroluminescence intensity on a single pattern from InGaN/GaN light-emitting diodes fabricated on lens-shaped patterns

Hye Min Oh, Cheul-Ro Lee, Jin Soo Kim, Kihyun Pyun, more

Journal of the Korean Physical Society > 2015 > 66 > 2 > 266-269

We investigated the spatial distribution of light emission from InGaN/GaN light-emitting diodes (LEDs) fabricated on lens-shaped patterns (LSPs) by using confocal scanning electroluminescence microscopy (CSM). From three-dimensional CSM images measured by varying the position of the focal plane of a detector, the luminescence profiles from the InGaN/GaN LEDs were significantly changed with respect...

article

Spatial emission distribution of InGaN/GaN light-emitting diodes depending on the pattern structures

Kwanjae Lee, Hyunjung Lee, Cheul-Ro Lee, Jin Soo Kim, more

Materials Research Bulletin > 2014 > 58 > Complete > 121-125

We investigated the emission characteristics of InGaN/GaN light-emitting diodes (LEDs) fabricated on lens-shaped (LS) patterned-sapphire substrates (PSS) by using time-resolved photoluminescence (TRPL) and confocal-scanning-electroluminescence microscopy (CSEM). The carrier lifetimes evaluated from the TRPL spectra for the LEDs on the LS-PSS (LS-LEDs) at 10K were relatively shorter than those of the...

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INFONA - science communication portal

Search results for: Cheul-Ro Lee

New Charge Carrier Transport‐Assisting Paths in Ultra‐Long GaN Microwire UV Photodetector

Conformable, Thin, and Dry Electrode for Electrocardiography Using Composite of Silver Nanowires and Polyvinyl Butyral

Revisiting the thickness reduction approach for near-foldable capacitive touch sensors based on a single layer of Ag nanowire-polymer composite structure

1.4 µm-Thick Transparent Radio Frequency Transmission Lines Based on Instant Fusion of Polyethylene Terephthalate Through Surface of Ag Nanowires

Growth and characterization of n-AlGaN 1-D structures with varying Al composition using u-GaN seeds

III-nitride nanowires for solar light harvesting: A review

Dependence of Internal Crystal Structures of InAs Nanowires on Electrical Characteristics of Field Effect Transistors

Zr doping effect with low-cost solid-state reaction method to synthesize submicron Li4Ti5O12 anode material

Improvement of device performances, including electrostatic discharge characteristics, of InGaN/GaN light-emitting diodes by using a Si-doped graded superlattice

Flower-like light distribution inside InGaN-based light-emitting diodes operated in spectral range from violet to red

From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes

Light Switches: From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes (Adv. Funct. Mater. 18/2017)

Influences of graded superlattice on the electrostatic discharge characteristics of green InGaN/GaN light-emitting diodes

Efficiency enhancement of CIGS compound solar cell fabricated using homomorphic thin Cr2O3 diffusion barrier formed on stainless steel substrate

Electrophoretic deposition of CdZnS-ZnS QDs on InGaN/GaN MQW pillar structure

Emission characteristics of shape-engineered InAs/InAlGaAs quantum dots subjected to thermal treatments

Effects of growth temperatures on the characteristics of n-GaN nanorods–graphene hybrid structures

Se interlayer in CIGS absorption layer for solar cell devices

Periodic variation in the electroluminescence intensity on a single pattern from InGaN/GaN light-emitting diodes fabricated on lens-shaped patterns

Spatial emission distribution of InGaN/GaN light-emitting diodes depending on the pattern structures

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