Korea Advanced Nanofab Center

Yeongtong gu, South Korea

Korea Advanced Nanofab Center

Yeongtong gu, South Korea
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Cho Y.,Ewha Womans University | Kim E.,Ewha Womans University | Gwon M.,Ewha Womans University | Park H.-H.,Korea Advanced Nanofab Center | And 2 more authors.
Applied Physics Letters | Year: 2015

We compared nanopatterned Si solar cells with and without SiNx layers. The SiNx layer coating significantly improved the internal quantum efficiency of the nanopatterned cells at long wavelengths as well as short wavelengths, whereas the surface passivation helped carrier collection of flat cells mainly at short wavelengths. The surface nanostructured array enhanced the optical absorption and also concentrated incoming light near the surface in broad wavelength range. Resulting high density of the photo-excited carriers near the surface could lead to significant recombination loss and the SiNx layer played a crucial role in the improved carrier collection of the nanostructured solar cells. © 2015 AIP Publishing LLC.


Kim E.,Ewha Womans University | Cho Y.,Ewha Womans University | Sohn A.,Ewha Womans University | Kim D.-W.,Ewha Womans University | And 2 more authors.
Current Applied Physics | Year: 2016

The surface photovoltage (SPV) characteristics of periodic nanopillar (NP) arrays formed on Si wafers were investigated. The NP arrays exhibited broadband omnidirectional antireflection effects with Mie resonance. Kelvin probe force microscopy (KPFM) revealed that the positive fixed charges in SiNx layers induced band bending at the Si surface and increased surface photovoltage (SPV) at the NP top surface. Estimated SPV values, determined by the amount of surface band bending, were similar in NPs and planar counterparts. This finding suggests that field effect passivation by the dielectric layer coating could help improve photovoltaic performance of nanostructure-based Si solar cells and that KPFM may be a useful tool for the investigation of surface electrical properties of Si nanostructures. © 2015 Elsevier B.V. All rights reserved.


PubMed | Ewha Womans University, Korea Advanced Nanofab Center, Sungkyunkwan University, State University of New York at Buffalo and Incheon National University
Type: | Journal: Scientific reports | Year: 2015

Periodical nanocone-arrays were employed in an emitter region for high efficient Si solar cells. Conventional wet-etching process was performed to form the nanocone-arrays for a large area, which spontaneously provides the graded doping features for a selective emitter. This enables to lower the electrical contact resistance and enhances the carrier collection due to the high electric field distribution through a nanocone. Optically, the convex-shaped nanocones efficiently reduce light-reflection and the incident light is effectively focused into Si via nanocone structure, resulting in an extremely improved the carrier collection performances. This nanocone-arrayed selective emitter simultaneously satisfies optical and electrical improvement. We report the record high efficiency of 16.3% for the periodically nanoscale patterned emitter Si solar cell.


Kim S.,Korea Institute of Science and Technology | Geum D.-M.,Korea Institute of Science and Technology | Geum D.-M.,Seoul National University | Park M.-S.,Korea Institute of Science and Technology | And 2 more authors.
Solar Energy Materials and Solar Cells | Year: 2015

In this work, we developed wafer bonding techniques to bond GaAs and Si wafers. Wafer bonding was carried out at room temperature without high temperature annealing processes. The bonded interface showed a low interface resistance of 8.8×10-3 Ω cm2. We also exploited the new bonding techniques to fabricate a GaAs solar cell on a Si substrate. The solar cell showed a high energy conversion efficiency (13.25%) even without an anti reflection coating. The performance of the fabricated GaAs/Si solar cell was comparable to that of a homogeneous GaAs solar cell grown on a GaAs substrate.∗Corresponding author. © 2015 Elsevier B.V. All rights reserved.


Kim H.,Incheon National University | Park H.-H.,Korea Advanced Nanofab Center | Kim J.,Incheon National University
Materials Science in Semiconductor Processing | Year: 2016

Transparent and single crystalline indium-tin-oxide (ITO) nanowires (NWs) were grown by sputtering method. A thin Ni film of 5 nm was deposited before ITO sputtering. Thermal treatment forms Ni nanoparticles, which act as templates to diffuse Ni into the sputtered ITO layer to grow single crystalline ITO NWs. This Ni diffusion through an ITO NW was investigated by transmission electron microscope to observe the Ni-tip sitting on a single crystalline ITO NW. Meanwhile, a single crystalline ITO structure was found at bottom and body part of a single ITO NW without remaining of Ni atoms. This indicates the Ni atoms diffuse through the oxygen vacancies of ITO structure. Rapid thermal process (RTP) applied to generate an initial stage of a formation of Ni nanoparticles with variation in time periods to demonstrate the existence of an optimum condition to initiate ITO NW growth. Modulation in ITO sputtering condition was applied to verify the ITO NW growth or the ITO film growth. The Ni-assisted grown ITO layer has an improved electrical conductivity while maintaining a similar transmittance value to that of a single ITO layer. Electrically conductive and optically transparent ITO nanowire-coated surface morphology would provide a great opportunity for various photoelectric devices. © 2016 Elsevier Ltd. All rights reserved.


Seo J.,Seoul National University | Kim T.-H.,Oak Ridge National Laboratory | Chung S.-H.,U.S. National Institute of Standards and Technology | Oh Y.,Seoul National University | And 2 more authors.
Applied Physics Letters | Year: 2010

We have fabricated an ultrahigh-vacuum-processed, ordered, single-crystalline nanodot array. By mapping the magnetization of the nanodots with spin polarized scanning tunneling microscopy in the same chamber where they were grown, we are able to understand how the short-range order of the nanodot array is determined by the magnetostatic dipole interaction among neighboring nanodots. We also demonstrate tuning the magnetic interaction in the nanodot array by controlling those magnetic energies. Further magnetic simulations support the observed results consistently. © 2010 American Institute of Physics.


PubMed | Korea Advanced Nanofab Center and Incheon National University
Type: | Journal: Scientific reports | Year: 2016

Could defect-considered void formation in metal-oxide be actively used? Is it possible to realize stable void formation in a metal-oxide layer, beyond unexpected observations, for functional utilization? Herein we demonstrate the effective tailoring of void formation of NiO for ultra-sensitive UV photodetection. NiO was formed onto pre-sputtered ZnO for a large size and spontaneously formed abrupt p-NiO/n-ZnO heterojunction device. To form voids at an interface, rapid thermal process was performed, resulting in highly visible light transparency (85-95%). This heterojunction provides extremely low saturation current (<0.1nA) with an extraordinary rectifying ratio value of over 3000 and works well without any additional metal electrodes. Under UV illumination, we can observe the fast photoresponse time (10ms) along with the highest possible responsivity (1.8A W(-1)) and excellent detectivity (210(13) Jones) due to the existence of an intrinsic-void layer at the interface. We consider this as the first report on metal-oxide-based void formation (Kirkendall effect) for effective photoelectric device applications. We propose that the active adoption of defect-considered Kirkendall-voids will open up a new era for metal-oxide based photoelectric devices.


PubMed | Korea Advanced Nanofab Center, Venture Institute, Korea Institute of Science and Technology and Seoul National University
Type: | Journal: Scientific reports | Year: 2016

Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called Si photonics). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates.


Park S.-J.,Korea Institute of Machinery and Materials | Lee S.-W.,Korea Institute of Machinery and Materials | Jeong S.,Korea Institute of Machinery and Materials | Lee J.-H.,Korea Institute of Machinery and Materials | And 4 more authors.
Nanoscale Research Letters | Year: 2010

For the improved surface plasmon-coupled photoluminescence emission, a more accessible fabrication method of a controlled nanosilver pattern array was developed by effectively filling the predefined hole array with nanosilver colloid in a UV-curable resin via direct nanoimprinting. When applied to a glass substrate for light emittance with an oxide spacer layer on top of the nanosilver pattern, hybrid emission enhancements were produced from both the localized surface plasmon resonance-coupled emission enhancement and the guided light extraction from the photonic crystal array. When CdSe/ZnS nanocrystal quantum dots were deposited as an active emitter, a total photoluminescence intensity improvement of 84% was observed. This was attributed to contributions from both the silver nanoparticle filling and the nanoimprinted photonic crystal array. © 2010 The Author(s).


Jeong N.,Korea Institute of Energy Research | Hong S.-K.,Korea Institute of Energy Research | Kim C.,Korea Institute of Energy Research | Kim K.,Korea Advanced Nanofab Center
Journal of the American Ceramic Society | Year: 2015

Direct integration of nanostructures into macroscopic substrates is very important for their practical applications. In this work, we report a simple method that can be introduced for the Sn-catalyzed growth of alumina nanowires on ceramic substrates such as porous disk, monolith, and foam. Our study focuses on the role of the Sn catalysts in the formation mechanisms governing nanowire growth. Using the proposed approach, hair- or grass-like tufts of 20 nm diameter nanowires grow on the surface of the ~3 μm diameter Sn particles, in a tip growth mechanism. The nanowires of α-phased polycrystalline structure grow and are packed via a complex process involving batch-by-batch, branching, and amalgamation growth. The detailed observations reveal that the Sn catalyst is key to tailoring the growth patterns of the nanowires. In addition, cathodoluminescence studies highlight the potential optical applications of the alumina nanowires. © 2015 The American Ceramic Society.

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