Jisook Oh

Bio: Jisook Oh is an academic researcher from Yonsei University. The author has contributed to research in topics: Dye-sensitized solar cell & Nanowire. The author has an hindex of 3, co-authored 5 publications receiving 135 citations.

Synthesis of a ZnS Shell on the ZnO Nanowire and Its Effect on the Nanowire-Based Dye-Sensitized Solar Cells

Abstract: A thin ZnS shell was formed on ZnO nanowires using ZnSO4 and thiourea in an NH4OH (ZTA) precursor solution, and its effect on the performance of a dye-sensitized solar cell (DSSC) was investigated. As compared to hydrothermal and successive ionic layer adsorption and reaction methods, it was observed that the ZnS shell was effectively synthesized on the ZnO nanowires using the ZTA solution. ZnO nanowires with a ZnS shell had lower absorption intensities over the entire wavelength range compared with those of nanowires without the ZnS shell, which can cause dye to absorb more light in the DSSC operation. Because the intensity of visible emission decreased after the formation of a ZnS shell on the ZnO nanowires, it is proposed that surface defects that provide recombination sites will be reduced at the anode/electrolyte interface. The cell performance of the ZnO nanowire-based DSSC was greatly improved by the deposition of a thin ZnS shell onto the ZnO nanowires in the ZTA solution, which resulted from the ...

Etch Behavior of ALD Al2O3 on HfSiO and HfSiON Stacks in Acidic and Basic Etchants

Abstract: For the integration of advance gate stacks, selective wet etching of an Al2O3 capping layer on top of high-k dielectrics was studied. From the fundamental etch study on the single-layer Al2O3, HfSiO and HfSiON thin films were prepared by atomic layer deposition (ALD). Using the etch rate information of each single layer, several optimized etch conditions in acidic and basic etchants including H3PO4, NH4OH, and TMAH resulted in wet etch selectivities of Al2O3 to high-k materials higher than 50:1. As a result, the Al2O3 capping layer on Si/SiO2/high-k multi-layer gate stack could be completely removed without thinning of the underlying high-k thin films. Finally, the etch mechanisms of Al2O3 in acidic and basic etchants were studied and the etch rates of Al2O3 were determined as functions of [Hþ] and [OH ]. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3554729] All rights reserved.

Successive ionic layer adsorption and reaction of ZnSe shells for ZnO nanowire-based dye-sensitized solar cells

Abstract: Thin ZnSe layers were deposited on ZnO nanowires by a novel successive ionic layer adsorption and reaction technique in order to solve recombination problems in ZnO nanowire-based dye-sensitized solar cells (DSSCs). Cell efficiency increased from 0.1 to 1.3–1.4% with the deposition of a 9- to13-nm-thick ZnSe shell on ZnO nanowires due to a large increase in JSC. The dramatic increase in JSC and cell efficiency is due to the facilitation of electron transfer related to ambipolar diffusion by the formation of a type II band alignment and the suppression of recombination in the presence of the ZnSe shell.

Effect of post-etch cleaning on Ru-capped extreme ultraviolet lithography photomask

Abstract: Ru-capped extreme ultraviolet lithography photomasks require cleaning after patterning of the absorber layer. In this study, it was confirmed that, during Cl 2 dry etching to remove the absorber layer, RuCl 3 was formed on the Ru capping layer surface, and the surface roughness thereby deteriorated. Therefore, the changes in RuCl 3 formation and surface roughness with various cleaning processes were investigated. Among the treatments used, i . e ., sulfuric peroxide mixture, an ammonia peroxide mixture or ozonated water (DIO 3 ), DIO 3 exhibited the most effective Cl removal efficiency and surface roughness recovery. DIO 3 treatment successfully reduced the Cl-terminated Ru surface to its original state and decreased the surface roughness to the pre-Cl 2 -etched Ru value.

Three-dimensional macro-structures of two-dimensional nanomaterials

Abstract: If two-dimensional (2D) nanomaterials are ever to be utilized as components of practical, macroscopic devices on a large scale, there is a complementary need to controllably assemble these 2D building blocks into more sophisticated and hierarchical three-dimensional (3D) architectures. Such a capability is key to design and build complex, functional devices with tailored properties. This review provides a comprehensive overview of the various experimental strategies currently used to fabricate the 3D macro-structures of 2D nanomaterials. Additionally, various approaches for the decoration of the 3D macro-structures with organic molecules, polymers, and inorganic materials are reviewed. Finally, we discuss the applications of 3D macro-structures, especially in the areas of energy, environment, sensing, and electronics, and describe the existing challenges and the outlook for this fast emerging field.

Assembly of one dimensional inorganic nanostructures into functional 2D and 3D architectures. Synthesis, arrangement and functionality

Abstract: This review will focus on the synthesis, arrangement, structural assembly, for current and future applications, of 1D nanomaterials (tubes, wires, rods) in 2D and 3D ordered arrangements. The ability to synthesize and arrange one dimensional nanomaterials into ordered 2D or 3D micro or macro sized structures is of utmost importance in developing new devices and applications of these materials. Micro and macro sized architectures based on such 1D nanomaterials (e.g. tubes, wires, rods) provide a platform to integrate nanostructures at a larger and thus manageable scale into high performance electronic devices like field effect transistors, as chemo- and biosensors, catalysts, or in energy material applications. Carbon based, metal oxide and metal based 1D arranged materials as well as hybrid or composite 1D materials of the latter provide a broad materials platform, offering a perspective for new entries into fascinating structures and future applications of such assembled architectures. These architectures allow bridging the gap between 1D nanostructures and the micro and macro world and are the basis for an assembly of 1D materials into higher hierarchy domains. This critical review is intended to provide an interesting starting point to view the current state of the art and show perspectives for future developments in this field. The emphasis is on selected nanomaterials and the possibilities for building three dimensional arrays starting from one dimensional building blocks. Carbon nanotubes, metal oxide nanotubes and nanowires (e.g. ZnO, TiO2, V2O5, Cu2O, NiO, Fe2O3), silicon and germanium nanowires, and group III–V or II–VI based 1D semiconductor nanostructures like GaS and GaN, pure metals as well as 1D hybrid materials and their higher organized architectures (foremost in 3D) will be focussed. These materials have been the most intensively studied within the last 5–10 years with respect to nano–micro integration aspects and their functional and application oriented properties. The critical review should be interesting for a broader scientific community (chemists, physicists, material scientists) interested in synthetic and functional material aspects of 1D materials as well as their integration into next higher organized architectures.

Recent advances in solar cells based on one-dimensional nanostructure arrays

Abstract: As the demand for renewable energy resource is growing rapidly worldwide, a variety of energy materials and technologies are being developed. In this review, we aim to summarize recent developments in the state-of-the-art research on energy harvesting technologies such as thin-film Si or Ge, CdTe, GaAs, organic, hybrid, and dye-sensitized solar cells (DSSCs) utilizing one-dimensional (1D) nanomaterials, mainly semiconductor nanowires, nanocones, nanotubes and nanofibers, which are prepared by vapor–liquid–solid method, colloidal lithography, template-guided growth, or electrospinning. Moreover, the future challenges (such as efficiency improvement and natural resource limitations) and prospects of nanostructured solar cells are proposed.

Recent progress of one-dimensional ZnO nanostructured solar cells

Abstract: One-dimensional (1D) ZnO nanostructures have widely been studied over the last decade, not only because of their rich morphologies produced by various methods, but also because of their wide applications in optics, electronics, piezoelectronics, sensing, etc. Particularly, as an environmental friendly material, 1D ZnO nanostructures have intensively been studied for clean and sustainable solar energy devices. This article gives a comprehensive overview of the progress made in the different types of 1D ZnO nanostructure solar cells. Herein the synthetic methods are not in the main focus and are summarized in the form of tables, rather we mainly emphasize the most exciting applications of 1D ZnO nanostructured solar cells, such as (2D and 3D) dye- and quantum dot-sensitized, bulk heterojunctions, p–n and Schottky junctions, and integrated devices. In the end we share our views related to the perspectives in this field.

Conversion Reactions of Cadmium Chalcogenide Nanocrystal Precursors

Abstract: We survey the chemical reactions between common precursors used in the synthesis of metal chalcogenide nanocrystals and outline how they affect the mechanism and kinetics of nanocrystal growth. We emphasize syntheses of cadmium selenide and cadmium sulfide where a variety of metal and chalcogenide precursors have been explored, though this is supplemented by studies of zinc and lead chalcogenide formation where appropriate. This review is organized into three sections, highlighting kinetics, metal precursors, and chalcogenide precursors, respectively. Section I is dedicated to the role of precursor conversion as a source of monomers and the importance of the supply rate on nanocrystal nucleation and growth. Section II describes the structure and reactivity of cadmium carboxylates, phosphonates, and chalcogenolates. Section III describes the reaction chemistry of commonly employed chalcogenide precursors and the mechanisms by which they react with metal precursors.