• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.24.2-24.2
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• 2009

Nanostuctures such as nanodot and nanowire have been extensively studied as building blocks for nanoscale devices. However, the direct growth of the nanostuctures at the desired position is one of the most important requirements for realization of the practical devices with high integrity. Self-assembled nanotemplate is one of viable methods to produce highly-ordered nanostructures because it exhibits the highly ordered nanometer-sized pattern without resorting to lithography techniques. And selective epitaxial growth (SEG) can be a proper method for nanostructure fabrication because selective growth on the patterned openings obtained from nanotemplate can be a proper direction to achieve high level of control and reproducibility of nanostructucture fabrication. Especially, SiGe has led to the development of semiconductor devices in which the band structure is varied by the composition and strain distribution, and nanostructures of SiGe has represented new class of devices such nanowire metal-oxide-semiconductor field-effect transistors and photovoltaics. So, in this study, various shaped SiGe nanostructures were selectively grown on Si substrate through ultrahigh vacuum chemical vapor deposition (UHV-CVD) of SiGe on the hexagonally arranged Si openings obtained using nanotemplates. We adopted two types of nanotemplates in this study; anodic aluminum oxide (AAO) and diblock copolymer of PS-b-PMMA. Well ordered and various shaped nanostructure of SiGe, nanodots and nanowire, were fabricated on Si openings by combining SEG of SiGe to self-assembled nanotemplates. Nanostructure fabrication method adopted in this study will open up the easy way to produce the integrated nanoelectronic device arrays using the well ordered nano-building blocks obtained from the combination of SEG and self-assembled nanotemplates.

• Journal of Sensor Science and Technology
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• v.29 no.3
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• pp.187-193
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• 2020

Ultraviolet (UV) sensors are widely applied in industrial and military fields such as environmental monitoring, medicine and astronomy. Zinc oxide (ZnO) is considered as one of the promising materials for UV sensors because of its ease of fabrication, wide bandgap (3.37 eV) and high chemical stability. In this study, we used the hydrothermal growth of ZnO to form two types of ZnO nanostructures (Nanoflower and nanorod) and applied them to a UV sensor. To improve the performance of the UV sensor, the hydrothermal growth was used in a two-step process for fabricating ZnO hierarchical nanostructures. The fabricated ZnO hierarchical nanostructure improved the performance of the UV sensor by increasing the ratio of volume to surface area and the number of nanojunctions compared to one-step hydrothermal grown ZnO nanostructure. The UV sensor based on the ZnO hierarchical nanostructure had a maximum photocurrent of 44 ㎂, which is approximately 3 times higher than that of a single nanostructure. The UV sensor fabrication method presented in this study is simple and based on the hydrothermal solution process, which is advantageous for large-area production and mass production; this provides scope for extensive research in the field of UV sensors.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.159-160
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• 2010

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.62-67
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• 2016

This paper presents a silicon nanostructure array embedded in a polymer film. The silicon nanostructure array was fabricated by using basic microelectromechanical systems (MEMS) processes such as photolithography, reactive ion etching, and anisotropic KOH wet etching. The fabricated silicon nanostructure array was transferred into polymer substrates such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polycarbonate (PC) through the hot-embossing process. In order to determine the transfer conditions under which the silicon nanostructures do not fracture, hot-embossing experiments were performed at various temperatures, pressures, and pressing times. Transfer was successfully achieved with a pressure of 1 MPa and a temperature higher than the transition temperature for the three types of polymer substrates. The transferred silicon nanostructure array was electrically evaluated through measurements with a semiconductor parameter analyzer (SPA).

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1493-1494
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• 2011

CdS nanostructure materials have been fabricated in porous anodic aluminum oxide (AAO) template by using chemical bath deposition (CBD). These nanostructure materials had uniform diameters of about 15e200 nm, which correspond to the pore sizes of the templates used, and the length was up to 40 mm. X-ray diffraction (XRD) investigation demonstrates that CdS nanostructure materials were hexagonal polycrystalline in nature. As the pore diameter of AAO templates was enlarged, the preferential orientation of c-axis was improved. From PL analysis, the sulfur-deficient defects at the surfaces of CdS nanostructure materials were increasedwhen the samplewas synthesized in the template with larger pore diameter.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.459.1-459.1
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• 2014

Because both $TiO_2$ and ZnO has superior characteristic optically and electrically, there are various of research for these materials. However, they have large band gap energy which correspond with not visible light, but UV light. To make up for this disadvantage, Quantum dots (CdS, CdSe) which can absorb the visible light could be deposited on $ZnO/TiO_2$ nanostructure so that the the photoelectrochecmical cell can absorb the light that has larger region of wavelength. Both $TiO_2$ and ZnO can be grown to one-dimensional nanowire structure at low temperature through solutional method. Three-dimensional hierarcical $ZnO/TiO_2$ nanostructure is fabricated by applying these process. Large surface area of this structure make the light absorbed more efficiently. Through type 2 like-cascade energy band structure of nanostructure, the efficient separation of electron-hole pairs is expected. Photoelectrochemical charateristics are found by using these nanostructure to photoelectrode.

• Proceedings of the Korean Vacuum Society Conference
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• 1993.07a
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• pp.4-4
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• 1993

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.31.1-31.1
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• 2010

Various ZnO nanostructures were synthesized and ZnO nanostructure-based self-assembled transistors were fabricated. Compared to spindle and flower like nanostructure, the ZnO nanorod (NR) structure showed much stronger gate controllability, and greatly enhanced device performance, demonstrating that this structural variation leads to significant differences of the nanostructure network-based device performance. Also, patterned dry transfer-printing technique that can generate monolayer-like percolating networks of ZnO NRs has been developed. The method exploits the contact area difference between NR-NR and NR-substrate, rather than elaborate tailoring of surface chemistry or energetic. The devices prepared by the transferring method exhibited on/off current ratio, and mobility of ${\sim}2.7{\times}10^4$ and ${\sim}1.03\;cm^2/V{\cdot}s$, respectively. Also, they exhibited showing lower off-current and stronger gate controllability due to defined-channel between electrodes and monolayer-like network channel configuration. With multilayer stacks of nanostructures on stamp, the monolayer-like printing can be repeated many times, possibly on large area substrate, due to self-regulating printing characteristics. The method may enable high-performance macroelectronics with materials that have high aspect ratio.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.25.2-25.2
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• 2011

The tungsten oxide wire-like nanostructure is fabricated by deposition and thermal oxidation of tungsten metal on porous single wall carbon nanotubes (SWNTs). The morphology and crystalline quality of materials are investigated by SEM, TEM, XRD and Raman analysis. The results prove that $WO_3$ wire-like nanostructure fabricated on SWNTs show highly porous structures. Exposure of the sensors to NH3 gas in the temperature range of 150~300$^{\circ}C$ resulted in the highest sensitivity at $250^{\circ}C$ with quite rapid response and recovery time. Response time as a function of test concentrations and NH3 gas sensing mechanism is reported and discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.623-623
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• 2008