• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.34.1-34.1
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• 2009

A great deal of attention has been focused on ZnO nanowires for various electronics and optoelectronics applications. in the pursuit of next generation nanodevices, it would be highly preferred if well-ordered ZnO nanowires of lower dimension could be fabricated on silicon. Before the growth of nanowires, silicon substrates were selectively etched using silicon nitride as masking layer. Vertical aligned ZnO nanowires were grown by metal organic chemical vapor deposition on patterned silicon substrate. The shape of nanostructures was greatly influenced by the micropatterned surface of the substrate. The aspect ratio, packing fraction and the number density of nanowires on top surface are around 10, 0.8 and $10^7\;per\;mm^2$, respectively, whereas the values are 20, 0.3 and $5\times10^7\;per\;mm^2$, respectively, towards the bottom of the cavity. XRD patterns suggest that the nanostructures have good crystallinity. High-resolution transmission electron microscopy confirmed the single crystalline growth of the ZnO nanowires along [0001] direction.

• Current Photovoltaic Research
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• v.4 no.3
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• pp.124-129
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• 2016

Recently industry has voiced a need for optimally designing the production process of low-cost, high-quality ingots by improving productivity and reducing production costs with the Czochralski process. Crystalline defect control is important for the production of high-quality ingots. Also oxygen is one of the most important impurities that influence crystalline defects in single crystals. Oxygen is dissolved into the silicon melt from the silica crucible and incorporated into the crystalline a far larger amount than other additives or impurities. Then it is eluted during the cooling process, there by causing various defect. Excessive quantities of oxygen degrade the quality of silicone. However an appropriate amount of oxygen can be beneficial. because it eliminates metallic impurities within the silicone. Therefore, when growing crystals, an attempt should be made not to eliminate oxygen, but to uniformly maintain its concentration. Thus, the control of oxygen concentration is essential for crystalline growth. At present, the control of oxygen concentration is actively being studied based on the interdependence of various factors such as crystal rotation, crucible rotation, argon flow, pressure, magnet position and magnetic strength. However for methods using a magnetic field, the initial investment and operating costs of the equipment affect the wafer pricing. Hence in this study simulations were performed with the purpose of producing low-cost, high-quality ingots through the development of a process to optimize oxygen concentration without the use of magnets and through the following. a process appropriate to the defect-free range was determined by regulating the pulling rate of the crystals.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.314-318
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• 2010

We fabricated a plasma texturing for multi-crystalline silicon cells using reactive ion etching (RIE). Multi-crystalline Si cells have not benefited from the cost-effective wet-chemical texturing processes that reduce front surface reflectance on single-crystal wafers. Elimination of plasma damage has been achieved while keeping front reflectance to extremely low levels. We will discuss reflectance, quantum efficiency and conversion efficiency for multi-crystalline Si solar cell by each RIE process conditions.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.62-68
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• 2012

The conversion efficiency of solar cells depending on incident angle of light is important for building-integrated photovoltaics (BIPV) applications. The quantum efficiency is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy shining on the solar cell. The analysis of angle dependence of quantum efficiencies give more information upon the variation of power output of a solar cell by the incident angle of light. The variations in power output of solar cells with increasing angle of incidence is different for the type of cell structures. In this study we present the results of the quantum efficiency measurement of single-crystalline silicon solar cells and a-Si:H thin-film solar cells with the angle of incidence of light. As a result, as the angle of incidence increases in single-crystalline silicon solar cells, quantum efficiency at all wavelength (300~1,100 nm) of light were reduced. But in case of a-Si:H thin-film solar cells, quantum efficiency was increased or maintained at the angle of incidence from 0 degree to about 40 degrees and dramatically decrease at more than 40 degrees in the range of visible light. This results of quantum efficiency with increasing incident angle were caused by haze and interference effects in thin-film structure. Thus, the structural optimization considering incident angle dependence of solar cells is expected to benefit BIPV.

• Composites Research
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• v.24 no.6
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• pp.56-63
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• 2011

The objective of this study is to investigate appropriate bonding methods of solar cells in order to apply solar cells, which have been receiving particular attention as a renewable energy due to fossil energy depletion and environment issues, to composite structures. Back-contact solar cells with approximately 24.2% energy conversion efficiency were used in this study. Since silicon-based solar cells are mechanically fragile, the secondary-bonding methods using adhesive were examined in this study. The experiment was conducted with three kinds of bonding materials such as EVA film, Resin film and elastic adhesive. The performance of solar cells for three types of adhesives under mechanical loading on test specimens is conducted. In addition, the measuring equipment was designed to evaluate the performance of the solar cells under mechanical loading in real time and the fracture characteristics depending on bonding materials were evaluated. The reason decreasing solar cells efficiency were analyzed and considered by Fractography. The results show that the solar cell performance is largely affected by bonding techniques. Moreover, the bonding method using elastic adhesive shows best solar cell efficiency.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.70-75
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• 1998

The ZnS-SiO$_2$ composite films were fabricated by codeposition from two independent sources. The optical properties and microstructures of these composite films were investigated. The refractive indices of the composite films were compared those by Drude's fomula and showed a good agreement. it showed that microstructures of composite films are an armorphous. But microstructures of composite films with ion assisted deposition are changed from an armorphous to crystalline with increasing Zn mole fractions. We designed and fabricated a single layer antireflection coating on the crystalline silicon substrate using the refractive index of the composite films.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1507_1508
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• 2009

This study proposes a composite right/left-handed transmission line (CRLH-TL) that permits switching between the right-handed (RH) and left-handed (LH) modes using single crystalline silicon (SCS) RF MEMS switches. It is possible to change modes from the RH to LH mode, or vice versa, by controlling the admittance of capacitors and the impedance of inductors using switch operations. The proposed switchable CRLH-TL consists of SCS RF MEMS switches, metal-insulator-metal (MIM) capacitors and shunt inductors. At 8 GHz, the fabricated device shows a phase response of $87^{\circ}$ with an insertion loss of 2.7 dB in the LH mode, and a phase response of $-77^{\circ}$ with an insertion loss of 0.56 dB in the RH mode.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.736-742
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• 2000

Mass removed from crystalline silicon samples during high power single-pulse laser ablation was studied by measuring the resulting crater morphology with a white light interferometric microscope. The volume and depth of the craters show a strong nonlinear change as the laser irradiance increases across a threshold value, that is, approximately $2.2{\times}10^{10}\;W/cm^2$. Time-resolved shadowgraph images of the ablation plume show the ejection of large particulates from the sample for laser irradiance above the threshold, with a time delay of about 300-400 nsec. The thickness of superheated liquid layer near the critical temperature was numerically estimated, considering the transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency). The estimated thickness of the superheated layer at a delay time of 200 nsec agreed with the measured crater depths, suggesting that induced transparency promotes the formation of a deep superheated liquid layer which leads to an explosive boiling responsible for the sudden increase of crater volume and depth.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1463-1465
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• 1994

The electrical characteristics of $Al/Ta_2O_5/Si$ metal-oxide-semiconductor (MOS) capacitors were studied. $Ta_2O_5$ films on p-type silicon had been prepared by ionized cluster beam epitaxy technique (ICBE). This $Ta_2O_5$ films have low leakage current, high breakdown strength and low flat band shift. In this research, a single crystalline cpitaxial film of $Ta_2O_5$ has been grown on p-Si wafer using an ICBE technique. The native oxide layer ($SiO_2$) on the silicon substrate was removed below $500^{\circ}C$ by use of an accelerated arsenic ion beam, instead of a high temperature deposition. $Ta_2O_5$ films formed by ICBE technique can be received considerable attention for applications to coupling capacitors, gate dielectrics in MOS devices, and memory storage capacitor insulator because of their high dielectric constants above 20 and low temperature process.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.150-151
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• 2007

We present an one-axis parallel-plate type of bulk micromachined torsional micromirror array with single crystalline silicon (SCS) fabricated on the glass substrate. Structurally, bottom electrodes (amophous silicon) in this mirror are DRIEed along the aluminum mirror patterns on SCS, which are self-aligned with mirror plates. Tracing the history of the micromirror study, we found that few papers have been published on research for uniform driving voltages based upon the tilting direction. If there is a slight misalignment during anodic bonding between top (mirror plate) and bottom electrodes, the non-uniformity of driving voltage will be led depending on two different tilting direction. This paper discusses how much the pull-in voltages can be different due to misalignment between two electrodes. Moreover, We achieve uniform pull-in voltage regardless of misalignments in photolithography and anodic-bonding between two individual layers.