• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1022-1025
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• 2005

The effect of substrate surface to the formation of ZnO nanostructures has been investigated using Si (111), $Al_2O_3$(C-plane) $Al_2O_3$(A-plane), and $Al_2O_3$(R-plane) substrates. The growth temperature was controlled from 500$^{\circ}C$ ${\sim}$ 600$^{\circ}C$, and the luminescence properties were investigated by a series of photoluminescence (PL) measurements at the elevating temperatures. ZnO nanostructures grown on Si substrate show strong UV emission intensity along with green emission positioned at 3.22 eV and 2.5 eV, respectively. However, green emission was not observed from the ZnO nanostructures grown on $Al_2O_3$ substrates. It is explained in terms of the difference of the surface energy between Si and $Al_2O_3$. Also, the origin of UV emissions has been discussed by using the temperature-dependent PL. The distinction of the PL spectra is interpreted in terms of the difference of the impurity included in the nanostructures.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.04c
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• pp.10-11
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• 1994

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.105-108
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• 2011

Newly-developed fabrication of a p-n heterojunction diode constructed with a p-Si nanowire (NW) and an n-ZnO nanoparticle (NP) thin-film by the dielectrophoresis (DEP) technique is demonstrated in this study. With the bias of 20 Vp-p at the input frequency of 1 MHz, the most efficient assembly of the n-ZnO NPs is shown for the fabrication of the p-n heterojunction diode with a p-Si NW. The p-n heterojunction diode fabricated in this study represents current rectifying characteristics with the turn on voltage of 1.1 V. The diode can be applied to the fabrication of optoelectrical devices such as photodetectors, light-emitting diodes (LEDs), or solar cells based on the high conductivity of the NW and the high surface to volume ratio of the NP thin film.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.623-626
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• 2010

We synthesized ZnO nanowires patterned on Si substrate and investigated the field emission properties of the nanowires. Firstly, Au catalyst layers were fabricated on Si substrate by photo-lithography and lift-off process. The diameter of Au pattern was $50\;{\mu}m$ and the pattern was arrayed as $4{\times}4$. ZnO nanowires were grown on the Au catalyst pattern by the aid of Au liquid phase. The orientation of the ZnO nanowires was vertical on the whole. Sufficient brightness was obtained when the electric field was $5.4\;V/{\mu}m$ and the emission current was $5\;mA/cm^2$. The threshold electric field was $5.4\;V/{\mu}m$ in the $4{\times}4$ array of ZnO nanowires, which is quite lower than that of the nanowires grown on the flat Si substrate. The lower threshold electric field of the patterned ZnO nanowires could be attributed to their vertical orientation of the ZnO nanowires.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.227-235
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• 2001

In this work, Zn$_2$SiO$_4$:Mn phosphors were prepared by solid state reaction. The effect of sintering/reduction temperature, flow rate of H$_2$-5%/$N_2$-95% mix gas, and ball milling conditions have been investigated on the sake of PDP(Plasma Display Panel) application. The characteristics such as particle morphology and photoluminescence of prepared phosphors were compared to those of commercial Zn$_2$SiO$_4$:Mn Phosphors. It was found that the Phosphor synthesized at 130$0^{\circ}C$ with 0.08 Mn concentration had a maximum brightness, This brightness was increased more 20% by reduction treatment under 100me/min flow rate of 5%H$_2$-95%$N_2$ mixed gas. The size of particles decreased under 3$\mu\textrm{m}$ after ball milling. Especially, higher luminescence was obtained in our Zn$_2$SiO$_4$:Mn phosphors than commercial Zn$_2$SiO$_4$:Mn phosphors, so that they are able to be applied for PDP.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.111-118
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• 1996

In order to improve the chemical durability of glass in the $Na_2O$-CaO-$SiO_2$ system, it was investigated in the effect of $B_2O_3$ and ZnO addition and changing amount of each composition, $Na_2O$, $Al_2O_3$, $Li_2O$. In this minimize the change of softening point of glass was as follow.(wt%)$B_2O_3$:3.36%, ZnO:2.88%, $Na_2O$:9.93%, $Al_2O_3$, $Li_2O$:0.19%, $SiO_2$:70.56%, CaO:11.22%, $K_2O$:0.14%

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1361-1363
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• 1997

Zinc oxide-based MOV was fabricated with $SiO_2$ additive ranging from 0.5 to 4.0 mol%, and the microstructure and electrical characteristics were investigated. $Zn_2SiO_4$ phase formed by $SiO_2$ additive was distributed at ZnO grains, grain boundaries, and multiple grain junctions. As the content of $SiO_2$ additive increases, average grain size decreased from 40.6 to $26.9{\mu}m$ due to the Pinning effect by $Zn_2SiO_4$ at grain boundaries Breakdown voltage and nonlinear exponent increased, and leakage current decreased in the range of $11.2{\sim}6.14{\mu}A$ with an increasing $SiO_2$. Donor concentration and interface state density decreased, and barrier height increased in the range of $0.71{\sim}1.04eV$ with an increasing $SiO_2$. While, as the content of $SiO_2$ additive, apparent dielectric constant decreased, peak frequency of dissipation factor decreased in the range of $6.45{\times}10^5{\sim}3.00{\times}10^5Hz$, and dissipation peak was $0.31{\sim}0.22$ at Peak frequency.

• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.337-341
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• 2010

In this work, the nanocrystalline ZnO/polycrystalline(poly) aluminum nitride(AlN)/ Si-layered structure was fabricated for humidity sensor applications based on surface acoustic wave(SAW). The ZnO film was used as a sensitive material layer. The ZnO and AlN(0002) were deposited by a sol-gel process and a pulse reactive magnetron sputtering, respectively. The ZnO sensitive films coated on AlN have a hexagonal wurtzite structure after the thin films annealed at $400^{\circ}C$, $500^{\circ}C$ and $600^{\circ}C$. The surface of the film exhibits sponginess and a nanometer particle size(below 50 nm). The largest shift in the frequency response was at approximately 200 kHz(the relative humidity: 10 %~90 %) for the structure annealed at $400^{\circ}C$. The effect of the change in the environmental temperature on the frequency response of the SAW humidity sensor was also investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.236.1-236.1
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• 2015

The surface morphology of front transparent conductive oxide (TCO) films is very important to achieve high current density in amorphous silicon (a-Si) thin film solar cells since it can scatter the light in a better way. In this study, we present the low cost hydrothermal deposited uniform zinc oxide (ZnO) nano-flower structure with various aspect ratios for a-Si thin film solar cells. The ZnO nano-flower structures with various aspect ratios were grown on the RF magnetron sputtered AZO films. The diameters and length of the ZnO nano-flowers was controlled by varying the annealing time. The length of ZnO nano-flowers were varied from 400 nm to $2{\mu}m$ while diameter was kept higher than 200 nm to obtain different aspect ratios. The ZnO nano-flowers with higher surface area as compared to conventional ZnO nano structure are preferred for the better light scattering. The conductivity and crystallinity of ZnO nano-flowers can be enhanced by annealing in hydrogen atmosphere at 350 oC. The vertical aligned ZnO nano-flowers showed higher haze ratio as compared to the commercially available FTO films. We also observed that the scattering in the longer wavelength region was favored for the high aspect ratio of ZnO nano-flowers. Therefore, we proposed low cost and vertically aligned ZnO nano-flowers for the high performance of thin film solar cells.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.274-282
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• 1999

The In doped ZnO(ZnO:In)thin films sensitive to $NH_3$ gas were prepared by the double layer depositions of In film by vacuum evaporation and ZnO film by rf magnetron sputtering method onto a $SiO_2$/Si wafer substrate, and subsequent heat treatment process. The structural and electrical characteristics of the ZnO:In thin films were studied as a function of heat treatment temperature by x-ray diffraction, scanning electron microscope and 4 point probing method. And the dependence of the sensitivity, the selectivity and the time response of the thin films on heat treatment temperature was investigated. The thin film heat-treated at $400^{\circ}C$ showed the highest sensitivity of 140% at an operating temperature of $300^{\circ}C$. The sensitivity towards CO, $NO_x$, gases observed in the same temperature.