Al-doped ZnO(AZO) thin films were synthesized using atomid layer deposition(ALD), which acurately controlledthe uniform film thickness of the AZO thin films. To investigate the electrical and optical properites of the AZO thin films,AZO films using ALD was controlled to be three different thicknesses (50nm, 100nm, and 150nm). The structural, chemical,electrical, and optical properties of the AZO thin films were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy,field-emssion scanning electron microscopy, atomic force microscopy, Hall measurement system, and UV-Visspectrophotometry. As the thickness of the AZO thin films increased, the crystallinity of the AZO thin films gradually increased,and the surface morphology of the AZO thin films were transformed from a porous structure to a dense structure. The averagesurface roughnesses of the samples using atomic force microscopy were ~3.01nm, ~2.89nm, and ~2.44nm, respectively. Asthe thickness of the AZO filmsincreased, the surface roughness decreased gradually. These results affect the electrical and opticalproperties of AZO thin films. Therefore, the thickest AZO thin films with 150nm exhibited excellent resistivity (~7.00×10−4Ω·cm), high transmittance (~83.2%), and the best FOM (5.71×10−3Ω−1). AZO thin films fabricated using ALD may be usedas a promising cadidate of TCO materials for optoelectronic applications.

An effect of thermal annealing on activating phosphorus (P) atoms in ZnO nanorods (NR) grown using a hydrothermal process was investigated. NH4H2PO4 used as a dopant source reacted with Zn2+ ions and Zn3(PO4)2 sediment was produced in the solution. The fact that most of the input P elements are concentrated in the Zn3(PO4)2 sediment was confirmed using an energy dispersive spectrometer (EDS). After the hydrothermal process, ZnO NRs were synthesized and their PL peaks were exhibited at 405 and 500 nm because P atoms diffused to the ZnO crystal from the Zn3(PO4)2 particles. The solubility of the Zn3(PO4)2 initially formed sediment varied with the concentration of NH4OH. Before annealing, both the structural and the optical properties of the P-doped ZnO NR were changed by the variation of P doping concentration, which affected the ZnO lattice parameters. At low doping concentration of phosphorus in ZnO crystal, it was determined that a phosphorus atom substituted for a Zn site and interacted with two VZn, resulting in a PZn-2VZn complex, which is responsible for p-type conduction. After annealing, a shift of the PL peak was found to have occurred due to the unstable P doping state at high concentration of P, whereas at low concentration there was little shift of PL peak due to the stable P doping state.

In the present work, ZnO nanofibers were applied to electrode materials for the detection of cholesterol. ZnO nanofibers were synthesized using the electrospinning technique with zinc acetate as a precursor. Electrospinning-synthesized ZnO nanofibers were uniformly distributed by properly controlling the electrospinning parameters. After the calcination treatment, nanofibers of pure ZnO phase were synthesized. Then, these fibers were successfully placed on Au-coated glass substrates by dispersion of ZnO nanofibers in ethanol, dropping, and drying, in sequence. Cholesterol oxidase was then immobilized onto the surface of the ZnO nanofibers. To enhance the immobilization, Nafion was additionally applied. The sensing performances of the fabricated ZnO nanofibers-based sensors were analyzed by cyclic voltammetry in terms of cholesterol concentration ranging from 100 to 400 mg/dl. In the I-V curves, measured by cyclic voltammetry, the ZnO nanofiber-based sensor showed a proportional current behavior with cholesterol concentrations in phosphate buffered saline solution. The sensitivity was measured and found to be 30.7nA/mM·cm2, which is comparable to the values reported in the literature. After not only optimizing the shape of the ZnO nanofibers but also improving the adhesion nature between the ZnO nanofibers and the Au conducting layer, these fibers can be a good candidate for electrode materials in devices used to detect low concentrations of cholesterol in blood.

The effects of a Ni coating on the sensing properties of nano ZnO:Ni based gas sensors were studied for CH4 and CH3CH2CH3 gases. Nano ZnO sensing materials were prepared by the hydrothermal reaction method. The Ni coatings on the nano ZnO surface were deposited by the hydrolysis of zinc chloride with NH4OH. The weight % of Ni coating on the ZnO surface ranged from 0 to 10 %. The nano ZnO:Ni gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the nano ZnO : Ni sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns showed that nano ZnO : Ni powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The particle size of nano ZnO powders was about 250 nm. The sensitivity of nano ZnO:Ni based sensors for 5 ppm CH4 gas and CH3CH2CH3 gas was measured at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity of the ZnO:Ni sensor to CH4 gas and CH3CH2CH3 gas was observed at Ni 4 wt%. The response and recovery times of 4 wt% Ni coated ZnO:Ni gas sensors were 14 s and 15 s, respectively.

The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at 200˚C and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

ZnO thin films co-doped with Mg and Ga (MxGyZzO, x+y+z=1, x=0.05, y=0.02 and z=0.93) were preparedon glass substrates by RF magnetron sputtering with different sputtering powers ranging from 100W to 200W at a substratetemperature of 350oC. The effects of the sputtering power on the structural, morphological, electrical, and optical propertiesof MGZO thin films were investigated. The X-ray diffraction patterns showed that all the MGZO thin films were grown asa hexagonal wurtzite phase with the preferred orientation on the c-axis without secondary phases such as MgO, Ga2O3, orZnGa2O4. The intensity of the diffraction peak from the (0002) plane of the MGZO thin films was enhanced as the sputteringpower increased. The (0002) peak positions of the MGZO thin films was shifted toward, a high diffraction angle as thesputtering power increased. Cross-sectional field emission scanning electron microscopy images of the MGZO thin filmsshowed that all of these films had a columnar structure and their thickness increased with an increase in the sputtering power.MGZO thin film deposited at the sputtering power of 200W showed the best electrical characteristics in terms of the carrierconcentration (4.71×1020cm−3), charge carrier mobility (10.2cm2V−1s−1) and a minimum resistivity (1.3×10−3Ωcm). A UV-visible spectroscopy assessment showed that the MGZO thin films had high transmittance of more than 80% in the visibleregion and that the absorption edges of MGZO thin films were very sharp and shifted toward the higher wavelength side, from270nm to 340nm, with an increase in the sputtering power. The band-gap energy of MGZO thin films was widened from3.74eV to 3.92eV with the change in the sputtering power.

We have examined the co-doping effects of 1/2mol% NiO and 1/4mol% Cr2O3 (Ni:Cr=1:1) on the reaction,microstructure, and electrical properties, such as the bulk defects and the grain boundary properties, of ZnO-Bi2O3-Sb2O3 (ZBS;Sb/Bi=0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Ni,Cr-doped ZBS, ZBS(NiCr) varistors werecontrolled using the Sb/Bi ratio. Pyrochlore (Zn2Bi3Sb3O14), α-spinel (Zn7Sb2O12), and δ-Bi2O3 were detected for all ofcompositions. For the sample with Sb/Bi=1.0, the Pyrochlore was decomposed and promoted densification at lowertemperature by Ni rather than by Cr. A homogeneous microstructure was obtained for all of the samples affected by α-spinel.The varistor characteristics were not dramatically improved (non-linear coefficient, α=5~24), and seemed to formZni..(0.17eV) and Vo.(0.33eV) as dominant defects. From impedance and modulus spectroscopy, the grain boundaries werefound to have been divided into two types, i.e., one is tentatively assigned to ZnO/Bi2O3 (Ni,Cr)/ZnO (0.98eV) and the otheris assigned to a ZnO/ZnO (~1.5eV) homojunction.

In this study we aimed to examine the co-doping effects of 1/6mol% Co3O4 and 1/4mol% Cr2O3 (Co:Cr=1:1)on the reaction, microstructure, and electrical properties, such as the bulk defects and the grain boundary properties, of ZnO-Bi2O3-Sb2O3 (ZBS; Sb/Bi=0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Co,Cr-doped ZBS, ZBS(CoCr)varistors were controlled using the Sb/Bi ratio. Pyrochlore (Zn2Bi3Sb3O14), α-spinel (Zn7Sb2O12), and δ-Bi2O3 were formed inall systems. Pyrochlore was decomposed and promoted densification at lower temperature on heating in Sb/Bi=1.0 by Cr ratherthan Co. A more homogeneous microstructure was obtained in all systems affected by α-spinel. In ZBS(CoCr), the varistorcharacteristics were improved (non-linear coefficient, α=20~63), and seemed to form Zni..(0.20eV) and Vo.(0.33eV) asdominant defects. From impedance and modulus spectroscopy, the grain boundaries were found to be composed of anelectrically single barrier (0.94~1.1eV) that is, however, somewhat sensitive to ambient oxygen with temperature. The phasedevelopment, densification, and microstructure were controlled by Cr rather than by Co but the electrical and grain boundaryproperties were controlled by Co rather than by Cr.

We aimed to examine the co-doping effects of 1/6mol% Mn3O4 and 1/4mol% Cr2O3 (Mn:Cr=1:1) on the reaction,microstructure, and electrical properties, such as the bulk defects and grain boundary properties, of ZnO-Bi2O3-Sb2O3 (ZBS;Sb/Bi=0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Mn,Cr-doped ZBS, ZBS(MnCr) varistors werecontrolled using the Sb/Bi ratio. Pyrochlore (Zn2Bi3Sb3O14), α-spinel (Zn7Sb2O12), and δ-Bi2O3 (also β-Bi2O3 at Sb/Bi≤1.0)were detected for all of the systems. Mn and Cr are involved in the development of each phase. Pyrochlore was decomposedand promoted densification at lower temperature on heating in Sb/Bi=1.0 system by Mn rather than Cr doping. A morehomogeneous microstructure was obtained in all systems affected by α-spinel. In ZBS(MnCr), the varistor characteristics wereimproved dramatically (non-linear coefficient, α=40~78), and seemed to form Vo.(0.33eV) as a dominant defect. Fromimpedance and modulus spectroscopy, the grain boundaries can be seen to have divided into two types, i.e. one is tentativelyassigned to ZnO/Bi2O3 (Mn,Cr)/ZnO (0.64~1.1eV) and the other is assigned to the ZnO/ZnO (1.0~1.3eV) homojunction.

ZnO nanorods were successfully fabricated on Zn foil by chemical bath deposition (CBD) method. The ZnO precursor concentration and immersion time affected the surface morphologies, structure, and electrical properties of the ZnO nanorods. As the precursor concentration increased, the diameter of the ZnO nanorods increased from ca. 50 nm to ca. 150 nm. The thicknesses of the ZnO nanorods were from ca. 1.98μm to ca. 2.08μm. ZnO crystalline phases of (100), (002), and (101) planes of hexagonal wurtzite structure were confirmed by XRD measurement. The fabricated ZnO nanorods showed a photoluminescene property at 380 nm. Especially, the ZnO nanorods deposited for 6 h in solution with a concentration of 0.005M showed a stronger (101) peak than they did (100) or (002) peaks. In addition, these ZnO nanorods showed a good electrical property, with the lowest resistance among the four samples, because the nanorods were densely in contact and relatively without pores. Therefore, a ZnO nanorod substrate is useful as a highly sensitive biochip substrate to detect biomolecules using an electrochemical method.

The purpose of this study is to investigate the crystalline structure and optical properties of (GaZn)(NO) powders prepared by solid-state reaction between GaOOH and ZnO mixture under NH3 gas flow. While ammoniation of the GaOOH and ZnO mixture successfully produces the single phase of (GaZn)(NO) solid solution within a GaOOH rich composition of under 50 mol% of ZnO content, this process also produces a powder with coexisting (GaZn)(NO) and ZnO in a ZnO rich composition over 50 mol%. The GaOOH in the starting material was phase-transformed to α-, β-Ga2O3 in the NH3 environment; it was then reacted with ZnO to produce ZnGa2O4. Finally, the exchange reaction between nitrogen and oxygen atoms at the ZnGa2O4 powder surface forms a (GaZn)(NO) solid solution. Photoluminescence spectra from the (GaZn)(NO) solid solution consisted of oxygen-related red-emission bands and yellow-, green- and blue-emission bands from the Zn acceptor energy levels in the energy bandgap of the (GaZn)(NO) solid solutions.

ZnO thin films were grown on a sapphire substrate by RF magnetron sputtering. The characteristics of the thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL), and Hall effect. The substrate temperature and growth time were kept constant at 200˚C at 30 minutes, respectively. The RF power was varied within the range of 200 to 500 W. ZnO thin films on sapphire substrate were grown with a preferred C-axis orientation along the (0002) plan; X-ray diffraction peak shifted to low angles and PL emission peak was red-shifted with increasing RF power. In addition, the electrical characteristics of the carrier density and mobility decreased and the resistivity increased. In the electrical and optical properties of ZnO thin films under variation of RF power, the crystallinity improved and the roughness increased with increasing RF power due to decreased oxygen vacancies and the presence of excess zinc above the optimal range of RF power. Consequently, the crystallinity of the ZnO thin films grown on sapphire substrate was improved with RF sputtering power; however, excess Zn resulted because of the structural, electrical, and optical properties of the ZnO thin films. Thus, excess RF power will act as a factor that degrades the device characteristics.

목적: 본 연구는 기본적인 하이드로젤 콘택트렌즈 재료에 zinc oxide nanoparticles와 SiNc[silicon 2,3-naphthalocyanine bis(trihexylsilyloxide)]을 첨가제로 사용하여 친수성 콘택트렌즈 고분자를 중합하고 물리적 및 광학적 특성을 평가하였으며, 특히 자외선 투과율을 측정하여 ZnO nanoparticles와 SiNc의 자외선 차단 안의료용 렌즈 소재로의 활용도를 알아보았다. 방법: ZnO nanoparticles와 SiNc을 첨가제로 사용하였으며, HEMA, NVP, MMA, FMA와 교차결합제인 EGDMA 그리고 AIBN을 개시제로 사용하여 공중합 하였다. 또한 제조된 렌즈의 물리적 특성을 평가하기 위해 함수율, 굴절률, 인장강도 및 분광투과율을 측정하였다. 결과: ZnO nanoparticles와 SiNc을 첨가한 각각의 조합에서는 함수율과 굴절률에서 큰 차이를 나타내지 않아 ZnO nanoparticles와 SiNc이 함수율과 굴절률을 변화시키지 않는 것으로 나타났다. 또한 자외선 영역의 투과도가 현저히 감소하여 ZnO nanoparticles와 SiNc이 자외선을 차단하는 것으로 나타났다. 결론: ZnO nanoparticles와 SiNc의 경우, 함수율 및 굴절률 등의 물성을 변화시키지 않으면서 자외선을 차단할 수 있는 렌즈 재료로 유용하게 활용될 것으로 기대된다.

Nanostructures of ZnO, such as nanowires, nanorods, nanorings, and nanobelts have been actively studied andapplied in electronic or optical devices owing to the increased surface to volume ratio and quantum confinement that theyprovide. ZnO seed layer (about 40nm thick) was deposited on Si(100) substrate by RF magnetron sputtering with power of60 W for 5 min. ZnO nanorods were grown on ZnO seed layer/Si(100) substrate at 95oC for 5 hr by hydrothermal methodwith concentrations of Zn(NO3)2·6H2O [ZNH] and (CH2)6N4 [HMT] precursors ranging from 0.02M to 0.1M. We observed themicrostructure, crystal structure, and photoluminescence of the nanorods. The ZnO nanorods grew with hexahedron shape tothe c-axis at (002), and increased their diameter and length with the increase of precursor concentration. In 0.06 M and 0.08M precursors, the mean aspect ratio values of ZnO nanorods were 6.8 and 6.5; also, ZnO nanorods had good crystal quality.Near band edge emission (NBE) and a deep level emission (DLE) were observed in all ZnO nanorod samples. The highestpeak of NBE and the lower DLE appeared in 0.06 M precursor; however, the highest peak of DLE and the lower peak ofNBE appeared in the 0.02 M precursor. It is possible to explain these phenomena as results of the better crystal quality andhomogeneous shape of the nanorods in the precursor solution of 0.06 M, and as resulting from the bed crystal quality and theformation of Zn vacancies in the nanorods due to the lack of Zn++ in the 0.02 M precursor.

Two-dimensional (2D) nano patterns including a two-dimensional Bravais lattice were fabricated by laser interference lithography using a two step exposure process. After the first exposure, the substrate itself was rotated by a certain angle, 90˚ for a square or rectangular lattice, 75˚ for an oblique lattice, and 60˚ for a hexagonal lattice, and the 90˚ and laser incident angle changed for rectangular and the 45˚ and laser incident angle changed for a centered rectangular; we then carried out a second exposure process to form 2D bravais lattices. The band structure of five different 2D nano patterns was simulated by a beam propagation program. The presence of the band-gap effect was shown in an oblique and hexagonal structure. The oblique latticed ZnO nano-photonic crystal array had a pseudo-bandgap at a frequency of 0.337-0.375, 0.575-0.596 and 0.858-0.870. The hexagonal latticed ZnO nano-crystallite array had a pseudo-bandgap at a frequency of 0.335-0.384 and 0.585-0.645. The ZnO nano structure with an oblique and hexagonal structure was grown through the patterned opening window area by a hydrothermal method. The morphology of 2D nano patterns and ZnO nano structures were investigated by atomic force microscopy and scanning electron microscopy. The diameter of the opening window was approximately 250 nm. The height and width of ZnO nano-photonic crystals were 380 nm and 250 nm, respectively.

1-D ZnO nanowires have been attractive for their peculiar properties and easy growth at relatively low temperature. The length, diameter, and density of ZnO nanowires were determined by the several synthetic parameters, such as PEI concentration, growth time, temperature, and zinc salt concentration. The ZnO nanowires were grown on the<001> oriented seed layer using the hydrothermal process with zinc nitrate and HMTA (hexamethylenetetramine) and their structure and optical properties were characterized. The morphology, length and diameter of the nanowires were strongly affected by the relative and/or absolute concentration of Zn2+ and OH-1 and the hydrothermal temperature. When the concentrations of the zinc nitrate HMTA were the same as 0.015 M, the length and diameter of the nanowires were 1.97μm and 0.07μm, respectively, and the aspect ratio was 28.1 with the preferred orientation along the<001> direction. XRD and TEM results showed a high crystallinity of the ZnO nanowires. Optical measurement revealed that ZnO nanowires emitted intensive stimulated UV at 376 nm without showing visible emission related to oxygen defects.

We report the structural characterization of BixZn1-xO thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, BixZn1-xO thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure α-Bi2O3 or the tetragonal structure β-Bi2O3 by means of XRD θ-2θ measurements, as the observed diffraction peaks of the 2θ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure α-Bi2O3 at 28.064 and the reflection of the (201) plane for the tetragonal structure β-Bi2O3 at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure α-Bi2O3 phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite BixZn1-xO thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of α-Bi2O3. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the α-Bi2O3 phase in the wurtzite (Bi)ZnO matrix.

Nano-indium-coated ZnO:In thick films were prepared by a hydrothermal method. ZnO:In gas sensors were fabricated by a screen printing method on alumina substrates. The gas sensing properties of the gas sensors were investigated for hydrocarbon gas. The effects of the indium concentration of the ZnO:In gas sensors on the structural and morphological properties were investigated by X-ray diffraction and scanning electron microscopy. XRD patterns revealed that the ZnO:In with wurtzite structure was grown with (1 0 0), (0 0 2), and (1 0 1) peaks. The quantity of In coating on the ZnO surface increased with increasing In concentration. The sensitivity of the ZnO:In sensors was measured for 5 ppm CH4 gas and CH3CH2CH3 gas at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity to CH4 gas and CH3CH2CH3 gas of the ZnO:In sensors was observed at the In 6 wt%. The response and recovery times of the 6 wt% indiumcoated ZnO:In gas sensors were 19 s and 12 s, respectively.

The processes for the preparation of ZnO powder by using EAF(electric arc furnace)dust was studied by wetting method which are divided to two steps, carried out of the elution processes by various concentrations of sulfuric acid is reacted with EAF dust as the former, and the latter were performed by a number of specified processes, which are leaching process depends on various pH, cementation, ozone and heat treatment processes etc. Experimental results showed that the appropriate pH range is pH7.5~8.0 and the resulting zinc content is range of 37~38%, the residual quantities of the heavy metals are less than 3ppm individually by cementation process except Mn, even though the Mn metal could not be removed by cementation process but was removed up to 0.2ppm by the ozone process from 70ppm initially. Finally, 80.2% of ZnO was obtained by the heat treatment at 500℃.

ZnO nanorods for gas sensors were prepared by a hydrothermal method. The ZnO gas sensors were fabricated on alumina substrates by a screen printing method. The gas-sensing properties of the ZnO nanorods were investigated for CH4 gas. The effects of growth time on the structural and morphological properties of the ZnO nanorods were investigated by X-ray diffraction and scanning electron microscope. The XRD patterns of the nanocrystallized ZnO nanorods showed a wurtzite structure with the (002) predominant orientation. The diameter and length of the ZnO nanorods increased in proportion to the growth time. The sensitivity of the ZnO sensors to 5 ppm CH4 gas was investigated for various growth times. The ZnO sensors exhibited good sensitivity and rapid response-recovery characteristics to CH4 gas, and both traits were dependent on the growth time. The highest sensitivity of the ZnO sensors to CH4 gas was observed with the growth time of 7 h. The response and recovery times were 13 s and 6 s, respectively.