• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.229-230
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• 2008

We have studied the structural and optical properties of ZnO thin film deposited on glass by RF magnetron sputtering as functions of working pressures. The grain sizes were decreased as the working pressures were increased. The average optical transmissions over all exceeded 80% for ZnO films deposited in 20, 25 and 300m torr working pressures. And the transmission spectra patterns were almost same. While the transmission spectra pattern of ZnO film deposited in 35nm torr was different with other spectra patterns obtained in 20, 25 and 30nm torr working pressures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1043-1047
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• 2005

To investigate the electrical properties of the ZnO films which are interested in the next generation of short wavelength LEDs and Lasers, our ZnO thin films were deposited by RF sputtering system. At sputtering process of ZnO thin films, substrate temperature, work pressure respectively is $300^{\circ}C$ and 5.2 mTorr, and the purity of target is ZnO 5N. The thickness of ZnO thin films was about $2.1\;{\mu}m$ at SEM analysis after sputtering process. Phosphorus (P) and arsenic (As) were diffused into the undoped ZnO thin films sputtered by RF magnetron sputtering system in ampoule tube which was below $5\times10^{-7}$ Torr. The dopant sources of phosphorus and arsenic were $Zn_3P_2$ and $ZnAs_2$. Those diffusion was perform at 500, 600, and $700^{\circ}C$ during 3 hr. We found the diffusion condition of the conductive ZnO films which had n- and p-type properties. Our ZnO thin film has not only very high carrier concentration of above $10^{17}/cm^3$ but also low resistivity of below $2.0\times10^{-2}\;{\Omega}cm$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.532-542
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• 1996

The electrical and optical properties of the annealed $LiNbO_{3}$ single crystal with congruently melting composition and MgO or ZnO doped $LiNbO_{3}$ single crystal grown by the FZ method. The electrical and optical properties such as electrical conductivity, dielectric constant (Curie temperature), electro-mechanical coupling factor, optical transmittance and refractive indices of the grown crystals were measured and the nonlinear refractive indices of the grown crystals were calculated theoretically. The doping effects of MgO and ZnO were investigated by comparing the electrical and optical properties of the undoped $LiNbO_{3}$ single crystal and those of the $LiNbO_{3}$ single crystals doped with MgO or ZnO.

• Journal of Sensor Science and Technology
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• v.15 no.2
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• pp.84-89
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• 2006

Highly concentrated p-type ZnO thin films can be obtained by doping of N, P and As elements. In this study, undoped ZnO buffer layers were prepared on a (0001) sapphire substrate by a ultra high vaccum pulsed laser deposition(UHV-PLD) method. ZnO buffer layers were deposited with various deposition temperature($400{\sim}700^{\circ}C$) at 350 mtorr of oxygen working pressure. Arsenic doped(1 wt%) ZnO thin films were deposited on the ZnO buffer layers by UHV-PLD. Crystallinity of the samples were evaluated by X-ray diffractometer and scanning electron microscopy. Optical, electrical properties of the ZnO thin films were estimated by photoluminescence(PL) and Hall measurements. The optimal condition of the undoped ZnO buffer layer for the deposition of As-doped ZnO thin films was at $600^{\circ}C$ of deposition temperature.

• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1320-1325
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• 1998

ZnGa2O4: Mn phosphors were prepared by a new chemical process, and their photoluminescence and electron paramagnetic resonance characteristics were investigated. The chemical method showed a low temperature formation of phosphors and a rod-type shape of particles. The strong ultraviolet emission was observed in the undoped ZnGa2O4 phosphor, while strong green emission in the Mn2+-activated ZnGa2O4 phosphor. The green emission intensity of the phosphor prepared by the chemical method was much stronger than that prepared by the conventional method. This difference with preparation methods was interpreted as due to the difference in the distribution of Mn2+ in the host lattice. From EPR results, it was explained that the line intensity of the undoped ZnGa2O4 is associated with the electrical conductivity of this material and the concentration quenching of green luminescence of ZnGa2O4: Mn at higher Mn2+ concentration is attributed to the coupling by exchange interaction between Mn2+ ions.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.351-355
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• 2010

Transparent conducting aluminum-doped ZnO thin films were deposited using a sol-gel process. In this study, the important deposition parameters were investigated thoroughly to determine the appropriate procedures to grow large area thin films with low resistivity and high transparency at low cost for device applications. The doping concentration of aluminum was adjusted in a range from 1 to 4 mol% by controlling the precursor concentration. The annealing temperatures for the pre-heat treatment and post-heat treatment was $250^{\circ}C$ and 400-$600^{\circ}C$, respectively. The SEM images show that Al doped and undoped ZnO films were quite uniform and compact. The XRD pattern shows that the Al doped ZnO film has poorer crystallinity than the undoped films. The crystal quality of Al doped ZnO films was improved with an increase of the annealing temperature to $600^{\circ}C$. Although the structure of the aluminum doped ZnO films did not have a preferred orientation along the (002) plane, these films had high transmittance (> 87%) in the visible region. The absorption edge was observed at approximately 370 nm, and the absorption wavelength showed a blue-shift with increasing doping concentration. The ZnO films annealed at $500^{\circ}C$ showed the lowest resistivity at 1 mol% Al doping.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.327-327
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• 2009

ZnO with a large band gap (~3.37 eV) and exciton binding energy (~60 meV), is suitable for optoelectronic applications such as ultraviolet (UV) light emitting diodes (LEDs) and detectors. However, the ZnO-based p-n homojunction is not readily available because it is difficult to fabricate reproducible p-type ZnO with high hall concentration and mobility. In order to solve this problem, there have been numerous attempts to develop p-n heterojunction LEDs with ZnO as the n-type layer. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducible availability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices. In particular, a number of ZnO films show UV band-edge emission with visible deep-level emission, which is originated from point defects such as oxygen vacancy, oxygen interstitial, zinc interstitial[1]. Thus, defect-related peak positions can be controlled by variation of growth or annealing conditions. In this work, the undoped ZnO film was grown on the p-GaN:Mg film using RF magnetron sputtering method. The undoped ZnO/p-GaN:Mg heterojunctions were annealed in a horizontal tube furnace. The annealing process was performed at $800^{\circ}C$ during 30 to 90 min in air ambient to observe the variation of the defect states in the ZnO film. Photoluminescence measurements were performed in order to confirm the deep-level position of the ZnO film. As a result, the deep-level emission showed orange-red color in the as-deposited film, while the defect-related peak positions of annealed films were shifted to greenish side as increasing annealing time. Furthermore, the electrical resistivity of the ZnO film was decreased after annealing process. The I-V characteristic of the LEDs showed nonlinear and rectifying behavior. The room-temperature electroluminescence (EL) was observed under forward bias. The EL showed a weak white and strong yellowish emission colors (~575 nm) in the undoped ZnO/p-GaN:Mg heterojunctions before and after annealing process, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2005.08a
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• pp.108-108
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• 2005

• Korean Journal of Materials Research
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• v.2 no.5
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• pp.360-365
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• 1992

Ga-doped polycrystalline ZnO films on glass substrates were prepared by sputtering the targets, which had been prepared by sintering discs consisting of ZnO powder and various amounts of G$a_2O_3$, to investigate the effects of gallium doping and sputtering conditions on electrical properties. Optimizing the RF power density, argon gas pressure and gallium content, transparent Ga-doped ZnO films with resistivity less than 1$0^{-3}$ohm-cm are obtained. Electron concentration of undoped and Ga-doped ZnO films are order of $10^{18}$, $10^{21}$/c$m^2$respectively. After heat treatment in air and $N_2atmosphere, $ the resistivity of Ga-doped ZnO films increases by about two orders of magnitude. The optical transmission is above 80% in the visible range and the optical band widens as the Ga content increases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.368-376
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• 1996

$LiNbO_{3}$ single crystals (undoped, 5 mol% MgO-doped and 5 mol% ZnO-doped) were grown by the floating zone method which has the characteristics of a compositional homogeneity and uniform distribution of the dopants. The optimum growth condition was established experimentally and the defect structures such as domain structure, dislocation structure, slip band, and microtwins were characterized using a microscopic method.