• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.209-214
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• 2023

The effect of thermal annealing on defect recovery of in-core neutron-irradiated 4H-SiC was investigated. Au/SiC Schottky diodes were manufactured using a 4H-SiC epitaxial wafer that was neutron-irradiated at the HANARO research reactor. The electrical characteristics of their epitaxial layers were analyzed under various conditions, including different neutron fluences (1.3 × 10¹⁷ and 2.7 × 10¹⁷ neutrons/cm²) and annealing times (up to 2 h at 1700 ℃). Capacity-voltage measurements showed high carrier compensation in the neutron-irradiated samples and a recovery tendency that increased with annealing time. The carrier density could be recovered up to 77% of the bare sample. Deep-level-transient spectroscopy revealed intrinsic defects of 4H-SiC with energy levels 0.47 and 0.68 eV below the conduction-band edge, which were significantly increased by in-core neutron irradiation. A previously unknown defect with a high electron-capture cross-section was discovered at 0.36 eV below the conduction-band edge. All defect concentrations decreased with 1700 ℃ annealing; the decrease was faster when the defect level was shallow.

• ETRI Journal
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• v.11 no.4
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• pp.75-83
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• 1989

The diffusion mechanism of Si in GaAs was investigated using different diffusion sources based on the Si-Ga-As ternary phase equilibria. The Si profiles are measured with secondary ion mass spectrometry and differ significantly for sources taken from the different phase fields in the ternary phase diagram. Neutral As vacancy diffusion is proposed for acceptor Si diffusion anneals using a Ga - Si - GaAs source. Donor Si diffusion using As - rich sources and a Si -GaAs tie line source shows concentration dependent diffusion behavior. Concentration dependent diffusion coefficients of donor Si for As - rich source diffusion were found to be related to net ionized donor concentration and showed three regimes of different behavior: saturation regime, intermediate regime,and intrinsic regime. Ga vacancies are proposed to be responsible for donor Si diffusionin GaAs: $Si_Ga^+V_Ga^-$ (donor Si -acceptor Gavacancy) complex for the extrinsic regime and neutral $V_G$a, for the intrinsic regime.The Si - GaAs tie line source resulted in two branch profiles, intermediate between the As - rich and the Ga - rich source diffusion cases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.327-340
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• 1996

In this study, a series of $LiNbO_{3}$ crystals with different [Li]/[Nb] ratios, congruent $LiNbO_{3}$ crystals with doped Mg and with Mg and codoped with Mn were grown by the Czocharalski method. These were investigated by UV and IR spectrophotometry. Stoichiometry dependences of the UV absorption edge and the $OH^{-}$ absorption spectra were studied with different [Li]/[Nb] ratios. The position of the UV absorption edge adn the shape and peak point of the $OH^{-}$ absorption spectra changed monotonously upto a critical concentration of Mg ions. The mechanism of the incorporation of Mg ions changes at this concentration. The decomposition of the $OH^{-}$ absorption spectra using a Gaussian lineshape function showed that in Li-deficient crystals the absorption spectra consist of five components in contrast to more or less perfect stoichiometric crystals which reveal to three components. On the basis of these results, the intrinsic and the extrinsic defect structure models in $LiNbO_{3}$ crystals were examined. The behaviour of $\nu$ (OH) reflects the defect structure and supports the Li-site vacancy model as the intrinsic defect structure model and the corresponding extrinsic defect model. A brief discussion is also given of the behaviour of $\nu$ (OH) in $LiNbO_{3}$ crystals simultaneously doped with several kinds of impurity.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.248-256
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• 1992

This paper has reviewed some of the basic principles that underlie the field of defect chemistry in simple ATi$O_3$(A=Ca, Sr, Ba) perovskites. Frenkel defects in perovskite structure is very much unlikely, and Schottky defects and intrinsic electronic defects in undoped materials are negligibly small compared with background acceptor impurities. The electrical properties of perovskite ceramics are dependent on the aliovalent impurities. Since perovskite structure is a ternary system, the stoiohiometry between cations as well as cation-anion ratio will affect defect structure and electrical properties. BaTi$O_3$and SrTi$O_3$show a limited deviation from the cation stoichiometry while CaTi$O_3$has significant excess CaO and Ti$O_2$solubility.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.931-937
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• 1998

The electrical conductivity of undoped mtile was measured in the oxygen partial pressure range of $1~10{-23}$atm and temperature range of $700~1300^{\circ}C$ to investigate the defect types and the electrical properties. The data(logu/logPoz) were divided into the five regions. Therefore the five dominant defect types such as $Ti_nO_{2n-1}$, Ti, Vo, Vo due to impurity, and n-p transition or p-type conduction with the Poz and the temperature were proposed. The formation enthalpies calculated from these experimental results were found to be 10.2eV for Ti, and 4. 92eV for Vo in intrinsic range.

• Current Photovoltaic Research
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• v.1 no.2
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• pp.115-121
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• 2013

ZnO film has been used for CIGS solar cells as a buffer layer as itself or by doping Mg and Sn; ZnO film also has been used as a transparent conducting layer by doping Al or B for solar cells. Since ZnO itself is a host material for many applications it is necessary to understand the electrical and optical properties of ZnO film itself with various preparation conditions. We prepared ZnO films by converting ZnS precursor into ZnO film by thermal annealing. ZnO film was formed at low temperature as low as $500^{\circ}C$ by annealing a ZnS precursor layer in air. In the air annealing, the electrical resistivity decreased monotonically with increasing annealing temperature; the intensity of the green photoluminescence at 505 nm increased up to $750^{\circ}C$ annealing. The electrical resistivity further decreased and the intensity of green emission also increased in reducing atmospheres. The results suggest that deep-level defects originated by oxygen vacancy enhanced green emission, which reduce light transmittance and enhance the recombination of electrons in conduction band and holes in valence. More oxidizing environment is necessary to obtain defect-free ZnO film for higher transparency.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.157-161
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• 2019

Independent control of electronic and thermal transport behaviors is one of the most effective approaches to enhance the performance of thermoelectric materials. To address this, many researches on the relationship between defect structures and thermoelectric properties have been carried out since defects are intrinsic ingredients of polycrystalline materials. Recently, experimental results of simultaneously improved electronic and thermal transport properties have been reported via the formation of 0-dimensional point defects. Here, theoretical backgrounds to the engineering of electronic and thermal transport behaviors by the formation of point defects are discussed and related experimental considerations are also presented in order to provide a practical guide for the development of highperformance thermoelectric materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1034-1037
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• 2003

Microcrystalline silicon(c-Si:H) thin-film solar cells are prepared with intrinsic Si-layer by hot wire CVD. The operating parameters of solar cells are strongly affected by the filament temperature ($T_f$) during intrinsic layer. Jsc and efficiency abruptly decreases with elevated $T_f$ to $1400^{\circ}C$. This deterioration of solar cell parameters are resulted from increase of crystalline volume fraction and corresponding defect density at high $T_f$. The heater temperature ($T_h$) are also critical parameter that controls device operations. Solar cells prepared at low $T_h$ ($<200^{\circ}C$) shows a similar operating properties with devices prepared at high $T_f$, i.e. low Jsc, Voc and efficiency. The origins for this result, however, are different with that of inferior device performances at high $T_f$. In addition the phase transition of the silicon films occurs at different silane concentration (SC) by varying filament temperature, by which highest efficiency with SC varies with $T_f$.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1598-1600
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• 2003

Microcrystalline silicon(c-Si:H) thin-film solar cells are prepared with intrinsic Si-layer by hot wire CVD. The operating parameters of solar cells are strongly affected by the filament temperature ($T_f$) during intrinsic layer. Jsc and efficiency abruptly decreases with elevated $T_f$ to $1400^{\circ}C$. This deterioration of solar cell parameters are resulted from increase of crystalline volume fraction and corresponding defect density at high $T_f$ The heater temperature ($T_h$) are also critical parameter that controls device operations. Solar cells prepared at low $T_h$ (<$200^{\circ}C$) shows a similar operating properties with devices prepared at high $T_f$, i.e. low Jsc, Voc and efficiency. The origins for this result, however, are different with that of inferior device performances at high $T_f$. In addition the phase transition of the silicon films occurs at different silane concentration (SC) by varying filament temperature, by which highest efficiency with SC vanes with $T_f$.

• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.128-134
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• 1982

The electrical conductivity of n-type polycrystalline MnOx-Ti$O_2$ system containing 0.40, 0.80, and 1.60 mol % of manganese oxide has been measured from 100 to 400$^{\circ}$C and 1100 to 1300$^{\circ}$C under oxygen partial pressures of$10^{-8}\;to\;10^{-1}$ atm. Plots of log conductivity vs. reciprocals of absolute temperature at constant $Po_2$'s are found to be linear with an inflection, and the activation energies obtained from the slopes appear to be an enough average 0.18eV for the extrinsic and 3.70eV for the intrinsic. The log $\sigma$ vs. log $Po_2$ are found to be linear at $Po_2$'s of $10^{-8}\;to\;10^{-1}$atm. The conductivity dependences on $Po_2$at the two temperature regions are closely approximated by $\sigma{\propto}$Po_2$-1}6$ for the extrinsic and $${\sigma}{\propto}Po_2^{-1}4}$$ for the intrinsic, respectively. The predominant defects are believed to be Vo-2e' and $Ti^3$${\cdot}$interstitial at the extrinsic and intrinsic. From the interpretations of conductivity dependences on temperature and$Po_2$ , the conduction mechanisms and possible band models are proposed.