• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.312-317
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• 2004

High dose ($3{\times}10^{16}cm^{-2}$) implantation of Fe or Ni ions into bulk, single-crystal ZnO substrates was carried out at substrate temperature of ${\sim}350^{\circ}C$ to avoid amorphization of the implanted region. The samples were subsequently annealed at $700^{\circ}C$ to repair some of the residual implant damage. X-Ray Diffraction did not show any evidence of secondary phase formation in the ZnO. The Ni implanted samples remained paramagnetic but the Fe-implanted ZnO showed evidence of ferromagnetism with an approximate Curie temperature of ${\sim}$240K. Preliminary X-Ray Photoelectron Spectroscopy measurements showed the Fe to be ill the 2+ oxidation state. The earrler density in the implanted region still appears to be too low to support carrier-meditated origin of the ferromagnetism and formation of bound magnetic polarons may be one potential explanation for the observed magnetic properties, No evidence of the Anomalous Hall Effect could be found in the Fe-implanted ZnO, but its transport properties were dominated by the conventional or ordinary Hall effect.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.6
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• pp.253-256
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• 2004

Growth of ZnO epitaxial films have been carried out on (0001) sapphire substrates by RF magnetron sputtering. The single crystalline ZnO films of the thickness about 400-500 mm were grown successfully. At the various substrate temperatures of 200～$600^{\circ}C$, the growth behavior and optical properties of the epitaxial films have been characterized. As-grown ZnO films were annealed at the temperatures of 400, 600 and $800^{\circ}C$ respectively in order to characterize the optical properties. The carrier concentration of ZnO films annealed at the temperature of $600^{\circ}C$ was measured $2.6${\times}$10^{16}\textrm{cm}^{-3}$ by Hall measurements.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.226-226
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• 2012

The electronic and electrical properties of nickel oxide (NiO) thin films were investigated by reflection electron energy loss spectroscopy (REELS), x-ray photoelectron spectroscopy (XPS), and Hall Effect measurements. REELS spectra revealed that the band gap of the NiO thin film was increased from 3.50 eV to 4.02 eV after annealing the sample at $800^{\circ}C$. Our XPS spectra showed that the amount of Ni2O3 decreased after annealing. The Hall Effect results showed that the doping type of the sample changed from n type to p type after annealing. The resistivity decreased drastically from $4.6{\times}10^3$ to $3.5{\times}10^{-2}$ ${\Omega}{\cdot}cm$. The mobility of NiO thin films was changed form $3.29{\times}10^3$ to $3.09{\times}10^5cm^2/V{\cdot}s$. Our results showed that the annealing temperature plays a crucial role in increasing the carrier concentration and the mobility which leads to lowering resistivity of NiO thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.362-362
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• 2012

Graphene-based materials have been gaining the unprecedented academic and industrial applications, due to the unique charge transport as a new kind of 2-dimensional materials. The applications incorporate electronic devices, nonvolatile memories, batteries, chemical sensors, etc. based on the electrical, mechanical, structural, optical, and chemical features newly reported. The current work employs thermal chemical vapor deposition involving H2 and CH4, in order to synthesize the 2-dimensional graphene materials. The qualitative/quantitative characterizations of the synthesized graphene materials are evaluated using Raman spectroscopy and Hall Measurements, In particular, the effect of processing variables is systematically investigated on the formation of graphene materials through statistical design of experiments. The optimized graphene materials will be attempted towards the potential applications to flat-panel displays.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.82-91
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• 1991

Molecular beam epitaxial growth of GaAs on Si substrate and the results on its analysis are reported. Epitaxy was performed on two different types of the substrate under various grwth conditions, and was analyzed by scanning and transmission electron microscopes, X-ray diffractometer, photoluminescence and Hall measurements. GaAs epitaxial layer has better crystalline quality when it was grown on a tilt-cut substrate. The stress seems to be releaxed more easily when multi-quantum well was introduced in the buffer layer. The epilayer was doped unintentionally with Si during growth due to the diffusion of the substrate. Also observed is that the quantum efficiency of excitonic radiative recombination of the heteroepitaxy is not as good as that of the homoepitaxy in the same doping level.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.357-360
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• 2011

N-doped ZnO nanofilms were prepared by plasma enhanced atomic layer deposition method. $Zn(C_{2}H_{5})_{2}$, $O_{2}$ and $N_{2}$ were used as Zn, O and N sources, respectively, for N-doped ZnO films under variation of radio frequency (rf) power from 50-300W. Structural, optical and electrical properties of as-grown ZnO films were investigated with Xray diffraction(XRD), photoluminescence(PL) and Hall-effect measurements, respectively. Nitrogen content and p-type conductivity in ZnO nanofilms increased with the rf power.

• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.7-13
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• 2005

Bismuth thin films were prepared on glass substrate with RF magnetron sputtering and effects of substrate temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth after nucleation and the onset of coalescense of grains at 393 K were observed with field emission secondary electron microscopy. Continuous thin films could not be obtained above 473 K because of grain segregation and island formation. Hall effect measurements showed that substrate heating yields the decrease of carrier density and the increase of mobility. Resistivity of bismuth film has its minimum (about 0.7 x 10/sup -3/ Ωcm) in range of 403～433 K. Annealing of bismuth films deposited at room temperature was carried out in a radiation furnace with flowing hydrogen gas. The change of resistivity was not significant due to cancellation of the decrease of carrier density and the increase of mobility. The abrupt change of electrical properties of film annealed above 523 K was found to be caused by partial oxidation of bismuth layer in x-ray diffraction analysis.

• Advances in Energy Research
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• v.1 no.1
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• pp.79-95
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• 2013

The purpose of this paper is to investigate the surface temperatures of the shelter of three public buildings in the city of Xanthi, in northern Greece. The buildings were built in different time periods and consequently they have different technical characteristics. Respectively, we survey the three following buildings that have been built in 1880 (Municipality Hall of Xanthi), in 1970 (Municipality Amphitheatre) and in 2002 (Bank offices building). Data have been gathered by the use of thermal camera and the survey has been conducted from January up to July. The data gathered regard measurements of the surface temperature of the exterior walls of the shelters, both inside and outside. The study aims at the evaluation of the thermal behavior of the shelter of buildings, which built in different time and under different regulations. The gathered data of the surface temperatures compare the different thermal behavior of the shelter. The analysis of the results and diagrams show that the thick masonry of the traditional Municipality Hall offers an insulation that is adequate. The building of 1970, which was constructed with the previous buildings regulation, has thermal losses due to inadequate insulation. The new building of 2002 has low thermal losses.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.141-154
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• 1996

Intrinsic layers of homoepitaxial InP grown by the hydride vapor phase epitaxy (VPE) technique were investigated by Fourier-transform photoluminescence(FTPL) and variable temperature Hall measurements. The effect of process variables (i.e., source zone temperature and inlet mole fractions of HCl and $PH_{3}$) on the backgroudn impurity levels was investigated. The background carrier concentration was found to decrease with decreasing source zone temperature and increasing HCl, but was relatively independent of $PH_{3}$ for the range of mole fraction studied. The presence of background donors and acceptors was clearly verified in the FTPL spectra, and the major impurities were tentatively identified as Si donors and Zn acceptors as well as some unidentified acceptors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.472-476
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• 2007

In this study, we investigated methods for p-type ZnO deposition as well as stability enhancement of its properties. The film was prepared by co-depositing AlAs and ZnO in a RF magnetron sputtering system. Property variation was monitored with photoluminescence and Hall measurements by stressing the films at $250^{\circ}C$ for various duration upto 144 hours. Results indicated that co-deposition is a useful method for p-type ZnO preparation. In particular, pre-treatment in 30% $H_2O_2$ for 1min was observed to be effective in reducing the property variation taking place during the subsequent high temperature processes.