• Korean Journal of Materials Research
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• v.12 no.3
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• pp.195-199
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• 2002

Planar Hall effect of ferromagnetic GaMnAs thin films was investigated for the first time. The films were grown in an optimized growth condition via molecular beam epitaxy at low temperatures. For the optimization of the growth conditions, we used reflection high-energy electron diffraction, electrical conductivity, double crystal x-ray diffraction, and superconducting quantum interference device measurements techniques. We observed that the difference between the longitudinal resistance and the transverse resistance matches the planar Hall resistance. The ratio of the planar Hall resistance at saturation magnetic field to that at zero reached above 500%.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.269-276
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• 1993

Co/Pd multilayered thin films with various ratios of Co sublayers to Pd sublayers(nCo/nPd = 1/4, 2/4, 3/4, 5/4) were fabricated at different substrate temperatures($R.\;T.,\;100,\;150,\;200\;^{\circ}C$) with the conventional vacuum evaporation method, and their Hall voltage hysteresis curves were measured. These Hall curves were decomposed on the basis of the superpose of the transverse Hall effect term from the magnetizations of Co and Pd sublayers and the magnetoresistivity term, by the optimal fitting method. In the results, both of the ferromagnetic and anti ferromagnetic states coexisted through whole samples, and the uniaxial or unidirectional easy axis type Hall hysteresis curves occured were dependent upon the effects of the exchange anisotropy between both magnetic states and the domain wall pinning by the antiferromagnet inclusions.

• Journal of the Korean Magnetics Society
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• v.19 no.4
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• pp.133-137
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• 2009

$MnGeP_2$ thin films grown on GaAs exhibit room-temperature ferromagnetism with $T_C{\sim}$320 K, based on both magnetization and resistance measurements. The coercive fields at 5, 250, and 300 K are 3870, 1380 and 155 Oe, respectively. The anomalous Hall effect was observed, indicating spin polarization of the carriers. Hysteresis has been observed in both magnetoresistance and Hall measurements. The current-voltage characteristics of a $MnGeP_2$ film grown on an n-type GaAs substrate display semiconducting behavior.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.205-210
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• 2008

Titanium-doped indium oxide (ITiO) films were prepared on soda-lime glass substrate using a magnetic null discharge (MND) sputter source. The ITiO thin films containing 10wt.% Ti showed the minimum resistivity of $\rho=5.5{\times}10^{-3}{\Omega}-cm$. The optical transmittance increases from 70% at 450 nm to 80% at 700 nm in visible spectrum. Photoelectron peaks for In 3d, Ti 2p, O 1s and C1s were detected for the ITiO film in the binding energy range of 0 to 1100 eV. The surface roughness of the sample showed a change from 10 nm to 50 nm. The ITiO film used for TCO layer of DSCs exhibited an energy conversion efficiency of about 3.8% at light intensity of 100 mW/$cm^2$.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.269-274
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• 2003

The electrical, optical and structural properties of ZnNiO thin _ films deposited on Si substrates using rf-magnetron sputtering method have been investigated before and after the thermal annealing processes. The crystallinity of the ZnNiO thin film become degraded with increasing the Ni contents. This is mainly because the lattice of the thin film was expanded due to the oxygen-deficient conditions. Concerning the electrical properties of the thin film, the carrier concentration increases ($6.81\times10^{14}\textrm{cm}^{-2}$) and Hall mobility decreases (36.3 $\textrm{cm}^2$/Vㆍs) with higher doping concentration of Ni. However, the carrier concentration and Hall mobility became low ($1.10\times10^{14}\textrm{cm}^2$ and high (209.6 $\textrm{cm}^2$/Vㆍs), respectively, after the thermal annealing process at $1000 ^{\circ}C$. We also observed a strong luminescene center peaking at 546 nm in photoluminescence spectra, which was caused by a deep level center in the ZnO band gap with oxygen deficient ZnNiO structure.

• Korean Journal of Materials Research
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• v.18 no.10
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• pp.552-556
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• 2008

Modified thermal annealing was applied to the activation of the polycrystalline silicon films doped as p-type through implantation of $B_2H_6$. The statistical design of experiments was successfully employed to investigate the effect of rapid thermal annealing on activation of polycrystalline Si doped as p-type. In this design, the input variables are furnace temperature, power of halogen lamps, and alternating magnetic field. The degree of ion activation was evaluated as a function of processing variables, using Hall effect measurements and Raman spectroscopy. The main effects were estimated to be furnace temperature and RTA power in increasing conductivity, explained by recrystallization of doped ions and change of an amorphous Si into a crystalline Si lattice. The ion activation using rapid thermal annealing is proven to be a highly efficient process in low temperature polycrystalline Si technology.

• Journal of Magnetics
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• v.5 no.4
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• pp.139-142
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• 2000

The interlayer coupling between adjacent ferromagnetic layers was examined for CoFe/Cu/NiFe trilayer systems. A series of films of CoFe (20 nm)/Cu($t_{cu}$)/NiFe (20 nm) trilayers with Cu spacer thickness, $t_{cu}$, in the range of 1~10 m was deposited on Si(100) wafers at room temperature by DC magnetron sputtering. In order to understand the dependence of the magnetic interaction between ferromagnetic $Co_{90}Fe_{10}$ (wt.%) and $Ni_{81}Fe_{19}$ (wt.%) layers separated by a nonmagnetic Cu spacer on the Cu layer thickness, we investigated the derivative ferromagnetic resonance (FMR) spectra. The FMR results were analyzed using the model of Layadi and Art-man for interlayer interaction. The interlayer coupling constant decreases in an oscillatory manner as the Cu spacer thickness increases up to 10 nm and approaches zero above 10 nm. The interlayer coupling constant is positive for all samples. Hence, it seems that the exchange coupling between adjacent CoFe and NiFe layers separated by a Cu layer is ferromagnetic.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.66-67
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• 2003

Bismuth (Bi) has been an attractive materials for studying spin dependent transport properties because it shows very large magnetoresistance (MR) resulting from its highly anisotropic Fermi surface, low carrier concentrations, long carrier mean free path 1 and small effective carrier mass m*[1-3]. With all the intriguing properties, difficulty in fabrication of high quality Bi thin films may have prevented extensive application of Bi in magnetic field sensing and spin-injection devices. Previous works found that the surface roughness and small grain size in 100-200 nm of Bi thin film made by evaporation and sputtering are major causes of low MR. Although relatively higher MR in electrodeposited Bi followed by annealing was reported, it still suffers from rough sulfate roughness which is so severs that it is hardly able to make a field sensing and spin-injection device using conventional photolithography process.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.230-238
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• 2000

We present the magnetisation reversal dynamics of epitaxial Fe thin films grown on GaAs(001) and InAs(001) studied as a function of field sweep rate in the range 0.01-160 kOe/s using magneto-optic Kerr effect (MOKE). For 55 and 250 ${\AA}$ Fe/GaAs(001), we find that the hysteresis loop area A follows the scaling relation A ∝ H$\^$${\alpha}$/ with ${\alpha}$=0.03∼0.05 at low sweep rates and 0.33-0.40 at high sweep rates. For the 150 ${\AA}$ Fe/InAs(001) film, ${\alpha}$ is found to be ∼0.02 at low sweep rates and ∼0.17 at high sweep rates. The differing values of ${\alpha}$ are attributed to a change of the magnetisation reversal process with increasing sweep rate. Domain wall motion dominates the magnetisation reversal at low sweep rates, but becomes less significant with increasing sweep rate. At high sweep rates, the variation of the dynamic coercivity H$\sub$c/ is attributed to domain nucleation dominating the reversal process. The results of magnetic relaxation studies for easy-axis reversal are consistent with the sweeping of one or more walls through the entire probed region (∼100 $\mu\textrm{m}$). Domain images obtained by scanning Kerr microscopy during the easy cubic axis reversal process reveal large area domains separated by zigzag walls.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.347-347
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• 2012

Nickel Oxide (NiO) is a transition metal oxide of the rock salt structure that has a wide band gap of 3.5 eV. It has a variety of specialized applications due to its excellent chemical stability, optical, electrical and magnetic properties. In this study, we concentrated on the application of NiO thin film for transparent conducting oxide. The energy band structure, electronic and optical properties of Nickel Oxide (NiO) thin films grown on Si by using electron beam evaporation were investigated by X-Ray Photoelectron Spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and UV-Spectrometer. The band gap of NiO thin films determined by REELS spectra was 3.53 eV for the primary energies of 1.5 keV. The valence-band offset (VBO) of NiO thin films investigated by XPS was 3.88 eV and the conduction-band offset (CBO) was 1.59 eV. The UV-spectra analysis showed that the optical transmittance of the NiO thin film was 84% in the visible light region within an error of ${\pm}1%$ and the optical band gap for indirect band gap was 3.53 eV which is well agreement with estimated by REELS. The dielectric function was determined using the REELS spectra in conjunction with the Quantitative Analysis of Electron Energy Loss Spectra (QUEELS)-${\varepsilon}({\kappa},{\omega})$-REELS software. The Energy Loss Function (ELF) appeared at 4.8, 8.2, 22.5, 38.6, and 67.0 eV. The results are in good agreement with the previous study [1]. The transmission coefficient of NiO thin films calculated by QUEELS-REELS was 85% in the visible region, we confirmed that the optical transmittance values obtained with UV-Spectrometer is the same as that of estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS within uncertainty. The inelastic mean free path (IMFP) estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS is consistent with the IMFP values determined by the Tanuma-Powell Penn (TPP2M) formula [2]. Our results showed that the IMFP of NiO thin films was increased with increasing primary energies. The quantitative analysis of REELS provides us with a straightforward way to determine the electronic and optical properties of transparent thin film materials.