• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.210-214
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• 2007

We have studied optical transitions of Gd-implanted GaN epilayers. Photoluminescence transition intensity at 590 nm at T=5 K diminishes and its center position moves to short avelength (blue shift) with increasing temperature up to 200 K. Above T=200 K, the transition intensity increases with increasing temperature while the center position remains the same. We believe that such anomalous optical transition behavior is due to the effect of rare-element in the semiconductor host material and lattice imperfection which was occurred during the implantation process well as.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.341-344
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• 1999

We reported compositional separation(CS) into Co-enriched and Cri-enriched components inside the grains of Co-Cr based thin films prepared by rf sputtering. CS strongly depends on the sputtering conditions of substrate temperature and target composition. Tuning the microstructure of the Co-Cr films is important in order to employ the CS for high-density magnetic recording. We investigated the origin of CS from thermodynamic viewpoint. We employ a spinodal decomposition-like model to describe the origin of the CS in Co-Cr films. We consider the total free energy of the Co-Cr films as the sum of several free energies of; 1) thermodynamic mixing entropy of a binary solid solution, 2) magnetic ordering interaction(MOI) energy below the Curie temperature, and 3) excess interaction energy(XS) caused by the sputtering process as a function of temperature and composition. Those energies distorted the total free energy like the spinodal decomposition and caused the compositionally separated fine microstructure inside the grains. If the second derivative of the total free energy with respect to Cr composition becomes negative at a given substrate temperature, we may observe a metastable compositional separation inside the Co-Cr alloy films. We expect to exploit the microstructure of CS for ultra-high density magnetic recording.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.155-159
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• 2003

Polycrystalline $Ti_{1-x}Co_xO_2$ thin films on $SiO_2$ (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition. Microstructures and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed $Ti_{1-x}Co_xO_2$ thin films with $x{\leq}0.05$ showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the $Ti_{1-x}Co_xO_2$ (TCO) phases. On the other hand, in case of thin films above x=0.05, Co clusters formed in a homogeneous $Ti_{1-x}Co_xO_2$ Phase, and the overall ferromagnetic (FM) properties depended on both $FM_{TCO}$ and $FM_{Co}$. Co clusters with about 10nm-150nm size decreased the value of Mr (the remanent magnetization) and increased the saturation magnetic field.

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.57-61
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• 2002

In this study, the effect of ammonium chloride on the electrodeposition of CoP magnetic alloy film was investigated. The correlation between the electrodeposition condition and the magnetic properties was tried to elucidate by the electro- analytical tests such as cyclic voltammetry. It was observed that the magnetic properties of the films were varied extensively with the ammonium chloride contents in the solution. The reason why the magnetic properties of the films were varied with the addition of ammonium chloride was thought that the addition of ammonium chloride controlled the electrocrystallization of CoP kinetically by charge transfer and increased the grain size and the orientation factor. This may cause the variation of the magnetic properties of CoP films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.105-109
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• 2002

The wet etching characteristics of magnetic materials such as NiFe and CoFe were investigated in terms of etch rate and etch profile by using variouus etching solutions (etchants). Among the various etching solutions, HNO$_3$, HCl, and H$_2$SO$_4$were selected for the etching of magnetic materials and showed distinct results. In the case of NiFe films, faster etch rate were obtained with HNO$_3$solution. When NiFe films ere etched with HCl solution, white etch residues were found on the surface of etched films. From FEAES analysis of these etch residues, they were proved to be by-product from the reaction of NiFe with Cl element. CoFe thin films showed the similar trend to the case of NiFe films. They were etched fast in HNO$_3$ solution while Chl solution represented slow etching. The etch profiles of CoFe films showed smooth etch profile but revealed the partial etching around the patterns in HNO$_3$solution of relatively high concentration. It was observed that the etched surface was clean and smooth, and that white etch residues were also remained on the etched films.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.74-78
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• 1998

High quality single cystal Bi, Gd : YIG films have been grown on GCMZGG wafers by LPE techniques. The magnetic, magneto-optic and sensor properties of the films have been investigated. The films showed high linearity with almost no hystersis, saturaton Faraday rotation angle of 45$^{\circ}$, saturation field of about 1.1 kOe, Verdet constant of 5.6$^{\circ}$ /(Oe, cm) at room temperature, and temperture coefficient of Verset constant of 0.0056$^{\circ}$ /(Oe, cm, $^{\circ}C$) in the range of 0 $^{\circ}C$~100 $^{\circ}C$. The sensor made out of the film exhibited highly linear signal in the range of 3 A-300 A.

• Journal of the Korean Magnetics Society
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• v.15 no.6
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• pp.303-306
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• 2005

Effect of a ferromagnetic layer thickness on a narrow domain wall width is investigated. It is found that the narrow domain wall is formed in ferromagnetic/nonmagnetic/ferromagnetic multi layer structure with a loc at interlayer exchange coupling, and that the width of the narrow domain wall is affected by the ferromagnetic layer thickness. We performed micromagnetics simulations for the $Fe_1/Cr/Fe_2$ system with the local interlayer exchange coupling, with fixed thickness (20-nm) of $Fe_2$ layer and various $Fe_1$ layer thickness (1, 2, 4, and 6 nm). Consequently, we confirmed that the thinner the $Fe_1$ layer thickness, the thinner the width of the domain wall is formed, because of the surface energy nature of the interlayer exchange coupling.

• Journal of the Korean institute of surface engineering
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• v.50 no.2
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• pp.119-124
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• 2017

Due to the high saturation magnetization (~2.4 T), $Fe_{16}N_2$ is interesting for the thin film application such as an actuator, data record storage and sensor etc. In this study, Fe-N thin films were deposited on Si(001) substrate with various power and deposition time by DC magnetron sputtering, in order to get high portion of $Fe_{16}N_2$ phase. Surface morphology, phase formation and magnetic properties were measured. As a result, Saturation magnetization and Remanence magnetization reach to ~2.45 T and 1.41T. But, Coercivity was not enough in this experiments. Its value lower than 100 Oe. Which is very close to theoretical value.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.963-968
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• 2000

Magnetic properties and microstructures of Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films were investigated as a function of addition of element Ag, (X$\_$Ag/=0 to 6 at.%) and annealing temperature, T$\_$a/=300$\^{C}$ to 600$\^{C}$. In the case of adding Ag, magnetic properties of Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films were improved than those of Ag-free Fe$\_$93/Zr$_3$B$_4$thin films. The prominent soft magnetic properties with coercivity of 1.1 Oe, saturation magnetization of 2.2 T and permeability of 5400 at 50㎒ were obtained from Fe$\_$88/Zr$_3$B$_4$Ag$\_$5/ thin film annealed was lower than that of Fe-base or Co-base thin films reported previously. Such enhanced magnetic properties are presumably attributed to the format in ultra fine grains. Also, the reduced eddy current loss in the annealed sample is due to refined micro magnetic domains with increasing the amount of Ag in Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films.

• 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.