• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.263-271
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• 1994

We have produced $Co_{1-x}Pt_{x}(X\;=\;0.53\;and\;0.75)$ alloy films by DC magnetron sputtering at various substrate temperatures and sputtering pressures. Sputter-deposited Co-Pt alloy films showed a strong (111) texture, and the degree of (111) texture of the as-deposited film was found to depend on the substrate temperature and Ar pressure. However, we observed that the degree of (111) texture did not affect the magnetic properties. In addition, we have investigated the effect of heat-treatment on magnetic properties of these films. While the magnetic properties of the $Co_{0.25}Pt_{0.75}$ alloy films showed no noticeable changes, the coercivities and the squarenesses of the $Co_{0.47}Pt_{0.53}$ alloy films were drastically increased by annealing. Structural analysis using transmission electron microscopy(TEM) and x-ray diffractornetry(XRD) revealed that $CoPt(L1_{0})$ and $CoPt_3(L1_{2})$ ordered phases, respectively, were formed, each with a strong (111) texture. By comparing the magnetic properties between $CoPt(L1_{0})$ and $CoPt_3(L1_{2})$ ordered phases in relation to the atomic arrangements in a unit cell, we conclude that the magnetic anisotropy in the Co-Pt alloy system depends mainly on the atomic arrangements of Co and Pt.

• Journal of the Korean Magnetics Society
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• v.17 no.4
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• pp.162-165
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• 2007

We investigated the effects of the capping layer materials on the crystallization of the amorphous top-CoFeB (t-CoFeB) electrode and the magnetoresistance properties of the magnetic tunnel junctions (MTJs). When the hcp(002)-textured Ru capping layer was used, the amorphous t-CoFeB was crystallized to bcc-CoFe(110). The CoFe(110)/Ru(002) texture relation can be minimized the lattice mismatch down to 5.6%. However, when the fine polycrystalline but almost amorphous TiAl or amorphous ZrAl were used, the amorphous t-CoFeB was crystallized to bcc-CoFe(002). When the amorphous capping materials were used, the evolution of the t-CoFeB texture was affected mainly by the MgO(001) texture. Consequently, the M ratios of the annealed MTJ capped with the ZrAl and TiAl (72.7 and 71.8%) are relatively higher than that of the MTJ with Ru capping layer (46.7%). In conclusions, the texture evolution of the amorphous t-CoFeB during the post deposition annealing could be controlled by the crystallinity of the adjacent capping layer and in turn, it affects the TMR ratio of MTJs.

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.165-172
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• 1998

Epitaxial ultrathin films of $CoSi_2$ and double heteroepitaxial structure of Si/$CoSi_2$/Si(lll) were prepared on Si(111)-$7\times{7}$ substrate by in situ solid-phase epitaxy in a ultrahigh vacuum(LHV). The phase, chemical composition, crystallinity, and the microsructure of the Si/$CoSi_2$/Si(lll) interface were investigated by 2-MeV $^4He^{++}$ ion backscattering spectrometry, X-ray diffraction, and high-resolution transmission electron microscopy. The growth mode of the Co film was the Stransky-Krastanov type with texture when the substrate temperature was room temperature. A-type $CoSi_2$ ultrathin film was grown by deposition of about 50A Co on Si(ll1)-$7\times{7}$ substrate followed by in situ annealing at $700^{\circ}C$ for 10 min. The matching face relationships were $CoSi_2$[110]//Si[110] and $CoSi_2$(002)//Si(002) with no misorientation angle. The A-type $CoSi_2$/Si(lll) interface was abrupt and coherent. The best epi-Si/epi-$CoSi_2$2(A-type)/Si(lll) structure was obtained by deposition of Si film on the CoSii at $500^{\circ}C$ followed by in situ annealing at $700^{\circ}C$ for 10 min in UHV.

• Journal of Magnetics
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• v.3 no.2
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• pp.44-48
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• 1998

Scanning Electron Microscopy with Polarization Analysis (SEMPA) was used to image the surface magnetic domain structure of the 100 ${\mu}{\textrm}{m}$ thick 3% Si-Fe sheet. The thin-gauged 3% Si-Fe strips with magnetic induction ($B_{10}$) from 1.98 to 1.57 Tesla were prepared via conventional metallurgical processes including melting, hot-and cold-rolling, intermediate annealing and final annealing. Using SEMPA, it was observed that the $B_{10}$ (1.98 T) Tesla sample was almost composed of 180$^{\circ}$ stripe domains which are parallel to rolling direction. On the other hand the 3% Si-Fe sheet with $B_{10}$ (1.57 T) Tesla was composed of large 180$^{\circ}$stripe domains that are slanted about 30$^{\circ}$to the rolling direction and complex magnetic domain structures like tree and zigzag pattern. The 180$^{\circ}$stripe domains, which covered a major part of the sample, had (110)<001> Goss texture parallel to the rolling direction. The domain walls between 180$^{\circ}$stripe domains were the conventional Bloch type walls. On the other hand, the 90$^{\circ}$domains, which covered minor part on edge of the sample, were observed in (200) grains. The domain walls between 90$^{\circ}$domains were the Neel type walls. In high magnification, the elliptical singularity at the Neel walls was clearly observed.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.460-468
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• 2022

Due to its high electrical conductivity, low contact resistance, good weldability and high corrosion resi-stance, gold is widely used in electronic components such as connectors and printed circuit boards (PCB). Gold ion salts currently used in gold plating are largely cyan-based salts and non-cyanic salts. The cya-nide bath can be used for both high and low hardness, but the non-cyanide bath can be used for low hardness plating. Potassium gold cyanide (KAu(CN)₂) as a cyanide type and sodium gold sulfite (Na₃[Au(SO)₃]₂) salt as a non-cyanide type are most widely used. Although the cyan bath has excellent performance in plating, potassium gold cyanide (KAu(CN)₂) used in the cyan bath is classified as a poison and a toxic substance and has strong toxicity, which tends to damage the positive photoresist film and make it difficult to form a straight side-wall. There is a need to supplement this. Therefore, it is intended to supplement this with an eco-friendly process using sodium sulfite sodium salt that does not contain cyan. Therefore, the main goal is to form a gold plating layer with a controllable hardness using a non-cyanide gold plating solution. In this study, the composition of a non-cyanide gold plating solution that maintains hardness even after annealing is generated through gold-palladium alloying by adding thallium, a crystal regulator among electrolysis factors affecting the structure and hardness, and changes in plating layer structure and crystallinity before and after annealing the correlation with the hardness.

• Journal of Magnetics
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• v.11 no.1
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• pp.25-29
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• 2006

Recent experiments have demonstrated high TMR ratios in MTJs with the MgO barrier [1,2]. The CoFeB/MgO/CoFeB junctions showed better properties than the CoFe/MgO/CoFe junctions because the MgO layer had a good crystalline structure with (001) texture and smooth and sharp interface between CoFeB/MgO [3]. The amorphous CoFeB with 20 at%B starts the crystallization at $340^{\circ}C$ [4] and this crystallization of the CoFeB helps obtaining the high TMR ratio. In this work, the compositional changes in the MgO barrier and at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization were studied in annealed MTJs. XPS depth profiles were utilized. TEM analyses showed that the MgO barrier had (100) texture on CoFeB in the junctions. B in the bottom CoFeB layer diffused into the MgO barrier and B-oxide was formed at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.556-562
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• 2011

We carried out this study to evaluate the grain refining in and the mechanical properties of alloys that undergo severe plastic deformation (SPD). Conventional rolling (CR) and cross-roll rolling (CRR) as SPD methods were used with Ni-20Cr alloy as the experimental material. The materials were cold rolled to a thickness reduction of 90% and subsequently annealed at $700^{\circ}C$ for 30 min to obtain a fully recrystallized microstructure. For the annealed materials after the cold rolling, electron back-scattered diffraction (EBSD) analysis was carried out to investigate the grain boundary characteristic distributions (GBCDs). The CRR process was more effective when used to develop the grain refinement relative to the CR process; as a result, the grain size was refined from $70{\mu}m$ in the initial material to $4.2{\mu}m$ (CR) and $2.4{\mu}m$ (CRR). These grain refinements have a direct effect on improving the mechanical properties; in this case, the microhardness, yield and tensile strength showed significant increases compared to the initial material. In particular, the CRR-processed material showed more effective values relative to the CR-processed materials. The different texture distributions in the CR (001//ND) and CRR (111//ND) were likely the cause of the increase in the mechanical properties. These findings suggest that CRR can result in materials with a smaller grain size, improved texture development and improved mechanical properties after recrystallization by a subsequent annealing process.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.339-339
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• 2002

In the RABiTS approach to coated conductor development, successful (both economic and technological) depends on the refinement and optimization of each of three important components: the metal tape substrate, the buffer layer(s), and the HTS layer. Here we will report on the ORNL approach and progress in each of these areas. - Most applications will require metal tapes with low magnetic hysteresis, mechanical strength, and excellent crystalline texture. Some of these requirements are competing. We report on progress in obtaining a good combination of these characteristics on metal alloys of Ni-Cr and Ni-W. - The deposition of appropriate buffer layers is a crucial step. Recently, base research has shown that the presence of a stable sulfur superstructure present on the metal surface is needed for the nucleation and epitaxial growth of vapor-deposited seed buffer layers such as YSZ, CeO$_2$ and SrTiO$_3$. We report on the details and control of this superstructure for nickel tapes, as well as recent results for Cu and Ni-13%Cr. - Processes for deposition of the HTS coating must economically provide large values of the figure-of-merit for conductors, current x length. At ORNL, we have devoted efforts to a precursor/post-annealing approach to YBCO coatings, for which the deposition and reaction steps are separate. We describe motivation for and progress toward developing this approach. - Finally, we address some issues for the implementation of coated conductors in real applications, including the need for texture control and electrical stabilization of the HTS coating.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.901-908
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• 1999

Effects of LPMOCVD process parameters on the properties of TiO2 thin film were investigated. Depositions were made in the range of temperature 300-67$0^{\circ}C$ with various TTIP(Titanium Tetraisopropoxide) concentrations by contrlling bubbler temperature(40-8$0^{\circ}C$) and/or flow rate(30-90 sccm). Post annealing treatments were carried out at 500-80$0^{\circ}C$ range in the air. Films deposited at 40$0^{\circ}C$ have denser morphology than those of films deposited at 50$0^{\circ}C$ and $600^{\circ}C$ due to slower deposition rate. Bubbler temperature can affect on the deposition rate in mass transfer controlled regime such as 50$0^{\circ}C$ or higher but not below 50$0^{\circ}C$ where surface reaction rate becomes important. On the contrary for films deposited above 50$0^{\circ}C$ flow rate can raise deposition rate but eventually saturate it at the 50 sccm and above due to retarded adhesion of decomposed species. But for films deposited at 40$0^{\circ}C$ deposition rate increases stadily with flow rate. As the film becomes more porous A(200) texture can not be developed and AnataselongrightarrowRutile transition kinetics increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.519-522
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• 2002

Ag (silver) can be used for YBa$_2$Cu$_3$O$\_$7-$\delta$/(YBCO) coated conductor tape as the substrate on which YBCO can be deposited directly because of the chemical compatibility of Ag with YBCO. We have fabricated rolled Ag tapes with various total reduction ratios and different thicknesses. As-rolled Ag tape was recrystallized at 750$^{\circ}C$ for 30min in air and vacuum of 10$\^$-3/ torr. The orientation distribution functions (ODF) calculated from three x-ray pole figures of as-rolled and recrystallized tapes were analysed. As the total reduction ratio increased from 94 to 98%, the development of {110}texture of as-rolled Ag improved. Under the present experimental condition, maximum {110}ODF value of Ag tape was obtained for the sample with 94% total reduction ratio which was recrystallized at 750$^{\circ}C$ for 30min in vacuum of 10$\^$-3/ torr.