• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.199-212
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• 2023

Diffusion is a powerful tool to understand geological processes recorded in terrestrial rocks as well as extraterrestrial materials. Since the diffusive exchange of elements or isotopes may have occurred differently in the solar nebula (high temperature and rapid cooling) and on the parent bodies (fluid-assisted thermal metamorphism at relatively low temperature), it is particularly important to model elemental or isotopic diffusion profiles within the mineral grains to better understand the evolution of the early solar system. A numerical model with the finite difference method for the fast grain boundary diffusion was established for the exchange of elements or isotopes between constituent minerals in a closed system. The fast grain boundary diffusion numerical model was applied to 1) ²⁶Mg variation in plagioclase of an amoeboid olivine aggregate (AOA) from a CH chondrite and 2) Fe-Mg interdiffusion between chondrules, AOA, and matrix minerals in a CO chondrite. Equilibrium isotopic fractionation and equilibrium partitioning were also included in the numerical model, based on the assumption that equilibrium can be reached at the interfaces of mineral crystals. The numerical model showed that diffusion profiles observed in chondrite samples likely resulted from the diffusive exchange of elements or isotopes between the constituent minerals. This study also showed that the closure temperature is determined not only by the mineral with the slowest diffusivity in the system, but also strongly depends on the constituent mineral abundances.

• Korean Journal of Materials Research
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• v.20 no.6
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• pp.338-343
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• 2010

As an alternative to the W plug used in MOSFETs, a Cu plug with a NiSi contact using Ta / TaN as a diffusion barrier is currently being considered. Conventionally, Ni was first deposited and then NiSi was formed, followed by the barrier and Cu deposition. In this study, Ti was employed as a barrier material and simultaneous formation of the NiSi contact and Cu plug / Ti barrier was attempted. Cu(100 nm) / Ti / Ni(20 nm) with varying Ti thicknesses were deposited on a Si substrate and annealed at $4000^{\circ}C$ for 30 min. For comparison, Cu/Ti/NiSi thin films were also formed by the conventional method. Optical Microscopy (OM), Scanning Probe Microscopy (SPM), X-Ray Diffractometry (XRD), and Auger Electron Microscopy (AES) analysis were performed to characterize the inter-diffusion properties. For a Ti interlayer thicker than 50 nm, the NiSi formation was incomplete, although Cu diffusion was inhibited by the Ti barrier. For a Ti thickness of 20 nm and less, an almost stoichiometric NiSi contact along with the Cu plug and Ti barrier layers was formed. The results were comparable to that formed by the conventional method and showed that this alternative process has potential as a formation process for the Cu plug/Ti barrier/NiSi contact system.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.383-390
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• 2005

Effect of applying a DC voltage on the interfacial reaction at the metal to zirconia interface was investigated utilizing an oxygen ionic conductivity of partially stabilized zirconia. The joining of copper rod and zirconia tube was carried out in Ar gas atmosphere at $1000^{\circ}C$. There are two type of the joining. The one is the reaction bond consisting of copper and zirconia was dominated by surface reaction with a undetectable very thin layer. It was found that copper elements were diffused to zirconia side, but that Zr ions were not diffused to copper side. These results mean application of a DC voltage to migrate oxygen to the copper-zirconia interface can oxidize metal at the copper-zirconia interface and the bonding reaction between zirconia and copper oxide may occur. The other is the reaction bonding was dominated by interdiffusion with a very thick interface layer. This result mean application of a DC voltage can reduce zirconia at the interface. The bonding reaction is to be an alloying between Zr and Cu.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.449-452
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• 1998

We have studied the oxidatio nrte of $Si_{1-x}Ge_{x}$ epitaxial layer grown by MBE(molecular beam epitaxy). Oxidation were performed at 700.deg. C, 800.deg. C, 900.deg. C, and 1000.deg. C. After the oxidation, the results of AES(auger electron spectroscopy) showed that Ge was completely rejected out of the oxide and pile up at $SiO_{2}/$Si_{1-x}Ge_{x}$ interface. It is shown that the presence of Ge at the $SiO_{2}$/$Si_{1-x}Ge_{x}$ interface changes the dry oxidation rate. The dry oxidation rate was equal to that of pure Si regardless of Ge mole fraction at 700.deg. C and 800.deg.C, while it was decreased at both 900.deg. C and 1000.deg.C as the Ge mole fraction was increased. The ry oxidation rates were reduced for heavy Ge concentration, and large oxidation time. In the parabolic growth region of $Si_{1-x}Ge_{x}$ oxidation, The parabolic rate constant are decreased due to the presence of Ge-rich layer. After the longer oxidation at the 1000.deg.C, AES showed that Ge peak distribution at the $SiO_{2}$/$Si_{1-x}Ge_{x}$ interface reduced by interdiffusion of silicon and germanium.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.734-737
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• 2004

The metal-ferroelectric-semiconductor (MFS) structure is widely studied for nondestructive readout (NDRO) memory devices, but conventional MFS structure has a critical problem. It is difficult to obtain ferroelectric films like PZT on Si substrate without interdiffusion of impurities such as Pb, Ti and other elements. In order to solve these problems, the metal-ferroelectric-insulator-semiconductor (MFIS) structure has been proposed with a buffer layer of high dielectric constant such as MgO, $Y_2O_3$, and $CeO_2$. In this study, the etching characteristics (etch rate, selectivity) of MgO thin films were etched using $Cl_2/Ar$ plasma. The maximum etch rate of 85 nm/min for MgO thin films was obtained at $Cl_2$(30%)/Ar(70%) gas mixing ratio. Also, the etch rate was measured by varying the etching parameters such as ICP rf power, dc-bias voltage, and chamber pressure. Plasma diagnostics was performed by Langmuir probe (LP) and optical emission spectroscopy (OES).

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.121-127
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• 1994

The capability for application of rf magnetron sputterred and post annealed BaTiO$_{3}$ thin films in dielectrics AC drived TFELD(thin film electroluminescent device) was investigated. The dielectric constant of the thin films slightly increased up to about 25 with increase fothe post annealing temperature in the range of 210$^{\circ}C$-480$^{\circ}C$. The dielectric loss was about 0.005-0.01 except for the high frequency range above 100kHz and nearly independent on post annealing temperature. The BaTiO$_{3}$ thin film used for TFELD was annealed at 480.deg. C and Si$_{3}$N$_{4}$ thin film was inserted between BaTiO$_{3}$, lower dielecrics and ZnS:Mn, phosphor layer for stable driving of the device and for fear of interdiffusion. Regardless of the frequency of the applied sine wave voltage, the threshold voltage of the prepared TFELD was 65volt and saturated brightness was about 3000cd/m$^{2}$ at 130volt(2kHz sine wave), 65volt above V$_{TH}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.208-212
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• 2008

This paper reports physical properties of in situ boron doped silicon films made from boron source gas and silane ($SiH_4$) gas in a conventional low-pressure chemical vapor deposition vertical furnace. If the p-type polysilicon is formed by boron implantation into undoped polysilicon, the plasma nitridation (PN) process is added on the oxide in order to suppress boron penetration that can be caused during the thermal treatments used in fabrication. In-situ boron doped polysilicon deposition can complete p-type polysilicon film with only one deposition process and need not the PN process, because there is not interdiffusion of dopant at the intermediate temperatures of the subsequent steps. Since in-situ boron doped polysilicon films have higher work function than that of n-type polysilicon and they are compatible with the underlying oxide, they may be promising materials for improving memory cell characteristics if we make its profit of these physical properties.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.482-485
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• 2011

$La_{0.6}Sr_{0.4}MnO_3$ (LSMO) thin films, which are known as colossal magnetoresistance materials, were prepared on fused silica thin films by conventional RF magnetron sputtering, and the interfacial reactions between them were investigated by rapid thermal processing. Various analyses, namely, X-ray diffraction, transmission electron microscopy combined with energy adispersive X-ray spectrometry, and secondary ion mass spectrometry, were performed to explain the mechanism of the interfacial reactions. In the case of an LSMO film annealed at $800^{\circ}C$, the layer distinction against the underplayed $SiO_2$ was well preserved. However, when the annealing temperature was raised to $900^{\circ}C$, interdiffusion and interreaction occurred. Most of the $SiO_2$ and part of the LSMO became amorphous silicate that incorporated La, Sr, and Mn and contained a lot of bubbles. When the annealing temperature was raised to $950^{\circ}C$, the whole stack became an amorphous silicate layer with expanded bubbles. The thermal instability of LSMO on fused silica should be an important consideration when LSMO is integrated into Si-based solid-state devices.

• Applied Microscopy
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• v.27 no.3
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• pp.235-241
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• 1997

The microstructure of intermixed $Zn_{1-x}Fe_xSe$ layers in the (ZnSe/FeSe) superstrates grown on (00l) GaAs substrates has been investigated by high -resolution transmission electron microscopy and computer simulations of lattice images. Computer image simulations have been performed by the multislice method under various sample thicknesses and defocusing conditions. The simulated lattice images were compared with the experimental lattice images. Also, CuAu-I type ordering was often observed in the intermixed $Zn_{1-x}Fe_xSe$ alloys. This CuAu-I type ordered structure consists of alternating ZnSe and FeSe monolayers along the <100> and <110> directions.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.248-250
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• 1987

Transparent CdS films with low electrical restivity on glass substrates were prepared by coating a CdS slurry which contained 10 wt.% $CdCl_2$, and sintering in a nitrogen atmosphere at $600^{\circ}C$ for 2hr. All-polycrystalline CdS/CdTe solar cells were fabricated by coating CdTe slurries, which contained 1.0 or 4.5 wt.% $CdCl_2$, on the sintered CdS films and sintering at $700^{\circ}C$ for various periods of sintering. The spectral responses of the sintered CdS/CdTe solar cells were measured and compared with theoretically calculated quantum efficiency. The spectral responses of the sintered CdS/CdTe solar cells in the short-wavelength region decreases with-increasing sintering time. The poor response in this region is attributed to the existence of the Cd-S-Te solid solution in the compositional junction. The decrease in the maximum response in the long-wavelength region as the sintering exceeds certain time appears to be caused by the increase in the depth of the buried homo junction and by the increase in the series resistance. The $CdCl_2$ in the CdTe layer during sintering enchances the interdiffusion of S, Te or donor impurities across the metallurgical Junction causing the formation of deeper n-p junction in the CdTe layer.