• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.19-19
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• 2002

Perovskite-type titanate dielectrics have attracted much attention in memory devices such as DRAMs or FeRAMs due to their high dielectric constants. However, low volatility of the Ba, Sr, Pb or Zr precursors with only thd ligands has limitations in obtaining high quality thin films by liquid source metal organic chemical vapor deposition (LS-MOCVD) processes. To improve the volatility of these precursors, many attempts have been made such as adding polyether ligands to satisfy the coordinative saturation. We report the synthesis of new precursors Ba(thd)₂(tmeea) and Sr(thd)₂(tmeea), where tmeea = tris[2-(2-methoxyethoxy)ethyl]amino, and LS-MOCVD of barium strontium titanate (BSTO) thin films using these precursors. Due to increased basicity of amines compared with ethers, it is expected that the nitrogen-donor ligand will make a strong bond to a metal than an analogous oxygen-donor ligand, consequently improving the volatility and thermal behavior of these precursors. Thin films of BSTO were grown on Pt(111)/SiO₂/Si(100) substrates by LS-MOCVD using a cocktail source consisting of the conventional Ti precursor Ti(thd)₂(O/sup i/Pr), and these new Ba and Sr precursors. As-grown films were characterized by XPS, SEM, XRD, XRF, and C-V and I-V measurements. BSTO films grown at 420℃ were stoichiometric barium strontium titanate with very smooth surface morphology and their dielectric constants were found to be as targe as 450. Dependence of the composition, microstructure and the electrical properties of the BSTO films on the growth temperature, annealing temperature, working pressure, and the composition of the cocktail source will be discussed.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.401-407
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• 2010

We studied the influence of different types of metal electrodes on the performance of solution-processed zinc tin oxide (ZTO) thin-film transistors. The ZTO thin-film was obtained by spin-coating the sol-gel solution made from zinc acetate and tin acetate dissolved in 2-methoxyethanol. Various metals, Al, Au, Ag and Cu, were used to make contacts with the solution-deposited ZTO layers by selective deposition through a metal shadow mask. Contact resistance between the metal electrode and the semiconductor was obtained by a transmission line method (TLM). The device based on an Al electrode exhibited superior performance as compared to those based on other metals. Kelvin probe force microscopy (KPFM) allowed us to measure the work function of the oxide semiconductor to understand the variation of the device performance as a function of the types metal electrode. The solution-processed ZTO contained nanopores that resulted from the burnout of the organic species during the annealing. This different surface structure associated with the solution-processed ZTO gave a rise to a different work function value as compared to the vacuum-deposited counterpart. More oxygen could be adsorbed on the nanoporous solution-processed ZTO with large accessible surface areas, which increased its work function. This observation explained why the solution-processed ZTO makes an ohmic contact with the Al electrode.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.5 s.347
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• pp.11-16
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• 2006

This paper reports the correlation between dielectric constant and degree of amorphism of the hybrid type SiOC thin films. SiOC thin films were deposited by high density plasma chemical vapor deposition using bistrimethyl- silylmethane(BTMSM,$H_{9}C_{3}-Si-CH_{2}-Si-C_{3}H_{9}$) and oxygen precursors with various flow rate ratio. As-deposited film and annealed films at $400^{\circ}C$ were analyzed by XRD. The SiOC thin films were amorphous from XRD patterns. For quantitative analysis, the diffraction pattern of the samples was transformed to radial distribution function by Fourier analysis, and then compared with each other. The degree of amorphism of annealed films was higher than that of as-deposited ones. The dielectric constant varied in accordance with flow rate ratio of precursors. The lowest dielectric constant was obtained from the as-deposited film which has the highest degree of amorphism after annealing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.239-242
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• 1998

Ca $F_2$ films have superior gate insulator properties than conventional gate insulator such as $SiO_2$, Si $N_{x}$, $SiO_{x}$, and T $a_2$ $O_{5}$ to the side of lattice mismatch between Si substrate and interface trap charge density( $D_{it}$). Therefore, this material is enable to apply Thin Film Transistor(TFT) gate insulator. Most of gate oxide film have exhibited problems on high trap charge density, interface state in corporation with O-H bond created by mobile hydrogen and oxygen atom. This paper performed Ca $F_2$ property evaluation as MIM, MIS device fabrication. Ca $F_2$ films were deposited at the various substrate temperature using a thermal evaporation. Ca $F_2$ films was grown as polycrystalline film and showed grain size variation as a function of substrate temperature and RTA post-annealing treatment. C-V, I-V results exhibit almost low $D_{it}$(1.8$\times$10$^{11}$ $cm^{-1}$ /le $V^{-1}$ ) and higher $E_{br}$ (>0.87MV/cm) than reported that formerly. Structural analysis indicate that low $D_{it}$ and high $E_{br}$ were caused by low lattice mismatch(6%) and crystal growth direction. Ca $F_2$ as a gate insulator of TFT are presented in this paper paperaper

• Bulletin of the Korean Chemical Society
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• v.25 no.11
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• pp.1661-1666
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• 2004

The reaction of titanium tetraisopropoxide with 2 equiv of N,N-diethyl acetoacetamide affords Ti($O^iPr)_2(CH_3COCHCONEt_2)_2$ (1) as colorless crystals in 80% yield. Compound 1 is characterized by spectroscopic (Mass and $^1H/^{13}C$ NMR) and microanalytical data. Molecular structure of 1 has been determined by a single crystal X-ray diffraction study, which reveals that it is a monomeric, cis-diisopropoxide and contains a six coordinate Ti(IV) atom with a cis($CONEt_2$), trans($COCH_3$) configuration (1a) in a distorted octahedral environment. Variable-temperature $^1H$ NMR spectra of 1 indicate that it exists as an equilibrium mixture of cis, trans (1a) and cis, cis (1b) isomers in a 0.57 : 0.43 ratio at -20$^{\circ}C$ in toluene-$d_8$ solution. Thermal properties of 1 as a MOCVD precursor for titanium dioxide films have been evaluated by thermal gravimetric analysis and vapor pressure measurement. Thin films of pure anatase titanium dioxide (after annealing above 500$^{\circ}C$ under oxygen) have been grown on Si(100) with precursor 1 in the substrate temperature range of 350- 500$^{\circ}$ using a bubbler-based MOCVD method.

• Polymer(Korea)
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• v.33 no.6
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• pp.520-524
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• 2009

The effects of oxidative degradation on the performance of crosslinked polyethylene pipes were analyzed by the investigation of tensile properties and chemical structure change of the pipes during oxidative degradation. Annealing at high temperatures or UV irradiation method was used to induce the oxidative degradation of the crosslinked polyethylene pipes and the effects of the die temperature on the oxidative degradation of the pipes were also investigated. The tensile properties and chemical structure change of the pipes were investigated by universal testing machine and FT-IR, respectively. With the progress of thermo-oxidative degradation the tensile strength of the pipes slowly decreased but the elongation at break rapidly decreased, and the chemical structure of the pipes also changed considerably because of the introduced oxygen molecules. These results would be useful in estimating the performance deterioration of the crosslinked polyethylene pipes due to the oxidative degradation during production and storage.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.341-345
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• 2008

The SiOC film of carbon centered system was prepared using bistrimethylsilylmethane and oxygen mixed precursor by the chemical vapor deposition. The chemical properties of the SiOC film were analyzed by the contact anlge and FTIR spectra. The dielectric constant of the deposited films decreased after annealing process, and the correlation between the increasing the BTMSM/$O_2$ flow rate ratio and the dielectric constant did not exist. However, the trend of increasing or decreasing of the dielectric constant repeated and there is the correlation ship between the dielectric constant and the Si-O-C bond in the range of $950{\sim}1200\;cm^{-1}$. The dielectric constant decreased between samples with the chemical shift. The lowest dielectric constant was 1.65 at the sample, which was observed the chemical shift.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.956-960
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• 1998

The interfacial reaction between the CoINb bilayer and the $SiO_2$ substrate in the temperature range of $330^{\circ}C$-$800^{\circ}C$ in a vacuum has been investigated by X-ray photoelectron spectroscopy, glancing angle XRD, Auger Electron Spectroscopy and Atomic force microscopy. The Co and Nb were actively interdiffused at $600^{\circ}C$, and the layer inversion completed at $700^{\circ}C$. NbO was formed by interfacial reaction between the Nb interlayer and the $SiO_2$ substrate, while $Nb_20_5$ was formed on the surface by reaction of Nb with oxygen in the ambients. Free Si atoms obtained by the reaction between Nb and $SiO_2$ formed silicides like CoSi and $Nb_5Si_3$ by reacting with Co and Nb remnants. The sheet resistance of the Co/Nb bilayer increased substantially after annealing at $800^{\circ}C$. which is due to the agglomeration of the Co layer to reduce its surface energy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.441-448
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• 2002

The electrical properties of the GaN-based green light emitting diodes(LEDs) with the Mg-doped p-GaN layer activated in $N_2$ or $O_2$ ambient have been compared. For the $N_2$ -ambient activation the current-voltage behavior of LEDs has been found to be improved when the Mg dopants activation was performed in the higher temperature. However, for the $O_2$-ambient activation the current-voltage characteristic has been observed to be enhanced when the Mg dopants activation was carried out in the lower temperature. The minimum forward voltage at 20mA was obtained to be 4.8 V for LEDs with the p-GaN layer activated at $900^{\circ}C$ in the $N_2$ ambient and 4.5V for LEDs with the p-GaN layer treated at $700^{\circ}C$ in the $O_2$ambient, repectively. The forward voltage reduction of the LEDs treated in the $O_2$-ambient may be related to the oxygen co-doping of the p-GaN layer during the activation process. The $O_2$ -ambient activation process is useful for the enhancement of the LED performance as well as the fabrication process since this process can activate the Mg dopants in the low temperature.

• Current Photovoltaic Research
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• v.3 no.1
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• pp.32-38
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• 2015

CIGS solar cell consisted of various films. In this research, we investigated electrode materials in $Cu(In,Ga)Se_2$ (CIGS) cells, including Al-doped ZnO (ZnO:Al), intrinsic ZnO (i-ZnO), and Al films. The sputtered ZnO:Al film with a sputtering power at 200W showed the lowest series resistance and highest cell efficiency. The electrical resistivity of the 200-W sputtered ZnO:Al film was $5.2{\times}10^{-4}{\Omega}{\cdot}cm$ by the rapid thermal annealing at $200^{\circ}C$ for 1 min. The electrical resistivity of i-ZnO was not measurable due to its high resistance. But the optical transmittance was highest with less oxygen supply and high efficiency cell was achieved with $O_2/(Ar+O_2)$ ratio was 1% due to the increase of short-circuit current. No significant change in the cell performance by inserting a Ni layer between Al and ZnO:Al films was observed.