• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.6
• /
• pp.410-415
• /
• 1999

$Ba_{1-x}Sr_xTiO_3$ thin films with various ratio of Sr (X = 0.4, 0.5, 0.6) were grown $Pt/TiN/SiO_2/Si$ subastrate by RF magnetron sputtering deposition. As, Ag, and Cu films were deposited on $Ba_{1-x}Sr_xTiO_3$ thin films as top electrodes by using a thermal evaporator. The electrical properties of $Ba_{1-x}Sr_xTiO_3$ thin films for various compositions were characterized and the physical properties at interface between $Ba_{1-x}Sr_xTiO_3$ thin films and top electrodes were evaluated in terms of the work function difference. At x =0.5, the degradation of capacitance is lower to the other compositions. As negative biasapplied, the specimen with Cu top electrode has board saturation region and low leakage current since work function of Cu is bigger than other electrodes.$ Ba_{0.5}Sr_{0.5}TiO_3$ thin films with Cu top electrode, the dielectric constant was measured to the value of 354 at 1 kHz and the leakage current was obtained to the value of $5.26\times10^{-6}A/cm2$ at the forward bias of 2 V.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.119-119
• /
• 2016

Over the last years the anodic formation of ordered $TiO_2$ nanotube layers has created significant scientific interest. Titanium oxide nanotube formation on the titanium or titanium alloy surface is expected to be important to improve cell adhesion and proliferation under clinical conditions. It should be possible to control the nanotube size and morphology for biomedical implant use by controlling the applied voltage, alloying element, current density, anodization time, and electrolyte. $TiO_2$ nanotubes show excellent biocompatibility, and the open volume in the tubes may be exploited as a drug release platform and so on. Therefore, in this study, Nanotube shape on the Ti-29Nb-xHf alloys with applied potentials was reserched. $TiO_2$ nanotube formation on Ti-29Nb-xHf alloys was carried out using anodization technique as a function of applied DC potential (10 V to 30 V and 30 V to 10 V) and anodization time for 60~120 min in $1MH_3PO_4$ with small additions of (0.8 wt. %, to 1.2 wt. %) NaF. The morphology change of anodized Ti-29Nb-xHf alloys was determined by FE-SEM, XRD, and EDS.

• Korean Journal of Metals and Materials
• /
• v.46 no.10
• /
• pp.691-699
• /
• 2008

Electrochemical characteristics of Ti-30Ta-xZr alloys coated with HA/TiN by using magnetron sputtering method were studied. The Ti-30Ta containing Zr(3, 7, 10 and 15wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and coating, and then coated with HA/TiN, respectively, by using DC and RF-magnetron sputtering method. The analyses of coated surface and coated layer were carried out by using optical microscope(OM), field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). The electrochemical characteristics were examined using potentiodynamic (-1,500 mV~ + 2,000 mV) and A.C. impedance spectroscopy(100 kHz ~ 10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The microstructure of homogenized Ti-30Ta-xZr alloys showed needle-like structure. In case of homogenized Ti-30Ta-xZr alloys, a-peak was increased with increasing Zr content. The thickness of TiN and HA coated layer showed 400 nm and 100 nm, respectively. The corrosion resistance of HA/TiN-coated Ti-30Ta-xZr alloys were higher than that of the non-coated Ti-30TaxZr alloys, whic hindicate better protective effect. The polarization resistance($R_p$) value of HA/TiN coated Ti-30Ta-xZr alloys showed $8.40{\times}10^5{\Omega}cm^2$ which was higher than that of non-coated Ti-30Ta-xZr alloys.

• Journal of the Korean Ceramic Society
• /
• v.33 no.6
• /
• pp.718-724
• /
• 1996

Deformation mechanism map of Langdon-Mohammed type for YBa2Cu3O7-x superconducting ceramic was constructed by considering mechanisms of Nabarro-Herring Coble and powder-law creep and grain boundary sliding (GBS) with an accommodation by grain boundary diffusion. The map was found consistent with experi-mental results not only of the creep the also of the superplastic deformation. It showed the transition from interface reaction-controlled to the grain boundary diffusion-controlled GBS mechanism at about 1 ${\mu}{\textrm}{m}$ grain size and 100 MPa flow stress in agreement with the experimental results.

• Progress in Superconductivity
• /
• v.3 no.1
• /
• pp.87-90
• /
• 2001

We designed a high temperature superconducting rapid single flux quantum(RSFQ) T flip-flop(TFF) circuit using Xic and WRspice. According to the optimized circuit parameters, we fabricated the TFF circuit with $Y_1$$Ba_2$Cu$_3$$O_{7-x}$(YBCO) interface-controlled Josephson junctions. The whole circuit was comprised of five epitaxial layers including YBCO ground plane. The interface-controlled Josephson junction was fabricated with natural junction barrier that was formed by interface-treatment process. In addition, we report second design for a new flip-flop without ground palne.e.

• Korean Journal of Materials Research
• /
• v.13 no.5
• /
• pp.338-342
• /
• 2003

Adhesion between Cu and low-k films has been investigated. Low-k films deposited using a mixture of hexamethyldisilane(HMDS) and Para-xylene had a dielectric constant as low as 2.7, showing the thermally stable properties up to $400^{\circ}C$. In this study, Ti glue layer, boron dopant, and $N_2$plasma treatment were used to improve adhesion property of between Cu and low-k films. Ti glue layer slightly improved adhesion property. After $N_2$plasma treatment, the adhesion property was significantly improved due to the increased roughness and the formation of new binding states between Ti and plasma-treated PPpX : HMDS. However, $300^{\circ}C$ annealing of $N_2$plasma treated sample caused the diffusion of Cu into the PPpX : HMDS, degrading the low-k properties. In the case of Cu(B)/Ti/PPpX : HMDS, the adhesion was remarkably increased. This enhanced adhesion was attributed to formation of Ti-boride at the Cu-Ti interface. It is because the formed Ti-boride prevented the diffusion of Cu into the PPpX : HMDS and the Cu-Ti reaction at the Ti interface.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2013.05a
• /
• pp.79-80
• /
• 2013

The purpose of this study was to investigate $2^{nd} $nanotube formed surface observation of the Ti-25Ta-xZr alloys using ATO(anodic titanium oxide) technique. Ti-25Ta-xZr alloy was anodized in 1M $H_3PO_4$ electrolytes containing 0.8 Wt. % NaF at room temperature. After formation of nanotube was achieved out, nanotube was eliminated, and then anodization was carried out repeatedly. The microstructures, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and process of nanotube growth by using ATO method was examined by optical microscopy (OM), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The ${\alpha}$ phase and ${\beta}$ phases were affected to form the second nanotube morphology of Ti-25Ta-xZr alloys.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.188.2-188.2
• /
• 2015

The presence of the conduction interface in epitaxial $LaAlO_3/SrTiO_3$ thin films has opened up challenging applications which can be expanded to next-generation nano-electronics. The metallic conduction path is associated with two adjacent insulating materials. Such device structure is applicable to frequency-dependent impedance spectroscopy. Impedance spectroscopy allows for simultaneous measurement of resistivity and dielectric constants, systematic identification of the underlying electrical origins, and the estimation of the electrical homogeneity in the corresponding electrical origins. Such unique capability is combined with the intentional control on the interface composition composed of $SrTiO_3$ and $CaTiO_3$, which can be denoted by $SrxCa1-_xTiO_3$. The underlying $Sr_xCa1-_xTiO_3$ interface was deposited using pulsed-laser deposition, followed by the epitaxial $LaAlO_3$ thin films. The platinum electrodes were constructed using metal shadow masks, in order to accommodate 2-point electrode configuration. Impedance spectroscopy was performed as the function of the relative ratio of Sr to Ca. The respective impedance spectra were analyzed in terms of the equivalent circuit models. Furthermore, the impedance spectra were monitored as a function of temperature. The ac-based characterization in the 2-dimensional conduction path supplements the dc-based electrical analysis. The artificial manipulation of the interface composition will be discussed towards the electrical application of 2-dimensional materials to the semiconductor devices in replacement for the current Si-based devices.

• Proceedings of the IEEK Conference
• /
• 1998.06a
• /
• pp.453-456
• /
• 1998

The electrical properties of $Si_{1-x}Ge_{x}$ samples have been investigated. The sample structures were grown by MBE (molecular geam epitaxy) with Ge mole-fraction of x=0.0, x=0.05, x=0.1, and x=0.2. To examine the influence of the thermal processing, the $O_{2}$ and N$_{2}$ process were performed at 800[.deg. C] and 900[.deg. C], respectively. After this thermal process, hall measurements have been done over a wide range of the ambient temperature between 320[.deg. K] and 10[.deg. K] to find the temperature dependence using the comparessed-He gas system. The Ge-rich layer has been formed at the $SiO_{2}$/SiGe interface and it has an effect on the hall mobility. And it has been found that hall mobility was increased by the $N_{2}$ annealing process comparing with dry oxidation process at both 800[.deg.C] and900[.deg. C].

• Journal of the Korean Vacuum Society
• /
• v.4 no.S2
• /
• pp.84-89
• /
• 1995

The growth and the film characteristics of heteroepitaxial $Si_{1-x}Ge_x$ films growth by the Rapid Thermal Chemical Vapor Deposition(RTCVD)method are described. For the growth of $Si_{1-x}Ge_x$ heteroepitaxial layers, $SiH_4/GeH_4/H_2$gas mixtures are used. The growth conditions are varied to investigate their effects on the Si/Ge composition ratios, the interface abruptness and crystalline properties. The Si/Ge composition ratios are analyzed with the RBS and the SIMS techniques, and the interface abruptness are deduced from these data. The crystalline properties are analyzed from TEM pictures. The experimental data shows that the crystalline perfection is excellent at the growth temperature of as low as $650^{\circ}C$, and the composition ratios change linearly with $SiH_4/GeT_$$ gas mixing ratios in our experimental ranges. Boron doping experiments are also performed using 200 ppm $B_2H_6$ source gas. The doping profiles are measured with SIMS technique. The SIMS data shows that the doping abruptness can be controlled within about 200$\AA$/decade.