Byong Ho Kim

The Analysis of Oxygen Plasma Pretreatment for Improving Anodic Bonding

The oxygen plasma surface treatment of silicon and glass was studied for improving the characteristics of anodic bonding. By contact-angle measurements, we calculated the surface energy which is the sum of polar and dispersion components. The results showed that oxygen-plasma-induced distinctive high-polar and low-dispersion characteristics and caused the total surface energy to increase even at low power or short plasma exposure times for both silicon and glass surfaces. The highly polar-component-induced surface was maintained for over 100 days. On increasing plasma power and exposure time, it was observed that surface roughness increased. The oxygen plasma treatment was significantly efficient to reduce the contaminants on the surface, which was the main factor in degrading bonding strength and electrical properties of the interface. In the tensile test, the oxygen plasma treatment led to higher bonding strength than a conventional anodic bonding method.

Electrical Properties of Pt/SrBi2Ta2O9/CeO2/SiO2/Si Structure for Nondestructive Readout Memory

Memory window and leakage current density of Pt/SrBi2Ta2O9/CeO2/SiO2/Si structure have been investigated for non destructive read out memory. Coercive field that decisively affects on the memory window becomes greater by the interposition of the CeO2 insulator between SrBi2Ta2O9 and SiO2 and thus the memory window also increases with an electric field to the SrBi2Ta2O9. A typical value of memory window for Pt/SrBi2Ta2O9(140 nm)/CeO2/SiO2/Si is in the range of 0.5 – 3.0 V, which is high enough for the non destructive read out memory, at the applied voltage of 3 – 9 V. The leakage current density is remained at 3 ×10-8 A/cm2 until the applied voltage increases up to 10 V.

Effects of Al content on the electrical properties of LaxAlyOz films grown on TiN substrate by atomic layer deposition

The effects of Al content on the electrical properties of LaxAlyOz films grown on TiN substrate by atomic layer deposition technique were investigated. With increasing Al content, the leakage current characteristics improved, but the dielectric constant became smaller. Postannealing of the films at temperatures up to 500°C reduced the leakage current density due to thermal stabilization by the addition of Al. For the 25-nm-thick La2.4AlO3.3 film, the authors obtained a dielectric constant of 22 and a leakage current density of 10−7A∕cm2 at 1V after postannealing at 450°C, which gives an equivalent oxide thickness of 3.8nm.

Microwave dielectric properties of the (1−x)LaAlO3–xTiO2 system

Compositions in the (1-x)LaAlO{sub 3}-xTiO{sub 2} system were prepared in order to modify the negative temperature coefficient of the resonant frequency ({tau}{sub f}) of LaAlO{sub 3}. The microwave dielectric properties and phases of these compositions were investigated. X-ray powder diffraction results showed that LaAlO{sub 3} and TiO{sub 2} form a solid solution in the composition range from x = 0 to x = 0.6. The dielectric properties of the (1-x)LaAlO{sub 3}-xTiO{sub 2} system exhibit nonmonotonic behavior with compositions. The low permittivity and negative {tau}{sub f} of LaAlO{sub 3} appear to dominate the dielectric properties of the (1-x)LaAlO{sub 3}-xTiO{sub 2} system for TiO{sub 2} concentrations as large as 60%.

Spectral Properties of Nd3+-Doped RO·Na2O·Al2O3·P2O5 (R=Mg, Ca, Ba) Glass System

The dependence of spectral properties of the Nd3+-doped (45- x)RO xNa2O2.5Al2O352.5P2O5 (R=Mg, Ca, Ba, 0≤x ≤31, mol%) glasses on RO and on its substitution with Na2O was investigated. Absorption, fluorescence spectra and lifetimes were measured. Both the stimulated emission cross section and the spontaneous emission probability for the 4F3/2→4I11/2 transition of Nd3+ in glass were calculated. The results indicate that the effect of RO depends on its ionic field strength and that the substitution of RO with Na2O loosens the glass structure so as to lower the degree of disorder of the phosphate chain structure. A stimulated emission cross section as large as 4.2×10-20 cm2 and half-lifetime concentration as high as 8×1020 ions/cm3 were obtained.

Characteristics of tapped microstrip bandpass filter in BiNbO4 ceramics

The dielectric properties of BiNbO4 (BN ceramics) sintered at low temperature with CuO and V2O5 additives were determined. BN ceramics containing 0.07 wt% V2O5 and 0.03–0.05 wt% CuO sintered at 900 °C had a dielectric constant of 44.3, temperature coefficient of resonance frequency τf of 2 p.p.m. °C-1 and Qxfo value of 22 000. A multilayer type band pass filter using tapped resonators and conventional resonators was designed at 1.855 GHz and PCS (personal communication system) applications. By adopting an input/output-tapping scheme the chip filter structure becomes simpler and needs fewer layers than using the conventional input/output-coupling scheme. The green ceramic sheet the for band pass filter was manufactured by a tape casting process and a multilayer type band pass filter was fabricated with a silver electrode. The simulated characteristics, including spurious resonance of the designed filters, are compared with the measured ones. The measured frequency of both exhibited similar tendencies. Even though the centered frequency was measured to shift about 90 MHz downward, the characteristics at pass band and spurious resonance characteristics were similar to that of a simulation.

Dielectric and electric properties of sol-gel derived PZT and PNZT thin films

Abstract Ferroelectric Pb(Zr0.52Ti0.48)O3(PZT) and Pb(1−x/2)Nbx(Zr0.52Ti0.48)(1−x)O3(PNZT) thin films have been fabricated on Pt/Ti/SiO2/Si substrate using Sol-Gel technique. Two kinds of fast annealing method, F-I (repetition of intermediate and final annealing) and F-II (one final annealing after repetition of intermediate annealing) were used for preparation of multi-coated PZT and PNZT thin films. 270 nm PZT films and 180 nm PNZT films were prepared and characterized by dielectric and electric properties. 3% Nb doped PNZT thin film with 5% excess Pb had a capacitance density of 24.0 fF/ μ m2, a dielectric loss of 0.13, a switchable polarization of 15.8 μ C/cm2and a coercive field of 32.7 kV/cm, respectively. The leakage current density of the film was as low as 1.47 × 10−7A/cm2at 1.5V.