• Korean Journal of Materials Research
• /
• v.4 no.6
• /
• pp.662-668
• /
• 1994

The physical and electrical characteristics of sub-l0nm thick capacitor dielectrics formed by wet oxidation of silicon nitride(oxide/nitride composite) and by removing the top oxide of oxidized silicon nitride(0xynitride) are described. For the capacitors with an oxide/nitride composite layer, the capacitance decreases sharply, but the breakdown field increases with an increase in the wet oxidation time at $900^{\circ}C$. For the capacitors with oxynitride layers, the values of both the capacitance and the breakdown field increase with increasing wet oxidation time. The reduction of effective thickness and the improved quality of oxynitride film are responsible for the improved capacitance and increased breakdown fields, respectively. In addition, intrinsic TDDB characteristics and early breakdown failure rate of oxynitride film are improved with increasing oxidation time. Consequently, the oxynitride film is suitable for dynamic memories as a thin dielectric film.

• Korean Journal of Materials Research
• /
• v.3 no.4
• /
• pp.352-360
• /
• 1993

A nitride layer was df'posited on the thermal oxide layer by LPCVD process. ONO(oxidenitricle oxide) capacitors with various thickness of component layer wore fabricated by wet reoxidation of the nitride with and without anrwalmg treatment and their properties were investigated. As a result of observation on the refrative index and etching behavior of the ONO fIlms, the nitride layer OF 40 A thick ness was not so dense that the bottom oxide during the reoxidation process and the capability of securing the capacitance decreased. The conduction current in the ONO multl-Iayer dielctric film was reduced as the bottom(or top) oxide layer became thicker. However, in the case of oxide with thickness more than 50A, it merely plays a factor of reduction in capacitance, and the effect of barrier for hole injection was not so much increased. Annealing of the nitride laypr bpfore reoxidation did not show a grpat effects on the refractive index and capacitance of the film, however, the annealing process increased the breakdown voltage by 2${\cdot}$V.

• The Journal of the Korea Contents Association
• /
• v.18 no.10
• /
• pp.425-430
• /
• 2018

The battery system of an electric vehicle suffers from the problem the battery output and the service life decrease at low temperature. A Positive Temperature Coefficient(PTC) heater is used for maintaining room temperature but is heavy due to a complicated insulation structure. The larger the weight is, the lower the fuel economy of the electric vehicle is. On the other hand a induction heater have a simple insulation structure, which is effective in weight reduction and has a rapid temperature rise. The induction heater consists of an LC resonance circuit. The larger the capacitance is, the higher the price and weight is. Therefore, the inductance should be increased to reduce the capacitance. Also, the main heat source of the induction heater is coreloss. So, it is important to optimize inductance and coreloss in terms of electromagnetic field design. In this paper, the inductance and the coreloss according to the change of the induction heater structure were optimized through the Taguchi method and Finite Element Method(FEM) simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.10 s.352
• /
• pp.10-21
• /
• 2006

We have studied the characteristics of oxide VCSELS when their off-current and on-current are kept small in order to find out the possibility of low current operation. A large signal equivalent circuit model has been used. By comparing measured data and simulation results, the parameters of the large signal models are obtained including the capacitances. Using the large signal model, we have investigated the effects of capacitance and on/off currents upon the turn-on/turn-off characteristics and eye diagram. According to the experiment and simulation, the depletion capacitance, which has been neglected, is found to have significant influence on the him-on delay and eye-diagram. Therefore, for high speed and low current operation, the reduction of the depletion capacitance is essential.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.12 no.2
• /
• pp.186-192
• /
• 2012

Half-rail stacked drivers are used to reduce power consumption of the drivers for synchronous buck converters. In this paper, the stacked driver is optimized by matching the average charging and discharging currents used by high-side and low-side drivers. By matching the two currents, the average intermediate bias voltage can remain constant without the aid of the voltage regulator as long as the voltage ripple stays within the window defined by the hysteresis of the regulator. Thus the optimized driver in this paper can minimize the power consumption in the regulator. The current matching requirement yields the value for the intermediate bias voltage, which deviates from the half-rail voltage. Furthermore the required capacitance is also reduced in this design due to decreased charging current, which results in significantly reduced die area. The detailed analysis and design of the stacked driver is verified through simulations done using 5V MOSFET parameters of a typical 0.35-${\mu}m$ CMOS process. The difference in power loss between the conventional half-rail driver and the proposed driver is less than 1%. But the conventional half-rail driver has excess charge stored in the capacitor, which will be dissipated in the regulator unless reused by an external circuit. Due to the reduction in the required capacitance, the estimated saving in chip area is approximately 18.5% compared to the half-rail driver.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.1799-1805
• /
• 2014

In this article, we described about the preparation and electrochemical properties of a flexible energy storage system based on a plastic polyethylene terephthalate (PET) substrate. The PET treated with UV/ozone was fabricated with multilayer films composed of 30 polyaniline (PANi)/graphene oxide (GO) bilayers using layer-by-layer assembly of positively charged PANi and negatively charged GO. The conversion of GO to the reduced graphene oxide (RGO) in the multilayer film was achieved using hydroiodic acid vapor at $100^{\circ}C$, whereby PANi structure remained nearly unchanged except a little reduction of doping state. Cyclic voltammetry and charge/discharge curves of 30 PANi/RGO bilayers on PET substrate (shorten to PANi-$RGO_{30}$/PET) exhibited an excellent volumetric capacitance, good cycling stability, and rapid charge/discharge rates despite no use of any metal current collectors. The specific capacitance from charge/discharge curve of the PANi-$RGO_{30}$/PET electrode was found to be $529F/cm^3$ at a current density of $3A/cm^3$, which is one of the best values yet achieved among carbon-based materials including conducting polymers. Furthermore, the intrinsic electrical resistance of the PANi-$RGO_{30}$/PET electrodes varied within 20% range during 200 bending cycles at a fixed bend radius of 2.2 mm, indicating the increase in their flexibility by a factor of 225 compared with the ITO/PET electrode.

• Journal of the Korean Ceramic Society
• /
• v.28 no.4
• /
• pp.261-268
• /
• 1991

The dielectric properties and microstructure of SrTiO3-based grain boundary layer (GBL) capacitor were investigated, and SrTiO3 GBL capacitor was made by penetrating the Frit (PbO-Bi2O3-B2O3 system). The Nb2O5-doped SrTiO3 ceramics were fired for 4-hours, at 145$0^{\circ}C$ in H2-N2 atomsphere to get semiconductive ceramics. The grain size of SrTiO3 sintered at reduction atmosphere had increased as the amount of Nb2O5 increases and then decreased as the amount of Nb2O5 exceeded 0.2 mole%. Insulating reagents which contained PbO-Bi2O3-B2O3 system frit and oxide mixture were printed on the each semiconductive ceramics and fired at varying temperature and for different holding time. The optimum dielectric properties could be obtained by second heat treatment at 110$0^{\circ}C$ for 1 hour, when frit paste was printed. A SrTiO3-based GBLC had the apparent permitivity of about 3.2$\times$104, the dielectric loss of 0.01~0.02 and the stable temperature coefficient of capacitance. The influence of frit paste on dielectric properties was similiar to that of oxide paste but the stability of temperature property of capacitance was improved.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.849-860
• /
• 2016

The high-switching-frequency operation of power converters can achieve high power density through size reduction of passive components, such as capacitors, inductors, and transformers. However, a small-output capacitor that has small capacitance and low effective series resistance changes the small-signal model of the converter power stage. Such a capacitor can make the converter unstable by increasing the crossover frequency in the transfer function of the small-signal model. In this paper, the design and implementation of a high-frequency LLC resonant converter are presented to verify the power density enhancement achieved by decreasing the size of passive components. The effect of small output capacitance is analyzed for stability by using a proper small-signal model of the LLC resonant converter. Finally, proper design methods of a feedback compensator are proposed to obtain a sufficient phase margin in the Bode plot of the loop gain of the converter for stable operation at 500 kHz switching frequency. A theoretical approach using MATLAB, a simulation approach using PSIM, and experimental results are presented to show the validity of the proposed analysis and design methods with 100 and 500 kHz prototype converters.

• Journal of the Korean Applied Science and Technology
• /
• v.19 no.2
• /
• pp.79-85
• /
• 2002

The cutaneous tolerability of detergent formulations can be improved by means of suitable additives. They complex the surfactant molecules lowering the concentration of their free monomeric species. Proteins derivatives used as additives for detergency are usually prepared by partial hydrolysis of plant reserve proteins. The main purpose of the hydrolytic cleavage is to make them water soluble and suitable for liquid products. Water solubility and stability are obtained by means of complexation with surfactants which also increase their actual hydrophobicity, an important parameter affecting cosmetic properties of proteins. Transepidermal water loss (TEWL) and electric capacitance (EC) have been adopted as investigation technigues to evaluate the skin integrity/damage in vitro tests, The performance of native wheat protein / surfactant complexes has been compared with traditional protein hydrolysates as detergent additives. The results show a noticeable reduction of skin irritation in surfactant formulations with addition of native wheat protein.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.173-179
• /
• 2018

Electrochemical characterization was conducted on poly(vinyl alcohol) (PVA)-ceramic composite (PVA-CC) separators for supercapacitor applications. The PVA-CC separators were fabricated by mixing various ceramic particles including aluminum oxide ($Al_2O_3$), silicon dioxide ($SiO_2$), and titanium dioxide ($TiO_2$) into a PVA aqueous solution. These ceramic particles help to create amorphous regions in the crystalline structure of the polymer matrix to increase the ionic conductivity of PVA. Supercapacitors were assembled using PVA-CC separators with symmetric activated carbon electrodes and electrochemical characterization showed enhanced specific capacitance, rate capability, cycle life, and ionic conductivity. Supercapacitors using the $PVA-TiO_2$ composite separator showed particularly good electrochemical performance with a 14.4% specific capacitance increase over supercapacitors using the bare PVA separator after 1000 cycles. With regards to safety, PVA becomes plasticized when immersed in 6 M KOH aqueous solution, thus there was no appreciable loss in tear resistance when the ceramic particles were added to PVA. Thus, the enhanced electrochemical properties can be attained without reduction in safety making the addition of ceramic nanoparticles to PVA separators a cost-effective strategy for increasing the ionic conductivity of separator materials for supercapacitor applications.