• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.344-348
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• 2011

A layer of $TiO_2$ thin film less than ~200nm in thickness, as a blocking layer, was deposited by 13.56 MHz radio frequency magnetron sputtering method directly onto the anode electrode to be isolated from the electrolyte in dye-sensitized solar cells (DSCs). This is to prevent the electrons from back-transferring from the electrode to the electrolyte ($I^-/{I_3}^-$). The presented DSCs were fabricated with working electrode of F:$SnO_2$(FTO) glass coated with blocking $TiO_2$ layer, dye-attached nanoporous $TiO_2$ layer, gel electrolyte and counter electrode of Pt-deposited FTO glass. The effects of blocking layer were studied with respect to impedance and conversion efficiency of the cells. The, electrochemical impedances of DSCs using this electrode were $R_1$: 13.9, $R_2$: 15.0, $R_3$: 10.9 and $R_h$: $82{\Omega}$. The $R_2$ impedance related by electron movement from nanoporous $TiO_2$ to TCO showed lower than that of normal DSCs. The photo-conversion efficiency of prepared DSCs was 5.97% ($V_{oc}$: 0.75V, $J_{sc}$: 10.5 mA/$cm^2$, ff: 0.75) and approximately 1% higher than general DSCs sample.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.9
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• pp.449-454
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• 2002

A rectangular straight microchannel, integrated with the resistance temperature detectors(RTDs) for temperature sensing and a micro-heater for generating the Temperature gradient along the channel, was fabricated. Its dimension is 57${\mu}{\textrm}{m}$(H)$\times$200${\mu}{\textrm}{m}$(W)$\times$48,050${\mu}{\textrm}{m}$(L), and RTDs were placed at the inner-channel wall. Si wafer was used as a substrate. For the fabrication of RTDs, 5300$\AA$ thick Pt/Ti layer was sputtered on a Pyrex glass wafer. Finally, the glass wafer was bonded with Si wafer by anodic bonding, so that the RTDs are located inside the microchannel. Temperature coefficient of resistance(TCR) values of the fabricated Pt-RTDs were 2800~2950ppm$^{\circ}C$ and the variation of TCR value In the range of O~10$0^{\circ}C$ was less than 0.3％. Therefore, it was proved that the fabricated Pt-RTDs without annealing were excellent as temperature sensors. The temperature distribution in the microchannel was investigated as a function of mass flow rate and heating power. The temperature increase rate diminished with decreasing the applied power and increasing the mass flow rate. It was confirmed from the comparison with the simulation results that the temperature measured inside the microchannel is more accurate than measuring the temperature measured at the outer wall. The proposed temperature sensing method and microchannel are expected to be useful in microfluidics researches.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.748-752
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• 2004

The Hydrogenated amorphous carbon (a-C:H) thin films are deposited to fabricate suppored layer on silicon substrate with a closed field unbalanced magnetron(CFUBM) sputtering system. This study focuses on the characteristic of Diamond like carbon (DLC) films and Pb(Zr,Ti)$O_3$ (PZT) films for membrane structure. The deposition rate and the surface roughness of DLC fims decrease with DC bias voltage. hardness is 26 GPa at -200 V. Interface of DLC/Si and Pt/DLC layers was excellent.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.114-120
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• 1994

We have been successfully fabricated the low nois HEMT device with AlGaAs and GaAs structure. The epitazial layer with n-type AlgaAs and undoped GaAs was grown by molecular beam epitaxy(MBE) system. Ohmic resistivity of the ource and drain contact is below 5${\times}10^{6}{\Omega}{\cdot}cm^{2}$ by the rapid thermal annealing (RTA) process. The ideality factor of the Schottky gate is below 1.6 and the gate material was Ti/Pt/Au. The HEMTs with 0.25$\mu$m-long and 200$\mu$m-wide gates have exhibited a noise figure of 0.65dB with associated gain of 9dB at 12GHz, and a transconductance of 208mS/mm.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.8
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• pp.927-933
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• 2006

The structural and electrical characteristics of PLZT thin films fabricated onto $Pt/IrO_2/Ir/Ti/SiO_2/Si$ substrates by a pulsed laser deposition were investigated to develop the high dielectric thin films for capacitor layer of semiconductor memory devices The slim region 14/50/50 PLZT thin films were fabricated by PLD and estimated the characteristics for memory application 14/50/50 PLZT thin films have crystallize into perovskite structure at the $600^{\circ}C$ deposition temperature, 200 mTorr of oxygen pressure, and 2 $J/cm^2$ of laser energy density. In this condition PLZT thin films had the dielectric constant as high as 985, storage charge density 8.17 ${\mu}C/cm^2$ and charging time 0.20 ns. Leakage current density was less than $10^{-10}A/cm^2$ up to 5 V bias voltage.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.106-109
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• 2012

A low power methane gas sensor with microheater was fabricated by silicon bulk micromachining technology. In order to heat up the sensing layer to operating temperature, a platinum (Pt) micro heater was embedded in the gas sensor. The line width and gap of the microheater was 20 ${\mu}m$ and 4.5 ${\mu}m$, respectively. Zinc oxide (ZnO) nanowhisker arrays were grown on a sensor from a ZnO seed layer using a hydrothermal method. A 200 ml aqueous solution of 0.1 mol zinc nitrate hexahydrate, 0.1 mol hexamethylenetetramine, and 0.02 mol polyethylenimine was used for growing ZnO nanowhiskers. Temperature distribution of the sensor was analyzed by infrared thermal camera. The optimum temperature for highest sensitivity was found to be $250^{\circ}C$ although relatively high (64%) sensitivity was obtained even at as low a temperature as $150^{\circ}C$. The power consumption was 72 mW at $250^{\circ}C$, and only 25 mW at $150^{\circ}C$.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.163-168
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• 2003

In the present study, the piezoelectricity and polarization of multilayer ceramic actuator, being designed to stack PMN-PZ-PT ceramic layers and Ag-Pd electrode layers alternatively, were investigated under a consideration of geometric factor, the volume ratio of the ceramic to the electrode layers. The actuators were fabricated by tape casting of $0.2Pb(Mg_{1/3}Nb_{2/3)O_3-0.38PbZrO_3-0,42PbTiO_3$ followed by lamination and burnout & co-firing processes. The actuators of $10\times10\times0.6~2\textrm{mm}^3$ in size were formed in a way that $60 ~ 200\mu\textrm{m}$ thick were stacked alternatively with $5\mu\textrm{m}$ thick electrode layer. Increases in polarization and electric field-induced displacement with thickness of the ceramic layer were attributed to change of $90^{\circ}$/$180^{\circ}$ domain ratio, which was affected by interlayer internal stress. The piezoelectricity and actuation behaviors were found to depend upon the volume ratio (or thickness ratio) of ceramic to electrode layers.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.483-487
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• 2010

To fabricate $TiO_2$ nanoparticle-based dye sensitized solar cells (DSSCs) at a low-temperature, DSSCs were fabricated using hydropolymer and ZnO nanoparticles composites for the electron transport layer around a low-temperature ($200^{\circ}C$). ZnO nanoparticle with 20 nm and 60 nm diameter were used and Pt was deposited as a counter electrode on ITO/glass using an RF magnetron sputtering. We investigate the effect of ZnO nanoparticle concentration in hydropolymer and ZnO nanoparticle solution on the photoconversion performance of the low temperature fabricated ($200^{\circ}C$) DSSCs. Using cis-bis(isothiocyanato)bis(2,20 bipyridy1-4,40 dicarboxylato) ruthenium (II) bis-tetrabutylammonium (N719) dye as a sensitizer, the corresponding device performance and photo-physical characteristics are investigated through conventional physical characterization techniques. The effect of thickness of the ZnO photoelectrode and the morphology of the ZnO nanoparticles with the variations of hydropolymer to ZnO ratio on the photoconversion performance are also investigated. The morphology of the ZnO layer after sintering was examined using a field emission scanning electron microscope (FE-SEM). 60 nm ZnO nanoparticle DSSCs showed an incident photon-to-current conversion efficiency (IPCE) value of about 7% higher than that of 20 nm ZnO nanoparticle DSSCs. The maximum parameters of the short circuit current density ($J_{sc}$), the open circuit potential ($V_{oc}$), fill factor (ff), and efficiency ($\eta$) in the 60 nm ZnO nanoparticle-based DSSC devices were 4.93 mA/$cm^2$, 0.56V, 0.40, and 1.12%, respectively.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.807-811
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• 2000

CeO$_2$ and SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin films for MFISFET (Metal-ferroelectric-insulator-semiconductor-field effect transistor) were deposited by r.f. sputtering and pulsed laser ablation method, respectively. The effects of sputtering gas ratio(Ar:O$_2$) during deposition for CeO$_2$ films were investigated. The CeO$_2$ thin films deposited on Si(100) substrate at $600^{\circ}C$ exhibited (200) preferred orientation. The preferred orientation, Brain size and surface roughness of films decreased with increasing oxygen to argon gas ratio. The films deposited under the condition of Ar:O$_2$= 1 : 1 showed the best C- V characteristics. The leakage current of films showed the order of 10$^{-7}$ ~10$^{-8}$ A at 100kV/cm. The SBT thin films on CeO$_2$/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure with SBT film annealed at 80$0^{\circ}C$, the memory window width was 0.9V at 5V The leakage current density of Pt/SBT/CeO$_2$/Si structure annealed at 80$0^{\circ}C$ was 4$\times$10$^{-7}$ /$\textrm{cm}^2$ at 5V.

• Transactions on Electrical and Electronic Materials
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• v.12 no.5
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• pp.193-196
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• 2011

Lead zirconate titanate (PZT)/ bismuth ferrite (BFO) multilayer thin films have been fabricated by the spin-coating method on Pt(200 nm)/Ti(10 nm)/$SiO_2$(100 nm)/p-Si(100) substrates using $BiFeO_3$ and $Pb(Zr_{0.52}Ti_{0.48})O_3$ metal alkoxide solutions. The PZT/BFO multilayer thin films show a uniform and void-free grain structure, and the grain size is smaller than that of PZT single films. The reason for this is assumed to be that the lower BFO layers play an important role as a nucleation site or seed layer for the formation of homogeneous and uniform upper PZT layers. The dielectric constant and dielectric losses decreased with increasing number of coatings, and the six-layer PZT/BFO thin film has good properties of 162 (dielectric constant) and 0.017 (dielectric losses) at 1 kHz. The remnant polarization and coercive field of three-layer PZT/BFO thin films were 13.86 ${\mu}C/cm^2$ and 37 kV/cm respectively.