• Korean Journal of Materials Research
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• v.29 no.5
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• pp.322-327
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• 2019

Hole carrier selective MoOx film is obtained by atomic layer deposition(ALD) using molybdenum hexacarbonyl[$Mo(CO)_6$] as precursor and ozone($O_3$) oxidant. The growth rate is about 0.036 nm/cycle at 200 g/Nm of ozone concentration and the thickness of interfacial oxide is about 2 nm. The measured band gap and work function of the MoOx film grown by ALD are 3.25 eV and 8 eV, respectively. X-ray photoelectron spectroscopy(XPS) result shows that the $Mo^{6+}$ state is dominant in the MoOx thin film. In the case of ALD-MoOx grown on Si wafer, the ozone concentration does not affect the passivation performance in the as-deposited state. But, the implied open-circuit voltage increases from $576^{\circ}C$ to $620^{\circ}C$ at 250 g/Nm after post-deposition annealing at $350^{\circ}C$ in a forming gas ambient. Instead of using a p-type amorphous silicon layer, high work function MoOx films as hole selective contact are applied for heterojunction silicon solar cells and the best efficiency yet recorded (21 %) is obtained.

• Current Photovoltaic Research
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• v.10 no.4
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• pp.95-100
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• 2022

Solar cell is a device that converts photon energy into electrical energy. Therefore, absorption of solar spectrum light is one of the most important characteristics to design the solar cell structures. Various methods have emerged to reduce optical losses, such as textured surfaces, back contact solar cells, anti-reflection layers. Here, the anti-reflection coating (ARC) layer is typically utilized whose refractive index value is between air (~1) and silicon (~4) such as SiN_x layer (~1.9). This research is to print a material called polydimethylsiloxane (PDMS) to form a double anti-reflection layer. Light with wavelength in the range of 0.3 to 1.2 micrometers does not share a wavelength with solar cells. It is confirmed that the refractive index of PDMS (~1.4) is an ARC layer which decreases the reflectance of light absorption region on typical p-type solar cells with SiN_x layer surface. Optimized PDMS printing with analyzing optical property for cell structure can be the effective way against outer effects by encapsulation.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2434-2440
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• 2018

A new type of piezoelectric micromachined ultrasonic transducer (pMUT) with high resonant frequency was developed by using a thin lead zirconate titanate (PZT) as an insulation layer on a floating $10{\mu}m$ silicon membrane. The PZT insulation layer facilitated acoustic impedance matching at active pMUT, leading to a high performance in the acoustic conversion property compared with the transducer using $SiO_2$ insulation layer. The fabricated ultrasonic devices were wirelessly measured by connecting two identical acoustic transducers to two separate ports in a single network analyzer simultaneously. The acoustic wave emitted from a transducer induced a $3.16{\mu}W$ on the other side of the transducer at a distance of 2 cm. The transducer performances in terms of device diameters, PZT thickness, annealings, and different DC polings, etc. were investigated. COMSOL simulation was also performed to predict the device performances prior to fabrication. Based on the COMSOL simulation, the device was fabricated and the results were compared.

• Solar Energy
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• v.5 no.2
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• pp.46-53
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• 1985

Hydrogenated amorphous silicon solar cells which are fabricated by photo-chemical vapor deposition (photo-CVD) system has been investigated. In the photo-CVD system which consists of three separate reaction chambers, low-pressure mercury lamp has been used as a light source. The main reactant ($Si_2H_6/He$) gases which are premixed with a small amount of mercury vapor in a mercury-vaporizer kept at $50^{\circ}C$ have been used. Using $C_2H_2$ and $SiH_2(CH_3)_2$ as the carbon source, p-type wide band gap a-SiC:H films have been obtained. The result has been found that the undoped layers of the pin/substrate solar cells are influenced by the residual impurities, such as phosphorus and boron during the deposition process. By minimizing the effect of the impurities in the i-layer and optimizing conditions at the p-layer and p/i interface, the energy conversion efficiency of 9.61 % under AM-1 ($100mW/Cm^2$) has been achieved for pin/substrate solar cells illuminated through their p-layers, using the three separate reaction chamber apparatus. It is expected that a-SiC:H solar cells with the energy conversion efficiency over 10% have been fabricated by Photo-CVD method.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.229-235
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• 2002

This paper presents the fabrication of polycrystalline thin film transistor(TFT) using sequential lateral solidification(SLS) of amorphous silicon. The fabricated SLS TFT showed high Performance suitable for active matrix liquid crystal display(AMLCD). The SLS process involves (1) a complete melting of selected area via irradiation through a patterned mask, and (2) a precisely controlled pulse translation of the sample with respect to the mask over a distance shorter than the super lateral growth(SLG) distance so that lateral growth extended over a number of iterative steps. The SLS experiment was performed with 550$\AA$ a-Si using 308nm XeCl laser having $2\mu\textrm{m}$ width. Irradiated laser energy density is 310mJ/$\textrm{cm}^2$ and pulse duration time was 25ns. The translation distance was 0.6$\mu$m/pulse, 0.8$\mu$m/pulse respectively. As a result, a directly solidified grain was obtained. Thin film transistors (TFTs) were fabricated on the poly-Si film made by SLS process. The characteristics of fabricated SLS p -type poly-Si TFT device with 2$\mu\textrm{m}$ channel width and 2$\mu\textrm{m}$ channel length showed the mobility of 115.5$\textrm{cm}^2$/V.s, the threshold voltage of -1.78V, subthreshold slope of 0.29V/dec, $I_{off}$ current of 7$\times$10$^{-l4}$A at $V_{DS}$ =-0.1V and $I_{on}$ / $I_{off}$ ratio of 2.4$\times$10$^{7}$ at $V_{DS}$ =-0.1V. As a result, SLS TFT showed superior characteristics to conventional poly-Si TFTs with identical geometry.y.y.y.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.303-307
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• 2006

In this paper, we have designed the p-type metal-oxide semiconductor field-effect transistor(pMOSFET) for SiGe devices with gate lengths of $0.9{\mu}m$ and $0.1{\mu}m$using the TCAD simulators. The electrical characteristics of devices have been investigated over the temperatures of 300 and 77K. We have used the two carrier transfer models(hydrodynamic model and drift-diffusion model). We how that the drain current is higher in the hydrodynamic model than the drift-diffusion model. When the gate length is $0.9{\mu}m$, the threshold voltage shows -0.97V and -1.15V for 300K and 77K, respectively. The threshold voltage is, however, nearly same at $0.1{\mu}m$ for 300K and 77K.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.367-373
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• 2011

It is described that the proton beam induces micro defects and electronic deep levels in Cz single crystal silicon. Enhance signal-to-noise ratio, Coincidence Doppler Broadening Positron Annihilation Spectroscopy has been applied to study of characteristics of p type and n type silicon samples. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The samples were exposed by 4.0 MeV proton beams ranging from 0 to ${\sim}10^{14}$ ptls. The S-parameter values were increased as increasing the irradiated proton beam, that indicated the defects generate more.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.8-9
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• 2006

Hafnium oxide ($HfO_2$) thin films were deposited on p-type (100) silicon wafers by atomic layer deposition (ALD) using TEMAHf and $O_3$. Prior to the deposition of $HfO_2$ films, a thin Hf ($10\;{\AA}$) metal layer was deposited. Deposition temperature of $HfO_2$ thin film was $350^{\circ}C$ and its thickness was $150\;{\AA}$. Samples were then annealed using furnace heating to temperature ranges from 500 to $900^{\circ}C$. The MOS capacitor of round-type was fabricated on Si substrates. Thermally evaporated $3000\;{\AA}$-thick AI was used as top electrode. In this work, We study the interface characterization of $HfO_2$/Hf/Si MOS capacitor depending on annealing temperature. Through AES(Auger Electron Spectroscopy), capacitance-voltage (C-V) and current-voltage (I-V) analysis, the role of Hf layer for the better $HfO_2$/Si interface property was investigated. We found that Hf meta1 layer in our structure effective1y suppressed the generation of interfacial $SiO_2$ layer between $HfO_2$ film and silicon substrate.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.27-31
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• 2000

A series experiments were performed to evaluate mechanical behavior of non-oxide boride type ceramics formed on the AISI 1040 plain carbon steel. Boronizing was performed in a slurry salt bath consisting of borax, boric acid, and ferro-silicon at $950^{\circ}C$ for 2-6h. The AISI 1040 steel used as substrate material was containing 0.4%C, 0.13%Si, 0.65%Mn, 0.02%P, 0.014%S. The presence of non-oxide boride type ceramics $Fe_2B $ and FeB formed on the surface of steel was confirmed by metallographic technique and X-ray diffraction (XRD) analysis. The hardness of borides measured via Vickers indenter with a load of 2N reached a microhardness of up to 1800 DPN. The hardness of unborided steel was 185 DPN. The fracture toughness of borides measured by means of Vickers indenter with a load of 10N was about 2.30 MPa.$m^{1/2}$. The thickness of boride layers ranged from 72$\mu\textrm{m}$ to 145$\mu\textrm{m}$. Boride layers have a columnar morphology.

• Journal of Sensor Science and Technology
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• v.24 no.4
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• pp.219-223
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• 2015

Indium free consisting of three alternating layers GTO/Ag/GTO has been fabricated by radio-frequency (RF) sputtering for the applications as transparent conducting electrodes and the structural, electrical and optical properties of the gallium tin oxide (GTO) films were carefully studied. The gallium tin oxide thin films deposited at room temperature are found to have an amorphous structure. Hall Effect measurements show a strong influence on the conductivity type where it changed from n-type to p-type at $700^{\circ}C$. GTO/Ag/GTO multilayer structured electrode with a few nm of Ag layer embedded is fabricated and show the optical transmittance of 86.48% in the visible range (${\lambda}$ = 380~770 nm) and quite low electrical resistivity of ${\sim}10^{-5}{\Omega}cm$. The resultant power conversion efficiency of 2.60% of the multilayer based OPV (GAG) is lower than that of the reference commercial ITO. GTO/Ag/GTO multilayer is a promising transparent conducting electrode material due to its low resistivity, high transmittance, low temperature deposition and low cost components.