• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.174-177
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• 1991

Fluorine-doped $SnO_2\;(SnO_2:F)$ films were prepared in ordinary atmosphere on borosilicate glass substrates using pyrosol deposition method starting from the solutions composed of $SnCl_4-5H_2O-NH_4F-CH_3OH-H_2O-HCl$ in an attempt to develop transparent conductors for use in amorphous silicon (a-Si) solar cello. The deposition rate of films increased with the increase in the content of $H_2O$, whereas it decreased with increasing the content of $CH_3OH$. When air was used as the carrier gas, the lowest electrical resistivity was obtained from a solution having $CH_3OH/H_2O$ mol ratio of about $2{\sim}3$ in the solution. The use of $N_2$ of the same flow rate as the carrier gab resulted always in the high resistive films, but the resistivity of the films decreased continuously with the increase in the content of $H_2O$. The surface morphology and preferred orientation of films were also affected by the solvent composition and the content of HCl in the solution. The room-temperature resistance of the films were fairly stable after heat-treatments up to $600^{\circ}C$.

• Transactions on Electrical and Electronic Materials
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• 제12권2호
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• pp.72-75
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• 2011

In this study, $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3+0.9$ mol% $K_{5.4}Cu_{1.3}Ta_{10}O_{29}+x$ mol% $K_4CuNb_8O_{23}$ (x = 0, 0.2, 0.6, 0.8) ceramics were prepared by a conventional mixed oxide method. Their microstructure and electric properties were investigated. The secondary phase was made by virtue of $K_4CuNb_8O_{23}$ (KCN) addition in the $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3$ system ceramics. However, the sinterability of the ceramics increased with increasing $K_4CuNb_8O_{23}$ content. At the 0.6 mol% $K_4CuNb_8O_{23}$ added composition ceramics sintered at $1,060^{\circ}C$, kp and $d_{33}$ showed the optimum values of 0.39 and 145 pC/N, respectively, suitable for piezoelectric actuator application.

• 한국전기전자재료학회논문지
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• 제31권3호
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• pp.165-170
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• 2018

In this study, double-layered TCO (transparent conductive oxide) films were produced by depositing two distinct TCO materials: $SnO_2$ works as an n-type layer and ITO (indium-doped tin oxide) serves as a transparent conductor. Both transparent conductive oxide-films were sequentially deposited by sputtering. The electrical and optical properties of single-layered TCO films ($SnO_2$) and double-layered TCO ($ITO/SnO_2$) films were investigated. A TCO-embedding photodetector was realized through the formation of an $ITO/SnO_2/p-Si/Al$ layered structure. The remarkably high rectifying ratio of 400.64 was achieved with the double-layered TCO device, compared to 1.72 with the single-layered TCO device. This result was attributed to the enhanced electrical properties of the double-layered TCO device. With respect to the photoresponses, the photocurrent of the double-layered TCO photodetector was significantly improved: 1,500% of that of the single-layered TCO device. This study suggests that, due to the electrical and optical benefits, double-layered TCO films are effective for enhancing the photoresponses of TCO photodetectors. This provides a useful approach for the design of photoelectric devices, including solar cells and photosensors.

• 한국전기전자재료학회논문지
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• 제25권3호
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• pp.198-203
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• 2012

In this study, $[Li_{0.04}(Na_{0.5}K_{0.5})_{0.96}](Nb_{0.86}Ta_{0.10}Sb_{0.04})O_3+xSrO$ (x=0, 0.0025, 0.005, 0.0075) ceramics were synthesized by the conventional mixed oxide method. The X-ray diffraction patterns demonstrated that ceramics possessed single perovskite structure. The SEM images indicate that microstructure can be obviously affected by a small amount of added SrO. The phase transition temperature tetragonal-cubic($T_c$) and orthorhombic-tetragonal($T_{o-t}$) shifts downward and upward with the increase of Sr addition, respectively. The excellent piezoelectric properties of $d_{33}=170[pC/N]$, $k_p=0.37$, $Q_m=64.12$, $T_{o-t}=153^{\circ}C$ and $T_c=370^{\circ}C$ were obtained from the 0.25 mol% Sr added ceramics sintered at $1,120^{\circ}C$ for 1 h.

• Current Photovoltaic Research
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• 제8권1호
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• pp.6-11
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• 2020

The power conversion efficiency (PCE) of a two-terminal tandem solar cell depends upon the tunnel-recombination junction (TRJ) between the top and bottom sub-cells. An optimized TRJ in a tandem cell helps improve its open-circuit voltage (V_oc), short-circuit current density (J_sc), fill factor (FF), and efficiency (PCE). One of the parameters that affect the TRJ is the buffer layer thickness. Therefore, we investigated various TRJs by varying the thickness of the buffer or intermediate layer (TRJ-buffer) in between the highly doped p-type and n-type layers of the TRJ. The TRJ-buffer layer was p-type nc-Si:H, with a doping of 0.06%, an activation energy (E_a) of 43 meV, an optical gap (E_g) of 2.04 eV, and its thickness was varied from 0 nm to 125 nm. The tandem solar cells we investigated were a combination of a heterojunction with intrinsic thin layer (HIT) bottom sub-cell and an a-Si:H (amorphous silicon) top sub-cell. The initial cell efficiency without the TRJ buffer was 7.65% while with an optimized buffer layer, its efficiency improved to 11.74%, i.e., an improvement in efficiency by a factor of 1.53.

• ETRI Journal
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• 제14권1호
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• pp.40-51
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• 1992

$0.25{\mu} m$ 급 pMOSFET소자를 구현하기 위해, $P^+$ 폴리실리콘을 적용한 pMOS를 제작하였으며, $p^+$ 폴리실리콘 게이트 소자에서 심각하게 문제가 되고 있는 붕소이온 침투현상을 조사하고 붕소이온 침투가 일어나지 않는 최적열처리온도를 조사하였다. 소자제조 공정중 게이트 공정만 전자선 (EBML300)을 이용하여 직접묘사하고 그 이외의 공정은 stepper(gline) 을 사용하는 Mix & Match 방법을 사용하였다. 또한 붕소이온 침투현상을 억제하기 위한 한가지 예로서, 실리콘산화막과 실리콘질화막을 적층한 ONO(Oxide/Nitride/Oxide) 구조를 게이트 유전체로 적용한 소자를 제작하여 그 가능성을 조사하였다. 그 결과 $850^{\circ}C$의 온도와 $N_2$ 분위기에서 30분동안 열처리 하였을 경우, 붕소이온의 침투현상이 일어나지 않음을 SIMS(Secondary Ion Mass Spectrometer) 분석 및 C-V(Capacitance-Voltage) 측정으로 확인할 수 있었으며 그 이상의 온도에서는 붕소이온이 침투되어 flat band전압(Vfb)을 변화시킴을 알았다. 6nm의 얇은 게이트 산화막 및 $0.1{\mu} m$ 이하의 LDD(Lightly Doped Drain) $p^-$의 얇은 접합을 형성함으로써 소자의 채널길이가 $0.2 {\mu} m$까지 짧은 채널효과가 거의 없는 소자제작이 가능하였으며, 전류구동능력은 $0.26\muA$/$\mu$m(L=0.2$\mu$m, V$_DS$=2.5V)이었고, subthreshold 기울기는 89-85mV/dec.를 얻었다. 붕소이온의 침투현상을 억제하기 위한 한가지 방법으로 ONO 유전체를 소자에 적용한 결과, $900^{\circ}C$에서 30분의 열처리조건에서도 붕소이온 침투현상이 일어나지 않음으로 미루어 , $SiO_2$ 게이트 유전체보다 ONO 게이트 유전체가 boron 침투에 대해서 좋은 장벽 역활을 함을 알았다. ONO 게이트 유전체를 적용한 소자의 경우, subthreshold특성은 84mV/dec로서 좋은 turn on,off 특성을 얻었으나, ONO 게이트 유전체는 막자체의 누설전류와 실리콘과 유전체 계면의 고정전하량인 Qss의 양이 공정조건에 따라 변화가 심해서 문턱전압 조절이 어려워 소자적용시 문제가 된다. 최근 바닥 산화막(bottom oxide) 두께가 최적화된 ONO 게이트 유전체에 대하 연구가 활발히 진행됨을 미루어, 바닥 산화막 최적화가 된다면 더 좋은 결과가 예상된다.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.41-44
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• 2014

본 연구에서는 $TiO_2$에 나이오븀 (Nb) 도펀트가 주입되었을 때의 활성화 에너지를 홀 효과 측정 시스템과 온도에 따른 photoluminescence (PL) 실험을 통하여 살펴보았다. Nb 이 도핑 된 n형 아나타제 $TiO_2$ 박막은 pulsed laser deposition (PLD) 기법으로 $SrTiO_3$기판에 성장되었다. 측정 결과, Nb 도너의 활성화 에너지 값은 홀 효과 측정에서는 14.52 meV, PL 측정에서는 6.72 meV로 다소 차이를 보였다. 이 결과는 기존의 어셉터 물질의 활성화 에너지들과는 차이를 나타내고 있으며, 향후 본 연구와 같은 shallow 도너 준위의 활성화 에너지 연구에 대한 더 많은 연구가 필요할 것으로 판단된다.

• 한국세라믹학회지
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• 제31권10호
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• pp.1147-1158
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• 1994

From Zr(O-nC3H7)4-H2O-C2H5OH-HNO3 starting solutions, MgO-doped stabilized zirconia fibers with varying content of MgO (10~18 mol%) from different MgO sources were fabricated by sol-gel method. The MgO sources used are magnesium nitrate hexahydrate, magnesium acetate tetrahydrate, and magnesium ethylate. The phase transformation studies of a drawn MgO-ZrO2 fiber were carried out using X-ray diffraction, IR spectroscopy, and Raman spectroscopy. The microstructure, tensile strength, and microporosity of fibers were investigated using SEM, tensile strength test, and microporosimeter. Although various MgO sources such as magnesium nitrate, acetate, and ethylate were used, the crystallization behavior of MgO-ZrO2 fibers at different temperatures could be summarized as follows: CubiclongrightarrowMetastable TetragonallongrightarrowMonocliniclongrightarrowCoexistence of Monoclinic and CubiclongrightarrowCubic(trace of monoclinic). At 150$0^{\circ}C$, the phase transformation of MgO-ZrO2 fibers shows the following change depending on the amount of MgO[Mg(NO3)2.6H2O]: At 10 mol%, both monoclinic and cubic phase coexist, at 12 mol%, monoclinic phase decreases rapidly, and then at 14 mol%, only cubic phase remains. When the MgO-ZrO2 fibers containing 12 mol% magnesium nitrate were heated at 80$0^{\circ}C$ for 1hr, average tensile strength of fibers is 4.0 GPa at diameters of 20 to 30 ${\mu}{\textrm}{m}$. As the heat-treatment temperatures increase to 100$0^{\circ}C$ for 1 hr, tensile strength of MgO-ZrO2 fibers decreases rapidly to 0.7 GPa.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.422-448
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• 1996

Low-temperature epitaxial growth of Si and SiGe layers of Si is one of the important processes for the fabrication of the high-speed Si-based heterostructure devices such as heterojunction bipolar transistors. Low-temperature growth ensures the abrupt compositional and doping concentration profiles for future novel devices. Especially in SiGe epitaxy, low-temperature growth is a prerequisite for two-dimensional growth mode for the growth of thin, uniform layers. UHV-ECRCVD is a new growth technique for Si and SiGe epilayers and it is possible to grow epilayers at even lower temperatures than conventional CVD's. SiH and GeH and dopant gases are dissociated by an ECR plasma in an ultrahigh vacuum growth chamber. In situ hydrogen plasma cleaning of the Si native oxide before the epitaxial growth is successfully developed in UHV-ECRCVD. Structural quality of the epilayers are examined by reflection high energy electron diffraction, transmission electron microscopy, Nomarski microscope and atomic force microscope. Device-quality Si and SiGe epilayers are successfully grown at temperatures lower than 600℃ after proper optimization of process parameters such as temperature, total pressure, partial pressures of input gases, plasma power, and substrate dc bias. Dopant incorporation and activation for B in Si and SiGe are studied by secondary ion mass spectrometry and spreading resistance profilometry. Silicon p-n homojunction diodes are fabricated from in situ doped Si layers. I-V characteristics of the diodes shows that the ideality factor is 1.2, implying that the low-temperature silicon epilayers grown by UHV-ECRCVD is truly of device-quality.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.388-388
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• 2010

In this study, Ferroelectric vinylidene fluoride-trifluoroethylene (VF2-TrFE) copolymer films were directly deposited on degenerated Si (n+, $0.002\;{\Omega}{\cdot}cm$) using by spin coating method. A 1~5 wt% diluted solution of purified vinylidene fluoride-trifluoroethylene (VF2:TrFE = 70:30) in a dimethylformamide (DMF) solvent were prepared and deposited on silicon wafers at a spin rate of 2000 ~ 4000 rpm for 2 ~ 30 seconds. After annealing in a vacuum ambient at 100 ~ $200^{\circ}C$ for 60 min, upper aluminum electrodes were deposited by vacuum evaporation for electrical measurement. X-ray diffraction results showed that the VF2-TrFE films on Si substrates had $\beta$-phase of copolymer structures. The capacitance on highly doped Si wafer showed hysteresis behavior like a butterfly shape and this result indicates clearly that the copolymer films have ferroelectric properties. The typical measured remnant polarization ($P_r$) and coercive filed ($E_c$) values were about $5.7\;{\mu}C/cm^2$ and 710 kV/em, respectively, in an applied electric field of ${\pm}$ 1.5 MV/em. The gate leakage current densities measured at room temperature was less than $7{\times}10^{-7}\; A/cm^2$ under a field of 1 MV/cm.