• 한국세라믹학회지
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• 제49권6호
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• pp.631-636
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• 2012

Conventional SONOS (poly-silicon/oxide/nitride/oxide/silicon) type memory is associated with a retention issue due to the continuous demand for scaled-down devices. In this study, $Al_2O_3/Y_2O_3/SiO_2$ (AYO) multilayer structures using a high-k $Y_2O_3$ film as a charge-trapping layer were fabricated for nonvolatile memory applications. This work focused on improving the retention properties using a $Y_2O_3$ layer with different tunnel oxide thickness ranging from 3 nm to 5 nm created by metal organic chemical vapor deposition (MOCVD). The electrical properties and reliabilities of each specimen were evaluated. The results showed that the $Y_2O_3$ with 4 nm $SiO_2$ tunnel oxide layer had the largest memory window of 1.29 V. In addition, all specimens exhibited stable endurance characteristics (program/erasecycles up to $10^4$) due to the superior charge-trapping characteristics of $Y_2O_3$. We expect that these high-k $Y_2O_3$ films can be candidates to replace $Si_3N_4$ films as the charge-trapping layer in SONOS-type flash memory devices.

• 한국표면공학회지
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• 제53권1호
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• pp.9-14
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• 2020

CuS (copper sulfide) thin films having the same thickness of 100nm were deposited on the glass substrates using by radio frequency (RF) magnetron sputtering method. RF powers were applied as a process variable for the growth of CuS thin films. The structural and optical properties of CuS thin films deposited under different power conditions (40-100W) were studied. XRD analysis revealed that all CuS thin films had hexagonal crystal structure with the preferential growth of (110) planes. As the sputtering power increased, the relative intensity of the peak with respect to the (110) planes decreased. The peaks of the two bands (264cm^-1 and 474cm^-1) indicated in the Raman spectrum exactly matched the typical spectral values of the covellite (CuS). The size and shape of the grains constituting the surface of the CuS thin films deposited under the power condition ranging from 40W to 80W hardly changed. However, the spacing between crystal grains tended to increase in proportion to the increase in sputtering power. The maximum transmittance of CuS thin films grown at 40W to 80W ranged from 50 % to 51 % based on 580nm wavelength, and showed a relatively small decrease of 48% at 100W. The band gap energy of the CuS thin films decreased from 2.62eV (at 40W) to 2.56eV (at 100W) as the sputtering power increased.

• 한국분말재료학회지
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• 제17권6호
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• pp.456-463
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• 2010

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and $1.14\;{\mu}m$. The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.

• 한국표면공학회지
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• 제41권3호
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• pp.88-93
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• 2008

Ir-Re thin films with Ti interlayer were deposited onto the tungsten carbide substrate by ion beam assisted DC magnetron sputtering. The Ir-Re films were prepared with targets of having two atomic percent of 7:3 and 5:5. The microstructure and surface analysis of the specimen were conducted by using SEM, XRD and AFM. Mechanical properties such as hardness and adhesion strength of Ir-Re thin film also were examined. The interlayer of pure titanium was formed with 100 nm thickness. The film growth of Ir-30at.%Re was faster than that of Ir-50at.%Re in the same deposition conditions. Ir-Re thin films consisted of dense and columnar structure irrespective of the different target compositions. The values of hardness and adhesion strength of Ir-30at.%Re thin film coated on WC substrate were higher than those of Ir-50at.%Re thin film.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.176-176
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• 2007

Flat-panel direct conversion detectors used in compound substance of semiconductor are being studied for digital x-ray imaging. Recently, such detectors are deposited by physical vapor deposition(PVD) generally. But, most of materials (HgI2, PbI2, TlBr, PbO) deposited by PVD have shown difficult fabrication and instability for large area x-ray imaging. Consequently, in this paper, we propose applicable potentialities for screen printing method that is coated on a substrate easily. It is compared to electrical properties among semiconductors such as $HgI_2$, $PbI_2$, PbO, HgBrI, InI, and $TlPbI_3$ under investigation for direct conversion detectors. Each film detector consists of an ~25 to $35\;{\mu}m$ thick layer of semiconductor and was coated onto the substrate. Substrates of $2cm{\times}2cm$ have been used to evaluate performance of semiconductor radiation detectors. Dark current, sensitivity and physics properties were measured. Leakage current of $HgI_2$ as low as $9pA/mm^2$ at the operation bias voltage of ${\sim}1V/{\mu}m$ was observed. Such a value is not better than PVD process, but it is easy to be fabricated in high quality for large area x-ray Imaging. Our future efforts will concentrate on optimization of growth of film thickness that is coated onto a-Si TFT array.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.158-161
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• 2004

We have studied a lifetime in organic light-emitting diodes depending on buffer layer. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. And the cathode for electron injection was LiAl. Phthalocyanine Copper(CuPc), Poly(3,4-ethylenedioxythiophene):poly (PEDOT:PSS), or poly (9-vinylcarbazole)(PVK) material was used as a buffer layer. A thermal evaporation was performed to make a thickness of 40nm of TPD layer at a rate of $0.5{\sim}1\;{\AA}/s$ at a base pressure of $5{\times}10^{-6}\;torr$. A material of tris(8-hydroxyquinolinate) Aluminum($Alq_3$) was used as an electron transport and emissive layer. A thermal evaporation of $Alq_3$ was done at a deposition rate of $0.7{\sim}0.8[{\AA}/s]$ at a base pressure of $5{\times}10^{-6}\;torr$. By varying the buffer material, hole injection at the interface could be controlled because of the change in work function. Devices with CuPc and PEDOT:PSS buffer layer are superior to the other PVK buffer layer.

• Transactions on Electrical and Electronic Materials
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• 제17권4호
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• pp.196-200
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• 2016

We have developed new electrostatic discharge (ESD) protection devices with, bidirectional flip chip transient voltage suppression. The devices differ in their epitaxial (epi) layers, which were grown by reduced pressure chemical vapor deposition (RPCVD). Their ESD properties were characterized using current-voltage (I-V), capacitance-voltage (C-V) measurement, and ESD analysis, including IEC61000-4-2, surge, and transmission line pulse (TLP) methods. Two BD-FCTVS diodes consisting of either a thick (12 μm) or thin (6 μm), n-Si epi layer showed the same reverse voltage of 8 V, very small reverse current level, and symmetric I-V and C-V curves. The damage found near the corner of the metal pads indicates that the size and shape of the radius governs their failure modes. The BD-FCTVS device made with a thin n- epi layer showed better performance than that made with a thick one in terms of enhancement of the features of ESD robustness, reliability, and protection capability. Therefore, this works confirms that the optimization of device parameters in conjunction with the doping concentration and thickness of epi layers be used to achieve high performance ESD properties.

• 한국진공학회지
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• 제7권2호
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• pp.104-111
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• 1998

저압 MOCVD 방법을 이용하여 InGaAs/InP 양자우물구조를 성장하였다. 성장 정지 시간에 따른 photoluminescence특성의 변화를 통하여 계면구조를 분석하였다. InP표면을 $PH_3$ 분위기로, InGaAs표면을 $AsH_3$분위기로 유지하며 성장을 정지하는 경우에는 성장 정지 시간이 길어짐에 따라 불순물 유입에 의한 것으로 생각되는 PL반가폭의 증가를 관찰하였다. InP표면에 AsH3을 공급하는 경우에는 As-P교환에 의해 우물층 두께가 증가하여 PL피크가 저에너지로 이동하였고, 반가폭의 변화는 크지 않았다. 계면 양자우물구조를 형성하여 As-P 교환작용에 대해 조사하였고, 1-2monolayer가 InAs유효두께로 계산되었다. InGaAs 표면에 $PH_3$을 공급한 결과, PL피크가 고에너지로 이동하는 것을 관찰하였고 동시에 반가폭도 증가 하였다. 이는 메모리 효과에 의해 InP층으로 As침투를 억제하고, InGaAs표면에서의 국부적 인 As-P교환에 의한 것으로 생각된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.230-230
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• 2010

유기물 반도체 화합물인 Cu-Pc(copper(II)-phthalocyanine)는 우수한 전기적 광학적 특성을 가지며, OLED, MISFET등 소자로서의 활용도가 높다. Cu-Pc 화합물은 $\alpha$-phase, $\beta$-phase, $\gamma$-phase를 포함하는 여러 가지 다결정 polymer로 존재할 수 있다. 가장 잘 알려진 구조로는 열적으로 준안정적인 $\alpha$-phase와 열적으로 안정적인 $\beta$-phase가 있다. Cu-Pc 박막의 구조 및 흡수 특성과 전기적 특성에 대한 기술이 확실히 규명되지 않아 본 연구에서는 두께와 열처리 조건에 따른 결정성 및 방향성을 조사하기 위하여 $\alpha$-phase와 $\beta$-phase의 phase transition 현상 및 전기적 광학적 특성을 규명 하고자 한다. 진공증착 방법 중 하나인 PVD 방법의 thermal evaporation deposition을 이용하여 glass, ITO 기판위에 두께와 열처리에 따른 전기적?광학적 특성을 연구하였다. Cu-Pc 박막의 성장두께는 5nm~50nm 이내로 fluxmeter 및 thickness monitor를 이용하여 제어하였다. 5nm~50nm의 두께에 따른 기판온도를 $200^{\circ}C$로 고정하여 전열 처리 및 후열 처리하여 온도에 따른 박막을 성장한 후, 결정 구조 및 특성 변화와 phase transition 분석하였다. 제작된 Cu-Pc의 박막은 $\alpha$-phase와 $\beta$-phase로 구분할 수 있으며, 열처리에 따른 phase transition 현상이 뚜렷함을 알 수 있다. XRD(X-ray diffraction)를 통하여 박막에 대한 결정 구조 분석 및 FE-SEM(field emission scanning electron microscopy)와 AFM(atomic force microscopy)을 이용하여 Cu-Pc 박막의 구조적 결정성과 방향성 등, 표면 상태와 형상구조에 대해 표면의 특성을 측정하며, 광 흡수도(UV-visible absorption spectra)을 이용하여 phase transition 현상에 따른 I-V 특성을 비교분석 하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.382-382
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• 2010

$TaO_2$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility in achieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFETchannel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. The atomic structure of amorphous and crystalline Tantalum oxide ($TaO_2$) gate dielectrics thin film on Si (100) were grown by utilizing atomic layer deposition method was examined using Ta-K edge x-ray absorption spectroscopy. By using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) the electronic and optical properties was obtained. In this study, the band gap (3.400.1 eV) and the optical properties of $TaO_2$ thin films were obtained from the experimental inelastic scattering cross section of reflection electron energy loss spectroscopy (REELS) spectra. EXAFS spectra show that the ordered bonding of Ta-Ta for c-$TaO_2$ which is not for c-$TaO_2$ thin film. The optical properties' e.g., index refractive (n), extinction coefficient (k) and dielectric function ($\varepsilon$) were obtained from REELS spectra by using QUEELS-$\varepsilon$(k, $\omega$)-REELS software shows good agreement with other results. The energy-dependent behaviors of reflection, absorption or transparency in $TaO_2$ thin films also have been determined from the optical properties.