• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.151.1-151.1
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• 2016

Complex oxide heterointerfaces have been extensively explored in the past due to the novel phenomenon emerging at such interfaces that differ from their individual bulk counterparts. The integration of a ferromagnetic (FM) material with the superconducting (SC) material leading to proximity effect is one of the commonly studied phenomenon in these heterostructures. In continuation, we have stabilized the FM layer La0.7Ca0.3MnO3 (LCMO) on SC material YBa2Cu3O7-${\delta}$ (YBCO) using pulsed laser deposition technique and explored the structural, magnetic, electrical and magneto-transport properties of this heterostructure. ${\Phi}$-scan measurements confirm the epitaxial nature of LCMO/YBCO heterostructure grown on single crystalline SrTiO3 substrate. The FM transition of LCMO and SC transition of YBCO are observed in the magnetization measurements of the bilayer structure. Through electrical measurements, we understood that the proximity effect leads to lowering of the SC transition of YBCO. The role of interface in the bilayer structure is also realized through electrical transport measurements.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.338.2-338.2
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• 2016

Al doped ZnO (AZO) thin films were deposited on Si substrates with rod-shaped-surface by pulsed laser deposition method (PLD). Si-rods were prepared through chemical etching. To analyze the influence on the formation of the rod structure, samples with various chemical etching conditions such as AgNO3/HF ratio, etching time, and solution temperature were prepared. The morphology of Si-rod structures were examined by FE-SEM. Fig. 1 shows a typical structure of n-AZO/p-Si-rod juncions. The fabricated n-AZO/p-Si-rod devices exhibited p-n diode current-voltage characteristics. We compared the I-V characteristics of n-AZO/p-Si-rod devices with the samples without Si-rod structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.142-142
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• 2009

Zinc Oxide (ZnO)는 wurtzite 결정구조를 가지고 있으며, 밴드갭 에너지가 약 3.4eV인 산화물 반도체 이다. GaN가 도핑된 ZnO 박막을 Pulsed Laser Deposition (PLD) 법을 이용하여 사파이어 기판과 실리콘 기판에 각각 증착하였다. $500^{\circ}C$의 증착온도에서 1at%~10at%까지의 GaN 도핑농도에 따른 ZnO 박막의 결정성, 성분 분석을 비롯한 전기적 특성을 조사하였다. 첨가된 GaN의 농도에 따라 ZnO 박막의 결정성이 변화하였으며, 농도 변화에 상관없이 ZnO(002) 방향으로 성장함을 알 수 있었다. 또한 실리콘 기판에 증착한 GaN-doped ZnO 박막은 5at%에서 $9.3\;{\times}\;10-3{\Omega}cm$, 10at%에서 $9.2\;{\times}\;10-3{\Omega}cm$의 비저항 값을 가지며 각각 p-type 특성을 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.432-432
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• 2009

본 연구에서는 HW-PLD(Hot-walled Pulsed Laser Deposition) 법을 이용하여 ZnO 나노와이어를 $Al_2O_3$ 기판 위에 성장하였다. 성장된 ZnO 나노와이어는 SEM, XRD, PL 분석을 통하여 구조적 특성을 확인하였으며, 성장된 나노와이어를 photolithography 공정을 통하여 FET(Field Effect Transistor)소자를 제작하였다. 제작된 소자의 I-V 특성 측정 결과 Ti/Au 전극과 ZnO nanowire 채널 간에 ohmic 접합이 형성된 것을 확인하였으며 게이트 전압의 증가에 따라 소스와 드레인 사이의 전류가 증가하는 전형적인 n-type FET소자 특성을 나타내었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.539-542
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• 2002

The effect of the superconducting film thickness on the surface resistance has been investigated. Superconducting YBCO thin films have been grown on MgO substrates by pulsed laser deposition. The dependence of the orientation of YBCO film on thickness has been investigated by X-ray diffraction technique. X-ray diffraction indicated that the film orientation was changed by increasing the film thickness and by changing the substrate temperature. The microwave properties of the films with mixed orientations of a-axis and c-axis will be reported for the applications of microwave devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.108-112
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• 2010

Design of experiment (DOE) method is employed for a systematic and highly efficient optimization of Ga-doped ZnO thin films synthesized by pulsed laser deposition (PLD) process. We sequentially adopted fractional-factorial design (FD) and central composite design (CCD) of the DOE methods. In fractional-FD stage, significant factors to make conductive electrode are found to target-substrate (T-S) distance and oxygen partial pressure. Moreover, correlation among the process factors is elucidated using surface profile modeling. Electrical properties of the GZO films grown on a glass substrate had been optimized to find that the lowest electrical resistivity of about $1.8'10^{-4}Wcm$ which was acquired with the T-S distance and the oxygen pressure of 4 cm and 7 mTorr, respectively. During the DOE-fueled optimization process, the transparency of the GZO films is ensured higher than 85 %.

• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.156-159
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• 2013

The electrical properties of ZnO nanowire field effect transistors (FETs) have been investigated depending on various diameters of nanowires. The ZnO nanowires were synthesized with an Au catalyst on c-plane $Al_2O_3$ substrates using hot-walled pulsed laser deposition (HW-PLD). The nanowire FETs are fabricated by conventional photo-lithography. The diameter of ZnO nanowires is simply controlled by changing the thickness of the Au catalyst metal, which is confirmed by FE-SEM. It has been clearly observed that the ZnO nanowires showed different diameters simply depending on the thickness of the Au catalyst. As the diameter of ZnO nanowires increased, the threshold voltage of ZnO nanowires shifted to the negative direction systematically. The results are attributed to the difference of conductive layer in the nanowires with different diameters of nanowires, which is simply controlled by changing the catalyst thickness. The results show the possibility for the simple method of the fabrication of nanowire logic circuits using enhanced and depleted mode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.135-138
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• 2001

We report the structural ,optical and electrical properties of ZnO thin films depending on the variation of the film thickness. The properties of the films deposited on sapphire (001) substrates using a pulsed laser deposition technique (PLD) were characterized with XRD, hall measurement and photoluminescence (PL). In our study, the increase of the thickness of ZnO thin films shows the improvement of the structural and optical properties. The electric properties of the films were also well matched with the structural and optical properties

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.161-164
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• 1999

We have fabricated the direct-coupled planar type 1st-order SQUID gradiometers. The gradiometer consists of moats or slots in SQUID loop. It is made by YBa$_2Cu_3O_7$ thin films using pulsed laser deposition method on SrTiO$_3$ single crystal and bi-crystal substrates. We have studied the effects of slots and moats in SQUID loop by measuring the voltage modulation signals under uniform field and 1st-order gradient, and the noise properties under non-shielded environment.

• 한국초전도학회:학술대회논문집
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• v.13
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• pp.70-70
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• 2003