• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.233-233
• /
• 2013

유기물/무기물 나노복합체를 이용하여 제작한 비휘발성 메모리 소자는 간단한 공정과 플렉서블 기기 응용 가능성 때문에 많은 연구가 진행되고 있다. 다양한 나노입자를 포함한 고분자 박막에 대한 연구는 많이 진행되었지만, 비휘발성 메모리소자에서 CdSe/InP 나노입자를 사용한 나노복합체의 전기적 안정성과 동작 메커니즘에 대한연구는 미흡하다. 본 연구는 CdSe/InP 코어/쉘 나노입자가 poly (N-vinylcarbazole) (PVK) 박막에 분산되어 있는 나노복합체를 이용하여 메모리 소자를 제작하여 전기적 특성과 안정성을 관찰 하였다. 소자 제작을 위해PVK 고분자를 용매인 클로로벤젠에 용해한 후, 헥산에 안정화 되어있는 CdSe/InP 나노입자를 초음파 교반기를 사용하여 고르게 섞었다. Indium-tin-oxide (ITO)가 증착한 유리 기판을 화학물질로 세척한 후 기판 위에 CdSe/InP 나노입자와 절연성 고분자인 PVK가 혼합된 용액을 스핀코팅 방법으로 도포하여 나노입자가 포함된 고분자 박막층을 형성하여 저항 변화층으로 사용하였다. 형성된 박막 위에 마스크를 사용하여 Al 상부전극을 고진공에서 열 증착하여 비휘발성 메모리 소자를 제작하였다. 제작된 소자의 전류-전압(I-V) 특성을 측정한 결과 동일전압에서 전도도가 좋은 상태 (ON)와 좋지 않은 상태 (OFF)인 두 개의 상태상 존재한다는 것을 확인하였고, CdSe/InP인 나노입자가 포함된 소자와 포함되지 않은 소자의 전기적 특성을 비교 분석하였다. 두 상태의 안정성을 ON 또는OFF 상태의 스트레스를 측정하여 두 상태의 안정성을 확인하였고, 실험결과를 바탕으로 메모리 소자의 동작 메커니즘을 기술하였다.

• Journal of Industrial Convergence
• /
• v.20 no.12
• /
• pp.79-85
• /
• 2022

Recently, a smartphone manufactured on a flexible substrate has been released as an electronic device, and research on a stretchable electronic device is in progress. In this paper, a silicon-based stretchable material is made and used as a substrate to implement and evaluate an optical sensor device using oxide semiconductor. To this end, a substrate that stretches well at room temperature was made using a silicone-based solution rubber, and the elongation of 350% of the material was confirmed, and optical properties such as reflectivity, transmittance, and absorbance were measured. Next, since the surface of these materials is hydrophobic, oxygen-based plasma surface treatment was performed to clean the surface and change the surface to hydrophilicity. After depositing an AZO-based oxide film with vacuum equipment, an Ag electrode was formed using a cotton swab or a metal mast to complete the photosensor. The optoelectronic device analyzed the change in current according to the voltage when light was irradiated and when it was not, and the photocurrent caused by light was observed. In addition, the effect of the optical sensor according to the folding was additionally tested using a bending machine. In the future, we plan to intensively study folding (bending) and stretching optical devices by forming stretchable semiconductor materials and electrodes on stretchable substrates.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.381-381
• /
• 2012

유기물/무기물 나노 복합체를 이용하여 제작한 메모리 소자는 저전력 구동, 간단한 공정, 플렉서블한 성격과 같은 장점 때문에 많은 연구가 진행되고 있다. 다양한 유기물/무기물 나노 복합체를 이용한 비휘발성 메모리 소자에 대한 연구는 많이 진행되었으나, fullerene 계열의 [6,6]-phenyl-C85 butyric acid methyl ester (PCBM) 나노 입자와 poly (methylmethacrylate) (PMMA)의 나노 복합체를 사용하여 제작한 유기 쌍안정성 메모리 소자의 전기적 특성과 메커니즘에 대한 연구는 미흡하다. 본 연구에서는 기억층으로 PMMA 박막 안에 분산되어 있는 PCBM 나노 입자를 트랩층으로 사용하는 메모리 소자를 제작하여 전기적 특성 및 안정성에 대하여 관찰하였다. 소자제작을 위하여 PCBM 나노 입자를 PMMA와 함께 용매인 클로로벤젠에 용해한 후에 초음파 교반기를 사용하여 두 물질을 고르게 섞었다. Indium-tin-oxide 가 코팅된 glass위에 PCBM 나노 입자와 PMMA가 섞인 나노 복합체를 스핀 방법으로 적층한 후, 열을 가해 클로로벤젠을 제거하여 PCBM 나노 입자가 PMMA 안에 분산되어 있는 전하 수송 층을 형성하였다. 형성된 전하수송 층 위에 열 증착 방식으로 상부 Al 전극을 형성하여 유기 쌍안정성 메모리 소자를 제작하였다. 제작된 소자의 전류-전압 (I-V) 측정 결과 특정 전하 수송 층의 두께에서는 큰 ON/OFF 전류 비율을 보여준다. PMMA만을 사용한 소자에서는 I-V 메모리 특성이 나타나지 않는 결과로부터 PCBM 나노 입자가 전하 수송 층 내에서 메모리 특성의 역할을 한다는 것을 보여준다. 전류-시간 (I-t) 측정 결과로 소자의 ON/OFF 전류 비율이 시간이 지남에 따라 큰 감쇠 없이 104 s까지 103값을 지속적으로 유지되어 메모리 소자의 안정성을 보여주었다. 실험의 결과로 PCBM이 포함된 메모리 소자의 메커니즘과 전하 수송 층의 두께에 따른 메모리 특성을 설명하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.350-350
• /
• 2011

ZnO는 II-VI족 화합물 반도체로서 3.37 ev의 band gap energy와 60 mv의 exciton binding energy를 가지며 차세대 소자로 다양한 분야에서 연구되어지고 있다. ZnO 박막과는 다르게 ZnO nano structure는 효율성과 특성 향상의 이점으로 태양전지와 투명전극 소자에 많은 연구가 되고 있으며 UV 레이저, 가스센서, LED, 압전소자, Field Emitting Transistor (FET) 등 다양한 응용분야에서 연구되고 있다. 본 연구에서는 유리 기판 위에 RF Magnetron sputtering법을 이용해 ZnO buffer layer를 다양한 두께(~1,000${\AA}$)로 증착한 뒤, Zn powder (99.99%)를 지름 2inch 석영관 안에 넣어 Thermal furnace장비를 이용하여 Thermal Evaporation법으로 약 500$^{\circ}C$에서 30분 동안 촉매 없이 성장 하였다. 수직성장된 ZnO 나노 구조체의 특성을 전계방출주사전자현미경(SEM), X-선 회절패턴(XRD), UV-spectra를 이용하여 분석하였다. SEM 분석을 통하여 ZnO buffer layer위에 성장된 ZnO 나노 구조체는 직경이 약 ~50 nm, 길이가 ~2 um까지 성장을 보였으며, XRD 측정결과, ZnO 우선 성장 방향(002)을 확인하였다. 두 가지 측정을 통하여 ZnO buffer layer의 유무에 따라 성장 특성이 향상되었음을 확인하였으며, 이는 buffer layer가 seed 역할을 한 것으로 사료된다. UV-spectra 측정을 통하여 가시광 영역(400~780 nm)에서 60%대의 투과도를 보여 가시광 영역에서 투명성을 요구하는 전자 소자 및 광소자 등에 적용 가능성을 확인하였다. 이 연구를 통하여 우수한 투과도를 가지며 유리 기판위에 수직성장된 ZnO 나노구조체는 태양전지와 플렉서블 디스플레이 등 다양한 활용 분야를 제시할 수 있다.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.3
• /
• pp.37-41
• /
• 2019

Sheet resistance reduction in the Ag nanowire (NW) coated films is accomplished with slight improvement of optical properties for the application of transparent conducting electrodes by using $O_2$ plasma treatment. The sheet resistance was optimized after 30 seconds $O_2$ plasma treatment, showing the 27 % of maximum decrease of sheet resistance. It is found that the $O_2$ plasma treatment get rid of the residual organic materials at the junction of Ag NWs. However, the Ag NWs may be also snapped by the excessive $O_2$ plasma treatment can showing the collapses of Ag NWs networks. Furthermore, the optical properties such as optical transmittance and haze were monotonically improved with the $O_2$ plasma treatment time until 90 seconds.

• Applied Chemistry for Engineering
• /
• v.30 no.1
• /
• pp.23-28
• /
• 2019

We report a supercapacitor cable, which consists of three-dimensional (3D) porous graphene coated onto the surface of carbon thread. The 3D porous framework of graphene was constructed by microwave-activated process using a graphene oxide-coated carbon thread. The use of microwave irradiation enabled to convert graphene oxide into reduced graphene oxide without any reducing agents and activate graphene sheets into exfoliated and porous graphene sheets. Combining two wire electrodes with a polymer gel electrolyte successfully completed supercapacitor device in a form of cable construction. The supercapacitor cables were highly flexible, and thus can be transformed into various shapes of devices and be integrated into textile items. A high area-capacitance of 38.1 mF/cm was obtained at a scan rate of 10 mV/s. This capacitance was retained 88% of its original value at 500 mV/s. The cycle life was also demonstrated by repeating a charge/discharge process during 10,000 cycles even under bent states, showing a high capacitance retention of 96.5%.

• Applied Chemistry for Engineering
• /
• v.26 no.3
• /
• pp.275-279
• /
• 2015

Poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) has attracted a great deal of attention as a transparent conductive material for organic solar cells or organic light-emitting diodes due to its high electrical conductivity, optical transparency, and excellent mechanical flexibility. It is well known that a solvent doping for PEDOT : PSS thin-films significantly increases the conductivity of films. In this paper, the effect of various kinds of solvent doping and post-treatment on the electrical and structural properties of PEDOT : PSS thin-films is investigated. The solvent doping greatly increases the conductivity of PEDOT : PSS thin-films up to 884 S/cm. A further enhancement of the conductivity of PEDOT : PSS thin-films is achieved by the solvent post-treatment which raises the conductivity up to 1131 S/cm. The enhancement is mainly caused by the depletion of insulating PSS and forming conducting PEDOT-rich granular networks. Strong optical absorption peaks at the wavelength of 225 nm of PEDOT : PSS thin-films indicate the depletion of insulating PSS by post-treatment. We believe that the solvent post-treatment is a promising method to achieve highly conductive transparent PEDOT : PSS thin-films for applications in efficient, low-cost and flexible organic devices.

• Journal of Convergence for Information Technology
• /
• v.10 no.9
• /
• pp.28-34
• /
• 2020

In this paper, an optical sensor based on an AZO semiconductor material is fabricated on an OHP film with high transmittance, and the characteristics of the optical element and the properties of the semiconductor material are described. In order to realize a flexible optical device, which is a major issue in the field of near-electronic devices, a transparent and bendable OHP film was used as a substrate. In addition, ITO, which is used for mass production as a transparent electrode and a semiconductor material, is expensive due to the scarcity of indium. Therefore, it is necessary to find a material that can replace it. The optical and electrical properties of the Au/Al/AZO/OHP structure are implemented to evaluate whether AZO is possible. It was found that devices and materials had no characteristic change by bending, and these results provide a possibility for application to a next-generation device. However, it is necessary to remove fine scratches on the surface of the OHP film, as well as optimized devices based on materials and structures that can improve the photocurrent.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.1
• /
• pp.17-22
• /
• 2011

ZnO-based thin-film transistors (TFTs) have been fabricated and the mechanical characteristics of electric circuits, such as stress, strain, and deformation are analyzed by the finite element method (FEM). In this study, a mechanical-stability design guide for such systems is proposed; this design takes into account the stress and deformation of the bridge to estimate the stress distribution in an $SiO_2$ film with 0 to 5% stretched on 0.5-${\mu}m$-thick. The predicted buckle amplitude of $SiO_2$ bridges agrees well with experimental results within 0.5% error. The stress and strain at the contact point between bridges and a pad were measured in a previous structural analysis. These structural analysis suggest that the numerical measurement of deformation, SU-8 coating thickness for Neutral Mechanical Plane (NMP) and ITO electrode size on a dielectric layer was useful in enhancing the structural and electrical stabilities.

• Journal of the Korean Vacuum Society
• /
• v.20 no.5
• /
• pp.327-332
• /
• 2011

Plasma polymerized styrene (ppS) thin films were prepared on ITO coated glass substrates for a MIM (metal-insulator-metal) structure with thermally evaporated Au thin film as metal contact. Also the ppS thin films were applied as organic insulator to a MIS (metal-insulatorsemiconductor) device with thermally evaporated pentacene thin film as organic semiconductor layer. After the I-V and C-V measurements with MIM and MIS structures, the ppS revealed relatively higher dielectric constant of k=3.7 than those of the conventional poly styrene and very low leakage current density of $1{\times}10^{-8}Acm^{-2}$ at electric field strength of $1MVcm^{-1}$. The MIS structure with the ppS dielectric layer showed negligible hysteresis in C-V characteristics. It would be therefore expected that the proposed ppS could be applied as a promising dielectric/insulator to organic thin film transistors, organic memory devices, and flexible organic electronic devices.