• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.104-104
• /
• 2011

ZnO는 3.37 eV의 넓은 에너지 밴드갭을 갖는 투명 전도성 반도체이며 우수한 전기적, 광학적 특성으로 인해 광원소자 개발을 위한 새로운 물질로 많은 주목을 받아왔다. 더욱이, ZnO는 쉽게 나노구조 형성이 가능하기 때문에 이를 응용한 가스센서, 염료감응태양전지, 광검출기 등의 소자 개발이 활발히 이루어지고 있다. 최근에는 GaN 기반 발광다이오드 (light emitting diode, LED)의 광추출 효율을 향상시키기 위한 ZnO 나노구조 응용에 관한 연구가 보고되고 있다. GaN 기반 LED의 경우 반도체 물질과 공기 사이의 높은 굴절률 차이로 인하여 낮은 광추출 효율을 나타낸다. 이를 해결하기 위한 방법으로 표면 roughening, texturing 등 에칭공정을 이용해 광추출 효율을 개선하려는 연구들이 보고되고 있으나, 복잡한 공정과정을 필요로 하고 에칭공정에 의한 소자 표면 손상으로 전기적 특성이 나빠질 수 있다. 반면 전기화학증착법으로 성장된 ZnO 나노구조를 이용할 때, 보다 간단한 방법으로 쉽고 빠르게 나노구조를 형성할 수 있고 낮은 공정온도를 가지기 때문에 소자의 전기적 특성에 큰 영향을 주지 않는다. 수직방향으로 잘 정렬된 ZnO 나노구조를 갖는 LED의 경우 내부 Fresnel 반사 손실을 효과적으로 줄여 발광 효율을 크게 향상시킬 수 있다. 따라서, ZnO 나노구조의 성장제어 및 성장특성을 분석하는 것은 매우 중요하다. 본 연구에서는 ITO glass 위에 ZnO 나노구조를 성장하고 그 특성을 분석하였다. ITO glass 기판 위에 RF magnetron 스퍼터를 사용하여 Al 도핑된 ZnO (AZO)를 얇게 증착한 후 전기화학증착법으로 ZnO 나노구조를 성장하였다. 농도, 인가전압, 공정시간 등 다양한 공정조건을 변화시키면서 성장 메커니즘을 분석하였고, scanning electron microscope (SEM) 및 X-ray diffraction (XRD)을 통하여 구조 및 결정성 등을 분석하였다. 또한, UV-Visible-NIR spectrophotometer를 사용하여 투과율을 실험적으로 측정하여 ZnO 나노구조의 광학적 특성을 분석하였고, rigorous coupled wave analysis (RCWA) 방법을 사용하여 계면에서 발생하는 내부 반사율을 계산함으로써 나노구조의 효과를 이론적으로 분석하였다.

• Journal of the Semiconductor & Display Technology
• /
• v.12 no.2
• /
• pp.13-17
• /
• 2013

In lighting system where several large-area organic light-emitting diode (OLED) lighting panels are involved, panel aging may appear differently from each other, resulting in a falling-off in lighting quality. To achieve uniform light output across large-area OLED lighting panels, we have employed an optical feedback circuit. Light output from each OLED panel is monitored by the optical feedback circuit that consists of a photodiode, I-V converter, 10-bit analogdigital converter (ADC), and comparator. A photodiode generates current by detecting OLED light from one side of the glass substrate (i.e., edge emission). Namely, the target luminance from the emission area (bottom emission) of OLED panels is monitored by current generated from the photodiode mounted on a glass edge. To this end, we need to establish a mapping table between the ADC value and the luminance of bottom emission. The reference ADC value corresponds to the target luminance of OLED panels. If the ADC value is lower or higher than the reference one (i.e., when the luminance of OLED panel is lower or higher than its target luminance), a micro controller unit (MCU) adjusts the pulse width modulation (PWM) used for the control of the power supplied to OLED panels in such a way that the ADC value obtained from optical feedback is the same as the reference one. As such, the target luminance of each individual OLED panel is unchanged. With the optical feedback circuit included in the lighting system, we have observed only 2% difference in relative intensity of neighboring OLED panels.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.35 no.1
• /
• pp.80-85
• /
• 2022

ZnO-based transparent conductive films have been widely studied to achieve high performance optoelectronic devices such as next generation flexible and transparent display systems. In order to achieve a transparent flexible ZnO-based device, a low temperature growth technique using a flexible polymer substrate is required. In this work, high quality flexible ZnO films were grown on colorless polyimide substrate using atomic layer deposition (ALD). Transparent ZnO films grown from 80 to 200℃ were fabricated with a metal-semiconductor-metal structure photodetectors (PDs). As the growth temperature of ZnO film increases, the photocurrent of UV PDs increases, while the sensitivity of that decreases. In addition, it is found that the response times of the PDs become shorter as the growth temperature increases. Based on these results, we suggest that high-quality ZnO film can be grown below 200℃ in an atomic layer deposition system, and can be applied to transparent and flexible UV PDs with very fast response time and high photocurrent.

• Journal of the Semiconductor & Display Technology
• /
• v.20 no.4
• /
• pp.161-166
• /
• 2021

Errors in the semiconductor process are generated by a change in the state of the equipment, and errors usually arise when the state of the equipment changes or when parts that make up the equipment have flaws. In this investigation, we anticipated that aging of the mass flow controller in the plasma enhanced chemical vapor deposition SiO2 thin film deposition method caused a minute flow rate shift. In seven cases, fourier transformation infrared film quality analysis of the deposited thin film was used to characterize normal and pathological processes. The plasma condition was monitored using optical emission spectrometry data as the flow rate changed during the procedure. Preprocessing was used to apply the collected OES data to the artificial immune system algorithm, which was then used to process diagnosis. Through comparisons between datasets, the learning algorithm compared classification accuracy and improved the method. It has been confirmed that data characterized as a normal process and abnormal processes with differing flow rates may be discriminated by themselves using the artificial immune system data mining method.

• Korean Journal of Crystallography
• /
• v.17 no.2
• /
• pp.60-65
• /
• 2006

표면 및 계면층의 결정구조, 결함구조, 불순물 편석, 표면의 전자 구조, 원자 진동 등과 같은 산화물의 표면물성은 촉매, 센서, 소결, 마찰, 부식 등과 같은 분야에서 그 특성을 좌우한다. 고체 표면의 결정구조 해석 수단으로 저에너지 이온산란 분광법이 유용한 도구로 알려져 있는데, 이 방법의 뛰어난 표면민감성은 표면에서의 효과적인 이온 중성화 과정에 기인한다. $He^+$, $Ne^+$, $Ar^+$ 등과 같은 이온은 Auger 중성화 과정에 의하여 쉽게 중성원자화 되고, 중성화 확율의 타겟에 대한 의존성이 낮기 때문에 이온빔으로서 종종 사용된다. 산란각도를 180$^{\circ}$로 고정하여 산란이온 검출기를 설치한 직충돌 이온산란 분광법의 경우는 산란된 이온의 궤적이 입사궤도와 거의 동일하기 때문에 산란궤적의 계산이 간단해지고, 수 층 깊이의 원자구조의 해석이 가능해진다. 본 고에서는 고체 표면의 원자구조를 실공간에서 해석할 수 있는 직충돌 이온산란 분광법에 대하여 측정의 기본원리, 측정장치, 간단한 분석 예 등에 관하여 기술하고자 하며, 다음 편에서는 복잡한 표면구조를 가지는 반도체 표면에서 직충돌 이온산란분광법의 이용하여 해석한 예를 중심으로 기술하고자 한다.

• Journal of Radiation Protection and Research
• /
• v.9 no.1
• /
• pp.19-25
• /
• 1984

There is not yet an universal method of electron dosimetry. The Authors measured dose distributions of the electron beams from Clinac-18 by means of silicon detector connected to X-Y recorder, and compared them in water phantom with dose distributions measured by film and ion chamber, both inserted in polystyrene phantom. The results are as followings, 1. Dose in build-up region increased with the field size for all energy, and depth dose profiles of $6{\sim}12MeV$ beam under the depth of maximum dose were independent of field size, but those of 15 and 18 MeV beam were dependent on the field size. 2. The widths of penumbra by semiconductor detector were narrower than those by film for same energy beam. 3. Depth dose profiles by three different dosimeter did not coincide each other. In the build-up region, dose by semiconductor detector was lower than that by any other dosimeter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.451-451
• /
• 2009

CdTe는 에너지밴드갭이 1.45eV인 직접천이헝 II-VI 화합물 반도체로서 높은 광홉수율과 가시광 영역의 에너지밴드캡으로 태양전지, x-선 검출기 등에 널리 사용되고 있다. 본 연구에서는 Metal Organic Chemical Vapor Deposition (MOCVD)으로 Si 기판위에 CdTe 에피 박막을 성장 하고자 하였다. Cd, Te의 금속유기 화합물로는 Dimethylcadmium(DmCd)과 Diisopropyltellurium(DIPTe)을 사용하였다. 기판으로는 Si 을 사용하였으며 박막성장 온도를 $360^{\circ}C\;{\sim}\;500^{\circ}C$로 제어하여 에피박막이 형성되는 조건을 얻고자 하였다. $360^{\circ}C$, $450^{\circ}C$에서 성장된 CdTe박막은 다양한 방향이 존재하는 다결정 구조 였으며 $500^{\circ}C$의 경우 단결정 에피 박막 성장이 이루어졌음을 확인하였다. 본 연구를 통한 CdTe 에피박막은 기존의 열증착 등으로 제조되는 다결정 CdTe 박막과 비교하여 높은 에너지변환 효율을 얻을 것으로 기대된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.7
• /
• pp.513-522
• /
• 2020

This paper describes a relative navigation algorithm using PSD(Position Sensitive Detector) and heterogeneous sensor fusion. In order to perform relative navigation between a target and a chaser, a hardware system is constructed and simulations are conducted, using the relative navigation algorithm considering the hardware system. By analyzing errors through the simulations, advantages of using the heterogeneous sensor fusion are found. Finally, navigation performance is verified under an experimental environment established to obtain sensor data from the hardware system for data post-processing.

• Transactions of the KSME C: Technology and Education
• /
• v.5 no.1
• /
• pp.1-6
• /
• 2017

From early simple bulky detectors to show the existence of some specific material, sensor has been developed to miniature smart sensors embedded signal capabilities with a help of nano/micro engineering such as innovative nano materials and semiconductor process technologies. Due to recently fast sales of smart phones with simple telephone function plus many sensors, internet accessing capabilities, easy user downloadable "app" softwares, smart sensor industry market has expanded very fast. If driver-less cars, wearable electronic devices and smart robots will be introduced into market in near future, development of many various smart sensors will be needed.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.3
• /
• pp.38-49
• /
• 1998

The 3rd generation optical pick-up used popularly in resent years is composed of many optical and electronic components such as laser diode, photo diode, beam splitter, objective lens, grating lens, concave lens, collimator lens etc. Therefore, the design of its optical system and its main base which the said optical and electronic components are set on, is complicated and needs high precision. Its assembly and adjustment in the production line is also difficult. This complication and the demand of high precision get its production cost to be high and its reliability to be low. In this paper, the 4th generation optical pick-up is designed and developed, with the hologram device which laser diode. photo diode, beam splitter. and grating lens are integrated in. This optical pick-up reduces the number of points of adjustment by 3, compared with the 3rd generation optical pick-up of which the number of points of adjustment is 6. This optical pickup also decreases by 4 the number of points of W bonding to have bad influence on environmental reliability, decreases by about 10 the number of parts, and establishes about 20% cost-down of material cost, compared with the 3rd generation optical pick-up.