• 한국레이저가공학회지
• /
• 제16권1호
• /
• pp.1-4
• /
• 2013

The optical properties of III-V compound semiconductor structure was investgated by photoreflectance (PR). The results show two signals at 1.42 and 1.73eV. These are attributed to the bandgap energy of GaAs, AlGaAs, respectively. Also, AlGaAs region showed weak signal. This signal is attributed to carbon or si defect.

• 한국정밀공학회지
• /
• 제22권12호
• /
• pp.16-21
• /
• 2005

Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for the manipulation of light. The existence of a photonic bandgap, a frequency range in which the propagation of light is prevented in all directions, makes photonic crystal very useful in application where the spatial localization of light is required, for example waveguide, beam splitter, and cavity. However, the fabrication of 3 dimensional photonic crystals is still difficult process. A concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air and perforated with two dimensional lattice of hole. The fabrication of Si master with pillar structure using hot embossing process is investigated for two dimensional, low-index-contrast photonic crystal waveguide. From our research we show that the multiple stamp copy process proved to be feasible and useful.

• 한국물환경학회지
• /
• 제26권4호
• /
• pp.707-712
• /
• 2010

Nitrogen-doped $TiO_2$ particles have been successfully prepared using titanium tetraisopropoxide as the Ti source and urea as the nitrogen source. As-prepared nitrogen-doped $TiO_2$ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller method (BET) and ultraviolet-visible light (UV-vis) absorption spectra techniques. Photocatalytic degradation of Methylene Blue (MB) has been carried out in both solar light (UV-vis) and the visible region (${\lambda}=420nm$). Nitrogen-doped $TiO_2$ exhibits higher activity than the commercial $TiO_2$ photocalyst, particularly under visible-light irradiation because bandgap of nitrogen-doped $TiO_2$ becomes remarkably decreased.

• Macromolecular Research
• /
• 제12권2호
• /
• pp.189-194
• /
• 2004

When water is evaporated quickly from a water-based colloidal suspension, colloidal particles protrude from the water surface, distorting it and generating lateral capillary forces between the colloidal particles. The protruded colloidal particles are then assembled into ordered colloidal crystalline domains that float on the water surface on account of their having a lower effective density than water. These colloidal crystal domains then assemble together by lateral capillary force and convective flow; the generated colloidal crystal has grain boundaries. The single domain size of the colloidal crystal could be controlled, to some extent, by changing the rate of water evaporation, but it seems very difficult to fabricate a single crystal over a large area of the water's surface without reorienting each colloidal crystal domain. To reorient such colloidal crystal domains, a glass plate was dipped into the colloidal suspension at a tilted angle because the meniscus (airwaterglass plate interface) is pinned and thinned by further water evaporation. The thinning meniscus generated a shear force and reoriented the colloidal crystalline domains into a single domain.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2011년도 제42회 하계학술대회
• /
• pp.1650-1651
• /
• 2011

본 논문에서는 가변안내표지판(VMS)용 멀티-채널 LED Driver IC를 설계 연구 하였다. 설계한 LED Driver IC의 채널 수는 96 채널을 기본으로 하여 여분의 64채널을 추가로 구성하였다. VDD는 동작 환경에 따라 사용할 수 있게 12V, 6V, 3.3V로 구성하였다. 각 채널당 전류는 20mA로 일정한 전류가 흐를 수 있도록 하였다. 온도 변화에 따른 전류 변화로 인한 LED 휘도특성 변화를 줄이기 위해 트랜지스터를 여러단으로 쌓아 회로를 구성하였으며 내부 회로에 PTAT과 Bandgap Reference를 이용하여 트랜지스터에 안정적인 전원이 공급될 수 있게 구성하였다. 본 논문에 사용된 공정은 동부 0.13um 공정으로 최대 3.3V까지 사용할 수 있지만 12V및 6V에도 사용할 수 있게 트랜스지터를 쌓는 회로를 구성하였다.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
• /
• pp.68-68
• /
• 2003

SiC는 wide bandgap 물질로서 그 material properties로 인하여, high tmperature, high power, high frequency영역으로의 사용이 기대되는 물질이다. 따라서 SiC에 대한 기본적인 연구와 더불어, 그 소자 제작 및 응용에의 연구가 절실한 시점이다. 이에, SiC 기본적인 소자중 하나인 Schottky diode에 대해 연구하였다. 본 논문은 Schottky contact 물질로써 현재까지 연구가 미비한 Ru을 사용하였다. Ru은 Pt 계열물질로써, 다른 metal에 비하여 열역학적으로 안정하며, 또한 그의 산소 화합물인 RuO2는 다른 oxide에 비하여 전도성 이 높은 장점을 가지고 있다. 따라서 Ru-SiC diode는 이러한 측면에서 연구할 만한 가치가 있다.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
• /
• pp.58-58
• /
• 2003

최근 전자재료분야 중 고집적 소자를 다루는 분야에서는 산화규소 유전박막의 두께가 얇아짐에 따라 상부전극과 하부기판 사이에서 발생하는 누설전류가 큰 문제가 되었다. 따라서 이를 극복하기 위해 고유전상수를 가진 두꺼운 유전박막을 사용하기 시작하였는데, 그 중 대표적 인 것이 하프늄옥사이드(HfO2)와 알루미나(A12O3)이다. HfO2의 장점은 큰 유전상수를 갖는다는 것이고, A1203의 장점은 열적 안정성 이 뛰어나며, 높은 bandgap에너지를 갖는 것인데, 이 둘의 장점을 살려서 보다 편리한 방법으로 박막을 증착한 것이 바로 HfAlO이다.

• 한국전기전자재료학회논문지
• /
• 제31권3호
• /
• pp.177-181
• /
• 2018

We prepared ZnS thin films via chemical bath deposition (CBD) in an aqueous solution of ammonia ($NH_3$) and hydrazine ($N_2H_4$). The composition ratio of hydrazine used was 0%, 17%, 22%, 29%, or 50%. We investigated the effects of hydrazine and ammonia on the growth, and the structural and optical properties of ZnS in terms of surface uniformity, voids, and grain size. We found that during the growth of ZnS films, hydrazine was very effective for improving the surface morphology and layer uniformity with fast layer formation, while it had no effect on the bandgap energy, $E_g$.

• 전기학회논문지
• /
• 제66권9호
• /
• pp.1351-1358
• /
• 2017

In this work, we investigated radiation hardness of GaN-based transistors which are strong candidates for next-generation power electronics. Field effect transistors with three types of gate structures including metal Schottky gate, recessed gate, and p-AlGaN layer gate were fabricated on AlGaN/GaN heterostructure on Si substrate. The devices were irradiated with energetic protons and alpha-particles. The irradiated transistors exhibited the reduction of on-current and the shift of threshold voltage which were attributed to displacement damage by incident energetic particles at high fluence. However, FET operation was still maintained and leakage characteristics were not degraded, suggesting that GaN-based FETs possess high potential for radiation-hardened electronics.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.83-84
• /
• 2009

Thin film solar cells based on CIGS continue to be a leading candidate for thin film photovoltaic devices due to their appropriate bandgap, long-term stability, and low-cost production. To date, the most successful technique for the deposition of a CIGS absorber layer has been based on the co-evaporation However, the evaporation process is difficult to scale-up for large-area manufacturing the sputtering and Selenizaton process has been a promising method for low-cost and large-scale production of high quality CIGS In this study, we have used Cu and CuIn alloy targets for precursor deposition the precursor deposited by sputtering Cu and CuIn targets and $CuInSe_2$ thin film is manufactured by Selenization process