• Bulletin of the Korean Chemical Society
• /
• v.29 no.4
• /
• pp.822-826
• /
• 2008

We report the cathodoluminescence and aging properties of a series of green phosphors of formula $Sr_{1-x}M_xGa_2S_4$:Eu (x = 0.0-1.0, M = Ba or Ca) that have potential applications in field emission displays (FEDs). The series of phosphors was synthesized via NaBr-aided solid-state reactions in a flowing $H_2S$ stream. A low level ($\sim$20%) of Ba or Ca substitution for Sr in $SrGa_2S_4$:Eu maintains the orthorhombic phase of pure $SrGa_2S_4$:Eu phosphors. Further, a low level ($\sim$20%) of Ba or Ca substitution for Sr in $SrGa_2S_4$:Eu provides various green colors and sufficient brightness for FED applications. Substitution of Ba or Ca for Sr in $SrGa_2S_4$:Eu also improved the stability of the phosphor when it was operated under electron-beam irradiation of 5 kV.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.375-375
• /
• 2011

Cu(In1-xGax)Se2 (CIGS)박막증착법 중 금속 전구체의 셀렌화 공정법은 다른 제조 방법에 비해 대면적 생산에 유리하고, 비교적 공정 과정이 간단하다는 장점이 있다. 이 제조 방법은 금속 전구체를 만든 후에 셀렌화 공정을 하게 된다. 셀렌화 공정은 대부분 H2Se 가스를 사용하지만 유독성으로 사용하는데 주의해야 한다. 본 실험은 H2Se를 사용하지 않고 Se원료를 주입하기 위해 Se cracker를 사용했고 금속 전구체 증착과 셀렌화를 동시에 하는 반응성 스퍼터링 후 열처리 법을 이용하여 CIGS 박막을 증착 했다. CIGS의 박막의 Cu/[In+Ga], Ga/[In+Ga]비를 변화시켜 특성변화를 관찰했다. Cu/[In+Ga]비가 감소할수록 CIGS의 결정방향인 (112) 이 우세하게 발달했고 Ga/[In+Ga]비가 증가할수록 CIGS의 결정면 사이의 값이 작아지기 때문에 CIGS peak의 2-Theta 값이 증가하게 된다. CIGS 박막 태양전지의 구조는 Al/Ni/ITO/i-ZnO/CdS/CIGS/Mo/glass 제작했다. CIGS박막의 조성비가 Cu/[In+Ga]=0.84, Ga/[In+Ga]=0.24인 박막태양전지에서 개방전압 0.48 V, 단락전류밀도 33.54 mA/cm2, 충실도 54.20% 그리고 변환효율 8.63%를 얻었다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.16 no.4
• /
• pp.162-165
• /
• 2006

The selective growth of InCaN/AlGaN light emitting diodes was performed by mixed-source hydride vapor phase epitaxy (HVPE). In order to grow the InGaN/AlGaN heterosturcture consecutively, a special designed multi-sliding boat was employed in our mixed-source HVPE system. Room temperature electroluminescence spectum of the SAG-InGaN/AlGaN LED shows an emission peak wavelength of 425 nm at injection current 20 mA. We suggest that the mixed-source HVPE method with multi-sliding boat system is possible to be one of the growth methods of III-nitrides LEDs.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.220-224
• /
• 2000

AlGaAs/GaAs HBT를 이용하여 1.9 GHz 대역 2단 MMIC 전력증폭기를 설계하였다. HBT의 실측 S 파라미터를 이용하여 정합회로를 설계하였으며, 목적에 따라 적절한 형태의 출력 정합 회로를 하이브리드 형태로 칩 외부에 부가할 수 있도록 설계하였다. HBT의 실측정 S 파라미터의 fitting을 통하여 비선형 등가모델을 추출하였고, load-pull 시뮬레이션으로 최대 출력 정합 임피던스를 결정하였다. 시뮬레이션 결과, 29 dBm의 출력 전력, 40 %의 전력 부가 효율, 그리고 16 dB의 전력 이득을 얻었다.

• Korean Journal of Acupuncture
• /
• v.28 no.1
• /
• pp.171-177
• /
• 2011

Objectives : This study is designed to evaluate the effect of Hyun-Ga therapy for the scoliosis patient with Lumbago. Methods : After treatment with Hyun-Ga therapy compared with Cobb's angle and Visual Analog Scale (VAS). Results : After six treatments with Hyun-Ga therapy in one case, significant decrease in Cobb's angle and Visual Analog Scale (VAS) was observed. Conclusions : Hyun-Ga therapy might be effective for the scoliosis patient with Lumbago. It will be attempted to more patients in the future.

• Journal of the Korean Chemical Society
• /
• v.48 no.4
• /
• pp.371-378
• /
• 2004

The $SrGa_2S_4:Eu^{2+}$ green emitting phosphor has been studied as a luminous device for CRT (Cathode Ray Tube) or FED (Field Emission Display) and EL (Electroluminescence). This phosphor, also, is under noticed for LED (Lighting Emitting Diode) phosphor, which makes use of excitation characteristics of long wavelength region. The $SrGa_2S_4:Eu^{2+}$ phosphor was prepared generally conventional synthesis method using flux. However, this method needs high heat-treated temperature, long reaction time, complex process and harmful $H_2S$or $CS_2$ gas. In this works, therefore, we have synthesized $SrGa_2S_4:Eu^{2+}$ using SrS, $Ga_2S_3$, and EuS as starting materials, and the mixture gas of 5% H2/95% N2 was used to avoid the $H_2S$or $CS_2$. We investigated the luminescence characteristic of $SrGa_2S_4:Eu^{2+}$ phosphor prepared in various synthesis conditions, performed post-treatment and sieving process for application to LED.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.11 no.6
• /
• pp.500-504
• /
• 2001

The present approach based on the genetic algorithm with improved selections of bonds was adopted to extract a bridged T equivalent circuit elements of $\times10\mu m^2$InGaP/GaAs HBT. the small-signal model parameters were extracted using the genetic algorithm from S-parameters measured at different frequencies under multiple forward-active biases, which demonstrate physically meaningful values and consistency. The agreement between the measured and modeled S-parameters is excellent over the frequency range of 2 to 26.5GHz.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.8
• /
• pp.1203-1210
• /
• 1989

A cross-sectional transmission electorn microscopy study of the MBE grown GaAs/Al0.3 Ga0.7As layers was carried out at high-resolution so that the atomic arrangement of the well, barrier and the interface could be understood on an atomic level. Results show that the images reveal directly the atomic structure of the GaAs, Al0.3Ga0.3 Ga0.7 As interface is sharply defined but is not smooth on the atomic scale. The roughness arises from the presence of hills with heights of several{002} GaAs interplanar spacings. The atomic arrangement at the interface is almost completely coherent without any structural disorder. Alloy clustering at the interface was not observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.823-827
• /
• 2001

The AgInS$_2$epilayers with chalcopyrite structure grown by using a hot-wall epitaxy (HWE) method have been confirmed to be a high quality crystal. From the optical absorption measurement, the temperature dependence of the energy band gap on the AgInS$_2$/GaAs was derived as the Varshni's relation of Eg(T)=2.1365 eV-(9.89${\times}$10$\^$-3/ eV)T$^2$/(2930+T). After the as-grown AgInS$_2$/GaAs was annealed in Ag-,S-, and In-atmosphere, the origin of point defects of the AgInS$_2$/GaAs has been investigated by using the photoluminescence (PL) at 10 K. The native defects of V$\_$Ag/, V$\_$s/, Ag$\_$int/, and S$\_$int/ obtained from PL measurement were classified to donors or acceptors type. And, we concluded that the heat-treatment in the S-atmosphere converted the AgInS$_2$/GaAs to optical p-type. Also, we confirmed that the In in the AgInS$_2$/GaAs did net from the native defects because the In in AgInS$_2$did exist as the form of stable bonds.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.2
• /
• pp.79-82
• /
• 2003

GaN nanoparticles were synthesized by the pulsed laser deposition (PLD) process on $SiO_2$substrate after irradiating the surface of the GaN sintered pellet by the ArF (193 nm) excimer laser. At this moment Ar gas pressure of 100 Pa, 50 Pa, 10 Pa and 1 Pa were applied during the ablation process and laser power of 100 mJ and 200 mJ were also applied. The synthesized fan nanoparticles were characterized by XRD, SEM, TEM, XPS and optical absorption spectra. The synthesized GaN nanoparticles had the crystallite sizes of 20~30 nm, and besides, GaN nanoparticles synthesized under low Ar gas pressure compared to the others corresponded with stoichiometry, and the optical band edge of the GaN nanoparticles was blueshifted.