• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.387-392
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• 2019

$Dy^{3+}$ and $Eu^{3+}$-co-doped $La_2MoO_6$ phosphor thin films were deposited on sapphire substrates by radio-frequency magnetron sputtering at various growth temperatures. The phosphor thin films were characterized using X-ray diffraction (XRD), scanning electron microscopy, ultraviolet-visible spectroscopy, and fluorescence spectrometry. The optical transmittance, absorbance, bandgap, and photoluminescence intensity of the $La_2MoO_6$ phosphor thin films were found to depend on the growth temperature. The XRD patterns demonstrated that all the phosphor thin films, irrespective of growth temperatures, had a tetragonal structure. The phosphor thin film deposited at a growth temperature of $100^{\circ}C$ indicated an average transmittance of 85.3% in the 400~1,100 nm wavelength range and a bandgap energy of 4.31 eV. As the growth temperature increased, the bandgap energy gradually decreased. The emission spectra under ultraviolet excitation at 268 nm exhibited an intense red emission line at 616 nm and a weak emission line at 699 nm due to the $^5D_0{\rightarrow}^7F_2$ and $^5D_0{\rightarrow}^7F_4$ transitions of the $Eu^{3+}$ ions, respectively, and also featured a yellow emission band at 573 nm, resulting from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of the $Dy^{3+}$ ions. The results suggest that $La_2MoO_6$ phosphor thin films can be used as light-emitting layers for inorganic thin film electroluminescent devices.

• 센서학회지
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• 제29권5호
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• pp.328-331
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• 2020

In this study, a highly crystalline SnO₂ thin film was formed using a sol-gel process. In addition, a SnO₂ thin-film transistor was successfully fabricated. The fabricated SnO₂ thin-film transistor exhibited conventional n-type semiconductor properties, with a mobility of 0.1 cm² V^-1 s^-1, an on/off current ratio of 1.2 × 10⁵, and a subthreshold swing of 2.69. The formed SnO₂ had a larger bandgap (3.95 eV) owing to the bandgap broadening effect. The fabricated photosensor exhibited a responsivity of 1.4 × 10^-6 Jones, gain of 1.43 × 10⁷, detectivity of 2.75 × 10^-6 cm Hz^1/2 W^-1, and photosensitivity of 4.67 × 10².

• Environmental Engineering Research
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• 제24권4호
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• pp.566-571
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• 2019

One-pot hydrothermal route was adopted to synthesize Al:BiVO₄, at 4 h and 8 h reaction durations, by adding 1% aluminiumoxide powder (w/v) to the precursors. The products were investigated using several characterization techniques that conform a significant morphological change and a decrease in bandgap energy of the materials upon Al modification of scheelite monoclinic bismuth vanadate matrix at both hydrothermal durations. Antibacterial experiments were performed against methicillin-resistant Staphylococcus aureus in visible light condition to harness the photoxidation property of Al-doped BiVO₄ and compare to that of unaltered BiVO₄. Minimum inhibitory concentration of the synthesized materials was identified. The results indicate that Al-doping on BiVO₄ has a significant effect on its photocatalytic antibacterial performance. Al:BiVO₄ synthesized at 8 h hydrothermal treatment parades excellent sunlight-driven photocatalysis compared to the one synthesized at 4 h.

• 한국결정성장학회지
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• 제32권4호
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• pp.121-127
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• 2022

초광역대 반도체인 β-Ga₂O₃은 고전력 반도체 소재에 대한 유망한 응용으로 인해 큰 주목을 받고 있다. 5가지 다른 다형 중 가장 안정적인 상인 β-Ga₂O₃는 4.9 eV의 넓은 밴드갭과 8 MV/cm의 높은 항복 전계를 갖는다. 또한, 이는 용융 소스로부터 성장될 수 있어 전력반도체용 SiC, GaN 및 다이아몬드와 같은 다른 와이드 밴드갭 반도체보다 더 높은 성장률과 더 낮은 제조 비용으로 성장이 가능하다. 이 연구에서 β-Ga₂O₃ 단결정 성장은 EFG(edge-defined film-fed growth) 방법에 의해 성장되었다. 성장 방향과 주면을 각각 β-Ga₂O₃ 결정의 [010] 방향과 (100)면으로 성장하였다. Raman 분석의 스펙트럼으로 β-Ga₂O₃ 잉곳의 결정상과 불순물을 확인하였고, 고해상도 X선 회절(HRXRD)을 이용하여 결정 품질과 결정 방향을 분석하였다. 또한 EFG 방법으로 성장한 β-Ga₂O₃ 리본형태의 잉곳을 각 위치별로 결정 품질과 다양한 특성을 체계적으로 분석하였다.

• Advances in nano research
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• 제10권5호
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• pp.415-422
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• 2021

Silicene, a 2D allotrope of silicon, is predicted to be a potential material for future transistor that might be compatible with present silicon fabrication technology. Similar to graphene, silicene exhibits the honeycomb lattice structure. Consequently, silicene is a semimetallic material, preventing its application as a field-effect transistor. Therefore, this work proposes the uniform doping bandgap engineering technique to obtain the n-type silicene nanosheet. By applying nearest neighbour tight-binding approach and parabolic band assumption, the analytical modelling equations for band structure, density of states, electrons and holes concentrations, intrinsic electrons velocity, and ideal ballistic current transport characteristics are computed. All simulations are done by using MATLAB. The results show that a bandgap of 0.66 eV has been induced in uniformly doped silicene with phosphorus (PSi₃NW) in the zigzag direction. Moreover, the relationships between intrinsic velocity to different temperatures and carrier concentration are further studied in this paper. The results show that the ballistic carrier velocity of PSi₃NW is independent on temperature within the degenerate regime. In addition, an ideal room temperature subthreshold swing of 60 mV/dec is extracted from ballistic current-voltage transfer characteristics. In conclusion, the PSi₃NW is a potential nanomaterial for future electronics applications, particularly in the digital switching applications.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권4호
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• pp.528-533
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• 2016

A low voltage high PSRR CMOS Bandgap circuit capable of generating a stable voltage of less than 1 V (0.8 V and 0.5 V) robust to Process, Voltage and Temperature (PVT) variations is proposed. The high PSRR of the circuit is guaranteed by a low-voltage current mode regulator at the central aspect of the bandgap circuitry, which isolates the bandgap voltage from power supply variations and noise. The isolating current mirrors create an internal regulated voltage $V_{reg}$ for the BG core and Op-Amp rather than the VDD. These current mirrors reduce the impact of supply voltage variations. The proposed circuit is implemented in a $0.35{\mu}m$ CMOS technology. The BGR circuit occupies $0.024mm^2$ of the die area and consumes $200{\mu}W$ from a 5 V supply voltage at room temperature. Experimental results demonstrate that the PSRR of the voltage reference achieved -118 dB at frequencies up to 1 kHz and -55 dB at 1 MHz without additional circuits for the curvature compensation. A temperature coefficient of $60 ppm/^{\circ}C$ is obtained in the range of -40 to $120^{\circ}C$.

• 전기전자학회논문지
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• 제20권2호
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• pp.192-195
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• 2016

본 논문에서는 저항과 BJT를 사용하지 않고 sub-threshold 영역에서 동작하는 저전압, 저전력 기준전압 발생기를 설계하였다. CTAT 전압 발생기는 두 개의 NMOS 트랜지스터를 이용하여 구성하였고, 충분한 영역의 CTAT 전압을 발생시키기 위해 바디 바이어스 회로를 이용하였다. PTAT 전압 발생기는 PTAT 전압을 생성하기 위해 MOS 트랜지스터 입력 쌍의 서로 다른 사이즈 비를 이용하는 차동증폭기 형태로 구성하였다. 제안한 회로는 $0.18-{\mu}m$ 표준 CMOS 공정으로 설계되었다. 시뮬레이션 결과로 290mV의 출력 기준 전압을 가지며, -$20^{\circ}C$ 에서 $120^{\circ}C$의 온도 변화에서 92 ppm/$^{\circ}C$의 전압 변화 지수와 전원전압 0.63V에서 15.7nW의 소모 전력을 갖는 것을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.1093-1096
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• 2003

본 논문에서는, CMOS APS Image Sensor 내에 포함되어 회로의 면적을 줄인 새롭게 제안된 CMOS Bandgap Reference Bias Generator (BGR)를 온도 및 방사능에 대한 응답을 실험하였다. 제안된 BGR 회로의 설계 목표는 V/sub DD/는 2.5V이상이고, V/sub ref/는 0.75V ± 0.5mV 마진을 가지게 하는 것이다. 제안된 BGR회로는 Level Shifter를 갖는 Differential OP-amp단과 Feedback-Loop를 가지는 Cascode Current Mirror를 사용하여 저전압에서도 동작을 가능하게 하였으며, 높은 출력저항 특성을 가지도록 하였다. 제안된 BGR회로는 하이닉스 0.18㎛ ( triple well two-poly five-metal ) CMOS 공정을 이용하여 Test Chip을 제작하였다. 온도의 변화와 Co-60 노출조건 하에서 Total ionization dose (TID) effect된 BGR회로의 V/sub ref/를 측정하여, 이를 평가하였다. 온도에 대한 반응은, 25℃ 일 때의 V/sub ref/에 대해, 각각 45 ℃에서 0.128%. 70℃에서 0.768% 변화하였다. 그리고 온도가 25℃일 때 50krad와 100krad의 방사능을 조사 하였을 경우, V/sub ref/는 각각 2.466%, 그리고 4.612% 변화하였다.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.576-581
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• 2023

The Ga₂O₃ thin films were deposited using an RF sputtering system and the effect of crystallographic and optical properties under rapid thermal annealing conditions on Ga₂O₃ thin film was evaluated. A rapid thermal annealing method can fabricate a crystalline Ga₂O₃ thin film which is applied to various fields with a low cost and a high efficiency compared with the conventional post-annealing method. In this study, the Ga₂O₃ treated at 900℃ for 1 min showed the beta and gamma phases in XRD measurement. In optical properties, the crystalline Ga₂O₃ represented a high transmittance of more than 80% in the visible region and was calculated with a high optical bandgap energy of 4.58 eV. The beta and gamma phases Ga₂O₃ can be obtained by adjusting the rapid thermal annealing temperatures, and the various properties such as the optical bandgap energy can be controlled. Moreover, it is expected that crystalline Ga₂O₃ can be applied to various devices by controlling not only temperature but process time.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3841-3848
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• 2022

The effect of modifiers on the optical features and radiation defying ability of the Eu³⁺ ions doped multi constituent glasses was examined. XRD has established the amorphous nature of the specimen. The presence of various functional/fundamental groups in the present glasses was analyzed through FTIR spectra. The physical, structural and elastic traits of the glasses were explored. The variation in the structural compactness of the glass structure according to the incorporated modifier was enlightened to describe their suitability for a better shielding media. For the examined glasses, the metallization criterion value varied in the range 0.613-0.692, indicating the non-metallic character of the glasses with possible nonlinear optical applications. The computed elastic moduli expose the Li-containing glass (BTLi:Eu) to be tightly packed and rigid, which is a requirement for a better shielding channel. Furthermore, the optical bandgap and the Urbach energy values are calculated based on the optical absorption spectra. The evaluated bonding parameters revealed the nature of the fabricated glasses covalent. In addition, we investigated the radiation attenuation attributes of the prepared Eu³⁺ ions doped multi constituent glasses using Phy-X software. We determined the linear attenuation coefficient (LAC) and reported the influence of the five oxides Li₂O₃, CaO, BaO, SrO, and ZnO on the LAC values. The LAC varied between 0.433 and 0.549 cm^-1 at 0.284 MeV. The 39B₂O₃-25TeO₂-15Li₂O₃-10Na₂O-10K₂O-1Eu₂O₃ glass has a much smaller LAC than the other glasses.