티타늄 실리사이드 감지소자의 결함에 의한 Band-gap의 제어

윤용수 ( Yong Soo Yoon ),정일현 ( Il Hyun Jung ) 한국공업화학회 2002 공업화학 Vol.13 No.8

공공의 존재와 그레인의 크기, 결정화도, 불순물과 같은 결함들은 band gap의 결정과 막의 응용성에 중요한 역할을 하며 실험 조건에 따라 다양한 특성을 나타내고 있다. 본 연구에서 a-Si:H는 rf파워가 증가할수록 공공이 많이 존재하였으며, 열처리 시간을 증가시켰을 때 막의 결정성, band gap과 결함수 모두 증가하였다. 또한 그레인 수가 증가할수록 band gap과 결함수는 감소하는 것으로 나타났으며, 결함수와 band gap은 서로 비례 관계에 있다. 따라서 특정 센서에 응용하기 위한 막은 결함수를 제어하므로써 적절한 band gap을 가지게 할 수 있다. The defects, such as vacancy, grain size, the degree of crystalline, impurities (or doping materials) etc., play an important role in the determination of band gap and the application of film. They show various properties, depending on experimental conditions. In this work, it was found that vacancy with increasing rf-power was plentifully existed in a-Si:H film and the crystallinity of a film, the band-gap and the number of defects increased with long annealing time. It was shown that the band-gap and the defect-number decreased with increasing the density of grain. The number of defects was found to the be in proportion to the band gap. Consequently, we found that the band-gap with controlling the number of defect can be variously applied in the specific sensor.

Interface States in Bilayer Graphene Encapsulated by Hexagonal Boron Nitride

Lee, Kayoung,Liu, En-Shao,Watanabe, Kenji,Taniguchi, Takashi,Nah, Junghyo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.48

<P>The threshold voltages at the onset of conduction for electron and hole branches can provide information on band gap values or interface states in a gap. We measured conductivity of bilayer graphene encapsulated by hexagonal boron nitride as a function of back and top gates, where another bilayer graphene is used as a top gate. From the measured conductivity the transport gap values were extracted assuming zero interface trap states, and they are close to the theoretically expected gap values. From a little discrepancy an average density of interface states per energy within a band gap (<I>D</I><SUB>it</SUB>) is also estimated. The data clearly show that <I>D</I><SUB>it</SUB> decreases as a bilayer graphene band gap increases rather than being constant. Despite the decreasing trend of <I>D</I><SUB>it</SUB>, interestingly the total interface states within a gap increases linearly as a band gap increases. This is because of ∼2 × 10<SUP>10</SUP> cm<SUP>-2</SUP> interface states localized at band edges even without a band gap, and other gap states are equally spread over the gap.</P> [FIG OMISSION]</BR>

코발트 불순물을 첨가한 Ga2Se3단결정의 광학적 에너지 띠간격의 온도의존성에 대한 열역학적 함수 추정

이영환,윤재태,박광호,김덕태,현승철 대한시과학회 2016 대한시과학회지 Vol.18 No.3

Purpose: We have investigated the optical energy band gaps' dependence of Ga2Se3 and Ga2Se3 : Co2+ single crystals grown by Chemical Transport Method on temperature. As results of these, we could estimate thermodynamic functions. Methods: We made the quartz ampoules for growing Ga2Se3 and Ga2Se3 : Co2+ single crystals with Ga(6N, 2 mol), Se(6N, 3 mol), Co(4N, 0.1 mol%) and transporting agent I(6N, 6㎎/㎤) under 5 ×10-5 torr. Positioned the ampoule in the middle of the two zones furnace and eliminated the residual impurities from the growing site. For growing Ga2Se3 and Ga2Se3 : Co2+ single crystals, we maintained 6 days at 890℃ in the starting site and 780℃ in the growing site, respectively. To obtain the temperature dependence of the energy band gaps near the fundamental absorption edge, we measured the optical absorption spectra by using UV-VIS-NIR spectrophotometer(Hitachi, U-3501) with cryostat(Air Products, SH-4). Results and Consideration: The optical absorption spectrum of Ga2Se3 and Ga2Se3 : Co2+ single crystals was increased abruptly at 576 ㎚ and 594 ㎚ region, respectively. Also, the temperature dependence of the energy band gaps was estimated from the Varshni equation. Conclusions: The grown single crystals had cubic structures and the lattice constants were a = 5.442 Å and 5.672 Å for Ga2Se3 and Ga2Se3 : Co2+ single crystals, respectively. The optical energy band gaps obtained from the optical absorption spectra were direct transition types. The temperature dependence of the energy band gaps was applied well to Varshni equation and it was given that Eg(0) = 2.177 eV, α= 7.8 ×10-4 eV/K, β= 378 K and Eg(0) = 2.069 eV, α= 1.2 ×10-3 eV/K, β= 349 K for Ga2Se3 and Ga2Se3 : Co2+ single crystals, respectively. And the thermodynamic functions, entropy(SCV), heat capacity(CCV), and enthalpy(HCV), could be estimated from the temperature dependence of the optical energy band gaps. 목 적: 화학수송법으로 성장시킨 Ga2Se3 및 Ga2Se3 : Co2+ 단결정의 광학적 에너지 띠 간격 energy band gap의 온도의존성을 규명하고, 이로부터 기초적 열역학 함수를 추정고자 한다. 방 법: gallium(99.9999 %, 2 mol), selenium(99.9999 %, 3 mol), cobalt(99.99 %, 0.1 mol %) 그리고수송물질로 iodine(99.99 %, 6 mg/cm3)을 함께 석영관에 넣고 내부를 5×10-6 torr로 유지하면서 봉입하여성장용 ampoule을 만들었다. 성장용 ampoule을 2단 전기로의 중앙에 위치시키고, 결정 성장측의 잔류불순물을 깨끗이 제거한 후, 시료 출발측을 890 ℃, 성장측을 780 ℃로 6일간 유지하여 단결정을 성장시켰다. 기초 흡수단 부근에서 에너지 띠 간격의 온도의존성을 구하기 위하여 저온장치(Air Products, SH-4)가 부착된 UV-VIS-NIR spectrophotometer(Hitachi, U-3501)를 사용하여 광흡수 스펙트럼을 측정하였다. 결과 및 고찰: Ga2Se3 및 Ga2Se3 : Co2+ 단결정들의 광흡수 스펙트럼은 순수한 Ga2Se3 단결정의 경우 570 nm영역에서, Ga2Se3 : Co2+ 단결정의 경우 594 nm영역에서 광흡수가 급격히 증가하여 cobalt를 첨가한 단결정의 기초 흡수단이 장파장 측으로 이동됨을 볼 수 있었다. 또한 에너지 띠 간격의 온도의존성은 Varshni 가 제안한 실험식으로부터 구하였다. 결 론: 성장된 단결정의 구조는 cubic구조이었고, 이들의 격자상수 값은 Ga2Se3 및 Ga2Se3 : Co2+ 단결정들에 대하여 각각 a = 5.442 Å, a = 5.672 Å이었다. 광흡수 스펙트럼으로부터 구한 optical energy band gap(Eg)의 band구조는 직접 전이형이었고, 에너지 띠 간격의 온도의존성은 Varshni방정식이 잘 적용되었다. 이때 구한 상수 값은 Ga2Se3 단결정의 경우 Eg(0) = 2.177 eV, α= 7.8×10-4eV/K, β= 378 K로 주어지고, Ga2Se3 : Co2+단결정의 경우 Eg(0) = 2.089 eV, α= 1.20×10-3 eV/K, β= 349 K로 주어졌다. 이들 값으로부터 구한 에너지 띠 간격의 온도의존성으로부터 열역학 함수인 entropy(SCV), heat capacity(CCV), enthalpy(HCV) 값을 추정할 수 있었다.

Estimation of Thermodynamic Functions from the Optical Energy Band Gaps' Dependence of Ga2Se3 and Co-doped Ga2Se3 Single Crystals on Temperature

Young-Hwan Lee,Jae-Tae Youn,Kwang-Ho Park,Duck-Tae Kim,Seung-Cheol Hyun 대한시과학회 2016 대한시과학회지 Vol.18 No.3

목 적: 화학수송법으로 성장시킨 Ga2Se3 및 Ga2Se3 : Co2+ 단결정의 광학적 에너지 띠 간격 energy band gap의 온도의존성을 규명하고, 이로부터 기초적 열역학 함수를 추정고자 한다. 방 법: gallium(99.9999 %, 2 mol), selenium(99.9999 %, 3 mol), cobalt(99.99 %, 0.1 mol %) 그리고 수송물질로 iodine(99.99 %, 6 mg/cm3)을 함께 석영관에 넣고 내부를 5×10-6 torr로 유지하면서 봉입하여 성장용 ampoule을 만들었다. 성장용 ampoule을 2단 전기로의 중앙에 위치시키고, 결정 성장측의 잔류불순 물을 깨끗이 제거한 후, 시료 출발측을 890 ℃, 성장측을 780 ℃로 6일간 유지하여 단결정을 성장시켰다. 기초 흡수단 부근에서 에너지 띠 간격의 온도의존성을 구하기 위하여 저온장치(Air Products, SH-4)가 부 착된 UV-VIS-NIR spectrophotometer(Hitachi, U-3501)를 사용하여 광흡수 스펙트럼을 측정하였다. 결과 및 고찰: Ga2Se3 및 Ga2Se3 : Co2+ 단결정들의 광흡수 스펙트럼은 순수한 Ga2Se3 단결정의 경우 570 nm영역에서, Ga2Se3 : Co2+ 단결정의 경우 594 nm영역에서 광흡수가 급격히 증가하여 cobalt를 첨가한 단 결정의 기초 흡수단이 장파장 측으로 이동됨을 볼 수 있었다. 또한 에너지 띠 간격의 온도의존성은 Varshni 가 제안한 실험식으로부터 구하였다. 결 론: 성장된 단결정의 구조는 cubic구조이었고, 이들의 격자상수 값은 Ga2Se3 및 Ga2Se3 : Co2+ 단결정 들에 대하여 각각 a = 5.442 Å, a = 5.672 Å이었다. 광흡수 스펙트럼으로부터 구한 optical energy band gap(Eg)의 band구조는 직접 전이형이었고, 에너지 띠 간격의 온도의존성은 Varshni방정식이 잘 적용되었 다. 이때 구한 상수 값은 Ga2Se3 단결정의 경우 Eg(0) = 2.177 eV, α= 7.8×10-4eV/K, β= 378 K로 주어 지고, Ga2Se3 : Co2+단결정의 경우 Eg(0) = 2.089 eV, α= 1.20×10-3 eV/K, β= 349 K로 주어졌다. 이들 값 으로부터 구한 에너지 띠 간격의 온도의존성으로부터 열역학 함수인 entropy(SCV), heat capacity(CCV), enthalpy(HCV) 값을 추정할 수 있었다. Purpose: We have investigated the optical energy band gaps' dependence of Ga2Se3 and Ga2Se3 : Co2+ single crystals grown by Chemical Transport Method on temperature. As results of these, we could estimate thermodynamic functions. Methods: We made the quartz ampoules for growing Ga2Se3 and Ga2Se3 : Co2+ single crystals with Ga(6N, 2 mol), Se(6N, 3 mol), Co(4N, 0.1 mol%) and transporting agent I(6N, 6㎎/㎤) under 5 ×10-5 torr. Positioned the ampoule in the middle of the two zones furnace and eliminated the residual impurities from the growing site. For growing Ga2Se3 and Ga2Se3 : Co2+ single crystals, we maintained 6 days at 890℃ in the starting site and 780℃ in the growing site, respectively. To obtain the temperature dependence of the energy band gaps near the fundamental absorption edge, we measured the optical absorption spectra by using UV-VIS-NIR spectrophotometer(Hitachi, U-3501) with cryostat(Air Products, SH-4). Results and Consideration: The optical absorption spectrum of Ga2Se3 and Ga2Se3 : Co2+ single crystals was increased abruptly at 576 ㎚ and 594 ㎚ region, respectively. Also, the temperature dependence of the energy band gaps was estimated from the Varshni equation. Conclusions: The grown single crystals had cubic structures and the lattice constants were a = 5.442 Å and 5.672 Å for Ga2Se3 and Ga2Se3 : Co2+ single crystals, respectively. The optical energy band gaps obtained from the optical absorption spectra were direct transition types. The temperature dependence of the energy band gaps was applied well to Varshni equation and it was given that Eg(0) = 2.177 eV, α= 7.8 ×10-4 eV/K, β= 378 K and Eg(0) = 2.069 eV, α= 1.2 ×10-3 eV/K, β= 349 K for Ga2Se3 and Ga2Se3 : Co2+ single crystals, respectively. And the thermodynamic functions, entropy(SCV), heat capacity(CCV), and enthalpy(HCV), could be estimated from the temperature dependence of the optical energy band gaps.

Universal Mechanism of Band-Gap Engineering in Transition-Metal Dichalcogenides

Kang, Mingu,Kim, Beomyoung,Ryu, Sae Hee,Jung, Sung Won,Kim, Jimin,Moreschini, Luca,Jozwiak, Chris,Rotenberg, Eli,Bostwick, Aaron,Kim, Keun Su American Chemical Society 2017 NANO LETTERS Vol.17 No.3

<P>van der Waals two-dimensional (2D) semiconductors have emerged as a class of materials with promising device characteristics owing to the intrinsic band gap. For realistic applications, the ideal is to modify the band gap in a controlled manner by a mechanism that can be generally applied to this class of materials. Here, we report the observation of a universally tunable band gap in the family of bulk 2H transition metal dichalcogenides (TMDs) by in situ surface doping of Rb atoms. A series of angle-resolved photoemission spectra unexceptionally shows that the band gap of TMDs at the zone corners is modulated in the range of 0.8-2.0 eV, which covers a wide spectral range from visible to near-infrared, with a tendency from indirect to direct band gap. A key clue to understanding the mechanism of this band-gap engineering is provided by the spectroscopic signature of symmetry breaking and resultant spin-splitting, which can be explained by the formation of 2D electric dipole layers within the surface bilayer of TMDs. Our results establish the surface Stark effect as a universal mechanism of band-gap engineering on the basis of the strong 2D nature of van der Waals semiconductors.</P>

질화물계 반도체 GaP1-x Nx의 에너지 밴드갭 계산

정호용(Ho Yong Chung),김대익(Dae Ik Kim) 한국전자통신학회 2017 한국전자통신학회 논문지 Vol.12 No.5

본 연구에서는 무질서 효과가 고려된, 새로이 가정한 가상 결정 근사법을 갖는 empirical pseudopotential method를 사용하여 온도와 조성비 변화에 따른 3원계 질화물계 화합물 반도체 GaP1-xNx의 휨 매개변수 및 에너지 밴드갭을 계산하였다. 300K의 조성비 구간(0≤x≤0.05)에서 에너지 밴드갭들이 급격히 감소하며, 해당하는 계산된 휨 매개변수가 13.1eV임을 알 수 있었다. 에너지 밴드갭 계산 결과로부터 굴절률 n과 실수부 유전상수 함수 ε를 계산하였고, 에너지 밴드갭 계산 결과는 실험치를 대체로 잘 설명하였다. The energy band gaps and the bowing parameters of zincblende GaP1-xNx on the variation of temperature and composition are determined by using an empirical pseudopotential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter calculated is 13.1eV and the energy band gaps are decreased rapidly for GaP1-xNx (0≤x≤0.05, 300K). A refractive index n and a function of real dielectric constant are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

Extending absorption of near-infrared wavelength range for high efficiency CIGS solar cell via adjusting energy band

Lingling Yan,Yiming Bai,Bo Yang,Nuofu Chen,Zhan'ao Tan,Tasawar Hayat,Ahmed Alsaedi 한국물리학회 2018 Current Applied Physics Vol.18 No.4

The efficient photon harvesting in near infrared wavelength range is still a challenging problem for high performance Cu(In1-x, Gax)Se2 (CIGS) solar cell. Herein, adjusting the energy band distribution of CIGS solar cell could provide significant academic guidance for devices with superior output electric power. To understand the role of each functional layer, the optimal 3000 nm CIGS absorber layer with 1.3 eV bandgap and 30 nm CdS buffer layer were firstly obtained via simulating the uniform band-gap structures. By introducing CIGS absorber layer with a double grading Ga/(GaþIn) profile, the power conversion efficiency of the double gradient band gap cell is superior to that of uniform band-gap cell through extending absorption of near-infrared wavelength range. Upon optimization, the best power conversion efficiency of CIGS with a double gradient band gap solar cell is improved significantly to 24.90%, among the best values reported in literatures, which is an 8.17% relative increase compared with that of the uniform band-gap cell. Our findings provide a theoretical guide toward the design of high performance solar cells and enrich the understandings of the energy band engineering for developing of novel semiconductor devices.

Tuning of Optical Band Gap: Genesis of Thickness Regulated Al Doped ZnO Nano-Crystalline Thin Films Formulated by Sol–Gel Spin Coating Approach

M. Reefaz Rahman,M. Nasir Uddin,Tasnim Ashrafy,Mostofa Washif,M. Rakib Uddin,Mahbubul Hoq,Ahmed Hasnain Jalal 한국전기전자재료학회 2022 Transactions on Electrical and Electronic Material Vol.23 No.3

Intrinsic zinc oxide thin fi lms have defi ciencies in terms of structural, optical and electronic characteristics, which has given rise to researches on metal doped zinc oxide fi lms in the interest of enhancing its characteristics. Indium tin oxide, Au, Ag, Pt and Ti; which are extensively used in industrial level thin film applications but aluminum has low cost than those metals, so by doping with this on ZnO thin films, its performance and quality on the morphological, elemental, structural, optical and electrical attributes were analyzed in this research. Tuning of ZnO nanocrystalline thin fi lms’ optical band gap, doped by diff erent materials simplifi es possible elements for photonic applications. Sol–gel spin coating method has been used for these analyses which was accustomed to gain the Al doped ZnO (AZO) parent compounds on silicon-glass substrates. Ultra violet visible spectrophotometer was used to determine band gap tuning characteristics, urbach energy, transmittance and absorption properties. The Moss-Burstein outcome imprints the blue shift with thickness increment of the absorption end and there is a clear relationship between band gap and urbach energy. Tuning of band gap value varies from 3.22 eV to 3.26 eV by varying the fi lm thickness from 100 to 300 nm. A non-linear, non-monotonic relation has been seen for the change of optical and structural parameters of AZO thin fi lms. Deep research of structural and optical properties represents important information to get a better perspective of band gap dependence on structural properties.

Theoretical analysis of transient wave propagation in the band gap of phononic system

Lin, Yi-Hsien,Ma, Chien-Ching Techno-Press 2013 Interaction and multiscale mechanics Vol.6 No.1

Phononic system composed of periodical elastic structures exhibit band gap phenomenon, and all elastic wave cannot propagate within the band gap. In this article, we consider one-dimensional binary materials which are periodically arranged as a 20-layered medium instead of infinite layered system for phononic system. The layered medium with finite dimension is subjected to a uniformly distributed sinusoidal loading at the upper surface, and the bottom surface is assumed to be traction free. The transient wave propagation in the 20-layered medium is analyzed by Laplace transform technique. The analytical solutions are presented in the transform domain and the numerical Laplace inversion (Durbin's formula) is performed to obtain the transient response in time domain. The numerical results show that when a sinusoidal loading with a specific frequency within band gap is applied, stress response will be significantly decayed if the receiver is away from the source. However, when a sinusoidal force with frequency is out of band gap, the attenuation of the stress response is not obvious as that in the band gap.

조성비 변화에 따른 질화물계 화합물 반도체 Iny Ga₁-yAs1- x Nx의 에너지 밴드갭과 광학상수 계산

정호용(Ho-Yong Chung),김대익(Dae-Ik Kim) 한국전자통신학회 2019 한국전자통신학회 논문지 Vol.14 No.5

본 연구에서는 band anticrossing 모델을 사용하여 온도와 조성비 변화에 따른 4원계 질화물계 화합물 반도체 Iny Ga₁-yAs1- x Nx 의 에너지 밴드갭과 광학상수를 계산하였다. 300K의 조성비 구간(0≤x≤0.05, 0≤y≤1.0)에서 에너지 밴드갭들이 연속적으로 감소하며, 계산된 휨 매개변수는 0.522eV가 사용되었다. 에너지 밴드갭 계산 결과는 다른 연구 결과와 대체로 잘 일치하였다. 또한 에너지 밴드갭 결과를 새롭게 제안한 모델식에 적용하여 굴절률 n과 고주파 유전상수 ε를 계산하였다. The energy band gaps and optical constants of zincblende Iny Ga₁-yAs1- x Nx on the variation of temperature and composition are determined by using band anticrossing method. The energy band gaps are decreasing continuously in Iny Ga₁-yAs1- x Nx (0≤x≤0.05, 0≤y≤1.0, 300K) and the bowing parameter is calculated as 0.522eV. The calculation results of energy band gaps are consistent with those of other studies. A refractive index n and a high-frequency dielectric constant ε are calculated by a proposed modeling equation using the results of energy band gaps.