• Title/Summary/Keyword: amorphous silicon (a-Si)

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Performance Improvement of Flexible Thin Film Si Solar Cells using Graphite Substrate (그라파이트 기판을 이용한 유연 박막 실리콘 태양전지 특성 향상)

  • Lim, Gyeong-yeol;Cho, Jun-sik;Chang, Hyo Sik
    • Korean Journal of Materials Research
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    • v.29 no.5
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    • pp.317-321
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    • 2019
  • We investigated the characteristics of nano crystalline silicon(nc-Si) thin-film solar cells on graphite substrates. Amorphous silicon(a-Si) thin-film solar cells on graphite plates show low conversion efficiency due to high surface roughness, and many recombination by dangling bonds. In previous studies, we deposited barrier films by plasma enhanced chemical vapor deposition(PECVD) on graphite plate to reduce surface roughness and achieved ~7.8 % cell efficiency. In this study, we fabricated nc-Si thin film solar cell on graphite in order to increase the efficiency of solar cells. We achieved 8.45 % efficiency on graphite plate and applied this to nc-Si on graphite sheet for flexible solar cell applications. The characterization of the cell is performed with external quantum efficiency(EQE) and current density-voltage measurements(J-V). As a result, we obtain ~8.42 % cell efficiency in a flexible solar cell fabricated on a graphite sheet, which performance is similar to that of cells fabricated on graphite plates.

Fabrication of Highly Efficient Nanocrystalline Silicon Thin-Film Solar Cells Using Flexible Substrates (유연기판을 이용한 고효율 나노결정질 실리콘 박막 태양전지 제조)

  • Jang, Eunseok;Kim, Sol Ji;Lee, Ji Eun;Ahn, Seung Kyu;Park, Joo Hyung;Cho, Jun-Sik
    • Current Photovoltaic Research
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    • v.2 no.3
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    • pp.103-109
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    • 2014
  • Highly efficient hydrogenated nanocrystalline silicon (nc-Si:H) thin-film solar cells were prepared on flexible stainless steel substrates using plasma-enhanced chemical vapor deposition. To enhance the performance of solar cells, material properties of back reflectors, n-doped seed layers and wide bandgap nc-SiC:H window layers were optimized. The light scattering efficiency of Ag back reflectors was improved by increasing the surface roughness of the films deposited at elevated substrate temperatures. Using the n-doped seed layers with high crystallinity, the initial crystal growth of intrinsic nc-Si:H absorber layers was improved, resulting in the elimination of the defect-dense amorphous regions at the n/i interfaces. The nc-SiC:H window layers with high bandgap over 2.2 eV were deposited under high hydrogen dilution conditions. The vertical current flow of the films was enhanced by the formation of Si nanocrystallites in the amorphous SiC:H matrix. Under optimized conditions, a high conversion efficiency of 9.13% (Voc=0.52, Jsc=25.45mA/cm2, FF = 0.69) was achieved for the flexible nc-Si:H thin-film solar cells.

A Study on Implanted and Annealed Antimony Profiles in Amorphous and Single Crystalline Silicon Using 10~50 keV Energy Bombardment (비정질 및 단결정 실리콘에서 10~50 keV 에너지로 주입된 안티몬 이온의 분포와 열적인 거동에 따른 연구)

  • Jung, Won-Chae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.11
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    • pp.683-689
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    • 2015
  • For the formation of N+ doping, the antimony ions are mainly used for the fabrication of a BJT (bipolar junction transistor), CMOS (complementary metal oxide semiconductor), FET (field effect transistor) and BiCMOS (bipolar and complementary metal oxide semiconductor) process integration. Antimony is a heavy element and has relatively a low diffusion coefficient in silicon. Therefore, antimony is preferred as a candidate of ultra shallow junction for n type doping instead of arsenic implantation. Three-dimensional (3D) profiles of antimony are also compared one another from different tilt angles and incident energies under same dimensional conditions. The diffusion effect of antimony showed ORD (oxygen retarded diffusion) after thermal oxidation process. The interfacial effect of a SiO2/Si is influenced antimony diffusion and showed segregation effects during the oxidation process. The surface sputtering effect of antimony must be considered due to its heavy mass in the case of low energy and high dose conditions. The range of antimony implanted in amorphous and crystalline silicon are compared each other and its data and profiles also showed and explained after thermal annealing under inert N2 gas and dry oxidation.

Property of Nickel Silicides on ICP-CVD Amorphous Silicon with Silicidation Temperature (ICP-CVD 비정질 실리콘에 형성된 처리온도에 따른 저온 니켈실리사이드의 물성 변화)

  • Kim, Jong-Ryul;Choi, Young-Youn;Park, Jong-Sung;Song, Oh-Sung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.2
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    • pp.303-310
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    • 2008
  • We fabricated hydrogenated amorphous silicon(a-Si:H) 140 nm thick film on a 180nmSiO2/Si substrate with an inductively-coupled plasma chemical vapor deposition(ICP-CVD) equipment at 250C. Moreover, 30 nm-Ni film was deposited with a thermal-evaporator sequently. Then the film stack was annealed to induce silicides by a rapid thermal annealer(RTA) at 200500C in every 50C for 30 minuets. We employed a four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscope(FE-SEM), transmission electron microscope(TEM), and scanning probe microscope(SPM) in order to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure evolution, and surface roughness, respectively. We confirmed that nano-thick high resistive Ni3Si, mid-resistive Ni2Si, and low resistive NiSi phases were stable at the temperature of <300, 350450C, and >450C, respectively. Through SPM analysis, we confirmed the surface roughness of nickel silicide was below 12 nm, which implied that it was superior over employing the glass and polymer substrates.

Importance of Gate SiNx Properties Related to a-Si:H TFT Instability

  • Tsai, Chien-Chien;Lee, Yeong-Shyang;Shih, Ching-Chieh;Hsu, Chung-Yi;Liang, Chung-Yu;Lin, Y.M.;Gan, Feng-Yuan
    • 한국정보디스플레이학회:학술대회논문집
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    • 2006.08a
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    • pp.711-714
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    • 2006
  • Properties of silicon nitride (SiNx) film including physical and electrical characteristics have been studied for improving the stability of hydrogenated amorphous silicon thin-film transistors (a-Si TFTs) in active-matrix liquid-crystal displays (AMLCDs). The instability of a-Si:H TFTs is estimated by accelerated stress test of both bias-temperature stress and bias-illumination stress. The results show that the deposition conditions of SiNx films with higher power and lower pressure are the best choice for improving the on-current and stability of TFTs.

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Characteristics of low temperature poly-Si thin film transistor using excimer laser annealing (엑시머 레이저를 이용한 저온 다결정 실리콘 박막 트랜지스터의 특성)

  • Kang, Soo-Hee;Kim, Yong-Hoon;Han, Jin-Woo;Seo, Dae-Shik;Han, Jeong-In
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.06a
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    • pp.430-431
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    • 2006
  • This letter reports the fabrication of polycrystalline silicon thin-film transistors (poly-Si TFT) on flexible plastic substrates using amorphous silicon (a-Si) precursor films by sputter deposition. The a-Si films were deposited with mixture gas of argon and helium to minimize the argon incorporation into the film. The precursor films were then laser crystallized using XeCl excimer laser irradiation and a four-mask-processed poly-Si TFTs were fabricated with fully self-aligned top gate structure.

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Synthesis of Silicon Carbide Nano-Powder from a Silicon-Organic Precursor by RF Inductive Thermal Plasma (RF 유도 열플라즈마를 이용한 유기 용매로 부터의 탄화규소 나노 분말 합성)

  • Ko, Sang-Min;Koo, Sang-Man;Kim, Jin-Ho;Cho, Woo-Seok;Hwang, Kwang-Taek
    • Journal of the Korean Ceramic Society
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    • v.49 no.6
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    • pp.523-527
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    • 2012
  • Silicon carbide (SiC) has recently drawn an enormous amount of industrial interest due to its useful mechanical properties, such as its thermal resistance, abrasion resistance and thermal conductivity at high temperatures. In this study, RF thermal plasma (PL-35 Induction Plasma, Tekna CO., Canada) was utilized for the synthesis of high-purity SiC powder from an organic precursor (hexamethyldisilazane, vinyltrimethoxysilane). It was found that the SiC powders obtained by the RF thermal plasma treatment included free carbon and amorphous silica (SiO2). The SiC powders were further purified by a thermal treatment and a HF treatment, resulting in high-purity SiC nano-powder. The particle diameter of the synthesized SiC powder was less than 30 nm. Detailed properties of the microstructure, phase composition, and free carbon content were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), a thermogravimetric (TG) analysis, according to the and Brunauer-Emmett-Teller (BET) specific surface area from N2 isotherms at 77 K.

Property of Nano-thick Silicon Films Fabricated by Low Temperature Inductively Coupled Plasma Chemical Vapor Deposition Process (저온 ICP-CVD 공정으로 제조된 나노급 실리콘 박막의 물성)

  • Shen, Yun;Sim, Gapseop;Choi, Yongyoon;Song, Ohsung
    • Korean Journal of Metals and Materials
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    • v.49 no.4
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    • pp.313-320
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    • 2011
  • 100 nm-thick hydrogenated amorphous silicon (αSi:H) films were deposited on a glass and glass/30 nm Ni substrates by inductively-coupled plasma chemical vapor deposition (ICP-CVD) at temperatures ranging from 100 to 550C. The sheet resistance, microstructure, phase transformation and surface roughness of the films were characterized using a four-point probe, AFM (atomic force microscope), TEM (transmission electron microscope), AES (Auger electron spectroscopy), HR-XRD(high resolution X-ray diffraction), and micro-Raman spectroscopy. A nano-thick NiSi phase was formed at substrate temperatures >400C. AFM confirmed that the surface roughness did not change as the substrate temperature increased, but it increased abruptly to 6.6 nm above 400C on the glass/30 nm Ni substrates. HR-XRD and micro-Raman spectroscopy showed that all the Si samples were amorphous on the glass substrates, whereas crystalline silicon appeared at $550^{\circ}C$ on the glass/30 nm Ni substrates. These results show that crystalline NiSi and Si can be prepared simultaneously on Ni-inserted substrates.

TCO Workfunction Engineering with Oxygen Reactive Sputtering Method for Silicon Heterojunction Sola Cell Application

  • Bong, Seong-Jae;Kim, Seon-Bo;An, Si-Hyeon;Park, Hyeong-Sik;Lee, Jun-Sin
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.492-492
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    • 2014
  • On account of the good conductivity and optical properties, TCO is generally used in silicon heterojunction solar cell since the emitter material, hydrogenated amorphous silicon (a-Si:H), of the solar cell has low conductivity compare to the emitter of crystalline silicon solar cell. However, the work function mismatch between TCO layer and emitter leads to band-offset and interfere the injection of photo-generated carriers. In this study, work function engineering of TCO by oxygen reactive sputtering method was carried out to identify the trend of band-offset change. The open circuit voltage and short circuit current are noticeably changed by work function that effected from variation of oxygen ratio.

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Fabrication and Characteristics of poly-Si thin film transistors by double-metal induced lteral crystallization at 400C (이중 금속 측면 결정화를 이용한 400C 다결정 실리콘 박막 트랜지서터 제작 및 그 특성에 관한 연구)

  • 이병일;정원철;김광호;안평수;신진욱;조승기
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.34D no.4
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    • pp.33-39
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    • 1997
  • The crystallization temperature of an amorphous silicon (a-Si) can be lowered down to 400.deg. C by a new method : Double-metal induced lateral crystallization (DMILC). The a-Si film was laterally crystallized from Ni and Pd deposited area, and its lateral crystallization rate reaches up to 0.2.mu.m/hour at that temperature and depends on the overlap length of Ni and Pd films; the shorter the overlap length, the faster the rate. Poly-Silicon thin film transistors (poly-Si TFT's) fabricated by DMILC at 400.deg. C show a field effect mobility of 38.5cm3/Vs, a minimum leakage current of 1pA/.mu.m, and a slope of 1.4V/dec. The overlap length does not affect the characteristics of the poly-Si TFT's, but determines the lateral crystallization rate.

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