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

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Microstructural improvement in polycrystalline Si films by crystallizing with vapor transport of Al/Ni chlorides

  • Eom, Ji-Hye;Lee, Kye-Ung;Jun, Young-Kwon;Ahn, Byung-Tae
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.315-318
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    • 2004
  • We developed a vapor induced crystallization (VIC) process for the first time to obtain high quality polycrystalline Si films by sublimating the mixture of AlCl3 and NiCl2. The VIC process enhanced the crystallization of amorphous silicon thin films. The LPCVD amorphous silicon thin films were completely crystallized after 5 hours at 480 C. It is known that needle-like grains with very small width grow in the Ni-metal induced lateral crystallization. In our new method, the width of grains is larger because the grain can also grow perpendicular to the needle growth direction. Also the interface between the merging grain boundaries was coherent. As the results, a polycrystalline film with superior microstructure has been obtained.

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Diode Equivalent Parameters of Solar Cell

  • Iftiquar, Sk Md;Dao, Vinh Ai;Yi, Junsin
    • Current Photovoltaic Research
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    • v.3 no.4
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    • pp.107-111
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    • 2015
  • Current characteristic curve of an illuminated solar cell was used to determine its reverse saturation current density (J0), ideality factor (n) and resistances, by using numerical diode simulation. High efficiency amorphous silicon, heterojunction crystalline Si (HIT), plastic and organic-inorganic halide perovskite solar cell shows n=3.27 for a-Si and n=2.14 for improved HIT cell as high and low n respectively, while the perovskite and plastic cells show n=2.56 and 2.57 respectively. The J0 of these cells remain within 7.1×107 and 1.79×108A/cm2 for poorer HIT and improved perovskite solar cell respectively.

A Study of Crystalline Behaviour on As+ Ion-Implanted Silicon (As 이온 주입된 Si의 결정성 거동에 관한 연구)

  • Mun, Yeong-Hui;Song, Yeong-Min;Kim, Jong-O
    • Korean Journal of Materials Research
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    • v.9 no.1
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    • pp.99-103
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    • 1999
  • We investigated the crystalline behavior in active ion implanted silicon through Raman spectroscopy. Four a-Si(amorphous Si) peaks were observed that are related to the ion implantation induced a-Si layer. After the isochronical anneal(30min). and isothermal anneal(450C), noticeable recovery of crystalline-Si peak at 519cm\ulcorner and peak center shift of the a-Si TO from 465cm\ulcorner to 480cm\ulcorner were observed by RNM(Random Network Model). By applying RNM and SCLM(Spatial Correlation Length Model), the peak center and FWHM(the Full Width at half Maximum) of a-Si were changed dramatically between T\ulcorner=200C and 300C. From the results, it can be said that there is an abrupt structural change at this temperature region.

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Effect of Annealing on a-Si:H Thin Films Fabricated by RF Magnetron Sputtering (RF 스퍼터를 이용하여 제작된 a-Si:H 박막의 어닐링 효과에 관한 연구)

  • Kim, Do-Yun;Kim, In-Soo;Choi, Se-Young
    • Korean Journal of Materials Research
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    • v.19 no.2
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    • pp.102-107
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    • 2009
  • The effect of annealing under argon atmosphere on hydrogenated amorphous silicon (a-Si:H) thin films deposited at room temperature and 300C using Radio Frequency (RF) magnetron sputtering has been investigated. For the films deposited at room temperature, there was not any increase in hydrogen content and optical band gap of the films, and as a result, quality of the films was not improved under any annealing conditions. For the films deposited at 300C, on the other hand, significant increases in hydrogen content and optical band gap were observed, whereas values of microstructure parameter and dark conductivity were decreased upon annealing below 300C. In this study, it was proposed that the Si-HX bonding strength is closely related to deposition temperature. Also, the improvement in optical, electrical and structural properties of the films deposited at 300C was originated from thermally activated hydrogen bubbles, which were initially trapped at microvoids in the films.

a-Si:H in TFT-LCD that integrated Gate driver circuit : Instability effect by temperature (Gate 구동 회로를 집적한 TFT-LCD에서 a-Si:H TFT의 온도에 따른 Instability 영향)

  • Lee, Bum-Suk;Yi, Jun-Sin
    • Proceedings of the KIEE Conference
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    • 2006.07d
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    • pp.2061-2062
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    • 2006
  • a-Si(amorphous silicon) TFT(thin film transistor)는 TFT-LCD(liquid crystal display)의 화소 스위칭(switching) 소자로 폭넓게 이용되고 있다. 현재는 a-Si을 이용하여 gate drive IC를 기판에 집적하는 ASG(amorphous silicon gate) 기술이 연구, 적용되고 있는데 이때 가장 큰 제약은 문턱 전압(Vth)의 이동이다. 특히 고온에서는 문턱 전압의(Vth) 이동이 가속화 되고, Ioff current가 증가 하게 되고, 저온(0C)에서는 전류 구동능력이 상온(25C) 상태에서 같은 게이트 전압(Vg)에 대해서 50% 수준으로 감소하게 된다. 특히 ASG 회로는 여러 개의 TFT로 구성되는데, 각각의 TFT가 고온에서 Vth shift 값이 다르게 되어 설계시 예상하지 못 한 고온에서의 화면 무너짐 현상 즉 고온 노이즈 불량이 발생 할 수 있다. 고온 노이즈 불량은 고온에서의 각 TFT의 문턱전압 및 IDVG 특성을 측정한 결과 고온 노이즈 불량에 영향을 주는 인자가 TFT의 width와 기생 capacitor비 hold TFT width가 영향을 주는 것으로 실험 및 시뮬레이션 결과 확인이 되었다. 발생 mechanism은 ASG 회로는 AC 구동을 하기 때문에 Voff 전위에 ripple이 발생 되는데 특히 고온에서 ripple이 크게 증가 하여 출력 signal에 영향을 주어 불량이 발생하는 것을 규명하였다.

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Control of Plasma Characteristic to Suppress Production of HSRS in SiH4/H2 Discharge for Growth of a-Si: H Using Global and PIC-MCC Simulation

  • Won, Im-Hui;Gwon, Hyeong-Cheol;Hong, Yong-Jun;Lee, Jae-Gu
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.312-312
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    • 2011
  • In SiH4/H2 discharge for growth process of hydrogenated amorphous silicon (a-Si:H), silane polymers, produced by SiH2 + Sin-1H2n SinH2n+2, have no reactivity on the film-growing surface. However, under the SiH2 rich condition, high silane reactive species (HSRS) can be produced by electron collision to silane polymers. HSRS, having relatively strong reactivity on the surface, can react with dangling bond and form Si-H2 networks which have a close correlation with photo-induced degradation of a-Si:H thin film solar cell [1]. To find contributions of suggested several external plasma conditions (pressure, frequency and ratio of mixture gas) [2,3] to suppressing productions of HSRS, some plasma characteristics are studied by numerical methods. For this study, a zero-dimensional global model for SiH4/H2 discharge and a one-dimensional particle-in-cell Monte-Carlo-collision model (PIC-MCC) for pure SiH4 discharge have been developed. Densities of important reactive species of SiH4/H2 discharge are observed by means of the global model, dealing 30 species and 136 reactions, and electron energy probability functions (EEPFs) of pure SiH4 discharge are obtained from the PIC-MCC model, containing 5 charged species and 15 reactions. Using global model, SiH2/SiH3 values were calculated when pressure and driving frequency vary from 0.1 Torr to 10 Torr, from 13.56 MHz to 60 MHz respectively and when the portion of hydrogen changes. Due to the limitation of global model, frequency effects can be explained by PIC-MCC model. Through PIC-MCC model for pure SiH4, EEPFs are obtained in the specific range responsible for forming SiH2 and SiH3: from 8.75 eV to 9.47 eV [4]. Through densities of reactive species and EEPFs, polymerization reactions and production of HSRS are discussed.

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The improvement of the stability of hydrogenated amorphous silicon (수소화된 비정질 실리콘박막의 안정성향상에 관한 연구)

  • 이재희
    • Journal of the Korean Vacuum Society
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    • v.8 no.1
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    • pp.51-54
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    • 1999
  • Hydrogenated amorphous silicon (a-Si:H) films are fabricated by Argon radical annealing (ArRA). The deposition rate of continuously deposited a-Si:H film is 1.9 \AA/s. As ArRA time are increased to 0.5 and 1 minute, the deposition rate are increased to 2.8 \AA/s and 3.3 AA/s. The deposition rate of a-si:H films with 2 and 3 minutes ArRA time are 3.3 \AA/s. As the ArRA time is increased, the optical band gap and the hydrogen contents in the a-Si:H films are increased and slightly decreased. The light-induced degradation of ArRA treated a-Si:H films are less than that of continuously deposited a-Si:H film. The dark conductivity and the conductivity activation energy (Ea) of continuously deposited a-Si:H film are decreased to 1/25 in room temperature and increased to 0.09eV By 1 hour light soaking, respectively. The dark conductivity and Ea of ArRA treated a-Si:H film decreased to 1/3 in room temperature and increased to 0.03eV by 1 hour light soaking, respectively. We could improve the stability of a-Si:H films under the light soaking by ArRA technique and discussed the microscopic process of ArRA technique.

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Characteristics of Poly-Si TFTs Fabricated on Flexible Substrates using Sputter Deposited a-Si Films

  • Kim, Y.H.;Moon, D.G.;Kim, W.K.;Han, J.I.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07a
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    • pp.297-300
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    • 2005
  • The characteristics of polycrystalline silicon thin-film transistors (poly-Si TFTs) fabricated using sputter deposited amorphous silicon (a-Si) precursor films are investigated. The a-Si films were deposited on flexible polymer substrates using argon-helium mixture gases to minimize the argon incorporation into the film. The precursor films were then laser annealed by using a XeCl excimer laser and a four-mask-processed poly-Si TFT was fabricated with fully self-aligned top gate structure. The fabricated pMOS TFT showed field-effect mobility of 32.4cm2/Vs and on/off ratio of 106.

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A Study on Amorphous Silicon Film Deposition by Laser CVD (Laser CVD에 의한 비정질 실리콘 박막 형성에 관한 연구)

  • Yoo, H.S.;Park, G.Y.;Ryou, J.H.;Cho, T.H.;Kim, J.H.;Sung, Y.K.
    • Proceedings of the KIEE Conference
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    • 1993.07b
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    • pp.1277-1279
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    • 1993
  • As a highly information-oriented society developes, various kinds of amorphous semiconductor devices, such as solar cells, electrographic printers, image sensors, and flat-panel televisions, have been developed as man/machine interfaces. This paper proposed the laser CVD techniques to deposit hydrogenated amorphous silicon thin film on glass or dielectric substrate at low temperatures. Varying the deposition conditions, we examined optical and electrical charateristics of a-Si:H film deposited by Laser CVD.

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A Study on Microstructure and Tribological Behavior of Superhard Ti-Al-Si-N Nanocomposite Coatings (초고경도 Ti-Al-Si-N 나노복합체 코팅막의 미세구조 및 트라이볼로지 거동에 관한 연구)

  • Heo, Sung-Bo;Kim, Wang Ryeol
    • Journal of Surface Science and Engineering
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    • v.54 no.5
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    • pp.230-237
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    • 2021
  • In this study, the influence of silicon contents on the microstructure, mechanical and tribological properties of Ti-Al-Si-N coatings were systematically investigated for application of cutting tools. The composition of the Ti-Al-Si-N coatings were controlled by different combinations of TiAl2 and Ti4Si composite target powers using an arc ion plating technique in a reactive gas mixture of high purity Ar and N2 during depositions. Ti-Al-Si-N films were nanocomposite consisting of nanosized (Ti,Al,Si)N crystallites embedded in an amorphous Si3N4/SiO2 matrix. The instrumental analyses revealed that the synthesized Ti-Al-Si-N film with Si content of 5.63 at.% was a nanocomposites consisting of nano-sized crystallites (5-7 nm in dia.) and a three dimensional thin layer of amorphous Si3N4 phase. The hardness of the Ti-Al-Si-N coatings also exhibited the maximum hardness value of about 47 GPa at a silicon content of ~5.63 at.% due to the microstructural change to a nanocomposite as well as the solid-solution hardening. The coating has a low friction coefficient of 0.55 at room temperature against an Inconel alloy ball. These excellent mechanical and tribological properties of the Ti-Al-Si-N coatings could help to improve the performance of machining and cutting tool applications.