铸造单晶硅中的微枝晶生长-李杭霏 -solarbe文库

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铸造单晶中的生长微孪晶李杭霏原帅余学功教授杨德仁教授浙江大学硅材料重点实验室硅材料国家重点实验室 State Key Laboratory of Silicon Materials 目录背景介绍实验结果与讨论结论背景随着人口数量越来越多，温室气体排放量亦逐年上升，为了缓解全球气温上涨的趋势，大力发展清洁能源的需求越来越迫切 atomic Hydro- eletronic 22 15 风能太阳能 95 单晶电池片多晶电池片铸造单晶电池片背景 5X. Gu, et al. , Seed-assisted cast quasi-single crystalline silicon for photovoltaic application Towards high efficiency and low cost silicon solar cells, Solar Energy Materials and Solar Cells, 2012, 101, 95-101. H. Zhang,et al., Nucleation and bulk growth control for high efficiency silicon ingot casting, Journal of Crystal Growth, 2011, 3181, 283-287. A Lantreibecq, et, al., micro-twins and dislocations characterization in monolike Si using TEM and in-situ TEM. Extended Defects In Semiconductors 2016 EDS 2016, Sep 2016, Les Issambres, France. 201 Schematic diagram of growth of mono-like Si [001] testing,slicing,polishing texturing Modules slicing 背景 6 N. Stoddard,,et, al., Castingsingle crystal silicon novel defect profiles from BP Solar s mono2 TM wafers, Solid State Phenomena, 2008, 131, 1-8. D. Hu, et, al., The characteristics of sub-grains in the mono-like silicon crystals grown with directional solidification method, in 38th IEEE Photovoltaic Specialists Conference PVSC, 2012, IEEE. Figure1. PL image aCast polysilicon； b cast-monocrystalline Si a b Figure2PL image of monocrystalline a1bottom； a2middle； a3top 主要缺陷 Red zone Red zone 杂质 Metals, C,N 背景 7 Figure2. a.SE image of ecth lines b.EBSD mapping of fig.a 腐蚀线沿 2个方向呈平行分布实验 50μm 50μm 15 6 c m 1cm 1cm 156 cm a b dac Figure1. a.vertically sliced samples etched image b.horizonally sliced samples etched image c.PL image； d.OM-image of horizonally sliced samples 5 cm 001010 001 8 010 100 001 001 110 010 100 001 010 100 001 010 实验样品切割方式 9 3 types 1. 单根 2. “Y” 型 3. “V” 型 100 100 90° 100 100 100100 110 100 112 112 70.5° 110 100 Twi n 90° 70 ° Figure a.SEM imagevertically sliced etched sample； b.SEM imagevertically sliced etched sample； c,d schematic diagram of making TEM samples by FIB c d 5 001 110 实验 10 Figure. Sample 1 a BF-image; bHR-TEM image; c.SAD image d.HAADF image [110] 实验 1 带轴， region1处的样品为孪晶枝晶，以 {111}为对称面；枝晶生长方向为 B a 110 b Twin lamell a [001] 002 -11-1 -111 c [110] d [11 0] d 70° 00-2 -11-1 1-1-1 [110] Twin lamella Pt Si [002] -220 220 a c d b [100] Figure. Sample 3 a, bSE image; C.HAADF image d. SAD image 实验 3 3样品为 {100}取向 112 001 010 100 a 001 projectionb d c length hunders μms- several cms 112 width 10-30nm {111} 112 Horizon tally projection 讨论 13 Figure1.EDS mapping of source of twins C Growth Direction 1 2FIB Figure2.HR-TEM limage of 1, 2 500μm 实验 Twin boundary Figure.S/L interface during crystal growth ; EBSD image of dendry; Schematic diagram of crystal growth K. Fujiwara et al. / Scripta Materialia 57 2007 81–84 讨论 [001] α β [001] 讨论生长界面模型 seed {001} 红区固液界面孪晶区分凝系数 N 0.0007 C0.07 C N Figure . OM,SE picture EDS mapping of particles around twins C Growth Direction 讨论 C， N等在固液界面处的偏析，过饱和后形成的杂质点可能为孪晶形核原因杂质过冷生长速率分凝高密度 T 低密度 T 形核密度晶粒尺寸形核密度晶粒尺寸 b a Figure . OM picture of samples from different ingot 讨论 Figure 1. EBIC test a. 300K b. 100K dislocation cluster Twins Figure 2. Picture of Si ingot at the bottom 300K b 100K a b 此类生长微孪晶对电学性能影响很小，亦有抑制位错增殖的效果实验总结 1. 在铸造单晶硅底部、籽晶上方区域分布宽度为 10-30nm，长度几百微米 -几 cm沿生长的微孪晶 2. 微孪晶有 3种形态独立、 V型、 Y型 3. 可能的形核原因为固液界面处的杂质点 4. 孪晶的密度、长度与杂质浓度有关，浓度越高，孪晶密度高，长度小 5. 长孪晶具有抑制拼接缝处位错的潜在应用谢谢您的聆听李杭霏