铸造单晶硅中的微枝晶生长-李杭霏
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, 318(1), 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: a:Cast polysilicon； b: cast-monocrystalline Si a b Figure2PL image of monocrystalline: a1:bottom； a2:middle； a3:top 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 image:vertically sliced etched sample； b.SEM image:vertically 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; b:HR-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, b:SE image; C.HAADF image d. SAD image 实验 3# 3#样品为 {100}取向 112 001 010 100 (a) (001) projection(b) (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 C:0.07 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
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