摘要
对超冶金级硅进行不同条件下的热退火实验研究。利用金相显微镜、电子背散射衍射和X射线衍射仪分别对退火前后多晶硅不同部位的位错、晶界和择优生长取向进行表征。结果表明:退火前后多晶硅中的位错密度大小分布顺序始终是中部<底部<顶部。随着退火温度的升高,位错密度逐渐减小;小角度晶界不断减少,直至消失;CSL晶界比例先增加后减小。在1200℃下退火3h后,多晶硅中的孪晶晶界∑3达到28%;多晶硅上、中、下部的晶粒分别获得最佳择优生长取向,这将对后续硅材料的加工及多晶硅太阳能电池转化效率的提高起到促进作用。
Effect of thermal annealing on the upgraded metallurgical grade（UMG）-Si was investigated under different conditions.The dislocation,grain boundaries and preferred growth orientation of Si ingot were characterized by optical microscopy,electron back scattering diffraction（EBSD） and X-ray diffractometry（XRD）,respectively.The arrange order of dislocation density of Si ingot is from the lowest in the middle to the lower in the bottom and low in the top before and after annealing.And it decreases gradually with increase of the annealing temperature.The number of small angle grain boundaries declines gradually until disappears whereas the proportion of coincidence site lattice（CSL） grain boundaries increases firstly and then decreases.The twin boundary Σ3 reaches the highest proportion of 28% after annealing at 1 200 ℃ for 3 h.Furthermore,the crystal grains in different positions gain the best preferred growth orientation,which can promote the following machining of Si ingot and the conversion efficiency of solar cells.
基金
Project(SKL2009-8)supported by the State Key Laboratory of Silicon Materials,Zhejiang University,China
Project(NCET-07-0387)supported by the New Century Excellent Researcher Award Program from Ministry of Education of China
关键词
超冶金级硅
退火
位错密度
晶界
upgraded metallurgical grade（UMG-Si）
annealing
dislocation density
grain boundaries
