In situ investigation of the structural defect generation and evolution during the directional solidification of 〈110〉 seeded growth Si
In situ investigation of the structural defect generation and evolution during the directional solidification of 〈110〉 seeded growth Si
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DOI：
10.1016/j.actamat.2016.06.004
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发表时间：
2016-08
期刊：
影响因子：
9.4
通讯作者：
M. Tsoutsouva;T. R. –. Béridot;G. Regula;G. Reinhart;J. Baruchel;F. Guittonneau;L. Barrallier;N. Mangelinck-Noël
中科院分区：
文献类型：
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作者：
M. Tsoutsouva;T. R. –. Béridot;G. Regula;G. Reinhart;J. Baruchel;F. Guittonneau;L. Barrallier;N. Mangelinck-Noël
本工作致力于对硅在凝固方向取向<110>的单晶种子上凝固的生长机制进行先进的现场x射线成像和补充现场研究。它旨在加深对整个硅晶体生长过程中发生的现象的基本理解，特别关注对光伏应用有害的缺陷形成机制。即对晶粒成核、晶界形成和演化、晶粒竞争、缠绕发生、位错产生以及与结构缺陷的相互作用进行了探讨和分析。双晶的成核优先发生在样品边缘的{111}切面上，在那里固-液-汽三相点线也与坩埚相互作用，以及在固-液界面的晶界凹槽（固-固-液三相线）上，两个晶粒在凹槽的{111}切面上或凹槽中竞争。增强的过冷和/或应力积累水平被发现是晶粒成核的驱动力。此外，还证明了孪晶的形成具有在生长过程中释放晶体中储存的应力的特性。然而，当晶粒处于直接竞争或被挤压在晶粒之间时，最初在孪晶位置形成的晶粒会发生严重的变形。此外，我们通过x射线布拉格衍射成像表明，一方面，在凝固过程中，相干Σ3 <111>晶界有效地阻止了生长位错的传播，而另一方面，在遇到Σ3 <111>或Σ9 <110>晶界时，位错在非相干和/或不对称Σ27a <110>水平上发射。事实上，偏离理想重合取向的晶界作为位错源在周围晶体内扩散。
This work is dedicated to the advancedin situX-ray imaging and complementaryex situinvestigations of the growth mechanisms when silicon solidifies on a monocrystalline seed oriented <110> in the solidification direction. It aims at deepening the fundamental understanding of the phenomena that occur throughout silicon crystal growth with a particular focus on mechanisms of formation of defects detrimental for photovoltaic applications. Namely, grain nucleation, grain boundary formation and evolution, grain competition, twining occurrence, dislocation generation and interaction with structural defects are explored and analysed. Nucleation of twin crystals preferentially occurs on {111} facets at the edge of the sample where solid – liquid – vapor triple point lines exist in interaction also with the crucible as well as, at grain boundary grooves at the solid – liquid interface (solid – solid – liquid triple lines), where two grains are in competition, either on the {111} facets of the groove or in the groove. Enhanced undercooling and/or stress accumulation levels are found to act as driving forces for grain nucleation. Additionally, it is demonstrated that twin formation has the property to relax stresses stored in the crystal during the growth process. However, grains formed initially in twin position can undergo severe distortion when they are in direct competition or when they are squeezed in – between grains. Moreover, we show by X-ray Bragg diffraction imaging that on the one hand, coherent Σ3 <111> grain boundaries efficiently block the propagation of growth dislocations during the solidification process, while on the other hand, dislocations are emitted at the level of incoherent and/or asymmetric Σ27a <110> at the encounter with either Σ3 <111> or Σ9 <110> grain boundaries. Indeed, grain boundaries that deviate from the ideal coincidence orientation act as dislocation sources that spread inside the surrounding crystals.