X-ray Based in Situ Investigation of Silicon Growth Mechanism Dynamics—Application to Grain and Defect Formation

Abstract

<jats:p>To control the final grain structure and the density of structural crystalline defects in silicon (Si) ingots is still a main issue for Si used in photovoltaic solar cells. It concerns both innovative and conventional fabrication processes. Due to the dynamic essence of the phenomena and to the coupling of mechanisms at different scales, the post-mortem study of the solidified ingots gives limited results. In the past years, we developed an original system named GaTSBI for Growth at high Temperature observed by Synchrotron Beam Imaging, to investigate in situ the mechanisms involved during solidification. X-ray radiography and X-ray Bragg diffraction imaging (topography) are combined and implemented together with the running of a high temperature (up to 2073 K) solidification furnace. The experiments are conducted at the European Synchrotron Radiation Facility (ESRF). Both imaging techniques provide in situ and real time information during growth on the morphology and kinetics of the solid/liquid (S/L) interface, as well as on the deformation of the crystal structure and on the dynamics of structural defects including dislocations. Essential features of twinning, grain nucleation, competition, strain building, and dislocations during Si solidification are characterized and allow a deeper understanding of the fundamental mechanisms of its growth.</jats:p>

Interplay between facetting and confinement in directional solidification of silicon: A direct comparison between experiments and phase-field simulations

“…It is composed of a high temperature (up to 1800 • C) directional solidification (DS) furnace coupled with synchrotron radiation X-ray imaging techniques (Bragg diffraction imaging and radiography). A more detailed description of the device and of the X-ray imaging methods can be found in Ouaddah et al [9]. The Si samples (38 mm × 5.8 mm × 0.3 mm), housed in a boron nitride crucible, are introduced inside the DS furnace.…”

“…The ultimate goal of this paper is to shed some light on this matter by drawing a comparison between experimental investigations and phase field simulations. Experimental investigations are based on directional solidification experiments of thin model samples in which the interface dynamics and generation of structural defects is characterized by in situ X-ray imaging during solidification [9].…”

Nonlinear Thomson scattering from a tightly focused circularly polarized laser with varied incident-pulse durations

“…More complex and nonlinear phenomena begin to appear in intense laser fields, among which high-order harmonic radiation [15] can most practicably be applied as an x-ray or even a γ-ray source. Twisted x-rays have great application prospects in multiple fields including modern astrophysics [16], imaging and information technology [17], and grain formation [18].…”

Generation of dislocation clusters at triple junctions of random angle grain boundaries during cast growth of silicon ingots

“…Actually, there is no residual stress in non-coherent GBs, 26) while a residual stress exists at CSL GBs. 17,[26][27][28][29] It is suggested that non-coherent GBs would not have significant internal energy for defect generation. 29) Those properties have been applied to design HP and SMART Si ingots with an optimum dislocation density.…”

“…Ouaddar has reported that, no local strain is accumulated at Σ3{111} GBs except at their terminations, while a local strain is accumulated at GBs with Σ > 3 during the crystal growth; the degree of the strain would increase with increasing the Σ number. 27) According to the CSL theory, 25) when a GB is connected with a pair of Σ3 GBs, the Σ-number of the GB segment between the connected lines triples and the area nearby the segment would be distorted during the cast growth. Similarly, the vicinity of a junction of GBs would be distorted, due to their low symmetry and non-coherency, as observed in a junction of CSL GBs.…”