Read-Me file dataset of “Singly-twinned growth of Si crystals upon chemical modification” 
Saman Moniri, Xianghui Xiao, and Ashwin J. Shahani
Contact: moniri@umich.edu

Research Overview: 
During crystallization a continuum of patterns could emerge due to the interplay of growth kinetics, material or solution chemistry, and crystallographic defects. The coherent twin boundary is widely known to catalyze growth in pristine crystals including polycrystalline Si. Much remains unknown about the impact of changing the chemical environment of the crystallization process through the deliberate addition of trace metallic species – termed chemical modification. Pristine Si has been reported to grow through the classical model of two parallel twin planes acting in concert to enable steady state propagation of the solid-liquid interfaces. Here, we achieve a new vision on the growth process via in situ synchrotron X-ray microtomography and further corroborated by ex situ crystallographic investigation. We find that steady-state growth is impossible in chemically modified alloys that consist of trace (0.1 wt.%) Sr. This is because the Sr modifier poisons the concave re entrant grooves, thereby de activating the advantage of the twin plane re entrant edge mechanism and leading to a singly twinned interface. This study may serve as a proxy to chemically modified crystallization pathways of eutectic Si in Al Si alloys and, more broadly, as a framework for the crystallization mediated synthesis of materials.

Methods: 
The data file contains X-ray projection images collected at the Advanced Photon Source in Argonne National Laboratory (Lemont, IL). Pre-processing of data involved extraction and reconstruction of projection images from the .hdf raw data file using TomoPy toolbox in Python. Then, computer vision algorithms were developed in MATLAB to process (segment) the images followed by 3D visualization and quantitative analysis.

File Inventory:
The data is comprised of 22 directories, each housing one .hdf file of the X-ray projections recorded during solidification of Al-Si-Cu-Sr. The subdirectory named ‘Exp365…’ is the X-ray projection data of the fully molten sample, while the last subdirectory named ‘Exp386…’ correspond to the fully solidified sample. The flat and dark projections are also included as two separate .hdf files (total file count: 24). The raw data file is in .hdf format and can be reconstructed into .tiff, e.g., by using the TomoPy toolbox in Python.

Funding Information:
•	NSF CAREER program under award number 1847855
•	Argonne National Laboratory. Grant Number: DE‐AC02‐06CH11357

Use and Access: 
This data set is made available under a Creative Commons Attribution license (CCBY). Restrictions apply for publishing with the data presented here. Please contact author Saman Moniri (moniri@umich.edu) for further information and permission.

Suggested Citation to the Data: 
Saman Moniri, Xianghui Xiao, and Ashwin J. Shahani, “Singly-twinned growth of Si crystals upon chemical modification” [Data set]. University of Michigan - Deep Blue. https://doi.org/10.7302/812m-d307