Nanoindentation-Driven Formation of Textured Hexagonal Silicon Crystals

We present a comprehensive theoretical and experimental investigation into the formation of micrometer-sized, textured hexagonal silicon (hd-Si) crystals via nanoindentation followed by annealing. Using first-principles calculations and molecular dynamics simulations, we elucidate the underlying mechanisms of pressure-driven phase transformations, emphasizing the role of elastic and plastic deformation in stabilizing the hd-Si phase. Complementing the theoretical findings, advanced characterization techniques, including polarized Raman spectroscopy, high-resolution transmission electron microscopy (TEM), and electron energy-loss spectroscopy (EELS), confirm the formation of nanometer-sized grains, characterized by slight misorientations and organized into large domains. This combined approach establishes nanoindentation as a powerful tool for tailoring metastable phases of silicon, with potential for integration into advanced semiconductor and optoelectronic technologies. Furthermore, this methodology offers a pathway for engineering other semiconductor systems, such as SiGe, to achieve direct-bandgap materials, paving the way for next-generation on-chip devices.