Pressure-driven phase transitions and reduction of dimensionality in 2D silicon nanosheets.

ABSTRACT: In-situ high-pressure synchrotron X-ray powder diffraction studies up to 21?GPa of CVD-grown silicon 2D-nanosheets establish that the structural phase transitions depend on size and shape. For sizes between 9.3(7) nm and 15.2(8) nm we observe an irreversible phase transition sequence from I (cubic)???II (tetragonal)???V (hexagonal) during pressure increase and during decompression below 8?GPa the emergence of an X-ray amorphous phase. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and atomic force microscopy (AFM) images of this X-ray amorphous phase reveal the formation of significant numbers of 1D nanowires with aspect ratios?>?10, which are twinned and grow along the <111> direction. We discovered a reduction of dimensionality under pressure from a 2D morphology to a 1D wire in a material with a diamond structure. MD simulations indicate the reduction of thermal conductivity in such nanowires.

SUBMITTER: Hwang GC 

PROVIDER: S-EPMC6303324 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature