Recovery of hexagonal Si-IV nanowires from extreme GPa pressure
Abstract
We use Raman spectroscopy in tandem with transmission electron microscopy and density functional theory simulations to show that extreme (GPa) pressure converts the phase of silicon nanowires from cubic (Si-I) to hexagonal (Si-IV) while preserving the nanowire's cylindrical morphology. In situ Raman scattering of the longitudinal transverse optical (LTO) mode demonstrates the high-pressure Si-I to Si-II phase transition near 9 GPa. Raman signal of the LTO phonon shows a decrease in intensity in the range of 9–14 GPa. Then, at 17 GPa, it is no longer detectable, indicating a second phase change (Si-II to Si-V) in the 14–17 GPa range. Recovery of exotic phases in individual silicon nanowires from diamond anvil cell experiments reaching 17 GPa is also shown. Raman measurements indicate Si-IV as the dominant phase in pressurized nanowires after decompression. Transmission electron microscopy and electron diffraction confirm crystalline Si-IV domains in individual nanowires. Computational electromagnetic simulations suggest that heating from the Raman laser probe is negligible and that near-hydrostatic pressure is the primary driving force for the formation of hexagonal silicon nanowires.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 12, 2016
- Source ID
- 10.1063/1.4948576
Entities
People
- Bennett E. Smith
- Evan H. Abramson
- Paden B. Roder
- Peter J. Pauzauskie
- Xuezhe Zhou
Organizations
- Air Force Office of Scientific Research
- National Science Foundation
- Pacific Northwest National Laboratory
- University of Washington