Mapping the "forbidden" transverse-optical phonon in single strained silicon (100) nanowire

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Strain engineering in silicon nanowires is key to unlocking new electronic and optical properties.
• Fabrication and characterization of strained nanowires present significant challenges.
• Accurate strain analysis is crucial for developing advanced semiconductor devices.

Purpose of the Study:

• To develop and validate a novel method for analyzing strain in single tensile strained silicon nanowires.
• To investigate the strain behavior and mechanical properties of silicon nanowires.
• To enhance the sensitivity and precision of strain characterization at the nanoscale.

Main Methods:

• Fabrication of silicon nanowires from 15 nm thick tensile strained silicon membranes.
• Development of a high-resolution polarized Raman spectroscopy technique.
• Excitation and detection of "forbidden" transverse-optical (TO) phonons.
• Analysis of Raman spectra using 3D field distribution and various polarizations.
• Simultaneous probing of local TO and longitudinal-optical (LO) phonons.

Main Results:

• Successfully excited and detected "forbidden" TO phonons in single tensile strained silicon nanowires.
• Demonstrated significantly higher sensitivity for TO phonon measurement in nanowires compared to thin layers.
• Obtained in-plane and out-of-plane strain profiles in individual nanowires.
• Established a correlation between sample geometry and measurement sensitivity.

Conclusions:

• The developed Raman spectroscopy method offers a highly sensitive approach for strain analysis in silicon nanowires.
• The findings provide new insights into the mechanical properties of strained silicon nanowires.
• This work overcomes key characterization challenges, paving the way for novel nanowire-based functionalities.