Composition- and Temperature-Resolved Raman Shift of Silicon.

Area of Science:

• Materials Science
• Solid State Physics
• Spectroscopy

Background:

• Raman spectroscopy is a key technique for probing material properties.
• Understanding the behavior of silicon-germanium (SiGe) alloys is crucial for semiconductor applications.
• The temperature and composition dependence of Raman shifts in SiGe alloys requires a deeper mechanistic understanding.

Purpose of the Study:

• To formulate the composition and temperature dependence of the Raman shift in Si and SiGe alloys.
• To explore the underlying mechanisms using bond order-length-strength correlation and local bond average approaches.
• To quantitatively analyze the factors contributing to phonon softening in SiGe alloys.

Main Methods:

• Utilized bond order-length-strength correlation and local bond average approaches.
• Developed a model where Raman shift (Δω) is proportional to zE^1/2/d.
• Incorporated temperature and composition-dependent changes in bond length (d) and energy (E).

Main Results:

• Verified the relationship Δω ∝ zE^1/2/d for Si and SiGe.
• Quantitatively reproduced the thermally induced phonon softening in SiGe alloys.
• Identified bond thermal expansion and energy loss as primary drivers of frequency redshift.

Conclusions:

• The study provides quantitative information on bond energy and reference frequencies influencing Raman shifts.
• Gained deeper insight into the fundamental mechanism of Raman shift variations.
• Demonstrated the utility of Raman spectroscopy for investigating bonding thermodynamics.