Raman Studies of Surface Temperature in Laser-Heated Semiconductors.
Abstract
This project explored the uses of pulsed laser Raman scattering as a technique for studying vibrational or phonon temperatures in Si with nanosecond time resolution. Raman scattering is unique in its ability to probe in a highly selective way populations of specific phonon modes. Knowledge of how phonon populations evolve in time of fundamental importance in understanding how semiconductors respond to intense laser pulses such as in pulsed laser annealing of semiconductor surfaces. This information is crucial for understanding the dynamics of rapid laser-induced melting. Raman scattering was performed with a heat/probe sequence derived from a frequency doubled Nd:YAG-laser-pumped or N2-laser-pumped dye lasers. Initial results showed low phonon populations, consistent with only a 300-400 K temperature rise after a 10 nsec heat pulse with energy sufficient to melt the Si surface. Final results, however, indicate a population rise equivalent to a 1500 + or - 300 K phonon temperature. This is consistent with normal 1685 K melting temperature of Si. These results were confirmed in second order Raman scattering with 150 nsec pulses from a 10 kHz frequency-doubled Nd:YAG laser. Thus we measure melting-temperature phonon populations in several phonon branches. Additional experiments were done to measure the optical absorption in transiently heated silicon-on-sapphire. We found absorption consistent with that of molten Si from 0.8 eV to 3.1 eV.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 07, 1985
- Accession Number
- ADA151377
Entities
People
- A. D. Compaan
Organizations
- Kansas State University