Thermodynamic and kinetic studies of pulsed laser annealing from transient conductivity measurements
Abstract
Simultaneous measurements of the transient conductance and time-dependent surface reflectance of the melt and solidification dynamics produced by pulsed laser irradiation of Si are reviewed. These measurements demonstrate that the melting temperature of amorphous Si is reduced 200 + or = 50 K from that of crystalline Si and that explosive crystallization in amorphous Si is mediated by thin (less than or equal to 20 nm) molten layer that propagates at approx. 15 m/sec. Studies with 3.5 nsec pulses permit an estimate of the dependence of the solidification velocity on undercooling. Measurements of the effect of As impurities on the solidification velocity demonstrate that high As concentrations decrease the melting temperature of Si (approx. 150 K for 7 at. %), which can result in surface nucleation to produce buried melts. Finally, the silicon-germanium alloy system is shown to be ideal model system for the study of superheating and undercooling. The Si50Ge50 alloy closely models amorphous Si, and measurements of layered Si-Ge alloy structures indicate superheating up to 120 K without nucleation of internal melts.
- Publication:
-
Presented at Symp. on the Sci. Basis for Nucl. Waste Management
- Pub Date:
- November 1985
- Bibcode:
- 1985sbnw.symp.....P
- Keywords:
-
- Crystallization;
- Laser Annealing;
- Reaction Kinetics;
- Silicon;
- Thermodynamic Properties;
- Ion Implantation;
- Phase Transformations;
- Pulsed Lasers;
- Superheating;
- Lasers and Masers