Heidelberg 1999 – wissenschaftliches Programm
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Q: Quantenoptik
Q 30: Poster: Optische Technik
Q 30.11: Poster
Dienstag, 16. März 1999, 16:30–18:30, PH
Effect of high Power CO2 Laser Pulses and Thermal Annealing on the electrical Properties of n-Si — •Ahmed A. I. Khalil1 and M. Mounir2 — 1National Institute of Laser Enhanced Science (NILES), Cairo University, Giza, EGYPT — 2Faculty of Science, Cairo University, Giza, EGYPT
In this work we have measured the a.c. electrical conductivity and dielectric constant at different temperatures and frequencies on pure and irradiated samples of n-Si by using TEA CO2 laser (λ=10.6 µm). It was found that the a.c. conductivity of unirradiated, unannealed, and irradiated samples of n-Si were increased with increasing temperature, frequency and time of annealing. The increase of the number of laser shots will decrease the conductivity and also the dielectric constant which may be due to formation of traps which decrease the number of carriers. The activation energies for all samples at different temperature regions were calculated. Mechanism of the annealing processes are discussed in connection with this dependence and the threshold intensity for such damage was determined. The possibility to find microdefects was also noted by using scanning Electron Microscope (SEM).
The dipolar relaxation time was calculated theoretically and studied as a function of temperature. The lattice mismatch in the grain boundaries causes a planer array of localized states, being able to capture free carriers. The accumulated charge constitutes an electrostatic barrier impending carriers from free motion.