Time-resolved x-ray diffraction studies of laser annealing and photostriction in silicon

John R Buschert, Purdue University

Abstract

Part I. Time resolved x-ray diffraction at grazing incidence is used to observe a silicon crystal exposed to intense pulsed laser irradiation. The Bragg peak is shown to disappear during melting and then gradually reappear as the surface recrystallizes. A new scan method is introduced which keeps the grazing angle constant and allows the surface temperature to be directly related to the position of the Bragg peak. Part II. The photo-excitation of charge carriers in silicon is expected to cause a contraction of the lattice due to a coupling between the band gap and the lattice parameter called the deformation potential. This photostriction is demonstrated using a pulsed excimer laser to generate the carriers and time resolved x-ray diffraction to see the lattice contraction. A simple model is proposed which determines the carrier concentration and temperature using diffusion equations and recombination. The model is consistent with a photostriction constant greater by a factor of five than the presently accepted value. Some discussion is given of the reasons for such a discrepancy. The method promises to be useful technique for the study of deformation potentials and transport phenomena.

Degree

Ph.D.

Advisors

Colella, Purdue University.

Subject Area

Condensation

COinS