Date of Award

Spring 2008

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

Leonid Tsybeskov

Second Advisor

Hussein I. Hanafi

Third Advisor

Marek Sosnowski

Abstract

In this thesis, Raman Scattering of free standing porous silicon on sapphire samples of controllably varying porosity is studied. The free standing, fully crystalline porous silicon films were prepared by electrochemical etching and the porous structure were lifted-off by a procedure based on electro-polishing. During Raman scattering measurements, the samples are exposed to relatively high intensity laser radiation. Free-standing porous Si sample temperature and thermal conductivity are calculated by comparing intensities of Stokes and anti-Stokes Raman peaks. Compared to crystalline Si, we find strong decrease in thermal conductivity accompanied by a change in the phonon spectra. Also, comparing Stokes and anti-Stokes Raman spectra, we find that porous Si is a nano-composite material with a complex morphology and variety of crystallites sizes. The porous silicon layers can be used for thermal isolation and as floating substrates for lattice-mismatched hetero-integration.

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