Date of Award

Summer 2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical/Computer Engineering

Committee Director

Hani E. Elsayed-Ali

Committee Member

Helmut Baumbart

Committee Member

Charles Sukenik

Committee Member

Gon Namkoong

Abstract

Surface morphology during the growth of Si on Si(111)-(7x7) by femtosecond pulsed laser deposition (fsPLD) is studied using reflection high-energy electron diffraction (RHEED) at different temperatures. The growth of Si on Si(111) has received considerable attention as a model system of homoepitaxy. PLD is a deposition technique that uses much more energetic species (atoms and ions) compared to other physical vapor deposition (PVD), such as in molecular beam epitaxy. In this work, in situ reflection high energy electron diffraction (RHEED) was used to study the dynamics of PLD of Si on Si(111)-(7x7). Epitaxial growth of Si/Si(111)-(7x7) at temperatures as low as 210°C was observed. For this substrate temperature, no change in RHEED patterns after growth, and only reduction in intensity during deposition was observed.

Surface Debye temperature of the topmost layer of the Si(111)-7x7 is measured by using RHEED. The diffraction intensity is distorted by the thermal vibration amplitude of atoms on the topmost layer of the surface.

Influence of Si deposition on the temperature of Si(111) to (7x7) phase transition is also studied. The phase transition showed that Si deposition lowers the transition temperature. A Ti-sapphire laser (100 fs, 800 nm, 1 kHz) was used to ablate a Si target on Si(111)-(1x1) during quenching from high temperature. The RHEED intensity was observed as the substrate was exposed to the Si plume and the Si(111) substrate was quenched. The RHEED patterns showed a shift in the transition temperature from 840°C without the plume to 820°C with the plume.

With laser fluence below the damage threshold, laser enhanced epitaxial growth shows a great improvement in deposit Si on Si(111)-7x7 at low temperature (room temperature).

DOI

10.25777/vff7-rn15

ISBN

9781109331332

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