Date of Award

Summer 2002

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Hani Elsayed-Ali

Committee Member

Sacharia Albin

Committee Member

Vishnu K. Lakdawala

Call Number for Print

Special Collections LD4331.E55 H43 2002

Abstract

The dynamics of femtosecond pulsed laser deposition (fsPLD) of Si(!00)-1 x I and Si(!00)-2x I homoepitaxy are studied by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). The effects of substrate temperature, laser fluence and the pressure of a passive gas on the Si(!00)-1 x I growth mode are discussed. It is shown that films grow following the Volmer-Weber (3D) growth mode. The substrate temperature largely affects the morphology of the grown film. Below ~ 400 °C (at laser fluence of~ 1.9 J/cm2), randomly oriented 3D clusters are grown. This is shown as the disappearance of the RHEED elastic peaks, leaving just a diffused pattern. Above that temperature (at the same laser fluence), on the other hand, transmission patterns are obtained, owing to the formation of crystalline 3D clusters. For a constant temperature, the laser fluence is also seen to affect the growth mode. Below ~ 0.8 J/cm2(for deposition at~ 430 °C), RHEED elastic peaks disappear due to the loss of long range order, while above that value transmission patterns (due to the growth of crystalline 3D clusters) are obtained. In order to emphasize the dependence of the growth dynamics on the surface reconstruction, fsPLD of Si/Si(I00)-2x 1 is also studied. Under the studied conditions, films grow by step-flow, which is seen as no change in the RHEED pattern. The average terrace width, as measured by the specular beam splitting, is seen to remain unchanged during deposition. Under the current experimental conditions, no RHEED oscillations (indicating layer-by-layer growth) are seen. Finally, the dependence of the growth dynamics on the laser pulse duration is obtained by comparing the results of fsPLD to those of nsPLD. With nsPLD, polycrystalline films are grown, as indicated by the ring RHEED pattern.

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DOI

10.25777/w589-0e78

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