Date of Award

6-1994

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Materials Science and Engineering

Supervisor

G.C. Weatherly

Co-Supervisor

I. Emesh

Abstract

This project focused on advancing the knowledge of chemical vapour
deposition (CVD) PbTiO₃ thin films for future work on lead zirconate titanate or PZT
(PbZrᵪT₁_ᵪO₃) through an understanding of the structural, chemical and electrical
properties of the material.

A study of the individual oxides, TiO₂ and PbOᵪ, prepared also by CVD, was
made using transmission electron microscopy (TEM), scanning electron microscopy
(SEM), Raman spectroscopy and x-ray diffraction (XRD), before a low pressure, low
temperature process for PbTiO₃ was developed. The major factors in controlling the
film composition and thickness uniformity were identified. The formation sequence
for CVO PbTiO₃ films involved individual oxides of Ti and Pb, rather than
pyrochlore-type phases. A Pb-rich composition ensured the formation of perovskite,
however it resulted in the formation of a thin PbOᵪ surface layer. Removal of this
layer by etching gave improved electrical properties. Capacitance measurements
typically varied less than 1% over the frequency range and gave ε' values from
60-155. At 1 kHz, tan δ was ~0.01 and the resistivity was ~10¹¹Ω.cm.

TEM examination of as-deposited films of PbTiO₃ revealed no macro-domains existed. After post-deposition annealing twinned structures acting as domains were
found in grains, ~0.1 μm in size. The origin of the theoretical minimum grain size
for twinning in PbTiO₃ thin films is discussed. A classification scheme for domain structures was developed based on thin films of PbTiO₃ and PZT. Similarities were
drawn between these domain structures and their bulk counterparts.

The multi-layered bottom electrode of Pt and Ti used in this study was found
to react at temperatures ≤515°C. At higher temperatures (698°C), the Ti layer was
completely consumed, however the top surface of the Pt layer remained unaffected.


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