Type of Document Master's Thesis Author Dickerson, Bryan Douglas Jr. Author's Email Address email@example.com URN etd-9997-12315 Title Characterization of Ferroelectric Films by Spectroscopic Ellipsometry Degree Master of Science Department Materials Science and Engineering Advisory Committee
Advisor Name Title Desu, Seshu B. Committee Chair Curtin, William A. Jr. Committee Member Kenik, Edward A. Committee Member Keywords
Date of Defense 1997-09-10 Availability unrestricted AbstractProcess dependent microstructural effects in ferroelectric SrBi2Ta2O9 (SBT) thin films
were characterized and distinguished from material dependent optical properties using a
systematic multi-layer modeling technique. Variable angle spectroscopic ellipsometry
(VASE) models were developed by sequentially testing Bruggeman effective-media
approximation (EMA) layers designed to simulate microstructural effects such as
surface roughness, porosity, secondary phases, and substrate interaction.
Cross-sectional analysis by atomic force microscopy (AFM), transmission and scanning
electron microscopy (TEM) and (SEM) guided and confirmed the structure of
multi-layer models for films produced by pulsed laser deposition (PLD), metal-organic
chemical vapor decomposition (MOCVD), and metal-organic deposition (MOD).
VASE was used to estimated the volume percentage of second phase Bi2O3 in SBT
thin films made by MOD. Since Bi2O3 was 10 orders of magnitude more conductive
than SBT, second phase Bi2O3 produced elevated leakage currents. Equivalent circuits
and percolation theory were applied to predict leakage current based on Bi2O3 content
and connectivity. The complex role of excess Bi2O3 in the crystallization of SBT was
reviewed from a processing perspective. VASE helped clarify the nature of the
interaction between SBT films and Si substrates. When SBT was deposited by MOD
and annealed on Si substrates, the measured capacitance was reduced from that of SBT
on Pt due mainly to the formation of amorphous SiO2 near the SBT/Si interface. VASE
showed that the thickness and roughness of the SiO2 reaction layer increased with
annealing temperature, in agreement with TEM measurements. Unlike PZT, SBT
crystallization was not controlled by substrate interaction.
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