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Epitaxial Growth of Ferroelectric Titanate Layers by Sol-Gel Routes
Muhammad Salameh
Prof. Eric P. Kvam
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Objectives Show BaTiO3 is an insulator Adjust orientation and control strains Control growth
Integrate with Joel (did not have chance to attempt)
Reduce fatigue of polarization; Increase Lifetime After certain amts of switching there has been
degradation of performance and poor retention of stored information
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What is a Ferroelectric?
A Ferroelectric Material (Crystal): Exhibits spontaneous electric polarization below
Curie Temperature Has polarization that can be reversed by
application of an electric field Permanent electric dipole moment possessed by
all pyroelectric (polar) materials that may be reoriented by the application of an electrical field
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Why Barium Titanate?
Chemical Formula - BaTiO3 In the pure form it is an electrical insulator
When doped to be a semi-conductor it exhibits positive temperature of co-efficient of resistivity (PTCR) properties in the polycrystalline form
Has high Tc and Pr over singe crystals Also BaTiO3 exhibits ferroelectric properties and
is an excellent photorefractive material
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Preparation of Sol-Gel Films
Cutting and Cleaning Substrates Make Sol-Gel (process of making the thin films)
solution Spin Coating Low Temp./ High Temp Annealing Metallography, XRD, Optical Microscopy, SEM Top electrode and Probe Station
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Example of Substrate
Pt
SiO2
Si
BaTi03
Pt
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Metallography
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SEM Pictures
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Probe Station
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Hysteresis
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Capacitance v. Voltage
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XRD
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XRD Plot
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XRD Plot
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BaTiO3 on MgO Substrate
Why? Has crystalline structure that match the thin film
i.e. grow epitaxially Chemically compatible
Film deposited on substrate, film and substrate will expand equally when annealed
Thermal expansion rates different then substrate will strain or break film