Transcript Part One

Epitaxial Growth of Ferroelectric Titanate
Layers by Sol-Gel Routes
Muhammad Salameh
Prof. Eric P. Kvam
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
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
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
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
Example of Substrate
Pt
BaTi03
Pt
SiO2
Si
Metallography
SEM Pictures
Probe Station
Hysteresis
Capacitance v. Voltage
XRD
XRD Plot
XRD Plot
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