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

SiO2

Si

BaTi03

Pt

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