Self-Assembled Barium Titanate Nanoscale Films by Molecular Beam Epitaxy
Student: Tim Morgan
Degree: Ph.D., May 2018
Major Professor: Dr. Greg Salamo
Research Area(s):
Nanoscience & Engineering
Background/Relevance
- Barium titanate (BTO) is a ferroelectric material with giant polarization, dielectric constant and surface charge and tunable with electric field, strain, light and composition.
- BTO has no native growth window since no constituents are volatile.
Innovation
- Approach to locking in stoichiometry is novel and opens up an easier way to grow BTO.
- Co-deposition reduces growth time in half with less calibration time
- Highest d33 values of BTO reported by PFM
Approach
- Use Molecular Beam Epitaxy (MBE) to grow films barium rich in both shuttered RHEED & co-deposited methods.
- Measure strength of ferroelectricity using piezoforce microscopy
Conclusions
- Excess barium self-limits the stoichiometry of barium titanate
- Barium titanate self-assembles when grown using co-deposition with excess barium
- Higher piezoelectric coefficients of barium titanate are measured after solvent cleaning
Future Work
- Investigate defects and growth mechanisms using XTEM
- Investigate ferroelectric properties of single monolayer of BTO