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Temperature-Dependent Electrical Characterization of Multiferroic BFO Thin Films. Danielle Hitchen, Sid Ghosh, K. Hassan, K. Banerjee, J. Huang Electrical and Computer Engineering Rutgers University. Outline . Motivation Multiferroics Hysteresis: The Enabling Property Ferroelectricity

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temperature dependent electrical characterization of multiferroic bfo thin films

Temperature-Dependent Electrical Characterization of Multiferroic BFO Thin Films

Danielle Hitchen, Sid Ghosh, K. Hassan, K. Banerjee, J. Huang

Electrical and Computer Engineering

Rutgers University

outline
Outline
  • Motivation
  • Multiferroics
  • Hysteresis: The Enabling Property
  • Ferroelectricity
  • Bismuth Ferrite: Material of Choice
  • Procedures
  • Challenges
  • Data Results
  • Conclusion
  • Acknowledgements
motivation
Motivation

Storage limitations on existing memory devices as well as

the desire for faster write/erase capability on non-volatile

memory devices has increased the demand for better

materials that accord with standard integrated circuit

requirements. [3]

[1]

[2]

[1] http://imgs.tootoo.com/ff/29/ff290e10431d97b15c18ebd08e952f36.jpg

[2] http://www.computerrepairmaintenance.com/images/flash-drive.png

[3] Zambrano, Raffaele. “Applications and issues for ferroelectric NVMs.” Materials Science in Semiconductor Processing 5

(2003) 305-310.

multiferroic materials
Multiferroic Materials
  • Discovered less than a century ago, ferroics relate to the ancient study of magnetism
  • Ferroic materials can be:
    • Ferroelectric
    • Ferromagnetic
    • Ferroelastic
  • Multiferroics exhibit two or more of these properties simultaneously
hysteresis the enabling property
Hysteresis: The Enabling Property

Hysteresis: the ‘memory’

a material retains of a

previously applied

energy field

[4]

[4] http://www.daviddarling.info/images/hysteresis_loop.jpg

ferroelectricity
Ferroelectricity

Ferroelectric materials possess a spontaneous, stable polarization that switches hysteretically in an applied electric field.

[5]

[5] http://www.fujitsu.com/img/MICRO/fme/microelectronics/fram/ferroelectric_material.jpg

ferroelectricity1
Ferroelectricity
  • Polarization characteristics change when subjected to varying
    • Pressure
    • Temperature
    • Applied Voltage
  • These unique properties make the material useful for many different applications
bismuth ferrite our material of choice
Bismuth Ferrite: Our Material of Choice
  • BFO is multiferroic at room temperature– a rarity among multiferroics
  • Has strong ferroelectric, but weak ferromagnetic properties
  • Crystalline structure, as well as polarization, alters in varying temperature
  • We hope to see how well BFO functions as a capacitor
  • Goal: document the changes in polarization that occur as the temperature changes

Fractal ferroelectric domains in thin

films of multiferroic BiFeO3.

[6]

[6] http://www.esc.cam.ac.uk/teaching/mineral-sciences/minsci-part-IA

procedure
Procedure

The probe (left) controls temperature and

pressure in the chamber housing the sample.

Leakage current is plotted in the semiconductor

precision analyzer (above).

challenges
Challenges
  • The samples were not uniformly dielectric; finding good contacts was difficult
  • Careful probing was necessary due to the properties of the material
  • Equipment broke down several times
  • Redeposition of the contacts appeared to influence the functionality of the devices
data varied dielectric behavior
Data: Varied Dielectric Behavior

Data is from

ten contacts

on a single

sample

taken at room

temperature.

data polarization
Data: Polarization

Device became

more resistive as

temperature

increased; this is

evidenced by the

shape of the curve.

[4]

Ideal Hysteresis

data remanent polarization
Data: Remanent Polarization

Polarization shows

an increasing

trend at higher

temperatures; this

is not what is

expected, and may

relate to the

increasing current

leakage.

data current leakage
Data: Current Leakage

At increasing

temperatures,

our device leaks

more current, as

expected.

The curved data

points are

representative of

a dielectric; a linear

slope would be a

purely resistive

device.

data remanent current leakage
Data: Remanent Current Leakage

As temperatures

increase, we see

an increasingly

leaky device.

(All data was taken

At -1.5V.)

Current leakage

is high at high

temperatures

(20nA/cm2

vs. 2.0E5 nA/cm2).

conclusion
Conclusion
  • Dielectric behavior did not characterize the behavior of this material
  • There was non-uniformity in the samples that DID exhibit capacitive polarization
  • The contact deposition process may have influenced functionality
  • Dielectric behavior degraded at higher temperatures, as expected
acknowledgements
Acknowledgements

I would like to thank the National Science Foundation and the US Department of Defense for funding my research (EEC-NSF Grant # 0755115 and CMMI-NSF Grant # 1016002), as well as the University of Illinois at Chicago for hosting my undergraduate research program.

I would also like to express my thanks to the directors of my program, Professors Christos Takoudis and Greg Jursich, as well as to Professor Siddhartha Ghosh who advised me in my research.

Finally, thank you Koushik Banerjee, Jun Huang, Khaled Hassan and Hsu Bo for informing my research, assisting with the equipment, and providing me with necessary literature.