CONDUCTION MECHANISMS IN AMORPHOUS AND CRYSTALLINE TANTALUM OXIDE THIN FILMS

Open Access
Author:
Bontempo, Brian
Graduate Program:
Engineering Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 02, 2010
Committee Members:
  • Dr Micheal Lanagan, Thesis Advisor
  • Michael T Lanagan, Thesis Advisor
Keywords:
  • pulsed-ed reactive sputtering
  • tantalum oxide
  • conduction mechanisms
Abstract:
Capacitors provide energy storage for a number of devices, from pacemakers to railguns. Researchers are pursuing new materials to construct capacitors in an attempt to create higher power, higher energy storage devices with less loss in energy in the charged state. This research initiative explores tantalum pentoxide (Ta2O5) capacitors of approximately 1.5 micrometer thickness deposited via pulsed-dc reactive sputtering. Relative permittivity and dielectric loss were explored for the tantalum oxide films. Current was measured for both amorphous and crystalline samples as a function of voltage, temperature, and time. Analyzing these data revealed that at low electric fields conduction was ohmic. Nonlinear behavior at high fields was fitted for Schottky and Poole-Frenkel mechanisms. It appears that both amorphous and crystalline samples were dominated by Poole-Frenkel conduction. However amorphous samples had a leakage current that was several orders of magnitude lower than the polycrystalline samples. The AC conductivity was measured for amorphous and crystalline samples across a range of frequencies, and compared to the DC values. At low frequencies, amorphous samples had conductivities approaching the DC values, but crystalline samples remained much higher than their DC values.