Thickness effects on the AC and DC electrical behavior of RF-sputtered BaTiO3 nano-capacitors with Pt or Ni electrodes

Nano-scale BaTiO3 capacitors with Ni electrodes were sputtered on Si wafers to
determine the effects of electrode thickness on the measured dielectric properties. The BaTiO3 was deposited to a thickness of approximately 150 nm, while the Ni electrodes were deposited at approximately 25, 100, and 230 nm as determined by focused ion beam cross-sectional analysis. All devices were found to have a linear I-V response at ±1 V that transitioned to a nonlinear mechanism that remained active until the maximum test voltage of ±100 V. The I-V data also showed the resistances at 1 V decreasing by about 150 GΩ for the 25 nm thick electrodes. Hysteresis plots showed paraelectric behavior for all electrode thicknesses, with measured permittivity ranging from approximately 600 to
1400, with the 100 nm thick electrodes giving the highest permittivity. AC impedance data showed a decrease in permittivity from approximately 1100 to 550 with a decrease in electrode thickness from 230 nm to 100 nm, with losses remaining below 0.10 at 1, 10, and 100 kHz. At 25 nm electrode thickness, the permittivity was found to decrease from about 1050 to 250 and the loss to increase from approximately 0.06 to 0.57 as the test frequency was increased from 1 to 100 kHz. Temperature testing gave activation energies for conduction of 0.055, 0.653, and 1.106 eV for the 230, 100, and 25 nm thick films, respectively. The results suggest that the electrodes play a critical role in thin film capacitor performance.