Europhys. Lett.
Volume 76, Number 6, December 2006
Page(s) 1144 - 1150
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 24 November 2006
Europhys. Lett., 76 (6), pp. 1144-1150 (2006)
DOI: 10.1209/epl/i2006-10402-4

Electron transport properties in $\chem{CoAlO}$ composite antidot arrays

Y. G. Ma, H. J. Liu and C. K. Ong

Centre for Superconducting and Magnetic Materials, Department of Physics National University of Singapore - 2 Science Drive 3, Singapore 117542, Singapore

received 9 June 2006; accepted in final form 30 October 2006
published online 24 November 2006

A complex disordered system composed of composite material and mesoscopic pore arrays was developed by depositing CoAlO composite thin films on the multiporous anodic aluminum oxide (AAO) membranes. In the disordered antidot arrays, self-connectivity of the metallic phase was dependent on the local conduction geometries. This led to locally variable thresholds for electron percolation. Metallic and semiconductor-like conduction behaviors were simultaneously found in the antidot arrays at thickness less than $15\un{nm}$, while the reference continuous films only showed metallic behavior. The observed non-monotonous resistance-temperature relations were explained by configuring a tetragonally oriented random resistor network related to the constrained conduction geometries, where electron conductions controlled by both percolation and tunneling coexisted. The tunneling effect was more evidently manifested in an antidot array with increased structural disorders. In this case the temperature dependence of resistance well followed the typical power law mode, $\exp[\ab{const}/T^{\alpha }]$ with $\alpha = 1/2$. It was consistent with the characteristic of highly disordered metallic granular systems, where Coulomb charging energy as well as the aluminum oxide barrier would play a key role for electron tunneling between nanometer-sized granules. Our experimental results indicated that electron conductions in a composite antidot array were closely related to its constrained mesoscopic geometries.

73.23.-b - Electronic transport in mesoscopic systems.
72.80.Tm - Composite materials.

© EDP Sciences 2006