Study of Ag thin films deposited on porous silicon

The experimental results of DC I-V measurements of Ag thin films on porous silicon are presented. The 200 Å thick Ag thin films were deposited by RF magnetron sputtering. The substrate is p-type anodized porous silicon containing a random fractal surface structure with various size dimensions. For comparison, Ag thin films were also deposited on HNO3 oxidized porous silicon. All porous silicon samples were analyzed by X-ray diffraction, SEM, PL, and FTIR spectroscopy, before and after oxidation. DC I-V measurements were performed on the Ag thin films. Nonlinear I-V behavior has been observed which can be explained by the random tunneling junction network model. The nonlinear I-V behavior strongly relates to the surface roughness which affects the tunneling effect at the interconnections of junction resistors. For a smooth surface of oxidized porous silicon, the deposited Ag thin films have a linear I-V relation in two current regions, but their resistances drop sharply in two discontinuous steps. Fractal-like I-V behavior, which needs more detailed investigation, was also observed.