Nanostructured Si Thin Films for Supercapacitor Applications

Abstract

Nanostructured silicon thin films are of interest as an electrode material for supercapacitor and Li-ion battery applications. In this work silicon thin films with varied nanostructure were created using RF magnetron sputter deposition. The sputter deposition was performed at 0.27W/cm2, 0.49 W/cm2, and 1.23 W/cm2 to observe the effect of sputtering power on the resulting film nanostructure. In preparation for electrical measurements, all films were deposited onto thermally evaporated copper films on glass substrates. Atomic force microscopy (AFM), coupled with computer-automated image analysis was used to quantify average grain size and size distribution in the sputtered films. A 24% decrease in average grain size was found as the deposition rate increased from 0.7 Å/s to 0.9 Å/s over the range of sputtering powers examined. Preliminary cyclic voltammetry was pursued using a symmetric electrode capacitor arrangement and an organic electrolyte to examine the charge storage behavior of the Si films. These results will be described in the context of the thin film nanostructures observed.