Columnar Thin Films for Three-Dimensional Microbatteries

Controlled-porosity Si thin films suitable for use as high-aspect-ratio microbattery electrodes were produced using the glancing angle deposition (GLAD) technique. GLAD is a high-vacuum physical vapor deposition method that can be used to produce a variety of film morphologies from most vacuum-compatible materials. No lithographic steps were required to create the porous, columnar thin films. Initial electrochemical results indicate large gravimetric and areal capacities (3600 mAh/g, 90 mu Ah/cm(2), respectively), and good capacity retention (3000 mAh/g after 70 charge/discharge cycles) can be obtained from Si vertical post morphology films. Areal capacity and capacity retention can likely be further improved by optimizing the film morphology, electrode material composition, and cycling conditions.