Tantalum oxide (Ta2O5) is widely known for its high chemical, thermal and hydrothermal stability. In this study, a sol-gel method has been developed to produce homogenous, i.e., defect and pin-hole free, ultrathin films of Ta2O5. These were coated onto a porous substrate by means of dip-coating, and subsequently fired at 400 degrees C. Despite their small thickness of only 30-40 nm, the films showed very low gas permeation. (C) 2012 Elsevier B.V. All rights reserved.