Fatigue-resistant silicon films coated with nanoscale alumina layers

The fatigue properties of monocrystalline Si thin films coated with nanoscale alumina layers (ranging from 4.2 to 50 nm) are compared to those of uncoated Si films, in air at 30 °C, 50% relative humidity (RH) and 80 °C, 90% RH. The presence of alumina coatings results in more than two orders of magnitude longer fatigue lives, even though subcritical cracking of alumina occurs. The effects of the alumina coating thickness on the overall fatigue degradation behavior are discussed.