Devitrification and Delayed Crazing of SiO₂ on Single‐Crystal Silicon and Chemically Vapor‐Deposited Silicon Nitride

The linear growth rate of cristobalite was measured in thin SiO₂ films on silicon and chemically vapor‐deposited silicon nitride. The presence of trace impurities from alumina furnace tubes greatly increased the crystal growth rate. Under clean conditions, the growth rate was still 1 order of magnitude greater than that for internally nucleated crystals in bulk silica. Crystallized films cracked and lifted from the surface after exposure to atmospheric water vapor. The crystallization and subsequent crazing and lifting of protective SiO₂ films on silicon nitride should be considered in long‐term applications.