Wet etching mechanism of Er2O3 grown on Si by molecular beam epitaxy

We report on wet etching mechanism of erbium oxide in a sulfuric acid solution within the nanometer scale. The experiments were performed on 300 nm thick Er2O3 thin films formed on Si substrate by molecular beam epitaxy (MBE). The etching mechanism was greatly effected by surface morphology and was different for Er2O3 on Si (111) compared to Er2O3 on Si(100) orientation samples. The chemical etching kinetics was analysed in detail by determining the etching rates and activation energy. The well-defined patterns were formed to explain etching anisotropy. The lateral isotropic etching can be achieved for both orientation Er2O3 (110), (111) samples, however the macroscopic etching anisotropy of Er2O3(110) thin film is governed by the shape of nanometer size crystalline grains and their in-plane alignment. The model based on surface morphology was introduced to explain the lateral etching anisotropy of Er2O3(110) thin film, finally.