Erbium oxide coatings were prepared by mid-frequency pulsed magnetron sputtering at different sputtering powers and substrate temperatures. Atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and nanoindentation were used to investigate surface morphologies, compositions, crystallization behavior, and mechanical properties of the coatings, respectively. The thermal stability of the coating structure was also investigated. A monoclinic phase was observed in the erbium oxide coatings prepared at substrate temperatures below 350 degrees C. A cubic phase was obtained by elevating the temperature to 500 degrees C. The monoclinic phase coatings deposited at elevated substrate temperatures showed high phase stability. The coatings with a cubic phase exhibited higher hardness and elastic modulus than those with a monoclinic phase, attributable to a narrower bond length distribution and a shorter average bond length. (C) 2011 Elsevier B.V. All rights reserved.