Monoclinic phase of erbium oxide coatings fabricated by pulsed magnetron sputtering

Abstract

Erbium oxide coatings were fabricated by midfrequency pulsed reactive magnetron sputtering by varying the deposition conditions with respect to the sputtering power from 78 W to 124 W and substrate temperature from room temperature to 677 ℃. Atomic force microscopy, nanoindentation, X-ray diffraction and grazing incidence X-ray diffraction were used to investigate the coatings’ surface morphology, mechanical properties and crystallization behaviors. Electrical properties of the coatings were also measured. Erbium oxide coatings fabricated by pulsed magnetron sputtering have high deposition rate, varying from 28 nm/min to 68nm/min. A monoclinic Er2O3 phase is obtained in the coatings. The crystalline quality of the coatings decreases with the increasing of the sputtering power. The diffraction intensity of monoclinic phase decreases as the substrate temperature was increased from room temperature to 500 ℃ and 677 ℃. It is believed that the high deposition rate and low substrate temperature could lead to the formation of the monoclinic Er2O3 coatings. The hardness and elastic modulus of the coatings deposited at substrate temperatures from room temperature to 677 ℃ vary from 11.9 GPa to 15.7 GPa and from 179 GPa to 225 GPa, respectively. The coatings deposited from room temperature to 677℃ all have high resistivity, varying from 1.5×1012 Ω ·cm to 3.1×1012 Ω ·cm, meeting the requirements of the insulating coatings in application to fusion reactor.