Research On Wettability Of Holmium Oxide Films Deposited By Magnetron Sputtering

Rare earth metal oxides with unique electronic structures have been potential candidates for applications such as catalysts,high dielectric constant gate oxides,laser dopants and magneto-optical memory.In nature Ho₂O₃ exists in beryllium yttrium,cerium lanthanite and other rare earth ores.Prior to this,people have been concerned about the excellent optical and electrical properties of Ho₂O₃ and ignored the research on the hydrophobic properties and other comprehensive properties of Ho₂O₃.In this paper,Ho₂O₃ films under different deposition conditions were prepared by grazing angle radio frequency?RF?magnetron sputtering.X-ray diffraction?XRD?,scanning electron microscope?SEM?,and X-ray photoelectron spectroscopy?XPS?were used to study the structure,morphology,and chemical composition of the films,respectively.The contact angle measuring instrument,nano-indentation instrument and tribometer were used to test the wetting properties and mechanical properties of the film,respectively.A group of samples with different substrate bias voltages were selected at annealing 1000 ?,and their wettability and mechanical stability were observed.The main research contents are as follows:?1?The effects of sputtering power on the morphology,structure,wettability and mechanical properties of Ho₂O₃ films are studied.With the increase of sputtering power,the film changes from amorphous to crystalline.When the sputtering power is 250 W,the maximum contact angle of 101.1°is obtained after exposure to laboratory environment for 240 h.As sputtering power is 100 W,the hardness and elastic modulus increase to the maximum values of 15.2 GPa.?2?The effects of deposition temperature on the morphology,structure,wettability and mechanical properties of Ho₂O₃ films are studied.As the deposition temperature increases,the crystallinity of the film gradually increases.The maximum roughness of film is obtained when the deposition temperature is 500 ?.The maximum contact angle of 109.5°is obtained after exposure to laboratory environment for 240 h.When the deposition temperature is 600 ?,the maximum hardness value is 11.5 GPa.?3?The effects of substrate bias voltages on the morphology,structure,wettability and mechanical properties of Ho₂O₃ films are studied.With the increase of the bias voltage,the crystallinity of the film does not change significantly,and the surface roughness of the film gradually decreases.When the film is floating,the maximum contact angle of 127.6°is obtained after exposure to laboratory environment for 240 h.When the bias voltage is-80 V,the maximum hardness of the film is 13.7 GPa.When the voltage is-40 V,the wear resistance is good and the friction coefficient is 0.173.?4?The essential reason for the rare earth metal oxides?Ho₂O₃,Sm₂O₃,CeO₂?films change from hydrophilic to hydrophobic are studied.Hydrophilic process:First,the films exposed to the atmosphere react with water vapor to form the hydroxide,and then the hydroxide further reacts with carbon dioxide in the air to form the carbonate;Hydrophobic process:After exposure to laboratory environment for a longer time?240h?,volatile organic compounds in the air are adsorbed on the carbonate surface layer that has been completely reacted.The enhancement of the C-C bond content is the key to change from hydrophilic to hydrophobic.?5?The effect of annealing on morphology,structure,wettability and mechanical properties of Ho₂O₃ films with different substrate bias are studied.After annealing at1000 ?,the film changed from the original cubic Ho₂O₃ to the coexisting structure of cubic Ho₂O₃ and hexagonal Ho₂O₃,the roughness decreases overall,the hardness decreases with increasing bias,the friction coefficient value is basically stable at0.472-0.497,and the wettability is relatively stable.When bias voltage is-40 V,the maximum of contact angle is 110.0°after exposure to laboratory environment for 240 h and all films are hydrophobic.