Structural and Optical Properties of HfLaO Films Prepared by RF Magnetron Sputtering

HfLaO films doped with different La contents,varying from 17% to 37%,were deposited using RF magnetron sputtering.The structure,thermal stability,surface morphology,and optical properties of HfLaO films were investigated by X-ray diffraction(XRD),atomic force microscope(AFM) and spectrophotometry.The results indicate that as-deposited HfLaO with 25% 37% La films are amorphous.With the increase of La contents,the crystallization temperature for HfLaO films is increased.The HfLaO film with 37% La remains amorphous even after annealed at 900℃.The AFM images show amorphous HfLaO films,which imply a good thermal stability have a relatively smooth surface.The average transmittance in the visible range is above 82% for all the films.The amorphous structure yields films of significantly higher transparency than the polycrystalline structure does.The refractive indices of the films are determined to be in the range 1.77 1.87.As the La concent increases the refractive indices of the films are initially increased and then decreased.The optical band gap of the HfLaO films decreases to 5.9eV(La 17%),5.87eV(La 25%),5.8eV(La 33%),5.77eV(La 37%),respectively.