Optical and microstructural properties of hafnium dioxide thin films

Abstract We have applied a variety of analytical tools to educe the composition and morphology of thin films of hafnium dioxide deposited under a variety of conditions. Surface analytical techniques include scanning electron microscopy, transmission electron microscopy, electron diffraction, Rutherford backscattering spectrometry, and X-ray photoelectron spectroscopy. The results from these measurements are correlated with the observed optical properties. Electron diffraction reveals that films deposited below 300 °C are amorphous and spectrophotometry uncovers a small optical inhomogeneity. The refractive index and inhomogeneity are strongly influenced by the oxygen backfill present during film condensation. Ion-assisted deposition (IAD) removes the optical inhomogeneity, increases the refractive index, and eliminates the air-to-vacuum spectral shift observed in films deposited without IAD. In addition, low energy IAD is found to increase the refractive indices of the films without affecting the optical inhomogeneity. This is explained by the preferential sputtering of hydroxide from the growing film surface by the low energy ions.

[1]  J. Biersack,et al.  A Monte Carlo computer program for the transport of energetic ions in amorphous targets , 1980 .

[2]  Flemming Besenbacher,et al.  Large-angle scattering of light ions in the weakly screened Rutherford region , 1980 .

[3]  M. Nishibori,et al.  Porosity of MgF2 Films—Evaluation Based on Changes in Refractive Index Due to Adsorption of Vapors , 1969 .

[4]  K. Wandelt,et al.  An X-ray photoelectron spectroscopy study of the chemical changes in oxide and hydroxide surfaces induced by Ar+ ion bombardment , 1978 .

[5]  John A. Thornton,et al.  Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings , 1974 .

[6]  H. Macleod,et al.  Thin-Film Optical Filters , 1969 .

[7]  G. Wehner,et al.  Sputtering Yields at Very Low Bombarding Ion Energies , 1962 .

[8]  K. Siegbahn.  ESCA : atomic, molecular and solid state structure studied by means of electron spectroscopy , 1967 .

[9]  P. Baumeister,et al.  Use of hafnium dioxide in multilayer dielectric reflectors for the near uv. , 1977, Applied optics.

[10]  Angela Duparré,et al.  Structure-related bulk losses in ZrO2 optical thin films , 1990 .

[11]  I. Ibrahim,et al.  Polymorphic Behavior of Thin Evaporated Films of Zirconium and Hafnium Oxides , 1970 .

[12]  Robert D. Heidenreich,et al.  Fundamentals of Transmission Electron Microscopy , 1964 .

[13]  G. Hass,et al.  Optical properties of evaporated magnesium oxide films in the 0.22-8micro wavelength region. , 1972, Applied optics.

[14]  D L Wood,et al.  Optical properties of cubic hafnia stabilized with yttria. , 1990, Applied optics.

[15]  E. L. Fuller,et al.  Heats of immersion in the zirconium oxide-water system , 1972 .

[16]  David Smith,et al.  Refractive index of some oxide and fluoride coating materials. , 1979, Applied optics.

[17]  S. Y. Kim,et al.  Ion assisted deposition of thermally evaporated Ag and Al films. , 1989, Applied optics.

[18]  H. Pulker,et al.  Correlation between film structure and sorption behaviour of vapour deposited ZnS, cryolite and MgF2 films , 1972 .

[19]  E. Larsen.  ZIRCONIUM AND HAFNIUM CHEMISTRY. , 1970 .

[20]  J. Gasiot,et al.  A simple method for the determination of the optical constants n, k and the thickness of a weakly absorbing thin film , 1976 .

[21]  E Pelletier,et al.  Automatic determination of the optical constants of inhomogeneous thin films. , 1982, Applied optics.

[22]  P. Martin,et al.  Modification of the optical and structural properties of dielectric ZrO2 films by ion‐assisted deposition , 1984 .

[23]  K. Müller,et al.  Model for ion‐assisted thin‐film densification , 1986 .

[24]  M E Zhabotinski,et al.  Coherent-optic suppression of scratch noise on optical sound records. , 1983, Applied optics.

[25]  I. Malitson.  Interspecimen Comparison of the Refractive Index of Fused Silica , 1965 .

[26]  R. Glang,et al.  Handbook of Thin Film Technology , 1970 .

[27]  D. A. Shirley,et al.  High-Resolution X-Ray Photoemission Spectrum of the Valence Bands of Gold , 1972 .