Accession Number:

ADA614723

Title:

Structure and Optical Properties of Nanocrystalline Hafnium Oxide Thin Films (PostPrint)

Descriptive Note:

Journal article

Corporate Author:

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE

Report Date:

2014-09-01

Pagination or Media Count:

12.0

Abstract:

Hafnium oxide HfO2 films were grown by sputter-deposition by varying deposition temperature Ts in a wide range of 25700C. The deposited HfO2 films were characterized by studying their growth behavior, microstructure, and optical properties. Characterization of the films employing a wide range of analytical techniques indicate a clear functional relationship between processing conditions, structure, morphology, and optical properties. HfO2 films were amorphous at Ts 6 200C, at which point a structural transformation occurs. HfO2 films grown at Ts200C were nanocrystalline, stabilized in a monoclinic structure. The nanocrystalline HfO2 films exhibit a strong 111 texturing. The average crystallite size of HfO2 films increased from10 nm to 20 nm with increasing Ts. Electron and atomic force microscopy measurements also correlated with the crystalline behavior, as well as an evenly distributed network of spherical shaped crystallites for the nanocrystalline HfO2 films. Density 447 of HfO2 films probed using X-ray reflectivity and ellipsometry data analysis indicate that the q values are strongly dependent on Ts 447 varied in the range of 7.369.14 gcm3. The higher end of 447 values were noted only for HfO2 films grown at relatively higher Ts indicating the crystalline nature accounts for the q improvement. The band gap values of the films varied in the range of 5.786.170.03 eV for Ts 25700C. Index of refraction at 550 nm increased from 1.80 to 2.09, which also correlates with the characteristic feature of improved structural order, packing density of HfO2 films with increasing Ts. Based on the observed results, a correlation between growth conditions, microstructure and optical constants is established.

Subject Categories:

  • Inorganic Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE