K. Mehrotra, J. B. Oliver, and J. C. Lambropoulos, "Nano-indentation of single-layer optical oxide thin films grown by electron-beam deposition," Appl. Opt. 54, 2435-2440 (2015)
Mechanical characterization of optical oxide thin films is performed using nano-indentation, and the results are explained based on the deposition conditions used. These oxide films are generally deposited to have a porous microstructure that optimizes laser induced damage thresholds, but changes in deposition conditions lead to varying degrees of porosity, density, and possibly the microstructure of the thin film. This can directly explain the differences in the mechanical properties of the film studied here and those reported in literature. Of the four single-layer thin films tested, alumina was observed to demonstrate the highest values of nano-indentation hardness and elastic modulus. This is likely a result of the dense microstructure of the thin film arising from the particular deposition conditions used.
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Fifty-five standard cubic centimeters (sccm) of were used as a process gas for reactive deposition above the plasma chamber to increase both the reactivity of the plasma and the oxidation of the film.
Table 2.
Extracted Near-Surface Mechanical Properties Corresponding to Penetration Depths of –15% of the Total Film Thickness
Single-layer Thin Film
Elastic Modulus (GPa)
Hardness (GPa)
Hafnia
Silica
Alumina
Niobia
Table 3.
Comparisons of Bulk and Film Properties Reported Here and in the Literature
55 sccm of ; amorphous; ; substrate temperature 130°C
PEVCD, plasma enhanced chemical vapor deposition; PIAD, plasma ion-assisted deposition.
Indicates that for these materials, the biaxial modulus was converted to Young’s modulus (using Poisson ratio values [7]) for purposes of comparison to this study.
EMA/EFA, effective medium approximation/effective field approximation.
Tables (3)
Table 1.
Process Parameters for Electron-Beam Deposition (including Plasma-Assisted Deposition) of Single-Layer Coatingsa
Fifty-five standard cubic centimeters (sccm) of were used as a process gas for reactive deposition above the plasma chamber to increase both the reactivity of the plasma and the oxidation of the film.
Table 2.
Extracted Near-Surface Mechanical Properties Corresponding to Penetration Depths of –15% of the Total Film Thickness
Single-layer Thin Film
Elastic Modulus (GPa)
Hardness (GPa)
Hafnia
Silica
Alumina
Niobia
Table 3.
Comparisons of Bulk and Film Properties Reported Here and in the Literature
55 sccm of ; amorphous; ; substrate temperature 130°C
PEVCD, plasma enhanced chemical vapor deposition; PIAD, plasma ion-assisted deposition.
Indicates that for these materials, the biaxial modulus was converted to Young’s modulus (using Poisson ratio values [7]) for purposes of comparison to this study.
EMA/EFA, effective medium approximation/effective field approximation.