Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

Abstract

Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

High Precision Detection of Change in Intermediate Range Order of Amorphous Zirconia-Doped Tantala Thin Films Due to Annealing

“…The polyhedra are predominantly distorted octahedra (∼80% for Ta, ∼60% for Zr, [10]). It has been shown that the first peak of GðrÞ for pure a-Ta 2 O 5 closely resembles the corresponding peak of crystalline Ta 2 O 5 [15]. We find that the coordination of Ta by O (n TaO ) is 6.13 whereas n ZrO is 6.14; both values are for as-deposited sample.…”

“…Further details on the GIPDF data collection method and its merits, in particular pertaining to doped tantala coatings, are discussed in Ref. [15]. The total scattering data were reduced to the normalized structure factor SðqÞ after applying identical corrections on all samples for air scattering, absorption, Compton scattering, polarization effects, and geometric effects due to the detector footprint [15][16][17].…”

Observation of a Correlation Between Internal friction and Urbach Energy in Amorphous Oxides Thin Films

“…In order to explain the impact of stress relaxation on energy loss one has to consider that the measurement were done only at room temperature, hence, only the reduction of TLS density having a barrier height of about 0.5 eV is probed. Energy barriers of interest at room temperature correspond to equilibrium configurations formed by several PSUs, as suggested in a recent work 19,41 . The recent observations of ref.…”

Sol‐gel derived TiNb2O7 dielectric thin films for transparent electronic applications

“…It might be correlated with the short‐range order of amorphous TNO films. The annealing process may increase the cross‐linking of primary structural unit to improve the poor short‐range order in an amorphous material . The lowest states in conduction band are localized if the short‐range order of amorphous TNO decreases.…”

“…The annealing process may increase the cross-linking of primary structural unit to improve the poor short-range order in an amorphous material. 12 The lowest states in conduction band are localized if the short-range order of amorphous TNO decreases. This might be due to the effect of scattering which is related to the amorphization of TNO films annealed at low temperature.…”