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Title: Unveiling the cation ratio mediated structural modifications in TiO 2 :GeO 2 mixtures for gravitational-wave detectors
Abstract Amorphous thin films of Ti doped GeO2are of interest for coatings of the mirrors in gravitational wave detectors (GWDs) due to their low internal friction (Vajenteet al2021Phys. Rev. Lett.127071101). The addition of Ti to amorphous GeO2(a-GeO2) enables tailoring of the optical and structural properties of the mixtures. However, the specific modifications that occur in the amorphous network with the addition of Ti are not known. In this work, x-ray photoelectron spectroscopy is used to identify modifications to the bonding of Ge and Ti atoms in mixtures of Ti dopeda-GeO2with different Ti cation content. The formation of (Ti–O–Ge) bonds is evidenced from: (1) the presence of a peak which intensity increases with Ti content and causes a shift to lower binding energy (BE) of the core level O 1speak; (2) the shift to higher BE of the Ti 2p3/2peak and a decrease in the energy split; and (3) the shift to lower BE of the Ge 3d5/2peak and increase in the energy split. These changes reflect modifications to the bonding when Ge replaces Ti in Ti–O–Ti bonds and Ti replaces Ge in Ge–O–Ge bonds due to their difference in electronegativity. A decrease in the O–O nearest-neighbour distance due to the incorporation of Ti atom is also observed from the broadening of the valence band spectra. The results show the 0.44 Ti dopeda-GeO2mixture has a balance between the (Ti–O–Ge) and the (Ge–O–Ge) networks, not observed in Ti poor and Ti rich mixtures. This finding could have important consequences in the optimisation of amorphous Ti dopeda-GeO2mixtures for low internal friction coatings of GWDs.  more » « less
Award ID(s):
2309297
PAR ID:
10538757
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
IOP
Date Published:
Journal Name:
Classical and Quantum Gravity
Volume:
41
Issue:
10
ISSN:
0264-9381
Page Range / eLocation ID:
105007
Subject(s) / Keyword(s):
amorphous oxide thin films, amorphous oxide compounds, TiO2, GeO2, x-ray photoelectron spectroscopy
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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