  Glasses are nonequilibrium solids with properties highly dependent on their
method of preparation. In vapor-deposited molecular glasses, structural
organization could be readily tuned with deposition rate and substrate
temperature. Herein, we show the atomic arrangement of strong network forming
GeO2 glass is modified at medium range (< 2 nm) through vapor deposition at
elevated temperatures. Raman spectral signatures distinctively show the
population of 6-membered GeO4 rings increases at elevated substrate
temperatures. Deposition near the glass transition temperature is more
efficient than post-growth annealing in modifying atomic structure at medium
range. The enhanced medium range organization correlates with reduction of the
room temperature internal friction. Identifying the microscopic origin of room
temperature internal friction in amorphous oxides is paramount to design the
next generation interference coatings for mirrors of the end test masses of
gravitational wave interferometers, in which the room temperature internal
friction is a main source of noise limiting their sensitivity.

Materials Science