Characterization of nanoscale porosity and cracking in amorphous solid water thin films

Pugh, Devin Michelle, Materials Science & Engineering, University of Virginia
Jesser, William, School of Engineering and Applied Science, University of Virginia
Dukes, Edmond, AS-Physics (PHYS), University of Virginia

In this thesis, we vapor deposit amorphous solid water (ASW) ice thin films at low temperatures (20 K -120 K) under ultra high vacuum (UHV) conditions. We control the nanoscale porosity in thin (600 nm -700 nm) ASW films by varying the deposition temperature and angle of incidence of H₂O. We then investigate the interaction of energetic O₂⁺ oxygen molecules with ASW ice films. A combination of a quartz crystal microbalance (QCM) and an optical interference method lead to a precise determination of film density before, during, and after ion beam exposure. We find that irradiation of ASW thin films by high-energy (80 keV) O₂⁺ ions decreases the porosity. Increasing the deposition angle increased the porosity.
After reaching a critical mass, vapor deposited ASW ice thin films release internal stress by cracking. We present new experimental observations of the dependence of ASW thin film cracking on the deposition angle. We present in situ imaging of bulk cracking in ASW films during deposition.
A new optical system was built to study the backscattering of light from amorphous ice samples. A light backscattering experiment from ASW samples which used a beamsplitter to reach zero phase angle is presented. The backscattered light was used to characterize the onset of cracking in ASW thin films. In this work, we were able to see for the first time the opposition effect for amorphous ice samples.

MS (Master of Science)
ice thin films
All rights reserved (no additional license for public reuse)
Issued Date: