Optical properties of ultra-thin niobium nitride films for single photon detectors
Name
1006428014-MIT.pdf
Description
Full printable version
Size
8.13 MB
Format
Adobe PDF
Checksum (MD5)
af5a24ad268c8ae4941f72634efb7f06
Author(s)
Archer, Lucy Elizabeth
Advisor(s)
Karl K. Berggren and Vladan Vuletic.
Alternative Title
Optical properties of ultra-thin NbN films for single photon detectors
Date Issued
2017
Publisher
Massachusetts Institute of Technology
Abstract
In this thesis I made a study of the properties of reactively sputtered ultra-thin films of niobium nitride (NbN) and niobium titanium nitride (NbTiN). Using Variable Angle Spectral Ellipsometry (VASE), I found that the optical properties of NbN films appear to have a critical thickness above which the optical parameters stabilize. I also found that the deposition process has better stability over time for thicker films than for thinner ones; that is, when films are deposited weeks apart, the thinner films show more variation in thickness and optical properties than do the thicker films. The data also suggest that the crystallinity of the substrate upon which the NbN is deposited has a significant effect on the optical parameters. The set of films deposited for the optical study was also tested against a universal scaling law for thin film superconductors, which seems to support the existence of the critical thickness, below which the properties change significantly and do not conform to the power law scaling that holds for thicker films. Finally, I explored recipes for depositing NbTiN with our sputtering system, in the hope of creating films that have better properties than NbN to be used in device manufacturing. I was able to create films with the same properties as our current NbN films with minimal optimization, and further work in this area should result in NbTiN films that are better than our NbN films.
Description
Thesis: S.M., Massachusetts Institute of Technology, Department of Physics, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-78).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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