Hope College Physics Department
Research Experiences for Undergraduates
|Project Title:||Effect of carrier density on nonlinear emissions from superconducting resonators|
|Student Name:||Jinu Thomas|
|Student's Home Institution:||Oakton Community College|
|Research Advisor:||Dr. Stephen Remillard|
|Source of Support:||
This material is based upon work supported by the National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811.
Radio frequency devices made from high temperature superconductors ideally
exhibit no nonlinear behavior of the surface impedance with respect to the
RF magnetic field. The non-linearity of Tl2Ba2CaCu2O8-x (TBCCO-2212) was found
to depend on carrier doping x, with grain boundaries contributing more significantly
in under-doped films (x>0.2) as compared to those optimally doped (x=0.05).
The doping level was tuned by annealing TBCCO-2212 thin films in a reducing
nitrogen atmosphere at temperatures ranging from 2500C to 4000C. The microwave
current dependent surface impedance of both pre- and post-annealed films was
measured. Using the critical temperature as an indicator of carrier density,
it was found that under-doped samples have larger nonlinear grain boundary
losses as indicated by a weaker variation of surface reactance with surface
Publications and Presentations:
S.K. Remillard, J. Thomas, M.M. Bischak, C.J. Goodson; "Effect of Carrier Doping on Nonlinear Distortion of Microwave Signals by Superconducting Thin Films," Applied Superconductivity Conference, Portland, OR, October 8-12, 2012.