Hope College Physics Department
Research Experiences for Undergraduates
Summer 2011
Project Summary

 

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 resistance.
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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.

 

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