CNAM Colloquium: Chris Richardson, Laboratory for Physical Sciences

Date
Thu, Oct 19, 2017 2:00 pm - 3:30 pm

Description

SPEAKER: Chris Richardson, Laboratory for Physical Sciences

Title: Structure first approach to superconducting materials development

Abstract: Elemental superconductors are generally forgiving of modest concentrations of chemical impurities and insensitive to microstructure. However, superconducting quantum circuits have shown that the superconducting loss tangent is sensitive to some aspects of material synthesis and device fabrication.

This material focused seminar will explore some of these aspects using high-purity, single-crystal, thin-film aluminum grown via molecular beam epitaxy on silicon substrates. The metamorphic Al-Si interface is characterized by x-ray diffraction and scanning transmission electron microscopy, and found to have an abrupt interface that results in crystal relaxation within a few monolayers of the substrate interface and no measurable interfacial layers. Molecular Dynamic Simulations predict complete strain relaxation through a primary and secondary dislocation interface network that are experimentally verified. Quarter-wave coplanar waveguide resonators are fabricated and characterization below 150mK demonstrate correlations between aluminum structure and resonator performance and internal quality factors near 1x10^6". Quantum device implications of various structural observations will also be discussed.

HOST: Fred Wellstood