Tunnel junction thermometry and thermalisation of electrons

Tommy Holmqvist

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

In this work, normal metal and superconducting tunnel junctions have been studied. In particular applications in low temperature electronic thermometry are investigated. The double oxidation method for achieving high resistance junctions is described and shown to produce high quality devices. A new invention, the single junction thermometer (SJT), is described, and proof of the concept experiments demonstrating the functionality of the device are described. A key feature of the SJT is a well controlled electromagnetic environment surrounding a single junction. It is shown that embedding a single junction within arrays of other junctions is a superior way for controlling the environment as compared to previously proposed methods. Improved thermalisation of electrons is shown to be beneficial for the performance of superconducting RSFQ (Rapid Single Flux Quantum) devices. The so called grey zone of the most basic of these devices, the balanced comparator, is investigated. Improved performance based on metallic cooling fins has been achieved. In the same spirit improved thermalisation of the Coulomb blockade thermometers extends their operation towards lower temperatures. A method employing thick metallic islands was developed and tested to this end.
Translated title of the contributionTunnel junction thermometry and thermalisation of electrons
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Kaivola, Matti, Supervising Professor
  • Pekola, Jukka, Thesis Advisor
Print ISBNs978-952-60-3078-4
Electronic ISBNs978-952-60-3079-1
Publication statusPublished - 2010
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • thermometry
  • Coulomb blockade thermometer
  • single junction thermometer
  • tunnel junctions

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