Josephson tunnel junctions using Langmuir-Blodgett films

Ultra thin organic films produced by the Langmuir-Blodgett (LB) technique have been the subject of extensive research and have the potential for a range of applications. This thesis is concerned with the possibility of applying LB films as an insulating layer to produce a tunnelling barrier. Experimental details on LB deposition, junction fabrication and measuring techniques are presented. Experimental results on monolayers are also presented and monolayer properties, particularly viscous properties, are discussed. It was found that the Langmuir trough geometry has strong effects on pressure-area isotherms. Junctions with stearic acids LB layers and with AL, Sn or Pb-In as the base electrode were fabricated and measured on a computerised data acquisition system. The capacitance measurements of Al/Oxide/LB/Pb junctions showed a linear relationship between the inverse capacitance and the number of monolayers. Both Sn/Oxide/LB/Pb and Sn/Oxide/Pb junctions showed tunnelling. No tunnelling characteristics were observed in Pb-In/Oxide/LB/Pb junctions. Theoretical models assuming filaments penetrating through the LB layers were derived and predict the filament radius to be 1-100 nm and the separation between adjacent filaments to be of the order of 100μm.