The simulation of the electronic transport properties of nanoscale devices

Research output: ThesisDoctoral Thesis


A quantum-mechanical equation of motion simulation for electronic transport has been developed. A tight-binding basis is used, which has the advantages that complex electronic structures can be described and systems with arbitrary geometry can be considered. It is used to investigate fundamental issues for transport in complex and inhomogeneous nanoscale systems.

The technique is applied to a number of simple systems to verify the validity of the approach and to investigate its potential scope. The method is also applied to a number of important problems in the field of spintronics. Current-perpendicular-to-the-plane giant magnetoresistance (CPP GMR) in thin film magnetic multilayers is simulated, and non-local interfaces resistances associated with mean-free-path effects are considered. Conduction electron spin-relaxation is also simulated by incorporating the spin-orbit interaction into the method. Spin-relaxation times for the technologically important materials copper and cobalt are calculated, and its effect on transport
is simulated.

A significant mean-free-path effect is observed for a simple model of CPP GMR. The non-local part of the interface resistance is found to depend upon the ordering of layers in a multilayer, and upon the size of the mean-free-path. However the GMR is barely modified by these effects, and an interpretation is given which explains recent theoretical and experimental results on similar systems. A GMR of 67% is calculated for a realistic device structure, Co4 Cu3 Co4 , and the effect is found to be dominated by spin-dependent interface resistances.

The direct simulation of spin-relaxation by the incorporation of the spin-orbit
interaction is the first such calculation of its kind. Spin relaxation times of 25ps and 0.4ps, for Cu and Co respectively have been calculated - assuming realistic resistivities. These times are in good agreement with recent optical and transport measurements.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Univ Leeds, University of Leeds, Sch Phys & Astron
  • Morgan, G.J., Supervisor, External person
Award date23 Nov 2005
Publication statusPublished - 2005

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