The simulation of the electronic transport properties of nanoscale devices

Keith Patrick McKenna

The simulation of the electronic transport properties of nanoscale devices

Physics

Research output: Thesis › Doctoral Thesis

Abstract

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 language	English
Qualification	Doctor of Philosophy
Awarding Institution	Univ Leeds, University of Leeds, Sch Phys & Astron
Supervisors/Advisors	Morgan, G.J., Supervisor, External person
Award date	23 Nov 2005
Publisher	University of Leeds;
Publication status	Published - 2005

Cite this

@phdthesis{940c7937bc4b4c018dcc5e450079f76b,

title = "The simulation of the electronic transport properties of nanoscale devices",

abstract = "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 transportis 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-orbitinteraction 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.",

author = "McKenna, {Keith Patrick}",

year = "2005",

language = "English",

publisher = "University of Leeds;",

school = "Univ Leeds, University of Leeds, Sch Phys & Astron",

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TY - BOOK

T1 - The simulation of the electronic transport properties of nanoscale devices

AU - McKenna, Keith Patrick

PY - 2005

Y1 - 2005

N2 - 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 transportis 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-orbitinteraction 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.

AB - 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 transportis 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-orbitinteraction 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.

M3 - Doctoral Thesis

PB - University of Leeds;

ER -