Publikationsserver der RWTH Aachen University
XPS and transport studies of oxide barriers in tunnel magnetoresistance junctions
Abstract
dc:descriptionThe thesis work treats the UV light-assisted oxidation of ultra-thin Al films to be employed as insulating barriers in TMR junctions. The oxidations of the ultra-thin Al layers (1-2 nm) was monitored by XPS a surface sensitive and element specific technique. The oxidation process and kinetics were analysed in terms of the Cabrera-Mott theory of thin film oxidation. Evidence is found in the XPS spectra of the Al 2p core levels for the existence of a complex surface oxide layer of the type Al2O3+x. The oxidation rate agrees fairly well with the inverse logarithmic law of Cabrera-Mott theory. However agreement with the direct logarithmic law is also found. Direct UV light-assisted oxidation by virtue of the photoemission of electrons from the Al layer accelerates the oxidation of the Al layer grown on smooth epitaxial Fe but not on the rougher polycrystalline Co layers. Shadow mask deposited and microstructured junctions were fabricated and their tunneling characteristics studied. Of special interest were the bias dependence and temperature dependence of the tunnel conductance and the TMR ratio. These were analyzed with fairly good success in terms of the Glazmann-Matveev model of inelastic tunneling via chains of localized defect states in the tunnel barrier. The Glazmann-Matveev model enables the separation of the elastic and the inelastic components of the tunnel conductivity at different temperatures and bias voltages.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2004
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Kittur, Harish
- Contributors dc:contributor
-
- Güntherodt, Gernot
Subjects
dc:subject × 8Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- eng