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Title: Exploiting resistive macro to nano scale metal electrodes in Schottky barrier structures
Author: Penate Quesada, L.
ISNI:       0000 0001 3482 6941
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2009
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This thesis investigates the use of thin resistive metal electrodes in the formation of Schottky barrier structures where the resistance measured along the electrode exhibits a characteristic change as a function of temperature dictated by the Schottky barrier properties. A combination of optical and resistance measurements (15-300K) on thin Al films were undertaken. Deviations of the real and imaginary parts of the . dielectric function from bulk valuek were significant for films thinner than ~15nm. The observed trend was confirmed by evaluating the resistivity data. The estimated thickness threshold for which the resistivity ratio (pjilm/pbulk) -- -I} became significantly greater than unity is ~8 nm for Al films. Thinner Al film showed poor inter-grain connectivity and a deteriorating interface quality. Resistance measurements on macro-scale Al and Pt electrodes and micro-scale Pt electrodes on p-type Si revealed a marked resistance increase by a factor of up to six over a temperature interval of 40-60K when decreasing temperature. The characteristic change of resistance is due to thermal confinement of charge carriers in the metal electrode, preventing any conduction channel through the substrate. This behaviour was modelled by considering the electrode and the substrate as two resistors in parallel with the Schottky barrier (barrier height determined by applying theory of thermionic emission) acting as the connecting component. The electrical and structural properties of Focused Ion Beam deposited Pt nanowires were analysed. EDX analysis revealed metal rich grains (atomic composition 31%Pt) in a large non-metallic matrix. Resistivity measurements (15-300K) indicated insulating behaviour with the room-temperature resistivity varying from 80 to 300 times higher than that of bulk Pt. Temperature dependent current-voltage measurements exhibited non-linear behaviour with the non-linearity increasing with decreasing temperature. The conduction mechanism can be explained in terms of a disordered solid with inter-grain tunnelling.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available