Abstracts Category : Other

Investigations on III-Nitrides nanostructures: application to Renewable Energies and Bio-Sensing

by Rodriguez Paul Soto

This thesis, entitled Investigations on III-Nitrides Nanostructures: Application to Renewable Energies and Bio-Sensing, presents the work done at the Instituto de Sistemas Optoelectrnicos y Microtecnologa (ISOM). The main objective of the presented work is: To investigate the potential of III-nitride (In(Ga)N, in particular) thin films/nanostructures for biosensors and water-splitting. The investigated structures have varying In contents (from medium to high) and varying morphologies, that are: thin compact InGaN films, InGaN nanowall networks, InGaN nanocolumns and InN quantum dots The thesis addresses: The molecular beam epitaxy growth of the mentioned thin films/nanostructures, on either GaN templates or Si(111) substrates, and their detailed morphological, structural, optical and electrochemical characterization. The insight and systematic evaluation of their electrochemical performance, for their final employment in bio-sensing and water-splitting applications. The work is presented as follows: Chapter I: The motivation for the work (including state of the art) and main goals of the thesis are explained. Chapter II: The fundamental properties of the employed material (III-nitrides) and employed nanostructures (nanocolumns and quantum dots (QDs)) are given. Due to their importance for the thesis development, the fundamental properties having a direct impact on the electrochemical activity of the employed material (III-nitrides). Chapter III: Details about experimental techniques used for the thesis realization are presented: epitaxial growth technique (MBE), morphological characterization (SEM and AFM), structural characterization (X-ray diffraction and TEM), optical characterization (PL, CL and SNOM), as well as chemical (GC) characterization. Chapter IV: Application related characterization of the structures, grown on both GaN templates and on Si(111), is addressed. For this, a general overview of electrochemistry for metals and (non degenerated n-type) semiconductors electrodes is provided after which a discussion on the (degenerated n-type semiconductor) high Incontent InGaN electrode is given. The biosensor concept is introduced as are the parameters that characterize its performance. A general introduction to water-splitting is given (both induced by electrolysis or with the aid of a non-degenerated semiconductor (photo)-electrode). Important parameters needed to fully characterize the water-splitting process/device will be highlighted. Chapter V: Specifications concerning the thin film/nanostructures growth. The samples fabricated and studied throughout this thesis, contain the following structures: (a) Grown on GaN templates: (i) high Indium (In) content InGaN single layers (ii) InN QDs on the top of (previously addressed) InGaN single layers (b) Grown on Si(111) substrate: (iii) high In-content InGaN single layers (iv) InGaN nanowall networks (v) InN QDs directly on top of the substrate, and also on the top of (previously addressed) InGaN single layers and nanowall networks (vi) InGaN nanocolumnsAdvisors/Committee Members: Calleja Pardo, Enrique, Gaevi, Zarko.