In-plane anisotropic nanocolumnar films for advanced functional applications

Abstract

Nowadays, the development of new materials entails the preparation of systems with properties that can be predicted and controlled as a function of final technology applications. This perspective is also a requirement by the development of nanostructured materials intended for different final functional applications (optics, magnetism, chemistry, electronics, etc). The work included in this thesis deals with nanostructured thin films and the analysis of a series of related applications. A customary definition of thin film is that of a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness, that provides a new characteristic or property to the substrate material where it has been deposited. Thin films of functional materials are directly or indirectly involved in a large series of applications and are essential for the advance technological areas such as optoelectronics, photonics, magnetism and many others. This wide range of applications is possible thanks to the large variety of materials that can be processed in form of thin films, encompassing inorganic and organic compounds, metals, polymers etc. The present work focuses on oxides, namely ITO, SiO2, and TiO2 and addresses applications related with their electrical, optical and surface wetting applications. In this thesis the method of choice to prepare nanostructured thin films of the aforementioned materials is physical vapour deposition (PVD) in the so-called glancing angle deposition (GLAD) configuration. The main objective of this thesis is the control, enhance and manipulation of anisotropic microstructural properties of thin films prepared at glancing angle deposition to develop advanced functional applications. To control the microstructural properties of GLAD thin films, in the present work, plasma is used to assist the growth of GLAD thin films. Chapters 3 and 4 illustrate the use of plasmas to modify the microstructure of the GLAD thin films during their growth.In these chapters will be study the singular electrical and optical properties of ITO thin films grown at glancing angle deposition and some plasmonic applications developed with these materials Moreover, in the present work we describe a process to fabricate anisotropic surface systems by depositing GLAD thin films on a PDMS substrate which is latter-on subjected to a stretching deformation. The obtained system presents outstanding anisotropic optical and wetting properties (Chapter 5 y 6). The main conclusion in this thesis has been developed two different ways to control, enhance and manipulate anisotropic properties in GLAD thin films. The first one consists of the control of the microstructure at the nano-scale and relays on assisting the growth of the film with a plasma during deposition. The second one appears at the micro-scale and is produced by a combination of factors involving the mechanical deformation on flexible polymers.