Novel nanostructured thin film heterostructures: Growth, nanoscale characterization and properties.

摘要

During my graduate study, I have been involved in the growth of new nano heterostructures grown by Pulsed Laser Deposition and by Laser MBE with the emphasis on understanding the thin film growth process by a new paradigm of Domain Matching Epitaxy (DME) and to integrate them on substrates like silicon, sapphire and new metallic substrates like Ni with exciting technological applications.; The DME involves matching of integral multiples of lattice planes (diffracting as well as nondiffracting) between the film and the substrate, and this matching could be different in different directions. The idea of matching planes is derived from the basic fact that during thin film growth lattice relaxation involves generation of dislocations whose Burgers vectors correspond to missing or extra planes, rather than lattice constants. In the DME framework, the conventional lattice matching epitaxy (LME) becomes a special case where matching of lattice constants results from matching of lattice planes with a relatively small misfit of less than 7-8%. In large lattice mismatch systems, epitaxial growth of thin films is possible by matching of domains where integral multiples of lattice planes match across the interface.; The work done in my doctoral study is divided into two main segments, (a) Growth of layered nanostructures and (b) growth of nanostructured composite thin films. The three systems studied under the first segment are (1) Growth of epitaxial self-aligned insulating films on metals (Cu) and its integration with Si (100). (2) Growth and integration of LSMO with Si (100). (3) Growth of Si on Ni substrates (highly textured) with TiN as a buffer layer. The heterostructures studied under the second part are (1) Role of Self-assembled Gold Nanodots in Improving the Electrical and Optical Characteristics of Zinc Oxide Films and (2) Growth of high quality epitaxial ZnO-Pt Nanocomposite and ZnO/Pt, Nanolayer Structures on Sapphire (0001).; The epitaxial growth of these heterostructures was carried out by Pulsed laser deposition and laser MBE. The epitaxial relationships are given in each case are shown to be due to domain matching epitaxy. X-Ray diffraction and Transmission Electron Microscopy studies confirm the relationship between film and substrate. Also, electrical and optical measurements were done, in order to study the change in these properties.