This work has been motivated by the outstanding need to prepare suitable substrate for growth of III-nitride heteroepitaxial thin films. The issue of lattice and thermal expansion mismatches between the substrates and overlayers, which results in a high threading dislocation density in the films, is seen to be detrimental to photon and carrier transport in these systems. Thus, looking for appropriate substrates or modifying substrates appropriately, has attracted enormous attentions. The work includes the chemical and structural modifications of silicon, gallium arsenide and sapphire substrates, to obtain appropriate characteristics. The work also consists of a significant portion on the adsorption and desorption characteristic of Ga metal on various high and low index silicon surfaces. This study not only complements the search for substrate for GaN growth, but also in other interesting aspects of initial stages of metal/semiconductor interface formation, evolution of superstructural 2D- surface phases and formation of sub-nanodimension metal nanostructures and delta doped.

The emergence of colloidal semiconductor nanocrystals has generated great fundamental and technical interest in recent years. The size dependent emission property for Cadmium Selenide quantum dots renders it indispensable in the field of nanocrystal-based emitters used in electronic and bioelectronic devices. Investigation of these semiconductor quantum dots reveals the evolution of the electronic structure from an extended solid state to the molecular limit, an extremely important issue of basic and applied research in condensed matter physics. The work presented in this book mainly deals with the synthesis and characterization of chemically synthesized CdSe nanoparticles. A detailed investigation of the optical, structural and morphological properties of CdSe QDs and their correlation with both core and surface has been carried out. The theoretical aspect of quantum confinement and stability of CdSe quantum dots with organic and inorganic layers, are correlated to understand the surface modification aspects. Finally CdSe-polymer nanocomposites were discussed for their potential application in biomarkers and photo-electronic devices.