Gold–polymethylmethacrylate (PMMA) nanocomposites were fabricated with a photoreduction method using UV irradiation. The irradiated samples are compared with unirradiated ones to investigate the mechanism of gold nanoparticle formation and the effect of UV irradiation and polymer matrix on the morphology of the particles. The triangular gold nanoparticles were formed in polymer medium at a specific concentration of gold salt and UV exposure. The particle size decreased when the gold salt to polymer ratio was increased. The samples were analysed using UV–Vis spectroscopy, Fourier transform infrared spectrometry, atomic force microscopy, x-ray diffraction, small angle x-ray scattering and x-ray photoelectron spectroscopy. The interfacial interaction of Au nanoparticles and PMMA polymer has been discussed.

Exploiting interfacial excess (Γ), Laplace pressure jump (ΔP), surface work, and coupling them to surface reactivity have led to the synthesis of undercooled metal particles. Metastability is maintained by a core-shell particle architecture. Fracture of the thin shell leads to solidification with concomitant sintering. Applying Scherer's constitutive model for loaddriven viscous sintering on the undercooled particles implies that they can form conductive traces. Combining metastability to eliminate heat and robustness of viscous sintering, an array of conductive metallic traces can be prepared, leading to plethora of devices on various flexible and/or heat sensitive substrates. Besides mechanical sintering, chemical sintering can be performed, which negates the need of either heat or load. In the latter, connectivity is hypothesized to occur via a Frenkel's theory of sintering type mechanism. This work reports heat-free, ambient fabrication of metallic conductive interconnects and traces on all types of substrates.

Large-area gallium nitride (GaN) micro- and nanopillar (NP) arrays were fabricated by plasma etching of lithographically patterned GaN thin-film grown on Si substrate. Deep-ultraviolet lithography, inductively coupled plasma (ICP) etching, and subsequent chemical treatments were effectively utilized to fabricate GaN pillars with diameters ranging from 250 nm to 10 μm. The impact of various plasma etching process parameters and chemical etchants on the morphology, strain, and surface defects of these NPs were studied using scanning-electron microscopy, photoluminescence (PL), and Raman spectroscopy. It was found that the shape of the NPs can be controlled by the substrate temperature during the plasma etch and by using different gas chemistries. Room-temperature PL and Raman spectroscopy measurements revealed significant strain relaxation in 250 nm diameter pillars as compared to 10 μm diameter pillars. PL measurement also indicated that the surface damage from the plasma etch can be removed by etching in KOH-ethylene glycol solution. Post-ICP selective wet chemical etch enabled us to fabricate functional structures such as micro- and nanodisks of GaN, which potentially could be utilized in nitride-based resonators and lasers.

Cubic silicon carbide (3C-SiC) thin films were grown on (100) and (111) Si substrates by CVD technique using hexamethyldisilane (HMDS) as the source material in a resistance heated furnace. HMDS was used as the single source for both Si and C though propane was available for the preliminary carbonization. For selective epitaxial growth, patterned Si (100) substrates were used. The effect of different growth parameters such as substrate orientation, growth temperature, precursor concentration, etc on growth was examined to improve the film quality. The surface morphology, microstructure and crystallinity of grown films were studied using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS).

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Zirconium oxide (ZrO 2 ) films have been deposited on Ge-rich SiGe heterolayers at 150 • C by the microwave plasma enhanced chemical vapour deposition (PECVD) technique using zirconium tetra-tert-butoxide. The possible conduction mechanisms in deposited ZrO 2 films have been investigated at both room and high temperature. It is found that the conduction mechanism is dominated by Schottky emission at a low electric field (E < 1.2 MV cm −1 ). The intrinsic barrier height between Al and ZrO 2 was found to be 0.83 eV. The trap-assisted Poole-Frenkel conduction mechanism is found to take place at a relatively high electric field (E > 1.2 MV cm −1 ). The extracted trap energy is about 0.78 eV from the conduction band of ZrO 2 . It is shown that the current in ZrO 2 films exhibits strong temperature dependence at a low electric field. The trapping behaviour of the charge carriers in thin ZrO 2 gate dielectric stacks during constant gate voltage stress of metal-oxide-semiconductor capacitors has also been investigated.

Ion Irradiation is a technologically important technique to modify the surfaces. We have investigated the patterning of InP(111) surfaces by low energy (3 keV) as well as high energy (1.5 Mev) ion beams. After low energy ion irradiation, surfaces exhibit well defined nano dots which ripen at initial stages but exhibit fragmentations at high fluences. The surface rms, at both the energies, displays a similar behaviour of initially increasing with increasing fluences but decreasing for higher fluences. The studies show some common features at these low and high energies, like the smoothening of surface beyond the a/c transition.