No description available.

This thesis addresses the advantages and challenges of strained silicon/silicon germanium (Si/SiGe) metal oxide on semiconductor field effect transistors (MOSFETs) from the mixed-signal perspective using electrical characterisation. It is divided into three main sections. The first section addresses the compatibility of strain engineering with other performance boosters like high k/metal gate stacks. The mixed-signal performance of strained SiGe pMOSFETs with hafnium silicate/titanium silicon-nitride (HfSiOx/TiSiN) gate stacks has beer using MOSFET electrical characterisation techniques. The strain induced performance enhancements usually reported at long gate lengths are shown to be reproducible at short gate lengths with some caveats. These caveats are that the challenges of effective channel length mismatch from strain-suppressed boron diffusion and source-drain parasitic resistances from unoptimized silicidation of SiGe are addressed. It is demonstrated that the enhancement in the open load voltage gain (self gain) of the SiGe devices compared with the Si control increases as the gate length is reduced. This is due to the lower lateral diffusion of the boron junction implants in compressively strained SiGe inducing better electrostatic integrity.

No description available.

Field effect transistors (FETs) are a key component of modern electronic devices. They require a semiconducting material that is traditionally made from doped silicon. Recently however it has been shown that porphyrin systems can be used in the same capacity. This thesis therefore describes the investigation of new methods of porphyrin functionalization to synthesise 1,4,5,8-tetraazaanthracene-bridged porphyrin arrays, and their application to the synthesis of extended arrays for use in FETs. The 1,4,5,8- tetraazaanthracene bridge is synthesised through the condensation of a porphyrin alpha-dione with 1,2,4,5-tetraaminobenzene. Accordingly, the synthesis of an extended array requires a porphyrin tetra-one monomer unit. Two methods for the synthesis of porphyrin tetra-ones have been investigated. The first approach attempts to adapt Knudsen's hydroxylation of an aryl halide by sodium benzaldoximate to a porphyrin system. Initial regiospecific halogenation of a porphyrin has been successfully achieved. However when hydroxylation was attempted, partial dehalogenation of the substrate was observed; and when applied to the synthesis of the porphyrin tetra-one the methodology failed. The second approach involves the allylic oxidation of a chlorin (a reduced porphyrin) on silica. The transformation's mechanism has been thoroughly investigated and it has been successfully applied to the synthesis of a porphyrin tetra-one. This methodology has then been applied to the synthesis of extended porphyrin arrays. A sample incorporating 12 porphyrin units has been successfully constructed. It has been characterised by NMR, MALDI, GPC and UV-VIS spectroscopy. By comparison with previous results it has been concluded that the aromatic system- which spans 181 Ǻngstroms from end to end- can be described as a series of weakly interacting chromophores, in agreement with theoretical predictions made by Hush. In addition a medium-scale synthesis of an array incorporating four porphyrins has been achieved so that it may now be tested as the semiconducting material in a FET.