Experimental studies of optical properties in undoped and modulation-doped v-groove quantum wires (QWR) are presented. The results show good agreement with theoretical predictions. The investigation of undoped samples demonstrates the successful fabrication of high quality samples with small wire dimensions, exhibiting narrow linewidths and large subband spacings. Calculations from the Schrodinger solver show good agreement with the experimental results. Information about the shape of the confining potential is obtained from magneto-optical measurements where anisotropic shrinkage and binding energies of the excitons are measured. In high excitation power experiments the suppression of the excitonic recombination is observed due to screening and phase space filling. Photoluminescence excitation experiments reveal an inefficient carrier intersubband relaxation. Extending the optical investigations to modulation-doped samples, the formation of a one-dimensional electron gas can be observed. As a strong indication for this is the presence of a Fermi edge singularity (FES). Furthermore, Poisson-Schrodinger calculations show that the increased electron density in the conduction band leads to modified confinement energies. This was confirmed in magneto photoluminescence (MPL) experiments, where the diamagnetic shift of the luminescence from the first excited state is stronger than in the undoped case, as the state is squeezed further into the corners of the QWR. Recombination of the ground state electrons with different hole states appears as a fine structure in MPL spectra. Detailed analysis provides clear evidence of the FES. The expected temperature sensitivity of the FES is observed for lattice and electron heating. The FES intensity is also reduced at high excitation powers. The role of hole localisation and subband coupling is discussed. At applied magnetic fields the coupling of bands induces an enhancement of the singularity. Finally, the behaviour of hot carriers is investigated with time-resolved and electro-photoluminescence measurements. Long luminescence lifetimes indicate that electron-hole separation occurs due to the pinch-off between the QWR and the side quantum well. The field dependence of the electron heating shows quite clearly that LO phonon scattering is the dominant relaxation process at electron temperatures above ~40 K.

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The chemical and topographical nature of a polymer surface can be changed by non-equilibrium glow discharge treatment. Surface modification of polysulfone and polyethersulfone was examined using a variety of plasma treatments at a fixed power, pressure and treatment time. The modification observed was found to be dependent upon the type of feed gas employed. Tetrafluoromethane plasmas fluorinate polymer surfaces. The influence of polymeric structure on the extent of modification was examined. Phenyl ring containing polymers experienced a greater extent of modification compared to saturated polymers. The extent of modification is dependent upon both the fluorination mechanism and the surface affinity. Plasmas contain a variety of species accompanied by an electromagnetic spectrum. The role of vacuum ultraviolet radiation in a plasma was investigated as a function of feed gas (argon, krypton, xenon and oxygen) on polyethylene and polystyrene, in an oxygen atmosphere. The xenon vacuum ultraviolet treatment gave rise to the greatest oxidation whilst the O(_2) vacuum ultraviolet treatment was found to result in the least oxidation. The activation mechanisms varied with the feed gas chosen for the experiment. Non-equilibrium glow discharge treatment can alter the transport properties of gases permeating through an asymmetric polysulfone membrane. The selectivity and permeability alter as a function of the treatment. The deposition of a methane plasma polymer onto the surface of the membrane resulted in an increase in the gas flux. Similarly CF(_4) plasma treatment also gave rise to an increase in the gas flux. The deposition of a methane plasma polymer followed by a CF(_4) plasma treatment resulted in a decrease in gas flux and a small increase in the oxygen/nitrogen selectivity.

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Thesis (PhD)--University of South Australia, 1993

230 leaves : ill., diags., graphs, photos, tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1980

Thesis (PhD)--University of South Australia, 1993