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Four-terminal in-situ dc electrical resistance measurements and Raman spectra of residual Vicker indentations in single crystals of Si was used to determine the influence of temperature on the occurrence of indentation-induced phase transitions in Si. The finding shows that the sample temperature in the range of 150 to 300 K at which a Vickers diamond indentation is made has a strong influence on the occurrence of indentation-induced phase transition within the plastically deformed zone around the indentation.

Magnetoresistance measurements were used to study magnetization reversal in permalloy wire junction structures.

Magneto-optical Kerr effect was employed to analyze the magnetoresistance (MR) behavior of micron-sized Ni80Fe20 wires made by electron-beam lithography and lift-off methods. The magnetization reversal processes and MR properties in these wires having periodically modulated width were investigated. Results show that there were strong changes in magnetization reversal processes and MR properties as the lateral shape of the wires changes.

Far infrared analysis was used to investigate plasmon excitation and self-coupling in a bi-periodically modulated two-dimensional electron gas (2DEG). The results showed that for the interdigitated grating gates, the 2DEG was modulated at a period twice as long as that of the grating fingers by differentially biasing alternates. The plasmon frequencies decreased with the increasing amplitude of the gas density modulation.

Resonant microwave-assisted and dc transport are examined in degenerately doped silicon single electron transistors and a model based on hopping is developed through localized impurity states. The non-monotonic power dependence of the resonant current under irradiation is consistent with spatial Rabi oscillations between localized states.

A study was conducted to determine the ability for the low temperature electronics to carry out faster measurements using phosphorous-doped single electron transistor. Findings highlight the various measurement strategies and consequences on electron heating and noise.

A study was conducted to determine the influence of microwave irradiation on the source-drain current of a silicon single electron transistor, with fixed source-drain and gate voltages, at a temperature of 4 K. The results provide insight into the origin of the sharp resonances with high quality factor formed due to the source-drain current changes that evolve from the microwave induced spatial redistributions of localized electrons in the single electron transistor.

A novel measurement technique for the measurement of the sheet resistance, at microwave frequencies, of conducting films supported on thin dielectric substrates is presented. This method is used to characterize the sheet resistance of semiconductor samples in the frequency range 120-175 GHz and the results are compared to the dc values obtained by conventional techniques.

The domain configurations in permalloy wires with a wide size range of a central bridge prepared on a GaAs substrate are investigated in both their demagnetized and remanent states using magnetic force microscopy (MFM). The structures especially with narrow bridges suggest a possible way of detecting the domain wall resistivity in a low magnetic field, while providing insight into the domain wall reversal process in flat wire structures.

The pseudo-Hall effect (PHE) and anisotropic magnetoresistance (AMR) in a micronscale [Ni.sub.80][Fe.sub.20] sixterminal device, fabricated by optical lithography and wet chemical etching from a high quality UHV grown 30 [Angstrom] Au/300 [Angstrom] [Ni.sub.80][Fe.sub.20] film, have been studied. The magnetisation reversal in different parts of the device has been measured using magneto-optical Kerr effect (MOKE). The device gives a 50% change in PHE voltage with an ultrahigh sensitivity of 7.3%[Oe.sup.-1] at room temperature. The correlation between the magnetisation, magneto-transport properties, lateral shape of the device and directions of the external applied field is discussed based on extensive MOKE, AMR and PHE results. Index Terms -- pseudo-Hall effect, magnetoresistance, magnetisation reversal, MOKE

The magnetization reversal and magnetic anisotropy in Co network structures have been studied using magneto-optic Kerr effect (MOKE). An enhancement of the coercivity is observed in the network structures and is attributed to the pinning of domain walls by the hole edges in the vicinity of which the demagnetizing field spatially varies. We find that the magnetization reversal process is dominated by the intrinsic unaxial anisotropy (2[K.sub.u]/[M.sub.s] [approximately equals] 200 Oe) in spite of the shape anisotropy induced by the hole edges. The influence of the cross-junction on the competition between the intrinsic uniaxial anisotropy and the induced shape anisotropy is discussed using micromagnetic simulations. Index Terms--Coercivity, magnetic anisotropy, network structures.

The magnetisation reversal processes and magnetoresistance behaviour in micron-sized [Ni.sub.80][Fe.sub.20] wires with triangular and rectangular modulated width have been studied. The wires were fabricated by electron beam lithography and a lift-off process. A combination of magnetic force microscopy (MFM), magneto-optical Kerr effect (MOKE) and magnetoresistance (MR) measurements shows that the lateral geometry of the wires greatly influences the magnetic and transport properties. The width modulations modify not only the shape-dependent demagnetising fields, but also the current density. The correlation between the lateral geometry, the magnetic and the transport properties is discussed based on MFM, MOKE and MR results. Index Terms--magnetoresistance, magnetisationation reversal, MFM, MOKE