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Magnetic properties of a thin Co/Pt layer can be controlled and modified by low energy Ga irradiation. Collisional intermixing of the elements was responsible for this modification.

The growth and the simulation of structures produced by a combination of evaporation and lithography are reported. Quasi-one-dimensional (quasi-1D) and one-dimensional structures in which the gold islands are arranged in a single row where the lateral size is only a few nanometers are created with this method.

Results show that tunnel resistances are crucial features in highly disordered arrays whereas in a two-dimensional array it is the total resistance of the minimal resistance path.

We propose a new, to our knowledge, method for determining the two main critical parameters of periodic one-dimensional lamellar structures, namely, linewidths and etched depths. The method is simple and requires only two measurements for the phase of the zero-transmitted order under two orthogonal polarizations. It is inspired by the analogy between subwavelength gratings and anisotropic homogeneous thin films. The method is tested with experimental data obtained with a Mach-Zehnder interferometer. Etched depths and linewidths derived from the interferograms and electromagnetic theory are compared with scanning-electron-microscope observations.

Research was conducted to examine electron transport in metallic dot arrays. The objective is to show that for a highly disordered one-dimensional multijunction array, with the broad junction length distribution corresponding to the technology, the mean threshold voltage Vth for a given maximal tunnel resistance can increase. The desired result may reveal either a way to increase the threshold voltages for a given technology or permit the larger, more controllable dimensions.

A study presents the electrical and microwave characteristics of high electron mobility transistors (HEMT) using X-ray lithography processing. The DC characteristics are similar to those obtained using electron beam lithography. A maximum intrinsic transconductance of 575 mS/mm shows the absence of damage to the substrate due to X-ray radiation. A device with shortest gate length has a current gain cutoff frequency of 70 gigahertz and that having the lowest gate resistance has a maximum oscillation frequency of 105 gigahertz.

A study was conducted on damage generation and its effects on GaAs/(Ga,Al)As quantum wells. Point defects were found to cause the disordering of layer structures during annealing at low doses while cascade mixing produces the intermixing at high doses. Strong segregation of the defects was observed in GaAs layers. AlAs was also found to be resistant to amorphization and delayed the amorphization process in GaAs quantum-well layers. The study showed AlAs'potential for device applications due to its effectivity in preventing GaAs quantum well damage and controlling defects during annealing.

A geometrically constrained magnetic domain wall was introduced in La0.7Sr0.3MnO3 micrometric devices in order to gain low field magnetoresistance in manganites. It was possible to identify large resistance switches in low fields. It is clear that very large sharp resistance switches in quite low fields can be achieved at room temperature in manganite-based devices.

A study was conducted to analyze the magnetoresistance and domain structure off submicron NiFe wires and crosses to examine the dependence of magnetoresistance on the detailed domain configurations. The wires and crosses were prepared using advanced electron beam lithography methods. Experimental results indicated that the sample supported a variation of the resistance during sweeping of the magnetic field.

We report the first observation of magnetization reversal in [(CoNi/Pt).sub.6] small elements connected to a large area through submicron wide channels. squares of size ranging from 0.2 [[micro]meter] x 0.2 [[micro]meter] to 10 [[micro]meter] x 10 [[micro]meter] and wire channels of linewidth ranging from 0.05 [[micro]meter] to 0.5 [[micro]meter] were fabricated by electron beam lithography and ion beam etching, and then studied by magnetooptical Kerr microscopy. Switching fields for magnetization and the reversal behavior of these dot elements were found to depend on the channel width, thereby providing a way of studying domain wall propagation in the wire channels. Index Terms - Domain wall motion, magnetization reversal, domain imaging, nanofabrication.

Presents a study which investigated the optical characteristics of selectively intermixed gallium arsenide/gallium aluminum arsenide quantum wires by gallium[sup+] masked implantation. Experimental details; Results and discussion; Conclusion.

Presents a study which investigated the intermixing of gallium arsenide/(gallium, aluminum)arsenide heterointerfaces by Ga[sup] implantation and annealing. Experimental details; Results and discussion; Conclusions.

We report on the magnetization reversal process and switching field behavior in permalloy ([Ni.sub.80][Fe.sub.20]) wire structures investigated by magneto-optic Kerr effect (MOKE) and magnetoresistance (MR) measurements. A combination of electron beam lithography and a lift-off process has been utilized to fabricate three sets of wire structures from a 30 [Angstrom] Au/300 [Angstrom] [Ni.sub.80][Fe.sub.20]/GaAs(100) continuous film: straight wires, elbow wires, and cross wires with width w=0.5 - 50 [micro]m and length l=200 [micro]m. We found that the switching field and reversal behavior in the elbow and the cross wires depend upon the junction geometry, which nucleates or suppresses reverse domains according to the wire width. Consequently the junction determines the magnetization reversal process and switching field in the elbow and cross wires. Index Terms--Domain configurations, magnetization reversal, mesoscopic structures, switching field.

To obtain low field magnetoresistance (MR) in manganites, we have introduced a geometrically constrained magnetic domain wall (DW) in La[sub 0.7]Sr[sub 0.3]MnO[sub 3] micrometric devices. Nanoconstrictions artificially induced using high resolution e-beam lithography are shown to effectively reduce the DW width leading to strongly enhanced DW resistance. Sharp and large resistance switches result from the appearance and annihilation of the DWs. Room temperature sharp resistance switches, with a MR of 16%, are evidenced in a manganite-based device. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The domain structures of epitaxial Fe (20 nm)/GaAs(100) circular dot arrays (diameters from 50 to 1 μm) were studied with magnetic force microscopy. A transition from a single domain to a multidomain remanent state was observed upon reducing the dot diameter beneath 10 μm in dot arrays with the separation twice the dot diameter. When the separation is reduced to half the dot diameter, the single domain states were found to “collapse” into stripe-like multidomain states due to local dipole coupling between dots. Micromagnetic simulations further suggest that for ultrathin Fe dots of less than about 2 nm thickness the diameter does not have a significant influence on the domain structures due to a dramatic reduction of the dipole energy. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]