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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.

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.

The current scanning near-field optical microscopy has been developed with optical-fiber probes obtained by use of either laser-heated pulling or chemical etching. For high-resolution near-field imaging, the detected signal is rapidly attenuated as the aperture size of the probe decreases. It is thus important to fabricate probes optimized for beth spot size and optical transmission. We present a two-step fabrication that allowed us to achieve an improved performance of the optical-fiber probes. Initially, a C[O.sub.2] laser-heated pulling was used to produce a parabolic transitional taper ending with a top thin filament. Then, a rapid chemical etching with 50% buffered hydrofluoric acid was used to remove the thin filament and to result in a final conical tip on the top of the parabolic transitional taper. Systematically, we obtained optical-fiber nanoprobes with the apex size as small as 10 nm and the final cone angle varying from 15 [degrees] to 80 [degrees]. It was found that the optical transmission efficiency increases rapidly as the taper angle increases from 15 [degrees] to 50 [degrees], but a further increase in the taper angle gives rise to important broadening of the spot size. Finally, the fabricated nanoprobes were used in photon-scanning tunneling microscopy, which allowed observation of etched double lines and grating structures with periods as small as 200 nm. OCIS codes: 180.5810, 060.2310.

A study was conducted on the structural characteristics of GaAs/GaAlAs quantum wires. These wires are capable of promoting strong mixing rates after high-dose implantation. Large lateral modulations of the effective band gap and small interdiffusion lengths were observed. Further observation also showed the presence of one-dimensional quantization energies ranging from 11 to 20 meV in the structures. The study shows that the GaAs/GaAlAs quantum well can be effectively used to produce efficient quantum-well wires.

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.

Abstract Background A critical step in the fabrication of biochips is the controlled placement of probes molecules on solid surfaces. This is currently performed by sequential deposition of probes on a target surface with split or solid pins. In this article, we present a cost-effective procedure namely microcontact printing using stamps, for a parallel deposition of probes applicable for manufacturing biochips. Results Contrary to a previous work, we showed that the stamps tailored with an elastomeric poly(dimethylsiloxane) material did not require any surface modification to be able to adsorb oligonucleotides or PCR products. The adsorbed DNA molecules are subsequently printed efficiently on a target surface with high sub-micron resolution. Secondly, we showed that successive stamping is characterized by an exponential decay of the amount of transferred DNA molecules to the surface up the 4th print, then followed by a second regime of transfer that was dependent on the contact time and which resulted in reduced quality of the features. Thus, while consecutive stamping was possible, this procedure turned out to be less reproducible and more time consuming than simply re-inking the stamps between each print. Thirdly, we showed that the hybridization signals on arrays made by microcontact printing were 5 to 10-times higher than those made by conventional spotting methods. Finally, we demonstrated the validity of this microcontact printing method in manufacturing oligonucleotides arrays for mutations recognition in a yeast gene. Conclusion The microcontact printing can be considered as a new potential technology platform to pattern DNA microarrays that may have significant advantages over the conventional spotting technologies as it is easy to implement, it uses low cost material to make the stamp, and the arrays made by this technology are 10-times more sensitive in term of hybridization signals than those manufactured by conventional spotting technology.

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.

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.

Analyzes the characteristics of argon implantation-induced amorphization of silicon at room temperature. Information on the damage calculations and the critical damage energy density model; Details on the experiment; Results of the study.

Provides information on a study that examined both experimentally and theoretically the generation of damage in GaAs due to ion implantation through mask openings of small dimensions. Experimental procedure; Results and discussion on the study; Conclusions.

Domain wall velocity measurements in ultrathin Pt/Co(0.6 nm)/Pt narrow magnetic wires with perpendicular anisotropy are reported. Tracks (0.45 and 0.9 microns wide) are defined by drawing twins of parallel etched/irradiated lines with a focused [Ga.sup.+] beam (FIB). In these films, irradiation induces a large decrease in coercivity due to Co-Pt intermixing at the interfaces, as checked in areas submitted to various fluences. At the same field, the domain wall propagates at far higher velocities in a 0.45 [micro]m track than in the virgin film. It is explained by the calculated irradiation fluence profile. Hence, irradiation can be used to design structures where the magnetic information propagates very rapidly under a small applied field. Index Terms--Ion irradiation patterning, magnetic domain wall dynamics, ultrathin narrow magnetic wires.

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]