[en] We have measured the evolution of the excess-vacancy region created by a 2 MeV, 10¹⁶/cm² Si implant in the silicon surface layer of silicon-on-insulator substrates. Free vacancy supersaturations were measured with Sb dopant diffusion markers during postimplant annealing at 700, 800, and 900 C, while vacancy clusters were detected by Au labeling. We demonstrate that a large free vacancy supersaturation exists for short times, during the very early stages of annealing between the surface and the buried oxide (1 μm below). Afterwards, the free vacancy concentration returns to equilibrium in the presence of vacancy clusters. These vacancy clusters form at low temperatures and are stable to high temperatures, i.e., they have a low formation energy and high binding energy

[en] Measurements of the binding energy (E_b) of vacancies to vacancy clusters formed in silicon following high-energy ion implantation are reported. Vacancy clusters were created by 2 MeV, 2 x 10¹⁵ cm^-2 dose Si implant and annealing. To prevent recombination of the excess vacancies (V^ex) with interstitials from the implant damage near the projected range (R_p), a Si-on-insulator substrate was used such that the R_p damage was separated from the V^ex by the buried oxide (BOX). Two V^ex regions were observed: one in the middle of the top Si layer (V₁^ex) and the other at the front Si/BOX interface (V₂^ex). The rates of vacancy evaporation were directly measured by Au labeling following thermal treatments at temperatures between 800 and 900 C for times ranging from 600 to 1800 s. The rate of vacancy evaporation from V₂^ex was observed to be greater than from V₁^ex. The binding energy of vacancies to clusters in the middle of the silicon top layer was 3.2±0.2 eV as determined from the kinetics for vacancy evaporation

[en] It has recently become possible to synthesize a class of nanostructured materials by ion implantation. The implanted ions aggregate into crystallographically oriented nanoscale inclusions in the host material. We have performed simulations of the magnetization curves for such assemblies of nanoscale Fe inclusions in a nonmagnetic host. We use random positions for the magnetic particles (not a regular grid) and include magnetostatic interactions in detail. We find that these materials are not adequately described by standard noninteracting theories-interactions have a significant effect. In particular, interactions can mask the effects of crystallite orientation, producing nearly isotropic hysteresis curves. The use of a noninteracting model could thus lead one to conclude, incorrectly, that the inclusions are randomly oriented. [copyright] 2001 American Institute of Physics

[en] It has been shown recently that Au labeling [V. C. Venezia, D. J. Eaglesham, T. E. Haynes, A. Agarwal, D. C. Jacobson, H.-J. Gossmann, and F. H. Baumann, Appl. Phys. Lett. 73, 2980 (1998)] can be used to profile vacancy-type defects located near half the projected range ((1/2) R_p) in MeV-implanted Si. In this letter, we have determined the ratio of vacancies annihilated to Au atoms trapped (calibration factor ''k'') for the Au-labeling technique. The calibration experiment consisted of three steps: (1) a 2 MeV Si⁺ implant into Si(100) followed by annealing at 815 degree sign C to form stable excess vacancy defects; (2) controlled injection of interstitials in the (1/2) R_p region of the above implant via 600 keV Si⁺ ions followed by annealing to dissolve the {311} defects; and (3) Au labeling. The reduction in Au concentration in the near-surface region (0.1-1.6 μm) with increasing interstitial injection provides the most direct evidence so far that Au labeling detects the vacancy-type defects. By correlating this reduction in Au with the known number of interstitials injected, it was determined that k=1.2±0.2 vacancies per trapped Au atom. (c) 2000 American Institute of Physics

[en] In this work we demonstrate that the defects that are created by 2-MeV Si ions can interact with dopant atoms both during implantation and during post-implant annealing. We show that the interstitials and vacancies created during MeV Si implantation result in a radiation enhanced diffusion of B and Sb markers, respectively, when the temperature of implantation is above the threshold temperature for formation of mobile dopant complexes. With the use of these dopant markers we also demonstrate that a vacancy-rich near surface region results during post-implant annealing of MeV implanted silicon. The depth distribution and the thermal evolution of clustered vacancies was measured by a Au labeling technique

[en] The formation mechanism of the ohmic Au/Ni/p-GaN contact has been investigated. We found that it is essential to (i) deposit a structure of Au and Ni in the proper deposition sequence, and (ii) anneal the bilayer structure in an oxygen containing ambient. Our findings indicated that oxygen assists the layer-reversal reactions of the metallized layers to form a structure of NiO/Au/p-GaN. The presence of oxygen during annealing appears to increase the conductivity of the p-GaN. It is further suggested that Ni removes or reduces the surface contamination of the GaN sample before or during layer reversal. In the final contact structure, an Au layer, which has a large work function, is in contact with the p-GaN substrate. The presence of Au in the entire contacting layer improves the conductivity of the contact. An ohmic formation mechanism based on our experimental results is proposed and discussed in this work. (c) 2000 American Institute of Physics

[en] Magneto-optically active nanocomposite structures have been created by using ion implantation and thermal processing to form precipitated layers of ferromagnetic α-Fe or ferrimagnetic Fe₃O₄ that are embedded in the near-surface region of (100)-oriented yttrium stabilized ZrO₂ (YSZ). When Fe-implanted YSZ is annealed at 1100 degree sign C in Ar+4%H₂, the redox conditions are sufficiently reducing so that metallic Fe is the stable phase. At lower temperatures the annealing conditions become less reducing and Fe₃O₄ becomes the stable phase. Transmission electron microscopy and x-ray diffraction studies established that each α-Fe or Fe₃O₄ particle is a single crystal that is crystallographically aligned with respect to the YSZ host. Magneto-optical effects due to both the α-Fe and Fe₃O₄ nanophase precipitates were found and characterized using magnetic circular dichroism. These magneto-optical effects have potential applications in integrated-optical devices. (c) 2000 American Institute of Physics