Relationship of the 3P0 decay model to other strong decay models

The 3P0 decay model is briefly reviewed. Possible improvements, partly motivated by the examination of a microscopic description of a quark - anti-quark pair creation, are considered. They can provide support for the one-body character of the model which, otherwise, is difficult to justify. To some extent, they point to a boost effect that most descriptions of processes involving a pair creation cannot account for.Comment: 4 pages, 2 .eps figures; Contribution to the BARYONS 2002 Conference, 3.-8. March 2002, JLab, US

Silicon implantation in GaAs

The electrical properties of room-temperature Si implants in GaAs have been studied. The implantations were done at 300 keV with doses ranging from 1.7×10^13 to 1.7×10^15 cm^–2. The implanted samples were annealed with silicon nitride encapsulants in H2 atmosphere for 30 min at temperatures ranging from 800 to 900°C to electrically activate the implanted ions. Results show that the implanted layers are n type, which implies that the Si ions preferentially go into Ga sites substitutionally. For low-dose implants, high (~90%) electrical activation of the implanted ions is achieved and the depth distribution of the free-electron concentration in the implanted layer roughly follows a Gaussian. However, for high-dose implants, the activation is poor (<15% for a 900 °C anneal) and the electron concentration profile is flat and deeper than the expected range

Dominant moving species in the formation of amorphous NiZr by solid-state reaction

The displacements of W and Hf markers have been monitored by backscattering of MeV He to study the growth of the amorphous NiZr phase by solid-state reaction. We find that the Ni is the dominant moving species in this reaction

Radioactive silicon as a marker in thin-film silicide formation

A new technique using radioactive 31Si (half-life =2.62 h), formed in a nuclear reactor, as a marker for studying silicide formation is described. A few hundred angstroms of radioactive silicon is first deposited onto the silicon substrate, followed immediately by the deposition of a few thousand angstroms of the metal. When the sample is heated, a silicide is first formed with the radioactive silicon. Upon further silicide formation, this band of radioactive silicide can move to the surface of the sample if silicide formation takes place by diffusion of the metal or by silicon substitutional and/or vacancy diffusion. However, if the band of radioactive silicide stays at the silicon substrate interface it can be concluded that silicon diffuses by interstitial and/or grain-boundary diffusion. This technique was tested by studying the formation of Ni2Si on silicon at 330 °C. From a combination of ion-beam sputtering, radioactivity measurement, and Rutherford backscattering it is found that the band of radioactive silicide moves to the surface of the sample during silicide formation. From these results, implanted noble-gas marker studies and the rate dependence of Ni2Si growth on grain size, it is concluded that nickel is the dominant diffusing species during Ni2Si formation, and that it moves by grain-boundary diffusion

Thermal reaction of Al/Ti bilayers with contaminated interface

We have studied some new aspects of thermal reactions in Al/Ti bilayers in which the interface is purposely contaminated with oxygen. After annealing at a temperature of 460 °C, an Al_3Ti compound forms at the interface, moreover some Al diffuses through the Ti to form a compound at the free surface. The amount of aluminum at the free surface can be as large as at the interface. Nucleation and lateral growth of Al_3Ti at the interface are locally unfavorable. This results in a competition between the lateral growth of Al_3Ti at the Al/Ti interface and the diffusion of Al to the free surface. Once full coverage by Al_3Ti is obtained at the Al/Ti interface, the diffusion of Al to the surface becomes negligible

Effect of dose rate on ion beam mixing in Nb-Si

The influence of dose rate, i.e., ion flux, on ion beam mixing in Nb‐Si bilayer samples was measured at room temperature and 325 °C. At the higher temperature, an increase in dose rate of a factor of 20 caused a decrease in the thickness of the mixed layer by a factor of 1.6 for equal total doses. At room temperature, the same change in flux had no effect on mixing. These results are consistent with radiation‐enhanced diffusion theory in the recombination‐limited regime

Dissociation mechanism for solid-phase epitaxy of silicon in the Si <100>/Pd2Si/Si (amorphous) system

Solid-phase epitaxial growth (SPEG) of silicon was investigated by a tracer technique using radioactive 31Si formed by neutron activation in a nuclear reactor. After depositing Pd and Si onto activated single-crystal silicon substrates, Pd2Si was formed with about equal amounts of radioactive and nonradioactive Si during heating at 400 °C for 5 min. After an 1-sec annealing stage (450-->500 °C in 1 h) this silicide layer, which moves to the top of the sample during SPEG, is etched off with aqua regia. From the absence of radioactive 31Si in the etch, it is concluded that SPEG takes place by a dissociation mechanism rather than by diffusion

Quadexciton cascade and fine structure splitting of the triexciton in a single quantum dot

We report the properties of emission lines associated with the cascaded recombination of a quadexciton in single GaAlAs/AlAs quantum dots, studied by means of polarization-resolved photoluminescence and single-photon correlation experiments. It is found that photons which are emitted in a double-step 4X-3X process preserve their linear polarization, similarly to the case of conserved polarization of correlated photons in the 2X-X cascade. In contrast, an emission of either co-linear or cross-linear pairs of photons is observed for the 3X-2X cascade. Each emission line associated with the quadexciton cascade shows doublet structure in the polarization-resolved photoluminescence experiment. The maximum splitting is seen when the polarization axis is chosen along and perpendicular to the [110] crystallographic direction. This effect is ascribed to the fine structure splitting of the exciton and triexciton states in the presence of an anisotropic confining potential of ae dot. We also show that the splitting in the triexciton state surpasses that in the exciton state by a factor up to eight and their ratio scales with the energy distance between the 3X and X emission lines, thus, very likely, with a lateral size and/or a composition of the dot.Comment: submitted to Physical Review

Structural difference rule for amorphous alloy formation by ion mixing

We formulate a rule which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results we have obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process