Vertically aligned boron nanowires in self‐assembled large‐scale arrays with excellent uniformity and high density have been fabricated using radio‐frequency magnetron sputtering of boron and B2O3 powder onto various substrates. The nanowires thus produced are several tens of micrometers long and 20–80 nm wide, with typically platform‐shaped tips (see Figure for a high‐magnification SEM image).

Well-aligned boron nanowire arrays were grown vertically on silicon substrates over areas up to several tens of square centimeters using radio-frequency magnetron sputtering of highly pure boron. During growth and self-assembly of boron nanowire arrays, no template or catalyst was needed. The morphology, structure, and composition of the self-organized boron nanowires were characterized in detail using scanning electron microscopy, transmission electron microscopy, and electron energy-loss spectroscopy. Our results might provide insight into the controllable formation of a wide variety of ordered nanostructures with advanced properties.

The evolution of interface structure of ␣-Fe/Nd 2 Fe 14 B nanocomposites prepared by crystallization of amorphous Nd 9 Fe 83 Co 3 B 5 has been investigated by employing positron annihilation techniques. Positron lifetime studies show that there are two kinds of interface structures in the ␣-Fe/Nd 2 Fe 14 B nanocomposites prepared at 700°C. One characterized by a positron lifetime of 155 ps is determined to be the interfacial amorphous layer with a densely packed structure. The other has a more loosely packed atomic structure with vacancy-sized free volumes. The volume fraction of the amorphous layer decreases with increasing annealing temperature and only the interface structure with vacancies is retained after annealing at temperatures Tу950°C. Coincident Doppler broadening studies of the positron-electron annihilation ␥ quanta show that the interfacial free volumes with a large size in the nanocomposites made at 700°C are predominantly surrounded by the nonmagnetic atoms Nd and B, which is believed to weaken the magnetic exchange coupling between the crystallites in the nanocomposites.

For a detailed understanding of high-temperature processes in complex solids the identification of the sublattice on which thermal defects are formed is of basic interest. Theoretical studies in intermetallic compounds favor a particular sublattice for thermal vacancy formation. In the present study we detect in ordered MoSi2 thermal vacancies with a low formation enthalpy of H(F)(V)=(1.6+/-0.1) eV, and we succeed in showing by experimental and theoretical efforts that they are preferentially formed on the Si sublattice. By these data self-diffusion in MoSi2 can be understood.