We analyze a method to selectively grow straight, vertical gallium nitride nanowires by plasma-assisted molecular beam epitaxy (MBE) at sites specified by a silicon oxide mask, which is thermally grown on silicon (111) substrates and patterned by electron-beam lithography and reactive-ion etching. The investigated method requires only one single molecular beam epitaxy MBE growth process, i.e., the SiO2 mask is formed on silicon instead of on a previously grown GaN or AlN buffer layer. We present a systematic and analytical study involving various mask patterns, characterization by scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy, as well as numerical simulations, to evaluate how the dimensions (window diameter and spacing) of the mask affect the distribution of the nanowires, their morphology, and alignment, as well as their photonic properties. Capabilities and limitations for this method of selective-area growth of nanowires have been identified. A window diameter less than 50 nm and a window spacing larger than 500 nm can provide single nanowire nucleation in nearly all mask windows. The results are consistent with a Ga diffusion length on the silicon dioxide surface in the order of approximately 1 μm.

A rare case of ossifying fibroma of the temporal bone is presented. Fibro-osseous lesions are benign neoplasms but may show an aggressive behaviour when invading important anatomical structures. The lack of experience in the treatment of those tumours is reflected in the small relative literature. The purpose of this paper is to contribute to the few cases already reported.

The quantitative interdependencies of growth conditions, crystal defects and electrical/electronic properties of InN thin films, grown by plasma-assisted molecular beam epitaxy on GaN (0001) buffer layers have been investigated. InN epilayers with thickness near 700 nm, grown under different substrate temperature and/or growth rate, have been analyzed. Bulk electron concentration (N bulk ) and mobility values were extracted for each InN film using the inverted version of the multilayer Petritz model, subtracting the conductivity of a corresponding 120 nm InN film. The results indicate a significant reduction of the threading dislocation density by enhancing the diffusion length of indium adatoms during InN growth, through increase of substrate temperature and reduction of growth rate. The electrical characteristics deteriorate with increasing threading dislocation density. Assuming threading dislocations as exclusive sources of donors in InN, their charge state could be between +1 and +2 per c lattice constant length of dislocation line for N bulk ≈ 4.0-5.7×10 17 cm −3 , and approximately +2 or larger for N bulk ≈ 1.5-1.8×10 18 cm −3 . The scattering effect of threading dislocations is significantly weaker compared to reported theoretical calculations, i.e. it would correspond to an order of magnitude lower threading dislocation density than the experimentally observed density in the range of 10 10 cm −2 .