Chemical bonding of nitrogen formed by nitridation of crystalline and amorphous aluminum oxide studied by X-ray photoelectron spectroscopy.

Numerous efforts have already been made to optimize nitridation of crystalline sapphire (c-AlO) substrates whereas very little attention has been paid to nitridation of amorphous aluminum oxide layers (a-AlO ). An extensive analysis of the reaction of amorphous aluminum oxide films with nitrogen species is thus needed to clarify the mechanisms of nitrogen incorporation into such layers and to control their properties. In this work X-ray photoelectron spectroscopy was used to determine the chemical state of nitrogen formed by nitrogen plasma treatment of c-AlO and 15 nm thick a-AlO layers grown by atomic layer deposition on Si and sapphire substrates.

Effectiveness of toluene mineralization by gas-phase oxidation over Co(II)/SiO catalyst with ozone.

The results of experimental study on effectiveness of gas-phase total oxidation of toluene towards carbon dioxide and water with the aid of ozone over Co(II)/SiO catalyst are presented in this work. The main objective of the work was to determine ozone demand necessary for total mineralization of toluene at the temperature range of 40-100°C chosen to minimize catalyst poisoning by water. Complete mineralization of toluene was possible if sufficient ozone/toluene ratio was maintained in the gas supplied to the reactor.

Selective area formation of GaN nanowires on GaN substrates by the use of amorphous Al O nucleation layer.

Examples are presented that application of amorphous Al O nucleation layer is an efficient way of controlling spatial distribution of GaN nanowires grown by plasma-assisted molecular beam epitaxy. On GaN/sapphire substrates Al O stripes induce formation of GaN nanowires while a compact GaN layer is formed outside the stripes. We show that the ratio of nanowire length h to the thickness of the compact layer d can be tailored by adjusting impinging gallium and nitrogen fluxes.

Reflectance and fast polarization dynamics of a GaN/Si nanowire ensemble.

Optical phenomena in an ensemble of high-quality GaN nanowires (NWs) grown on a Si substrate have been studied by reflectance and time-resolved luminescence. Such NWs form a structure that acts as a virtual layer that specifically reflects and polarizes light and can be characterized by an effective refractive index. In fact we have found that the NW ensembles of high NW density (high filling fraction) behave rather like a layer of effective medium described by the Maxwell Garnett approximation.

High-resolution X-ray diffraction analysis of strain distribution in GaN nanowires on Si(111) substrate.

In this work, the influence of micro- and macro-deformation profiles in GaN nanowires (NWs) on the angular intensity distribution of X-ray diffraction are studied theoretically. The calculations are performed by using kinematical theory of X-ray diffraction and assuming the deformation decays exponentially from the NW/substrate interface. Theoretical modeling of X-ray scattering from NWs with different deformation profiles are carried out.