We investigated different AlN nano-systems using spectroscopic methods. Experiments were performed at the Synchrotron Radiation Facility of the Laboratori Nazionali di Frascati using both XANES (x-ray absorption near edge spectroscopy) and FTIR (Fourier transform infrared spectroscopy) techniques in order to investigate materials with both interesting tribological and electronic properties. Comparisons have been performed between measurements by standard x-ray diffraction (XRD) and x-ray absorption (XRS) at the K-edge of Al, a spectroscopy method sensitive to the local order and correlated to the local and empty density of states of this wide band-gap semiconductor. Preliminary XAS simulations at the Al K edge are also presented. Correlations between XRD and XAS have been drawn, since x-ray absorption reveals structural information complementary to that addressed by x-ray diffraction. Moreover, a comparison has been performed by infrared (IR) absorption both in the mid- and in the far-IR ranges between different AlN forms: namely, powders, nanoparticles and nanotubes. Data clearly show changes connected with the electronic properties and the optical phonon modes of AlN nano-systems.
J. Phys.: Condens. Matter 18 (2006) S2095–S2104

Abstract. For theoretical simulation on AlN nanotubes (NTs) of different chiralities (armchair-and zigzag-type) and uniform diameters, we have considered their single-walled (SW) 1D periodic models. For this aim, we have performed ab initio DFT calculations on AlN SW NTs using formalism of the localized Gaussian-type atomic functions as implemented in CRYSTAL-03 computer code. We have shown that the smaller the diameter of AlN single-walled nanotube is, the closer its electronic and structural properties to AlN bulk. We have analysed an influence of N vacancies (neutral F centres) created by either soft irradiation of nanotubes or under experimental conditions of their growth, on the atomic and electronic structure of AlN SW NTs. We have found the small inward relaxation of the Al nearest neighbours and the N next-nearest neighbours around each point defect formed on 1 nm AlN NTs of both chiralities. Presence of N vacancy in both types of nanotubes has resulted in appearance of the two defect energy levels in their band gaps consisting of mainly 3s and 3p states of the nearest Al atoms.
Journal of Physics: Conference Series 93 (2007) 012005