ORIGINAL PAPER N-K electron energy-loss near-edge structures for TiN/VN layers: an ab initio and experimental study Petr Lazar & Josef Redinger & Johannes Strobl & Raimund Podloucky & Boriana Rashkova & Gerhard Dehm & Gerald Kothleitner & Sašo Šturm & Kerstin Kutschej & Christian Mitterer & Christina Scheu Received: 3 September 2007 / Revised: 23 October 2007 / Accepted: 19 November 2007 # Springer-Verlag 2007 Abstract We study N-K-edge electron energy-loss near-edge structures for well-defined TiN/VN bilayers grown on a MgO (100) substrate by both calculations and experiments. The structural relaxations and the electronic structure of TiN/VN multilayers are calculated using the Vienna Ab Initio Simulation Package computer code, which uses density functional theory to describe the electronic interaction. The effects of the core hole created in the excitation process are included in the calculations. For VN, off-stoichiometric effects due to nitrogen vacancies are modelled. The partial density of states (PDOS) for the N-K edge of atoms in the vicinity of the TiN/MgO interface revealed that two new peaks appear between 7 and 9 eV instead of a broad shoulder typical for the bulk. For the VN/TiN interface, the PDOS is modified only slightly, owing to similar bonding on both sides of the interface, and is thus very similar to the respective bulk spectra. An experimental spectrum taken at the VN/TiN interface is, however, well described by an average of the simulated spectra for VN and TiN bulk (interface). Such a finding is characteristic of an intermixed interface. Keywords Spectroscopy/theory . Interface/surface analysis . Thin films Introduction Transition-metal nitrides like TiN and VN exhibit techno- logically interesting combinations of physical and chemical properties such as very high melting points, high hardness, corrosion resistance and good chemical and thermal stability [1]. These properties class them among the refractory compounds and make them important candidates for many technological applications, in particular as hard coatings for cutting tools. Furthermore, several experimen- tal studies have demonstrated the correlation between microstructure and hardness of TiN/VN multilayers [2–5], which—in single crystal form—may reach hardness as high as 56 GPa [2], harder than the pure constituents. Such coatings are promising for applications where extremely high hardness and wear resistance are needed. The favourable increase of multilayer hardness is limited at elevated temperatures, where TiN/VN multilayers start to interdiffuse [6, 7], resulting in a degradation of the coating Anal Bioanal Chem DOI 10.1007/s00216-007-1759-0 P. Lazar (*) : J. Redinger : J. Strobl Institute of General Physics, Vienna University of Technology, 1040 Vienna, Austria e-mail: petr.lazar@tuwien.ac.at R. Podloucky Department of Physical Chemistry, University of Vienna, 1090 Vienna, Austria B. Rashkova : G. Dehm Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences and Department of Materials Physics, Montanuniversität Leoben, 8700 Leoben, Austria G. Kothleitner Research Institute for Electron Microscopy, Graz University of Technology, 8010 Graz, Austria S. Šturm Department for Nanostrucured Materials, Jozef Stefan Institute, 1000 Ljubljana, Slovenia K. Kutschej : C. Mitterer : C. Scheu Department of Physical Metallurgy & Materials Testing, Montanuniversität Leoben, 8700 Leoben, Austria