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The vibrational properties of orthorhombic MgCu2O3 compound have been investigated within the framework of the density functional perturbation theory (DFPT) as well as experimentally, to validate the computational results. MgCu2O3 was synthesized by solid‐state reaction and characterized by synchrotron‐based X‐ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The DFT + U‐based first principle calculations were performed to obtain the correct electronic ground state and the band structure of this compound. The same DFT + U methodology was employed along with DFPT calculations for obtaining vibrational properties: phonon density of states and phonon band structure. The atomic vibrations for each mode were also analyzed, and the Raman and the IR active modes are identified. Experimentally observed Raman and infrared (IR) spectra agree well with the computed ones. [ABSTRACT FROM AUTHOR]

Depth-resolved positron annihilation studies have been carried out on nitrogen-implanted Si to investigate defect evolution and thermal stability. Si(1 0 0) wafers have been implanted with 60 keV N+ ions to a fluence of 1 x 1014 and 1 x 1015 ions/cm2. From positron diffusion analysis of defect-sensitive S-parameter profiles, it is found that the higher dose sample undergoes a two-step annealing process consisting of annealing of deep level defects, followed by vacancy agglomeration near the surface at 873 K. For the low dose sample, however, nitrogen vacancy complexes are the only major defects remaining at 873 K. Annealing at 1073 K is sufficient to remove all kinds of open volume defects present in the samples. [ABSTRACT FROM AUTHOR]

In spite of the large amount of tribological work carried out to explain the friction and wear mechanism in diamond-like carbon (DLC) films, some of the core issues relating to the evolution of reactive species across sliding interfaces and their role on the friction and wear mechanism remain unclear. The phase composition, film density and hydrogen content present in a DLC film can be tailored by substrate biasing during film deposition to achieve a nearly vanishing friction coefficient. Furthermore, nitrogen doping in DLC films significantly improves wear resistance, and sliding occurs in a nearly wearless regime. Undoped and nitrogen-doped DLC films exhibit a nearly frictionless value with ultra-low wear behavior when tests are performed in argon, nitrogen and methane atmospheres. The antifriction and antiwear properties of the DLC films were improved with the reduction of adsorbed oxygen impurities on the film surface. This behavior was understood by correlating the oxygen impurities present at the surface/subsurface region of the DLC film while using x-ray photoelectron spectroscopy and depth-resolved Auger electron spectroscopy. [ABSTRACT FROM AUTHOR]