A series of glasses xMgO-(1-x)SiO(2) with compositions from enstatite MgSiO(3) (x=0.5) to forsterite Mg(2)SiO(4) (x=0.667) in mole fraction intervals of x approximately 0.02 have been prepared by containerless levitation techniques and CO(2) laser heating. Polarized and depolarized Raman spectra measured at ambient conditions for all these glasses show systematic and smooth band intensity changes with composition. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged SiO(4) tetrahedra (Q(i), species analysis) undoubtedly shows that bridging oxygens are present in all glasses studied even in the limit of the forsterite composition where bridged Si(2)O(7) (6-) ionic dimers are formed. Furthermore the relative amounts of the Q(i) species change smoothly with composition while at high MgO content "free" oxygens are present presumably forming Mg-O-Mg bridges, which contribute to the glass stability at these compositions. Raman spectra measurements at different temperature below T(g) show small alterations in the Q(i) species in the MgSiO(3) region while no changes were observed in the Mg(2)SiO(4) region. The Boson peak frequency is practically invariant on both composition and temperature and this is in contrast to the systematics followed by most silicate glasses. It is suggested that at compositions near the forsterite ioniclike glasses are formed arising from a very fragile liquid.

The structural characteristics of novel alkaline-earth suborthosilicate glasses along the compositional join (1 - x)(Ca(0.5)Mg(0.5)O) - xSiO(2) with 0.28 ≤ x ≤ 0.33 are investigated using high resolution (29)Si and (17)O nuclear magnetic resonance spectroscopy. The structures of these glasses consist of isolated Q(0) and Q(1) anionic species and Mg(2+) and Ca(2+) countercations that are held together by Coulombic interactions. The concentration of the Q(1) species rapidly decreases with decreasing SiO(2) content and becomes undetectable in the glass with x = 28 mol %. The compositional variation of the physical properties of these glasses such as glass transition temperature and density can be attributed to the Q-speciation in the structure. The NBOs are associated with a random distribution of the alkaline-earth cations in their nearest neighbor coordination shell. The resulting random packing of dissimilar Ca-NBO and Mg-NBO coordination polyhedra may give rise to structural and topological frustration responsible for the unusual glass-forming ability of these suborthosilicate liquids with extremely low SiO(2) contents. Finally, the composition and the formation of Q(1) species necessitate the formation of free O(2-) ions in the structure of these glasses that are only bonded to Mg(2+) and Ca(2+) cations. The (17)O NMR results presented in this study allow for direct observation of such oxygen species.

The thermal decomposition of SiC surface provides, perhaps, the most promising method for the epitaxial growth of graphene on a material useful in the electronics platform. Currently, efforts are focused on a reliable method for the growth of large‐area, low‐strain epitaxial graphene that is still lacking. Here, a novel method for the fast, single‐step epitaxial growth of large‐area homogeneous graphene film on the surface of SiC(0001) using an infrared CO2 laser (10.6 μm) as the heating source is reported. Apart from enabling extreme heating and cooling rates, which can control the stacking order of epitaxial graphene, this method is cost‐effective in that it does not necessitate SiC pre‐treatment and/or high vacuum, it operates at low temperature and proceeds in the second time scale, thus providing a green solution to EG fabrication and a means to engineering graphene patterns on SiC by focused laser beams. Uniform, low–strain graphene film is demonstrated by scanning electron microscopy, X‐ray photoelectron spectroscopy, secondary ion‐mass spectroscopy, and Raman spectroscopy. Scalability to industrial level of the method described here appears to be realistic, in view of the high rate of CO2‐laser‐induced graphene growth and the lack of strict sample–environment conditions.