Browsing by Author "Dimitrov, D."

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Chemical vapour deposition growth and Raman characterization of graphene layers and carbon nanotubes
(2016-01-01)
Lai, Y-C
;
Rafailov, P. M.
;
Vlaikova, E.
;
Marinova, V.
;
Lin, S. H.
Single-layer graphene films were grown by chemical vapour deposition (CVD) on Cu foil. The CVD process was complemented by plasma enhancement to grow also vertically aligned multiwalled carbon nanotubes using Ni nanoparticles as catalyst. The obtained samples were characterized by Raman spectroscopy analysis. Nature of defects in the samples and optimal growth conditions leading to achieve high quality of graphene and carbon nanotubes are discussed.
Chemical vapour deposition growth of graphene layers on metal substrates
(2014-01-01)
Lai, Y-C
;
Yu, S-C
;
Rafailov, P. M.
;
Vlaikova, E.
;
Valkov, S.
Graphene layers were grown by chemical vapour deposition (CVD) on Si wafers covered by a SiO2 substrate layer and a Ni interlayer, and on copper and nickel foil. The obtained graphene layers were characterized by Raman spectroscopy. The films grown on SiO2/Ni substrate and Ni foil comprise mainly multilayer defect-rich graphene, while those on Cu foil exhibit the spectroscopic fingerprint of relatively defect-free single-layer graphene due to the low carbon solubility in copper and the suitably chosen substrate position in a quasi-closed volume. Optimal growth conditions and the nature of defects in the layers are discussed.
Structural and optical properties of LuVO4 single crystals
(2017-01-01)
Dimitrov, D.
;
Rafailov, P.
;
Marinova, V.
;
Babeva, T.
;
Goovaerts, E.
The synthesis of large single crystals with good optical quality which is a preliminary condition for the practical applications of these materials frequently is complicated. It is found that large LuVO4 single crystals with high optical quality are possible to be prepared using high temperature solution growth method. It is obtained by X-ray crystallographic analysis that the grown crystals possess centrosymmetric tetragonal structure with the point group symmetry D-4h and space group I41/amd (zircon-type structure). The unit cell parameters of a = 7.0236 angstrom, b = 7.0236 angstrom, c = 6.2293 angstrom, volume = 307.30(3) angstrom(3) are measured. The crystals composition as well as vanadium oxidation state were measured in order to confirm that the crystal phase is mainly LuVO4. Optical transmission and Raman Spectroscopy are further performed on LuVO4 single crystal to reveal the optical quality and structure details