@misc{GomezAlvarezMoralesMendezetal., author = {Gomez-Alvarez, Miguel Angel and Morales, Carlos and M{\´e}ndez, Javier and Campo, Adolfo del and Urbanos, Fernando J. and D{\´i}az, Aar{\´o}n and Res{\´e}ndiz, Luis and Flege, Jan Ingo and Granados, Daniel and Soriano, Leonardo}, title = {A Comparative Study of the ZnO Growth on Graphene and Graphene Oxide: The Role of the Initial Oxidation State of Carbon}, series = {C - Journal of Carbon Research}, volume = {6}, journal = {C - Journal of Carbon Research}, number = {2}, issn = {2311-5629}, doi = {10.3390/c6020041}, pages = {18}, abstract = {The role of the oxidation state of carbon on the early stages of growth of metal oxides was studied for the particular case of ZnO deposition on graphene and graphene oxide on SiO2 (G/SiO2 and GO/SiO2, respectively) substrates. The growth was carried out by thermal evaporation of metallic Zn under an oxygen atmosphere at room temperature. This technique permits quasi-equilibrium conditions during the oxide growth, allowing the characterization of the fundamental interaction between ZnO and the graphene-based substrates. Although in both cases ZnO follows a Volmer-Weber growth mode controlled by nucleation at defects, the details are different. In the case of the GO/SiO2 substrate, the nucleation process acts as a bottleneck, limiting the coverage of the complete surface and allowing the growth of very large ZnO structures in comparison to G/SiO2. Moreover, by studying the Zn-LMM Auger spectra, it is shown how the initial nature of the substrate influences the composition of the ZnO deposit during the very early stages of growth in terms of Zn/O atomic ratio. These results are compared to those previously reported regarding ZnO growth on graphite and graphene on Cu (G/Cu). This comparison allows us to understand the role of different characteristics of graphene-based substrates in terms of number of defects, oxidation state, graphene support substrate and number of graphene layers.}, language = {en} } @misc{HernandezGomezPrietoMoralesetal., author = {Hern{\´a}ndez-G{\´o}mez, Cayetano and Prieto, Pilar and Morales, Carlos and Serrano, Aida and Flege, Jan Ingo and M{\´e}ndez, Javier and Garc{\´i}a-P{\´e}rez, Julia and Granados, Daniel and Soriano, Leonardo}, title = {Structural defects on graphene generated by deposition of CoO: effect of electronic coupling of graphene}, series = {Materials}, volume = {17}, journal = {Materials}, number = {13}, publisher = {MDPI AG}, address = {Basel}, issn = {1996-1944}, doi = {10.3390/ma17133293}, abstract = {Understanding the interactions in hybrid systems based on graphene and functional oxides is crucial to the applicability of graphene in real devices. Here, we present a study of the structural defects occurring on graphene during the early stages of the growth of CoO, tailored by the electronic coupling between graphene and the substrate in which it is supported: as received pristine graphene on polycrystalline copper (coupled), cleaned in ultra-high vacuum conditions to remove oxygen contamination, and graphene transferred to SiO2/Si substrates (decoupled). The CoO growth was performed at room temperature by thermal evaporation of metallic Co under a molecular oxygen atmosphere, and the early stages of the growth were investigated. On the decoupled G/SiO2/Si samples, with an initial low crystalline quality of graphene, the formation of a CoO wetting layer is observed, identifying the Stranski-Krastanov growth mode. In contrast, on coupled G/Cu samples, the Volmer-Weber growth mechanism is observed. In both sets of samples, the oxidation of graphene is low during the early stages of growth, increasing for the larger coverages. Furthermore, structural defects are developed in the graphene lattice on both substrates during the growth of CoO, which is significantly higher on decoupled G/SiO2/Si samples mainly for higher CoO coverages. When approaching the full coverage on both substrates, the CoO islands coalesce to form a continuous CoO layer with strip-like structures with diameters ranging between 70 and 150 nm.}, language = {en} }