Study of the early stages of growth of Co oxides on oxide substrates

Díaz-Fernández, D.; Méndez, Javier; Yubero, F.; Domínguez-Cañizares, G.; Gutiérrez, Alejandro; Soriano, L.

doi:10.1002/sia.5366

Cited by 12 publications

(7 citation statements)

References 24 publications

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“…Besides, three more factors can complement this explanation helping to promote the copper oxidation: 1) metal nanoclusters tend to lose electrons and ionize; [ 51 ] 2) the reducing chemical nature of copper, which tends to reduce the oxides in contact with it becoming itself oxidized; and 3) zinc 3d orbitals are completely full, which induces less reactivity with O 2 and allows the presence of metal Zn even at such high pressures, two orders of magnitude higher than for other oxides, such as Co or Ni, using the same evaporation technique. [ 52,53 ] Thus, zinc is deposited on graphene first as a metal and only becomes oxidized once the oxidation process of copper has finished since all the intercalated species have been consumed (see Figure S2b, Supporting Information). Under this description, depending on the initial amount of intercalated species and the initial state of graphene (local work function values of graphene and copper and the initial electronic coupling between them), the thicknesses of the metal zinc deposit and the copper oxide layer can vary.…”

Section: Resultsmentioning

confidence: 99%

Electronic Decoupling of Graphene from Copper Induced by Deposition of ZnO: A Complex Substrate/Graphene/Deposit/Environment Interaction

Morales

Urbanos

Campo

et al. 2020

Adv Materials Inter

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has been a turning point in the study and application of 2D materials. In this sense, the very high ballistic transport distances of the order of the micron and very large carrier mobility [2][3][4] combined with the absorption of 2.3% of visible light, [5] places graphene as an extraordinary candidate for new optoelectronic devices. On the other hand, graphene's impermeability to most gases [6] makes it also a promising candidate for ultrathin passivation coating. [7] However, this idealistic view contrasts with the reduced number of real applications to industry and/or produced mass electronic devices. Without doubt, this frustrating fact is related to the difficulty to grow large areas of non-defective graphene, but also with the complexity of the interaction of graphene with other materials (substrates, multilayer systems) and/or media (gas, liquids) in contact with it, which leads to changes of the graphene properties.Focusing on this last point, the substrate plays a very important role in the electronic properties of graphene due to the strength of the bonding between both. As Weatherup et al. summarized, [7] depending on the position of the d valence band states with respect to the Fermi level, [8] two different interactions are reported for metallic substrates. In the case of Ni, Co, Fe, or Pd, the strong hybridization between π graphene states and metal d states leads to the destruction of the linear dispersion of graphene at the K point. For weak interactions, such as Cu, Au, Ag, and Pt, this linear dispersion is preserved but charge transfer between metal and graphene normally shifts the Fermi level position, leading to doping of graphene. Moreover, for SiC (0001) a covalent bonding between the substrate and the first carbon layer also prevents good electrical properties of graphene. [9,10] In all these cases, this interaction can be modulated or suppressed by controlled intercalation of metallic atoms at high temperatures, [11,12] or even at room temperature for alkaline elements. [13,14] The formation of an oxidized layer between substrate and graphene [15,16] can also decouple graphene from substrates.Nevertheless, the last description offers again a simplified view of the problem. The majority of the experimental and This study presents experimental data of the interactions and reactions that occur during the early stages of the growth of ZnO on graphene supported on polycrystalline copper and the subsequent changes on the electronic properties of the graphene. The combination of substrate, graphene, and intercalated species (such as oxygen and water molecules) between graphene and copper due to air exposure, together to the evaporation of metallic zinc under oxygen atmosphere, induces the electronic decoupling of the graphene from copper by the formation of a nanometric layer of copper oxide. In particular, the final stage consists in the formation of a complex interface formed by ZnO/ZnO 1−x /Zn/G/Cu 2 O/Cu. The role of each actor is discussed in terms of a galvanic corrosion reaction of the met...

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Section: Resultsmentioning

confidence: 99%

Electronic Decoupling of Graphene from Copper Induced by Deposition of ZnO: A Complex Substrate/Graphene/Deposit/Environment Interaction

Morales

Urbanos

Campo

et al. 2020

Adv Materials Inter

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“…ZnO was deposited on both substrates in successive evaporations, the sample being analyzed in-situ by XPS after each step. A complete explanation of the procedure for the estimation of the amount of deposited material for each step can be found elsewhere [39,43]. Ex-situ AFM and Raman spectroscopy measurements were performed for a set of samples with different ZnO coverages, precisely those of interest for the characterization of the early stages of growth.…”

Section: Methodsmentioning

confidence: 99%

A Comparative Study of the ZnO Growth on Graphene and Graphene Oxide: The Role of the Initial Oxidation State of Carbon

Gomez-Alvarez

Morales

Méndez

et al. 2020

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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.

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“…the formation of an initial CoO wetting layer followed by the growth of CoO islands. Other studies involving CoO/oxide interfaces have also been reported [9,10,11,12]. In general, cobalt oxides grow on other oxides in the form of CoO (Co 2+ ) using reactive thermal evaporation as the growth method.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, CoO grows in a Frank van der Merwe form, i.e. layer by layer mode, on Al2O3 and MgO, whereas it grows in a Volmer-Webber manner, i,e, islands mode, on SiO2 [11].…”

Section: Introductionmentioning

confidence: 99%

Controlled ultra-thin oxidation of graphite promoted by cobalt oxides: Influence of the initial 2D CoO wetting layer

Morales

Díaz-Fernández

Mossanek

et al. 2020

Applied Surface Science

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Study of the early stages of growth of Co oxides on oxide substrates

Cited by 12 publications

References 24 publications

Electronic Decoupling of Graphene from Copper Induced by Deposition of ZnO: A Complex Substrate/Graphene/Deposit/Environment Interaction

Electronic Decoupling of Graphene from Copper Induced by Deposition of ZnO: A Complex Substrate/Graphene/Deposit/Environment Interaction

A Comparative Study of the ZnO Growth on Graphene and Graphene Oxide: The Role of the Initial Oxidation State of Carbon

Controlled ultra-thin oxidation of graphite promoted by cobalt oxides: Influence of the initial 2D CoO wetting layer

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