Atomic and electronic structure of a copper/graphene interface as prepared and 1.5 years after

We report the results of X-ray spectroscopy and Raman measurements of as-prepared graphene on a high quality copper surface and the same materials after 1.5 years under different conditions (ambient and low humidity). The obtained results were compared with density functional theory calculations of the formation energies and electronic structures of various structural defects in graphene/Cu interfaces. For evaluation of the stability of the carbon cover, we propose a two-step model. The first step is oxidation of the graphene, and the second is perforation of graphene with the removal of carbon atoms as part of the carbon dioxide molecule. Results of the modeling and experimental measurements provide evidence that graphene grown on high-quality copper substrate becomes robust and stable in time (1.5 years). However, the stability of this interface depends on the quality of the graphene and the number of native defects in the graphene and substrate. The effect of the presence of a metallic substrate with defects on the stability and electronic structure of graphene is also discussed.Comment: 18 pages, 6 figures, accepted to Appl. Surf. Sc

Protecting, copper, by, graphene, coating:, XPS, and, DFT, studies

This work is partially supported by Russian Foundation for Basic Research (grant No. 14-02-00006)

The Stability of Hybrid Perovskites with UiO-66 Metal–Organic Framework Additives with Heat, Light, and Humidity

This study is devoted to investigating the stability of metal–organic framework (MOF)-hybrid perovskites consisting of CH3NH3PbI3 (MAPbI3) and UiO-66 without a functional group and UiO-66 with different COOH, NH2,and F functional groups under external influences including heat, light, and humidity. By conducting crystallinity, optical, and X-ray photoelectron spectra (XPS) measurements after long-term aging, all of the prepared MAPbI3@UiO-66 nanocomposites (with pristine UiO-66 or UiO-66 with additional functional groups) were stable to light soaking and a relative humidity (RH) of 50%. Moreover, the UiO-66 and UiO-66-(F)4 hybrid perovskite films possessed a higher heat tolerance than the other two UiO-66 with the additional functional groups of NH2 and COOH. Tthe MAPbI3@UiO-66-(F)4 delivered the highest stability and improved optical properties after aging. This study provides a deeper understanding of the impact of the structure of hybrid MOFs on the stability of the composite films. © 2022 by the authors.Russian Foundation for Basic Research, РФФИ, (21-52-52002)Ministry of Education, MOE, (109M4074, 111L9006)Ministry of Education and Science of the Russian Federation, MinobrnaukaNational Taiwan University, NTU, (111L7818)National Science and Technology Council, NSTC, (109-2628-E-002-008-MY3, 110-2923-E-002-007-MY3, 111-2124-M-002-021, 111-2628-E-002-009, 111-2634-F-002-016, 111-2923-E-002-006-MY3)The XPS measurements were supported by Russian Foundation for Basic Research (projects No. 21-52-52002). I.S.Z. and A.I.K gratefully acknowledge the funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program). C.-C.C. is grateful for the financial support from the National Science and Technology Council (NSTC) in Taiwan (111-2634-F-002-016, 109-2628-E-002-008-MY3, 110-2923-E-002-007-MY3, 111-2923-E-002-006-MY3, 111-2628-E-002-009, 111-2124-M-002-021), the Top University Project of National Taiwan University (111L7818), and the Ministry of Education (MOE) in Taiwan (109M4074 and 111L9006)

Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation

This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications

FORMATION BIOCOMPATIBLE SURFACE OF THE TITANIUM MATERIALS BY ION IMPLANTATION

X-ray photoelectron spectroscopy (XPS) is used to study the effect of implantation of phosphorus and calcium ions on the structure and electronic structure o f the surface of the titanium samples. After ion implantation of P+ and / or Ca+ the structures are formed on the surface of the samples which has favorable effect on the biocompatibility.Работа выполнена при поддержке гранта РФФИ-Урал № 13-08-96007

The characterization of Co-nanoparticles supported on graphene

The results of density functional theory calculations and measurements using X-ray photoelectron spectroscopy of Co-nanoparticles dispersed on graphene/Cu are presented. It is found that for low cobalt thickness (0.02-0.06 nm) the Co forms islands distributed non-homogeneously which are strongly oxidized under exposure to air to form cobalt oxides. At greater thicknesses up to 2 nm the upper Co-layers are similarly oxidized whereas the lower layers contacting the graphene remain metallic. The measurements indicate a Co2+ oxidation state with no evidence of a 3+ state appearing at any Co thickness, consistent with CoO and Co[OH]2. The results show that thicker Co (2 nm) coverage induces the formation of a protective oxide layer while providing the magnetic properties of Co nanoparticles. © This journal is The Royal Society of Chemistry 20151551sciescopu