Trivalent zirconium and hafnium ions in yttria-based transparent ceramics

Electron paramagnetic resonance spectra of transparent yttria-based ceramics with zirconium and hafnium additives contain signals with close parameters due to paramagnetic Zr3+ and Hf3+ ions, which have similar ground-state electron configurations of [Kr]4d 1 and [Xe]5d 1, respectively. © 2013 Pleiades Publishing, Ltd

Investigation of the conditions for the formation of SiCN-based coatings in arc discharge with self-heated hollow cathode

Method for low-temperature (<200°C) deposition of SiCN-based coatings in a large volume chamber (0.3 m 3 ) by decomposition of organosilicon precursor in nitrogen-argon plasma of discharge with self-heated hollow cathode and remote anode (40 cm) at pressure of ∼1 mTorr was investigated. The analysis of the composition of coatings by IR spectroscopy and the analysis of plasma composition are carried out by optical emission spectroscopy. The influence of discharge current (10-40 A) and the flow of gas mixture (5-15 sccm hexamethyldisilazane and 60 sccm Ar-N 2 mixture) on plasma composition and elemental composition of coatings was investigated. It is shown that the degree of decomposition of precursor molecules is increased with growth of the current and with increase of Ar content in the gas mixture. © 2018 Web Portal IOP. All rights reserved.The study was financially supported by the Russian Science Fund, grant No. 18-79-00233

Investigation of a new method of the organosilicon compounds activation by a low-energy electron beam for SiCN-coatings deposition

The article describes a new method of organosilicon compounds activation by low energy electron beam for SiCN coatings deposition. The composition of the beam plasma in a hexamethyldisilazane-containing gas medium was studied, and it was shown that the precursor molecules decomposition degree increases with the beam current and nonmonotonically depends on the electron beam energy. The application of a low-energy electron beam for the plasma-chemical vapor decomposition of hexamethyldisilazane and for samples heating up by electron beam to 600°C makes it possible to obtain SiCN-based coatings with a hardness up to 18 GPa and thickness ~1 μm for 1 h. © 2020 The Japan Society of Vacuum and Surface Science. All rights reserved.The study was financially supported by the Russian Science Fund, grant No. 18-79-00233

Stability of boron-doped graphene/copper interface: DFT, XPS and OSEE studies

Two different types of boron-doped graphene/copper interfaces synthesized using two different flow rates of Ar through the bubbler containing the boron source were studied. X-ray photoelectron spectra (XPS) and optically stimulated electron emission (OSEE) measurements have demonstrated that boron-doped graphene coating provides a high corrosion resistivity of Cu-substrate with the light traces of the oxidation of carbon cover. The density functional theory calculations suggest that for the case of substitutional (graphitic) boron-defect only the oxidation near boron impurity is energetically favorable and creation of the vacancies that can induce the oxidation of copper substrate is energetically unfavorable. In the case of non-graphitic boron defects oxidation of the area, a nearby impurity is metastable that not only prevent oxidation but makes boron-doped graphene. Modeling of oxygen reduction reaction demonstrates high catalytic performance of these materials.Comment: 15 pages, 8 figures, to appear in Appl. Surf. Sc

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

Surface modification of field emission cathodes made of artificial carbon-based material

While the field emission acts at the technical vacuum level conditions (10-5 Pa) and electrons emitted from cathode, the ion bombardment exists and continuously modifies the cathode surface. Using X-ray photoelectron spectroscopy (XPS) we studied the electronic structure of thin surface layer of artificial carbon-based materials (ACB) used as field emission cathodes (FEC). The research resulted in the spectra of the samples B-1300, B-1500, B-1900. After spectra processing features analysis shows the change in type of hybridization of the original material. This change is supported by three characteristic spectral features: asymmetry of the core levels spectrum lines change, the satellite structure transformation, Auger-line and modification. So the initial material had sp2 type of hybridization, the spectra show that in thin surface layer a new phase with sp3-hybridization exists and we can conclude formation of nanoclusters with diamond-phase in thin surface layer of cathode. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Structural defects induced by Fe-ion implantation in TiO2

X-ray photoelectron spectroscopy (XPS) and resonant x-ray emission spectroscopy (RXES) measurements of pellet and thin film forms of TiO$_2$ with implanted Fe ions are presented and discussed. The findings indicate that Fe-implantation in a TiO$_2$ pellet sample induces heterovalent cation substitution (Fe$^{2+}\rightarrow$ Ti$^{4+}$) beneath the surface region. But in thin film samples, the clustering of Fe atoms is primarily detected. In addition to this, significant amounts of secondary phases of Fe$^{3+}$ are detected on the surface of all doped samples due to oxygen exposure. These experimental findings are compared with density functional theory (DFT) calculations of formation energies for different configurations of structural defects in the implanted TiO$_2$:Fe system. According to our calculations, the clustering of Fe-atoms in TiO$_2$:Fe thin films can be attributed to the formation of combined substitutional and interstitial defects. Further, the differences due to Fe doping in pellet and thin film samples can ultimately be attributed to different surface to volume ratios.Comment: 7+ pages, 3 Figure, to appear in J. Appl. Phy