Papers by Keyword: XPS

Abstract: The present communication focuses on the bilayer graphene formation on a Ge doped 4H-SiC surface. The 4H-SiC epilayer was grown by CVD with Germane (GeH₄) as the dopant precursor. This easily leads to the formation of Ge islands as well as graphene on the 4H-SiC surface. The Ge island decorated surface was studied by Raman spectroscopy, XPS, and TEM. It was found that the bilayer graphene is free standing and that the native oxides act as a buffer layer on the surface, covering the Ge islands. The intensity variations of the Ge component in the XPS spectra indicate that Ge atoms can be buried in the SiC surface. The TEM analysis revealed that the graphene layers are in the form of flakes, which can also be rived vertically with the support of the Ge islands on SiC surface.

Abstract: Large area film deposition was performed by means of multitarget reactive magnetron sputtering from metallic targets (Pb, Ti, Zr) with a diameter of 200 mm onto Cu-coated Kapton® HN substrates. High-power pulse sputtering has been employed for the Zr-target (or alternatively for the Ti-target). Film composition profiles were evaluated by XPS and RBS. Piezoelectric properties were investigated by PFM.

Abstract: A nanocomposite TiAlBN (n-TiAlBN) coating has been successfully deposited via RF magnetron sputtering by varying the nitrogen-to-total gas flow ratio (R_N) at a substrate temperature of 300 °C. The coating was deposited on AISI 316 substrates using a single Ti-Al-BN hot-pressed target. The crystal phases, grain size and chemical composition of the coatings were measured using the glancing angle X-ray diffraction analysis (GAXRD) and X-ray photoelectron spectroscopy (XPS). The grains size of the n-TiAlBN coating was found to be within the range of 3.5 to 5.7 nm calculated using Scherrer’s formula. The n-TiAlBN coating reached a nitride saturated state at a higher R_N (e.g >15%) with the amount of boron concentration to be around 9 at. %. Further, reducing the R_N (e.g. 5%) has increased the boron concentration to 16.17 at. %. This paper shows that by carefully control the nitrogen-to-total gas flow ratio (R_N) in the n-TiAlBN coating, it indeed gives a significant effect on its crystallographic structure, grain size, and chemical compositions.

Abstract: A technique is developed for fabrication of a shell from glass-metal composite based on the borate glass and aluminum alloy. The metal–glass interface was studied by the optical and atomic force microscopy, it was found the presence of a diffuse layer with thickness of about 1 micron. The diffuse layer composition was studied by the XPS.

Abstract: Cd_1-xZn_xS thin films were grown on soda-lime glass substrates by chemical-bath deposition (CBD). The surface morphology, thickness, composition, state of the constituent elements and optical properties of the films were studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), step height measurement instrument, X-ray photoelectron spectroscopy (XPS) and spectrophotometer, respectively. The affect of annealing for the Cd_1-xZn_xS thin films was studied. The Cd_1-xZn_xS thin films had cubic crystal structure and the average transmittance was 86.8% in the visible range with the optical band gap of 2.61eV and the films thickness was about 50nm. The atomic ratio of (Cd + Zn): S increased after annealing.

Abstract: A plasma enhanced atomic layer deposition process has been demonstrated for Lanthanum oxide films using La (thd)₃ precursor and oxygen plasma. The chemical and electrical properties of La₂O₃ ultra-thin films on Si (100) substrates before and after post-annealing in N₂ ambient have been investigated. X-ray photoelectron spectroscopic revealed that interface reactions take place after annealing process which lead to oxygen insufficiency, as well as the balance band offset decreases with the increase of annealing temperature. The capacitance-voltage and current-voltage characteristics show La₂O₃ capacitors annealed at 900 °C have negligible hysteresis, smaller interface trap density in comparison with as-deposited samples, but larger flat band voltage and higher gate-leakage current density due to the appearance of oxygen vacancy in the La₂O₃ films.

Abstract: On the basis of the invariant imbedding method the equations describing energy spectra of X-ray photoelectron emission by layers of a finite thickness are presented. The analytical decisions describing angular distributions of electrons emitted by layer were received in small-angle approximation and neglect the backscattering factor. Approbation of the received decisions is executed on the basis of comparison with results of Monte-Carlo simulation. The limitations of the theory neglecting with processes of an electron elastic scattering are shown.

Abstract: In the present study, Li-B-H films contained LiBH₄ and Li₂B₁₂H₁₂ were fabricated under different hydrogen pressures (20, 70 Pa) at ambient temperature by pulsed laser deposition (PLD). The corrosion behaviors of the films were studied over a time of 1-24 h in the air at ambient temperature. Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze the formed oxidation film. The results indicated that an oxidation film with obvious cracks and holes were formed, which was composed by Li₂B₄O₇ and Li₂CO₃. The films were mainly reacted with H₂O and CO₂, so the oxidation of Li-B-H could be prevented by avoiding exposed to air.

Abstract: In the paper, there are presented XPS results of surface layer formed after electrochemical polishing of AISI 316L (EN 1.4404) stainless steel at high current density of 2000 A/dm². For the investigation, electrolyte based on orthophosphoric (H₃PO₄) and sulfuric (H₂SO₄) acids in proportions 3:2, was used. The obtained results have shown, that high current density has considerably influences the composition of passive layer formed after electrochemical treatment. The study was focused mainly on the amount of carcinogenic nickel, sensitization chromium compounds on the sixth degree of oxidation as well as the [(Cr+3.3∙Mo)/Fe] coefficient.

Abstract: Ti-containing coatings as chromate replacement were prepared on electrogalvanized steel. Zinc coatings were deposited from a weak acid chloride bath. Cr-free conversion coatings were deposited from bath composed of: TiCl₃, H₂SiF₆, H₂O₂ and oxalic acid. XPS was used to evaluate chemical composition of the coatings as a function of deposition time. Deposited coating were of conversion type. Regardless of the achieved conversion coating thickness, Zn from the substrate was always present. In the coatings were identified: Zn₂SiO₄ / Zn₄Si₂O₇(OH)₂, ZnTiO₃, ZnO, Zn (OH)₂, Zn⁰, SiOx and Ti-O-Si in varying proportions. The chemical composition of the outer surface of the coating depended on deposition time, e.g. in a time interval 0-300 s 30 fold increase of the Si:Ti ratio and 20 fold of the Si:Zn ratio were observed. Estimated thickness of conversion coating was 3, 14, 35, and 100 nm for the time deposition of 1, 40, 80 and 300 s respectively. It is the proposed model for distinguishing Zn (0) phase from Zn (2+) quantitatively, based on the Zn L₃M₄₅M₄₅ spectrum. The composition of the ZnTiSi conversion coating determined its mechanical properties and corrosion resistance. Standard tests carried out showed that the coatings obtained at the time of 20-40 s had the best corrosion performance and mechanical resistance