•The samples of silica glass were used as hosts for implantation with Bi+2 ions.•The dose dependences of characteristic Urbach energy and width of the optical gap for direct interband transitions ...were determined and plotted.•The functional dependence of disordering effective cross-section on the ion fluence has been proved experimentally.•New optically active oxygen deficient center (ODC) was discovered in glassy silica: Bi-modified ODC.
We have studied optical properties of glassy silicon dioxide (Hongan Silica Glass Store, China) irradiated with 30 keV bismuth ions. A broadening with a low-energy shift of absorption edge was found for the samples treated with 1 × 1016 – 3 × 1017 сm–2 ion fluences. The dose dependences of characteristic Urbach energy and width of the optical gap for direct interband transitions were determined and plotted. Based on the linear-type correlation between Urbach energy and optical gap width, the D/K ratio of deformation potential constants was established as well. The constancy of the D/K ratio for silicon dioxide at different fluences of bismuth ions indicates the proportionality between the values of the optical gap and band tails length, which are associated with the static atomic disorder of SiO2 host-matrix. An explanation of the obtained regularities was given using the quasi-dynamic (thermodynamic) approach. It was postulated that structural damage caused by ion-beam treatment determines Boltzmann entropy's magnitude as a combination of system various microstates. The functional dependence of σ-parameter (disordering effective cross-section) on the ion fluence has been established and proved experimentally.
The influence of the quality of welding thin steel sheets on the physical and mechanical properties of electric steel has been studied using Lamb waves. It is shown that Lamb waves excited in the ...zero symmetric mode are an effective source of information about the state of the material both in the welded joint of the plates and in the zone of base metal not affected by thermal influences. Markers of the quality of welded joints are determined. It is established that the most informative parameters are the phase velocity of a Lamb wave and its amplitude. Based on velocity measurements, macroscopic anisotropy of the acoustic properties of the material is found. It is assumed that the origin of this anisotropy is due to residual stresses arising in the technological process of processing steel sheets. The results obtained are of interest for specialized quality control of butt joints in thin steel sheets.
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•Systematic studies of the formation of SiC layer on carbon ions-bombarded surface of Si were performed.•Amorphization of carbon substrate at low fluence of ion beam were ...detected.•Absence of the segregation of carbon impurities were observed for low fluences.•Formation of high-quality 6H-SiC films at highest fluence were detected.•Excessive carbon demonstrate tendency to formation of oxidized disordered nanostructures.
Systematic studies of the gradual fabrication by means of carbon ion-implantation of high-quality 6H-SiC layers on silicon surfaces have been carried out. The fluence of carbon ions varied from 5 × 1015 cm−2 to 1017 cm−2. Results of first-principle calculations, X-ray diffraction (XRD), and Raman spectroscopy demonstrate the amorphization of silicon substrate without any tendency to the segregation of carbon in the samples synthesized at low fluencies. The formation of a SiO2-like structure at this stage was also detected. X-ray photoelectron spectroscopy (XPS), XRD, and Raman spectroscopy demonstrate that an increase in carbon content at 1017 cm−2 fluence leads to the growth of 6H-SiC films on the surface of the amorphous silicon substrate. Atomic force microscopy (AFM) data obtained also demonstrates the decreasing of surface roughens after the formation of SiC film. XPS and Raman spectra suggest that excessive carbon content leaves the SiC matrix via the formation of an insignificant amount of partially oxidized carbon nanostructures. Optical measurements also support the claim of high-quality 6H-SiC film formation in the samples synthesized at 1017 cm−2 fluence and demonstrate the absence of any detectable contribution of nanostructures formed from excessive carbon on the optical properties of the material under study.
The ultraviolet (UV) absorption spectra were studied in UV–Vis–IR quartz glasses exposed to the rhenium ion irradiation at the energy of 30 keV. An increase in ion fluence (5 × 10
15
–5 × 10
17
cm
2
...) is found to result in a characteristic fan-shaped broadening of the optical absorption edge of glasses. The results were interpreted in the context of the generalized Urbach rule (the approximation of ion radiation induced quasi-dynamic disorder). The effective radiation disorder cross section of a glass matrix was evaluated from the dose dependence of characteristic Urbach energy. This parameter was found to vary between 1.07 × 10
–17
–1.2 × 10
–18
cm
2
with increasing fluence. The optical gap width of implanted samples was estimated via the Tautz method for allowed direct interband transitions. The relationship between the second-order deformation potential constants, revealing the correlation between the Urbach energy and the optical gap width in a SiO
2
quartz glass matrix was established using the equivalence principle of static and dynamic structural disorder.
•Nanometer silica films were synthesized by different methods and processed in hydrogen plasma.•Low-temperature luminescence excited by synchrotron radiation in VUV region was studied.•The conversion ...of hydrogen passivated emission centers was observed.•The luminescence of quantum dots was manifested in the emission spectra.
Optically active defects in modified silicon oxide films on a silicon substrate have been studied by low-temperature photoluminescence (PL) spectroscopy using excitation by synchrotron radiation in the vacuum ultraviolet region. Films of dry thermal silicon oxide obtained by treatment of stoichiometric SiO2 in hydrogen plasma, films of wet thermal silicon oxide, and films with low dielectric constant (so called "low-k" dielectrics) have been studied. Investigations of various type SiO2 films detect the PL centers, which can be conditionally divided into two groups. The first group includes intrinsic point defects, the different variants of oxygen-deficient centers (ODCs). The second group contains centers like the spatially confined excitons in silicon quantum dots (SiQDs). It is shown that SiQDs differ in spectral characteristics, are formed in different ways, due to the transformation and clustering of point defects such as E'-centers, ODC(I) and ODC(II). In this case, the size and spectral properties of quantum dots depend on the mechanism of their formation. Schemes for the conversion of these defects are proposed.
It was found that for wet films and nonstoichiometric SiOx films treated in hydrogen plasma, "metastable" centers ODC(I) and ODC(II) arise only under the action of synchrotron radiation in the region of interband or exciton absorption and then they decay because of radiative relaxation. The absence of stable ODC centers in these films is due to their clustering and the formation of SiQDs. In "low-k" mesoporous films, on the contrary, silicon quantum dots SiQDs are not formed, but ODC(I) and ODC(II) centers are clearly manifested. A scheme of electronic transitions upon indirect excitation of silicon quantum dots through exciton states of the SiO2 matrix is considered. The presented results demonstrate the possibility of controlling the optical properties of silicon thin-film structures by creating in them both oxygen-deficient point defects and quantum dots of various sizes.
In the current paper, we report the results of surface modification of cubic Y2O3 films employing carbon-ion implantation. The characterization results demonstrate the formation of a stable yttrium ...oxalate-based structure with cavities filled with carbon clusters. Theoretical simulations demonstrate that the incorporation of eighteen-atom carbon clusters into the cavities of Y2(C2O4)3 does not lead to valuable changes in the crystal structure of yttrium oxalate. X-ray diffraction and optical measurements demonstrate that the subsurface bulk area of cubic yttrium oxide remains unperturbed. The oxalate “skin” thickness with embedded carbon clusters is estimated to be approximately 10 nm. The prospective employing the method to manage optical properties and increase the biocompatibility of yttria and lanthanide oxides are discussed.
•Formation of oxalate phase on yttrium oxide surface after carbon implantation have been observed.•The presence of carbon clusters inside cavities in oxalate matrix were proposed.•Formation of carbon clusters filed oxalate “skin” does not affect optical properties of yttrium oxide bulk area.
The results of metallographic studies and laboratory comparative adhesion strength tests of the coating with the base and abrasive wear by Brinell–Havorth method of weld powder coatings on nickel ...base with a width of weld layer of 20–80 mm and a height of 3–9 mm in one pass and samples of 40Kh steel have been presented. The adhesion strength of coating with hardness of 38–42 HRC was 400–480 MPa. It has been revealed that, at a hardness of the weld layer of 58–61 HRC, the wear resistance of coatings is higher than that of 40Kh steel in normalized and the improved state by 10 and 4.6 times respectively.
Thermal destruction processes of paramagnetic GeE'-centers in two different types of GeO2 glass have been studied. By investigating the temperature dependence of the electron emission typical of ...these processes, we found that the electron energy is sensitive to the structural disorder. The obtained results obtained were interpreted within the framework of modified Perel-Karpus model for the ionization of local centers in electric field. It was found that the electron-phonon coupling for GeE'-centers is a parameter that depends on the structure. We have shown that relatively weak electron-phonon coupling and low values of internal electric field are characteristic features of glassy GeO2 with high degree of continual disorder. Thus, the structural disorder, that at least depends on the synthesis conditions, can be considered as an effective tool governing the fundamental and functional properties of the glass.
•The thermal destruction process of GeE'-centers is accompanied by electron emission.•Emission parameters sensitive to degree of structural disordering were determined.•Disorder increasing in glassy GeO2 leads to reduction of electron-phonon coupling.
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