Computer-aided analysis of cutting processes for brittle materials

This paper is focused on 3D computer simulation of cutting processes for brittle materials and silicon wafers. Computer-aided analysis of wafer scribing and dicing is carried out with the use of the ANSYS CAE (computer-aided engineering) software, and a parametric model of the processes is created by means of the internal ANSYS APDL programming language. Different types of tool tip geometry are analyzed to obtain internal stresses, such as a four-sided pyramid with an included angle of 120° and a tool inclination angle to the normal axis of 15°. The quality of the workpieces after cutting is studied by optical microscopy to verify the FE (finite-element) model. The disruption of the material structure during scribing occurs near the scratch and propagates into the wafer or over its surface at a short range. The deformation area along the scratch looks like a ragged band, but the stress width is rather low. The theory of cutting brittle semiconductor and optical materials is developed on the basis of the advanced theory of metal turning. The fall of stress intensity along the normal on the way from the tip point to the scribe line can be predicted using the developed theory and with the verified FE model. The crystal quality and dimensions of defects are determined by the mechanics of scratching, which depends on the shape of the diamond tip, the scratching direction, the velocity of the cutting tool and applied force loads. The disunity is a rate-sensitive process, and it depends on the cutting thickness. The application of numerical techniques, such as FE analysis, to cutting problems enhances understanding and promotes the further development of existing machining technologies. © 2017 Author(s)

Luminescence of Li6Gd(BO3)3 crystals upon ultraviolet and inner-shell excitations

The paper presents the results of the study on luminescence and electronic excitations in Li6Gd(BO3)3 single crystals. The optical and luminescence spectroscopy with a sub-nanosecond time resolution upon selective photoexcitation in the energy range from 3.0 to 650 eV was used to investigate in detail the luminescence of both the Gd3+ host ions and Ce3+ impurity ions as well as the processes of energy transfer between them. The intrinsic ultraviolet emission at 3.95-3.97 eV due to Pj6→S7/28 transitions in the Gd3+ host ion and the fast luminescence at 2.8-3.0 eV due to 5d→4f1 dipole-allowed transitions in the Ce3+ impurity ion were studied upon excitations through the intracenter, charge transfer, band-to-band, and inner-shell transitions. The specificity of the energy transfer upon excitation of photoluminescence in the energy range of absorption of the inner shells of different atoms of the crystal, as well as in the energy region of the giant resonance of 4d-4f transitions was revealed. On the basis of the experimental data, the bandgap Eg=9.3 eV, the minimum energy of the 5d→4 f1 and charge transfer transitions were determined. The expected positions of the ground states of the 4fn and 4fn-15d levels of trivalent lanthanide ions as well as the 4fn+1 and 4f n5d levels of divalent ions were calculated for all the lanthanide ions in Li6Gd(BO3)3 host crystal. © 2012 Elsevier B.V. All rights reserved

Ultraviolet-visible spectroscopic characterization of lanthanum beryllate crystals doped with Er, Nd, or Pr ions

Spectroscopic characterization of lanthanum beryllate La2Be2O5 (BLO) single crystals doped with trivalent ions of Eu, Nd or Pr, was carried out in the ultraviolet-visible spectral range using synchrotron radiation spectroscopy in combination with conventional optical absorption and luminescence spectroscopy techniques. On the basis of the obtained data, the energy level diagram for these trivalent impurity ions in BLO host lattice was developed; the optical and electronic properties of the crystals were determined; the possibility of the 4f-4f, 4f-5d and charge transfer transitions was analyzed; spectroscopic properties of the lattice defects formed during the introduction of trivalent impurity ions in the BLO host lattice, were investigated. We found that the lattice defects are responsible for a wide-band photoluminescence (PL) in the energy region of 400–600 nm. The most efficient excitation of the defect photoluminescence in the energy gap of BLO occurs in broad PL excitation-bands at 270 and 240 nm. The PL intensity of defects depends on the type of impurity ion and increases in the sequence: Pr-Nd-Er. © 2016, Pleiades Publishing, Ltd

Program complex for simulation of kinetics of tunneling electron transfer in organic and inorganic systems

В настоящей работе разработан учебный программный комплекс для моделирования кинетики туннельного переноса электрона в органических и неорганических системах. В данной работе развит математический формализм и выполнено численное моделирование кинетики туннельного переноса электрона в условиях диффузионно-контролируемой подвижности дефектов. Разработанный комплекс будет внедрен в образовательный процесс для проведения практикума по курсу «Моделирование биологических процессов и систем» для студентов, изучающих биомедицинскую инженерию.The present work is devoted to development of laboratory program complex for simulation of tunneling electron transfer in organic and inorganic systems. In the present paper the mathematical formalism was developed and computational modeling of tunneling electron transfer in conditions of diffused-controlled mobility of defects was carried out. The program complex will be implemented for laboratory session of discipline «Modeling of biological processes and systems» for students studying biomedical engineering

Spectroscopic study of red-light-emitting centers in K2Al 2B2O7: Fe single crystals

We report on spectroscopic study of red-light-emitting centers in K 2Al2B2O7 (KABO) single crystals containing ca. 2 ppm of Fe3+. Owing to the low Fe3+- concentration, KABO does not show noticeable absorption due to Fe3+ d-d-transitions in the visible spectral region, but it exhibits the charge-transfer (CT) UV-absorption bands O-Fe at 4.7, 5.7 and 6.5 eV. The red photoluminescence at 1.675 eV (FWHM = 0.173 eV) is due to intracenter 4T1 (4G) → 6A1 (6S) transitions in Fe3+ ions. Because of partial overlapping of the fundamental absorption edge of the crystal, where mobile excitons are created, and a broad CT absorption band at 6.5 eV, the most intensive red emission occurs at 7 K upon excitation in the excitonic energy region. The presence of two nonequivalent Al2O7 clusters in KABO lattice provides two different types of red-light-emitting centers in the form of Fe3+ ion occupied the Al3+ tetrahedral site. Superposition of their luminescence bands determines both the spectrum and temperature dependence of red emission in KABO at T = 7-80 K: two bands with the ratio of intensities of ca. 2:1 are 20 meV-shifted relative to each other; two-stage thermal quenching obeys the Mott law with ET = 9 and 20 meV. © 2013 Elsevier B.V. All rights reserved

Optical and photoelectron spectroscopy studies of KPb2Cl 5 and RbPb2Cl5 laser crystals

The paper presents the results of experimental study of electronic structure of RbPb2Cl5 and KPb2Cl5 laser crystals performed by the optical and photoelectron spectroscopy methods. On the basis of the optical absorption and low-temperature reflection spectra of these crystals we have determined the energy positions of the edges of the low-energy tail of the host absorption, the positions of the first excitonic absorption peaks, and exciton binding energies. The bandgap widths of these crystals at 8 K were estimated as Eg = 4.83 and 4.79 eV, respectively. Qualitative and quantitative analysis of RbPb2Cl 5 and KPb2Cl5 crystals were made on the basis of the core states photoelectron spectra. The elemental composition of the (0 0 1) surfaces of the crystals, the chemical state of the host atoms, the electronic structure of the valence band of the crystals were discussed on the basis on the spectroscopic data. © 2012 Elsevier B.V. All rights reserved

Radiation-stimulated processes in SrMgF4 single crystals irradiated with fast electrons

Large single crystals of SrMgF4 (SMF), grown by the Bridgman method, were studied (T = 7–350 K, E = 1.2–6.2 eV) for both the pristine unirradiated and irradiated by an electron-beam (Ee = 10 MeV, D = 100–160 kGy, Φmax = 5 × 1015 electrons/cm2) SMF-crystals. The optical absorption spectra at different radiation doses were determined. The luminescence spectra were studied upon excitation with visible/ultraviolet light (PL), or X-ray radiation (XRL). The PL excitation (PLE) spectra under UV-radiation, the temperature dependence curves for the luminescence intensity of steady-state XRL and PL recorded monitoring emission at different energies, as well as low-temperature thermoluminescence were studied. The paper discusses the effect of electron-beam irradiation on the optical and luminescence properties of SMF crystals, the temperature dependence of the luminescence intensity and low-temperature thermoluminescence of irradiated SMF crystals. © 2021 Elsevier B.V.Nuclear Physics, NPSiberian Branch, Russian Academy of Sciences, SB RAS, (RFMEFI62119X0022)Ministry of Education and Science of the Russian Federation, Minobrnauka, (FEUZ-2020-0060)Ministry of Education and Science of the Republic of Kazakhstan, (AP08855672)Ural Federal University, UrFUFunding text 1: The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, project № FEUZ-2020-0060 ), the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant № AP08855672 ). All the crystals examined were grown in framework of the state assignment of IGM SB RAS. The X-ray excited measurements were performed at the shared research center SSTRC based on the VEPP-4—VEPP-2000 complex at Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences (Novosibirsk, Russia) using equipment supported by project RFMEFI62119X0022 . The authors are grateful to A.Yu. Sofronova and M.N. Sarychev (UrFU) for assistance with low-temperature measurements.Funding text 2: The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, project № FEUZ-2020-0060), the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant № AP08855672). All the crystals examined were grown in framework of the state assignment of IGM SB RAS. The X-ray excited measurements were performed at the shared research center SSTRC based on the VEPP-4—VEPP-2000 complex at Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences (Novosibirsk, Russia) using equipment supported by project RFMEFI62119X0022. The authors are grateful to A.Yu. Sofronova and M.N. Sarychev (UrFU) for assistance with low-temperature measurements

Optical and electronic properties of undoped La2Be2O5 single crystals in the far ultraviolet energy range

The optical and electronic properties of undoped La2Be2O5 single crystals were determined using low-temperature (T = 10 K) far ultraviolet (4.9-33 eV) synchrotron radiation spectroscopy, optical absorption spectroscopy (T = 80 and 320 K), and calculations for the dispersions of the optical functions. On the basis of the obtained data we determined the Urbach's formula parameters and the cut-off energy Ec = 5.49 eV at 80 K for the low-energy tail of the host absorption, the bandgap Eg = 6.78 eV at 10 K, the energy threshold for the creation of unrelaxed excitons Eex = 6.28 eV, and other electronic properties. © 2015 Optical Society of America

Effect of An Electron Beam Irradiation on Optical and Luminescence Properties of LiBaAlF6 Single Crystals

Paper reports the effect of a 10 keV, 110 keV and 10 MeV electron beam irradiation on optical and luminescence properties of LiBaAlF6 (LBAF) single crystals at 10, 90, and 293 K. Five absorption bands at 2.0, 3.2, 4.3, 4.9 and 5.5 eV were revealed in irradiated crystals in the energy range of 1.2–9.5 eV. Several PL emission bands (1.7–1.8, 2.2 and 2.5–3.5 eV) related to defects were found in the luminescence spectra at room temperature, while only one luminescence band at E = 2.2 eV appears at T = 90 K in LBAF crystals after a 10 MeV electron bombardment. The PL excitation spectra and time-response for these emission bands were studied at 10, 90, and 293 K. Thermoluminescence (TL) of irradiated crystals was studied in the temperature range of 90–740 K. New TL glow peaks at 166, 530 and 670 K were revealed and their parameters were determined. Temperature dependence of relative photoluminescence yield recorded monitoring emission at the 1.87 and 2.23 eV in the temperature range from 130 to 450 K, were fitted using five quenching processes related to TL glow peaks revealed in our research. Significant similarity in the manifestation of radiation-induced defects for LBAF and previously studied LiBaF3 single crystals is noted. The effect of an electron beam irradiation on optical and luminescence properties of LBAF single crystals and possible origin of the radiation defects were discussed. © 2017 Elsevier B.V.This work was partially supported by the Ministry of Education and Science of the Russian Federation (Contract No.02.A03.21.0006) (the basic part of the government mandate), the Center of Excellence "Radiation and Nuclear Technologies" (Competitiveness Enhancement Program of Ural Federal University, Russia), HASYLAB DESY (Project No.20110843), Estonian Research Council (projects IUT2-26 and PUT1081). We are grateful to Ludmila Isaenko for providing the crystals examined and Eugene Vasilchenko for recording a high-temperature TL glow curve