MCBÜ Açıkerişim Sistemi :: Browsing by Author "Can N."

Browsing by Author "Can N."

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Luminescence of levitated Zr-Ba-La-Al-Na fluoride glass
(1997) Yang B.; Townsend P.; Can N.
Radioluminescence, cathodoluminescence, and thermoluminescence of Zr-Ba-La-Al-Na (ZBLAN) fluoride glass reveal different aspects of the intrinsic imperfections and impurities which control the emission. Except for weak low-temperature thermoluminescence signals which could be attributed to rare-earth impurities, the majority of the emission bands were common to all samples. These are considered to arise from intrinsic electron-hole recombination processes, either during relaxed exciton emission or at intrinsic defect sites in the glass network. Deconvolution of the spectra indicates that six emission bands occur in all the samples. Production of crystallite inclusions or intrinsic defects enhance the signal intensities. The luminescence is shown to be a useful probe of the quality of the ZBLAN glass, both in the preform stage, and after fiber drawing, even when working with the very high grade material produced by gas film levitation growth. © 1997 The American Physical Society.
Comparisons of tin depth profile analyses in float glass
(Elsevier, 1998) Townsend P.D.; Can N.; Chandler P.J.; Farmery B.W.; Lopez-Heredero R.; Peto A.; Salvin L.; Underdown D.; Yang B.
Data are presented showing the profile of tin diffusion during the production of float glass, by measuring non-destructively the refractive index profiles in the diffused layer. The optical waveguide modes give unequivocal evidence for an anomaly in the tin depth distribution. The results are compared with those from sectioning techniques, used in depth profiles determined by ion beam analyses and cathodoluminescence (CL). There is agreement between these methods which confirm the presence of a maximum in the tin concentration below the surface which had been in contact with the tin bath (this had been linked by Mössbauer data to a rise in the Sn4+ concentration). The ion beam analyses record different depth profiles for Si, Na and Ca. The Sn4+ feature increases the refractive index, as does the diffusion of Sn2+. The index becomes constant at large tin concentrations. We suggest that Sn4+ is linked to CL emission at 2.68 eV and Sn2+ to the 1.97 eV CL emission. Iron impurities give a 1.73 eV signal. Contrary to earlier suggestions, we propose that the luminescence associated with the presence of tin arises from intrinsic defects stabilised by the tin, not from tin acting directly as a luminescence site. © 1998 Elsevier Science B.V.
Radioluminescence and thermoluminescence of rare earth element and phosphorus-doped zircon
(Mineralogical Society of America, 2000) Karali T.; Can N.; Townsend P.D.; Rowlands A.P.; Hanchar J.M.
The radioluminescence and thermoluminescence spectra of synthetic zircon crystals doped with individual trivalent rare earth element (REE) ions (Pr, Sm, Eu, Gd, Dy, Ho Er, and Yb) and P are reported in the temperature range 25 to 673 K. Although there is some intrinsic UV/blue emission from the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the REE3+ states. The shapes of the glow curves are different for each dopant, and there are distinct differences between glow peak temperatures for different rare-earth lines of the same element. Within the overall set of signals there are indications of linear trends in which some glow peak temperatures vary as a function of the ionic size of the rare earth ions. The temperature shifts of the peaks are considerable, up to 200°, and much larger than those cited in other rare-earth-doped crystals of LaF3 and Bi4Ge3O12. The data clearly suggest that the rare-earth ions are active both in the trapping and luminescence steps, and hence the TL occurs within localized defect complexes that include REE3+ ions.
Luminescence from copper nanoparticles
(2001) Townsend P.D.; Brooks R.; Hole D.E.; Wu Z.; Turkler A.; Can N.; Suarez-Garcia A.; Gonzalo J.
The presence of copper nanoparticles in alumina and silica modifies their luminescence, and the changes in spectra are influenced by variations in the nanoparticle size distributions. Luminescence signals are sensitive to the total defect population. Thus the luminescence not only reflects changes caused by thermal annealing, which can modify both intrinsic defects and the copper nanoparticles, but also responds to the method of preparation of thin film layers. Copper nanoparticle influence on luminescence is reported both for ion-implanted bulk silica and for copper in pulsed laser deposition within alumina. Luminescence thus potentially offers a non-destructive monitor of the layer quality, reproducibility and growth conditions, as well as the state and size of the copper nanoparticles.
Nonextensive thermostatistical approach to the thermoluminescence decay
(2004) Kayacan O.; Can N.
In this study, thermoluminescence decay is investigated within Tsallis thermostatistics (TT). We believe that this is the first attempt to handle the thermoluminescence decay process within TT. The generalized form of glow intensity vs temperature is examined and the effect of the nonextensitivity is shown for various values of the entropic index q. The results are interpreted in terms of the entropic index q and the occupied trap density n. © 2003 Elsevier B.V. All rights reserved.
Ionoluminescence of silicates for ceramic uses at cryogenic temperatures; [Ionoluminiscencia de silicatos de utilizacion en ceramica a temperaturas criogenicas]
(Sociedad Espanola de Ceramica y Vidrio, 2004) Garcia-Guinea J.; Hole D.; Finch A.; Correcher V.; Valle-Fuentes F.J.; Can N.; Townsend P.D.
Requirements on accurate physical properties need new characterization techniques for structural defects. The use of light ions such as H+ and He+ with MeV energies allows penetration to a depth of several microns in most materials producing strong luminescence to gain information on the defect structures present. Examples of ionoluminescence spectra of silicates for ceramic uses are included such as Mn2+-Fe3+ coupled pairs in quartz, Dy3+ in zircon, hatch-twinning in microcline and spontaneous strain and sodium in albite. In cryogenic thermal conditions tectosilicates display both, reorganization of Mn2+ and Fe 3+ centres plus a large enlargement of the UV-blue emissions by stress mechanisms. Nesosilicates, i.e., zircon, shows differences such as existence of REE and (Dy3+) and a selective reduction of some UV-blue peaks, e.g., at 340 and 400 nm.
A generalized method for handling first- and second-order thermal desorption and thermoluminescence
(Elsevier, 2004) Kayacan O.; Can N.
The influence of the nonextensivity on first- and second-order thermal desorption is investigated. A theoretical model for analyzing first- and second-order desorption spectra and glow curves were been presented [J. Appl. Phys. 51 (1980) 2594]. In addition, thermoluminescence decay has been recently investigated within Tsallis thermostatistics (TT). In this manner, our study considers this model and the effect of the nonextensivity is shown for various values of the entropic index q. © 2003 Elsevier B.V. All rights reserved.
Structural characterization and luminescence properties of an isonicotinic acid N-oxide Mn(II) complex
(Elsevier Ltd, 2004) Can N.; Sözerli Can S.E.; Ataç A.; Bardak F.
An isonicotinic acid N-oxide Mn(II) compound was synthesized and characterized on the basis of elemental analysis and X-ray crystallography. In the complex, Mn(II) ions are coordinated by six water molecules, and the coordination number of the Mn(II) ion is six. FTIR spectra of the compound free isonicotinic acid N-oxide (INO) have been recorded in the range 4000-400 cm -1. Cathodoluminescence (CL) spectra from the Mn(II) complex have been recorded. The luminescence data were interpreted in terms of the emission band at 480 nm. The green luminescence (∼480 nm) arises from the Mn 2+ transition 4T1 (4G) →6A1 (6S). It shows weak vibronic structure, short lifetimes less than 250 μs, and indicates that Mn 2+ is octahedrally coordinated, occupying sites with similar distortions. The lifetime and intensity of the signal is temperature dependent, and the parameters are reported for the 480 nm emission line. © 2004 Elsevier Ltd. All rights reserved.
Effect of material nonlinearity on symmetric aluminum metal-matrix laminated composite beams under a bending moment
(SAGE Publications Ltd, 2004) Sayman O.; Čllioģlu H.; Meriç C.; Can N.
In this study, an elastic-plastic stress analysis is carried out on symmetric laminated composite beams subjected to a bending moment. The composite beam is to be strain hardening. The Tsai-Hill theory is used as a yield criterion in the solution. The Bernoulli and Euler hypotheses are assumed to be valid. The beam lay-up sequences are chosen as [90°/0°]s, [30°/-30°]s,[45°/-45°] s, and [60°/-60°]s. The bending moment starting plastic yielding is found to be highest for [30°/-30°]s orientation. αx residual stress component is found to be highest at the upper and lower surfaces. However σx residual stress component becomes the highest at the elastic and plastic boundary for further expansion of the plastic region. The transverse displacement is obtained at the free end, numerically.
A simple method for calculating the number of atoms in ion implanted samples from the RBS yield
(Association for Scientific Research, 2004) Can N.; Belik H.G.
A simple method that computes the number of atoms in implanted samples from the integral of the elastic backscattering yield, using a pocket calculator, is represented. The energy dependence E2, of the Rutherford law and the screening of the nuclear charge by the electron cloud is considered. The method is based on the assumption that the stopping power is a linearly decreasing function of the energy in the range from 1.4 MeV to 2MeV. The total yield can be integrated analytically, and the number of atoms in the sample can then be ascertained by an iteration procedure that can be accomplished with a scientific pocket calculator. The results obtained are compared with the values obtained using the computer simulation code for RBS spectra RUMP.
Application of ion implantation for synthesis of copper nanoparticles in a zinc oxide matrix for obtaining new nonlinear optical materials
(2004) Stepanov A.L.; Khaibullin R.I.; Can N.; Ganeev R.A.; Ryasnyansky A.I.; Buchal C.; Uysal S.
We have obtained a layered composite material by implantation of single crystal zinc oxide (ZnO) substrates with 160-keV Cu+ ions to a dose of 1016 or 1017 cm-2. The composite was studied by linear optical absorption spectroscopy; the nonlinear optical characteristics were determined by means of Z-scanning at a laser radiation wavelength of 532 nm. The appearance of the optical plasmon resonance bands in the spectra indicated that ion implantation to the higher dose provides for the formation of copper nanoparticles in a sub-surface layer of ZnO. The new nonlinear optical material comprising metal nanoparticles in a ZnO matrix exhibits the phenomenon of self-defocusing and possesses a high nonlinear absorption coefficient (β = 2.07 × 10-3 cm/W). © 2004 MAIK "Nauka/Interperiodica".
The role of rare earth elements and Mn2+ point defects on the luminescence of bavenite
(Elsevier, 2005) Garcia-Guinea J.; Correcher V.; Quejido A.; Laiglesia A.; Can N.
Natural fibrous crystals of bavenite (Ca4Be2Al 2Si9O26(OH)2) collected in intra-granitic pegmatite bodies of Bustarviejo (Madrid, Spain) have been examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe (EMPA) and inductively coupled plasma-mass spectrometry (ICP-MS). The strong luminescence emissions of bavenite using thermoluminescence (TL), cathodoluminescence (CL) and its thermal stability have been recorded, looking for new physical properties and new phosphor or dosimetric uses. The bavenite luminescence takes place in the 5d electron shell that interacts strongly with the crystal field; the spectra bands assignment are Gd 3+ (319 nm), Sm3+ (562 and 594 nm), Dy3+ (572 nm) and Tb3+ (495 nm). A Mn2+ band at about 578 nm in Ca2+ sites is present as a broad band that overlaps with the Dy 3+, Sm3+ and Tb3+ bands. Mn2+ is a transition metal ion that has an electron configuration of 3d5 and interacts strongly with the crystal field (d → d) transition. Stability tests at different temperatures show clearly that the TL glow curves at 400 nm in both irradiated and non-irradiated bavenite samples track the typical pattern of a system produced by a continuous trap distribution. The ICP-MS analyses show concentrations of Yb = 29.7 ppm, Dy = 22.7 ppm, Sm = 9.45 ppm, Nd = 8.95 ppm and Gd = 8.15 ppm in the bavenite lattice. © 2004 Elsevier B.V. All rights reserved.
Application for Tsallis thermostatistics to half-width method used in thermoluminescence glow peaks in analysis of thermal desorption spectra
(Elsevier, 2005) Kayacan O.; Can N.; Karabulut Y.; Afsar O.
Several methods have been developed in the analysis of the thermoluminescence glow peaks, and in particular when applied to thermoluminescence (TL) dosimetry and TL dating of archaeological and geological minerals. Some of these methods are identical to those developed for the study of thermal desorption. Such a method is called half-width method where a shape factor is introduced. Recently TL decay and thermal desorption process have been studied using a nonextensive formalism, namely Tsallis thermostatistics. In the present work, we consider the half-width method because it is the easiest one to estimate the activation energy. Importantly, we give the generalized form of the activation energy for all order of kinetics. We also investigate the influence of the nonextensivity on the shape factor parameter and on the activation energy. © 2004 Elsevier B.V. All rights reserved.
Nonlinear optical absorption of ZnO doped with copper nanoparticles in the picosecond and nanosecond pulse laser field
(OSA - The Optical Society, 2005) Ryasnyansky A.; Palpant B.; Debrus S.; Ganeev R.; Stepanov A.; Can N.; Buchal C.; Uysal S.
The nonlinear absorption of nanocomposite layers based on ZnO implanted with Cu+ ions with an energy of 160 keV in implantation doses of 1016 and 1017 ions/cm2 was investigated. The values of the nonlinear absorption coefficient were measured by the Z-scan method at a wavelength of 532 nm by use of nanosecond and picosecond laser pulses. Possible optical applications of these materials are discussed. © 2005 Optical Society of America.
Optical properties and luminescence of metallic nanoclusters in ZnO:Cu
(2005) Karali T.; Can N.; Valberg L.; Stepanov A.L.; Townsend P.D.; Buchal Ch.; Ganeev R.A.; Ryasnyansky A.I.; Belik H.G.; Jessett M.L.; Ong C.
Copper nanoparticles have been formed in a zinc oxide (ZnO) substrate by Cu implantation at 160 keV. The implant layer shows amorphised behaviour as monitored by the RBS data and optical absorption indicates the surface plasmon resonance peak characteristic of copper nanoparticles. There is nonlinear optical absorption from the Cu nanoparticles. There are numerous changes in the luminescence responses which include a variety of green and yellow emission bands. During excitation there were changes in the cathodoluminescence intensity and lifetime influenced by the surface events, including some unusual features, which may be considered in terms of interactions with surface water and ice. Radioluminescence signals oscillate between the normal emission bands and the wide red line emission from free Zn. Overall ZnO is, therefore, an unexpectedly interesting host for dispersed Cu nanoparticles, not least because the optical features may be compatible with the semiconductor aspects of ZnO. © 2005 Elsevier B.V. All rights reserved.
Luminescence as a probe of phase changes in transition metal complexes
(2005) Can N.; Sozerli-Can S.E.; Townsend P.D.; Yang B.; Atac A.; Peto A.
Precise determination of phase transitions by x-ray analysis requires doses which can cause lattice damage. An alternative initial probe is feasible with radioluminescence temperature measurements, as the spectra, intensity and luminescence lifetimes can all alter discontinuously at a phase transition. The method reduces the total dose by ̃104. Sensitivity to surface contaminants is also possible, as in the case of powder analysis with X-rays. The success of the method has been demonstrated with two compounds, (a) HgI 2{NC5H4C(O)NH2} and (b) Mn(H 2O)6 (O-C6H4NO2) 2, where transitions were recorded at 120 and 230K for (a) and at 110, 145, 205 and 275K for (b). © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Spectroscopic and luminescence properties of an isonicotinic acid
(2005) Can N.; Ataç A.; Bardak F.; Sözerli Can Ş.E.
An isonicotinic acid N-oxide Zn(II) compound was characterized on the basis of elemental analysis. FTIR spectra of the compound and free isonicotinic acid N-oxide (INO) were recorded in the range 4000-400 cm-1. Cathodoluminescence (CL) spectra from the Zn(INO)2 complex were recorded. The luminescence data were interpreted in terms of the emission band at 470 nm. The green luminescence (∼ 470 nm) arises from Zn2- transition 4T1(4G) → 6A 1 (6S). It shows a weak vibronic structure, and short lifetimes less than 150 μs. The lifetime and intensity of the signal are temperature dependent, and the parameters are reported for the 470 nm emission line. © TÜİTAK.
Kinetic characterization of MgB4O7: Dy,Na thermoluminescent phosphor
(Institute of Physics Publishing, 2006) Karsu E.C.; Gökçe M.; Ege A.; Karali T.; Can N.; Prokic M.
Dosimeters of MgB4O7 doped with Dy and Na have many valuable features such as high sensitivity, tissue equivalence, low fading, non-requirement of annealing and insensitivity to light. Thermoluminescence studies of Dy and Na doped MgB4O7 samples showed that a glow emission peaked at about 195 °C. In this study, the trapping parameters associated with the main dosimetric peak, namely at 195 °C, of Dy and Na doped MgB4O7 are investigated. Isothermal luminescence decay, glow curve shape, initial rise (linear regression) and Tm - Tstop methods were used. We report the results on the kinetic behaviour and activation energy determination of the peak occurring at 195 °C with a moderate heating rate of 2 °C s-1. The average activation energies obtained by the isothermal luminescence decay method, glow curve shape method and initial rise method are calculated to be 1.03 eV, 0.95 eV and 0.89 eV, respectively. The methods mentioned above indicate that the dosimetric peak may consist of one or more second-order components. The frequency factors obtained by the three methods are 3.5 × 1010 s-1, 1.6 × 109 s-1 and 3.4 × 108 s-1, respectively. Results obtained using all these methods are compared and discussed. © 2006 IOP Publishing Ltd.
Optical properties of Cu implanted ZnO
(2006) Cetin A.; Kibar R.; Ayvacikli M.; Can N.; Buchal Ch.; Townsend P.D.; Stepanov A.L.; Karali T.; Selvi S.
Nanoparticles of Cu have been made in zinc oxide crystals by ion implantation. The Cu ions were implanted at 400 keV into the (0 0 0 1) face of a single crystal. After implantation and after post-irradiation annealing there are numerous changes in the luminescence responses which include a variety of green and yellow emission bands. Following annealing at temperatures up to 1000 °C a green luminescence near 525 nm was observed which has been associated with the isolated Cu ions. The changes between as implanted and annealed luminescence signals suggests that the implants generate clustering or nanoparticle formation of Cu but anneals dissociate them. © 2006 Elsevier B.V. All rights reserved.
TL and EPR studies of Cu, Ag and P doped Li2B4O 7 phosphor
(2006) Can N.; Karali T.; Townsend P.D.; Yildiz F.
Key characteristics of a newly prepared tissue-equivalent, highly sensitive thermoluminescence dosimeter, Li2B4O7:Cu,Ag,P, are presented. The material was developed at the Institute of Nuclear Sciences, Belgrade, in the form of sintered pellets. A new preparation procedure has greatly increased the sensitivity of the basic copper activated lithium borate and the glow curve of Li2B4O7 : Cu,Ag,P consists of a well-defined main dosimetric peak situated at about 460-465 K with a sensitivity which is about four to five times higher than that of LiF : Mg,Ti (TLD-100). The exceptionally good response features of Li2B 4O7 : Cu,Ag,P are attributed to the incorporation of Cu as a dopant. Both low and high temperature emission spectra are presented and the origins of the various emission bands are considered. Additional data are provided from electron paramagnetic resonance measurements. © 2006 IOP Publishing Ltd.

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