Defect studies of ZnO single crystals electrochemically doped with hydrogen

Science.gov (United States)

Čížek, J.; Žaludová, N.; Vlach, M.; Daniš, S.; Kuriplach, J.; Procházka, I.; Brauer, G.; Anwand, W.; Grambole, D.; Skorupa, W.; Gemma, R.; Kirchheim, R.; Pundt, A.

2008-03-01

Various defect studies of hydrothermally grown (0001) oriented ZnO crystals electrochemically doped with hydrogen are presented. The hydrogen content in the crystals is determined by nuclear reaction analysis and it is found that already 0.3at.% H exists in chemically bound form in the virgin ZnO crystals. A single positron lifetime of 182ps is detected in the virgin crystals and attributed to saturated positron trapping at Zn vacancies surrounded by hydrogen atoms. It is demonstrated that a very high amount of hydrogen (up to ˜30at.%) can be introduced into the crystals by electrochemical doping. More than half of this amount is chemically bound, i.e., incorporated into the ZnO crystal lattice. This drastic increase of the hydrogen concentration is of marginal impact on the measured positron lifetime, whereas a contribution of positrons annihilated by electrons belonging to O-H bonds formed in the hydrogen doped crystal is found in coincidence Doppler broadening spectra. The formation of hexagonal shape pyramids on the surface of the hydrogen doped crystals by optical microscopy is observed and discussed.

EPR study of electron bombarded alkali- and alkaline-earth halide crystal surfaces

Science.gov (United States)

Fryburg, G. C.; Lad, R. A.

1975-01-01

An EPR study of electron bombarded LiF, NaCl, KCl, CaF2 and BaF2 polycrystalline surfaces has shown that small metal particles are formed on the surfaces of the crystals. Identification was made from CESR signals. The symmetric line-shape of the signals, even at 77 K, indicated that the particles were less than 0.5 micron in diameter. Signals due to F centers were observed in LiF but not in the other halides. Implications to metal deposition are considered.

Sodium doping in ZnO crystals

Science.gov (United States)

Parmar, N. S.; Lynn, K. G.

2015-01-01

ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1-3.5) × 1017 cm-3. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a NaZn level at ˜(220-270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4-5) orders of magnitude at room temperature.

Effect of Li and NH4 doping on the crystal perfection, second harmonic generation efficiency and laser damage threshold of potassium pentaborate crystals

Science.gov (United States)

Vigneshwaran, A. N.; Kalainathan, S.; Raja, C. Ramachandra

2018-03-01

Potassium pentaborate (KB5) is an excellent nonlinear optical material especially in the UV region. In this work, Li and NH4 doped KB5 crystals were grown using slow evaporation solution growth method. The incorporation of dopant has been confirmed and analysed by Energy dispersive X-ray analysis (EDAX), Inductively coupled plasma (ICP) analysis and Raman spectroscopy. The crystalline perfection of pure and doped KB5 crystals was studied by High resolution X-ray diffraction (HRXRD) analysis. Structural grain boundaries were observed in doped crystals. Second harmonic generation was confirmed for pure and doped crystals and output values revealed the enhancement of SHG efficiency in doped crystals. Resistance against laser damage was carried out using 1064 nm Nd-YAG laser of pulse width 10 ns. The laser damage threshold value is increased in Li doped crystal and decreased in NH4 doped crystal when compared to pure KB5 crystal.

Thermoluminescence and F centers of manganese doped NaCl and NaCl-CKl crystals exposed to gamma radiation

International Nuclear Information System (INIS)

Somera, L.; Cruz Z, E.; Roman L, J.; Hernandez A, J. M.; Murrieta S, H.

2015-10-01

Alkali halides crystals doped with rare earths or transition metals have been widely studied due to the luminescence properties. In particular, NaCl and KCl single crystals present thermally stimulated luminescence (Tl) after gamma irradiation. The NaCl and the NaCl KCl mixed crystal doped with manganese (MnCl 2 ) impurity were grown by using the Czochralski method. The emission characteristic of Mn 2+ was observed at 543 nm. The crystals were exposed between 0.02 and 10 kGy gamma dose from 60 Co irradiator. Optical absorption at room temperature shows the peaked band at 452 nm corresponding to the manganese impurity. The F bands, was ascribed to the electron trapped in the anion vacancy in the lattice, were obtained at 452 nm and 455 nm belonging to NaCl:Mn and NaCl KCl:Mn, respectively. The F band increases as the doses increase and it was bleaching by the UV light at 470 nm. The glow curves of the samples show the first glow peak between 92-103 degrees C, while the second main peak was observed at 183 degrees C for the undoped NaCl and at 148 and 165 degrees C for the NaCl:Mn and NaCl-KCl:Mn, respectively. The main peak was slowly bleaching when the irradiated sample was illuminated with F (470 nm) light. Optical bleaching confirms that the F center has an important participation in the thermoluminescent response. The glow curves structure from the thermal bleaching suggests the participation of different kind of traps. Also, the kinetics parameters such as activation energy (E), frequency factor (s) and the kinetic order (b) were investigated. (Author)

Thermoluminescence and F centers of manganese doped NaCl and NaCl-CKl crystals exposed to gamma radiation

Energy Technology Data Exchange (ETDEWEB)

Somera, L.; Cruz Z, E.; Roman L, J. [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Hernandez A, J. M.; Murrieta S, H., E-mail: ecruz@nucleares.unam.mx [UNAM, Instituto de Fisica, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

2015-10-15

Alkali halides crystals doped with rare earths or transition metals have been widely studied due to the luminescence properties. In particular, NaCl and KCl single crystals present thermally stimulated luminescence (Tl) after gamma irradiation. The NaCl and the NaCl KCl mixed crystal doped with manganese (MnCl{sub 2}) impurity were grown by using the Czochralski method. The emission characteristic of Mn{sup 2+} was observed at 543 nm. The crystals were exposed between 0.02 and 10 kGy gamma dose from {sup 60}Co irradiator. Optical absorption at room temperature shows the peaked band at 452 nm corresponding to the manganese impurity. The F bands, was ascribed to the electron trapped in the anion vacancy in the lattice, were obtained at 452 nm and 455 nm belonging to NaCl:Mn and NaCl KCl:Mn, respectively. The F band increases as the doses increase and it was bleaching by the UV light at 470 nm. The glow curves of the samples show the first glow peak between 92-103 degrees C, while the second main peak was observed at 183 degrees C for the undoped NaCl and at 148 and 165 degrees C for the NaCl:Mn and NaCl-KCl:Mn, respectively. The main peak was slowly bleaching when the irradiated sample was illuminated with F (470 nm) light. Optical bleaching confirms that the F center has an important participation in the thermoluminescent response. The glow curves structure from the thermal bleaching suggests the participation of different kind of traps. Also, the kinetics parameters such as activation energy (E), frequency factor (s) and the kinetic order (b) were investigated. (Author)

Sodium doping in ZnO crystals

International Nuclear Information System (INIS)

Parmar, N. S.; Lynn, K. G.

2015-01-01

ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10 17  cm −3 . Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na Zn level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature

Growth of 4-(dimethylamino) benzaldehyde doped triglycine sulphate single crystals and its characterization

International Nuclear Information System (INIS)

Rai, Chitharanjan; Sreenivas, K.; Dharmaprakash, S.M.

2009-01-01

Single crystals of triglycine sulphate (TGS) doped with 1 mol% of 4-(dimethylamino) benzaldehyde (DB) have been grown from aqueous solution at ambient temperature by slow evaporation technique. The effect of dopant on the crystal growth and dielectric, pyroelectric and mechanical properties of TGS crystal have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. FTIR spectra were employed to confirm the presence of 4-(dimethylamino) benzaldehyde in TGS crystal, qualitatively. The dielectric permittivity has been studied as a function of temperature by cooling the sample at a rate of 1 deg. C/min. An increase in the Curie temperature T c =51 deg. C (for pure TGS, T c =48.5 deg. C) and decrease in maximum permittivity has been observed for doped TGS when compared to pure TGS crystal. Pyroelectric studies on doped TGS were carried out to determine pyroelectric coefficient. The Vickers's hardness of the doped TGS crystals along (0 1 0) face is higher than that of pure TGS crystal for the same face. Domain patterns on b-cut plates were observed using scanning electron microscope. The low dielectric constant, higher pyroelectric coefficient and higher value of hardness suggest that doped TGS crystals could be a potential material for IR detectors.

Growth of 4-(dimethylamino) benzaldehyde doped triglycine sulphate single crystals and its characterization

Science.gov (United States)

Rai, Chitharanjan; Sreenivas, K.; Dharmaprakash, S. M.

2009-11-01

Single crystals of triglycine sulphate (TGS) doped with 1 mol% of 4-(dimethylamino) benzaldehyde (DB) have been grown from aqueous solution at ambient temperature by slow evaporation technique. The effect of dopant on the crystal growth and dielectric, pyroelectric and mechanical properties of TGS crystal have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. FTIR spectra were employed to confirm the presence of 4-(dimethylamino) benzaldehyde in TGS crystal, qualitatively. The dielectric permittivity has been studied as a function of temperature by cooling the sample at a rate of 1 °C/min. An increase in the Curie temperature Tc=51 °C (for pure TGS, Tc=48.5 °C) and decrease in maximum permittivity has been observed for doped TGS when compared to pure TGS crystal. Pyroelectric studies on doped TGS were carried out to determine pyroelectric coefficient. The Vickers's hardness of the doped TGS crystals along (0 1 0) face is higher than that of pure TGS crystal for the same face. Domain patterns on b-cut plates were observed using scanning electron microscope. The low dielectric constant, higher pyroelectric coefficient and higher value of hardness suggest that doped TGS crystals could be a potential material for IR detectors.

An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

International Nuclear Information System (INIS)

Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap; Tanemura, Masaki

2016-01-01

The synthesis of large-area monolayer tungsten disulphide (WS 2 ) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS 2 crystals using tungsten hexachloride (WCl 6 ) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl 6 in ethanol was drop-casted on SiO 2 /Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS 2 crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS 2 single crystalline monolayer can be grown using the WCl 6 precursor. Our finding shows an easier and effective approach to grow WS 2 monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction

Defect-induced local variation of crystal phase transition temperature in metal-halide perovskites.

Science.gov (United States)

Dobrovolsky, Alexander; Merdasa, Aboma; Unger, Eva L; Yartsev, Arkady; Scheblykin, Ivan G

2017-06-26

Solution-processed organometal halide perovskites are hybrid crystalline semiconductors highly interesting for low-cost and efficient optoelectronics. Their properties are dependent on the crystal structure. Literature shows a variety of crystal phase transition temperatures and often a spread of the transition over tens of degrees Kelvin. We explain this inconsistency by demonstrating that the temperature of the tetragonal-to-orthorhombic phase transition in methylammonium lead triiodide depends on the concentration and nature of local defects. Phase transition in individual nanowires was studied by photoluminescence microspectroscopy and super-resolution imaging. We propose that upon cooling from 160 to 140 K, domains of the crystal containing fewer defects stay in the tetragonal phase longer than highly defected domains that readily transform to the high bandgap orthorhombic phase at higher temperatures. The existence of relatively pure tetragonal domains during the phase transition leads to drastic photoluminescence enhancement, which is inhomogeneously distributed across perovskite microcrystals.Understanding crystal phase transition in materials is of fundamental importance. Using luminescence spectroscopy and super-resolution imaging, Dobrovolsky et al. study the transition from the tetragonal to orthorhombic crystal phase in methylammonium lead triiodide nanowires at low temperature.

Radiative recombination in doped indium phosphide crystals

International Nuclear Information System (INIS)

Negreskul, V.V.; Russu, E.V.; Radautsan, S.I.; Cheban, A.G.; AN Moldavskoj SSR, Kishinev. Inst. Prikladnoj Fiziki)

1975-01-01

Photoluminiscence spectra of nondoped n-InP and their change upon doping with silicon, cadmium, zinc and copper impurities were studied. The shortest wave band at 1.41 eV is connected with radiative electron transition from a shallow donor level (probably silicon) to valent zone, while the band with maximum at 1.37 - 1.39 eV is due to radiative electron transition to an acceptor level whose energy depends upon the nature and concentration of impurity implanted. The luminescence of Light-doped p-InP crystals enables to estimate the ionization energies of acceptor levels in cadmium (Esub(a)=0.043 eV) and zinc (Esub(a)=0.027 eV). Energies of acceptor levels (0.22 and 0.40 eV) due to copper impurity are determined. Intensity of edge emission in the specimens light-doped with silicon is higher than in the nondoped n-InP crystals

Local Polar Fluctuations in Lead Halide Perovskite Crystals

Science.gov (United States)

Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.

2017-03-01

Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3 NH3 PbBr3 ) and all-inorganic (CsPbBr3 ) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3 .

Sodium doping in ZnO crystals

Energy Technology Data Exchange (ETDEWEB)

Parmar, N. S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States)

2015-01-12

ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10{sup 17 }cm{sup −3}. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na{sub Zn} level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature.

Growth of 4-(dimethylamino) benzaldehyde doped triglycine sulphate single crystals and its characterization

Energy Technology Data Exchange (ETDEWEB)

Rai, Chitharanjan, E-mail: raichitharanjan@gmail.co [Department of Physics, Mangalore University, Mangalagangotri 574 199 (India); Kalpataru First Grade Science College, Tiptur 572 202 (India); Sreenivas, K. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Dharmaprakash, S.M., E-mail: smdharma@yahoo.co [Department of Physics, Mangalore University, Mangalagangotri 574 199 (India)

2009-11-15

Single crystals of triglycine sulphate (TGS) doped with 1 mol% of 4-(dimethylamino) benzaldehyde (DB) have been grown from aqueous solution at ambient temperature by slow evaporation technique. The effect of dopant on the crystal growth and dielectric, pyroelectric and mechanical properties of TGS crystal have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. FTIR spectra were employed to confirm the presence of 4-(dimethylamino) benzaldehyde in TGS crystal, qualitatively. The dielectric permittivity has been studied as a function of temperature by cooling the sample at a rate of 1 deg. C/min. An increase in the Curie temperature T{sub c}=51 deg. C (for pure TGS, T{sub c}=48.5 deg. C) and decrease in maximum permittivity has been observed for doped TGS when compared to pure TGS crystal. Pyroelectric studies on doped TGS were carried out to determine pyroelectric coefficient. The Vickers's hardness of the doped TGS crystals along (0 1 0) face is higher than that of pure TGS crystal for the same face. Domain patterns on b-cut plates were observed using scanning electron microscope. The low dielectric constant, higher pyroelectric coefficient and higher value of hardness suggest that doped TGS crystals could be a potential material for IR detectors.

Growth and characterization of magnesium chloride and lanthanum chloride doped strontium tartrate crystals - gel method

International Nuclear Information System (INIS)

Kalaiarasi, S.; Jaikumar, D.

2014-01-01

Growth of single crystals of doped strontium tartrate by controlled diffusion of strontium chloride into the silica gel charged with tartaric acid at room temperature is narrated. In this study, we synthesized magnesium chloride (5% and 10%) doped strontium tartrate crystals and Lanthanum chloride (5%, 10% and 15%) doped strontium tartrate crystals are grown. The crystal structure of the compound crystals was confirmed by single crystal X-ray diffraction. The Fourier transform infrared spectrum of pure and doped crystals are recorded and analyzed. The UV-Vis-NIR spectrum analysis reveals that the optical study of the grown crystals. The second harmonic generation efficiency was measured by using Kurtz powder technique with Nd:YAG laser of wavelength 1064 nm. (author)

PHOTOCATALYTIC ACTIVITIES of Ag+ DOPED ZIF-8 and ZIF-L CRYSTALS

Directory of Open Access Journals (Sweden)

Berna Topuz

2016-09-01

Full Text Available Photocatalysis is expected to contribute to the solution of environmental problems such as water and air pollution in the near future. The design of photocatalysts with high electron-hole generation rates, high surface areas and high light absorption capacities is crucial in producing sustainable and cost-effective photocatalytic processes. Titania, zirconia, copper oxide, zinc oxide, iron oxide are widely used photocatalysts which have good light absorption capacities with moderate surface areas depending on the synthesis conditions. In the last decade metal organic frameworks (MOFs have been used in photocatalytic applications due to their very high surface areas up to 1000s of m2/g and adequate light absorption capacities. In this study zeolitic imidazolate framework (ZIF based MOF photocatalytsts were prepared and the effect of silver (Ag doping on the photocatalytic activity of ZIF-8 and ZIF-L crystals was investigated. Ag doped ZIF-8 and ZIF-L crystals were prepared and their activities in the photocatalytic removal of methylene blue (MB dye under UV irradiation were determined for the first time in the literature. Doped ZIF-8 and ZIF-L crystals showed better photocatalytic activities compared to the undoped crystals. 100% of MB was removed with 5 mole% Ag+ doped ZIF-8 in 40 min. The photocatalytic activity decreased beyond 5% doping level since Ag+ ions may have segregated due to a possible solid state solubility limit of Ag+ ions in the crystal lattice of ZIF-8. ZIF-L crystals possessed lower photocatalytic activities compared to ZIF-8 crystals.

High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

Science.gov (United States)

Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; Scarpulla, Michael A.

2018-05-01

Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 1016 and 1020 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 1017 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 1017/cm3 range is observed for samples quenched at 200-300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 1016 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 1018 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

Crystal and electronic structure study of Mn doped wurtzite ZnO nanoparticles

Directory of Open Access Journals (Sweden)

O.M. Ozkendir

2016-08-01

Full Text Available The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.

Tunable photonic crystals with partial bandgaps from blue phase colloidal crystals and dielectric-doped blue phases.

Science.gov (United States)

Stimulak, Mitja; Ravnik, Miha

2014-09-07

Blue phase colloidal crystals and dielectric nanoparticle/polymer doped blue phases are demonstrated to combine multiple components with different symmetries in one photonic material, creating a photonic crystal with variable and micro-controllable photonic band structure. In this composite photonic material, one contribution to the band structure is determined by the 3D periodic birefringent orientational profile of the blue phases, whereas the second contribution emerges from the regular array of the colloidal particles or from the dielectric/nanoparticle-doped defect network. Using the planewave expansion method, optical photonic bands of the blue phase I and II colloidal crystals and related nanoparticle/polymer doped blue phases are calculated, and then compared to blue phases with no particles and to face-centred-cubic and body-centred-cubic colloidal crystals in isotropic background. We find opening of local band gaps at particular points of Brillouin zone for blue phase colloidal crystals, where there were none in blue phases without particles or dopants. Particle size and filling fraction of the blue phase defect network are demonstrated as parameters that can directly tune the optical bands and local band gaps. In the blue phase I colloidal crystal with an additionally doped defect network, interestingly, we find an indirect total band gap (with the exception of one point) at the entire edge of SC irreducible zone. Finally, this work demonstrates the role of combining multiple - by symmetry - differently organised components in one photonic crystal material, which offers a novel approach towards tunable soft matter photonic materials.

Alkali metal and alkali earth metal gadolinium halide scintillators

Science.gov (United States)

Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

2016-08-02

The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

Energy Technology Data Exchange (ETDEWEB)

Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp; Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2016-02-01

The synthesis of large-area monolayer tungsten disulphide (WS{sub 2}) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS{sub 2} crystals using tungsten hexachloride (WCl{sub 6}) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl{sub 6} in ethanol was drop-casted on SiO{sub 2}/Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS{sub 2} crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS{sub 2} single crystalline monolayer can be grown using the WCl{sub 6} precursor. Our finding shows an easier and effective approach to grow WS{sub 2} monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction.

High p-Type Doping, Mobility, and Photocarrier Lifetime in Arsenic-Doped CdTe Single Crystals

Energy Technology Data Exchange (ETDEWEB)

Kuciauskas, Darius [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagaoka, Akira [Kyoto University; University of Utah; McCoy, Jedidiah [Washington State University; Scarpulla, Michael A. [University of Utah

2018-05-08

Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10^16 and 10^20 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10^17 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 10^17/cm3 range is observed for samples quenched at 200-300 degrees C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10^16 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10^18 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

Electrolytic coloration and spectral properties of hydroxyl-doped potassium chloride single crystals

International Nuclear Information System (INIS)

Gu Hongen; Wu Yanru

2011-01-01

Hydroxyl-doped potassium chloride single crystals are colored electrolytically at various temperatures and voltages using a pointed cathode and a flat anode. Characteristic OH - spectral band is observed in the absorption spectrum of uncolored single crystal. Characteristic O - , OH - , U, V 2 , V 3 , O 2- -V a + , F, R 2 and M spectral bands are observed simultaneously in absorption spectra of colored single crystals. Current-time curve for electrolytic coloration of hydroxyl-doped potassium chloride single crystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained. - Highlights: → Expanded the traditional electrolysis method. → Hydroxyl-doped potassium chloride crystals were colored electrolytically for the first time. → Useful V, F and F-aggregate color centers were produced in colored crystals. → V color centers were produced directly and F and F-aggregate color centers indirectly.

High temperature reactions between molybdenum and metal halides

International Nuclear Information System (INIS)

Boeroeczki, A.; Dobos, G.; Josepovits, V.K.; Hars, Gy.

2006-01-01

Good colour rendering properties, high intensity and efficacy are of vital importance for high-end lighting applications. These requirements can be achieved by high intensity discharge lamps doped with different metal halide additives (metal halide lamps). To improve their reliability, it is very important to understand the different failure processes of the lamps. In this paper, the corrosion reactions between different metal halides and the molybdenum electrical feed-through electrode are discussed. The reactions were studied in the feed-through of real lamps and on model samples too. X-ray photoelectron spectroscopy (XPS) was used to establish the chemical states. In case of the model samples we have also used atomic absorption spectroscopy (AAS) to measure the reaction product amounts. Based on the measurement results we were able to determine the most corrosive metal halide components and to understand the mechanism of the reactions

Photorefractive effect at 775 nm in doped lithium niobate crystals

Energy Technology Data Exchange (ETDEWEB)

Nava, G.; Minzioni, P.; Cristiani, I.; Degiorgio, V. [Department of Electrical, Computer, and Biomedical Engineering, and CNISM, University of Pavia, 27100 Pavia (Italy); Argiolas, N.; Bazzan, M.; Ciampolillo, M. V.; Pozza, G.; Sada, C. [Physics and Astronomy Departement, University of Padova, 35131 Padova (Italy)

2013-07-15

The photorefractive effect induced by 775-nm laser light on doped lithium niobate crystals is investigated by the direct observation in the far field of the transmitted-beam distortion as a function of time. Measurements performed at various Zr-doping concentrations and different light intensities show that the 775-nm light beam induces a steady-state photorefractive effect comparable to that of 532-nm light, but the observed build-up time of the photovoltaic field is longer by three-orders of magnitude. The 775-nm photorefractivity of lithium niobate crystals doped with 3 mol. % ZrO{sub 2} or with 5.5 mol. % MgO is found to be negligible.

Quasicharacteristic radiation of relativistic electrons at orientation motion in lithium halides crystals along charged planes and axes

Science.gov (United States)

Maksyuta, N. V.; Vysotskii, V. I.; Efimenko, S. V.

2016-07-01

The paper deals with the investigation of the orientation motion of relativistic electrons in charged (111) planes and charged [110] axes of lithium halides ionic crystals of LiF, LiCl, LiBr and LiI. On the basis of these investigations the spectra of quasicharacteristic radiation for the electron beams with various Lorentz-factors both in planar and axial cases have been calculated numerically.

Electrolytic coloration and spectral properties of hydroxyl-doped potassium bromide single crystals

International Nuclear Information System (INIS)

Qi, Lan; Song, Cuiying; Gu, Hongen

2013-01-01

Hydroxyl-doped potassium bromide single crystals are colored electrolytically at various temperatures and voltages by using a pointed cathode and a flat anode. The characteristic OH − spectral band is observed in absorption spectrum of uncolored single crystal. The characteristic O − , OH − , U, V 2 , O 2− −V a + , M L1 , F and M spectral bands are observed simultaneously in absorption spectra of colored single crystals. Current–time curve for electrolytic coloration of hydroxyl-doped potassium bromide single crystal and its relationship with electrolytic coloration processes are given. Production and conversion of color centers are explained. - Highlights: ► We expanded the traditional electrolysis method. ► Hydroxyl-doped potassium bromide crystals were colored electrolytically for the first time. ► Useful V, F and F-aggregate color centers were produced in colored crystals. ► V color centers were produced directly and F as well as F-aggregate color centers indirectly.

Growth and characterization of KDP crystals doped with L-aspartic acid.

Science.gov (United States)

Krishnamurthy, R; Rajasekaran, R; Samuel, Bincy Susan

2013-03-01

Potassium Dihydrogen Phosphate (KDP) doped with L-aspartic acid has been grown by solvent slow evaporation technique from a mixture of aqueous solution of KDP and 0.7% of L-aspartic acid at room temperature. The grown crystals were characterized by powder X-ray diffraction, UV-visible, FTIR analysis. The doping of aspartic acid was confirmed by FTIR spectrum. The Nonlinear optical property (SHG) of L-aspartic acid doped KDP has been confirmed. Microhardness studies were carried out on the grown crystal. Copyright © 2012 Elsevier B.V. All rights reserved.

Crystal growth and luminescence properties of Pr-doped LuLiF4 single crystal

International Nuclear Information System (INIS)

Sugiyama, Makoto; Yanagida, Takayuki; Yokota, Yuui; Kurosawa, Shunsuke; Fujimoto, Yutaka; Yoshikawa, Akira

2013-01-01

0.1, 1, and 3% Pr (with respect to Lu) doped LuLiF 4 (Pr:LuLiF 4 ) single crystals were grown by the micro-pulling-down (μ-PD) method. Transparency of the grown crystals was higher than 70% in the visible wavelength region with some absorption bands due to Pr 3+ 4f-4f transitions. Intense absorption bands related with the Pr 3+ 4f-5d transitions were observed at 190 and 215 nm. In radioluminescence spectra, Pr 3+ 5d-4f emissions were observed at 220, 240, 340, and 405 nm. In the pulse height spectra recorded under 137 Cs γ-ray excitation, the Pr 3% doped sample showed the highest light yield of 2050 photons/MeV and the scintillation decay time of it exhibited 23 and 72 ns also excited by 137 Cs γ-ray. -- Highlights: ► 0.1, 1, and 3% Pr-doped LuLiF 4 single crystals were grown by the μ-PD method. ► Pr 3+ 5d-4f emission peaks appeared at 220, 240, 340, and 405 nm ► The Pr 3%:LuLiF 4 crystal showed the highest light yield of 2050 photons/MeV

Building up an electrocatalytic activity scale of cathode materials for organic halide reductions

International Nuclear Information System (INIS)

Bellomunno, C.; Bonanomi, D.; Falciola, L.; Longhi, M.; Mussini, P.R.; Doubova, L.M.; Di Silvestro, G.

2005-01-01

A wide investigation on the electrochemical activity of four model organic bromides has been carried out in acetonitrile on nine cathodes of widely different affinity for halide anions (Pt, Zn, Hg, Sn, Bi, Pb, Au, Cu, Ag), and the electrocatalytic activities of the latter have been evaluated with respect to three possible inert reference cathode materials, i.e. glassy carbon, boron-doped diamond, and fluorinated boron-doped diamond. A general electrocatalytic activity scale for the process is proposed, with a discussion on its modulation by the configuration of the reacting molecule, and its connection with thermodynamic parameters accounting for halide adsorption

Study of the growth and pyroelectric properties of TGS crystals doped with aniline-family dipolar molecules

Science.gov (United States)

Zhang, Kecong; Song, Jiancheng; Wang, Min; Fang, Changshui; Lu, Mengkai

1987-04-01

TGS crystals doped with aniline-family dipolar molecules (aniline, 2-aminobenzoic acid, 3-aminobenzoic acid, 3-aminobenzene-sulphonic acid, 4-aminobenzenesulphonic acid and 4-nitroraniline) have been grown by the slow-cooling solution method. The influence of these dopants on the growth habits, crystal morphology pyroelectric properties, and structure parameters of TGS crystals has been systematically investigated. The effects of the domain structure of the seed crystal on the pyroelectric properties of the doped crystals have been studied. It is found that the spontaneous polarization (P), pyroelectric coefficient (lambda), and internal bias field of the doped crystals are slightly higher than those of the pure TGS, and the larger the dipole moment of the dopant molecule, the higher the P and lambda of the doped TGS crystal.

V color centers in electrolytically colored hydroxyl-doped sodium chloride crystals

International Nuclear Information System (INIS)

Gu Hongen; Song Cuiying; Han Li

2006-01-01

Hydroxyl-doped sodium chloride crystals were successfully colored electrolytically by using pointed anode and flat cathode at various temperatures and under various electric field strengths. V 2 and V 3 color centers were produced in the colored crystals. Current-time curves for the electrolytic colorations were given, and activation energy for the V 2 and V 3 color center migration was determined. Production of the V 2 and V 3 color centers and formation of current zones for the electrolytic colorations of the hydroxyl-doped sodium chloride crystals are explained

Sublimation Properties of Pentaerythritol Tetranitrate Single Crystals Doped with Its Homologs

Energy Technology Data Exchange (ETDEWEB)

Bhattacharia, Sanjoy K.; Maiti, Amitesh; Gee, Richard H.; Weeks, Brandon L.

2012-07-20

Pentaerythritol tetranitrate (PETN) is a secondary explosive used extensively in military and commercial applications. Coarsening of PETN during long-term storage changes the physical properties such as surface area and particle morphology which are important factors in initiation and performance. Doping of impurities was proposed to slow the coarsening process since impurities were shown to modify both the kinetic and thermodynamic properties. In this paper, we discuss how doping of PETN with its homologs of dipentaerythritol hexanitrate (diPEHN) and tripentaerytritol octanitrate (triPEON) affect kinetic and thermodynamic parameters. Pure and homolog doped PETN single crystals were prepared by solvent evaporation in acetone at room temperature. Doping concentrations for this study were 1000 ppm, 5000 ppm, and 10000 ppm. Activation energy and vapor pressure of pure and doped PETN single crystals were obtained from thermogravimetric analysis data.

Mobile interstitial model and mobile electron model of mechano-induced luminescence in coloured alkali halide crystals

International Nuclear Information System (INIS)

Chandra, B.P.; Singh, Seema; Ojha, Bharti; Shrivastava, R.G.

1996-01-01

A theoretical study is made on the mobile interstitial and mobile electron models of mechano-induced luminescence in coloured alkali halide crystals. Equations derived indicate that the mechanoluminescence intensity should depend on several factors like strain rate, applied stress, temperature, density of F-centres and volume of crystal. The equations also involve the efficiency and decay time of mechanoluminescence. Results of mobile interstitial and mobile electron models are compared with the experimental observations, which indicated that the latter is more suitable as compared to the former. From the temperature dependence of ML, the energy gaps between the dislocation band and ground state of F-centre is calculated which are 0.08, 0.072 and 0.09 eV for KCl, KBr and NaCl crystals, respectively. The theory predicts that the decay of ML intensity is related to the process of stress relaxation in crystals. (author). 33 refs., 5 figs., 1 tab

Scintillation properties of pure and Ca-doped ZnWO4 crystals

International Nuclear Information System (INIS)

Danevich, F.A.; Shkulkova, O.G.; Henry, S.; Kraus, H.; McGowan, R.; Mikhailik, V.B.; Telfer, J.

2008-01-01

Following the investigations of the structure and scintillation properties of Ca-doped zinc tungstate powder [phys. stat. sol. (a) 204, 730 (2007)] a single-crystal of ZnWO 4 -Ca (0.5 mol%) was grown and characterised. The relative light output, energy resolution and decay characteristics were measured for pure and Ca-doped ZnWO 4 scintillators. An increase in the light yield of ∝40% compared with the undoped crystal, and an energy resolution 9.6% ( 137 Cs) were obtained for Ca-doped ZnWO 4 . The observed improvement is attributed to the reduction of self-absorption (bleaching) of the crystal. The cause of bleaching as well as the possible contribution of scattering is discussed. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Defect formation and magnetic properties of Co-doped GaN crystal and nanowire

International Nuclear Information System (INIS)

Shi, Li-Bin; Liu, Jing-Jing; Fei, Ying

2013-01-01

Theoretical calculation based on density functional theory (DFT) and generalized gradient approximation (GGA) has been carried out in studying defect formation and magnetic properties of Co doped GaN crystal and nanowire (NW). Co does not exhibit site preference in GaN crystal. However, Co occupies preferably surface sites in GaN NW. Transition level of the defect is also investigated in GaN crystal. We also find that Co Ga (S) in NW does not produce spin polarization and Co Ga (B) produces spontaneous spin polarization. Ferromagnetic (FM) and antiferromagnetic (AFM) couplings are analyzed by six different configurations. The results show that AFM coupling is more stable than FM coupling for Co doped GaN crystal. It is also found from Co doped GaN NW calculation that the system remains FM stability for majority of the configurations. Magnetic properties in Co doped GaN crystal can be mediated by N and Ga vacancies. The FM and AFM stability can be explained by Co 3d energy level coupling

Chemical composition of cadmium selenochromite crystals doped with indium, silver and gallium

International Nuclear Information System (INIS)

Bel'skij, N.K.; Ochertyanova, L.I.; Shabunina, G.G.; Aminov, T.G.

1985-01-01

The high accuracy chemical analysis Which allows one to observe doping effect on the cadmium selenochromite crystal composition is performed. The problem on the possibility of impurity atom substitution for basic element is considered on the basis of data of atomic-absorption analysis of doped crystals. The crystals of cadmium selenochromite doped with indium by chromium to cadmium ratio are distributed into two groups and probably two types of substitution take place. At 0.08-1.5 at.% indium concentrations the Cr/Cd ratio >2. One can assume that indium preferably takes cadmium tetrahedral positions whereas at 1.5-2.5 at. % concentrations the Cr/Cd ratio =2 and cadmium is substituted for silver which does not contradict crystallochemical and physical properties of this compound. In crystals with gallium the Cr/Cd ratio <2. Gallium preferably substitutes chromium

Muonium centers in the alkali halides

International Nuclear Information System (INIS)

Baumeler, H.; Kiefl, R.F.; Keller, H.; Kuendig, W.; Odermatt, W.; Patterson, B.D.; Schneider, J.W.; Savic, I.M.

1986-01-01

Muonium centers (Mu) in single crystals and powdered alkali halides have been studied using the high-timing-resolution transverse field μSR technique. Mu has been observed and its hyperfine parameter (HF) determined in every alkali halide. For the rocksalt alkali halides, the HF parameter A μ shows a systematic dependence on the host lattice constant. A comparison of the Mu HF parameter with hydrogen ESR data suggests that the Mu center is the muonic analogue of the interstitial hydrogen H i 0 -center. The rate of Mu diffusion can be deduced from the motional narrowing of the nuclear hyperfine interaction. KBr shows two different Mu states, a low-temperature Mu I -state and a high-temperature Mu II -state. (orig.)

Superconductivity in Sm-doped CaFe2As2 single crystals

Science.gov (United States)

Dong-Yun, Chen; Bin-Bin, Ruan; Jia, Yu; Qi, Guo; Xiao-Chuan, Wang; Qing-Ge, Mu; Bo-Jin, Pan; Tong, Liu; Gen-Fu, Chen; Zhi-An, Ren

2016-06-01

In this article, the Sm-doping single crystals Ca1 - x Sm x Fe2As2 (x = 0 ˜ 0.2) were prepared by the CaAs flux method, and followed by a rapid quenching treatment after the high temperature growth. The samples were characterized by structural, resistive, and magnetic measurements. The successful Sm-substitution was revealed by the reduction of the lattice parameter c, due to the smaller ionic radius of Sm3+ than Ca2+. Superconductivity was observed in all samples with onset T c varying from 27 K to 44 K upon Sm-doping. The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples. Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x > 0.10. The doping dependences of the c-axis length and onset T c were summarized. The high-T c observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution. Project supported by the National Natural Science Foundation of China (Grant No. 11474339), the National Basic Research Program of China (Grant Nos. 2010CB923000 and 2011CBA00100), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07020100).

Yb-doped rod-type photonic crystal fibers for single-mode amplification

DEFF Research Database (Denmark)

Poli, Frederica; Passaro, Davide; Cucinotta, Annamaria

2009-01-01

The competition among the guided modes in rod-type photonic crystal fibers with a low refractive index ring in the Yb-doped core is investigated with an amplifier model to demonstrate the effective higher-order mode suppression.......The competition among the guided modes in rod-type photonic crystal fibers with a low refractive index ring in the Yb-doped core is investigated with an amplifier model to demonstrate the effective higher-order mode suppression....

Microstructural, optical and electrical properties of Cl-doped CdTe single crystals

Directory of Open Access Journals (Sweden)

Choi Hyojeong

2016-09-01

Full Text Available Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3 and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot. It was shown that Cl dopant suppressed the unwanted secondary (5 1 1 crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

Space growth studies of Ce-doped Bi12SiO20 single crystal

International Nuclear Information System (INIS)

Zhou, Y.F.; Wang, J.C.; Tang, L.A.; Pan, Z.L.; Chen, N.F.; Chen, W.C.; Huang, Y.Y.; He, W.

2004-01-01

Ce-doped Bi 12 SiO 20 (BSO) single crystal was grown on board of the Chinese Spacecraft-Shenzhou No. 3. A cylindrical crystal, 10 mm in diameter and 40 mm in length, was obtained. The morphology of crystals is significantly different for ground- and space-grown portions. The space- and ground-grown crystals have been characterized by Ce concentration distribution, X-ray rocking curve absorption spectrum and micro-Raman spectrum. The results show that the quality of Ce-doped BSO crystal grown in space is more homogeneous and more perfect than that of ground grown one

Molecular reorientation of dye doped nematic liquid crystals in the laser illumination

International Nuclear Information System (INIS)

San, S. E.; Koeysal, O.; Ecevit, F. N.

2002-01-01

In this study it is investigated how dye doped nematic liquid crystals reorient under the illumination of laser beam whose wavelength is appropriate to absorbance characteristics of the doping dye. Nematic liquid crystal E7 is used with anthraquinone dye 1% wt/wt in the preparation of the sample and this material is filled in homegenously aligned measurement cell having 15 μm thickness. Mechanism of molecular reorientation includes the absorbance effects of the energy of laser by doping dye and this reorientation causes the refractive index of the material to be changed. There are potential application possibilities of such molecular reorientation based effects in nonlinear optics such as real time holography whose basis is grating diffraction that is observed and investigated in the frame of fundamentals of molecule light interaction mechanisms. Experimental analyses allowed finding characteristic values of diffraction signals depending on physical parameters of set up for a dye doped liquid crystal system and this system provided a 20 % diffraction efficiency under the optimum circumstances

Thermopower, electrical and Hall conductivity of undoped and doped iron disilicide single crystals

Energy Technology Data Exchange (ETDEWEB)

Heinrich, A; Behr, G; Griessmann, H; Teichert, S; Lange, H

1997-07-01

The electrical transport properties of {beta}-FeSi{sub 2} single crystals have been investigated in dependence on the purity of the source material and on doping with 3d transition metals. The transport properties included are electrical conductivity, Hall conductivity and thermopower mainly in the temperature range from 4K to 300K. The single crystals have been prepared by chemical transport reaction in a closed system with iodine as transport agent. In undoped single crystals prepared with 5N Fe both electrical conductivity and thermopower depend on the composition within the homogeneity range of {beta}-FeSi{sub 2} which is explained by different intrinsic defects at the Si-rich and Fe-rich phase boundaries. In both undoped and doped single crystals impurity band conduction is observed at low temperatures but above 100K extrinsic behavior determined by shallow impurity states. The thermopower shows between 100K and 200K a significant phonon drag contribution which depends on intrinsic defects and additional doping. The Hall resistivity is considered mainly with respect to an anomalous contribution found in p-type and n-type single crystals and thin films. In addition doped single crystals show at temperatures below about 130K an hysteresis of the Hall voltage. These results make former mobility data uncertain. Comparison will be made between the transport properties of single crystals and polycrystalline material.

Impact of the organic halide salt on final perovskite composition for photovoltaic applications

KAUST Repository

Moore, David T.

2014-08-01

The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material.Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt\\'s anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films. © 2014 Author(s).

Impact of the organic halide salt on final perovskite composition for photovoltaic applications

Directory of Open Access Journals (Sweden)

David T. Moore

2014-08-01

Full Text Available The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material. Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt's anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films.

Development of alkali halide-optics for high power-IR laser

International Nuclear Information System (INIS)

Pohl, L.

1989-01-01

In this work 'Development of Alkali Halide-Optics for High Power-IR Laser' we investigated the purification of sodiumchloride-, potassiumchloride- and potassiumbromide-raw materials. We succeeded to reduce the content of impurities like Cu, Pb, V, Cr, Mn, Fe, Co and Ni in these raw materials to the lower of ppb's by a Complex-Adsorption-Method (CAM). Crystals were grown from purified substances by 'Kyropoulos' method'. Windows were cur thereof, polished and measured by FTIR-spectroscopy. Analytical data showed, that the resulting crystals were of lower quality than the raw materials. Because of this fact crystal-growing-conditions have to undergo a special improvement. Alkali halide windows from other sources on the market had been tested. (orig.) [de

A new fundamental hydrogen defect in alkali halides

International Nuclear Information System (INIS)

Morato, S.P.; Luety, F.

1978-01-01

Atom hydrogen in neutral (H 0 ) and negative (H - ) form on substitutional and interstitial lattice sites gives rise to well characterized model defects in alkali-halides (U,U 1 ,U 2 ,U 3 centers), which have been extensively investigated in the past. When studying the photo-decomposition of OH - defects, a new configuration of atomic charged hidrogen was discovered, which can be produced in large quantities in the crystal and is apparently not connected to any other impurity. This new hidrogen defect does not show any pronounced electronic absorption, but displays a single sharp local mode band (at 1114cm -1 in KCl) with a perfect isotope shift. The defect can be produced by various UV or X-ray techniques in crystais doped with OH - , Sh - or H - defects. A detailed study of its formation kinetics at low temperature shows that it is primarily formed by the reaction of a mobile CI 2 - crowdion (H-center) with hidrogen defects [pt

Water activated doping and transport in multilayered germanane crystals

International Nuclear Information System (INIS)

Young, Justin R; Johnston-Halperin, Ezekiel; Chitara, Basant; Cultrara, Nicholas D; Arguilla, Maxx Q; Jiang, Shishi; Fan, Fan; Goldberger, Joshua E

2016-01-01

The synthesis of germanane (GeH) has opened the door for covalently functionalizable 2D materials in electronics. Herein, we demonstrate that GeH can be electronically doped by incorporating stoichiometric equivalents of phosphorus dopant atoms into the CaGe 2 precursor. The electronic properties of these doped materials show significant atmospheric sensitivity, and we observe a reduction in resistance by up to three orders of magnitude when doped samples are measured in water-containing atmospheres. This variation in resistance is a result of water activation of the phosphorus dopants. Transport measurements in different contact geometries show a significant anisotropy between in-plane and out-of-plane resistances, with a much larger out-of-plane resistance. These measurements along with finite element modeling results predict that the current distribution in top-contacted crystals is restricted to only the topmost, water activated crystal layers. Taken together, these results pave the way for future electronic and optoelectronic applications utilizing group IV graphane analogues. (paper)

Measuring of nonlinearity of dye doped liquid crystals using of self phase modulation effect

International Nuclear Information System (INIS)

Abedi, M.; Jafari, A.; Tajalli, H.

2007-01-01

Self phase modulation in dye doped liquid crystals has investigated and the nonlinearity of dye doped liquid crystals is measured by this effect. The Self phase modulation effect can be used for producing optical micro rings that have many applications in photonics and laser industries.

Electrical conduction studies in ferric-doped KHSO 4 single crystals

Science.gov (United States)

Sharon, M.; Kalia, A. K.

1980-03-01

Direct-current conductivity of ferric-doped (138, 267, and 490 ppm) single crystals of KHSO 4 has been studied. The mechanism for the dc conduction process is discussed. It is observed that the ferric ion forms a (Fe 3+-two vacancies) complex and the enthaply for its formation is 0.09 ± 0.01 eV. It is proposed that each ferric ion removes two protons from each HSO 4 dimer. The conductivity plot shows the presence of intrinsic and extrinsic regions. It is proposed that in the intrinsic region the dimer of HSO -4 breaks reversibly to form a long-chain monomer-type structure. The conductivity in the KHSO 4 crystal is proposed to be controlled by the rotation of HSO -4 tetrahedra along the axis which contains no hydrogen atom. Isotherm calculation for the trivalent-doped system is applied to this crystal and the results are compared with Co 2+-doped KHSO 4 crystal. The distribution coefficient of ferric ion in the KHSO 4 single crystal is calculated to be 4.5 × 10 -1. Ferric ion causes tapering in the crystal growth habit of KHSO 4 and it is believed to be due to the presence of (Fe 3+-two vacancies) complex. The enthalpy values for the various other processes are as follows: enthalpy for the breakage of HSO -4 dimer ( Hi) = 1.28 ± 0.01 eV; enthalpy for the rotation of HSO -4 tetrahedron ( Hm) = 0.58 ± 0.01 eV.

Highly reproducible alkali metal doping system for organic crystals through enhanced diffusion of alkali metal by secondary thermal activation.

Science.gov (United States)

Lee, Jinho; Park, Chibeom; Song, Intek; Koo, Jin Young; Yoon, Taekyung; Kim, Jun Sung; Choi, Hee Cheul

2018-05-16

In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K 2 picene single crystal, while only parts of the crystal are doped and transformed into K 2 picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping.

Studies on various properties of pure and Li-doped Barium Hydrogen Phosphate (BHP) single crystals

Energy Technology Data Exchange (ETDEWEB)

Nallamuthu, D. [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216, Tamil Nadu (India); Selvarajan, P., E-mail: pselvarajanphy@yahoo.co.i [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216, Tamil Nadu (India); Freeda, T.H. [Physics Research Centre, S.T. Hindu College, Nagercoil 629002 (India)

2010-12-15

Single crystals of pure and Li-doped barium hydrogen phosphate (BHP) were grown by solution method with gel technique. Various properties of the harvested crystals were studied by carrying out single crystal and powder XRD, FTIR, TG/DTA, microhardness and dielectric studies. Atomic absorption study was carried out for Li-doped BHP crystal to check the presence of Li dopants. Unit cell dimensions and diffracting planes of the grown crystals have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Density of the grown crystals was calculated using the XRD data. Thermal stability of the samples was checked by TG/DTA studies. Mechanical and dielectric characterizations of the harvested pure and Li-doped BHP crystals reveal the mechanical strength and ferroelectric transition. The observed results are reported and discussed.

Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals

International Nuclear Information System (INIS)

Raghavan, C.M.; Sankar, R.; Mohan Kumar, R.; Jayavel, R.

2008-01-01

Effect of amino acids (L-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern

Guided mode gain competition in Yb-doped rod-type photonic crystal fibers

DEFF Research Database (Denmark)

Poli, Federica; Passaro, Davide; Cucinotta, Annamaria

2009-01-01

The gain competition among the guided modes in Yb-doped rod-type photonic crystal fibers with a low refractive index core is investigated with a spatial model to demonstrate the fiber effective single-mode behaviour.......The gain competition among the guided modes in Yb-doped rod-type photonic crystal fibers with a low refractive index core is investigated with a spatial model to demonstrate the fiber effective single-mode behaviour....

Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals.

Science.gov (United States)

Luo, Yanqi; Khoram, Parisa; Brittman, Sarah; Zhu, Zhuoying; Lai, Barry; Ong, Shyue Ping; Garnett, Erik C; Fenning, David P

2017-11-01

Optoelectronic devices based on hybrid perovskites have demonstrated outstanding performance within a few years of intense study. However, commercialization of these devices requires barriers to their development to be overcome, such as their chemical instability under operating conditions. To investigate this instability and its consequences, the electric field applied to single crystals of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) is varied, and changes are mapped in both their elemental composition and photoluminescence. Synchrotron-based nanoprobe X-ray fluorescence (nano-XRF) with 250 nm resolution reveals quasi-reversible field-assisted halide migration, with corresponding changes in photoluminescence. It is observed that higher local bromide concentration is correlated to superior optoelectronic performance in CH 3 NH 3 PbBr 3 . A lower limit on the electromigration rate is calculated from these experiments and the motion is interpreted as vacancy-mediated migration based on nudged elastic band density functional theory (DFT) simulations. The XRF mapping data provide direct evidence of field-assisted ionic migration in a model hybrid-perovskite thin single crystal, while the link with photoluminescence proves that the halide stoichiometry plays a key role in the optoelectronic properties of the perovskite. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal diffusion boron doping of single-crystal natural diamond

Energy Technology Data Exchange (ETDEWEB)

Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Wu, Henry; Morgan, Dane [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Blanchard, James P. [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Zhou, Weidong [Department of Electrical Engineering, NanoFAB Center, University of Texas at Arlington, Arlington, Texas 76019 (United States); Gong, Shaoqin [Department of Biomedical Engineering and Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2016-05-28

With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

Thermal diffusion boron doping of single-crystal natural diamond

International Nuclear Information System (INIS)

Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang; Wu, Henry; Morgan, Dane; Blanchard, James P.; Zhou, Weidong; Gong, Shaoqin

2016-01-01

With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

Microscopic Mechanism of Doping-Induced Kinetically Constrained Crystallization in Phase-Change Materials.

Science.gov (United States)

Lee, Tae Hoon; Loke, Desmond; Elliott, Stephen R

2015-10-07

A comprehensive microscopic mechanism of doping-induced kinetically constrained crystallization in phase-change materials is provided by investigating structural and dynamical dopant characteristics via ab initio molecular dynamics simulations. The information gained from this study may provide a basis for a fast screening of dopant species for electronic memory devices, or for understanding the general physics involved in the crystallization of doped glasses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermomechanical measurements of lead halide single crystals

Czech Academy of Sciences Publication Activity Database

Nitsch, Karel; Rodová, Miroslava

2002-01-01

Roč. 234, č. 2 (2002), s. 701-709 ISSN 0370-1972 R&D Projects: GA AV ČR IAA2010926 Institutional research plan: CEZ:AV0Z1010914 Keywords : PbX 2 (X=Cl, Br, I) * coefficients of linear thermal expansion * polymorphism in lead halides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2002

Local Polar Fluctuations in Lead Halide Perovskite Crystals

Energy Technology Data Exchange (ETDEWEB)

Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.

2017-03-01

Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) leadhalide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-tohead Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.

Growth and characterization of Sm3+ doped cerium oxalate single crystals

Directory of Open Access Journals (Sweden)

Minu Mary C

2016-07-01

Full Text Available Single crystals of Sm3+ doped cerium oxalate decahydrate were synthesized using single diffusion gel technique and the conditions influencing the size, morphology, nucleation density and quality of the crystals were optimized. Highly transparent single crystals of average size 3 mm × 2 mm × 1 mm with well-defined hexagonal morphology were grown during a time period of two weeks. X-ray powder diffraction analysis revealed that the grown crystals crystallize in the monoclinic system with space group P21/c as identical with the pure cerium oxalate. The various functional groups of the oxalate ligand and the water of crystallization were identified by Fourier transform infrared spectroscopy. The photoluminescence spectrum of the Sm3+ doped cerium oxalate indicated that the Sm3+ ions are optically active in the cerium oxalate matrix. The crystal has a strong and efficient orange red emission with a wavelength peak at 595 nm and hence can be effectively used for optical amplification. Microhardness measurements of the crystal revealed that they belong to the soft material category.

Characterization of pure and copper-doped iron tartrate crystals

Indian Academy of Sciences (India)

Single crystal growth of pure and copper-doped iron tartrate crystals bearing composition Cu Fe(1−) C4H4O6 · H2O, where = 0, 0.07, 0.06, 0.05, 0.04, 0.03, is achieved using gel technique. The elemental analysis has been done using energy-dispersive X-ray analysis (EDAX) spectrum. The characterization studies ...

Antimicrobial activity and second harmonic studies on organic non-centrosymmetric pure and doped ninhydrin single crystals

Science.gov (United States)

Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.

2013-03-01

In this paper, we report the successful growth of pure, Cu2+ ions and Cd2+ ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu2+ and Cd2+ ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd2+ and Cu2+ doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus.

Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

International Nuclear Information System (INIS)

Li Shang-Sheng; Li Xiao-Lei; Su Tai-Chao; Jia Xiao-Peng; Ma Hong-An; Huang Guo-Feng; Li Yong

2011-01-01

High-quality p-type boron-doped IIb diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond. (cross-disciplinary physics and related areas of science and technology)

Effects of Na and K co-doping on growth and scintillation properties of Eu:SrI_2 crystals

International Nuclear Information System (INIS)

Ito, Tomoki; Yokota, Yuui; Kurosawa, Shunsuke; Kral, Robert; Pejchal, Jan; Ohashi, Yuji; Kamada, Kei; Nikl, Martin; Yoshikawa, Akira

2016-01-01

We grew Na and K co-doped Eu:SrI_2 [Na,Eu:SrI_2 and K,Eu:SrI_2] crystals by a modified micro-pulling-down method to reveal the co-doping effects on the crystal growth and scintillation properties. The non-codoped, Na0.5%, Na1.0%, K0.5% and K1.0%,Eu:SrI_2 crystals indicated high transparency while the milky parts were generated in the Na5.0% and K5.0%,Eu:SrI_2 crystals. The light yields of Na,Eu:SrI_2 and K,Eu:SrI_2 crystals under γ-ray irradiation were decreased by the Na and K co-doping. On the other hand, there was a small change within 940–1020 ns in the decay times by the Na and K co-doping. In the light yield proportionality under γ-ray irradiation, the non-proportionality in the low energy region was improved by Na and K co-doping. - Highlights: • Na or K co-doped Eu:SrI_2crystals were grown by the modified μ-PD method. • The milky parts were generated in the Na5.0% and K5.0%,Eu:SrI_2crystals. • The light yield of Eu:SrI_2was decreased by the Na or K co-doping. • The decay times of Eu:SrI_2were almost constant by the Na or K co-doping. • The non-proportionalitywas improved in the low energy region by the K co-doping.

Potassium acceptor doping of ZnO crystals

Directory of Open Access Journals (Sweden)

Narendra S. Parmar

2015-05-01

Full Text Available ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 1016 cm−3. IR measurements show a local vibrational mode (LVM at 3226 cm−1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm−1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Potassium acceptor doping of ZnO crystals

Science.gov (United States)

Parmar, Narendra S.; Corolewski, Caleb D.; McCluskey, Matthew D.; Lynn, K. G.

2015-05-01

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ˜1 × 1016 cm-3. IR measurements show a local vibrational mode (LVM) at 3226 cm-1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O-H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm-1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Potassium acceptor doping of ZnO crystals

Energy Technology Data Exchange (ETDEWEB)

Parmar, Narendra S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States); Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States); Corolewski, Caleb D.; McCluskey, Matthew D. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

2015-05-15

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 10{sup 16} cm{sup −3}. IR measurements show a local vibrational mode (LVM) at 3226 cm{sup −1}, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm{sup −1}. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Thermal optical nonlinearity in photonic crystal fibers filled with nematic liquid crystals doped with gold nanoparticles

Science.gov (United States)

Lesiak, Piotr; Budaszewski, Daniel; Bednarska, Karolina; Wójcik, Michał; Sobotka, Piotr; Chychłowski, Miłosz; Woliński, Tomasz R.

2017-05-01

In this work we studied a newly reported class of nonlinear effects observed in 5CB liquid crystals doped with gold nanoparticles (GNPs). The size of the GNP was determined by direct TEM imaging and by X-ray scattering of the diluted NP solution. GNPs was coated by thiols with the ratio of mesogenic to n-alkyl thiols varying from 1:2 to 1:1. The research involved comparing properties of both undoped and doped 5CB (nematic LC) by infiltrating LC cell and microholes of the photonic crystal fiber (PCF) separately. In our experiment the PCF fiber type LMA-10 made by NKT Photonics as host material has been used.

Room temperature ferromagnetism in Fe-doped semiconductor ZrS2 single crystals

Science.gov (United States)

Muhammad, Zahir; Lv, Haifeng; Wu, Chuanqiang; Habib, Muhammad; Rehman, Zia ur; Khan, Rashid; Chen, Shuangming; Wu, Xiaojun; Song, Li

2018-04-01

Two dimensional (2D) layered magnetic materials have obtained much attention due to their intriguing properties with a potential application in the field of spintronics. Herein, room-temperature ferromagnetism with 0.2 emu g‑1 magnetic moment is realized in Fe-doped ZrS2 single crystals of millimeter size, in comparison with diamagnetic behaviour in ZrS2. The electron paramagnetic resonance spectroscopy reveals that 5.2wt% Fe-doping ZrS2 crystal exhibit high spin value of g-factor about 3.57 at room temperature also confirmed this evidence, due to the unpaired electrons created by doped Fe atoms. First principle static electronic and magnetic calculations further confirm the increased stability of long range ferromagnetic ordering and enhanced magnetic moment in Fe-doped ZrS2, originating from the Fe spin polarized electron near the Fermi level.

Chemical forms of 35S in KCl crystals doped with elementary 35S. Pt. 1

International Nuclear Information System (INIS)

Maddock, A.G.; Todorovsky, D.S.

1983-01-01

KCl crystals have been doped with 35 S at low chemical concentrations. Upon solution of the doped crystals in cyanide solution and analysis by the method of Kasrai and Maddock, the 35 S appears in the same chemical forms as are found for the 35 S produced in similar crystals by the (n, p) reaction. Reactions are suggested whereby these products may be produced. (orig.)

Types of defect ordering in undoped and lanthanum-doped Bi2201 single crystals

International Nuclear Information System (INIS)

Martovitsky, V. P.

2006-01-01

Undoped and lanthanum-doped Bi2201 single crystals having a perfect average structure have been comparatively studied by x-ray diffraction. The undoped Bi2201 single crystals exhibit very narrow satellite reflections; their half-width is five to six times smaller than that of Bi2212 single crystals grown by the same technique. This narrowness indicates three-dimensional defect ordering in the former crystals. The lanthanumdoped Bi2201 single crystals with x = 0.7 and T c = 8-10 K exhibit very broad satellite reflections consisting of two systems (modulations) misoriented with respect to each other. The modulation-vector components of these two modulations are found to be q 1 = 0.237b* + 0.277c* and q 2 = 0.238b* + 0.037c*. The single crystals having a perfect average structure and a homogeneous average distribution of doping lanthanum consist of 70-to 80-A-thick layers that alternate along the c axis and have two different types of modulated superlattice. The crystals having a less perfect average structure also consist of alternating layers, but they have different lanthanum concentrations. The low value of T c in the undoped Bi2201 single crystals (9.5 K) correlates with three-dimensional defect ordering in them, and an increase in T c to 33 K upon lanthanum doping can be related to a thin-layer structure of these crystals and to partial substitution of lanthanum for the bismuth positions

Anomalous doping of a molecular crystal monitored with confocal fluorescence microscopy: Terrylene in a p-terphenyl crystal

Science.gov (United States)

Białkowska, Magda; Deperasińska, Irena; Makarewicz, Artur; Kozankiewicz, Bolesław

2017-09-01

Highly terrylene doped single crystals of p-terphenyl, obtained by co-sublimation of both components, showed bright spots in the confocal fluorescence images. Polarization of the fluorescence excitation spectra, blinking and bleaching, and saturation behavior allowed us to attribute them to single molecules of terrylene anomalously embedded between two neighbor layers of the host crystal, in the (a,b) plane. Such an orientation of terrylene molecules results in much more efficient absorption and collection of the fluorescence photons than in the case of previously investigated molecules embedded in the substitution sites. The above conclusion was supported by quantum chemistry calculations. We postulate that the kind of doping considered in this work should be possible in other molecular crystals where the host molecules are organized in a herringbone pattern.

Crystal growth, optical properties, and laser operation of Yb3+-doped NYW single crystal

Science.gov (United States)

Cheng, Y.; Xu, X. D.; Yang, X. B.; Xin, Z.; Cao, D. H.; Xu, J.

2009-11-01

Laser crystal Yb3+-doped NaY(WO4)2 (Yb:NYW) with excellent quality has been grown by Czochralski technique. The rocking curves from (400) plane of as-grown Yb:NYW crystal was measured and the full-width value at half-maximum was 19.92″. The effective segregation coefficients were measured by the X-ray fluorescence method. The polarized absorption spectra and the fluorescence spectra of Yb:NYW crystal were measured at room temperature. The fluorescence decay lifetime of Yb3+ ion in NYW crystal has been investigated. The spectroscopic parameters of Yb:NYW crystal are calculated and compared with those of Yb:YAG crystal. A continuous wave output power of 3.06 W at 1031 nm was obtained with a slope efficiency of 42% by use of diode pumping.

Making and Breaking of Lead Halide Perovskites

KAUST Repository

Manser, Joseph S.

2016-02-16

A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80–150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic–inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

Effect of additionally introduced Zn and Eu dopants on the photoluminescence spectra of Er-doped GaN crystals

International Nuclear Information System (INIS)

Mezdrogina, M.M.; Krivolapchuk, V.V.; Petrov, V.N.; Rodin, S.N.; Cherenkov, A.V.

2006-01-01

It is shown that the effect of dopants on the photoluminescence spectrum depends on the conductivity type of the initial GaN crystals. The sensitizing effect of emission is observed in wurtzite p-GaN crystals doped with Er. The same effect was previously observed in such crystals doped with Eu and Zn. In n-type GaN crystals sequentially doped with Eu, Zn, and Er, the emission is observed in visible and infrared ranges of the photoluminescence spectrum [ru

2D halide perovskite-based van der Waals heterostructures: contact evaluation and performance modulation

Science.gov (United States)

Guo, Yaguang; Saidi, Wissam A.; Wang, Qian

2017-09-01

Halide perovskites and van der Waals (vdW) heterostructures are both of current interest owing to their novel properties and potential applications in nano-devices. Here, we show the great potential of 2D halide perovskite sheets (C4H9NH3)2PbX4 (X  =  Cl, Br and I) that were synthesized recently (Dou et al 2015 Science 349 1518-21) as the channel materials contacting with graphene and other 2D metallic sheets to form van der Waals heterostructures for field effect transistor (FET). Based on state-of-the-art theoretical simulations, we show that the intrinsic properties of the 2D halide perovskites are preserved in the heterojunction, which is different from the conventional contact with metal surfaces. The 2D halide perovskites form a p-type Schottky barrier (Φh) contact with graphene, where tunneling barrier exists, and a negative band bending occurs at the lateral interface. We demonstrate that the Schottky barrier can be turned from p-type to n-type by doping graphene with nitrogen atoms, and a low-Φh or an Ohmic contact can be realized by doping graphene with boron atoms or replacing graphene with other high-work-function 2D metallic sheets such as ZT-MoS2, ZT-MoSe2 and H-NbS2. This study not only predicts a 2D halide perovskite-based FETs, but also enhances the understanding of tuning Schottky barrier height in device applications.

Luminescent unit computerization to research spectral characteristics of fine film alkali halide crystal

International Nuclear Information System (INIS)

Zhalimbetov, T.; Zhabetov, A.; Moldagaliev, A.; Sarmukhanov, E.; Shunkeev, K.; Shunkeev, S.; Abdullin, K.; Tokmoldin, C.

2002-01-01

The fundamental optical absorption of ion crystals characterizes the creation of different free low energetic electronic excitation (the excitons and electron-hole pairs), but their straight registration is not possible because of incommensurable big absorption factor of alkali halide monocrystals. So to registration the spectrums of alkali halide monocrystal very fine layers are necessary. We have received fine films of Nal and KCl in system of KCl-Nal-KCl, KCl-KI-KCl on the base of universal vacuum post VUP-4, VUP-5 by thermal evaporation. A unique spectral unit has been created For this on the basic the SDL-2 complex. Complex consists of radiator, systems of condensers, monochromators MDR-12 and MDR-23, receivers of radiation, controller by unit. Connect and control of monochromators by means of IBM-compatible computer has been created. Kinematics schemes of monochromators provide consequent removing on output slot of monochromatic radiation in operating range of each diffraction lattice and indication its wavelength. The tumbling diffraction lattices is done the crossbar engines SHDR-711. For this special plate of control and block of reinforcement for crossbar engines in monochromators MDR-12 and MDR-23 are designed and constructed. Created controller of monochromators consists of double cascade preamplifier on transistors n-p-n type (815G) and logical scheme, constructed on summers and K555 series triggers. The preamplifier is used for reinforcement of signal to available amplifier on transistors KT837D. The logical scheme reduces the number of used categories of bidirectional port and enables unhooking the feeding to the windings of crossbar engine at conservation of previous combination of signals. The connection controller of monochromators is done through controller of port of computer with use the parallel interface. For installing computerized system of collection and data processing is provided marketed by means of modern object-oriented programming

Refractive Indices in Undoped and MgO-Doped Near-Stoichiometric LiTaO3 Crystals

Science.gov (United States)

Nakamura, Masaru; Higuchi, Shinji; Takekawa, Shunji; Terabe, Kazuya; Furukawa, Yasunori; Kitamura, Kenji

2002-04-01

Undoped and MgO (0.5 and 1.0-mol%)-doped near-stoichiometric LiTaO3 (SLT) crystals were grown from off-congruent Li-rich solutions (Li˜ 60 mol%) by the double-crucible Czochralski method using a continuous SLT ceramic grain charging system. Curie temperatures of the undoped and MgO (0.5 and 1.0-mol%)-doped SLT crystals are 688, 694 and 695°C, respectively. The ordinary and extraordinary refractive indices (no, ne) of these crystals were measured by the prism coupling technique in the wavelength range from 0.440 to 1.050 μm at room temperature, and the temperature-independent Sellmeier equations for each crystal were derived from the measured refractive index data. no of the SLT crystal was almost the same as that of a congruent-melt LiTaO3 (CLT) crystal, while ne of the SLT crystal was lower than that of the CLT crystal. ne was lower than no for the SLT crystal, similar to as in the case of the LiNbO3 crystal. The refractive indices of the SLT crystal, no and ne, were found to be almost independent of MgO concentration at the doping level of 0.5 and 1.0 mol%.

Nucleation and Crystal Growth of Organic-Inorganic Lead Halide Perovskites under Different Relative Humidity.

Science.gov (United States)

Gao, Hao; Bao, Chunxiong; Li, Faming; Yu, Tao; Yang, Jie; Zhu, Weidong; Zhou, Xiaoxin; Fu, Gao; Zou, Zhigang

2015-05-06

Organic-inorganic lead halide perovskite compounds are very promising materials for high-efficiency perovskite solar cells. But how to fabricate high-quality perovksite films under controlled humidity conditions is still an important issue due to their sensitivity to moisture. In this study, we investigated the influence of ambient humidity on crystallization and surface morphology of one-step spin-coated perovskite films, as well as the performance of solar cells based on these perovskite films. On the basis of experimental analyses and thin film growth theory, we conclude that the influence of ambient humidity on nucleation at spin-coating stage is quite different from that on crystal growth at annealing stage. At the spin-coating stage, high nucleation density induced by high supersaturation prefers to appear under anhydrous circumstances, resulting in layer growth and high coverage of perovskite films. But at the annealing stage, the modest supersaturation benefits formation of perovskite films with good crystallinity. The films spin-coated under low relative humidity (RH) followed by annealing under high RH show an increase of crystallinity and improved performance of devices. Therefore, a mechanism of fast nucleation followed by modest crystal growth (high supersaturation at spin-coating stage and modest supersaturation at annealing stage) is suggested in the formation of high-quality perovskite films.

Effect of additionally introduced Zn and Eu dopants on the photoluminescence spectra of Er-Doped GaN crystals

International Nuclear Information System (INIS)

Mezdrogina, M. M.; Krivolapchuk, V. V.; Petrov, V. N.; Rodin, S. N.; Cherenkov, A. V.

2006-01-01

It is shown that the effect of dopants on the photoluminescence spectrum depends on the conductivity type of the initial GaN crystals. Sensitization of emission is observed in wurtzite p-GaN crystals doped with Er. The same effect was previously observed in such crystals doped with Eu and Zn. In n-type GaN crystals sequentially doped with Eu, Zn, and Er, emission is observed in the visible (λ = 360-440 and 530-560 nm) and IR (λ = 1.54 μm) spectral regions

Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals

KAUST Repository

Peng, Wei

2017-06-28

Unintentional self-doping in semiconductors through shallow defects is detrimental to optoelectronic device performance. It adversely affects junction properties and it introduces electronic noise. This is especially acute for solution-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of (C6H5C2H4NH3)2PbI4･(CH3NH3PbI3)n-1 (n=1, 2, and 3)—over three orders of magnitude lower than those of typical three-dimensional hybrid perovskites—by analyzing their conductivity behavior. We propose that crystallization of hybrid perovskites containing large organic cations suppresses defect formation and thus favors a low self-doping level. To exemplify the benefits of this effect, we demonstrate extraordinarily high light-detectivity (1013 Jones) in (C6H5C2H4NH3)2PbI4･(CH3NH3PbI3)n-1 photoconductors due to the reduced electronic noise, which makes them particularly attractive for the detection of weak light signals. Furthermore, the low self-doping concentration reduces the equilibrium charge carrier concentration in (C6H5C2H4NH3)2PbI4･(CH3NH3PbI3)n-1, advantageous in the design of p-i-n heterojunction solar cells by optimizing band alignment and promoting carrier depletion in the intrinsic perovskite layer, thereby enhancing charge extraction.

Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals

KAUST Repository

Peng, Wei; Yin, Jun; Ho, Kang-Ting; Ouellette, Olivier; de Bastiani, Michele; Banavoth, Murali; El Tall, Omar; Shen, Chao; Miao, Xiaohe; Pan, Jun; Alarousu, Erkki; He, Jr-Hau; Ooi, Boon S.; Mohammed, Omar F.; Sargent, Edward H.; Bakr, Osman

2017-01-01

-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of (C6H5C2H4NH3)2PbI4･(CH3NH3PbI3)n-1 (n=1, 2, and 3)—over three orders

Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

OpenAIRE

Scolari, Lara; Gauza, Sebastian; Xianyu, Haiqing; Zhai, Lei; Eskildsen, Lars; Alkeskjold, Thomas Tanggaard; Wu, Shin-Tson; Bjarklev, Anders Overgaard

2009-01-01

We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability ...

Guiding and amplification properties of rod-type photonic crystal fibers with sectioned core doping

Science.gov (United States)

Selleri, S.; Poli, F.; Passaro, D.; Cucinotta, A.; Lægsgaard, J.; Broeng, J.

2009-05-01

Rod-type photonic crystal fibers are large mode area double-cladding fibers with an outer diameter of few millimeters which can provide important advantages for high-power lasers and amplifiers. Numerical studies have recently demonstrated the guidance of higher-order modes in these fibers, which can worsen the output beam quality of lasers and amplifiers. In the present analysis a sectioned core doping has been proposed for Ybdoped rod-type photonic crystal fibers, with the aim to improve the higher-order mode suppression. A full-vector modal solver based on the finite element method has been applied to properly design the low refractive index ring in the fiber core, which can provide an increase of the differential overlap between the fundamental and the higher-order mode. Then, the gain competition among the guided modes along the Yb-doped rod-type fibers has been investigated with a spatial and spectral amplifier model. Simulation results have shown the effectiveness of the sectioned core doping in worsening the higher-order mode overlap on the doped area, thus providing an effective single-mode behavior of the Yb-doped rod-type photonic crystal fibers.

HOMO-LUMO analysis of multi walled carbon nanotubes doped Tetrafluoro Phthalate crystals for nonlinear optical applications

Science.gov (United States)

Latha, B.; Kumaresan, P.; Nithiyanantham, S.; Sampathkumar, K.

2018-01-01

The MWCNTs doped Tetrafluoro Phthalate (C6H2F4O4) precious stones are constantly having higher transmission rate contrasted with immaculate Tetrafluoro Phthalate crystal. The dependability of Tetrafluoro Phthalate crystal was enhanced by doping MWCNTs.The basic, synthetic, optical, mechanical and non-direct optical properties of the doped precious crystals were dissected with the portrayal concentrates, for example, powder XRD, FT-IR, UV-Visible, Hardness and SHG estimations individually. The dopants are relied upon to substitute the carbon iotas in the Tetrafluoro Phthalate grid because of their change of valency and in addition vicinity of ionic sweep. The strength and charge delocalization of the particle were additionally concentrated on by characteristic security orbital (NBO) examination. The HOMO-LUMO energies depict the charge exchange happens inside the atom. Atomic electrostatic potential has been dissected. The SHG productivity of the immaculate and colors doped TFP crystals were additionally contemplated utilizing Nd:YAG Q-exchanged laser.

CRYSTAL-QUASICHEMICAL ANALYSIS OF DEFECT SUBSYSTEM OF DOPED PbTe: Sb CRYSTALS AND Pb-Sb-Te SOLID SOLUTIONS

Directory of Open Access Journals (Sweden)

D.M. Freik

2014-05-01

Full Text Available Within crystalquasichemical formalism models of point defects of crystals in the Pb-Sb-Te system were specified. Based on proposed crystalquasichemical formulae of antimony doped crystals PbTe:Sb amphoteric dopant effect was explained. Mechanisms of solid solution formation for РbТе-Sb2Те3: replacement of antimony ions lead sites  with the formation of cation vacancies  (I or neutral interstitial tellurium atoms  (II were examined. Dominant point defects in doped crystals PbTe:Sb and РbТе-Sb2Те3 solid solutions based on p-PbTe were defined. Dependences of concentration of dominant point defects, current carriers and Hall concentration on content of dopant compound and the initial deviation from stoichiometry in the basic matrix were calculated.

Crystal Growth Technology

Science.gov (United States)

Scheel, Hans J.; Fukuda, Tsuguo

2004-06-01

This volume deals with the technologies of crystal fabrication, of crystal machining, and of epilayer production and is the first book on industrial and scientific aspects of crystal and layer production. The major industrial crystals are treated: Si, GaAs, GaP, InP, CdTe, sapphire, oxide and halide scintillator crystals, crystals for optical, piezoelectric and microwave applications and more. Contains 29 contributions from leading crystal technologists covering the following topics: General aspects of crystal growth technology Silicon Compound semiconductors Oxides and halides Crystal machining Epitaxy and layer deposition Scientific and technological problems of production and machining of industrial crystals are discussed by top experts, most of them from the major growth industries and crystal growth centers. In addition, it will be useful for the users of crystals, for teachers and graduate students in materials sciences, in electronic and other functional materials, chemical and metallurgical engineering, micro-and optoelectronics including nanotechnology, mechanical engineering and precision-machining, microtechnology, and in solid-state sciences.

Stress-Induced Crystallization of Ge-Doped Sb Phase-Change Thin Films

NARCIS (Netherlands)

Eising, Gert; Pauza, Andrew; Kooi, Bart J.

The large effects of moderate stresses on the crystal growth rate in Ge-doped Sb phase-change thin films are demonstrated using direct optical imaging. For Ge6Sb94 and Ge7Sb93 phase-change films, a large increase in crystallization temperature is found when using a polycarbonate substrate instead of

Enhanced photorefractive properties in Hf, Ce and Cu co-doped LiNbO{sub 3} crystals for holographic application

Energy Technology Data Exchange (ETDEWEB)

Zhang, Tao, E-mail: tzhang_hit02@yahoo.com [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China); Wang, Xin; Geng, Tao; Tong, Chengguo [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Kang, Chong [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China)

2015-04-25

Graphical abstract: Correlation spots of 200 holograms in a Hf, Ce and Cu co-doped LiNbO{sub 3}. - Highlights: • Several doped LiNbO{sub 3} crystals with various level of Hf doping were grown by Cz method. • IR peak shift is attributed to the complex defect change at different level of Hf. • Enhanced photorefractive properties have been got with higher Hf-doping level. • Reduced defect and increased photoconductivity are responsible for optical properties. • 200 holograms’ experiment is realized in a coherent volume 0.073 cm{sup 3}. - Abstract: Hf, Ce and Cu co-doped LiNbO{sub 3} crystals with various level of Hf doping were grown in air by a conventional Cz method. The infrared spectra were measured to discuss the defect structures and the mechanism of the absorption peak shift in these crystals. The light-induced scattering of the crystals was evaluated by the transmitted light method. The influence of the Hf-doping level on the photorefractive properties of Hf, Ce and Cu co-doped LiNbO{sub 3} crystals was studied via two-beam coupling. It is found that proper doping Hf is an efficient method to enhance the comprehensive photorefractive properties of the LiNbO{sub 3}. Using one of these crystals as medium, 200 holograms storage and correlation experiments based on angle fractal multiplexing have been realized in a coherent volume 0.073 cm{sup 3}. Moreover the diffraction efficiency is uniform and the storage density has reached 2.2 Gb/cm{sup 3}.

Optical tuning of photonic bandgaps in dye-doped nematic liquid crystal photonic crystal fibers

DEFF Research Database (Denmark)

Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard; Hermann, David Sparre

2005-01-01

An all-optical modulator is demonstrated, which utilizes a pulsed 532 nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid crystal. In order to investigate the time response of the LCPBG fiber device, a low-power CW probe...... laser was coupled into the fiber together with the pulsed pump laser of 2.3 mW and we have demonstrated a modulation frequency of up to 2 kHz....

Improvement of several properties of lead tungstate crystals with different doping ions

CERN Document Server

Auffray, Etiennette; Baccaro, Stefania; Cecilia, Angelica; Dafinei, Ioan; Diemoz, Marcella; Jarolímek, O; Korzhik, Mikhail; Lecoq, Paul; Nikl, M

1998-01-01

A very good radiation resistance of Lead Tungstate crystals is mandatory for their use in the high precision electromagnetic calorimeter of the CMS experiment at LHC. Since the beginning of 1996 we have organised systematic investigations of the parameters influencing the radiation hardness of this crystal. Two classes of parameters have been particularly studied, the first one related to the control of the stoichiometry and structure associated defects, the second one connected with the suppression and the charge compensation of existing defects with different kinds of doping ions. This paper reports about the second part of this study and complements a first paper where the role of the stoichiometry was already discussed. Results of tests are given on a significant statistical sample of full size crystals ( 23cm) which show a considerable improvement in the optical properties and the radiation resistance of appropriately doped crystals.

Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

Directory of Open Access Journals (Sweden)

Simon A. Bretschneider

2014-04-01

Full Text Available The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We discuss the crystal and band structure of perovskite materials currently implemented in solar cells and the impact of the crystal properties on ferroelectricity, ambipolarity, and the properties of excitons.

Crystal growth and doping

International Nuclear Information System (INIS)

Paorici, C.

1980-01-01

Section 1 contains a self-consistent review of the basic growth features. After a short introduction concerning the driving force acting in a crystallization process, three main topics are broadly discussed: (i) interface kinetics; (ii) transport kinetics, and (iii) growth stability conditions. On point (i), after definition of the nature of interface, using Temkin's model, the growth mechanisms predicted by Burton, Cabrera and Frank (BCF) and bidimensional nucleation theories are fully developed. On points (ii) and (iii), the differential equations of the constitutional (concentration) and thermal fields are presented and discussed in terms of relevant approximations, suitable boundary conditions and limit values expected in order to have growth stability. Section 2 reports various experimental procedures for growing bulk crystals from the melt, from solutions and from the vapour phase. The basic concepts of Section 1 are amply employed for a critical discussion of possibilities, advantages and drawbacks of the methods described. Along the same lines, in Section 3 the principal epitaxial deposition procedures are highlighted. Section 4 contains a brief account of doping and of stoichiometry-defect control procedures. There is a long, carefully chosen list of bibliographical references. (author)

Thermally and optically stimulated radiative processes in Eu and Y co-doped LiCaAlF6 crystal

International Nuclear Information System (INIS)

Fukuda, Kentaro; Yanagida, Takayuki; Fujimoto, Yutaka

2015-01-01

Yttrium co-doping was attempted to enhance dosimeter performance of Eu doped LiCaAlF 6 crystal. Eu doped and Eu, Y co-doped LiCaAlF 6 were prepared by the micro-pulling-down technique, and their dosimeter characteristics such as optically stimulated luminescence (OSL) and thermally stimulated luminescence (TSL) were investigated. By yttrium co-doping, emission intensities of OSL and TSL were enhanced by some orders of magnitude. In contrast, scintillation characteristics of yttrium co-doped crystal such as intensity of prompt luminescence induced by X-ray and light yield under neutron irradiation were degraded

Crystallization behavior of Ge-doped eutectic Sb70Te30 films in optical disks

International Nuclear Information System (INIS)

Khulbe, Pramod K.; Hurst, Terril; Mansuripur, Masud; Horie, Michikazu

2002-01-01

We report laser-induced crystallization behavior of binary Sb-Te and ternary Ge-doped eutectic Sb70Te30 thin film samples in a typical quadrilayer stack as used in phase-change optical disk data storage. Several experiments have been conducted on a two-laser static tester in which one laser operating in pulse mode writes crystalline marks on amorphous film or amorphous marks on crystalline film, while the second laser operating at low-power cw mode simultaneously monitors the progress of the crystalline or amorphous mark formation in real time in terms of the reflectivity variation. The results of this study show that the crystallization kinetics of this class of film is strongly growth dominant, which is significantly different from the crystallization kinetics of stochiometric Ge-Sb-Te compositions. In Sb-Te and Ge-doped eutectic Sb70Te30 thin-film samples, the crystallization behavior of the two forms of amorphous states, namely, as-deposited amorphous state and melt-quenched amorphous state, remains approximately same. We have also presented experiments showing the effect of the variation of the Sb/Te ratio and Ge doping on the crystallization behavior of these films

Modified dynamical equation for dye doped nematic liquid crystals

Energy Technology Data Exchange (ETDEWEB)

Manohar, Rajiv, E-mail: rajlu1@rediffmail.co [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow 226007 (India); Misra, Abhishek Kumar; Srivastava, Abhishek Kumar [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow 226007 (India)

2010-04-15

Dye doped liquid crystals show changed dielectric properties in comparison to pure liquid crystals. These changes are strongly dependent on the concentration of dye. In the present work we have measured dielectric properties of standard nematic liquid crystals E-24 and its two guest host mixtures of different concentrations with Anthraquinone dye D5. The experimental results are fitted using linear response and in the light of this we have proposed some modifications in the dynamical equation for the nematic liquid crystals by introducing two new variables as dye concentration coefficients. The limitations of the proposed equation in high temperature range have also been discussed. With the help of the proposed dynamical equation for the guest-host liquid crystals (GHLCs) it is possible to predict the various parameters like rotational viscosity, dielectric anisotropy and relaxation time for GHLCs at other concentrations of dye in liquid crystals theoretically.

Photoluminescence characteristics of Pb-doped, molecular-beam-epitaxy grown ZnSe crystal layers

International Nuclear Information System (INIS)

Mita, Yoh; Kuronuma, Ryoichi; Inoue, Masanori; Sasaki, Shoichiro; Miyamoto, Yoshinobu

2004-01-01

The characteristic green photoluminescence emission and related phenomena in Pb-doped, molecular-beam-epitaxy (MBE)-grown ZnSe crystal layers were investigated to explore the nature of the center responsible for the green emission. The intensity of the green emission showed a distinct nonlinear dependence on excitation intensity. Pb-diffused polycrystalline ZnSe was similarly examined for comparison. The characteristic green emission has been observed only in MBE-grown ZnSe crystal layers with moderate Pb doping. The results of the investigations on the growth conditions, luminescence, and related properties of the ZnSe crystal layers suggest that the green emission is due to isolated Pb replacing Zn and surrounded with regular ZnSe lattice with a high perfection

Non-destructive local determination of doping additions and main components in single crystals

International Nuclear Information System (INIS)

Ehksperiandova, L.P.; Blank, A.B.; Kukhtina, N.N.; Afanasiadi, L.I.

1994-01-01

Procedures for local non-destructive determination of elements in optical and scintillation single crystals are developed. They are applied for determination of the main components (in cadmium tungstate) and doping additions (tellurium in zinc selenide, europium in gadolinium silicate). The metrological characteristics of the developed micro-analysis methods are estimated. Segregation of the main components and doping additions in the objects under consideration are investigated. Tellurium is found to be distributed uniformly on the cross-sections of bulk zinc selenide single crystals. The segregation of europium along gadolinium silicate ingots is almost absent. On the cross-section surface of cadmium tungstate single crystals the microregions are found characterized by the prevailing contents of cadmium or tungsten

Dislocation unpinning model of acoustic emission from alkali halide ...

Indian Academy of Sciences (India)

The present paper reports the dislocation unpinning model of acoustic emis- sion (AE) from ... Acoustic emission; dislocation; alkali halide crystals; plastic deformation. ..... [5] T Nishimura, A Tahara and T Kolama, Jpn. Metal Inst. 64, 339 (2000).

Thermal, dielectric studies on pure and amino acid ( L-glutamic acid, L-histidine, L-valine) doped KDP single crystals

Science.gov (United States)

Kumaresan, P.; Moorthy Babu, S.; Anbarasan, P. M.

2008-05-01

Amino acids ( L-glutamic acid, L-histidine, L-valine) doped potassium dihydrogen phospate crystals are grown by solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mol% to 10 mol%. The solubility data for all dopants concentration were determined. There is variation in pH value and hence, there is habit modification of the grown crystals were characterized with UV-VIS, FT-IR studies, SHG trace elements and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. UV-Visible spectra confirm the improvement in the transparency of these crystals on doping metal ions. FT-IR spectra reveal strong absorption band between 1400 and 1600 cm -1 for metal ion doped crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material and it also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Bulk growth of undoped and Nd3+ doped zinc thiourea chloride (ZTC) monocrystal: Exploring the remarkably enhanced structural, optical, electrical and mechanical performance of Nd3+ doped ZTC crystal for NLO device applications

Science.gov (United States)

Anis, Mohd; Muley, Gajanan. G.

2017-05-01

In current scenario good quality crystals are demanded for NLO device application hence present communication is aimed to grow bulk crystal and investigate the doping effect of rare earth element Nd3+ on structural, linear-nonlinear optical, luminescence, mechanical and dielectric properties of zinc thiourea chloride (ZTC) crystal. The ZTC crystal of dimension 21×10×8 mm3 and the Nd3+ doped ZTC crystal of dimension 27×17×5 mm3 have been grown from aqueous solution by slow evaporation technique. The elemental analysis of Nd3+ doped ZTC single crystal has been performed by means of energy dispersive spectroscopic technique. The powder X-ray diffraction technique has been employed to confirm the crystalline phase and identify the effect of Nd3+ doping on structural dimensions of ZTC crystal. The grown crystals have been characterized by UV-Vis-NIR study in the range of 190-1100 nm to ascertain the enhancement in optical transparency of ZTC crystal facilitated by dopant Nd3+. The recorded transmittance data has been utilized to investigate the vital optical constants of grown crystals. The second order nonlinear optical behavior of grown crystals has been evaluated by means of Kurtz-Perry test and the second harmonic generation efficiency of Nd3+ doped ZTC crystal is found to be 1.24 times higher than ZTC crystal. The luminescence analysis has been performed to examine the electronic purity and the color centered photoluminescence emission nature of pure and Nd3+ doped ZTC crystals. The influence of Nd3+ ion on mechanical behavior of ZTC crystal has been investigated by means of microhardness studies. The nature of dielectric constant and dielectric loss of pure and Nd3+ doped ZTC crystal has been examined in the range of 40-100 °C under dielectric study. The Z-scan technique has been employed using the He-Ne laser to investigate the third order nonlinear optical (TONLO) nature of Nd3+ doped ZTC single crystal. The magnitude of TONLO susceptibility, absorption

Hydrogen bonding intermolecular effect on electro-optical response of doped 6PCH nematic liquid crystal with some azo dyes

Science.gov (United States)

Kiani, S.; Zakerhamidi, M. S.; Tajalli, H.

2016-05-01

Previous studies on the electro-optical responses of dye-doped liquid crystal have shown that dopant material have a considerable effect on their electro-optical responses. Despite the studies carried out on electro-optical properties of dye-doped liquid crystal, no attention has been paid to study of the interaction and structural effects in this procedure. In this paper, linear dyes and with similar structure were selected as dopants. The only difference in used dyes is the functional groups in their tails. So, doping of these dyes into liquid crystals determines the influence of interaction type on electro-optical behaviours of the doped systems. Therefore, in this work, two aminoazobenzene (;A-dye;: hydrogen bond donor) and dimethyl-aminoazobenzene (;B-dye;) dyes with different compositional percentages in liquid crystal host were used. Electro-optical Kerr behaviour, the pre-transition temperature and third order nonlinear susceptibility were investigated. The obtained results effectively revealed that type of interactions between the dye and liquid crystal is determinative of behavioral difference of doped system, compared to pure liquid crystal. Also, pre-transitional behaviour and thereupon Kerr electro-optical responses were affected by formed interactions into doped systems. In other words, it will be shown that addition of any dopants in liquid crystal, regardless of the nature of interactions, cannot cause appropriate electro-optical responses. In fact, type of dye, nature of interactions between dopant and liquid crystalline host as well as concentration of dye are the key factors in selecting the appropriate liquid crystal and dopant dye.

Two-Dimensional Halide Perovskites for Emerging New- Generation Photodetectors

DEFF Research Database (Denmark)

Tang, Yingying; Cao, Xianyi; Chi, Qijin

2018-01-01

Compared to their conventional three-dimensional (3D) counterparts, two-dimensional (2D) halide perovskites have attracted more interests recently in a variety of areas related to optoelectronics because of their unique structural characteristics and enhanced performances. In general, there are two...... distinct types of 2D halide perovskites. One represents those perovskites with an intrinsic layered crystal structure (i.e. MX6 layers, M = metal and X = Cl, Br, I), the other defines the perovskites with a 2D nanostructured morphology such as nanoplatelets and nanosheets. Recent studies have shown that 2D...... halide perovskites hold promising potential for the development of new-generation photodetectors, mainly arising from their highly efficient photoluminescence and absorbance, color tunability in the visible-light range and relatively high stability. In this chapter, we present the summary and highlights...

The characterization of tungsten disulfide single crystals doped with gold

International Nuclear Information System (INIS)

Dumcenco, D.O.; Huang, Y.S.; Tiong, K.K.; Liang, C.H.; Chen, C.H.

2007-01-01

Single crystals of WS 2 doped with gold (WS 2 :Au) have been grown by the chemical vapour transport method using iodine as a transporting agent. Hall measurements indicate that the samples are p-type in nature. The doping effect of the materials are characterized by conductivity, surface photovoltage and piezo reflectance measurements. The higher conductivity respect to that of the undoped one suggests that more charge carriers are available for conduction in the doped compound. The surface photovoltage spectrum reveals an impurity level located below the A exciton. The direct band-edge excitonic transition energies for WS 2 :Au show redshifts and the broadening parameters of the excitonic transition features increase due to impurity scattering. (authors)

Crystal growth and optical properties of CdS-doped lead silicate glass

International Nuclear Information System (INIS)

Liu Hao; Liu Qiming; Zhao Xiujian

2007-01-01

The crystal growth and optical properties of CdS microcrystallite-doped lead silicate glass is investigated in this paper. The existence of CdS nanocrystals was confirmed via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results reveal that a two-stage heat-treat procedure can produce a better size distribution of CdS nanocrystals than a one-stage heat-treat procedure in glasses. The second harmonic generation (SHG) from the base glass and CdS microcrystallite doped glasses was observed, and the effects of the heat treatments and the thermal poling temperature on the crystallization of CdS and second-order harmonic (SH) intensity were discussed, respectively. It is indicated that samples doped with CdS microcrystallite showed larger SH intensity than that of the base glass. Use of a higher thermal poling temperature than the glass transformation temperature does not result in a good SH intensity in glasses

Blue luminescence in Tm3+-doped KGd(WO4)2 single crystals

International Nuclear Information System (INIS)

Gueell, F.; Mateos, X.; Gavalda, Jna.; Sole, R.; Aguilo, M.; Diaz, F.; Massons, J.

2004-01-01

Up-conversion blue emissions of trivalent thulium ions in monoclinic KGd(WO 4 ) 2 single crystals at 454 and 479 nm are reported for a single pump laser source at 688 nm. We grew thulium-doped KGd(WO 4 ) 2 single crystals at several concentrations from 0.1% to 10%. We recorded a polarized optical absorption spectrum for the 3 F 2 + 3 F 3 energy levels of thulium at room temperature and low temperature (6 K). From the low temperature emission spectra we determined the splitting of the 3 H 6 ground state. The blue emissions are characterized as a function of the dopant concentration and temperature from 10 K to room temperature. To our knowledge, this is the first time that sequential two-photon excitation process (STEP) generated blue emissions in thulium-doped single crystals with a single excitation wavelength

Specific features of doping with antimony during the ion-beam crystallization of silicon

Energy Technology Data Exchange (ETDEWEB)

Pashchenko, A. S., E-mail: as.pashchenko@gmail.com; Chebotarev, S. N.; Lunin, L. S. [Russian Academy of Sciences, Southern Scientific Center (Russian Federation); Irkha, V. A. [Special Engineering and Technology Department “Inversiya” Ltd. (Russian Federation)

2016-04-15

A method of doping during the growth of thin films by ion-beam crystallization is proposed. By the example of Si and Sb, the possibility of controllably doping semiconductors during the ion-beam crystallization process is shown. A calibrated temperature dependence of the antimony vapor flow rate in the range from 150 to 400°C is obtained. It is established that, an increase in the evaporator temperature above 200°C brings about the accumulation of impurities in the layer growth direction. Silicon layers doped with antimony to a concentration of 10{sup 18} cm{sup –3} are grown. It is shown that, as the evaporator temperature is increased, the efficiency of the activation of antimony in silicon nonlinearly decreases from ~10{sup 0} to ~10{sup –3}.

Crystal growth, structure and phase studies on gold halides

NARCIS (Netherlands)

Janssen, Eugenius Maria Wilhelmus Janssen

1977-01-01

Only very corrosive substances attack gold, the most noble metal. In this study the reactivity and the phase diagrams of gold with the halogens chlorine, bromine and iodine have been investigated. owing to the noble behaviour of gold, its halides are sensitive to heat; on heating they decompose into

Crystal growth and evaluation of scintillation properties of Eu and alkali-metal co-doped LiSrAlF{sub 6} single crystals for thermal neutron detector

Energy Technology Data Exchange (ETDEWEB)

Wakahara, Shingo; Yokota, Yuui; Yamaji, Akihiro; Fujimoto, Yutaka; Sugiyama, Makoto; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Pejchal, Jan [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Institute of Physics AS CR, Cukrovarnicka 10, Prague 16253 (Czech Republic); Kawaguchi, Noriaki [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Tokuyama, Co. Ltd., Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Fukuda, Kentaro [Tokuyama, Co. Ltd., Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

2012-12-15

In recent work, Na co-doping have found to improve the light output of Eu doped LiCaAlF{sub 6} (Eu:LiCAF) for thermal neutron scintillator. We grew Eu 2% and alkali metal 1% co-doped LiSAF crystals by Micro-Pulling down method to understand the effect of alkali metal co-doping on scintillation properties and mechanism compared with LiCAF. In photo- and {alpha}-ray induced radio-luminescence spectra of the all grown crystals, the emissions from d-f transition of Eu{sup 2+} were observed. Without relation to excitation source, decay times of co-doped LiSAF were longer than Eu only doped one. The light yield of Na, K and Cs co-doped LiSAF under {sup 252}Cf neutron excitation were improved. Especially, K co-doped Eu:LiSAF reached 33200 ph/n, which outperformed Eu only doped one by approximately 20% (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Thermally and optically stimulated radiative processes in Eu and Y co-doped LiCaAlF{sub 6} crystal

Energy Technology Data Exchange (ETDEWEB)

Fukuda, Kentaro, E-mail: ken-fukuda@tokuyama.co.jp [Tokuyama Corporation, 1-1 Mikage-cho, Shunan-shi, Yamaguchi 745-8648 (Japan); Yanagida, Takayuki; Fujimoto, Yutaka [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu, Fukuoka 808-0196 (Japan)

2015-06-01

Yttrium co-doping was attempted to enhance dosimeter performance of Eu doped LiCaAlF{sub 6} crystal. Eu doped and Eu, Y co-doped LiCaAlF{sub 6} were prepared by the micro-pulling-down technique, and their dosimeter characteristics such as optically stimulated luminescence (OSL) and thermally stimulated luminescence (TSL) were investigated. By yttrium co-doping, emission intensities of OSL and TSL were enhanced by some orders of magnitude. In contrast, scintillation characteristics of yttrium co-doped crystal such as intensity of prompt luminescence induced by X-ray and light yield under neutron irradiation were degraded.

Luminescent decay and spectra of impurity-activated alkali halides under high pressure

International Nuclear Information System (INIS)

Klick, D.I.

1977-01-01

The effect of high pressure on the luminescence of alkali halides doped with the transition-metal ions Cu + and Ag + and the heavy-metal ions In + and Tl + was investigated to 140 kbar. Measurement of spectra allowed the prediction of kinetic properties, and the predictions agree with lifetime data

Thermo- and electro-optical properties of photonic liquid crystal fibers doped with gold nanoparticles

Directory of Open Access Journals (Sweden)

Agata Siarkowska

2017-12-01

Full Text Available Thermo- and electro-optical properties of a photonic liquid crystal fiber (PLCF enhanced by the use of dopants have been investigated. A 6CHBT nematic liquid crystal was doped with four different concentrations of gold nanoparticles (NPs, 0.1, 0.3, 0.5 and 1.0 wt %, for direct comparison of the influence of the dopant on the properties of the PLCF. The thermo-optical effects of the liquid crystal doped with gold NPs were compared in three setups, an LC cell, a microcapillary and within the PLCF, to determine if the observed responses to external factors are caused by the properties of the infiltration material or due to the setup configuration. The results obtained indicated that with increasing NP doping a significant reduction of the rise time under an external electric field occurs with a simultaneous decrease in the nematic–isotropic phase transition temperature, thus improving the thermo- and electro-optical properties of the PLCF.

Thermo- and electro-optical properties of photonic liquid crystal fibers doped with gold nanoparticles.

Science.gov (United States)

Siarkowska, Agata; Chychłowski, Miłosz; Budaszewski, Daniel; Jankiewicz, Bartłomiej; Bartosewicz, Bartosz; Woliński, Tomasz R

2017-01-01

Thermo- and electro-optical properties of a photonic liquid crystal fiber (PLCF) enhanced by the use of dopants have been investigated. A 6CHBT nematic liquid crystal was doped with four different concentrations of gold nanoparticles (NPs), 0.1, 0.3, 0.5 and 1.0 wt %, for direct comparison of the influence of the dopant on the properties of the PLCF. The thermo-optical effects of the liquid crystal doped with gold NPs were compared in three setups, an LC cell, a microcapillary and within the PLCF, to determine if the observed responses to external factors are caused by the properties of the infiltration material or due to the setup configuration. The results obtained indicated that with increasing NP doping a significant reduction of the rise time under an external electric field occurs with a simultaneous decrease in the nematic-isotropic phase transition temperature, thus improving the thermo- and electro-optical properties of the PLCF.

Synthesis, characterization and anti-microbial activity of pure, Cu2+ and Cd2+ doped organic NLO l-arginine trifluoroacetate single crystals

Science.gov (United States)

Prasanyaa, T.; Haris, M.; Jayaramakrishnan, V.; Amgalan, M.; Mathivanan, V.

2013-10-01

Optically transparent Cu2+ and Cd2+ doped l-arginine trifluoroacetate (LATF) single crystals were grown from its aqueous solution using the slow solvent evaporation technique. The grown crystals were characterized by powder x-ray diffraction to confirm the monoclinic crystal structure. The percentage of transmittance measured using the ultraviolet-visible-near infrared spectrophotometer was found to be more than 80% for doped crystals. The functional group analysis of the grown crystals has been made by Fourier transform infrared spectroscopy. Thermogravimetric/differential thermal analysis was performed for the grown crystals. An atomic absorption study was carried out to determine the presence of Cu2+ and Cd2+. The hardness of the grown crystals was assessed and the results show a significant variation in the hardness value between the pure and doped LATF crystals. The second harmonic generation measurements show that Cu2+ doped LATF is 2.8 times greater and Cd2+ doped is 2.6 times greater than KDP. The anti-bacterial and anti-fungal activities of the title compound were performed using the disc diffusion method against standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillus niger and Aspergillus flavus.

Synthesis, characterization and anti-microbial activity of pure, Cu2+ and Cd2+ doped organic NLO l-arginine trifluoroacetate single crystals

International Nuclear Information System (INIS)

Prasanyaa, T; Haris, M; Amgalan, M; Mathivanan, V; Jayaramakrishnan, V

2013-01-01

Optically transparent Cu 2+ and Cd 2+ doped l-arginine trifluoroacetate (LATF) single crystals were grown from its aqueous solution using the slow solvent evaporation technique. The grown crystals were characterized by powder x-ray diffraction to confirm the monoclinic crystal structure. The percentage of transmittance measured using the ultraviolet–visible–near infrared spectrophotometer was found to be more than 80% for doped crystals. The functional group analysis of the grown crystals has been made by Fourier transform infrared spectroscopy. Thermogravimetric/differential thermal analysis was performed for the grown crystals. An atomic absorption study was carried out to determine the presence of Cu 2+ and Cd 2+ . The hardness of the grown crystals was assessed and the results show a significant variation in the hardness value between the pure and doped LATF crystals. The second harmonic generation measurements show that Cu 2+ doped LATF is 2.8 times greater and Cd 2+ doped is 2.6 times greater than KDP. The anti-bacterial and anti-fungal activities of the title compound were performed using the disc diffusion method against standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillus niger and Aspergillus flavus. (paper)

Doping properties of cadmium-rich arsenic-doped CdTe single crystals: Evidence of metastable AX behavior

Science.gov (United States)

Nagaoka, Akira; Kuciauskas, Darius; Scarpulla, Michael A.

2017-12-01

Cd-rich composition and group-V element doping are of interest for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe, but the critical details concerning point defects are not yet fully established. Herein, we report on the properties of arsenic doped CdTe single crystals grown from Cd solvent by the travelling heater method. The photoluminescence spectra and activation energy of 74 ± 2 meV derived from the temperature-dependent Hall effect are consistent with AsTe as the dominant acceptor. Doping in the 1016 to 1017/cm3 range is achieved for measured As concentrations between 1016 and 1020/cm3 with the highest doping efficiency of 40% occurring near 1017 As/cm3. We observe persistent photoconductivity, a hallmark of light-induced metastable configuration changes consistent with AX behavior. Additionally, quenching experiments reveal at least two mechanisms of increased p-type doping in the dark, one decaying over 2-3 weeks and the other persisting for at least 2 months. These results provide essential insights for the application of As-doped CdTe in thin film solar cells.

Crystal growth, characterization and theoretical studies of alkaline earth metal-doped tetrakis(thiourea)nickel(II) chloride.

Science.gov (United States)

Agilandeshwari, R; Muthu, K; Meenatchi, V; Meena, K; Rajasekar, M; Aditya Prasad, A; Meenakshisundaram, S P

2015-02-25

The influence of Sr(II)-doping on the properties of tetrakis(thiourea)nickel(II) chloride (TTNC) has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies of doped specimens confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the Sr(II) are observed by scanning electron microscopy. The incorporation of metal into the host crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The nonlinear optical properties of the doped and undoped specimens were studied. Theoretical calculations were performed using the Density functional theory (DFT) method with B3LYP/LANL2DZ as the basis set. The molecular geometry and vibrational frequencies of TTNC in the ground state were calculated and the observed structural parameters of TTNC are compared with parameters obtained from single crystal X-ray studies. The atomic charge distributions are obtained by Mulliken charge population analysis. The first-order molecular hyperpolarizability, polarizability and dipole moment were derived. Copyright © 2014 Elsevier B.V. All rights reserved.

Microwave-assisted self-doping of TiO2 photonic crystals for efficient photoelectrochemical water splitting

KAUST Repository

Zhang, Zhonghai

2014-01-08

In this article, we report that the combination of microwave heating and ethylene glycol, a mild reducing agent, can induce Ti3+ self-doping in TiO2. A hierarchical TiO2 nanotube array with the top layer serving as TiO2 photonic crystals (TiO2 NTPCs) was selected as the base photoelectrode. The self-doped TiO2 NTPCs demonstrated a 10-fold increase in visible-light photocurrent density compared to the nondoped one, and the optimized saturation photocurrent density under simulated AM 1.5G illumination was identified to be 2.5 mA cm-2 at 1.23 V versus reversible hydrogen electrode, which is comparable to the highest values ever reported for TiO2-based photoelectrodes. The significant enhancement of photoelectrochemical performance can be ascribed to the rational coupling of morphological and electronic features of the self-doped TiO 2 NTPCs: (1) the periodically morphological structure of the photonic crystal layer traps broadband visible light, (2) the electronic interband state induced from self-doping of Ti3+ can be excited in the visible-light region, and (3) the captured light by the photonic crystal layer is absorbed by the self-doped interbands. © 2013 American Chemical Society.

Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

KAUST Repository

Abutaha, Anas I.; Sarath Kumar, S. R.; Alshareef, Husam N.

2013-01-01

We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature

Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED

International Nuclear Information System (INIS)

Xiang, Weidong; Zhong, Jiasong; Zhao, Yinsheng; Zhao, Binyu; Liang, Xiaojuan; Dong, Yongjun; Zhang, Zhimin; Chen, Zhaoping; Liu, Bingfeng

2012-01-01

Highlights: ► The YAG:Ce,Mn single crystal was well synthesized by the Czochralski (CZ) method. ► The emission intensity of the sample has been influenced after annealing. ► Annealed in the air at 1200 °C was the most optimal annealing condition. ► The single crystal could be used in the white light LED which emitted by blue light. - Abstract: The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300–500 nm wavelength range. The emission spectrum of the crystal consists of a peak around 538 nm when excited by 460 nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.

Relationship between thermoluminescence and X-ray induced luminescence in alkali halides

International Nuclear Information System (INIS)

Aguilar, M.; Lopez, F.J.; Jaque, F.

1978-01-01

The wavelength spectra of thermoluminescence and X-ray induced luminescence in pure and divalent cation doped alkali halides, in the temperature range LNT-RT have been studied. The more important conclusion is that the wavelength spectra in both cases are very similar. This allows a new point of view to be presented on thermoluminescence mechanisms. (author)

Optical Study of Liquid Crystal Doped with Multiwalled Carbon Nanotube

Science.gov (United States)

Gharde, Rita A.; Thakare, Sangeeta Y.

2014-11-01

Liquid crystalline materials have been useful for display devices i.e watches, calculators, automobile dashboards, televisions, multi media projectors etc. as well as in electro tunable lasers, optical fibers and lenses. Carbon nanotube is chosen as the main experimental factor in this study as it has been observed that Carbon Nano Tube influence the existing properties of liquid crystal host and with the doping of CNT can enhance1 the properties of LC. The combination of carbon nanotube (CNT) and liquid crystal (LC) materials show considerable interest in the scientific community due to unique physical properties of CNT in liquid crystal. Dispersion of CNTs in LCs can provide us a cheap, simple, versatile and effective means of controlling nanotube orientation on macroscopic scale with no restrictions on nanotube type. LCs have the long range orientational order rendering them to be anisotropic phases. If CNTs can be well dispersed in LC matrix, they will align with their long axes along the LC director to minimize distortions of the LC director field and the free energy. In this paper, we doped liquid crystal (Cholesteryl Nonanoate) by a small amount of multiwall carbon nanotube 0.05% and 0.1% wt. We found that by adding carbon nanotube to liquid crystals the melting point of the mixture is decreased but TNI is increased. It has been also observed that with incereas in concentration of carbon nanotube into liquid crystal shows conciderable effect on LC. The prepared samples were characterized using various techniques to study structural, thermal and optical properties i.e PMS, FPSS, UV-Vis spectroscopy, FT-IR measurements, and DTA.

Study of the effect of doping on the temperature stability of the optical properties of germanium single crystals

Energy Technology Data Exchange (ETDEWEB)

Podkopaev, O. I. [Joint-Stock Company “Germanium” (Russian Federation); Shimanskiy, A. F., E-mail: shimanaf@mail.ru [Siberian Federal University (Russian Federation); Kopytkova, S. A.; Filatov, R. A. [Joint-Stock Company “Germanium” (Russian Federation); Golubovskaya, N. O. [Siberian Federal University (Russian Federation)

2016-10-15

The effect of doping on the optical transmittance of germanium single crystals is studied by infrared Fourier spectroscopy. It is established that the introduction of silicon and tellurium additives into germanium doped with antimony provides a means for improving the temperature stability of the optical properties of the crystals.

Study of the effect of doping on the temperature stability of the optical properties of germanium single crystals

International Nuclear Information System (INIS)

Podkopaev, O. I.; Shimanskiy, A. F.; Kopytkova, S. A.; Filatov, R. A.; Golubovskaya, N. O.

2016-01-01

The effect of doping on the optical transmittance of germanium single crystals is studied by infrared Fourier spectroscopy. It is established that the introduction of silicon and tellurium additives into germanium doped with antimony provides a means for improving the temperature stability of the optical properties of the crystals.

Defect modes in silver-doped photonic crystals made by holography using dichromated gelatin

Science.gov (United States)

Dai, Rui; Chen, Shujing; Ren, Zhi; Wang, Zhaona; Liu, Dahe

2012-10-01

The defect mode in silver-doped photonic crystals is investigated. 1D and 3D photonic crystals were made by holography using dichromated gelatin mixed with silver nitrate. By controlling the concentration of the silver nitrate, the defect mode was observed in the bandgaps of the holographic photonic crystals. The numerical simulations were made, and the results showed the consistency with the experimental observations.

Optical properties of tungsten disulfide single crystals doped with gold

International Nuclear Information System (INIS)

Dumcenco, D.O.; Hsu, H.P.; Huang, Y.S.; Liang, C.H.; Tiong, K.K.; Du, C.H.

2008-01-01

Single crystals of WS 2 doped with gold have been grown by the chemical vapour transport method using iodine as a transporting agent. X-ray diffraction (XRD) pattern analysis revealed presence of mixed three-layer rhombohedral (3R) and two-layer hexagonal (2H) polytypes for the doped crystals while the undoped one shows only 2H form. Hall measurements indicate that the samples are p-type in nature. The doping effects of the materials are characterized by surface photovoltage (SPV), photoconductivity (PC) and piezoreflectance (PzR) measurements. Room temperature SPV and PC spectra reveal a feature located at ∼60 meV below the A exciton and has been tentatively assigned to be an impurity level caused by Au dopant. Excitonic transition energies of the A, B, d and C excitons detected in PzR spectra show red shift due to the presence of a small amount of Au and the broadening parameters of the excitonic transition features increase due to impurity scattering. The values of the parameters that describe the electron (exciton)-phonon interaction of excitonic transitions of A-B are about two times larger than that of d-C excitonic pairs. The possible assignments of the different origins of A-B and d-C excitonic pairs have been discussed

Crystallization characteristics of Mg-doped Ge2Sb2Te5 films for phase change memory applications

International Nuclear Information System (INIS)

Fu Jing; Shen Xiang; Nie Qiuhua; Wang Guoxiang; Wu Liangcai; Dai Shixun; Xu Tiefeng; Wang, R.P.

2013-01-01

Highlights: ► Mg-doped Ge 2 Sb 2 Te 5 (GST) phase change films with higher resistance and better thermal stability have been proposed. ► The increase of Mg content result in an enhancement in crystallization temperature, activation energy and electrical resistance. ► The proper Mg addition in GST can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase. ► The formation of covalent Mg-Sb and Mg-Te bonds contribute to the enhancement thermal stability in Mg-doped GST films. - Abstract: Mg-doped Ge 2 Sb 2 Te 5 (GST) films with different Mg doping concentrations have been prepared, and their crystallization behavior, structure and electrical properties have been systematically investigated for phase-change memory applications. The results show that the addition of Mg into GST films could result in an enhancement in crystallization temperature, activation energy and electrical resistance compared with the conventional GST films, indicating that a good amorphous thermal stability. On the other hand, the proper Mg concentration ranging from 13.6 to 31.1 at.% can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase and suppress the formation of the hexagonal close-packed (hcp) crystalline phase. X-ray photoelectron spectra (XPS) further confirm that the formation of covalent Mg-Sb and Mg-Te bonds contribute to the enhanced thermal stability in Mg-doped GST films.

Improved ferroelectric and pyroelectric parameters in iminodiacetic acid doped TGS crystal

Science.gov (United States)

Rai, Chitharanjan; Sreenivas, K.; Dharmaprakash, S. M.

2010-01-01

Single crystals of Iminodiacetic acid (HN(CH 2COOH) 2) doped Triglycine sulphate (IDATGS) has been grown from aqueous solution at constant temperature by slow evaporation technique. The concentration of the dopant in the TGS solution was 2 mol%. The X-ray diffraction analysis indicates that there is significant change in the lattice parameters compared to pure TGS crystal. The IDATGS crystal has larger transition temperature and observed higher and uniform figure of merit over most part of the ferroelectric phase. These crystals also exhibit higher internal bias field and micro-hardness number compared to pure TGS. Therefore IDATGS may be a potential material for IR detectors.

Crystal growth and properties of PbI2 doped with Fe and Ni

International Nuclear Information System (INIS)

Rybak, O.V.; Lun', Yu.O.; Bordun, I.M.; Omelyan, M.F.

2005-01-01

A procedure is described for doping PbI 2 monocrystals with Fe and Ni during vapor-phase growth in a closed system in the presence of excess iodine. The rate of mass transfer in the system and the doping level of the crystals are shown to be governed by the dopant content in the source material and the source temperature. The effect of Fe and Ni doping on the low-temperature (5 K) exciton photoluminescence spectrum of PbI 2 is discussed [ru

Optical properties of Ni-doped MgGa2O4 single crystals grown by floating zone method

International Nuclear Information System (INIS)

Suzuki, Takenobu; Hughes, Mark; Ohishi, Yasutake

2010-01-01

The single crystal growth conditions and spectroscopic characterization of Ni-doped MgGa 2 O 4 with inverse-spinel structure crystal family are described. Single crystals of this material have been grown by floating zone method. Ni-doped MgGa 2 O 4 single crystals have broadband fluorescence in the 1100-1600 nm wavelength range, 1.6 ms room temperature lifetime, 56% quantum efficiency and 1.05x10 -21 cm 2 stimulated emission cross section at the emission peak. This new material is very promising for tunable laser applications covering the important optical communication and eye safe wavelength region.

Electrolytic coloration of O22--doped NaCl crystals

International Nuclear Information System (INIS)

Qin Fang; Gu Hongen; Song Cuiying; Wang Na; Guo Meili; Wang Fen; Liu Jia

2007-01-01

O 2 2- -doped NaCl crystals are colored electrolytically by using a pointed cathode and a flat anode at various temperatures and voltages, which mainly benefit from appropriate coloration temperatures and voltages as well as anode structure of used electrolysis apparatus. Characteristic OH - , U, V 2 m , U A , V 2 , V 3 , O 2- -V a + complex, F, R 1 , R 2 and M absorption bands are observed in absorption spectra of the colored crystals. Production and conversion of color centers in electrolytic coloration is explained. Current-time curves for electrolytic colorations and their relationships with electrolytic colorations were given

Optical properties of pure and Ce3+ doped gadolinium gallium garnet crystals and epitaxial layers

International Nuclear Information System (INIS)

Syvorotka, I.I.; Sugak, D.; Wierzbicka, A.; Wittlin, A.; Przybylińska, H.; Barzowska, J.; Barcz, A.; Berkowski, M.; Domagała, J.; Mahlik, S.; Grinberg, M.; Ma, Chong-Geng

2015-01-01

Results of X-ray diffraction and low temperature optical absorption measurements of cerium doped gadolinium gallium garnet single crystals and epitaxial layers are reported. In the region of intra-configurational 4f–4f transitions the spectra of the bulk crystals exhibit the signatures of several different Ce 3+ related centers. Apart from the dominant center, associated with Ce substituting gadolinium, at least three other centers are found, some of them attributed to the so-called antisite locations of rare-earth ions in the garnet host, i.e., in the Ga positions. X-ray diffraction data prove lattice expansion of bulk GGG crystals due to the presence of rare-earth antisites. The concentration of the additional Ce-related centers in epitaxial layers is much lower than in the bulk crystals. However, the Ce-doped layers incorporate a large amount of Pb from flux, which is the most probable source of nonradiative quenching of Ce luminescence, not observed in crystals grown by the Czochralski method. - Highlights: • Ce 3+ multicenters found in Gadolinium Gallium Garnet crystals and epitaxial layers. • High quality epitaxial layers of pure and Ce-doped GGG were grown. • Luminescence quenching of Ce 3+ by Pb ions from flux detected in GGG epitaxial layers. • X-ray diffraction allows measuring the amount of the rare-earth antisites in GGG

Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of Single Crystals

NARCIS (Netherlands)

Brenes, Roberto; Guo, D.; Osherov, Anna; Noel, Nakita K.; Eames, Christopher; Hutter, E.M.; Pathak, Sandeep K.; Niroui, Farnaz; Friend, Richard H.; Islam, M. Saiful; Snaith, Henry J.; Bulović, Vladimir; Savenije, T.J.; Stranks, Samuel D.

2017-01-01

Metal halide perovskites are generating enormous excitement for use in solar cells and light-emission applications, but devices still show substantial non-radiative losses. Here, we show that by combining light and atmospheric treatments, we can increase the internal luminescence quantum

Influence of microgravity on Ce-doped Bi12 SiO20 crystal defect

Indian Academy of Sciences (India)

TECS

studied by comparing space grown BSO crystal with ground grown one. These results show ... fractive properties (Aldrich et al 1971; Peltier and. Micheron ... The shape of interface changes from concave to convex by suppressing ... cations. Figure 1. Parts of Ce doped BSO crystals: (a) space growth and (b) ground growth.

Scintillation and optical properties of Pb-doped YCa{sub 4}O(BO{sub 3}){sub 3} crystals

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, Yutaka, E-mail: fuji-you@tagen.tohoku.ac.jp [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); JSPS, 8 Ichibanmachi, Chiyoda-ku, Tokyo 102-8472 (Japan); Yanagida, Takayuki; Yokota, Yuui [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Kawaguchi, Noriaki [Tokuyama Corporation, 3 Shibuya Shibuya-ku, Tokyo 150-8383 (Japan); Fukuda, Kentaro [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tokuyama Corporation, 3 Shibuya Shibuya-ku, Tokyo 150-8383 (Japan); Totsuka, Daisuke [Nihon Kessho Kogaku Co., Ltd., 810-5 Nobe-cho Tatebayashi Gunma (Japan); Watanabe, Kenichi; Yamazaki, Atsushi [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Chani, Valery [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yoshikawa, Akira [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); NICHe, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2011-10-01

This communication reports optical properties and radiation responses of Pb{sup 2+} 0.5 and 1.0 mol%-doped YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) single crystals grown by the micro-pulling-down ({mu}-PD) method for neutron scintillator applications. The crystals had no impurity phases according to the results of X-ray powder diffraction. These Pb{sup 2+}-doped crystals demonstrated blue-light luminescence at 330 nm because of Pb{sup 2+1}S{sub 0}-{sup 3}P{sub 0,1} transition in the photoluminescence spectra. The main emission decay component was determined to be about 250-260 ns under 260 nm excitation wavelength. When irradiated by a {sup 252}Cf source, the relative light yield of 0.5% Pb{sup 2+}-doped crystal was about 300 ph/n that was determined using the light yield of a reference Li-glass scintillator.

Induced Magnetic Anisotropy in Liquid Crystals Doped with Resonant Semiconductor Nanoparticles

Directory of Open Access Journals (Sweden)

Vicente Marzal

2016-01-01

Full Text Available Currently, there are many efforts to improve the electrooptical properties of liquid crystals by means of doping them with different types of nanoparticles. In addition, liquid crystals may be used as active media to dynamically control other interesting phenomena, such as light scattering resonances. In this sense, mixtures of resonant nanoparticles hosted in a liquid crystal could be a potential metamaterial with interesting properties. In this work, the artificial magnetism induced in a mixture of semiconductor nanoparticles surrounded by a liquid crystal is analyzed. Effective magnetic permeability of mixtures has been obtained using the Maxwell-Garnett effective medium theory. Furthermore, permeability variations with nanoparticles size and their concentration in the liquid crystal, as well as the magnetic anisotropy, have been studied.

Thickness-dependent photovoltaic effects in miscut Nb-doped SrTiO3 single crystals

International Nuclear Information System (INIS)

Yue Zengji; Zhao Kun; Zhao Songqing; Lu Zhiqing; Li Xiaoming; Ni Hao; Wang Aijun

2010-01-01

The photovoltaic effects of Nb-doped SrTiO 3 single crystals with different thicknesses were investigated under the illumination of ultraviolet pulsed lasers. The peak photovoltage increased and then decreased quickly with the decrease in crystal thickness, and a maximum photovoltage occurred for the 180 μm-thick crystal. The photovoltaic response time decreased monotonically with decreasing crystal thickness. The present results suggested the promising potential of reducing crystal thickness in high sensitivity detectors with fast response.

Photoluminescence of Copper-Doped Lithium Niobate Crystals

Science.gov (United States)

Gorelik, V. S.; Pyatyshev, A. Yu.; Sidorov, N. V.

2018-05-01

The photoluminescence (PL) of copper-doped lithium niobate single crystals is studied using different UV-Vis light-emitting diodes and a pulse-periodic laser with a wavelength of 266 nm as excitation radiation sources. With the resonance excitation from a 527-nm light-emitting diode, the intensity of PL increases sharply (by two orders of magnitude). When using a 467-nm light-emitting diode for excitation, the PL spectrum is characterized by the presence of multiphonon lines in the range of 520-620 nm.

Dislocation unpinning model of acoustic emission from alkali halide ...

Indian Academy of Sciences (India)

AE) from alkali halide crystals. Equations are derived for the strain dependence of the transient AE pulse rate, peak value of the AE pulse rate and the total number of AE pulse emitted. It is found that the AE pulse rate should be maximum for a ...

Exploiting the natural doping gradient of Nd:YLF crystals for high-power end pumped lasers

CSIR Research Space (South Africa)

Bollig, C

2008-01-01

Full Text Available decided to use crystals of a doping concentration below the 0.5% previously used. In addition, researchers decided to exploit the natural doping gradient along the length of the boule, which is especially pronounced at low concentrations but commonly...

TL and OSL studies on lithium borate single crystals doped with Cu and Ag

International Nuclear Information System (INIS)

Rawat, N.S.; Kulkarni, M.S.; Tyagi, M.; Ratna, P.; Mishra, D.R.; Singh, S.G.; Tiwari, B.; Soni, A.; Gadkari, S.C.; Gupta, S.K.

2012-01-01

Lithium borate (LBO) single crystals doped with Cu and Ag (0.25 mol% each) (Li 2 B 4 O 7 :Cu,Ag) are grown by the Czochralski method. The thermoluminescence readout on Li 2 B 4 O 7 :Cu,Ag crystals showed three glow peaks at∼375, 441 and 516 K for the heating rate of 1 K/s. The thermoluminescence sensitivity of the grown Li 2 B 4 O 7 :Cu,Ag single crystals is found to be 5 times TLD-100 and a linear dose response in the range 1 mGy to 1 kGy. The glow curve deconvolution reveals nearly first order kinetics for all the three peaks with trap depths 0.77, 1.25 and 1.34 eV respectively and corresponding frequency factors 1.6×10 9 , 1.3×10 13 and 6.8×10 11 s −1 . The continuous wave optically stimulated luminescence (CW-OSL) measurements were performed on the LBO:Cu,Ag single crystals using blue light stimulation. The traps responsible for the three thermoluminescence peaks in Li 2 B 4 O 7 :Cu,Ag are found to be OSL sensitive. The qualitative correlation between TL peaks and CW-OSL response is established. The photoluminescence studies show that in case of co-doping of Ag in LBO:Cu the emission at 370 nm in Cu states dominates over the transitions in Ag states implying doping of Ag plays a role as sensitizer when co-doped with Cu and increases overall emission. - Highlights: ► Growth of crack free single crystals of Li2B4O7 :Cu and Ag. ► Study of TL and OSL parameters for Li2B4O7 :Cu and Ag. ► Correlation of OSL with TL peaks. ► Optimization of OSL readout time with respect to residual TL.

Guiding and amplification properties of rod-type photonic crystal fibers with sectioned core doping

DEFF Research Database (Denmark)

Selleri, Stefano; Poli, Federica; Passaro, Davide

2009-01-01

Rod-type photonic crystal fibers are large mode area double-cladding fibers with an outer diameter of few millimeters which can provide important advantages for high-power lasers and amplifiers. Numerical studies have recently demonstrated the guidance of higher-order modes in these fibers, which...... can worsen the output beam quality of lasers and amplifiers. In the present analysis a sectioned core doping has been proposed for Yb-doped rod-type photonic crystal fibers, with the aim to improve the higher-order mode suppression. A full-vector modal solver based on the finite element method has...

Influence of MgSO{sub 4} doping on the properties of zinc tris–thiourea sulphate (ZTS) single crystals

Energy Technology Data Exchange (ETDEWEB)

Selvapandiyan, M., E-mail: mselvapandiyan@rediffmail.com [Department of Physics, Sri Vidya Mandir Arts and Science College, Uthangarai 635 207 (India); Arumugam, J. [Department of Physics, Sri Vidya Mandir Arts and Science College, Uthangarai 635 207 (India); Sundaramoorthi, P. [Department of Physics, Thiruvalluvar Government Arts College, Rasipuram 637 401 (India); Sudhakar, S. [CSIR–National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110 012 (India)

2013-12-15

Highlights: •The influence of MgSO{sub 4} doping on the properties of ZTS single crystals grown at room temperature. •Thermal stability of the crystals increased with incorporation of Mg atom. •Energy band gap was estimated from UV–vis spectra. •ZTS is a potential material for frequency conversion. •Both pure and doped ZTS crystals are belonging to category of typical insulating materials. -- Abstract: The influence of MgSO{sub 4} doping on the properties of zinc tris–thiourea sulphate single crystals grown at room temperature by slow evaporation solution growth technique was studied. Powder XRD analysis confirmed the orthorhombic crystal structure with noncentrosymmetric space group Pca2{sub 1}. The mechanical properties of the grown crystals were analysed by Vicker’s microhardness method. Functional groups present in the materials were identified by FTIR spectral analysis in the range between 4000 and 400 cm{sup −1}. The UV–Vis spectrum indicates that the UV cut-off wavelength of the crystals has less than 297 nm. The thermal stability of the grown crystals was determined with the aid of thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Second order nonlinear optical behaviour of the grown crystals have been confirmed by Kurtz powder second harmonic generation (SHG) test.

Effect of L-Cysteine doping on growth and some characteristics of potassium dihydrogen phosphate single crystals

Science.gov (United States)

Mahadik, Ashwini; Soni, P. H.; Desai, C. F.

2017-12-01

Among quite a number of technologically important NLO materials, Potassium Dihydrogen Phosphate (KDP) is one of the most favourable ones for second harmonic generation applications, such as in electro-optic modulators, parametric oscillators and harmonic generators. The authors report here their studies on KDP crystals doped with L-Cysteine (1 mol% and 2 mol%). The dopant inclusion in the crystals was confirmed using Fourier transform infrared (FT-IR) spectroscopy and Powder X-Ray Diffraction (XRD). The XRD results also confirm the tetragonal structure with lattice parameters a = b = 7.45 Å and c = 6.98 Å. The presence of functional groups of crystals was analyzed using the FTIR spectra. For band gap evaluation, UV-Vis spectra were used and it was found to be 3.41 eV, 4.40eVand 4.50 eV, respectively in the cases of pure KDP, 1 mol% and 2 mol% L-Cysteine dopings. The spectra quality indicates good transparency of the doped crystals in the visible region, a feature quite desirable for applications in optoelectronics.

Refractometry of TGS crystals doped with L-threonine impurity under uniaxial pressure

Energy Technology Data Exchange (ETDEWEB)

Stadnyk, V. I., E-mail: vasylstadnyk@ukr.net; Kiryk, Yu. I. [Lviv National University (Ukraine)

2013-07-15

The temperature and spectral dependences of the refractive indices of triglycine sulphate (TGS) crystals doped with L-threonine impurity have been investigated. It is established that the introduction of an impurity weakens the temperature dependence of refractive indices. The electronic polarizability, refractions, and parameters of UV oscillators of mechanically deformed impurity crystals are calculated. The temperature coefficients of the phase transition shift are determined.

Refractometry of TGS crystals doped with L-threonine impurity under uniaxial pressure

International Nuclear Information System (INIS)

Stadnyk, V. I.; Kiryk, Yu. I.

2013-01-01

The temperature and spectral dependences of the refractive indices of triglycine sulphate (TGS) crystals doped with L-threonine impurity have been investigated. It is established that the introduction of an impurity weakens the temperature dependence of refractive indices. The electronic polarizability, refractions, and parameters of UV oscillators of mechanically deformed impurity crystals are calculated. The temperature coefficients of the phase transition shift are determined

Electrical Properties of Zn-Phthalocyanine and Poly (3-hexylthiophene Doped Nematic Liquid Crystal

Directory of Open Access Journals (Sweden)

Y. Karakuş

2011-01-01

Full Text Available An E7 coded nematic liquid crystal was doped with zinc phthalocyanine and poly (3-hexylthiophene. A variety of properties including relaxation time, absorption coefficient, and critical frequency of this doped system were investigated using impedance spectroscopy. The doped systems displayed increased absorption coefficients in the range 0.22–0.55 and relaxation times from 5.05×10−7 s to 3.59×10−6 s with a decrease in the critical frequency from 3.54 MHz to 2.048 MHz.

Studies on transport properties of copper doped tungsten diselenide single crystals

Science.gov (United States)

Deshpande, M. P.; Parmar, M. N.; Pandya, Nilesh N.; Chaki, Sunil; Bhatt, Sandip V.

2012-02-01

During recent years, transition metal dichalcogenides of groups IVB, VB and VIB have received considerable attention because of the great diversity in their transport properties. 2H-WSe 2 (Tungsten diselenide) is an interesting member of the transition metal dichalcogenide (TMDC's) family and known to be a semiconductor useful for photovoltaic and optoelectronic applications. The anisotropy usually observed in this diamagnetic semiconductor material is a result of the sandwich structure of Se-W-Se layers interacting with each other, loosely bonded by the weak Van der Waals forces. Recent efforts in studying the influence of the anisotropic electrical and optical properties of this layered-type transition metal dichalcogenides have been implemented by doping the samples with different alkali group elements. Unfortunately, little work is reported on doping of metals in WSe 2. Therefore, it is proposed in this work to carry out a systematic growth of single crystals of WSe 2 by doping it with copper in different proportions i.e. Cu xWSe 2 ( x=0, 0.5, 1.0) by direct vapour transport technique. Transport properties like low and high temperature resistivity measurements, high pressure resistivity, Seebeck coefficient measurements at low temperature and Hall Effect at room temperature were studied in detail on all these samples. These measurements show that tungsten diselenide single crystals are p-type whereas doped with copper makes it n-type in nature. The results obtained and their implications are discussed in this paper.

Defect formation and desorption of metal atoms from alkali halide crystals under low energy electron bombardment studied by optical absorption and mass spectroscopy

International Nuclear Information System (INIS)

Seifert, N.R.

1993-04-01

This work presents an extensive investigation of electronically induced desorption of ground-state alkali atoms from alkali halides and for the first time correlates directly the desorption with the stability and spatial distribution of the defects formed during bombardment. The electron impact results in the formation of stable F-centers and F-center clusters in the bulk of the crystals. In striking contrast a significant metallization of the surface is observed. Even at temperatures as low as 90 deg C the metallization is achieved within the time resolution of our detection system, which can only be explained by the rapid diffusion of hot holes. Superimposed to the fast and short diffusion of hot holes is the slow F-center diffusion. Measuring the distribution of defects with low energy ion sputtering techniques indicates that at least in the case of LiF the observed diffusion constant of F-centers agrees with values derived by using methods different from that applied here. At low temperatures the formation of F-center clusters and metal on the surface dominates. Colloid formation clearly requires higher temperatures (typically around 200 deg C). This is a strong evidence that efficient F-center diffusion is necessary for the formation of metallic particles (colloids) in the bulk of the crystals. Desorption of alkali atoms from alkali halides at temperatures around room temperature is due to weakly bound alkali atoms. For elevated temperatures the stability of the metallic clusters in the bulk of the crystals (i.e. colloids) are the rate limiting process. (author)

Thermoluminescence studies of Nd doped Bi_4Ge_3O_1_2 crystals irradiated by UV and beta sources

International Nuclear Information System (INIS)

Karabulut, Y.; Canimoglu, A.; Ekdal, E.; Ayvacikli, M.; Can, N.; Karali, T.

2016-01-01

Thermoluminescence (TL) glow curves of pure and rare earth doped bismuth germanate (BGO) were investigated under UV and beta radiation. The glow curves of pure BGO crystal present different patterns for both kinds of radiation. The TL glow curves of BGO crystals doped with Nd ions are similar to that of pure BGO under UV radiation. The kinetic parameters, kinetic order (b), activation energy (E) and frequency factor (s) of the TL glow curves of pure BGO crystal have been determined by peak shape method. Activation energies of 3 peaks obtained by PS were found to be 1.81, 1.15 and 1.78, respectively. - Highlights: • Thermoluminescence properties of pure and Nd doped BGO crystals. • Irradiated by UV and beta for TL glow curve analysis. • Evaluation of kinetic parameters by PS method.

Investigation of self-frequency doubling crystals, yttrium calcium oxyborate (YCOB), doped with neodymium or ytterbium

Science.gov (United States)

Ye, Qing

1999-09-01

There is a need for low cost red, green, and blue (RGB) lasers for a number of commercial applications such as high-resolution laser printing, full color laser display. While semiconductor lasers still have both availability (green and blue) and beam quality (red) problems, nonlinear frequency conversion of diode-pumped solid state lasers are good alternatives. Among them, self- frequency doubling is an attractive approach because of its simpler design and lower cost. Unfortunately, few known crystals possess self-frequency doubling property. A newly discovered yttrium calcium oxyborate (YCOB) can fill in the role because it has adequate lasing and nonlinear frequency conversion efficiency. More importantly, YCOB crystal melts congruently so that high quality, large size single crystals can be grown using conventional Czochralski melt pulling technique. The thermal mechanical properties, linear and nonlinear optical properties of YCOB, laser properties of Nd:YCOB and Yb:YCOB crystals were investigated. Based on the calculated second harmonic phase matching angles, Nd:YCOB laser rods were fabricated. Self-frequency doubled green emission with 62 mW output power and red emission with 16 mW output power were successfully demonstrated using diode-pumping. It is the first time to achieve the continuous wave (cw) red lasing in Nd doped rare-earth calcium oxyborates. Rare-earth ions doping in YCOB crystal can not only achieve lasing, but also affect the physical and chemical properties of the crystal. The stability field of YCOB is reduced in proportion to both the ionic size differences from yttrium and doping concentrations of the rare-earth ions. The doping also changes the linear and nonlinear optical properties of the material. For example, the second harmonic conversion efficiency of 20% Yb doped YCOB was enhanced by more than 15% compared to undoped YCOB. The absorption cutoff edge of 20% Yb:YCOB was red- shift by more than 60 nm. Similar effects were observed in

Fabrication of Microcapsules for Dye-Doped Polymer-Dispersed Liquid Crystal-Based Smart Windows.

Science.gov (United States)

Kim, Mingyun; Park, Kyun Joo; Seok, Seunghwan; Ok, Jong Min; Jung, Hee-Tae; Choe, Jaehoon; Kim, Do Hyun

2015-08-19

A dye-doped polymer-dispersed liquid crystal (PDLC) is an attractive material for application in smart windows. Smart windows using a PDLC can be operated simply and have a high contrast ratio compared to those of other devices that employed photochromic or thermochromic material. However, in conventional dye-doped PDLC methods, dye contamination can cause problems and has a limited degree of commercialization of electric smart windows. Here, we report on an approach to resolve dye-related problems by encapsulating the dye in monodispersed capsules. By encapsulation, a fabricated dye-doped PDLC had a contrast ratio of >120 at 600 nm. This fabrication method of encapsulating the dye in a core-shell structured microcapsule in a dye-doped PDLC device provides a practical platform for dye-doped PDLC-based smart windows.

Recombination luminescence of Cu and/or Ag doped lithium tetraborate single crystals

Energy Technology Data Exchange (ETDEWEB)

Romet, I. [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); Aleksanyan, E. [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); A. Alikhanyan National Science Laboratory, 2 Br. Alikhanyan Str., 0036 Yerevan (Armenia); Brik, M.G. [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); College of Sciences, Chongqing University of Posts and Telecommunications, 400065 Chongqing (China); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Corradi, G. [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege M. út 29-33, H-1121 Budapest (Hungary); Kotlov, A. [Photon Science at DESY, Notkestrasse 85, 22607 Hamburg (Germany); Nagirnyi, V., E-mail: vitali.nagirnoi@ut.ee [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); Polgár, K. [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege M. út 29-33, H-1121 Budapest (Hungary)

2016-09-15

Complex investigations of thermostimulated luminescence (TSL) and radioluminescence properties of Li{sub 2}B{sub 4}O{sub 7} (LTB), LTB:Cu, LTB:Ag and LTB:Cu, Ag crystals suitable for tissue equivalent dosimeters were carried out in the temperature range 4.2–700 K. TSL, cathodoluminescence and X-ray excited luminescence spectra are compared to those measured under photoexcitation. The emission band at 4.6 eV in LTB:Ag is reliably related to Ag{sup +} ions based on the comparison of the results of optical spectroscopy studies and first principle calculations. Energy transfer from the relaxed exited state of the Ag{sup +} ion to the Cu{sup +} ion in double-doped LTB:Cu, Ag crystals is demonstrated. Thermostimulated recombination of charge carriers in irradiated crystals is seen to take place mainly at oxygen sites at low temperatures and at impurity sites at high temperatures. For the first time, the appearance of the low-temperature TSL peak at 90 K is assigned to ionic processes in LTB crystals. The appearance of pyroelectric flashes due to the lattice relaxation in the temperature region 90–240 K is demonstrated and their surface-related nature clarified. In accordance with EPR studies the dosimetric TSL peaks in copper and silver doped LTB crystals are attributed to thermally released electrons recombining with Cu{sup 2+} and Ag{sup 2+} centres.

Optical bistability in erbium-doped yttrium aluminum garnet crystal combined with a laser diode.

Science.gov (United States)

Maeda, Y

1994-01-10

Optical bistability was observed in a simple structure of an injection laser diode combined with an erbium-doped yttrium aluminum garnet crystal. Since a hysteresis characteristic exists in the relationship between the wavelength and the injection current of a laser diode, an optical memory function capable of holding the output status is confirmed. In addition, an optical signal inversion was caused by the decrease of transmission of the erbium-doped yttrium aluminum garnet crystal against the red shift (principally mode hopping) of the laser diode. It is suggested that the switching time of this phenomenon is the time necessary for a mode hopping by current injection.

Growth and properties of oxygen- and ion-doped Bi2Sr2CaCu2O8+δ single crystals

Science.gov (United States)

Mitzi, D. B.; Lombardo, L. W.; Kapitulnik, A.; Laderman, S. S.; Jacowitz, R. D.

1990-04-01

A directional solidification method for growing large single crystals in the Bi2Sr2CaCu2O8+δ system is reported. Ion doping, with replacement of La for Sr and Y for Ca, as well as oxygen doping in these crystals has been explored. Doped and undoped crystals have been characterized using microprobe analysis, x-ray diffraction, thermogravimetric analysis, and magnetic and Hall measurements. Ion doping results in little change of the superconducting transition for substitution levels below 20-25%, while beyond this level the Meissner signal broadens and the low-temperature Meissner signal decreases. Microprobe analysis and x-ray diffraction performed on these more highly substituted single crystals provide evidence for inhomogeneity and phase segregation into regions of distinct composition. Annealing unsubstituted crystals in increasing partial pressures of oxygen reversibly depresses the superconducting transition temperature from 90 (as made) to 77 K (oxygen pressure annealed), while the carrier concentrations, as determined from Hall effect measurements, increase from n=3.1(3)×1021 cm-3 (0.34 holes per Cu site) to 4.6(3)×1021 cm-3 (0.50 holes per Cu site). No degradation of the Meissner transition or other indications of inhomogeneity or phase segregation with doping are noted, suggesting that oxygen-doped Bi2Sr2CaCu2O8+δ is a suitable system for pursuing doping studies. The decrease in Tc with concentration for 0.34<=n<=0.50 indicates that a high-carrier-concentration regime exists in which Tc decreases with n and suggests that this decrease does not arise from material inhomogeneity or other materials problems. An examination of the variation of Tc with the density of states and lattice constants for all of the doped and undoped superconducting samples considered here indicates that changes in Tc with doping are primarily affected by changes in the density of states (or carrier concentration) rather than by structural variation induced by the doping.

Thermoluminescence dependence on the wavelength of monochromatic UV-radiation in Cu-doped KCl and KBr at room temperature

Energy Technology Data Exchange (ETDEWEB)

Perez R, A.; Piters, T.; Aceves, R.; Rodriguez M, R.; Perez S, R., E-mail: rperez@cifus.uson.mx [Universidad de Sonora, Departamento de Investigaciones en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico)

2014-08-15

Thermoluminescence (Tl) dependence on the UV irradiation wavelengths from 200 to 500 nm in Cu-doped KCl and KBr crystals with different thermal treatment has been analyzed. Spectrum of the Tl intensity of each material show lower intensity at wavelengths longer than 420 nm. The Tl intensity depends on the irradiation wavelength. Structure of the Tl intensity spectrum of each sample is very similar to the structure of its optical absorption spectrum, indicating that at each wavelength, monochromatic radiation is absorbed to produce electronic transitions and electron hole pairs. Thermoluminescence of materials with thermal treatment at high temperature shows electron-hole trapping with less efficiency. The results show that Cu-doped alkali-halide materials are good detectors of a wide range of UV monochromatic radiations and could be used to measure UV radiation doses. (Author)

Thermoluminescence dependence on the wavelength of monochromatic UV-radiation in Cu-doped KCl and KBr at room temperature

International Nuclear Information System (INIS)

Perez R, A.; Piters, T.; Aceves, R.; Rodriguez M, R.; Perez S, R.

2014-08-01

Thermoluminescence (Tl) dependence on the UV irradiation wavelengths from 200 to 500 nm in Cu-doped KCl and KBr crystals with different thermal treatment has been analyzed. Spectrum of the Tl intensity of each material show lower intensity at wavelengths longer than 420 nm. The Tl intensity depends on the irradiation wavelength. Structure of the Tl intensity spectrum of each sample is very similar to the structure of its optical absorption spectrum, indicating that at each wavelength, monochromatic radiation is absorbed to produce electronic transitions and electron hole pairs. Thermoluminescence of materials with thermal treatment at high temperature shows electron-hole trapping with less efficiency. The results show that Cu-doped alkali-halide materials are good detectors of a wide range of UV monochromatic radiations and could be used to measure UV radiation doses. (Author)

Physical and chemical properties of a Ga-doped ZnO crystal

International Nuclear Information System (INIS)

Stashans, Arvids; Olivos, Katia; Rivera, Richard

2011-01-01

First-principles calculations based on density functional theory and strengthened by Hartree-Fock computations have been performed to study a Ga-doped wurtzite-type ZnO crystal. The large 108-atom supercell used throughout this work allows one to model a single point defect within the periodic supercell model. Thus, the Ga impurity produced purely local effects on the properties of the material. The electronic band structure was obtained for both pure and impurity-doped materials. The occurrence of free electrons in the conduction band was observed after the incorporation of Ga, implying the Ga dopant's contribution to n-type electrical conductivity in the ZnO crystal, in agreement with known experimental data. An analysis of the charges on atoms and obtained atomic displacements in the region surrounding the defect showed that there is some alteration in the chemical bonding because of the presence of Ga atoms. In particular, the ionic bonding is strengthened in the defect's neighbourhood.

Physical and chemical properties of a Ga-doped ZnO crystal

Energy Technology Data Exchange (ETDEWEB)

Stashans, Arvids; Olivos, Katia; Rivera, Richard, E-mail: arvids@utpl.edu.e [Grupo de FisicoquImica de Materiales, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

2011-06-01

First-principles calculations based on density functional theory and strengthened by Hartree-Fock computations have been performed to study a Ga-doped wurtzite-type ZnO crystal. The large 108-atom supercell used throughout this work allows one to model a single point defect within the periodic supercell model. Thus, the Ga impurity produced purely local effects on the properties of the material. The electronic band structure was obtained for both pure and impurity-doped materials. The occurrence of free electrons in the conduction band was observed after the incorporation of Ga, implying the Ga dopant's contribution to n-type electrical conductivity in the ZnO crystal, in agreement with known experimental data. An analysis of the charges on atoms and obtained atomic displacements in the region surrounding the defect showed that there is some alteration in the chemical bonding because of the presence of Ga atoms. In particular, the ionic bonding is strengthened in the defect's neighbourhood.

Magnetic and luminescent properties of vanadium-doped ZnSe crystals

Energy Technology Data Exchange (ETDEWEB)

Radevici, Ivan, E-mail: ivarad@utu.fi [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau (Moldova, Republic of); Nedeoglo, Natalia; Sushkevich, Konstantin [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau (Moldova, Republic of); Huhtinen, Hannu [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Nedeoglo, Dmitrii [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau (Moldova, Republic of); Paturi, Petriina [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)

2016-12-15

Magnetic and photoluminescence properties of vanadium-doped ZnSe crystals with impurity concentrations varied by changing the V amount in the source material from 0.03 to 0.30 at% are studied in 5–300 K temperature range. Investigation of magnetic properties shows that the studied concentrations of vanadium impurity that should not disturb crystal lattice are insignificant for observing ferromagnetic behaviour even at low temperatures. The contribution of V impurity to edge emission and its influence on infra-red emission are discussed. Similarities of magnetic and luminescent properties induced by vanadium and other transition metal impurities are discussed.

Radiation chemistry of the alkali halides

International Nuclear Information System (INIS)

Robinson, V.J.; Chandratillake, M.R.

1987-01-01

By far the most thoroughly investigated group of compounds in solid-state radiation chemistry are the alkali halides. Some of the reasons are undoubtedly practical: large single crystals of high purity are readily prepared. The crystals are transparent over a wide range of wavelengths. They are more sensitive to radiation damage than most other ionic solids. The crystals have simple well-defined structures, and the products of radiolysis have also in many cases been clearly identified by a variety of experimental techniques, the most important being optical methods and electron paramagnetic resonance (EPR). In recent years the application of pulse techniques-radiolysis and laser photolysis-has yielded a wealth of information concerning the mechanisms of the primary processes of radiation damage, on the one hand, and of thermal and photolytic reactions that the radiolysis products undergo, on the other

Energy transfer processes in Er-doped crystals

International Nuclear Information System (INIS)

Georgescu, Serban; Toma, Octavian

2005-01-01

In this paper, the microparameters characteristic to various energy-transfer processes in erbium doped crystals are estimated using the Dexter theory. For all the investigated processes, electric dipole-dipole interaction between donor and acceptor ions is assumed. The spectra appearing in Dexter's expression of the microparameter are simulated as a superposition of Lorentzian lines, knowing the positions of both initial and final Stark levels, and calibrated using the Judd-Ofelt model. This approach can give an estimation of the importance of the energy-transfer processes. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Photodynamic Processes in Fluoride Crystals Doped with Ce3+

Directory of Open Access Journals (Sweden)

Pavlov V.V.

2015-01-01

Full Text Available Integrated studies of photoelectric phenomena and their associated photodynamic processes in LiCaAlF6, LiLuF4, LiYF4, LiY0,5Lu0,5F4, SrAlF5 crystals doped with Ce3+ ions have been carried out using the combination of the methods of optical and dielectric spectroscopy. The numerical values of the basic parameters of photodynamic processes and their spectral dependence in 240 – 310 nm spectral range are evaluated. It has been shown that the most probable process, which leads to the photoionization of Ce3+ ions in LiYxLu1-xF4:Ce3+ (x=0; 0,5; 1 and LiCaAlF6:Ce3+ crystals, is excited-state absorption to the states of mixed configurations of Ce3+ ions localized near/in the conduction band of crystal.

Pyroelectric properties of phosphoric acid-doped TGS single crystals

International Nuclear Information System (INIS)

Saxena, Aparna; Fahim, M; Gupta, Vinay; Sreenivas, K

2003-01-01

Pyroelectric properties of phosphoric acid (H 3 PO 4 )-doped triglycine sulfate (TGSP) single crystals grown from solutions containing 0.1-0.5 mol of H 3 PO 4 have been studied. Incorporation of H 3 PO 4 into the crystal lattice is found to induce an internal bias field (E b ) and is observed through the presence of a sustained polarization and pyroelectricity beyond the transition temperature. The internal bias field has been estimated theoretically by fitting the experimentally measured data on temperature dependence of the pyroelectric coefficient (λ), dielectric constant (ε') and polarization (P). A high E b value in the range 9 x 10 3 -15.5 x 10 4 V m -1 is obtained for crystals grown with 0.1-0.5 mol of H 3 PO 4 in the solution, and a specific concentration of 0.2-0.25 mol of H 3 PO 4 in the solution during crystal growth is found to be optimum for a high figure of merit for detectivity, F d = 428 μC m -2 K -1

Oxygen vacancies effect on ionic conductivity and relaxation phenomenon in undoped and Mn doped PZN-4.5PT single crystals

International Nuclear Information System (INIS)

Kobor, Diouma; Guiffard, Benoit; Lebrun, Laurent; Hajjaji, Abdelowahed; Guyomar, Daniel

2007-01-01

AC-impedance spectroscopic studies in the temperature range 550-700 deg. C are carried out on undoped and Mn doped PZN-PT single crystals grown by the flux method. The variation of dielectric permittivity with temperature at different frequencies shows normal ferroelectric and relaxor-like dependence for the doped and undoped crystals, respectively. Temperature-dependent spectroscopic modulus plots reveal a much broader peak for PZN-4.5PT + 1%Mn compared with that for PZN-4.5PT, which is different from the dielectric behaviour of the doped one. Complex modulus imaginary part (Z-prime) versus real part (Z') plots fit well with one semicircle thus indicating only bulk contribution. The relaxation observed in the spectroscopic plots was assigned to mobile relaxor species such as oxygen vacancies and ions. No such relaxation could be observed for PZN-4.5PT + 1%Mn in the dielectric measurements. For both undoped and Mn doped crystals, the conduction behaviour was modelled by the universal dynamic response equation and by the NTC (negative temperature coefficient) materials resistance-temperature behaviour. A large difference in behaviour was found between the two single crystals such as the thermistor coefficients and the activation energy values, which could explain the increase in the thermal stability observed in the Mn doped PZN-PT single crystals by many studies

Growth and properties of oxygen- and ion-doped Bi2Sr2CaCu2O8+δ single crystals

International Nuclear Information System (INIS)

Mitzi, D.B.; Lombardo, L.W.; Kapitulnik, A.; Laderman, S.S.; Jacowitz, R.D.

1990-01-01

A directional solidification method for growing large single crystals in the Bi 2 Sr 2 CaCu 2 O 8+δ system is reported. Ion doping, with replacement of La for Sr and Y for Ca, as well as oxygen doping in these crystals has been explored. Doped and undoped crystals have been characterized using microprobe analysis, x-ray diffraction, thermogravimetric analysis, and magnetic and Hall measurements. Ion doping results in little change of the superconducting transition for substitution levels below 20--25%, while beyond this level the Meissner signal broadens and the low-temperature Meissner signal decreases. Microprobe analysis and x-ray diffraction performed on these more highly substituted single crystals provide evidence for inhomogeneity and phase segregation into regions of distinct composition. Annealing unsubstituted crystals in increasing partial pressures of oxygen reversibly depresses the superconducting transition temperature from 90 (as made) to 77 K (oxygen pressure annealed), while the carrier concentrations, as determined from Hall effect measurements, increase from n=3.1(3)x10 21 cm -3 (0.34 holes per Cu site) to 4.6(3)x10 21 cm -3 (0.50 holes per Cu site)

Synthesis and characterization of lithium fluoride nano crystals doped with silver

International Nuclear Information System (INIS)

Rosario M, B. R.; Ramirez C, G.; Encarnacion E, E. K.; Sosa A, M. A.

2017-10-01

Thermoluminescence (Tl) is the emission of light by certain materials to be heated below its incandescence temperature, having previously been exposed to an exciting agent such as ionizing radiation. Lithium fluoride (LiF) is the thermoluminescent material used in the manufacture of Tl-100 dosimeters. What morphological characteristics (size, crystallinity) do the nano crystals of pure lithium fluoride (LiF) have when doped with silver (Ag) by the precipitation method? The objective of this study was to synthesize and characterize the LiF nano crystals doped with silver (Ag) in concentrations of 0.02, 0.04, 0.06, 0.08, 0.1 and 0.2%. The samples were synthesized using as reagents; distilled water, ammonium fluoride (NH 4 F), lithium chloride (LiCl), silver nitrate (AgNO 3 ); and materials such as: 0.1 mg precision balance, spatulas, test piece, magnetic stirrer, beaker, volumetric flask, burette, burette clamp, key and magnetic stirring wand. In the characterization process we used and X-ray diffractometer (XRD) with which we obtained the X-ray diffraction spectrum with well-defined peaks that are characteristic of LiF. Using the Scherrer equation we calculate the sizes of nano crystals. This study demonstrates that is possible to synthesize LiF using new dopant materials. (Author)

Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

International Nuclear Information System (INIS)

Guss, Paul; Mukhopadhyay, Sanjoy; Guise, Ron; Yuan, Ding

2010-01-01

Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF 3 :Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to 137 Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF 3 :Ce-loaded sample have been made using 137 Cs sources. Figure 2 shows an energy spectrum acquired for CeF 3 . The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr 3 crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% 138 La component of lanthanum leads to significant self-activity, which will be a problem for very large detector volumes. Yet a significant

Studies in crystal structure and luminescence properties of Eu3+-doped metal tungstate phosphors for white LEDs

International Nuclear Information System (INIS)

Lee, Gwan-Hyoung; Kang, Shinhoo

2011-01-01

The correlation between the crystal structure and luminescent properties of Eu 3+ -doped metal tungstate phosphors for white LEDs was investigated. Red-emitting A 4-3x (WO 4 ) 2 :Eu x 3+ (A=Li, Na, K) and B (4-3x)/2 (WO 4 ) 2 :Eu x 3+ (B=Mg, Ca, Sr) phosphors were synthesized by solid-state reactions. The findings confirmed that these phosphors exhibited a strong absorption in the near UV to green range, due to the intra-configurational 4f-4f electron transition of Eu 3+ ions. The high doping concentration of Eu 3+ enhanced the absorption of near UV light and red emission without any detectable concentration quenching. Based on the results of a Rietveld refinement, it was attributed to the unique crystal structure. In the crystal structure of the Eu 3+ -doped metal tungstate phosphor, the critical energy transfer distance is larger than 5 A so that exchange interactions between Eu 3+ ions would occur with difficulty, even at a high doping concentration. The energy transfer between Eu 3+ ions, which causes a decrease in red emission with increasing concentration of Eu 3+ , appears to be due to electric multi-polar interactions. In addition, the Eu-O distance in the host lattice affected the shape of emission spectrum by splitting of emission peak at the 5 D 0 → 7 F 2 transition of Eu 3+ . - Highlights: → Eu 3+ -doped metal tungstate was synthesized as a red phosphor for white LEDs. → Crystal structure is tetragonal with a space group of I4 1 /c. → A strong absorption in the near UV to green range was observed. → High doping of Eu 3+ enhanced the absorption of near UV light and red emission.

Optical spectroscopy of Nd3+/Mg2+ co-doped LiTaO3 laser crystal

International Nuclear Information System (INIS)

Zhang, P X; Hang, Y; Gong, J; Zhao, C C; Yin, J G; Zhang, L H; Zhu, Y Y

2013-01-01

A Nd 3+ and Mg 2+ co-doped LiTaO 3 single crystal has been grown successfully by the Czochralski method. The polarized absorption spectra of the crystal were measured and investigated. The peak absorption cross-sections at 806 and 810 nm were 4.17 × 10 −20 cm 2 and 4.47 × 10 −20 cm 2 with a full width at half maximum of 29 and 17 nm for σ- and π-polarization, respectively. Based on the Judd–Ofelt theory, the spectral parameters of Nd 3+ in the as-grown crystal were investigated in detail. Moreover, the emission probabilities, branching ratio and radiative lifetime for the transitions from 4 F 3/2 were calculated. The radiative lifetime of 4 F 3/2 was calculated to be 159 μs and the luminescent quantum efficiency of the 4 F 3/2 manifold was about 81.13%. The results were also compared with other Nd 3+ doped crystals. (paper)

The photorefractive characteristics of bismuth-oxide doped lithium niobate crystals

International Nuclear Information System (INIS)

Zheng, Dahuai; Yao, Jiaying; Kong, Yongfa; Liu, Shiguo; Zhang, Ling; Chen, Shaolin; Xu, Jingjun

2015-01-01

Bismuth-doped lithium niobate (LN:Bi) crystals were grown by Czochralski method and their optical damage resistance, photorefraction, absorption spectra, and defect energy levels were investigated. The experimental results indicate that the photorefractive properties of LN:Bi were enhanced as compared with congruent one, the photorefractive response time was greatly shortened, the photorefractive sensitivity was increased, and the diffraction efficiency of near-stoichiometric LN:Bi (SLN:Bi) reached 31.72% and 49.08% at 532 nm and 488 nm laser, respectively (light intensity of 400 mW/cm 2 ). An absorption peak at about 350 nm was observed in the absorption spectrum of LN:Bi. And the defect energy levels simulation indicates new defect levels appear in the forbidden gap of LN:Bi crystals. Therefore bismuth can act as photorefractive centers in LN crystals

The photorefractive characteristics of bismuth-oxide doped lithium niobate crystals

Energy Technology Data Exchange (ETDEWEB)

Zheng, Dahuai; Yao, Jiaying [School of Physics, Nankai University, Tianjin 300071 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Kong, Yongfa, E-mail: kongyf@nankai.edu.cn [School of Physics, Nankai University, Tianjin 300071 (China); MOE Key Laboratory of Weak-Light Nonlinear Photonics and TEDA Applied Physics School, Nankai University, Tianjin 300457 (China); R and D Center, Taishan Sports Industry Group, Leling 253600 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Liu, Shiguo [School of Physics, Nankai University, Tianjin 300071 (China); Zhang, Ling; Chen, Shaolin [MOE Key Laboratory of Weak-Light Nonlinear Photonics and TEDA Applied Physics School, Nankai University, Tianjin 300457 (China); Xu, Jingjun [School of Physics, Nankai University, Tianjin 300071 (China); MOE Key Laboratory of Weak-Light Nonlinear Photonics and TEDA Applied Physics School, Nankai University, Tianjin 300457 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China)

2015-01-15

Bismuth-doped lithium niobate (LN:Bi) crystals were grown by Czochralski method and their optical damage resistance, photorefraction, absorption spectra, and defect energy levels were investigated. The experimental results indicate that the photorefractive properties of LN:Bi were enhanced as compared with congruent one, the photorefractive response time was greatly shortened, the photorefractive sensitivity was increased, and the diffraction efficiency of near-stoichiometric LN:Bi (SLN:Bi) reached 31.72% and 49.08% at 532 nm and 488 nm laser, respectively (light intensity of 400 mW/cm{sup 2}). An absorption peak at about 350 nm was observed in the absorption spectrum of LN:Bi. And the defect energy levels simulation indicates new defect levels appear in the forbidden gap of LN:Bi crystals. Therefore bismuth can act as photorefractive centers in LN crystals.

Optical properties of alkali halide crystals from all-electron hybrid TD-DFT calculations

Energy Technology Data Exchange (ETDEWEB)

Webster, R., E-mail: ross.webster07@imperial.ac.uk; Harrison, N. M. [Thomas Young Centre, Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Bernasconi, L. [Rutherford Appleton Laboratory, STFC, Harwell Oxford, Didcot OX11 0QX (United Kingdom)

2015-06-07

We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of the optical gap and exciton binding energy. The formation of bound excitons by photoexcitation is observed in all the studied systems and this is shown to be correlated to specific features of the Hartree-Fock exchange component of the TD-DFT response kernel. All computed optical gaps and exciton binding energies are however markedly below estimated experimental and, where available, 2-particle Green’s function (GW-Bethe-Salpeter equation, GW-BSE) values. We attribute this reduced exciton binding to the incorrect asymptotics of the B3LYP exchange correlation ground state functional and of the TD-B3LYP response kernel, which lead to a large underestimation of the Coulomb interaction between the excited electron and hole wavefunctions. Considering LiF as an example, we correlate the asymptotic behaviour of the TD-B3LYP kernel to the fraction of Fock exchange admixed in the ground state functional c{sub HF} and show that there exists one value of c{sub HF} (∼0.32) that reproduces at least semi-quantitatively the optical gap of this material.

Spectroscopic, Homo-Lumo and NLO studies of tetra fluoro phthalate doped Coumarin crystals using DFT method

Science.gov (United States)

Latha, B.; Kumaresan, P.; Nithiyanantham, S.; Sampathkumar, K.

2017-08-01

In the present examination, a methodical study has been done on the development of unadulterated and Coumarin doped Tetrafluoro Phthalate precious stones. Powder X-beam diffraction studies were done and the cross section parameters were computed by minimum square technique in pure and doped crystals. FT-IR, UV-Vis, Thermal, Micro-hardness and Dielectric studies were additionally done for the pure and doped crystals. The tentatively watched FT-IR and FT-Raman groups were allotted to various ordinary methods of the atom. The steadiness and charge delocalization of the particle were likewise concentrations were done by characteristic security orbital (NBO) examination. The HOMO-LUMO energies depict the charge exchange happens inside the particle. Atomic electrostatic potential has been broken down the electronic properties such as excitation energies, oscillator quality, wavelengths and HOMO-LUMO energies were acquired by time-subordinate DFT (TD-DFT) approach. The SHG of pure and doped TFP stones were examined through Nd:YAG Q-exchanged laser.

Large polarons in lead halide perovskites

OpenAIRE

Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

2017-01-01

Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3 ? framewor...

Optical switching in nonlinear photonic crystals lightly doped with nanostructures

Energy Technology Data Exchange (ETDEWEB)

Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Lipson, R H [Department of Chemistry, University of Western Ontario, London, ON N6A 5B7 (Canada)

2008-01-14

A possible switching mechanism has been investigated for nonlinear photonic crystals doped with an ensemble of non-interacting three-level nanoparticles. In this scheme, an intense pump laser field is used to change the refractive index of the nonlinear photonic crystal while a weaker probe field monitors an absorption transition in the nanoparticles. In the absence of the strong laser field the system transmits the probe field when the resonance energy of the nanoparticles lies near the edge of the photonic band gap due to strong coupling between the photonic crystal and the nanoparticles. However, upon application of an intense pump laser field the system becomes absorbing due to a band edge frequency shift that arises due to a nonlinear Kerr effect which changes the refractive index of the crystal. It is anticipated that the optical switching mechanism described in this work can be used to make new types of photonic devices.

Crystal growth and scintillation properties of Pr-doped oxyorthosilicate for different concentration

Energy Technology Data Exchange (ETDEWEB)

Totsuka, Daisuke, E-mail: totsuka@mail.tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Nihon Kessho Kogaku Co. Ltd (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe) 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Fujimoto, Yutaka [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Pejchal, Jan [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Institute of Physics AS CR, Cukrovarnicka 10, Prague 6, 162-53 (Czech Republic); Yokota, Yuui [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yoshikawa, Akira [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe) 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

2011-07-01

0.05, 0.1 and 0.25 mol% Pr (with respect to Lu) doped Lu{sub 2}SiO{sub 5} (LSO) single crystals were grown by the micro-pulling down ({mu}-PD) method. The grown crystals were transparent, and a slight segregation of Pr{sup 3+} was observed both in the crystal cross-section and growth direction. Transparency in the visible wavelength range was about 80% in all the crystals. Intense absorptions related with the Pr{sup 3+} 4f-5d transitions were observed around 230 and 255 nm, and weak absorptions due to the 4f-4f transitions were detected around 450 nm. In radioluminescence spectra, the Pr{sup 3+} 5d-4f transitions were observed around 275and 310 nm, and emissions due to the 4f-4f transition were observed around 500 nm. In the pulse height analysis using {sup 137}Cs gamma-ray excitation, Pr 0.1% doped sample showed the highest light yield of 2,800 ph/MeV. In the decay time measurements using different excitation sources (photoluminescence, X- and gamma-ray), two different processes related to the 5d-4f emission peaks were found. Fast decay component corresponds to direct excitation of Pr{sup 3+} (4-6 ns) and slower component (25 ns) reflects the energy migration process from the host lattice to the emission center.

Optical properties of Ho3+-doped NaGd(WO4)2 crystal for laser materials

International Nuclear Information System (INIS)

Wang, Hongyan; Li, Jianfu; Jia, Guohua; You, Zhenyu; Yang, Fugui; Wei, Yanping; Wang, Yan; Zhu, Zhaojie; Lu, Xiuai; Tu, Chaoyang

2007-01-01

Holmium doped sodium gadolinium tungstate crystals with sizes of about O20 mm x 40 mm were grown successfully by the Czochralski technique along the (0 0 1) orientation. Polarized absorption spectra, fluorescence spectra and fluorescence decay curve of Ho 3+ -doped NaGd(WO 4 ) 2 have been recorded at room temperature. Based on the Judd-Ofelt theory, three intensity parameters were obtained. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetimes as well as the branching ratios were calculated. The fluorescence lifetime τ f of the 5 S 2 level was measured to be 5 μs

Fabricating large two-dimensional single colloidal crystals by doping with active particles

NARCIS (Netherlands)

van der Meer, B; Filion, L; Dijkstra, M

2016-01-01

Using simulations we explore the behaviour of two-dimensional colloidal (poly)crystals doped with active particles. We show that these active dopants can provide an elegant new route to removing grain boundaries in polycrystals. Specifically, we show that active dopants both generate and are

Influences of Silver-Doping on the Crystal Structure, Morphology and Photocatalytic Activity of TiO2 Nanofibers

DEFF Research Database (Denmark)

Barakat, Nasser A. M.; Kanjwal, Muzafar Ahmed; Al-Deyab, Salem S.

2011-01-01

Doping of titanium dioxide nanofibers by silver nanoparticles revealed distinct improvement in the photocatalytic activ-ity; however other influences have not been investigated. In this work, effect of sliver-doping on the crystal structure, the nanofibrous morphology as well as the photocatalyti...

Single mode dye-doped polymer photonic crystal lasers

DEFF Research Database (Denmark)

Christiansen, Mads Brøkner; Buss, Thomas; Smith, Cameron

2010-01-01

Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode...... emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e. g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be -0.045 or -0...

Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi2Te2Se

International Nuclear Information System (INIS)

Kushwaha, S. K.; Gibson, Q. D.; Cava, R. J.; Xiong, J.; Ong, N. P.; Pletikosic, I.; Weber, A. P.; Fedorov, A. V.; Valla, T.

2014-01-01

A comparative study of the properties of topological insulator Bi 2 Te 2 Se (BTS) crystals grown by the vertical Bridgeman method is described. Two defect mechanisms that create acceptor impurities to compensate for the native n-type carriers are compared: Bi excess, and light Sn doping. Both methods yield low carrier concentrations and an n-p crossover over the length of the grown crystal boules, but lower carrier concentrations and higher resistivities are obtained for the Sn-doped crystals, which reach carrier concentrations as low as 8 × 10 14  cm −3 . Further, the temperature dependent resistivities for the Sn-doped crystals display strongly activated behavior at high temperatures, with a characteristic energy of half the bulk band gap. The (001) cleaved Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum oscillations due to the topological surface state electrons. Angle resolved photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy (E F ) for the Sn-doped crystals falls cleanly in the surface states with no interference from the bulk bands, which the Dirac point for the surface states lies approximately 60 meV below the top of the bulk valence band maximum, and allows for a determination of the bulk and surface state carrier concentrations as a function of Energy near E F . Electronic structure calculations that compare Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity, with a localized impurity band that acts as a charge buffer occurring inside the bulk band gap. We propose that the special resonant level character of Sn in BTS gives rise to the exceptionally low carrier concentrations and activated resistivities observed

The molecular ordering phenomenon in dye-doped nematic liquid crystals

International Nuclear Information System (INIS)

Prakash Yadav, Satya; Pandey, Kamal Kumar; Kumar Misra, Abhishek; Kumar Tripathi, Pankaj; Manohar, Rajiv

2011-01-01

The experimental results of this work point out the role of the guest dye molecules in the molecular ordering of nematic liquid crystals. We have discussed the changes in the energies of interactions between rod-like nematic molecules and anthraquinone dye by considering the presence of steric and dipole-dipole interactions in the dye-doped system. The concentration of the dye plays an important role in the determination of molecular ordering in such dye-doped systems. Below a certain concentration of dye (known as the critical concentration), where the interaction between the dye molecules can be neglected, the addition of dye molecules introduces some disorder into the system in the form of domain formation. Above this critical concentration, this disorder is small.

The molecular ordering phenomenon in dye-doped nematic liquid crystals

Energy Technology Data Exchange (ETDEWEB)

Prakash Yadav, Satya; Pandey, Kamal Kumar; Kumar Misra, Abhishek; Kumar Tripathi, Pankaj; Manohar, Rajiv, E-mail: rajiv.manohar@gmail.com [Liquid Crystal Research Laboratory, Physics Department, University of Lucknow, Lucknow-226007 (India)

2011-03-15

The experimental results of this work point out the role of the guest dye molecules in the molecular ordering of nematic liquid crystals. We have discussed the changes in the energies of interactions between rod-like nematic molecules and anthraquinone dye by considering the presence of steric and dipole-dipole interactions in the dye-doped system. The concentration of the dye plays an important role in the determination of molecular ordering in such dye-doped systems. Below a certain concentration of dye (known as the critical concentration), where the interaction between the dye molecules can be neglected, the addition of dye molecules introduces some disorder into the system in the form of domain formation. Above this critical concentration, this disorder is small.

Growth of rare-earth doped single crystal yttrium aluminum garnet fibers

Science.gov (United States)

Bera, Subhabrata; Nie, Craig D.; Harrington, James A.; Cheng, Long; Rand, Stephen C.; Li, Yuan; Johnson, Eric G.

2018-02-01

Rare-earth doped single crystal (SC) yttrium aluminum garnet (YAG) fibers have great potential as high-power laser gain media. SC fibers combine the superior material properties of crystals with the advantages of a fiber geometry. Improving processing techniques, growth of low-loss YAG SC fibers have been reported. A low-cost technique that allows for the growth of optical quality Ho:YAG single crystal (SC) fibers with different dopant concentrations have been developed and discussed. This technique is a low-cost sol-gel based method which offers greater flexibility in terms of dopant concentration. Self-segregation of Nd ions in YAG SC fibers have been observed. Such a phenomenon can be utilized to fabricate monolithic SC fibers with graded index.

Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

Energy Technology Data Exchange (ETDEWEB)

Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

2017-03-31

The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

Growth and characterization of La2CoMnO6 crystals doped with Pb

International Nuclear Information System (INIS)

Milenov, T.I.; Rafailov, P.M.; Abrashev, M.V.; Nikolova, R.P.; Nakatsuka, A.; Avdeev, G.V.; Veleva, M.N.; Dobreva, S.; Yankova, L.; Gospodinov, M.M.

2010-01-01

Crystals of La 2 CoMnO 6 doped with Pb were grown by the high temperature solution growth method. Several crystals were examined by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), X-ray single-crystal diffractometry and polarized Raman spectroscopy. Some variations in the composition of different crystals are observed, however, within the volume of each distinct crystal the composition is found to be fairly constant. Crystals with lateral dimensions larger than 2 mm and thicker than 1 mm contain structural defects as twin lamellae and surface roughness. The results from the characterization of the grown crystals with X-ray diffraction and Raman spectroscopy are consistent with an assumption for a coexistence of an ordered monoclinic and a disordered orthorhombic phase.

A crystal chemistry approach for high-power ytterbium doped solid-state lasers: diffusion-bonded crystals and new crystalline hosts

International Nuclear Information System (INIS)

Gaume, R.

2002-11-01

This work deals with ytterbium based crystals for high-power laser applications. In particular, we focus our interest in reducing crystal heating and its consequences during laser operation following two different ways. First, we review the specific properties of ytterbium doped solid-state lasers in order to define a figure-of-merit which gives the evaluation of laser performances, thermo-mechanical and thermo-optical properties. Bearing in mind this analysis, we propose a set of theoretical tools, based on the crystallographic structure of the crystal and its chemical composition, to predict thermo-mechanical and optical potentials. This approach, used for the seek of new Yb 3+ -doped materials for high-power laser applications, shows that simple oxides containing rare-earths are favorable. Therefore, the spectroscopic properties of six new materials Yb 3+ :GdVO 4 , Yb 3+ :GdAlO 3 , Yb 3+ :Gd 2 O 3 , Yb 3+ :Sc 2 SiO 5 , Yb 3+ :CaSc 2 O 4 and Yb 3+ :SrSc 2 O 4 are described. The second aspect developed in this work deals with thermal properties enhancement of already well characterized laser materials. Two different ways are explored: a) elaboration by diffusion bonding of end-caps lasers with undoped crystals (composite crystals). Thus, different composites were obtained and a fairly lowering of thermal lensing effect was observed during laser operation. b) strengthening of crystalline structures by ionic substitution of one of its constituents. We demonstrate how crystal growth ability can be improved by a cationic substitution in the case of Yb 3+ :BOYS, a largely-tunable laser material which is of great interest for femtosecond pulses generation. (author)

Raman and NMR study in MgO-doped LiNbO3 crystal

International Nuclear Information System (INIS)

Hu, L.J.; Chang, Y.H.; Chang, C.S.; Yang, S.J.; Hu, M.L.; Tse, W.S.

1991-01-01

This paper reports on the MgO-doped LiNbO 3 crystal grown and studied by NMR and Raman techniques. The solubility of MgO in the LiNbO 3 crystal is as much as 30 mole %. It is shown in NMR spectra that the number of Nb 5+ cations at A-site (Li-site) decrease as Mg concentration increased when the Mg content is lower than 5 mole %. The vibration of (NbO 6 ) octahedron and translations involving Li + and Mg 2+ cations motion can be identified by replacing Nb 5+ and Li + cations with Ta 5+ and Mg 2+ cations through Raman spectra. The 115 cm -1 and 151 cm -1 peaks are due to the translational modes of Mg 2+ and Li + cations. The doping mechanisms of MgO are proposed

The investigation of Ce doped ZnO crystal: The electronic, optical and magnetic properties

Science.gov (United States)

Wen, Jun-Qing; Zhang, Jian-Min; Qiu, Ze-Gang; Yang, Xu; Li, Zhi-Qin

2018-04-01

The electronic, optical and magnetic properties of Ce doped ZnO crystal have been studied by using first principles method. The research of formation energies show that Ce doped ZnO is energetically stable, and the formation energies reduce from 6.25% to 12.5% for Ce molar percentage. The energy band is still direct band gap after Ce doped, and band gap increases with the increase of Cesbnd Ce distance. The Fermi level moves upward into conduction band and the DOS moves to lower energy with the increase of Ce concentration, which showing the properties of n-type semiconductor. The calculated optical properties imply that Ce doped causes a red-shift of absorption peaks, and enhances the absorption of the visible light. The transition from ferromagnetic to antiferromagnetic has been found in Ce doped ZnO.

Monocrystallomimicry in the aerosols of ammonium and cesium halides

International Nuclear Information System (INIS)

Melikhov, I.V.; Kitova, E.N.; Kozlovskaya, EhD.; Kamenskaya, A.N.; Mikheev, N.B.; Kulyukhin, S.A.

1997-01-01

It is experimentally shown that initial CsI and NH 4 Hal nanocrystals combining into mixed aggregates of polyhedral form (pseudo monocrystals) are formed in the process of cocrystallization of ammonium halide and cesium iodide. The origination and growth of the pseudo monocrystals on the account of successive addition of initial crystals is described by the Fokker-Plank equation [ru

Influence of PbCl2 content in PbI2 solution of DMF on the absorption, crystal phase, morphology of lead halide thin films and photovoltaic performance in planar perovskite solar cells

International Nuclear Information System (INIS)

Wang, Mao; Shi, Chengwu; Zhang, Jincheng; Wu, Ni; Ying, Chao

2015-01-01

In this paper, the influence of PbCl 2 content in PbI 2 solution of DMF on the absorption, crystal phase and morphology of lead halide thin films was systematically investigated and the photovoltaic performance of the corresponding planar perovskite solar cells was evaluated. The result revealed that the various thickness lead halide thin film with the small sheet-like, porous morphology and low crystallinity can be produced by adding PbCl 2 powder into PbI 2 solution of DMF as a precursor solution. The planar perovskite solar cell based on the 300-nm-thick CH 3 NH 3 PbI 3−x Cl x thin film by the precursor solution with the mixture of 0.80 M PbI 2 and 0.20 M PbCl 2 exhibited the optimum photoelectric conversion efficiency of 10.12% along with an open-circuit voltage of 0.93 V, a short-circuit photocurrent density of 15.70 mA cm −2 and a fill factor of 0.69. - Graphical abstract: The figure showed the surface and cross-sectional SEM images of lead halide thin films using the precursor solutions: (a) 0.80 M PbI 2 , (b) 0.80 M PbI 2 +0.20 M PbCl 2 , (c) 0.80 M PbI 2 +0.40 M PbCl 2 , and (d) 0.80 M PbI 2 +0.60 M PbCl 2 . With the increase of the PbCl 2 content in precursor solution, the size of the lead halide nanosheet decreased and the corresponding thin films gradually turned to be porous with low crystallinity. - Highlights: • Influence of PbCl 2 content on absorption, crystal phase and morphology of thin film. • Influence of perovskite film thickness on photovoltaic performance of solar cell. • Lead halide thin film with small sheet-like, porous morphology and low crystallinity. • Planar solar cell with 300 nm-thick perovskite thin film achieved PCE of 10.12%.

Pyroelectric properties of phosphoric acid-doped TGS single crystals

Energy Technology Data Exchange (ETDEWEB)

Saxena, Aparna; Fahim, M; Gupta, Vinay; Sreenivas, K [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

2003-12-21

Pyroelectric properties of phosphoric acid (H{sub 3}PO{sub 4})-doped triglycine sulfate (TGSP) single crystals grown from solutions containing 0.1-0.5 mol of H{sub 3}PO{sub 4} have been studied. Incorporation of H{sub 3}PO{sub 4} into the crystal lattice is found to induce an internal bias field (E{sub b}) and is observed through the presence of a sustained polarization and pyroelectricity beyond the transition temperature. The internal bias field has been estimated theoretically by fitting the experimentally measured data on temperature dependence of the pyroelectric coefficient ({lambda}), dielectric constant ({epsilon}') and polarization (P). A high E{sub b} value in the range 9 x 10{sup 3}-15.5 x 10{sup 4} V m{sup -1} is obtained for crystals grown with 0.1-0.5 mol of H{sub 3}PO{sub 4} in the solution, and a specific concentration of 0.2-0.25 mol of H{sub 3}PO{sub 4} in the solution during crystal growth is found to be optimum for a high figure of merit for detectivity, F{sub d} = 428 {mu}C m{sup -2} K{sup -1}.

Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

International Nuclear Information System (INIS)

Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

2002-01-01

Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

Study of thermoluminescence in K Cl crystals doped with Sr2+

International Nuclear Information System (INIS)

Russo, D.M.B.

1990-01-01

An attempt is made to correlate the F and Z 1 (F center modified by the presence of a two-valence impurity pair and and positive ion vacancy) and a V center, with the T L curve peaks observed in pure K Cl crystals doped with Sr 2+ , irradiated at room temperature. (L.C.J.A.)

Crystallization Mechanism and Phase Transition Properties of W-doped VO2 Synthesized by Hydrothermal Method

Directory of Open Access Journals (Sweden)

LI Yao

2017-11-01

Full Text Available VO2 sol was firstly prepared using vanadyl sulfate as a vanadium source by precipitation-peptization method. Then tungsten(W doping vanadium dioxide(W-VO2 was prepared by hydrothermal crystallization of prepared sol with the presence of ammonium metatungstate. The morphologies, crystal structure of the as-prepared samples and phase transition properties were studied by X-ray diffraction(XRD, field emission scanning electron microscope(FESEMand differential scanning calorimetry(DSC analysis. The results indicate that rod-like W-VO2(B crystal with length of 1-2μm and radius of 100-200nm is firstly formed during hydrothermal treatment for 4-48h at 280℃, then the rod-like crystal dissolves gradually and sheet-like or snowflake-like crystal is formed with the phase transition from W-VO2(B to W-VO2(M and eventually, the W-VO2(M crystals can further grow up while the W-VO2(B gradually dissolves; the phase transition temperature of VO2 decreases with the increase in W doping content, and the phase transition temperature of W-VO2(M reduces to about 28℃ when the nominal dopant concentration is 6.0%(atom fraction.The "nucleation-growth-transformation-ripening" mechanism is proposed as the formation mechanism based on the hydrothermal crystallization and morphological evolution process of W-VO2(M.

Nonlinear Optical Characteristics of Crystal VioletDye Doped Polystyrene Films by Using Z-Scan Technique

Directory of Open Access Journals (Sweden)

Mahasin F. Hadi

2017-07-01

Full Text Available Z-scan technique was employed to study the nonlinear optical properties (nonlinear refractive index and nonlinear absorption coefficient for crystal violet doped polystyrene films as a function of doping ratio in chloroform solvent. Samples exhibits in closed aperture Z-scan positive nonlinear refraction (self-focusing. While in the open aperture Z-scan gives reverse saturation absorption (RSA (positive absorption for all film with different doping ratio making samples candidates for optical limiting devices for protection of sensors and eyes from energetic laser light pulses under the experimental conditions.

Growth and scintillation properties of Ce{sup 3+}-doped (Y{sub 1-x}Gd{sub x})AlO{sub 3} crystals

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, Yutaka; Wakahara, Shingo; Suzuki, Shotaro; Kurosawa, Shunsuke [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Yoshikawa, Akira [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2012-12-15

The optical and scintillation properties of 0.5% fixed Ce-doped (Y{sub 1-x}Gd{sub x})AlO{sub 3} single crystals have been investigated at three different levels of Gd doping: x = 0.2, 0.4 and 0.6. Single crystal of the Ce{sup 3+}-doped (Y{sub 0.8}Gd{sub 0.2})AlO{sub 3}, (Y{sub 0.6}Gd{sub 0.4})AlO{sub 3} and (Y{sub 0.4}Gd{sub 0.6})AlO{sub 3} were successfully grown by {mu}-PD technique in nitrogen atmosphere. From X-ray diffraction analysis, no impurity phase was detected for the grown Ce-doped crystals. Ce-doped (Y{sub 0.6}Gd{sub 0.4})AlO{sub 3} crystal demonstrated highest fluorescence quantum efficiency ({proportional_to} 25%) with improvement of excitation efficiency due to the Gd-doping. When irradiated by the alpha-rays from a {sup 241}Am source, all the Ce-doped crystals showed luminescence band that corresponding to 5d (t{sub 2g})-4f transition of Ce{sup 3+}. The scintillation decay time was characterized by two components; the fast component (5-15 ns) is ascribed to 5d-4f transition of Ce{sup 3+}, while the slow one (100-200 ns) may be related to energy transfer between Ce{sup 3+} and Gd{sup 3+} ion. According to the result of {sup 137}Cs gamma-ray irradiated pulse height spectra compared with BGO scintillator, the relative scintillation light output was found to be about 12200 {+-} 1220 (Gd 20%) and 16000 {+-} 1600 (Gd 40%) ph/MeV. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Radiation Induced Color Centers in a La Doped PWO Crystal

CERN Document Server

Deng, Qun

1998-01-01

This report presents result of a study on radiation induced color center densities in a La doped lead tungstate ( PWO) crystal. The creation and annihilation constants of radiation induced color centers were determined by using transmittance data measured for a PWO sample before and during Co-60 gamma ray irradiation at a dose rate of 15 rad/hr. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/hr. The result was found to be in a good agreement with experimental data, indicating that this model of color center kinetics can be used to predict behavior of PWO crystals under irradiation.

Zinc(II) halide complexes with 2-methoxyaniline ligand: Synthesis, characterization, thermal analyses, crystal structure determination and luminescent properties

Science.gov (United States)

Amani, Vahid

2018-03-01

Three new mononuclear zinc(II) complexes, [Zn(2-MeO-C6H4NH2)2X2] (X is Cl in 1, Br in 2 and I in 3), were prepared from the reactions of ZnX2 with 2-methoxyaniline (2-MeO-C6H4NH2) ligand in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurements by slow evaporation of methanol solution at room temperature. The three complexes were thoroughly characterized by thermogravimetric analysis, elemental analysis (CHNO), spectral methods (IR, UV-Vis, 13C{1H}NMR, 1H NMR and luminescence), and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the zinc(II) cation is four-coordinated in a distorted tetrahedral configuration by two N atoms from two 2-methoxyanyline ligands and two halide anions. Also, in these complexes intermolecular interactions, for example Nsbnd H⋯X hydrogen bonds (in 1-3), Csbnd H⋯X hydrogen bonds (in 3), Csbnd H⋯π interactions (in 1 and 2) and π⋯π interactions (in 3), are effective in the stabilization of the crystal structures. In addition, the luminescence spectra of all complexes in methanolic solution show that the intensity of their emission bands is stronger than that for free 2-methoxyaniline ligand.

Single crystal growth and nonlinear optical properties of Nd3+ doped STGS crystal for self-frequency-doubling application

Science.gov (United States)

Chen, Feifei; Wang, Lijuan; Wang, Xinle; Cheng, Xiufeng; Yu, Fapeng; Wang, Zhengping; Zhao, Xian

2017-11-01

The self-frequency-doubling crystal is an important kind of multi-functional crystal materials. In this work, Nd3+ doped Sr3TaGa3Si2O14 (Nd:STGS) single crystals were successfully grown by using Czochralski pulling method, in addition, the nonlinear and laser-frequency-doubling properties of Nd:STGS crystals were studied. The continuous-wave laser at 1064 nm was demonstrated along different physical axes, where the maximum output power was obtained to be 295 mW for the Z-cut samples, much higher than the Y-cut (242 mW) and X-cut (217 mW) samples. Based on the measured refractive indexes, the phase matching directions were discussed and determined for type I (42.5°, 30°) and type II (69.5°, 0°) crystal cuts. As expected, self-frequency-doubling green laser at 529 nm was achieved with output powers being around 16 mW and 12 mW for type I and type II configurations, respectively.

Design and characterization of Ga-doped indium tin oxide films for pixel electrode in liquid crystal display

International Nuclear Information System (INIS)

Choi, J.H.; Kang, S.H.; Oh, H.S.; Yu, T.H.; Sohn, I.S.

2013-01-01

Indium tin oxide (ITO) thin films doped with various metal atoms were investigated in terms of phase transition behavior and electro-optical properties for the purpose of upgrading ITO and indium zinc oxide (IZO) films, commonly used for pixel electrodes in flat panel displays. We explored Ce, Mg, Zn, and Ga atoms as dopants to ITO by the co-sputtering technique, and Ga-doped ITO films (In:Sn:Ga = 87.4:6.7:5.9 at.%) showed the phase transition behavior at 210 °C within 20 min with high visible transmittance of 91% and low resistivity of 0.22 mΩ cm. The film also showed etching rate similar to amorphous ITO, and no etching residue on glass surfaces. These results were confirmed with the film formed from a single Ga-doped ITO target with slightly different compositions (In:Sn:Ga = 87:9:4 at.%). Compared to the ITO target, Ga-doped ITO target left 1/4 less nodules on the target surface after sputtering. These results suggest that Ga-doped ITO films could be an excellent alternative to ITO and IZO for pixel electrodes in thin film transistor liquid crystal display (TFT-LCD). - Highlights: ► We report Ga-doped In–Sn–O films for a pixel electrode in liquid crystal display. ► Ga-doped In–Sn–O films show phase transition behavior at 210 °C. ► Ga-doped In–Sn–O films show high wet etchability and low resistivity

Solution-Phase Synthesis of Cesium Lead Halide Perovskite Nanowires.

Science.gov (United States)

Zhang, Dandan; Eaton, Samuel W; Yu, Yi; Dou, Letian; Yang, Peidong

2015-07-29

Halide perovskites have attracted much attention over the past 5 years as a promising class of materials for optoelectronic applications. However, compared to hybrid organic-inorganic perovskites, the study of their pure inorganic counterparts, like cesium lead halides (CsPbX3), lags far behind. Here, a catalyst-free, solution-phase synthesis of CsPbX3 nanowires (NWs) is reported. These NWs are single-crystalline, with uniform growth direction, and crystallize in the orthorhombic phase. Both CsPbBr3 and CsPbI3 are photoluminescence active, with composition-dependent temperature and self-trapping behavior. These NWs with a well-defined morphology could serve as an ideal platform for the investigation of fundamental properties and the development of future applications in nanoscale optoelectronic devices based on all-inorganic perovskites.

Finding New Perovskite Halides via Machine learning

Directory of Open Access Journals (Sweden)

Ghanshyam ePilania

2016-04-01

Full Text Available Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning via building a support vector machine (SVM based classifier that uses elemental features (or descriptors to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

Finding New Perovskite Halides via Machine learning

Science.gov (United States)

Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

2016-04-01

Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

Tunable multicolor and white-light upconversion luminescence in Yb3+/Tm3+/Ho3+ tri-doped NaYF4 micro-crystals.

Science.gov (United States)

Lin, Hao; Xu, Dekang; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

2015-09-01

NaYF4 micro-crystals with various concentrations of Yb(3+) /Tm(3+) /Ho(3+) were prepared successfully via a simple and reproducible hydrothermal route using EDTA as the chelating agent. Their phase structure and surface morphology were studied using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns revealed that all the samples were pure hexagonal phase NaYF4. SEM images showed that Yb(3+)/Tm(3+)/Ho(3+) tri-doped NaYF4 were hexagonal micro-prisms. Upconversion photoluminescence spectra of Yb(3+)/Tm(3+)/Ho(3+) tri-doped NaYF4 micro-crystals with various dopant concentrations under 980 nm excitation with a 665 mW pump power were studied. Tunable multicolor (purple, purplish blue, yellowish green, green) and white light were achieved by simply adjusting the Ho(3+) concentration in 20%Yb(3+)/1%Tm(3+)/xHo(3+) tri-doped NaYF4 micro-crystals. Furthermore, white-light emissions could be obtained using different pump powers in 20%Yb(3+)/1%Tm(3+)/1%Ho(3+) tri-doped NaYF4 micro-crystals at 980 nm excitation. The pump power-dependent intensity relationship was studied and relevant energy transfer processes were discussed in detail. The results suggest that Yb(3+)/Tm(3+) Ho(3+) tri-doped NaYF4 micro-crystals have potential applications in optoelectronic devices such as photovoltaic, plasma display panel and white-light-emitting diodes. Copyright © 2014 John Wiley & Sons, Ltd.

Single mode dye-doped polymer photonic crystal lasers

International Nuclear Information System (INIS)

Christiansen, Mads B; Buß, Thomas; Smith, Cameron L C; Petersen, Sidsel R; Jørgensen, Mette M; Kristensen, Anders

2010-01-01

Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e.g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be −0.045 or −0.066 nm K -1 , depending on the material

Solid-state reaction kinetics and optical studies of cadmium doped magnesium hydrogen phosphate crystals

Science.gov (United States)

Verma, Madhu; Gupta, Rashmi; Singh, Harjinder; Bamzai, K. K.

2018-04-01

The growth of cadmium doped magnesium hydrogen phosphate was successfully carried out by using room temperature solution technique i.e., gel encapsulation technique. Grown crystals were confirmed by single crystal X-ray diffraction (XRD). The structure of the grown crystal belongs to orthorhombic crystal system and crystallizes in centrosymmetric space group. Kinetics of the decomposition of the grown crystals were studied by non-isothermal analysis. Thermo gravimetric / differential thermo analytical (TG/DTA) studies revealed that the grown crystal is stable upto 119 °C. The various steps involved in the thermal decomposition of the material have been analysed using Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova equations for evaluating various kinetic parameters. The optical studies shows that the grown crystals possess wide transmittance in the visible region and significant optical band gap of 5.5ev with cut off wavelength of 260 nm.

Correlations between entropy and volume of melting in halide salts

International Nuclear Information System (INIS)

Akdeniz, Z.; Tosi, M.P.

1991-09-01

Melting parameters and transport coefficients in the melt are collated for halides of monovalent, divalent and trivalent metals. A number of systems show a deficit of entropy of melting relative to the linear relationships between entropy change and relative volume change on melting that are found to be approximately obeyed by a majority of halides. These behaviours are discussed on the basis of structural and transport data. The deviating systems are classified into three main classes, namely (i) fast-ion conductors in the high-temperature crystal phase such as AgI, (ii) strongly structured network-like systems such as ZnCl 2 , and (iii) molecular systems melting into associated molecular liquids such as SbCl 3 . (author). 35 refs, 1 fig., 3 tabs

Spontaneous and stimulated emission in Sm3+-doped YAl3(BO3)4 single crystal

International Nuclear Information System (INIS)

Ryba-Romanowski, Witold; Lisiecki, Radosław; Beregi, Elena; Martín, I.R.

2015-01-01

Single crystals of YAl 3 (BO 3 ) 4 doped with trivalent samarium were grown by the top-seeded high temperature solution method and their absorption and emission spectra were investigated. Optical pumping into prominent absorption band around 405 nm feeds the 4 G 5/2 metastable level giving rise to intense visible luminescence distributed in several spectral lines with the most intense line around 600 nm characterized by a branching ratio of 0.42 and peak emission cross section of 0.25×10 −20 cm 2 . Optical amplification at 600 nm with a gain coefficient of 2.9 cm −1 was achieved during a pump-and-probe experiment. - Highlights: • YAB:Sm crystal grown by the top-seeded high temperature solution method. • Spectroscopic qualities relevant for visible laser operation. • YAB:Sm single crystal used in a pump-and-probe experiment. • Optical amplification properties of samarium doped YAl 3 (BO 3 ) 4

Thermal, Dielectric Studies on Pure and Amino Acid L-Glutamic Acid, L-Histidine L-Valine Doped Potassium Dihydrogen Phosphate Single Crystals

Science.gov (United States)

Kumaresan, P.; Babu, S. Moorthy; Anbarasan, P. M.

Amino acids (L-Glutamic acid, L-Histidine, L-Valine) doped potassium dihydrogen phosphate crystals were grown by the solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mole % to 10 mole %. The solubility data for all dopant concentrations were determined. The variation in pH and the corresponding habit modification of the grown crystals were characterized with UV - VIS, FT-IR and SHG trace elements, and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Formation of temperature fields in doped anisotropic crystals under spatially inhomogeneous light beams passing through them

Energy Technology Data Exchange (ETDEWEB)

Zaitseva, E. V.; Markelov, A. S.; Trushin, V. N., E-mail: trushin@phys.unn.ru; Chuprunov, E. V. [Nizhni Novgorod State University (Russian Federation)

2013-12-15

The features of formation of thermal fields in potassium dihydrophosphate crystal doped with potassium permanganate under a 532-nm laser beam passing through it have been investigated. Data on the influence of birefringence on the temperature distribution in an anisotropic crystal whose surface is illuminated by a spatially modulated light beam are presented.

Scintillation properties of YAlO3 doped with Lu and Nd perovskite single crystals

Science.gov (United States)

Akatsuka, Masaki; Usui, Yuki; Nakauchi, Daisuke; Kato, Takumi; Kawano, Naoki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

2018-05-01

YAlO3 (YAP) single crystals doped with Lu and Nd were grown by the Floating Zone (FZ) method to evaluate their scintillation properties particularly emissions in the near-infrared (NIR) range. The Nd concentration was fixed to 0 or 1 mol% while the Lu concentration was varied from 0 to 30%. When X-ray was irradiated, the scintillation of Nd-doped samples was observed predominantly at 1064 nm due to 4F3/2 → 4I11/2 transition of Nd3+. In contrast, a weak emission around 700 nm appeared in the samples doped with only Lu, and the emission origin was attributed to defect centers. In the Nd3+-doped samples, the decay time was 94-157 μs due to the 4f-4f transitions of Nd3+ whereas the Lu-doped samples showed signal with the decay time of 1.45-1.54 ms. The emission origin of the latter signal was attributed to the perovskite lattice defect.

Highly Efficient Broadband Yellow Phosphor Based on Zero-Dimensional Tin Mixed-Halide Perovskite.

Science.gov (United States)

Zhou, Chenkun; Tian, Yu; Yuan, Zhao; Lin, Haoran; Chen, Banghao; Clark, Ronald; Dilbeck, Tristan; Zhou, Yan; Hurley, Joseph; Neu, Jennifer; Besara, Tiglet; Siegrist, Theo; Djurovich, Peter; Ma, Biwu

2017-12-27

Organic-inorganic hybrid metal halide perovskites have emerged as a highly promising class of light emitters, which can be used as phosphors for optically pumped white light-emitting diodes (WLEDs). By controlling the structural dimensionality, metal halide perovskites can exhibit tunable narrow and broadband emissions from the free-exciton and self-trapped excited states, respectively. Here, we report a highly efficient broadband yellow light emitter based on zero-dimensional tin mixed-halide perovskite (C 4 N 2 H 14 Br) 4 SnBr x I 6-x (x = 3). This rare-earth-free ionically bonded crystalline material possesses a perfect host-dopant structure, in which the light-emitting metal halide species (SnBr x I 6-x 4- , x = 3) are completely isolated from each other and embedded in the wide band gap organic matrix composed of C 4 N 2 H 14 Br - . The strongly Stokes-shifted broadband yellow emission that peaked at 582 nm from this phosphor, which is a result of excited state structural reorganization, has an extremely large full width at half-maximum of 126 nm and a high photoluminescence quantum efficiency of ∼85% at room temperature. UV-pumped WLEDs fabricated using this yellow emitter together with a commercial europium-doped barium magnesium aluminate blue phosphor (BaMgAl 10 O 17 :Eu 2+ ) can exhibit high color rendering indexes of up to 85.

Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe1‑x Rh x )2As2 from London penetration depth measurements

Science.gov (United States)

Kim, Hyunsoo; Tanatar, M. A.; Martin, C.; Blomberg, E. C.; Ni, Ni; Bud’ko, S. L.; Canfield, P. C.; Prozorov, R.

2018-06-01

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe1‑x Rh x )2As2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth . Single crystals with doping levels representative of an underdoped regime x  =  0.039 ( K), close to optimal doping x  =  0.057 ( K) and overdoped x  =  0.079 ( K) and x  =  0.131( K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the power-law, . The exponent n varies non-monotonically with x, increasing to a maximum n  =  2.5 for x  =  0.079 and rapidly decreasing towards overdoped compositions to 1.6 for x  =  0.131. This behavior is qualitatively similar to the doping evolution of the superconducting gap anisotropy in other iron pnictides, including hole-doped (Ba,K)Fe2As2 and 3d-electron-doped Ba(Fe,Co)2As2 superconductors, finding a full gap near optimal doping and strong anisotropy toward the ends of the superconducting dome in the T-x phase diagram. The normalized superfluid density in an optimally Rh-doped sample is almost identical to the temperature-dependence in the optimally doped Ba(Fe,Co)2As2 samples. Our study supports the universal superconducting gap variation with doping and pairing at least in iron based superconductors of the BaFe2As2 family.

Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

International Nuclear Information System (INIS)

Gontad, F.; Conde, J.C.; Filonovich, S.; Cerqueira, M.F.; Alpuim, P.; Chiussi, S.

2013-01-01

We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p + -nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm 2 is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm 2 promote partial crystallization of the amorphous structures

Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

Energy Technology Data Exchange (ETDEWEB)

Gontad, F., E-mail: fran_gontad@yahoo.es [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Conde, J.C. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Filonovich, S.; Cerqueira, M.F.; Alpuim, P. [Department of Physics, University of Minho, Campus de Azurém, 4800-058 Guimarães (Portugal); Chiussi, S. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain)

2013-06-01

We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p{sup +}-nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm{sup 2} is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm{sup 2} promote partial crystallization of the amorphous structures.

The effect of hydrostatic pressure on conductivity behaviour of needle crystals of iodine and oxygen doped niobium-sulphur compounds

International Nuclear Information System (INIS)

Balla, D.D.; Bondarenko, A.V.; Obolenskij, M.A.; Beletskij, V.I.; Chashka, Kh.B.

1985-01-01

The effect of the hydrostatic pressures up to 11 kbar on conductivity behaviour of the needle crystal of iodine and oxygen doped niobium-sulphur compounds were studied in the temperature range 4.2-300 K. It is shown that in the temperature range 110-300 K conductivity is thermal activated (P=1 bar). Below 110 K the Mott characteristic is observed. Under hydrostatic pressure the deviations from Mott characteristic occurs. The analysis of data suggested that crystals are doped semiconductors

Scintillation and optical properties of Sn-doped Ga2O3 single crystals

Science.gov (United States)

Usui, Yuki; Nakauchi, Daisuke; Kawano, Naoki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

2018-06-01

Sn-doped Ga2O3 single crystals were synthesized by the Floating Zone (FZ) method. In photoluminescence (PL) under the excitation wavelength of 280 nm, we observed two types of luminescence: (1) defect luminescence due to recombination of the donor/acceptor pairs which appears at 430 nm and (2) the nsnp-ns2 transitions of Sn2+ which appear at 530 nm. The PL and scintillation decay time curves of the Sn-doped samples were approximated by a sum of exponential decay functions. The faster two components were ascribed to the defect luminescence, and the slowest component was owing to the nsnp-ns2 transitions. In the pulse height spectrum measurements under 241Am α-rays irradiation, all the Sn-doped Ga2O3 samples were confirmed to show a full energy absorption peak but the undoped one. Among the present samples, the 1% Sn-doped sample exhibited the highest scintillation light yield (1,500 ± 150 ph/5.5 MeV-α).

Electrical properties of Hg3In2Te6 crystals doped with gadolinium

International Nuclear Information System (INIS)

Gorlej, P.M.; Grushka, O.G.; Frasunyak, V.M.

2002-01-01

The temperature dependences of electrical conductivity, the Hall coefficient, thermoelectric power, and the transversal Nernst-Ettingshausen effect of Hg 3 In 2 Te 6 crystals doped with gadolinium are investigated. It is shown that, under strong doping, the Fermi level descends and remains in the upper half of the energy gap in the impurity miscibility range, while the transparency of crystals is decreasing essentially. It causes the impurity self-compensation and preservation of bipolar conductivity typical of intrinsic semiconductors. In this case, the band gap, mobility ratio b=μ n /μp, and effective mass ratio m p /m n (n -electrons, p-holes) are reduced. Experimental results are explained by using the model of disordered semiconductor, in which the borders between forbidden and allowed energy bands are blurred and the transfer of electrons and holes occurs on the corresponding percolation levels because of the presence of the large density of localized states

Luminescence and scintillation properties of Ce-doped Cs2ZnCl4 crystals

Science.gov (United States)

Sugawara, K.; Koshimizu, M.; Yanagida, T.; Fujimoto, Y.; Haruki, R.; Nishikido, F.; Kishimoto, S.; Asai, K.

2015-03-01

In this study, we have synthesized scintillation materials based on Ce-doped Cs2ZnCl4 crystals. The light yield was enhanced by up to 20% by doping Cs2ZnCl4 with Ce3+ ions. In the scintillation time profiles, fast components exhibited decay time constants on the order of nanoseconds, which was ascribed to Auger-free luminescence (AFL). The light yield of the AFL component decreased at 10 mol% Ce3+ concentration, which is mainly attributed to the reabsorption of AFL photons inside the crystals by Ce3+ ions, as seen in the scintillation spectra. Long components had decay time constants of approximately 30 ns. In addition, at 10 mol% Ce3+ concentration, a prominent band appeared at approximately 500 nm in the scintillation spectrum, which was not observed in the photoluminescence spectra. The long components in the scintillation time profiles and the 500 nm band in the scintillation spectra were tentatively attributed to self-trapped excitons perturbed by Ce3+ ions.

Study of nonlinear effects in photonic crystals doped with nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, N6A 3K7 Ontario (Canada)

2008-07-14

A theory of nonlinear phenomena has been developed for a photonic crystal in the presence of a pump and a coupling laser field. The crystal is doped with an ensemble of four-level nanoparticle impurities. It is considered that the impurity particles are not only interacting with the photonic crystal but also with each other via dipole-dipole interaction. An expression for the susceptibility has been obtained using the density matrix method. The nonlinear effects due to the coupling and the pump fields have been included in the formulation. The absorption spectrum has been calculated in the presence of the strong coupling and pump fields for an isotropic photonic crystal made from dielectric spheres. The photonic crystal has a gap to midgap ratio of about 21%. It is predicted that the absorption spectrum in the photonic crystal can have zero, one, two or three absorptionless states by tuning one of the transition energies within the bands. This is an interesting phenomenon which can be used to make photonic switching devices. We have also calculated the absorption spectrum in the presence of the dipole-dipole interaction. It is found that a symmetric absorption spectrum changes to an asymmetric one due to this interaction. It is also found that there is a large enhancement in the absorption and the dispersion simultaneously for certain values of the detuning and concentration.

Study of nonlinear effects in photonic crystals doped with nanoparticles

International Nuclear Information System (INIS)

Singh, Mahi R

2008-01-01

A theory of nonlinear phenomena has been developed for a photonic crystal in the presence of a pump and a coupling laser field. The crystal is doped with an ensemble of four-level nanoparticle impurities. It is considered that the impurity particles are not only interacting with the photonic crystal but also with each other via dipole-dipole interaction. An expression for the susceptibility has been obtained using the density matrix method. The nonlinear effects due to the coupling and the pump fields have been included in the formulation. The absorption spectrum has been calculated in the presence of the strong coupling and pump fields for an isotropic photonic crystal made from dielectric spheres. The photonic crystal has a gap to midgap ratio of about 21%. It is predicted that the absorption spectrum in the photonic crystal can have zero, one, two or three absorptionless states by tuning one of the transition energies within the bands. This is an interesting phenomenon which can be used to make photonic switching devices. We have also calculated the absorption spectrum in the presence of the dipole-dipole interaction. It is found that a symmetric absorption spectrum changes to an asymmetric one due to this interaction. It is also found that there is a large enhancement in the absorption and the dispersion simultaneously for certain values of the detuning and concentration

Single-Crystal Growth of Cl-Doped n-Type SnS Using SnCl2 Self-Flux.

Science.gov (United States)

Iguchi, Yuki; Inoue, Kazutoshi; Sugiyama, Taiki; Yanagi, Hiroshi

2018-06-05

SnS is a promising photovoltaic semiconductor owing to its suitable band gap energy and high optical absorption coefficient for highly efficient thin film solar cells. The most significant carnage is demonstration of n-type SnS. In this study, Cl-doped n-type single crystals were grown using SnCl 2 self-flux method. The obtained crystal was lamellar, with length and width of a few millimeters and thickness ranging between 28 and 39 μm. X-ray diffraction measurements revealed the single crystals had an orthorhombic unit cell. Since the ionic radii of S 2- and Cl - are similar, Cl doping did not result in substantial change in lattice parameter. All the elements were homogeneously distributed on a cleaved surface; the Sn/(S + Cl) ratio was 1.00. The crystal was an n-type degenerate semiconductor with a carrier concentration of ∼3 × 10 17 cm -3 . Hall mobility at 300 K was 252 cm 2 V -1 s -1 and reached 363 cm 2 V -1 s -1 at 142 K.

Chloride, bromide and iodide scintillators with europium

Science.gov (United States)

Zhuravleva, Mariya; Yang, Kan

2016-09-27

A halide scintillator material is disclosed where the halide may comprise chloride, bromide or iodide. The material is single-crystalline and has a composition of the general formula ABX.sub.3 where A is an alkali, B is an alkali earth and X is a halide which general composition was investigated. In particular, crystals of the formula ACa.sub.1-yEu.sub.yI.sub.3 where A=K, Rb and Cs were formed as well as crystals of the formula CsA.sub.1-yEu.sub.yX.sub.3 (where A=Ca, Sr, Ba, or a combination thereof and X=Cl, Br or I or a combination thereof) with divalent Europium doping where 0.ltoreq.y.ltoreq.1, and more particularly Eu doping has been studied at one to ten mol %. The disclosed scintillator materials are suitable for making scintillation detectors used in applications such as medical imaging and homeland security.

Lead Halide Perovskite Nanocrystals in the Research Spotlight: Stability and Defect Tolerance

Science.gov (United States)

2017-01-01

This Perspective outlines basic structural and optical properties of lead halide perovskite colloidal nanocrystals, highlighting differences and similarities between them and conventional II–VI and III–V semiconductor quantum dots. A detailed insight into two important issues inherent to lead halide perovskite nanocrystals then follows, namely, the advantages of defect tolerance and the necessity to improve their stability in environmental conditions. The defect tolerance of lead halide perovskites offers an impetus to search for similar attributes in other related heavy metal-free compounds. We discuss the origins of the significantly blue-shifted emission from CsPbBr3 nanocrystals and the synthetic strategies toward fabrication of stable perovskite nanocrystal materials with emission in the red and infrared parts of the optical spectrum, which are related to fabrication of mixed cation compounds guided by Goldschmidt tolerance factor considerations. We conclude with the view on perspectives of use of the colloidal perovskite nanocrystals for applications in backlighting of liquid-crystal TV displays. PMID:28920080

Growth and electrical properties of (Mn,F) co-doped 0.92Pb(Zn 1/3Nb 2/3)O 3-0.08PbTiO 3 single crystal

Science.gov (United States)

Zhang, Shujun; Lebrun, Laurent; Randall, Clive A.; Shrout, Thomas R.

2004-06-01

The growth and characterization of (Mn,F) doped Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3 (PZNT) single crystals are reported in this paper. The typical single crystal obtained is up to 30 mm size with dark brown color. The crystal lattice parameters of doped PZNT crystal are slightly decreased compared to the pure one. The room temperature dielectric permittivity along direction is about 6000, which is lower than that of the pure PZNT8 because of the dopants. The Curie temperature of the doped crystal is about 180°C while the ferroelectric phase transition temperature is around 100°C, which are higher than those of the pure PZNT8 single crystal. The remnant polarization and coercive field of oriented doped crystal measured at 1 Hz and 10 kV/cm field are about 27 μC/cm 2 and 4.2 kV/cm, respectively. The room temperature mechanical quality factor is ˜300. Piezoelectric coefficient of oriented doped crystal is higher than 3500 pC/N and the longitudinal electromechanical coupling factor is larger than 93%. The piezoelectric properties of doped PZNT single crystal with temperature and orientations are also reported in this paper. The valence state of the manganese dopant was determined by electron spin resonance, indicating no Mn 4+ in the crystals, suggesting the valence of manganese ions in PZNT crystals may be 2+, which acts as a hardener, stabilizes the domain wall and pins the domain wall motion, on the other hand, the dopant will enter Ti 4+ position, shifting the crystal composition to higher PT content.

Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi{sub 2}Te{sub 2}Se

Energy Technology Data Exchange (ETDEWEB)

Kushwaha, S. K., E-mail: kushwaha@princeton.edu; Gibson, Q. D.; Cava, R. J. [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States); Xiong, J.; Ong, N. P. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Pletikosic, I. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 11973 (United States); Weber, A. P. [National Synchrotron Light Source, Brookhaven National Lab, Upton, New York 11973 (United States); Fedorov, A. V. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Valla, T. [Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 11973 (United States)

2014-04-14

A comparative study of the properties of topological insulator Bi{sub 2}Te{sub 2}Se (BTS) crystals grown by the vertical Bridgeman method is described. Two defect mechanisms that create acceptor impurities to compensate for the native n-type carriers are compared: Bi excess, and light Sn doping. Both methods yield low carrier concentrations and an n-p crossover over the length of the grown crystal boules, but lower carrier concentrations and higher resistivities are obtained for the Sn-doped crystals, which reach carrier concentrations as low as 8 × 10{sup 14} cm{sup −3}. Further, the temperature dependent resistivities for the Sn-doped crystals display strongly activated behavior at high temperatures, with a characteristic energy of half the bulk band gap. The (001) cleaved Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum oscillations due to the topological surface state electrons. Angle resolved photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy (E{sub F}) for the Sn-doped crystals falls cleanly in the surface states with no interference from the bulk bands, which the Dirac point for the surface states lies approximately 60 meV below the top of the bulk valence band maximum, and allows for a determination of the bulk and surface state carrier concentrations as a function of Energy near E{sub F}. Electronic structure calculations that compare Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity, with a localized impurity band that acts as a charge buffer occurring inside the bulk band gap. We propose that the special resonant level character of Sn in BTS gives rise to the exceptionally low carrier concentrations and activated resistivities observed.

Hybrid Ytterbium-doped large-mode-area photonic crystal fiber amplifier for long wavelengths

DEFF Research Database (Denmark)

Petersen, Sidsel Rübner; Alkeskjold, Thomas T.; Poli, Federica

2012-01-01

A large-mode-area Ytterbium-doped photonic crystal fiber amplifier with build-in gain shaping is presented. The fiber cladding consists of a hexagonal lattice of air holes, where three rows are replaced with circular high-index inclusions. Seven missing air holes define the large-mode-area core. ...

Crystal Growth and Spectroscopic characterization of chloride and bromide single crystals doped with rare earth ions for the mid infrared amplification

International Nuclear Information System (INIS)

Ferrier, A.

2007-12-01

This work is devoted to the study of low phonon energy crystals doped with rare earth ions for the realisation of diode-pumped solid state laser sources emitting in the middle infrared. For that purpose, pure and (Er 3+ or Pr 3+ ) doped single crystals of KPb 2 Cl 5 and Tl 3 PbX 5 (X=Cl, Br) have been elaborated by using the Bridgman-Stockbarger method. These non-hygroscopic and congruent melting materials have been found to exhibit phase transitions during the cooling process but which do not limit the elaboration of centimeter-size single crystals. The spectroscopic study of the Er 3+ doped compounds has been performed both at high and low temperatures. It thus appears that these systems present long fluorescence lifetimes and relatively large gain cross sections favorable for a laser emission around 4.5μm. It has been demonstrated further that the up-conversion processes resulting from excited-state absorptions of the Er 3+ ions around the pumping wavelength as well as the energy transfer processes between the Er 3+ ions do not lead to significant optical losses for the laser system. The derived parameters then have been used to build a model and simulate the laser operation of the system following diode pumping around 800 nm. In the end, the spectroscopic study of the Pr 3+ ion in various materials has allowed us to evidence large emission cross sections associated with long fluorescence lifetimes, now favorable to a laser emission around 5μm. (author)

Can Cu(II) ions be doped into the crystal structure of potassium hydrogen tartrate?

OpenAIRE

Srinivasan, Bikshandarkoil R.; Remesh, H.

2015-01-01

The differing binding preferences of the hydrogen tartrate ligand (HC4H4O6)- namely {\\mu}7-octadentate mode for potassium ion and bidentate mode for cupric ion rules out the doping (incorporation) of any Cu(II) ion into the crystal structure of potassium hydrogen tartrate. Hence, the claim of growth of copper doped potassium hydrogen tartrate viz. K0.96Cu0.04C4H5O6 by Mathivanan and Haris, Indian J Pure App Phys 51 (2013) 851-859 is untenable.

Optical properties and radiation response of Ce3+-doped GdScO3 crystals

International Nuclear Information System (INIS)

Yamaji, Akihiro; Fujimoto, Yutaka; Futami, Yoshisuke; Yokota, Yuui; Kurosawa, Shunsuke; Kochurikhin, Vladimir; Yanagida, Takayuki; Yoshikawa, Akira

2012-01-01

10%-Ce doped GdScO 3 perovskite type single crystal was grown by the Czochralski process. The Ce concentration in the crystal was measured. No impurity phases were observed by powder X-ray diffraction analysis. We evaluated the optical and radiation properties of the grown crystal. Ce:GdScO 3 crystal showed photo- and radio-luminescence peaks due to Ce 3+ of 5d-4f transition and colour centre. The photoluminescence decay time was sub-ns order. The relative light yield under 5.5 MeV alpha-ray excitation was calculated to be approximately 9% of BGO. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Scintillation and optical properties of Ce{sup 3+}-doped CaGdAl{sub 3}O{sub 7} single crystals

Energy Technology Data Exchange (ETDEWEB)

Mori, Masaki, E-mail: masaki.mori.mz4@ms.naist.jp [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); Nakauchi, Daisuke; Okada, Go [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); Fujimoto, Yutaka [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579 (Japan); Kawaguchi, Noriaki [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); Koshimizu, Masanori [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579 (Japan); Yanagida, Takayuki [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan)

2017-06-15

The single crystals of 0, 0.6, 1, 1.6 and 2 mol% Ce doped CaGdAl{sub 3}O{sub 7} (Ce:CGAM) were grown by the Floating Zone method, and investigated on photoluminescence (PL) and scintillation properties. In the PL spectra, a broad emission appeared over 380–500 nm under 280 and 360 nm excitations with the quantum yield of 33.8–38.8%. Under a vacuum ultraviolet excitation (90 nm) using a synchrotron source, non-doped CGAM single crystal showed broad emissions over 250–650 nm. The PL decay time profiles followed a monotonic exponential decay with a decay time constant of around 33 ns. The scintillation spectra were similar to those of PL. All of the samples exhibited a clear photoabsorption peak and Compton edge in the pulse height spectra measured under {sup 137}Cs γ-ray irradiation, and the absolute scintillation light yield (LY) was highest for the 2% Ce-doped sample with the value of 3300±300 ph/MeV. The scintillation decay profiles were approximated by a third order exponential decay function, and the extracted decay time of Ce{sup 3+} emission component was around 36–44 ns. Among all the samples, 2%Ce:CGAM single crystal sample showed the best afterglow level as a scintillator under X-ray irradiation. - Highlights: •Ce{sup 3+}-doped CaGdAl{sub 3}O{sub 7} single crystals were synthesized by the FZ method. •Optical and scintillation properties of Ce{sup 3+}-doped CaGdAl{sub 3}O{sub 7} were investigated. •Photoabsorption peak in a pulse height spectrum was clearly observed under γ-rays.

Rapid synthesis of nitrogen doped titania with mixed crystal lattice via microwave-assisted hydrothermal method

International Nuclear Information System (INIS)

Zhang Peilin; Liu Bin; Yin Shu; Wang Yuhua; Petrykin, Valery; Kakihana, Masato; Sato, Tsugio

2009-01-01

A microwave-assisted hydrothermal method was employed to synthesize nitrogen doped titania nanoparticles. Due to the high heating efficiency of microwave, rapid synthesis could be achieved in comparison with the conventional oven. Mixed crystal lattice was found existing in the obtained product, and the phase transformation behaviour under calcination was studied by XRD measurement together with Raman spectroscopy in details. The obtained nitrogen doped titania showed high specific surface area, about 300 m 2 g -1 . Photocatalytic activity in destructing NO x gas by the prepared sample exceeded that of commercial titania (P 25) or nitrogen doped titania synthesized by conventional hydrothermal method, under both visible-light and ultraviolet-light irradiation.

Growth and Properties of Oxygen and Ion Doped BISMUTH(2) STRONTIUM(2) Calcium COPPER(2) Oxygen (8+DELTA) Single Crystals

Science.gov (United States)

Mitzi, David Brian

1990-01-01

A directional solidification method for growing large single crystals in the Bi_2Sr _2CaCu_2O _{8+delta} system is reported. Ion substitutions, with replacement of La for Sr and Y for Ca, as well as oxygen doping in these crystals has been explored. Ion doping results in little change of the superconducting transition for substitution levels below 20-25% (as a result of simultaneous oxygen intercalation), while beyond this level, the Meissner signal broadens and the low temperature Meissner signal decreases. Microprobe analysis and x-ray diffraction performed on these more highly substituted single crystals, provides evidence for inhomogeneity and phase segregation into regions of distinct composition. Annealing unsubstituted crystals in increasing partial pressures of oxygen reversibly depresses the superconducting transition temperature from 90K (as made) to 77K (oxygen pressure annealed) while the Hall concentrations increase from n = 3.1(3) times 10 ^{21} cm^{ -3} (0.34 holes/Cu site) to 4.6(3) times 10^{21} cm^{-3} (0.50 holes/Cu site). Further suppression of T_{c} to 72K is possible by annealing in oxygen pressures up to 100atm. No degradation of the Meissner transition or other indications of inhomogeneity or phase segregation with doping are noted, suggesting that oxygen doped Bi_2Sr _2CaCu_2O _{8+delta} is a suitable system for pursuing doping studies. The decrease in T _{c} with concentration for 0.34 <=q n <=q 0.50 indicates that a high carrier concentration regime exists where T_{c} decreases with n and suggests that this decrease does not arise from material inhomogeneity or other materials problems. The physical properties of these Bi _2Sr_2CaCu _2O_{8+delta} crystals, in this high carrier concentration regime, will be discussed.

Exciton-relaxation dynamics in lead halides

International Nuclear Information System (INIS)

Iwanaga, Masanobu; Hayashi, Tetsusuke

2003-01-01

We survey recent comprehensive studies of exciton relaxation in the crystals of lead halides. The luminescence and electron-spin-resonance studies have revealed that excitons in lead bromide spontaneously dissociate and both electrons and holes get self-trapped individually. Similar relaxation has been also clarified in lead chloride. The electron-hole separation is ascribed to repulsive correlation via acoustic phonons. Besides, on the basis of the temperature profiles of self-trapped states, we discuss the origin of luminescence components which are mainly induced under one-photon excitation into the exciton band in lead fluoride, lead chloride, and lead bromide

Co-doped sodium chloride crystals exposed to different irradiation temperature

Energy Technology Data Exchange (ETDEWEB)

Ortiz-Morales, A. [Unidad Profesional Interdisciplinaria de Ingenieria y Tecnologias Avanzadas, IPN, Av. Instituto Politecnico Nacional 2580, Col. La Laguna Ticoman, 07340 Mexico D.F., Mexico and Unidad de Irradiacion y Segurid (Mexico); Cruz-Zaragoza, E.; Furetta, C. [Unidad de Irradiacion y Seguridad Radiologica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, A.P. 70-543, 04510 Mexico D.F (Mexico); Kitis, G. [Nuclear Physics Laboratory, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Flores J, C.; Hernandez A, J.; Murrieta S, H. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP. 20-364, 01000 Mexico D.F (Mexico)

2013-07-03

Monocrystals of NaCl:XCl{sub 2}:MnCl{sub 2}(X = Ca,Cd) at four different concentrations have been analyzed. The crystals were exposed to different irradiation temperature, such as at room temperature (RT), solid water (SW), dry ice (DI) and liquid nitrogen (LN). The samples were irradiated with photon from {sup 60}Co irradiators. The co-doped sodium chloride crystals show a complex structure of glow curves that can be related to different distribution of traps. The linearity response was analyzed with the F(D) index. The F(D) value was less than unity indicating a sub-linear response was obtained from the TL response on the function of the dose. The glow curves were deconvoluted by using the CGCD program based on the first, second and general order kinetics.

An heterogeneous nucleation model for the irradiation coloring of alkali halides

International Nuclear Information System (INIS)

Aguilar, M.; Jaque, F.; Agullo-Lopez, F.

1980-01-01

An heterogeneous nucleation model for the radiation-induced coloring of alkali halides is presented. The model assumes a primary mechanism producing F and H pairs, followed by secondary thermally activated reactions including F-H recombination as well interstitial capture. The existence of a very unstable interstitial aggregate is explicitely considered. The model is able to account for the three-stages structure of the F-coloring curve and the inhibition in the occurrence of the late-stage by lowering dose-rate or by impurity doping

Growth and luminescent properties of the Ce, Pr doped NaCl single crystals grown by the modified micro-pulling-down method

International Nuclear Information System (INIS)

Yokota, Yuui; Yanagida, Takayuki; Fujimoto, Yutaka; Nikl, Martin; Yoshikawa, Akira

2010-01-01

We have investigated luminescent properties of nondope, Ce and Pr doped NaCl [nondope NaCl, Ce:NaCl, Pr:NaCl] single crystals grown by a modified micro-pulling-down method with a removable chamber system. Nondope, Ce 1% and Pr 1% doped NaCl crystals with a single phase of NaCl structure were obtained and the crystals indicated general crystal quality by the X-ray rocking curve measurement. For the nondope NaCl and Pr:NaCl crystals, the transmittance spectra indicated almost more than 60% in the wavelength from 200 to 800 nm and an absorption of Ce 3+ ion was observed in the transmittance spectrum of Ce:NaCl crystal. The emission spectrum originated from Ce 3+ 5d-4f transition appeared around 300 nm in the photoluminescence spectrum and the decay time was 19.7 ns.

Growth and Dielectric Properties of Ta-Doped La2Ti2O7 Single Crystals

Directory of Open Access Journals (Sweden)

Hui Wang

2018-02-01

Full Text Available High-quality Ta-doped La2Ti2O7 (Ta-LTO single crystal of about 40 mm in length and 5 mm in diameter was successfully prepared by the optical floating zone method. An X-ray rocking curve reveals that the crystal of LTO has excellent crystalline quality. As-grown crystals were transparent after annealing in air and the transmittance is up to 76% in the visible and near-infrared region. X-ray diffraction showed that this compound possessed a monoclinic structure with P21 space group. The dielectric properties were investigated as functions of temperature (0~300 °C and frequency (102 Hz~105 Hz. Dielectric spectra indicated an increase in the room-temperature dielectric constant accompanied by a drop in the loss tangent as a result of the Ta doping. One relaxation was observed in the spectra of electric modulus, which was ascribed to be related to the oxygen vacancy. The dielectric relaxation with activation energy of 1.16 eV is found to be the polaron hopping caused by the oxygen vacancies.

Halide based MBE of crystalline metals and oxides

Energy Technology Data Exchange (ETDEWEB)

Greenlee, Jordan D.; Calley, W. Laws; Henderson, Walter; Doolittle, W. Alan [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, Georgia (United States)

2012-02-15

A halide based growth chemistry has been demonstrated which can deliver a range of transition metals using low to moderate effusion cell temperatures (30-700 C) even for high melting point metals. Previously, growth with transition metal species required difficult to control electron beam or impurity inducing metal organic sources. Both crystalline oxide and metal films exhibiting excellent crystal quality are grown using this halide-based growth chemistry. Films are grown using a plasma assisted Molecular Beam Epitaxy (MBE) system with metal-chloride precursors. Crystalline niobium, cobalt, iron, and nickel were grown using this chemistry but the technology can be generalized to almost any metal for which a chloride precursor is available. Additionally, the oxides LiNbO{sub 3} and LiNbO{sub 2} were grown with films exhibiting X-ray diffraction (XRD) rocking curve full-widths at half maximum of 150 and 190 arcseconds respectively. LiNbO{sub 2} films demonstrate a memristive response due to the rapid movement of lithium in the layered crystal structure. The rapid movement of lithium ions in LiNbO{sub 2} memristors is characterized using impedance spectroscopy measurements. The impedance spectroscopy measurements suggest an ionic current of.1 mA for a small drive voltage of 5 mV AC or equivalently an ionic current density of {proportional_to}87 A/cm{sup 2}. This high ionic current density coupled with low charge transfer resistance of {proportional_to}16.5 {omega} and a high relaxation frequency (6.6 MHz) makes this single crystal material appealing for battery applications in addition to memristors. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Effect of Mg$^{2+}$ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd$_{3}$Al$_{2}$Ga$_{3}$O$_{12}$ crystals

CERN Document Server

Lucchini, M.T.; Bohacek, P.; Gundacker, S.; Kamada, K.; Nikl, M.; Petrosyan, A.; Yoshikawa, A.; Auffray, E.

2016-01-01

Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd3Al2Ga3O12 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd3Al2Ga3O12 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd3Al2Ga3O12 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

Growth and properties of oxygen doped Bi2Sr2CaCu2O8+δ single crystals

International Nuclear Information System (INIS)

Kapitulnik, A.; Mitzi, D.B.

1990-01-01

This paper reports results on oxygen doped single crystals in the Bi 2 Sr 2 CaCu 2 O 8+δ system grown by a directional solidification method. Annealing of as made crystals in increasing partial pressure of oxygen reversibly depresses the superconducting transition temperature from 90K (as made) to 77K (oxygen pressure annealed). Magnetic and photoemission properties of these crystals will be discussed

Growth and luminescent properties of the Ce, Pr doped NaCl single crystals grown by the modified micro-pulling-down method

Energy Technology Data Exchange (ETDEWEB)

Yokota, Yuui, E-mail: y-yokota@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan); Yanagida, Takayuki; Fujimoto, Yutaka [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan); Nikl, Martin [Institute of Physics, Academy of Sciences of the Czech Republic/6253, Prague (Czech Republic); Yoshikawa, Akira [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan)

2010-03-15

We have investigated luminescent properties of nondope, Ce and Pr doped NaCl [nondope NaCl, Ce:NaCl, Pr:NaCl] single crystals grown by a modified micro-pulling-down method with a removable chamber system. Nondope, Ce 1% and Pr 1% doped NaCl crystals with a single phase of NaCl structure were obtained and the crystals indicated general crystal quality by the X-ray rocking curve measurement. For the nondope NaCl and Pr:NaCl crystals, the transmittance spectra indicated almost more than 60% in the wavelength from 200 to 800 nm and an absorption of Ce{sup 3+} ion was observed in the transmittance spectrum of Ce:NaCl crystal. The emission spectrum originated from Ce{sup 3+} 5d-4f transition appeared around 300 nm in the photoluminescence spectrum and the decay time was 19.7 ns.

Crystal growth, spectroscopic characterization, and continuous wave laser operation of Nd3+-doped LiLuF4 crystal

Science.gov (United States)

Zhao, C. C.; Hang, Y.; Zhang, L. H.; He, X. M.; Yin, J. G.; Li, R.; Yu, T.; Chen, W. B.

2011-04-01

Nd3+-doped LiLuF4 single crystal with high optical quality was grown by Czochralski technique. The segregation coefficient of Nd3+ in LiLuF4 crystal was determined by the inductively coupled plasma atomic emission spectrometry method. Polarized absorption and fluorescence spectra were investigated. The peak absorption cross section at 792 nm and peak emission cross section at 1053 nm are 6.94×10-20 and 7.60×10-20 cm2, respectively. With a laser-diode as the pump source, a maximum 6.22 W continuous-wave laser output at 1053 nm has been obtained with a slope efficiency of 37.2% with respect to the pump power.

Excitonic and electron-hole mechanisms of the creation of Frenkel defect in alkali halides

International Nuclear Information System (INIS)

Lushchik, A.; Kirm, M.; Lushchik, Ch.; Vasil'chenko, E.

2000-01-01

Excitonic and electron-hole (e-h) mechanisms of stable F centre creation by VUV radiation in alkali halide crystals are discussed. In KCl at 4.2 K, the efficiency of stable F-H pair creation is especially high at the direct optical formation of triplet excitons with n=1. At 200-400 K, the creation processes of stable F centres in KCl are especially efficient at the formation of one-halide exciton in the Urbach tail of an exciton absorption. In KCl and KBr, the decay of a cation exciton (∼20 eV) causes the formation of two e-h pairs, while in NaCl a cation exciton (33.5 eV) decays into two e-h and an anion exciton. An elastic uniaxial stress of a crystal excited by VUV radiation decreases the mean free path of excitons before their self-trapping (KI) and increases the mean free path of hot holes before self-trapping (NaCl)

A study of the ac Stark effect in doped photonic crystals

Energy Technology Data Exchange (ETDEWEB)

Haque, I; Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, ON, N6A 3K7 (Canada)

2007-04-16

In this paper we present calculations of level populations and susceptibility for an ensemble of five-level atoms doped in a photonic crystal, using the master equation method. The atoms in the ensemble interact with the crystal which acts as a reservoir and are coupled with two strong pump fields and a weak probe field. It is found that, by manipulating the resonance energy associated with one of the decay channels of the atom, the system can be switched between an inverted and a non-inverted state. We have also observed the ac Stark effect in these atoms and have shown that due to the role played by the band structure of the photonic crystal, it is possible to switch between an absorption state and a non-absorption state of the atomic system. This is a very important finding as techniques of rendering material systems transparent to resonant laser radiation are very desirable in the fabrication of novel optical and photonic devices.

Crystal Growth and Scintillation Properties of Eu2+ doped Cs4CaI6 and Cs4SrI6

Science.gov (United States)

Stand, L.; Zhuravleva, M.; Chakoumakos, B.; Johnson, J.; Loyd, M.; Wu, Y.; Koschan, M.; Melcher, C. L.

2018-03-01

In this work we present the crystal growth and scintillation properties of two new ternarymetal halide scintillators activated with divalent europium, Cs4CaI6 and Cs4SrI6. Single crystals of each compound were grown in evacuated quartz ampoules via the vertical Bridgman technique using a two-zone transparent furnace. Single crystal X-ray diffraction experiments showed that both crystals have a trigonal (R-3c) structure, with a density of 3.99 g/cm3 and 4.03 g/cm3. The radioluminescence and photoluminescence measurements showed typical luminescence properties due to the 5d-4f radiative transitions in Eu2+. At this early stage of development Cs4SrI6:Eu and Cs4CaI6:Eu have shown very promising scintillation properties, with light yields and energy resolutions of 62,300 ph/MeV and 3.3%, and 51,800 photons/MeV and 3.6% at 662 keV, respectively.

Synthesis, characterization and computational studies of zinc(ii)-halide complexes with a bidentate Schiff base ligand (2,5-MeO-ba).sub.2./sub.En: the crystal structure of (2,5-MeO-ba).sub.2./sub.En

Czech Academy of Sciences Publication Activity Database

Khalaji, A.D.; Mighani, H.; Gholinejad, M.; Grivani, G.; Jalali Akerdi, S.; Fejfarová, Karla; Dušek, Michal

2013-01-01

Roč. 54, č. 4 (2013), s. 766-773 ISSN 0022-4766 Institutional research plan: CEZ:AV0Z10100521 Keywords : zinc(II) halides * Schiff base * crystal structure * density functional theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.501, year: 2013

Mechanical properties of pure and doped InP single crystals under concentrated loading

International Nuclear Information System (INIS)

Boyarskaya, Yu.S.; Grabko, D.Z.; Medinskaya, M.I.; Palistrant, N.A.

1997-01-01

The mechanical properties of pure and doped (Fe, Zn, Sn) InP single crystals were investigated in the temperature interval from 293 to 600 K. It was shown that impurity hardening (the microhardness increase) was more pronounced at elevated temperatures than at 293 K. This is conditioned by braking of the moving dislocations with impurities which is more observed in the the high temperature region. The obvious anisotropy of the scratch hardness was revealed at room temperature for the (001) face of crystals under investigation. This anisotropy decreased sharply in increasing the temperature from 293 to 600 K

Simulation of core-level binding energy shifts in germanium-doped lead telluride crystals

International Nuclear Information System (INIS)

Zyubin, A.S.; Dedyulin, S.N.; Yashina, L.V.; Shtanov, V.I.

2007-01-01

To simulate the changes in core-level binding energies in germanium-doped lead telluride, cluster calculations of the changes in the electrostatic potential at the corresponding centers have been performed. Different locations of the Ge atom in the crystal bulk have been considered: near vacancies, near another dopant site, and near the surface. For calculating the potential in the clusters that model the bulk and the surface of the lead telluride crystal (c-PbTe), the electron density obtained in the framework of the Hartree-Fock and hybrid density functional theory (DFT) methods has been used [ru

Luminescence of single crystals of manganese doped zinc indium binary sulfides

International Nuclear Information System (INIS)

Arama, Efim; Vovc, Victor; Gheorghita, Eugene Iv.; Pintea, Valentina

2013-01-01

Radiative recombination spectra of Mn-doped ZnIn 2 S 4 single crystals have been analyzed in the work. The emission spectra interval close to its maximum (1,91±0,2) eV contains a number of the special features which were identified by us as intra-center transitions. We attribute the special features observed on the complex emission spectra to this type of transition by their decomposition into simple lines, using Alentsev -Foch method. (authors)

X-ray diffraction topography observations of the core in Bi12SiO20 crystals doped with Mn

International Nuclear Information System (INIS)

Milenov, T.I.; Botev, P.A.; Rafailov, P.M.; Gospodinov, M.M.

2004-01-01

The core region in a bismuth silicate--Bi 12 SiO 20 (BSO) crystal doped with Mn was examined by X-ray double-crystal diffraction topography. Specific features were observed in the topographies as lines and contrast differences that point to defects occupying the central part of the crystal. We discuss the nature of these defects and propose an explanation in terms of stacking faults arranged in different structures

Protons in neutron-irradiated and thermochemically reduced MgO crystals doped with lithium impurities

International Nuclear Information System (INIS)

Gonzalez, R.; Pareja, R.; Chen, Y.

1992-01-01

H - (hydride) ions have been observed in lithium-doped MgO crystals which have been neutron irradiated or thermochemically reduced (TCR). Infrared-absorption measurements have been used to identify the local modes of the H - ions in these crystals. The concentration of the H - ions in the neutron-irradiated crystals is found to be far less than that found in the TCR crystals. The thermal stability of H - and oxygen vacancies in both oxidizing and reducing atmospheres are investigated. The emergence of sharp structures due to OH - ions is attributed to the displacements of substitutional Li + ions, leaving behind unperturbed OH - ions, via a mechanism of rapid radiation-induced diffusion during irradiation in a reactor. Results of neutron-irradiated MgO:Li, which had previously been oxidized at high temperature, are also presented

Effect of Mg"2"+ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd_3Al_2Ga_3O_1_2 crystals

International Nuclear Information System (INIS)

Lucchini, M.T.; Babin, V.; Bohacek, P.; Gundacker, S.; Kamada, K.; Nikl, M.; Petrosyan, A.; Yoshikawa, A.; Auffray, E.

2016-01-01

Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd_3Al_2Ga_3O_1_2 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd_3Al_2Ga_3O_1_2 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd_3Al_2Ga_3O_1_2 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

Praseodymium Cuprate Thin Film Cathodes for Intermediate Temperature Solid Oxide Fuel Cells: Roles of Doping, Orientation, and Crystal Structure.

Science.gov (United States)

Mukherjee, Kunal; Hayamizu, Yoshiaki; Kim, Chang Sub; Kolchina, Liudmila M; Mazo, Galina N; Istomin, Sergey Ya; Bishop, Sean R; Tuller, Harry L

2016-12-21

Highly textured thin films of undoped, Ce-doped, and Sr-doped Pr 2 CuO 4 were synthesized on single crystal YSZ substrates using pulsed laser deposition to investigate their area-specific resistance (ASR) as cathodes in solid-oxide fuel cells (SOFCs). The effects of T' and T* crystal structures, donor and acceptor doping, and a-axis and c-axis orientation on ASR were systematically studied using electrochemical impedance spectroscopy on half cells. The addition of both Ce and Sr dopants resulted in improvements in ASR in c-axis oriented films, as did the T* crystal structure with the a-axis orientation. Pr 1.6 Sr 0.4 CuO 4 is identified as a potential cathode material with nearly an order of magnitude faster oxygen reduction reaction kinetics at 600 °C compared to thin films of the commonly studied cathode material La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ . Orientation control of the cuprate films on YSZ was achieved using seed layers, and the anisotropy in the ASR was found to be less than an order of magnitude. The rare-earth doped cuprate was found to be a versatile system for study of relationships between bulk properties and the oxygen reduction reaction, critical for improving SOFC performance.

Dielectric Losses and Charge Transfer in Antimony-Doped TlGaS2 Single Crystal

Science.gov (United States)

Asadov, S. M.; Mustafaeva, S. N.

2018-03-01

Effect of semimetallic antimony (0.5 mol % Sb) on the dielectric properties and ac-conductivity of TlGaS2-based single crystals grown by the Bridgman-Stockbarger method has been studied. The experimental results on the frequency dispersion of dielectric coefficients and the conductivity of TlGa0.995Sb0.005S2 single crystals allowed the revealing of the dielectric loss nature, the charge transfer mechanism, and the estimation of the parameters of the states localized in the energy gap. The antimony-doping of the TlGaS2 single crystal leads to an increase in the density of states near the Fermi level and a decrease in the average time and average distance of hopes.

The effect of cadmium doping of Pbsub(1-x)Snsub(x)Te crystals and thin layers on the electrical properties of the system

International Nuclear Information System (INIS)

Silberg, E.

1982-06-01

In the present work the doping characteristics and electrical properties of Cd-doped bulk crystals (as-grown and annealed) and LPE layers of Pbsub(1-x)Snsub(x)Te, 0<=x<=0.25, were studied using Hall effect, resistivity and Cd-solubility measurements. The bulk crystals were doped by Cd-diffusion in a two-temperature-zone furnace and the LPE layers by adding Cd to the growth solution. Cd doping was used to produce uniform n-type LPE layers of Pbsub(1-x)Snsub(x)Te and the process proved to be a controllable and reproducible method for the production of good quality material with low electron concentration and high electron mobility. These qualities are very important in obtaining improved electrooptical devices. (H.K.)

A thermoluminescence study of Z2-centres in terbium-doped NaCl crystals

International Nuclear Information System (INIS)

Reddy, K.N.; Ahmed, I.M.; Pandaraiah, N.; Rao, U.V.S.; Babu, V.H.

1983-01-01

Thermoluminescence (TL), optical absorption are used to correlate thermal annealing of Z 2 -centres with TL peak occurring around 110 0 C in terbium-doped NaCl crystals. The TL glow peak occurring around 190 0 C is attributed to the thermal annealing of F-centres. The thermal activation parameters are calculated for both Z 2 - and F-centre peaks. (author)

Fabrication and characterization of rubidium/formamidinium-incorporated methylammonium-lead-halide perovskite solar cells

Science.gov (United States)

Kato, Masataka; Suzuki, Atsushi; Ohishi, Yuya; Tanaka, Hiroki; Oku, Takeo

2018-01-01

Fabrication and characterization of perovskite solar cells using mesoporous TiO2 as an electron transporting layer and 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene as a hole-transporting layer were performed for improving the photovoltaic performance. Additive effects of formamidinium (FA), rubidium (Rb), chlorine (Cl) and bromine (Br) into the methylammonium-lead-halide perovskite crystal on the photovoltaic properties and microstructures were investigated. The photovoltaic parameters of short-circuit current density, conversion efficiency, the surface morphology and domain in the perovskite crystal were characterized. The slight addition of FACl and RbBr to the CH3NH3PbI3 crystal provided homogeneous microstructures with the dispersed crystal domains, which improved the photovoltaic performance. The excess addition of Cl to the perovskite crystal caused nanorod-like crystals, which degraded the photovoltaic performance.

Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

Science.gov (United States)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

Optical and X-ray absorption spectroscopy in lead doped lithium fluoride crystals

Energy Technology Data Exchange (ETDEWEB)

Somma, F; Aloe, P; D' Acapito, F; Montereali, R M; Polosan, S; Secu, M; Vincenti, M A, E-mail: somma@fis.uniroma3.it

2010-11-15

LiF:Pb doped crystals were successfully grown by Kyropoulos method, starting with drying powders. The presence of Pb{sup 2+} ions in the LiF crystals were evidenced by the absorption band at 278 nm and by 375 nm photoluminescence. The presence of some other Pb structures with oxygen compounds in the as made samples was evidenced, decreasing after some annealing procedures. The local environment and valence state of Pb in LiF were studied by X-ray Absorption Spectroscopy at the Pb L{sub III} and L{sub I} edges. XANES data reveal that Pb is present as Pb{sup 2+} whereas EXAFS data show that it is incorporated in the crystal and not forming PbF{sub 2} precipitates. Identical spectra are obtained for samples as prepared and after thermal annealing up to 650 deg. C demonstrating the stability of the incorporation site. Also the concentration of Pb in the crystal has no effect on the location site of the metal as the same spectrum is obtained for specimens with different dopant concentrations.

Large polarons in lead halide perovskites

Science.gov (United States)

Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

2017-01-01

Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility. PMID:28819647

The study of nonlinear two-photon phenomenon in photonic crystals doped with nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, N6A 3K7 (Canada)

2007-02-28

A theory of the nonlinear two-photon absorption has been developed in a photonic crystal doped with an ensemble of four-level nanoparticles. We have considered that the nanoparticles are interacting with the photonic crystal. An expression of two-photon absorption has been obtained by using the density matrix method. The effect of the dipole-dipole interaction has also been included in the formulation. Interesting new phenomena have been predicted. For example, it is found that the inhibition of two-photon absorption can be turned on and off when the decay resonance energies of the four-level nanoparticles are moved within the energy band.

Fast neutron irradiation and thermal properties of doped nonstoichiometric lithium potassium sulphate crystals

International Nuclear Information System (INIS)

Kassem, M.E.; Gomaa, N.G.; El-Khatib, A.M.

1990-01-01

The influence of point defects introduced by fast neutron irradiations with neutron fluences up to 1.08 x 10 10 n/cm 2 on the thermal properties of pure and doped Li 1.4 K 0.6 SO 4 single crystals are studied in the vicinity of high temperature phase transition at 705 K. The temperature dependence of specific heat is found to be shifted towards lower temperature with the increase of neutron fluence, and can be affected by the presence of Cu 2+ dopant. The change in the value of the specific heat can be attributed to the presence of internal strain generated inside the crystal. (author)

Photovoltaic Rudorffites: Lead-Free Silver Bismuth Halides Alternative to Hybrid Lead Halide Perovskites.

Science.gov (United States)

Turkevych, Ivan; Kazaoui, Said; Ito, Eisuke; Urano, Toshiyuki; Yamada, Koji; Tomiyasu, Hiroshi; Yamagishi, Hideo; Kondo, Michio; Aramaki, Shinji

2017-10-09

Hybrid CPbX 3 (C: Cs, CH 3 NH 3 ; X: Br, I) perovskites possess excellent photovoltaic properties but are highly toxic, which hinders their practical application. Unfortunately, all Pb-free alternatives based on Sn and Ge are extremely unstable. Although stable and non-toxic C 2 ABX 6 double perovskites based on alternating corner-shared AX 6 and BX 6 octahedra (A=Ag, Cu; B=Bi, Sb) are possible, they have indirect and wide band gaps of over 2 eV. However, is it necessary to keep the corner-shared perovskite structure to retain good photovoltaic properties? Here, we demonstrate another family of photovoltaic halides based on edge-shared AX 6 and BX 6 octahedra with the general formula A a B b X x (x=a+3 b) such as Ag 3 BiI 6 , Ag 2 BiI 5 , AgBiI 4 , AgBi 2 I 7 . As perovskites were named after their prototype oxide CaTiO 3 discovered by Lev Perovski, we propose to name these new ABX halides as rudorffites after Walter Rüdorff, who discovered their prototype oxide NaVO 2 . We studied structural and optoelectronic properties of several highly stable and promising Ag-Bi-I photovoltaic rudorffites that feature direct band gaps in the range of 1.79-1.83 eV and demonstrated a proof-of-concept FTO/c-m-TiO 2 /Ag 3 BiI 6 /PTAA/Au (FTO: fluorine-doped tin oxide, PTAA: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], c: compact, m: mesoporous) solar cell with photoconversion efficiency of 4.3 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical and structural characterization of GaSb and Te-doped GaSb single crystals

International Nuclear Information System (INIS)

Tirado-Mejia, L.; Villada, J.A.; Rios, M. de los; Penafiel, J.A.; Fonthal, G.; Espinosa-Arbelaez, D.G.; Ariza-Calderon, H.; Rodriguez-Garcia, M.E.

2008-01-01

Optical and structural properties of GaSb and Te-doped GaSb single crystals are reported herein. Utilizing the photoreflectance technique, the band gap energy for doped samples was obtained at 0.814 eV. Photoluminescence (PL) spectra showed a peak at 0.748 eV that according to this research, belongs to electronic states of pure GaSb and not to the longitudinal optical (LO) phonon replica as has been reported by other authors. Analysis of the full width at half maximum (FWHM) values of X-ray diffraction, as well as micro-Raman peaks showed that the inclusion of Te decreases the crystalline quality

Scintillation properties of Er-doped Y3Al5O12 single crystals

International Nuclear Information System (INIS)

Yamaji, Akihiro; Ogino, Hiraku; Fujimoto, Yutaka; Suzuki, Akira; Yanagida, Takayuki; Yokota, Yuui; Kurosawa, Shunsuke; Yoshikawa, Akira

2013-01-01

Er-doped Y 3 Al 5 O 12 single crystals with different Er concentrations of 0.1, 1.0, 10, 30, and 50% were grown by the micro-pulling down method. There were several absorption lines due to the Er 3+ 4f-4f transitions in the transmittance spectra and these lines correspond to the transitions from the ground state of 4 I 15/2 to the excited states. The photo- and radio-luminescence spectra showed Er 3+ 4f-4f emissions. Relative light yield under 5.5 MeV alpha-ray irradiation of Er 0.1%:Y 3 Al 5 O 12 was estimated to be 63% of that of Bi 4 Ge 3 O 12 . -- Highlights: •Er doped Y 3 Al 5 O 12 single crystal scintillators were grown with different Er concentrations. •Optical properties associated with 4f-4f transition were evaluated. •Radio luminescence spectra measurements were performed under 5.5 MeV alpha-ray irradiation. •The highest light yield was estimated to be 63% of that of Bi 4 Ge 3 O 12 under 5.5 MeV alpha-ray irradiation

Contribution to knowledge of radiation damage in KCl crystals doped with Sr

International Nuclear Information System (INIS)

Sordi, G.-M.A.A.

1974-11-01

The radiation damages in KCl crystals doped with Sr ++ using thermo-ionic technique (ITC) and optical absorption measurements were studied. The variation of the entropy for the dipole jump starting from results reported by several authors was calculated. The irradiation effects with three different exposures were analysed: irradiation with gamma rays; irradiation with fast neutrons added to gamma irradiation; and irradiation with thermal neutrons together with fast neutrons and gamma rays. (Author) [pt

Mechanoluminescence by impulsive deformation of γ-irradiated Er-doped CaF2 crystals

International Nuclear Information System (INIS)

Brahme, Nameeta; Shukla, Manju; Bisen, D.P.; Kurrey, U.; Choubey, Anil; Kher, R.S.; Singh, Manisha

2011-01-01

An impulsive technique has been used for mechanoluminescence (ML) measurements in γ-irradiated Er doped CaF 2 crystals. When the ML is excited impulsively by the impact of moving piston on to γ-irradiated CaF 2 :Er crystals, two peaks are observed in ML intensity with time and it is seen that the peak intensities of first and second peaks (I m1 and I m2 ) increase with increasing impact velocity. However the time corresponding to first and second peaks (t m1 and t m2 ) shifts towards shorter time values with increasing impact velocity. It is also seen that the total ML intensity I Total initially increases with the impact velocity and then it attains a saturation value for higher values of the impact velocity. We have presented a theoretical explanation for the observed results. - Research highlights: → Impulsive technique has been used for mechanoluminescence (ML) studies in γ-irradiated Er doped CaF 2 crystals. → ML intensity exhibited two peaks with time (I m1 and I m2 ), where the intensity of both the peaks increased with increasing impact velocity. → The time of occurrence of the peaks (t m1 and t m2 ) reduced with increasing the impact velocity. → Total ML intensity (I Total ) first increases and then attains a saturation value with an increment in the impact velocity. → A theoretical explanation is presented to the observed results.

Basic mechanisms of color centres production by excitons in activated alkali halides

International Nuclear Information System (INIS)

Vale, G.

1981-01-01

The paper deals with some peculiarities of colour centers formation which are caused by introduction of the activator in alkali halide crystals. The crystals of KBr and KI activated with Tl + , In + , Sn ++ in concentrations 10 17 -10 18 cm -3 and irradiated with ultraviolet light are studied. Excitation spectra of photostimulated activator luminescence and thermoluminescence were measured. The kinetics of the photostimulated activator luminescence is studied. The conclusion is made that the activator does not affect the primary reaction of exciton decay with F-H pair generation, but only the secondary reactions of colour center production [ru

Optical properties and radiation response of Ce{sup 3+}-doped GdScO{sub 3} crystals

Energy Technology Data Exchange (ETDEWEB)

Yamaji, Akihiro; Fujimoto, Yutaka; Futami, Yoshisuke; Yokota, Yuui; Kurosawa, Shunsuke [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kochurikhin, Vladimir [General Physics Institute, 38 Vavilov Str., 119991 Moscow (Russian Federation); Yanagida, Takayuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Yoshikawa, Akira [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2012-12-15

10%-Ce doped GdScO{sub 3} perovskite type single crystal was grown by the Czochralski process. The Ce concentration in the crystal was measured. No impurity phases were observed by powder X-ray diffraction analysis. We evaluated the optical and radiation properties of the grown crystal. Ce:GdScO{sub 3} crystal showed photo- and radio-luminescence peaks due to Ce{sup 3+} of 5d-4f transition and colour centre. The photoluminescence decay time was sub-ns order. The relative light yield under 5.5 MeV alpha-ray excitation was calculated to be approximately 9% of BGO. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Understanding the Effects of NaCl, NaBr and Their Mixtures on Silver Nanowire Nucleation and Growth in Terms of the Distribution of Electron Traps in Silver Halide Crystals

Directory of Open Access Journals (Sweden)

Yunjun Rui

2018-03-01

Full Text Available In recent years, many research groups have synthesized ultra-thin silver nanowires (AgNWs with diameters below 30 nm by employing Cl− and Br− simultaneously in the polyol process. However, the yield of AgNWs in this method was low, due to the production of Ag nanoparticles (AgNPs as an unwanted byproduct, especially in the case of high Br− concentration. Here, we investigated the roles of Cl− and Br− in the preparation of AgNWs and then synthesized high aspect ratio (up to 2100 AgNWs in high yield (>85% AgNWs using a Cl− and Br− co-mediated method. We found that multiply-twinned particles (MTPs with different critical sizes were formed and grew into AgNWs, accompanied by a small and large amount of AgNPs for the NaCl and NaBr additives, respectively. For the first time, we propose that the growth of AgNWs of different diameters and yields can be understood based on the electron trap distribution (ETD of the silver halide crystals. For the case of Cl− and Br− co-additives, a mixed silver halide crystal of AgBr1−xClx was formed, rather than the AgBr/AgCl mixture reported previously. In this type of crystal, the ETD is uniform, which is beneficial for the synthesis of AgNWs with small diameter (30~40 nm and high aspect ratio. AgNW transparent electrodes were prepared in air by rod coating. A sheet resistance of 48 Ω/sq and transmittance of 95% at 550 nm were obtained without any post-treatment.

Optical spectroscopy of Ho{sup 3+}-doped SrWO{sub 4} scheelite crystal

Energy Technology Data Exchange (ETDEWEB)

Li Jianfu; Jia Guohua; Zhu Zhaojie; You Zhenyu; Wang Yan; Wu Baichang; Tu Chaoyang [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, State Key Laboratory of Structural Chemistry and National Engineering Research Center for Optoelectronic Crystalline Materials, Fuzhou, Fujian 350002 (China)

2007-04-07

Ho{sup 3+}-doped SrWO{sub 4} crystal was grown by the Czochralski method. The polarized absorption and emission spectra together with the fluorescent decay curve were measured at room temperature. The intensity parameters, radiative lifetimes and branching ratios were calculated based on the Judd-Ofelt theory. The stimulated emission cross-sections of the potential laser transitions were determined using the reciprocity method.

Composition and crystal structure of N doped TiO2 film deposited at different O2 flow rate by direct current sputtering.

Science.gov (United States)

Ding, Wanyu; Ju, Dongying; Chai, Weiping

2011-06-01

N doped Ti02 films were deposited by direct current pulse magnetron sputtering system at room temperature. The influence of 02 flow rate on the crystal structure of deposited films was studied by Stylus profilometer, X-ray photoelectron spectroscopy, and X-ray diffractometer. The results indicate that the 02 flow rate strongly controls the growth behavior and crystal structure of N doped Ti02 film. It is found that N element mainly exists as substitutional doped state and the chemical stiochiometry is near to TiO1.68±0.06N0.11±0.01 for all film samples. N doped Ti02 film deposited with 2 sccm (standard-state cubic centimeter per minute) 02 flow rate is amorphous structure with high growth rate, which contains both anatase phase and rutile phase crystal nucleuses. In this case, the film displays the mix-phase of anatase and rutile after annealing treatment. While N doped Ti02 film deposited with 12 cm(3)/min 02 flow rate displays anatase phase before and after annealing treatment. And it should be noticed that no TiN phase appears for all samples before and after annealing treatment. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Radiation-induced color centers in La-doped PbWO sub 4 crystals

CERN Document Server

Deng, Q; Zhu, R Y

1999-01-01

This report presents the result of a study on radiation-induced color center densities in La-doped lead tungstate (PbWO sub 4) crystals. The creation and annihilation constants of radiation-induced color centers were determined by using transmittance data measured for a PbWO sub 4 sample before and during sup 6 sup 0 Co gamma-ray irradiation at a dose rate of 15 rad/h. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/h. The result was found to be in good agreement with experimental data, indicating that the behaviour of PbWO sub 4 crystals under irradiation can be predicted according to this model.

Micro-Holograms in a Methyl Red-Doped Polymer-Dispersed Liquid Crystal (E48:PVP

Directory of Open Access Journals (Sweden)

N. P. Hermosa II

2003-06-01

Full Text Available Feasibility of a holographic point-by-point storage in a methyl red-doped Polymer-Dispersed LiquidCrystal (PDLC is determined. Micro-holograms (gratings are recorded next to each other. Smallestgrating diameter obtained is 69.9 mm, with minimum grating distance of 80 mm. Recording of adjacentgrating reduces the diffraction efficiency of existing grating by 17% (average.

Comparative study of neutron irradiation and carbon doping in MgB2 single crystals

International Nuclear Information System (INIS)

Krutzler, C.; Zehetmayer, M.; Eisterer, M.; Weber, H. W.; Zhigadlo, N. D.; Karpinski, J.

2007-01-01

We compare the reversible and irreversible magnetic properties of superconducting carbon doped and undoped MgB 2 single crystals before and after neutron irradiation. A large number of samples with transition temperatures between 38.3 and 22.8 K allows us to study the effects of disorder systematically. Striking similarities are found in the modification of the reversible parameters by irradiation and doping, which are discussed in terms of impurity scattering and changes of the Fermi surface. The irreversible properties are influenced by two counteracting mechanisms: they are enhanced by the newly introduced pinning centers but degraded by changes in the thermodynamic properties. Accordingly, the large neutron induced defects and the small defects from carbon doping lead to significantly different effects on the irreversible properties. Finally, the fishtail effect caused by all kinds of disorder is discussed in terms of an order-disorder transition of the flux-line lattice

Single-mode amplification in Yb-doped rod-type photonic crystal fibers for high brilliance lasers

DEFF Research Database (Denmark)

Poli, F.; Lægsgaard, Jesper; Passaro, D.

2009-01-01

This paper presents the effect of a low refractive index ring in the Yb-doped rod-type photonic crystal fibre core on the guided mode propagation and analyzed through a spatial and spectral amplifier model. The ring provides a higher differential overlap between the fundamental mode (FM...... to identify a proper ring characteristic that is width, position and refractive index. Then rod-type PCF designs have been optimized with a full-vector modal solver based on the finite-element method. Then, the amplification properties of the Yb-doped rod-type PCFs have been investigated by assuming a forward...

Growth and laser action of Yb: YVO4 crystals with low Yb doping concentration

Science.gov (United States)

Zhong, Degao; Teng, Bing; Li, Jianhong; Zhang, Shiming; Zhang, Bingtao; Wang, Chao; Tian, Xueping; Liu, Junhai

2012-11-01

Yb: YVO4 single crystals with low doping concentrations of Yb3+ less than 0.3 at% were grown using the Czochralski method. The polarized absorption spectra were measured at room temperature. Strong anisotropy exists in the absorption spectra, resulting in almost entirely different features for π-polarization and σ-polarization. The laser emission spectrum and relationship curve between the output power and absorbed pump power (Pabs) were measured. The continuous-wave laser action of Yb: YVO4 single crystal in a range of 1020.4-1026.3 nm was realized by using a high-power diode laser as the pump source.

High-resolution photoluminescence spectroscopy of Sn-doped ZnO single crystals

International Nuclear Information System (INIS)

Kumar, E. Senthil; Mohammadbeigi, F.; Boatner, L.A.; Watkins, S.P.

2016-01-01

Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-type dopants. Here we present high-resolution photoluminescence (PL) spectroscopy studies of unintentionally doped and Sn-doped ZnO single crystals grown by the chemical vapor transport method. Doped samples showed greatly increased emission from the I 10 bound exciton transition that was recently proven to be related to the incorporation of Sn impurities based on radio-isotope studies. The PL linewidths are exceptionally sharp for these samples, enabling a clear identification of several donor species. Temperature-dependent PL measurements of the I 10 line emission energy and intensity dependence reveal a behavior that is similar to other shallow donors in ZnO. Ionized donor bound-exciton and two-electron satellite transitions of the I 10 transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Sn-related donor bound exciton follows a linear relationship with donor binding energy (Haynes rule) similar to recently observed carbon related donors, and confirming the shallow nature of this defect center, which was recently attributed to a Sn Zn double donor compensated by an unknown single acceptor.

Perovskite-Perovskite Homojunctions via Compositional Doping.

Science.gov (United States)

Dänekamp, Benedikt; Müller, Christian; Sendner, Michael; Boix, Pablo P; Sessolo, Michele; Lovrincic, Robert; Bolink, Henk J

2018-05-11

One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI 2 , obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

Photofragmentation of metal halides

International Nuclear Information System (INIS)

Veen, N.J.A. van.

1980-01-01

The author deals with photodissociation of molecules of alkali halides. It is shown that the total absorption cross section consists of two contributions arising from transitions to excited states of total electronic angular momentum Ω=0 + and Ω=1. From the inversion of the absorption continua potential energy curves of the excited states can be constructed in the Franck-Condon region. It is found that for all alkali halides the 0 + state is higher in energy than the Ω=1 state. Extensive studies are reported on three thallium halides, TlI, TlBr and TlCl at various wavelengths covering the near ultraviolet region. (Auth.)

Microwave-assisted self-doping of TiO2 photonic crystals for efficient photoelectrochemical water splitting

KAUST Repository

Zhang, Zhonghai; Yang, Xiulin; Hedhili, Mohamed N.; Ahmed, Elaf S.; Shi, Le; Wang, Peng

2014-01-01

In this article, we report that the combination of microwave heating and ethylene glycol, a mild reducing agent, can induce Ti3+ self-doping in TiO2. A hierarchical TiO2 nanotube array with the top layer serving as TiO2 photonic crystals (TiO2 NTPCs

Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped Lu2SiO5 crystal

International Nuclear Information System (INIS)

Li, D Z; Xu, X D; Zhou, D H; Xia, C T; Wu, F; Xu, J; Cong, Z H; Zhang, J; Tang, D Y

2011-01-01

High quality Nd 3+ -doped Lu 2 SiO 5 (Nd:LSO) crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). Room temperature absorption and fluorescence spectra and fluorescence lifetime of the Nd:LSO crystal were measured and analyzed. The Judd-Ofelt intensity parameters Ω 2,4,6 were obtained to be 2.59, 4.90, and 5.96×10 -20 cm 2 , respectively. The absorption and emission cross sections and the branching ratios were calculated. The peak emission cross section is 5.8 and 6.6×10 -20 cm 2 at 1075 and 1079 nm, respectively, with full width at half maximum (FWHM) of 2.8 and 5.1 nm in turn. Pumped by a laser diode, a maximum 2.54 W continuous-wave laser output has been obtained with a slope efficiency of 32%. All the results show that this crystal is a promising laser material

Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped Lu2SiO5 crystal

Science.gov (United States)

Li, D. Z.; Xu, X. D.; Zhou, D. H.; Xia, C. T.; Wu, F.; Xu, J.; Cong, Z. H.; Zhang, J.; Tang, D. Y.

2011-01-01

High quality Nd3+-doped Lu2SiO5 (Nd:LSO) crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). Room temperature absorption and fluorescence spectra and fluorescence lifetime of the Nd:LSO crystal were measured and analyzed. The Judd-Ofelt intensity parameters Ω2,4,6 were obtained to be 2.59, 4.90, and 5.96×10-20 cm2, respectively. The absorption and emission cross sections and the branching ratios were calculated. The peak emission cross section is 5.8 and 6.6×10-20 cm2 at 1075 and 1079 nm, respectively, with full width at half maximum (FWHM) of 2.8 and 5.1 nm in turn. Pumped by a laser diode, a maximum 2.54 W continuous-wave laser output has been obtained with a slope efficiency of 32%. All the results show that this crystal is a promising laser material.

Positrons in ionic crystals

International Nuclear Information System (INIS)

Pareja, R.

1988-01-01

Positron annihilation experiments in ionic crystals are reviewed and their results are arranged. A discussion about the positron states in these materials is made in the light of these results and the different proposed models. The positronium in alkali halides is specially considered. (Author)

Material Exchange Property of Organo Lead Halide Perovskite with Hole-Transporting Materials

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Seigo Ito

2015-10-01

Full Text Available Using X-ray diffraction (XRD, it was confirmed that the deposition of hole-transporting materials (HTM on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between the CH3NH3PbI3 perovskite and HTM layers. The solvent for HTM also changed the perovskite crystal. In order to suppress the crystal change, doping by chloride ion, bromide ion and 5-aminovaleric acid was attempted. However, the doping was unable to stabilize the perovskite crystal against HTM deposition. It can be concluded that the CH3NH3PbI3 perovskite crystal is too soft and flexible to stabilize against HTM deposition.

INTERRELATION OF ACIDITY-BASICITY, SOLUBILITY AND ABILITY TO INTERACTION OF HALIDES OF MX AND M'X2 (M - Li ÷ Cs, M' - Be ÷ Ba, X - Cl ÷ I TYPES

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V. F. Zinchenko

2015-11-01

Full Text Available The size-charge factor of basicity for definition of the acid-base properties of alkaline both alkaline-earth metals and Be halides is offered. The certain interrelation of the specified factor, and also the magnitudes connected with energy of a crystal lattice (temperature of boiling and enthalpy of evaporation of salt with its solubility in water, and also with enthalpy of hydration is established. It is shown that the minimum solubility possess alkaline metals halides (KCl for chlorides, RbBr for Rubidium halides and CsI for alkaline metals halides as a whole at which value of the factor of basicity is equal to 0.83, i.e. it is slightly less than 1. Among alkaline-earth metals halides the lowest solubility has BaCl2 with the highest value of the factor of basicity (0.4. An absolute value of enthalpy of hydration for salts crystal-hydrates possesses tens kJ/mol H2O and increases with reduction of the factor of basicity at transition from metals chlorides to iodides, and also at cationic substitution by easier analogue. Qualitative correlation between a difference of basicity of binary halides and their ability to interaction with formation of complex compounds of various degree of durability is established. At an average difference of basicities 0.4 in halide systems are formed incongruently melting, and at 0.6-0.8 and more – congruently melting compounds. Forecasting of solubility of complex halide of CsSrCl3 composition on the basis of its value of equalized basicity is carried out.

Calcium phosphate cements with strontium halides as radiopacifiers.

Science.gov (United States)

López, Alejandro; Montazerolghaem, Maryam; Engqvist, Håkan; Ott, Marjam Karlsson; Persson, Cecilia

2014-02-01

High radiopacity is required to monitor the delivery and positioning of injectable implants. Inorganic nonsoluble radiopacifiers are typically used in nondegradable bone cements; however, their usefulness in resorbable cements is limited due to their low solubility. Strontium halides, except strontium fluoride, are ionic water-soluble compounds that possess potential as radiopacifiers. In this study, we compare the radiopacity, mechanical properties, composition, and cytotoxicity of radiopaque brushite cements prepared with strontium fluoride (SrF2 ), strontium chloride (SrCl2 ·6H2 O), strontium bromide (SrBr2 ), or strontium iodide (SrI2 ). Brushite cements containing 10 wt % SrCl2 ·6H2 O, SrBr2 , or SrI2 exhibited equal to or higher radiopacity than commercial radiopaque cements. Furthermore, the brushite crystal lattice in cements that contained the ionic radiopacifiers was larger than in unmodified cements and in cements that contained SrF2 , indicating strontium substitution. Despite the fact that the strontium halides increased the solubility of the cements and affected their mechanical properties, calcium phosphate cements containing SrCl2 ·6H2 O, SrBr2 , and SrI2 showed no significant differences in Saos-2 cell viability and proliferation with respect to the control. Strontium halides: SrCl2 ·6H2 O, SrBr2 , and SrI2 may be potential candidates as radiopacifiers in resorbable biomaterials although their in vivo biocompatibility, when incorporated into injectable implants, is yet to be assessed. Copyright © 2013 Wiley Periodicals, Inc.

Magnetic, electric and electron magnetic resonance properties of orthorhombic self-doped La1-xMnO3 single crystals

International Nuclear Information System (INIS)

Markovich, V; Fita, I; Shames, A I; Puzniak, R; Rozenberg, E; Yuzhelevski, Ya; Mogilyansky, D; Wisniewski, A; Mukovskii, Ya M; Gorodetsky, G

2003-01-01

The effect of lanthanum deficiency on structural, magnetic, transport, and electron magnetic resonance (EMR) properties has been studied in a series of La 1-x MnO 3 (x = 0.01, 0.05, 0.11, 0.13) single crystals. The x-ray diffraction study results for the crystals were found to be compatible with a single phase of orthorhombic symmetry. The magnetization curves exhibit weak ferromagnetism for all samples below 138 K. It was found that both the spontaneous magnetization and the coercive field increase linearly with x. The pressure coefficient dT N /dP decreases linearly with self-doping, from a value of 0.68 K kbar -1 for La 0.99 MnO 3 to 0.33 K kbar -1 for La 0.87 MnO 3 . The resistivity of low-doped La 0.99 MnO 3 crystal is of semiconducting character, while that of La 0.87 MnO 3 depends weakly on temperature between 180 and 210 K. It was found that the magnetic and transport properties of the self-doped compounds may be attributed to a phase separation involving an antiferromagnetic matrix and ferromagnetic clusters. The latter phases as well as their paramagnetic precursors have been directly observed by means of EMR

Hot working alkali halides for laser window applications

International Nuclear Information System (INIS)

Koepke, B.G.; Anderson, R.H.; Stokes, R.J.

1975-01-01

The techniques used to hot work alkali halide crystals into laser window blanks are reviewed. From the point of view of high power laser window applications one of the materials with a high figure of merit is KCl. Thus the materials examined are KCl and alloys of KCl-KBr containing 5 mole percent KBr. The fabrication techniques include conventional and constrained press forging, isostatic press forging and hot rolling. Optical properties are paramount to the ultimate usefulness of these materials. Results on the optical properties of the hot worked material are included together with mechanical properties and microstructural data

Impacts of Co-doping on the superconductivity and the orbital ordering state in Fe1-xCoxSe single crystal studied by the electrical transport.

Science.gov (United States)

Urata, Takahiro; Tanabe, Yoichi; Heguri, Satoshi; Tanigaki, Katsumi

2015-03-01

In the FeSe with the simplest crystal structure in the Fe-based superconductor families, although both the superconductivity and the orbital ordering states are investigated, the relation between them is still unclear. Here, we report Co doping effects on the superconductivity and the orbital ordering state in Fe1-xCoxSe single crystals. The electrical transport measurements demonstrated that the superconductivity vanishes at 4 % Co doping while the orbital ordering state may be robust against Co doping. Present results suggest that the orbital ordering state is not related to the emergence of the superconductivity in FeSe.

Structured alkali halides for medical applications

International Nuclear Information System (INIS)

Schmitt, B.; Fuchs, M.; Hell, E.; Knuepfer, W.; Hackenschmied, P.; Winnacker, A.

2002-01-01

Image plates based on storage phosphors are a major application of radiation defects in insulators. Storage phosphors absorb X-ray quanta creating trapped electron-hole pairs in the material. Optical stimulation of the electron causes recombination leading to light emission. Application of image plates requires an optimal compromise between resolution (represented by the modulation transfer function (MTF)) and sensitivity. In our paper we present a new solution of the problem of combining a high MTF with a high sensitivity by structuring the image plates in form of thin needles acting as light guides. This suppresses the lateral spread of light which is detrimental to resolution. As doped CsBr, e.g. CsBr:Ga [Physica Medica XV (1999) 301], can pose a good storage phosphor evaporated layers are of interest in computed radiography. Needle structured CsI:Tl is used as scintillator in direct radiography [IEEE Trans. Nucl. Sci. 45 (3) (1998)]. CsBr layers have been produced by evaporation in vacuum and in inert gas atmosphere varying pressure and temperature. The resulting structures are of fibrous or columnar nature being in good agreement with the zone model of Thornton [Ann. Rev. Mater. Sci. 7 (1977) 239]. A zone model for CsBr has been developed. Measurements on doped alkali halide image plates having needle structure show good MTF at high sensitivity making a significant progress in image plate technology

The steady-state and transient electron transport within bulk zinc-blende indium nitride: The impact of crystal temperature and doping concentration variations

International Nuclear Information System (INIS)

Siddiqua, Poppy; O'Leary, Stephen K.

2016-01-01

Within the framework of a semi-classical three-valley Monte Carlo electron transport simulation approach, we analyze the steady-state and transient aspects of the electron transport within bulk zinc-blende indium nitride, with a focus on the response to variations in the crystal temperature and the doping concentration. We find that while the electron transport associated with zinc-blende InN is highly sensitive to the crystal temperature, it is not very sensitive to the doping concentration selection. The device consequences of these results are then explored.

Coloration of chromium-doped yttrium aluminum garnet single-crystal fibers using a divalent codopant

International Nuclear Information System (INIS)

Tissue, B.M.; Jia, W.; Lu, L.; Yen, W.M.

1991-01-01

We have grown single-crystal fibers of Cr:YAG and Cr,Ca:YAG under oxidizing and reducing conditions by the laser-heated-pedestal-growth method. The Cr:YAG crystals were light green due to Cr 3+ in octahedral sites, while the Cr,Ca:YAG crystals were brown. The presence of the divalent codopant was the dominant factor determining the coloration in these single-crystal fibers, while the oxidizing power of the growth atmosphere had little effect on the coloration. The Cr,Ca:YAG had a broad absorption band centered at 1.03 μm and fluoresced from 1.1 to 1.7 μm, with a room-temperature lifetime of 3.5 μs. The presence of both chromium and a divalent codopant were necessary to create the optically-active center which produces the near-infrared emission. Doping with only Ca 2+ created a different coloration with absorption in the blue and ultraviolet. The coloration in the Cr,Ca:YAG is attributed to Cr 4+ and is produced in as-grown crystals without irradiation or annealing, as has been necessary in previous work

Growth and holographic data storage properties of near-stoichiometric LiTaO{sub 3} crystals doped with Mn

Energy Technology Data Exchange (ETDEWEB)

Zhang Tao [College of Science, Harbin Engineering University, Harbin 150001 (China)], E-mail: tzhang_hit02@yahoo.com; Dong Yantang; Geng Tao; Dai Qiang [College of Science, Harbin Engineering University, Harbin 150001 (China); Xu Yuheng [School of Astronautics, Harbin Institute of Technology, Harbin 150001 (China)

2009-03-15

A series of Mn-doped near-stoichiometric LiTaO{sub 3} crystals were grown from a Li-rich (Li/Nb = 1.38, atomic ratio) and varying level of Mn-doping melt using a Cz furnace equipped with a radio frequency generator. The etching experiment reveals that as-grown polarized Mn:SLN has single ferroelectric domain structures under optical microscope. By two-beam coupling experiment, we measured and systematically analyzed the photorefractive properties such as the dynamic range, the sensitivity and the loss of signal-to-noise-ratio coefficient. Based on Mn (0.05 wt%):SLN crystal, a big capacity storage of 100 holograms in a coherent volume of 0.085 cm{sup 3} have been fulfilled successfully and the storage density arrived 0.93 Gbits cm{sup -3}.

Energy transfer and infrared-to-visible upconversion luminescence of Er3+/Yb3+-codoped halide modified tellurite glasses

International Nuclear Information System (INIS)

Zhang, Q.Y.; Feng, Z.M.; Yang, Z.M.; Jiang, Z.H.

2006-01-01

We report on the energy transfer and frequency upconversion spectroscopic properties of Er 3+ -doped and Er 3+ /Yb 3+ -codoped TeO 2 -ZnO-Na 2 O-PbCl 2 halide modified tellurite glasses upon excitation with 808 and 978 nm laser diode. Three intense emissions centered at around 529, 546 and 657 nm, alongwith a very weak blue emission at 410 nm have clearly been observed for the Er 3+ /Yb 3+ -codoped halide modified tellurite glasses upon excitation at 978 nm and the involved mechanisms are explained. The quadratic dependence of fluorescence on excitation laser power confirms the fact that the two-photon contribute to the infrared to green-red upconversion emissions. And the blue upconversion at 410 nm involved a sequential three-photon absorption process

Thermoluminescence of Z1 centres in Sr-doped KCl

International Nuclear Information System (INIS)

Kamavisdar, V.S.; Moholkar, S.C.; Deshmukh, B.T.

1980-01-01

It is well known for alkali halides doped with divalent metal impurities that exposure to high energetic radiation and subsequent F band bleaching leads to the formation of Z 1 centres. Optical absorption measurements have shown that a low concentration of Z 1 centres is produced along with F centres during irradiation without any optical bleaching. Now the question is whether Z 1 centres are really formed along with F centres during irradiation. The aim of the present paper was to study the formation of a small amount of Z 1 centres during irradiation with the help of optical absorption and thermoluminescence measurements. The crystals of KCl:Sr were exposed to γ-rays for different doses. The TL curve for the crystal exposed to a minimum dose of γ-rays shows a TL peak at 457 K and a weak shoulder in the region 400 K to 408 K. The TL curve of the crystal exposed to maximum dose of rays shows the peak at 408 K with a greater intensity. Upon F band bleaching 408 K peak increases in intensity and optical absorption is also broadened. It is shown that the peak at 457 K is due to F centres and the peak at 408 K is due to Z 1 centres. These results clearly show that a small anount of Z 1 centres is really formed along with F centres during irradiation. (author)

Crystal growth and scintillation properties of Lu substituted CeBr.sub.3./sub. single crystals

Czech Academy of Sciences Publication Activity Database

Ito, T.; Yokota, Y.; Kurosawa, S.; Král, Robert; Kamada, K.; Pejchal, Jan; Ohashi, Y.; Yoshikawa, A.

2016-01-01

Roč. 452, Oct (2016), s. 65-68 ISSN 0022-0248. [American Conference on Crystal Growth and Epitaxy /20./ (ACCGE) / 17th Biennial Workshop on Organometallic Vapor Phase Epitaxy (OMVPE) / 2nd 2D Electronic Materials Symposium. Big Sky, MT, 02.08.2015-07.08.2015] Institutional support: RVO:68378271 Keywords : radiation * halides * scintillator materials * crystal growth Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.751, year: 2016

Crystal structure of a Zn-doped derivative of the Li17Ge4 compound

International Nuclear Information System (INIS)

Lacroix-Orio, L.; Tillard, M.; Belin, C.

2008-01-01

The compound Li 17-ε Zn ε Ge 4 has been obtained as a side product during the preparation of the intermetallic compound Li 8 Zn 2 Ge 3 from the elements. Its structure has been determined from single crystal X-ray diffraction intensities measured at 173 K. It crystallizes in the cubic system, F4-bar3m space group, a = 18.842(1) A, Z = 20. Its crystal structure is slightly different from those so far reported in the literature for the Zn-free phase Li 17 Ge 4 , particularly concerned are the positions and the site occupations of Li atoms. Most likely, these structural variations result from the presence of a small Zn concentration in the compound. The Zn doping atom has been found only at the specific Li 4d site (about 3 at.% Zn)

Enhanced light emission in photonic crystal nanocavities with Erbium-doped silicon nanocrystals

International Nuclear Information System (INIS)

Makarova, Maria; Sih, Vanessa; Vuckovic, Jelena; Warga, Joe; Li Rui; Dal Negro, Luca

2008-01-01

Photonic crystal nanocavities are fabricated in silicon membranes covered by thermally annealed silicon-rich nitride films with Erbium-doped silicon nanocrystals. Silicon nitride films were deposited by sputtering on top of silicon on insulator wafers. The nanocavities were carefully designed in order to enhance emission from the nanocrystal sensitized Erbium at the 1540 nm wavelength. Experimentally measured quality factors of ∼6000 were found to be consistent theoretical predictions. The Purcell factor of 1.4 was estimated from the observed 20-fold enhancement of Erbium luminescence

Boron, phosphorus, and gallium determination in silicon crystals doped with gallium

International Nuclear Information System (INIS)

Shklyar, B.L.; Dankovskij, Yu.V.; Trubitsyn, Yu.V.

1989-01-01

When studying IR transmission spectra of silicon doped with gallium in the range of concentrations 1 x 10 14 - 5 x 10 16 cm -3 , the possibility to quantity at low (∼ 20 K) temperatures residual impurities of boron and phosphorus is ascertained. The lower determination limit of boron is 1 x 10 12 cm -3 for a sample of 10 nm thick. The level of the impurities in silicon crystals, grown by the Czochralski method and method of crucible-free zone melting, is measured. Values of boron and phosphorus concentrations prior to and after their alloying with gallium are compared

Nature of the superionic transition in Ag+ and Cu+ halides

International Nuclear Information System (INIS)

Keen, D.A.; Hull, S.; Barnes, A.C.; Berastegui, P.; Crichton, W.A.; Madden, P.A.; Tucker, M.G.; Wilson, M.

2003-01-01

Silver and copper halides generally display an abrupt (first-order) transition to the superionic state. However, powder diffraction studies and molecular dynamics (MD) simulations of AgI under hydrostatic pressure both indicate that a continuous superionic transition occurs on heating. The gradual onset of the highly conducting state is accompanied by an increasing fraction of dynamic Frenkel defects, a peak in the specific heat and anomalous behavior of the lattice expansion. Similar methods have been employed to investigate the proposed continuous superionic transition between the two ambient pressure face centered cubic phases of CuI. This is difficult to examine experimentally, because the hexagonal β phase exists over a narrow temperature range between the γ (cation ordered) and α (cation disordered) phases. MD simulations performed with the simulation box constrained to remain cubic at all temperatures show that, although limited Cu + Frenkel disorder occurs within γ-CuI, CuI undergoes an abrupt superionic transition at 670 K to the superionic α phase. This is supported by powder neutron diffraction studies of CuI lightly doped with Cs + to prevent stabilization of the β phase. The implications of these results on the phase transitions of other copper and silver halide superionic conductors are discussed

Ytterbium-doped large-mode-area photonic crystal fiber amplifier with gain shaping for use at long wavelengths

DEFF Research Database (Denmark)

Petersen, Sidsel Rübner; Alkeskjold, Thomas T.; Poli, Federica

2012-01-01

A large-mode-area Ytterbium-doped photonic crystal fiber amplifier with efficient suppression of amplified spontaneous emission is presented. The fiber cladding consists of a hexagonal lattice of air holes, where three rows are replaced with circular high-index inclusions. Seven missing air holes...

Crystal-field investigations of rare-earth-doped wide band gap semiconductors

CERN Multimedia

Muller, S; Wahl, U

Crystal field investigations play a central role in the studies of rare earth doped semiconductors. Optical stark level spectroscopy and lattice location studies of radioactive rare earth isotopes implanted at ISOLDE have provided important insight into these systems during the last years. It has been shown that despite a major site preference of the probe atoms in the lattice, several defect configurations do exist. These sites are visible in the optical spectra but their origin and nature aren't deducible from these spectra alone. Hyperfine measurements on the other hand should reveal these defect configurations and yield the parameters necessary for a description of the optical properties at the atomic scale. In order to study the crystal field with this alternative approach, we propose a new concept for perturbed $\\gamma\\gamma$-angular correlation (PAC) experiments at ISOLDE based on digital signal processing in contrast to earlier analog setups. The general functionality of the spectrometer is explained ...

Origin of the defects-induced ferromagnetism in un-doped ZnO single crystals

Science.gov (United States)

Zhan, Peng; Xie, Zheng; Li, Zhengcao; Wang, Weipeng; Zhang, Zhengjun; Li, Zhuoxin; Cheng, Guodong; Zhang, Peng; Wang, Baoyi; Cao, Xingzhong

2013-02-01

We clarified, in this Letter, that in un-doped ZnO single crystals after thermal annealing in flowing argon, the defects-induced room-temperature ferromagnetism was originated from the surface defects and specifically, from singly occupied oxygen vacancies denoted as F+, by the optical and electrical properties measurements as well as positron annihilation analysis. In addition, a positive linear relationship was observed between the ferromagnetism and the F+ concentration, which is in support with the above clarification.

Giant coercivity in ferromagnetic Co doped ZnO single crystal thin film

International Nuclear Information System (INIS)

Loukya, B.; Negi, D.S.; Dileep, K.; Kumar, N.; Ghatak, Jay; Datta, R.

2013-01-01

The origin of ferromagnetism in ZnO doped with transition metal impurities has been discussed extensively and appeared to be a highly controversial and challenging topic in today's solid state physics. Magnetism observed in this system is generally weak and soft. We have grown Co:ZnO up to 30 at% Co in single crystal thin film form on c-plane sapphire. A composition dependent coercivity is observed in this system which reaches peak value at 25 at% Co, the values are 860 Oe and 1149 Oe with applied field along parallel and perpendicular to the film substrate interface respectively. This giant coercivity might pave the way to exploit this material as a magnetic semiconductor with novel logic functionalities. The findings are explained based on defect band itinerant ferromagnetism and its partial interaction with localized d electrons of Co through charge transfer. Besides large coercivity, an increase in the band gap with Co concentration has also been observed along with blue emission peak with long tail confirming the formation of extended point defect levels in the host lattice band gap. - Highlights: • Co doped ZnO ferromagnetic single crystal thin film. • Giant coercivity in Co:ZnO thin film which may help to turn this material into application. • Cathodoluminescence (CL) data showing increase in band gap with Co concentrations. • A theoretical proposal is made to explain the observed giant coercivity

Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

Science.gov (United States)

Chen, Maozhou; Dai, Haitao; Wang, Dongshuo; Yang, Yue; Luo, Dan; Zhang, Xiaodong; Liu, Changlong

2018-03-01

In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

Defect types and room temperature ferromagnetism in N-doped rutile TiO2 single crystals

Science.gov (United States)

Qin, Xiu-Bo; Li, Dong-Xiang; Li, Rui-Qin; Zhang, Peng; Li, Yu-Xiao; Wang, Bao-Yi

2014-06-01

The magnetic properties and defect types of virgin and N-doped TiO2 single crystals are probed by superconducting quantum interference device (SQUID), X-ray photoelectron spectroscopy (XPS), and positron annihilation analysis (PAS). Upon N doping, a twofold enhancement of the saturation magnetization is observed. Apparently, this enhancement is not related to an increase in oxygen vacancy, rather to unpaired 3d electrons in Ti3+, arising from titanium vacancies and the replacement of O with N atoms in the rutile structure. The production of titanium vacancies can enhance the room temperature ferromagnetism (RTFM), and substitution of O with N is the onset of ferromagnetism by inducing relatively strong ferromagnetic ordering.

Highly resistive C-doped hydride vapor phase epitaxy-GaN grown on ammonothermally crystallized GaN seeds

Science.gov (United States)

Iwinska, Malgorzata; Piotrzkowski, Ryszard; Litwin-Staszewska, Elzbieta; Sochacki, Tomasz; Amilusik, Mikolaj; Fijalkowski, Michal; Lucznik, Boleslaw; Bockowski, Michal

2017-01-01

GaN crystals were grown by hydride vapor phase epitaxy (HVPE) and doped with C. The seeds were high-structural-quality ammonothermally crystallized GaN. The grown crystals were highly resistive at 296 K and of high structural quality. High-temperature Hall effect measurements revealed p-type conductivity and a deep acceptor level in the material with an activation energy of 1 eV. This is in good agreement with density functional theory calculations based on hybrid functionals as presented by the Van de Walle group. They obtained an ionization energy of 0.9 eV when C was substituted for N in GaN and acted as a deep acceptor.

Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

KAUST Repository

Abutaha, Anas I.

2013-02-06

We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature of the laser deposition process on LaAlO3 (100) substrates. The change in surface termination of the LaAlO3 substrate with temperature induces a change in AZO film orientation. The anisotropic nature of electrical conductivity and Seebeck coefficient of the AZO films showed a favored thermoelectric performance in c-axis oriented films. These films gave the highest power factor of 0.26 W m−1 K−1 at 740 K.

Investigations of the stability of the neutral silver atom in Nasub(x)Agsub(1-x)Cl-mixed crystals by EPR-spectroscopy

International Nuclear Information System (INIS)

Muessig, T.; Granzer, F.

1983-01-01

In most of the theories of the photographic process in the classical silver halide systems, the neutral silver atom, Ag 0 , still plays an important role. Up till now, however, all attempts failed to detect the Ag 0 in pure AgCl and AgBr, while its detection in NaCl, weakly doped with Ag does not impose any problems applying EPR-spectroscopy. Benefiting from some peculiarities of the NaCl-AgCl-phase diagram, Nasub(x)Agsub(1-x)Cl-mixed crystals were grown and the stability of the Ag 0 -centre was followed by EPR-measurements. From the results obtained by gradually augmenting the Ag-content up to 30 mol.% and cooling down the crystals to 20 K, there seems to be only little chance, to detect the neutral silver atom in pure AgCl, even at very low temperatures by EPR-spectroscopy. Simultaneously the-EPR signal of the Ag 2 + -centre was studied and the occurrence of a very strong EPR-line at g = 1.88 in decomposed mixed crystals was interpreted. (author)

Effect of defects induced by doping and fast neutron irradiation on the thermal properties of lithium ammonium sulphate crystals

International Nuclear Information System (INIS)

Kandil, S.H.; Ramadan, T.A.; Darwish, M.M.; Kassem, M.E.; El-Khatib, A.M.

1994-01-01

Structural defects were introduced in lithium ammonium sulphate crystals (LAS) either in the process of crystal growth (in the form of foreign ions) or by neutron irradiation. The effect of such defects on the thermal properties of LAS crystals was studied in the temperature range 300-500 K. It was assumed that the doped LAS crystals are composed of a two-phase system having different thermal parameters in each phase. The specific heat at constant pressure, C p , of irradiated samples was found to decrease with increasing irradiation doses. The thermal expansion of LAS crystals was found to be dependent on neutron irradiation, and was attributed to two processes: the release of new species and the trapping process. (author)

Experimental and theoretical study of pure and doped crystals: Gd2O2S, Gd2O2S:Eu3+ and Gd2O2S:Tb3+

Science.gov (United States)

Wang, Fei; Chen, Xiumin; Liu, Dachun; Yang, Bin; Dai, Yongnian

2012-08-01

Quantum chemistry and experimental method were used to study on pure and doped Gd2O2S crystals in this paper. The band structure and DOS diagrams of pure and doped Gd2O2S crystals which calculated by using DFT (Density Functional Theory) method were illustrated to explain the luminescent properties of impurities in crystals. The calculations of the crystal structure were finished by using the program of CASTEP (Cambridge Sequential Total Energy Package). The samples showed the characteristic emissions of Tb3+ ions with 5D4-7FJ transitions and Eu3+ ions with 5D0-7FJ transitions which emit pure green luminescence and red luminescence respectively. The experimental excitation spectra of Tb3+ and Eu3+ doped Gd2O2S are in agreement of the DOS diagrams over the explored energy range, which has allowed a better understanding of different luminescence mechanisms of Tb3+ and Eu3+ in Gd2O2S crystals.

Optically stimulated luminescence (OSL) from Ag-doped Li2B4O7 crystals

International Nuclear Information System (INIS)

Kananen, B.E.; Maniego, E.S.; Golden, E.M.; Giles, N.C.; McClory, J.W.; Adamiv, V.T.; Burak, Ya.V.; Halliburton, L.E.

2016-01-01

Optically stimulated luminescence (CW-OSL) is observed from Ag-doped lithium tetraborate (Li 2 B 4 O 7 ) crystals. Photoluminescence, optical absorption, and electron paramagnetic resonance (EPR) are used to identify the defects participating in the OSL process. As-grown crystals have Ag + ions substituting for Li + ions. They also have Ag + ions occupying interstitial sites. During a room-temperature exposure to ionizing radiation, holes are trapped at the Ag + ions that replace Li + ions and electrons are trapped at the interstitial Ag + ions, i.e., the radiation forms Ag 2+ (4d 9 ) ions and Ag 0 (4d 10 5s 1 ) atoms. These Ag 2+ and Ag 0 centers have characteristic EPR spectra. The Ag 0 centers also have a broad optical absorption band peaking near 370 nm. An OSL response is observed when the stimulation wavelength overlaps this absorption band. Specifically, stimulation with 400 nm light produces an intense OSL response when emission is monitored near 270 nm. Electrons optically released from the Ag 0 centers recombine with holes trapped at Ag 2+ ions to produce the ultraviolet emission. The OSL response is progressively smaller as the stimulation light is moved to longer wavelengths (i.e., away from the 370 nm peak of the absorption band of the Ag 0 electron traps). Oxygen vacancies are also present in the Ag-doped Li 2 B 4 O 7 crystals, and their role in the OSL process as a secondary relatively short-lived electron trap is described.

Crystal chemical substitutions and doping of YBa2Cu3Ox and related superconductors

International Nuclear Information System (INIS)

Skakle, J.M.S.

1998-01-01

This review covers the literature on cationic and anionic substitutions and their effect on the properties of YBCO. Reported solubility limits are given, together with crystal symmetry and trends in unit cell parameters with dopant concentration. The dopant site is considered; this is additionally complex in the case of copper substitution because of the two distinct copper sites in the crystal structure. The effect of the dopant on the critical temperature, T c , is reviewed; the literature is often contradictory due to the dual effects of variable oxygen content and the nature of the dopant. Preparation methods appear to have an effect on solubility limits, crystal symmetry and T c . Also, the methods used to determine solubility limits are often imprecise which can lead to contradictions. The magnetic properties of doped materials are reviewed; for some dopants, particularly the magnetic lanthanides, antiferromagnetism and superconductivity co-exist. The related RBa 2 Cu 3 O δ phases (R=lanthanide), their structure, properties and behaviour on doping are reviewed in a similar way. For the larger rare earths, the related systems R 1+x Ba 2-x Cu 3 O δ are reviewed; as x increases, the transition temperature decreases and compositions R 1.5 Ba 1.5 Cu 3 O δ are semiconducting. The upper and lower solubility limit changes with R, and for R=Dy, the upper limit is 2 Cu 3 O δ , cannot be prepared in air since substitution of La onto the Ba site occurs, forming the Ba-deficient solid solutions. (orig.)

Structure of polyvalent metal halide melts

International Nuclear Information System (INIS)

Tosi, M.P.

1990-12-01

A short review is given of recent progress in determining and understanding the structure of molten halide salts involving polyvalent metal ions. It covers the following three main topics: (i) melting mechanisms and types of liquid structure for pure polyvalent-metal chlorides; (ii) geometry and stability of local coordination for polyvalent metal ions in molten mixtures of their halides with alkali halides; and (iii) structure breaking and electron localization on addition of metal to the melt. (author). 28 refs, 3 figs, 1 tab

Session 6: Liquid-phase chloro-benzene hydrogenolysis over alkali-doped zirconia supported palladium catalysts

Energy Technology Data Exchange (ETDEWEB)

Aramendia, M.A.; Borau, V.; Jimenez, C.; Marinas, A.; Marinas, J.M.; Moreno, J.M.; Ruiz, J.R.; Urbano, F.J. [University of Cordoba. Marie Curie Building, Dept. of Organic Chemistry (Spain)

2004-07-01

Chlorinated hydrocarbons constitute one of the most important kind of organic pollutants due to their environmental impact and noxious effects. Catalytic hydro-dehalogenation is now emerging as a promising non-destructive alternative technology whereby the chlorinated waste is converted to products with a commercial value. It is simple, safe, effective, and it ensures, in many instances, the regeneration of the initial raw material. One of the main problems of catalytic hydro-dehalogenation arise from the deactivating effect of the hydrogen halide released as by product. This can be surpassed by, for example, adding a base, such as NaOH, or modification of the catalyst in order to neutralize the hydrogen halide released. In conclusion, the alkali modification of the zirconia supported catalysts did not enhance the catalytic activity in comparison to the undoped Pd/ZrO{sub 2}. Moreover, the lithium doped catalyst exhibits very poor results in initial rate and final chloro-benzene conversion. This could be related to the reduction in BET surface area caused by the doping together with a lower enhancement of the surface basicity of the doped catalysts. (authors)

Upconverting crystal/dextran-g-DOPE with high fluorescence stability for simultaneous photodynamic therapy and cell imaging

International Nuclear Information System (INIS)

Wang, HanJie; Wang, Sheng; Liu, Zhongyun; Dong, Chunhong; Chang, Jin; Yang, Jiumin; Gong, Xiaoqun

2014-01-01

To date, the application of photodynamic therapy in deep tissue has been severely restricted by the limited penetration depth of excitation light, such as UV light and visible light. In this work, a protocol of upconverting crystal/dextran-g-DOPE nanocomplex (UCN/dextran-g-DOPE) was developed. The nanocomplex was assembled from the hydrophobic upconverting nanoparticle (UCN) core and hydrophilic lipid shell. The photosensitizer zinc phthalocyanine (ZnPc) loaded UCN/dextran-g-DOPE offers possibilities to overcome the problem mentioned above. The UCN core works as a transducer to convert deeply penetrating near-infrared light to visible light to activate ZnPc for photodynamic therapy. The dextran-g-DOPE lipid shell is used for loading ZnPc and protecting the whole system from nonspecific absorbance or corrosion during the transportation. The experiment results show that the nanocomplex is an individual sphere with an average size of 30 nm. The ZnPc was activated to produce singlet oxygen successfully by the upconverting fluorescence emitted from UCN. The nanocomplex has high fluorescence stability in alkaline or neutral buffer solutions. Importantly, the ZnPc loaded UCN/dextran-g-DOPE nanocomplex showed a significant inhibitory effect on tumor cells after NIR exposure. Our data suggest that a ZnPc loaded UCN/dextran-g-DOPE nanocomplex may be a useful nanoplatform for future PDT treatment in deep-cancer therapy based on the upconverting mechanism. (paper)

Fabrication of large-volume, low-cost ceramic lanthanum halide scintillators for gamma ray detection : final report for DHS/DNDO/TRDD project TA-01-SL01.

Energy Technology Data Exchange (ETDEWEB)

Boyle, Timothy J.; Ottley, Leigh Anna M.; Yang, Pin; Chen, Ching-Fong; Sanchez, Margaret R.; Bell, Nelson Simmons

2008-10-01

This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density

Investigation of crystal structure, dielectric and magnetic properties in La and Nd co-doped BiFeO{sub 3} multiferroics

Energy Technology Data Exchange (ETDEWEB)

Singh, Ompal [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Agarwal, Ashish, E-mail: aagju@yahoo.com [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Sanghi, Sujata [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Das, Amitabh [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Anju [Department of Physics, Chaudhary Devi Lal University, Sirsa 125025, Haryana (India)

2017-03-15

For the investigation of the crystal structure, dielectric properties and magnetic properties of La and Nd co-doped BiFeO{sub 3} multiferroics; Bi{sub 0.8}La{sub 0.2−x}Nd{sub x}FeO{sub 3} (x=0.075, 0.1, 0.125) samples were prepared through solid state reaction method. Rietveld refinement of the obtained XRD patterns shows that there is change in crystal structure in these samples. At higher concentration of La (at x=0.075), the crystal structure was found to have mixed symmetry with rhombohedral and triclinic phases, while with equal concentration of both the dopants (at x=0.1), the structure changes to mixed symmetry having rhombohedral and orthorhombic phases. At higher concentration of Nd (at x=0.125), again mixed symmetry was established having both phases of the previous composition but approximately in reverse fraction. In dielectric analysis, x=0.1 sample showed the highest values of dielectric constant (ε′) and dielectric loss (tan δ). For x=0.125 sample, it was observed that the dielectric constant and dielectric loss response are improved. The magnetic characterization (M–H loops) indicates the significant enhancement in magnetisation with increasing concentration of Nd. Nd doping leads to the destruction of spiral modulation, forming the antiferromagnets, and visualisation of improved magnetisation via canting of spins. - Highlights: • La and Nd co-doped BiFeO{sub 3} were synthesized. • Change in crystal structure is observed. • Significant enhancement in magnetisation is observed.

An effective neodimium segregation coefficient in neodimium-doped yttrium-aluminum-garnet crystal growth by pulling method

International Nuclear Information System (INIS)

Shiroki, Ken-ichi; Kuwano, Yasuhiko

1978-01-01

Effective Nd segregation coefficient in the Nd:YAG (Nd-doped Y 3 Al 5 O 12 ) crystal growth by pulling method was determined precisely over 0 -- 1.3 atom% Nd concentration range at a 0.6 mm hr -1 growth rate. Two Nd:YAG crystals (-- 20 g) were grown from a large melt (-- 1 kg). Neodymium concentrations in the crystals and residual melts were estimated by fluorescent X-ray analysis, and a value of 0.21 was obtained as the effective segregation coefficient. Next, the optical absorption coefficient of Nd:YAG crystal at 5889 A absorption peak was measured in order to analyze a small specimen for Nd by optical absorption measurements. The optical absorption coefficient of 0.97 mm -1 .atom% -1 was determined in this way. The Nd concentrations, calculated by the segregation coefficient, agreed well with those obtained by optical absorption measurements at 5889 A for six successively grown Nd:YAG crystals. Therefore, the obtained segregation coefficient, 0.21, was confirmed as a reliable value for the Nd:YAG crystal growth by the pulling method. (auth.)

Halide-Dependent Electronic Structure of Organolead Perovskite Materials

KAUST Repository

Buin, Andrei; Comin, Riccardo; Xu, Jixian; Ip, Alexander H.; Sargent, Edward H.

2015-01-01

-based perovskites, in line with recent experimental data. As a result, the optimal growth conditions are also different for the distinct halide perovskites: growth should be halide-rich for Br and Cl, and halide-poor for I-based perovskites. We discuss stability

Untitled

African Journals Online (AJOL)

2007-06-20

Jun 20, 2007 ... spectra of the Yb doped crystals were measured at room and liquid nitrogen temperatures. The spectra were found to consist of ... Rubidium halides, absorption spectra, divalentytterbium ions and metal vapour phase diffusion, introduction ..... Optical. Absorption, Emission and. Excitation Spectra of Eu in the.

Ultrafast crystallization and thermal stability of In-Ge doped eutectic Sb70Te30 phase change material

International Nuclear Information System (INIS)

Lee Meiling; Miao Xiangshui; Ting Leehou; Shi Luping

2008-01-01

Effect of In and Ge doping in the form of In 2 Ge 8 Sb 85 Te 5 on optical and thermal properties of eutectic Sb 70 Te 30 alloys was investigated. Crystalline structure of In 2 Ge 8 Sb 85 Te 5 phase change material consists of a mixture of phases. Thermal analysis shows higher crystallization temperature and activation energy for crystallization. Isothermal reflectivity-time measurement shows a growth-dominated crystallization mechanism. Ultrafast crystallization speed of 30 ns is realized upon irradiation by blue laser beam. The use of ultrafast and thermally stable In 2 Ge 8 Sb 85 Te 5 phase change material as mask layer in aperture-type super-resolution near-field phase change disk is realized to increase the carrier-to-noise ratio and thermal stability

Development of Halide and Oxy-Halides for Isotopic Separations

Energy Technology Data Exchange (ETDEWEB)

Martin, Leigh R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Johnson, Aaron T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Pfeiffer, Jana [Idaho National Lab. (INL), Idaho Falls, ID (United States); Finck, Martha R. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2014-10-01

The goal of this project was to synthesize a volatile form of Np for introduction into mass spectrometers at INL. Volatile solids of the 5f elements are typically those of the halides (e.g. UF6), however fluorine is highly corrosive to the sensitive internal components of the mass separator, and the other volatile halides exist as several different stable isotopes in nature. However, iodide is both mono-isotopic and volatile, and as such presents an avenue for creation of a form of Np suitable for introduction into the mass separator. To accomplish this goal, the technical work in the project sought to establish a novel synthetic route for the conversion NpO2+ (dissolved in nitric acid) to NpI3 and NpI4.

Single crystal growth of pure and Nd-doped Y2O3 by flotating zone method with Xe arc lamp imaging furnace

International Nuclear Information System (INIS)

Tsuiki, H.; Kitazawa, K.; Fueki, K.; Masumoto, T.; Shiroki, K.

1980-01-01

Single crystals of undoped and Nd-doped yttrium oxide were grown by the floating zone method with a Xe arc lamp imaging furnace. The crystals were grown in the and directions. Transparent and subgrain-free single crystals were obtained at a growth rate of 30-60 mm/h for the undoped yttrium oxide. Facets of the cubic [100] and [211] were observed though the high temperature phase of the crystal is hexagonal. Dislocation densities of undoped yttrium oxide are given. (orig./WE)

Photonic Crystal Fibers

National Research Council Canada - National Science Library

Kristiansen, Rene E

2005-01-01

This report results from a contract tasking Crystal Fibre A/S as follows: Crystal Fibre will conduct research and development of large mode area, dual clad multi-core Yb-doped photonic crystal fiber...

NMRON on a mixed halide antiferromagnet, (54Mn)Mn(Cl0.6Br0.4)2.4H2O

International Nuclear Information System (INIS)

Chaplin, D.H.; Harker, S.J.; Hutchison, W.D.; Bowden, G.J.

2000-01-01

Full text: Recently we reported on the significant gains that can be made in Low Temperature Nuclear Orientation (LTNO) of the magnetically dominant species in an antiferromagnetic single crystal by heterogeneous mixing of the halide ligands. This new approach relies on enhanced nuclear spin lattice relaxation (NSLR) at the magnetic ion, in this case Mn, through broadbanded electronic magnons, in the cooled, single crystal host. Whereas the isomorphous terminal compounds ( 54 Mn)MnCI 2 .4H 2 O and ( 54 Mn)MnBr 2 .4H 2 O, have yielded zero field directional anisotropies of only 5% and 14%, respectively, from the daughter gamma from the long-lived parent 54 Mn, the mixed halides have yielded up to 40% zero field gamma anisotropy at the same base temperature of about 7-8 millikelvin. This improved zero field LTNO provides sufficient sensitivity to enable meaningful NMRON studies of the details of the hyperfine parameters at the Mn site in these mixed halide systems. In this paper we provide the NMRON results for single crystal ( 54 Mn)Mn(CI 0.6 Br 0.4 ) 2 .4H 2 O and compare them with the two terminal compounds which possess surprisingly different NMR responses due to different ratios of magnetic exchange to magnetic anisotropy fields. It is shown that whereas the static magnetic hyperfine field at the Mn nucleus is largely unchanged, and the spin flop field nicely interpolates when compared with the terminal compounds, there are significant differences in the pseudoquadrupolar splittings and sub-resonance linewidths

The density and compositional analysis of titanium doped sapphire single crystal grown by the Czocharlski method

Science.gov (United States)

Kusuma, H. H.; Ibrahim, Z.; Othaman, Z.

2018-03-01

Titanium doped sapphire (Ti:Al2O3) crystal has attracted attention not only as beautiful gemstones, but also due to their applications as high power laser action. It is very important crystal for tunable solid state laser. Ti:Al2O3 crystals have been success grown using the Czocharlski method with automatic diameter control (ADC) system. The crystals were grown with different pull rates. The structure of the crystal was characterized with X-Ray Diffraction (XRD). The density of the crystal was measurement based on the Archimedes principle and the chemical composition of the crystal was confirmed by the Energy Dispersive X-ray (EDX) Spectroscopy. The XRD patterns of crystals are showed single main peak with a high intensity. Its shows that the samples are single crystal. The Ti:Al2O3 grown with different pull rate will affect the distribution of the concentration of dopant Ti3+ and densities on the sapphire crystals boules as well on the crystal growth process. The increment of the pull rate will increase the percentage distribution of Ti3+ and on the densities of the Ti:Al2O3 crystal boules. This may be attributed to the speed factor of the pull rate of the crystal that then caused changes in the heat flow in the furnace and then causes the homogeneities is changed of species distribution of atoms along crystal.

Effect of defects induced by doping and fast neutron irradiation on the thermal properties of lithium ammonium sulphate crystals

Energy Technology Data Exchange (ETDEWEB)

Kandil, S.H.; Ramadan, T.A.; Darwish, M.M. (Alexandria Univ. (Egypt). Dept. of Materials Science); Kassem, M.E.; El-Khatib, A.M. (Alexandria Univ. (Egypt). Dept. of Physics)

1994-05-01

Structural defects were introduced in lithium ammonium sulphate crystals (LAS) either in the process of crystal growth (in the form of foreign ions) or by neutron irradiation. The effect of such defects on the thermal properties of LAS crystals was studied in the temperature range 300-500 K. It was assumed that the doped LAS crystals are composed of a two-phase system having different thermal parameters in each phase. The specific heat at constant pressure, C[sub p], of irradiated samples was found to decrease with increasing irradiation doses. The thermal expansion of LAS crystals was found to be dependent on neutron irradiation, and was attributed to two processes: the release of new species and the trapping process. (author).

Effect of γ-irradiation on the lattice parameter and colour centre concentration in pure Ca2+, Sr2+ and Eu2+ doped KCl crystals

International Nuclear Information System (INIS)

Damm, J.Z.; Stepien-Damm, J.

1980-01-01

The changes of lattice parameter and colour centre concentration are examined in KCl crystals (both pure and Me 2+ -doped) irradiated by γ-rays at room temperature. For the pure crystals the relative volume change vs. F-centre concentration plot reveals the presence of two stages, one ascribed to the introduction of colour centre pairs (or F centres only) and other to the generation of new dislocations (or new dislocations with trapped-hole centres). In Me 2+ doped crystals the lattice expansion bears a complex character (in the initial irradiation stage a transient maximum appears). Additional anomaly appears in Eu 2+ KCl in the high-dose range where in spite of a distinct F-centre concentration drop a marked raise of the lattice parameter is observed. (author)

Thermal, spectral and laser characteristics of Nd doped La0.05Lu0.95VO4 crystal

Science.gov (United States)

Xu, Honghao; Han, Shuo; Yu, Haohai; Wang, Zhengping; Wang, Jiyang; Zhang, Huaijin; Tang, Dingyuan

2014-02-01

A 0.25 at% Nd doped La0.05Lu0.95VO4 mixed crystal was grown by the Czochralski method. The thermal properties including thermal expansion, specific heat, thermal diffusion, and thermal conductivity were systematically studied. Meanwhile the reasons for cracking of this mixed crystal were also discussed. The refractive index at wavelengths of 633 nm and 1539 nm were obtained with the prism coupling method. The polarized absorption and fluorescence spectra of the crystal were also measured at room temperature. It was found that the fluorescence lifetime of 4F3/2 manifold for Nd3+ in Nd:La0.05Lu0.95VO4 is about 90 μs. Diode-pumped continuous-wave (CW) laser operations at 1.06 μm with a- and c-cut crystals were demonstrated. For the a-cut crystal a maximum output power of 5.41 W was obtained at an incident pump power of 12.9 W. Different from the a-cut crystal, the laser spectrum of the c-cut crystal was found to be dual-wavelength.

Thermal annealing of high dose radiation induced damage at room temperature in alkali halides. Stored energy, thermoluminiscence and colouration

International Nuclear Information System (INIS)

Delgado, L.

1980-01-01

The possible relation between stored energy, thermoluminiscence and colour centre annealing in gamma and electron irradiated alkali halides is studied. Thermoluminiscence occurs at temperature higher than the temperature at which the main stored energy peak appears. No stored energy release is detected in additively coloured KCl samples. Plastic deformation and doping with Ca and Sr induce a stored energy spectrum different from the spectrum observed in pure and as cleaved samples, but the amount of stored energy does not change for a given irradiation dose. Capacity of alkali halides to sotore energy by irradiation increases as the cation size decreases. It appears that most of the observed release is not related to annealing processes of the radiation induced anion Frenkel pairs. The existence of damage in the cation sublattice with which this energy release might be related is considered. (auth.)

Role of dopant concentration, crystal phase and particle size on microbial inactivation of Cu-doped TiO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sahu, Manoranjan; Wu Bing; Zhu Liying; Jacobson, Craig; Wang Weining; Jones, Kristen; Goyal, Yogesh; Tang, Yinjie J; Biswas, Pratim, E-mail: pbiswas@wustl.edu [Department of Energy, Environmental and Chemical Engineering, Washington University in St Louis, St Louis, MO 63130 (United States)

2011-10-14

The properties of Cu-doped TiO{sub 2} nanoparticles (NPs) were independently controlled in a flame aerosol reactor by varying the molar feed ratios of the precursors, and by optimizing temperature and time history in the flame. The effect of the physico-chemical properties (dopant concentration, crystal phase and particle size) of Cu-doped TiO{sub 2} nanoparticles on inactivation of Mycobacterium smegmatis (a model pathogenic bacterium) was investigated under three light conditions (complete dark, fluorescent light and UV light). The survival rate of M. smegmatis (in a minimal salt medium for 2 h) exposed to the NPs varied depending on the light irradiation conditions as well as the dopant concentrations. In dark conditions, pristine TiO{sub 2} showed insignificant microbial inactivation, but inactivation increased with increasing dopant concentration. Under fluorescent light illumination, no significant effect was observed for TiO{sub 2}. However, when TiO{sub 2} was doped with copper, inactivation increased with dopant concentration, reaching more than 90% (>3 wt% dopant). Enhanced microbial inactivation by TiO{sub 2} NPs was observed only under UV light. When TiO{sub 2} NPs were doped with copper, their inactivation potential was promoted and the UV-resistant cells were reduced by over 99%. In addition, the microbial inactivation potential of NPs was also crystal-phase-and size-dependent under all three light conditions. A lower ratio of anatase phase and smaller sizes of Cu-doped TiO{sub 2} NPs resulted in decreased bacterial survival. The increased inactivation potential of doped TiO{sub 2} NPs is possibly due to both enhanced photocatalytic reactions and leached copper ions.

Evaluation of Ce3+ and alkali metal ions Co-doped LiSrAlF6 crystalline scintillators

International Nuclear Information System (INIS)

Wakahara, Shingo; Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Pejchal, Jan; Kurosawa, Shunsuke; Suzuki, Shotaro; Kawaguchi, Noriaki; Fukuda, Kentaro; Yoshikawa, Akira

2013-01-01

High scintillation efficiency of Eu-doped LiSrAlF 6 (LiSAF) and LiCaAlF 6 (LiCAF) codoped with alkali metal ions has been reported in our recent studies. Thus in this paper, we demonstrated the scintillation properties of 1% Ce-doped LiSAF crystals with 1% alkali metal ions co-doping to increase the light yield and understand the scintillation mechanism. The crystals showed intense emission band corresponding to the 5d-4f transition of Ce 3+ , and their light yields under thermal neutron excitation were higher than that of the Ce only doped crystal. Especially, the light yield of Ce–Na co-doped crystal exceeded about two times that of Ce only doped one. -- Highlights: ► Ce-doped and alkali metal co-doped LiSAF crystals were grown by μ-PD method. ► Alkali metal co-doped crystals showed higher light yield than Ce only doped crystal. ► Decay time of alkali metal co-doped LiSAF were longer than that of Ce only doped one

Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

Energy Technology Data Exchange (ETDEWEB)

Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

2014-10-15

Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

Synergistic effect of non-covalent interaction in colloidal nematic liquid crystal doped with magnetic functionalized single-walled carbon nanotubes

Science.gov (United States)

Dalir, Nima; Javadian, Soheila

2018-03-01

Single-walled carbon nanotubes (SWCNTs), CNT@Fe3O4, and Fe3O4 nanocomposites were doped to eutectic uniaxial nematic liquid crystal (NLC's) (E5CN7) to improve physiochemical properties such as phase transition temperature, activation energy (Ea), dielectric anisotropy, and electro-optical properties. The thermal study of nematic phase shows a decrease in the nematic to isotropic phase transition temperature as CNT is doped. However, higher doping concentration of CNTs leads to the further increase in transition temperature. The anchoring effect or π-π interaction plays a key role in N-I phase transition. The functionalization of SWCNTs with Fe3O4 diminishes the CNT aggregation while the magnetic susceptibility is increased. The functionalized CNT doping to NLC's decrease significantly the phase transition temperature compared to doping of non-functionalized CNTs. Attractive interaction between guest and host molecules by magnetic and geometry effect increased the enthalpy and entropy of phase transition in the SWCNT@Fe3O4 sample compared to non-functionalized CNT doped system. Also, the Ea values are decreased as SWCNT@Fe3O4 is doped to pure E5CN7. The difference of N-I phase transition temperature was observed in Fe3O4 and CNT@Fe3O4 compared to SWCNT doped systems. Finally, dielectric anisotropy was increased in the doped system compared to pure NLC.

Luminescence properties of pure and Eu-doped SrI{sub 2} crystals purified by a “Liquinert” process and grown by vertical Bridgman method

Energy Technology Data Exchange (ETDEWEB)

Kawai, Taketoshi, E-mail: buri@p.s.osakafu-u.ac.jp [Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai, Osaka 599-8531 (Japan); Sakuragi, Shiro; Hashimoto, Satoshi [Union Materials Inc. 1640 Oshido, Tone-machi, Ibaraki 300-1602 (Japan)

2016-08-15

We have prepared high quality crystals of pure SrI{sub 2} and Eu-doped SrI{sub 2} by our original “Liquinert” process and investigated their luminescence properties. Under the excitation with the 193 nm light of an ArF excimer laser, which corresponds to the wavelength above the bandgap of SrI{sub 2} bulk crystals, the pure and Eu doped SrI{sub 2} crystals exhibit no luminescence band related to defects or impurities around 560 nm. This fact indicates that the crystals prepared by the “Liquinert” process contain lower defects and/or impurities. When the Eu-doped SrI{sub 2} crystals are excited with the 325 nm light of a He–Cd laser, only the luminescence band due to the 5d→4f transition in the Eu{sup 2+} ions is observed around 425 nm. The 425 nm band observed at a forward configuration exhibits the shift to the longer wavelength side and the decrease of the luminescence intensity with increasing Eu concentration. The Eu concentration dependences of the peak wavelength and luminescence intensity are simulated on the basis of a simple self-absorption model. - Highlights: • Our original “Liquinert” process allows us to prepare high quality crystals of SrI{sub 2}. • No luminescence band related with impurities and/or defects is observed. • The 425 nm luminescence bands due to Eu{sup 2+} ions are affected by a self-absorption. • A simple self-absorption model reproduces the changes of the 425 nm bands.

Radiation Damage in Scintillating Crystals

CERN Document Server

Zhu Ren Yuan

1998-01-01

Crystal Calorimetry in future high energy physics experiments faces a new challenge to maintain its precision in a hostile radiation environment. This paper discusses the effects of radiation damage in scintillating crystals, and concludes that the predominant radiation damage effect in crystal scintillators is the radiation induced absorption, or color center formation, not the loss of the scintillation light yield. The importance of maintaining crystal's light response uniformity and the feasibility to build a precision crystal calorimeter under radiation are elaborated. The mechanism of the radiation damage in scintillating crystals is also discussed. While the damage in alkali halides is found to be caused by the oxygen or hydroxyl contamination, it is the structure defects, such as oxygen vacancies, cause damage in oxides. Material analysis methods used to reach these conclusions are presented in details.

Light scattering in additively colored alkali-halide crystals

International Nuclear Information System (INIS)

Trakhbrot, B.M.

1979-01-01

Studied is extinction in ultra-violet, visible and infrared spectrum ranges, caused by light scattering in additively colored KCl and KBr crystals. The crystals were prepared of the powder. The specimens were annealed in saturated potassium vapours: KBr - at 600-630 deg C, KCl - at 700 deg C. While investigating the spectra it is observed that the optical density of the specimens processed in such a regime is more than 2 in the ultraviolet and visible spectrum ranges at the 0.1-0.05 cm thickness of the specimens. In the infrared spectra the growth of the extinction coefficient with the wave length decrease is observed. The spectrum character shows IR radiation scattering by the defects in the crystal lattice. The attempt of determination of the scattering centres nature is taken. It is shown that the possible centres causing the light scattering observed can be colloid and quasicolloid centres in the additively colored materials

Magnonic Crystal Theory of the Spin-Wave Frequency Gap in Low-Doped $La_{1-x}Ca_{x}MnO_{3}$ Manganites

OpenAIRE

Krawczyk, M.; Puszkarski, H.

2005-01-01

A theory of three-dimensional (3D) hypothetical magnonic crystal (conceived as the magnetic counterpart of the well-known photonic crystal) is developed and applied to explain the existence of a spin-wave frequency gap recently revealed in low-doped manganites $La_{1-x}Ca_{x}MnO_{3}$ by neutron scattering. A successful confrontation with the experimental results allows us to formulate a working hypothesis that certain manganites could be regarded as 3D magnonic crystals existing in nature.

Enhanced performance of an S-band fiber laser using a thulium-doped photonic crystal fiber

Science.gov (United States)

Muhammad, A. R.; Emami, S. D.; Hmood, J. K.; Sayar, K.; Penny, R.; Abdul-Rashid, H. A.; Ahmad, H.; Harun, S. W.

2014-11-01

This work proposes a new method to enhance the performance of an S-band fiber laser by using a thulium-doped photonic crystal fiber (PCF). The proposed method is based on amplified spontaneous emission (ASE) suppression provided by the thulium-doped PCF unique geometric structure. The enhanced performance of this filter based PCF is dependent on the short and long cut-off wavelength characteristics that define the fiber transmission window. Realizing the short wavelength cut-off location requires the PCF cladding to be doped with a high index material, which provides a refractive index difference between the core and cladding region. Achieving the long cut-off wavelength necessitates enlarging the size of the air holes surrounding the rare-earth doped core region. The PCF structure is optimized so as to achieve the desired ASE suppression regions of below 0.8 μm and above 1.8 μm. The laser performance is simulated for different host media, namely pure silica, alumino-silicate, and fluoride-based fiber ZBLAN based on this thulium-doped PCF design. The host media spectroscopic details, including lifetime variations and quantum efficiency effect on the lasing emission are also discussed. Information on the filter based PCF design is gathered via a full-vectorial finite element method analysis and specifically a numerical modelling solution for the energy level rate equation using the Runge-Kutta method. Results are analyzed for gain improvement, lasing cavity, laser efficiency and effect of core size diameter variation. Results are compared with conventional thulium-doped fiber and thulium-doped PCF for every single host media. We observe that the ZBLAN host media is the most promising candidate due to its greater quantum efficiency.

Enhanced performance of an S-band fiber laser using a thulium-doped photonic crystal fiber

International Nuclear Information System (INIS)

Muhammad, A R; Emami, S D; Penny, R; Ahmad, H; Harun, S W; Hmood, J K; Sayar, K; Abdul-Rashid, H A

2014-01-01

This work proposes a new method to enhance the performance of an S-band fiber laser by using a thulium-doped photonic crystal fiber (PCF). The proposed method is based on amplified spontaneous emission (ASE) suppression provided by the thulium-doped PCF unique geometric structure. The enhanced performance of this filter based PCF is dependent on the short and long cut-off wavelength characteristics that define the fiber transmission window. Realizing the short wavelength cut-off location requires the PCF cladding to be doped with a high index material, which provides a refractive index difference between the core and cladding region. Achieving the long cut-off wavelength necessitates enlarging the size of the air holes surrounding the rare-earth doped core region. The PCF structure is optimized so as to achieve the desired ASE suppression regions of below 0.8 μm and above 1.8 μm. The laser performance is simulated for different host media, namely pure silica, alumino-silicate, and fluoride-based fiber ZBLAN based on this thulium-doped PCF design. The host media spectroscopic details, including lifetime variations and quantum efficiency effect on the lasing emission are also discussed. Information on the filter based PCF design is gathered via a full-vectorial finite element method analysis and specifically a numerical modelling solution for the energy level rate equation using the Runge–Kutta method. Results are analyzed for gain improvement, lasing cavity, laser efficiency and effect of core size diameter variation. Results are compared with conventional thulium-doped fiber and thulium-doped PCF for every single host media. We observe that the ZBLAN host media is the most promising candidate due to its greater quantum efficiency. (paper)

Genesis, challenges and opportunities for colloidal lead halide perovskite nanocrystals

Science.gov (United States)

Akkerman, Quinten A.; Rainò, Gabriele; Kovalenko, Maksym V.; Manna, Liberato

2018-05-01

Lead halide perovskites (LHPs) in the form of nanometre-sized colloidal crystals, or nanocrystals (NCs), have attracted the attention of diverse materials scientists due to their unique optical versatility, high photoluminescence quantum yields and facile synthesis. LHP NCs have a `soft' and predominantly ionic lattice, and their optical and electronic properties are highly tolerant to structural defects and surface states. Therefore, they cannot be approached with the same experimental mindset and theoretical framework as conventional semiconductor NCs. In this Review, we discuss LHP NCs historical and current research pursuits, challenges in applications, and the related present and future mitigation strategies explored.

Two-Dimensional Lead(II) Halide-Based Hybrid Perovskites Templated by Acene Alkylamines: Crystal Structures, Optical Properties, and Piezoelectricity.

Science.gov (United States)

Du, Ke-Zhao; Tu, Qing; Zhang, Xu; Han, Qiwei; Liu, Jie; Zauscher, Stefan; Mitzi, David B

2017-08-07

A series of two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) crystals, based on acene alkylamine cations (i.e., phenylmethylammonium (PMA), 2-phenylethylammonium (PEA), 1-(2-naphthyl)methanammonium (NMA), and 2-(2-naphthyl)ethanammonium (NEA)) and lead(II) halide (i.e., PbX 4 2- , X = Cl, Br, and I) frameworks, and their corresponding thin films were fabricated and examined for structure-property relationship. Several new or redetermined crystal structures are reported, including those for (NEA) 2 PbI 4 , (NEA) 2 PbBr 4 , (NMA) 2 PbBr 4 , (PMA) 2 PbBr 4 , and (PEA) 2 PbI 4 . Non-centrosymmetric structures from among these 2D HOIPs were confirmed by piezoresponse force microscopy-especially noteworthy is the structure of (PMA) 2 PbBr 4 , which was previously reported as centrosymmetric. Examination of the impact of organic cation and inorganic layer choice on the exciton absorption/emission properties, among the set of compounds considered, reveals that perovskite layer distortion (i.e., Pb-I-Pb bond angle between adjacent PbI 6 octahedra) has a more global effect on the exciton properties than octahedral distortion (i.e., variation of I-Pb-I bond angles and discrepancy among Pb-I bond lengths within each PbI 6 octahedron). In addition to the characteristic sharp exciton emission for each perovskite, (PMA) 2 PbCl 4 , (PEA) 2 PbCl 4 , (NMA) 2 PbCl 4 , and (PMA) 2 PbBr 4 exhibit separate, broad "white" emission in the long wavelength range. Piezoelectric compounds identified from these 2D HOIPs may be considered for future piezoresponse-type energy or electronic applications.

High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties.

Science.gov (United States)

Jaffe, Adam; Lin, Yu; Beavers, Christine M; Voss, Johannes; Mao, Wendy L; Karunadasa, Hemamala I

2016-04-27

We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3 (+), X = Br(-) or I(-)) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites' precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material's resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(Br x I1-x )3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors.

Investigation on nonlinear optical and dielectric properties of L-arginine doped ZTC crystal to explore photonic device applications

Directory of Open Access Journals (Sweden)

Anis Mohd

2016-09-01

Full Text Available The present study is focused to explore the photonic device applications of L-arginine doped ZTC (LA-ZTC crystals using nonlinear optical (NLO and dielectric studies. The LA-ZTC crystals have been grown by slow evaporation solution technique. The chemical composition and surface of LA-ZTC crystal have been analyzed by means of energy dispersive spectroscopy (EDS and surface scanning electron microscopy (SEM techniques. The Vicker’s microhardness study has been carried out to determine the hardness, work hardening index, yield strength and elastic stiffness of LA-ZTC crystal. The enhanced SHG efficiency of LA-ZTC crystal has been ascertained using the Kurtz-Perry powder SHG test. The closed-and-open aperture Z-scan technique has been employed to confirm the third order nonlinear optical nature of LA-ZTC crystal. The Z-scan transmittance data has been utilized to calculate the superior cubic susceptibility, nonlinear refractive index, nonlinear absorption coefficient and figure of merit of LA-ZTC crystal. The behavior of dielectric constant and dielectric loss of LA-ZTC crystal at different temperatures has been investigated using the dielectric analysis.

Controlled Crystal Grain Growth in Mixed Cation-Halide Perovskite by Evaporated Solvent Vapor Recycling Method for High Efficiency Solar Cells.

Science.gov (United States)

Numata, Youhei; Kogo, Atsushi; Udagawa, Yosuke; Kunugita, Hideyuki; Ema, Kazuhiro; Sanehira, Yoshitaka; Miyasaka, Tsutomu

2017-06-07

We developed a new and simple solvent vapor-assisted thermal annealing (VA) procedure which can reduce grain boundaries in a perovskite film for fabricating highly efficient perovskite solar cells (PSCs). By recycling of solvent molecules evaporated from an as-prepared perovskite film as a VA vapor source, named the pot-roast VA (PR-VA) method, finely controlled and reproducible device fabrication was achieved for formamidinium (FA) and methylammonium (MA) mixed cation-halide perovskite (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 . The mixed perovskite was crystallized on a low-temperature prepared brookite TiO 2 mesoporous scaffold. When exposed to very dilute solvent vapor, small grains in the perovskite film gradually unified into large grains, resulting in grain boundaries which were highly reduced and improvement of photovoltaic performance in PSC. PR-VA-treated large grain perovskite absorbers exhibited stable photocurrent-voltage performance with high fill factor and suppressed hysteresis, achieving the best conversion efficiency of 18.5% for a 5 × 5 mm 2 device and 15.2% for a 1.0 × 1.0 cm 2 device.

Special features of the formation of high-conductivity phases of halides of alkali metals at superhigh pressures

International Nuclear Information System (INIS)

Babushkin, A.N.; Babushkina, G.V.

1999-01-01

The halides of alkali metals are the simplest crystals with the ionic nature of chemical bonds and are used widely as modelling materials in high-pressure physics. As a result of previous theoretical and experimental (optical, structural, electro-physical and shock-waves) investigations it was shown that these materials may be characterised by the overlapping of the valency and conduction bands and by the formation of groups of free charge carriers at pressures of the megabaric level. However, the authors know of no data on the direct investigations of the electrophysical properties of the halides of alkali metals at such high static pressures. The end of this investigation was to examine the temperature dependences of the electrical conductivity and thermal EMF of halides of alkali metals AX (A = Na, K, Rb, Cs, X = Cl, Br, I) in a wide temperature range at pressures from 10 to 50 GPa in order to reveal the general leisure since governing the change of their electronic structures, in particular, the transition to the state with the activation-type or metallic conductivity

Properties of transition metal-doped zinc chalcogenide crystals for tunable IR laser radiation

International Nuclear Information System (INIS)

DeLoach, L.D.; Page, R.H.; Wilke, G.D.

1995-01-01

The spectroscopic properties of Cr 2+ , Co 2+ , and Ni 2+ -doped single crystals of ZnS, ZnSe, and ZnTe have been investigated to understand their potential application as mid-IR tunable solid-state laser media. The spectroscopy indicated divalent Cr was the most favorable candidate for efficient room temperature lasing, and accordingly, a laser-pumped laser demonstration of Cr:ZnS and Cr:ZnSe has been performed. The lasers' output were peaked at ∼ 2.35 μm and the highest measured slope efficiencies were ∼ 20% in both cases

Neutron transmutation doping

Energy Technology Data Exchange (ETDEWEB)

Jun, Byung Jin

2001-09-01

HE OVERALL STATE OF THE ART RELATED WITH NEUTRON TRANSMUTATION DOPING(NCT) IS SURVEYED. ITEMS RELATED FOR THE REALIZATION OF NTD IN HANARO IS FOCUSED. IN ADDITION TO THE UNIFORM IRRADIATION AND ACHIEVING THE TARGET RESISTIVITY WHICH ARE THE MOST IMPORTANT TECHNICAL REQUIREMENTS FOR THE NTD, OTHER ITEMS SUCH AS THE FUNCTION AND ROLE OF NTD, MARKET TREND, QUALITY CONTROL ARE INCLUDED. MEANWHILE THE ONLY ADVANTAGE OF NTD IS ACHIEVING VERY HIGH UNIFORMITY OF DOPING, IT HAS SEVERAL DISADVANTAGES DUE TO THE USE OF NUCLEAR REACTOR. THEREFORE THE SEMICONDUCTOR INDUSTRY HAS CONTINUED DEVELOPMENT OF TECHNOLOGY TO REPLACE NTD, AND THE DEMAND OF NTD HAD BEEN DECREASED A LOT DURING 1990S. AS THE DEMAND FOR LARGE CRYSTAL INCREASES, HOWEVER, THE NTD DEMAND BEGAN TO INCREASE AGAIN FROM 2000. SINCE THE DEMAND FOR THE LARGER CRYSTAL WILL BE CONTINUED IN THE FUTURE, THE ROLE OF NTD WOULD BE NEEDED FOR THE LONGER TIME. IN ORDER TO MITIGATE THIS TREND OF DEMAND, THE REACTOR SHOULD BE CAPABLE OF ACCEPTING LARGE CRYSTAL AND THE EFFORT TO IMPROVE DOPING UNIFORMITY AND TO REDUCE THE COST SHOULD CONTINUED.

Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

Science.gov (United States)

Chen, Kun; Tüysüz, Harun

2015-11-09

The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermoluminescence of LaAlO3 crystals doped with Eu and Ce - Dy ions exposed to ultraviolet and gamma radiation

International Nuclear Information System (INIS)

Oliveira, Vitor H.; Faria, Luiz O.; Silva, Edna S.

2011-01-01

Due to environmental problems such as degradation of the ozone layer and control of radiation levels in units of radiation, new dosimetric materials with high sensitivity for ultraviolet (UV) and gamma radiation are of great interest for applications in environmental dosimetry. In this context, this paper presents the results of a systematic investigation of the thermoluminescent (TL) response of LaAlO 3 crystals doped with different concentrations of trivalent optically active ions exposed to UV and gamma radiation doses. The work has been performed under a direct cooperation between the Institute of Inorganic Chemistry in Moscow (IGIC), responsible for crystal growth, and the Center for Development of Nuclear Technology (CDTN), responsible for the study of its luminescent properties. In this context, samples doped with 1% of Eu 3+ , 1% Ce 3+ , 5% of Ce 3+ and also co-doped with 5% Ce 3+ and 1% Dy 3+ were grown under hydrothermal conditions. The investigation was divided into two fronts, one for gamma radiation and the other for UV radiation. In the investigation with gamma radiation the best TL response has been obtained from LaAlO 3 :Eu. This crystal has shown good sensitivity and excellent linearity between TL output and the delivered gamma doses ranging from 0.1 to 10.0 mGy. In addition, its TL curve is quite similar to the Al 2 O 3 :C, a commercial TL phosphor with high sensitivity to gamma radiation. In the investigation with UV radiation the best response has been achieved for co-doped LaAlO 3 :Ce,Dy. They have excellent sensitivity and good linearity for spectral irradiances ranging from 0.042 to 1.2 mJ.cm -2 . (author)

Solid solutions of gadolinium doped zinc oxide nanorods by combined microwave-ultrasonic irradiation assisted crystallization

Science.gov (United States)

Kiani, Armin; Dastafkan, Kamran; Obeydavi, Ali; Rahimi, Mohammad

2017-12-01

Nanocrystalline solid solutions consisting of un-doped and gadolinium doped zinc oxide nanorods were fabricated by a modified sol-gel process utilizing combined ultrasonic-microwave irradiations. Polyvinylpyrrolidone, diethylene glycol, and triethylenetetramine respectively as capping, structure directing, and complexing agents were used under ultrasound dynamic aging and microwave heating to obtain crystalline nanorods. Crystalline phase monitoring, lattice parameters and variation, morphology and shape, elemental analysis, functional groups, reducibility, and the oxidation state of emerged species were examined by PXRD, FESEM, TEM, EDX, FTIR, micro Raman, H2-TPR, and EPR techniques. Results have verified that irradiation mechanism of gelation and crystallization reduces the reaction time, augments the crystal quality, and formation of hexagonal close pack structure of Wurtzite morphology. Besides, dissolution of gadolinium within host lattice involves lattice deformation, unit cell distortion, and angular position variation. Structure related shape and growth along with compositional purity were observed through microscopic and spectroscopic surveys. Furthermore, TPR and EPR studies elucidated more detailed behavior upon exposure to the exerted irradiations and subsequent air-annealing including the formed oxidation states and electron trapping centers, presence of gadolinium, zinc, and oxygen disarrays and defects, as well as alteration in the host unit cell via gadolinium addition.

Junction Propagation in Organometal Halide Perovskite-Polymer Composite Thin Films.

Science.gov (United States)

Shan, Xin; Li, Junqiang; Chen, Mingming; Geske, Thomas; Bade, Sri Ganesh R; Yu, Zhibin

2017-06-01

With the emergence of organometal halide perovskite semiconductors, it has been discovered that a p-i-n junction can be formed in situ due to the migration of ionic species in the perovskite when a bias is applied. In this work, we investigated the junction formation dynamics in methylammonium lead tribromide (MAPbBr 3 )/polymer composite thin films. It was concluded that the p- and n- doped regions propagated into the intrinsic region with an increasing bias, leading to a reduced intrinsic perovskite layer thickness and the formation of an effective light-emitting junction regardless of perovskite layer thicknesses (300 nm to 30 μm). The junction propagation also played a major role in deteriorating the LED operation lifetime. Stable perovskite LEDs can be achieved by restricting the junction propagation after its formation.

Comparative study of the singularity in the optical properties of congruent doped LiNbO3 crystals

International Nuclear Information System (INIS)

Jaque, F.; Han, T.P.J.; Lifante, G.

2003-01-01

A comparison of the optical properties such as optical absorption band edge, ordinary and extraordinary refractive indices, powder second harmonic generation and the non-linear coefficient, d 33 , of congruent LiNbO 3 crystals doped with di-, tri- and hexa-valent cations is reported. It has been found that the referred parameters show a clear concentration singularity depending on the valency of the cation. A charge compensation mechanism is proposed to explain the role of the cation. The experimental data of n o and n e are described by a generalised Sellmeier equation considering the different ions sites in the crystal

Growth and characterization of air annealing Tb-doped YAG:Ce single crystal for white-light-emitting diode

International Nuclear Information System (INIS)

Gong, Maogao; Xiang, Weidong; Liang, Xiaojuan; Zhong, Jiasong; Chen, Daqin; Huang, Jun; Gu, Guorui; Yang, Cheng; Xiang, Run

2015-01-01

Highlights: • We report preparation of transparent Ce,Tb:YAG single crystal by Czochralski method. • The effect of annealing on Ce,Tb:YAG single crystal had been investigated. • The Ce,Tb:YAG single crystal after annealing exhibited better optical performance. • The Ce,Tb:YAG single crystal could be used as an ideal candidate for WLED. - Abstract: We report the preparation of transparent Ce and Tb co-doped Y 3 Al 5 O 12 single crystal by the Czochralski method. The characterization of the resulting single crystal was accomplished by using X-ray powder diffractometer, scanning electron microscopy and energy dispersive X-ray spectroscopy. Absorption peak of the single crystal at about 460 nm has been obtained from ultraviolet–visible absorption spectrometer and their intensity is changed with different annealing condition. Its optical properties also have been investigated using fluorescence spectrometer. What’s more, its photoelectric parameters were studied by LED fast spectrometer. The constructed single crystal based white-light-emitting diode exhibits a high luminous efficiency of 140.89 lm/W, and a correlated color temperature of 4176 K as well as a color rendering index of 56.7, which reveal the prominent feasibility of the present single crystal material in white-light-emitting diode application

Growth and characterization of air annealing Tb-doped YAG:Ce single crystal for white-light-emitting diode

Energy Technology Data Exchange (ETDEWEB)

Gong, Maogao [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Zhong, Jiasong; Chen, Daqin [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Jun; Gu, Guorui; Yang, Cheng; Xiang, Run [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China)

2015-08-05

Highlights: • We report preparation of transparent Ce,Tb:YAG single crystal by Czochralski method. • The effect of annealing on Ce,Tb:YAG single crystal had been investigated. • The Ce,Tb:YAG single crystal after annealing exhibited better optical performance. • The Ce,Tb:YAG single crystal could be used as an ideal candidate for WLED. - Abstract: We report the preparation of transparent Ce and Tb co-doped Y{sub 3}Al{sub 5}O{sub 12} single crystal by the Czochralski method. The characterization of the resulting single crystal was accomplished by using X-ray powder diffractometer, scanning electron microscopy and energy dispersive X-ray spectroscopy. Absorption peak of the single crystal at about 460 nm has been obtained from ultraviolet–visible absorption spectrometer and their intensity is changed with different annealing condition. Its optical properties also have been investigated using fluorescence spectrometer. What’s more, its photoelectric parameters were studied by LED fast spectrometer. The constructed single crystal based white-light-emitting diode exhibits a high luminous efficiency of 140.89 lm/W, and a correlated color temperature of 4176 K as well as a color rendering index of 56.7, which reveal the prominent feasibility of the present single crystal material in white-light-emitting diode application.

Making and Breaking of Lead Halide Perovskites

KAUST Repository

Manser, Joseph S.; Saidaminov, Makhsud I.; Christians, Jeffrey A.; Bakr, Osman; Kamat, Prashant V.

2016-01-01

To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice

Polarization-Independent Electrically Tunable Holographic Polymer Dispersed Liquid Crystals Grating Doped with Chiral Molecules

Directory of Open Access Journals (Sweden)

Hui LI

2017-08-01

Full Text Available This study proposes a holographic grating made of polymer dispersed liquid crystal (PDLC, with a small amount of chiral molecules doped into PDLC material. The major advantage of this grating is that it is independent of light polarization. This characteristic was verified by applying the interference beam intensity of a He-Cd laser at 150 mW/cm2, with an incidence angle between the two interference beams of 24°, for an irradiation curing duration of 120 s. The observed periodic structure of the grating is consistent with the theoretical value. As chiral molecules are doped, nematic-LC experiences a phase-change in the grating. However, the electro-optical features are only slightly affected. This proposed grating has greatly potential in 3D imaging because of its polarization-independent feature.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16312

Spectroscopy and decay kinetics of Pr3+-doped chloride crystals for 1300-nm optical amplifiers

International Nuclear Information System (INIS)