Crystal growth of HVPE-GaN doped with germanium

NASA Astrophysics Data System (ADS)

Iwinska, M.; Takekawa, N.; Ivanov, V. Yu.; Amilusik, M.; Kruszewski, P.; Piotrzkowski, R.; Litwin-Staszewska, E.; Lucznik, B.; Fijalkowski, M.; Sochacki, T.; Teisseyre, H.; Murakami, H.; Bockowski, M.

2017-12-01

Crystallization by hydride vapor phase epitaxy method of gallium nitride single crystals doped with germanium and properties of the obtained material are described in this paper. Growth was performed in hydrogen and nitrogen carrier gas. The results were studied and compared. Influence of different flows of germanium tetrachloride, precursor of germanium, on the grown crystals was investigated. Ammonothermal GaN substrates were used as seeds for crystallization. Structural, electrical, and optical properties of HVPE-GaN doped with germanium are presented and discussed in detail. They were compared to properties of HVPE-GaN doped with silicon and also grown on native seeds of high quality.

Photorefractivity in a Titanium Doped ZnCdTe Crystal

NASA Technical Reports Server (NTRS)

Davis, M.; Collins, L.; Dyer, K.; Tong, J.; Ueda, A.; Chen, H.; Chen, K.-T.; Burger, A.; Pan, Z.; Morgan, S. H.

1997-01-01

Single crystals of Zn(.04)Cd(.96)Te was grown by horizontal physical vapor transport (PVT) method and doped by annealing with TiTe2 powder at 600 C for six days. Photorefractive two-beam coupling, along with photoluminescence and absorption spectroscopy, were used to characterize the ZnCdTe:Ti crystal. At 1.32 micrometers, the photorefractive gain has been measured as a function of the grating period. A gain of about 0.16/cm was obtained at an intensity of about 0.1 W/sq cm. The results of this titanium doped ZnCdTe crystal are compared to that of vanadium-doped CdTe crystals reported previously.

Magnesium oxide doping reduces acoustic wave attenuation in lithium metatantalate and lithium metaniobate crystals

NASA Technical Reports Server (NTRS)

Croft, W.; Damon, R.; Kedzie, R.; Kestigian, M.; Smith, A.; Worley, J.

1970-01-01

Single crystals of lithium metatantalate and lithium metaniobate, grown from melts having different stoichiometries and different amounts of magnesium oxide, show that doping lowers temperature-independent portion of attenuation of acoustic waves. Doped crystals possess optical properties well suited for electro-optical and photoelastic applications.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2008-02-05

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 hysteresismore » measurements reveal an increase of coercive field due to the formation of single domain pattern.« less

Mechanism of radiative recombination in acceptor-doped bulk GaN crystals

NASA Astrophysics Data System (ADS)

Godlewski, M.; Suski, T.; Grzegory, I.; Porowski, S.; Bergman, J. P.; Chen, W. M.; Monemar, B.

1999-12-01

Optical and electrical properties of acceptor-doped bulk GaN crystals are discussed. Though introducing Zn and Ca to bulk GaN does not significantly change electron concentration, it results in the appearance of a blue photoluminescence band accompanying the relatively strong yellow band usually present. Highly resistive GaN : Mg crystals are obtained when high amount of Mg is introduced to the Ga melt during high-pressure synthesis. Change of electrical properties of Mg-doped bulk crystals is accompanied by the appearance of a strong blue emission of GaN similar to that in Ca- and Zn-doped crystals. Optically detected magnetic resonance investigations indicate a multi-band character of this blue emission and suggest possible mechanism of compensation in acceptor-doped bulk GaN.

Structural, optical, mechanical and dielectric studies of pure and doped L-Prolinium trichloroacetate single crystals.

PubMed

Renuka, N; Ramesh Babu, R; Vijayan, N; Vasanthakumar, Geetha; Krishna, Anuj; Ramamurthi, K

2015-02-25

In the present work, pure and metal substituted L-Prolinium trichloroacetate (LPTCA) single crystals were grown by slow evaporation method. The grown crystals were subjected to single crystal X-ray diffraction (XRD), powder X-ray diffraction, FTIR, UV-Visible-NIR, hardness, photoluminescence and dielectric studies. The dopant concentration in the crystals was measured by inductively coupled plasma (ICP) analysis. Single crystal X-ray diffraction studies of the pure and metal substituted LPTCA revealed that the grown crystals belong to the trigonal system. Ni(2+) and Co(2+) doping slightly altered the lattice parameters of LPTCA without affecting the basic structure of the crystal. FTIR spectral analysis confirms the presence of various functional groups in the grown crystals. The mechanical behavior of pure and doped crystals was analyzed by Vickers's microhardness test. The optical transmittance, dielectric and photoluminescence properties of the pure and doped crystals were analyzed. Copyright © 2014 Elsevier B.V. All rights reserved.

Growth and properties of benzil doped benzimidazole (BMZ) single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in; Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012; Sukumar, M.

2010-09-15

In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure andmore » doped benzimidazole crystals measured using Kurtz powder test.« less

Doping of germanium and silicon crystals with non-hydrogenic acceptors for far infrared lasers

DOEpatents

Haller, Eugene E.; Brundermann, Erik

2000-01-01

A method for doping semiconductors used for far infrared lasers with non-hydrogenic acceptors having binding energies larger than the energy of the laser photons. Doping of germanium or silicon crystals with beryllium, zinc or copper. A far infrared laser comprising germanium crystals doped with double or triple acceptor dopants permitting the doped laser to be tuned continuously from 1 to 4 terahertz and to operate in continuous mode. A method for operating semiconductor hole population inversion lasers with a closed cycle refrigerator.

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

NASA Astrophysics Data System (ADS)

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.

Ultratough single crystal boron-doped diamond

DOEpatents

Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

2015-05-05

The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

Growth and characterization of crystals for room temperature I.R. detectors and second harmonic generation devices

NASA Technical Reports Server (NTRS)

Lal, R. B.

1995-01-01

One of the major objectives of this program was to modify the triglycine sulfate (TGS) crystals with suitable dopants and variants to achieve better pyroelectric properties and improved infrared detectivities (D(sup *)), and higher Curie transition temperature compared to undoped TGS crystals. Towards these objectives, many promising dopants, both inorganic and organic, were investigated in the last few years. These dopants gave significant improvement in the D(sup *) value of the infrared detectors fabricated from the grown crystals with no significant increase in the Curie temperature (49 C). The IR detectors were fabricated at EDO/Barnes Engineering Division, Shelton, CT. In the last one year many TGS crystals doped with urea were grown using the low temperature solution crystal growth facility. It is found that doping with urea, the normalized growth yield increased significantly compared to pure TGS crystals and there is an improvement in the pyroelectric and dielectric constant values of doped crystals. This gave a significant increase in the materials figure of merits. The Vicker's hardness of 10 wt percent urea doped crystals is found to be about three times higher in the (010) direction compared to undoped crystals. This report describes in detail the results of urea doped TGS crystals.

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

NASA Astrophysics Data System (ADS)

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.

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

PubMed

Prasanyaa, T; Jayaramakrishnan, V; Haris, M

2013-03-01

In this paper, we report the successful growth of pure, Cu(2+) ions and Cd(2+) ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu(2+) and Cd(2+) 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 Cd(2+) and Cu(2+) 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. Copyright © 2012 Elsevier B.V. All rights reserved.

Theoretical investigation of the formation of basal plane stacking faults in heavily nitrogen-doped 4H-SiC crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taniguchi, Chisato; Ichimura, Aiko; Ohtani, Noboru, E-mail: ohtani.noboru@kwansei.ac.jp

The formation of basal plane stacking faults in heavily nitrogen-doped 4H-SiC crystals was theoretically investigated. A novel theoretical model based on the so-called quantum well action mechanism was proposed; the model considers several factors, which were overlooked in a previously proposed model, and provides a detailed explanation of the annealing-induced formation of double layer Shockley-type stacking faults in heavily nitrogen-doped 4H-SiC crystals. We further revised the model to consider the carrier distribution in the depletion regions adjacent to the stacking fault and successfully explained the shrinkage of stacking faults during annealing at even higher temperatures. The model also succeeded inmore » accounting for the aluminum co-doping effect in heavily nitrogen-doped 4H-SiC crystals, in that the stacking fault formation is suppressed when aluminum acceptors are co-doped in the crystals.« less

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

NASA Astrophysics Data System (ADS)

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.

Ytterbium-doped borate fluoride laser crystals and lasers

DOEpatents

Schaffers, Kathleen I.; DeLoach, Laura D.; Payne, Stephen A.; Keszler, Douglas A.

1997-01-01

A new class of solid state laser crystals and lasers are formed from Yb-doped borate fluoride host crystals. The general formula for the host crystals is MM'(BO.sub.3)F, where M, M' are monovalent, divalent aria trivalent metal cations. A particular embodiment of the invention is Yb-doped BaCaBO.sub.3 F (Yb:BCBF). BCBF and some of the related derivative crystals are capable of nonlinear frequency conversion, whereby the fundamental of the laser is converted to a longer or shorter wavelength. In this way, these new crystals can simultaneously serve as self-frequency doubling crystals and laser materials within the laser resonator.

Study on structural, morphological, optical and thermal properties of guanidine carbonate doped nickel sulfate hexahydrate crystal.

PubMed

Silambarasan, A; Rajesh, P; Ramasamy, P

2015-01-05

The single crystal of guanidine carbonate doped nickel sulfate hexahydrate was grown from solution for ultraviolet filters. The single crystal XRD confirms that the grown single crystal belongs to the tetragonal system with the space group of P4₁2₁2. The crystallinity of the grown crystal was estimated by powder X-ray diffraction studies. The optical transmission and thermal stability of as-grown guanidine carbonate doped nickel sulfate single crystals have been studied. The optical transmission spectrum demonstrates the characteristics of ultraviolet filters. The TG/DTA studies confirm the thermal properties of grown crystals. Thermo-gravimetric analysis showed that the dehydration temperature of the guanidine carbonate doped nickel sulfate crystal is about 100 °C, which is much higher than that of pure nickel sulfate hexahydrate (NSH) crystals which is 72 °C. The growth behaviors and dislocation density were detected under the high resolution XRD and etching studies respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Nonlinear optical and microscopic analysis of Cu2+ doped zinc thiourea chloride (ZTC) monocrystal

NASA Astrophysics Data System (ADS)

Ramteke, S. P.; Anis, Mohd; Pandian, M. S.; Kalainathan, S.; Baig, M. I.; Ramasamy, P.; Muley, G. G.

2018-02-01

Organometallic crystals offer considerable nonlinear response therefore, present article focuses on bulk growth and investigation of Cu2+ ion doped zinc thiourea chloride (ZTC) crystal to explore its technological impetus for laser assisted nonlinear optical (NLO) device applications. The Cu2+ ion doped ZTC bulk single crystal of dimension 03 × 2.4 × 0.4 cm3 has been grown from pH controlled aqueous solution by employing slow solvent evaporation technique. The structural analysis has been performed by means of single crystal X-ray diffraction technique. The doping of Cu2+ ion in ZTC crystal matrix has been confirmed by means of energy dispersive spectroscopic (EDS) technique. The origin of nonlinear optical properties in Cu2+ ion doped ZTC crystal has been studied by employing the Kurtz-Perry test and Z-scan analysis. The remarkable enhancement in second harmonic generation (SHG) efficiency of Cu2+ ion doped ZTC crystal with reference to ZTC crystal has been determined. The He-Ne laser assisted Z-scan analysis has been performed to determine the third order nonlinear optical (TONLO) nature of grown crystal. The TONLO parameters such as susceptibility, absorption coefficient, refractive index and figure of merit of Cu-ZTC crystal have been evaluated using the Z-scan transmittance data. The laser damage threshold of grown crystal to high intensity of Nd:YAG laser is found to be 706.2 MW/cm2. The hardness number, work hardening index, yield strength and elastic stiffness coefficient of grown crystal has been investigated under microhardness study. The etching study has been carried out to determine the growth likelihood, nature of etch pits and surface quality of grown crystal.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podkopaev, O. I.; Shimanskiy, A. F., E-mail: shimanaf@mail.ru; Kopytkova, S. A.

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.

Growth, improved thermal stability and spectral properties of Yb3+-ions doped high temperature phase α-Ba3Gd(BO3)3 crystals co-doped by Sr2+, Ca2+ and La3+ ions

NASA Astrophysics Data System (ADS)

Pan, Shangke; Zhang, Jianyu; Pan, Jianguo

2018-02-01

To investigate the cause of the thermal instability of Yb3+-ions doped Ba3Gd(BO3)3 crystal grown from Czochralski technique, the low temperature phase β-Ba3Gd(BO3)3 powder was synthesized at the temperature of 800 °C. To inhibit the phase transition of high temperature phase Yb:α-Ba3Gd(BO3)3 during the crystal growth process, co-doping ions Sr2+, Ca2+ and La3+ ions were introduced in Yb:α-Ba3Gd(BO3)3 crystal. The melting point increased and the thermal stability of Yb:α-Ba3Gd(BO3)3 crystal was improved by co-doping ions. The absorption peaks of co-doped crystals centered at 976 nm with FWHM of 11, 11 and 12 nm and the absorption cross sections were 3.40 × 10-21 cm2, 4.00 × 10-21 cm2 and 2.66 × 10-21 cm2, respectively. The emission cross sections at 1040 nm were 2.19 × 10-21 cm2, 2.53 × 10-21 cm2 and 1.93 × 10-21 cm2, respectively. The fluorescence times of co-doped by Sr2+, Ca2+ and La3+ ions were shorter than that of Yb:α-Ba3Gd(BO3)3 crystal. So Yb:α-Ba3Gd(BO3)3 crystals co-doped by Sr2+, Ca2+ and La3+ ions will be more suitable for LD-pumping laser.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhe, E-mail: zhenzhe1201@sina.com; Yang, Lei; Hang, Yin

Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy{sup 3+} in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy{sup 3+}-TGG crystal were studied. The paramagnetic behavior is observed down to 10 K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS–NIR) at room temperature. The Verdet constants increase at measured wavelengths and highmore » thermal stability was found in Dy{sup 3+}-doped TGG, as compared to the properties of pure TGG, indicating that Dy{sup 3+}-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS–NIR wavelengths. - Graphical abstract: Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) and pure TGG single crystals were grown by Czochralski method. The Dy{sup 3+}-doped TGG possesses 20–30% higher Verdet values in reference to TGG independently on wavelength.« less

Growth and characterization of pure and glycine doped cadmium thiourea sulphate (GCTS) crystals

NASA Astrophysics Data System (ADS)

Lawrence, M.; Thomas Joseph Prakash, J.

2012-06-01

The pure and glycine doped cadmium thiourea sulphate (GCTS) single crystals were grown successfully by slow evaporation method at room temperature. The concentration of dopant in the mother solution was 1 mol%. There is a change in unit cell. The Fourier transform infrared spectroscopy study confirms the incorporation of glycine into CTS crystal. The doped crystals are optically better and more transparent than the pure ones. The dopant increases the hardness value of the material. The grown crystals were also subjected to thermal and NLO studies.

Effects of doping impurity and growth orientation on dislocation generation in GaAs crystals grown from the melt: A qualitative finite-element study

NASA Astrophysics Data System (ADS)

Zhu, X. A.; Tsai, C. T.

2000-09-01

Dislocations in gallium arsenide (GaAs) crystals are generated by excessive thermal stresses induced during the crystal growth process. The presence of dislocations has adverse effects on the performance and reliability of the GaAs-based devices. It is well known that dislocation density can be significantly reduced by doping impurity atoms into a GaAs crystal during its growth process. A viscoplastic constitutive equation that couples the microscopic dislocation density with the macroscopic plastic deformation is employed in a crystallographic finite element model for calculating the dislocation density generated in the GaAs crystal during its growth process. The dislocation density is considered as an internal state variable and the drag stress caused by doping impurity is included in this constitutive equation. A GaAs crystal grown by the vertical Bridgman process is adopted as an example to study the influences of doping impurity and growth orientation on dislocation generation. The calculated results show that doping impurity can significantly reduce the dislocation density generated in the crystal. The level of reduction is also influenced by the growth orientation during the crystal growth process.

Ytterbium-doped borate fluoride laser crystals and lasers

DOEpatents

Schaffers, K.I.; DeLoach, L.D.; Payne, S.A.; Keszler, D.A.

1997-10-14

A new class of solid state laser crystals and lasers are formed from Yb-doped borate fluoride host crystals. The general formula for the host crystals is MM{prime}(BO{sub 3})F, where M, M{prime} are monovalent, divalent aria trivalent metal cations. A particular embodiment of the invention is Yb-doped BaCaBO{sub 3}F (Yb:BCBF). BCBF and some of the related derivative crystals are capable of nonlinear frequency conversion, whereby the fundamental of the laser is converted to a longer or shorter wavelength. In this way, these new crystals can simultaneously serve as self-frequency doubling crystals and laser materials within the laser resonator. 6 figs.

Spectroscopic studies of gel grown zinc doped calcium hydrogen phosphate dihydrate crystals

NASA Astrophysics Data System (ADS)

Suryawanshi, V. B.; Chaudhari, R. T.

2018-05-01

The influence of zinc doping on the gel grown calcium hydrogen phosphate dihydrate crystals was studied using the spectroscopic techniques, which included SEM, FTIR and EDAX. It was found that, zinc ions transform the morphology of brushite crystals from rectangular plate shaped crystals to branching microcrystal patterns. However in FT-IR spectroscopy, as compared to undoped brushite crystals few vibrations were shifted to higher value. The observed changes in the vibrations were due to the impact of zinc ions. EDAX techniques is use to determine the percentage composition of elements present in the doped crystals. It revealed that the sample was of a mixed composition.

Dielectric and domain studies on Fe doped KNbO3 single crystal

NASA Astrophysics Data System (ADS)

Shamkuwar, Sanjaykumar H.; Patil, Naresh M.; Korde, Vivek B.; Pradnyakar, Namrata V.

2018-05-01

Synthesis of Fe doped KNbO3 single crystals by flux method is reported here. The effect of Fe-doping on phase transition temperatures of KNbO3 single crystals was investigated using dielectric studies. The phase transition temperatures were found to be 225°C and 425°C which almost same as reported by others. The domain studies were carried out using metallurgical microscope and it shows the presence of 60° and 90° domains in the grown crystals.

Bulk crystal growth of Ga2O3

NASA Astrophysics Data System (ADS)

Kuramata, Akito; Koshi, Kimiyoshi; Watanabe, Shinya; Yamaoka, Yu; Masui, Takekazu; Yamakoshi, Shigenobu

2018-02-01

This paper describes the bulk crystal growth of β-Ga2O3 using edge-defined film-fed growth (EFG) process. We first describe the method of the crystal growth and show that large-size crystal with width of up to 6 inch can be grown. Then, we discuss the way to control electrical properties. In the discussion, we give some experimental results of residual impurity measurement, intentional doping using Si and Sn for n-type doping and Fe for insulating doping.

Quasi four-level Tm:LuAG laser

NASA Technical Reports Server (NTRS)

Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Hutcheson, Ralph L. (Inventor); Rodriguez, Waldo J. (Inventor)

1997-01-01

A quasi four-level solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG-based host material doped to a final concentration between about 2% and about 7% thulium (Tm) ions. For the more heavily doped final concentrations, the LuAG-based host material is a LuAG seed crystal doped with a small concentration of Tm ions. Laser diode arrays are disposed transversely to the laser crystal for energizing the Tm ions.

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

PubMed

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.

Growth and characterization of metal doped and quasi mixed crystals based on ZnCd(SCN)4

NASA Astrophysics Data System (ADS)

Latha, C.; Mahadevan, C. K.; Guo, Li; Liu, Jinghe

2018-03-01

In order to understand the effect of forming hybrid crystals by doping with metallic impurities or by quasi mixing on the physicochemical properties of the basic material crystal, we have grown by the free evaporation method at room temperature and characterized (chemically, structurally, optically and electrically) un-doped and K+/Ca2+/Mn2+/Mg2+/Cu2+ doped (with 1 mol% concentration) ZnCd(SCN)4 and ZnxCd(2-x)(SCN)4 (with x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) single crystals. Single crystals could be grown with x = 0.0 (leading to Cd(SCN)2) but not when x = 2.0 (leading to Zn(SCN)2). Results obtained in the present study through X-ray diffraction and EDAX spectral measurements indicate the formation of the above hybrid crystals. The optical (UV-Vis-NIR spectral and SHG efficiency) measurements indicate significant changes in optical transmittance and SHG efficiency due to doping as well as quasi mixing. Dielectric measurements made in the temperature range 40-150 °C with a fixed frequency of 1 kHz indicate a normal dielectric behavior for all the eleven crystals grown. Moreover, the present study indicates an increase of dielectric constant and SHG efficiency when ZnCd(SCN)4 crystal is doped with a metallic impurity whereas a decrease of dielectric constant and SHG efficiency when quasi mixing is done.

Influence of carbon on the thermoluminescence and optically stimulated luminescence of α-Al2O3:C crystals

NASA Astrophysics Data System (ADS)

Yang, Xin-Bo; Li, Hong-Jun; Bi, Qun-Yu; Cheng, Yan; Tang, Qiang; Xu, Jun

2008-12-01

α-Al2O3:C crystal shows excellent thermoluminescence (TL) and optically stimulated luminescence (OSL) properties but the real role carbon plays in this crystal is still not clearly understood so far. In this work, α-Al2O3:C crystal doping with different amounts of carbon were grown by the temperature gradient technique, and TL and OSL properties of as-grown crystals were investigated. Additionally, a mechanism was proposed to explain the role of carbon in forming the TL and OSL properties of α-Al2O3:C. TL and OSL intensities of as-grown crystals increase with the increasing amount of carbon doping in the crystal, but no shift is found in the glow peak location at 465 K. As the amount of carbon doping in the crystals decreases, OSL decay rate becomes faster. With the increase in heating rate, the integral TL response of as-grown crystals decreases and glow peak shifts to higher temperatures. TL response decrease rate increases with the increasing amount of carbon doping in the crystals. All the TL and OSL response curves of as-grown crystals show linear-sublinear-saturation characteristic, and OSL dose response exhibits higher sensitivity and wider linear dose range than that of TL. The crystal doping with 5000 ppm carbon shows the best dosimetric properties. Carbon plays the role of a dopant in α-Al2O3:C crystal and four-valent carbon anions replace the two-valent anions of oxygen during the crystal growth process, and large amounts of oxygen vacancies were formed, which corresponds to the high absorption coefficient of F and F+ centers in the crystals.

Effect of doping of KDP crystal with amino acid L-arginine on the strength properties and character of laser damage

NASA Astrophysics Data System (ADS)

Dolzhenkova, E. F.; Kostenyukova, E. I.; Bezkrovnaya, O. N.; Pritula, I. M.

2017-11-01

Studied were the strength characteristics of KDP crystals doped with L-arginine under a concentrated load and irradiation of the first harmonic YAG:Nd3+ laser. The crystals were obtained by means of the temperature reduction method on a point seed, the content of L-arginine in the aqueous solution being 0.3, 0.4, 1.0 and 1.4 wt%. The character of the dependence of KDP microhardness versus the concentration of amino acid in the crystal was investigated. The regularities of brittle damage of the doped KDP crystal at mechanical testing and laser irradiation were shown to be similar. As confirmed in the study, the planes of easy crack extension in the crystal are {2 2 1}, (1 0 0), and (0 0 1) planes, the cracks mainly propagate parallel to {2 2 1} planes. The mechanical and laser strength values of doped KDP crystals were evaluated.

Transition-metal doped sulfide, selenide, and telluride laser crystal and lasers

DOEpatents

Krupke, W.F.; Page, R.H.; DeLoach, L.D.; Payne, S.A.

1996-07-30

A new class of solid state laser crystals and lasers are formed of transition metal doped sulfide, selenide, and telluride host crystals which have four fold coordinated substitutional sites. The host crystals include II-VI compounds. The host crystal is doped with a transition metal laser ion, e.g., chromium, cobalt or iron. In particular, Cr{sup 2+}-doped ZnS and ZnSe generate laser action near 2.3 {micro}m. Oxide, chloride, fluoride, bromide and iodide crystals with similar structures can also be used. Important aspects of these laser materials are the tetrahedral site symmetry of the host crystal, low excited state absorption losses and high luminescence efficiency, and the d{sup 4} and d{sup 6} electronic configurations of the transition metal ions. The same materials are also useful as saturable absorbers for passive Q-switching applications. The laser materials can be used as gain media in amplifiers and oscillators; these gain media can be incorporated into waveguides and semiconductor lasers. 18 figs.

Transition-metal doped sulfide, selenide, and telluride laser crystal and lasers

DOEpatents

Krupke, William F.; Page, Ralph H.; DeLoach, Laura D.; Payne, Stephen A.

1996-01-01

A new class of solid state laser crystals and lasers are formed of transition metal doped sulfide, selenide, and telluride host crystals which have four fold coordinated substitutional sites. The host crystals include II-VI compounds. The host crystal is doped with a transition metal laser ion, e.g., chromium, cobalt or iron. In particular, Cr.sup.2+ -doped ZnS and ZnSe generate laser action near 2.3 .mu.m. Oxide, chloride, fluoride, bromide and iodide crystals with similar structures can also be used. Important aspects of these laser materials are the tetrahedral site symmetry of the host crystal, low excited state absorption losses and high luminescence efficiency, and the d.sup.4 and d.sup.6 electronic configurations of the transition metal ions. The same materials are also useful as saturable absorbers for passive Q-switching applications. The laser materials can be used as gain media in amplifiers and oscillators; these gain media can be incorporated into waveguides and semiconductor lasers.

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

NASA Astrophysics Data System (ADS)

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.

Laser Materials Search and Characterization

DTIC Science & Technology

2014-05-30

AgBr doped with dysprosium ions are obtained by extrusion, and their optical and spectral properties are studied. Task 3. Waveguides based on LiF...fluoride are obtained by extrusion for the first time. Task 4. Spectroscopic properties of Dy3+ ions in chalcogenide crystals and fibers are studied...Task 5. Crystals and ceramics doped with rare-earth ions , as well as glasses and crystals doped with bismuth ions , are synthesized. Their

Comparative study of nondoped and Eu-doped SrI2 scintillator

NASA Astrophysics Data System (ADS)

Yanagida, Takayuki; Koshimizu, Masanori; Okada, Go; Kojima, Takahiro; Osada, Junya; Kawaguchi, Noriaki

2016-11-01

Optical and scintillation properties of nondoped and Eu 3% doped SrI2 crystals grown by the Vertical Bridgman method were investigated. Eu-doped crystal showed an intense single band emission at 430 nm due to the Eu2+ 5d-4f transitions in both photoluminescence and scintillation while the nondoped crystal had a complex spectral shape. The latter emission consists of mainly four bands: 360 nm, 540 nm, 410 nm and 430 nm. The origins of 360 nm and 540 nm were self-trapped exciton and unexpected impurity, respectively. The origins of 410 and 430 nm lines were ascribed to F center in different I sites. Under 137Cs γ-ray irradiations, both crystals showed a clear photoabsorption peak. The scintillation light yields of the nondoped and Eu-doped SrI2 resulted 33,000 ph/MeV and 82,000 ph/MeV, respectively. The energy resolution at 662 keV of Eu-doped was 4% while that of the non-doped SrI2 was 8%.

Scintillation properties of Pr 3+-doped lutetium and yttrium aluminum garnets: Comparison with Ce 3+-doped ones

NASA Astrophysics Data System (ADS)

Mares, Jiri A.; Nikl, Martin; Beitlerova, Alena; Blazek, Karel; Horodysky, Petr; Nejezchleb, Karel; D'Ambrosio, Carmelo

2011-12-01

Scintillation properties of Pr 3+-doped LuAG and YAG crystals were investigated and compared with those of Ce 3+-doped ones. The highest L.Y.'s were observed with the longest shaping time 10 μs. They can reach up to ˜16,000 ph/MeV or ˜23,500 ph/MeV for LuAG:Pr and LuAG:Ce, respectively. Energy resolutions (FWHM) are a bit better with LuAG:Pr than those of LuAG:Ce, e.g. at 662 keV FWHM are around 6% and between 8-12%, respectively. There were observed no large changes in proportionality of Pr 3+- or Ce 3+-doped LuAG or YAG crystals but the best proportionality has YAP:Ce crystal. Pr 3+- or Ce 3+-doped LuAG crystals exhibit slow decay components in the time range 1.5-3.5 μs while those of YAG ones have shorter decay components between 0.3-1.7 μs.

Bismuth doping effect on crystal structure and photodegradation activity of Bi-TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Wu, Ming-Chung; Chang, Yin-Hsuan; Lin, Ting-Han

2017-04-01

The bismuth precursor is adopted as dopant to synthesize bismuth doped titanium dioxide nanoparticles (Bi-TiO2 NPs) with sol-gel method following by the thermal annealing treatment. We systematically developed a series of Bi-TiO2 NPs at several calcination temperatures and discovered the corresponding crystal structure by varying the bismuth doping concentration. At a certain 650 °C calcination temperature, the crystal structure of bismuth titanate (Bi2Ti2O7) is formed when the bismuth doping concentration is as high as 10.0 mol %. The photocatalytic activity of Bi-TiO2 NPs is increased by varying the doping concentration at the particular calcination temperature. By the definition X-ray diffraction (XRD) structural identification, a phase diagram of Bi-TiO2 NPs in doping concentration versus calcination temperature is provided. It can be useful for further study in the crystal structure engineering and the development of photocatalyst.

Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

NASA Astrophysics Data System (ADS)

Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

2016-07-01

Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm-2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm-2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

Mg,Ce co-doped Lu2Gd1(Ga,Al)5O12 by micro-pulling down method and their luminescence properties

NASA Astrophysics Data System (ADS)

Kamada, Kei; Yamaguchi, Hiroaki; Yoshino, Masao; Kurosawa, Shunsuke; Shoji, Yasuhiro; Yokota, Yuui; Ohashi, Yuji; Pejchal, Jan; Nikl, Martin; Yoshikawa, Akira

2018-04-01

The effects of Mg co-doping on the scintillation properties of Ce:Lu2Gd1(Ga,Al)5O12 (LGGAG) single crystals with different Ga/Al ratios were investigated. Mg co-doped and non co-doped Ce:LGGAG single crystals were grown by the micro-pulling down (µ-PD) method and then cut, polished and annealed for each measurement. Absorption spectra, radioluminescence (RL) spectra, pulse height spectra, and scintillation decay were measured to reveal the effect of Mg co-doping. Ce4+ charge transfer (CT) absorption band peaking at ∼260 nm was observed in Mg co-doped samples, which is in good agreement with previous reports for the Ce4+ CT absorption band in other garnet-based crystals. The scintillation decay time tended to be accelerated and the light yield tended to be decreased by Mg co-doping at higher Ga concentrations.

DC electrical conductivity measurements for pure and titanium oxide doped KDP Crystals grown by gel medium

NASA Astrophysics Data System (ADS)

Mareeswaran, S.; Asaithambi, T.

2016-10-01

Now a day's crystals are the pillars of current technology. Crystals are applied in various fields like fiber optic communications, electronic industry, photonic industry, etc. Crystal growth is an interesting and innovative field in the subject of physics, chemistry, material science, metallurgy, chemical engineering, mineralogy and crystallography. In recent decades optically good quality of pure and metal doped KDP crystals have been grown by gel growth method in room temperature and its characterizations were studied. Gel method is a very simple and one of the easiest methods among the various crystal growth methods. Potassium dihydrogen phosphate KH2PO4 (KDP) continues to be an interesting material both academically and technologically. KDP is a delegate of hydrogen bonded materials which possess very good electrical and nonlinear optical properties in addition to interesting electro-optic properties. We made an attempt to grow pure and titanium oxide doped KDP crystals with various doping concentrations (0.002, 0.004, 0.006, 0.008 and 0.010) using gel method. The grown crystals were collected after 20 days. We get crystals with good quality and shaped crystals. The dc electrical conductivity (resistance, capacitance and dielectric constant) values of the above grown crystals were measured at two different frequencies (1KHz and 100 Hz) with a temperature range of 500C to 1200C using simple two probe setup with Q band digital LCR meter present in our lab. The electrical conductivity increases with the increase of temperature. Dielectric constants value of titanium oxide doped KDP crystal was slightly decreased compared with pure KDP crystals. Results were discussed in details.

Influence of doping on thermal diffusivity of single crystals used in photonics: measurements based on thermal wave methods.

PubMed

Bodzenta, Jerzy; Kaźmierczak-Bałata, Anna; Wokulska, Krystyna B; Kucytowski, Jacek; Łukasiewicz, Tadeusz; Hofman, Władysław

2009-03-01

Three crystals used in solid-state lasers, namely, yttrium aluminum garnet (YAG), yttrium orthovanadate (YVO(4)), and gadolinium calcium oxoborate (GdCOB), were investigated to determine the influence of dopants on their thermal diffusivity. The thermal diffusivity was measured by thermal wave method with a signal detection based on mirage effect. The YAG crystals were doped with Yb or V, the YVO(4) with Nd or Ca and Tm, and the GdCOB crystals contained Nd or Yb. In all cases, the doping caused a decrease in thermal diffusivity. The analysis of complementary measurements of ultrasound velocity changes caused by dopants leads to the conclusion that impurities create phonon scattering centers. This additional scattering reduces the phonon mean free path and accordingly results in the decrease of the thermal diffusivity of the crystal. The influence of doping on lattice parameters was investigated, additionally.

Ribbon Growth of Single Crystal GaAs for Solar Cell Application.

DTIC Science & Technology

1981-11-01

Entered) 20. Abstract (Cont.) 7growth techniques, dendrite seeds, and melt chemistry were optimized during the course of the program; however...Faceted Web. 10 Crystal Grown From a Melt Doped With 1.0 Atomic% Ge. 17 The Ge-Doped Crystals Grew at Low Undercooling and Contained Flatter Textured-Web...Ge Melt Doping. The 18 Textured-Web Sections Were the Widest Achieved at Small Undercooling, ɝ.0°C. 12 Radiation Exchange Between the Melt Surface

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

PubMed

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.

Growth and characterization of pure and Ca2+ doped MnHg(SCN)4 single crystals

NASA Astrophysics Data System (ADS)

Latha, C.; Mahadevan, C. K.; Guo, Li; Liu, Jinghe

2018-05-01

Manganese-mercury thiocyanate, MnHg(SCN)4, crystal is considered to be an important organometallic nonlinear optical (NLO) material exhibiting higher thermal stability and second harmonic generation (SHG) efficiency. In order to understand the effect of Ca2+ as an impurity on the physicochemical properties, we have grown pure and Ca2+ doped (with a concentration of 1 mol%) MnHg(SCN)4 single crystals by the free evaporation of solvent method and characterized structurally, chemically, optically and electrically by adopting the available standard methods. Results obtained indicate that Ca2+ doping increases significantly the optical transmittance, SHG efficiency, and DC electrical conductivity and decreases the dielectric loss factor (improves the crystal quality), and AC electrical conductivity without distorting the crystal structure. Also, the low dielectric constant (εr) values observed for both the pure and doped crystals considered at near ambient temperatures indicate the possibility of using these crystals not only as potential NLO materials (useful in the photonics industry) but also as promising low εr value dielectric materials (useful in the microelectronics industry).

Enhance the performance of liquid crystal as an optical switch by doping CdS quantum dots

NASA Astrophysics Data System (ADS)

Ahmed, Sudad S.; Ibrahim, Rawa K.; Al-Naimee, Kais; Naje, Asama N.; Ibrahim, Omar A.; Majeed, K. A.

2018-05-01

The electrical and optical properties results were studied for Cadmium Sulphide (CdS) Nanoparticles / Nematic liquid crystal (5CB) mixtures. Doping of CdS nanoparticles increases the spontaneous polarization and response time, the increase is due to large dipole-dipole interaction between the liquid crystal (LC) molecules and CdS nanoparticles, which increase the anchoring energy. The electro-optic measurements revealed a decrease (∼40%) in threshold voltage, and faster response time in doped sample cells than Pure 4'-n-pentyl-4-cyanobiphenyl (5CB) nematic liquid crystal.

Characterization of Strain Due to Nitrogen Doping Concentration Variations in Heavy Doped 4H-SiC

NASA Astrophysics Data System (ADS)

Yang, Yu; Guo, Jianqiu; Raghothamachar, Balaji; Chan, Xiaojun; Kim, Taejin; Dudley, Michael

2018-02-01

Highly doped 4H-SiC will show a significant lattice parameter difference with respect to the undoped material. We have applied the recently developed monochromatic contour mapping technique for 4H-SiC crystals to a 4H-SiC wafer crystal characterized by nitrogen doping concentration variation across the whole sample surface using a synchrotron monochromatic x-ray beam. Strain maps of 0008 and - 2203 planes were derived by deconvoluting the lattice parameter variations from the lattice tilt. Analysis reveals markedly different strain values within and out of the basal plane indicating the strain induced by nitrogen doping is anisotropic in the 4H-SiC hexagonal crystal structure. The highest strain calculated along growth direction [0001] and along [1-100] on the closed packed basal plane is up to - 4 × 10-4 and - 2.7 × 10-3, respectively. Using an anisotropic elasticity model by separating the whole bulk crystal into numerous identical rectangular prism units, the measured strain was related to the doping concentration and the calculated highest nitrogen level inside wafer crystal was determined to be 1.5 × 1020 cm-3. This is in agreement with observation of double Shockley stacking faults in the highly doped region that are predicted to nucleate at nitrogen levels above 2 × 1019 cm-3.

Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi.

PubMed

Srinivasan, Bhuvanesh; Boussard-Pledel, Catherine; Dorcet, Vincent; Samanta, Manisha; Biswas, Kanishka; Lefèvre, Robin; Gascoin, Franck; Cheviré, François; Tricot, Sylvain; Reece, Michael; Bureau, Bruno

2017-03-23

Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge 20 Te 77 Se₃ glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge 20 Te 77 Se₃) 100- x M x (M = Cu or Bi; x = 5, 10, 15), obtained by vacuum-melting and quenching techniques, were found to have multiple crystalline phases and exhibit increased electrical conductivity due to excess hole concentration. These materials also have ultra-low thermal conductivity, especially the heavily-doped (Ge 20 Te 77 Se₃) 100- x Bi x ( x = 10, 15) samples, which possess lattice thermal conductivity of ~0.7 Wm -1 K -1 at 525 K due to the assumable formation of nano-precipitates rich in Bi, which are effective phonon scatterers. Owing to their high metallic behavior, Cu-doped samples did not manifest as low thermal conductivity as Bi-doped samples. The exceptionally low thermal conductivity of the Bi-doped materials did not, alone, significantly enhance the thermoelectric figure of merit, zT. The attempt to improve the thermoelectric properties by crystallizing the chalcogenide glass compositions by excess doping did not yield power factors comparable with the state of the art thermoelectric materials, as these highly electrically conductive crystallized materials could not retain the characteristic high Seebeck coefficient values of semiconducting telluride glasses.

Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi

PubMed Central

Srinivasan, Bhuvanesh; Boussard-Pledel, Catherine; Dorcet, Vincent; Samanta, Manisha; Biswas, Kanishka; Lefèvre, Robin; Gascoin, Franck; Cheviré, François; Tricot, Sylvain; Reece, Michael; Bureau, Bruno

2017-01-01

Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge20Te77Se3 glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge20Te77Se3)100−xMx (M = Cu or Bi; x = 5, 10, 15), obtained by vacuum-melting and quenching techniques, were found to have multiple crystalline phases and exhibit increased electrical conductivity due to excess hole concentration. These materials also have ultra-low thermal conductivity, especially the heavily-doped (Ge20Te77Se3)100−xBix (x = 10, 15) samples, which possess lattice thermal conductivity of ~0.7 Wm−1 K−1 at 525 K due to the assumable formation of nano-precipitates rich in Bi, which are effective phonon scatterers. Owing to their high metallic behavior, Cu-doped samples did not manifest as low thermal conductivity as Bi-doped samples. The exceptionally low thermal conductivity of the Bi-doped materials did not, alone, significantly enhance the thermoelectric figure of merit, zT. The attempt to improve the thermoelectric properties by crystallizing the chalcogenide glass compositions by excess doping did not yield power factors comparable with the state of the art thermoelectric materials, as these highly electrically conductive crystallized materials could not retain the characteristic high Seebeck coefficient values of semiconducting telluride glasses. PMID:28772687

Habit modification of epsomite in the presence of urea

NASA Astrophysics Data System (ADS)

Ramalingom, S.; Podder, J.; Narayana Kalkura, S.; Bocelli, G.

2003-01-01

The pure and urea doped epsomite (MgSO 4·7H 2O) crystals were grown at low temperature by the slow cooling technique. The effect of pH on the growth rate of pure MgSO 4·7H 2O was studied. It was found that the higher pH values increased the growth rate and the size of the crystals. The quantity of urea present in the doped magnesium sulphate crystals was estimated. The incorporation of urea into the mother solution was found to promote the growth rate. The habit of the crystals changed from orthorhombic to tetragonal. Further, there was an increase of microhardness of the crystals on doping of urea.

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

NASA Astrophysics Data System (ADS)

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.

Li+, Na+ and K+ co-doping effects on scintillation properties of Ce:Gd3Ga3Al2O12 single crystals

NASA Astrophysics Data System (ADS)

Yoshino, Masao; Kamada, Kei; Kochurikhin, Vladimir V.; Ivanov, Mikhail; Nikl, Martin; Okumura, Satoshi; Yamamoto, Seiichi; Yeom, Jung Yeol; Shoji, Yasuhiro; Kurosawa, Shunsuke; Yokota, Yuui; Ohashi, Yuji; Yoshikawa, Akira

2018-06-01

Ce0.5%: Ce:Gd3Ga3Al2O12(GGAG) single crystals co-doped with 500at.ppm Li+, Na+ and K+ were grown by using the micro-pulling down method. The smooth Ce4+ charge transfer absorption below 350 nm and decay time acceleration were observed in Li co-doped sample. Na+ and K+ co-doping did not show a large effect on the acceleration of decay time compared with Li co-doping. Ce0.5%:GGAG single crystals co-doped with 500 at.ppm Li+ were also grown by the Czochralski method. Optical, scintillation properties and timing performance were evaluated to investigate the effect of univalent alkali metal ions co-doping on Ce:GGAG scintillators. The scintillation decay curves were accelerated by Li co-doping: the decay time was significantly accelerated to 54.8 ns (47%) for the faster component and 158 ns (53%) for the slower component. The light output was 94% of the non co-doped Ce:GGAG standard. The coincidence time resolution was improved to 258 ps by Li co-doping.

Ytterbium- and neodymium-doped vanadate laser hose crystals having the apatite crystal structure

DOEpatents

Payne, Stephen A.; Kway, Wayne L.; DeLoach, Laura D.; Krupke, William F.; Chai, Bruce H. T.

1994-01-01

Yb.sup.3+ and Nd.sup.3+ doped Sr.sub.5 (VO.sub.4).sub.3 F crystals serve as useful infrared laser media that exhibit low thresholds of oscillation and high slope efficiencies, and can be grown with high optical quality. These laser media possess unusually high absorption and emission cross sections, which provide the crystals with the ability to generate greater gain for a given amount of pump power. Many related crystals such as Sr.sub.5 (VO.sub.4).sub.3 F crystals doped with other rare earths, transition metals, or actinides, as well as the many structural analogs of Sr.sub.5 (VO.sub.4).sub.3 F, where the Sr.sup.2+ and F.sup.- ions are replaced by related chemical species, have similar properties.

Effect of doping with nickel ions on the structural state of a zinc oxide crystal

NASA Astrophysics Data System (ADS)

Dubinin, S. F.; Sokolov, V. I.; Parkhomenko, V. D.; Maksimov, V. I.; Gruzdev, N. B.

2009-10-01

The fine structure of a hexagonal zinc oxide crystal doped with nickel ions of the composition Zn1 - x Ni x O has been studied using neutron diffraction and magnetic measurements. It is established that even at very low doping levels ( x = 0.0004), the crystal undergoes local distortions in basal planes of the initial hexagonal lattice. The local distortions are assumed to be sources of the formation of ferromagnetism in compounds of this class.

Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals

NASA Astrophysics Data System (ADS)

Sinha, Nidhi; Goel, Neeti; Singh, B. K.; Gupta, M. K.; Kumar, Binay

2012-06-01

Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (Tc) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications.

Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid

DOE PAGES

Jiang, Hong -Chen; Devereaux, T.; Kivelson, S. A.

2017-08-07

We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t–J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ = 0) spin-1/2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole permore » unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. In conclusion, our results may be relevant to kagome lattice herbertsmithite upon doping.« less

Effect of severe plastic deformation on the structure and crystal-lattice distortions in the Ni3(Al, X) ( X = Ti, Nb) intermetallic compound

NASA Astrophysics Data System (ADS)

Kazantseva, N. V.; Pilyugin, V. P.; Danilov, S. E.; Kolosov, V. Yu.

2015-05-01

A systematic combined study of crystal lattice distortions caused by doping and by severe plastic deformation (SPD) of Ti- and Nb-doped Ni3Al intermetallic compound has been carried out using methods of X-ray diffraction, electron microscopy, and electrical-resistance measurements. The degree of imperfection of the alloys has been estimated based on the results obtained by all three methods. The degree of structural perfection of niobium-doped crystals was found to be higher than in the case of Ti doping. The character of stresses (tensile stresses after doping; and compressive stresses after SPD) in the crystal lattice has been established and their values have been calculated. A significant increase in the density of dislocations, point defects, and lattice curvature has been found after SPD. A nanocrystalline structure is formed in these alloys, but no complete disordering of the intermetallic phase is observed.

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

PubMed

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.

Structural and optical properties of indium-doped highly conductive ZnO bulk crystals grown by the hydrothermal technique

NASA Astrophysics Data System (ADS)

Wang, Buguo; Claflin, Bruce; Look, David; Jiménez, Juan

2018-02-01

Indium-doped ZnO bulk crystals grown by the hydrothermal method are highly-conductive, with resistivity at 0.01 Ωcm at room temperature as revealed by Hall-effect measurement. In this paper we report on structural and optical properties of these crystals. The grown In:ZnO crystals have been studied by high resolution X-ray diffraction, micro-Raman scattering and low-temperature photoluminescence and cathodoluminescence. It was found that the c lattice parameter of the grown In:ZnO crystal expanded 0.06% with respect to the lithium-doped ZnO crystal seed, and the In-doped ZnO overgrew the seed crystal pseudomorphically but with high quality crystallinity; the X-ray rocking curves show the FWHM of the Zn face and O faces are only 0.05° and 0.1° ; and the indium concentration in the crystal reaches the solubility limit. Raman spectra show strain relaxation gradually from the regrowth interface as well as a weak spectral feature at 723 cm-1. The peak at 312 cm-1 noticed in hydrothermally grown In:ZnO nanostructures does not appear in our In-doped crystals, indicating that this peak may be associated with specific defects (e.g. surface related) of the nanostructures. Photoluminescence measurements show that an indium donor bound exciton peak I9 (In0X) is the dominant peak in the PL spectrum, located at 3.3586 eV on the zinc face and 3.3577 eV on the oxygen face. Both of them deviated from the consensus literature value of 3.3567 eV, probably due to strain in the crystal induced by impurities.

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

NASA Astrophysics Data System (ADS)

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.

Fast growth of n-type 4H-SiC bulk crystal by gas-source method

NASA Astrophysics Data System (ADS)

Hoshino, Norihiro; Kamata, Isaho; Tokuda, Yuichiro; Makino, Emi; Kanda, Takahiro; Sugiyama, Naohiro; Kuno, Hironari; Kojima, Jun; Tsuchida, Hidekazu

2017-11-01

Fast growth of n-type 4H-SiC crystals was attempted using a high-temperature gas-source method. High growth rates exceeding 9 mm/h were archived at a seed temperature of 2550 °C, although the formation of macro-step bunching caused doping fluctuation and voids in the grown crystal. We investigated a trade-off between growth-rate enhancement and macro-step formation and how to improve the trade-off. By controlling the growth conditions, the growth of highly nitrogen-doped 4H-SiC crystals without the doping fluctuation and void formation were accomplished under a high growth rate exceeding 3 mm/h, maintaining the density of threading screw dislocations in the same level with the seed crystal. The influence of growth parameters on nitrogen incorporations into grown crystals was also surveyed.

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

NASA Astrophysics Data System (ADS)

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.

Growth and characterization of materials for tunable lasers in the near infrared spectral region

NASA Technical Reports Server (NTRS)

Powell, Richard C.; Martin, Joel J.

1988-01-01

During this reporting period, work proceeded in two directions. The first was the development of crystal growth procedures for rare earth doped LiYF4 crystals. The procedures for growth and pre-growth treatment of starting materials for undoped LiYF4 crystals were established and good optical quality materials were grown. A significant amount of time was spent trying to establish the optimum growth parameters for Yb(3+)-doped crystals. Unfortunately, it has proven difficult to obtain large size boules of high optical quality crystals of LiYF4 with doping concentrations of Yb(3+) of several percent. Because of these problems, this research is to be changed to attempt doping with other trivalent rare earth ions such as Ho, Er, and Tm. The second research area was investigating the potential of LiNbO3:Mg,Cr and LiNbO3:Mg,Cr,Yb as possible laser materials. The results are summarized.

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

NASA Astrophysics Data System (ADS)

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.

Theoretical study of the characteristics of a continuous wave iron-doped ZnSe laser

NASA Astrophysics Data System (ADS)

Pan, Qikun; Chen, Fei; Xie, Jijiang; Wang, Chunrui; He, Yang; Yu, Deyang; Zhang, Kuo

2018-03-01

A theoretical model describing the dynamic process of a continuous-wave Fe2+:ZnSe laser is presented. The influence of some of the operating parameters on the output characteristics of an Fe2+:ZnSe laser is studied in detail. The results indicate that the temperature rise of the Fe2+:ZnSe crystal is significant with the use of a high power pump laser, especially for a high doped concentration of crystal. The optimal crystal length increases with decreasing the doped concentration of crystal, so an Fe2+:ZnSe crystal with simultaneous doping during growth is an attractive choice, which usually has a low doped concentration and long length. The laser pumping threshold is almost stable at low temperatures, but increases exponentially with a working temperature in the range of 180 K to room temperature. The main reason for this phenomenon is the short upper level lifetime and serious thermal temperature rise when the working temperature is higher than 180 K. The calculated optimum output mirror transmittance is about 35% and the performance of a continuous-wave Fe2+:ZnSe laser is more efficient at a lower operating temperature.

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

NASA Astrophysics Data System (ADS)

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.

Interplay of superconductivity and magnetic fluctuations in single crystals of BaFe2-xCoxAs2

NASA Astrophysics Data System (ADS)

Bag, Biplab; Kumar, Ankit; Banerjee, S. S.; Vinod, K.; Bharathi, A.

2018-04-01

We report unusual pinning response in optimally doped and overdoped single crystals of BaFe2-xCoxAs2. Here we use magneto-optical imaging technique to measure the local magnetization response which shows an unusual transformation from low temperature diamagnetic state to high temperature positive magnetization response. Our data suggests coexistence of magnetic fluctuation along with superconductivity in the optimally doped crystal. The strength of magnetic fluctuations is the strongest in the optimally doped compound with the highest Tc.

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

NASA Astrophysics Data System (ADS)

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.

Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique

DTIC Science & Technology

2017-10-09

doped BaTiO3 single crystal) could be also fabricated by using a BaTiO3 ceramics with the same compositional gradient (Fig. 8). This result has...piezoelectric applications. Compositionally PZT ceramics lie near the MPB between the tetragonal and rhombohedral phases and MPB compositions ...single crystal growth) technique are suitable to grow a variety of “n- and p-type doped” perovskite single crystals of complicated compositions . The

Theoretical modeling of diode-laser-pumped 3-μm Er3+ crystal lasers

NASA Astrophysics Data System (ADS)

Tikerpae, Mark; Jackson, Stuart D.; King, Terence A.

1997-05-01

We present results from a theoretical model that has been developed to simulate the 3-micrometer laser transition in Er3+ doped Y3Al5O12 (YAG), Y2Sc2Ga3O12 (YSGG), LiYF4 (YLF) and BaY2F8 (BaYF) host crystals. The rate equations for the lowest seven energy levels of Er3+ were solved numerically and laser action was simulated under cw, gain-switched (pulse pumped) and Q-switched operation with optical pumping at wavelengths of 975 nm and 795 nm. The relative performance of each laser crystal was compared under identical pumping and cavity conditions to establish the optimum crystal host, doping concentration and pump wavelength for each mode of operation. Some unexpected saturation effects were investigated that could limit the maximum practical pump fluence used for high energy Q-switched systems. We investigate possible additional multi-ion energy transfer processes that may cause the decrease in efficiency that is observed experimentally at high Er3+ ion concentrations. In addition, lower laser level deactivation by co-doping with Pr3+ in BaYF was simulated and compared with singly doped Er:BaYF for a range of Er3+ and Pr3+ concentrations. It was found that co-doping was not as effective as the cooperative upconversion process present in singly doped Er3+ crystals for efficient laser operation.

Patterning of silver nanoparticles on visible light-sensitive Mn-doped lithium niobate photogalvanic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Xiaoyan; Ohuchi, Fumio; Hatano, Hideki

2011-08-01

Visible light-induced polarization-dependent photochemical deposition of silver nanoparticles (AgNPs) has been demonstrated using Mn-doped congruent LiNbO{sub 3} (CLN) single crystals. Mn-doped CLN has a strong absorption over a wide region of the visible spectrum that allowed effective visible light irradiation for photochemical deposition. The AgNPs deposition on Mn-doped CLN was compared with that on non-doped congruent LiNbO{sub 3}, and together these further confirmed that the photochemical deposition on LiNbO{sub 3} is caused by the strong photogalvanic effect.

Synthesis of n-type semiconductor diamond single crystal under high pressure and high temperature

NASA Astrophysics Data System (ADS)

Li, Yong; Li, Shangsheng; Song, Mousheng; She, Yanchao; Wang, Qiang; Guan, Xuemao

2017-12-01

In this paper, diamond single crystal co-doped with sulfur and boron was successfully synthesized at the fixed pressure of 6.0 GPa and temperature range of 1535 K. Sulfur was detected in the co-doped diamond by Fourier Transform Infrared Spectroscopy (FTIR) and the corresponding characteristic peak located at 848 cm-1. Interestingly, Hall effect measurements indicated that the diamond co-doped with sulfur and boron exhibited n-type semiconductor behaviour. Furthermore, the Hall mobility and carrier concentration of the co-doped diamond higher than those of the boron-doping diamond.

Sub-Kelvin resistance thermometer

NASA Technical Reports Server (NTRS)

Castles, Stephen H. (Inventor)

1992-01-01

A device capable of accurate temperature measurement down to 0.01 K of a particular object is discussed. The device is comprised of the following: a heat sink wafer; a first conducting pad bonded near one end of the heat sink wafer; a second conducting pad bonded near the other end of the heat sink wafer; and an oblong doped semiconductor crystal such as germanium. The oblong doped semiconductor crystal has a third conducting pad bonded on its bottom surface with the oblong doped semiconductor crystal bonded to the heat sink wafer by having the fourth conducting pad bonded to the first conducting pad. A wire is bonded between the second and third conducting pads. Current and voltage wires bonded to the first and second conducting pads measure the change in resistance of the oblong doped semiconductor crystal; this indicates the temperature of the object whose temperature is to be measured.

Temperature tuning of lasing emission from dye-doped liquid crystal at intermediate twisted phase

NASA Astrophysics Data System (ADS)

Liao, Kuan-Cheng; Lin, Ja-Hon; Jian, Li-Hao; Chen, Yao-Hui; Wu, Jin-Jei

2015-07-01

Temperature tuning of lasing emission from dye-doped cholesteric liquid crystal (CLC) at intermediate twisted phase has been demonstrated in this work. With heavily doping of 42.5% chiral molecules into the nematic liquid crystals, the shifts of photonic bandgap versus temperature is obviously as thermal controlling of the sample below the certain value. By the differential scanning calorimetr measuremet, we demonstrate the phase transition from the CLC to the smectic phase when the temperature is lowered to be about 15°C. Between CLC and smectic phase, the liquid crystal mixtures are operated at intermediate twisted phase that can be used the temperature related refractive mirror. After pump by the Q-switched Nd:YAG laser, the lasing emission from this dye doped LC mixtures has been demonstrated whose emission wavelength can be tuned from 566 to 637 nm with 1.4°C variation.

Probing the crystal structure landscape by doping: 4-bromo, 4-chloro and 4-methylcinnamic acids.

PubMed

Desiraju, Gautam R; Chakraborty, Shaunak; Joseph, Sumy

2018-06-11

Accessing the data points in the crystal structure landscape of a molecule is a challenging task, either experimentally or computationally. We have charted the crystal structure landscape of 4-bromocinnamic acid (4BCA) experimentally and computationally: experimental doping is achieved with 4-methylcinnamic acid (4MCA) to obtain new crystal structures; computational doping is performed with 4-chlorocinnamic acid (4CCA) as a model system, because of the difficulties associated in parameterizing the Br-atom. The landscape of 4CCA is explored experimentally in turn, also by doping it with 4MCA, and is found to bear a close resemblance to the landscape of 4BCA, justifying the ready miscibility of these two halogenated cinnamic acids to form solid solutions without any change in crystal structure. In effect, 4MCA, 4CCA and 4BCA form a commutable group of crystal structures, which may be realized experimentally or computationally, and constitute the landscape. Unlike the results obtained by Kitaigorodskii and others, all but two of the multiple solid solutions obtained in the methyl-doping experiments take structures that are different from the hitherto observed crystal forms of the parent compounds. Even granted that the latter might be inherently polymorphic, this unusual observation provokes the suggestion that solid solution formation may be used to probe the crystal structure landscape. The influence of pi...pi interactions, weak hydrogen bonds and halogen bonds in directing the formation of these new structures is also seen. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of L-aspartic acid on the growth, structure and spectral studies of Zinc (tris) Thiourea Sulphate (ZTS) single crystals

NASA Astrophysics Data System (ADS)

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

2014-11-01

Single crystals of pure and L-aspartic acid doped Zinc (Tris) Thiourea Sulphate (ZTS) were grown from aqueous solution by solution growth method. The cell parameters and structure of the grown crystals were determined by X-ray diffraction studies. The presence of functional group in the compound has been confirmed by FTIR and FT-Raman analysis. The optical transparency range has been studied through UV-Vis spectroscopy. TGA/DTA studies show thermal stability of the grown crystals. Microhardness study reveals that the hardness number (Hv) increases with load for pure and doped ZTS crystals. Dielectric studies have been carried out and the results are discussed. The second harmonic generation was confirmed for L-aspartic acid doped ZTS which is greater than pure ZTS.

Tuning the functional properties of PMN-PT single crystals via doping and thermoelectrical treatments

NASA Astrophysics Data System (ADS)

Luo, Laihui; Dietze, Matthias; Solterbeck, Claus-Henning; Luo, Haosu; Es-Souni, Mohammed

2013-12-01

Single crystals based on solid solutions of lead-magnesium-niobate (PMN) and lead titanate (PT) have emerged as highly promising multifunctional systems combining piezoelectric, pyroelectric, and electro-optic properties that surpass by far those of the best known lead-zirkonium-titanate ceramics. In this paper we present new findings on how the phase transition temperature and the dielectric and ferroelectric properties can be tuned depending on crystal composition, orientation, and thermoelectrical treatment. Mn-doped and pure 0.72PbMg1/3Nb2/3O3-0.28PbTiO3 (0.72PMN-0.28PT) single crystals with ⟨111⟩ and ⟨001⟩ orientations were investigated. A special attention was devoted to field cooling (FC), i.e., cooling under electric field from different temperatures. The results illustrate different findings that were not reported before: the Curie temperature, i.e., ferroelectric-paraelectric transition temperature, is enhanced after field cooling of the Mn-doped, ⟨001⟩-oriented crystal while such a shift is not observed in the ⟨111⟩-oriented and the non-doped crystals. In addition, substantial polarization suppression occurs in the Mn-doped crystals upon FC from high temperature regardless of orientation. Based on piezoforce microscopy of the domain structure that shows suppression of domain growth following field cooling from 200 °C, we propose a mechanism for polarization suppression based on domain pinning by charged defects. The practical importance of our results lies in showing the opportunity offered by a proper choice of crystal composition and poling conditions for tuning the functional properties of PMN-PT single crystals for a specific application. This should contribute to the understanding of their properties towards advanced sensor and transducers devices.

Characteristics of color optical shutter with dye-doped polymer network liquid crystal.

PubMed

Lee, G H; Hwang, K Y; Jang, J E; Jin, Y W; Lee, S Y; Jung, J E

2011-03-01

The optical properties and the theoretical prediction of color optical shutter with dye-doped polymer network liquid crystal (PNLC) were investigated. The view-angle dependence of reflectance according to the bias conditions showed distinctive characteristics, which could be explained from the effects of dye absorption and path length. It was also shown that the thickness dependence of reflectance was strongly influenced by the light-scattering coefficient. Our experimental results matched up well with the theoretical prediction based on the light scattering of liquid crystals in polymer network and the absorption of dichroic dye. This work indicates potential to improve the optical device using dye-doped liquid crystal-polymer composite.

Luminescence of Ga2O3 Crystals Excited with a Runaway Electron Beam

NASA Astrophysics Data System (ADS)

Burachenko, A. G.; Beloplotov, D. V.; Prudaev, I. A.; Sorokin, D. A.; Tarasenko, V. F.; Tolbanov, O. P.

2017-12-01

The spectra and amplitude-time characteristics of the radiation of studied Sn and Fe-doped Ga2O3 crystals excited with a runaway electron beam and an excilamp with a wavelength of 222 nm were investigated. The main contribution to the luminescence of samples in the region of 280-900 nm under excitation with a beam was shown to be made by cathodoluminescence. In the Fe-doped crystal, a new cathodeand photoluminescence band was detected within a wavelength range of 650-850 nm. In the Sn-doped crystal, Vavilov-Cherenkov radiation was detected in the region of 280-300 nm using a monochromator and a photomultiplier.

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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.

Vapor Growth and Characterization of Cr-Doped ZnSe Crystals

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Feth, Shari; Volz, M. P.; Matyi, R.; George, M. A.; Chattopadhyay, K.; Burger, A.; Lehoczky, S. L.

1999-01-01

Cr-doped ZnSe single crystals were grown by a self-seeded physical vapor transport technique in both vertical (stabilized) and horizontal configurations. The source materials were mixtures of ZnSe and CrSe. Growth temperatures were in the range of 1140-1150 C and the furnace translation rates were 1.9-2.2 mm/day. The surface morphology of the as-grown crystals was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Different features of the as-grown surface of the vertically and horizontally grown crystals suggest that different growth mechanisms were involved in the two growth configurations. The [Cr] doping levels were determined to be in the range of 1.8-8.3 x 10 (exp 19) cm (exp -3) from optical absorption measurements. The crystalline quality of the grown crystals were examined by high-resolution triple-crystal X-ray diffraction (HRTXD) analysis.

Influence of bis-thiourea nickel nitrate on the structural, optical, electrical, thermal and mechanical behavior of a KDP single crystal for NLO applications

NASA Astrophysics Data System (ADS)

Rasal, Y. B.; Shaikh, R. N.; Shirsat, M. D.; Kalainathan, S.; Hussaini, S. S.

2017-03-01

A single crystal of bis-thiourea nickel nitrate (BTNN) doped potassium dihydrogen phosphate (KDP) has been grown from solution at room temperature by a slow evaporation technique. The cell parameters of the grown crystals were determined using single crystal x-ray diffraction analysis. The different functional groups of the grown crystal were confirmed using Fourier transform infrared analysis. The improved optical parameters of the grown crystal have been evaluated in the range of 200-900 nm using UV-visible spectral analysis. The grown crystal was transparent in the entire visible region and the band gap value was found to be 4.96 eV. The influence of BTNN on the third order nonlinear optical properties of KDP crystal has been investigated by means of the Z-scan technique. The second harmonic generation (SHG) efficiency of grown crystal measured using a Nd-YAG laser is 1.98 times higher than that of pure KDP. The third order nonlinear optical susceptibility (χ 3) and nonlinear absorption coefficient (β) of BTNN doped KDP crystal is found to be 1.77  ×  10-5 esu and 5.57  ×  10-6 cm W-1 respectively. The laser damage threshold (LDT) energy for the grown crystal has been measured by using a Q-switched Nd:YAG laser source. The bis-thiourea nickel nitrate shows authoritative impact on the dielectric properties of doped crystal. The influence of bis-thiourea nickel nitrate on the mechanical behavior of KDP crystal has been investigated using Vickers microhardness intender. The thermal behavior of BTNN doped KDP crystal has been analyzed by TGA/DTA analysis.

Infrared photorefractive effect in doped KNbO3 crystals

NASA Astrophysics Data System (ADS)

Medrano, C.; Zgonik, M.; Liakatas, I.; Günter, P.

1996-11-01

The photorefractive sensitivity of potassium niobate crystals doped with Ce, Co, Cu, Fe, Mn, Ni, and Rh and double-doped with Mn and Rh is investigated over an extended spectral range. We present experimental evidence on extrinsic properties important for the photorefractive effect, such as absorption and effective trap density. Photorefractive gratings are investigated with two-wave mixing experiments. Results on exponential gain, response time, and photorefractive sensitivity at near-infrared wavelengths are reported. The best photorefractive sensitivities at 860 and 1064 nm were obtained in crystals doped with Rh, Fe, Mn, and Mn-Rh. This makes them suitable for applications at laser-diode wavelengths; at 1064 nm, however, Rh:KNbO3 shows a better photorefractive sensitivity than the others. .

Optical spectroscopy of disordered Ca3Ga2Ge4O14 crystal doped with manganese

NASA Astrophysics Data System (ADS)

Burkov, Vladimir; Alyabyeva, Liudmila; Mill, Boris; Kotov, Viacheslav

2018-05-01

Circular dichroism, absorption and luminescence spectra of single crystalline manganese doped calcium gallogermanate Ca3Ga2Ge4O14:Mn were investigated in 300-850 nm wavelength region in wide temperature range 8-300 K. Careful analysis of experimental results revealed presence of electron transitions typical for sixfold coordinated trivalent manganese ions with d4 electron configuration. Thus, manganese ions doping the crystal matrix of CCG incorporate into lattice in 1a octahedral site-positions substituting Ga3+ ions. The results obtained were compared with investigation of isostructural to CGG manganese doped langasite crystals, La3Ga5SiO14:Mn where dopant is in octahedral Mn4+ state.

Room temperature ferromagnetism in Fe-doped semiconductor ZrS2 single crystals

NASA Astrophysics Data System (ADS)

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.

Superconductivity in Sm-doped CaFe2As2 single crystals

NASA Astrophysics Data System (ADS)

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).

Diffusion Mechanisms of Ag atom in ZnO crystal: A First Principles Study

NASA Astrophysics Data System (ADS)

Masoumi, Saeed; Noori, Amirreza; Nadimi, Ebrahim

2017-12-01

Zinc oxide (ZnO) is currently under intensive investigation, as a result of its various applications in micro, nano and optoelectronics. However, a stable and reproducible p-type doping of ZnO is still a main challenging issue. Group IB elements such as Au, Cu and Ag, are promising candidates for p-type doping. Particularly, Ag atoms has been shown to be able to easily diffuse through the crystal structure of ZnO and lead to the p-type doping of the host crystal. However, the current understanding of Ag defects and their mobility in the ZnO crystal is still not fully explored. In this work, we report the results of our first-principles calculations based on density functional theory for Ag defects, particularly the interstitial and substitutional defects in ZnO crystal. Defect formation energies are calculated in different charged states as a function of Fermi energy in order to clarify the p-type behaviour of Ag-doped ZnO. We also investigate the diffusion behaviour and migration paths of Ag in ZnO crystal in the framework of density functional theory applying climbing image (CI) nudged elastic band method (NEB).

Te-and Zn-Doped InSb Crystals Grown in Microgravity

NASA Technical Reports Server (NTRS)

Ostrogorsky, A. G.; Marin, C.; Volz, M.; Bonner, W. A.; Duffar, T.

2004-01-01

In 2002, within the SUBSA (Solidification Using a Baffle in Sealed Ampoules) investigation, seven doped InSb crystals were grown in microgravity at the International Space Station. The key goals of the SUBSA investigation are: (a) to clarify the origin of the melt convection in space laboratories; (b) to reduce melt convection to the level which allows reproducible diffusion-controlled segregation; (e) to explore the submerged baffle process and liquid encapsulation in microgravity. 30 crystal growth experiments were conducted in the ground unit, to optimize the design of flight ampoules and to test the transparent SUBSA furnace developed by TecMasters Inc. The specially designed furnace, allowed observation of the crystal growth process (melting, seeding, motion of the solid-liquid interface, etc.). In the summer of 2002, eight crystal growth experiments were conducted in the Microgravity Science Glovebox (MSG) facility at the ISS. Four Te-doped (k = 0.5) and three Zn-doped (k2.9) crystals were grown on undoped seeds. In one experiment, we were not able to seed and grow. The seven grown crystals were sectioned and analyzed using SIMS. The design of the SUBSA ampoules, the segregation data and the video images obtained during the SUBSA flight experiments will be presented and discussed.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siddiqua, Poppy; O'Leary, Stephen K., E-mail: stephen.oleary@ubc.ca

2016-03-07

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.

Crystal Growth of Undoped and Doped ZnSe

NASA Technical Reports Server (NTRS)

Davis, Swanson L.; Chen, K.-T.; George, M. A.; Shi, D. T.; Collins, W. E.; Burger, Arnold

1997-01-01

The surface morphology of freshly cleaved ZnSe single crystal grown by the physical vapor transport (PVT) method was investigated by Atomic Force Microscopy (AFM) and the results were correlated with Differential Scanning Calorimetry (DSC) data. Selenium precipitates have been revealed in undoped doped ZnSe crystals having a size of about 50 nm. A transition temperature around 221 C in the DSC measurements is interpreted as the eutectic temperature of Se-saturated ZnSe. The AFM images of doped ZnSe also show that possible Cr clusters are uniformly distributed and they have an estimated size of about 6 nm.

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

NASA Astrophysics Data System (ADS)

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.

Enhancing the blue shift of SHG signal in GaSe:B/Ce crystal

NASA Astrophysics Data System (ADS)

Karatay, Ahmet; Yuksek, Mustafa; Ertap, Hüseyin; Elmali, Ayhan; Karabulut, Mevlut

2018-02-01

The influence of Ce3+ on the wavelength of second harmonic generation (SHG) signal in boron doped GaSe crystals have been investigated. We found that by substitution of Ce3+ with B3+, SHG signal shifted to lower wavelength. In addition, the nonlinear absorption (NA) properties and ultrafast dynamics of pure, 1 at.% B3+ and 0.5 at.% B3++ 0.5 at.% Ce3+ doped GaSe crystals have been studied by open aperture Z-scan and ultrafast pump probe spectroscopy techniques. From the open aperture Z-scan experiments we observed that all of the crystals showed nonlinear absorption (NA). However, pump-probe experiments revealed that when GaSe crystal is doped, the NA signal turns into a bleaching signal with different lifetimes depending on the type and concentration of the dopant atoms.

Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources.

PubMed

Ganem, Joseph; Bowman, Steven R

2013-11-01

Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence.

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

NASA Astrophysics Data System (ADS)

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.

Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

NASA Astrophysics Data System (ADS)

Ganem, Joseph; Bowman, Steven R.

2013-11-01

Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence.

Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

PubMed Central

2013-01-01

Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence. PMID:24180684

UV-light-induced one-color and two-color photorefractive effects in congruent and near-stoichiometric LiNbO 3:Mg crystals

NASA Astrophysics Data System (ADS)

Qiao, Haijun; Xu, Jingjun; Tomita, Yasuo; Zhu, Dengsong; Fu, Bo; Zhang, Guoquan; Zhang, Guangyin

2007-03-01

We describe the ultraviolet-light one-color photorefraction (UV-OPR) at 351 nm in LiNbO3 crystals with different Mg-doping concentrations and [Li]/[Nb] ratios. It is shown that as the Mg-doping concentration and/or the [Li]/[Nb] ratio increase, the refractive index change and the two-beam coupling gain increase but the response time decreases. It is also shown that the recording sensitivity as large as ∼27 cm/J is obtainable at a recording intensity of ∼1 W/cm2 in near-stoichiometric LiNbO3 doped with 2 mol% Mg. This sensitivity is approximately one order of magnitude higher than those for other LiNbO3 crystals. We also describe the ultraviolet-light-gating two-color photorefraction (UV-TPR) using 365 nm gating and 633 nm recording beams in LiNbO3 crystals with different Mg-doping concentrations and [Li]/[Nb] ratios. It is shown that UV-TPR is only observed in near-stoichiometric crystals and the grating-formation dynamics strongly depend on the Mg concentration.

Fabrication of a dye-doped liquid crystal light shutter by thermal curing of polymer

NASA Astrophysics Data System (ADS)

Yu, Byeong-Hun; Ji, Seong-Min; Kim, Jin-Hun; Huh, Jae-Won; Yoon, Tae-Hoon

2017-07-01

We report a thermal curing method for fabrication of a dye-doped polymer-stabilized liquid crystal (PSLC) light shutter, which can prevent the decrease in absorption and discoloration of the dye caused by the UV curing process. We found that the measured transmittance in the opaque state of a dye-doped PSLC cell fabricated by thermal curing was approximately 35% lower than that of a dye-doped PSLC cell fabricated by UV curing. Thermal curing can be an alternative approach for fabrication of a dye-doped PSLC light shutter which can be used to provide high visibility of a see-through display.

Scanning Tunneling Microscopy/Spectroscopy study on Optimally Potassium Doped Single Crystal BaFe2 As 2

NASA Astrophysics Data System (ADS)

Ma, Jihua; Li, Ang; Zhang, Chenglin; Dai, Pengcheng; Pan, Shuheng

2011-03-01

The iron pnictide parent compound material can be brought into superconducting state by chemical doping. It is worthwhile to study and compare the hole- and electron-doped iron pnictides. Among the well-known family of AEFe 2 As 2 (AE=Ca, Sr, Ba), the scanning tunneling microscopy/spectroscopy study on hole-doped samples is insufficient. In this talk we will present high resolution STM/STS results on (001) surface of the optimally doped single crystal Ba 0.6 K0.4 Fe 2 As 2 (Tc ~ 37 K). With the data we will discuss the spatial variation of the superconducting energy gap.

Method of fabricating optical waveguides by ion implantation doping

DOEpatents

Appleton, B.R.; Ashley, P.R.; Buchal, C.J.

1987-03-24

A method for fabricating high-quality optical waveguides in optical quality oxide crystals by ion implantation doping and controlled epitaxial recrystallization is provided. Masked LiNbO/sub 3/ crystals are implanted with high concentrations of Ti dopant at ion energies of about 360 keV while maintaining the crystal near liquid nitrogen temperature. Ion implantation doping produces an amorphous, Ti-rich nonequilibrium phase in the implanted region. Subsequent thermal annealing in a water-saturated oxygen atmosphere at up to 1000/degree/C produces solid-phase epitaxial regrowth onto the crystalline substrate. A high-quality crystalline layer results which incorporates the Ti into the crystal structure at much higher concentrations than is possible by standard diffusion techniques, and this implanted region has excellent optical waveguiding properties.

The Ni and Co substitutions in iron chalcogenide single crystals

NASA Astrophysics Data System (ADS)

Bezusyy, V. L.; Gawryluk, D. J.; Malinowski, A.; Berkowski, M.; Cieplak, Marta Z.

2015-03-01

We study the ab-plane resistivity and Hall effect in Fe1-yMyTe0.65Se0.35 single crystals with M =Co or Ni, and y up to 0.2. The crystals are grown by Bridgman's method. The low-temperature Hall coefficient RH changes sign to negative for crystals with y exceeding 0.135 (Co) and 0.06 (Ni), consistent with the electron doping induced by these impurities. However, the RH remains positive for all samples at high T, suggesting that remnant hole pockets survive the doping, but the holes become localized at low T in heavily doped crystals. Superconducting transition temperature (Tc) approaches zero for y = 0.14 (Co), and 0.03 (Ni), while the resistivity at the Tc onset is only weakly affected by Co doping, but it increases strongly for the Ni. These results suggest that in case of Co impurity the Tc suppression may be attributed to electron doping. On the other hand, the Ni substitution, in addition to electron doping, induces strong localization effects at small impurity contents. Using two-band conduction model we argue that the localization of electron carriers is responsible for strong superconductivity suppression by Ni impurity. Supported by EC through the FunDMS Advanced Grant of the ERC (FP7 Ideas), by the Polish NCS Grant 2011/01/B/ST3/00462, and by the French-Polish Program PICS 2012. Performed in the laboratories co-financed by NanoFun Project POIG.02.02.00-00-025/09.

Giant increase of critical current density and vortex pinning in Mn doped K{sub x}Fe{sub 2−y}Se{sub 2} single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Mingtao; Zhang, Jincang, E-mail: jczhang@staff.shu.edu.cn; Materials Genome Institute, Shanghai University, Shanghai 200444

2014-11-10

We report a comparative study of the critical current density (J{sub c}) and vortex pinning among pure and Mn doped K{sub x}Fe{sub 2−y}Se{sub 2} single crystals. It is found that the J{sub c} values can be greatly improved by Mn doping and post-quenching treatment when comparing to pristine pure sample. In contrast to pure samples, an anomalous second magnetization peak (SMP) effect is observed in both 1% and 2% Mn doped samples at T = 3 K for H∥ab but not for H∥c. Referring to Dew-Hughes and Kramer's model, we performed scaling analyses of the vortex pinning force density vs magnetic field inmore » 1% Mn doped and quenched pristine crystals. The results show that the normal point defects are the dominant pinning sources, which probably originate from the variations of intercalated K atoms. We propose that the large nonsuperconducting K-Mn-Se inclusions may contribute to the partial normal surface pinning and give rise to the anomalous SMP effect for H∥ab in Mn doped crystals. These results may facilitate further understanding of the superconductivity and vortex pinning in intercalated iron-selenides superconductors.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah

Here, 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 secondmore » 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 cm 2/Vs at room temperature. A doping limit in the low 10 17/cm 3 range is observed for samples quenched at 200–300 °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.« less

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

DOE PAGES

Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; ...

2018-05-07

Here, 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 secondmore » 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 cm 2/Vs at room temperature. A doping limit in the low 10 17/cm 3 range is observed for samples quenched at 200–300 °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.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Xiaoyang; Frisbie, Daniel

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.

Comparative study of optical and scintillation properties of Tm3+:YAG, and Tm3+:LuAG single crystals

NASA Astrophysics Data System (ADS)

Fujimoto, Yutaka; Sugiyama, Makoto; Yanagida, Takayuki; Wakahara, Shingo; Suzuki, Shotaro; Kurosawa, Shunsuke; Chani, Valery; Yoshikawa, Akira

2013-09-01

The optical and scintillation properties of Tm3+-doped yttrium aluminum garnet Y3Al5O12 (YAG) and Tm3+-doped lutetium aluminum garnet Lu3Al5O12 (LuAG) are compared. The Tm3+-doped single crystals were grown by the micro-pulling down (μ-PD) technique. Both crystals demonstrated some emission peaks originated from 4f-4f forbidden transition of Tm3+ under 241Am alpha-ray excitation. The scintillation decay time of Tm3+-doped YAG was similar to that of LuAG. When irradiated by the gamma-rays from a 137Cs source, the relative scintillation light yields of Tm:YAG was 90% greater than that of Tm:LuAG.

Advancing radiation balanced lasers (RBLs) in rare-earth (RE)-doped solids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hehlen, Markus Peter

2016-11-21

These slides cover the following topics: Mid-IR lasers in crystals using two-tone RBL (Single-dopant two-tone RBLs: Tm 3+, Er 3+, and Co-doped two-tone RBLs: (Yb 3+, Nd 3+) and (Ho 3+, Tm 3+); Advanced approaches to RBL crystals (Precursor purification, Micro-pulling-down crystal growth, and Bridgman crystal growth); Advanced approaches to RBL fibers (Materials for RBL glass fibers, Micro-structured fibers for RBL, and Fiber preform synthesis); and finally objectives.

Bridgman-Stockbarger growth of SrI2:Eu2+ single crystal

NASA Astrophysics Data System (ADS)

Raja, A.; Daniel, D. Joseph; Ramasamy, P.; Singh, S. G.; Sen, S.; Gadkari, S. C.

2018-05-01

Strontium Iodide (SrI2): Europium Iodide (EuI2) was purified by Zone-refinement process. Europium doped strontium iodide (SrI2:Eu2+) single crystal was grown by modified vertical Bridgman - Stockbarger technique. Photoluminescence (PL) excitation and emission (PLE) spectra were measured for Eu2+ doped SrI2 crystal. The sharp emission was recorded at 432 nm. Scintillation properties of the SrI2:Eu2+ crystal were checked by the gamma ray spectrometer using 137Cs gamma source.

Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes.

PubMed

García-García, Amanda; Vergaz, Ricardo; Algorri, José Francisco; Quintana, Xabier; Otón, José Manuel

2015-01-01

The inclusion of nanoparticles modifies a number of fundamental properties of many materials. Doping of nanoparticles in self-organized materials such as liquid crystals may be of interest for the reciprocal interaction between the matrix and the nanoparticles. Elongated nanoparticles and nanotubes can be aligned and reoriented by the liquid crystal, inducing noticeable changes in their optical and electrical properties. In this work, cells of liquid crystal doped with high aspect ratio multi-walled carbon nanotubes have been prepared, and their characteristic impedance has been studied at different frequencies and excitation voltages. The results demonstrate alterations in the anisotropic conductivity of the samples with the applied electric field, which can be followed by monitoring the impedance evolution with the excitation voltage. Results are consistent with a possible electric contact between the coated substrates of the LC cell caused by the reorientation of the nanotubes. The reversibility of the doped system upon removal of the electric field is quite low.

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

PubMed

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.

Rotational Symmetry Breaking in a Trigonal Superconductor Nb-doped Bi 2 Se 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asaba, Tomoya; Lawson, B. J.; Tinsman, Colin

2017-01-27

The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi 2Se 3) is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb)-doped Bi 2Se 3. As a result,more » the in-plane magnetic torque signal vanishes every 60°. More importantly, the superconducting hysteresis loop amplitude is enhanced along one preferred direction, spontaneously breaking the rotational symmetry. This observation indicates the presence of nematic order in the superconducting ground state of Nb-doped Bi 2Se 3.« less

Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

DOEpatents

Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

1981-01-01

This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

Electrically tunable liquid crystal photonic bandgap fiber laser

NASA Astrophysics Data System (ADS)

Olausson, Christina B.; Scolari, Lara; Wei, Lei; Noordegraaf, Danny; Weirich, Johannes; Alkeskjold, Thomas T.; Hansen, Kim P.; Bjarklev, Anders

2010-02-01

We demonstrate electrical tunability of a fiber laser using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate an all-spliced laser cavity based on a liquid crystal photonic bandgap fiber mounted on a silicon assembly, a pump/signal combiner with single-mode signal feed-through and an ytterbium-doped photonic crystal fiber. The laser cavity produces a single-mode output and is tuned in the range 1040- 1065 nm by applying an electric field to the silicon assembly.

Solid-state reaction kinetics of neodymium doped magnesium hydrogen phosphate system

NASA Astrophysics Data System (ADS)

Gupta, Rashmi; Slathia, Goldy; Bamzai, K. K.

2018-05-01

Neodymium doped magnesium hydrogen phosphate (NdMHP) crystals were grown by using gel encapsulation technique. Structural characterization of the grown crystals has been carried out by single crystal X-ray diffraction (XRD) and it revealed that NdMHP crystals crystallize in orthorhombic crystal system with space group Pbca. Kinetics of the decomposition of the grown crystals has been studied by non-isothermal analysis. The estimation of decomposition temperatures and weight loss has been made from the thermogravimetric/differential thermo analytical (TG/DTA) in conjuncture with DSC studies. 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.

Growth and characterization of divalent transition metal ions doped zinc hydrogen phosphate single crystals

NASA Astrophysics Data System (ADS)

D'Souza, Delma; Jagannatha, N.; Nagaraja, K. P.; Rohith, P. S.; Pradeepkumar, K. V.

2018-05-01

Zinc hydrogen phosphate (ZnHP) single crystal co-doped with divalent transition metal ions Cobalt (Co2+) and Cadmium (Cd2+) is grown by gel technique in silica hydro gel media. The presence of Co2+ and Cd2+ dopants in the ZnHP crystal was confirmed by Energy Dispersive X-ray Analysis (EDAX).FTIR spectra of the grown crystal depict the stretching and bending vibration of PO4 units, water of crystallization and metal-oxygen bonds. Powder XRD analysis reveals that the grown crystal belongs to monoclinic system with spacegroup P 21. The thermal stability of the grown crystal is rectified from TG-DSC studies.

Evolution of electrical properties and domain configuration of Mn modified Pb(In1/2Nb1/2)O3-PbTiO3 single crystals

NASA Astrophysics Data System (ADS)

Qiao, Huimin; He, Chao; Yuan, Feifei; Wang, Zujian; Li, Xiuzhi; Liu, Ying; Guo, Haiyan; Long, Xifa

2018-04-01

The acceptor doped relaxor-based ferroelectric materials are useful for high power applications such as probes in ultrasound-guided high intensity focused ultrasound therapy. In addition, a high Curie temperature is desired because of wider temperature usage and improved temperature stability. Previous investigations have focused on Pb(Mg1/3Nb2/3)O3-PbTiO3 and Pb(Zn1/3Nb2/3)O3-PbTiO3 systems, which have a ultrahigh piezoelectric coefficient and dielectric constant, but a relatively low Curie temperature. It is desirable to study the binary relaxor-based system with a high Curie temperature. Therefore, Pb(In1/2Nb1/2)O3-PbTiO3 (PINT) single crystals were chosen to study the Mn-doped influence on their electrical properties and domain configuration. The evolution of ferroelectric hysteresis loops for doped and virgin samples exhibit the pinning effect in Mn-doped PINT crystals. The relaxation behaviors of doped and virgin samples are studied by fit of the modified Curie-Weiss law and Volgel-Fucher relation. In addition, a short-range correlation length was fitted to study the behavior of polar nanoregions based on the domain configuration obtained by piezoresponse force microscopy. Complex domain structures and smaller short-range correlation lengths (100-150 nm for Mn-doped PINT and >400 nm for pure PINT) were obtained in the Mn-doped PINT single crystals.

Crystal growth and near infrared optical properties of Pr 3+ doped lead halide materials for resonantly pumped eye safe laser applications

NASA Astrophysics Data System (ADS)

Jones, Ivy Krystal

In this dissertation the material development and optical spectroscopy of Pr3+ activated low phonon energy halide crystals is presented for possible applications in resonantly pumped eye-safe solid-state laser gain media. In the last twenty years, the developments in fiber and diode lasers have enabled highly efficient resonant pumping of Pr3+ doped crystals for possible lasing in the 1.6--1.7 microm region. In this work, the results of the purification, crystal growth, and near-infrared (NIR) spectroscopic characterization of Pr3+ doped lead (II) chloride, PbCl2 and lead (II) bromide, PbBr2 are presented. The investigated PbCl2 and PbBr2 crystals are non-hygroscopic with maximum phonon energies between ~180--200 cm-1, which enable efficient emission in the NIR spectral region (~ 1.6 microm) from the 3F3/3F4 → 3H4 transition of Pr3+ ions. The commercial available starting materials were purchased as ultra dry, high purity (~ 99.999 %) beads and purified through a combination of zone-refinement and halogenation. The crystal growth of Pr3+ doped PbCl 2 and PbBr2 was performed via vertical Bridgman technique using a two-zone furnace. The resulting Pr3+ doped PbCl 2 and PbBr2 crystals exhibited characteristic IR absorption bands in the 1.5--1.7 microm region (3H4 → 3F3/3F4), which allow for resonant pumping using commercial diode lasers. A broad IR emission band centered at ~1.6 microm was observed under ~1445 nm diode laser excitation from both Pr3+ doped halides. This dissertation presents comparative spectroscopic results for Pr 3+:PbCl2 and Pr3+:PbBr2 including NIR absorption and emission studies, lifetime measurements, modelling of radiative and non-radiative decay rates, determination of transition cross-section, and the net effective gain cross sections.

Structural, chemical and physical properties of pure and La3+ doped L-Threonine acetate crystals

NASA Astrophysics Data System (ADS)

Senthamizhan, A.; Sambathkumar, K.; Nithiyanantham, S.; Venkatachalapathy, M.; Rajkamal, N.

2017-12-01

The pure and La3+ doped L- Threonine crystals can be grown by slow evaporation techniques. The crystal structure were examined through X-Ray diffraction (XRD) analysis, confirmed the P212121 system. The quantitative nature of dopant can be analyzed with Inductively Coupled Plasma (ICP) study. The Fourier Transform Infra-Red (FTIR) and Fourier Transform (FT- Raman) investigations yields the possible stretching/bonding with their functional groups and the qualitative/quantitative nature of both crystals is analyzed. The optical behavior of crystals can be studied through Ultra Violet (UV) - Visible spectrometer. The mechanical, thermal and decomposition studies can be carried out through Vickers hardness test, Thermo Gravometric Analysis (TGA) and Differential Thermal Analysis (DTA). The Non Linear Optical (NLO) properties are found more than Potassium Phosphate (KDP) through Kurtz powders technique. The dielectric and optical absorption studies for both pure and L-doped crystals were studied and interpreted all the properties. The La3+ dopant increases the properties are investigated.

Crystal field parameters and energy levels scheme of trivalent chromium doped BSO

NASA Astrophysics Data System (ADS)

Petkova, P.; Andreici, E.-L.; Avram, N. M.

2014-11-01

The aim of this paper is to give an analysis of crystal field parameters and energy levels schemes for the above doped material, in order to give a reliable explanation for experimental data. The crystal field parameters have been modeled in the frame of Exchange Charge Model (ECM) of the crystal field theory, taken into account the geometry of systems, with actually site symmetry of the impurity ions. The effect of the charges of the ligands and covalence bonding between chromium cation and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the crystal field parameters we simulated the scheme of energy levels of chromium ions by diagonalizing the matrix of the Hamiltonian of the doped crystal. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison with experiment shows that the results are quite satisfactory which justify the model and simulation scheme used for the title system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rout, Dipak; Vijaya, R.; Centre for Lasers and Photonics, Indian Institute of Technology Kanpur, Kanpur 208016

Well-ordered opaline photonic crystals are grown by inward growing self-assembly method from Rhodamine B dye-doped polystyrene colloids. Subsequent to self-assembly, the crystals are infiltrated with gold nanoparticles of 40 nm diameter. Measurements of the stopband features and photoluminescence intensity from these crystals are supplemented by fluorescence decay time analysis. The fluorescence decay times from the dye-doped photonic crystals before and after the infiltration are dramatically different from each other. A lowered fluorescence decay time was observed for the case of gold infiltrated crystal along with an enhanced emission intensity. Double-exponential decay nature of the fluorescence from the dye-doped crystal gets convertedmore » into single-exponential decay upon the infiltration of gold nanoparticles due to the resonant radiative process resulting from the overlap of the surface plasmon resonance with the emission spectrum. The influence of localized surface plasmon due to gold nanoparticles on the increase in emission intensity and decrease in decay time of the emitters is established.« less

Crystal field parameters and energy levels scheme of trivalent chromium doped BSO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petkova, P.; Andreici, E.-L.; Avram, N. M., E-mail: n1m2marva@yahoo.com

The aim of this paper is to give an analysis of crystal field parameters and energy levels schemes for the above doped material, in order to give a reliable explanation for experimental data. The crystal field parameters have been modeled in the frame of Exchange Charge Model (ECM) of the crystal field theory, taken into account the geometry of systems, with actually site symmetry of the impurity ions. The effect of the charges of the ligands and covalence bonding between chromium cation and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of themore » crystal field parameters we simulated the scheme of energy levels of chromium ions by diagonalizing the matrix of the Hamiltonian of the doped crystal. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison with experiment shows that the results are quite satisfactory which justify the model and simulation scheme used for the title system.« less

Sodium doping in ZnO crystals

NASA Astrophysics Data System (ADS)

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.

Interfacing superconducting qubits and telecom photons via a rare-earth-doped crystal.

PubMed

O'Brien, Christopher; Lauk, Nikolai; Blum, Susanne; Morigi, Giovanna; Fleischhauer, Michael

2014-08-08

We propose a scheme to couple short single photon pulses to superconducting qubits. An optical photon is first absorbed into an inhomogeneously broadened rare-earth doped crystal using controlled reversible inhomogeneous broadening. The optical excitation is then mapped into a spin state using a series of π pulses and subsequently transferred to a superconducting qubit via a microwave cavity. To overcome the intrinsic and engineered inhomogeneous broadening of the optical and spin transitions in rare-earth doped crystals, we make use of a special transfer protocol using staggered π pulses. We predict total transfer efficiencies on the order of 90%.

High Mobility Transport Layer Structures for Rhombohedral Si/Ge/SiGe Devices

NASA Technical Reports Server (NTRS)

Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Kim, Hyun-Jung (Inventor); Lee, Kunik (Inventor)

2017-01-01

An electronic device includes a trigonal crystal substrate defining a (0001) C-plane. The substrate may comprise Sapphire or other suitable material. A plurality of rhombohedrally aligned SiGe (111)-oriented crystals are disposed on the (0001) C-plane of the crystal substrate. A first region of material is disposed on the rhombohedrally aligned SiGe layer. The first region comprises an intrinsic or doped Si, Ge, or SiGe layer. The first region can be layered between two secondary regions comprising n+doped SiGe or n+doped Ge, whereby the first region collects electrons from the two secondary regions.

Temperature dependent fluorescence spectra arise from change in excited-state intramolecular proton transfer potential of 4‧-N,N-dimethylamino-3-hydroxyflavone-doped acetonitrile crystals

NASA Astrophysics Data System (ADS)

Furukawa, Kazuki; Yamamoto, Norifumi; Hino, Kazuyuki; Sekiya, Hiroshi

2016-01-01

The effect of intermolecular interaction on excited-state intramolecular proton transfer (ESIPT) in 4‧-N,N-dimethylamino-3-hydroxyflavone (DMHF) doped in acetonitrile crystals was investigated by measuring the temperature dependence of fluorescence excitation and fluorescence spectra. A solid/solid phase transition of DMHF-doped acetonitrile crystals occurred in the temperature between 210 and 218 K. Significant differences in the spectral profiles and shifts in the fluorescence spectra were observed in the low- and high-temperature regions of the phase transition. The temperature dependence of the ESIPT potential of DMHF is discussed.

Growth and characterization of pure and Cadmium chloride doped KDP Crystals grown by gel medium

NASA Astrophysics Data System (ADS)

Kalaivani, M. S.; Asaithambi, T.

2016-10-01

Crystal growth technology provides an important basis for many industrial branches. Crystals are the unrecognized pillars of modern technology. Without crystals, there is no electronic industry, no photonic industry, and no fiber optic communications. Single crystals play a major role and form the strongest base for the fast growing field of engineering, science and technology. Crystal growth is an interdisciplinary subject covering physics, chemistry, material science, chemical engineering, metallurgy, crystallography, mineralogy, etc. In past few decades, there has been a keen interest on crystal growth processes, particularly in view of the increasing demand of materials for technological applications. Optically good quality pure and metal doped KDP crystals have been grown by gel method at room temperature and their characterization have been studied. Gel method is a much uncomplicated method and can be utilized to synthesize crystals which are having low solubility. Potassium dihydrogen orthophosphate KH2PO4 (KDP) continues to be an interesting material both academically and industrially. KDP is a representative of hydrogen bonded materials which possess very good electro - optic and nonlinear optical properties in addition to interesting electrical properties. Due to this interesting properties, we made an attempt to grow pure and cadmium chloride doped KDP crystals in various concentrations (0.002, 0.004, 0.006, 0.008 and 0.010) using gel method. The grown crystals were collected after 20 days. We get crystals with good quality and shaped. The dc electrical conductivity (resistance, capacitance and dielectric constant) values were measured at frequencies in the range of 1 KHZ and 100 HZ of pure and cadmium chloride added crystal with a temperature range of 400C to 1300C using simple two probe setup with Q band digital LCR meter present in our lab. The electrical conductivity increases with increase of temperature. The dielectric constants of metal doped KDP crystals were slightly decreased compared to pure KDP crystals.

Method of fabricating optical waveguides by ion implantation doping

DOEpatents

Appleton, Bill R.; Ashley, Paul R.; Buchal, Christopher J.

1989-01-01

A method for fabricating high-quality optical waveguides in optical quality oxide crystals by ion implantation doping and controlled epitaxial recrystallization is provided. Masked LiNbO.sub.3 crystals are implanted with high concentrations of Ti dopant at ion energies of about 350 keV while maintaining the crystal near liquid nitrogen temperature. Ion implantation doping produces an amorphous, Ti-rich nonequilibrium phase in the implanted region. Subsequent thermal annealing in a water-saturated oxygen atmosphere at up to 1000.degree. C. produces solid-phase epitaxial regrowth onto the crystalline substrate. A high-quality single crystalline layer results which incorporates the Ti into the crystal structure at much higher concentrations than is possible by standard diffusion techniques, and this implanted region has excellent optical waveguides properties.

Compositional analysis of dilute nitride doped indium antimonide bulk crystal by VDS technique

NASA Astrophysics Data System (ADS)

Deshpande, Manisha; Maske, Dilip; Choudhari, Rashmi; Arora, Brij Mohan; Gadkari, Dattatray

2016-05-01

Dilute nitrides are suitable materials for fabrication of devices in detection of long wavelength infrared region. Dilute nitride doped Indium antimonide bulk crystals were grown using vertical directional solidification technique. The compositional characteristics of the crystals were carried out using EDS. The analysis was simulated and compared with observations using DTSA II software for accuracy. The ingots have uniform composition of Indium and Antimony. The actual nitrogen composition measured using EDS was 0.136% for doped nitrogen composition 0.1% except near conical end where it was 0.1%. The study of bonding between nitrogen, Indium and antimony was carried out using SIMS. The analysis shows strong presence of In-N bonding along with In-Sb bonds which indicates nitrogen has replaced antimony atoms in crystal lattice.

Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

NASA Astrophysics Data System (ADS)

Heczko, O.; Drahokoupil, J.; Straka, L.

2015-05-01

Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni50.0Mn28.5Ga21.5 single crystal, the boron doping increased magnetic coercivity from few Oe to 270 Oe while not affecting the transformation behavior and 10 M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolution of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.

Analysis of intrinsic optical bistability in Tm-doped laser-related crystals

NASA Astrophysics Data System (ADS)

Noginov, M. A.; Vondrova, M.; Casimir, D.

2003-11-01

We predict and theoretically study intrinsic optical bistability (IOB) mediated by nonlinear energy transfer processes in rare-earth-doped laser-related crystals. In particular, we investigate Tm-Ho and Tm-Yb systems, in which avalanche pumping is overimposed by energy transfer up-conversion. We predict that IOB can be experimentally observed in (Tm,Yb):BaY2F8 crystals in a wide range of experimentally achievable parameters.

Crystal Growth Furnace - An overview of the system configuration and planned experiments on the First United States Microgravity Laboratory mission

NASA Technical Reports Server (NTRS)

Srinivas, R.; Schaefer, D. A.

1992-01-01

The Crystal Growth Furnace (CGF) system configuration for the First United States Microgravity Laboratory (USML-1) mission is reviewed, and the planned on-orbit experiments are briefly described. The CGF is configured to accommodate four scientific experiments involving crystal growth which are based on the classical Bridgman method and CVT method, including vapor transport crystal growth of mercury cadmium telluride; crystal growth of mercury zinc telluride by directional solidification; seeded Bridgman growth of zinc-doped cadmium telluride; and Bridgman growth of selenium-doped gallium arsenide.

Nanoparticles Doped Liquid Crystal Filled Photonic Bandgap Fibers

NASA Astrophysics Data System (ADS)

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

2008-10-01

We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum to the one achieved with undoped liquid crystals. New interesting features such as frequency dependent behavior and a transmission spectrum with tunable attenuation on the short wavelength side of the bandgap suggest a potential application of this device as a tunable all-in-fiber gain equalization filter. The tunability of the device is demonstrated by changing the temperature of the liquid crystal and by varying both the amplitude and the frequency of the applied external electric field.

Single crystal Ce doped scintillator material with garnet structure sensitive to gamma ray and neutron radiation

NASA Astrophysics Data System (ADS)

Solodovnikov, D.; Weber, M. H.; Haven, D. T.; Lynn, K. G.

2012-08-01

A mixed garnet scintillator host material is obtained from the melt—Yttrium Gadolinium Gallium Aluminum Garnet (YGGAG). In addition to the high thermal and chemical stability and radiation hardness found in garnet crystals, it offers sensitivity to neutrons due to the presence of Gd atoms, has lower melting temperature than yttrium aluminum garnet, and similar crystallization behavior suitable for growth of large volume crystals. Crystals of YGGAG doped with Ce of 10×10×10 mm3 have already demonstrated energy resolution of 10% at 662 keV.

Study of cobalt effect on structural and optical properties of Dy doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Pandey, Praveen C.

2018-05-01

The present study has been carried out to investigate the effect of Co doping on structural and optical properties of Dy doped ZnO nanoparticles. We have prepared pure Zinc oxide, Dy (1%) doped ZnO and Dy (1%) doped ZnO co-doped with Co(2%) with the help of simple sol-gel combustion method. The structural analysis carried out using X-ray diffraction spectra (XRD) indicates substitution of Dy and Co at Zn site of ZnO crystal structure and hexagonal crystal structure without any secondary phase formation in all the samples. The surface morphology was analyzed by transmission electron microscopy (TEM). Absorption study indicates that Dy doping causes a small shift in band edge, while Co co-doping results significant change is absorption edge as well as introduce defect level absorption in the visible region. The band gap of samples decreases due to Dy and Co doping, which can be attributed to defect level formation below the conduction band in the system.

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.

PubMed

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

2018-06-06

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe 1-x Rh x ) 2 As 2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth [Formula: see text]. Single crystals with doping levels representative of an underdoped regime x  =  0.039 ([Formula: see text] K), close to optimal doping x  =  0.057 ([Formula: see text] K) and overdoped x  =  0.079 ([Formula: see text] K) and x  =  0.131([Formula: see text] K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the power-law, [Formula: see text]. 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)Fe 2 As 2 and 3d-electron-doped Ba(Fe,Co) 2 As 2 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) 2 As 2 samples. Our study supports the universal superconducting gap variation with doping and [Formula: see text] pairing at least in iron based superconductors of the BaFe 2 As 2 family.

Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe 1–xRh x) 2As 2 from London penetration depth measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Hyunsoo; Tanatar, M. A.; Martin, C.

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe 1–xRh x) 2As 2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth Δλ( T). Single crystals with doping levels representative of an underdoped regime x = 0.039 ( T c = 15.5 K), close to optimal doping x = 0.057 ( T c = 24.4 K) and overdoped x = 0.079 ( T c = 21.5 K) and x = 0.131( T c = 4.9 K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n,more » by fitting the data to the power-law, Δλ = AT n. 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)Fe 2As 2 and 3d-electron-doped Ba(Fe,Co) 2As 2 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) 2As 2 samples. In conclusion, our study supports the universal superconducting gap variation with doping and pairing at least in iron based superconductors of the BaFe 2As 2 family.« less

Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe 1–xRh x) 2As 2 from London penetration depth measurements

DOE PAGES

Kim, Hyunsoo; Tanatar, M. A.; Martin, C.; ...

2018-05-08

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe 1–xRh x) 2As 2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth Δλ( T). Single crystals with doping levels representative of an underdoped regime x = 0.039 ( T c = 15.5 K), close to optimal doping x = 0.057 ( T c = 24.4 K) and overdoped x = 0.079 ( T c = 21.5 K) and x = 0.131( T c = 4.9 K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n,more » by fitting the data to the power-law, Δλ = AT n. 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)Fe 2As 2 and 3d-electron-doped Ba(Fe,Co) 2As 2 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) 2As 2 samples. In conclusion, our study supports the universal superconducting gap variation with doping and pairing at least in iron based superconductors of the BaFe 2As 2 family.« less

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pashchenko, A. S., E-mail: as.pashchenko@gmail.com; Chebotarev, S. N.; Lunin, L. S.

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 temperaturemore » is increased, the efficiency of the activation of antimony in silicon nonlinearly decreases from ~10{sup 0} to ~10{sup –3}.« less

Temperature lowering program for homogeneous doping in flux growth

NASA Astrophysics Data System (ADS)

Qiwei, Wang; Shouquan, Jia

1989-10-01

Based on the mass conservation law and the Burton-Prim-Slichter equation, the temperature program for homogeneous doping in flux growth by slow cooling was derived. The effect of various factors, such as initial supersaturation, solution volume, growth kinetic coefficient and degree of mixing in the solution on growth rate, crystal size and temperature program is discussed in detail. Theoretical analysis shows that there is a critical crystal size above which homogeneous doping is impossible.

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

PubMed

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.

The effect of deuteration and doping on the phase transition temperature of grown glycine phosphite single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perumal, R., E-mail: perumal-cgc@yahoo.co.uk; Chandru, A. Lakshmi; Babu, S. Moorthy

The Glycinium Phosphite (GPI) compound is a representative of hydrogen-bonded ferroelectric crystals. The ordering of protons could be expected below the room temperature (225 K). Crystals grown from the milipore water as well as deuterated solvents respectively. The corresponding hydrogen bond distance was stretched out due to the effect of isotopic substitution that increase the phase transition temperature. Further to improve the phase transition temperature, GPI crystal was doped with organic complexing agent and various metals and the obtained results are presented.

Electromechanical properties of engineered lead free potassium sodium niobate based materials =

NASA Astrophysics Data System (ADS)

Rafiq, Muhammad Asif

K0.5Na0.5NbO3 (KNN), is the most promising lead free material for substituting lead zirconate titanate (PZT) which is still the market leader used for sensors and actuators. To make KNN a real competitor, it is necessary to understand and to improve its properties. This goal is pursued in the present work via different approaches aiming to study KNN intrinsic properties and then to identify appropriate strategies like doping and texturing for designing better KNN materials for an intended application. Hence, polycrystalline KNN ceramics (undoped, non-stoichiometric; NST and doped), high-quality KNN single crystals and textured KNN based ceramics were successfully synthesized and characterized in this work. Polycrystalline undoped, non-stoichiometric (NST) and Mn doped KNN ceramics were prepared by conventional ceramic processing. Structure, microstructure and electrical properties were measured. It was observed that the window for mono-phasic compositions was very narrow for both NST ceramics and Mn doped ceramics. For NST ceramics the variation of A/B ratio influenced the polarization (P-E) hysteresis loop and better piezoelectric and dielectric responses could be found for small stoichiometry deviations (A/B = 0.97). Regarding Mn doping, as compared to undoped KNN which showed leaky polarization (P-E) hysteresis loops, B-site Mn doped ceramics showed a well saturated, less-leaky hysteresis loop and a significant properties improvement. Impedance spectroscopy was used to assess the role of Mn and a relation between charge transport - defects and ferroelectric response in K0.5Na0.5NbO3 (KNN) and Mn doped KNN ceramics could be established. At room temperature the conduction in KNN which is associated with holes transport is suppressed by Mn doping. Hence Mn addition increases the resistivity of the ceramic, which proved to be very helpful for improving the saturation of the P-E loop. At high temperatures the conduction is dominated by the motion of ionized oxygen vacancies whose concentration increases with Mn doping. Single crystals of potassium sodium niobate (KNN) were grown by a modified high temperature flux method. A boron-modified flux was used to obtain the crystals at a relatively low temperature. XRD, EDS and ICP analysis proved the chemical and crystallographic quality of the crystals. The grown KNN crystals exhibit higher dielectric permittivity (29,100) at the tetragonal-to-cubic phase transition temperature, higher remnant polarization (19.4 ?C/cm2) and piezoelectric coefficient (160 pC/N) when compared with the standard KNN ceramics. KNN single crystals domain structure was characterized for the first time by piezoforce response microscopy. It could be observed that - oriented potassium sodium niobate (KNN) single crystals reveal a long range ordered domain pattern of parallel 180° domains with zig-zag 90° domains. From the comparison of KNN Single crystals to ceramics, It is argued that the presence in KNN single crystal (and absence in KNN ceramics) of such a long range order specific domain pattern that is its fingerprint accounts for the improved properties of single crystals. These results have broad implications for the expanded use of KNN materials, by establishing a relation between the domain patterns and the dielectric and ferroelectric response of single crystals and ceramics and by indicating ways of achieving maximised properties in KNN materials. (Abstract shortened by ProQuest.).

Compositional analysis of dilute nitride doped indium antimonide bulk crystal by VDS technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deshpande, Manisha, E-mail: manishauj@gmail.com; Department of Physics, Mithibai College, Vile Parle; Maske, Dilip

2016-05-06

Dilute nitrides are suitable materials for fabrication of devices in detection of long wavelength infrared region. Dilute nitride doped Indium antimonide bulk crystals were grown using vertical directional solidification technique. The compositional characteristics of the crystals were carried out using EDS. The analysis was simulated and compared with observations using DTSA II software for accuracy. The ingots have uniform composition of Indium and Antimony. The actual nitrogen composition measured using EDS was 0.136% for doped nitrogen composition 0.1% except near conical end where it was 0.1%. The study of bonding between nitrogen, Indium and antimony was carried out using SIMS.more » The analysis shows strong presence of In-N bonding along with In-Sb bonds which indicates nitrogen has replaced antimony atoms in crystal lattice.« less

Luminescence and Excitation Spectra of U 3+ doped RbY 2 Cl 7 Single Crystals

DOE PAGES

Karbowiak, M.; Murdoch, K.; Drożdżyński, J.; ...

1996-08-01

Uranium(3+) doped single crystals of RbY 2 Cl 7 with a uranium concentration of 0.05% and 0.2% were grown by the Bridgman-Stockbarger method using RbU 2 Cl 7 as the doping substance. Polished plates of ca. 5 mm in diameter were used for measurements of luminescence and excitation spectra. And since the U 3+ ions occupy two somewhat different site symmetries, a splitting of all observed f-f bands was observed. Furthermore, the analysis of the spectra enabled definitively an assignment of 22 crystal field bands for both site symmetries as well as the total crystal field splitting of the groundmore » level, equal to 473 cm -1 and 567 cm -1 for the first and second site symmetry, respectively.« less

Engineering a light-emitting planar defect within three-dimensional photonic crystals

PubMed Central

Liu, Guiqiang; Chen, Yan; Ye, Zhiqing

2009-01-01

Sandwich structures, constructed from a planar defect of rhodamine-B (RhB)-doped titania (TiO2) and two photonic crystals, were synthesized via the self-assembly method combined with spin-coating. The modification of the spontaneous emission of RhB molecules in such structures was investigated experimentally. The spontaneous emission of RhB-doped TiO2 film with photonic crystals was reduced by a factor of 5.5 over a large bandwidth of 13% of the first-order Bragg diffraction frequency when compared with that of RhB-doped TiO2 film without photonic crystals. The angular dependence of the modification and the photoluminescence lifetime of RhB molecules demonstrate that the strong and wide suppression of the spontaneous emission of the RhB molecules is due to the presence of the photonic band gap. PMID:27877309

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

PubMed

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.

One-Step Synthesis of Monodisperse In-Doped ZnO Nanocrystals

NASA Astrophysics Data System (ADS)

Wang, Qing Ling; Yang, Ye Feng; He, Hai Ping; Chen, Dong Dong; Ye, Zhi Zhen; Jin, Yi Zheng

2010-05-01

A method for the synthesis of high quality indium-doped zinc oxide (In-doped ZnO) nanocrystals was developed using a one-step ester elimination reaction based on alcoholysis of metal carboxylate salts. The resulting nearly monodisperse nanocrystals are well-crystallized with typically crystal structure identical to that of wurtzite type of ZnO. Structural, optical, and elemental analyses on the products indicate the incorporation of indium into the host ZnO lattices. The individual nanocrystals with cubic structures were observed in the 5% In-ZnO reaction, due to the relatively high reactivity of indium precursors. Our study would provide further insights for the growth of doped oxide nanocrystals, and deepen the understanding of doping process in colloidal nanocrystal syntheses.

Phosphate ytterbium-doped single-mode all-solid photonic crystal fiber with output power of 13.8 W

PubMed Central

Wang, Longfei; He, Dongbing; Feng, Suya; Yu, Chunlei; Hu, Lili; Qiu, Jianrong; Chen, Danping

2015-01-01

Single-mode ytterbium-doped phosphate all-solid photonic crystal fiber (AS-PCF) with 13.8 W output power and 32% slope efficiency was reported. By altering the diameter of the rods around the doped core and thus breaking the symmetry of the fiber, a polarization-maintaining AS-PCF with degree of polarization of >85% was also achieved, for the first time to knowledge, in a phosphate PCF. PMID:25684731

Correlating optical infrared and electronic properties of low tellurium doped GaSb bulk crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roodenko, K., E-mail: kroodenko@intelliepi.com; Liao, P.-K.; Lan, D.

2016-04-07

Control over the Te doping concentration is especially challenging in the mass-production of optically transparent, high-resistivity Te-doped GaSb crystals. Driven by the necessity to perform fast, robust, and non-destructive quality control of the Te doping homogeneity of the optically transparent large-diameter GaSb wafers, we correlated electronic and optical infrared properties of Te-doped GaSb crystals. The study was based on the experimental Hall and Fourier-Transform Infrared (FTIR) data collected from over 50 samples of the low-doped n-type material (carrier concentration of 6 × 10{sup 16} cm{sup −3} to 7 × 10{sup 17} cm{sup −3}) and the Te-doped p-type GaSb (4.6 ×more » 10{sup 15} cm{sup −3} to 1 × 10{sup 16} cm{sup −3}). For the n-type GaSb, the analysis of the FTIR data was performed using free carrier absorption model, while for the p-type material, the absorption was modeled using inter-valence band absorption mechanism. Using the correlation between the Hall and the IR data, FTIR maps across the wafers allow a fast and reliable way to estimate carrier concentration profile within the wafer.« less

Studies of absorption coefficient cum electro-optic performance of polymer dispersed liquid crystal doped with CNT and dichroic dye

NASA Astrophysics Data System (ADS)

Sharma, Vandna; Kumar, Pankaj

2017-11-01

Absorption coefficient of doped polymer dispersed liquid crystals (PDLCs) is a critical factor for their device performance and depends on dopants parameters like solubility, order parameter and extinction coefficients, in addition to configuration and orientation of the droplets. In this study, a fixed amount (0.125% wt/wt) of multiwall carbon nanotubes (CNTs) and orange azo dichroic dye was doped in PDLC and measured the OFF state absorption coefficient. Considering the theory based on Beer's law and followed by extinction coefficients of CNT and dye, the OFF state transmission for dye doped PDLC was found lower compared to CNT doped PDLC. As a result, absorption coefficient for dye doped PDLC was higher and resulted in the superior contrast ratio. The experimental results were found be consistent with the theoretical results.

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

NASA Astrophysics Data System (ADS)

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.

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

PubMed

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.

Improved ferroelectric and pyroelectric parameters in iminodiacetic acid doped TGS crystal

NASA Astrophysics Data System (ADS)

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.

Effect of crystal size distribution on thermoelectric performance for Lanthanum-doped strontium titanate bulk material

NASA Astrophysics Data System (ADS)

Zhang, Boyu; Wang, Jun; Yaer, Xinba; Huo, Zhenzhen; Wu, Yin; Li, Yan; Miao, Lei; Liu, Chengyan; Zou, Tao; Ma, Wen

2015-07-01

Effect of crystal size distribution on thermoelectric performance of Lanthanum-doped strontium titanate (La-SrTiO3) ceramics are investigated in this study. Thermoelectric performance measurement, coupled with microstructure studies, shows that the electrical conductivity strongly depends on the crystal size, potential barrier on the grain boundary and porosity. Meantime, because the average potential barriers height are increased along with the reduction of crystal size, the Seebeck coefficients are increased by energy filtering effect at the large number of grain boundaries. As a result, by controlling of crystal size distribution, ZT value of La-SrTiO3 is improved.

Comparison of luminescence property of gamma-ray irradiated Tb3+ -doped and Ce3+ co-doped potassium halide single crystals.

PubMed

Bangaru, S; Ravi, D; Saradha, K

2017-05-01

Single crystals of KCl and KBr singly and doubly doped with Tb 3 + and Ce 3 + , respectively, were successfully grown using the Bridgeman technique. This work reports the comparative luminescence behavior and optical absorption characterization of non-irradiated and γ-ray-irradiated single crystals of these materials. The existing defect and the defect created by γ-ray irradiation were monitored by optical absorption spectra. The excitation and emission spectra of these materials were measured at room temperature with a spectrofluorometer and the pertaining results were compared. The F-band comparison was made when bleached with F-light for 2 mins. The trap-level changes in KCl and KBr when it is singly and doubly doped enabled us to draw conclusions on the nature of the defect and on the recombination processes involved. Copyright © 2016 John Wiley & Sons, Ltd.

Microstructure, crystallization and shape memory behavior of titania and yttria co-doped zirconia

DOE PAGES

Zeng, Xiao Mei; Du, Zehui; Schuh, Christopher A.; ...

2015-12-17

Small volume zirconia ceramics with few or no grain boundaries have been demonstrated recently to exhibit the shape memory effect. To explore the shape memory properties of yttria doped zirconia (YDZ), it is desirable to develop large, microscale grains, instead of submicron grains that result from typical processing of YDZ. In this paper, we have successfully produced single crystal micro-pillars from microscale grains encouraged by the addition of titania during processing. Titania has been doped into YDZ ceramics and its effect on the grain growth, crystallization and microscale elemental distribution of the ceramics have been systematically studied. With 5 mol%more » titania doping, the grain size can be increased up to ~4 μm, while retaining a large quantity of the desired tetragonal phase of zirconia. Finally, micro-pillars machined from tetragonal grains exhibit the expected shape memory effects where pillars made from titania-free YDZ would not.« less

Electrical conduction studies in ferric-doped KHSO 4 single crystals

NASA Astrophysics Data System (ADS)

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.

Growth, Crystal Structure, Theoretical Analysis and Properties of Te4+-Doped KTiOPO4

NASA Astrophysics Data System (ADS)

Liu, Lintao; Yao, Qian; Zhang, Junying; Dong, Weimin; Li, Jing; Wang, Jiyang; Boughton, Robert I.

2018-04-01

A single crystal of Te4+-doped KTiOPO4(Te:KTP) has been grown by the flux method. The electronic structure and density of states of KTiOPO4 (KTP) and Te:KTP were calculated from first principles. As the results reveal, there is no change in the space group or lattice structure of Te:KTP, but that some increase in lattice parameters occurred. The chemical composition of Te:KTP was analyzed using x-ray photoelectron spectroscopy (XPS). The possible existence of Ti3+ has been evaluated by measuring the electron paramagnetic resonance spectrum, and the results reveal that the ion is absent from this crystal. It was observed that Te4+ doping reduces the conductivity of the crystal from measurements of its conductivity at different temperatures and frequencies, indicating that Te:KTP has excellent electro-optical properties. The effect of Te4+ doping on the second harmonic generation in KTP was also studied. The thermal expansion, thermal diffusivity, thermal conductivity and specific heat capacity of KTP and Te:KTP were determined.

Structural characterization of ultrathin Cr-doped ITO layers deposited by double-target pulsed laser ablation

NASA Astrophysics Data System (ADS)

Cesaria, Maura; Caricato, Anna Paola; Leggieri, Gilberto; Luches, Armando; Martino, Maurizio; Maruccio, Giuseppe; Catalano, Massimo; Grazia Manera, Maria; Rella, Roberto; Taurino, Antonietta

2011-09-01

In this paper we report on the growth and structural characterization of very thin (20 nm) Cr-doped ITO films, deposited at room temperature by double-target pulsed laser ablation on amorphous silica substrates. The role of Cr atoms in the ITO matrix is carefully investigated with increasing doping content by transmission electron microscopy (TEM). Selected-area electron diffraction, conventional bright field and dark field as well as high-resolution TEM analyses, and energy dispersive x-ray spectroscopy demonstrate that (i) crystallization features occur despite the low growth temperature and small thickness, (ii) no chromium or chromium oxide secondary phases are detectable, regardless of the film doping levels, (iii) the films crystallize as crystalline flakes forming large-angle grain boundaries; (iv) the observed flakes consist of crystalline planes with local bending of the crystal lattice. Thickness and compositional information about the films are obtained by Rutherford back-scattering spectrometry. Results are discussed by considering the combined effects of growth temperature, smaller ionic radius of the Cr cation compared with the trivalent In ion, doping level, film thickness, the double-target doping technique and peculiarities of the pulsed laser deposition method.

Thermal conductivity investigation of adhesive-free bond laser components

NASA Astrophysics Data System (ADS)

Li, Da; Hong, Pengda; Vedula, MahaLakshmi; Meissner, Helmuth E.

2017-02-01

An interferometric method has been developed and employed at Onyx Optics, Inc. to accurately measure the thermal conductivity of laser-active crystals as function of dopant concentration or inactive materials such as single crystals, optical ceramics and glasses relative to a standard of assumed to be known thermal conductivity [1]. This technique can also provide information on heat transfer resistance at the interface between two materials in close thermal contact. While the technique appears generally applicable to composites between optically homogeneous materials, we report on thermal conductivities and heat transfer coefficients of selected adhesive-free bond (AFB®) laser composites. Single crystal bars and AFB bonded crystal doublets with the combinations of various rare-earth (Nd3+, Yb3+, Er3+, and Tm3+ trivalent ion doped YAG, and un-doped YAG have been fabricated with the AFB technique. By loading the test sample in a vacuum cryostat, with a precisely controlled heat load at one end of the doublets, the temperature distribution inside the single crystal or the composite samples can been precisely mapped by measuring the optical path difference interferometrically, given the material's thermal-optical properties. No measurable heat transfer resistance can be identified for the AFB interfaces between low-concentration doped YAG and un-doped YAG. For the heavily doped RE3+:YAG, for example, 10% Yb:YAG, the thermal conductivity measured in our experiment is 8.3 W/m•K, using the thermal conductivity of undoped YAG reported in [1] as basis. The thermal transfer resistance of the AFB interface with un-doped YAG, if there is any at the AFB interface, could be less than 1.29×10-6 m2•K/W.

Ultraviolet-infrared laser-induced domain inversion in MgO-doped congruent LiNbO3 and near stoichiometric LiTaO3 crystals

NASA Astrophysics Data System (ADS)

Zhi, Ya'nan; Qu, Weijuan; Liu, De'an; Sun, Jianfeng; Yan, Aimin; Liu, Liren

2008-08-01

Laser-induced domain inversion is a promising technique for domain engineering in LiNbO3 and LiTaO3. The ultraviolet-infrared laser induced domain inversions in MgO-doped congruent LiNbO3 and near stoichiometric LiTaO3 crystals are investigated for the first time here. Within the wavelength range from 351 to 799 nm, the different reductions of nucleation field induced by the focused continuous laser irradiation are systematically investigated in the MgO-doped congruent LiNbO3 crystals. The investigation of ultrashort-pulse laser-induced domain inversion in MgO-doped congruent LiNbO3 is performed with 800 nm wavelength irradiation. The focused continuous ultraviolet laser-induced ferroelectric domain inversion in the near stoichiometric LiTaO3 is also investigated. The different physical explanations, based on space charge field and defect formation, are presented for the laser-induced domain inversion, and the solid experimental proofs are also presented. The results provide the solid experimental proofs and feasible schemes for the further investigation of laser-induced domain engineering in MgO-doped LiNbO3 and near stoichiometric LiTaO3 crystals. The important characteristics of domain inversion, including domain wall and internal field, in LiNbO3 crystals are also investigated by the digital holographic interferometry with an improved reconstruction method, and some creative experimental results and conclusions are achieved.

Synthesis, crystal structure and magnetic properties of superconducting single crystals of HgBa2CuO4+δ

NASA Astrophysics Data System (ADS)

Bertinotti, A.; Viallet, V.; Colson, D.; Marucco, J.-F.; Hammann, J.; Forget, A.; Le Bras, G.

1996-02-01

Single crystals of HgBa2CuO4+δ of submillimetric sizes were grown with the same one step, low pressure, gold amalgamation technique used to obtain single crystals of HgBa2Ca2Cu3O8+δ. Remarkable superconducting properties are displayed by the samples which are optimally doped as grown. The sharpness of the transition profiles of the magnetic susceptibility, its anisotropy dependence and the volume fraction exhibiting the Meissner effect exceed the values obtained with the best crystal samples of Hg-1223. X-rays show that no substitutional defects have been found in the mercury plane, in particular no mixed occupancy of copper at the mercury site. The interstitial oxygen content at (1/2, 1/2, 0) δ = 0.066+/-0.008 is about one third that observed in optimally doped Hg-1223, resulting in an identical doping level per CuO2 plane in both compounds.

Coilable single crystal fibers of doped-YAG for high power laser applications

NASA Astrophysics Data System (ADS)

Maxwell, Gisele; Soleimani, Nazila; Ponting, Bennett; Gebremichael, Eminet

2013-05-01

Single crystal fibers are an intermediate between laser crystals and doped glass fibers. They can combine the advantages of both by guiding laser light and matching the efficiencies found in bulk crystals, making them ideal candidates for high-power laser and fiber laser applications. In particular, a very interesting feature of single crystal fiber is that they can generate high power in the eye-safe range (Er:YAG) with a high efficiency, opening new possibilities for portable directed energy weapons. This work focuses on the growth of a flexible fiber with a core of dopant (Er, Nd, Yb, etc…) that will exhibit good waveguiding properties. Direct growth or a combination of growth and cladding experiments are described. We have, to date, demonstrated the growth of a flexible foot long 45 microns doped YAG fiber. Scattering loss measurements at visible wavelengths along with dopant profile characterization are also presented. Laser characterization for these fibers is in progress.

Dielectric properties of highly resistive GaN crystals grown by ammonothermal method at microwave frequencies

NASA Astrophysics Data System (ADS)

Krupka, Jerzy; Zajåc, Marcin; Kucharski, Robert; Gryglewski, Daniel

2016-03-01

Permittivity, the dielectric loss tangent and conductivity of semi-insulating Gallium Nitride crystals have been measured as functions of frequency from 10 GHz to 50 GHz and temperature from 295 to 560 K employing quasi TE0np mode dielectric resonator technique. Crystals were grown using ammonothermal method. Two kinds of doping were used to obtain high resistivity crystals; one with deep acceptors in form of transition metal ions, and the other with shallow Mg acceptors. The sample compensated with transition metal ions exhibited semi-insulating behavior in the whole temperature range. The sample doped with Mg acceptors remained semi-insulating up to 390 K. At temperatures exceeding 390 K the conductivity term in the total dielectric loss tangent of Mg compensated sample becomes dominant and it increases exponentially with activation energy of 1.14 eV. It has been proved that ammonothermal method with appropriate doping allows growth of high quality, temperature stable semi-insulating GaN crystals.

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

NASA Astrophysics Data System (ADS)

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.

Defect chemistry and characterization of (Hg, Cd)Te

NASA Technical Reports Server (NTRS)

Vydyanath, H. R.

1981-01-01

Single crystal samples of phosphorus doped Hg sub 0.8 Cd sub 0.2 Te were anneald at temperatures varying from 450 C to 600 C in various Hg atmospheres. The samples were quenched to room temperature from the annealing temperatures. Hall effect and mobility measurements were performed at 77 K on all these samples. The results indicate the crystals to be p type for a total phosphorus concentration of 10 to the 19th power/cu cm in all the samples. The hole concentration at 77 K increases with increasing Hg pressures at 450 C and 500 C contrary to the observation in undoped crystals. Also, at low Hg pressures the concentration of holes in the phosphorus doped crystals is lower than in the undoped crystals. The hole concentration in all the samples is lower than the intrinsic carrier concentration at the annealing temperatures. The hole mobility in the doped crystals is similar to that in the undoped crystals. A defect model according to which phosphorus behaves as a single acceptor interstitially, occupying Te lattice sites while it acts as a single donor occupying Hg lattice sites was established. Equilibrum constants established for the incorporation of all the phosphorus species explain the experimental results

Single crystal fibers for high power lasers

NASA Astrophysics Data System (ADS)

Kim, W.; Florea, C.; Baker, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; O'Connor, S.; Villalobos, G.; Bayya, S.; Aggarwal, I. D.; Sanghera, J. S.

2012-11-01

In this paper, we present our recent results in developing cladded-single crystal fibers for high power single frequency fiber lasers significantly exceeding the capabilities of existing silica fiber based lasers. This fiber laser would not only exploit the advantages of crystals, namely their high temperature stability, high thermal conductivity, superior environmental ruggedness, high propensity for rare earth ion doping and low nonlinearity, but will also provide the benefits from an optical fiber geometry to enable better thermal management thereby enabling the potential for high laser power output in short lengths. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by Laser Heated Pedestal Growth (LHPG) process. The mechanical, optical and morphological properties of these fibers have been characterized. The fibers are very flexible and show good overall uniformity. We also measured the optical loss as well as the non-radiative loss of the doped crystal fibers and the results show that the fibers have excellent optical and morphological quality. The gain coefficient of the crystal fiber matches the low quantum defect laser model and it is a good indication of the high quality of the fibers.

Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heczko, O., E-mail: heczko@fzu.cz; Drahokoupil, J.; Straka, L.

2015-05-07

Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni{sub 50.0}Mn{sub 28.5}Ga{sub 21.5} single crystal, the boron doping increased magnetic coercivity from few Oe to 270 Oe while not affecting the transformation behavior and 10 M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolutionmore » of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.« less

Broadband pulsed difference frequency generation laser source centered 3326 nm based on ring fiber lasers

NASA Astrophysics Data System (ADS)

Chen, Guangwei; Li, Wenlei

2018-03-01

A broadband pulsed mid-infrared difference frequency generation (DFG) laser source based on MgO-doped congruent LiNbO3 bulk is experimentally demonstrated, which employs a homemade pulsed ytterbium-doped ring fiber laser and a continuous wave erbium-doped ring fiber laser to act as seed sources. The experimental results indicate that the perfect phase match crystal temperature is about 74.5∘C. The maximum spectrum bandwidth of idler is about 60 nm with suitable polarization states of fundamental lights. The central wavelength of idlers varies from 3293 nm to 3333 nm over the crystal temperature ranges of 70.4-76∘C. A jump of central wavelength exists around crystal temperature of 72∘C with variation of about 30 nm. The conversion efficiency of DFG can be tuned with the crystal temperature and polarization states of fundamental lights.

Efficient eye-safe neodymium doped composite yttrium gallium garnet crystal laser.

PubMed

Yu, Haohai; Wang, Shuxian; Han, Shuo; Wu, Kui; Su, Liangbi; Zhang, Huaijin; Wang, Zhengping; Xu, Jun; Wang, Jiyang

2014-03-15

We report a laser-diode pumped continuous-wave (cw) and passively Q-switched eye-safe laser at about 1.42 μm with the neodymium-doped yttrium gallium garnet (Nd:YGG) crystal for the first time to our knowledge. The composite Nd:YGG crystal was developed originally. A systematic comparison of laser performance between the homogeneously doped and composite Nd:YGG crystal was made, which showed that the composite Nd:YGG manifested less thermally induced effects. Cw output power of 2.06 W was obtained with the slope efficiency of 20.7%. With a V:YAG as a saturable absorber, the passive Q-switching at 1.42 μm was gotten with the pulse width, pulse energy, and peak power of 34 ns, 46.7 μJ, and 1.4 kW, respectively. The present work should provide a potential candidate for the generation of eye-safe lasers.

Conversion of broadband thermal radiation in lithium niobate crystals of various compositions

NASA Astrophysics Data System (ADS)

Syuy, A. V.; Litvinova, M. N.; Goncharova, P. S.; Sidorov, N. V.; Palatnikov, M. N.; Krishtop, V. V.; Likhtin, V. V.

2013-05-01

The conversion of the broadband thermal radiation in stoichiometric ( R = 1) lithium niobate single crystals that are grown from melt with 58.6 mol % of LiO2, congruent ( R = Li/Nb = 0.946) melt with the K2O flux admixture (4.5 and 6.0 wt %), and congruent melt and in congruent single crystals doped with the Zn2+, Gd3+, and Er3+ cations is studied. It is demonstrated that the conversion efficiency of the stoichiometric crystal that is grown from the melt with 58.6 mol % of LiO2 is less than the conversion efficiency of congruent crystal. In addition, the stoichiometric and almost stoichiometric crystals and the doped congruent crystals exhibit the blue shift of the peak conversion intensity in comparison with a nominally pure congruent crystal. For the congruent crystals, the conversion intensities peak at 520 and 495 nm, respectively.

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

NASA Astrophysics Data System (ADS)

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.

Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection

NASA Technical Reports Server (NTRS)

Hu, Z. W.; Thomas, B. R.; Chernov, A. A.

2001-01-01

Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection.

PubMed

Hu, Z W; Thomas, B R; Chernov, A A

2001-06-01

Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

Optical parameters and dispersion behavior of potassium magnesium chloride sulfate single crystals doped with Co+2 ions

NASA Astrophysics Data System (ADS)

Abu El-Fadl, A.; Abd-Elsalam, A. M.

2018-05-01

Single crystals of potassium magnesium chloride sulfate (KMCS) doped with cobalt ions were grown by slow cooling method. Powder XRD study confirmed the monoclinic structure of the grown crystals. The functional group vibrations were checked through FTIR spectroscopy measurements. In optical studies, the absorbance behavior of the crystals and their optical energy gap were established by Tauc plot. The refractive index, the extinction coefficient and other optical constants were calculated for the grown crystals. The normal dispersion of the refractive index was analyzed according to single oscillator Sellmeier's model. The Urbach's rule was applied to analyze the localized states density in the forbidden gap.

The structural, electronic and optical properties of Nd doped ZnO using first-principles calculations

NASA Astrophysics Data System (ADS)

Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Wu, Hua; Yang, Xu

2018-04-01

The density functional theory calculations using general gradient approximation (GGA) applying Perdew-Burke-Ernzerhof (PBE) as correlation functional have been systematically performed to research the formation energy, the electronic structures, band structures, total and partial DOS, and optical properties of Nd doping ZnO with the content from 6.25% to 12.5%. The formation energies are negative for both models, which show that two structures are energetically stable. Nd doping ZnO crystal is found to be a direct band gap semiconductor and Fermi level shifts upward into conduction band, which show the properties of n-type semiconductor. Band structures are more compact after Nd doping ZnO, implying that Nd doping induces the strong interaction between different atoms. Nd doping ZnO crystal presents occupied states at near Fermi level, which mainly comes from the Nd 4f orbital. The calculated optical properties imply that Nd doping causes a red-shift of absorption peaks, and enhances the absorption of the visible light.

Fast Response and Spontaneous Alignment in Liquid Crystals Doped with 12-Hydroxystearic Acid Gelators.

PubMed

Lin, Hui-Chi; Wang, Chih-Hung; Wang, Jyun-Kai; Tsai, Sheng-Feng

2018-05-07

The spontaneous vertical alignment of liquid crystals (LCs) in gelator (12-hydroxystearic acid)-doped LC cells was studied. Gelator-induced alignment can be used in both positive and negative LC cells. The electro-optical characteristics of the gelator-doped negative LC cell were similar to those of an LC cell that contained a vertically aligned (VA) host. The rise time of the gelator-doped LC cell was two orders of magnitude shorter than that of the VA host LC cell. The experimental results indicate that the gelator-induced vertical alignment of LC molecules occurred not only on the surface of the indium tin oxide (ITO) but also on the homogeneous alignment layer. Various LC alignments (planar, hybrid, multistable hybrid, and vertical alignments) were achieved by modulating the doped gelator concentrations. The multistable characteristic of LCs doped with the gelator is also presented. The alignment by doping with a gelator reduces the manufacturing costs and provides a means of fabricating fast-responding, flexible LC displays using a low-temperature process.

2 inch size Czochralski growth and scintillation properties of Li+ co-doped Ce:Gd3Ga3Al2O12

NASA Astrophysics Data System (ADS)

Kamada, Kei; Shoji, Yasuhiro; Kochurikhin, Vladimir V.; Yoshino, Masao; Okumura, Satoshi; Yamamoto, Seiichi; Yeom, Jung Yeol; Kurosawa, Shunsuke; Yokota, Yuui; Ohashi, Yuji; Nikl, Martin; Yoshino, Masao; Yoshikawa, Akira

2017-03-01

The 2 inch size Li 0.15 and 1.35 mol% co-doped Ce:Gd3Al2Ga3O12 single crystals were prepared by the Czochralski (Cz) method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Li co-doping. Ce4+ CT absorption below 350 nm is clearly enhanced by Li co-doping as same as divalent ions co-doping. By 1.35 at.% Li co-doping, light yield was decrease to 88% of the Ce: GAGG standard and decay time was accelerated to 34.3ns 21.0%, 84.6ns 68.7%, 480ns 10.3%. The timing resolution measurement for a pair of 3 × 3 × 3mm3 size Li,Ce:GAGG scintillator crystals was performed using Si-PMs and the timing resolution of the 1.35 at.% Li co-doped Ce:GAGG was 218ps.

Echo spectroscopy of TLS of multiwell adiabatic potential for Pr3+ activator centers in Y2SiO5

NASA Astrophysics Data System (ADS)

Malyukin, Yuri V.; Borysov, R. S.; Zhmurin, P. N.; Lebedenko, A. N.; Grinyov, Boris V.; Znamenskii, N. I.; Manykin, Eduard A.; Orlov, Yu. V.; Petrenko, E. A.; Yukina, T. G.

2002-05-01

Based on the investigation of the temperature dependence of the two-pulse phonon echo amplitude on the 3H4 3Po resonant optical transition of the Pr3+ doped ions in the Y2SiO5 crystal, unusual for crystals, low-temperature mechanisms of Pr3+ spectral line broadening caused by the interaction of doped ions with TLS have been found. The constants characterizing the interaction of the doped Pr3+ ions with phonons and TLS have been determined.

Doping- and irradiation-controlled pinning of vortices in BaFe 2 (As 1 - x P x ) 2 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, L.; Jia, Y.; Schlueter, J. A.

We report on the systematic evolution of vortex pinning behavior in isovalent doped single crystals of BaFe 2 (As 1 - x P x ) 2 . Proceeding from optimal doped to overdoped samples, we find a clear transformation of the magnetization hysteresis from a fishtail behavior to a distinct peak effect, followed by a reversible magnetization and Bean-Livingston surface barriers. Strong point pinning dominates the vortex behavior at low fields whereas weak collective pinning determines the behavior at higher fields. In addition to doping effects, we show that particle irradiation by energetic protons can tune vortex pinning in thesemore » materials.« less

Doping- and irradiation-controlled pinning of vortices in BaFe{<_2}(As{<_1-x}P{<_x}){<_2} single crystals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, L.; Jia, Y.; Schlueter, J. A.

We report on the systematic evolution of vortex pinning behavior in isovalent doped single crystals of BaFe{sub 2}(As{sub 1-x}P{sub x}){sub 2}. Proceeding from optimal doped to overdoped samples, we find a clear transformation of the magnetization hysteresis from a fishtail behavior to a distinct peak effect, followed by a reversible magnetization and Bean-Livingston surface barriers. Strong point pinning dominates the vortex behavior at low fields whereas weak collective pinning determines the behavior at higher fields. In addition to doping effects, we show that particle irradiation by energetic protons can tune vortex pinning in these materials.

Doping effects of Co and Cu on superconductivity and magnetism in Fe1+yTe0.6Se0.4 single crystals.

PubMed

Zhang, Z T; Yang, Z R; Li, L; Ling, L S; Zhang, C J; Pi, L; Zhang, Y H

2013-01-23

We report on the investigation of Co and Cu substitution effects on superconductivity and magnetism in Fe(1+y)Te(0.6)Se(0.4) single crystals. The parent Fe(1.01)Te(0.59)Se(0.41) shows a nodeless bulk superconductivity as revealed in heat capacity measurement, which is gradually suppressed by either Co or Cu doping. It is found that the Co or Cu doping mainly serves as scatterers rather than charge carrier doping, which is in agreement with the DFT calculation (2010 Phys. Rev. Lett. 105 157004) reported by Wadati et al. In comparison with Cu doping, Co doping shows a stronger influence on magnetism while a less evident suppression effect on superconductivity. Upon substitution of Co for Fe, a Schottky heat capacity anomaly develops gradually at low temperatures, implying the existence of a paramagnetic moment in the Co-doped samples. In contrast, Cu doping may mainly serve as non-magnetic scatterers, where no Schottky anomaly is observed.

Sensitivity-enhanced Tm3+/Yb3+ co-doped YAG single crystal optical fiber thermometry based on upconversion emissions

NASA Astrophysics Data System (ADS)

Yu, Lu; Ye, Linhua; Bao, Renjie; Zhang, Xianwei; Wang, Li-Gang

2018-03-01

Optical thermometry based on Y3Al5O12 (YAG) single crystal optical fiber with end Tm3+/Yb3+ co-doped is presented. The YAG crystal fiber with end Tm3+/Yb3+ co-doped was grown by laser heated pedestal growth (LHPG) method. Under a 976 nm laser diode excitation, the upconversion (UC) emissions, originating from 3F2,3 →3H6 and 3H4 →3H6 transitions of Tm3+ ions, were investigated in the temperature range from 333 K to 733 K. Interestingly, the UC emission intensity of 3F2,3 →3H6 transition was significantly enhanced with increase of temperature, as compared with the other Tm3+/Yb3+ co-doped materials. The temperature dependence of fluorescence intensity ratio (FIR) of these two emission bands (3F2,3/3H4 →3H6) suggests that this doped YAG crystal fiber can be used as a highly sensitive optical thermal probe, which demonstrates a high absolute sensitivity with the maximum value of 0.021 K-1 at 733 K. In addition, due to the compact structure, strong mechanical strength and high thermal stability, such thermal probe may be a more promising candidate for temperature sensor with a high spatial resolution.

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

PubMed

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.

Controllable fabrication of Pt nanocatalyst supported on N-doped carbon containing nickel nanoparticles for ethanol oxidation.

PubMed

Yu, Jianguo; Dai, Tangming; Cao, Yuechao; Qu, Yuning; Li, Yao; Li, Juan; Zhao, Yongnan; Gao, Haiyan

2018-08-15

In this paper, platinum nanoparticles were deposited on a carbon carrier with the partly graphitized carbon and the highly dispersive carbon-coated nickel particles. An efficient electron transfer structure can be fabricated by controlling the contents of the deposited platinum. The high resolution transmission electron microscopy images of Pt 2 /Ni@C N-doped sample prove the electron transfer channel from Pt (1 1 1) crystal planes to graphite (1 0 0) or Ni (1 1 1) crystal planes due to these linked together crystal planes. The Pt 3 /Ni@C N-doped with low Pt contents cannot form the electron transfer structure and the Pt 1 /Ni@C N-doped with high Pt contents show an obvious aggregation of Pt nanoparticles. The electrochemical tests of all the catalysts show that the Pt 2 /Ni@C N-doped sample presents the highest catalytic activity, the strongest CO tolerance and the best catalytic stability. The high performance is attributed to the efficient electronic transport structure of the Pt 2 /Ni@C N-doped sample and the synergistic effect between Pt and Ni nanoparticles. This paper provides a promising method for enhancing the conductivity of electrode material. Copyright © 2018 Elsevier Inc. All rights reserved.

Optically pumped cerium-doped LiSrAlF{sub 6} and LiCaAlF{sub 6}

DOEpatents

Marshall, C.D.; Payne, S.A.; Krupke, W.F.

1996-05-14

Ce{sup 3+}-doped LiSrAlF{sub 6} crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF{sub 6} with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF{sub 6} type of chemical formula, e.g. Ce-doped LiCaAlF{sub 6} and LiSrGaF{sub 6}, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator. 10 figs.

Optically pumped cerium-doped LiSrAlF.sub.6 and LiCaAlF.sub.6

DOEpatents

Marshall, Christopher D.; Payne, Stephen A.; Krupke, William F.

1996-01-01

Ce.sup.3+ -doped LiSrAlF.sub.6 crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF.sub.6 with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF.sub.6 type of chemical formula, e.g. Ce-doped LiCaAlF.sub.6 and LiSrGaF.sub.6, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator.

Crystal Structure and Photocatalytic Activity of Al-Doped TiO2 Nanofibers for Methylene Blue Dye Degradation.

PubMed

Lee, Deuk Yong; Lee, Myung-Hyun; Kim, Bae-Yeon; Cho, Nam-Ihn

2016-05-01

Al-TiO2 nanofibers were prepared using a sol-gel derived electrospinning by varying the Al/Ti molar ratio from 0 to 0.73 to investigate the effect of Al doping on the crystal structure and the photocatalytic activity of Al-TiO2 for methylene blue (MB) degradation. XRD results indicated that as the Al/Ti molar ratio rose, crystal structure of Al-TiO2 was changed from anatase/rutile (undoped), anatase (0.07-0.18), to amorphous phase (0.38-0.73), which was confirmed by XPS and Raman analysis. The degradation kinetic constant increased from 7.3 x 10(-4) min(-1) to 4.5 x 10(-3) min(-1) with the increase of Al/Ti molar ratios from 0 to 0.38, but decreased to 3.4 x 10(-3) min(-1) when the Al/Ti molar ratio reached 0.73. The Al-TiO2 catalyst doped with 0.38 Al/Ti molar ratio demonstrated the best MB degradation. Experimental results indicated that the Al doping in Al-TiO2 was mainly attributed to the crystal structure of TiO2 and the photocatalytic degradation of MB.

Doping effects on the relaxation of frustration and magnetic properties of YMn0.9Cu0.1O3

NASA Astrophysics Data System (ADS)

Xiao, L. X.; Xia, Z. C.; Wang, X.; Ni, Y.; Yu, W.; Shi, L. R.; Jin, Z.; Xiao, G. L.

2017-12-01

The crystal structure and magnetic properties of hexagonal YMn0.9Cu0.1O3 single crystal are systematically investigated. The refinement results of XRD show the lattice constant decreases, which is unusually due to the doped Cu2+ ion has a larger ionic radius than the Mn3+ ions. The XPS results show that the coexistence of Mn2+, Mn3+ and Mn4+ ions in YMn0.9Cu0.1O3 single crystal. Magnetization measurements show that Cu doped YMn0.9Cu0.1O3 and parent YMnO3 have almost the same antiferromagnetic transition temperature TN, which indicates the AFM interaction is robust in the geometry frustrated system. Because doping directly destroy some of the Mn3+ ions nets, the relaxation of frustration of Mn in-plane 2D triangular geometry network leads to the significantly decrease of Mn3+ ions AFM interaction. In addition, the coexistence and competition between the ferromagnetic and antiferromagnetic interactions among the Mn2+, Mn3+ and Mn4+ ions lead to a complicated and irreversible magnetization behavior in YMn0.9Cu0.1O3 single crystal.

Effect of K-doping on structural and optical properties of ZnO thin films

NASA Astrophysics Data System (ADS)

Xu, Linhua; Li, Xiangyin; Yuan, Jun

2008-09-01

In this work, K-doped ZnO thin films were prepared by a sol-gel method on Si(111) and glass substrates. The effect of different K-doping concentrations on structural and optical properties of the ZnO thin films was studied. The results showed that the 1 at.% K-doped ZnO thin film had the best crystallization quality and the strongest ultraviolet emission ability. When the concentration of K was above 1 at.%, the crystallization quality and ultraviolet emission ability dropped. For the K-doped ZnO thin films, there was not only ultraviolet emission, but also a blue emission signal in their photoluminescent spectra. The blue emission might be connected with K impurity or/and the intrinsic defects (Zn interstitial and Zn vacancy) of the ZnO thin films.

Widely tunable band gap in a multivalley semiconductor SnSe by potassium doping

NASA Astrophysics Data System (ADS)

Zhang, Kenan; Deng, Ke; Li, Jiaheng; Zhang, Haoxiong; Yao, Wei; Denlinger, Jonathan; Wu, Yang; Duan, Wenhui; Zhou, Shuyun

2018-05-01

SnSe, a group IV-VI monochalcogenide with layered crystal structure similar to black phosphorus, has recently attracted extensive interest due to its excellent thermoelectric properties and potential device applications. Experimental electronic structure of both the valence and conduction bands is critical for understanding the effects of hole versus electron doping on the thermoelectric properties, and to further reveal possible change of the band gap upon doping. Here, we report the multivalley valence bands with a large effective mass on semiconducting SnSe crystals and reveal single-valley conduction bands through electron doping to provide a complete picture of the thermoelectric physics. Moreover, by electron doping through potassium deposition, the band gap of SnSe can be widely tuned from 1.2 eV to 0.4 eV, providing new opportunities for tunable electronic and optoelectronic devices.

The mechanism of the UV band edge photorefractivity suppression in highly doped LiNbO3:Zr crystals

NASA Astrophysics Data System (ADS)

Xin, Fei-fei

2017-11-01

The ultraviolet (UV) band edge photorefractivity of LiNbO3:Zr at 325 nm has been investigated. The experimental results show that the resistance against photorefraction at 325 nm is quite obvious but not as strong as that at 351 nm, when the doping concentration of Zr reaches 2.0 mol%. It is reported that the photorefractivity in other tetravalently doped LiNbO3 crystals, such as LiNbO3:Hf and LiNbO3:Sn, is enhanced dramatically with doping concentration over threshold. Here we give an explicit explanation on such seemly conflicting behaviors of tetravalently doped LiNbO3, which is ascribed to the combined effect of increased photoconductivity and the absorption strength of the band edge photorefractive centers.

Ultraviolet photorefraction at 325 nm in doped lithium niobate crystals

NASA Astrophysics Data System (ADS)

Xin, Feifei; Zhang, Guoquan; Bo, Fang; Sun, Haifeng; Kong, Yongfa; Xu, Jingjun; Volk, Tatyana; Rubinina, Natalia M.

2010-02-01

We studied the photorefractive effect of lithium niobate (LiNbO3) doped with Mg, Zn, In, Hf, or codoped with Mg and Fe at an ultraviolet (UV) wavelength down to 325 nm. It is found that the UV photorefraction of LiNbO3 doped with Mg, Zn, In, or Hf was enhanced significantly as compared to that of the nominally pure LiNbO3. Our results show that the property of resistance against photorefraction in highly Mg, Zn, In, or Hf doped LiNbO3 is true only in the visible and near-infrared wavelength range. By contrast, these crystals exhibit excellent photorefractive characteristics at UV wavelength of 325 nm, even better than those at 351 nm. For example, the photorefractive two-wave coupling gain coefficient Γ and the photorefractive recording sensitivity at 325 nm were measured to be ˜38 cm-1 and 37.7 cm/J, respectively, in a LiNbO3 crystal doped with 9 mol % Zn. The photorefractive response time of a Mg:LiNbO3 with a 9 mol % Mg was measured to be 73 ms with a total recording intensity of 614 mW/cm2 at 325 nm. In highly Mg, Zn, In, or Hf doped LiNbO3 crystals, diffusion dominates over photovoltaic effect and electrons are the dominant charge carriers in UV photorefraction at 325 nm. The results are also of interest to the study on the defect structure of LiNbO3 near to the absorption edge.

Properties of Lu3Al5O12, Lu3Al5O12:Pr, Lu3Al5O12:Pr,Mo, and (Lu1-x Y x )3Al5O12:Pr scintillator crystals

NASA Astrophysics Data System (ADS)

Talik, E.; Kusz, J.; Guzik, A.; Szubka, M.; Balin, K.; Kisielewski, J.; Wierzchowski, W.; Malinowska, A.; Strojny-Nedza, A.; Pajaczkowska, A.; Drozdowski, W.

2017-05-01

Lattice parameters, magnetic susceptibility, electronic structure, distribution of the elements and thermal properties were examined for single crystals of Lu3Al5O12 (LuAG) and (Lu1-x Y x )3Al5O12 (LuYAG) (x  =  0.25, 0.50, 0.75), either pure or doped with Pr and optionally co-doped with Mo, which are predicted as potential fast and efficient scintillators. It was indicated that specific cage-like surrounding of rare earth and aluminum ions built from oxygen ions and proper doping can influence the thermal conductivity and the emission process. Maximum light emission (LY) was observed at praseodymium concentration about 0.3 at.%. The growth atmosphere (Ar or N2) influences the crystal quality. Additional molybdenum doping below 0.01 at% concentration increases LY.

Effect of potassium doping on electronic structure and thermoelectric properties of topological crystalline insulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roychowdhury, Subhajit; Biswas, Kanishka, E-mail: kanishka@jncasr.ac.in; Sandhya Shenoy, U.

2016-05-09

Topological crystalline insulator (TCI), Pb{sub 0.6}Sn{sub 0.4}Te, exhibits metallic surface states protected by crystal mirror symmetry with negligibly small band gap. Enhancement of its thermoelectric performances needs tuning of its electronic structure particularly through engineering of its band gap. While physical perturbations tune the electronic structure of TCI by breaking of the crystal mirror symmetry, chemical means such as doping have been more attractive recently as they result in better thermoelectric performance in TCIs. Here, we demonstrate that K doping in TCI, Pb{sub 0.6}Sn{sub 0.4}Te, breaks the crystal mirror symmetry locally and widens electronic band gap, which is confirmed bymore » direct electronic absorption spectroscopy and electronic structure calculations. K doping in Pb{sub 0.6}Sn{sub 0.4}Te increases p-type carrier concentration and suppresses the bipolar conduction via widening a band gap, which collectively boosts the thermoelectric figure of merit (ZT) to 1 at 708 K.« less

Luminescence spectra of chromium-doped LiGaO 2 crystals as indicator of their phase heterogeneity

NASA Astrophysics Data System (ADS)

Meylman, Mikhail L.

2006-02-01

The luminescent properties of chromium-doped LiGaO2 single crystals grown from melt by Cz pulling technique are considered and compared with similar data for the other stable crystalline compounds in Li2O-Ga2O3 oxide system. It is proposed that co-crystallization of large LiGaO2 single crystal and a great number of LiGa5O8 spinel microcrystallites of nano scale dimensions is the key cause for appearance of numerous inclusions observed in LiGaO2 plates used as substrates at the III nitride films epitaxial growth.

A short review of theoretical and empirical models for characterization of optical materials doped with the transition metal and rare earth ions

NASA Astrophysics Data System (ADS)

Su, P.; Ma, C.-G.; Brik, M. G.; Srivastava, A. M.

2018-05-01

In this paper, a brief retrospective review of the main developments in crystal field theory is provided. We have examined how different crystal field models are applied to solve the problems that arise in the spectroscopy of optically active ions. Attention is focused on the joint application of crystal field and density functional theory (DFT) based models, which takes advantages of strong features of both individual approaches and allows for obtaining a complementary picture of the electronic properties of a doped crystal with impurity energy levels superimposed onto the host band structure.

Transfiguring structural, optical and dielectric properties of cadmium thiourea acetate crystal by the addition of L-threonine for laser assisted device applications

NASA Astrophysics Data System (ADS)

Kulkarni, Rupali B.; Anis, Mohd; Hussaini, S. S.; Shirsat, Mahendra D.

2018-03-01

Present investigation reports the growth of pure and L-threonine (LT) doped cadmium thiourea acetate (CTA) crystals by slow solution evaporation technique followed by structural, optical and dielectric characterization studies. A bulk single crystal of LT-CTA has been grown at temperature 38 °C. The single crystal x-ray diffraction technique has been employed to confirm the structural parameters of pure and LT doped CTA crystals. The increase in optical transparency of LT-CTA crystal was ascertained in the range of 200 to 900 nm using UV-visible spectral analysis. The widened optical band gap of the LT-CTA crystal is found to be 4.7 eV. Pure and doped crystals are subjected to FT-IR analysis to indicate the presence of functional groups quantitatively. Appreciable enhancement in second harmonic generation (SHG) efficiency of LT-CTA crystal with reference to parent CTA was confirmed from Kurtz-Perry SHG test (1.31 times of CTA crystal). The assertive influence of LT on electrical properties of grown crystals has been investigated in the temperature range 35 °C-120 °C. Electronic purity and the color centered photoluminescence emission nature of pure and IA-CTA crystals were justified by luminescence analysis. With the aid of single beam Z-scan analysis, the Kerr lensing nonlinearity was identified and the magnitude of TONLO parameters has been determined. The cubic susceptibility (χ3) and figure of merit (FOM) was found to be 4.81 × 10-4esu and 978.35. Results vitalize LT-CTA for laser stabilization systems.

Edge facet dynamics during the growth of heavily doped n-type silicon by the Czochralski-method

NASA Astrophysics Data System (ADS)

Stockmeier, L.; Kranert, C.; Raming, G.; Miller, A.; Reimann, C.; Rudolph, P.; Friedrich, J.

2018-06-01

During the growth of [0 0 1]-oriented, heavily n-type doped silicon crystals by the Czochralski (CZ) method dislocation formation occurs frequently which leads to a reduction of the crystal yield. In this publication the evolution of the solid-liquid interface and the formation of the {1 1 1} edge facets are analyzed on a microscopic scale as possible reason for dislocation formation in heavily n-type doped [0 0 1]-oriented CZ crystals. A correlation between the length of the {1 1 1} edge facets and the curvature of the interface is found. They ultimately promote supercooled areas and interrupted growth kinetics, which increase the probability for dislocation formation at the boundary between the {1 1 1} edge facets and the atomically rough interface.

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

PubMed

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.

Holographic recording in a doubly doped lithium niobate crystal with two wavelengths: a blue laser diode and a green laser

NASA Astrophysics Data System (ADS)

Komori, Yuichi; Ishii, Yukihiro

2010-08-01

A doubly-doped LiNbO3 (LN) crystal has been well used as a nonvolatile two-wavelength recording material. By using two levels of the crystal, two-kind holograms can be recorded on one crystal; a hologram is recorded with a 405-nm blue laser diode (LD) for a deep Mn level, and another hologram is with a 532-nm green laser for a shallow Fe level. The recording capacity doubles. A 780-nm LD is non-volatile reconstructing source since the LD line is insensitive to both levels. Multiplexed reconstructed images are demonstrated by using a sharp angular selectivity of a volume LN crystal keeping Bragg condition with spherical reconstructions.

Influence of Surrounding Dielectrics on the Data Retention Time of Doped Sb2Te Phase Change Material

NASA Astrophysics Data System (ADS)

Jedema, Friso; in `t Zandt, Micha; Wolters, Rob; Gravesteijn, Dirk

2011-02-01

The crystallization properties of as-deposited and laser written amorphous marks of doped Sb2Te phase change material are found to be only dependent on the top dielectric layer. A ZnS:SiO2 top dielectric layer yields a higher crystallization temperature and a larger crystal growth activation energy as compared to a SiO2 top dielectric layer, leading to superior data retention times at ambient temperatures. The observed correlation between the larger crystallization temperatures and larger crystal growth activation energies indicates that the viscosity of the phase change material in the amorphous state is dependent on the interfacial energy between the phase change material and the top dielectric layer.

Resonant optical scattering in nanoparticle-doped polymer photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baumberg, J. J.; Pursiainen, O. L.; Spahn, P.

2009-11-15

A broadband hyperspectral technique is used to measure the coherent optical backscatter across a wide spectral bandwidth, showing the resonant suppression of the photon transport mean free path around the photonic bandgap of a shear-assembled polymer photonic crystal. By doping with carbon nanoscale scatterers that reside at specific points within the photonic crystal lattice, the ratio between photon mean free path and optical penetration is tuned from 10 to 1, enhancing forward scatter at the expense of back-scatter. The back-scattering strength of different polarisations is not explained by any current theory.

Investigation on growth and macro-defects of Er3+-doped BaY2F8 laser crystal

NASA Astrophysics Data System (ADS)

Wang, Shuai; Ruan, Yongfeng; Tsuboi, Taiju; Zhang, Shouchao; Wang, Youfa; Tong, Hongshuang

2013-08-01

Large BaY2F8 and Er3+-doped BaY2F8 single crystals were grown by the temperature gradient method. Three kinds of macro-defects were found in BaY2F8 single crystals. These macro-defects include cracks, growth striations and straight pipes. The morphologies and distribution regularities of these macro-defects were observed and studied using a solid polarization microscope. The formation mechanisms and the methods of eliminating these defects were discussed.

Radiation-damage-assisted ferroelectric domain structuring in magnesium-doped lithium niobate

NASA Astrophysics Data System (ADS)

Jentjens, L.; Peithmann, K.; Maier, K.; Steigerwald, H.; Jungk, T.

2009-06-01

Irradiation of 5% magnesium-doped lithium niobate crystals (LiNbO3:Mg) with high-energy, low-mass 3He ions, which are transmitted through the crystal, changes the domain reversal properties of the material. This enables easier domain engineering compared to non-irradiated material and assists the formation of small-sized periodically poled domains in LiNbO3:Mg. Periodic domain structures exhibiting a width of ≈520 nm are obtained in radiation-damaged sections of the crystals. The ferroelectric poling behavior between irradiated and non-treated material is compared.

Crystal-field effects in fluoride crystals for optical refrigeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hehlen, Markus P

2010-01-01

The field of optical refrigeration of rare-earth-doped solids has recently seen an important breakthrough. The cooling of a YLiF{sub 4} (YLF) crystal doped with 5 mol% Yb3+ to 155 K by Seletskiy et al [NPhot] has surpassed the lowest temperatures ({approx}170 K for {approx}100 mW cooling capacity) that are practical with commercial multi-stage thermoelectric coolers (TEC) [Glaister]. This record performance has advanced laser cooling into an application relevant regime and has put first practical optical cryocoolers within reach. The result is also relevant from a material perspective since for the first time, an Yb3+-doped crystal has outperformed an Yb3+-doped glass.more » The record temperature of 208 K was held by the Yb3+-doped fluorozirconate glass ZBLAN. Advanced purification and glass fabrication methods currently under development are expected to also advance ZBLAN:Yb3+ to sub-TEC temperatures. However, recent achievements with YLF:Yb3+ illustrate that crystalline materials may have two potentially game-changing advantajes over glassy materials. First, the crystalline environment reduces the inhomogeneous broadening of the Yb3+ electronic transitions as compared to a glassy matrix. The respective sharpening of the crystal-field transitions increases the peak absorption cross section at the laser excitation wavelength and allows for more efficient pumping of the Yb3+ ions, particularly at low temperatures. Second, many detrimental impurities present in the starting materials tend to be excluded from the crystal during its slow growth process, in contrast to a glass where all impurities present in the starting materials are included in the glass when it is formed by temperature quenching a melt. The ultra high purity required for laser cooling materials [PRB] therefore may be easier to realize in crystals than in glasses. Laser cooling occurs by laser excitation of a rare-earth ion followed by anti-Stokes luminescence. Each such laser-cooling cycle extracts thermal energy from the solid and carries it away as high-entropy light, thereby cooling the material. In the ideal case, the respective laser-cooling power is given by the pump wavelength ({lambda}{sub p}), the mean fluorescence wavelength ({bar {lambda}}{sub L}), and the absorption coefficient (a{sub r}) of the pumped transition. These quantities are solely determined by crystal field interactions. On one hand, a large crystal-field splitting offers a favorably large difference of {lambda}{sub p} - {bar {lambda}}{sub L} and thus a high cooling efficiency {eta}{sub cool} = ({lambda}{sub p} - {bar {lambda}}{sub L})/{bar {lambda}}{sub L}. On the other hand, a small crystal-field splitting offers a high thermal population (n{sub i}) of the initial state of the pumped transition, giving a high pump absorption coefficient and thus high laser cooling power, particularly at low temperatures. A quantitative description of crystal-field interactions is therefore critical to the understanding and optimization of optical refrigeration. In the case of Yb3+ as the laser cooling ion, however, development of a crystal-field model is met with substantial difficulties. First, Yb3+ has only two 4/multiplets, {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2}, which lead to at most 7 crystal-field levels. This makes it difficult, and in some cases impossible, to evaluate the crystal-field Hamiltonian, which has at least 4 parameters for any Yb3+ point symmety lower than cubic. Second, {sup 2}F{sub 7/2}{leftrightarrow}{sup 2}F{sub 5/2} transitions exhibit an exceptionally strong electron-phonon coupling compared to 4f transitions of other rare earths. This makes it difficult to distinguish electronic from vibronic transitions in the absorption and luminescence spectra and to reliably identify the crystal-field levels. Yb3+ crystal-field splittings reported in the literature should thus generally be viewed with caution. This paper explores the effects of crystal-field interactions on the laser cooling performance of Yb3+-doped fluoride crystals. It is shown that the total crystal-field splitting of the {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2} multiplets of Yb3+ can be estimated from crystal-field splittings of other rare-earth-doped fluoride crystals. This approach takes advantage of an extensive body of experimental work from which Yb3+ doped fluoride crystals with favorable laser cooling properties might be identified. Section 2 reviews the crystal-field splitting of the 4f electronic states and introduces the crystal-field strength as a means to predict the total crystal-field splitting of the {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2} multiplets. Section 3 illustrates the effect of the total {sup 2}F{sub 7/2} crystal field splitting on the laser cooling power. Finally, Section 4 compiles literature data on crystal-field splittings in fluoride crystals from which the {sup 2}F{sub 7/2} splitting is predicted.« less

Energy levels scheme simulation of divalent cobalt doped bismuth germanate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreici, Emiliana-Laura, E-mail: andreicilaura@yahoo.com; Petkova, Petya; Avram, Nicolae M.

The aim of this paper is to simulate the energy levels scheme for Bismuth Germanate (BGO) doped with divalent cobalt, in order to give a reliable explanation for spectral experimental data. In the semiempirical crystal field theory we first modeled the Crystal Field Parameters (CFPs) of BGO:Cr{sup 2+} system, in the frame of Exchange Charge Model (ECM), with actually site symmetry of the impurity ions after doping. The values of CFPs depend on the geometry of doped host matrix and by parameter G of ECM. First, we optimized the geometry of undoped BGO host matrix and afterwards, that of dopedmore » BGO with divalent cobalt. The charges effect of ligands and covalence bonding between cobalt cations and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the CFPs we simulate the energy levels scheme of cobalt ions, by diagonalizing the matrix of the doped crystal Hamiltonian. Obviously, energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison of obtained results with experimental data shows quite satisfactory, which justify the model and simulation schemes used for the title system.« less

Synthesis and characterization of Gd-doped magnetite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Honghu; Iowa State Univ., Ames, IA; Malik, Vikash

There has been rising interest in the synthesis of magnetite nanoparticles due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. We investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizesmore » under the conditions tested (0–10 at% Gd 3+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. These results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd 3+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe (3-x)Gd xO 4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method.« less

Synthesis and characterization of Gd-doped magnetite nanoparticles

DOE PAGES

Zhang, Honghu; Iowa State Univ., Ames, IA; Malik, Vikash; ...

2016-10-04

There has been rising interest in the synthesis of magnetite nanoparticles due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. We investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizesmore » under the conditions tested (0–10 at% Gd 3+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. These results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd 3+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe (3-x)Gd xO 4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method.« less

Habit control of deuterated potassium dihydrogen phosphate crystal for laser applications

NASA Astrophysics Data System (ADS)

Guzman, L. A.; Suzuki, M.; Fujimoto, Y.; Fujioka, K.

2016-03-01

In this study we investigate the habit of partially deuterated potassium dihydrogen phosphate (DKDP) crystals in the presence of Al3+ ions. We have grown single DKDP crystals in (50wt% and 80wt%) partially deuterated solutions and in solutions doped with Al3+ ions (2 ppm) by the point-seed rapid growth technique at controlled supercooling (ΔT=10°C). The growth length of each crystal face was measured and the aspect ratio was calculated. We found that crystals grown in partially deuterated solutions are similar in aspect ratio, while, crystals grown in deuterated solutions doped with Al3+ ions showed a relative change in aspect ratio, the crystal increased in size in the pyramidal direction (vertical axis direction). Crystal characteristics were also analyzed by X-ray diffraction, FTIR and Raman spectroscopy. We have speculated that the relative habit modification is due to a probably adsorption and inclusions of Al3+ ions in the prismatic section of the crystal.

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

NASA Astrophysics Data System (ADS)

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.

Effect of silver-doping on the crystal structure, morphology and photocatalytic activity of TiO2 nanofibers

NASA Astrophysics Data System (ADS)

Barakat, N. A. M.; Kim, H. Y.

2012-09-01

In this study, effect of sliver-doping on the crystal structure, the nanofibrous morphology and the photocatalytic activity of titanium oxide nanofibers have been investigated. Silver-doped TiO2 nanofibers having different silver contents were prepared by calcination of electrospun nanofiber mats consisting of silver nitrate, titanium isopropoxide and poly(vinyl acetate) at 600 °C. The results affirmed formation of silver-doped TiO2 nanofibers composed of anatase and rutile when the silver nitrate content in the original electrospun solution was more than 3 wt%. The rutile phase content was directly proportional with the AgNO3 concentration in the electrospun solution. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that increase the silver content strongly enhances the dye oxidation process.

Travelling-solvent floating-zone growth of the dilutely Co-doped spin-ladder compound Sr14(Cu, Co)24O41

NASA Astrophysics Data System (ADS)

Bag, Rabindranath; Karmakar, Koushik; Singh, Surjeet

2017-01-01

We present here crystal growth of dilutely Co-doped spin-ladder compounds Sr14(Cu 1-x, Cox)24O41 (x = 0, 0.01, 0.03, 0.05, 0.1) using the Travelling Solvent Floating Zone (TSFZ) technique associated with an image furnace. We carried out detailed microstructure and compositional analysis. The microstructure of the frozen-in FZ revealed two bands: a lower band consisting of well-aligned single-crystalline stripes of the phase Sr14(Cu, Co)24O41 embedded in the eutectic mixture of composition SrO 18% and (Cu, Co)O 82%; and an upper band consisting of a criss-crossed pattern of these stripes. These analyses were also employed to determine the distribution coefficient of the dopants in Sr14Cu24O41. The distribution coefficient turned out to be close to 1, different from Sr2CuO3 reported previously where Co tend to accumulate in the molten zone. Direct access to the composition of the frozen-in zone eliminated any previous ambiguities associated with the composition of the peritectic point of Sr14Cu24O41; and also the eutectic point in the binary SrO-CuO phase diagram. The lattice parameters show an anisotropic variation upon Co-doping with parameters a and b increasing, c decreasing; and with an overall decrease of the unit cell volume. Magnetic susceptibility measurements were carried out on the pristine and the Co-doped crystals along the principal crystallographic axes. The spin susceptibility of the x = 0.01 crystal exhibits a strong anisotropy, which is in stark contrast with the isotropic behaviour of the pristine crystal. This anisotropy seems to arise from the intradimer exchange interaction as inferred from the anisotropy of the dimer contribution to the susceptibility of the Co-doped crystal. The Curie-tail in the magnetic susceptibility of Sr14(Cu 1-x, Cox)24O41 (x = 0, 0.01, 0.03, 0.05, 0.1) crystals (field applied parallel to the ladder) was found to scale with Co-doping - the scaling is employed to confirm a homogeneous distribution of Co in a x = 0.1 crystal boule.

Fast Response and Spontaneous Alignment in Liquid Crystals Doped with 12-Hydroxystearic Acid Gelators

PubMed Central

Lin, Hui-Chi; Wang, Chih-Hung; Wang, Jyun-Kai; Tsai, Sheng-Feng

2018-01-01

The spontaneous vertical alignment of liquid crystals (LCs) in gelator (12-hydroxystearic acid)-doped LC cells was studied. Gelator-induced alignment can be used in both positive and negative LC cells. The electro-optical characteristics of the gelator-doped negative LC cell were similar to those of an LC cell that contained a vertically aligned (VA) host. The rise time of the gelator-doped LC cell was two orders of magnitude shorter than that of the VA host LC cell. The experimental results indicate that the gelator-induced vertical alignment of LC molecules occurred not only on the surface of the indium tin oxide (ITO) but also on the homogeneous alignment layer. Various LC alignments (planar, hybrid, multistable hybrid, and vertical alignments) were achieved by modulating the doped gelator concentrations. The multistable characteristic of LCs doped with the gelator is also presented. The alignment by doping with a gelator reduces the manufacturing costs and provides a means of fabricating fast-responding, flexible LC displays using a low-temperature process. PMID:29735937

Effect of Gd3+ Ions on the Thermal Behavior, Optical, Electrical and Magnetic Properties of PbS Thin Films

NASA Astrophysics Data System (ADS)

Ravishankar, S.; Balu, A. R.; Nagarethinam, V. S.

2018-02-01

This paper reports the effect of Gd doping concentration on the thermal behavior, structural, morphological, optical, electrical and magnetic properties of PbS thin films. Gd doping concentration in PbS was varied as 0 wt.%, 1 wt.%, 2 wt.%, 3 wt.% and 4 wt.%, respectively. Thermogravimetric-Differential Thermal Analysis curves confirm that both the undoped and doped films become well crystallized above 354°C and 342°C, respectively. X-ray diffraction studies confirm that all the films exhibit face-centered cubic crystal structure with a strong (2 0 0) preferential growth. Undoped films exhibit triangular-shaped grains which modify to small cuboids with Gd doping. Energy dispersive x-ray spectra confirm the presence of Gd in the doped films. Transmission electron microscopy images confirm the presence of nanosized grains for both the undoped and doped films. The doped films showed increased transparency and improved magnetic behaviour. The results obtained confirm that Gd3+, a rare earth ion, strongly influences the physical properties of PbS thin films to a large extent.

Intrinsic Studies of Materials.

DTIC Science & Technology

RELAXATION TIME , CRYSTAL LATTICES), (*RARE EARTH ELEMENTS, *ELECTRON TRANSITIONS), (*CRYSTAL DEFECTS, INTERACTIONS), EXCITATION, DOPING, LANTHANUM COMPOUNDS, PHONONS, ATOMIC ENERGY LEVELS, HOLMIUM, CHLORIDES, PRASEODYMIUM

Systematic study of vortex pinning and liquid-glass phase transition in BaFe2-x Ni x As2 single crystals

NASA Astrophysics Data System (ADS)

Vlasenko, V. A.; Sobolevskiy, O. A.; Sadakov, A. V.; Pervakov, K. S.; Gavrilkin, S. Yu.; Dik, A. V.; Eltsev, Yu. F.

2018-01-01

The vortex pinning and liquid-glass transition have been studied in BaFe2-x Ni x As2 single crystals with different doping levels (x = 0.065; 0.093; 0.1; 0.14; 0.18). We found that Ni-doped Ba-122 has rather narrow vortex-liquid state region. Our results show that the temperature dependence of the resistivity as well as I-V characteristics of Ni-doped Ba-122 is consistent with 3D vortex-glass model. It was found that δl-pinning gives the main contribution to overall pinning in 122 Ni-doped system. The vortex phase diagrams for different doping levels were built based on the obtained data of temperature of the vortex-glass transition T g and the upper critical magnetic field H c2.

Optical study of Tm-doped solid solution (Sc0.5Y0.5)2SiO5 crystal

NASA Astrophysics Data System (ADS)

Shi, Jiaojiao; Liu, Bin; Zheng, Lihe; Wang, Qingguo; Tang, Huili; Liu, Junfang; Su, Liangbi; Wu, Feng; Zhao, Hengyu; He, Nuotian; Li, Na; Li, Qiu; Guo, Chao; Xu, Jun; Yang, Kejian; Xu, Xiaodong; Ryba-Romanowski, Witold; Lisiecki, Radosław; Solarz, Piotr

2018-04-01

Tm-doped (Sc0.5Y0.5)2SiO5 (SYSO) crystals were grown by Czochralski method. The UV-VIR-NIR absorption spectra and the near-infrared emission spectra were measured and analysed by the Judd-Ofelt approach. Temperature influence on both absorption and emission spectra has been determined from the data recorded at room temperature and 10 K. It has been found that the structural disorder resulting from dissimilar ionic radii of Sc3+ and Y3+ in the solid solution (Sc0.5Y0.5)2SiO5 crystal brings about a strong inhomogeneous broadening of Tm3+ ions spectra. However, it affects the excited state relaxation dynamics inherent to thulium-doped Y2SiO5 and Sc2SiO5 hosts weakly.

The EPR study of Mn(2+) ion doped DADT single crystal produced under high pressure and temperature.

PubMed

Ceylan, Ümit; Tapramaz, Recep

2016-01-05

An EPR study on Cu(2+) and VO(2+) doped di ammonium d-tartrate single crystals has been reported in previous papers, but the same host did not accept Mn(2+) ion at the same reaction conditions in previous trials. In this study EPR study of Mn(2+) ion doped di ammonium d tartrate single crystal, (DADT) [(NH4)2C4H4O6], produced in a reactor under high pressure and high temperature. The electronic transitions were determined by the optical absorption spectrum. Hyperfine splitting and g values of the Mn(2+) ion forming a complex in the lattice were measured from experimental spectra and spin-spin dipolar splitting parameters D and E were found by the spectrum simulation techniques. Copyright © 2015 Elsevier B.V. All rights reserved.

Computer modelling of BaY2F8: defect structure, rare earth doping and optical behaviour

NASA Astrophysics Data System (ADS)

Amaral, J. B.; Couto Dos Santos, M. A.; Valerio, M. E. G.; Jackson, R. A.

2005-10-01

BaY2F8, when doped with rare earth elements, is a material of interest in the development of solid-state laser systems, especially for use in the infrared region. This paper presents the application of a computational technique, which combines atomistic modelling and crystal field calculations, in a study of rare earth doping of the material. Atomistic modelling is used to calculate the intrinsic defect structure and the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the dopant-crystal system. Energy levels are then calculated for the Dy3+-substituted material, and comparisons with the results of recent experimental work are made.

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

NASA Astrophysics Data System (ADS)

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.

Effect of Aluminum Doping on the Nanocrystalline ZnS:Al3+ Films Fabricated on Heavily-Doped p-type Si(100) Substrates by Chemical Bath Deposition Method

NASA Astrophysics Data System (ADS)

Zhu, He-Jie; Liang, Yan; Gao, Xiao-Yong; Guo, Rui-Fang; Ji, Qiang-Min

2015-06-01

Intrinsic ZnS and aluminum-doped nanocrystalline ZnS (ZnS:Al3+) films with zinc-blende structure were fabricated on heavily-doped p-type Si(100) substrates by chemical bath deposition method. Influence of aluminum doping on the microstructure, and photoluminescent and electrical properties of the films, were intensively investigated. The average crystallite size of the films varying in the range of about 9.0 ˜ 35.0 nm initially increases and then decreases with aluminum doping contents, indicating that the crystallization of the films are initially enhanced and then weakened. The incorporation of Al3+ was confirmed from energy dispersive spectrometry and the induced microstrain in the films. Strong and stable visible emission band resulting from the defect-related light emission were observed for the intrinsic ZnS and ZnS:Al3+ films at room temperature. The photoluminescence related to the aluminum can annihilate due to the self-absorption of ZnS:Al3+ when the Al3+ content surpasses certain value. The variation of the resistivity of the films that initially reduces and then increases is mainly caused by the partial substitute for Zn2+ by Al3+ as well as the enhanced crystallization, and by the enhanced crystal boundary scattering, respectively.

Elimination of a Photovoltaic Induced Fast Instability in Photorefractive Iron-doped Lithium Niobate Crystals

NASA Astrophysics Data System (ADS)

Evans, D. R.; Saleh, M. A.; Allen, A. S.; Pottenger, T. P.; Bunning, T. J.; Guha, S.; Basun, S. A.; Cook, G.

2002-03-01

An instability on the order of 10 ns is observed while writing volume gratings in bulk crystals of iron-doped lithium niobate using contra-directional two-beam coupling along the c-axis. This instability is attributed to the quasi-breakdown of the uniform component of the photovoltaic field [1], which affects the uniform electric field formed inside the crystal causing a change in the refractive index through the electro-optic effect. A method to eliminate this instability by coating the z-surfaces of the crystal with a transparent conductive coating will be presented. [1] A. Krumins, Z. Chen, and T. Shiosaki, Opt. Comm. 117 (1995) 147-150.

UV response on dielectric properties of nano nematic liquid crystal

NASA Astrophysics Data System (ADS)

Pandey, Kamal Kumar; Tripathi, Pankaj Kumar; Misra, Abhishek Kumar; Manohar, Rajiv

2018-03-01

In this work, we investigate the effect of UV light irradiation on the dielectric parameters of nematic liquid crystal (5CB) and ZnO nanoparticles dispersed liquid crystal. With addition of nanoparticles in nematic LC are promising new materials for a variety of application in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however we optimize the properties of liquid crystal and understand how the UV light irradiation interact the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor have discussed the pure nematic LC and dispersed/doped system after, during and before UV light exposure. The dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz-10 MHz in the nematic mesophase range.

Proton and Gamma Radiation Effects in Undoped, Single-doped and co-doped YLiF4 and LuLiF4

NASA Technical Reports Server (NTRS)

Lee, Hyung; Bai, Yingxin; Yu, Kirong; Singh, U.

2009-01-01

Proton and gamma radiation effects in various YLiF4 and LuLiF4 crystals have been investigated. The radiation induced color centers compared with six different kinds of crystal samples in ranges up to 200 krads and 200 MeV. The radiation induced absorption coefficients are strongly dependent on polarization and concentration of rare-earth ions.

Motion of Doped-Polymer-Cholesteric Liquid Crystal Flakes in a Direct-Current Electric Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trajkovska Petkoska, A.; Kosc, T.Z.; Marshall, K.L.

The behavior of polymer cholesteric liquid crystal (PCLC) flakes suspended in silicone oil host fluids has been explored in the presence of a direct-current electric field. In addition to “neat” (undoped) flakes, the PCLC material was doped with either conductive, carbon-based particles or highly dielectric inorganic particles to modify the dielectric properties of the resulting PCLC flakes. Doping with conductive particles produced flakes with a net charge, and they exhibited either translational or rotational motion depending on both the distribution of dopant within the flake and the dielectric characteristics of the host fluid. Flakes doped with titania (TiO2) particles reorientedmore » 90º when suspended in a host fluid with a differing dielectric permittivity« less

Irradiation effect on luminescence properties of fluoroperovskite single crystal (LiBaF3:Eu2+)

NASA Astrophysics Data System (ADS)

Daniel, D. Joseph; Madhusoodanan, U.; Nithya, R.; Ramasamy, P.

2014-03-01

Single crystals of pure and Eu2+ doped LiBaF3 have been grown from melt by using a vertical Bridgman-Stockbarger method. Effects induced by irradiation on europium doped LiBaF3 (lithium barium fluoride) single crystals were monitored by optical absorption, photoluminescence and thermoluminescence studies. The absorption bands of Eu2+ ions with peaks at 240, 290 and 320 nm were observed in the LiBaF3:Eu2+ crystal. Drastic increase in absorption was noted below 600 nm after gamma irradiation, which was dependent on the radiation dose. The additional absorption peak at around 570 nm was observed in irradiated crystal due to the ionization process Eu2+(-)e-→Eu3+. Photoluminescence of Eu2+ doped LiBaF3 single crystal shows sharp line peaked at ~359 nm and a broad band extending between 370 and 450 nm which shows a considerable reduction in Eu2+ PL intensity after gamma irradiation. Irradiated LiBaF3:Eu2+ sample has revealed three intense TL glow peaks at 128 °C (peak-1), 281 °C (peak-2) and 407 °C (peak-3). Activation energy (E) and frequency factor (s) of the latter two peaks were determined by various heating rate (VHR) method and graphical method.

Neutron transmutation doped Ge bolometers

NASA Technical Reports Server (NTRS)

Haller, E. E.; Kreysa, E.; Palaio, N. P.; Richards, P. L.; Rodder, M.

1983-01-01

Some conclusions reached are as follow. Neutron Transmutation Doping (NTD) of high quality Ge single crystals provides perfect control of doping concentration and uniformity. The resistivity can be tailored to any given bolometer operating temperature down to 0.1 K and probably lower. The excellent uniformity is advantaged for detector array development.

Flux free single crystal growth and characterization of FeTe1-xSx (x=0.00 and 0.10) crystals

NASA Astrophysics Data System (ADS)

Maheshwari, P. K.; Awana, V. P. S.

2018-05-01

We report synthesis of S doped FeTe1-xSx (x = 0.00 and 0.10) single crystals using flux free method via solid state reaction. Single crystal XRD patterns of FeTe1-xSx (x = 0.00 and 0.10) confirm the single crystalline property, as the crystals are grown in (00l) plane only. Powder XRD result of FeTe1-xSx (x = 0.00 and 0.10) crystals show that crystalline in tetragonal structure having P4/nmm space group. Rietveld refinement results show that both a and c lattice parameters decreases with S doping of 10% at Te site in FeTe1-xSx. Detailed scanning electron microscopy (SEM) image of FeTe0.90S0.10 shows that the growth of crystal is in slab-like morphology. Electrical resistivity measurement results onset confirm the superconductivity in S doped 10% sample at Te site and superconducting transition Tconset occurs at 9.5K and Tcoffset(ρ=0) occurs at 6.5K. ρ-T measurement has been performed under various magnetic field up to 12 Tesla down to 2K. Upper critical field Hc2(0), for x=0.10, which comes around 70Tesla, 60Tesla and 45Tesla of normal resistivity criterion ρn = 90%, 50% and 10% criterion respectively.

Recent developments in the growth, processing, and testing of rare earth doped YVO{sub 4} single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mizell, G.; Fay, W.R.; Alekel, T. III

1994-12-31

The production of the laser host material YVO{sub 4} via high temperature solution growth (HTSG) is described as a facile alternative for producing optical quality crystals for research. The effects of dopant concentration on optical absorption properties in 0.7% and 3% Nd:YVO{sub 4} crystals are discussed. The rare earths ions Ho{sup 3+} and Er{sup 3+} have been doped into YVO{sub 4} with the HTSG method, and inaugural optical properties of Ho{sub 0.04}Y{sub 0.96}VO{sub 4} are presented.

Smart window using a thermally and optically switchable liquid crystal cell

NASA Astrophysics Data System (ADS)

Oh, Seung-Won; Kim, Sang-Hyeok; Baek, Jong-Min; Yoon, Tae-Hoon

2018-02-01

Light shutter technologies that can control optical transparency have been studied extensively for developing curtain-free smart windows. We introduce thermally and optically switchable light shutters using LCs doped with push-pull azobenzene, which is known to speed up thermal relaxation. The liquid crystal light shutter can be switched between translucent and transparent states or transparent and opaque states by phase transition through changing temperature or photo-isomerization of doped azobenzene. The liquid crystal light shutter can be used for privacy windows with an initial translucent state or energy-saving windows with an initial transparent state.

Er3+-doped BaY2F8 crystal waveguides for broadband optical amplification at 1.5 μm

NASA Astrophysics Data System (ADS)

Toccafondo, V.; Cerqueira S., A.; Faralli, S.; Sani, E.; Toncelli, A.; Tonelli, M.; Di Pasquale, F.

2007-01-01

Integrated waveguide amplifiers based on high concentration Er3+ doped BaY2F8 crystals are numerically studied by combining a full-vectorial finite element based modal analysis and propagation-rate equations. Using realistic input data, such as the absorption/emission cross sections and Er level lifetimes measured on grown crystal samples, we investigate the amplifier performance by optimizing the total Er concentration. We predict optimum gain coefficient up to 5dB/cm and broad amplification bandwidth exceeding 80nm with 1480nm pumping.

Investigation of TiO2 photocatalyst performance for decolorization in the presence of hydrodynamic cavitation as hybrid AOP.

PubMed

Bethi, Bhaskar; Sonawane, S H; Rohit, G S; Holkar, C R; Pinjari, D V; Bhanvase, B A; Pandit, A B

2016-01-01

In this article, an acoustic cavitation engineered novel approach for the synthesis of TiO2, cerium and Fe doped TiO2 nanophotocatalysts is reported. The prepared TiO2, cerium and Fe doped TiO2 nanophotocatalysts were characterized by XRD and TEM analysis to evaluate its structure and morphology. Photo catalytic performance of undoped TiO2 catalyst was investigated for the decolorization of crystal violet dye in aqueous solution at pH of 6.5 in the presence of hydro dynamic cavitation. Effect of catalyst doping with Fe and Ce was also studied for the decolorization of crystal violet dye. The results shows that, 0.8% of Fe-doped TiO2 exhibits maximum photocatalytic activity in the decolorization study of crystal violet dye due to the presence of Fe in the TiO2 and it may acts as a fenton reagent. Kinetic studies have also been reported for the hybrid AOP (HAOP) that followed the pseudo first-order reaction kinetics. Copyright © 2015 Elsevier B.V. All rights reserved.

Role of Er3+ concentration in spectroscopic and laser performance of CaYAlO4 crystal

NASA Astrophysics Data System (ADS)

Lv, Shaozhen; Wang, Yan; Zhu, Zhaojie; You, Zhenyu; Li, Jianfu; Wang, Hongyan; Tu, Chaoyang

2015-04-01

Three heavily Er3+-doped CaYAlO4 single crystals were successfully grown by Czochralski method. The emission spectra and the fluorescence decay curves have been recorded at room temperature. A combination of experimental data, rate equation and Dexter theory are used to investigate the influence of Er3+ doping concentration on the spectra character and the inner cross relaxation of Er3+:CaYAlO4 crystal. Results show that the self terminate effect of the transition 4I11/2 → 4I13/2 can be suppressed by heavy Er3+doping. But if the doping concentration goes too high, the much larger cross relaxation coefficient of 4I11/2 level than that of 4I13/2 level would results in the increase of up-conversion emission and the quench of near and mid infrared emission. The laser performance was also studied. The maximum output power of 225 mW at 2733 nm was acquired with an optical conversion efficiency of 14.9%.

Fast-switching optically isotropic liquid crystal nano-droplets with improved depolarization and Kerr effect by doping high k nanoparticles.

PubMed

Kim, Byeonggon; Kim, Hyun Gyu; Shim, Gyu-Yeop; Park, Ji-Sub; Joo, Kyung-Il; Lee, Dong-Jin; Lee, Joun-Ho; Baek, Ji-Ho; Kim, Byeong Koo; Choi, Yoonseuk; Kim, Hak-Rin

2018-01-10

We proposed and analyzed an optically isotropic nano-droplet liquid crystal (LC) doped with high k nanoparticles (NPs), exhibiting enhanced Kerr effects, which could be operated with reduced driving voltages. For enhancing the contrast ratio together with the light efficiencies, the LC droplet sizes were adjusted to be shorter than the wavelength of visible light to reduce depolarization effects by optical scattering of the LC droplets. Based on the optical analysis of the depolarization effects, the influence of the relationship between the LC droplet size and the NP doping ratio on the Kerr effect change was investigated.

Physical properties of V 1-xTi xO₂ (0 < x < 0.187) single crystals

DOE PAGES

Kong, Tai; Masters, Morgan W.; Bud’ko, Sergey L.; ...

2015-02-13

Free standing, low strain, single crystals of pure and titanium doped VO₂ were grown out of an excess of V ₂O₅ using high temperature solution growth techniques. At T MI ~ 340 K, pure VO₂ exhibits a clear first-order phase transition from a high-temperature paramagnetic tetragonal phase (R) to a low-temperature non-magnetic monoclinic phase (M1). With Ti doping, another monoclinic phase (M2) emerges between the R and M1 phases. The phase transition temperature between R and M2 increases with increasing Ti doping while the transition temperature between M2 and M1 decreases.

The influence of Mg doping on the formation of Ga vacancies and negative ions in GaN bulk crystals

NASA Astrophysics Data System (ADS)

Saarinen, K.; Nissilä, J.; Hautojärvi, P.; Likonen, J.; Suski, T.; Grzegory, I.; Lucznik, B.; Porowski, S.

1999-10-01

Gallium vacancies and negative ions are observed in GaN bulk crystals by applying positron lifetime spectroscopy. The concentration of Ga vacancies decreases with increasing Mg doping, as expected from the behavior of the VGa formation energy as a function of the Fermi level. The concentration of negative ions correlates with that of Mg impurities determined by secondary ion mass spectrometry. We thus attribute the negative ions to MgGa-. The negative charge of Mg suggests that Mg doping converts n-type GaN to semi-insulating mainly due to the electrical compensation of ON+ donors by MgGa- acceptors.

Optical characteristics of novel bulk and nanoengineered laser host materials

NASA Astrophysics Data System (ADS)

Prasad, Narasimha S.; Sova, Stacey; Kelly, Lisa; Bevan, Talon; Arnold, Bradley; Cooper, Christopher; Choa, Fow-Sen; Singh, N. B.

2018-02-01

The hexagonal apatite single crystals have been investigated for their applications as laser host materials. Czochralksi and flux growth methods have been utilized to obtain single crystals. For low temperature processing (<100 0C), several techniques for crystal growth have been developed. The hexagonal apatite structure (space group P63/m) is characteristic of several compounds, some of which have extremely interesting and useful properties as laser hosts and bone materials. Calcium lanthanum silicate (Nd-doped) and lanthanum aluminate material systems were studied in detail. Nanoengineered calcium and lanthanum based silicates were synthesized by a solution method and their optical and morphological characteristics were compared with Czochralski grown bulk hydroxyapatite single crystals. Materials were evaluated by absorbance, fluorescence and Raman characteristics. Neodymium, iron and chromium doped crystals grown by a solution method showed weak but similar optical properties to that of Czochralski grown single crystals.

Effects of Ca/Sr ratio control on optical and scintillation properties of Eu-doped Li(Ca,Sr)AlF6 single crystals

NASA Astrophysics Data System (ADS)

Yokota, Yuui; Tanaka, Chieko; Kurosawa, Shunsuke; Yamaji, Akihiro; Ohashi, Yuji; Kamada, Kei; Nikl, Martin; Yoshikawa, Akira

2018-05-01

Eu-doped Li(Ca,Sr)AlF6 [Eu:LiCSAF] single crystals with various Ca/Sr ratios were grown by the micro-pulling-down method, and their optical and scintillation properties were investigated to reveal the effects of Ca/Sr ratio on optical and scintillation properties of the Eu:LiCSAF single crystals. The Li(Ca1-x-ySrxEuy)AlF6 single crystals could be grown in 0 ≤ x ≤ 0.1, 0.5 ≤ x ≤ 1.0 and y = 0.02 while the Eu:LiCSAF crystals with x = 0.2, 0.25 and 0.4 included two colquiriite-type phases with different lattice parameters. The Li(Ca1-x-ySrxEuy)AlF6 single crystal with x = 0.25 and y = 0.02 showed the highest light yield under neutron irradiation.

Generation of 103 fs mode-locked pulses by a gain linewidth-variable Nd,Y:CaF2 disordered crystal.

PubMed

Qin, Z P; Xie, G Q; Ma, J; Ge, W Y; Yuan, P; Qian, L J; Su, L B; Jiang, D P; Ma, F K; Zhang, Q; Cao, Y X; Xu, J

2014-04-01

We have demonstrated a diode-pumped passively mode-locked femtosecond Nd,Y:CaF2 disordered crystal laser for the first time to our knowledge. By choosing appropriate Y-doping concentration, a broad fluorescence linewidth of 31 nm has been obtained from the gain linewidth-variable Nd,Y:CaF2 crystal. With the Nd,Y:CaF2 disordered crystal as gain medium, the mode-locked laser generated pulses with pulse duration as short as 103 fs, average output power of 89 mW, and repetition rate of 100 MHz. To our best knowledge, this is the shortest pulse generated from Nd-doped crystal lasers so far. The research results show that the Nd,Y:CaF2 disordered crystal will be a potential alternative as gain medium of repetitive chirped pulse amplification for high-peak-power lasers.

Effect of Sequential Exposition to Short- and Long-Wavelength Radiation on the Optical Absorption in the Bismuth Titanium Oxide Crystal Doped by Aluminum

NASA Astrophysics Data System (ADS)

Dyu, V. G.; Kisteneva, M. G.; Shandarov, S. M.; Khudyakova, E. S.; Smirnov, S. V.; Kargin, Yu. F.

Changes in the spectral dependences of the optical absorption induced in the bismuth titanium oxide crystal doped by aluminum as a result of sequential exposition to cw laser radiation first with the wavelength λi = 532 nm and then with the longer wavelength λn = 633, 655, 663, 780, 871, or 1064 nm are investigated. Our experiments show that after the short-wavelength exposition to radiation with λi = 532 nm, the optical absorption in the crystal increases, and in the range 470-1000 nm, yields the spectrum whose form is independent of the initial crystal state. The subsequent exposition to longer-wavelength radiation leads to enhanced transmittance of the crystal in the examined spectral range. A maximum decrease of the optical absorption in the crystal is observed upon exposure to radiation with the wavelength λn = 663 nm.

Simulation of Laser Induced Thermal Damage in Nd:YVO4 Crystals

NASA Astrophysics Data System (ADS)

Nagi, Richie

Neodymium-doped yttrium orthovanadate (Nd:YVO4) is a commonly used gain medium in Diode Pumped Solid State (DPSS) lasers, but high heat loading of Nd:YVO4 at high pump powers (≥ 5 W) leads to thermal distortions and crystal fracture, which limits the utility of Nd:YVO 4 for high power applications. In this thesis, a Nd:YVO4 crystal suffered thermal damage during experiments for investigating the optical gain characteristics of the crystal. This thesis examines the thermal damage mechanisms in detail. Principally, laser induced melting, as well as laser induced thermal stress fracture were studied, all in the absence of stimulated emission in the crystal. The optical system for coupling the pump laser light into the crystal was first simulated in Zemax, an optical design software, and the simulations were then compared to the experimental coupling efficiency results, which were found to be in agreement. The simulations for the laser coupling system were then used in conjunction with LASCAD, a finite element analysis software, to obtain the temperatures inside the crystal, as a function of optical power coupled into the crystal. The temperature simulations were then compared to the experimental results, which were in excellent agreement, and the temperature simulations were then generalized to other crystal geometries and Nd doping levels. Zemax and LASCAD were also used to simulate the thermal stress in the crystal as a function of the coupled optical power, and the simulations were compared to experiments, both of which were found to be in agreement. The thermal stress simulations were then generalized to different crystal geometries and Nd doping levels as well.

KDP crystal doped with L-arginine amino acid: growth, structure perfection, optical and strength characteristics

NASA Astrophysics Data System (ADS)

Pritula, I. M.; Kostenyukova, E. I.; Bezkrovnaya, O. N.; Kolybaeva, M. I.; Sofronov, D. S.; Dolzhenkova, E. F.; Kanaev, A.; Tsurikov, V.

2016-07-01

Potassium Dihydrogen Phosphate (KDP) crystal doped with L-arginine (L-arg) amino acid with 1.4 wt% concentration in the solution was grown onto a point seed by the method of temperature reduction. For the first time an attempt was made to grow large-size (7 × 6 × 8 cm3) optically transparent crystals, which allowed to analyze the effect of L-arg additive on the physical properties of the different growth sectors ({100} and {101}) of KDP. The incorporation of L-arg into both growth sectors of the crystal was confirmed by the methods of optical and IR spectroscopy and found to be caused by the ability of the amino acid to form hydrogen bonds with the face {100} and electrostatically interact with the positively charged face {101} of KDP crystal. A slight variation in the unit cell parameters was reported, the elementary cell volume of KDP:L-arg crystal increased in comparison with the one of pure KDP by 2·10-2 and 2.07·10-2 Å3 in the sectors {100} and {101}, respectively. It was found that the doping of L-arg enhanced the SHG efficiency of KDP and depended on the crystal growth sectors. The SHG efficiency of KDP:L-arg was by a factor 2.53 and 3.95 higher in comparison with those of pure KDP for {101} and {100} growth sector, respectively. The doping was found to lead to softening of both faces by ∼3-10% and ∼14-17% in the sectors {101} and {100}, respectively. Investigation of the influence of L-arg molecules on the bulk laser damage threshold of the crystals showed that the bulk laser damage threshold of the samples of KDP:L-arg crystal was higher than the one of the pure crystal in the sector {101} and lower in the sector {100}. The correlation between microhardness and laser damage threshold were discussed. The study is helpful for further searching, designing and simulation of hybrid NLO materials.

Tuning Superconductivity in FeSe Thin Films via Magnesium Doping.

PubMed

Qiu, Wenbin; Ma, Zongqing; Liu, Yongchang; Shahriar Al Hossain, Mohammed; Wang, Xiaolin; Cai, Chuanbing; Dou, Shi Xue

2016-03-01

In contrast to its bulk crystal, the FeSe thin film or layer exhibits better superconductivity performance, which recently attracted much interest in its fundamental research as well as in potential applications around the world. In the present work, tuning superconductivity in FeSe thin films was achieved by magnesium-doping technique. Tc is significantly enhanced from 10.7 K in pure FeSe films to 13.4 K in optimized Mg-doped ones, which is approximately 1.5 times higher than that of bulk crystals. This is the first time achieving the enhancement of superconducting transition temperature in FeSe thin films with practical thickness (120 nm) via a simple Mg-doping process. Moreover, these Mg-doped FeSe films are quite stable in atmosphere with Hc2 up to 32.7 T and Tc(zero) up to 12 K, respectively, implying their outstanding potential for practical applications in high magnetic fields. It was found that Mg enters the matrix of FeSe lattice, and does not react with FeSe forming any other secondary phase. Actually, Mg first occupies Fe-vacancies, and then substitutes for some Fe in the FeSe crystal lattices when Fe-vacancies are fully filled. Simultaneously, external Mg-doping introduces sufficient electron doping and induces the variation of electron carrier concentration according to Hall coefficient measurements. This is responsible for the evolution of superconducting performance in FeSe thin films. Our results provide a new strategy to improve the superconductivity of 11 type Fe-based superconductors and will help us to understand the intrinsic mechanism of this unconventional superconducting system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mezdrogina, M. M., E-mail: Margaret.m@mail.ioffe.ru; Vinogradov, A. Ya.; Kuzmin, R. V.

For ZnO films, nanorods, and bulk single crystals doped with Er{sup +} ions, it is shown that the effect of codopants introduced into the cation and ion sublattices and the observation of a high-intensity emission band at the wavelength λ{sub max} = 1535 nm are defined by the local environment of the Er{sup +} ion. Doping of the films and single crystals with Er{sup +} ions by diffusion brings about an infrared (IR) emission band with a low intensity because of an inadequate concentration of impurity ions. The emission intensity of this band can be raised by introducing additional Ag,more » Au, or N{sup +} impurities into the ZnO films. The UV-emission intensity of the Er-doped films and single crystals at λ{sub max} = 368–372 nm is identical to that of the undoped films. ZnO nanorods doped with Er only or together with Al or Ga codopants exhibit only one IR band (at λ{sub max} = 1535 nm), whose intensity decreases upon the introduction of codopants. Doping of the nanorods with the N{sup +} gaseous impurity during growth (930 < T < 960°C) and then with the Er{sup +} impurity by diffusion does not yield a substantial increase in the IR-emission intensity compared to the that of the corresponding band for nanorods not doped with the N{sup +} impurity. In the Er-doped nanorods, whose photoluminescence spectra exhibit a high-intensity band at λ{sub max} = 1535 nm, the UV emission band at λ{sub max} = 372 nm is practically lacking.« less

All-Optical, Photonic Band Gap Modulation in Azobenzene Liquid Crystal Doped Cholesterics (Preprint)

DTIC Science & Technology

2006-10-01

4348 5e. TASK NUMBER RG 6. AUTHOR(S) Uladzimir A . Hrozhyk, Svetlana V . Serak, and Nelson V . Tabiryan (Beam Engineering for Advanced Measurements...modulation in azobenzene liquid crystal doped cholesterics Uladzimir A . Hrozhyk, Svetlana v . Serak, Nelson V . Tabiryan Beam Engineeringfor Advanced...Tsutsumi, Science, 1995,268, 1873. [6] T. Ikeda, J Mat. Chern., 2003,13, 2037. [7] A . Urbas, J. Klosterman, V . Tondiglia, L. Natarajan, R

Optical Tuning of the Reflection of Azobenzene Liquid Crystal Doped Cholesterics (Preprint)

DTIC Science & Technology

2007-04-01

RG 6. AUTHOR(S) Uladzimir A . Hrozhyk, Svetlana V . Serak, and Nelson V . Tabiryan (Beam Engineering for Advanced Measurements Corporation) Timothy...Reflection of Azobenzene Liquid Crystal Doped Cholesterics** By Uladzimir A . Hrozhyk, Svetlana V Serak, Nelson V . Tabil)lall * and Timothy 1. Bunning...1249. [5] T. Ikeda, O. Tsutsumi, Science 1995, 268, 1873. [6] T. Ikeda, J Mat. Chern. 2003, 13, 2037. [7] A . Urbas, J. Klosterman, V . Tondiglia, L

Structure symmetry determination and magnetic evolution in Sr 2Ir 1–xRh xO 4

DOE PAGES

Ye, Feng; Wang, Xiaoping; Hoffmann, Christina; ...

2015-11-23

We use single-crystal neutron diffraction to determine the crystal structure symmetry and to study the magnetic evolution in the rhodium doped iridates Sr 2Ir 1–xRh xO 4 (0 ≤ x ≤ 0.16). Throughout this doping range, the crystal structure retains a tetragonal symmetry (space group I4 1/a) with two distinct magnetic Ir sites in the unit cell forming staggered IrO 6 rotation. Upon Rh doping, the magnetic order is suppressed and the magnetic moment of Ir4+ is reduced from 0.21 μ B/Ir for x = 0 to 0.18 μ B/Ir for x = 0.12. As a result, the magnetic structuremore » at x = 0.12 is different from that of the parent compound while the moments remain in the basal plane.« less

Donor-acceptor-pair emission in fluorescent 4H-SiC grown by PVT method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xi, E-mail: liuxi@mail.sic.ac.cn; Zhuo, Shi-Yi; Gao, Pan

Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystalmore » in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.« less

Enhanced visible light activity of nano-titanium dioxide doped with multiple ions: Effect of crystal defects

NASA Astrophysics Data System (ADS)

Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Gopakumar Warrier, Krishna

2012-12-01

Titanium dioxide photocatalysts co-doped with iron(III) and lanthanum(III) have been prepared through a modified sol-gel method. Doping with Fe3+ resulted in a relatively lower anatase to rutile phase transformation temperature, while La3+ addition reduced the crystal growth and thus retarded the phase transformation of titania nanoparticles. The presence of Fe3+ ions shifted the absorption profile of titania to the longer wavelength side of the spectrum and enhanced the visible light activity. On the other hand, La3+ addition improved the optical absorption of titania nanoparticles. Both the dopants improved the life time of excitons by proper transferring and trapping of photoexcited charges. In the present work, considerable enhancement in photocatalytic activity under visible light was achieved through synergistic effect of optimum concentrations of the two dopants and associated crystal defects.

Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass

NASA Astrophysics Data System (ADS)

Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua

2013-10-01

Eu2+-Yb3+ co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu2+ indicated the partition of Eu2+ into FAP nanocrystals in glass ceramic. NIR emission due to the transition 2F→2F of Yb3+ ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu2+ to Yb3+, which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu2+-Yb3+ co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells.

Towards spontaneous parametric down-conversion at low temperatures

NASA Astrophysics Data System (ADS)

Akatiev, Dmitrii; Boldyrev, Kirill; Kuzmin, Nikolai; Latypov, Ilnur; Popova, Marina; Shkalikov, Andrey; Kalachev, Alexey

2017-10-01

The possibility of observing spontaneous parametric down-conversion in doped nonlinear crystals at low temperatures, which would be useful for combining heralded single-photon sources and quantum memories, is studied theoretically. The ordinary refractive index of a lithium niobate crystal doped with magnesium oxide LiNbO3:MgO is measured at liquid nitrogen and helium temperatures. On the basis of the experimental data, the coefficients of the Sellmeier equation are determined for the temperatures from 5 to 300 K. In addition, a poling period of the nonlinear crystal has been calculated for observing type-0 spontaneous parametric down-conversion (ooo-synchronism) at the liquid helium temperature under pumping at the wavelength of λp = 532 nm and emission of the signal field at the wavelength of λs = 794 nm, which corresponds to the resonant absorption line of Tm3+ doped ions.

Forisome Based Smart Materials

DTIC Science & Technology

2015-03-31

different temperature and humidity conditions to stimulate crystal formation and we were able to generate crystals (Fig. 3). Staing of crystal...natural forisomes to dope the solution with a nucleation site unfortunately without success. SEO proteins have 11 cysteines that may form sulfide

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

NASA Astrophysics Data System (ADS)

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.

Tunneling dynamics of double proton transfer in formic acid and benzoic acid dimers

NASA Astrophysics Data System (ADS)

Smedarchina, Zorka; Fernández-Ramos, Antonio; Siebrand, Willem

2005-04-01

Direct dynamics calculations based on instanton techniques are reported of tunneling splittings due to double proton transfer in formic and benzoic acid dimers. The results are used to assign the observed splittings to levels for which the authors of the high-resolution spectra could not provide a definitive assignment. In both cases the splitting is shown to be due mainly to the zero-point level rather than to the vibrationally or electronically excited level whose spectrum was investigated. This leads to zero-point splittings of 375MHz for (DCOOH)2 and 1107MHz for the benzoic acid dimer. Thus, contrary to earlier calculations, it is found that the splitting is considerably larger in the benzoic than in the formic acid dimer. The calculations are extended to solid benzoic acid where the asymmetry of the proton-transfer potential induced by the crystal can be overcome by suitable doping. This has allowed direct measurement of the interactions responsible for double proton transfer, which were found to be much larger than those in the isolated dimer. To account for this observation both static and dynamic effects of the crystal forces on the intradimer hydrogen bonds are included in the calculations. The same methodology, extended to higher temperatures, is used to calculate rate constants for HH, HD, and DD transfers in neat benzoic acid crystals. The results are in good agreement with reported experimental rate constants measured by NMR relaxometry and, if allowance is made for small structural changes induced by doping, with the transfer matrix elements observed in doped crystals. Hence the method used allows a unified description of tunneling splittings in the gas phase and in doped crystals as well as of transfer rates in neat crystals.

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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.

Spectral and laser properties of Er3+/Yb3+/Ce3+ tri-doped Ca3NbGa3Si2O14 crystal at 1.55 µm

NASA Astrophysics Data System (ADS)

Gong, Guoliang; Chen, Yujin; Lin, Yanfu; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

2018-04-01

An Er3+/Yb3+/Ce3+ tri-doped Ca3NbGa3Si2O14 (CNGS) crystal was grown by the Czochralski method. Spectral properties of the crystal, including the polarized absorption and fluorescence spectra, the fluorescence decay, as well as the energy transfer efficiency from Yb3+ to Er3+ were investigated in detail. End-pumped by a 976 nm diode laser, a 1556 nm continuous-wave laser with a maximum output power of 202 mW and a slope efficiency of 11.4% was achieved in the Er,Yb,Ce:CNGS crystal. The results indicate the Er,Yb,Ce:CNGS crystal is a promising 1.55 µm laser gain medium.

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

DOE PAGES

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

2017-12-04

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 10^16 to 10^17/cm^3 range is achieved for measured As concentrations between 10^16 and 10^20/cm^3 with the highest dopingmore » efficiency of 40% occurring near 10^17 As/cm^3. 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.« less

Low temperature thermoelectric properties of p-type doped single-crystalline SnSe

NASA Astrophysics Data System (ADS)

Wang, Si; Hui, Si; Peng, Kunling; Bailey, Trevor P.; Liu, Wei; Yan, Yonggao; Zhou, Xiaoyuan; Tang, Xinfeng; Uher, Ctirad

2018-04-01

SnSe single crystals have been widely studied lately as a result of their record high ZT and controversial low thermal conductivity. Much research has focused on the high-temperature properties of single crystals and polycrystalline SnSe, but few studies were carried out on the low-temperature properties of doped single-crystalline SnSe. To study the mechanism of the charge carrier and phonon scattering, and to eliminate the ambiguity of the high temperature thermal conductivity measurement, we performed low temperature transport characterization of Na-doped and Ag-doped single-crystalline SnSe by a longitudinal steady-state technique. The electronic transport property measurements suggest that Na is a more efficient p-type dopant in SnSe than Ag. In the thermal conductivity data, we observe pronounced dielectric peak around 10 K with magnitude dependent on the doping level. In the p-type doped samples, we found that our room temperature lattice thermal conductivities (>1.74 W m-1 K-1) are in general higher than those previously reported. Based on these findings, our study implies that the lattice thermal conductivity values of doped and pure single-crystalline SnSe were underestimated.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 10^16 to 10^17/cm^3 range is achieved for measured As concentrations between 10^16 and 10^20/cm^3 with the highest dopingmore » efficiency of 40% occurring near 10^17 As/cm^3. 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.« less

Magnetic impurity effect on charge and magnetic order in doped La1.5Ca0.5CoO4

NASA Astrophysics Data System (ADS)

Horigane, K.; Hiraka, H.; Tomiyasu, K.; Ohoyama, K.; Louca, D.; Yamada, K.

2012-02-01

Neutron scattering experiments were performed on single crystals of magnetic impurity doped cobalt oxides La1.5Ca0.5CoO4 to characterize the charge and spin orders. We newly found contrasting impurity effects. Two types of magnetic peaks are observed at q = (0.5,0,L) with L = half-integer and integer in La1.5Ca0.5CoO4, while magnetic peak at L = half-integer (integer) was only observed in Mn (Fe)-substituted sample. Although Mn and Fe impurities degrade charge and magnetic order, Cr impurity stabilizes the ordering at x = 0.5. Based on the crystal structural analysis of Cr doped sample, we found that the excess oxygen and change of octahedron around Co3+ were realized in Cr doped sample.

The Preparation Conditions of Chromium Doped ZnSe and Their Effect on the Infrared Luminescence Properties

NASA Technical Reports Server (NTRS)

Burger, A.; Chattopadhyay, K.; Ndap, J.-O.; Ma, X.; Morgan, S. H.; Rablau, C. I.; Su, C. H.; Feth, S.

2000-01-01

We report the investigation by photoluminescence lifetime measurements of the near-IR emissions from a series of chromium-doped ZnSe samples, correlated to their preparation conditions. The samples were polycrystalline or single crystals prepared by post growth diffusion doping or single crystals doped during growth by the physical vapor transport method. Room temperature lifetime values between 6 and 8 micro seconds were measured for samples with Cr2+ from low 10(exp 17) to high 10(exp 18) / cubic cm range. Lifetime data taken down to 78 K was found to be rather temperature independent, reconfirming previous reports indicating a quantum yield of the corresponding emission of close to 100% at room temperature. A strong decrease in the room temperature lifetime was found for chromium concentrations higher than 10(exp 19) / cubic CM.

Electrochemical Doping of Halide Perovskites with Ion Intercalation.

PubMed

Jiang, Qinglong; Chen, Mingming; Li, Junqiang; Wang, Mingchao; Zeng, Xiaoqiao; Besara, Tiglet; Lu, Jun; Xin, Yan; Shan, Xin; Pan, Bicai; Wang, Changchun; Lin, Shangchao; Siegrist, Theo; Xiao, Qiangfeng; Yu, Zhibin

2017-01-24

Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40% reduction of transmittance in the 450-850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.

Effects of Concentration of Nanoscale Tin-Doped Indium Oxide on Electrical Breakdown of High-Resistance Liquid Crystal

NASA Astrophysics Data System (ADS)

Liang, Bau-Jy; Liu, Don-Gey; Chang, Chih-Yuan; Shie, Wun-Yi

2011-05-01

According to our previous study, a high concentration of nanoscale tin-doped indium oxide (ITO) may be beneficial for protecting liquid crystal (LC) against attacks by electrostatic discharge (ESD). In this study, the influence of high-voltage stresses in an ESD test was investigated for cells doped with different concentrations of ITO. It was found that nano-ITO with a concentration of 0.4% in weight ratio deteriorated the physical properties of LC of transparency transition and charge retention. However, our experiment showed that the capability of ESD protection for the doped LC was still improved at the ITO concentration of 0.4 wt %. This finding supports the proposed model in our previous report. The role of ITO in the LC is not always beneficial, as discussed in this paper.

Positive hysteresis of Ce-doped GAGG scintillator

NASA Astrophysics Data System (ADS)

Yanagida, Takayuki; Fujimoto, Yutaka; Koshimizu, Masanori; Watanabe, Kenichi; Sato, Hiroki; Yagi, Hideki; Yanagitani, Takagimi

2014-10-01

Positive hysteresis and radiation tolerance to high-dose radiation exposure were investigated for Ce 1% and 3% doped Gd3(Al, Ga)5O12 (Ce:GAGG) crystal scintillator on comparison with other garnet scintillators such Ce:YAG, Ce:LuAG, Pr:LuAG, and ceramic Ce:GAGG. When they were irradiated by several Gy 60Co γ-rays, Ce 1% doped GAGG crystal exhibited ∼20% light yield enhancement (positive hysteresis). This is the first time to observe positive hysteresis in Ce doped GAGG. On the other hand, other garnet materials did not show the positive hysteresis and their light yields were stable after 800 Gy irradiation except Pr:LuAG. The light yield of Pr:LuAG decreased largely. When irradiated Ce:GAGG which showed positive hysteresis was evaluated in Synchrotron facility (UVSOR), new excitation band was created around 60 nm.

Doping evolution of the second magnetization peak and magnetic relaxation in (B a1 -xKx ) F e2A s2 single crystals

NASA Astrophysics Data System (ADS)

Liu, Yong; Zhou, Lin; Sun, Kewei; Straszheim, Warren E.; Tanatar, Makariy A.; Prozorov, Ruslan; Lograsso, Thomas A.

2018-02-01

We present a thorough study of doping dependent magnetic hysteresis and relaxation characteristics in single crystals of (B a1 -xKx ) F e2A s2 (0.18 ≤x ≤1 ). The critical current density Jc reaches maximum in the underdoped sample x =0.26 and then decreases in the optimally doped and overdoped samples. Meanwhile, the magnetic relaxation rate S rapidly increases and the flux creep activation barrier U0 sharply decreases in the overdoped sample x =0.70 . These results suggest that vortex pinning is very strong in the underdoped regime, but it is greatly reduced in the optimally doped and overdoped regime. Transmission electron microscope (TEM) measurements reveal the existence of dislocations and inclusions in all three studied samples x =0.38 , 0.46, and 0.65. An investigation of the paramagnetic Meissner effect (PME) suggests that spatial variations in Tc become small in the samples x =0.43 and 0.46, slightly above the optimal doping levels. Our results support that two types of pinning sources dominate the (B a1 -xKx ) F e2A s2 crystals: (i) strong δl pinning, which results from the fluctuations in the mean free path l and δ Tc pinning from the spatial variations in Tc in the underdoped regime, and (ii) weak δ Tc pinning in the optimally doped and overdoped regime.

Doping evolution of the second magnetization peak and magnetic relaxation in ( B a 1 - x K x ) F e 2 A s 2 single crystals

DOE PAGES

Liu, Yong; Zhou, Lin; Sun, Kewei; ...

2018-02-16

Here, we present a thorough study of doping dependent magnetic hysteresis and relaxation characteristics in single crystals of (Ba 1-xK x) Fe 2As 2 (0.18 ≤ x ≤ 1). The critical current density J c reaches maximum in the underdoped sample x = 0.26 and then decreases in the optimally doped and overdoped samples. Meanwhile, the magnetic relaxation rate S rapidly increases and the flux creep activation barrier U 0 sharply decreases in the overdoped sample x = 0.70. These results suggest that vortex pinning is very strong in the underdoped regime, but it is greatly reduced in the optimallymore » doped and overdoped regime. Transmission electron microscope (TEM) measurements reveal the existence of dislocations and inclusions in all three studied samples x = 0.38, 0.46, and 0.65. An investigation of the paramagnetic Meissner effect (PME) suggests that spatial variations in T c become small in the samples x = 0.43 and 0.46, slightly above the optimal doping levels. Our results support that two types of pinning sources dominate the (Ba 1-xK x) Fe 2As 2 crystals: (i) strong δl pinning, which results from the fluctuations in the mean free path l and δT c pinning from the spatial variations in T c in the underdoped regime, and (ii) weak δT c pinning in the optimally doped and overdoped regime.« less

Doping evolution of the second magnetization peak and magnetic relaxation in ( B a 1 - x K x ) F e 2 A s 2 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yong; Zhou, Lin; Sun, Kewei

Here, we present a thorough study of doping dependent magnetic hysteresis and relaxation characteristics in single crystals of (Ba 1-xK x) Fe 2As 2 (0.18 ≤ x ≤ 1). The critical current density J c reaches maximum in the underdoped sample x = 0.26 and then decreases in the optimally doped and overdoped samples. Meanwhile, the magnetic relaxation rate S rapidly increases and the flux creep activation barrier U 0 sharply decreases in the overdoped sample x = 0.70. These results suggest that vortex pinning is very strong in the underdoped regime, but it is greatly reduced in the optimallymore » doped and overdoped regime. Transmission electron microscope (TEM) measurements reveal the existence of dislocations and inclusions in all three studied samples x = 0.38, 0.46, and 0.65. An investigation of the paramagnetic Meissner effect (PME) suggests that spatial variations in T c become small in the samples x = 0.43 and 0.46, slightly above the optimal doping levels. Our results support that two types of pinning sources dominate the (Ba 1-xK x) Fe 2As 2 crystals: (i) strong δl pinning, which results from the fluctuations in the mean free path l and δT c pinning from the spatial variations in T c in the underdoped regime, and (ii) weak δT c pinning in the optimally doped and overdoped regime.« less

Impact of carrier doping on electrical properties of laser-induced liquid-phase-crystallized silicon thin films for solar cell application

NASA Astrophysics Data System (ADS)

Umishio, Hiroshi; Matsui, Takuya; Sai, Hitoshi; Sakurai, Takeaki; Matsubara, Koji

2018-02-01

Large-grain-size (>1 mm) liquid-phase-crystallized silicon (LPC-Si) films with a wide range of carrier doping levels (1016-1018 cm-3 either of the n- or p-type) were prepared by irradiating amorphous silicon with a line-shaped 804 nm laser, and characterized for solar cell applications. The LPC-Si films show high electron and hole mobilities with maximum values of ˜800 and ˜200 cm2 V-1 s-1, respectively, at a doping level of ˜(2-4) × 1016 cm-3, while their carrier lifetime monotonically increases with decreasing carrier doping level. A grain-boundary charge-trapping model provides good fits to the measured mobility-carrier density relations, indicating that the potential barrier at the grain boundaries limits the carrier transport in the lowly doped films. The open-circuit voltage and short-circuit current density of test LPC-Si solar cells depend strongly on the doping level, peaking at (2-5) × 1016 cm-3. These results indicate that the solar cell performance is governed by the minority carrier diffusion length for the highly doped films, while it is limited by majority carrier transport as well as by device design for the lowly doped films.

Effects of fabrication methods on spin relaxation and crystallite quality in Tm-doped ? powders studied using spectral hole burning

NASA Astrophysics Data System (ADS)

Lutz, Thomas; Veissier, Lucile; Thiel, Charles W.; Woodburn, Philip J. T.; Cone, Rufus L.; Barclay, Paul E.; Tittel, Wolfgang

2016-01-01

High-quality rare-earth-ion (REI) doped materials are a prerequisite for many applications such as quantum memories, ultra-high-resolution optical spectrum analyzers and information processing. Compared to bulk materials, REI doped powders offer low-cost fabrication and a greater range of accessible material systems. Here we show that crystal properties, such as nuclear spin lifetime, are strongly affected by mechanical treatment, and that spectral hole burning can serve as a sensitive method to characterize the quality of REI doped powders. We focus on the specific case of thulium doped ? (Tm:YAG). Different methods for obtaining the powders are compared and the influence of annealing on the spectroscopic quality of powders is investigated on a few examples. We conclude that annealing can reverse some detrimental effects of powder fabrication and, in certain cases, the properties of the bulk material can be reached. Our results may be applicable to other impurities and other crystals, including color centers in nano-structured diamond.

Catalyst-free growth of Al-doped SnO2 zigzag-nanobelts for low ppm detection of organic vapours

NASA Astrophysics Data System (ADS)

Sinha, Sudip Kumar; Ghosh, Saptarshi

2016-10-01

In this effort, we report on development of specific sensors dedicated for detection of two of these volatiles, namely ethanol and acetone, below the prescribed statutory limits. Single crystalline Al-doped SnO2 zigzag nanobelt structures were deposited on Si substrate by a catalyst-free thermal evaporation method. The Al-doped SnO2 zigzag nanostructures exhibit high sensitivity and repeatability together with coveted features like fast response and excellent stability. Structural attributes involving the crystal quality and morphology of Al-doped SnO2 zigzag nanobelts were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and transmission electron microscopy. The microscopic images revealed formation of randomly oriented 'zigzag-like' nanobelts with characteristic width between 60 nm and 200 nm and length of 50-300 μm. The Al-doping was observed to have a discerning effect in enhancing the sensitivity in comparison to the pristine nanowires by creating excess oxygen vacancies in the crystal lattice, confirmed through XPS and PL spectra.

Potassium acceptor doping of ZnO crystals

NASA Astrophysics Data System (ADS)

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.

Scintillation and optical properties of Sn-doped Ga2O3 single crystals

NASA Astrophysics Data System (ADS)

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).

Reconfiguring crystal and electronic structures of MoS 2 by substitutional doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Joonki; Tan, Teck Leong; Zhao, Weijie

Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS 2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking. Electronically, a strong interaction of the Nb impurity states with the host valence bands drastically and nonlinearly modifies the electronic band structure with the valencemore » band maximum of multilayer MoS 2 at the Γ point pushed upward by hybridization with the Nb states. Finally, when thinned down to monolayers, in stark contrast, such significant nonlinear effect vanishes, instead resulting in strong and broadband photoluminescence via the formation of exciton complexes tightly bound to neutral acceptors.« less

Reconfiguring crystal and electronic structures of MoS 2 by substitutional doping

DOE PAGES

Suh, Joonki; Tan, Teck Leong; Zhao, Weijie; ...

2018-01-15

Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS 2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking. Electronically, a strong interaction of the Nb impurity states with the host valence bands drastically and nonlinearly modifies the electronic band structure with the valencemore » band maximum of multilayer MoS 2 at the Γ point pushed upward by hybridization with the Nb states. Finally, when thinned down to monolayers, in stark contrast, such significant nonlinear effect vanishes, instead resulting in strong and broadband photoluminescence via the formation of exciton complexes tightly bound to neutral acceptors.« less

Making Porous Luminescent Regions In Silicon Wafers

NASA Technical Reports Server (NTRS)

Fathauer, Robert W.; Jones, Eric W.

1994-01-01

Regions damaged by ion implantation stain-etched. Porous regions within single-crystal silicon wafers fabricated by straightforward stain-etching process. Regions exhibit visible photoluminescence at room temperature and might constitute basis of novel class of optoelectronic devices. Stain-etching process has advantages over recently investigated anodic-etching process. Process works on both n-doped and p-doped silicon wafers. Related development reported in article, "Porous Si(x)Ge(1-x) Layers Within Single Crystals of Si," (NPO-18836).

Microstructure modification and oxygen mobility of CeZrO2 nanocrystal doped with Y and Fe metals

NASA Astrophysics Data System (ADS)

Hadi, A.; Shah, M. N. A.; Ismail, K. N.; Roslan, A. B.

2017-09-01

CeZrO2-nanocrystals doped with Y3+ and Fe2+ have been successfully synthesized using the microemulsion method. In this study, the synergetic effect of the synthesis parameters on the formation of structure and catalytic property were reported. XRD analysis found that both doped samples reveal the symmetrical cubic phase and mix in a homogeneous solid solution. The crystallite size of both samples was in nanoscale, which were 11 and 15 nm for CZF and CZY, respectively. This finding was consistent with the physical size investigated by TEM, which was approximately 10 nm for both samples. Meanwhile, isotherm profiles for both samples appeared as the type IV group in the IUPAC classification which was the mesoporous materials. CZY crystal had higher BET surface area than CZF crystal, which was 141.30 and 135.5 m2/g, respectively. Oxygen mobility study found that CZF crystal promotes to active at lower temperature, which is 274.2˚C, than CZY at 302.7˚C. CZF crystal also revealed the higher oxygen removal, which was 286.35 mmol/g, than CZY was 250.49 mmol/g. The doping of transition metal, Fe into CeZrO2 tended to reduce the oxygen mobility's activation temperature, while the addition of rare earth metal, Y into CeZrO2 leaded to remarkable increase of surface area.

Role of magnetism in superconductivity of BaFe 2As 2: Study of 5d Au-doped crystals

DOE PAGES

Li, Li; Cao, Huibo; McGuire, Michael A.; ...

2015-09-09

We investigate properties of BaFe 2As 2 (122) single crystals upon gold doping, which is the transition metal with the highest atomic weight. The Au substitution into the FeAs-planes of 122 crystal structure (Au-122) is only possible up to a small amount of ~3%. We find that 5d is more effective in reducing magnetism in 122 than its counter 3d Cu, and this relates to superconductivity. We provide evidence of short-range magnetic fluctuations and local lattice inhomogeneities that may prevent strong percolative superconductivity in Ba(Fe 1-xAu x)2As 2.

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

NASA Astrophysics Data System (ADS)

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.

Inorganic photochromic and cathodochromic recording materials.

NASA Technical Reports Server (NTRS)

Duncan, R. C., Jr.; Faughnan, B. W.; Phillips, W.

1971-01-01

Discussion of studies at RCA Laboratories of the properties of rare-earth-doped CaF2, transition-metal-doped SrTiO3 and iron- or sulfur-doped sodalite as photochromic materials which change color during light or electron beam exposures. Particular attention is given to their photochromic characteristics in single-crystal and powder forms and to their cathodochromic properties in powder form. Details are given on the photochromic mechanisms, spectra, optical density, thermal decay rates, and coloring and bleaching efficiency of their single crystals and on the diffuse reflectance spectra, saturated photochromic contrast ratio, switching and erase sensitivities, and cathodochromic excitation of their photochromic powders. The many attractive characteristics of these materials when used in display storage systems are indicated.

Photoluminescence and electrical properties of Eu-doped (Na0.5Bi0.5)TiO3 ferroelectric single crystals

NASA Astrophysics Data System (ADS)

Zhang, Haiwu; Zhao, Xiangyong; Deng, Hao; Chen, Chao; Lin, Di; Li, Xiaobing; Yan, Jun; Luo, Haosu

2014-02-01

Eu3+-doped Na0.5Bi0.5TiO3 (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in 7F0 → 5D0 excitation spectra reveal that Eu3+ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi3+ and Na+ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.

Study on optical properties of L-valine doped ADP crystal

NASA Astrophysics Data System (ADS)

Shaikh, R. N.; Anis, Mohd.; Shirsat, M. D.; Hussaini, S. S.

2015-02-01

Single crystal of L-valine doped ammonium dihydrogen phosphate has been grown by slow evaporation method at room temperature. The crystalline nature of the grown crystal was confirmed using powder X-ray diffraction technique. The different functional groups of the grown crystal were identified using Fourier transform infrared analysis. The UV-visible studies were employed to examine the high optical transparency and influential optical constants for tailoring materials suitability for optoelectronics applications. The cutoff wavelength of the title crystal was found to be 280 nm with wide optical band gap of 4.7 eV. The dielectric measurements were carried to determine the dielectric constant and dielectric loss at room temperature. The grown crystal has been characterized by thermogravimetric analysis. The second harmonic generation efficiency of the grown crystal was determined by the classical Kurtz powder technique and it is found to be 1.92 times that of potassium dihydrogen phosphate. The grown crystal was identified as third order nonlinear optical material employing Z-scan technique using He-Ne laser operating at 632.8 nm.

Synergistic effect of non-covalent interaction in colloidal nematic liquid crystal doped with magnetic functionalized single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

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.

Structure and crystallization of SiO2 and B2O3 doped lithium disilicate glasses from theory and experiment.

PubMed

Erlebach, Andreas; Thieme, Katrin; Sierka, Marek; Rüssel, Christian

2017-09-27

Solid solutions of SiO 2 and B 2 O 3 in Li 2 O·2SiO 2 are synthesized and characterized for the first time. Their structure and crystallization mechanisms are investigated employing a combination of simulations at the density functional theory level and experiments on the crystallization of SiO 2 and B 2 O 3 doped lithium disilicate glasses. The remarkable agreement of calculated and experimentally determined cell parameters reveals the preferential, kinetically controlled incorporation of [SiO 4 ] and [BO 4 ] at the Li + lattice sites of the Li 2 O·2SiO 2 crystal structure. While the addition of SiO 2 increases the glass viscosity resulting in lower crystal growth velocities, glasses containing B 2 O 3 show a reduction of both viscosities and crystal growth velocities. These observations could be rationalized by a change of the chemical composition of the glass matrix surrounding the precipitated crystal phase during the course of crystallization, which leads to a deceleration of the attachment of building units required for further crystal growth at the liquid-crystal interface.

Coherent Transient Systems Evaluation

DTIC Science & Technology

1993-06-17

europium doped yttrium silicate in collaboration with IBM Almaden Research Center. Research into divalent ion doped crystals as photon gated materials...noise limited model and ignore the non-ideal properties of the medium, nonlinear effects, spatial crosstalk, gating efficiencies, local heating, the...demonstration of the coherent transient continuous optical processor was performed in europium doped yttrium silicate. Though hyperfine split ground

Cobalt-doping-induced synthesis of ceria nanodisks and their significantly enhanced catalytic activity.

PubMed

Guo, Xiao-Hui; Mao, Chao-Chao; Zhang, Ji; Huang, Jun; Wang, Wa-Nv; Deng, Yong-Hui; Wang, Yao-Yu; Cao, Yong; Huang, Wei-Xin; Yu, Shu-Hong

2012-05-21

High-quality cobalt-doped ceria nanostructures with triangular column, triangular slab, and disklike shapes are synthesized by tuning the doping amount of cobalt nitrate in a facile hydrothermal reaction. The cobalt-doped ceria nanodisks display significantly enhanced catalytic activity in CO oxidation due to exposed highly active crystal planes and the presence of numerous surface defects. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural, thermal and optical properties of KTi(0.92)La(0.08)OPO4 and KTi(0.94)Nd(0.06)OPO4.

PubMed

Sadhasivam, S; Perumal, Rajesh Narayana; Ramasamy, P

2015-10-05

KTi0.92La0.08OPO4 (KTP:La) and KTi0.94Nd0.06OPO4 (KTP:Nd) single crystals are grown using high temperature top seeded flux growth technique. The strain derived from doping is calculated from Williamson-Hall relation. The packing structure and lattice parameter of the grown crystals are analyzed using single crystal X-ray diffraction. The bonding, distortion and change in inter-atomic distances by strain effects of doping are assessed by Raman spectroscopy. Thermal stabilities of grown crystals are evaluated by specific heat capacity measurement. Pronounced high specific heat capacity is recorded as 1.16 J/gK at 498 K for KTP:Nd. Second harmonic generation intensities are measured for KTP:Nd and KTP:La single crystal. Copyright © 2015 Elsevier B.V. All rights reserved.

Bridgman growth and luminescence properties of dysprosium doped lead potassium niobate crystal

NASA Astrophysics Data System (ADS)

Liu, Wenbin; Tian, Tian; Yang, Bobo; Xu, Jiayue; Liu, Hongde

2017-06-01

Dy-doped lead potassium niobate (Pb2KNb5O15, PKN) single crystal was grown by the modified vertical Bridgman method through spontaneous nucleation. The crystal was brownish, transparent and inclusion free. Five excitation peaks of Dy3+ ions were clearly seen from near ultraviolet region to blue range. It was unique that the excitation peaks in blue range were more intense, especially the one centered at 455 nm. The emission bands consisted of blue, yellow and red emissions, which were at about 487 nm, 573 nm and 662 nm respectively. The CIE chromaticity diagram of PKN:Dy indicated that white light and yellow light could be emitted when the crystal was excited under near ultraviolet light and blue light, respectively. Thus PKN:Dy crystal is a candidate material whose emitting light could be tunable through changing the excited light wavelength.

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

DOE PAGES

Paulauskas, I. E.; Jellison, G. E.; Boatner, L. A.; ...

2011-01-01

The photoelectrochemical stability and surface-alteration characteristics of doped and undoped n-type ZnO single-crystal photoanode electrodes were investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak depended on time and the NaOH concentration in the electrolyte, but were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with themore » significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. ZnO doping methods were found to be effective in increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.« less

Assessment of growth and spectral properties of Cr3+-doped La0.83Y0.29Sc2.88(BO3)4 crystal

NASA Astrophysics Data System (ADS)

Huang, Yisheng; Sun, Shijia; Lin, Zhoubin; Zhang, Lizhen; Wang, Guofu

2017-10-01

This paper reports the spectral characteristic of Cr3+-doped La0.83Y0.29 Sc2.88 (BO3)4 crystal. Cr3+-doped La0.83Y0.29Sc2.88 (BO3)4 crystal was grown from a flux of Li6B4O9 by the top seeded Solution growth method. Cr3+:La0.83Y0.29 Sc2.88 (BO3)4 crystal exhibits broad absorption and emission bands of Cr3+ ions. The absorption cross-section σa is 3.38 × 10-20 cm2 at 467 nm and 4.40 × 10-20 cm2 at 656 nm for E//c, respectively. The emission band with a peak at 906 nm has a full width at half maximum (FWHM) of 188 nm for E//c. The emission cross-section σe at 906 nm is 2.35 × 10-20 cm2 for E//c axis and 2.03 × 10-20 cm2 for E⊥c axis. The fluorescence lifetime of 4T2 → 4A2 transition is 37.7 μs. The investigated result indicates that it may be considered as a potential CW tunable laser crystal material.

Spectroscopic analysis and efficient diode-pumped 1.9 μm Tm3+-doped β'-Gd2(MoO4)3 crystal laser.

PubMed

Tang, Jianfeng; Chen, Yujin; Lin, Yanfu; Gong, Xinghong; Huang, Jianhua; Luo, Zundu; Huang, Yidong

2011-07-04

Tm3+-doped β'-Gd2(MoO4)3 single crystal was grown by the Czochralski method. Spectroscopic analysis was carried out along different polarizations. End-pumped by a quasi-cw diode laser at 795 nm in a plano-concave cavity, an average laser output power of 58 mW around 1.9 μm was achieved in a 0.93-mm-thick crystal when the output coupler transmission was 7.1%. The absorbed pump threshold was 8 mW and the slope efficiency of the laser was 57%. This crystal has smooth and broad gain curve around 1.9 μm, which shows that it is also a potential gain medium for tunable and short pulse lasers.

Switchable multiwavelength erbium-doped photonic crystal fiber ring laser based on a length of polarization-maintaining photonic crystal fiber

NASA Astrophysics Data System (ADS)

Cheng, Jianqun; Ruan, Shuangchen

2011-11-01

A switchable multi-wavelength Erbium-doped photonic crystal fiber (ED-PCF) ring laser based on a length of polarization-maintaining photonic crystal fiber(PM-PCF) is presented and demonstrated experimentally. A segment of ED-PCF is used as linear gain medium in the resonant cavity. Due to the polarization hole burning (PHB) caused by the PM-PCF and a polarization controller (PC), the laser can operate in stable dual- or triple- wavelength modes at room temperature. The optical signal-to-noise ratio (OSNR) of the laser without any wavelength-selective components is greater than 30 dB. The amplitude variations of lasing peaks in ten minutes are less than 0.26dB for two different operating modes.

Switchable multiwavelength erbium-doped photonic crystal fiber ring laser based on a length of polarization-maintaining photonic crystal fiber

NASA Astrophysics Data System (ADS)

Cheng, Jianqun; Ruan, Shuangchen

2012-03-01

A switchable multi-wavelength Erbium-doped photonic crystal fiber (ED-PCF) ring laser based on a length of polarization-maintaining photonic crystal fiber(PM-PCF) is presented and demonstrated experimentally. A segment of ED-PCF is used as linear gain medium in the resonant cavity. Due to the polarization hole burning (PHB) caused by the PM-PCF and a polarization controller (PC), the laser can operate in stable dual- or triple- wavelength modes at room temperature. The optical signal-to-noise ratio (OSNR) of the laser without any wavelength-selective components is greater than 30 dB. The amplitude variations of lasing peaks in ten minutes are less than 0.26dB for two different operating modes.

Anomalous magneto-elastic and charge doping effects in thallium-doped BaFe 2As 2

DOE PAGES

Sefat, Athena S.; Li, Li; Cao, Huibo B.; ...

2016-02-12

Within the BaFe 2As 2 crystal lattice, we partially substitute thallium for barium and report the effects of interlayer coupling in Ba 1-xTl xFe 2As 2 crystals. We demonstrate the unusual effects of magneto-elastic coupling and charge doping in this iron-arsenide material, whereby Néel temperature rises with small x, and then falls with additional x. Specifically, we find that Néel and structural transitions in BaFe 2As 2 (T N = T s = 133 K) increase for x = 0.05 (T N = 138 K, T s = 140 K) from magnetization, heat capacity, resistivity, and neutron diffraction measurements. Evidencemore » from single crystal X-ray diffraction and first principles calculations attributes the stronger magnetism in x = 0.05 to magneto-elastic coupling related to the shorter intraplanar Fe-Fe bond distance. With further thallium substitution, the transition temperatures decrease for x = 0.09 (T N = T s = 131 K), and this is due to charge doping. Lastly, we illustrate that small changes related to 3d transition-metal state can have profound effects on magnetism.« less

Anomalous magneto-elastic and charge doping effects in thallium-doped BaFe2As2

PubMed Central

Sefat, Athena S.; Li, Li; Cao, Huibo B.; McGuire, Michael A.; Sales, Brian; Custelcean, Radu; Parker, David S.

2016-01-01

Within the BaFe2As2 crystal lattice, we partially substitute thallium for barium and report the effects of interlayer coupling in Ba1-xTlxFe2As2 crystals. We demonstrate the unusual effects of magneto-elastic coupling and charge doping in this iron-arsenide material, whereby Néel temperature rises with small x, and then falls with additional x. Specifically, we find that Néel and structural transitions in BaFe2As2 (TN = Ts = 133 K) increase for x = 0.05 (TN = 138 K, Ts = 140 K) from magnetization, heat capacity, resistivity, and neutron diffraction measurements. Evidence from single crystal X-ray diffraction and first principles calculations attributes the stronger magnetism in x = 0.05 to magneto-elastic coupling related to the shorter intraplanar Fe-Fe bond distance. With further thallium substitution, the transition temperatures decrease for x = 0.09 (TN = Ts = 131 K), and this is due to charge doping. We illustrate that small changes related to 3d transition-metal state can have profound effects on magnetism. PMID:26867821

Structural phase transition in monolayer MoTe2 driven by electrostatic doping

NASA Astrophysics Data System (ADS)

Wang, Ying; Xiao, Jun; Zhu, Hanyu; Li, Yao; Alsaid, Yousif; Fong, King Yan; Zhou, Yao; Wang, Siqi; Shi, Wu; Wang, Yuan; Zettl, Alex; Reed, Evan J.; Zhang, Xiang

2017-10-01

Monolayers of transition-metal dichalcogenides (TMDs) exhibit numerous crystal phases with distinct structures, symmetries and physical properties. Exploring the physics of transitions between these different structural phases in two dimensions may provide a means of switching material properties, with implications for potential applications. Structural phase transitions in TMDs have so far been induced by thermal or chemical means; purely electrostatic control over crystal phases through electrostatic doping was recently proposed as a theoretical possibility, but has not yet been realized. Here we report the experimental demonstration of an electrostatic-doping-driven phase transition between the hexagonal and monoclinic phases of monolayer molybdenum ditelluride (MoTe2). We find that the phase transition shows a hysteretic loop in Raman spectra, and can be reversed by increasing or decreasing the gate voltage. We also combine second-harmonic generation spectroscopy with polarization-resolved Raman spectroscopy to show that the induced monoclinic phase preserves the crystal orientation of the original hexagonal phase. Moreover, this structural phase transition occurs simultaneously across the whole sample. This electrostatic-doping control of structural phase transition opens up new possibilities for developing phase-change devices based on atomically thin membranes.

Persistent magnetism in silver-doped BaF e 2 A s 2 crystals

DOE PAGES

Li, Li; Cao, Huibo; Parker, David S.; ...

2016-10-12

Here, we investigate the thermodynamic and transport properties of silver-substituted BaF e 2 A s 2 (122) crystals up to ~ 4.5 % . Similar to other transition-metal substitutions in 122, Ag diminishes the antiferromagnetic ( T N ) and structural ( T S ) transition temperatures, but unlike other electron-doped 122s, T N and T S coincide without splitting. Though magnetism drops precipitously to T N = 84 K at doping x = 0.029 , it only weakly changes above this x , settling at T N = 80 K at x = 0.045 . Compared to this persistentmore » magnetism in Ag-122, doping other group 11 elements of either Cu or Au in 122 diminished T N and induced superconductivity near T c = 2 K at x = 0.044 or 0.031, respectively. Ag-122 crystals show reflective surfaces with surprising thicker cross sections for x ≥ 0.019 , the appearance that is in contrast to the typical thin stacked layered feature seen in all other flux-grown x-122 and lower Ag-122. We found that this physical trait may be a manifest of intrinsic weak changes in c lattice and T N . Our theoretical calculations suggest that Ag doping produces strong electronic scattering and yet a relatively small disruption of the magnetic state, both of which preclude superconductivity in this system.« less

The Preparation Conditions of Chromium Doped ZnSe and Their Effect on The Infrared Luminescence Properties

NASA Technical Reports Server (NTRS)

Burger, A.; Chattopadhyay, K.; Ndap, J.-O.; Ma, X.; Morgan, S. H.; Rablau, C. I.; Su, C.-H.; Feth, S.; Page, Ralph H.; Schaffers, Kathleen I.;

Read-write holographic memory with iron-doped lithium niobate

NASA Technical Reports Server (NTRS)

Alphonse, G. A.; Phillips, W.

1975-01-01

The response of iron doped lithium niobate under conditions corresponding to hologram storage and retrieval is described, and the material's characteristics are discussed. The optical sensitivity can be improved by heavy chemical reduction of lightly doped crystals such that most of the iron is in the divalent state, the remaining part being trivalent. The best reduction process found to be reproducible so far is the anneal of the doped crystal in the presence of a salt such as lithium carbonate. It is shown by analysis and simulation that a page-oriented read-write holographic memory with 1,000 bits per page would have a cycle time of about 60 ms and a signal-to-noise ratio of 27 db. This cycle time, although still too long for a practical system, represents an improvement of two orders of magnitude over that of previous laboratory prototypes using different storage media.

Reversal of spontaneous magnetization and spontaneous exchange bias for Sm1-xYxCrO3: The effect of Y doping

NASA Astrophysics Data System (ADS)

Zhang, Hongguang; Wang, Jianhua; Xie, Liang; Fu, Dexiang; Guo, Yanyan; Li, Yongtao

2017-11-01

We report the crystal and electronic structures and magnetic properties of non-magnetic Y3+ ion doped SmCrO3 crystals. Structural distortion and electronic structure variation are caused by cation disorder due to Y doping. Although the spin moment of Sm3+ is diluted by nonmagnetic Y ions, spin reorientation continues to exist, and the temperature-dependent magnetization reversal effect and the spontaneous exchange bias effect under zero field cooling are simultaneously induced below Neel temperature. Significantly, the method of doping promotes the achievement of temperature dependent tunable switching of magnetization and sign of a spontaneous exchange bias from positive to negative. Our work provides more tunable ways to the sign reversal of magnetization and exchange bias, which have potential application in designing magnetic random access memory devices, thermomagnetic switches and spin-valve devices.

Chromium Diffusion Doping on ZnSe Crystals

NASA Technical Reports Server (NTRS)

Journigan, Troy D.; Chen, K.-T.; Chen, H.; Burger, A.; Schaffers, K.; Page, R. H.; Payne, S. A.

1997-01-01

Chromium doped zinc selenide crystal have recently been demonstrated to be a promising material for near-IR room temperature tunable lasers which have an emission range of 2-3 micrometers. In this study a new diffusion doping process has been developed for incorporation of Cr(+2) ion into ZnSe wafers. This process has been successfully performed under isothermal conditions, at temperatures above 800 C. Concentrations in excess of 10(exp 19) Cr(+2) ions/cu cm, an order of magnitude larger than previously reported in melt grown ZnSe material, have been obtained by diffusion doping, as estimated from optical absorption measurements. The diffusivity was estimated to be about 10(exp -8) sq cm/sec using a thin film diffusion model. Resistivity was derived from current-voltage measurements and in the range of 10(exp 13) and 10(exp 16) omega-cm. The emission spectra and temperature dependent lifetime data will also be presented and discussed.

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

NASA Astrophysics Data System (ADS)

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.

Aspects of rf-heating and gas-phase doping of large scale silicon crystals grown by the Float Zone technique

NASA Astrophysics Data System (ADS)

Zobel, F.; Mosel, F.; Sørensen, J.; Dold, P.

2018-05-01

Float Zone growth of silicon crystals is known as the method for providing excellent material properties. Basic principle of this technique is the radiofrequency induction heating, main aspects of this method will be discussed in this article. In contrast to other methods, one of the advantages of the Float Zone technique is the possibility for in-situ doping via gas phase. Experimental results on this topic will be shown and discussed.

Photoluminescence of Copper-Doped Lithium Niobate Crystals

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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.

Rewritable Optical Storage with a Spiropyran Doped Liquid Crystal Polymer Film.

PubMed

Petriashvili, Gia; De Santo, Maria Penelope; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Gary, Ramla; Barberi, Riccardo

2016-03-01

Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real-time image recording feature. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analytical electron microscopic studies and positron lifetime measurements in Al-doped MgO crystals

NASA Astrophysics Data System (ADS)

Pedrosa, M. A.; Pareja, R.; González, R.; Abraham, M. M.

1987-07-01

MgO crystals intentionally doped with Al were characterized by analytical electron microscopic examinations and positron lifetime measurements. Large spinel (MgO Al2O3) precipitates were observed in samples with high contents of Al. A well-defined crystallographic relationship between the precipitates and the matrix was found. The characteristics of positron lifetime spectra appear to depend on the valence state of the different impurities in the MgO lattice suggesting that positrons are trapped by vacancy impurity complexes.

Tunability range of 245 nm in a diode-pumped Tm:BaY2F8 laser at 1.9 μm: a theoretical and experimental investigation

NASA Astrophysics Data System (ADS)

Coluccelli, N.; Gatti, D.; Galzerano, G.; Cornacchia, F.; Parisi, D.; Toncelli, A.; Tonelli, M.; Laporta, P.

2006-12-01

Extremely wide wavelength tuning ranges of up to ˜300 nm around 1.9 μm are theoretically predicted in a Tm-doped BaY2F8 crystal, on the basis of near-infrared measurements of emission and absorption cross sections. A tunability interval of 245 nm, from 1849 nm to 2059 nm, has been demonstrated by room-temperature laser experiments using a 8% Tm-doped crystal.

Ultraviolet photorefractive effect in Mg-doped near-stoichiometric LiNbO 3

NASA Astrophysics Data System (ADS)

Zhu, Dengsong; Xu, Jingjun; Qiao, Haijun; Shi, Yanli; Gao, Feng; Li, Wei; Fu, Bo; Zhang, Guaquan; Zheng, Ke

2006-10-01

The ultraviolet photorefractive effect of Mg-doped near-stoichiometric LiNbO3 crystals prepared by vapor transport equilibration (VTE) technique was studied at 351 nm. It was found in the near-stoichiometric LiNbO3 crystals that the ultraviolet photorefractive effect could be enhanced greatly with the increase of Mg concentration. Based on the activation energy of dark decay of the photorefractive grating, possible centers responsible for the ultraviolet photorefractive effect were also discussed.

Forward to cryogenic temperature: laser cooling of Yb: LuLiF crystal

NASA Astrophysics Data System (ADS)

Zhong, Biao; Luo, Hao; Lei, Yongqing; Shi, Yanling; Yin, Jianping

2017-06-01

The high quality Yb-doped fluoride crystals have broad prospects for optical refrigeration. We have laser cooled the Yb:LuLiF crystal to a temperature below the limit of current thermoelectric coolers ( 180 K). The 5% Yb:LuLiF crystal sample has a geometry of 2 mm×2 mm×5 mm and was supported by two fibers of 200 μm in diameter. They were placed in a 2×10-4 Pa vacuum chamber with an environment temperature of 294.5 K. The 1019 nm CW laser of power 38.7 W was adopted to irradiate the sample. The temperature of the sample was measured utilizing the DLT methods. After 20 minutes of laser irradiation, the 5% Yb:LuLiF crystal sample was cooled down to 182.4 K. By further optimizing experimental conditions and increasing the doped Yb concentration, the Yb:LuLiF crystal might be optically cooled below the cryogenic temperature of 123K in the near future.

Homogeneity and variation of donor doping in Verneuil-grown SrTiO3:Nb single crystals

PubMed Central

Rodenbücher, C.; Luysberg, M.; Schwedt, A.; Havel, V.; Gunkel, F.; Mayer, J.; Waser, R.

2016-01-01

The homogeneity of Verneuil-grown SrTiO3:Nb crystals was investigated. Due to the fast crystal growth process, inhomogeneities in the donor dopant distribution and variation in the dislocation density are expected to occur. In fact, for some crystals optical studies show variations in the density of Ti3+ states on the microscale and a cluster-like surface conductivity was reported in tip-induced resistive switching studies. However, our investigations by TEM, EDX mapping, and 3D atom probe reveal that the Nb donors are distributed in a statistically random manner, indicating that there is clearly no inhomogeneity on the macro-, micro-, and nanoscale in high quality Verneuil-grown crystals. In consequence, the electronic transport in the bulk of donor-doped crystals is homogeneous and it is not significantly channelled by extended defects such as dislocations which justifies using this material, for example, as electronically conducting substrate for epitaxial oxide film growth. PMID:27577508

CdO as the archetypical transparent conducting oxide. Systematics of dopant ionic radius and electronic structure effects on charge transport and band structure.

PubMed

Yang, Yu; Jin, Shu; Medvedeva, Julia E; Ireland, John R; Metz, Andrew W; Ni, Jun; Hersam, Mark C; Freeman, Arthur J; Marks, Tobin J

2005-06-22

A series of yttrium-doped CdO (CYO) thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates at 410 degrees C by metal-organic chemical vapor deposition (MOCVD), and their phase structure, microstructure, electrical, and optical properties have been investigated. XRD data reveal that all as-deposited CYO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CYO thin films exhibit excellent optical transparency, with an average transmittance of >80% in the visible range. Y doping widens the optical band gap from 2.86 to 3.27 eV via a Burstein-Moss shift. Room temperature thin film conductivities of 8,540 and 17,800 S/cm on glass and MgO(100), respectively, are obtained at an optimum Y doping level of 1.2-1.3%. Finally, electronic band structure calculations are carried out to systematically compare the structural, electronic, and optical properties of the In-, Sc-, and Y-doped CdO systems. Both experimental and theoretical results reveal that dopant ionic radius and electronic structure have a significant influence on the CdO-based TCO crystal and band structure: (1) lattice parameters contract as a function of dopant ionic radii in the order Y (1.09 A) < In (0.94 A) < Sc (0.89 A); (2) the carrier mobilities and doping efficiencies decrease in the order In > Y > Sc; (3) the dopant d state has substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.

Lead zirconate titanate (PZT)-based thin film capacitors for embedded passive applications

NASA Astrophysics Data System (ADS)

Kim, Taeyun

Investigations on the key processing parameters and properties relationship for lead zirconate titanate (PZT, 52/48) based thin film capacitors for embedded passive capacitor application were performed using electroless Ni coated Cu foils as substrates. Undoped and Ca-doped PZT (52/48) thin film capacitors were prepared on electroless Ni coated Cu foil by chemical solution deposition. For PZT (52/48) thin film capacitors on electroless Ni coated Cu foil, voltage independent (zero tunability) capacitance behavior was observed. Dielectric constant reduced to more than half of the identical capacitor processed on Pt/SiO2/Si. Dielectric properties of the capacitors were mostly dependent on the crystallization temperature. Capacitance densities of almost 350 nF/cm2 and 0.02˜0.03 of loss tangent were routinely measured for capacitors crystallized at 575˜600°C. Leakage current showed dependence on film thickness and crystallization temperature. From a two-capacitor model, the existence of a low permittivity interface layer (permittivity ˜30) was suggested. For Ca-doped PZT (52/48) thin film capacitors prepared on Pt, typical ferroelectric and dielectric properties were measured up to 5 mol% Ca doping. When Ca-doped PZT (52/48) thin film capacitors were prepared on electroless Ni coated Cu foil, phase stability was influenced by Ca doping and phosphorous content. Dielectric properties showed dependence on the crystallization temperature and phosphorous content. Capacitance density of ˜400 nF/cm2 was achieved, which is an improvement by more than 30% compared to undoped composition. Ca doping also reduced the temperature coefficient of capacitance (TCC) less than 10%, all of them were consistent in satisfying the requirements of embedded passive capacitor. Leakage current density was not affected significantly by doping. To tailor the dielectric and reliability properties, ZrO2 was selected as buffer layer between PZT and electroless Ni. Only RF magnetron sputtering process could yield stable ZrO2 layers on electroless Ni coated Cu foil. Other processes resulted in secondary phase formation, which supports the reaction between PZT capacitor and electroless Ni might be dominated by phosphorous component. (Abstract shortened by UMI.)

Thermodynamic Vortex-Lattice Phase Transitions in Bi_2Sr_2CaCu_2O_8

NASA Astrophysics Data System (ADS)

Majer, Daniel

1996-03-01

Recent measurements by the microscopic Hall-sensor arrays technique of the anomalous second magnetization peak and the magnetization step at the first-order transition in Bi_2Sr_2CaCu_2O8 (BSCCO)(B. Khaykovich, E. Zeldov, D. Majer, T.W. Li, P.H. Kes, and M. Konczykowski, (preprint).) have revealed new evidence, which suggest that these two phenomena are of related origin. The first-order transition(E. Zeldov, D. Majer, M. Konczykowski, V.B. Geshkenbein, V.M. Vinokur, and H. Shtrikman, Nature 375), 373 (1995). at higher temperatures ends at a critical point and it seems that a second-order transition (the fish-tail) continues to lower temperatures. Local magnetization measurements were carried out on several as-grown BSCCO crystals (T_c~= 90 K) and on two crystals annealed in air at 500^circC (over-doped with T_c~= 83.5 K) and at 800^circC (optimally-doped, T_c~= 89 K). The annealing was used to change the oxygen stoichiometry of the crystals and as a consequence their anisotropy. All as-grown crystals from two sources show practically identical phase diagrams. The first-order phase transition lines in the B-T phase diagram of the annealed crystals however, are shifted significantly. In the over-doped crystal the line is shifted to higher fields, and the optimally-doped crystal to lower fields as compared to the as-grown crystals. Theoretical predictions of both the melting and the decoupling transitions in HTSC are anisotropy dependent, and the observed shifts can not be used to distinguish between these theories. However, the temperature dependence of the transition line in the decoupling scenario fits the observed data much better than the melting scenario. The first-order transition step vanishes in all three types of crystals at a critical point which is anisotropy dependent. At lower temperatures the second magnetization peak is observed. The second peak line in the B-T phase diagram of all the crystals measured starts very close to the critical point and is shifted by the same extent as the corresponding first-order transition line. The two lines seem to form one continuous phase transition line that changes from first-order to presumably second-order at the critical point. In collaboration with B. Khaykovich, T.W. Li, P.H. Kes, M. Konczykowski, and E. Zeldov.

Facile synthesis of 2-D Cu doped WO3 nanoplates with structural, optical and differential anti cancer characteristics

NASA Astrophysics Data System (ADS)

Mehmood, Faisal; Iqbal, Javed; Gul, Asma; Ahmed, Waqqar; Ismail, M.

2017-04-01

Simple chemical co-precipitation method has been employed to synthesize two dimensional copper (Cu) doped tungsten oxide (WO3) nanoplates. A numbers of characterization techniques have been used to investigate their structural, optical and biocompatible anti cancer properties. The XRD results have confirmed the monoclinic crystal structure of WO3 nanoplates, and also successful doping of Cu ions into the WO3 crystal lattice. The presence of functional groups and chemical bonding have been verified through FTIR and Raman spectroscopy. The SEM images demonstrate that both undoped and Cu doped WO3 samples have squares plate like morphology. The EDX spectra confirm the presence of Cu, W and O ions. Diffuse reflectance spectroscopy (DRS) analysis has revealed a substantial red-shift in the absorption edge and a decrease in the band gap energy of nanoplates with Cu doping. Photoluminescence spectroscopy has been used to study the presence of defects like oxygen vacancies. Furthermore, the differential cytotoxic properties of Cu doped WO3 samples have been evaluated against human breast (MCF-7) and liver (Hep-2) cancer cells with ectocervical epithelial (HECE) healthy cells. The present findings confirm that the Cu doped WO3 nanoplates can be used as an efficient biocompatible anti cancer agent.

Why Sn doping significantly enhances the dielectric properties of Ba(Ti1-xSnx)O3

NASA Astrophysics Data System (ADS)

Shi, Tao; Xie, Lin; Gu, Lin; Zhu, Jing

2015-02-01

Through appropriate doping, the properties of BaTiO3-based ferroelectrics can be significantly enhanced. To determine the physical process induced by the doping of Sn atoms in Ba(Ti0.8Sn0.2)O3, we performed high-resolution scanning transmission electron microscopy experiments and observed that the regions with low Sn content formed polar nano regions (PNRs) embedded in the matrix in Ba(Ti0.8Sn0.2)O3. The interactions among Sn, Ti, Ba and O atoms were determined using first principles calculations. Based on the characteristics of the electronic structure and crystal lattice strain fields, the effects of doping with Sn were investigated. The Sn doping not only changed the electronic structure of the crystal but also increased the dielectric properties of the PNRs. Moreover, the Sn doping was also responsible for the diffuse phase transition of the Ba(Ti1-xSnx)O3 material. The effects mentioned in this paper are universal in lead-free ferroelectrics, and similar elements such as Sb, Mg, and Zr may have the same functions in other systems. Thus, these results provide guidance for the design of the doping process and new systems of ferroelectric or relaxor materials.

Luminomagnetic Eu3+- and Dy3+-doped hydroxyapatite for multimodal imaging.

PubMed

Tesch, Annemarie; Wenisch, Christoph; Herrmann, Karl-Heinz; Reichenbach, Jürgen R; Warncke, Paul; Fischer, Dagmar; Müller, Frank A

2017-12-01

Multimodal imaging has recently attracted much attention due to the advantageous combination of different imaging modalities, like photoluminescence (PL) and magnetic resonance imaging (MRI). In the present study, luminescent and magnetic hydroxyapatites (HAp) were prepared via doping with europium (Eu 3+ ) and dysprosium (Dy 3+ ), respectively. Co-doping of Eu 3+ and Dy 3+ was used to combine the desired physical properties. Both lanthanide ions were successfully incorporated in the HAp crystal lattice, where they preferentially occupied calcium(I) sites. While Eu-doped HAp (Eu:HAp) exhibits dopant concentration dependent persistent PL properties, Dy-doped HAp (Dy:HAp) shows paramagnetic behavior due to the high magnetic moment of Dy 3+ . Co-doped HAp (Eu:Dy:HAp) nanoparticles combine both properties in one single crystal. Remarkably, multimodal co-doped HAp features enhanced PL properties due to an energy transfer from Dy 3+ sensitizer to Eu 3+ activator ions. Eu:Dy:HAp exhibits strong transverse relaxation effects with a maximum transverse relaxivity of 83.3L/(mmol·s). Due to their tunable PL, magnetic properties and cytocompatibility Eu:-, Dy:- and Eu:Dy:HAp represent promising biocompatible ceramic materials for luminescence imaging that simultaneously may serve as a contrast agent for MRI in permanent implants or functional coatings. Copyright © 2017 Elsevier B.V. All rights reserved.

Why Sn doping significantly enhances the dielectric properties of Ba(Ti1-xSnx)O3

PubMed Central

Shi, Tao; Xie, Lin; Gu, Lin; Zhu, Jing

2015-01-01

Through appropriate doping, the properties of BaTiO3-based ferroelectrics can be significantly enhanced. To determine the physical process induced by the doping of Sn atoms in Ba(Ti0.8Sn0.2)O3, we performed high-resolution scanning transmission electron microscopy experiments and observed that the regions with low Sn content formed polar nano regions (PNRs) embedded in the matrix in Ba(Ti0.8Sn0.2)O3. The interactions among Sn, Ti, Ba and O atoms were determined using first principles calculations. Based on the characteristics of the electronic structure and crystal lattice strain fields, the effects of doping with Sn were investigated. The Sn doping not only changed the electronic structure of the crystal but also increased the dielectric properties of the PNRs. Moreover, the Sn doping was also responsible for the diffuse phase transition of the Ba(Ti1-xSnx)O3 material. The effects mentioned in this paper are universal in lead-free ferroelectrics, and similar elements such as Sb, Mg, and Zr may have the same functions in other systems. Thus, these results provide guidance for the design of the doping process and new systems of ferroelectric or relaxor materials. PMID:25721479

Crystal growth and scintillation properties of Pr-doped SrI2 single crystals

NASA Astrophysics Data System (ADS)

Yokota, Yuui; Ito, Tomoki; Yoshino, Masao; Yamaji, Akihiro; Ohashi, Yuji; Kurosawa, Shunsuke; Kamada, Kei; Yoshikawa, Akira

2018-04-01

Pr-doped SrI2 (Pr:SrI2) single crystals with various Pr concentrations were grown by the halide-micro-pulling-down (H-μ-PD) method, and the scintillation properties were investigated. Pr1%:SrI2 single crystal with high transparency could be grown by the H-μ-PD method while Pr2, 3 and 5%:SrI2 single crystals included some cracks and opaque parts. In the photoluminescence spectrum of the Pr1%:SrI2 single crystal, an emission peak originated from the Pr3+ ion was observed around 435 nm while the radioluminescence spectra showed an emission peak around 535 nm for the undoped SrI2 and Pr:SrI2 single crystals. Light yields of Pr1, 2, 3 and 5%:SrI2 single crystals under γ-ray irradiation were 7700, 8700, 7200 and 6700 photons/MeV, respectively. Decay times of Pr1 and 2%:SrI2 single crystals under γ-ray irradiation were 55.9 and 35.0 ns of the fast decay component, and 435 and 408 ns of the slow decay component, respectively.

Structural and optical properties of pure and copper doped zinc oxide nanoparticles

NASA Astrophysics Data System (ADS)

Sajjad, Muhammad; Ullah, Inam; Khan, M. I.; Khan, Jamshid; Khan, M. Yaqoob; Qureshi, Muhammad Tauseef

2018-06-01

Pure and copper-doped zinc oxide nanoparticles (NPs) have been synthesized via chemical co-precipitation method where hydrazine is used as reducing agent and aqueous extract of Euphorbia milii plant as capping agent. Main objectives of the reported work are to investigate the effect of copper doping on crystal structure of ZnO nanoparticles; to study the effect of copper doping on optical band gap of ZnO nanoparticles and photoluminescence (PL) study of pure and copper-doped ZnO nanoparticles. To achieve the aforementioned objectives, XRD and SEM tests were performed for the identification and confirmation of crystal structure and morphology of the prepared samples. From XRD data the average grain size for pure ZnO was observed to be 24.62 nm which was first decreased to 18.95 nm for 5 wt% Cu-doped sample and then it was found to increase up to 37.80 nm as the Cu doping was increased to 7 wt%. Optical band gap of pure and Cu-doped ZnO nanoparticles was calculated from diffuse reflectance spectroscopy (DRS) spectra and was found to decrease from 3.13 eV to 2.94 eV as the amount of Cu increases up to 7 wt%. In photoluminescence study, PL technique was used and enhanced visible spectrum was observed. For further characterization FT-IR and EDX tests were also carried out.

Experimental Realization of Efficient, Room Temperature Single-Photon Sources with Definite Circular and Linear Polarizations

NASA Astrophysics Data System (ADS)

Boutsidis, Christos

In this thesis I present experimental demonstrations of room-temperature, single-photon sources with definite linear and circular polarizations. Definite photon polarization increases the efficiency of quantum communication systems. In contrast with cryogenic-temperature single-photon sources based on epitaxial quantum dots requiring expensive MBE and nanofabrication, my method utilizes a mature liquid crystal technology, which I made consistent with single-emitter fluorescence microscopy. The structures I have prepared are planar-aligned cholesteric liquid crystals forming 1-D photonic bandgaps for circularly-polarized light, which were used to achieve definite circularly-polarized fluorescence of single emitters doped in this environment. I also used planar-aligned nematic liquid crystals to align single molecules with linear dipole moments and achieved definite linearly-polarized fluorescence. I used single nanocrystal quantum dots, single nanodiamond color-centers, rare-earth-doped nanocrystals, and single terrylene and DiIC18(3) dye molecules as emitters. For nanocrystal quantum dots I observed circular polarization dissymmetry factors as large as ge = --1.6. In addition, I observed circularly-polarized resonances in the fluorescence of emitters within a cholesteric microcavity, with cavity quality factors of up to Q ˜ 250. I also showed that the fluorescence of DiIC18(3) dye molecules in planar-aligned nematic cells exhibits definite linear polarization, with a degree of polarization of rho = --0.58 +/- 0.03. Distributed Bragg reflectors form another type of microcavity that can be used to realize a single-photon source. I characterized the fluorescence from nanocrystal quantum dots doped in the defect layers of such microcavites, both organic and inorganic. Finally, to demonstrate the single-photon properties of single-emitter-doped cholesteric and nematic liquid crystal structures and distributed Bragg reflector microcavities, I present observations of photon antibunching from emitters doped in each of these structures. These experimental observations include photon antibunching from: nanocrystal quantum dots and nanodiamond color-centers doped in a cholesteric microcavity; terrylene and DiIC 18(3) dye molecules doped in nematic structures, and nanocrystal quantum dots doped in the distributed Bragg reflector microcavity. A value of the zero-time second-order coherence as low as g(2)(0) = 0.001 +/- 0.03 was measured. These results represent an important step forward in the realization of room temperature single-photon sources with definite polarization for secure quantum communication.

Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

PubMed Central

Parmar, Narendra S.; Yim, Haena; Choi, Ji-Won

2017-01-01

Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm−3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20–0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C. PMID:28272444

Microscopic, Transport and Thermodynamic properties of Ca10(Pt3As8)((Fe1-xTMx)2As2)5 (TM=Co, Ni) single crystals

NASA Astrophysics Data System (ADS)

Jiang, Shan; Ni, Ni

2015-03-01

Here we report detailed microscopic, transport and thermodynamic measurements on two series of high quality single crystals Ca10(Pt3As8)((Fe1-xTMx)2As2)5 (TM=Co, Ni). With electron doping on Fe sites, the structural/magnetic phase transitions in the parent compound were suppressed at a rate of roughly -7K per 0.01Co doping and -9K per 0.01Ni doping. Superconductivity emerges in the region of 0 . 048 < x < 0 . 20 for Co doping with optimal Tc of 13.5K (x = 0 . 11) while it occurs in the region of 0 . 035 < x < 0 . 11 for Ni doping with optimal Tc of 9.6K (x = 0 . 064). No coexistence of AFM and SC is observed, which is different from the well-studied 122 Fe-pnictides but reminiscent the one of La1111. The comparison of the effect between Co- and Ni- doping on 10-3-8 shows that rigid band approximation is likely working for these two dopants in this superconducting family.

Effect of cobalt doping on the mechanical properties of ZnO nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vahtrus, Mikk; Šutka, Andris

In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases weremore » close to theoretical strength indicating high quality of NWs. Dependence of mechanical properties on NW diameter was found for both doped and undoped ZnO NWs. - Highlights: •Effect of Co doping on the mechanical properties of ZnO nanowires is studied. •Co substitutes Zn atoms in ZnO crystal lattice. •Co addition affects crystal lattice parameters. •Co addition results in significantly decreased Young's modulus of ZnO. •Bending strength for doped and undoped wires is close to the theoretical strength.« less

Reentrant metal-insulator transition in the Cu-doped manganites La1-x Pbx MnO3 (x˜0.14) single crystals

NASA Astrophysics Data System (ADS)

Zhao, B. C.; Song, W. H.; Ma, Y. Q.; Ang, R.; Zhang, S. B.; Sun, Y. P.

2005-10-01

Single crystals of La1-x Pbx Mn1-y-z Cuy O3 ( x˜0.14 ; y=0 ,0.01,0.02,0.04,0.06; z=0.02 ,0.08,0.11,0.17,0.20) are grown by the flux growth technique. The effect of Cu doping at the Mn-site on magnetic and transport properties is studied. All studied samples undergo a paramagnetic-ferromagnetic transition. The Curie temperature TC decreases and the transition becomes broader with increasing Cu-doping level. The high-temperature insulator-metal (I-M) transition moves to lower temperature with increasing Cu-doping level. A reentrant M-I transition at the low temperature T* is observed for samples with y⩾0.02 . In addition, T* increases with increasing Cu-doping level and is not affected by applied magnetic fields. Accompanying the appearance of T* , there exists a large, almost constant magnetoresistance (MR) below T* except for a large MR peak near TC . This reentrant M-I transition is ascribed to charge carrier localization due to lattice distortion caused by the Cu doping at Mn sites.

Effects of increasing size and changing europium activator concentration in KCaI3 scintillator crystals

NASA Astrophysics Data System (ADS)

Lindsey, Adam C.; Zhuravleva, Mariya; Wu, Yuntao; Stand, Luis; Loyd, Matthew; Gokhale, Sasmit; Koschan, Merry; Melcher, Charles L.

2016-09-01

KCaI3:Eu crystals have been identified as very promising for use in spectroscopic detector applications related to nuclear nonproliferation and domestic security efforts. Initial studies have shown for small crystals a few mm3 in size with 3% europium dopant concentration, a high light yield of >70,000 ph/MeV and energy resolution of ≈3% at 662 keV is attainable which is comparable with the highest performance scintillators discovered. In this work, single crystals of KCaI3 with a range of Eu2+ doping between 0 and 5 at% substituting for Ca2+ were grown at 22 mm diameter and their performance for gamma-ray spectroscopy studied. Comparisons among crystals approximately Ø22 mm×22 mm (8.4 cm3 or ≈0.5 in3) provide a more accurate understanding of how scintillation performance changes with Eu doping and increased crystal size. KCaI3 in the undoped form is shown to be a highly efficient intrinsic scintillator with a defect-related emission at 404 nm which coexists with the Eu2+ 5d-4f emission in low dopant concentrations and is completely re-absorbed in more heavily doped crystals. For larger crystals, effects from self-absorption due to Eu activation become more evident by a near doubling of decay time for 0.5 in3 crystals as the activator is increased from 0.5 to 5.0 at% Eu. Comparisons of pulse-height spectra obtained for Ø22 mm×22 mm cylinders with varying Eu concentration suggests best performance is achieved using lower Eu additions closer to 0.5-1.0 at%. Using a modified crystal packaging featuring an offset reflector geometry, 0.5 in3 crystals of KCaI3:Eu can attain under 4% energy resolution at 662 keV.

Femtosecond laser pulse induced phase transition of Cr-doped Sb2Te1 films studied with a pump-probe system

NASA Astrophysics Data System (ADS)

Jiang, Minghui; Wang, Qing; Lei, Kai; Wang, Yang; Liu, Bo; Song, Zhitang

2016-10-01

The Femtosecond laser pulse induced phase transition dynamics of Cr-doped Sb2Te1 films was studied by real-time reflectivity measurements with a pump-probe system. It was found that crystallization of the as-deposited CrxSb2Te1 phase-change thin films exhibits a multi-stage process lasting for about 40ns.The time required for the multi-stage process seems to be not related to the contents of Cr element. The durations of the crystallization and amorphization processes are approximately the same. Doping Cr into Sb2Te1 thin film can improve its photo-thermal stability without obvious change in the crystallization rate. Optical images and image intensity cross sections are used to visualize the transformed regions. This work may provide further insight into the phase-change mechanism of CrxSb2Te1 under extra-non-equilibrium conditions and aid to develop new ultrafast phase-change memory materials.

Optical and electrical properties of heavily indium-doped CdS around the semiconductor-metal phase transition

NASA Astrophysics Data System (ADS)

Broser, I.; Broser, R.; Birkicht, E.

1990-04-01

Heavily indium-doped CdS crystals are studied by comparing their optical and electrical properties. It is shown that in the near infrared spectral region for highly conducting crystals the correlation of electrical conductivity and optical effects can still be understood in the frame of the classical Drude-Lorentz model. Even for high doping the relaxation time τ and the effective mass m ∗ of the electrons are not markedly different from the room temperature values of "pure" crystals. At photon energies near the band gap, however, optical spectra in transmission, reflectivity, and emission show clearly the existence of band-tails and screening effects. A different situation holds for a highly compensated specimen: They are in a wide temperature region highly isolating, show activated photoconductivity and special structures in the optical spectra near the band gap. Their properties can be explained by assuming a meandering bandbending due to the combined action of donors and acceptors and the assumption of spatially isolated electron and hole droplets [6].

Enhancement of thermoelectric figure of merit in β-Zn{sub 4}Sb{sub 3} by indium doping control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Pai-Chun, E-mail: pcwei68@gmail.com, E-mail: cheny2@phys.sinica.edu.tw; Hsu, Chia-Hao; Chang, Chung-Chieh

2015-09-21

We demonstrate the control of phase composition in Bridgman-grown β-Zn{sub 4}Sb{sub 3} crystals by indium doping, an effective way to overcome the difficulty of growing very pure β-Zn{sub 4}Sb{sub 3} thermoelectric material. The crystal structures are characterized by Rietveld refinement with synchrotron X-ray diffraction data. The results show an anisotropic lattice expansion in In-doped β-Zn{sub 4}Sb{sub 3} wherein the zinc atoms are partially substituted by indium ones at 36f site of R-3c symmetry. Through the elimination of ZnSb phase, all the three individual thermoelectric properties are simultaneously improved, i.e., increasing electrical conductivity and Seebeck coefficient while reducing thermal conductivity. Undermore » an optimal In concentration (x = 0.05), pure phase β-Zn{sub 4}Sb{sub 3} crystal can be obtained, which possesses a high figure of merit (ZT) of 1.4 at 700 K.« less

Effect of Te doping on FeSe superconductor synthesized by powder-in-tube

NASA Astrophysics Data System (ADS)

Imaduddin, A.; Nisa, K.; Yudanto, S. D.; Nugraha, H.; Siswayanti, B.

2017-04-01

FeSe is a superconducting material, which has the simplest crystal structure among the Fe-based superconductors. It has no arsenic element, which is very harmful to the human body. In this study, we analyzed the effects of milling time and Te doping on FeSe superconductors. The synthesis of the samples were carried out using powder-in-tube method in a SS304 stainless steel tube. After the pressing process, followed by the sintering process at 500° C for 20 hours, the samples were removed from the tubes. Later, we analyzed its crystal structures, surfaces morphology and the superconductivity properties. Δ-FeSe phase (hexagonal, non-superconductor) and β-FeSe (tetragonal, superconductor) were formed in the samples, including minor phases of Fe and Fe3Se4. Te doping changed the crystal structure from β-FeSe and Δ-FeSe into FeSe0.5Te0.5. In addition, the onset critical temperature (TC, onset) shifted to higher temperature.

Spectroscopic and crystal-field analysis of new Yb-doped laser materials

NASA Astrophysics Data System (ADS)

Haumesser, Paul-Henri; Gaumé, Romain; Viana, Bruno; Antic-Fidancev, Elisabeth; Vivien, Daniel

2001-06-01

Crystal-field effects are very important as far as laser performances of Yb-doped materials are concerned. In order to simplify the interpretation of low-temperature spectra, two tools derived from a careful examination of crystal-field interaction are presented. Both approaches are successfully applied in the case of new Yb-doped materials, namely Ca3Y2(BO3)4 (CYB), Ca3Gd2(BO3)4 (CaGB), Sr3Y(BO3)3 (SrYBO), Ba3Lu(BO3)3 (BLuB), Y2SiO5 (YSO), Ca2Al2SiO7 (CAS) and SrY4(SiO4)3O (SYS). The 2F7/2 splitting is particularly large in these materials and favourable to a quasi-three-level laser operating scheme. Calculations performed using the point charge electrostatic model for these compounds and using a consistent set of effective atomic charges confirm the experimental results. This should permit to use this model in a predictive approach.

Luminescence of BaBrI and SrBrI single crystals doped with Eu2+

NASA Astrophysics Data System (ADS)

Shalaev, A. A.; Shendrik, R.; Myasnikova, A. S.; Bogdanov, A.; Rusakov, A.; Vasilkovskyi, A.

2018-05-01

The crystal growth procedure and luminescence properties of pure and Eu2+-doped BaBrI and SrBrI crystals are reported. Emission and excitation spectra were recorded under ultraviolet and vacuum ultraviolet excitations. The energy of the first Eu2+ 4f-5d transition and SrBrI band gap are obtained. The electronic structure calculations were performed within GW approximation as implemented in the Vienna Ab Initio Simulation Package. The energy between lowest Eu2+ 5d state and the bottom of conduction band are found based on luminescence quenching parameters. The vacuum referred binding energy diagram of lanthanide levels was constructed using the chemical shift model.

Growth, structural, spectroscopic and optical characterization of barium doped calcium tartrate

NASA Astrophysics Data System (ADS)

Verma, Seema; Raina, Bindu; Gupta, Vandana; Bamzai, K. K.

2018-05-01

Barium doped calcium tartrates synthesized by controlled diffusion using silica gel technique at ambient temperature was characterized by single crystal X-ray diffraction which establishes monoclinic crystal system with volume of the unit cell 923.97(10) Ǻ3 and the space group being P21. UV - Vis characterization gives various linear optical constants like absorption, transmittance, reflectance, band gap, extinction coefficient, urbach energy, complex dielectric constant, optical and electrical conductivity. These constants are considered to be essential in characterizing materials that are used in various applications like fabrication of optoelectronic devices. FTIR spectrum establishes the presence of various bands of functional groups expected from metal tartrate with water of crystallization.

Heavily Yb-doped phosphate large-mode area all-solid photonic crystal fiber operating at 990 nm

NASA Astrophysics Data System (ADS)

Wang, Longfei; He, Dongbing; Feng, Suya; Yu, Chunlei; Hu, Lili; Qiu, Jianrong; Chen, Danping

2015-07-01

We demonstrate, for the first time to our knowledge, a 16 wt.% Yb-doped phosphate large-mode area all-solid photonic crystal fiber (AS-PCF) laser operating at 990 nm. By carefully tailoring the absorption and emission properties of the active glass and designing the structure of AS-PCF, the excitation of the 990 nm laser and the depression of the laser above 1 µm can be easily realized even without any wavelength-selective optics. The single-mode behavior of PCF with a 35 µm doped core, the largest core diameter of approximately 1 µm in phosphate fiber, is theoretically investigated by finite-difference time-domain method and experimentally confirmed.

Passively Q-switched Tm:BaY2F8 lasers

NASA Astrophysics Data System (ADS)

Yu, Haohai; Veronesi, Stefano; Mateos, Xavier; Petrov, Valentin; Griebner, Uwe; Parisi, Daniela; Tonelli, Mauro

2013-07-01

We demonstrate passive Q-switching (PQS) of the Tm-doped BaY2F8 (Tm:BYF) laser for the first time. The Tm:BYF laser is diode-pumped using an L-shaped hemispherical resonator. In the cw regime, the maximum output power with an 18% Tm-doped BYF crystal reached 1.12 W at ~1920 nm for an absorbed pump power of 3.06 W. In the PQS regime, maximum pulse energy (720 μJ) and peak power (17.1 kW) were obtained with an 8% Tm-doped BYF crystal and a Cr:ZnS saturable absorber with 92% low-signal transmission, again near 1920 nm, for a pulse width of ~40 ns and a repetition rate of 50 Hz.

Light-directing self-organized 1D and 3D chiral liquid crystalline nanostructures

NASA Astrophysics Data System (ADS)

Li, Quan; Bisoyi, Hari K.

2015-03-01

A brief overview of recent research and developments in our laboratory toward the fabrication and application of photoresponsive cholesteric liquid crystals, microshells and microdroplets, and blue phase is presented here. We have designed and synthesized a variety of light-driven chiral molecular switches and doped into achiral nematic liquid crystals hosts to obtain photoresponsive cholesteric liquid crystals and blue phase. By irradiation with light of suitable wavelengths, it has been possible to tune the reflection color of cholesteric liquid crystals and blue phase over a wide range across the visible spectrum. By doping upconversion nanoparticles into photoresponsive cholesteric liquid crystals, the reflection color tuning has been accomplished by irradiation with near infrared light. Moreover, cholesteric microshells have been fabricated which exhibit omnidirectional lasing. Similarly, cholesteric microdroplets have been found to display omnidirectional selective reflection and photonic cross communication. Wide-range non-mechanical beam steering has been demonstrated in a phoresponsive cholesteric liquid crystal sample. This short summary of our recent research work shows that the century old fascinating cholesteric liquid crystals have diverse opportunities to offer.

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

NASA Astrophysics Data System (ADS)

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.

Blue diode-pumped solid-state-laser based on ytterbium doped laser crystals operating on the resonance zero-phonon transition

DOEpatents

Krupke, William F.; Payne, Stephen A.; Marshall, Christopher D.

2001-01-01

The invention provides an efficient, compact means of generating blue laser light at a wavelength near .about.493+/-3 nm, based on the use of a laser diode-pumped Yb-doped laser crystal emitting on its zero phonon line (ZPL) resonance transition at a wavelength near .about.986+/-6 nm, whose fundamental infrared output radiation is harmonically doubled into the blue spectral region. The invention is applied to the excitation of biofluorescent dyes (in the .about.490-496 nm spectral region) utilized in flow cytometry, immunoassay, DNA sequencing, and other biofluorescence instruments. The preferred host crystals have strong ZPL fluorecence (laser) transitions lying in the spectral range from .about.980 to .about.992 nm (so that when frequency-doubled, they produce output radiation in the spectral range from 490 to 496 nm). Alternate preferred Yb doped tungstate crystals, such as Yb:KY(WO.sub.4).sub.2, may be configured to lase on the resonant ZPL transition near 981 nm (in lieu of the normal 1025 nm transition). The laser light is then doubled in the blue at 490.5 nm.

Defect levels of semi-insulating CdMnTe:In crystals

NASA Astrophysics Data System (ADS)

Kim, K. H.; Bolotinikov, A. E.; Camarda, G. S.; Hossain, A.; Gul, R.; Yang, G.; Cui, Y.; Prochazka, J.; Franc, J.; Hong, J.; James, R. B.

2011-06-01

Using photoluminescence (PL) and current deep-level transient spectroscopy (I-DLTS), we investigated the electronic defects of indium-doped detector-grade CdMnTe:In (CMT:In) crystals grown by the vertical Bridgman method. We similarly analyzed CdZnTe:In (CZT:In) and undoped CdMnTe (CMT) crystals grown under the amount of same level of excess Te and/or indium doping level to detail the fundamental properties of the electronic defect structure more readily. Extended defects, existing in all the samples, were revealed by synchrotron white beam x-ray diffraction topography and scanning electron microscopy. The electronic structure of CMT is very similar to that of CZT, with shallow traps, A-centers, Cd vacancies, deep levels, and Te antisites. The 1.1-eV deep level, revealed by PL in earlier studies of CZT and CdTe, were attributed to dislocation-induced defects. In our I-DLTS measurements, the 1.1-eV traps showed different activation energies with applied bias voltage and an exponential dependence on the trap-filling time, which are typical characteristics of dislocation-induced defects. We propose a new defect-trap model for indium-doped CMT crystals.

Gallium hole traps in irradiated KTiOPO{sub 4}:Ga crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grachev, V.; Meyer, M.; Malovichko, G.

2014-12-07

Nominally pure and gallium doped single crystals of potassium titanyl phosphate (KTiOPO{sub 4}) have been studied by Electron Paramagnetic Resonance at low temperatures before and after irradiation. Irradiation with 20 MeV electrons performed at room temperature and liquid nitrogen temperature caused an appearance of electrons and holes. Gallium impurities act as hole traps in KTiOPO{sub 4} creating Ga{sup 4+} centers. Two different Ga{sup 4+} centers were observed, Ga1 and Ga2. The Ga1 centers are dominant in Ga-doped samples. For the Ga1 center, a superhyperfine structure with one nucleus with nuclear spin ½ was registered and attributed to the interaction of galliummore » electrons with a phosphorus nucleus or proton in its surrounding. In both Ga1 and Ga2 centers, Ga{sup 4+} ions substitute for Ti{sup 4+} ions, but with a preference to one of two electrically distinct crystallographic positions (site selective substitution). The Ga doping eliminates one of the shortcomings of KTP crystals—ionic conductivity of bulk crystals. However, this does not improve significantly the resistance of the crystals to electron and γ-radiation.« less

Luminescence properties of Eu3+ doped CdF2 single crystals

NASA Astrophysics Data System (ADS)

Boubekri, H.; Diaf, M.; Guerbous, L.; Jouart, J. P.

2018-04-01

This paper reports the photoluminescence properties of Eu3+ doped CdF2 single crystals. The pulled crystals were prepared by use of the Bridgman technique from a vacuum furnace in fluoride atmosphere. Absorption, excitation and emission spectra of the crystal doped with three Eu3+ concentrations (0.02%, 0.1% and 0.6% mol.) were recorded at room temperature. The emission spectra exhibit a strong yellow and red emissions in the spectral range 550-720 nm which are assigned to 5D0 → 7FJ (J = 1, 2, 4) transitions and a weak infrared emission around 816 nm corresponding to 5D0 → 7F6 transition. The magnetic dipole emission (5D0 → 7F1) is the most intense for each Eu3+ concentration. The Judd-Ofelt intensity parameters Ω2, Ω4, Ω6 for 4f-4f transitions of Eu3+ ions were computed from the emission spectra using the 5D0 → 7FJ (J = 1, 2, 4, 6) transitions. Via these phenomenological intensity parameters, the spontaneous emission probabilities, branching ratios, radiative lifetimes, quantum efficiencies and emission cross-sections for the main Eu3+ emitting levels are evaluated.

Spectroscopic and laser characterization of Yb,Tm:KLu(WO4)2 crystal

NASA Astrophysics Data System (ADS)

Loiko, P. A.; Serres, J. M.; Mateos, X.; Demesh, M. P.; Yasukevich, A. S.; Yumashev, K. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

2016-01-01

We report on a comprehensive spectroscopic and laser characterization of monoclinic Yb,Tm:KLu(WO4)2 crystals. Stimulated-emission cross-section spectra corresponding to the 3F4 → 3H6 transition of Tm3+ ions are determined. The radiative lifetime of the 3F4 state of Tm3+ ions is 0.82 ms. The maximum Yb3+ → Tm3+ energy transfer efficiency is 83.9% for 5 at.% Yb - 8 at.% Tm doping. The fractional heat loading for Yb,Tm:KLu(WO4)2 is 0.45 ± 0.05. Using a hemispherical cavity and 5 at.% Yb - 6 at.% Tm doped crystal, a maximum CW power of 227 mW is achieved at 1.983-2.011 μm with a maximum slope efficiency η = 14%. In the microchip laser set-up, the highest slope efficiency is 20% for a 5 at.% Yb- 8 at.% Tm doped crystal with a maximum output power of 201 mW at 1.99-2.007 μm. Operation of Yb,Tm:KLu(WO4)2 as a vibronic laser emitting at 2.081-2.093 μm is also demonstrated.

Color centers inside crystallic active media

NASA Astrophysics Data System (ADS)

Mierczyk, Zygmunt; Kaczmarek, Slawomir M.; Kopczynski, Krzysztof

1995-03-01

This paper presents research results on color centers induced by radiation of a xenon lamp in non doped crystals of yttrium aluminum garnet Y3Al5O12 (YAG), strontium- lanthanum aluminate SrLaAlO4 (SLAO), strontium-lanthanum gallate SrLaGa3O7 (SLGO), and in doped crystals: Nd:YAG, Cr, Tm, Ho:YAG (CTH:YAG), Nd:SLAO and Nd:SLGO. In all these investigated crystals under the influence of intensive exposure by xenon lamp radiation additional bands connected with centers O-2, O2 and centers F came up near the short-wave absorption edge. In the case of doped crystals the observed processes are much more complicated. In crystals CTH:YAG the greatest perturbations in relation to basic state are present at the short-wave absorption edge, as well as on areas of absorption bands of ions Cr+3 and Tm+3 conditioning the sensibilization process of ions Ho+3. These spectral structure disturbances essentially influence the efficiency of this process, as proven during generating investigations. In the case of SrLaGa3O7:Nd+3 under the influence of exposure substantial changes of absorption spectrum occurred on spectral areas 346 divided by 368 nm, 429 divided by 441 nm and 450 divided by 490 nm. Those changes have an irreversible character. They disappear not before the plate is being held at oxidizing atmosphere. Investigations of laser rods Nd:SLGO, CTH:YAG, and Nd:YAG in a free generation demonstrated that the color centers of these crystals are induced by pomp radiation from the spectral area up to 450 nm.

Results for aliovalent doping of CeBr3 with Ca2+

NASA Astrophysics Data System (ADS)

Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Patrick Doty, F.; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Joshua; Yuan, Ding

2014-01-01

Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was used as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown, i.e., 1.9% of the CeBr3 molecules were replaced by CaBr2 molecules, to match our target replacement of 1 out of 54 cerium atoms be replaced by a calcium atom. Precisely the mixture was composed of 2.26 g of CaBr2 added to 222.14 g of CeBr3. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were studied using the density functional theory within the generalized gradient approximation. Calculated lattice parameters are in agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

Density functional theory study of dopant effect on formation energy of intrinsic point defects in germanium crystals

NASA Astrophysics Data System (ADS)

Yamaoka, S.; Kobayashi, K.; Sueoka, K.; Vanhellemont, J.

2017-09-01

During the last decade the use of single crystal germanium (Ge) layers and structures in combination with silicon (Si) substrates has led to a revival of defect research on Ge. Ge is used because of the much higher carrier mobility compared to Si, allowing to design devices operating at much higher frequencies. A major issue for the use of Ge single crystal wafers is the fact that all Czochralski-grown Ge (CZ-Ge) crystals are vacancy-rich and contain vacancy clusters that are much larger than the ones in Si. In contrast to Si, control of intrinsic point defect concentrations has not yet been realized at the same level in Ge crystals due to the lack of experimental data especially on dopant effects. In this study, we have evaluated with density functional theory (DFT) calculations the dopant effect on the formation energy (Ef) of the uncharged vacancy (V) and self-interstitial (I) in Ge and compared the results with those for Si. The dependence of the total thermal equilibrium concentrations of point defects (sum of free V or I and V or I paired with dopant atoms) at melting temperature on the type and concentration of various dopants is obtained. It was found that (1) Ge crystals will be more V-rich by Tl, In, Sb, Sn, As and P doping, (2) Ge crystals will be more I-rich by Ga, C and B doping, (3) Si doping has negligible impact. The dopant impact on Ef of V and I in Ge has a narrower range and is smaller than that in Si. The obtained results are useful to control grown-in V and I concentrations, and will perhaps also allow to develop defect-free ;perfect; Ge crystals.

Random lasing in dye-doped polymer dispersed liquid crystal film

NASA Astrophysics Data System (ADS)

Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

2016-09-01

A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

Effect of annealing on doping of graphene with molybdenum oxide

NASA Astrophysics Data System (ADS)

Ishikawa, Ryousuke; Watanabe, Sho; Nishida, Hiroki; Aoyama, Yuki; Oya, Tomoya; Nomoto, Takahiro; Tsuboi, Nozomu

2018-04-01

We investigated the effect of post-annealing on the doping of graphene with MoO3 in this study. The as-deposited molybdenum oxide thin film prepared using our method was not completely oxidized; in addition, it was in an amorphous state, due to which its doping effect was not significant. As the post-deposition annealing temperature was increased, the oxidation and crystallization of the molybdenum oxide progressed and the doping effect increased accordingly. After annealing at 350 °C, the holes were the most doped and the sheet resistance was the lowest. The doped graphene film obtained in this study shows higher doping effect and stability compared to other dopants.

Low-voltage tunable color in full visible region using ferroelectric liquid-crystal-doped cholesteric liquid-crystal smart materials

NASA Astrophysics Data System (ADS)

Lin, Jia-De; Lin, Jyun-Wei; Lee, Chia-Rong

2018-02-01

Electrical tuning of photonic bandgap (PBG) of cholesteric liquid crystal (CLC) without deformation within the entire visible region at low voltages is not easy to achieve. This study demonstrates low-voltage-tunable PBG in full visible region with less deformation of the PBG based on smart materials of ferroelectric liquid crystal doped CLC (FLC-CLC) integrating with electrothermal film heaters. Experimental results show that the reflective color of the FLC-CLC can be low-voltage-tuned through entire visible region. The induced temperature change is induced by electrically heating the electrothermal film heaters at low voltages at near the smectic-CLC transition temperature. Coaxial electrospinning can be used to develop smart fibrous devices with FLC/CLC-core and polymer-shell which color is tunable in full visible region at low voltages.

Thermally switchable photonic band-edge to random laser emission in dye-doped cholesteric liquid crystals

NASA Astrophysics Data System (ADS)

Ye, Lihua; Wang, Yan; Feng, Yangyang; Liu, Bo; Gu, Bing; Cui, Yiping; Lu, Yanqing

2018-03-01

By changing the doping concentration of the chiral agent to adjust the relative position of the reflection band of cholesteric liquid crystals and the fluorescence emission spectrum of the dye, photonic band-edge and random lasing were observed, respectively. The reflection band of the cholesteric phase liquid crystal can also be controlled by adjusting the temperature: the reflection band is blue-shifted with increasing temperature, and a reversible switch from photonic band-edge to random lasing is obtained. Furthermore, the laser line width can be thermally adjusted from 1.1 nm (at 27 °C) to 4.6 nm (at 32.1 °C). A thermally tunable polarization state of a random laser from dual cells was observed, broadening the field of application liquid crystal random lasers.

Variability of the resulting microdeformation field in the Zn1 - x V x Se crystals (0.01 ≤ x ≤ 0.10)

NASA Astrophysics Data System (ADS)

Maksimov, V. I.; Maksimova, E. N.; Surkova, T. P.

2018-01-01

A detailed neutronographic study of the bulk ZnSe crystals doped with vanadium up to the content commensurate with the solubility limit in a semiconductor matrix has been carried out for the first time at room temperature. The data that characterize nonuniformly-deformed states based on the cubic structural modification of the II-VI compounds are obtained. A simplified analysis of the broadening patterns of the diffraction profiles of main Bragg reflexes of the studied crystals shows that the resulting deformation covers macroscopic volumes, and the distribution of vanadium ions in the given cases may significantly deviate from the uniform distribution over volume. Relative to the initial cubic lattice, dominating trends towards symmetry changes preceding the phase stratification in the ZnSe crystals heavily doped with vanadium are revealed.

Characteristics of Un doped and Europium-dopedSrI2 Scintillator Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sturm, Benjamin; Cherepy, Nerine; Drury, Owen

2012-01-01

High energy resolution gamma-ray detectors that can be formed into relatively large sizes while operating at room temperature offer many advantages for national security applications. We are working toward that goal through the development of SrI{sub 2}(Eu) scintillator detectors, which routinely provide <;3.0% energy resolution at 662 keV with volumes >;10 cm{sup 3}. In this study, we have tested pure, undoped SrI{sub 2} to gain a better understanding of the scintillation properties and spectroscopic performance achievable without activation. An undoped crystal grown from 99.999% pure SrI{sub 2} pellets was tested for its spectroscopic performance, its light yield, and uniformity ofmore » scintillation light collection as a function of gamma-ray interaction position relative to the crystal growth direction. Undoped SrI{sub 2} was found to provide energy resolution of 5.3% at 662 keV, and the light collection nonuniformity varied by only 0.72% over the length of the crystal. Measurements of both a 3% Eu-doped and the undoped SrI{sub 2} crystal were carried out in the SLYNCI facility and indicate differences in their light yield non-proportionality. The surprisingly good scintillation properties of the pure SrI{sub 2} crystal suggests that with high-purity feedstock, further reduction of the Eu concentration can be made to grow larger crystals while not adversely impacting the spectroscopic performance.« less

Potassium acceptor doping of ZnO crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parmar, Narendra S., E-mail: nparmar@wsu.edu; Lynn, K. G.; Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814

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 observedmore » 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.« less

Co-doping effects on luminescence and scintillation properties of Ce doped (Lu,Gd)3(Ga,Al)5O12 scintillator

NASA Astrophysics Data System (ADS)

Yamaguchi, Hiroaki; Kamada, Kei; Kurosawa, Shunsuke; Pejchal, Jan; Shoji, Yasuhiro; Yokota, Yuui; Ohashi, Yuji; Yoshikawa, Akira

2016-11-01

Mg co-doping effects on scintillation properties of Ce:Lu1Gd2(Ga,Al)5O12 (LGGAG) were investigated. Mg 200 ppm co-doped Ce:LGGAG single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg co-doping. Ce4+ charge transfer absorption was observed below 300 nm in Mg,Ce:LGGAG which is in good agreement with previous reports. The scintillation decay times were accelerated by Mg co-doping.

Solid state optical refrigeration using stark manifold resonances in crystals

DOEpatents

Seletskiy, Denis V.; Epstein, Richard; Hehlen, Markus P.; Sheik-Bahae, Mansoor

2017-02-21

A method and device for cooling electronics is disclosed. The device includes a doped crystal configured to resonate at a Stark manifold resonance capable of cooling the crystal to a temperature of from about 110K to about 170K. The crystal host resonates in response to input from an excitation laser tuned to exploit the Stark manifold resonance corresponding to the cooling of the crystal.

Optical and dielectric studies of KH2PO4 crystal influenced by organic ligand of citric acid and L-valine: A single crystal growth and comparative study

NASA Astrophysics Data System (ADS)

Anis, Mohd; Hakeem, D. A.; Muley, G. G.

In the present study pure, citric acid (CA) and L-valine (LV) doped potassium dihydrogen phosphate (KDP) crystals have been grown with the aim to investigate the nonlinear optical applications facilitated by UV-visible, third order nonlinear optical (TONLO) and dielectric properties. The structural parameters of grown crystals have been confirmed by single crystal X-ray diffraction analysis. The enhancement in optical transparency of KDP crystal due to addition of CA and LV has been examined within 200-900 nm by means of UV-visible spectral analysis. In addition, the transmittance data have been used to evaluate the effect of dopants on reflectance, refractive index and extinction coefficient of grown crystals in the visible region. The Z-scan analysis has been performed at 632.8 nm to identify the nature of photoinduced nonlinear refraction and nonlinear absorption in doped KDP crystals. The influence of π-bonded ligand of dopant CA and LV on TONLO susceptibility (χ3), refractive index (n2) and absorption coefficient (β) of KDP crystals has been evaluated to discuss laser assisted device applications. The decrease in dielectric constant and dielectric loss of KDP crystal due to addition of CA and LV has been explored using the temperature dependent dielectric studies.

Effect of homolog doping on surface morphology and mass-loss rates from PETN crystals. Studies using atomic force microscope and thermo-gravimetric analysis

DOE PAGES

Bhattacharya, S. K.; Maiti, A; Gee, R. H.; ...

2012-08-28

Pentaerythritol tetranitrate (PETN) is an important energetic material and its performance as a secondary explosive depends strongly on the density as well as flow porosity of powdered material, which in turn is governed by the size and surface properties of the PETN crystallite particles. Historically there has been evidence that the surface properties of PETN particles can be strongly influenced by the presence of homolog impurities of PETN, in particular, dipentaerythritol hexanitrate (diPEHN) and tripentaerythritol octanitrate (triPEON), although not many systematic studies characterizing such influence exist. In this work we employ thermogravimetric analysis (TGA) to measure mass-loss rates at elevatedmore » temperatures and show that doping with a small amount of diPEHN and triPEON can reduce the mass-loss rate from PETN single-crystal surfaces by as much as 35 % as compared to undoped crystals. Arrhenius plots of mass-loss rates as a function of temperature suggest that the reduction in evaporation is not due to the change in activation barrier of the molecular evaporation process, but perhaps due to the impedance to the receding motion of the steps by the immobile impurities on the surface. Removal of surface impurities through gentle washing with ethanol leads to enhanced mass-loss rate relative to pure PETN suggesting a roughened surface morphology. Some surface roughening in doped crystals is supported by Atomic force microscopy (AFM) images of growth layers that show evidences of growth layer stacking and rough edges. Furthermore, we find that a larger amount of impurity added to the original solution does not necessarily lead to a more highly doped crystal, which could perhaps be interpreted as PETN crystals being able to accommodate only up to a certain weight percent of homolog impurities.« less

The synergistic effect of nitrogen-doped titanium dioxide/mercaptobenzoic acid/silver nanocomplexes for surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Feng, Jun; Bao, Wenyuan; Li, Lijun; Cheng, Hao; Huang, Wenyi; Kong, Hongxing; Li, Yanqing

2018-03-01

We synthesized titanium dioxide (TiO2) and nitrogen-doped TiO2 nanoparticles (N-TiO2 NPs) via a sol-hydrothermal method using ammonium chloride (NH4Cl) as the nitrogen (N) source. Furthermore, an N-TiO2/4-mercaptobenzoic acid (4-MBA)/silver (Ag) nanocomplex served as an active substrate for surface-enhanced Raman scattering (SERS) and was prepared by self-assembly. During SERS, the Raman signals of 4-MBA of the N-TiO2/MBA/Ag nanocomplexes exhibited higher intensity and sensitivity than pure TiO2/MBA/Ag, with 1% N doping in N-TiO2, producing the strongest Raman signals. We characterized the N-TiO2 hybrid materials by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible diffuse reflectance spectra. N doping did not influence the phase of the TiO2 crystal. The doped N entered into the crystal lattice of the TiO2, replacing some oxygen (O) to form Ti-O-N or Ti-N-O linkage. The results indicated that an appropriate amount of N doping could enhance the SERS performance of the TiO2 SERS substrate via N substitution doping. These doping forms were beneficial to the molecular charge transfer (CT), and this resulted in improved SERS performance for N-doped TiO2 NPs. We attributed this improvement to the formation of N-doping energy levels that were beneficial to the process of TiO2 to MBA molecule CT. This work not only enriched the nonmetal-doped CT mechanism in SERS but also provided several reference values for practical applications. [Figure not available: see fulltext.

Chrystal structure properties of Al-doped Li{sub 4}Ti{sub 5}O{sub 12} synthesized by solid state reaction method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandi, Dianisa Khoirum, E-mail: dianisa875@gmail.com; Suryana, Risa, E-mail: rsuryana@staff.uns.ac.id; Priyono, Slamet, E-mail: slam013@lipi.go.id

2016-02-08

This research aim is to analyze the effect of Aluminum (Al) doping in the structural properties of Al-doped Li{sub 4}Ti{sub 5}O{sub 12} as anode in lithium ion battery. Al-doped Li{sub 4}Ti{sub 5}O{sub 12} powders were synthesized by solid state reaction method. LiOH.H{sub 2}O, TiO{sub 2}, and Al{sub 2}O{sub 3} were raw materials. These materials were milled for 15 h, calcined at temperature of 750{sup o}C and sintered at temperature of 800{sup o}C. Mole percentage of doping Al (x) was varied at x=0; x=0.025; and x =0.05. Al-doped Li{sub 4}Ti{sub 5}O{sub 12} powders were synthesized by solid state reaction method. X-ray diffractionmore » was employed to determine the structure of Li{sub 4}Ti{sub 5}O{sub 12}. The PDXL software was performed on the x-ray diffraction data to estimate the phase percentage, the lattice parameter, the unit cell volume, and the crystal density. Al-doped Li{sub 4}Ti{sub 5}O{sub 12} has cubic crystal structure. Al-doping at x=0 and x=0.025 does not change the phase as Li{sub 4}Ti{sub 5}O{sub 12} while at x=0.050 the phase changes to the LiTiAlO{sub 4}. The diffraction patterns show that the angle shifted to the right as the increase of x which indicated that Al substitute Ti site. Percentage of Li{sub 4}Ti{sub 5}O{sub 12} phase at x=0 and x=0.025 was 97.8% and 96.8%, respectively. However, the lattice parameters, the unit cell volume, and the crystal density does not change significantly at x=0; x=0.025; and x=0.050. Based on the percentage of Li{sub 4}Ti{sub 5}O{sub 12} phase, the Al-doped Li at x=0 and x=0.025 is promising as a lithium battery anode.« less

Crystal growth and characterization of undoped and Dy-doped TlPb2Br5 for infrared lasers and nuclear radiation detection

NASA Astrophysics Data System (ADS)

Hömmerich, U.; Brown, E.; Kabir, A.; Hart, D.; Trivedi, S. B.; Jin, F.; Chen, H.

2017-12-01

We report results of the crystal growth and characterization of undoped and Dy-doped TlPb2Br5 for applications in infrared (IR) lasers and nuclear radiation detection. TlPb2Br5 (TPB) was synthesized from commercial starting materials of PbBr2 and TlBr and further purified through a combination of zone-refinement and directional solidification. For doping experiments, 2 wt% of DyBr3 was added to the purified TPB material. Crystal growth of TPB and Dy: TPB was carried out in a two-zone tube furnace by a vertical Bridgman method. Following optical excitation at ∼1.36 μm, the Dy: TPB crystal exhibited efficient mid-IR emission bands centered at 2.87 μm and 4.35 μm with room-temperature lifetimes of 9.5 ms and 5.2 ms, respectively. The peak emission cross-sections were determined to be ∼0.8 × 10-20 cm2 and ∼0.5 × 10-20 cm2, respectively, which makes Dy: TPB a promising candidate for mid-IR laser applications. Besides its potential as a solid-state laser host, an undoped TPB crystal was also tested for gamma-ray detection. Using Cs-137 and Am-241 sources resulted in energy resolutions for gamma-rays as good as 1-2% (FWHM) at room-temperature under non-optimized conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Righettoni, Marco; Pratsinis, Sotiris E., E-mail: sotiris.pratsinis@ptl.mavt.ethz.ch

Highlights: • Flame-made WO{sub 3} nanoparticles with closely controlled crystal and grain size. • Dynamic phase transition of annealing of pure and Si-doped WO{sub 3} by in situ XRD. • Irreversible evolution of WO{sub 3} crystallinity by heating/cooling during its annealing. • Si-doping alters the WO{sub 3} crystallinity dynamics and stabilizes nanosized WO{sub 3}. • Flame-made nano-WO{sub 3} can sense NO at the ppb level. - Abstract: Tungsten trioxide is a semiconductor with distinct applications in gas sensors, catalysis, batteries and pigments. As such the transition between its different crystal structures during its annealing are of interest, especially for sensormore » applications. Here, WO{sub 3} nanoparticles with closely controlled crystal and grain size (9–15 nm) and phase composition are made by flame spray pyrolysis and the formation of different WO{sub 3} phases during annealing is investigated. Most notably, the dynamic phase transition and crystal size evolution of WO{sub 3} during heating and cooling is monitored by in situ X-ray diffraction revealing how metastable WO{sub 3} phases can be captured stably. The effect of Si-doping is studied since it is used in practise to control crystal growth and phase transition during metal oxide synthesis and processing. Finally the influence of annealing on the WO{sub 3} sensing performance of NO, a lung inflammation tracer in the human breath, is explored at the ppb-level.« less

Studies on transport properties of copper doped tungsten diselenide single crystals

NASA Astrophysics Data System (ADS)

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.

Structural and spectroscopic properties of pure and doped LiCe(PO{sub 3}){sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdelhedi, M., E-mail: m_abdelhedi2002@yahoo.fr; Horchani-Naifer, K.; Dammak, M.

2015-10-15

Graphical abstract: Emission and excitation and spectra of Eu{sup 3+} doped LiCe(PO{sub 3}){sub 4} host lattice with 1, 2, 3 and 4 mol%. - Highlights: • Europium–doped LiCe(PO{sub 3}){sub 4} were prepared by flux method. • It was analyzed by infrared and Raman spectroscopy, and luminescence spectroscopy. • LiCe(PO{sub 3}){sub 4} doped with Eu{sup 3+} ions as luminophore host materials to produce an intense red. - Abstract: Single crystals of LiCe(PO{sub 3}){sub 4} polyphosphate have been synthesized by the flux method and its structural and luminescence properties have been investigated. This compound crystallizes in the space group C2/c with unitmore » cell dimensions a = 16.52(7) Å, b = 7.09(4) Å, c = 9.83 (4)Å, β = 126.29(4)°, Z = 8 and V = 927.84(3) Å{sup 3}. The obtained polytetraphosphate exhibits very small crystals and the dopant Eu{sup 3+} ions were successfully incorporated into the sites of Ce{sup 3+} ions of the host lattice. The spectroscopy properties confirm the potentiality of present LiCe(PO{sub 3}){sub 4} doped with Eu{sup 3+} ions as luminophore host materials to produce an intense red luminescence at 628 nm corresponding to {sup 5}D{sub 0} → {sup 7}F{sub 2} emission level and have significant importance in the development of emission optical systems.« less

The density and compositional analysis of titanium doped sapphire single crystal grown by the Czocharlski method

NASA Astrophysics Data System (ADS)

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.

Ionic displacement induced ferroelectricity in multiferroic Cr doped ZnO

NASA Astrophysics Data System (ADS)

Tiwari, Jeetendra Kumar; Ali, Nasir; Ghosh, Subhasis

2018-05-01

Cr doped ZnO thin film was grown on quartz substrate using RF magnetron sputtering. Room temperature magnetic and ferroelectric properties of Cr doped ZnO were investigated. It is shown that ZnO becomes ferromagnetic upon Cr doping. It is considered that breaking of centrosymmetry due strain developed by doping of Cr should be responsible for the ferroelectricity. These films were characterized by X-ray diffraction (XRD), which shows that the films possess crystalline structure with preferred orientation along the (002) crystal plane and there is no extra peak due to Cr i.e. single phase.

Dual-wavelength green laser with a 4.5 THz frequency difference based on self-frequency- doubling in Nd3+ -doped aperiodically poled lithium niobate.

PubMed

Maestre, H; Torregrosa, A J; Fernández-Pousa, C R; Rico, M L; Capmany, J

2008-05-01

We report a dual-wavelength continuous-wave laser at 542.4 and 546.8 nm based on an Nd(3+)-doped aperiodically poled lithium niobate crystal. Two fundamental infrared (IR) wavelengths at 1084.8 and 1093.6 nm are simultaneously oscillated and self-frequency-doubled to green. The aperiodic domain distribution patterned in the crystal allows for quasi-phase matched self-frequency-doubling of both IR fundamentals while avoiding their sum-frequency mixing.

On the possibility of laser cooling of Cr3+ ions doped crystals

NASA Astrophysics Data System (ADS)

Feofilov, S. P.; Kulinkin, A. B.

2018-01-01

The fluorescence of Cr3+ ions doped insulating crystals was studied under the excitation in the long-wavelength tail of the absorption spectrum ("laser cooling regime"). The 4T2 - 4A2 and 2E - 4A2 fluorescence spectra with a dominant anti-Stokes component were observed. Though no optical refrigeration was detected in the presented experiments, the spectroscopic results suggest that electron-phonon bands of Cr3+ ions are of interest for further investigations from the point of view of achieving optical refrigeration.

Stimulated Raman scattering in an optical parametric oscillator based on periodically poled MgO-doped stoichiometric LiTaO3.

PubMed

My, T-H; Robin, O; Mhibik, O; Drag, C; Bretenaker, F

2009-03-30

The evolution of the spectrum of a singly resonant optical parametric oscillator based on an MgO-doped periodically poled stoichiometric lithium tantalate crystal is observed when the pump power is varied. The onset of cascade Raman lasing due to stimulated Raman scattering in the nonlinear crystal is analyzed. Spurious frequency doubling and sum-frequency generation phenomena are observed and understood. A strong reduction of the intracavity Raman scattering is obtained by a careful adjustment of the cavity losses.

Multi-wavelength laser emission in dye-doped photonic liquid crystals.

PubMed

Wang, Chun-Ta; Lin, Tsung-Hsien

2008-10-27

Multi-wavelength lasing in a dye-doped cholesteric liquid crystal (CLC) cell is demonstrated. By adding oversaturated chiral dopant, the multi-photonic band CLC structure can be obtained with non-uniform chiral solubility. Under appropriate excitation, multi-wavelength lasing can be achieved with a multi-photonic band edge CLC structure. The number of lasing wavelengths can be controlled under various temperature processes. Nine wavelength CLC lasings were observed simultaneously. The wavelength range covers around 600-675nm. Furthermore, reversible tuning of multi-wavelength lasing was achieved by controlling CLC device temperature.

Fluorescence Properties of Fe2+- and Co2+-doped Hosts of CdMnTe Compositions as Potential Mid-Infrared Laser Materials

DTIC Science & Technology

2011-09-01

composition also affects the Co2+ and Fe2+ dopant lifetimes and temperature dependencies. Crystal growth effort is underway in order to improve the...single-crystalline samples of Fe2+ or divalent cobalt ion (Co2+)-doped CMT crystals were produced by Brimrose Corporation using a modified vertical...Bridgman technique (18). The starting high purity ingredients Cd, Mn, and Te along with the dopants (Fe and Co) are placed in a pre-cleaned and baked

Large-mode-area single-mode-output Neodymium-doped silicate glass all-solid photonic crystal fiber

PubMed Central

Li, Wentao; Chen, Danping; Qinling, Zhou; Hu, Lili

2015-01-01

We have demonstrated a 45 μm core diameter Neodymium-doped all-solid silicate glass photonic crystal fiber laser with a single mode laser output. The structure parameters and modes information of the fiber are both demonstrated by theoretical calculations using Finite Difference Time Domain (FDTD) method and experimental measurements. Maximum 0.8 W output power limited by launched pump power has been generated in 1064 nm with laser beam quality factor M2 1.18. PMID:26205850

Novel materials for high-efficiency solar cells

NASA Astrophysics Data System (ADS)

Kojima, Nobuaki; Natori, Masato; Suzuki, Hidetoshi; Inagaki, Makoto; Ohshita, Yoshio; Yamaguchi, Masafumi

2009-08-01

Our Toyota Technological Institute group has investigated various novel materials for solar cells from organic to III-V compound materials. In this paper, we report our recent results in conductivity control of C60 thin films by metal-doping for organic solar cells, and mobility improvement of (In)GaAsN compounds for III-V tandem solar cells. The epitaxial growth of Mg-doped C60 films was attempted. It was found that the epitaxial growth of Mg-doped C60 film was enabled by using mica (001) substrate in the low Mg concentration region (Mg/C60 molar ratio < 1). The crystal quality of the epitaxial Mg-doped C60 film was improved drastically in compared with micro-crystalline film on glass substrate. Such drastic improvement of crystal quality in the epitaxial films resulted significant increase in conductivity. This result may indicate the significant increase of carrier mobility. Crystal quality improvement of CBE-grown GaAsN materials was investigated. We achieved the reduction of residual impurity concentration by chemical reaction control on the growing surface by modifying flow sequence of precursors and by increasing step density on the surface by using a vicinal GaAs substrate. Furthermore, the improvement in carrier mobility was observed, and it was suggested that the reduction of both residual impurities and N-related defects leads this improvement.

Containerless processing of single crystals in low-G environment

NASA Technical Reports Server (NTRS)

Walter, H. U.

1974-01-01

Experiments on containerless crystal growth from the melt were conducted during Skylab missions SL3 and SL4 (Skylab Experiment M-560). Six samples of InSb were processed, one of them heavily doped with selenium. The concept of the experiment is discussed and related to general crystal growth methods and their merits as techniques for containerless processing in space. The morphology of the crystals obtained is explained in terms of volume changes associated with solidification and wetting conditions during solidification. All samples exhibit extremely well developed growth facets. Analysis by X-ray topographical methods and chemical etching shows that the crystals are of high structural perfection. Average dislocation density as revealed by etching is of the order of 100 per sq cm; no dislocation clusters could be observed in the space-grown samples. A sequence of striations that is observed in the first half of the selenium-doped sample is explained as being caused by periodic surface breakdown.

Growth and Spectral Assessment of Yb3+-Doped KBaGd(MoO4)3 Crystal: A Candidate for Ultrashort Pulse and Tunable Lasers

PubMed Central

Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Wang, Guofu

2013-01-01

In order to explore new more powerful ultrashort pulse laser and tunable laser for diode-pumping, this paper reports the growth and spectral assessment of Yb3+-doped KBaGd(MoO4)3 crystal. An Yb3+:KBaGd(MoO4)3 crystal with dimensions of 50×40×9 mm3 was grown by the TSSG method from the K2Mo2O7 flux. The investigated spectral properties indicated that Yb3+:KBaGd(MoO4)3 crystal exhibits broad absorption and emission bands, except the large emission and gain cross-sections. This feature of the broad absorption and emission bands is not only suitable for the diode pumping, but also for the production of ultrashort pulses and tunability. Therefore, Yb3+:KBaGd(MoO4)3 crystal can be regarded as a candidate for the ultrashort pulse and tunable lasers. PMID:23349892

Growth and spectral assessment of Yb(3+)-doped KBaGd(MoO4)3 crystal: a candidate for ultrashort pulse and tunable lasers.

PubMed

Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Wang, Guofu

2013-01-01

In order to explore new more powerful ultrashort pulse laser and tunable laser for diode-pumping, this paper reports the growth and spectral assessment of Yb(3+)-doped KBaGd(MoO(4))(3) crystal. An Yb(3+):KBaGd(MoO(4))(3) crystal with dimensions of 50×40×9 mm(3) was grown by the TSSG method from the K(2)Mo(2)O(7) flux. The investigated spectral properties indicated that Yb(3+):KBaGd(MoO(4))(3) crystal exhibits broad absorption and emission bands, except the large emission and gain cross-sections. This feature of the broad absorption and emission bands is not only suitable for the diode pumping, but also for the production of ultrashort pulses and tunability. Therefore, Yb(3+):KBaGd(MoO(4))(3) crystal can be regarded as a candidate for the ultrashort pulse and tunable lasers.

Spectroscopic and neutron detection properties of rare earth and titanium doped LiAlO 2 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickens, Peter T.; Marcial, José; McCloy, John

In this study, LiAlO2 crystals doped with rare-earth elements and Ti were produced by the CZ method and spectroscopic and neutron detection properties were investigated. Photoluminescence revealed no clear luminescent activation of LiAlO2 by the rare-earth dopants though some interesting luminescence was observed from secondary phases within the crystal. Gamma-ray pulse height spectra collected using a 137Cs source exhibited only a Compton edge for the crystals. Neutron modeling using Monte Carlo N-Particle Transport Code revealed most neutrons used in the detection setup are thermalized, and while using natural lithium in the crystal growth, which contains 7.6 % 6Li, a 10more » mm Ø by 10 mm sample of LiAlO2 has a 70.7 % intrinsic thermal neutron capture efficiency. Furthermore, the pulse height spectra collected using a 241Am-Be neutron source demonstrated a distinct neutron peak.« less

Sn-doped Bi 1.1Sb 0.9Te 2S bulk crystal topological insulator with excellent properties

DOE PAGES

S. K. Kushwaha; Pletikosic, I.; Liang, T.; ...

2016-04-27

A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons, and be growable as large, high quality bulk single crystals. Here we show that this materials obstacle is overcome by bulk crystals of lightly Sn-doped Bi 1.1Sb 0.9Te 2S grown by the Vertical Bridgeman method.more » We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunneling microscopy, transport studies, X-ray diffraction, and Raman scattering. We present this material as a high quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states.« less

Spectroscopic and neutron detection properties of rare earth and titanium doped LiAlO 2 single crystals

DOE PAGES

Dickens, Peter T.; Marcial, Jose; McCloy, John; ...

2017-05-17

In this study, LiAlO 2 crystals doped with rare-earth elements and Ti were produced by the CZ method and spectroscopic and neutron detection properties were investigated. Photoluminescence revealed no clear luminescent activation of LiAlO 2 by the rare-earth dopants though some interesting luminescence was observed from secondary phases within the crystal. Gamma-ray pulse height spectra collected using a 137Cs source exhibited only a Compton edge for the crystals. Neutron modeling using Monte Carlo N-Particle Transport Code revealed most neutrons used in the detection setup are thermalized, and while using natural lithium in the crystal growth, which contains 7.6% 6Li, amore » 10 mm Ø by 10 mm sample of LiAlO 2 has a 70.7% intrinsic thermal neutron capture efficiency. Furthermore, the pulse height spectra collected using a 241Am-Be neutron source demonstrated a distinct neutron peak.« less

Charge-transfer state excitation as the main mechanism of the photodarkening process in ytterbium-doped aluminosilicate fibres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobkov, K K; Rybaltovsky, A A; Vel'miskin, V V

2014-12-31

We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb{sup 2+} ions in the glass network under IR laser pumping at a wavelength λ = 915 nm and under UV irradiation with an excimer laser (λ = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb{sup 2+} ions and aluminium – oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicatemore » glass, has been identified: photoinduced Yb{sup 3+} charge-transfer state excitation. (optical fibres)« less

Preparation and optical characteristics of ZnSe nanocrystals doped glass by sol gel in situ crystallization method

NASA Astrophysics Data System (ADS)

Hao, Haiyan; Yao, Xi; Wang, Minqiang

2007-01-01

Homogeneous ZnSe nanocrystals doped SiO 2 glass was successfully prepared by sol-gel in situ crystallization method. The structure of the doped ZnSe nanocrystals was studied by X-ray diffraction (XRD). ZnSe nanocrystals in silica were about 4-10 nm analysed by transmission electron microscopy (TEM), which was consistent with the results of XRD estimated using Scherrer's formular. The quantum size effect in ZnSe nanocrystals was evidenced from the blue-shifts of the optical absorption edge, and the average size of ZnSe nanocrystals was estimated by the magnitude of blue shift according to the L.E. Brus' effective mass model. The size of ZnSe nanocrystals depending on annealing time and temperature was further discussed using XRF.

Highly-efficient mid-infrared CW laser operation in a lightly-doped 3 at.% Er:SrF2 single crystal.

PubMed

Su, Liangbi; Guo, Xinsheng; Jiang, Dapeng; Wu, Qinghui; Qin, Zhipeng; Xie, Guoqiang

2018-03-05

3 at.% Er:SrF 2 laser crystals with high optical quality were successfully grown using the temperature gradient technique (TGT). The intense mid-infrared emission was observed around 2.7 μm with excitation by a 970 nm LD. Based on the Judd-Ofelt theory, the emission cross-sections of the 4 I 13/2 - 4 I 11/2 transition were calculated by using the Fuchtbauer-Ladenburg (FL) method. Efficient continuous-wave laser operation at 2.8 µm was achieved with the lightly-doped 3 at.% Er:SrF 2 crystal pumped by a 970 nm laser diode. The laser output power reached up to 1.06 W with a maximum slope efficiency of 26%.

Extreme anisotropy and anomalous transport properties of heavily electron doped Lix(NH3)yFe2Se2 single crystals

NASA Astrophysics Data System (ADS)

Sun, Shanshan; Wang, Shaohua; Yu, Rong; Lei, Hechang

2017-08-01

We report the growth of heavily electron doped Li-NH3 intercalated FeSe single crystals that are free of material complexities and allow access to the intrinsic superconducting properties. Lix(NH3)yFe2Se2 single crystals show extremely large electronic anisotropy in both normal and superconducting states. They also exhibit anomalous transport properties in the normal state, which are believed to possibly be related to the anisotropy of relaxation time and/or temperature-dependent electron carrier concentration. Taking into account the great chemical flexibility of intercalants in the system, our findings provide a platform to understanding the origin of superconductivity in FeSe-related superconductors.

Electro-opto-thermal addressing bistable and re-addressable display device based on gelator-doped liquid crystals in a poly(N-vinylcarbazole) film-coated liquid crystal cell.

PubMed

Cheng, Ko-Ting; Tang, Yi; Liu, Cheng-Kai

2016-10-03

This paper reports an electro-opto-thermal addressing bistable and re-addressable display device based on gelator-doped liquid crystals (LCs) in a poly(N-vinylcarbazole) film-coated LC cell. The bistability and re-addressability of the devices were achieved through the formation of a rubbery LC/gel mixture at room temperature. The desired patterns were addressed, erased, and re-addressed by controlling the temperature, applied voltage, and UV light illumination. Moreover, grayscales were obtained by adjusting UV light intensity. The initiation, relaxation, rise, and fall times of photoconductive poly(N-vinylcarbazole) via UV light illumination of various intensities were also examined.

Computer modelling of the optical behaviour of rare earth dopants in BaY2F8

NASA Astrophysics Data System (ADS)

Jackson, R. A.; Valerio, M. E. G.; Couto Dos Santos, M. A.; Amaral, J. B.

2005-01-01

BaY2F8, when doped with rare earth elements is a material of interest in the development of solid-state laser systems, especially for use in the infrared region. This paper presents the application of a new computational technique, which combines atomistic modelling and crystal field calculations in a study of rare earth doping of the material. Atomistic modelling is used to calculate the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the dopant-crystal system. Comparisons with the results of recent experimental work on this material are made.

Dielectric properties of nematic liquid crystal doped with Fe3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Maleki, A.; Ara, M. H. Majles; Saboohi, F.

2017-04-01

The influence of Fe3O4 nanoparticles (NPs) on dielectric properties of planar and homeotropic oriented nematic liquid crystals (NLCs) were studied during the temperature interval of 298-322 °K. It was found that the dielectric permittivity was considerably increased by adding NPs mass percentages. The structural characterization of the synthesized NPs with the scale 14-18 nm has been analyzed by the X-ray diffraction and field-emission scanning electron microscopy results. The obtained dielectric anisotropy (?) and mean dielectric (?) have shown an immense increment in the value of 1% and 10% wt. NPs doped NLCs, respectively. These results were assigned to the strong dipole-dipole interaction between the superparamagnetic particles and the surrounding liquid crystal molecules.

All-optical switch based on doped graphene quantum dots in a defect layer of a one-dimensional photonic crystal.

PubMed

Sahrai, Mostafa; Abbasabadi, Majid

2018-01-20

We discuss the light pulse propagation in a one-dimensional photonic crystal doped by graphene quantum dots in a defect layer. The graphene quantum dots behave as a three-level quantum system and are driven by three coherent laser fields. It is shown that the group velocity of the transmitted and reflected pulses can be switched from subluminal to superluminal light propagation by adjusting the relative phase of the applied fields. Furthermore, it is found that by proper choice of the phase difference between applied fields, the weak probe field amplification is achieved through a one-dimensional photonic crystal. In this way, the result is simultaneous subluminal transmission and reflection.

The improved scintillation crystal lead tungstate scintillation for PET

NASA Astrophysics Data System (ADS)

Wan, Youbao; WU, Rurong; Xiao, Linrong; Zhang, Jianxin; Yang, Peizhi; Yan, Hui

2009-07-01

As a valuable material for the detecting of γ-ray, PbWO4 and BaF2:PbWO4 crystals were grown by a novel multi-crucible temperature gradient system developed by ourselves. Utilizing a topical partial heating method, this system can form a topical partial high temperature in its hearth. Thus this system could melt raw materials in step by step as requirement. The advantage of this method is that there would be solid obstruct left on the melt in the procedure of the crystal growing up. The left obstruct could prevent the volatilization of the component in the melt. Hence it is helpful for the composition homogenization in the crystal. The system also offers a sustaining device for multi-crucibles and thus it can grow many crystals simultaneity. The optical properties and scintillation properties of the crystals were studied. The results reveal that the ions doping improves the scintillation properties of the crystal. The transmittance spectra show that the transmittance of BaF2:PbWO4 crystals are better than that of PbWO4 crystals. For the PbWO4 crystals, their absorption edge is at 325nm, and their maximum transmittance is 68%. For the BaF2:PbWO4 crystals, their absorption edge is at 325nm and their maximum transmittance is upto76%. The X-ray excited luminescence spectra shows that the luminescence peak is at 420nm for the samples of PbWO4 crystal while the peak is at 430nm for the samples of BaF2:PbWO4 crystal respectively. The luminescence intensity of the samples of BaF2:PbWO4 crystal is about two times than that of PbWO4 crystal. And their peak shape is different for the two kind of crystal. The light yield of BaF2:PbWO4 crystals is about 2.9 times than that of PbWO4 crystal Analyzing these scintillation properties, we find that the VPb 3+ and VO- defects do harm for the optical properties of the crystal. Ions doping method could reduce the defect concentration and improving its illumination performance of the crystal. Specially, the doped F- ions in O2- site can induce the aberrance of the [WO4]2- tetrahedron and form [WO3F]- tetrahedron which has more active blue light yield, thus improve the light yield of the crystal. The improved light yield of BaF2:PbWO4 crystals is valuable for the medical diagnosing instrument PET and CT with high resolving power

Ferroelectric Tungsten Bronze Bulk Crystals and Epitaxial Thin Films for Electro-Optic Device Applications

DTIC Science & Technology

1984-07-01

improved, they show a considerable enhancement in electro - optic and photorefractive properties, specifically for Ce(3+)-doped SBN:60 crystals. The...concentration of impurity ions increased. Undoped SBN:60 single crystals have also been grown and they are almost striation-free and exhibit excellent electro - optic properties.

Growth and characterization of tunable solid state lasers in the near infrared spectral region

NASA Technical Reports Server (NTRS)

Powell, Richard C.; Martin, Joel J.

1990-01-01

This research resulted in the publication of two major papers. The major results include the development of improved crystal growth techniques for rare earth-doped LiYF4 crystals and the determination of laser-pumped laser characteristics of Tm:Ho:Y3Al5O12 crystals.

Influence of VO2+ ions on structural and optical properties of potassium succinate-succinic acid single crystal for non-linear optical applications

NASA Astrophysics Data System (ADS)

Juliet sheela, K.; Subramanian, P.

2018-04-01

A transparent and good optical quality semi organic single crystal of vanadium doped potassium succinate-succinic acid (KSSA) was synthesized by slow evaporation technique at room temperature. The structural perfection was supported by the powder XRD of the KSSA-VO2+ single crystal. Optical behavior of the material was discovered from the absorption and transmission spectra of UV-vis-NIR characterization. Functional group and presence of metal ion in the specimen are depicted from FTIR traces. From the photoluminescence studies, emission of wavelength in the violet region (418 nm) at the excitation of 243 nm could be ascertained. EDAX, SEM measurements identify presence of elements and pictures the step-line growth and the imperfection presents in the grown crystal. EPR analysis extracts the information about the local site symmetry around the impurity ion, molecular orbital coefficients, admixture coefficients and ground state wave function of VO2+ doped KSSA single crystal. Second harmonic generation (SHG) efficiency of the grown crystal was investigated to explore the NLO characteristic of the material.

History and current status of strontium iodide scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherepy, Nerine J.; Beck, Patrick R.; Payne, Stephen A.

Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI 2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI 2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu 2+-doped crystals. As a result, its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability makemore » SrI 2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI 2(Eu) radioisotope identifier is described.« less

Random lasing from dye-doped negative liquid crystals using ZnO nanoparticles as tunable scatters

NASA Astrophysics Data System (ADS)

Li, Long-Wu; Shang, Zhen-Zhen; Deng, Luogen

2016-09-01

This work demonstrates the realization of a lasing in scattering media, which contains dispersive solution of ZnO nanoparticles (NPs) and laser dye 4-dicyanomethylene-2-methyle-6-(p-dimethylaminostyryl)-4H-pyran(DCM) in negative liquid crystals (LCs) that was injected into a cell. The lasing intensity of the dye-doped negative LC laser can be tuned from low to high if the NPs concentration is increased. The tunability of the laser is attributable to the clusters-sensitive feature in effective refractive index of the negative LCs. Such a tunable negative liquid crystal laser can be used in the fabrication of new optical sources, optical communication, and liquid crystal laser displays. Project supported by the Doctoral Science Research Start-up Funding of Guizhou Normal University, China (Grant No. 11904-0514162) and the National Natural Science Foundation of China (Grant No. 11474021).

History and current status of strontium iodide scintillators

DOE PAGES

Cherepy, Nerine J.; Beck, Patrick R.; Payne, Stephen A.; ...

2017-09-15

Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI 2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI 2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu 2+-doped crystals. As a result, its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability makemore » SrI 2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI 2(Eu) radioisotope identifier is described.« less

Effect of thallium doping on the mobility of electrons in Bi{sub 2}Se{sub 3} and holes in Sb{sub 2}Te{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kudryashov, A. A.; Kytin, V. G.; Lunin, R. A.

2016-07-15

The Shubnikov–de Haas effect and the Hall effect in n-Bi{sub 2–x}Tl{sub x}Se{sub 3} (x = 0, 0.01, 0.02, 0.04) and p-Sb{sub 2–x}Tl{sub x}Te{sub 3} (x = 0, 0.005, 0.015, 0.05) single crystals are studied. The carrier mobilities and their changes upon Tl doping are calculated by the Fourier spectra of oscillations. It is found shown that Tl doping decreases the electron concentration in n-Bi{sub 2–x}Tl{sub x}Se{sub 3} and increases the electron mobility. In p-Sb{sub 2–x}Tl{sub x}Te{sub 3}, both the hole concentration and mobility decrease upon Tl doping. The change in the crystal defect concentration, which leads to these effects, ismore » discussed.« less

Towards room-temperature superconductivity in low-dimensional C60 nanoarrays: An ab initio study

NASA Astrophysics Data System (ADS)

Erbahar, Dogan; Liu, Dan; Berber, Savas; Tománek, David

2018-04-01

We propose to raise the critical temperature Tc for superconductivity in doped C60 molecular crystals by increasing the electronic density of states at the Fermi level N (EF) and thus the electron-phonon coupling constant in low-dimensional C60 nanoarrays. We consider both electron and hole dopings and present numerical results for N (EF) , which increases with the decreasing bandwidth of the partly filled hu- and t1 u-derived frontier bands with the decreasing coordination number of C60. Whereas a significant increase in N (EF) occurs in two-dimensional (2D) arrays of doped C60 intercalated in-between graphene layers, we propose that the highest-Tc values approaching room temperature may occur in bundles of nanotubes filled by one-dimensional (1D) arrays of externally doped C60 or La @C60 or in diluted three-dimensional (3D) crystals where quasi-1D arrangements of C60 form percolation paths.

Studies on output characteristics of stable dual-wavelength ytterbium-doped photonic crystal fiber laser

NASA Astrophysics Data System (ADS)

Tian, Hongchun; Zhang, Sa; Hou, Zhiyun; Xia, Changming; Zhou, Guiyao; Zhang, Wei; Liu, Jiantao; Wu, Jiale; Fu, Jian

2016-06-01

A stable dual-wavelength ytterbium-doped photonic crystal fiber laser pumped by a 976 nm laser diode has been demonstrated at room temperature. Single-wavelength, dual-wavelength laser oscillations are observed when the fiber laser operates under different pump power by using different length of fibers. Stable dual-wavelength radiation around 1045 nm and 1075 nm has been generated simultaneously at a high pump power directly from an ytterbium-doped fiber laser without using any spectral control mechanism. A small core ytterbium-doped PCF fabricated by the powder sinter direction drawn rod technology is used as gain medium. The pump power and fiber length which can affect the output characteristics of dual-wavelength fiber laser are analyzed in the experiment. Experiments confirm that higher pump power and longer fiber length favors 1075 nm output; lower pump power and shorter fiber length favors 1045 nm output. Those results have a good reference in multi-wavelength fiber laser.

Fabrication and characterization of cerium-doped barium titanate inverse opal by sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Yi; Zhu Yihua; Yang Xiaoling

Cerium-doped barium titanate inverted opal was synthesized from barium acetate contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a polystyrene (PS) opal. This procedure involves infiltration of precursors into the interstices of the PS opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the PS opal by calcination. The morphologies of opal and inverse opal were characterized by scanning electron microscope (SEM). The pores were characterized by mercury intrusion porosimetry (MIP). X-ray photoelectron spectroscopy (XPS) investigation showed the doping structure of cerium, barium and titanium. And powder X-ray diffraction allowsmore » one to observe the influence of doping degree on the grain size. The lattice parameters, crystal size and lattice strain were calculated by the Rietveld refinement method. The synthesis of cerium-doped barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three-dimensional photonic crystal devices. - Graphical abstract: Cerium-doped barium titanate inverted opal was synthesized from barium acetate acid contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a PS opal, which involves infiltration of precursors into the interstices of the PS opal template and removal of the PS opal by calcination.« less

Role of bromine doping on the photovoltaic properties and microstructures of CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Atsushi; Okada, Hiroshi; Oku, Takeo

Organic-inorganic hybrid heterojunction solar cells containing CH{sub 3}NH{sub 3}PbI{sub 3} perovskite compound were fabricated using mesoporous TiO{sub 2} as the electronic transporting layer and spirobifluorence as the hole-transporting layer. The purpose of the present study is to investigate role of bromine (Br) doping on the photovoltaic properties and microstructure of CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells. Photovoltaic, optical properties and microstructures of perovskite-based solar cells were investigated. The X-ray diffraction identified crystal structure of the perovskite layer doped with Br in the solar cell. Scanning electron microscopy observation showed a different behavior of surface morphology and the perovskite crystalmore » structure on the TiO{sub 2} mesoporous structure depending on extent amount of hydrogen doping of Br. The role of bromide halogen doping on the perovskite crystal structure and photovoltaic properties was due to improvement of carrier mobility, optimization of electron structure, band gap related with the photovoltaic parameters of V{sub oc}, J{sub sc} and η. Energy diagram and photovoltaic mechanism of the perovskite solar cells varied with halogen doping was discussed by experimental results.« less

Record power, ultra-broadband supercontinuum source based on highly GeO₂ doped silica fiber.

PubMed

Jain, D; Sidharthan, R; Moselund, P M; Yoo, S; Ho, D; Bang, O

2016-11-14

We demonstrate highly germania doped fibers for mid-infrared supercontinuum generation. Experiments ensure a highest output power of 1.44 W for a broadest spectrum from 700 nm to 3200 nm and 6.4 W for 800 nm to 2700 nm from these fibers, while being pumped by a broadband Erbium-Ytterbium doped fiber based master oscillator power amplifier. The effect of repetition frequency of pump source and length of germania-doped fiber has also been investigated. Further, germania doped fiber has been pumped by conventional supercontinuum source based on silica photonic crystal fiber supercontinuum source. At low power, a considerable broadening of 200-300 nm was observed. Further broadening of spectrum was limited due to limited power of pump source. Our investigations reveal the unexploited potential of germania doped fiber for mid-infrared supercontinuum generation. These measurements ensure the potential of germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being by pumped a 1060 nm or a 1550 nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized supercontinuum light source based on silica and germania fiber ever demonstrated to the date.

Low temperature coefficient of resistance and high gage factor in beryllium-doped silicon

NASA Technical Reports Server (NTRS)

Robertson, J. B.; Littlejohn, M. A.

1974-01-01

The gage factor and resistivity of p-type silicon doped with beryllium was studied as a function of temperature, crystal orientation, and beryllium doping concentration. It was shown that the temperature coefficient of resistance can be varied and reduced to zero near room temperature by varying the beryllium doping level. Similarly, the magnitude of the piezoresistance gage factor for beryllium-doped silicon is slightly larger than for silicon doped with a shallow acceptor impurity such as boron, whereas the temperature coefficient of piezoresistance is about the same for material containing these two dopants. These results are discussed in terms of a model for the piezoresistance of compensated p-type silicon.

Alkali earth co-doping effects on luminescence and scintillation properties of Ce doped Gd3Al2Ga3O12 scintillator

NASA Astrophysics Data System (ADS)

Kamada, Kei; Nikl, Martin; Kurosawa, Shunsuke; Beitlerova, Alena; Nagura, Aya; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-03-01

The Mg and Ca co-doped Ce:Gd3Al2Ga3O12 single crystals were prepared by micro pulling down method with a wide concentration range 0-1000 ppm of the codopants. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg and Ca co-doping. The scintillation decays were accelerated by both Mg and Ca codopants. Comparing to Ca co-doping, the Mg co-doped samples showed much faster decay and comparatively smaller light output decrease with increasing Mg dopant concentration.

A photoluminescence, thermoluminescence and electron paramagnetic resonance study of EFG grown europium doped lithium fluoride (LiF) crystals

NASA Astrophysics Data System (ADS)

Seth, Pooja; Swati, G.; Haranath, D.; Rao, S. M. D.; Aggarwal, Shruti

2018-07-01

Europium (Eu) doped LiF crystals have been grown by the Edge-defined film fed growth (EFG) technique. The designing and installation of the furnace used for the growth of the crystals have been discussed in detail. In the present study, Eu (Eu2O3) has been doped in LiF in different concentration (0.02-0.2 wt %). X-ray diffractometry (XRD) and Energy Dispersive X-ray (EDX) spectroscopy confirms the incorporation of Eu in LiF. The influence of Eu on LiF has been investigated through photoluminescence (PL), thermoluminescence (TL) and electron paramagnetic resonance (EPR) in as-grown and annealed crystals. PL emission spectra shows the presence of both Eu3+ and Eu2+ form in the as-grown crystals which is confirmed by EPR results. Whereas, in annealed crystals, Eu is present predominantly as Eu2+ form. This suggests that growing crystals at high temperature (∼900 °C) in argon gas atmosphere through EFG technique favours the reduction of Eu3+ → Eu2+. This reduction phenomenon has been explained on the basis of charge compensation model. TL study of the LiF: Eu (0.02-0.2 wt %) crystals has been done after irradiation with Co60 gamma rays. In this study, it has been observed that the TL intensity as well as glow curve structure of LiF: Eu crystals are a strong function of Eu concentration. The maximum TL is observed at Eu concentration of 0.05 wt% at which a well defined glow curve structure with a prominent peak at 185 °C and a small peak at 253 °C. Beyond this concentration (0.05 wt %), TL intensity decreases due to aggregation of defects in the host. The peak at 185 °C in LiF: Eu (0.05 wt %) is certainly due to the presence of Eu2+ associated defects which is also supported by the PL spectra. It has been observed that Eu doping have a key role in creation of more defect levels which lead to the increased number of electron and hole traps. Further, trapping parameters are analysed using glow curve deconvolution method to have an insight study of TL phenomena. Further, TL glow curve structure of as-grown and annealed crystal are distinct which may be attributed to the nature of defect traps formed inside the LiF.

Colour centres and nanostructures on the surface of laser crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulagin, N A

2012-11-30

This paper presents a study of structural and radiationinduced colour centres in the bulk and ordered nanostructures on the surface of doped laser crystals: sapphire, yttrium aluminium garnet and strontium titanate. The influence of thermal annealing, ionising radiation and plasma exposure on the spectroscopic properties of high-purity materials and crystals containing Ti, V and Cr impurities is examined. Colour centres resulting from changes in the electronic state of impurities and plasma-induced surface modification of the crystals are studied by optical, EPR and X-ray spectroscopies, scanning electron microscopy and atomic force microscopy. X-ray line valence shift measurements are used to assessmore » changes in the electronic state of some impurity and host ions in the bulk and on the surface of oxide crystals. Conditions are examined for the formation of one- and two-level arrays of ordered crystallites 10{sup -10} to 10{sup -7} m in size on the surface of crystals doped with irongroup and lanthanoid ions. The spectroscopic properties of the crystals are analysed using ab initio self-consistent field calculations for Me{sup n+} : [O{sup 2-}]{sub k} clusters. (interaction of laser radiation with matter. laser plasma)« less

Surface exciton emission of MgO crystals

NASA Astrophysics Data System (ADS)

Kuang, Wen-Jian; Li, Qing; Chen, Yu-Xiang; Hu, Kai; Wang, Ning-Hui; Xing, Fang-Li; Yan, Qun; Sun, Shuai-Shuai; Huang, Yan; Tao, Ye; Tolner, Harm

2013-09-01

MgO crystals have been exposed to vacuum ultraviolet (VUV) radiation from a synchrotron, with energies up to 9 eV, and the emitted light, at wavelengths above 200 nm, was observed. It is concluded that bulk excitons, play an important role in the diffusion of energy inside MgO crystals, resulting in 5.85 eV (212 nm) emission from the MgO terraces of large (0.2-2 µm) MgO : F crystals. In the case of aliovalent impurity doping, then the bulk exciton energy is also transferred to the Vk centres and 5.3 eV (235 nm) light is emitted. Both fluorine and silicon doping appear to promote UV surface emission, acting similarly to an ns2 ion inside MgO, while strong scandium doping is killing the surface emission completely. The 212 nm surface UV emission and the 235 nm bulk UV emission can be excited only at the bandgap edge. Broadband visible light, centred around 400 nm, is also emitted. Contrary to the UV emission, this is not generated when excited at the bandgap edge; instead, we find that it is only excited at sub-bandgap energies, with a maximum at the 5C surface excitation energy of 5.71 eV (217 nm) for the MgO terraces.

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

X-ray photoemission spectroscopy investigation of CaTiO{sub 3}:Eu for luminescence property: effect of Eu{sup 3+} ion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Kaichen; Zhao, Baijun; Gao, Lu, E-mail: gaolu@jlu.edu.cn

2016-06-15

Graphical abstract: The influence on the photoluminescent performance due to the electronic structure change in Eu-doped CaTiO{sub 3} of the specific core-level and valence band spectrum via X-ray photoemission spectroscopy were characterized. - Highlights: • Single phase CaTiO{sub 3} and CaTiO{sub 3}: Eu crystals were prepared under mild hydrothermal method. • Crystal structure, doping level and the relations to their luminescent property were discussed. • Charge compensation mechanism was discussed via valance band spectrum by XPS. - Abstract: Charge compensation of on-site Eu 4f–5d transition that determines the luminescent performance was confirmed with valance band spectrum. Influence of photoelectrons frommore » CaTiO{sub 3}: Eu to the corresponding luminescent performance was discussed based on the crystal structure, doping level and the relations to their luminescent property. This paper is important to further optimize the luminescent performance for improving the efficiency and reducing the cost in light emitting diode industry.« less

The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

PubMed Central

Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

2016-01-01

Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes. PMID:27608815

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE PAGES

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.; ...

2017-11-17

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Nonlinear optical properties of TeO2-P2 O5- ZnO-LiNbO3 glass doped with Er3+ ions

NASA Astrophysics Data System (ADS)

Miedzinski, R.; Fuks-Janczarek, I.; El Sayed Said, Y.

2016-10-01

A series of lithium niobate LiNbO3 (LN) single crystals doped with Er3+ were grown under the same conditions by melt-quenching method. The distribution coefficients of rare-earth (RE) elements in the "crystal-melt" system of LN were determined at the beginning of the crystal growth. Their dependence on the dopant concentration in melt for 0.4 and 0.8 wt % was investigated. The procedure is applied to RE-doped lithium niobate (LiNbO3), a material of great interest for optoelectronic applications. We have obtained the real χR(3) and imaginary parts χI(3) of the third-order, nonlinear optical susceptibility to the nonlinear refractive index n2 and the nonlinear absorption coefficient β that are valid for absorbing systems. We show that nonlinear refractive or absorptive effects are the consequence of the interplay between the real and imaginary parts of the third-order susceptibilities of the materials. The method for measuring non-linear absorption coefficients and nonlinear refractive index based on well-known Z-scan is presented.

Temperature dependence of luminescence behavior in Er3+-doped BaY2F8 single crystal

NASA Astrophysics Data System (ADS)

Wang, Shuai; Ruan, Yongfeng; Tsuboi, Taiju; Tong, Hongshuang; Wang, Youfa; Zhang, Shouchao

2013-12-01

BaY2F8 single crystals doped with Er3+ ions have been grown by the temperature gradient method. The absorption, excitation and emission spectra for Er3+-doped BaY2F8 crystals were measured at room temperature (297 K) and 12 K. The effect of temperature on the luminescence intensity and effective bandwidth was investigated in the range of 12-297 K. The temperature dependence of the fluorescence intensity ratio (FIR) for the 522 nm emission (2H11/2→4I15/2 transition) and the 552 nm emission (4S3/2→4I15/2 transition) was also studied in the range of 12-297 K. Based on the fitting FIR curve, the value of the constant term B (2.25) was obtained. The fitting FIR curve and FIR equation may have a potential application in the temperature measurement. In addition, the up-conversion spectrum at room temperature was recorded under excitation of 980 nm and the up-conversion mechanism was analyzed in detail.

Magnetic and Ferroelectric Anisotropy in Multiferroic FeVO4

NASA Astrophysics Data System (ADS)

Abdelhamid, Ehab; Dixit, Ambesh; Kimura, Kenta; Kimura, Tsuyoshi; Jayakumar, Onattu; Naik, Vaman; Naik, Ratna; Lawes, Gavin; Nadgorny, Boris

FeVO4 has been studied as a model system for understanding the magnetoelectric interaction mechanisms in low symmetry multiferroics. Triclinic FeVO4 is characterized by two antiferromagnetic phase transitions, occurring at TN 1 = 22 K and TN 2 = 15 K, with the latter transition signaling a break in the space inversion symmetry, accompanied by the development of a non-collinear magnetic order which induces ferroelectricity. Earlier measurements on polycrystalline FeVO4 doped with magnetic (Cr and Mn) as well as non magnetic (Zn) dopants indicate the stability of the two antiferromagnetic transition temperatures. In this work, single crystals of both undoped and doped FeVO4 were grown from flux. To track the changes in lattice parameters induced by changing the doping concentration (measured by EDAX), XRD and Raman spectra were obtained. By recording the magnetization along two different crystal orientations, we were able to confirm the easy magnetic axis in this structure. Finally, we obtain the crystal's ferroelectric polarization along two different directions in an attempt to further understand the mechanism responsible for the ferroelectric transition. This work is supported by the NSF under DMR-1306449.

Compensating vacancy defects in Sn- and Mg-doped In2O3

NASA Astrophysics Data System (ADS)

Korhonen, E.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; Galazka, Z.

2014-12-01

MBE-grown Sn- and Mg-doped epitaxial In2O3 thin-film samples with varying doping concentrations have been measured using positron Doppler spectroscopy and compared to a bulk crystal reference. Samples were subjected to oxygen or vacuum annealing and the effect on vacancy type defects was studied. Results indicate that after oxygen annealing the samples are dominated by cation vacancies, the concentration of which changes with the amount of doping. In highly Sn-doped In2O3 , however, these vacancies are not the main compensating acceptor. Vacuum annealing increases the size of vacancies in all samples, possibly by clustering them with oxygen vacancies.

Understanding the photoluminescence characteristics of Eu{sup 3+}-doped double-perovskite by electronic structure calculation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Binita; Halder, Saswata; Sinha, T. P.

2016-05-23

Europium-doped luminescent barium samarium tantalum oxide Ba{sub 2}SmTaO{sub 6} (BST) has been investigated by first-principles calculation, and the crystal structure, electronic structure, and optical properties of pure BST and Eu-doped BST have been examined and compared. Based on the calculated results, the luminescence properties and mechanism of Eu-doped BST has been discussed. In the case of Eu-doped BST, there is an impurity energy band at the Fermi level, which is formed by seven spin up energy levels of Eu and act as the luminescent centre, which is evident from the band structure calculations.

Delta-doping optimization for high quality p-type GaN

NASA Astrophysics Data System (ADS)

Bayram, C.; Pau, J. L.; McClintock, R.; Razeghi, M.

2008-10-01

Delta (δ -) doping is studied in order to achieve high quality p-type GaN. Atomic force microscopy, x-ray diffraction, photoluminescence, and Hall measurements are performed on the samples to optimize the δ-doping characteristics. The effect of annealing on the electrical, optical, and structural quality is also investigated for different δ-doping parameters. Optimized pulsing conditions result in layers with hole concentrations near 1018 cm-3 and superior crystal quality compared to conventional p-GaN. This material improvement is achieved thanks to the reduction in the Mg activation energy and self-compensation effects in δ-doped p-GaN.

Preparation of ordered mesoporous alumina-doped titania films with high thermal stability and their application to high-speed passive-matrix electrochromic displays.

PubMed

Jiang, Xiangfen; Bastakoti, Bishnu Prasad; Weng, Wu; Higuchi, Tetsuya; Oveisi, Hamid; Suzuki, Norihiro; Chen, Wei-Jung; Huang, Yu-Tzu; Yamauchi, Yusuke

2013-08-12

Ordered mesoporous alumina-doped titania thin films with anatase crystalline structure were prepared by using triblock copolymer Pluronic P123 as structure-directing agent. Uniform Al doping was realized by using aluminum isopropoxide as a dopant source which can be hydrolyzed together with titanium tetraisopropoxide. Aluminum doping into the titania framework can prevent rapid crystallization to the anatase phase, thereby drastically increasing thermal stability. With increasing Al content, the crystallization temperatures tend to increase gradually. Even when the Al content doped into the framework was increased to 15 mol %, a well-ordered mesoporous structure was obtained, and the mesostructural ordering was still maintained after calcination at 550 °C. During the calcination process, large uniaxial shrinkage occurred along the direction perpendicular to the substrate with retention of the horizontal mesoscale periodicity, whereby vertically oriented nanopillars were formed in the film. The resulting vertical porosity was successfully exploited to fabricate a high-speed and high-quality passive-matrix electrochromic display by using a leuco dye. The vertical nanospace in the films can effectively prevent drifting of the leuco dye. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tuning the Electrical and Thermal Conductivities of Thermoelectric Oxides through Impurity Doping

NASA Astrophysics Data System (ADS)

Torres Arango, Maria A.

Waste heat and thermal gradients available at power plants can be harvested to power wireless networks and sensors by using thermoelectric (TE) generators that directly transform temperature differentials into electrical power. Oxide materials are promising for TE applications in harsh industrial environments for waste heat recovery at high temperatures in air, because they are lightweight, cheaply produced, highly efficient, and stable at high temperatures in air. Ca3Co4O9(CCO) with layered structure is a promising p-type thermoelectric oxide with extrapolated ZT value of 0.87 in single crystal form [1]. However the ZT values for the polycrystalline ceramics remain low of ˜0.1-0.3. In this research, nanostructure engineering approaches including doping and addition of nanoinclusions were applied to the polycrystalline CCO ceramic to improve the energy conversion efficiency. Polycrystalline CCO samples with various Bi doping levels were prepared through the sol-gel chemical route synthesis of powders, pressing and sintering of the pellets. Microstructure features of Bi doped ceramic bulk samples such as porosity, development of crystal texture, grain boundary dislocations and segregation of Bi dopants at various grain boundaries are investigated from microns to atomic scale. The results of the present study show that the Bi-doping is affecting both the electrical conductivity and thermal conductivity simultaneously, and the optimum Bi doping level is strongly correlated with the microstructure and the processing conditions of the ceramic samples. At the optimum doping level and processing conditions of the ceramic samples, the Bi substitution of Ca results in the increase of the electrical conductivity, decrease of the thermal conductivity, and improvement of the crystal texture. The atomic resolution Scanning Transmission Electron Microscopy (STEM) Z-contrast imaging and the chemistry analysis also reveal the Bi-segregation at grain boundaries of CCO polycrystalline samples. In order to further decrease the thermal conductivity and increase the overall energy conversion efficiency of ceramic samples. The highest ZT value obtained is 0.32 at 973K for Ca and Co site Bi doping. The effect of the nanoinclusions on the performance and the microstructure of CCO were investigated as well.

Multiple delta doping of single crystal cubic boron nitride films heteroepitaxially grown on (001)diamonds

NASA Astrophysics Data System (ADS)

Yin, H.; Ziemann, P.

2014-06-01

Phase pure cubic boron nitride (c-BN) films have been epitaxially grown on (001) diamond substrates at 900 °C. The n-type doping of c-BN epitaxial films relies on the sequential growth of nominally undoped (p-) and Si doped (n-) layers with well-controlled thickness (down to several nanometer range) in the concept of multiple delta doping. The existence of nominally undoped c-BN overgrowth separates the Si doped layers, preventing Si dopant segregation that was observed for continuously doped epitaxial c-BN films. This strategy allows doping of c-BN films can be scaled up to multiple numbers of doped layers through atomic level control of the interface in the future electronic devices. Enhanced electronic transport properties with higher hall mobility (102 cm2/V s) have been demonstrated at room temperature as compared to the normally continuously Si doped c-BN films.

Kinetics of the current response in TlBr detectors under a high dose rate of {gamma}-ray irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gazizov, I. M., E-mail: gazizov@isotop.dubna.ru; Zaletin, V. M.; Kukushkin, V. M.

2012-03-15

The kinetics of the photocurrent response in doped and undoped TlBr samples subjected to irradiation with {gamma}-ray photons from a {sup 137}Cs source with the dose rate 0.033 to 3.84 Gy/min are studied. The crystals were grown by the directional crystallization of the melt method using the Bridgman-Stockbarger technique. The Pb impurity mass fraction introduced into the doped TlBr crystals was 1-10 ppm and amounted to 150 ppm for the Ca impurity. The crystals were grown in a vacuum, in bromine vapors, in a hydrogen atmosphere, and in air. Decay of the photocurrent is observed for extrinsic semiconductor crystals dopedmore » with bivalent cations (irrespective of the growth atmosphere), and also for crystals grown in hydrogen and crystals grown in an excess of thallium. The time constant of photocurrent decay {tau} amounted to 30-1400 s and was proportional to resistivity. It is shown that the current response can be related to photolysis in the TlBr crystals during irradiation with {gamma}-ray photons. The energy of hole traps responsible for a slow increase in the photo-current has been estimated and found to be equal to 0.6-0.85 eV.« less

Photo-induced changes of the surface band bending in GaN: Influence of growth technique, doping and polarity

NASA Astrophysics Data System (ADS)

Winnerl, Andrea; Pereira, Rui N.; Stutzmann, Martin

2017-05-01

In this work, we use conductance and contact potential difference photo-transient data to study the influence of the growth technique, doping, and crystal polarity on the kinetics of photo-generated charges in GaN. We found that the processes, and corresponding time scales, involved in the decay of charge carriers generated at and close to the GaN surface via photo-excitation are notably independent of the growth technique, doping (n- and p-types), and also crystal polarity. Hence, the transfer of photo-generated charges from band states back to surface states proceeds always by hopping via shallow defect states in the space-charge region (SCR) close to the surface. Concerning the charge carrier photo-generation kinetics, we observe considerable differences between samples grown with different techniques. While for GaN grown by metal-organic chemical vapor deposition, the accumulation of photo-conduction electrons results mainly from a combined trapping-hopping process (slow), where photo-generated electrons hop via shallow defect states to the conduction band (CB), in hydride vapor phase epitaxy and molecular beam epitaxy materials, a faster direct process involving electron transfer via CB states is also present. The time scales of both processes are quite insensitive to the doping level and crystal polarity. However, these processes become irrelevant for very high doping levels (both n- and p-types), where the width of the SCR is much smaller than the photon penetration depth, and therefore, most charge carriers are generated outside the SCR.

Solid-State Laser Cooling of Ytterbium-Doped Tungstate Crystals

DTIC Science & Technology

2001-01-01

namely the heavy metal fluoride glass ZBLAN and yttrium aluminum garnet . Favorable properties of the ytterbium-tungstates include exceptionally high...Optical refrigeration in Nd-doped yttrium aluminum garnet ,” Phys. Rev. Lett. 21, 1172 (1968). 2M.S. Chang, S.S. Elliott, T.K. Gustafson, C. Hu, and...idea gained experimental feasibility. Even with this tool, early failures to optically cool condensed media such as Nd3+ doped in yttrium aluminum

Transparent Oxyfluoride Nano-Glass-Ceramics Doped with Pr3+ and Pr3+-Yb3+ for NIR Emission

NASA Astrophysics Data System (ADS)

Gorni, Giulio; Cosci, Alessandro; Pelli, Stefano; Pascual, Laura; Durán, Alicia; Pascual, M. J.

2016-12-01

Pr3+-Yb3+ co-doped oxyfluoride glasses and glass-ceramics (GC) containing LaF3 nanocrystals have been prepared to obtain NIR emission of Yb3+ ions upon Pr3+ excitation in the blue region of the visible spectrum. Two different compositions have been tested 0.1-0.5 Pr-Yb and 0.5-1 Pr-Yb, in addition to Pr3+ singly doped samples. The crystallization mechanism of the nano-glass-ceramics was studied by DTA revealing that it occurs from a constant number of nuclei, the crystal growth being limited by diffusion. HR-TEM demonstrated that phase separation acts as precursor for LaF3 crystallization and a detailed analysis of the chemical composition (EDXS) revealed the enrichment in RE3+ ions inside the initial phase separated droplets, from which the LaF3 crystals are formed. The RE3+ ions incorporation inside LaF3 crystals was also proved by photoluminescence measurements showing Stark splitting of the RE3+ ions energy levels in the glass-ceramic samples. Lifetimes measurements showed the existence of a better energy transfer process between Pr3+ and Yb3+ ions in the glass-ceramics compared to the as made glass, and the highest value of energy transfer efficiency is 59% and the highest theoretical quantum efficiency is 159%, obtained for glass-ceramics GC0.1-0.5 Pr-Yb treated at 620 ºC-40 h.

Yb:YAG disc for high energy laser systems

NASA Astrophysics Data System (ADS)

Nejezchleb, Karel; Kubát, Jan; Å ulc, Jan; Jelínková, Helena

2017-02-01

Large Yb:YAG crystals were grown using of new improved technology enabling to produce YAG crystals without central growth defect. The crystals diameter reached 115-120mm and their central part was used for manufacturing of discs with the diameter larger than 55 mm. Both sides of this discs were polished and coated. Doping concentration of Yb3+ ions in Yb:YAG crystals was measured using of X-ray fluorescence spectrometry. Absorption coefficient of Yb:YAG was measured for different doping concentration of Yb3+ ions. Fluorescence decay time of Yb:YAG was measured at temperatures of 300K and 80 K. We found the fluorescence decay time of the values of 0.95-1 ms at both temperatures stable and independent on the Yb3+ doping concentration in the range of 1-10 at.% Yb/Y demonstrating high chemical purity of grown crystals. Optical homogeneity as measured using of Fizeau double pass interferometer at 633nm resulted with PV values lower than 0.15 λ on clear aperture of 35 mm. Polished surfaces were ideally parallel with the wedge lower than 2 arcsec. Uniformity of laser properties of Yb:YAG was verified by scanning of the disc as active media in plan-convex pulsed laser resonator pumped by semiconductor diode (wavelength 969 nm, pumping beam diameter 100 μm). It was confirmed, that newly developed technology allows to manufacture very large high quality Yb:YAG discs suitable for high power lasers and amplifiers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Qinglong; Chen, Mingming; Li, Junqiang

Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40%more » reduction of transmittance in the 450–850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.« less

Multicolour synthesis in lanthanide-doped nanocrystals through cation exchange in water

NASA Astrophysics Data System (ADS)

Han, Sanyang; Qin, Xian; An, Zhongfu; Zhu, Yihan; Liang, Liangliang; Han, Yu; Huang, Wei; Liu, Xiaogang

2016-10-01

Meeting the high demand for lanthanide-doped luminescent nanocrystals across a broad range of fields hinges upon the development of a robust synthetic protocol that provides rapid, just-in-time nanocrystal preparation. However, to date, almost all lanthanide-doped luminescent nanomaterials have relied on direct synthesis requiring stringent controls over crystal nucleation and growth at elevated temperatures. Here we demonstrate the use of a cation exchange strategy for expeditiously accessing large classes of such nanocrystals. By combining the process of cation exchange with energy migration, the luminescence properties of the nanocrystals can be easily tuned while preserving the size, morphology and crystal phase of the initial nanocrystal template. This post-synthesis strategy enables us to achieve upconversion luminescence in Ce3+ and Mn2+-activated hexagonal-phased nanocrystals, opening a gateway towards applications ranging from chemical sensing to anti-counterfeiting.

Sensing and splicing applications of small core Ge-doped photonic crystal fibers

NASA Astrophysics Data System (ADS)

Wang, Yiping; Brueckner, Sven; Kobelke, Jens; Rothhardt, Manfred; Ecke, Wolfgang; Willsch, Reinhardt; Bartelt, Hartmut

2008-04-01

Sensor related properties of a small core (4.1μm) Ge-doped photonic crystal fiber (PCF) are being reported. Fiber Bragg gratings with 35% and almost 100 % reflectivity were written in the Ge-doped PCF before and after hydrogen loading, respectively, by use of a UV laser. A 5.6pm/°C temperature sensitivity of the FBG was observed. Additionally, a novel method is demonstrated to splice such PCF by use of a commercial fusion splicer with default splice parameters for standard single mode fibers (SMF). No parameter adjustments are required to splice the PCF to various SMFs and a low splice loss of 1.0 ~ 1.4dB can be achieved. No splice interface emerges at the splice joint, which is of advantage for the sensing applications of such a PCF.

Experimental observation of the influence of furnace temperature profile on convection and segregation in the vertical Bridgman crystal growth technique

NASA Technical Reports Server (NTRS)

Neugebauer, G. T.; Wilcox, W. R.

1990-01-01

Azulene-doped naphtalene was directionally solidified using the vertical Bridgman-Stockbarger technique. Doping homogeneity and convection are determined as a function of the temperature profile in the furnace and the freezing rate. Convective velocities are two orders of magnitude lower when the temperature increases with height. The cross sectional variation in azulene concentration tends to be asymmetric. Neither rotation of the ampoule nor deliberate introduction of thermal asymmetries during solidification had a significant influence on cross sectional variations in doping. It is predicted that slow directional solidification under microgravity conditions can produce greater inhomogeneities than on earth. Thus when low freezing rates are necessary in order to avoid constitutional supercooling, it may be necessary to combine microgravity and magnetic fields in order to achieve homogeneous crystals.

Cold crucible Czochralski for solar cells

NASA Technical Reports Server (NTRS)

Trumble, T. M.

1982-01-01

The efficiency and radiation resistance of present silicon solar cells are a function of the oxygen and carbon impurities and the boron doping used to provide the proper resistivity material. The standard Czochralski process used grow single crystal silicon contaminates the silicon stock material due to the use of a quartz crucible and graphite components. The use of a process which replaces these elements with a water cooled copper to crucible has provided a major step in providing gallium doped (100) crystal orientation, low oxygen, low carbon, silicon. A discussion of the Cold Crucible Czochralski process and recent float Zone developments is provided.

Growth and characterization of Yb:Ho:YAG single crystal fiber

NASA Astrophysics Data System (ADS)

Yang, Yilun; Ye, Linhua; Bao, Renjie; Li, Shanming; Zhang, Peixiong; Xu, Min; Hang, Yin

2018-06-01

High quality Yb and Ho co-doped Y3Al5O12 single crystal fibers have been successfully grown by the laser heated pedestal growth method of up to 124 mm in length and 450 μm in diameter for the first time. The results of inductively coupled plasma-atomic emission spectrometry analysis, X-ray diffraction and Raman spectroscopy reveal that the lattice structure and doping concentrations of the SCF are the same as that of the bulk. Scanning electron microscopy microphotographs shows that the fibers only have minor diameter fluctuations within 0.5%.

Spin-State Transition in La1-xSrxCoO3 Single Crystals

NASA Astrophysics Data System (ADS)

Bhardwaj, S.; Prabhakaran, D.; Awasthi, A. M.

2011-07-01

We present a study of the thermal conductivity (κ), specific heat (Cp) and Raman spectra of La1-xSrxCoO3 (x = 0,0.1) single crystals. Both the specimens have low thermal conductivity and board Raman peaks, arising from strong scattering of phonons by lattice disorder, produced by (and doping-enhanced) spin-states admixture of the Co3+ ions. The thermal conductivity anomalously deviates from ˜1/T behaviour at high (room) temperatures, expected of an insulator. High-temperature specific heat reveals large decrease in the metal-insulator (M-I) transition temperature with Sr-doping.

Dynamical Jahn Teller distortion in single crystals of Cu(II) doped magnesium potassium phosphate hexahydrate: a variable temperature EPR study

NASA Astrophysics Data System (ADS)

PrabhuKantan, A.; Velavan, K.; Venkatesan, R.; Sambasiva Rao, P.

2003-05-01

Single crystal electron paramagnetic resonance (EPR) studies on Cu(II)-doped magnesium potassium phosphate hexahydrate have been carried out at room temperature. The temperature dependence of g and A values has been obtained for the polycrystalline sample and the ground state is unambiguously identified. These results indicate the existence of a dynamic Jahn-Teller distortion for Cu(II) ion. The g and A tensor direction cosines are evaluated and compared with Mg-O directions, which confirms that Cu(II) enters substitutionally in the lattice.

Cold crucible Czochralski for solar cells

NASA Astrophysics Data System (ADS)

Trumble, T. M.

The efficiency and radiation resistance of present silicon solar cells are a function of the oxygen and carbon impurities and the boron doping used to provide the proper resistivity material. The standard Czochralski process used grow single crystal silicon contaminates the silicon stock material due to the use of a quartz crucible and graphite components. The use of a process which replaces these elements with a water cooled copper to crucible has provided a major step in providing gallium doped (100) crystal orientation, low oxygen, low carbon, silicon. A discussion of the Cold Crucible Czochralski process and recent float Zone developments is provided.

Gelator-doped liquid-crystal phase grating with multistable and dynamic modes

NASA Astrophysics Data System (ADS)

Lin, Hui-Chi; Yang, Meng-Ru; Tsai, Sheng-Feng; Yan, Shih-Chiang

2014-01-01

We demonstrate a gelator-doped nematic liquid-crystal (LC) phase grating, which can be operated in both the multistable mode and the dynamic mode. Thermoreversible association and dissociation of the gelator molecules can vary and fix the multistable diffraction efficiencies of the gratings. A voltage (V) can also be applied to modulate dynamically the diffraction efficiencies of the grating, which behaves as a conventional LC grating. Experimental results show that the variations of the diffraction efficiencies in the multistable and dynamic modes are similar. The maximum diffraction efficiency is approximately 30% at V = 2 V.

Gelator-doped liquid-crystal phase grating with multistable and dynamic modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Hui-Chi, E-mail: huichilin@nfu.edu.tw; Yang, Meng-Ru; Tsai, Sheng-Feng

2014-01-06

We demonstrate a gelator-doped nematic liquid-crystal (LC) phase grating, which can be operated in both the multistable mode and the dynamic mode. Thermoreversible association and dissociation of the gelator molecules can vary and fix the multistable diffraction efficiencies of the gratings. A voltage (V) can also be applied to modulate dynamically the diffraction efficiencies of the grating, which behaves as a conventional LC grating. Experimental results show that the variations of the diffraction efficiencies in the multistable and dynamic modes are similar. The maximum diffraction efficiency is approximately 30% at V = 2 V.

Seven-core neodymium-doped phosphate all-solid photonic crystal fibers

NASA Astrophysics Data System (ADS)

Wang, Longfei; He, Dongbing; Feng, Suya; Yu, Chunlei; Hu, Lili; Chen, Danping

2016-01-01

We demonstrate a single-mode seven-core Nd-doped phosphate photonic crystal fiber with all-solid structure with an effective mode field diameter of 108 μm. The multicore fiber is first theoretically investigated through the finite-difference time-domain method. Then the in-phase mode is selected experimentally by a far-field mode-filtering method. The obtained in-phase mode has 7 mrad mode field divergences, which approximately agrees with the predicted 5.6 mrad in seven-core fiber. Output power of 15.5 W was extracted from a 25 cm fiber with slope efficiency of 57%.

Atomic force microscopy study on crystal growth of Cu 2+-doped L-arginine phosphate monohydrate crystals

NASA Astrophysics Data System (ADS)

Geng, Y. L.; Xu, D.; Wang, Y. L.; Du, W.; Liu, H. Y.; Zhang, G. H.; Wang, X. Q.; Sun, D. L.

2005-01-01

Sub-steps and defects of the {1 0 0} planes of Cu 2+-doped L-arginine phosphate monohydrate (LAP) crystals are observed by atomic force microscopy. Formation of sub-steps is not due to the stacking faults but a result of single LAP: Cu 2+ molecule acting as growth unit. Two-dimensional (2D) nuclei with the same height as sub-steps occur on the step-edges. Impurities of Cu 2+ ions cause steps bunch and macrosteps formation. Liquid inclusions in the form of long channels form when the macrosteps lose their stability. Numerous small 3D growth hillocks are found in the channels. The extra stress induced by the 3D islands can result in dislocations and steps mismatches.

Cross sections and quantum yields of the 3 micron emission for Er(3+) and Ho(3+) dopants in crystalsls

NASA Astrophysics Data System (ADS)

Payne, Stephen A.; Smith, Larry K.; Krupke, William F.

1995-05-01

The lifetime, quantum yields, and branching ratios for the 2.8 micron emissions of several Er-and Ho-doped fluorides and oxides were measured. Among the fluoride crystals examined, which included LiYF4, BaY2F8, LaF3, and KY3F10, only the Ho:LiFY4 systems showed any proof of nonradiative decay. Conversely, all the oxide crystals were affected by nonradiative processes, resulting in measured quantum yields ranging from 3.6% for Er:Y3Al5O12 to 62% for Er in Gd3Sc2Ga3O12. In addition, plots of the 2.8 micron emission cross sections for seven Er- and Ho-doped crystals were presented.

Growth and spectral-luminescent study of SrMoO4 crystals doped with Tm3+ ions

NASA Astrophysics Data System (ADS)

Dunaeva, E. E.; Zverev, P. G.; Doroshenko, M. E.; Nekhoroshikh, A. V.; Ivleva, L. I.; Osiko, V. V.

2016-03-01

SrMoO4 crystals doped with Tm3+ ions have been produced from a melt using the Czochralski method; their spectral-luminescent characteristics have been studied, and laser radiation has been generated at the wavelength of 1.94 μm using laser-diode excitation. The high absorption section at the wavelength of 795 nm, the fairly high luminescence section, the long lifetime at the upper laser level 3F4 of 1.5 ms, and a wide luminescence band allow one to hope for developing efficient tunable Tm3+: SrMoO4 crystal lasers with diode pumping in the range of 1.7-2.0 μm, which are capable of implementing SRS self-transformation of radiation into the middle IR band.

Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

NASA Astrophysics Data System (ADS)

Sahin, Bünyamin; Kaya, Tolga

2016-01-01

In this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and current-voltage (I-V) measurements. Structural properties of the CuO films were affected from doping. The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases. Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4 M% doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K-doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4 M% Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity.

Investigation of emission properties of doped aromatic derivative organic semiconductor crystals

NASA Astrophysics Data System (ADS)

Stanculescu, A.; Mihut, L.; Stanculescu, F.; Alexandru, H.

2008-04-01

Fluorescence measurements have been made on pure and doped bulk, mechanically polished wafers of crystalline m-DNB and benzil obtained by cutting ingots grown by the Bridgman-Stockbarger method modified for organic compounds crystallization. By comparison with pure matrices, we have investigated the effect of an inorganic dopant (iodine, silver, sodium) and of an organic dopant (m-DNB, naphthalene) on the emission characteristics (position and shape) of these molecular crystals. A slight shift of the emission peaks through high energy and an intense emission peak situated around 2.35 eV correlated with the local trapping level attributed to structural defects, which are involved in radiative processes, have been evidenced in iodine-doped m-DNB. The emission peak of m-DNB-doped benzil situated in the high-energy range (2.97 eV) is associated with direct emission activity of m-DNB, suggesting that this is an active impurity in benzil molecular matrix. We have not observed in benzil any evidence of indirect action of the impurity molecules (atoms) associated with the traps represented by the structural defects that generate changes in the energy levels of the neighbouring molecules and are correlated with different growth conditions. We have not remarked any involvement of the studied inorganic metallic impurities and of some organic impurities, such as naphthalene, in the radiative recombination processes in benzil matrix.

An experimental study of the local electronic structure of B-site gallium doped bismuth ferrite powders

NASA Astrophysics Data System (ADS)

Gholam, Turghunjan; Ablat, Abduleziz; Mamat, Mamatrishat; Wu, Rong; Aimidula, Aimierding; Bake, Muhammad Ali; Zheng, Lirong; Wang, Jiaou; Qian, Haijie; Wu, Rui; Ibrahim, Kurash

2017-08-01

The un-doped and gallium (Ga) doped multiferroic bismuth ferrite (BiFeO3) compounds were successfully synthesized by the hydrothermal technique. This is then followed by a series of detailed investigations into the influence of Ga doping on the structural, morphological, optical and magnetic properties of BiFe1 - xGaxO3 (0 ≤ x ≤ 0.15). X-ray diffraction (XRD) analyses reveal that B-site doping of Ga may lead to the transformation of its crystal structure from a rhombohedral with a space group of R3c to an orthorhombic with a space group of Pbnm phase. The scanning electron microscope (SEM) images show that doping with Ga causes a significant reduction in particle size, when compared to un-doped BiFeO3. X-ray absorption near-edge structure (XANES) spectra have also shown that as the substitution of Ga increases, the Fe K and Bi LIII-edge absorption spectra shift towards higher energy site. It also implies that doping of Ga affects the local structures of both Bi and Fe atoms. Distinct transmission band fluctuations, as shown by Fourier transform infrared (FT-IR) spectra, can provide significant evidence for a transformation in crystal structure, following the increase of Ga concentration. The magnetization hysteresis measurements show that the magnetization decreases when Ga content is x ≥ 0.05. Such a phenomenon mainly stems from the substitution of Fe for an excessive amount of Ga, resulting in reduction of both valence fluctuations and the magnetization in the BiFe1 - xGaxO3 system.

Nanopatterning of Group V Elements for Tailoring the Electronic Properties of Semiconductors by Monolayer Doping.

PubMed

Thissen, Peter; Cho, Kyeongjae; Longo, Roberto C

2017-01-18

Control of the electronic properties of semiconductors is primarily achieved through doping. While scaling down the device dimensions to the molecular regime presents an increasing number of difficulties, doping control at the nanoscale is still regarded as one of the major challenges of the electronic industry. Within this context, new techniques such as monolayer doping (MLD) represent a substantial improvement toward surface doping with atomic and specific doping dose control at the nanoscale. Our previous work has explained in detail the atomistic mechanism behind MLD by means of density-functional theory calculations (Chem. Mater. 2016, 28, 1975). Here, we address the key questions that will ultimately allow one to optimize the scalability of the MLD process. First, we show that dopant coverage control cannot be achieved by simultaneous reaction of several group V elements, but stepwise reactions make it possible. Second, using ab initio molecular dynamics, we investigate the thermal decomposition of the molecular precursors, together with the stability of the corresponding binary and ternary dopant oxides, prior to the dopant diffusion into the semiconductor surface. Finally, the effect of the coverage and type of dopant on the electronic properties of the semiconductor is also analyzed. Furthermore, the atomistic characterization of the MLD process raises unexpected questions regarding possible crystal damage effects by dopant exchange with the semiconductor ions or the final distribution of the doping impurities within the crystal structure. By combining all our results, optimization recipes to create ultrashallow doped junctions at the nanoscale are finally proposed.

Trade-off between Zr Passivation and Sn Doping on Hematite Nanorod Photoanodes for Efficient Solar Water Oxidation: Effects of a ZrO2 Underlayer and FTO Deformation.

PubMed

Subramanian, Arunprabaharan; Annamalai, Alagappan; Lee, Hyun Hwi; Choi, Sun Hee; Ryu, Jungho; Park, Jung Hee; Jang, Jum Suk

2016-08-03

Herein we report the influence of a ZrO2 underlayer on the PEC (photoelectrochemical) behavior of hematite nanorod photoanodes for efficient solar water splitting. Particular attention was given to the cathodic shift in onset potential and photocurrent enhancement. Akaganite (β-FeOOH) nanorods were grown on ZrO2-coated FTO (fluorine-doped tin oxide) substrates. Sintering at 800 °C transformed akaganite to the hematite (α-Fe2O3) phase and induced Sn diffusion into the crystal structure of hematite nanorods from the FTO substrates and surface migration, shallow doping of Zr atoms from the ZrO2 underlayer. The ZrO2 underlayer-treated photoanode showed better water oxidation performance compared to the pristine (α-Fe2O3) photoanode. A cathodic shift in the onset potential and photocurrent enhancement was achieved by surface passivation and shallow doping of Zr from the ZrO2 underlayer, along with Sn doping from the FTO substrate to the crystal lattice of hematite nanorods. The Zr based hematite nanorod photoanode achieved 1 mA/cm(2) at 1.23 VRHE with a low turn-on voltage of 0.80 VRHE. Sn doping and Zr passivation, as well as shallow doping, were confirmed by XPS, Iph, and M-S plot analyses. Electrochemical impedance spectroscopy revealed that the presence of a ZrO2 underlayer decreased the deformation of FTO substrate, improved electron transfer at the hematite/FTO interface and increased charge-transfer resistance at the electrolyte/hematite interface. This is the first systematic investigation of the effects of Zr passivation, shallow doping, and Sn doping on hematite nanorod photoanodes through application of a ZrO2 underlayer on the FTO substrate.

The effect of cation doping on the morphology, optical and structural properties of highly oriented wurtzite ZnO-nanorod arrays grown by a hydrothermal method

NASA Astrophysics Data System (ADS)

Hassanpour, A.; Guo, P.; Shen, S.; Bianucci, P.

2017-10-01

Undoped and C-doped (C: Mg2+, Ni2+, Mn2+, Co2+, Cu2+, Cr3+) ZnO nanorods were synthesized by a hydrothermal method at temperatures as low as 60 °C. The effect of doping on the morphology of the ZnO nanorods was visualized by taking their cross section and top SEM images. The results show that the size of nanorods was increased in both height and diameter by cation doping. The crystallinity change of the ZnO nanorods due to each doping element was thoroughly investigated by an x-ray diffraction (XRD). The XRD patterns show that the wurtzite crystal structure of ZnO nanorods was maintained after cation addition. The optical Raman-active modes of undoped and cation-doped nanorods were measured with a micro-Raman setup at room temperature. The surface chemistry of samples was investigated by x-ray photoelectron spectroscopy and energy-dispersive x-ray spectroscopy. Finally, the effect of each cation dopant on band-gap shift of the ZnO nanorods was investigated by a photoluminescence setup at room temperature. Although the amount of dopants (Mg2+, Ni2+, and Co2+) was smaller than the amount of Mn2+, Cu2+, and Cr3+ in the nanorods, their effect on the band structure of the ZnO nanorods was profound. The highest band-gap shift was achieved for a Co-doped sample, and the best crystal orientation was for Mn-doped ZnO nanorods. Our results can be used as a comprehensive reference for engineering of the morphological, structural and optical properties of cation-doped ZnO nanorods by using a low-temperature synthesis as an economical mass-production approach.

Lifshitz topological transitions, induced by doping and deformation in single-crystal bismuth wires

NASA Astrophysics Data System (ADS)

Nikolaeva, A. A.; Konopko, L. A.; Huber, T. E.; Kobylianskaya, A. K.; Para, Gh. I.

2017-02-01

The features associated with the manifestation of Lifshitz electron topological transitions (ETT) in glass-insulated bismuth wires upon qualitative changes to the topology of the Fermi surface are investigated. The variation of the energy spectrum parameters was implemented by doping Bi with an acceptor impurity Sn and using elastic strain of up to 2%, relative to the elongation in the weakly-doped p-type Bi wires. Pure and doped glass-insulated single-crystal bismuth with different diameters and (1011) orientations along the axis were prepared by the Ulitovsky liquid phase casting method. For the first time, ETT-induced anomalies are observed along the temperature dependences of the thermoemf α(T) as triple-changes of the α sign (given heavy doping of Bi wires with an acceptor impurity Sn). The concentration and energy position of the Σ-band given a high degree of bismuth doping with Sn was assessed using the Shubnikov-de Haas effect oscillations, which were detected both from L-electrons and from T-holes in magnetic fields of up to 14 T. It is shown that the Lifshitz electron-topological transitions with elastic deformation of weakly-doped p-type Bi wires are accompanied by anomalies along the deformation dependences of the thermoemf at low temperatures. The effect is interpreted in terms of the formation of a selective scattering channel of L-carriers into the T-band with a high density of states, which is in good agreement with existing theoretical ETT models.

Synthesis and characterization of barium hexaferrite with manganese (Mn) doping material as anti-radar

NASA Astrophysics Data System (ADS)

Susilawati, Doyan, Aris; Khalilurrahman

2017-01-01

Have been successfully synthesized barium powder doping Manganese hexaferrite with the expected potential as anti-radar material. Synthesis was done by using the co-precipitation method, the variation of the variable x concentrations used were 0; 0.2; 0.4; and 0.6 and calcined at temperatures of 400, 600 and 800°C. Characterization powders of hexaferrite have used XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), LCR (inductance, capacitance, and resistance) meter, and VSM (Vibrating Sample Magnetometer). The higher the concentration and temperature of calcinations given affect the color of the powder. The test results using XRD indicates that it has formed barium hexaferrite phase with a hexagonal crystal structure. Tests using SEM showed that all the constituent elements barium powder hexaferrite by doping Manganese powders have been spread evenly. XRD test results were confirmed by a test using a TEM showing the crystal structure and the powder was sized nano particles. The results from the LCR meter showed that the barium powder hexaferrite by doping Manganese that has been synthesized classified in semiconductor materials. The result from VSM showed that the value of coercivity magnetic powder doped barium hexaferrite Manganese is smaller when compared with barium hexaferrite without doping and belong to the soft magnetic. Based on the results of the synthesis and characterization, we can conclude that the barium powder heksaferrite by doping Manganese potential as a material anti-radar.

Method for the preparation of photochromic insulating crystals

DOEpatents

Abraham, Marvin M.; Boldu, Jose L.; Chen, Yok; Orera, Victor M.

1986-01-01

A method for preparing reversible-photochromic magnesium oxide (MgO) crystals. Single crystals of MgO doped with both lithium (Li) and nickel (Ni) are grown by a conventional arc fusion method. The as-grown crystals are characterized by an amber coloration. The crystals lose the amber coloration and become photochromic when they are thermochemically reduced by heating at temperatures greater than 1000.degree. K. in a hydrogen atmosphere. Alternate irradiation with UV and visible light result in rejuvenation and bleaching of the amber coloration, respectively.

Crystal-field analysis of U3+ ions in K2LaX5 (X=Cl, Br or I) single crystals

NASA Astrophysics Data System (ADS)

Karbowiak, M.; Edelstein, N.; Gajek, Z.; Drożdżyński, J.

1998-11-01

An analysis of low temperature absorption spectra of U3+ ions doped in K2LaX5 (X=Cl, Br or I) single crystals is reported. The energy levels of the U3+ ion in the single crystals were assigned and fitted to a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions at the Cs symmetry site. An analysis of the nephelauxetic effect and crystal-field splittings in the series of compounds is also reported.

Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.

2015-02-21

Initially, the alkaline-earth scintillator, CaI 2:Eu 2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI 2:Eu 2+ has the potential to exceed the excellent scintillation performance of SrI 2:Eu 2+. In fact, theoretical predictions for the light yield of CaI2:Eu 2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI 2:Eu 2+ scintillator, themore » performance of CaI 2:Eu 2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI 2:Eu 2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI 2:Eu 2+ and pure CaI 2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI 2:Eu 2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI 2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI 2:Eu 2+ and un-doped CaI 2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI 2:Eu 2+ and pure CaI 2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.« less

High output power of differently cut Nd:MgO:LiTaO3 CW lasers

NASA Astrophysics Data System (ADS)

Sun, D. H.; Liu, S. D.; Wang, D. Z.; Sang, Y. H.; Kang, X. L.; Liu, H.; Bi, Y.; Yan, B. X.; He, J. L.; Wang, J. Y.

2013-04-01

A high-quality Nd3+ and Mg2+ co-doped LiTaO3 (Nd:MgO:LT) crystal was grown by the Czochralski method. The polarized absorption spectra and fluorescence spectra were studied, and the absorption cross section was calculated by Judd-Ofelt (J-O) theory. The laser performance with different sample cuts of the crystal was investigated for the first time, and it was found that Nd:MgO:LT crystal with different cutting directions (a and c) exhibits different laser properties. By optimizing a partial reflectivity mirror in the laser experimental setting, a high continuous wave output power of 3.58 W was obtained at 1092 and 1076 nm with an optical-to-optical conversion efficiency of 22.78% and slope efficiency of 26.06%. The results indicate that Nd:MgO:LT crystal is a promising candidate for the manufacture of Nd3+ doped periodically poled MgO:LiTaO3 crystal (Nd:PPMgOLT), which should have considerable applications in self-frequency doubling and optical parametric oscillation laser devices.

Crystal Growth and Scintillation Properties of Ce Doped Gd3Ga,Al5O12 Single Crystals

NASA Astrophysics Data System (ADS)

Kamada, Kei; Yanagida, Takayuki; Pejchal, Jan; Nikl, Martin; Endo, Takanori; Tsutsumi, Kousuke; Fujimoto, Yutaka; Fukabori, Akihiro; Yoshikawa, Akira

2012-10-01

Ce1%, 2% and 3% doped Gd3(Ga,Al)5O12 (GAGG) single crystals were grown by the Cz method. Luminescence and scintillation properties were measured. Light yield change along the growth direction and effects of Ce concentration on scintillation properties in Ce:GAGG were studied. Ce3+ 5d-4f emission within 520-530 nm was observed in the Ce:GAGG crystals. The Ce1%:GAGG sample with 3×3×1 mm size showed the highest light yield of 46000 photon/MeV. The energy resolution was 7.8%@662 keV. With increasing solidification fraction, the LY were decreased. It is proposed that the increase of Ga concentration along the growth direction is the main cause of the decrease of LY. The scintillation decay times were accelerated with increasing Ce concentration in the Ce:GAGG crystals. The scintillation decay times were 92.0 ns, 79.1 ns and 68.3 ns in the Ce1, 2 and 3% GAGG, respectively.

Recent advancements in transparent ceramics and crystal fibers for high power lasers

NASA Astrophysics Data System (ADS)

Kim, W.; Baker, C.; Villalobos, G.; Florea, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; Bayya, S.; Sadowski, B.; Hunt, M.; Askins, C.; Peele, J.; Aggarwal, I. D.; Sanghera, J. S.

2013-05-01

In this paper, we present our recent progress in the development of rare-earth (Yb3+ or Ho3+) doped Lu2O3 and Y2O3 sesquioxides for high power solid state lasers. We have fabricated high quality transparent ceramics using nano-powders synthesized by a co-precipitation method. This was accomplished by developments in high purity powder synthesis and low temperature scalable sintering technology developed at NRL. The optical, spectral and morphological properties as well as the lasing performance from our highly transparent ceramics are presented. In the second part of the paper, we discuss our recent research effort in developing cladded-single crystal fibers for high power single frequency fiber lasers has the potential to significantly exceed the capabilities of existing silica fiber based lasers. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by the Laser Heated Pedestal Growth (LHPG) process. Our recent results on the development of suitable claddings on the crystal fiber core are discussed.

Comparative study of blue laser diode driven cerium-doped single crystal phosphors in application of high-power lighting and display technologies

NASA Astrophysics Data System (ADS)

Balci, Mustafa H.; Chen, Fan; Cunbul, A. Burak; Svensen, Øyvind; Akram, M. Nadeem; Chen, Xuyuan

2018-02-01

Cerium-doped single crystals (Ce:LuAG, Ce:YAG, Ce:GAGG, Ce:GdYAG) have been investigated as stationary phosphor candidates for blue laser driven solid-state lighting without heat sink. The luminous properties of the single crystals are superior compared to the commercial ceramic powder phosphor wheels (Ce3+: Y3Al5O12). The high-power blue laser diode driven temperature increase of the crystals versus quantum efficiency is experimentally measured and discussed. We have carried out realistic measurements at high excitation power levels and at high temperatures. Limitation of phosphors as stationary sources is determined for commercial usage. The measurements were done without any heat sink to see the relative comparison of SCPs in the worst-case scenarios. The results indicate that Gd and Ga addition decreases the luminescence quenching temperature. Based on their superior properties, these single crystals can serve as potential phosphor candidates for high-power blue diode laser driven picture projectors for the green and red channels.

Targeted Basic Studies of Ferroelectric and Ferroelastic Materials for Piezoelectric Transducer Applications.

DTIC Science & Technology

1983-03-01

PLZT ceramics. Low temperature studies on pure and doped PZTs have given the first clear indi- cation of the intrinsic (averaged) single domain...8217 11 4.0 PYROELECTRIC MATERIALS 27 4.1 Micro Composites 27 4.2 ’ Doped ’ Tungsten Bronze and TGS Structure Single Crystals 28 5.0 FERROELECTRIC...differences in piezo- electric activity, coupling constant and permittivity between differently doped PZTs are extrinsic and freeze out at 4°K. Extending

Compound semi-conductors and controlled doping thereof

NASA Technical Reports Server (NTRS)

Larkin, David J. (Inventor); Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor); Matus, Lawrence G. (Inventor)

1998-01-01

A method of controlling the amount of impurity incorporation in a crystal grown by a chemical vapor deposition process. Conducted in a growth chamber, the method includes the controlling of the concentration of the crystal growing components in the growth chamber to affect the demand of particular growth sites within the growing crystal thereby controlling impurity incorporation into the growth sites.

Crystal Growth and Optical Properties of Co2+ Doped SrLaGa3O7

DTIC Science & Technology

2001-01-01

Electron Spin Resonance, absorption spectra, gallate crystals, thermal annealing. 1. INTRODUCTION SrLaGa307 (SLGO) belongs to the family of binary... gallates of alkaline and rare earth metals. Crystal of these compounds have the tetragonal gehlenite (Ca 2AS12SiO 7) structure (space group: P-421ml, D 3 2d

Light-Driven Chiral Molecular Motors for Passive Agile Filters

DTIC Science & Technology

2014-05-20

liquid crystal , we fabricated the self-organized, phototubable 3D photonic superstructure, i.e. photoresponsive monodisperse cholesteric liquid...systems for applications. Here the new light-driven chiral molecular switch and upconversion nanoparticles, doped in a liquid crystal media, were...the bottom-up nanofabrication of intelligent molecular devices. Light-driven chiral molecular switches or motors in liquid crystal (LC) media that

Disorder in KHCO3 as studied by EPR and DTA in Cu2+ doped and gamma-irradiated single crystals

NASA Astrophysics Data System (ADS)

Koksal, F.; Karabulut, B.; Demir, D.; Icbudak, H.; Koseoglu, R.

2005-08-01

Kalicinite (KHCO3) single crystals were investigated by the electron paramagnetric resonance (EPR) technique in their Cu2+ doped and gamma- irradiated states. It is observed that the behavior of the spectrum is the same at ambient and low temperatures down to 113 K in consistence with the monoclinic symmetry of the crystal. However, when the temperature is increased to 313 K, only one site signals were observed at all orientations of the magnetic field for the Cu2+ doped samples as the site splitted signals overlap at this temperature. Furthermore, for the gamma-irradiated crystals, two sites were observed for the induced H(C)over dot O-3 and (C)over dot O-2(-) radicals at ambient temperature for an arbitrary orientation of the magnetic field. However, when the temperature is increased to 348 K, the signals due to the H(C)over dot O-3 radical overlap indicating only one site, but the signals due to (C)over dot O-2(-) the radical do not and continue to indicate the presence of the two sites. Therefore, we conclude that this one site transition at 313 K is due to the disordering of the proton vacancies, as the charge compensation of Cu2+ is fulfilled by K+ and proton holes. This indicates that the proton vacancies come to disorder at 313 K and the protons get disordered at 348 K. The differential thermal analysis results show two small endothermic peaks for the Cu2+ doped and gamma-irradiated samples at 313 and 348 K that were attributed to the disorder of the proton vacancies and protons, in consistency with the EPR results.

Boron doping induced thermal conductivity enhancement of water-based 3C-Si(B)C nanofluids.

PubMed

Li, Bin; Jiang, Peng; Zhai, Famin; Chen, Junhong; Bei, Guoping; Hou, Xinmei; Chou, Kuo-Chih

2018-08-31

In this paper, the fabrication and thermal conductivity (TC) of water-based nanofluids using boron (B)-doped SiC as dispersions are reported. Doping B into the β-SiC phase leads to the shrinkage of the SiC lattice due to the substitution of Si atoms (0.134 nm radius) by smaller B atoms (0.095 nm radius). The presence of B in the SiC phase also promotes crystallization and grain growth of obtained particles. The tailored crystal structure and morphology of B-doped SiC nanoparticles are beneficial for the TC improvement of the nanofluids by using them as dispersions. Using B-doped SiC nanoparticles as dispersions for nanofluids, a remarkable improvement in stability was achieved in SiC-B6 nanofluid at pH 11 by means of the Zeta potential measurement. By dispersing B-doped SiC nanoparticles in water-based fluids, the TC of the as-prepared nanofluids containing only 0.3 vol.% SiC-B6 nanoparticles is remarkably raised to 39.3% at 30 °C compared to the base fluids, and is further enhanced with the increased temperature. The main reasons for the improvement in TC of SiC-B6 nanofluids are more stable dispersion and intensive charge ions vibration around the surface of nanoparticles as well as the enhanced TC of the SiC-B dispersions.

Photoelectrochemical performance of W-doped BiVO4 thin films deposited by spray pyrolysis

NASA Astrophysics Data System (ADS)

Holland, S. Keith; Dutter, Melissa R.; Lawrence, David J.; Reisner, Barbara A.; DeVore, Thomas C.

2014-01-01

The effects of tungsten doping and hydrogen annealing on the photoelectrochemical (PEC) performance of bismuth vanadate (BiVO4) photoanodes for solar water splitting were studied. Thin films of BiVO were deposited on indium tin oxide-coated glass slides by ultrasonic spray pyrolysis of an aqueous solution containing bismuth nitrate and vanadium oxysulfate. Tungsten doping was achieved by adding either silicotungstic acid (STA) or ammonium metatungstate (AMT) to the precursor. The 1.7- to 2.2-μm-thick films exhibited a highly porous microstructure. Undoped films that were reduced at 375°C in 3% H exhibited the largest photocurrent densities under 0.1 W cm-2 AM1.5 illumination, where photocurrent densities of up to 1.3 mA cm-2 at 0.5 V with respect to Ag/AgCl were achieved. Films doped with 1% or 5% (atomic percent) tungsten from either STA or AMT exhibited reduced PEC performance and greater sample-to-sample performance variations. Powder x-ray diffraction data indicated that the films continue to crystallize in the monoclinic polymorph at low doping levels but crystallize in the tetragonal scheelite structure at higher doping. It is surmised that the phase and morphology differences promoted by the addition of W during the deposition process reduced the PEC performance as measured by photovoltammetry.

Study of linear optical parameters of sodium sulphide nano-particles added ADP crystals

NASA Astrophysics Data System (ADS)

Kochuparampil, A. P.; Joshi, J. H.; Dixit, K. P.; Jethva, H. O.; Joshi, M. J.

2017-05-01

Ammonium Dihydrogen Phosphate (ADP) is one of the nonlinear optical crystals. It is having various applications like optical mixing, electro-optical modulator, harmonic generators, etc. Chalcogenide compounds are poorly soluble in water and difficult to add in the water soluble ADP crystals. The solubility of Chalcogenide compounds can be increased by synthesizing the nano-structured samples with suitable capping agent. In the present study sodium sulphide was added in to ADP to modify its linear optical parameters. Sodium sulphide nano particles were synthesized by co-precipitation technique using Ethylene diamine as capping agent followed by microwave irradiation. The powder XRD confirmed the nano-structured nature of sodium sulphide nano particles. The solubility of nanoparticles of sodium sulphide increased significantly in water compared to the bulk. Pure and Na2S added ADP crystals were grown by slow solvent evaporation method at room temperature. The presence of sodium in ADP was confirmed by AAS. The UV-Vis spectra were recorded for all crystals. Various optical parameters like, transmittance, energy band gap, extinction coefficient, refractive index, optical conductivity, etc. were evaluated. The electronic polarizibility of pure and doped crystals calculated from energy band gap. The effect of doping concentration was found on various parameters.

Electrodeposition of Zn-doped α-nickel hydroxide with flower-like nanostructure for supercapacitors

NASA Astrophysics Data System (ADS)

You, Zheng; Shen, Kui; Wu, Zhicheng; Wang, Xiaofeng; Kong, Xianghua

2012-08-01

Zn-doped α-nickel hydroxide materials with flower-like nanostructures are synthesized by electrochemical deposition method. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (SEM) and electrochemical measurements. XRD spectra indicate nickel hydroxide doped with Zn is α-Ni(OH)2 with excellent crystallization. The SEM observation shows that the formation of Zn-doped Ni(OH)2 includes two steps: a honeycomb-like film forms on the substrate first, then flower-like particles forms on the films. The nickel hydroxide doped with 5% Zn can maintain a maximum specific capacitance of 860 F g-1, suggesting its potential application in electrochemical capacitors.

Dynamic control of mode field diameter and effective area by germanium doping of hexagonal photonic crystal fibers

NASA Astrophysics Data System (ADS)

Miyagi, Kazuya; Namihira, Yoshinori; Kasamatsu, Yuho; Hossain, Md. Anwar

2013-07-01

We demonstrate dynamic control of the effective area ( A eff) of photonic crystal fibers (PCFs) in the range of 18.1-8.22 μm2 and the mode field diameter in the range of 4.78-3.42 μm. This control was realized by altering their structural properties and varying the germanium (Ge) doping rate, which changed the refractive index difference (Δ n Ge) between 1.0 and 3.0% relative to the refractive index of the silica cladding. This was achieved by adjusting the Ge doping rate in the core and changing the radius ( d core) of the doped region, i.e., by changing the equivalent refractive index, using numerical calculations. Numerical results were verified by comparison with experimental results for a fabricated Gedoped PCF obtained by far-field scanning based on the ITU-T Petermann II definition. The proposed approach will simultaneously decrease Aeff and achieves high light confinement and high nonlinearity in PCFs. It enables architectonics/controllability of highly nonlinear PCFs with passive optical devices in photonic networks and life science applications.

Light-induced absorption and its relaxation under illumination of continuous wave ultraviolet light in Mn-doped near-stoichiometric LiNbO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Youwen; Kitamura, Kenji; Takekawa, Shunji

2005-04-01

The steady-state light-induced absorption and the temporal relaxation behavior under illumination of cw ultraviolet light in Mn-doped near-stoichiometric LiNbO{sub 3} with different crystal compositions are investigated. The ultraviolet-light-induced absorption has been assigned to small polarons Nb{sub Li}{sup 4+} by measuring the absorption spectra at room temperature. The dependences of relaxation behaviors (time constant and stretching factor) of light-induced absorption on various illumination conditions (intensity, polarization) and temperature are presented, which are very different from those observed in Fe-doped LiNbO{sub 3} illuminated with highly intense light pulse, though the temporal relaxation follows the same stretched-exponential decay behavior in both cases. Themore » results are explained reasonably by using the model of distance-dependent electron transition probabilities between localized deep traps and small polarons without any additional assumptions, and discussed to tailor doped near-stoichiometric LiNbO{sub 3} crystals for two-color holographic recording with cw laser light.« less

Direct measurement of the low temperature spin state transitions in La1-xSrxCoO3 (0.05 < x < 0.3)

NASA Astrophysics Data System (ADS)

Gulec, A.; Klie, R. F.

2014-12-01

Sr-doped LaCoO3 has a complex magnetic phase diagram, which is believed to be directly correlated to changes in the crystal structure and ordering of the Co3+ spin states. In this work, we study the low temperature Co3+-ion spin state transitions in Sr-doped LaCoO3 around the critical doping concentration where a metal to insulator transition has been observed using electron energy-loss spectroscopy of the O K-edge combined with the Co L-edge fine structure. We measure the local spin state of the Co3+-ions and we demonstrate that the Co3+ spin-state transition only occurs in La0.95Sr0.05CoO3 single-crystal materials in the temperature range accessible by LN2 in-situ cooling, while no structural symmetry change is observed. The presence of this low-temperature spin-state transition in La1-xSrxCoO3 (x < 0.17) has been proposed as the origin of the percolative magnetic ordering in doped LaCoO3.

Impact of vacancies on electronic properties of black phosphorus probed by STM

NASA Astrophysics Data System (ADS)

Riffle, J. V.; Flynn, C.; St. Laurent, B.; Ayotte, C. A.; Caputo, C. A.; Hollen, S. M.

2018-01-01

Black phosphorus (BP) is receiving significant attention because of its direct 0.4-1.5 eV layer-dependent bandgap and high mobility. Because BP devices rely on exfoliation from bulk crystals, there is a need to understand the native impurities and defects in the source material. In particular, samples are typically p-doped, but the source of the doping is not well understood. Here, we use scanning tunneling microscopy and spectroscopy to compare the atomic defects of BP samples from two commercial sources. Even though the sources produced crystals with an order of magnitude difference in impurity atoms, we observed a similar defect density and level of p-doping. We attribute these defects to phosphorus vacancies and provide evidence that they are the source of p-doping. We also compare these native defects to those induced by air exposure and show that they are distinct and likely more important for the control of electronic structure. These results indicate that impurities in BP play a minor role compared to vacancies, which are prevalent in commercially available materials, and call for better control of vacancy defects.

Synthesis, self-assembly, and properties of Mn doped ZnO nanoparticles.

PubMed

Barick, K C; Bahadur, D

2007-06-01

We report here a novel process to prepare Mn doped ZnO nanoparticles by a soft chemical route at low temperature. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and manganese acetate tetrahydrate heated under reflux to 160-175 degrees C using diethylene glycol as a solvent. X-ray diffraction analysis reveals that the Mn doped ZnO crystallizes in a wurtzite structure with crystal size of 15-25 nm. These nano size crystallites of Mn doped ZnO self-organize into polydisperse spheres in size ranging from 100-400 nm. Transmission Electron Microscopy image also shows that each sphere is made up of numerous nanocrystals of average diameter 15-25 nm. By means of X-ray photoelectron spectroscopy and electron spin resonance spectroscopy, we determined the valence state of Mn ions as 2+. These nanoparticles were found to be ferromagnetic at room temperature. Monodisperse porous spheres (approximately 250 nm) were obtained by size selective separation technique and then self-assembled in a closed pack periodic array through sedimentation with slow solvent evaporation, which gives strong opalescence in visible region.

Structural and optical properties of nanocrystalline ZnS and ZnS:Al films

NASA Astrophysics Data System (ADS)

Hurma, T.

2018-06-01

ZnS and ZnS:Al films have been deposited by ultrasonic spray pyrolysis (USP) method. Three different atomic ratios of aluminium were used as the dopant element. The effects of aluminum incorporation on structural and optical properties of the ZnS films have been investigated. The XRD analysis showed that the cubic structure of the ZnS was not much affected by Al doping. The crystal size of the films decreased, as the Al ratio increased. Al incorporation caused an increase in the intensity of ZnS films' peaks observed in Raman spectra and nearly symmetrical peaks were observed. Al doping caused a small decrease in optical band gap of the ZnS film. The coating of ZnS:Al films on the surface was quite good and there were not any deformation in their crystallization levels. Reflectance values of films are about 5% in the visible region but a little decrease is seen with aluminum doping. We can say that Al doping tends to improve the optical properties of the ZnS:Al films when compared with the undoped ZnS.

Photorefraction in the ultraviolet: Materials and effects

NASA Astrophysics Data System (ADS)

Laeri, F.; Jungen, R.; Angelow, G.; Vietze, U.; Engel, T.; Würtz, M.; Hilgenberg, D.

1995-10-01

Doped as well as nominally pure crystals of Lithium Niobate (LiNbO3), ι-Arginine Phosphate (LAP), Lithium Iodate (LiIO3), Potassium Dihydrogen Phosphate (KDP), Lithium Formate (LFM), Beta-Barium Borate (BBO), and lithium tetra borate were grown and investigated for photorefractive effects at ultraviolet wavelengths down to 333 nm. In nominally undoped LiNbO3 crystals strong beam coupling effects were observed. In contrast to the visible we revealed a diffusion-dominated charge transport mechanism based on holes, and a low photovoltaic field in the order of 550 V/cm. With such a crystal we investigated the modulation transfer function of a lensless image projection system based on a phase conjugation scheme. A spatial frequency response beyond 2800 line pairs per millimeter was observed. Photorefractive beam coupling was also obtained in LiIO3. Light-induced scattering was detected in iron-doped LiIO3 whereas as-grown LAP material did not exhibit any observable photorefractive effects. However, 100 kV X-ray irradiation seems to induce material defects which can lead to weak light-induced scattering at 351 nm. In all other above-mentioned materials, doped as well as undoped, light-induced scattering could not be observed. On the other hand, this is appreciated in all the applications where the crystals are used as nonlinear material for optical frequency conversion.

Diatom-templated TiO2 with enhanced photocatalytic activity: biomimetics of photonic crystals

NASA Astrophysics Data System (ADS)

He, Jiao; Chen, Daomei; Li, Yongli; Shao, Junlong; Xie, Jiao; Sun, Yuejuan; Yan, Zhiying; Wang, Jiaqiang

2013-11-01

The siliceous frustules with sophisticated optical structure endow diatoms with superior solar light-harvesting abilities for effective photosynthesis. The preserved frustules of diatom ( Cocconeis placentula) cells, as biophotonic crystals, were thus employed as both hard templates and silicon resources to synthesize TiO2 photocatalyst. Characterizations by a combination of physicochemical techniques proved that the bio-inspired sample is TiO2-coated SiO2 with biogenic C self-doped in. It was found that the synthesized composites exhibited similar morphologies to the original diatom templates. In comparison with commercial Degussa P25 TiO2, the C-doped TiO2/SiO2 catalyst exhibited more light absorption in the visible region and higher photocatalytic efficiency for photodegradation of rhodamine B under visible light due to the biomorphic hierarchical structures, TiO2 coating and C-doping.

Radio- and photoluminescence properties of Ce/Tb co-doped glasses with huntite-like composition

NASA Astrophysics Data System (ADS)

Lorenzi, Roberto; Golubev, Nikita V.; Ziaytdinova, Mariyam Z.; Jarý, Vítězslav; Babin, Vladimir; Malashkevich, Georgii E.; Paleari, Alberto; Sigaev, Vladimir N.; Fasoli, Mauro; Nikl, Martin

2018-04-01

Optical properties of yttria-aluminoborate (YAB) glasses with general composition 10(CexTbyY(1-x-y))-30Al2O3-60B2O3 are investigated and compared with data available on YAB crystals with huntite-like structure. Ce doped samples show optical features ascribable to preferential location of rare earth ions in sites with specific geometry similar to that observed in crystalline structures. Samples prepared with Tb ions as emission activator and Ce ions as sensitizer have been studied within the framework of non-radiative energy transfer. The resulting Förster radius is of 4.6 ± 0.5 Å comparable with that observed in Ce/Tb co-doped YAl3(BO3)4 crystals. The investigated materials possess radio- and photoluminescence emission efficiencies and performances comparable to that of crystalline counterparts with the advantage of having easiness of preparation and workability typical of glassy systems.

Effect of nitrogen on the growth of boron doped single crystal diamond

DOE PAGES

Karna, Sunil; Vohra, Yogesh

2013-11-18

Boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using microwave plasma assisted chemical vapor deposition. A modification in surface morphology of the film with increasing boron concentration in the plasma has been observed using atomic force microscopy. Use of nitrogen during boron doping has been found to improve the surface morphology and the growth rate of films but it lowers the electrical conductivity of the film. The Raman spectra indicated a zone center optical phonon mode along with a few additional bands at the lower wavenumber regions. The change in the peak profilemore » of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. Furthermore, sharpening and upshift of Raman line was observed in the film that was grown in presence of nitrogen along with diborane in process gas.« less

Frequency doubling of a tunable ytterbium-doped fibre laser in KTP crystals phase-matched in the XY and YZ planes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akulov, V A; Kablukov, S I; Babin, Sergei A

2012-02-28

This paper presents an experimental study of frequency doubling of a tunable ytterbium-doped fibre laser in KTP crystals phase-matched in the XY and YZ planes. In the XY plane, we obtained continuous tuning in the range 528 - 540 nm through intracavity frequency doubling. The second-harmonic power reached 450 mW for 18 W of multimode diode pump power, which was five times higher in comparison with single-pass frequency doubling. In a single-pass configuration in the YZ plane, we obtained a wide tuning range (527 - 551 nm) in the green spectral region and a second-harmonic power of {approx}10 mW. Themore » tuning range was only limited by the mechanical performance of the fibre Bragg grating and can potentially be extended to the entire lasing range of the ytterbium-doped fibre laser.« less

Czochralski and modified Bridgman-Stockbarger growth of pure, Cd 2+ and Nd 3+ doped benzil single crystals

NASA Astrophysics Data System (ADS)

Aggarwal, M. D.; Wang, W. S.; Tambwe, M.

1993-03-01

Pure, Cd2+ and Nd3+-doped benzil C6H5COCOC6H5 have been grown from melt using the Czochralski and modified Bridgman-Stockbarger methods. Angle-tuned second harmonic generation of pure benzil from Nd:YAG laser radiation of λ = 1.06 μm with a conversion efficiency η = I2w/Iw = 0.4% has been demonstrated. We have used a Nd:YAG pulse laser to measure the radiation damage threshold as 15.9 MW/cm2 (c-axis) and 23.9 MW/cm2 (a-axis) under the conditions that laser pulse width is 10 ns. Under the same conditions, the conversion efficiency of Nd3+ and Cd2+-doped benzil, η= I2w/Iw = 1.1%, has been demonstrated. The radiation threshold is higher than for pure benzil crystals.

Thermoelectric and magnetic properties of Cr-doped single crystal Bi2Se3 - Search for energy filtering

NASA Astrophysics Data System (ADS)

Cermak, P.; Ruleova, P.; Holy, V.; Prokleska, J.; Kucek, V.; Palka, K.; Benes, L.; Drasar, C.

2018-02-01

Thermoelectric effects are one of the promising ways to utilize waste heat. Novel approaches have appeared in recent decades aiming to enhance thermoelectric conversion. The theory of energy filtering of free carriers by inclusions is among the latest developed methods. Although the basic idea is clear, experimental evidence of this phenomenon is rare. Based on this concept, we searched suitable systems with stable structures showing energy filtering. Here, we report on the anomalous behavior of Cr-doped single-crystal Bi2Se3 that indicates energy filtering. The solubility of chromium in Bi2Se3 was studied, which is the key parameter in the formation process of inclusions. We present recent results on the effect of Cr-doping on the transport coefficients on a wide set of single crystalline samples. Magnetic measurements were used to corroborate the conclusions drawn from the transport and X-ray measurements.

Thermal equilibrium concentration of intrinsic point defects in heavily doped silicon crystals - Theoretical study of formation energy and formation entropy in area of influence of dopant atoms-

NASA Astrophysics Data System (ADS)

Kobayashi, K.; Yamaoka, S.; Sueoka, K.; Vanhellemont, J.

2017-09-01

It is well known that p-type, neutral and n-type dopants affect the intrinsic point defect (vacancy V and self-interstitial I) behavior in single crystal Si. By the interaction with V and/or I, (1) growing Si crystals become more V- or I-rich, (2) oxygen precipitation is enhanced or retarded, and (3) dopant diffusion is enhanced or retarded, depending on the type and concentration of dopant atoms. Since these interactions affect a wide range of Si properties ranging from as-grown crystal quality to LSI performance, numerical simulations are used to predict and to control the behavior of both dopant atoms and intrinsic point defects. In most cases, the thermal equilibrium concentrations of dopant-point defect pairs are evaluated using the mass action law by taking only the binding energy of closest pair to each other into account. The impacts of dopant atoms on the formation of V and I more distant than 1st neighbor and on the change of formation entropy are usually neglected. In this study, we have evaluated the thermal equilibrium concentrations of intrinsic point defects in heavily doped Si crystals. Density functional theory (DFT) calculations were performed to obtain the formation energy (Ef) of the uncharged V and I at all sites in a 64-atom supercell around a substitutional p-type (B, Ga, In, and Tl), neutral (C, Ge, and Sn) and n-type (P, As, and Sb) dopant atom. The formation (vibration) entropies (Sf) of free I, V and I, V at 1st neighboring site from B, C, Sn, P and As atoms were also calculated with the linear response method. The dependences of the thermal equilibrium concentrations of trapped and total intrinsic point defects (sum of free I or V and I or V trapped with dopant atoms) on the concentrations of B, C, Sn, P and As in Si were obtained. Furthermore, the present evaluations well explain the experimental results of the so-called ;Voronkov criterion; in B and C doped Si, and also the observed dopant dependent void sizes in P and As doped Si crystals. The expressions obtained in the present work are very useful for the numerical simulation of grown-in defect behavior, oxygen precipitation and dopant diffusion in heavily doped Si. DFT calculations also showed that Coulomb interaction reaches approximately 30 Å from p (n)-type dopant atoms to I (V) in Si.

Accurate X-ray diffraction studies of KTiOPO{sub 4} single crystals doped with niobium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Sorokina, N. I.; Alekseeva, O. A.

2017-01-15

Single crystals of potassium titanyl phosphate doped with 4% of niobium (КТР:4%Nb) and 6% of niobium (KTP:6%Nb) are studied by accurate X-ray diffraction at room temperature. The niobium atoms are localized near the Ti1 and Ti2 atomic positions, and their positions are for the first time refined independent of the titanium atomic positions. Maps of difference electron density in the vicinity of K1 and K2 atomic positions are analyzed. It is found that in the structure of crystal КТР:4%Nb, additional positions of K atoms are located farther from the main positions and from each other than in КТР and KTP:6%Nbmore » crystals. The nonuniform distribution of electron density found in the channels of the КТР:4%Nb structure is responsible for ~20% increase in the signal of second harmonic generation.« less