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  1. Spatial distribution of dissolved Pb,Hg,Cd,Cu and As in the Bohai Sea

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Characteristics of the spatial distribution of selected dissolved heavy metals were analyzed during large scale surveys from August 12 to 25.2003 in the Bohai Sea.Dissolved Pb was the only element with average concentrations higher than the grade-one sea water quality standard of China.The spatial distribution of dissolved Pb in surface water was similar to those of Cd,Cu and As,where the isopleths generally indicated decreasing values from the bays to the central areas.Only for Hg did the high concentrations not only appear in Liaodong Bay,Bohai Bay and Laizhou Bay,but also in the Central Area,viz.not only in inshore but also in offshore areas.Vertical distributions of dissolved Pb,Cd,Cu and As were largely uniform,while that of dissolved Hg increased with depth.We infer that the input of pollutants from land was the main influencing factor for the detected distribution patterns of dissolved heavy metals,followed by the dynamics of sea water,release from bottom sediments and biochemical processes.Comparing with historical data,average concentrations of dissolved heavy metals appear to decline in recent years.

  2. Theoretical study of heavy metal Cd, Cu, Hg, and Ni(II) adsorption on the kaolinite(0 0 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jian, E-mail: zhaojian0209@aliyun.com [Institute of Applied Physics and Computational Mathematics, PO Box 8009, Beijing 100088 (China); State Key Laboratory of Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); He, Man-Chao [State Key Laboratory of Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China)

    2014-10-30

    Highlights: • We investigated the adsorption of Cd, Cu, Hg, and Ni(II) on kaolinite(0 0 1) surface. • The adsorption capabilities of the kaolinite for HM atoms were Ni > Cu > Cd > Hg(II). • The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms. • The adsorption energy decreases with the coverage for Ni(II) atoms. - Abstract: Heavy metal pollution is currently of great concern because it has been recognized as a potential threat to air, water, and soil. Adsorption was one of the most popular methods for the removal of heavy metal. The adsorption of heavy metal Cd, Cu, Hg, and Ni(II) atoms on the hydroxylated (0 0 1) surface of kaolinite was investigated using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics were systematically studied for a wide range of coverage Θ [from 0.11 to 1.0 monolayers (ML)] and adsorption sites. The most stable among all possible adsorption sites for Cd(II) atom was the two-fold bridge site followed by the one-fold top site, and the top site was the most favorite adsorption site for Cu and Ni(II) atoms, while the three-fold hollow site was the most stable adsorption site for Hg(II) atom followed by the two-fold bridge site. The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms, thus indicating the higher stability of surface adsorption and a tendency to the formation of adsorbate islands (clusters) with increasing the coverage. However, the adsorption energy of Ni(II) atoms decreases when increasing the coverage. The adsorption capabilities of the kaolinite clay for the heavy metal atoms were in the order of Ni > Cu > Cd > Hg(II). The other properties of the Cd, Cu, Hg, and Ni(II)/kaolinite(0 0 1) system including the different charge distribution, the lattice relaxation, and the electronic density of states were also studied and discussed in detail.

  3. Zn, Cu, Cd and Hg binding to metallothioneins in harbour porpoises Phocoena phocoena from the southern North Sea

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    Jauniaux Thierry

    2006-02-01

    Full Text Available Abstract Background Harbour porpoises Phocoena phocoena from the southern North Sea are known to display high levels of Zn and Hg in their tissues linked to their nutritional status (emaciation. The question arises regarding a potential role of metallothioneins (MTs with regard to these high metal levels. In the present study, metallothionein detection and associated Zn, Cd, Cu and Hg concentrations were investigated in the liver and kidney of 14 harbour porpoises collected along the Belgian coast. Results Metallothioneins seemed to play a key role in essential metal homeostasis, as they were shown to bind 50% of the total hepatic Zn and 36% of the total hepatic Cu concentrations. Renal MTs also participated in Cd detoxification, as they were shown to bind 56% of the total renal Cd. Hg was mainly found in the insoluble fraction of both liver and kidney. Concomitant increases in total Zn concentration and Zn bound to MTs were observed in the liver, whereas Zn concentration bound to high molecular weight proteins remained constant. Cu, Zn and Cd were accumulated preferentially in the MT fraction and their content in this fraction increased with the amount in the hepatocytosol. Conclusion MTs have a key role in Zn and Cu homeostasis in harbour porpoises. We demonstrated that increasing hepatic Zn concentration led to an increase in Zn linked to MTs, suggesting that these small proteins take over the Zn overload linked to the poor body condition of debilitated harbour porpoises.

  4. Phase Stability and Electronic Structure of In-Free Photovoltaic Materials Cu2IISnSe4 (II: Zn, Cd, Hg)

    Science.gov (United States)

    Nakamura, Satoshi; Maeda, Tsuyoshi; Wada, Takahiro

    2011-05-01

    We have theoretically evaluated the phase stability and electronic structure of Cu2CdSnSe4 and Cu2HgSnSe4 and compared the results with those of Cu2ZnSnSe4. The enthalpies of formation for kesterite (KS), stannite (ST), and wurtz-stannite (WST) phases of Cu2ZnSnSe4 (CZTSe), Cu2CdSnSe4, and Cu2HgSnSe4 were calculated by first-principles calculations. In Cu2CdSnSe4 and Cu2HgSnSe4, the stannite (ST) phase is the most stable among these phases. The valence band maximum (VBM) of ST-type Cu2CdSnSe4 consists of antibonding orbitals of Cu 3d and Se 4p, while the conduction band minimum (CBM) consists of antibonding orbitals of Sn 5s and Se 4p. The VBM of Cu2HgSnSe4 also consist of antibonding orbitals of Cu 3d and Se 4p. However, the CBM of Cu2HgSnSe4 consists of antibonding orbitals of Hg 6s, Sn 5s, and Se 4p.

  5. Water Soluble Cationic Porphyrin Sensor for Detection of Hg2+, Pb2+, Cd2+, and Cu2+

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    Matibur Zamadar

    2016-01-01

    Full Text Available Here we report the sensing properties of the aqueous solution of meso-tetra(N-methyl-4-pyridylporphine tetrachloride (1 for simultaneous detection of toxic metal ions by using UV-vis spectroscopy. Cationic porphyrin 1 displayed different electronic absorptions in UV-vis region upon interacting with Hg2+, Pb2+, Cd2+, and Cu2+ ions in neutral water solution at room temperature. Quite interestingly, the porphyrin 1 showed that it can function as a single optical chemical sensor and/or metal ion receptor capable of detecting two or more toxic metal ions, particularly Hg2+, Pb2+, and Cd2+ ions coexisting in a water sample. Porphyrin 1 in an aqueous solution provides a unique UV-vis sensing system for the determination of Cd2+ in the presence of larger metal ions such as Hg2+, or Pb2+. Finally, the examination of the sensing properties of 1 demonstrated that it can operate as a Cu2+ ion selective sensor via metal displacement from the 1-Hg2+, 1-Pb2+, and 1-Cd2+.

  6. Particulate contacts to Si and CdTe: Al, Ag, Hg-Cu-Te, and Sb-Te

    Science.gov (United States)

    Schulz, Douglas L.; Ribelin, Rosine; Curtis, Calvin J.; Ginley, David S.

    1999-03-01

    Our team has been investigating the use of particle-based contacts in both Si and CdTe solar cell technologies. First, in the area of contacts to Si, powders of Al and Ag prepared by an electroexplosion process have been characterized by transmission electron microscopy (TEM), TEM elemental determination X-ray spectroscopy (TEM-EDS), and TEM electron diffraction (TEM-ED). These Al and Ag particles were slurried and tested as contacts to p- and n-type silicon wafers, respectively. Linear current-voltage (I-V) was observed for Ag on n-type Si, indicative of an ohmic contact, whereas the Al on p-type Si sample was non-ideal. A wet-chemical surface treatment was performed on one Al sample and TEM-EDS indicated a substantial decrease in the O contaminant level. The treated Al on p-type Si films exhibited linear I-V after annealing. Second, in the area of contacts to CdTe, particles of Hg-Cu-Te and Sb-Te have been applied as contacts to CdTe/CdS/SnO2 heterostructures prepared by the standard NREL protocol. First, Hg-Cu-Te and Sb-Te were prepared by a metathesis reaction. After CdCl2 treatment and NP etch of the CdTe layer, particle contacts were applied. The Hg-Cu-Te contacted cells exhibited good electrical characteristics, with Voc>810 mV and efficiencies > 11.5% for most cells. Although Voc>800 mV were observed for the Sb-Te contacted cells, efficiencies in these devices were limited to 9.1% presumably by a large series resistance (>20 Ω) observed in all samples.

  7. Survey of Heavy Metals (Cd, Pb, Hg, Zn and Cu Contamination in Sediment of Three Sites Anzali Wetland

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    M khosravi

    2011-06-01

    Full Text Available Background and Objectives:Anzali Wetland is one of the most important aquatic ecosystems of Iran which is located in south-west of the Caspian sea. This Wetland provides a suitable and non-market price habitat for valuable fish and aquatic animals which have an important role in the life cycle of this ecosystem. This study reports the results of some heavy metals contamination monitoring in superficial water of the Anzali Wetland, Iran.Materials and Methods: The samples were collected from three sites (east, center and west of Anzali Wetland, in each site three stations existed and each sample replicated three times.Results: The results showed high heavy metal levels in eastern site of wetland, where there were high levels of contamination. The mean of heavy metals concentration in sediment from Anzali Wetland were in order as Cd 157.023, Pb 3.646 and Hg 300.692 ng /g dried weight, Zn 186.953 and Cu 44.452 mg /g dried weight in eastern site. The concentration levels of heavy metals in three sites were in order as follows: Zn > Cu > Hg > Cd > Pb. Conclusion: Concentrations of heavy metals in eastern zone reflected metal loadings from anthropogenic sources located at and in the vicinity of the sampling sites.

  8. Experimental analysis of the simultaneous uptake of the heavy metals Cd, Hg, Pb, Cu, Zn, Se in the sporophore of mushrooms. Versuche ueber die simultane Aufnahme der Schwermetalle Cd, Hg, Pb, Cu, Zn und Se in Pilzfruchtkoerper

    Energy Technology Data Exchange (ETDEWEB)

    Suehs, K.

    With mushrooms of the species Agaricus bisporus and Boletus badius the simultaneous uptake of the heavy metals Cd, Hg, Pb, Cu, Zn, and Se from soil to the sporophore was studied. To avoid misleadingly overrated enrichmentfactors when comparing the heavy metal contents of dried mushrooms and soils, a so-called transfer factor TF[sub v] which is related to the volume is put to discussion here, this factor takes account of the relatively small amount of dry matter in mushrooms and of the different composition (that means specific weight) of the soils in question. With help of these transfer factors the conclusion is derived, that essential elements show a better enrichment behaviour than biologically superfluous heavy metals, at least this is true with the insignificantly contaminated soils we investigated. With Cd as an example of a ''superfluous'' element it is shown that there is a strict proportionality of Cd concentrations in the mushrooms and the corresponding soils, thus producing a constant transfer factor. Apart from this the uptake of copper into the mushrooms is promoted (growth of the transfer factor) by a larger Cd supply, whereas the other elements under investigation (even the classical antagonist Zn) are not significantly affected. Furthermore there is evidence that with increasing heavy metal concentration (Cd) first the fructification of the thallus is supported and moreover, that increasing age of this primary fungus corresponds with an increase of heavy metals in the mushrooms. (orig.)

  9. Physiological characterization of Chlamydomonas reinhardtii acclimated to chronic stress induced by Ag, Cd, Cr, Cu and Hg ions.

    Science.gov (United States)

    Nowicka, Beatrycze; Pluciński, Bartosz; Kuczyńska, Paulina; Kruk, Jerzy

    2016-08-01

    Acclimation to heavy metal-induced stress is a complex phenomenon. Among the mechanisms of heavy metal toxicity, an important one is the ability to induce oxidative stress, so that the antioxidant response is crucial for providing tolerance to heavy metal ions. The effect of chronic stress induced by ions of five heavy metals, Ag, Cu, Cr (redox-active metals) Cd, Hg (nonredox-active metals) on the green microalga Chlamydomonas reinhardtii was examined at two levels - the biochemical (content of photosynthetic pigments and prenyllipid antioxidants, lipid peroxidation) and the physiological (growth rate, photosynthesis and respiration rates, induction of nonphotochemical quenching of chlorophyll fluorescence). The expression of the genes which encode the enzymes participating in the detoxification of reactive oxygen species (APX1, CAT1, FSD1, MSD1) was measured. The other gene measured was one required for plastoquinone and α-tocopherol biosynthesis (VTE3). The application of heavy metal ions partly inhibited growth and biosynthesis of chlorophyll. The growth inhibition was accompanied by enhanced lipid peroxidation. An increase in the content of prenyllipid antioxidants was observed in cultures exposed to Cr2O7(2-), Cd(2+) (α- and γ-tocopherol and plastoquinone) and Cu(2+) (only tocopherols). The induction of nonphotochemical quenching was enhanced in cultures exposed to Cu(2+), Cr2O7(2-) and Cd(2+), as compared to the control. Chronic heavy metal-induced stress led to changes in gene expression dependent on the type and concentration of heavy metal ions. The up-regulation of antioxidant enzymes was usually accompanied by the up-regulation of the VTE3 gene. PMID:27104807

  10. Contribution to heavy metal monitoring (Zn, Cd, Hg, Cu, Ag, Pb, Cr, Ni) at the Baltic coast of Schleswig-Holstein using common mussels (1988/89)

    International Nuclear Information System (INIS)

    Heavy metal concentrations (Zn, Cd, Hg, Cu, Ag, Pb, Cr, Ni) in common mussels were measured at various sites along the Baltic coast of Schleswig-Holstein during different seasons in the period from 1988 to 1989. Measurements of heavy metal load in the summer of 1988/89 showed that Zn concentrations (150-900 μg.g-1) were the highest at all monitoring stations. Hg, Cu, and Ag levels were distinctly elevated and Pb levels only moderately so. Cd, Cr, and Ni levels were largely lower than the aforementioned. A comparison with data of 1979 show a marked rise in Hg levels at all stations and a more or less distinct upward trend for Cr, Zn, Ag, and Ni. Cd levels have markedly declined since 1975/76. (orig.)

  11. Determination of As, Cd, Cr, Cu, Hg, Sb and Se concentrations by radiochemical neutron activation analysis in different Brazilian regional diets

    International Nuclear Information System (INIS)

    Radiochemical separation procedures developed for the determination of seven elements: As, Cd, Cr, Cu, Hg, Sb and Se in different Brazilian regional diets are described. In the case of the elements As, Hg, Sb and Se, the procedure was based on retention in inorganic exchanger TFO (tin dioxide) and determination of Hg by extraction with Ni(DDC)2. For determination of Cd, Cr, Cu and Se the procedure chosen was based on retention in inorganic exchanger HMD (hydrated manganese dioxide) and extraction of Cu and Cd as diethyldithiocarbamate compounds. The accuracy and precision of the methods studied were tested by means of analyses of different reference materials-Due to the lack of data on trace element levels in Brazilian foodstuffs and diets, these methods were applied to determination of these elements in different Brazilian regional diets. These s were supplied by the Food and Experimental Nutrition Department of the Faculty of Pharmaceutical Science, University of Sao Paulo. The daily intake values for these diets are presented for As, Cd, Cr, Cu, Hg, Sb and Se. (author) 21 refs.; 6 tabs

  12. Seasonal Survey of Contaminants (Cd and Hg) and Micronutrients (Cu and Zn) in Edible Tissues of Cephalopods from Tunisia: Assessment of Risk and Nutritional Benefits

    OpenAIRE

    Rjeibi, Moncef; Metian, Marc; Hajji, Tarek; Guyot, Thierry; Rafika, Ben Chaouacha-Chekir; Bustamante, Paco

    2015-01-01

    International audience Concentrations of cadmium (Cd), copper (Cu), mercury (Hg) and zinc (Zn) were determined by atomic absorption spectrophotometry in the muscle tissues (arms and mantle) of three commercial cephalopods (Loligo vulgaris, Octopus vulgaris and Sepia officinalis) caught in three different Tunisian coastal regions. The highest concentrations found correspond to the essential elements Cu and Zn. Octopuses and cuttlefish showed the highest levels of those elements while squid ...

  13. Photocatalytic removal of M2+ (=Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) over new catalyst CuCrO2

    International Nuclear Information System (INIS)

    The metal ions M2+ (Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) are potentially toxic. Their electro deposition has been carried out in aqueous air-equilibrated CuCrO2 suspension upon visible illumination. The delafossite CuCrO2 is p-type semiconductor characterized by a low band gap (1.28 eV) and a long-term chemical stability. The corrosion rate is found to be 10-2 μmol m-2 month-1 in aqua regia. The oxide has been elaborated through nitrate route where the specific surface area is increased via the surface/bulk ratio. A correlation exists between the dark M2+ adsorption, the redox potential of M2+/0 couple and the conduction band of CuCrO2 positioned at -1.06 VSCE. Ag+ cannot be photoreduced because of its positive potential located far above the valence band. By contrast, Zn2+ is efficiently deposited due to the large driving force at the interface. The improved photoactivity of copper with a deposition percentage (90%) is attributed to the strong dark adsorption onto the surface catalyst. The results indicate a competitive effect with the water reduction; it has been observed that the M2+ deposition goes parallel with the hydrogen evolution. Such behavior is attributed to the low H2 over voltage when ultra fine aggregate of M islands are photodeposited onto CuCrO2 substrate

  14. Photocatalytic removal of M(2+) (Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) over new catalyst CuCrO(2).

    Science.gov (United States)

    Ketir, W; Bouguelia, A; Trari, M

    2008-10-30

    The metal ions M(2+) (Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) are potentially toxic. Their electro deposition has been carried out in aqueous air-equilibrated CuCrO(2) suspension upon visible illumination. The delafossite CuCrO(2) is p-type semiconductor characterized by a low band gap (1.28 eV) and a long-term chemical stability. The corrosion rate is found to be 10(-2) micromol m(-2)month(-1) in aqua regia. The oxide has been elaborated through nitrate route where the specific surface area is increased via the surface/bulk ratio. A correlation exists between the dark M(2+) adsorption, the redox potential of M(2+/0) couple and the conduction band of CuCrO(2) positioned at -1.06 V(SCE). Ag(+) cannot be photoreduced because of its positive potential located far above the valence band. By contrast, Zn(2+) is efficiently deposited due to the large driving force at the interface. The improved photoactivity of copper with a deposition percentage (90%) is attributed to the strong dark adsorption onto the surface catalyst. The results indicate a competitive effect with the water reduction; it has been observed that the M(2+) deposition goes parallel with the hydrogen evolution. Such behavior is attributed to the low H(2) over voltage when ultra fine aggregate of M islands are photodeposited onto CuCrO(2) substrate. PMID:18384943

  15. Proficiency test PLANTS 8 - determination of As, Cd, Cr, Cu, Hg, Pb, Se and Zn in dry carrot root powder

    International Nuclear Information System (INIS)

    Proficiency test PLANTS 8: determination of As, Cd, Cr, Cu, Hg, Pb, Se and Zn in dry carrot root powder has been described. The proficiency test has been provided by the Institute of Nuclear Chemistry and Technology with cooperation with POLLAB-CHEM/EURACHEM-PL and REFMAT Society according to ISO/IEC Guide 43-1:1997 and IUPAC International Harmonized Protocol (2006). Testing material was prepared from home-grown carrots which were air dried, milled and sieved. Particle fraction below 0.5 mm was collected and bottled in 20 g portions. Homogeneity testing shown that the material was homogenized for sample mass at least 250 mg. Assigned (reference) values and their uncertainties were established on the basis of the results of analysis provided by 3 reference laboratories. The testing samples were send to 25 laboratories participating in the proficiency test. 24 laboratories had send results. The results supplied by the participants were statistically evaluated. Values of z-score, zeta-score and En numbers were used for the evaluation of the participating laboratory performance. (authors)

  16. DNA Damage and Transcriptional Changes in the Gills of Mytilus galloprovincialis Exposed to Nanomolar Doses of Combined Metal Salts (Cd, Cu, Hg)

    OpenAIRE

    Rosani, Umberto; Manfrin, Chiara; Cajaraville Bereciartua, Miren Pilare; Raccanelli, Stefano; Pallavicini, Alberto; Venier, Paola

    2013-01-01

    [ENG]Aiming at an integrated and mechanistic view of the early biological effects of selected metals in the marine sentinel organism Mytilus galloprovincialis, we exposed mussels for 48 hours to 50, 100 and 200 nM solutions of equimolar Cd, Cu and Hg salts and measured cytological and molecular biomarkers in parallel. Focusing on the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we detected significant dose-related increases of cells with m...

  17. DNA Damage and Transcriptional Changes in the Gills of Mytilus galloprovincialis Exposed to Nanomolar Doses of Combined Metal Salts (Cd, Cu, Hg)

    OpenAIRE

    Varotto, Laura; Domeneghetti, Stefania; Rosani, Umberto; Manfrin, Chiara; Miren P. Cajaraville; Raccanelli, Stefano; Pallavicini, Alberto; Venier, Paola

    2013-01-01

    Aiming at an integrated and mechanistic view of the early biological effects of selected metals in the marine sentinel organism Mytilus galloprovincialis, we exposed mussels for 48 hours to 50, 100 and 200 nM solutions of equimolar Cd, Cu and Hg salts and measured cytological and molecular biomarkers in parallel. Focusing on the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we detected significant dose-related increases of cells with micronuclei and...

  18. A test of the stability of Cd, Cu, Hg, Pb and Zn profiles over two decades in lake sediments near the Flin Flon Smelter, Manitoba, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Percival, J.B.; Outridge, P.M., E-mail: outridge@nrcan.gc.ca

    2013-06-01

    Lake sediments are valuable archives of atmospheric metal deposition, but the stability of some element profiles may possibly be affected by diagenetic changes over time. In this extensive case study, the stability of sedimentary Cd, Cu, Hg, Pb and Zn profiles was assessed in dated sediment cores that were collected in 2004 from four smelter-affected lakes near Flin Flon, Manitoba, which had previously been cored in 1985. Metal profiles determined in 1985 were in most cases clearly reproduced in the corresponding sediment layers in 2004, although small-scale spatial heterogeneity in metal distribution complicated the temporal comparisons. Pre-smelter (i.e. pre-1930) increases in metal profiles were likely the result of long-range atmospheric metal pollution, coupled with particle mixing at the 1930s sediment surface. However, the close agreement between key inflection points in the metal profiles sampled two decades apart suggests that metals in most of the lakes, and Hg and Zn in the most contaminated lake (Meridian), were stable once the sediments were buried below the surface mixed layer. Cadmium, Cu and Pb profiles in Meridian Lake did not agree as well between studies, showing evidence of upward remobilization over time. Profiles of redox-indicator elements (Fe, Mn, Mo and U) suggested that the rate of Mn oxyhydroxide recycling within sediment was more rapid in Meridian Lake, which may have caused the Cd, Cu and Pb redistribution. - Highlights: • Sedimentary Cd, Cu, Hg, Pb and Zn profiles in four lakes were mostly unchanged over 19 years. • In one lake, Cd, Cu and Pb profiles were offset relative to the originals. • The offset could indicate diagenetic upcore dispersal of these metals.

  19. Determination of As, Cd, Cu, Hg and Pb in biological samples by modern electrothermal atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Sardans, Jordi, E-mail: j.sardans@creaf.uab.ca [Ecophysiological and Global Change Unit CSIC-CREAF, Edifici C, Universitat Autonoma de Barcelona, Bellaterra 08193, Barcelona (Spain); Montes, Fernando [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), C/ Senda del Rey 9. 28040 Madrid (Spain); Penuelas, Josep [Ecophysiological and Global Change Unit CSIC-CREAF, Edifici C, Universitat Autonoma de Barcelona, Bellaterra 08193, Barcelona (Spain)

    2010-02-15

    of this technique that reaches figures of merit equivalent to Inductively coupled plasma mass spectrometry (ICP-MS). Herein is presented an overview of recent advances and applications of (ETAAS) for the determination of As, Cd, Cu, Hg and Pb in biological samples drawn from studies over the last decade.

  20. Certification of trace element contents (As, Cd, Co, Cu, Fe, Mn, Hg, Na, Pb and Zn) in a fly ash obtained from the combustion of pulverised coal

    International Nuclear Information System (INIS)

    The element contents of As, Cd, Co, Cu, Fe, Mn, Hg, Na, Pb and Zn of a fly ash from pulverised coal are certified. The procedures and their results for the homogenisation, the contamination and homogeneity checks and the analytical campaign are reported. The certified mass fractions and indicative values for Cr, Ni, Th, V and water soluble sulphate are given. The work was carried out within the framework of the activities of the Community Bureau of Reference (BCR) of the Commission of the European Communities. (orig.)

  1. Evaluation of heavy metals (Cr, Fe, Ni, Cu, Zn, Cd, Pb and Hg) in water, sediments and water lily (Eichornia crassipes) from Jose Antonio Alzate dam

    International Nuclear Information System (INIS)

    Water, sediments and water lily (Eichornia crassipes) from the Jose Antonio Alzate Dam were analyzed in order to determine concentrations of chromium, iron, nickel, copper, zinc, cadmium, lead and mercury. Mercury, lead, chromium and iron were found in concentrations above permissible limits in water, and in high concentrations in sediments. Cadmium, nickel, copper and zinc never were found in concentrations above permissible limits in water. The highest concentrations of heavy metals in water lily were found in the root. Accumulation factors decreased in the following order: Zn> Cr> Fe> Ni> Cu> Pb> Hg and Cd. Statistical differences (α < 0.5) between the collection samples dates was observed. High correlations between metals concentrations in superficial water, sediment and water hyacinth were also observed. These correlations could indicate that the heavy metals studied here, are originated from a natural source such as sediments or from an industrial source. (Author)

  2. The thermodynamic characteristics of formation of mono- and binuclear biladiene Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) chelates in dimethylformamide solutions

    International Nuclear Information System (INIS)

    Thermodynamics of 1,2,3,7,8,12,13,17,18,19-decamethylbiladiene-a,c complexing with Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) acetates was studied. Fairmont enthalpies of corresponding metal complexes were analyzed using titration calorimetry. This allowed to calculate full set of thermodynamic properties of processes. Binuclear heteroligand complexes [M2L(AcO)2)] (M = Cd, Hg) formation is most entropy favorable processes, that is evidently conditioned by the deliverance of large number of DMFA molecules from coordinating spheres of two solvate-cations when tetrapyrrole ligand coordination, and it demonstrates high thermodynamic stability of given ligands

  3. HgTe-CdTe SUPERLATTICES

    OpenAIRE

    Smith, D.; Mcgill, T.

    1984-01-01

    We report on a theoretical study of the electronic properties of HgTe-CdTe superlattices. The band gap as a function of layer thickness, effective masses normal to the layer plane and tunneling length are compared to the corresponding (Hg, Cd)Te alloys. We find that the superlattice possesses a number of properties that may make it superior to the corresponding alloy as an infrared material.

  4. Can heavy metal pollution defend seed germination against heat stress? Effect of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination under high temperature.

    Science.gov (United States)

    Deng, Benliang; Yang, Kejun; Zhang, Yifei; Li, Zuotong

    2016-09-01

    Heavy metal pollution, as well as greenhouse effect, has become a serious threat today. Both heavy metal and heat stresses can arrest seed germination. What response can be expected for seed germination under both stress conditions? Here, the effects of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination were investigated at 20 °C and 40 °C. Compared with 20 °C, heat stress induced thermodormancy. However, this thermodormancy could be significantly alleviated by the addition of a low concentration of heavy metals. Heavy metals, as well as heat stress induced H2O2 accumulation in germinating seeds. Interestingly, this low concentration of heavy metal that promoted seed germination could be partly blocked by DMTU (a specific ROS scavenger), irrespective of temperature. Accordingly, H2O2 addition reinforced this promoting effect on seed germination, which was induced by a low concentration of heavy metal. Furthermore, we found that the NADPH oxidase derived ROS was required for seed germination promoted by the heavy metals. Subsequently, treatment of seeds with fluridone (a specific inhibitor of ABA) or ABA significantly alleviated or aggravated thermodormancy, respectively. However, this alleviation or aggravation could be partly attenuated by a low concentration of heavy metals. In addition, germination that was inhibited by high concentrations of heavy metals was also partly reversed by fluridone. The obtained results support the idea that heavy metal-mediated ROS and hormone interaction can finally affect the thermodormancy release or not. PMID:27239687

  5. Fe(II, Co(II, Ni(II, Cu(II, Zn(II, Cd(II and Hg(II Complexes of 4'-Nitrobenzylidene-2-Hydroxyl-3,5 Dinitroaniline

    Directory of Open Access Journals (Sweden)

    R. S. Srivastava

    1982-07-01

    Full Text Available Complexes of Fe(II, Co(II, Ni(II, Cu(II Zn(II, Cd(II, and Hg(II with 4'-nitrobenzylidene-2-hydroxy-3,5-dinitroaniline (hereafter abbreviated as nhd have been prepared and characterized by their microanalyses, molar conductance, magnetic susceptibility, electronic and IR spectra. The donor sites of the ligand have been derived from the results of infrared spectra.

  6. HgCdTe barrier infrared detectors

    Science.gov (United States)

    Kopytko, M.; Rogalski, A.

    2016-05-01

    In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

  7. DNA damage and transcriptional changes in the gills of mytilus galloprovincialis exposed to nanomolar doses of combined metal salts (Cd, Cu, Hg.

    Directory of Open Access Journals (Sweden)

    Laura Varotto

    Full Text Available Aiming at an integrated and mechanistic view of the early biological effects of selected metals in the marine sentinel organism Mytilus galloprovincialis, we exposed mussels for 48 hours to 50, 100 and 200 nM solutions of equimolar Cd, Cu and Hg salts and measured cytological and molecular biomarkers in parallel. Focusing on the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we detected significant dose-related increases of cells with micronuclei and other nuclear abnormalities in the treated mussels, with differences in the bioconcentration of the three metals determined in the mussel flesh by atomic absorption spectrometry. Gene expression profiles, determined in the same individual gills in parallel, revealed some transcriptional changes at the 50 nM dose, and substantial increases of differentially expressed genes at the 100 and 200 nM doses, with roughly similar amounts of up- and down-regulated genes. The functional annotation of gill transcripts with consistent expression trends and significantly altered at least in one dose point disclosed the complexity of the induced cell response. The most evident transcriptional changes concerned protein synthesis and turnover, ion homeostasis, cell cycle regulation and apoptosis, and intracellular trafficking (transcript sequences denoting heat shock proteins, metal binding thioneins, sequestosome 1 and proteasome subunits, and GADD45 exemplify up-regulated genes while transcript sequences denoting actin, tubulins and the apoptosis inhibitor 1 exemplify down-regulated genes. Overall, nanomolar doses of co-occurring free metal ions have induced significant structural and functional changes in the mussel gills: the intensity of response to the stimulus measured in laboratory supports the additional validation of molecular markers of metal exposure to be used in Mussel Watch programs.

  8. DNA damage and transcriptional changes in the gills of mytilus galloprovincialis exposed to nanomolar doses of combined metal salts (Cd, Cu, Hg).

    Science.gov (United States)

    Varotto, Laura; Domeneghetti, Stefania; Rosani, Umberto; Manfrin, Chiara; Cajaraville, Miren P; Raccanelli, Stefano; Pallavicini, Alberto; Venier, Paola

    2013-01-01

    Aiming at an integrated and mechanistic view of the early biological effects of selected metals in the marine sentinel organism Mytilus galloprovincialis, we exposed mussels for 48 hours to 50, 100 and 200 nM solutions of equimolar Cd, Cu and Hg salts and measured cytological and molecular biomarkers in parallel. Focusing on the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we detected significant dose-related increases of cells with micronuclei and other nuclear abnormalities in the treated mussels, with differences in the bioconcentration of the three metals determined in the mussel flesh by atomic absorption spectrometry. Gene expression profiles, determined in the same individual gills in parallel, revealed some transcriptional changes at the 50 nM dose, and substantial increases of differentially expressed genes at the 100 and 200 nM doses, with roughly similar amounts of up- and down-regulated genes. The functional annotation of gill transcripts with consistent expression trends and significantly altered at least in one dose point disclosed the complexity of the induced cell response. The most evident transcriptional changes concerned protein synthesis and turnover, ion homeostasis, cell cycle regulation and apoptosis, and intracellular trafficking (transcript sequences denoting heat shock proteins, metal binding thioneins, sequestosome 1 and proteasome subunits, and GADD45 exemplify up-regulated genes while transcript sequences denoting actin, tubulins and the apoptosis inhibitor 1 exemplify down-regulated genes). Overall, nanomolar doses of co-occurring free metal ions have induced significant structural and functional changes in the mussel gills: the intensity of response to the stimulus measured in laboratory supports the additional validation of molecular markers of metal exposure to be used in Mussel Watch programs. PMID:23355883

  9. Qualitative analysis of As, Ba, Cd, Cr, Zn, Fe, Mn, K, Hg, Pb y Cu, as constituents of Amatitlan Lake sediment by XRF

    International Nuclear Information System (INIS)

    Samples of fifteen sampling points were analyzed. Molybdenum X-ray tube with secondary excitation assembly, SiLi detector and deconvolution software AXIL were employed; self-standardization method based upon incoherent ratio was used for quantitative analysis of some elements. Ca, P, S, Ti, Mn, Fe, Cr, Zn, Cu, Ni, Ga, As, Pb, Ge, Sr and Pb, were found. As, Pb and Cu concentrations lower than 109 mg/lt, 119 mg/lt, and 500mg/lt, respectively, were measured. Hg was not detected. (author)

  10. MBE HgCdTe heterostructure detectors

    Science.gov (United States)

    Schulman, Joel N.; Wu, Owen K.

    1990-01-01

    HgCdTe has been the mainstay for medium (3 to 5 micron) and long (10 to 14 micron) wavelength infrared detectors in recent years. Conventional growth and processing techniques are continuing to improve the material. However, the additional ability to tailor composition and placement of doped layers on the tens of angstroms scale using molecular beam epitaxy (MBE) provides the opportunity for new device physics and concepts to be utilized. MBE-based device structures to be discussed here can be grouped into two categories: tailored conventional structures and quantum structures. The tailored conventional structures are improvements on familiar devices, but make use of the ability to create layers of varying composition, and thus band gap, at will. The heterostructure junction can be positioned independently of doping p-n junctions. This allows the small band gap region in which the absorption occurs to be separated from a larger band gap region in which the electric field is large and where unwanted tunneling can occur. Data from hybrid MBE/liquid phase epitaxy (LPE)/bulk structures are given. Quantum structures include the HgTe-CdTe superlattice, in which the band gap and transport can be controlled by alternating thin layers (tens of angstroms thick) of HgTe and CdTe. The superlattice has been shown to exhibit behavior which is non-alloy like, including very high hole mobilities, two-dimensional structure in the absorption coefficient, resonant tunneling, and anisotropic transport.

  11. Chemical beam epitaxy of CdTe, HgTe, and HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Benz, R.G. II; Wagner, B.K.; Rajavel, D.; Summers, C.J. (Physical Sciences Lab., Georgia Tech Research Inst., Atlanta, GA (USA))

    1991-05-01

    A chemical beam epitaxy (CBE) system has been implemented for the growth of CdTe, HgTe, and their alloys. The system is briefly described. Results on the cracking of the organometallic source gases are presented. Epitaxial layers have been grown from gas sources of diethylcadmium, diisopropyltelluride and Hg vapor, as well as conventional solid sources. Optical and electrical properties are reported, demonstrating the potential of CBE for growing high quality solar cell and infrared detector material. (orig.).

  12. Molecular structures, charge distributions, and vibrational analyses of the tetracoordinate Cu(II), Zn(II), Cd(II), and Hg(II) bromide complexes of p-toluidine investigated by density functional theory in comparison with experiments

    Science.gov (United States)

    Bardakçı, Tayyibe; Kumru, Mustafa; Altun, Ahmet

    2016-07-01

    The Cu(II), Zn(II), Cd(II), and Hg(II) bromide complexes of p-toluidine have been studied with B3LYP calculations by using def2-TZVP basis set at the metal atoms and using def2-TZVP and 6-311G+(d,p) basis sets at the remaining atoms. Both basis set combinations give analogous results, which validate the use of quickly converging 6-311G+(d,p) basis set in future studies. The molecular structures, atomic charge and spin distributions, and harmonic vibrational frequencies of the complexes have been calculated. The Zn, Cd and Hg complexes have been found to have distorted tetrahedral environments around the metal atoms whereas Cu complex has a square planar geometry. The NBO charge analysis have been found more accurate and less misleading compared with the Mulliken scheme. The present vibrational spectra calculations allow accurate assignment of the vibrational bands, which otherwise assigned tentatively in previous experimental-only studies.

  13. Synthesis, spectroscopic, antimicrobial and DNA cleavage studies of new Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes with naphthofuran-2-carbohydrazide Schiff base

    Science.gov (United States)

    Halli, Madappa B.; Sumathi, R. B.

    2012-08-01

    A series of Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes have been synthesized with newly synthesized Schiff base derived from naphthofuran-2-carbohydrazide and cinnamaldehyde. The elemental analyses of the complexes are confined to the stoichiometry of the type MLCl2 [M = Co(II) and Cu(II)], ML2Cl2 [M = Ni(II), Cd(II), Zn(II) and Hg(II)] respectively, where L is Schiff base ligand. Structures have been proposed from elemental analyses, IR, electronic, mass, 1H NMR, ESR spectral data, magnetic, and thermal studies. The measured low molar conductance values in DMF indicate that the complexes are non-electrolytes. Spectroscopic studies suggest coordination occurs through azomethine nitrogen and carbonyl oxygen of the ligand with the metal ions. The Schiff base and its complexes have been screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Salmonella typhi) and antifungal (Aspergillus niger, Aspergillus flavus, Cladosporium and Candida albicans) activities by minimum inhibitory concentration (MIC) method. The DNA cleavage studies by agarose gel electrophoresis method was studied for all the complexes.

  14. Allyl- iso-propyltelluride, a new MOVPE precursor for CdTe, HgTe and (Hg,Cd)Te

    Science.gov (United States)

    Hails, Janet E.; Cole-Hamilton, David J.; Stevenson, John; Bell, William

    2000-06-01

    The use of allyl- iso-propyltelluride as the tellurium precursor for the growth of CdTe, HgTe and (Hg,Cd)Te by metal organic vapour-phase epitaxy has been investigated. It has proved to be an efficient source of tellurium with growth rates for HgTe and (Hg,Cd)Te of up to 10 μm h -1 at 300°C. The best CdTe was grown at 4.5 μm h -1 under Me 2Cd-rich conditions at 300°C in the presence of Hg vapour.

  15. HgCdTe monolithic infrared detector

    Energy Technology Data Exchange (ETDEWEB)

    Yakushev, Maxim V.; Dvoretsky, Sergei A.; Kozlov, Alexander I.; Sabinina, Irina V.; Sidorov, Yu.G.; Sorochkin, Alexander V.; Fomin, Boris I.; Aseev, Alexander L. [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch RAS, Novosibirsk (Russian Federation)

    2010-06-15

    We report the processes of fabricating monolithic 32 x 32 infrared detector based on (310) HgCdTe/CdTe/ZnTe/ Si photosensitive heterostructure which was grown by a molecular-beam epitaxy technique in the free surface of ROIC cells. Optimum parameters of the technological processes were determined. The minimum temperature of preepitaxial thermal annealing in vacuum of ROIC was determined as 450 C. The dark and photo current-voltage characteristics were measured and analyzed. A good sensitivity of diodes was observed. The product R{sub 0} x A {proportional_to} 10{sup 5} Ohm x cm{sup 2}. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Biomonitoring of trace metals (Cu, Cd, Cr, Hg, Pb, Zn in Mali Ston Bay (eastern Adriatic using the Mediterranean blue mussel (1998-2005

    Directory of Open Access Journals (Sweden)

    Tomislav ZVONARIĆ

    2007-06-01

    Full Text Available In Mali Ston Bay, located on the eastern Adriatic coast, mussels and oysters have traditionally been cultivated. However, previous studies showed that water and sediments from Mali Ston Bay contain elevated levels of some trace metals, which was attributed to natural processes of sedimentation and drainage. In order to assess the bioavailability of trace metals in the bay, and to assess the health risk of consumption of shellfish species from Mali Ston Bay, a passive monitoring program was carried out in the period from December 1998 to August 2005. Samples of the whole soft tissue were collected seasonally at 4 shellfish breeding farms and analyzed for essential (Cu, Zn and non-essential (Cd, Cr, THg, Pb metals. Mean concentrations of analyzed metals in the edible tissue of mussels (Cd: 1.15 mg kg-1 d.wt.; Cr: 1.65 mg kg-1 d.wt.; Cu: 5.6 mg kg-1 d.wt.; THg: 0.15 mg kg-1 d.wt.; Pb: 1.09 mg kg-1 d.wt.; Zn: 139 mg kg-1 d.wt. fell in the range of values usually found in low to moderately contaminated marine coastal areas. Examination of the spatial pattern of contaminants showed that there were no statistically significant differences among stations in Mali Ston Bay regarding trace metal content. Concentrations of Cd, Cu, Cr and THg were significantly higher during the autumn-winter period, while concentrations of Pb and Zn did not depend on the sampling season. Among six analyzed metals, only concentrations of Cd and THg were significantly negatively correlated with the condition index of the mussels. Analysis of temporal trends during the 7 years of monitoring showed that metal concentrations had not changed with time. According to EU and WHO legislation, consumption of the edible tissue of the mussels was not harmful for humans since all the values were well below the permissible limits for fresh seafood. In addition, results of the evaluation of the risks to human health associated with consumption of the mussels containing trace metals suggest

  17. HgCdTe/CdTe multiple quantum wells

    International Nuclear Information System (INIS)

    This paper reports on HgCdTe/CdTe multiple quantum wells by molecular beam epitaxy which show room temperature photoluminescence and sharp absorption steps at mid-infrared wavelengths. Quantitative chemical mapping, performed by transmission electron microscopy, indicates minimal interdiffusion during growth. Annealing experiments performed at higher temperatures show that the interdiffusion coefficient is a strong function of the depth of the interface below the surface. Absorption spectra have been accurately modeled with a square well/envelope function approach. The films have been used to passively mode lock color center lasers and produce pulses as short as 120 fsec near 2.7 μm

  18. HgCdTe e-avalanche photodiode detector arrays

    OpenAIRE

    Anand Singh; Shukla, A. K.; Ravinder Pal

    2015-01-01

    Initial results on the MWIR e-APD detector arrays with 30 μm pitch fabricated on LPE grown compositionally graded p-HgCdTe epilayers are presented. High dynamic resistance times active area (R0A) product 2 × 106 Ω-cm2, low dark current density 4 nA/cm2 and high gain 5500 at -8 V were achieved in the n+-υ-p+ HgCdTe e-APD at 80 K. LPE based HgCdTe e-APD development makes this technology amenable for adoption in the foundries established for the conventional HgCdTe photovoltaic detector arrays w...

  19. Spectroscopic properties of some new azo-azomethine ligands in the presence of Cu2+, Pb2+, Hg2+, Co2+, Ni2+, Cd2+ and Zn2+ and their antioxidant activity

    Science.gov (United States)

    Shaghaghi, Zohreh

    2014-10-01

    Due to their potential applicability as selective receptors in optical sensors, two novel azo Schiff-base derivatives I and II are synthesized and characterized with FT-IR, 1H NMR and elemental analysis techniques. The optical response of azo groups of I and II towards Ni2+, Co2+, Cu2+, Pb2+, Hg2+, Zn2+ and Cd2+ metal ions is studied in DMSO by UV-vis spectroscopy. The absorption spectra of both compounds with cations show marked changes. In solution, azo Schiff-base I produces a cation induced 95 nm blue shift for Cu2+ ion from 555 nm to 460 nm with remarkable color change from red to yellow. Whereas no significant color change is observed upon addition of studied metal cations to the solution of ligand II or other metal ions to the solution of ligand I. Furthermore, Job's plot indicate 1:1 binding-stoichiometry for I with Cu2+ ion and Benesi-Hildebrand plot is used for the determination of its association constant. Therefore receptor I is highly specific for copper ions in DMSO solution. Finally, the study of antioxidant properties of I and II with DPPH method reveals high and significant activities.

  20. Approach to spatialize local to long-range atmospheric metal input (Cd, Cu, Hg, Pb) in epiphytic lichens over a meso-scale area (Pyrénées-Atlantiques, southwestern France).

    Science.gov (United States)

    Barre, Julien P G; Deletraz, Gaëlle; Frayret, Jérôme; Pinaly, Hervé; Donard, Olivier F X; Amouroux, David

    2015-06-01

    Geographically based investigations into atmospheric bio-monitoring usually provide information on concentration or occurrence data and spatial trends of specific contaminants over a specified study area. In this work, an original approach based on geographic information system (GIS) was used to establish metal contents (Hg, Cu, Pb, and Cd) in epiphytic lichens from 90 locations as atmospheric bio-monitors over a meso-scale area (Pyrénées-Atlantiques, southwestern France). This approach allows the integration of the heterogeneity of the territory and optimization of the sampling sites based on both socioeconomical and geophysical parameters (hereafter defined as urban, industrial, agricultural, and forested areas). The sampling strategy was first evaluated in several sites (n = 15) over different seasons and years in order to follow the temporal variability of the atmospheric metal input in lichens. The results demonstrate that concentration ranges remain constant over different sampling periods in "rural" areas (agricultural and forested). Higher variability is observed in the "anthropized" urban and industrial areas in relation to local atmospheric inputs. In this context, metal concentrations in lichens over the whole study show that (1) Hg and Cd are homogeneous over the whole territory (0.14 ± 0.04 and 0.38 ± 0.26 mg/kg, respectively), whereas (2) Cu and Pb are more concentrated in "anthropized" areas (9.3 and 11.9 mg/kg, respectively) than in "rural" ones (6.8 and 6.0 mg/kg, respectively) (Kruskall-Wallis, K(Cu) = 13.7 and K(Pb) = 9.7, p contamination source over a wider geographic scale. A multiple linear regression model was applied to give an integrated spatialization of the data. This showed significant relationships for Pb and Cu (adjusted r (2) of 0.39 and 0.45, respectively), especially with regards to variables such as industry and road densities (source factors) and elevation or water balance (remote factors). These

  1. Electrodeposited CdTe and HgCdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Basol, B.M.

    1988-01-15

    The processing steps necessary for producing high efficiency electrodeposited CdTe and HgCdTe solar cells are described. The key step in obtaining solar cell grade p-type CdTe and HgCdTe is the 'type conversion-junction formation' (TCJF) process. The TCJF process involves the heat treatment of the as-deposited n-type CdTe and HgCdTe layers at around 400 /sup 0/C. This procedure converts these n-type films into high resistivity p type and forms a rectifying junction between them and the underlying n-type window layers. Possible effects of oxygen on the TCJF process are discussed. The results of studies made on the structural, electrical and optical properties of the electrodeposited CdS, CdTe and HgCdTe films are presented. The resistivity of the electrodeposited HgCdTe can be made lower than that of CdTe. Consequently, solar cells made using the HgCdTe films have, on the average, better fill factors than those made using the CdTe layers, HgCdTe is also attractive for tandem-cell applications because of its variable band gap which can be easily tuned to the desired value. CdS/CdTe and CdS/HgCdTe heterojunction solar cells with 10.3% and 10.6% efficiency have been demonstrated using electrodeposition techniques and the TCJF process.

  2. Reduced leakage currents of CdZnTe radiation detectors with HgTe/HgCdTe superlattice contacts

    Science.gov (United States)

    Chang, Y.; Grein, C. H.; Becker, C. R.; Huang, J.; Ghosh, S.; Aqariden, F.; Sivananthan, S.

    2012-10-01

    Room-temperature-operating CdZnTe radiation detectors have high energy resolution, linear energy response and are capable of operating in normal counting and spectroscopic modes, hence are highly desirable for medical diagnosis, nondestructive industrial evaluations, homeland security, counterterrorism inspections and nuclear proliferation detection to ensure national and international nuclear safety. HgTe/HgCdTe superlattices can be designed to selectively transport one carrier species while hindering transport of the other. Specifically, one designs a large carrier effective mass for undesired carriers in the electric field direction, which results in low carrier velocities, and yet a density of states for undesired carrier that is lower than that of a comparable bulk semiconductor, which results in low carrier concentrations, hence a low current density under an electric field. The opposite carrier species can be designed to have a large velocity and high density of states, hence producing a large current density. By employing HgTe/HgCdTe superlattices as contact layers intermediate between CdZnTe absorbers and metal contacts, leakage currents under high electric fields are reduced and improved x-ray and γ-ray detector performance is anticipated. Pixilated CdZnTe radiation detectors arrays were fabricated and characterized to evaluate the effectiveness of HgTe/HgCdTe superlattices in reducing leakage currents. Current-voltage characteristics show that HgTe/HgCdTe superlattice contact layers consistently result in significantly reduced leakage currents relative to detectors with only metal contacts.

  3. Summary Abstract: HgTe–CdTe superlattices

    OpenAIRE

    McGill, T. C.; Smith, D L

    1983-01-01

    In their seminal paper on superlattices, Esaki and Tsu indicated that superlattices involving II-VI compounds and their alloys, could be of interest along with superlattices involving Group IV and III-V semiconductors. Independently, Schulman and McGill identified the Hg-Te-CdTe superlattice as an interesting case to study. HgTe and CdTe have the same crystal structure and lattice constrant to 0.3%. CdTe is a conventional zinc blende semiconductor with a band gap of about 1.6 eV; HgTe is a ze...

  4. Thermodynamic investigations of CdTe-HgTe solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nasar, A.; Shamsuddin, M. (Dept. of Metallurgical Engineering, Banaras Hindu Univ., Varanasi (India))

    1991-08-10

    The activity of CdTe in pseudobinary CdTe-HgTe solid solution (with CdTe added in 10 mol.% increments) has been determined in the temperature range 735-840 K by an electrochemical technique using LiCl-KCl+5 wt.% CdCl{sub 2} as the molten salt electrolyte. The activity of HgTe has been calculated by Gibbs-Duhem integration using the {alpha} function. From the e.m.f. values measured at different temperatures, various partial and excess thermodynamic quantities, namely {Delta}anti G{sup M}{sub CdTe}, {Delta}anti H{sup M}{sub CdTe}, {Delta}anti S{sup XS}{sub CdTe}, {Delta}anti G{sup XS}{sub CdTe} and {Delta}anti S{sup XS}{sub CdTe}, have been obtained. The corresponding thermodynamic parameters for HgTe have also been computed. The integral molar properties of the solid solutions have been estimated from the partial quantities of the two components, CdTe and HgTe. (orig.).

  5. Synthesis of HgBa2Ca3Cu4O10+δ(Hg-1234) and HgBa2Ca4Cu5O12+δ(Hg-1245) from oxygen controlled precursors under high pressure

    International Nuclear Information System (INIS)

    Effects of oxygen content in the precursor have been investigated on the synthesis of HgBa2Ca4Cu5O12+δ(Hg-1245) under high pressure. The superconducting phases continuously changed from Hg-1234 to Hg-1245 with reducing the oxygen content in the precursor of Ba2Ca4Cu5O11+δ. Samples of Hg- 1245 have been synthesized by optimizing the oxygen content of the precursor with the stoichiometric composition. (author)

  6. Thermoelectric Properties of Cu2HgSnSe4-Cu2HgSnTe4 Solid Solution

    Czech Academy of Sciences Publication Activity Database

    Navrátil, Jiří; Kucek, V.; Plecháček, T.; Černošková, E.; Laufek, František; Drašar, Č.; Knotek, P.

    2014-01-01

    Roč. 43, č. 10 (2014), s. 3719-3725. ISSN 0361-5235 R&D Projects: GA ČR GA13-33056S Institutional support: RVO:61389013 ; RVO:68378271 Keywords : quaternary diamond-like compounds * Cu2HgSnSe4 * Cu2HgSnTe4 Subject RIV: CA - Inorganic Chemistry Impact factor: 1.798, year: 2014

  7. Dislocation reduction in HgCdTe grown on CdTe/Si

    Science.gov (United States)

    Wijewarnasuriya, Priyalal S.

    2016-05-01

    Bulk-grown CdZnTe (Zn = 3%) substrates are the natural choice for HgCdTe epitaxy since it is lattice matched to long wave LW-HgCdTe alloy. However, lack of large area CdZnTe substrates, high production costs, and more importantly, the difference in thermal expansion coefficients between CdZnTe and silicon Read out Integrated Circuits (ROIC) are some of the inherent drawbacks of CdZnTe substrates. Consequently, Hg1-xCdxTe detectors fabricated on silicon substrates are an attractive alternative. Recent developments in the molecular beam epitaxy (MBE) buffer layer growth technology on Si substrates has revolutionized the HgCdTe research and offered a new dimension to HgCdTe-based IR technology. Si substrates provide advantages in terms of relatively large area (3 to 6-inch diameter is easily obtained) compared to CZT substrate materials, durability during processing, and reliability to thermal cycling. Innovations in Si-based composite substrates made it possible to fabricate very large-format IR arrays that offer higher resolution, low-cost arrays and more dies per wafer. Between Si substrates and HgCdTe has large lattice mismatch of 19%. This leads to dislocation densities of low-107 cm-2 for optimal growth of HgCdTe on silicon-based substrates as compared to the mid-104 cm-2 dislocation density of HgCdTe grown on CdZnTe. This paper present dislocation reduction by two orders of magnitude using thermal cycle anneal under Hg environment on HgCdTe grown on Si substrates and as well as defect reduction in Cd(Se)Te buffer layers grown on Si Substrates.

  8. Electronic structures of HgTe and CdTe surfaces and HgTe/CdTe interfaces

    Science.gov (United States)

    Schick, J. T.; Bose, S. M.; Chen, A.-B.

    1989-01-01

    A Green's-function method has been used to study the surface and interface electronic structures of the II-VI compounds HgTe and CdTe. Localized surface and resonance states near the cation-terminated (100) surface of CdTe and the anion-terminated surface of HgTe have been found for the ideal surfaces. The energies and strengths of these surface states are altered by surface perturbations. The bulk states near the surface are drastically modified by the creation of the surface, but the band gaps remain unchanged. Numerical evaluation of the local densities of states at the Gamma and J points shows that, at the (100) interface of HgTe/CdTe, the previously observed surface states are no longer present. However, in the interface region, bulk states of one material penetrate some distance into the other material.

  9. Metals concentration (Mn, Cu, Cd, Zn and Hg) in white sucker (Catostomus commersoni) and in northern pike (Esox lucius) upstream and downstream from the Moses-Saunders Dam on the St. Lawrence River near Cornwall (Ontario) and Massena (New York); Les metaux (Mn, Cu, Cd, Zn et Hg) des menuiers noirs (Catostomus commersoni) et des grands brochets (Esox lucius) de l'amont and de l'aval du barrage Moses-Saunders sur le fleuve Saint-Laurent pres de Cornwall (Ontario) et Massena (New York)

    Energy Technology Data Exchange (ETDEWEB)

    Lalonde, J. D.; Chapleau, F.; Brind' Amour, A.; Ridgway, L. L. [Ottawa Univ., Dept. of Biology, ON (Canada)

    1999-12-01

    Concentration of certain metals, such as Mn, Cu, Cd, Zn and Hg in white sucker and northern pike, caught upstream and downstream of the Moses-Saunders Power Dam on the St. Lawrence River near Cornwalll, Ontario and Massena New York, was investigated. The investigation was undertaken to establish the effects of the dam, more particularly the establishemnt, by flooding, of a 136 sq.km water reservoir in 1958 during the construction of the St. Lawrence Seaway. Results showed that whereas in the early years after the construction of the reservoir metal concentrations were high, after 37 years there was no difference in the mean concentration of metals in northern pike upstream or downstream, although Hg concentration increased with length both upstream and downstream. Zn concentration showed a length-related decrease downstream. With regard to the white sucker, it was found that on average, white sucker fish were five-times more contaminated with Hg upstream than downstream. Mn and Cu levels were also found to be higher upstream. Although there was no evidence of bioaccumulation of metals in this species, a review of relevant literature suggest a divergence of opinion on this subject. These authors suggest that the continuing high levels of contamination in white sucker in this lake is associated with the habit of this species to be in constant contact with the sediments, which may be highly contaminated locally. 27 refs., 5 tabs., 2 figs.

  10. Isothermal section of the Cu{sub 2}Se-HgSe-GeSe{sub 2} system at 670K and crystal structures of the compounds Cu{sub 2}HgGeSe{sub 4} and HT-modification of Cu{sub 2}HgGeS{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Olekseyuk, I.D. [Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk (Ukraine); Marchuk, O.V. [Department of Physical and Colloidal Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk (Ukraine)]. E-mail: marchuk@lab.univer.lutsk.ua; Gulay, L.D. [Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk (Ukraine); Zhbankov, O.Ye. [Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk (Ukraine)

    2005-08-02

    The isothermal section of quasi-ternary Cu{sub 2}Se-HgSe-GeSe{sub 2} system at 670K was constructed. The crystal structures of the compounds Cu{sub 2}HgGeSe{sub 4} (Cu{sub 2}FeSnS{sub 4} structure type, space group I4-bar 2m, a=0.57456(2)nm, c=1.10834(4)nm, R{sub I}=0.0468) and HT-modification of Cu{sub 2}HgGeS{sub 4} (Cu{sub 2}CdGeS{sub 4} structure type, space group Pmn2{sub 1}, a=0.76882(3)nm, b=0.65561(2)nm, c=0.63144(3)nm, R{sub I}=0.0835) were determined using X-ray powder diffraction. The Se atoms in the structure of the Cu{sub 2}HgGeSe{sub 4} compound are stacked in a close-packed arrangement with layers in the sequence ABC. Half of the tetrahedral interstices are occupied by Cu, Hg and Ge atoms. At the same time the S atoms in the structure of the HT-modification of Cu{sub 2}HgGeS{sub 4} are stacked in a close-packed arrangement with layers in the sequence AB. Half of the tetrahedral interstices are occupied by cations.

  11. Study of HgCdTe/CdTe interface structure grown by metal-organic chemical vapor deposition

    Science.gov (United States)

    Ma, Ke J.; Yu, Zhen Z.; Yanh, Jian R.; Shen, Shou Z.; He, Jin; Chen, Wei M.; Song, Xiangyun

    1991-11-01

    The interface of HgCdTe/CdTe thin film growth by MOCVD were investigated by high resolution electron microscope (HREM). It is shown that there is no monolayer abrupt interface between HgCdTe and CdTe films. The interface of HgCdTe/CdTe contains a lot of small and random distributed disorder regions. The disorder areas can be transformed into order one under long time electron beam irradiation.

  12. Study of Hg vacancies in (Hg,Cd)Te after THM growth and post-growth annealing by positron annihilation

    OpenAIRE

    Krause, R.; Klimakow, A.; Kießling, F. M.; Polity, A.; Gille, Peter; Schenk, M.

    1990-01-01

    Positron lifetime measurements have been performed to study vacancy defects in Hg0.78Cd0.22Te. Post-growth annealing under various Hg vapour pressure conditions have been used to create a well-defined number of Hg vacancies. The sensitivity range of the positron annihilation method was found to be 1015 < cHgvac

  13. ELECTRON TRANSFER IN Hg1-xCdxTe-CdTe HETEROSTRUCTURES

    OpenAIRE

    Boebinger, G.; Vieren, J.; Guldner, Y.; Voos, M.; Faurie, J.

    1987-01-01

    Far infrared magneto-absorption experiments performed at 1.6K in HgCdTe-CdTe heterojunctions show that a two-dimensional electron gas is formed in the HgCdTe layer at the HgCdTe-CdTe interface. The electron effective masses of the two populated subbands is obtained and compared to previous theoretical calculations. The electron transfer across the interface involves deep traps in the CdTe layers.

  14. Characterization of CdTe, HgTe, and Hg1-xCdxTe grown by chemical beam epitaxy

    Science.gov (United States)

    Wagner, B. K.; Rajavel, D.; Benz, R. G.; Summers, C. J.

    1991-10-01

    Detailed characterization of chemical beam epitaxially (CBE) grown CdTe and Hg1-xCdxTe layers are reported. These characterizations include photoluminescence, infrared transmission, energy dispersive x-ray analysis, and variable temperature (10-300 K) Hall effect and resistivity measurements. The results indicate that high quality HgCdTe layers can be grown by CBE.

  15. On the valence state of Hg in (Hg, Cr)Sr2CuO4+δ superconductor

    International Nuclear Information System (INIS)

    The 1201-type of superconducting samples of nominal composition (Hg0.7Cr0.3)Sr2CuO4+δ, were synthesised in partial vacuum and subsequently annealed in oxygen and argon. The Tc onset for the different samples is found to be ∼58 K. Hg LIII-edge measurements have clearly shows that Hg is in divalent state in all the (Hg,Cr)-1201 samples. (author)

  16. Point defects with lattice distortion in CdTe and HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Schick, J.T.; Morgan-Pond, C.G. (Department of Physics Astronomy, Wayne State University, Detroit, Michigan 48202 (US))

    1990-03-01

    Results of self-consistent, tight-binding supercell calculations of electronic defect levels and relaxation about defects for As, Sb, and Te interstitials in CdTe and for the Hg vacancy in HgTe are presented. Trends in the localized defect levels and the relaxation of the lattice seen for these defects and for Cd, Hg, and In interstitials, from previous calculations, are discussed. Te interstitials are found to have the largest lattice relaxation of these interstitials in their preferred tetrahedral positions. This may help explain the tendency for excess Te to condense into second-phase inclusions. It is also suggested that a strain-mediated interaction between Te interstitials and cation vacancies may promote the creation of Te antisites in Te-rich HgCdTe.

  17. Investigation of equilibrium in the system Mn-3-amino-1,2,4-trazole-H2O (Mnn+=Co,2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Ca3+, Al3+ and Fe3+)

    International Nuclear Information System (INIS)

    Complexing of 3-amino-1,2,4-triazole (amitrole) in aqueous solutions at 20 deg C, pH 4-9 at ion force values of 0.1, 0.5 and 1.0 mol/hp with ions contained in soils as macrocomponents and microelements (Co2+, Cd2+, Hg2+) has been studied by the method of pH-metric titration. It is shown that in the environment and in living organisms amitrole forms strong enough complexes and its major part is in the bound state

  18. HgCdTe APDs for free space optical communications

    Science.gov (United States)

    Rothman, J.; Lasfargues, G.; Abergel, J.

    2015-10-01

    HgCdTe avalanche photodiode single element detectors have been developed for a large scope of photon starved applications. The present communication is dedicated to use of these detectors for free space optical communications. In this perspective we present and discuss the sensitivity and bandwidth that has been measured directly on HgCdTe APDs and on detector modules. In particular, we report on the performance of TEC cooled large area detectors with sensitive diameters ranging from 30- 200 μm, characterised by detector gains of 2- 20 V/μW and noise equivalent input power of 0.1-1 nW for bandwidths ranging from 20 to 400 MHz. One of these detectors has been used during the lunar laser communication demonstration (LLCD) and the results The perspectives for high data rate transmission is estimated from the results of impulse response measurements on HgCdTe APDs. These results indicate that bandwidths close to 10 GHz can be achieved in these devices. The associated sensitivity at an APD gain of 100 is estimated to be below 4 photons rms (NEP<10 nW) for APDs operated at 300 K.

  19. Assessment of soil contamination by potentially toxic trace elements (PTSD) (As, Cd, Cu, Hg, Pb, Zn) in a lower plain of the Hron River according to Law no. 219/2008 Coll., by geo-accumulation index, anthropogenic factor and Tomlinson index

    International Nuclear Information System (INIS)

    Soil contamination by different PTSD may have different geogenic and anthropogenic origin and occurs in all countries of the world. The aim of this paper is to evaluate the soils contamination of a lower plain of the Hron River. This paper used the results of the thesis Soil contamination of the Hron River floodplain by trace elements (As, Cd, Cu, Hg, Pb, Zn) [1]. Soil contamination was evaluated by: Act. 219/2008 Coll. on the protection and use of agricultural land, by anthropogenic factor (AF), geo-accumulation index (IgeoE) and Tomlinson index - the index of the pollution load (PLI). (author)

  20. Cd/Hg cationic substitution in magic-sized CdSe clusters: Optical characterization and theoretical studies

    International Nuclear Information System (INIS)

    Highlights: • HgSe magic-sized clusters were prepared via Cd/Hg cationic exchange in pyridine. • Upon cationic exchange CdSe clusters behave differently from quantum dots or rods. • Theoretical calculations of magic-sized clusters agree well with experimental data. - Abstract: We examine conversion of magic-sized CdSe clusters (MSCs) into HgSe ones by means of Cd/Hg cation exchange. With this procedure Cd8Cd17– and Cd32–selenide clusters can be converted into corresponding Hg8–, Hg17– and Hg32–selenide ones. Upon cationic exchange MSCs behavior differs from that of bulkier counterparts – larger (2–3 nm) quantum dots. Unlike CdSe colloidal quantum dots, magic-sized clusters are converted in fast and complete manner without a formation of intermediate mixed CdxHg1−x compounds that was established on the basis of optical absorption spectroscopy and chemical composition analysis. These assumptions were supported by DFT quantum chemical calculations performed for Cd8–, Cd17– and Hg8–, Hg17–selenide model clusters. Energies of experimental and calculated optical transitions were compared in order to prove the isostructural character of cationic substitution in magic-sized clusters

  1. Magnetically tunable laser emission from Hg,CdTe

    International Nuclear Information System (INIS)

    Tunable spin-flip Raman and recombination laser emission from (Hg,Cd)Te have been observed using a chopped-cw CO2 laser as the pump. Peak powers of over 1 mW and average powers of over 100 μW have been obtained for both the spin-flip Raman and recombination emissions with conversion efficiencies of over 0.3%. A zero-field g factor of vertical-bar82vertical-barplus-or-minus3 has been measured, corresponding to a conduction band-edge effective-mass ratio of 0.0098plus-or-minus0.0004

  2. Luminescence studies of HgCdTe alloys

    OpenAIRE

    Hunter, A. T.; McGill, T. C.

    1982-01-01

    We report the observation in Hg_(1-x)Cd_(x)Te of band-to-band, band-to-acceptor, and donor-acceptor luminescence for material of x = 0.32 and 0.5, and bound exciton recombination luminescence, for material of x = 0.5. The band-to-band lineshape and variation in intensity with pump power are appropriate to an electron-hole plasma with recombination proceeding without wave vector conservation. Differences between the spectra among the four 0. 5 samples studied are attributed to variations in...

  3. MBE (Molecular Beam Epitaxial) growth characterization and electronic device processing of HgCdTe, HgZnTe related heterojunctions and HgCdTe-CdTe superlattices

    Science.gov (United States)

    Faurie, Jean-Pierre

    1987-06-01

    As the MBE growth technique has continued to improve for Hg(1-x)Cd(x)Te films, the prospects for films of larger area have begun to be explored. These larger area films are important for imaging arrays and will be especially vital in the future for the efficient production of Hg(1-x)Cd(x)Te material. The growth of MBE of uniform Hg(1-x)Cd(x)Te epilayer on a large substrate is very difficult to achieve because of the non-uniform distribution of the fluxes and on the non-uniform temperature of the substrate.

  4. HgTe and CdTe epitaxial layers and HgTe–CdTe superlattices grown by laser molecular beam epitaxy

    OpenAIRE

    Cheung, J. T.; Niizawa, G.; Moyle, J.; Ong, N. P.; Paine, B. M.; Vreeland, T., Jr.

    1986-01-01

    CdTe and HgTe epilayers and HgTe/CdTe superlattices have been grown by laser molecular beam epitaxy (laser MBE) on CdTe substrates. The power density of the laser radiation used to evaporate source materials was found to be a very important growth parameter. The superlattice structures have been characterized by helium ion backscattering spectrometry, x-ray double crystal diffractometry, and low temperature electrical transport measurements. Results indicate good crystallinity and very strong...

  5. Removal of Cd (II) and Hg(II) by chelating resin Chelex-100

    OpenAIRE

    Afaf Amara-Rekkab; Mohamed Amine Didi

    2015-01-01

    A sensitive, simple method for the determination of amounts of mixture of Hg2+and Cd2+ by spectrophotometry was described based on the formation of the Hg2+- Cd2+- PAN complex in water media. Optimal conditions such as reagent amounts, and pH for the Hg2+- Cd2+ determination were reported. It was found that the 2:1 PAN- Hg2+- Cd2+ complex dominate at pH 13.0. In another hand, the sorption of mixture mercury (II) and cadmium (II) from aqueous medium on a chelating resin Chelex 100 was studied...

  6. Potential Energy Surfaces for Reactions of X Metal Atoms (X = Cu, Zn, Cd, Ga, Al, Au, or Hg with YH4 Molecules (Y = C, Si, or Ge and Transition Probabilities at Avoided Crossings in Some Cases

    Directory of Open Access Journals (Sweden)

    Octavio Novaro

    2012-01-01

    Full Text Available We review ab initio studies based on quantum mechanics on the most important mechanisms of reaction leading to the C–H, Si–H, and Ge–H bond breaking of methane, silane, and germane, respectively, by a metal atom in the lowest states in Cs symmetry: X(2nd excited state, 1st excited state and ground state + YH4→ H3XYH → H + XYH3 and XH + YH3. with X = Au, Zn, Cd, Hg, Al, and G, and Y = C, Si, and Ge. Important issues considered here are (a the role that the occupation of the d-, s-, or p-shells of the metal atom plays in the interactions with a methane or silane or germane molecule, (b the role of either singlet or doublet excited states of metals on the reaction barriers, and (c the role of transition probabilities for different families of reacting metals with these gases, using the H–X–Y angle as a reaction coordinate. The breaking of the Y–H bond of YH4 is useful in the production of amorphous hydrogenated films, necessary in several fields of industry.

  7. Colloidally prepared CdHgTe and HgTe quantum dots with strong near-infrared luminescence

    Energy Technology Data Exchange (ETDEWEB)

    Rogach, A.L.; Kornowski, A.; Eychmueller, A.; Weller, H. [Hamburg Univ. (Germany). Inst. fuer Physikalische Chemie; Harrison, M.T.; Kershaw, S.V.; Burt, M.G. [Corning Research Centre, Suffolk (United Kingdom)

    2001-03-01

    Several series of CdHgTe composite nanocrystals were prepared using thiol-capped CdTe nanocrystal precursors to which subsequent layers of HgTe and CdTe were added. The position of the 'excitonic' photoluminescence peak measured at room temperature was red-shifted to the near infrared to give emission wavelengths ranging from 800 to 1100 nm depending on the quantum dot composition, with quantum efficiency (QE) significantly increased over the pure CdTe material (QE up to around 40%). Thiol-capped HgTe nanocrystals synthesized in aqueous solution show a broad photoluminescence with a QE of {proportional_to}50%. It has been shown using D{sub 2}O as a solvent that by varying the synthesis conditions it is possible to tune the luminescence of HgTe quantum dots to the desired wavelength in the range of 900-2000 nm. HgTe nanocrystals passivated at the surface with a thick CdS layer have been shown to be much more robust towards heating and ''aging'' of the optical properties. (orig.)

  8. A longitudinally electron-beam-pumped CdHgTe laser

    Science.gov (United States)

    Borisov, B. G.; Lavrushin, B. M.; Nasibov, A. S.; Sypchenko, M. N.; Sherman, B. L.

    1989-10-01

    Lasers have been fabricated utilizing CdHgTe/CdTe heterostructures which were grown by the liquid-phase epitaxy method. The epitaxial CdHgTe layer was the active region of the cavity and the CdTe substrate was passive. Laser action in Cd(0.65)Hg(0.35)Te was achieved at a wavelength of 1.48 micron, a temperature of 77 K, and an electron energy of 50 keV. A maximum external differential efficiency of 3.4 percent was achieved.

  9. BRIEF COMMUNICATIONS: Longitudinal electron-beam-pumped CdHgTe laser

    Science.gov (United States)

    Borisov, B. G.; Lavrushin, B. M.; Nasibov, A. S.; Sypchenko, M. N.; Sherman, B. L.

    1989-10-01

    A CdHgTe/CdTe heterostructure grown by liquid phase epitaxy was used to develop a laser. The CdHgTe epitaxial laser formed the active region whilst the CdTe substrate formed the passive part of the resonator. At an electron energy of 50 keV and a temperature of 77 K, lasing was obtained at 1.48 μm in Cd0.65Hg0.35Te. The maximum external differential efficiency was 3.4%.

  10. Coordination of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with 2,5-hexanedione bis(thiosemicarbazone), HBTS: crystal structure of cis-[Pd(HBTS)]Cl2 and 1-(2,5-dimethyl-1H-pyrrol-yl)-thiourea.

    Science.gov (United States)

    Jeragh, Bakir; El-Asmy, Ahmed A

    2014-09-15

    Metal complexes of Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pd2+ or Pt2+ with 2,5-hexanedione bis(thiosemicarbazone), HBTS; have been prepared and spectroscopically investigated. The empirical formulae of the complexes were suggested based on the elemental analysis. Single crystal of Pd(II) has been solved to be cis-form of square-planar geometry by the X-ray crystallography. 1H and 13C NMR spectra have been recorded for HBTS, Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) complexes, in DMSO-d6, showing the mode of chelation. The ligand acts as a neutral or a binegative tetradentate (N2S2) or neutral bidentate on the basis of FT-IR. The magnetic moments and electronic spectra provide information about the geometry of the complexes which supported by calculating the ligand field parameters for the Co(II) and Fe(III) complexes. The Ni(II) complex has subnormal magnetic moment (0.71 BM) indicative of a mixed stereochemistry of square-planar and tetrahedral structure. [Cu(HBTS-2H)] measured 0.93 BM indicating high interaction between the copper centers. The ligand may be ordered at the top of the spectrochemical series which giving high ligand field splitting energy (10 Dq=17,900 cm(-1) for Co2+ complex). The mass spectra of some complexes proved their stable chemical formulae while the TGA depicts the degradation steps and the final residue. In evaporating the mother liquor during the preparation of HBTS, new compound is obtained naming 1-(2,5-dimethyl-1H-pyrrol-yl)thiourea and its crystal was solved. PMID:24813284

  11. Coordination of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with 2,5-hexanedione bis(thiosemicarbazone), HBTS: Crystal structure of cis-[Pd(HBTS)]Cl2 and 1-(2,5-dimethyl-1H-pyrrol-yl)-thiourea

    Science.gov (United States)

    Jeragh, Bakir; El-Asmy, Ahmed A.

    2014-09-01

    Metal complexes of Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pd2+ or Pt2+ with 2,5-hexanedione bis(thiosemicarbazone), HBTS; have been prepared and spectroscopically investigated. The empirical formulae of the complexes were suggested based on the elemental analysis. Single crystal of Pd(II) has been solved to be cis-form of square-planar geometry by the X-ray crystallography. 1H and 13C NMR spectra have been recorded for HBTS, Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) complexes, in DMSO-d6, showing the mode of chelation. The ligand acts as a neutral or a binegative tetradentate (N2S2) or neutral bidentate on the basis of FT-IR. The magnetic moments and electronic spectra provide information about the geometry of the complexes which supported by calculating the ligand field parameters for the Co(II) and Fe(III) complexes. The Ni(II) complex has subnormal magnetic moment (0.71 BM) indicative of a mixed stereochemistry of square-planar and tetrahedral structure. [Cu(HBTS-2H)] measured 0.93 BM indicating high interaction between the copper centers. The ligand may be ordered at the top of the spectrochemical series which giving high ligand field splitting energy (10Dq = 17,900 cm-1 for Co2+ complex). The mass spectra of some complexes proved their stable chemical formulae while the TGA depicts the degradation steps and the final residue. In evaporating the mother liquor during the preparation of HBTS, new compound is obtained naming 1-(2,5-dimethyl-1H-pyrrol-yl)thiourea and its crystal was solved.

  12. Can graphene make better HgCdTe infrared detectors?

    Directory of Open Access Journals (Sweden)

    Shi Yanli

    2011-01-01

    Full Text Available Abstract We develop a simple and low-cost technique based on chemical vapor deposition from which large-size graphene films with 5-10 graphene layers can be produced reliably and the graphene films can be transferred easily onto HgCdTe (MCT thin wafers at room temperature. The proposed technique does not cause any thermal and mechanical damages to the MCT wafers. It is found that the averaged light transmittance of the graphene film on MCT thin wafer is about 80% in the mid-infrared bandwidth at room temperature and 77 K. Moreover, we find that the electrical conductance of the graphene film on the MCT substrate is about 25 times larger than that of the MCT substrate at room temperature and 77 K. These experimental findings suggest that, from a physics point of view, graphene can be utilized as transparent electrodes as a replacement for metal electrodes while producing better and cheaper MCT infrared detectors.

  13. ROIC for HgCdTe e-APD FPA

    Science.gov (United States)

    Chen, Guoqiang; Zhang, Junling; Wang, Pan; Zhou, Jie; Gao, Lei; Ding, Ruijun

    2013-08-01

    Ultra-low light imaging and passive/active dual mode imaging require very low noise optical receivers to achieve detection of fast and weak optical signal. HgCdTe electrons initiated avalanche photodiodes (e-APDs) in linear multiplication mode is the detector of choice thanks to its high quantum efficiency, high gain at low bias, high bandwidth and low noise factor. In my work, a passive/active dual mode readout integrated circuit (ROIC) of e-APD focal plane array (FPA) is designed. Unit cell circuit architecture of ROIC includes a capacitance feedback transimpedance amplifier (CTIA) as preamplifier of ROIC, a high voltage protection module, a comparator, a Sample-Hold circuit module, and output driver stage. There is a protection module in every unit cell circuit which can avoid ROIC to be damaged from avalanche breakdown of some diodes of detector. Conventional 5V CMOS process is applied to implement the high voltage protection with the small area rather than Laterally Diffused Metal Oxide Semiconductor (LDMOS) in high voltage BCD process in the limited 100um×100um pitch area. In CTIA module, three integration capacitances are included in the CTIA module, two of them are switchable to provide different well capacity and noise. Constraints such as pixel area, stability and power lead us design toward a simple one-stage cascade operational transconductance amplifier (OTA) as pre-amplifier. High voltage protection module can protect ROIC to be damaged because of breakdown of some avalanche diodes.

  14. The longitudinal translocation characters and the influencing factors of Hg, Cd in the soil

    Directory of Open Access Journals (Sweden)

    Zhang Yujuan

    2006-11-01

    Full Text Available Combining the methods of simulation test and field survey, the longitudinal distribution and the influencing factors of Hg and Cd in the profile in the typical sewage irrigation area were studied in this paper and the result shows: (1 the content distribution of Hg, Cd in the superficial soil profile was higher than that in the bottom and the content decreased with the increase of the depth, the translocation ability of the Hg, Cd in the garden mould and cinnamon soil were lower than that in the paddy soil and fluve-aquic soil, the longitudinal translocation ability of the Cd in the soil profile was stronger than that of Hg; (2 Hg was accumulated in the different soil and has the highest accumulation rate in the paddy soil and the lowest in the cinnamon soil; the translocation order of the Cd in the different was: garden mould > paddy soil > cinnamon soil > fluve-aquic soil; (3 the concentration of Hg, Cd in the soil leacheate increased with the concentration increase of Hg, Cd in the sewage, the migration rate increased with the roughness of the soil quality and decreased with the increase of pH and soil organic matter.

  15. Large format MBE HgCdTe on silicon detector development for astronomy

    Science.gov (United States)

    Hanold, Brandon J.; Figer, Donald F.; Lee, Joong; Kolb, Kimberly; Marcuson, Iain; Corrales, Elizabeth; Getty, Jonathan; Mears, Lynn

    2015-08-01

    The Center for Detectors at Rochester Institute of Technology and Raytheon Vision Systems (RVS) are leveraging RVS capabilities to produce large format, short-wave infrared HgCdTe focal plane arrays on silicon (Si) substrate wafers. Molecular beam epitaxial (MBE) grown HgCdTe on Si can reduce detector fabrication costs dramatically, while keeping performance competitive with HgCdTe grown on CdZnTe. Reduction in detector costs will alleviate a dominant expense for observational astrophysics telescopes. This paper presents the characterization of 2.5μm cutoff MBE HgCdTe/Si detectors including pre- and post-thinning performance. Detector characteristics presented include dark current, read noise, spectral response, persistence, linearity, crosstalk probability, and analysis of material defects.

  16. Additional evidence concerning the valence-band offset in HgTe/CdTe

    Science.gov (United States)

    Young, P. M.; Ehrenreich, H.

    1991-05-01

    The consistency of large values of the valence-band offset, Λ, in HgTe/CdTe superlattices with magneto-optical experiments is examined in light of data on a 90-Å HgTe/40-Å CdTe superlattice. The data are shown to be consistent with values Λ=400+/-40 meV rather than the much smaller cited values. This analysis, when considered with photoemission experiments, leaves intact the conclusion that HgTe/CdTe superlattices are best explained by a large offset.

  17. THE EFFECT OF pH ON BIOACCUMULATION OF Cd, Hg AND Pb BY WATER HYACINTH

    OpenAIRE

    Syahrul, Muh.

    2014-01-01

    Water hyacinth grows and multiplies rapidly in the water contaminated by heavy metals such as Cd, Hg, and Pb.. The water hyacinth was planted in Long Ashton media at varying pH, concentrations of Cd, Hg, and Pb and planting time. The roots adsorbed more Cd, Hg and Pb than the stalks and leaves. The maximum absorption was found at pH 5.0 and the minimum at pH 7.0. The higher the metal concentration in the media and longer the planting time, the absorption of the metal ion increased co...

  18. Proton irradiation of MWIR HgCdTe/CdZnTe

    Science.gov (United States)

    Fahey, Stephen; Velicu, Silviu; Bommena, Ramana; Zhao, Jun; Cowan, Vincent; Morath, Christian; Sivananthan, Sivalingam

    2015-09-01

    High performance infrared sensors are vulnerable to slight changes in defect densities and locations. For example in a space application where such sensors are exposed to proton irradiation capable of generating point defects the sensors are known to suffer performance degradation. The degradation can generally be observed in terms of dark current density and responsivity degradations. Here we report results of MWIR HgCdTe/CdZnTe single element diodes dark current densities before and after exposure to 63MeV protons at room temperature to a total ionizing dose of 100 kRad(Si). We find the irradiated diodes as a group show some signs of proton-induced damage in dark current.

  19. Applications of the Infrared Measurement Analyzer: Hydrogenated LWIR HgCdTe Detectors

    Science.gov (United States)

    Buurma, Christopher; Boieriu, Paul; Bommena, Ramana; Sivananthan, Sivalingam

    2013-11-01

    Low-cost silicon-based alternative substrates are an attractive choice for next-generation large-area high-resolution multicolor infrared (IR) detector arrays. However, the high density of dislocations formed during molecular-beam epitaxy growth of HgCdTe/CdTe/Si limits the performance of IR arrays, especially in the long-wavelength infrared (LWIR) region. Atomic hydrogen introduced by inductively coupled plasma (ICP) into HgCdTe is expected to passivate dislocations, bulk and surface defects, removing their contributions to dark current. Passivation using ICP hydrogenation can have different effects on HgCdTe photodiode performance, depending on which class of defects is being passivated. The infrared measurement analyzer (IRMA) was used to deconvolute the effects of hydrogenation on LWIR HgCdTe photodiodes through a reverse-modeling fit of the current-voltage ( I- V) characteristic. This approach results in a fit with fewer false minima, low parameter error and bias, and high confidence in extracted device parameters. A description of this tool and its application to hydrogenated HgCdTe LWIR detectors is presented. Lower dark currents have been observed after hydrogenation of fully fabricated devices. Model-fits performed on a wide variety of LWIR HgCdTe photodiodes suggest that hydrogenation provides both surface and bulk quality improvements. These benefits of ICP hydrogenation have been retained over several months.

  20. Recent progress in MBE grown HgCdTe materials and devices at UWA

    Science.gov (United States)

    Gu, R.; Lei, W.; Antoszewski, J.; Madni, I.; Umana-Menbreno, G.; Faraone, L.

    2016-05-01

    HgCdTe has dominated the high performance end of the IR detector market for decades. At present, the fabrication costs of HgCdTe based advanced infrared devices is relatively high, due to the low yield associated with lattice matched CdZnTe substrates and a complicated cooling system. One approach to ease this problem is to use a cost effective alternative substrate, such as Si or GaAs. Recently, GaSb has emerged as a new alternative with better lattice matching. In addition, implementation of MBE-grown unipolar n-type/barrier/n-type detector structures in the HgCdTe material system has been recently proposed and studied intensively to enhance the detector operating temperature. The unipolar nBn photodetector structure can be used to substantially reduce dark current and noise without impeding photocurrent flow. In this paper, recent progress in MBE growth of HgCdTe infrared material at the University of Western Australia (UWA) is reported, including MBE growth of HgCdTe on GaSb alternative substrates and growth of HgCdTe nBn structures.

  1. The Study on the Properties of CdTe Buffer Layer for MBE HgCdTe Epilayer%分子束外延HgCdTe薄膜的CdTe缓冲层特性研究

    Institute of Scientific and Technical Information of China (English)

    宋立媛; 唐利斌; 李艳辉; 孔令德; 陈雪梅

    2009-01-01

    CdTe是GaAs衬底上分子束外延(MBE)HgCdTe薄膜时的缓冲层,引入缓冲层的目的是减小失配位错,CdTe缓冲层的生长直接影响到后续HgCdTe薄膜的制备质量,然而目前现有文献鲜有报道CdTe缓冲层的最佳厚度.采用X射线双晶衍射、位错腐蚀坑密度(EPD)、FT-IR和椭圆偏振光谱的方法,从CdTe缓冲层厚度对位错密度的影响入手,分析并确定了理想的CdTe缓冲层厚度.%CdTe is the buffer layer of GaAs substrate for HgCdTe eoilayer grown by MBE,The purpose for introduction of buffer laver is to decrease the mismatched dislocation,the growth of CdTe buffer layer directly affects the quality of foilowing grown HgCdTe thin film.However,up to now only few papers have reported the optimum thickness for CdTe buffer layer.By using of X-ray double ervstal diffraction,EPD,FT-IR as well as soectroscopic ellipsometry the paper has studied the effects of the thickness on EPD for CdTe buffer layer,the optimum thickness of CdTe buffer layer has been obtained.

  2. Estimation of Thickness and Cadmium Composition Distributions in HgCdTe Focal Plane Arrays

    Science.gov (United States)

    Mouzali, S.; Lefebvre, S.; Rommeluère, S.; Ferrec, Y.; Primot, J.

    2016-09-01

    Mercury cadmium telluride (HgCdTe) is one of the most commonly used material systems for infrared detection. The performance of infrared focal-plane arrays (IRFPAs) based on this material is limited by several noise sources. In this paper, we focus on the fixed pattern noise, which is related to disparities between the spectral responses of pixels. In our previous work, we showed that spectral nonuniformities in a HgCdTe IRFPA were caused by inhomogeneities of thickness and cadmium composition in the HgCdTe layer, using an optical description of the pixel structure. We propose to use this bidimensional dependence combined with experimental spectral responses to estimate disparities of thickness and cadmium composition in a specific HgCdTe-based IRFPA. The estimation methods and the resulting maps are presented, highlighting the accuracy of this nondestructive method.

  3. Single Photon Sensitive HgCdTe Avalanche Photodiode Detector (APD) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A linear mode HgCdT electron-initiated avalanche photodiode (EAPD) capable of 1570nm photon detection efficiency (PDE) at >10 MHz will be developed. The Phase I...

  4. Ultra-low Noise, High Bandwidth, 1550nm HgCdTe APD Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Voxtel Inc. proposes to optimize the design of a large area, 1.55?m sensitive HgCdTe avalanche photodiode (APD) that achieves high gain with nearly no excess noise....

  5. Characteristics of HgCdTe epilayer grown by LPE using horizontal slider

    Indian Academy of Sciences (India)

    J K Radhakrishnan; S Sitharaman; S C Gupta

    2002-11-01

    The characteristics of HgCdTe epilayers grown in a modified horizontal slider system, are reported here. The surface morphology of the grown layers, their IR transmission characteristics, depth and lateral compositional uniformity, structural and electrical characteristics are discussed.

  6. Molecular beam epitaxy of CdTe and HgCdTe on large-area Si(100)

    Science.gov (United States)

    Sporken, R.; Lange, M. D.; Faurie, Jean-Pierre

    1991-09-01

    The current status of molecular beam epitaxy (MBE) of CdTe and HgCdTe on Si(100) is reviewed. CdTe and HgCdTe grow in the (111)B orientation on Si(100); monocrystalline films with two domains are obtained on most nominal Si(100) substrates, single domain films are grown on misoriented substrates and on nominal Si(100) preheated to 900-950 degree(s)C. Double-crystal x-ray rocking curves (DCRCs) with full-width at half-maximum (FWHM) as low as 110 arcsec are reported for HgCdTe on silicon; these layers are n-type, and electron mobilities higher than 5 X 104 cm2V-2s-1 are measured at 23 K for x equals 0.26. Excellent thickness and composition uniformity is obtained: standard deviation of the CdTe thickness 0.4% of the average thickness on 2-in. and 2.3% on 5-in., standard deviation of the Cd concentration in the HgCdTe layers 0.6% of the average concentration on 3-in. and 2.4% on 5-in. First results regarding growth of CdTe on patterned Si substrates are also reported.

  7. Detection of non stoichiometric vacancy defects in CdTe, HgTe and Hg1-xCdxTe by positron annihilation

    International Nuclear Information System (INIS)

    Native vacancies are evidenced from positron lifetime measurements in as-grown CdTe, HgTe and Hg0.8Cd0.2Te. The positron lifetime depends on the conducting type of the materials rather than on the growing conditions. The native vacancies have two levels of ionisation and are identified as Cd-vacancies (VCd) in CdTe. (author) 2 figs., 2 tabs., 9 refs

  8. Potentiodynamic oxidation of HgCdTe surface formed by fracture in solution

    International Nuclear Information System (INIS)

    The initial stages of the anodic oxidation of HgTe and HgCdTe were studied by applying a potentiostatic anodic scan to a fresh surface of the material, which was obtained by fracturing it in the anodizing solution and by inspecting it using Auger electron spectroscopy. It was found that a stable oxide formation is preceded by the dissolution of both the CdTe and the HgTe fractions of the alloy which behave as if they were separate entities. The dissolution of the CdTe fraction does not lead to the formation of a stable oxide; this is formed only after the dissolution of mercury. Following the HgTe dissolution peak, a potential region is observed in which the oxide grows with a current efficiency of unity. This implies that mercury should be a major constituent in the oxide and its marginal Auger signal in the oxide is attributed to the evaporation of the volatile HgO content under the action of the electron beam. Taking this into account, the oxide composition on Hg/sub 0.79/Cd/sub 0.21/Te is estimated to be Hg/sub 0.4/Cd/sub 0.6/TeO/sub 3/

  9. History of HgCdTe infrared detectors at BAE Systems

    Science.gov (United States)

    Reine, Marion B.

    2009-05-01

    This paper describes the history and current status of HgCdTe infrared detector technology at BAE Systems in Lexington, Massachusetts, whose corporate legacy includes Honeywell (1962-1991), Loral (1991-1996), and Lockheed Martin (1996-2000). The Honeywell Radiation Center was founded in 1962 in Boston, Massachusetts. Shortly thereafter, primitive HgCdTe samples began to arrive from the Honeywell Corporate Research Center in Hopkins, Minnesota for evaluation as possible IR detectors. In 1967, procedures for the growth of HgCdTe inhomogeneous large-grain-polycrystalline ingots by a modified Bridgman method were transferred from the Research Center to the Radiation Center. In 1968 the Radiation Center moved to new facilities in Lexington, Massachusetts. HgCdTe activities have expanded and evolved in the ensuing years, remaining in the Lexington, Massachusetts facilities up to the present. This paper reviews the role that the Honeywell/Loral/Lockheed Martin/BAE Systems facility in Lexington, Massachusetts has played in the success of HgCdTe as today's preeminent, highest performance, most versatile, and most widely applicable infrared detector material for the 1-30 μm spectral range. We examine the evolution of both photoconductive and photovoltaic HgCdTe detectors from early unpassivated ill-understood single-element devices through production of linear arrays and to today's large-format two-dimensional IR Focal Plane Arrays for the most demanding spaceborne applications. We examine the progress made in HgCdTe materials science and technology, including improved highly-homogeneous bulk crystal growth, liquid phase epitaxy and metalorganic vapor phase epitaxy. Various devices are used to illustrate the evolution of HgCdTe technology, including the n-type photoconductor, the trapping-mode photoconductor, and the two-layer LPE P-on-n heterojunction.

  10. CdTe and HgI2 crystals and detectors: present state and future

    International Nuclear Information System (INIS)

    After recalling the main properties of CdTe and HgI2 crystals from which the characteristics of these detectors will arise, the fabrication cycle is analysed at its various stages. The results at present achieved on CdTe and HgI2 detectors are analysed with a number of concrete applications in view such as medium power (0-200 keV) X and γ spectrometry, localisation of γ photons and solid ionisation chambers

  11. Quantum Calorimeters Based on HgCdTe Alloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA's next generation of x-ray observation missions require x-ray calorimeters with superior energy resolution. Semimetallic HgTe has already proven itself as an...

  12. Progress, challenges, and opportunities for HgCdTe infrared materials and detectors

    Science.gov (United States)

    Lei, Wen; Antoszewski, Jarek; Faraone, Lorenzo

    2015-12-01

    This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detector technology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth, device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well controlled p-type doping, lower cost, larger array format size, higher operating temperature, multi-band detection, and advanced plasma dry etching. Various new concepts and technologies are proposed and discussed that have the potential to overcome the existing primary challenges that are inhibiting the development of next generation HgCdTe infrared detector technology.

  13. HgTe/CdTe heterojunctions: A lattice-matched Schottky barrier structure

    OpenAIRE

    Kuech, T. F.; McCaldin, J. O.

    1982-01-01

    HgTe-CdTe lattice-matched heterojunctions were formed by the epitaxial growth of HgTe on CdTe substrates using a low-temperature metal organic chemical vapor deposition technique. These heterojunctions combine features of the Schottky barrier structure, due to the high carrier concentrations found in the semimetallic HgTe, with the structural perfection present in a lattice-matched heterojunction. The measured Schottky barrier height varied from 0.65 to 0.92 eV depending on the details of the...

  14. Stimulated emission from a CdTe/HgCdTe separate confinement heterostructure grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Mahavadi, K.K.; Bleuse, J.; Sivananthan, S.; Faurie, J.P. (Microphysics Laboratory, Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60680 (USA))

    1990-05-21

    We present the results of low-temperature photoluminescence and stimulated emission experiments performed on a CdTe/Hg{sub 0.45}Cd{sub 0.55}Te/Hg{sub 0.67}Cd{sub 0.33}Te multiquantum well separate confinement heterostructure grown by molecular beam epitaxy. The photoluminescence results suggest that because of the growth conditions, there is a strong interdiffusion in the multiquantum well region. Pulsed stimulated emission was observed from this structure up to 77 K.

  15. Study of CdTe and HgCdTe thin films obtained by electrochemical methods

    International Nuclear Information System (INIS)

    Cadmium telluride polycrystalline thin films were fabricated on SnO2-coated glass substrates by potentiostatic electrodeposition and characterized by X-ray diffraction, energy dispersive X-ray analyses (EDAX), optical and electrical measurements. The films dseposited at potentials more positive than -0.65 V vs.SCE were p-type but those deposited at more negative potentials were n-type. All CdTe thin films showed a band-gap energy about 1.45 eV and a large absorption coeffici-ent (a=105 cm-1) above de band edge. The addition of even small amounts of mercury to the CdTe produces higuer conductivity values and lower band-gap energies. We have prepared HgCdTe thin films where the band-gap energies ranged between 0.93 and 0.88 eV depending on the ratio of mercury to cadmium. Heat treatment at 3000C increases the crystalline diameter and alter the composition of the electrodeposited films, a decrease of the resistivity values was also observed. (Author)

  16. Chromo/Fluorogenic Detection of Co(2+), Hg(2+) and Cu(2+) by the Simple Schiff Base Sensor.

    Science.gov (United States)

    Saleem, Muhammad; Khang, Chung Ho; Kim, Moon-Hwan; Lee, Ki Hwan

    2016-01-01

    Herein, we reported the ditriazole Schiff base derivative 1 and evaluated its photophysical properties on induction of varieties of metal ions including Na(+), Ag(+), Ni(2+), Mn(2+), Pd(2+), Co(2+), Hg(2+), Cu(2+), Pb(2+), Cd(2+), Zn(2+), Sn(2+), Fe(2+), Fe(3+), Cr(3+) and Al(3+), in order to figure out its potential as ion sensor. The ligand 1 exhibited the strong colorimetric change in the reaction solution as well as absorption spectral shifting with the concomitant appearance of well-defined isosbestic points only upon Co(2+), Hg(2+) and Cu(2+) addition corroborates its applicability as multichannel ion detector. The different extent of spectral shifting as well as unique chromogenic change in the probe solution upon Co(2+), Hg(2+) and Cu(2+) introduction can be used as the discrimination tool for these metal ions. The ligand-metal binding stoichiometry was assessed by their optical response which was further supported by the FT-IR, NMR and mass spectrometric analysis. The association constant and the detection limits of the ligand toward Co(2+), Hg(2+) and Cu(2+) ions were calculated to be 1.52 × 10(-8), 3.26 × 10(-9), 1.16 × 10(-8) and 3.87 × 10(-10), 5.47 × 10(-11), 8.91 × 10(-11) M, respectively, employing the Benesi-Hilderbrand equation and 3 σ slope(-1) methods. Furthermore, the successive addition of Co(2+), Hg(2+) and Cu(2+) induce the constant decline in the fluorescence emission signal intensity of the probe. The quenching efficiency of the probe upon metallic induction was fitted to the Stern-Volmer equation which yielded the upward curvature in case of all the three metals ions (Co(2+), Hg(2+) and Cu(2+)) when (Io/I-1) was plotted against the quencher concentration indicating the occurrence of both the dynamic and static quenching process in the system with the average Stern-Volmer quenching constant values of 9.25 × 10(-7), 1.14 × 10(-7), 1.829 × 10(-7), respectively. PMID:26585349

  17. 199Hg and 63,65Cu NMR studies of mercury based high-Tc superconductors

    International Nuclear Information System (INIS)

    Hg-oxide ceramic high temperature superconductors were studied with 199Hg- and 63,65Cu- NMR spectroscopy. Room temperature spectra, spin-spin and spin-lattice relaxation times of samples with different superconducting transition temperatures are presented. A spin-lattice relaxation time of T1 = 35 msec and a spin-spin relaxation time of T2 = 1.6 msec is found for the 199 Hg-NMR. All samples exhibit similar characteristic powder spectra caused by an axially symmetric 199Hg spin interaction. The isotropic value and the anisotropy of the tensor relative to solid HgCl2 as a standard substance is estimated. Furthermore results of 63,65Cu NMR at a temperature of 4.2 K are presented. Also this signal shows a powder line shape (for I = 3/2)

  18. Phase transitions involving vacancy ordering in two metal mercuric iodides, Ag2HgI4 and Cu2HgI4

    Science.gov (United States)

    Lumsden, Mark; Steinitz, Michael; McAlduff, E. J.

    1995-06-01

    We have investigated the thermochromic order-disorder phase transitions in two superionic conducting compounds, Ag2HgI4 and Cu2HgI4, using capacitance dilatometry to determine the relative volume change, ΔV/V, at the transitions. We find an average ΔV/V of 9.6×10-3 for Ag2HgI4 at a transition temperature of 48.75 °C and an average ΔV/V of 4.0×10-3 for Cu2HgI4 at a transition temperature of 63 °C.

  19. Effect of thermal stress on the performance of HgCdTe/Si diodes and FPAs

    International Nuclear Information System (INIS)

    As a typical hetero-epitaxial material, the HgCdTe film which directly grows on the Si substrate possesses great residual stress for the large lattice and thermal expansion mismatch. Thermal stress caused by the thermal expansion mismatch dominates the stress mechanism after growth and seriously affects the device performance. In this paper, the performance of the HgCdTe/Si material, diodes and focal plane arrays under different thermal stress condition was studied. The experimental results indicate that the performance regularly changes with the thermal stress and all the results can be duplicated and recoverable. By analyzing the changes of the energy band under different stress conditions, it was found that the stress in the HgCdTe film impacts the film's characteristics. The HgCdTe film with tensile stress exhibits higher electron mobility, while with the compressive stress, the film exhibits higher hole mobility than that of the bulk HgCdTe crystal. Finally, the theoretical analysis can explain the experimental results well. (paper)

  20. A new circuit model of HgCdTe photodiode for SPICE simulation of integrated IRFPA

    Science.gov (United States)

    Saxena, Raghvendra Sahai; Saini, Navneet Kaur; Bhan, R. K.; Sharma, R. K.

    2014-11-01

    We propose a novel sub circuit model to simulate HgCdTe infrared photodiodes in a circuit simulator, like PSPICE. We have used two diodes of opposite polarity in parallel to represent the forward biased and the reverse biased behavior of an HgCdTe photodiode separately. We also connected a resistor in parallel with them to represent the ohmic shunt and a constant current source to represent photocurrent. We show that by adjusting the parameters in standard diode models and the resistor and current values, we could actually fit the measured data of our various HgCdTe photodiodes having different characteristics. This is a very efficient model that can be used for simulation of readout integrated circuit (ROIC) for HgCdTe IR photodiode arrays. This model also allows circuit level Monte Carlo simulation on a complete IRFPA at a single circuit simulator platform to estimate the non-uniformity for given processes of HgCdTe device fabrication and Si ROIC fabrication.

  1. Characterization of the native defects in HgTe, CdTe, Hg1-x, CdxTe by positron annihilation: evidence of native vacancies

    International Nuclear Information System (INIS)

    Direct evidence of native vacancies is found in as-grown CdxHg1-xTe single crystals prepared by the travelling heating method (THM). The vacancies have characteristics depending on the annealing undergone by the crystals after their growth and on the conduction type in the crystals. In as-grown CdTe and Cd0.7Hg0.3Te (THM), native vacancies are found in n-type materials. In as-grown HgTe and Cd0.2Hg0.8Te (THM), native vacancies are found in p materials. They disappear after stoechiometric annealings in which the crystals are converted n-type. From the positron lifetime at the vacancies, 320±4 ps, one can show that the native vacancies are metallic vacancies VCd in CdTe, VHg in HgTe, VHg or/and VCd in CdxHg1-xTe alloys. The concentration of the metallic vacancies is estimated in as-grown crystals. In as-grown p-type CdTe and Cd0.7Hg0.3Te (THM), in as-grown then subsequently p-type annealed HgTe and Cd0.2Hg0.8Te (THM), vacancy type defects are also found giving rise to lifetime of about 290 ps. These defects are also found in crystals grown by Bridgman method. The nature of these defects is discussed. The In doping effects on the metallic vacancies have been studied. It is shown that In addition increases the concentration of metallic vacancies in CdTe (In) (THM). Vacancy-In complexes appear for In concentrations of the order or above 1017 cm-3. These complexes disappear after decompensating annealings and only the metallic vacancies survive. Small vacancies clusters of two or three vacancies are found after deformation at room temperature in CdTe (Mn) (THM)

  2. Doping behavior of iodine in Hg/0.8/Cd/0.2/Te

    Science.gov (United States)

    Vydyanath, H. R.; Kroger, F. A.

    1982-01-01

    The defect state prevailing in iodine doped single-crystal samples of Hg0.8Cd0.2Te, annealed at 450-600 C in Hg vapor, has been deduced from Hall effect measurements on samples cooled to 77 K from the annealing temperature. Results are found to be similar to those previously obtained for iodine doped CdS, i.e. iodine acts as a single donor occupying Te lattice sites with a fraction paired with the native acceptor defects. The concentration of iodine on tellurium lattice sites increases with the partial pressure of Hg, whereas that of the pair species increases as the partial pressure of Hg decreases.

  3. HgO-added YBa2Cu3O7- superconductors

    Indian Academy of Sciences (India)

    Mangalesh Dixit; Shovit Bhattacharya; Rajneesh Mohan; Kiran Singh; P S R Krishna; Vilas Shelke; N K Gaur; R K Singh

    2004-08-01

    The HgO-added YBa2Cu3O7- (YBCO) superconductor has been studied for its structural and superconducting properties. Polycrystalline YBCO samples were synthesized through solid-state reaction method by adding HgO in different concentrations without using oxygen annealing. All the samples showed a sharp superconducting transition temperature around 90 K. The X-ray diffraction patterns of all the samples revealed monophasic Y-123 nature. The structural studies were carried out by neutron scattering and Rietveld analysis. The neutron scattering revealed that Hg is not incorporated in the Y-123 system and has shown optimum oxygen concentration. The significant role played by the HgO is to provide oxygen ambient through its decomposition, thus changing the oxygen balance in favour of high Cu-valence state.

  4. Spectral, thermal, electrochemical and analytical studies on Cd(II) and Hg(II) thiosemicarbazone complexes

    Science.gov (United States)

    El-Asmy, A. A.; El-Gammal, O. A.; Saleh, H. S.

    2008-11-01

    The coordination characteristic of the investigated thiosemicarbazones towards hazard pollutants, Cd(II) and Hg(II), becomes the first goal. Their complexes have been studied by microanalysis, thermal, electrochemical and spectral (electronic, IR and MS) studies. The substitutent (salicylaldehyde, acetophenone, benzophenone, o-hydroxy- p-methoxybenzophenone or diacetylmonoxime) plays an important role in the complex formation. The coordination sites were the S for thiosemicarbazide (HTS); NN for benzophenone thiosemicarbazone (HBTS); NS for acetophenone thiosemicarbazone (HATS) and salicylaldehyde thiosemicarbazone (H 2STS); NNS or NSO for diacetylmonoxime thiosemicarbazone (H 2DMTS). The stability constants of Hg(II) complexes were higher than Cd(II). The kinetic and thermodynamic parameters for the different thermal decomposition steps in the complexes have been evaluated. The activation energy values of the first step ordered the complexes as: [Cd(H 2STS)Cl 2]H 2O > [Cd(H 2DAMTS)Cl 2] > [Cd(HBTS) 2Cl 2]2H 2O > [Cd(HATS) 2Cl 2]. The CV of [Cd(H 2STS)Cl 2]H 2O and [Hg(HBTS)Cl 2] were recorded. The use of H 2DMTS as a new reagent for the separation and determination of Cd(II) ions from water and some synthetic samples using flotation technique is aimed to be discussed.

  5. Nonlinear terahertz response of HgTe/CdTe quantum wells

    International Nuclear Information System (INIS)

    Without breaking the topological order, HgTe/CdTe quantum wells can have two types of bulk band structure: direct gap type (type I) and indirect gap type (type II). We report that the strong nonlinear optical responses exist in both types of bulk states under a moderate electric field in the terahertz regime. Interestingly, for the type II band structure, the third order conductivity changes sign when chemical potentials lies below 10 meV due to the significant response of the hole excitation close to the bottom of conduction band. Negative nonlinear conductivities suggest that HgTe/CdTe quantum wells can find application in the gain medium of a laser for terahertz radiation. The thermal influences on nonlinear optical responses of HgTe/CdTe quantum wells are also studied

  6. Chelation Ion Chromatography on 1-(2-Pyridylazo-2-naphthol Sorbed Stannic Silicate: Selective Separation of Cd2+, Hg2+ and Pb2+ from some Transition Metal Ions

    Directory of Open Access Journals (Sweden)

    Rawat, J.P.

    2011-12-01

    Full Text Available Selective separation of three of the most toxic metal ions Cd2+, Hg2+ and Pb2+ has been achieved on a column packed with 1-(2-pyridylazo-2-naphthol (PAN sorbed stannic silicate using nitric acid solution of pH 1 and 6 as eluents. Adsorption behavior of several metal ions like Al3+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ on PAN sorbed stannic silicate from aqueous solution at different pH (from 1 to 6 was studied to calculate their distribution coefficients. In addition to the selective separation of Cd2+, Hg2+ and Pb2+ several binary separations of metal ions e. g., Hg2+ - Al3+, Pb2+ - Cr3+, Cd2+ - Cr3+ and Hg2+ - Cr3+ using aqueous solutions of pH 6 and pH 1 aseluents have been successfully achieved on PAN sorbed stannic silicate.

  7. Iodide retention by cinnabar (HgS) and chalcocite (Cu{sub 2}S)

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, H.L.; Balsley, S.D.; Brady, P.V.

    1995-07-01

    Sorption of iodide (I{sup {minus}}) on cinnabar (HgS) and chalcocite (Cu{sub 2}S) was examined as a function of pH at 25{degrees}C in a series of batch experiments. Calculated distribution ratios (K{sub d}) far exceed those reported for other minerals; maximal K{sub d}`s of 1375 cc/g (Cu{sub 2}S) and 3080 c/g (HgS) were observed between pH 4-5, but wre substantial at all pH`s measured (4 < pH < 10). Iodide sorption apparently occurs by the formation of an insoluble surface solid solution with exposed Hg and Cu sites. Surface solid solution formation is favored at low pH due to the lessened electrostatic repulsion of the iodide ion by the sulfide surfaces.

  8. Sensing behavior and logic operation of a colorimetric fluorescence sensor for Hg(2+)/Cu(2+) ions.

    Science.gov (United States)

    He, Tian; Lin, Cuiling; Gu, Zhengye; Xu, Luonan; Yang, Anle; Liu, Yuanyuan; Fang, Huajun; Qiu, Huayu; Zhang, Jing; Yin, Shouchun

    2016-10-01

    A BODIPY-based 1 as a colorimetric fluorescence sensor was synthesized, and its metal sensing property was investigated. 1 displayed high selectivity and sensitivity towards Hg(2+) and Cu(2+) ions among 15 different metal cations. The addition of Hg(2+) and Cu(2+) ions into 1 in CH3CN resulted in a significant bathochromic shift of the UV absorption spectra from 533nm to 560nm and 593nm, respectively, changing the corresponding colors from pink to purple and blue. When excited at 530nm, the fluorescence intensity of 1 was quenched over 75% upon addition of Hg(2+) ions, while 1 with Cu(2+) ions exhibited significant fluorescence enhancement with a 23nm red-shift. Based on these results, three logic gates (OR, IMPLICATION, and INHIBIT) were obtained by controlling the chemical inputs. PMID:27239948

  9. Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

    Science.gov (United States)

    Yakunin, M. V.; Suslov, A. V.; Popov, M. R.; Novik, E. G.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-02-01

    We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage Vg. This large overlap manifests itself in a much higher critical field Bc separating the range above it with a plain behavior of the Hall magnetoresistance ρx y(B ) , where the quantum peculiarities shift linearly with Vg, and the range below with a complicated behavior. In the latter case, specific structures in ρx y(B ) are formed like a double-N -shaped ρx y(B ) , reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative Vg as revealed (i) from fits to the low-field N -shaped ρx y(B ) , (ii) from the Fourier analysis of oscillations in ρx x(B ) , and (iii) from a specific behavior of ρx y(B ) at high positive Vg. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated Vg while the hole density p drops down from the value a factor of 6 larger than n at extreme negative Vg to almost zero at extreme positive Vg passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an

  10. Colloidal CdTe/HgTe quantum dots with high photoluminescence quantum efficiency at room temperature

    Science.gov (United States)

    Kershaw, Stephen V.; Burt, Mike; Harrison, Mike; Rogach, Andrey; Weller, Horst; Eychmüller, Alex

    1999-09-01

    We have used an aqueous colloidal growth technique to form hybrid CdTe/HgTe quantum dots with a broad, strong fluorescence in the infrared (800-1200 nm). The quantum efficiency is high, around 44%, when pumped in the visible (488 nm), and the excited state lifetime is around 130 ns, making the material interesting as an optical amplifier medium. Using a pump-probe experiment, we have demonstrated weak optical amplification in a dilute aqueous suspension of CdTe/HgTe dots in the short wavelength wing of the emission spectrum at 808 nm.

  11. Bioavailability of Cd, Zn and Hg in Soil to Nine Recombinant Luminescent Metal Sensor Bacteria

    OpenAIRE

    Olesja Bondarenko; Taisia Rõlova; Anne Kahru; Angela Ivask

    2008-01-01

    A set of nine recombinant heavy metal-specific luminescent bacterial sensors belonging to Gram-negative (Escherichia and Pseudomonas) and Gram-positive (Staphylococcus and Bacillus) genera and containing various types of recombinant metalresponse genetic elements was characterized for heavy metal bioavailability studies. All nine strains were induced by Hg and Cd and five strains also by Zn. As a lowest limit, the sensors were detecting 0.03 μg·L-1 of Hg, 2 μg·L-1 of Cd and 400 Î...

  12. Implantation effects on resonant Raman scattering in CdTe and Cd 0.23Hg 0.77Te

    Science.gov (United States)

    Ramsteiner, M.; Lusson, A.; Wagner, J.; Koidl, P.; Bruder, M.

    1990-04-01

    We have studied In + implanted CdTe and Cd 0.23Hg 0.77Te by resonant Raman scattering. The laser excitation was in resonance with the EO + Δ O band gap in CdTe or the E1 gap in Cd 0.23Hg 0.77Te. Under these conditions dipole forbidden but defect ind scattering by one longitudinal optical (LO) phonon as well as Fröhlich-induced two-LO phonon scattering is observed. In both cases scattering is found to be strongly affected by ion implantation. In + was implanted at an ion energy of 350 keV with doses ranging from 10 11 to 5×10 14 ions/cm 2. The intensity ratio of the one-LO phonon lines is found to be a quantitative measure of the implantation damage in CdTe and Cd 0.23Hg 0.77Te even for doses as low as 10 11 ions/cm 2. It is shown that the observed effects of implantation damage on resonant Raman scattering by LO phonons are due to a broadening and an energy shift of the corresponding resonances in the Raman scattering efficiency.

  13. (112)面CdTe/Cd1-yZnyTe,Hg1-xCdxTe/CdTe和CdTe/GaAs异质结的方向倾斜%Oriental Shift at CdTe/Cd1-yZnyTe, Hg1-xCdxTe/CdTe and CdTe/GaAs Heterojunctions Grown on (112) plane

    Institute of Scientific and Technical Information of China (English)

    刘义族; 于福聚

    2001-01-01

    用X射线双晶衍射(XDCD)法测得分子束外延(MBE)法生长的CdTe/Cd0.959Zn0.041Te(112)B异质结的倾斜角为0.2185°,而且朝[1-1-1]晶体学方向倾斜.为了获得较精确的倾斜角值,绘制了外延层和衬底衍射角的差值Δθ与绕样品表面法线旋转的角度φ之间的准正弦函数.为高分辨率透射电子显微镜(HRTEM)分析制备了MBE法生长的Hg0.535Cd0.465Te/CdTe/GaAs(1-12)B多层异质结的横截面薄膜. CdTe/GaAs异质结的HRTEM明场象表明CdTe(1-12)缓冲层相对于GaAs(1-12)衬底朝[1-1 1-]方向倾斜约3°,并且在Hg0.535Cd0.465Te/CdTe异质结,Hg0.535Cd0.465Te(1-12)外延膜相对于CdTe(1-12)缓冲层在[1 1-1]方向,即[1-1 1-]的反方向倾斜约1°.也分析了Hg0.535Cd0.465Te/CdTe/GaAs多层膜之间的倾斜角关系.

  14. Ohmic contacts on n-type Hg0.4Cd0.6Te

    International Nuclear Information System (INIS)

    In this paper the electrical characteristics of In, Sn, Au and Pt contacts on n-type Hg0.4Cd0.6Te formed in the presence and absence of prior In2+ implantation are examined. Measurements of specific contact resistance made using a Transmission Line Model have shown that the unimplanted In/Hg0.4Cd0.6Te and Sn/Hg0.4Te junctions gave values of ρc = 3.0 x 10-3 ohm.cm2. Auger sputter profiles of the as-deposited In/Hg0.4Cd0.6Te and Sn/Hg0.4Cd0.6Te interfaces have shown a significant in-diffusion of the metal overlayer. The influence of shallow In2+ implantation prior to metallization was an increase in ρc which occurred above a dose of 1013 ions/cm2. In contrast, Pt and Au formed Schottky barrier diodes on n-type Hg0.4Cd0.6Te with φb = 0.69 eV for Pt and φb = 0.79 eV for Au. With prior In2+ implantation both Pt and Au contacts exhibited an ohmic behavior with ρc = 2 x 10-1 ohm.cm2. These results have significance in the fabrication of devices for 1.0 - 2.5μm optical communications

  15. Bioavailability of Cd, Zn and Hg in Soil to Nine Recombinant Luminescent Metal Sensor Bacteria

    Directory of Open Access Journals (Sweden)

    Olesja Bondarenko

    2008-11-01

    Full Text Available A set of nine recombinant heavy metal-specific luminescent bacterial sensors belonging to Gram-negative (Escherichia and Pseudomonas and Gram-positive (Staphylococcus and Bacillus genera and containing various types of recombinant metalresponse genetic elements was characterized for heavy metal bioavailability studies. All nine strains were induced by Hg and Cd and five strains also by Zn. As a lowest limit, the sensors were detecting 0.03 μg·L-1 of Hg, 2 μg·L-1 of Cd and 400 μg·L-1 of Zn. Limit of determination of the sensors depended mostly on metal-response element, whereas the toxicity of those metals towards the sensor bacteria was mostly dependent on the type of the host bacterium, with Gram-positive strains being more sensitive than Gram-negative ones. The set of sensors was used to evaluate bioavailability of Hg, Cd and Zn in spiked soils. The bioavailable fraction of Cd and Zn in soil suspension assay (2.6 – 5.1% and 0.32 – 0.61%, of the total Cd and Zn, respectively was almost comparable for all the sensors, whereas the bioavailability of Hg was about 10-fold higher for Gram-negative sensor cells (30.5% of total Hg, compared to Gram-positive ones (3.2% of the total Hg. For Zn, the bioavailable fraction in soil-water suspensions and respective extracts was comparable (0.37 versus 0.33% of the total Zn. However, in the case of Cd, for all the sensors used and for Hg concerning only Gram-negative sensor strains, the bioavailable fraction in soilwater suspensions exceeded the water-extracted fraction about 14-fold, indicating that upon direct contact, an additional fraction of Cd and Hg was mobilized by those sensor bacteria. Thus, for robust bioavailability studies of heavy metals in soils any type of genetic metal-response elements could be used for the construction of the sensor strains. However, Gram-positive and Gram-negative senor strains should be used in

  16. Improved HgCdTe technology for high-performance infrared detectors

    Science.gov (United States)

    Ziegler, Johann; Bruder, Martin; Cabanski, Wolfgang A.; Figgemeier, Heinrich; Finck, Marcus; Menger, Peter; Simon, Thomas; Wollrab, Richard

    2002-08-01

    To meet the demands for high performance HgCdTe detectors at high yield and producibility, key processes have been optimized and new approaches have been developed. By a superior CdZnTe Bridgman growth process, dislocation densities crosstalk and improves Modulation Transfer Function. For high thermal cycles of the FPA, the flip-chip- technique has been optimized, leading to >2000 cycles for 640x512-FPA's. Producibility and reliability of AIM's MCT FPA technology are demonstrated.

  17. Photovoltaic properties of sintered CdS/CdTe solar cells doped with Cu

    International Nuclear Information System (INIS)

    In this paper, all polycrystalline CdS/CdTe solar cells doped with Cu are prepared by a screen printing and sintering method. Cell parameters of the sintered CdS/CdTe solar cells have been investigated in an attempt to find out the optimum doping conditions and concentrations of Cu by adding various amounts of CuCl2 either into CdTe layer or into back contact carbon layer. Cell parameters of the sintered CdS/CdTe solar cells which contained various amounts of CuCl2 in the CdTe layers before sintering stay at about the same values as the amount of CuCl2 increases up to 25 ppm, and then decreases sharply as the amount of CuCl2 further increases. The Cu added in the CdTe layer diffuses into the CdS layer during the sintering of the CdS-CdTe composite at 625 degrees C to densify the CdTe layer and causes the decrease in the optical transmission of CdS resulting in the degradation of the cell performance. In case the Cu dopant was dispersed in the back carbon paint and was followed by annealing, all cell parameters are improved significantly compared with those fabricated by adding CuCl2 in the CdTe layer before sintering. A sintered CdS/CdTe solar cell which contained 25 ppm CuCl2 in the carbon paste and was annealed at 350 degrees C for 10 min shows the highest efficiency. The efficiency of this cell is 12.4% under solar irradiation with an intensity of 80.4 mW/cm2

  18. Photoluminescence of Cu-doped CdTe and related stability issues in CdS/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Grecu, D. [University of Toledo, Toledo, Ohio 43606-3390 (United States); Compaan, A. D. [University of Toledo, Toledo, Ohio 43606-3390 (United States); Young, D. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Jayamaha, U. [First Solar LLC., Perrysburg, Ohio 43551 (United States); Rose, D. H. [First Solar LLC., Perrysburg, Ohio 43551 (United States)

    2000-09-01

    We explore Cu electronic states in CdTe using photoluminescence as the main investigative method. Our results are consistent with some Cu atoms occupying substitutional positions on the Cd sublattice and with others forming Frenkel pairs of the type Cu{sub i}{sup +}-V{sub Cd}{sup -} involving an interstitial Cu and a Cd vacancy. In addition, we find that Cu-doped CdTe samples exhibit a significant ''aging'' behavior, attributable to the instability of Cu acceptor states as verified by our Hall measurements. The aging appears to be reversible by a 150-200 degree sign C anneal. Our results are used to explain efficiency degradation of some CdTe solar-cell devices which use Cu for the formation of a backcontact. (c) 2000 American Institute of Physics.

  19. Arsenic complexes optical signatures in As-doped HgCdTe

    International Nuclear Information System (INIS)

    In this paper, the optical signatures of arsenic complexes in As-doped HgCdTe samples grown by molecular beam epitaxy are clearly identified using comparison between photoluminescence spectra, Extended X-Ray Absorption Fine Structure, and Hall measurements. The ionization energies of the different complexes are measured both by photoluminescence and Hall measurements.

  20. Relativistic K shell decay rates and fluorescence yields for Zn, Cd and Hg

    OpenAIRE

    C. Casteleiro; Parente, F.; Indelicato, Paul; P. Marques, J.

    2009-01-01

    In this work we use the multiconfiguration Dirac-Fock method to calculate the transition probabilities for all possible decay channels, radiative and radiationless, of a K shell vacancy in Zn, Cd and Hg atoms. The obtained transition probabilities are then used to calculate the corresponding fluorescence yields which are compared to existing theoretical, semi-empirical and experimental results.

  1. Surface tension of Hg-M (M - Cd, In, Sn, Tl, Pb, Bi) system amalgams

    International Nuclear Information System (INIS)

    Temperature and concentration dependences of surface tension of liquid amalgams of Hg-M binary systems (M - Cd, In, Sn, Tl, Pb, Bi) were studied. The revealed correlation of surface tension and electric conductivity of amalgams was explained by peculiarities of mercury energy spectrum, changes of density on Fermi level, adsorption processes and changes of surface layer thickness. 19 refs.; 8 figs.; 4 tabs

  2. Removal of Cd (II and Hg(II by chelating resin Chelex-100

    Directory of Open Access Journals (Sweden)

    Afaf Amara-Rekkab

    2015-03-01

    Full Text Available A sensitive, simple method for the determination of amounts of mixture of Hg2+and Cd2+ by spectrophotometry was described based on the formation of the Hg2+- Cd2+- PAN complex in water media. Optimal conditions such as reagent amounts, and pH for the Hg2+- Cd2+ determination were reported. It was found that the 2:1 PAN- Hg2+- Cd2+ complex dominate at pH 13.0. In another hand, the sorption of mixture mercury (II and cadmium (II from aqueous medium on a chelating resin Chelex 100 was studied in batch mode. Since the extraction kinetic was obtained, with a mixture of 0.1 g of resin and 5 mL of mixture at 1 mmol/L of initial concentration, extraction equilibrium was reached within 20 min of mixing. The influence of some parameters such as initial mixture ions concentrations, initial pH of aqueous solution, ion strength and the amounts of resin have been studied at fixed temperature (20±1°C. The optimum pH value level for quantitative sorption was up to 2.6. The best performance obtained was 97.1% of extraction yield equivalent to 15.65 mg/g of resin. The pseudo-first- order, pseudo-second-order models and the intra-particle diffusion model were used to describe the kinetic data and rate constants were evaluated.

  3. MBE based HgCdTe APDs and 3D LADAR sensors

    Science.gov (United States)

    Jack, Michael; Asbrock, Jim; Bailey, Steven; Baley, Diane; Chapman, George; Crawford, Gina; Drafahl, Betsy; Herrin, Eileen; Kvaas, Robert; McKeag, William; Randall, Valerie; De Lyon, Terry; Hunter, Andy; Jensen, John; Roberts, Tom; Trotta, Patrick; Cook, T. Dean

    2007-04-01

    Raytheon is developing HgCdTe APD arrays and sensor chip assemblies (SCAs) for scanning and staring LADAR systems. The nonlinear characteristics of APDs operating in moderate gain mode place severe requirements on layer thickness and doping uniformity as well as defect density. MBE based HgCdTe APD arrays, engineered for high performance, meet the stringent requirements of low defects, excellent uniformity and reproducibility. In situ controls for alloy composition and substrate temperature have been implemented at HRL, LLC and Raytheon Vision Systems and enable consistent run to run results. The novel epitaxial designed using separate absorption-multiplication (SAM) architectures enables the realization of the unique advantages of HgCdTe including: tunable wavelength, low-noise, high-fill factor, low-crosstalk, and ambient operation. Focal planes built by integrating MBE detectors arrays processed in a 2 x 128 format have been integrated with 2 x 128 scanning ROIC designed. The ROIC reports both range and intensity and can detect multiple laser returns with each pixel autonomously reporting the return. FPAs show exceptionally good bias uniformity China Lake. Excellent spatial and range resolution has been achieved with 3D imagery demonstrated both at short range and long range. Ongoing development under an Air Force Sponsored MANTECH program of high performance HgCdTe MBE APDs grown on large silicon wafers promise significant FPA cost reduction both by increasing the number of arrays on a given wafer and enabling automated processing.

  4. Arsenic complexes optical signatures in As-doped HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Gemain, F.; Robin, I. C.; Brochen, S.; Ballet, P.; Gravrand, O.; Feuillet, G. [CEA-LETI Minatec Campus, 17 rue des Martyrs, 38000 Grenoble (France)

    2013-04-08

    In this paper, the optical signatures of arsenic complexes in As-doped HgCdTe samples grown by molecular beam epitaxy are clearly identified using comparison between photoluminescence spectra, Extended X-Ray Absorption Fine Structure, and Hall measurements. The ionization energies of the different complexes are measured both by photoluminescence and Hall measurements.

  5. Lateral Diffusion Length Changes in HgCdTe Detectors in a Proton Environment

    Science.gov (United States)

    Hubbs, John E.; Marshall, Paul W.; Marshall, Cheryl J.; Gramer, Mark E.; Maestas, Diana; Garcia, John P.; Dole, Gary A.; Anderson, Amber A.

    2007-01-01

    This paper presents a study of the performance degradation in a proton environment of very long wavelength infrared (VLWIR) HgCdTe detectors. The energy dependence of the Non-Ionizing Energy Loss (NIEL) in HgCdTe provides a framework for estimating the responsivity degradation in VLWIR HgCdTe due to on orbit exposure from protons. Banded detector arrays that have different detector designs were irradiated at proton energies of 7, 12, and 63 MeV. These banded detector arrays allovedin sight into how the fundamental detector parameters degraded in a proton environment at the three different proton energies. Measured data demonstrated that the detector responsivity degradation at 7 MeV is 5 times larger than the degradation at 63 MeV. The comparison of the responsivity degradation at the different proton energies suggests that the atomic Columbic interaction of the protons with the HgCdTe detector is likely the primary mechanism responsible for the degradation in responsivity at proton energies below 30 MeV.

  6. Novel bimetallic thiocyanate-bridged Cu(II)-Hg(II) compounds—synthesis, X-Ray studies and magnetic properties

    Science.gov (United States)

    Machura, B.; Świtlicka, A.; Zwoliński, P.; Mroziński, J.; Kalińska, B.; Kruszynski, R.

    2013-01-01

    Seven novel heterobimetallic Cu/Hg polymers based on thiocyanate bridges have been synthesised and characterised by means of IR, EPR, magnetic measurements and single crystal X-Ray. Three of them, [Cu(pzH)4Hg(SCN)4]n (1) [Cu(indH)4Hg(SCN)4]n (2) and [Cu(ampy)2Hg(SCN)4]n (3), have one-dimensional coordination structure. Two compounds [Cu(pzH)2Hg(SCN)4]n (4) and [Cu(abzimH)Hg(SCN)4]n (5) form two-dimensional nets, whereas the complexes [Cu(pyCN)2Hg(SCN)4]n (6) and [Cu(pyCH(OH)(OMe))2Hg(SCN)4]n (7) are three-dimensional coordination polymers. The chains of 1 are connected by the intermolecular N-H•••N hydrogen bonds to the three dimensional net. In 2 the N-H•••S hydrogen bonds link the polymeric chains to the two dimensional layer extending along crystallographic (0 0 1) plane. The polymeric chains of compound 3 are joined by the intermolecular N-H•••N and N-H•••S hydrogen bonds to the three dimensional net. The polymeric layers of 4 are connected by the intermolecular N-H•••N hydrogen bonds to the three dimensional net.

  7. Studies on photoinduced effects in pulse-electrodeposited Ag/Hg-1212/CdSe hetero-nanostructures

    Indian Academy of Sciences (India)

    D D Shivagan; P M Shirage; S H Pawar

    2002-05-01

    Metal/superconductor/semiconductor (Ag/Hg-1212/CdSe) hetero-nanostructures have been fabricated using pulse-electrodeposition technique and are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The junction capacitance of Ag/Hg-1212, Hg-1212/CdSe and Ag/Hg-1212/CdSe heterojunctions is measured in dark and under laser irradiation at room temperature. The nature of the junction formed and built-in-junction potentials were determined. The increase in carrier concentration across the junction due to photo-irradiation has been observed.

  8. Development of megapixel HgCdTe detector arrays with 15 micron cutoff

    Science.gov (United States)

    Forrest, William J.; McMurtry, Craig W.; Dorn, Meghan L.; Pipher, Judith; Cabrera, Mario S.

    2016-06-01

    I. HistoryHgCdTe is a versatile II-VI semiconductor with a direct-bandgap tunable via the Hg:Cd ratio. Hg:Cd ratio = 53:47 (2.5 micron cutoff) was used on the NICMOS instrument on HST and the 2MASS. Increasing Hg:Cd ratio to 70:30 leads to a 5.4 micron cutoff, utilized in NEOWISE and many JWST instruments. Bailey, Wu et al. (1998) motivated extending this technology to 10 microns and beyond. Bacon, McMurtry et al. (2003, 2004) indicated significant progress toward this longwave (LW) goal.Warm-Spitzer has pioneered passive cooling to below 30 K in space, enabling the JWST mission.II. CurrentNASA's proposed NEOcam mission selected HgCdTe with a 10.6 micron cutoff because it promises natural Zodiacal background limited sensitivity with modest cooling (40 K). Teledyne Imaging Systems (TIS) is producing megapixel arrays with excellent performance (McMurtry, Lee, Dorn et al. (2013)) for this mission.III. FutureModest cooling requirements (circa 30 K) coupled with megapixel arrays and LW sensitivity in the thermal IR make HgCdTe attractive for many infrared instruments. For instance, the spectral signature of a terrestrial planet orbiting in the habitable zone of a nearby star will be the deep and wide absorption by CO_2 centered at 15 microns (Seager and Deming, 2010). LW instruments can enhance Solar System missions, such as exploration of the Enceladus geysers (Spencer, Buratti et al. 2006). Passive cooling will be adequate for these missions. Modern ground-based observatories will benefit from infrared capability out to the N band (7.5-13.6 microns). The required detector temperatures (30-40 K) are easily achievable using commercially available mechanical cryo-coolers (refrigerators).IV. Progress to dateTIS is developing megapixel HgCdTe arrays sensitive out to 15 microns under the direction of the University of Rochester. As a first step, we have produced arrays with a 13 micron cutoff. The initial measurements indicate very promising performance. We will present the

  9. InGaAs versus HgCdTe for short-wavelength infrared applications

    Science.gov (United States)

    Rogalski, Antoni; Ciupa, Robert

    1999-04-01

    The carrier lifetimes in In(subscript x)Ga(subscript 1-x)As (InGaAs) and Hg(subscript 1-x)Cd(subscript x)Te (HgCdTe) ternary alloys for radiative and Auger recombination are calculated for temperature 300 K in the short wavelength range 1.5 less than (lambda) less than 3.7 micrometer. Due to photon recycling, an order of magnitude enhancements in the radiative lifetimes over those obtained from the standard van Roosbroeck and Shockley expression, has been assumed. This theoretical prediction has been confirmed by good agreement with experimental data for n-type In(subscript 0.53)Ga(subscript 0.47)As. The possible Auger recombination mechanisms (CHCC, CHLH and CHSH processes) in direct-gap semiconductors are investigated. In both n-type ternary alloys, the carrier lifetimes are similar, and competition between radiative and CHCC processes take place. In p-type materials the carrier lifetime are also comparable, however the most effective channels of Auger mechanisms are: CHSH process in InGaAs, and CHLH process in HgCdTe. Next, the performance of heterostructure p-on-n photovoltaic devices are considered. Theoretically predicted R(subscript o)A values are compared with experimental data reported by other authors. In(subscript 0.53)Ga(subscript 0.47)As photodiodes have shown the device performance within a factor of 10 of theoretical limit. However, the performance of InGaAs photodiodes decreases rapidly at intermediate wavelengths due to mismatch-induced defects. HgCdTe photodiodes maintain high performance close to ultimate limit over a wider range of wavelengths. In this context technology of HgCdTe is considerably advanced since the same lattice parameter of this alloy over wide composition range.

  10. Surface Oxidative Characterization of LPE HgCdTe Epilayer Studied by X-ray Photoelectron Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    李毅; 易新建; 蔡丽萍

    2000-01-01

    The surface oxidative characterization of Liquid Phase Epitaxy (LPE) HgCdTe epilayer has been studied by X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). HgCdTe surface is exposed by various processing steps. After measurement and analysis, we draw a conclusion that the native oxide film can be reduced and removed by the solution of lactic acid in ethylene glycol after being etched by bromine in absolute ethyl alcohol. The result shows the main optical and electrical parameters have not been changed after the treatment and the processing method given here can successfully remove the native oxides of LPE HgCdTe epilayer to obtain a clean surface. It indicates that the pre-treatment before HgCdTe surface passivation can affect the passivant/HgCdTe interface properties.

  11. Investigation of Substrate Effects on Interface Strain and Defect Generation in MBE-Grown HgCdTe

    Science.gov (United States)

    Gu, R.; Lei, W.; Antoszewski, J.; Faraone, L.

    2016-05-01

    Si, Ge, and GaAs have been extensively investigated as alternative substrates for molecular-beam epitaxy (MBE) growth of HgCdTe and, at present, are widely used for HgCdTe-based infrared focal-plane arrays. However, the problem of high dislocation density in HgCdTe layers grown on these lattice-mismatched substrates has yet to be resolved. In this work, we investigated another alternative substrate, GaSb, which has a significantly smaller lattice mismatch with HgCdTe in comparison with Si, Ge, and GaAs, and is readily available as large-area, epiready wafers at much lower cost in comparison with lattice-matched CdZnTe substrates. The resultant stress due to lattice and thermal mismatch between the HgCdTe epilayer and various substrates has been calculated in this work using the elasticity matrix, and the corresponding stress distribution simulated using ANSYS. The simulated structures were matched by experimental samples involving MBE growth of HgCdTe on GaAs, GaSb, and CdZnTe substrates, and were characterized via reflection high-energy electron diffraction and x-ray diffraction analysis, followed by etch pit density (EPD) analysis. In comparison with other alternative substrates, GaSb is shown to have lower interface stress and lower EPD, rendering it an interesting and promising alternative substrate material for HgCdTe epitaxy.

  12. Biomonitoring potential of five sympatric Tillandsia species for evaluating urban metal pollution (Cd, Hg and Pb)

    Science.gov (United States)

    Sánchez-Chardi, Alejandro

    2016-04-01

    The present study quantifies non essential heavy metals highly toxic for biological systems (Pb, Hg and Cd) in five autochthonous epiphytic plants from Tillandsia genus (T. recurvata, T. meridionalis, T. duratii, T. tricholepis, T. loliacea) according to different traffic levels (reference, low, medium and high polluted sites) in Asunción (Paraguay). The three metals increased in polluted sites following Pb (till 62.99 ppm in T. tricholepis) > Cd (till 1.35 ppm in T. recurvata) > Hg (till 0.36 ppm in T. recurvata) and Pb and Cd levels were directly related to traffic flow. Although the species showed similar bioaccumulation pattern (namely, higher levels of metals in polluted sites), enrichment factors (maximum EF values 37.00, 18.16, and 11.90 for Pb, Hg, and Cd, respectively) reported T. tricholepis as the most relevant bioindicator due to its wide distribution and abundance in study sites, low metal content in control site and high metal contents in polluted sites, and significant correlations with traffic density of Pb and Cd. This study emphasizes the necessity of biomonitoring air pollution in areas out of air monitoring control such as Asunción, where the high levels of metal pollution especially Pb, may represent an increment of risk for the human population inhabiting this urban area.

  13. Cu Migration in Polycrystalline CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Da [Arizona State University; Akis, Richard [Arizona State University; Brinkman, Daniel [Arizona State University; Sankin, Igor [First Solar; Fang, Tian [First Solar; Vasileska, Dragica [Arizona State University; Ringhofer, Christian [Arizona State University

    2014-03-12

    An impurity reaction-diffusion model is applied to Cu defects and related intrinsic defects in polycrystalline CdTe for a better understanding of Cu’s role in the cell level reliability of CdTe PV devices. The simulation yields transient Cu distributions in polycrystalline CdTe during solar cell processing and stressing. Preliminary results for Cu migration using available diffusivity and solubility data show that Cu accumulates near the back contact, a phenomena that is commonly observed in devices after back-contact processing or stress conditions.

  14. Electron transport and cyclotron resonance in (211)-oriented HgTe--CdTe superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, C.A.; Meyer, J.R.; Wagner, R.J.; Bartoli, F.J. (Naval Research Laboratory, Washington, D. C. 20375 (USA)); Chu, X.; Faurie, J.P. (University of Illinois at Chicago, Chicago, Illinois 60680 (USA)); Ram-Mohan, L.R.; Xie, H. (Worcester Polytechnic Institute, Worcester, Massachusetts 01609 (USA))

    1990-03-01

    We discuss a magnetotransport and magneto-optical investigation of (211)-oriented HgTe--CdTe superlattices. Measurements were performed on seven {ital n}-type samples with well widths in the range 41--125 A and energy gaps between 0 and 128 meV. Both magnetotransport and magneto-optical results give evidence for an additional electron species besides the superlattice electrons and holes usually observed. We show that although these have quasi-two-dimensional character, their mobilities are quite sensitive to the superlattice well thickness. These findings are interpreted in terms of band bending and charge transfer from the CdTe substrate into the superlattice. We also discuss the first theoretical calculations of the band structure for (211)-oriented HgTe--CdTe heterostructures.

  15. Establishment of strongly overdoped states in the HgBa2Ca2Cu3O8+[delta] superconductor

    OpenAIRE

    Fujinami, K.; Ito, T.; Suematsu, H.; Matsuura, K.; Karppinen, Maarit; Yamauchi, H.

    1997-01-01

    Strongly overdoped HgBa2Ca2Cu3O8+δ (Hg-1223) samples with superconducting transitions as low as 97 K were successfully obtained by using HgO, Ca2CuO3, CuO, and mixtures of highly oxidized BaCuO2+ε (ε≈0.13) and/or BaO2 powders as starting materials for the high-pressure synthesis at 5 GPa and 950 °C. The overdoped state was confirmed by observing negative values for the Seebeck coefficient throughout the temperature range from Tc to 320 K in a thermoelectric power measurement. Also, both of th...

  16. Microscopic studies of radioactive Hg implanted in YBa2Cu3O6+x superconducting thin films

    International Nuclear Information System (INIS)

    YBa2Cu3O6+x (YBCO) superconducting thin films implanted with low doses of radioactive 197mHg and 199mHg isotopes were studied with a combination of nuclear and non-nuclear characterization techniques. We show that after implantation Hg lies on a unique site in the YBCO lattice and the critical temperature increases slightly with the increase of the 197Au concentration from the nuclear transmutation of 197Hg. (orig.)

  17. Low temperature interdiffusion in the HgCdTe/CdTe system, studied at near-atomic resolution

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Y.; Ourmazd, A.; Feldman, R.D. (AT T Bell Laboratories, Holmdel, New Jersey 07733 (US))

    1990-03-01

    By combining chemical lattice imaging and vector pattern recognition we determine, as a function of annealing temperature, the composition of individual atomic planes across each HgCdTe/CdTe interface of a multiquantum well stack. The resultant composition profiles, which directly reveal the chemical change across each interface at near atomic resolution, are analyzed in terms of linear and nonlinear diffusion theory, to deduce the interdiffusion coefficient and its activation energy. We find the interdiffusion coefficient to be nonlinear, and a sensitive function of the interface depth beneath the surface.

  18. Proton irradiation results for long-wave HgCdTe infrared detector arrays for NEOCam

    CERN Document Server

    Dorn, M; McMurtry, C; Hartman, S; Mainzer, A; McKelvey, M; McMurray, R; Chevara, D; Rosser, J

    2016-01-01

    HgCdTe detector arrays with a cutoff wavelength of ~10 ${\\mu}$m intended for the NEOCam space mission were subjected to proton beam irradiation at the University of California Davis Crocker Nuclear Laboratory. Three arrays were tested - one with 800 $\\mu$m substrate intact, one with 30 $\\mu$m substrate, and one completely substrate-removed. The CdZnTe substrate, on which the HgCdTe detector is grown, has been shown to produce luminescence in shorter wave HgCdTe arrays that causes elevated signal in non-hit pixels when subjected to proton irradiation. This testing was conducted to ascertain whether or not full substrate removal is necessary. At the dark level of the dewar, we detect no luminescence in non-hit pixels during proton testing for both the substrate-removed detector array and the array with 30 ${\\mu}$m substrate. The detector array with full 800 ${\\mu}$m substrate exhibited substantial photocurrent for a flux of 103 protons/cm$^2$-s at a beam energy of 18.1 MeV (~ 750 e$^-$/s) and 34.4 MeV ($\\sim$ 6...

  19. New roles for icosahedral clusters in intermetallic phases: micelle-like segregation of Ca-Cd and Cu-Cd interactions in Ca10Cd27Cu2.

    Science.gov (United States)

    Hadler, Amelia B; Harris, Nicholas A; Fredrickson, Daniel C

    2013-11-20

    Despite significant progress in the structural characterization of the quasicrystalline state, the chemical origins of long- and short-range icosahedral order remain mysterious and a subject of debate. In this Article, we present the crystal structure of a new complex intermetallic phase, Ca10Cd27Cu2 (mC234.24), whose geometrical features offer clues to the driving forces underlying the icosahedral clusters that occur in Bergman-type quasicrystals. Ca10Cd27Cu2 adopts a C-centered monoclinic superstructure of the 1/1 Bergman approximant structure, in which [110] layers of Bergman clusters in the 1/1 structure are separated through the insertion of additional atoms (accompanied by substantial positional disorder). An examination of the coordination environments of Ca and Cu (in the ordered regions) reveals that the structure can be viewed as a combination of coordination polyhedra present in the nearest binary phases in the Ca-Cd-Cu compositional space. A notable feature is the separation of Ca-Cd and Cu-Cd interactions, with Bergman clusters emerging as Ca-Cd Friauf polyhedra (derived from the MgZn2-type CaCd2 phase) encapsulate a Cu-Cd icosahedron similar to those appearing in Cu2Cd5. DFT chemical pressure calculations on nearby binary phases point to the importance of this segregation of Ca-Cd and Cu-Cd interactions. The mismatch in atomic size between Cu and Cd leads to an inability to satisfy Ca-Cu and Ca-Cd interactions simultaneously in the Friauf polyhedra of the nearby Laves phase CaCd2. The relegation of the Cu atoms to icosahedra prevents this frustration while nucleating the formation of Bergman clusters. PMID:24147875

  20. Study of alloy disorder in (Hg,Cd)Te with the use of infrared photoluminescence

    International Nuclear Information System (INIS)

    Infrared photoluminescence (PL) measurements were used to probe compositional disorder in semiconductor (Hg,Cd)Te alloy. PL was studied in Hg1-xCdxTe samples with x=0.38 and 0.57, fabricated by molecular beam epitaxy on GaAs substrates. Both as-grown and annealed in Hg vapor and in He atmosphere samples were studied. In all the samples, the PL peak energy was found to be red-shifted from the position of band-to-band recombination maximum expected from the energy gap of the material. The value of the shift depended on temperature. This effect was attributed to recombination of excitons localized at compositional fluctuations, and an analysis was carried out that provided a way for evaluation of a fluctuation measure. The amplitude of the fluctuations was shown to strongly decrease as a result of post-growth annealing.

  1. Investigation of magnetoabsorption at different temperatures in HgTe/CdHgTe quantum-well heterostructures in pulsed magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Platonov, V. V.; Kudasov, Yu. B.; Makarov, I. V.; Maslov, D. A.; Surdin, O. M. [Sarov Physical–Technical Institute—National Research Nuclear University MEPhI (Russian Federation); Zholudev, M. S.; Ikonnikov, A. V.; Gavrilenko, V. I. [Russian Academy of Sciences, Institute of Physics of Microstructures (Russian Federation); Mikhailov, N. N.; Dvoretsky, S. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2015-12-15

    The magnetoabsorption in magnetic fields as high as 40 T is investigated at T > 77 K in HgTe/CdHgTe quantum-well heterostructures (d{sub QW} ≈ 8 nm). The spectra reveal two lines associated both with intraband transition from the lower Landau level in the conduction band and with interband transition. It is shown that the band structure in these systems changes from inverted to normal with increasing temperature.

  2. Photoluminescence of Cu-doped CdTe and related stability issues in CdS/CdTe solar cells

    Science.gov (United States)

    Grecu, D.; Compaan, A. D.; Young, D.; Jayamaha, U.; Rose, D. H.

    2000-09-01

    We explore Cu electronic states in CdTe using photoluminescence as the main investigative method. Our results are consistent with some Cu atoms occupying substitutional positions on the Cd sublattice and with others forming Frenkel pairs of the type Cui+-VCd- involving an interstitial Cu and a Cd vacancy. In addition, we find that Cu-doped CdTe samples exhibit a significant "aging" behavior, attributable to the instability of Cu acceptor states as verified by our Hall measurements. The aging appears to be reversible by a 150-200 °C anneal. Our results are used to explain efficiency degradation of some CdTe solar-cell devices which use Cu for the formation of a backcontact.

  3. A Novel Method to Obtain Higher Deposition Rates of CdTe Using Low Temperature LPCVD for Surface Passivation of HgCdTe

    Science.gov (United States)

    Banerjee, Sneha; Dahal, Rajendra; Bhat, Ishwara B.

    2015-09-01

    The deposition rate of CdTe passivation films has been increased greatly by the implementation of a novel design of a graphite cracker cell. This cracker cell, consisting of an integrated diffuser, facilitates the efficient cracking of precursors. CdTe deposition rate has been increased from ~50 nm/h (without any cracker cell) to ~420 nm/h using this novel experimental set-up. H2 flow through the main gas flow line has been increased to obtain a progressive increase in deposition rates. CdTe deposited on high aspect ratio HgCdTe samples showed adequate conformal coverage on the side walls and also on the bottom of the trenches. Microwave photoconductive decay measurements were done on planar and patterned HgCdTe substrates at 77 K to extract the minority carrier lifetimes. There was a significant improvement in the lifetime of planar HgCdTe samples after CdTe passivation, though patterned HgCdTe samples showed a minor improvement. An additional annealing step was conducted at 250°C for 20 min in the presence of H2 after the deposition of CdTe passivation films. Minority carrier lifetimes improved further post-annealing, probably due to the formation of a graded interface between CdTe and HgCdTe.

  4. Convective influence on radial segregation during unidirectional solidification of the binary alloy HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Watring, D.A.; Gillies, D.C.; Lehoczky, S.L.; Szofran, F.R. [Marshall Space Flight Center, Huntsville, AL (United States). Space Sciences Lab.; Alexander, H. [Universities Space Research Association, Huntsville, AL (United States)

    1996-12-31

    In order to simulate the space environment for basic research into the crystal growth mechanism, Hg{sub 0.8}Cd{sub 0.2}Te crystals were grown by the vertical Bridgman-Stockbarger method in the presence of an applied axial magnetic field. The influence of convection, by magneto hydrodynamic damping, on mass transfer in the melt and segregation at the solid-liquid interface was investigated by measuring the axial and radial compositional variations in the grown samples. The reduction of convective mixing in the melt through the application of the magnetic field is found to have a large effect on radial segregation and interface morphology in the grown crystals. Direct comparisons are made with a Hg{sub 0.8}Cd{sub 0.2}Te crystal grown without field and also in the microgravity environment of space during the second United States Microgravity Payload Mission (USMP-2).

  5. Extending the operating temperature, wavelength and frequency response of HgCdTe heterodyne detectors

    Science.gov (United States)

    Spears, D. L.

    1980-01-01

    Near ideal optical heterodyne performance was obtained at GHz IF frequencies in the 10 micrometer wavelength region with liquid nitrogen cooled HgCdTe photodiodes. Heterodyne NEP's as low as 2.7 x 10 to the minus 20th power W/Hz at 100MHz, 5.4 x 10 to the minus 20th power W/Hz at 1.5 GHz, and 9.4 x 19 to the minus 20th power W/Hz at 3 GHz were achieved. Various physical phenomena which occur within a photodiode and affect heterodyne operation were examined in order to assess the feasibility of extending the operating temperature, wavelength, and frequency response of these HgCdTe photomixers.

  6. The structural and electronic properties of amorphous HgCdTe from first-principles calculations

    International Nuclear Information System (INIS)

    Amorphous mercury cadmium telluride (a-MCT) model structures, with x being 0.125 and 0.25, are obtained from first-principles calculations. We generate initial structures by computation alchemy method. It is found that most atoms in the network of amorphous structures tend to be fourfold and form tetrahedral structures, implying that the chemical ordered continuous random network with some coordination defects is the ideal structure for a-MCT. The electronic structure is also concerned. The gap is found to be 0.30 and 0.26 eV for a-Hg0.875Cd0.125Te and a-Hg0.75Cd0.25Te model structures, independent of the composition. By comparing with the properties of crystalline MCT with the same composition, we observe a blue-shift of energy band gap. The localization of tail states and its atomic origin are also discussed. (paper)

  7. Electrical properties of n-HgCdTe heteroepitaxial layers modified by ion etching

    International Nuclear Information System (INIS)

    Electrical properties of MBE-grown n-HgCdTe layers, both undoped and In-doped during growth and modified by ion etching are studied. It is established that initially neutral defects with a concentration ∼1017 cm-3 are present in these structures. These defects are activated by ion etching and form donor centers. Comparison of the obtained experimental results with the published data shows that these defects are formed at the growth stage of the structures. After the ion etching is stopped, donor centers decompose and for ∼5 x 103 min, the electron concentration in the structures is stabilized. The obtained data allow one to determine the amount of indium necessary for the obtainment of reproducible electron concentration in n-type regions of HgCdTe-based LED structures formed by ion etching.

  8. Absolute linearity measurements on a PV HgCdTe detector in the infrared

    Science.gov (United States)

    Theocharous, Evangelos

    2012-04-01

    The linearity-of-response characteristics of a photovoltaic (PV) HgCdTe detector were investigated at a number of wavelengths in the infrared, using the NPL linearity of detector response characterization facility. The measurements were performed with the test detector operating under conditions identical to those in which the detectors will be used in typical infrared radiometric applications. The deviation from linearity in the generated photocurrent was shown to be strongly dependent on the area of the detector being illuminated. Plots of the linearity factor versus generated photocurrent for different illuminated wavelengths were shown to overlap. The linearity factor was shown to be a function of the photon irradiance of the illuminating beam. This behaviour was similar to that exhibited by photoconductive (PC) HgCdTe detectors, indicating that Auger recombination was the dominant source of the deviation from linearity observed in the test detector.

  9. The Liquid-Liquid Extraction of Toxic Metals (Cd, Hg and Pb by Calixarenes

    Directory of Open Access Journals (Sweden)

    D. Max Roundhill

    2009-12-01

    Full Text Available Toxic metals (Cd, Hg and Pb are mostly present in the environment due to natural phenomenon and human activities as well. Exposure of these non-essential elements in the environment causes severe effects. They are known to cause problems in humans as well as in aquatic life. In this work, we demonstrate various studies regarding liquid-liquid extraction of selected ions with different functionalized calixarenes. This review article briefly discusses several molecular designs of calixarenes for divalent ion (Cd2+, Hg2+ and Pb2+ recognition; as well as the relationship between structure and selectivity of the macrocycles is elaborated. The article does not, however, attempt to cover all of the different approaches to these toxic metal ions extraction.

  10. Thermal stability of atomic layer deposition Al2O3 film on HgCdTe

    Science.gov (United States)

    Zhang, P.; Sun, C. H.; Zhang, Y.; Chen, X.; He, K.; Chen, Y. Y.; Ye, Z. H.

    2015-06-01

    Thermal stability of Atomic Layer Deposition Al2O3 film on HgCdTe was investigated by Al2O3 film post-deposition annealing treatment and Metal-Insulator-Semiconductor device low-temperature baking treatment. The effectiveness of Al2O3 film was evaluated by measuring the minority carrier lifetime and capacitance versus voltage characteristics. After annealing treatment, the minority carrier lifetime of the HgCdTe sample presented a slight decrease. Furthermore, the fixed charge density and the slow charge density decreased significantly in the annealed MIS device. After baking treatment, the fixed charge density and the slow charge density of the unannealed and annealed MIS devices decreased and increased, respectively.

  11. Interface roughness limited electron mobility in HgTe-CdTe superlattices

    Science.gov (United States)

    Meyer, J. R.; Arnold, D. J.; Hoffman, C. A.; Bartoli, F. J.

    1991-06-01

    It is demonstrated that interface roughness is the dominant low-temperature scattering mechanism for electrons in HgTe-CdTe superlattices with thin wells. Not only do the experimental mobilities follow the expected d6(W) dependence, but the observed temperature dependence is accurately reproduced by theory when the treatment of interface roughness scattering is generalized for narrow-gap superlattices. The fits to data yield roughness correlation lengths in the range 60-200 A.

  12. Magnetic activation of bipolar plasmas in HgTe-CdTe superlattices

    Science.gov (United States)

    Meyer, J. R.; Hoffman, C. A.; Bartoli, F. J.; Wojtowicz, T.; Dobrowolska, M.; Furdyna, J. K.; Chu, X.; Faurie, J. P.; Ram-Mohan, L. R.

    1991-08-01

    It is shown theoretically that in semimetallic HgTe-CdTe superlattices, there is a critical magnetic field above which minority carriers with density proportional to B-Bcrit are expected to coexist with majority carriers in the zero-temperature limit. Experimental confirmation of the magnetically activated bipolar plasma is provided by low-temperature magneto-optical data showing the emergence of minority holes in an n-type superlattice whenever B>Bcrit.

  13. Electrical doping of Hg Cd Te by ion implantation and heat treatments

    International Nuclear Information System (INIS)

    The general properties of junctions made by ion implantation in Hg Cd Te semiconductor are recalled structure of junctions made by implantation damage, defects, anneals, junctions made by active impurities. The effect of acceptor evolution in this semiconductor after heat treatments and a study of the kinetics are presented. Very high quality devices with very small size and large two-dimensional arrays are shown to be possibly achieved using ion implantation technique of junction formation in the semiconductor epilayers grown by LPE

  14. Study to improve the low frequency noise characteristics of (Hg,Cd)Te detectors

    Science.gov (United States)

    Broudy, R. M.

    1973-01-01

    Efforts made to identify and reduce the sources of l/f noise in 15 micron n-type (Hg,Cd)Te detectors operating at 77 K are reported. The investigation covered: evaluation of the influence of material properties and detector processing techniques, determination of the relative importance of surfaces, volumes, regions, and contracts, and generation of theoretical models for guidance of the experimental work.

  15. Electron Raman scattering in a HgS/CdS spherical quantum dot quantum well

    International Nuclear Information System (INIS)

    Electron Raman scattering (ERS) is investigated in a spherical HgS/CdS quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes of QDQW. Single parabolic conduction and valence bands are assumed. The selection rules for the processes are studied. Singularities in the spectra are found and interpreted. The ERS studied here can be used to provide direct information about the electron band structure of these systems. (semiconductor physics)

  16. Design of a ROIC for scanning type HgCdTe LWIR focal plane arrays

    OpenAIRE

    Yazıcı, Melik; Yazici, Melik; Kayahan, Hüseyin; Kayahan, Huseyin; Ceylan, Ömer; Ceylan, Omer; Gürbüz, Yaşar; Gurbuz, Yasar

    2010-01-01

    Design of a silicon readout integrated circuit (ROIC) for LWIR HgCdTe Focal Plane is presented. ROIC incorporates time delay integration (TDI) functionality over seven elements with a supersampling rate of three, increasing SNR and the spatial resolution. Novelty of this topology is inside TDI stage; integration of charges in TDI stage implemented in current domain by using switched current structures that reduces required area for chip and improves linearity performance. ROIC, in terms of...

  17. Development of a (Hg, Cd)Te photodiode detector, Phase 2. [for 10.6 micron spectral region

    Science.gov (United States)

    1972-01-01

    High speed sensitive (Hg,Cd)Te photodiode detectors operating in the 77 to 90 K temperature range have been developed for the 10.6 micron spectral region. P-N junctions formed by impurity (gold) diffusion in p-type (Hg, Cd) Te have been investigated. It is shown that the bandwidth and quantum efficiency of a diode are a constant for a fixed ratio of mobility/lifetime ratio of minority carriers. The minority carrier mobility and lifetime uniquely determine the bandwidth and quantum efficiency and indicate the shallow n on p (Hg,Cd) Te diodes are preferable as high performance, high frequency devices.

  18. On the nature of alloying in HgTeCdTe solid solutions at low temperatures from electrode potential measurements

    Science.gov (United States)

    Yadava, R. D. S.; Warrier, A. V. R.

    1991-05-01

    Electrode potentials at HgTe, CdTe and Hg 0.8Cd 0.2Te in 0.1 M KOH solution are measured at 20°C with reference to a saturated calomel electrode. A model for the interfacial electron transfer reaction in equilibrium is proposed. An analysis is presented to show that the alloying of HgTe and CdTe at low temperatures is non-ideal. The enthalpy of formation of the x = 0.2 alloy from the pure component phases in solid state at 20°C is found to be +2.1 kcal mol -1.

  19. Optical properties of CuCdTeO thin films sputtered from CdTe-CuO composite targets

    International Nuclear Information System (INIS)

    The effective complex dielectric function (ε) of Cu and O containing CdTe thin films is reported in the spectral range of 0.05 to 6 eV. The films were fabricated by rf sputtering from targets comprised by a mixture of CdTe and CuO powders with nominal Cu and O concentrations in the range of 2–10 at.%. Low concentration levels improved the crystalline quality of the films. Spectroscopic ellipsometry and transmittance measurements were used to determine ε. The critical point energies E1, E1 + Δ1, and E2 of CdTe are red-shifted with the incorporation of Cu and O. Also, an absorption band is developed in the infrared range which is associated with a mixture of CdTe and low resistivity phases Cu2−xTe according to an effective medium analysis. The elemental distribution of the films was mapped by energy dispersive X-ray spectroscopy using scanning transmission electron microscopy. - Highlights: • Incorporation of 2 to 10 at.% of Cu and O atoms in CdTe films • Improved crystalline quality with 2 and 3 at.% of Cu and O • Complex dielectric function of Cu and O containing CdTe thin films • Effective medium modeling of below band-gap absorption

  20. Phytoremediation of Hg and Cd from industrial effluents using an aquatic free floating macrophyte Azolla pinnata.

    Science.gov (United States)

    Rai, Prabhat Kumar

    2008-01-01

    The level of heavy metal pollution in Singrauli, an industrial region in India, was assessed and the phytoremediation capacity of a small water fern, Azolla pinnata R.BR (Azollaceae), was observed to purify waters polluted by two heavy metals, i.e., mercury (Hg) and cadmium (Cd) under a microcosm condition. Azolla pinnata is endemic to India and is an abundant and easy-growing free-floating water fern usually found in the rice fields, polluted ponds, and reservoirs of India. The fern was grown in 24 40-L aquariums containing Hg2+ and Cd2+ ions each in concentrations of 0.5, 1.0, and 3.0 mgL(-1) during the course of this study. The study revealed an inhibition of Azolla pinnata growth by 27.0-33.9% with the highest in the presence of Hg (II) ions at 0.5 mgL(-1) in comparison to the control After 13 days of the experiment, metal contents in the solution were decreased up to 70-94%. In the tissues of Azolla pinnata, the concentration of selected heavy metals during investigation was recorded between 310 and 740 mgKg(-1) dry mass, with the highest levelfoundfor Cd (II) treatment at 3.0 mgL(-1) containing a metal solution. PMID:19260224

  1. Update on Linear Mode Photon Counting with the HgCdTe Linear Mode Avalanche Photodiode

    Science.gov (United States)

    Beck, Jeffrey D.; Kinch, Mike; Sun, Xiaoli

    2014-01-01

    The behavior of the gain-voltage characteristic of the mid-wavelength infrared cutoff HgCdTe linear mode avalanche photodiode (e-APD) is discussed both experimentally and theoretically as a function of the width of the multiplication region. Data are shown that demonstrate a strong dependence of the gain at a given bias voltage on the width of the n- gain region. Geometrical and fundamental theoretical models are examined to explain this behavior. The geometrical model takes into account the gain-dependent optical fill factor of the cylindrical APD. The theoretical model is based on the ballistic ionization model being developed for the HgCdTe APD. It is concluded that the fundamental theoretical explanation is the dominant effect. A model is developed that combines both the geometrical and fundamental effects. The model also takes into account the effect of the varying multiplication width in the low bias region of the gain-voltage curve. It is concluded that the lower than expected gain seen in the first 2 × 8 HgCdTe linear mode photon counting APD arrays, and higher excess noise factor, was very likely due to the larger than typical multiplication region length in the photon counting APD pixel design. The implications of these effects on device photon counting performance are discussed.

  2. Single-Photon-Sensitive HgCdTe Avalanche Photodiode Detector

    Science.gov (United States)

    Huntington, Andrew

    2013-01-01

    The purpose of this program was to develop single-photon-sensitive short-wavelength infrared (SWIR) and mid-wavelength infrared (MWIR) avalanche photodiode (APD) receivers based on linear-mode HgCdTe APDs, for application by NASA in light detection and ranging (lidar) sensors. Linear-mode photon-counting APDs are desired for lidar because they have a shorter pixel dead time than Geiger APDs, and can detect sequential pulse returns from multiple objects that are closely spaced in range. Linear-mode APDs can also measure photon number, which Geiger APDs cannot, adding an extra dimension to lidar scene data for multi-photon returns. High-gain APDs with low multiplication noise are required for efficient linear-mode detection of single photons because of APD gain statistics -- a low-excess-noise APD will generate detectible current pulses from single photon input at a much higher rate of occurrence than will a noisy APD operated at the same average gain. MWIR and LWIR electron-avalanche HgCdTe APDs have been shown to operate in linear mode at high average avalanche gain (M > 1000) without excess multiplication noise (F = 1), and are therefore very good candidates for linear-mode photon counting. However, detectors fashioned from these narrow-bandgap alloys require aggressive cooling to control thermal dark current. Wider-bandgap SWIR HgCdTe APDs were investigated in this program as a strategy to reduce detector cooling requirements.

  3. Interactions between photoexcited NIR emitting CdHgTe quantum dots and graphene oxide

    Science.gov (United States)

    Jagtap, Amardeep M.; Varade, Vaibhav; Konkena, Bharathi; Ramesh, K. P.; Chatterjee, Abhijit; Banerjee, Arup; Pendyala, Naresh Babu; Koteswara Rao, K. S. R.

    2016-02-01

    Hydrothermally grown mercury cadmium telluride quantum dots (CdHgTe QDs) are decorated on graphene oxide (GO) sheets through physisorption. The structural change of GO through partial reduction of oxygen functional groups is observed with X-ray photoelectron spectroscopy in GO-QDs composites. Raman spectroscopy provides relatively a small change (˜1.1 times) in D/G ratio of band intensity and red shift in G band from 1606 cm-1 to 1594 cm-1 in GO-CdHgTe QDs (2.6 nm) composites, which indicates structural modification of GO network. Steady state and time resolved photoluminescence (PL) spectroscopy shows the electronic interactions between photoexcited near infrared emitting CdHgTe QDs and GO. Another interesting observation is PL quenching in the presence of GO, and it is quite effective in the case of smaller size QDs (2.6 nm) compared to the larger size QDs (4.2 nm). Thus, the observed PL quenching is attributed to the photogenerated electron transfer from QDs to GO. The photoexcited electron transfer rate decreases from 2.2 × 109 to 1.5 × 108 s-1 with increasing particle size from 2.6 to 4.2 nm. Photoconductivity measurements on QDs-GO composite devices show nearly 3 fold increase in the current density under photo-illumination, which is a promising aspect for solar energy conversion and other optoelectronic applications.

  4. Thermopower of ceramic HgBa2Ca2Cu3O8+x and HgBa2Ca3Cu4O10+x superconductors under pressure

    International Nuclear Information System (INIS)

    The temperature dependence of thermopower α of a sample, contained 75% HgBa2Ca2Cu3O8+x (Hg-1223 phase) and 10% HgBa2Ca3Cu4O10+x (Hg-1234 phase), was studied in a 95-300 K temperature range under hydrostatic pressure up to 10 kbar. Two superconductive transitions were observed at 132 and 118 K, which were thought to be associated with Hg-1223 and Hg-1234 phases, respectively. Pressure increases Tc of both phases with a rate of 0.2 K/kbar. At T=200 K, d ln α/dP ≅ 3,8 centre dot 10-3 kbar-1

  5. Sensitive and selective detection of Hg2+ and Cu2+ ions by fluorescent Ag nanoclusters synthesized via a hydrothermal method

    Science.gov (United States)

    Liu, Jing; Ren, Xiangling; Meng, Xianwei; Fang, Zheng; Tang, Fangqiong

    2013-09-01

    An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu2+. Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg2+ and Cu2+ ions sensors.An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a

  6. Preparation, characterization and evaluation of water-soluble L-cysteine-capped-CdS nanoparticles as fluorescence probe for detection of Hg(II) in aqueous solution

    International Nuclear Information System (INIS)

    Water-soluble L-cysteine-capped-CdS nanoparticles were prepared in aqueous solution at room temperature through a straightforward one-pot process by using safe and low-cost inorganic salts as precursors, and characterized by transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectrometry, spectrofluorometry and ultraviolet-visible spectrometry. The prepared L-cysteine-capped-CdS nanoparticles were evaluated as fluorescence probe for Hg(II) detection. The fluorescence quenching of the L-cysteine-capped-CdS nanoparticles depended on the concentration and pH of Hg(II) solution. Maximum fluorescence quenching was observed at pH 7.4 with the excitation and emission wavelengths of 360 nm and 495 nm, respectively. Quenching of its fluorescence due to Hg(II) at the 20 nmol l-1level was unaffected by the presence of 5 x 106-fold excesses of Na(I) and K(I), 5 x 105-fold excesses of Mg(II), 5 x 104-fold excesses of Ca(II), 500-fold excesses of Al(III), 91-fold excesses of Mn(II), 23.5-fold excesses of Pb(II), 25-fold excesses of Fe(III), 25-fold excesses of Ag(I), 8.5-fold excesses of Ni(II) and 5-fold excesses of Cu(II). Under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of Hg(II) ranging from 16 nmol l-1 to 112 nmol l-1. The limit of detection for Hg(II) was 2.4 nmol l-1. The developed method was applied to the detection of trace Hg(II) in aqueous solutions

  7. Synthesis protocol and superconducting properties of (Hg,Cr)Sr2CuO4+δ

    International Nuclear Information System (INIS)

    In this paper, we report the study of our results on the synthesis protocol and the superconducting properties of (Hg,Cr)Sr2CuO4+δ. We have used several distinct approaches for the synthesis of good quality (Hg, Cr)/Sr-1201 samples by varying the processing parameters such as starting materials, precursor and annealing treatments as well as the sample container. The (Hg, Cr)/Sr-1201 samples were synthesized in partial vacuum, and systematically characterized by powder XRD, χ-T, dc-electrical-resistance and dc-magnetization measurements. XRD data confirm that they are of tetragonal Hg/Ba-1201 type structure. Good quality (Hg, Cr)/Sr-1201 samples were obtained from the sample prepared using a strontium nitrate source with a maximum Tconset ∼ 60 K, which is higher than the samples prepared using a carbonate source Tconset ∼ 56 K). It is found that Tc is not affected by the subsequent Ar or O2 annealing treatment. Remarkably, the annealed samples show significant improvement in the diamagnetic transition

  8. Electrical Characterization of Cu Composition Effects in CdS/CdTe Thin-Film Solar Cells with a ZnTe:Cu Back Contact: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Li, J. V.; Duenow, J. N.; Kuciauskas, D.; Kanevce, A.; Dhere, R. G.; Young, M. R.; Levi, D. H.

    2012-07-01

    We study the effects of Cu composition on the CdTe/ZnTe:Cu back contact and the bulk CdTe. For the back contact, its potential barrier decreases with Cu concentration while its saturation current density increases. For the bulk CdTe, the hole density increases with Cu concentration. We identify a Cu-related deep level at {approx}0.55 eV whose concentration is significant when the Cu concentration is high. The device performance, which initially increases with Cu concentration then decreases, reflects the interplay between the positive influences and negative influences (increasing deep levels in CdTe) of Cu.

  9. Corresponding states principle and van der Waals potentials of Zn2, Cd2, and Hg2.

    Science.gov (United States)

    Wei, L M; Li, P; Qiao, L W; Tang, K T

    2013-10-21

    Based on the assumptions that the corresponding states principle is valid for the group 12 dimers and that the interaction potentials of these dimers can be described by the Tang-Toennies potential model, a set of correlation relations between the spectroscopic constants of these dimers are derived. Some recently measured spectroscopic constants satisfy these relations quite well, but older experimental data do not. These recent spectroscopic constants and the newly available dispersion coefficients are used to construct the entire van der Waals potentials of Zn2, Cd2, and Hg2. There are indications that the ground state Hg2 potential predicted by the present study is possibly the most accurate to date. No unequivocal conclusion can be made for Zn2 and Cd2 potentials. Compared with the recent experiments, the present Zn2 bond length is eight percent too small, and the present Cd2 bond length is eight percent too large. However, both Zn2 and Cd2 bond lengths predicted by the present study are in good agreement with the quantum Monte Carlo results. PMID:24160512

  10. Possible link between Hg and Cd accumulation in the brain of long-finned pilot whales (Globicephala melas).

    Science.gov (United States)

    Gajdosechova, Zuzana; Brownlow, Andrew; Cottin, Nicolas T; Fernandes, Mariana; Read, Fiona L; Urgast, Dagmar S; Raab, Andrea; Feldmann, Jörg; Krupp, Eva M

    2016-03-01

    The bioaccumulation of metals was investigated by analysis of liver, kidney, muscle and brain tissue of a pod of 21 long-finned pilot whales (Globicephala melas) of all ages stranded in Scotland, UK. The results are the first to report cadmium (Cd) passage through the blood-brain barrier of pilot whales and provide a comprehensive study of the long-term (up to 35 years) mammalian exposure to the environmental pollutants. Additionally, linear accumulation of mercury (Hg) was observed in all studied tissues, whereas for Cd this was only observed in the liver. Total Hg concentration above the upper neurochemical threshold was found in the sub-adult and adult brains and methylmercury (MeHg) of 2.2mg/kg was found in the brain of one individual. Inter-elemental analysis showed significant positive correlations of Hg with selenium (Se) and Cd with Se in all studied tissues. Furthermore, differences in the elemental concentrations in the liver and brain tissues were found between juvenile, sub-adult and adult groups. The highest concentrations of manganese, iron, zinc, Se, Hg and MeHg were noted in the livers, whereas Cd predominantly accumulated in the kidneys. High concentrations of Hg and Cd in the tissues of pilot whales presented in this study reflect ever increasing toxic stress on marine mammals. PMID:26748005

  11. Electron paramagnetic resonance studies in HgMo6S8 doped with Cu2+: evidence for cationic mobility

    International Nuclear Information System (INIS)

    Some of the Chevrel phase compounds are reported to exhibit unusual cationic mobilities, particularly those with transition metals. EPR evidence is presented for mobile Cu2+ ions in Cu2+-doped HgMo6S8. Evidence is also obtained for the existence of Hg+ ions, giving possible support for the model correlating the site change with the reaction A2+ + e-↔A+ during ionic conductivity. (author)

  12. XANES study of superconducting Hg0.85Mo0.15Sr2CuO4+δ

    International Nuclear Information System (INIS)

    The Hg-Sr based 1201-type Ba-free cuprate superconductor with nominal composition Hg0.85Mo0.15Sr2CuO4+δ has been synthesised and characterised. The Tc onset is 66 K. The Cu K-XANES of the oxygenated superconducting 1201 samples distinctly show the presence of monovalent copper unlike that in the other layered hole doped superconductors. (author)

  13. Cd, Pb and Hg Biomonitoring in Fish of the Mediterranean Region and Risk Estimations on Fish Consumption

    OpenAIRE

    Elisavet A. Renieri; Alegakis, Athanasios K; Michalis Kiriakakis; Marco Vinceti; Eren Ozcagli; Wilks, Martin F.; TSATSAKIS, ARISTIDIS M.

    2014-01-01

    Cadmium (Cd), lead (Pb) and mercury (Hg) are toxic metals with increasing interest due to their tendency to bioaccumulate in fish tissue which may pose a threat to human health via fish consumption. This review of the recent literature on Cd, Pb, Hg levels summarizes data of fish biomonitoring studies in the Mediterranean Sea in order to determine potential risks due to dietary intake of metals. The analytical methods applied are described, with Atomic Absorption Spectroscopy and Inductively ...

  14. Chalcophile elements Hg, Cd, Pb, As in Lake Umbozero, Murmansk Region, Russia

    DEFF Research Database (Denmark)

    Dauvalter, V.A.; Kashulin, N.A.; Lehto, J.; Jernström, Jussi

    2009-01-01

    affected by emissions and effluents from mining and metallurgical enterprises of the Murmansk Region, as well as air pollution of a global character. Surface and near-bottom maxima were found in the distributions of Pb and Cd in the water column. These two maxima appear to be associated with the cyclical...... growth of phytoplankton in surface water layers and with sedimentation of lifeless organisms and suspended particles in near-bottom layers. Average concentrations of Pb and Cd in the water column were more than the average value for water of lakes of the taiga zone. Pollution of Lake Umbozero led to......Investigations of Lake Umbozero, the second largest and the deepest lake of the Murmansk Region, were carried out to detect and define biogeochemical patterns of distribution of the chalcophile elements (Hg, Cd, Pb, As) in water, sediments and organs and tissues of whitefishes. Lake Umbozero is...

  15. Chalcophile elements Hg, Cd, Pb, As in Lake Umbozero, Murmansk Region, Russia

    DEFF Research Database (Denmark)

    Dauvalter, V.A.; Kashulin, N.A.; Lehto, J.;

    2009-01-01

    is affected by emissions and effluents from mining and metallurgical enterprises of the Murmansk Region, as well as air pollution of a global character. Surface and near-bottom maxima were found in the distributions of Pb and Cd in the water column. These two maxima appear to be associated with the cyclical...... growth of phytoplankton in surface water layers and with sedimentation of lifeless organisms and suspended particles in near-bottom layers. Average concentrations of Pb and Cd in the water column were more than the average value for water of lakes of the taiga zone. Pollution of Lake Umbozero led......Investigations of Lake Umbozero, the second largest and the deepest lake of the Murmansk Region, were carried out to detect and define biogeochemical patterns of distribution of the chalcophile elements (Hg, Cd, Pb, As) in water, sediments and organs and tissues of whitefishes. Lake Umbozero...

  16. Electron mobilities and quantum Hall effect in modulation-doped HgTe-CdTe superlattices

    Science.gov (United States)

    Hoffman, C. A.; Meyer, J. R.; Bartoli, F. J.; Lansari, Y.; Cook, J. W., Jr.; Schetzina, J. F.

    1991-10-01

    Photoassisted molecular-beam epitaxy and controlled modulation doping have been used to grow HgTe-CdTe superlattices with n-type carrier concentrations of up to 3×1017 cm-3. It is found that in contrast to Hg1-xCdxTe alloys where the electron mobility decreases strongly with donor concentration, μn in the modulation-doped superlattices is nearly independent of ND at large ND. We also discuss an observation of the quantum Hall effect associated with carriers distributed throughout the interior of a HgTe-CdTe superlattice. Whereas previous reports of quantized steps in the Hall conductivity have involved a small number of conduction channels (hence a small fraction of the superlattice periods), we observe plateaus at multiples of ~=200e2/h in a number of 200-period superlattices with high doping levels. This indicates participation by nearly all wells in the superlattice, and implies that the controlled doping is extremely uniform.

  17. Barium triel mercuride BaMxHg4-x and Ba3MxHg11-x (M = Ga, In, Cd)

    International Nuclear Information System (INIS)

    The systematic experimental and bond-theoretical study of the phase width of the BaAl4 structure type in the ternary system BaIn4-BaHg4 shows that this structure type is stable up to BaIn1.7Hg2.3 (tetragonal, tI10, space group I4/mmm, a = 474.2(3), c = 1228.7(9) pm, R1 = 0.0529). The planar 44 layers (M(2) site) are preferentially formed by In, whereas Hg occupies the tips (M(1) site) of the [M(1)M(2)4] square pyramids. The layers of the pyramids are connected via short M(1)-M(1) dumbbells (bonds a). The analysis of the calculated band structures of BaIn2Hg2 in comparison to BaIn4 and RbIn4 shows that contributions of Ba-d states (which are missing for RbIn4) and Hg-d states (which are missing in the pure indides) are significant. The respective compound with the smaller triel gallium (Hg-richest phase: BaGa1.9Hg2.1, tetragonal, oI40, space group I41/amd, a = 671.3(2), c = 2220.4(8) pm, Z = 8, R1 = 0.0641) forms a new superstructure of the BaAl4 structure with a partial ordering of three statistically occupied mixed Ga/Hg positions. The 44 nets are formed by an intermediate proportion of Ga/Hg. The tips of the pyramids are alternately formed by a Ga- and an Hg-rich position leading to smaller and larger bond lengths a' and a'', respectively, between the tip atoms and, consequently, a puckering of the 44 net. The two Hg-rich 3:11 compounds Ba3InHg10 and Ba3CdHg10 (orthorhombic, oI28, space group Immm, a = 513.96(8)/511.50(2), b = 993.8(2)/991.54(3), c = 1500.7(3)/1499.26(5) pm, Z = 2, R1 = 0.0619/0.0482) crystallize in the La3Al11 structure type, which is also observed for K3Hg11 and is closely related to the BaAl4 type: The square pyramidal nets are corrugated leading to a triplication of the BaAl4 unit cell along one of the tetragonal axes. In each third subcell the tips of adjacent pyramids are directly fused, this position being occupied exclusively by In and Cd. With the smaller triel gallium, the 3:11 compound Ba3Ga0.2Hg10.8 crystallizes in the Ba3ZnHg10

  18. Synthesis and Spectroscopic Study of a Chemosensor for Naked Eye Recognition of Cu2+ and Hg2+%一种裸眼识别Cu2+和Hg2+传感器的合成与性质研究

    Institute of Scientific and Technical Information of China (English)

    曹丽; 钱亚骜; 黄燕; 曹娟; 贾春满; 刘春玲; 张岐; 吕正荣

    2015-01-01

    Compound L ,as the procedural sensor for the detection of Cu2+ and Hg2+ ,was designed and synthesized based on the coumarin‐modified rhodamine derivative .The structure of compound L was characterized by NMR ,high resolution mass spec‐trometry and infrared method .Its sensing behavior toward various metal ions was investigated with absorbance methods .The study found that L had good selectivity and sensitivity for Cu2+ .When addition of various metal ions (Zn2+ ,Hg2+ ,Cu2+ , Fe3+ ,Cd2+ ,Co2+ ,Ni2+ ,Mg2+ ,Ca2+ ,Al3+ ,La3+ ,K+ ,Na+ ,Mn2+ ,Pb2+ and Ag+ ) ,only Cu2+ could induce a visible change of solution from colourless to pink and a new absorption band centered at 534 nm appear ,which indicated that compound L could be used for the naked eye detection of Cu2+ .From UV titration ,the detection limit was about 1.9 × 10-8 mol・ L -1 . Test strips based on L were fabricated ,and this test strips could act as a convenient and efficient Cu2+ test kit .The binding ratio of the complex of L‐Cu2+ was 1∶1 according to the Job’s plot and high resolution mass spectrometer (HRMS) experiments . Moreover ,Upon addition of 1 equiv .EDTA to the mixture of L and Cu2+ in DMSO solution ,colour changed from pink to al‐most colourless ,indicating that the EDTA replaced the receptor L to coordinate with Cu 2+ .Therefore ,L could be classified as a reversible sensor for Cu2+ .In addition ,when adding Hg2+ to L‐Cu2+ complexes ,a visible change of solution from pink to col‐ourless was observed ,while other metal ions didn’t cause this change .Thus ,L‐Cu2+ complex also could be used for the naked eye recognition of Hg2+ ,and the detection limit was calculated about 2.9 × 10-7 mol・L -1 according to the UV titration .Conse‐quently ,this procedural sensor L could be use for the orderly naked eye recognition of Cu2+ and Hg2+ .%设计合成了一种香豆素修饰的罗丹明类衍生物L ,用作程序型Cu2+与Hg2+检测传感器。采用核磁共振谱、高分

  19. Novel bimetallic thiocyanate-bridged Cu(II)-Hg(II) compounds-synthesis, X-Ray studies and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Machura, B., E-mail: basia@ich.us.edu.pl [Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 40-006 Katowice (Poland); Switlicka, A.; Zwolinski, P. [Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 40-006 Katowice (Poland); Mrozinski, J., E-mail: jmroz@wchuwr.chem.uni.wroc.pl [Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 St., 50-383 Wroclaw (Poland); Kalinska, B. [Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 St., 50-383 Wroclaw (Poland); Kruszynski, R., E-mail: rafal.kruszynski@p.lodz.pl [Department of X-Ray Crystallography and Crystal Chemistry, Institute of General and Ecological Chemistry, Technical University of Lodz, 116 Zeromski St., 90-924 Lodz (Poland)

    2013-01-15

    Seven novel heterobimetallic Cu/Hg polymers based on thiocyanate bridges have been synthesised and characterised by means of IR, EPR, magnetic measurements and single crystal X-Ray. Three of them, [Cu(pzH){sub 4}Hg(SCN){sub 4}]{sub n} (1) [Cu(indH){sub 4}Hg(SCN){sub 4}]{sub n} (2) and [Cu(ampy){sub 2}Hg(SCN){sub 4}]{sub n} (3), have one-dimensional coordination structure. Two compounds [Cu(pzH){sub 2}Hg(SCN){sub 4}]{sub n} (4) and [Cu(abzimH)Hg(SCN){sub 4}]{sub n} (5) form two-dimensional nets, whereas the complexes [Cu(pyCN){sub 2}Hg(SCN){sub 4}]{sub n} (6) and [Cu(pyCH(OH)(OMe)){sub 2}Hg(SCN){sub 4}]{sub n} (7) are three-dimensional coordination polymers. The chains of 1 are connected by the intermolecular N-H Bullet Bullet Bullet N hydrogen bonds to the three dimensional net. In 2 the N-H Bullet Bullet Bullet S hydrogen bonds link the polymeric chains to the two dimensional layer extending along crystallographic (0 0 1) plane. The polymeric chains of compound 3 are joined by the intermolecular N-H Bullet Bullet Bullet N and N-H Bullet Bullet Bullet S hydrogen bonds to the three dimensional net. The polymeric layers of 4 are connected by the intermolecular N-H Bullet Bullet Bullet N hydrogen bonds to the three dimensional net. - Graphical abstract: Novel bimetallic thiocyanate-bridged Cu(II)-Hg(II) compound-synthesis,X-Ray studies and magnetic properties. Highlights: Black-Right-Pointing-Pointer Novel heterobimetallic Cu/Hg coordination polymers were synthesised. Black-Right-Pointing-Pointer The multidimensional structures have been proved by single X-ray analysIs. Black-Right-Pointing-Pointer A variation in the crystalline architectures was observed depending on auxiliary ligands. Black-Right-Pointing-Pointer Magnetic measurements indicate weak exchange interaction between Cu(II) in the crystal lattices below 10 K.

  20. Ultrathin quantum wells of HgTe in CdTe: Interface states

    International Nuclear Information System (INIS)

    We present an exact calculation of the electronic structure of systems composed by a small number of HgTe layers into CdTe. Layer Green Functions are calculated from which interface state energies and density of states are obtained. We employ a realistic tight-binding method. Special attention is drawn to the anisotropic dispersion relation through the entire two-dimensional Brillouin zone for a monolayer of HgTe. Interface states depend sensitively on the valence-band-offset. A comparison is made with the single heterojunction case showing that the coupling between interfaces in the quantum well plays a minor role in determining the main features of such cases. (author). 15 refs, 5 figs

  1. 256 x 256 hybrid HgCdTe infrared focal plane arrays

    Science.gov (United States)

    Bailey, Robert B.; Kozlowski, Lester J.; Chen, Jenkon; Bui, Duc Q.; Vural, Kadri

    1991-05-01

    Hybrid HgCdTe 256 x 256 focal plane arrays have been developed to meet the sensitivity, resolution, and field-of-view requirements of high-performance medium-wavelength infrared (MWIR) imaging systems. The detector arrays for these hybrids are fabricated on substrates that reduce or eliminate the thermal expansion mismatch to the silicon readout circuit. The readouts are foundry-processed CMOS switched-FET circuits that have charge capacities greater than 107 electrons and a single video output capable of 10-MHz data rates. The high quantum efficiency, tunable absorption wavelength, and broad operating temperature range of these large HgCdTe staring focal plane arrays give them significant advantages over competing sensors. The mature Producible Alternative to CdTe for Epitaxy-1 (PACE-1) technology, using sapphire detector substrates, has demonstrated 256 x 256 MWIR arrays with mean laboratory noise equivalent temperature difference (NETO) of 9 mK for a 4.9-micron cutoff wavelength, 40-micron pixel size, and 80-K operating temperature. RMS detector response nonuniformities are less than 4 percent, and pixel yields are greater than 99 percent. The newly developed PACE-3 process uses silicon for the detector substrate to eliminate completely the thermal mismatch with the silicon readout circuit. It has the potential for similar performance in even larger array sizes. A 640 x 480 hybrid array is under development.

  2. Improving material characteristics and reproducibility of MBE HgCdTe

    Science.gov (United States)

    Edwall, D. D.; Zandian, M.; Chen, A. C.; Arias, J. M.

    1997-06-01

    This paper describes our progress to improve the material quality, reproducibility, and flexibility of molecular beam epitaxial (MBE) growth of HgCdTe. Data, statistics, and yields according to defined screen criteria are presented for n-type layer carrier concentration and mobility, void defect density, and dislocation density for more than 100 layers. Minority carrier lifetime data are also presented. Continued improvements in impurity reductiont have allowed us to achieve, for the first time, reproducible, low n-type carrier concentration in the mid-1014 cnr-3 range with high electron mobility. Data are presented that show that low dislocation density films are obtained for growth on CdZnTe substrates with a wide range of Zn concentration. Results are presented from a nine-growth run first pass success demonstration run to further assess material quality reproducibility and flexibility of wavelength band tuning. These results demonstrate the promising potential of MBE growth for flexible manufacturing of HgCdTe for infrared focal plane arrays.

  3. Extracting Cu Diffusion Parameters in Polycrystalline CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Akis, Richard [Arizona State Univeristy; Brinkman, Daniel [Arizona State Univeristy; Sankin, Igor [First Solar; Fang, Tian [First Solar; Guo, Da [Arizona State Univeristy; Dragica, Vasileska [Arizona State Univeristy; Ringhofer, Christian [Arizona State University

    2014-06-13

    It is well known that Cu plays an important role in CdTe solar cell performance as a dopant. In this work, a finite-difference method is developed and used to simulate Cu diffusion in CdTe solar cells. In the simulations, which are done on a two-dimensional (2D) domain, the CdTe is assumed to be polycrystal-line, with the individual grains separated by grain boundaries. When used to fit experimental Cu concentration data, bulk and grain boundary diffusion coefficients and activation energies for CdTe can be extracted. In the past, diffusion coefficients have been typically obtained by fitting data to simple functional forms of limited validity. By doing full simulations, the simplifying assumptions used in those analytical models are avoided and diffusion parameters can thus be determined more accurately.

  4. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  5. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-04-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  6. Magnetization study of mercurocuprate (Hg,Re)Sr2CuO4+

    Indian Academy of Sciences (India)

    S Balamurugan; I K Gopalakrishnan; J V Yakhmi; P Selvam

    2002-05-01

    The nominal (Hg1-Re)Sr2CuO4+ ( = 0.10 and 0.20) samples were synthesized at ∼ 920° C in partial vacuum. The compound with =0.10 exhibits superconductivity at ∼ 54 K while the composition = 0.20 is non-superconducting down to 5 K. On cooling below 10 K in an applied field of 4 kOe, the former causes a noticeable upturn in the field cooled (FC) magnetization signal. Such a change in magnetic response is also reflected in the magnetic hysteresis loop generated at 9 K. We attribute this effect to a paramagnetic contribution arising from Re in (Hg,Re)-1201 phase.

  7. Magnetization study of mercurocuprate (Hg, Re)Sr2CuO4+δ

    International Nuclear Information System (INIS)

    The nominal (Hg1-xRex)Sr2CuO4+δ (x = 0.10, 0.20) samples were synthesized at ∼920 degC in partial vacuum. The compound with x=0.10 exhibits superconductivity at ∼54 while the composition x =0.20 is non-superconducting down to 5 K. On cooling below 10 K in an applied field of 4 kOe, the former causes a noticeable upturn in the field cooled (FC) magnetization signal. Such a change in magnetic response is also reflected in the magnetic hysteresis loop generated at 9 K. We attribute this effect to a paramagnetic contribution arising from Re in (Hg, Re)-1201 phase. (author)

  8. The irreversibility line of (Hg, Cr)Sr2CuO4+δ superconductor

    International Nuclear Information System (INIS)

    Superconducting (Hg, Cr)-1201 phase was synthesized with a nominal composition Hg0.7, Cr0.3Sr2CuO4+δ by solid state reaction method in vacuum-sealed quartz-tube. X-ray diffraction (XRD) analysis of the sample showed a tetragonal symmetry with lattice parameters a = 3.842 (2) A and c = 8.641 (5) A. Ac-susceptibility, dc-magnetization, and dc-resistivity measurements indicate a Tc of 60 K. The irreversibility line (IRL) was obtained from the merging point of the zero field cooled (ZFC) and field cooled (FC) magnetization measurements at several applied fields. The fit H =A(1 -T / Tc)n gave a value of 2.55 for the exponent n. (author)

  9. Stabilizing CdTe/CdS solar cells with Cu-containing contacts to p-CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Dobson, K.D.; Visoly-Fisher, I.; Hodes, G.; Cahen, D. [Weizmann Inst. of Science, Rehovoth (Israel)

    2001-10-02

    High efficiency CdTe/CdS thin-film solar cells require low resistance contacts to p-CdTe, which is frequently achieved by addition of Cu. Decreases in cell efficiency over time, however, have been associated with Cu from the contact. The question that is considered here is if Cu is really detrimental to cell performance? By performing a series of thermal stress tests the authors reach a far more optimistic conclusion than what has hitherto been assumed.f (orig.)

  10. New development on the control of homoepitaxial and heteroepitaxial growth of CdTe and HgCdTe by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Faurie, J.P.; Sporken, R.; Sivananthan, S.; Lange, M.D. (Microphysics Lab., Physics Dept., Univ. of Illinois at Chicago, IL (USA))

    1991-05-01

    It is reported that rotation twins as well as reflection twins are easily formed in CdTe and HgCdTe grown by MBE in the (111) orientation. Twinning can be avoided by carefully controlling the substrate preparation and by applying very stringent growth conditions, mostly for the stability of Hg pressure and the real surface temperature of the substrate, which is extremely difficult to control when the substrate rotates. A comparison between HgCdTe twinned layers and twin-free layers has shown that electrically active acceptors and high hole mobility are associated with the presence of reflection twins and/or mercury-rich alloy zones due to Hg overpressure during the growth. Twin-free HgCdTe layers can exhibit etch pit density count two orders of magnitude lower than twinned layers. Twin-free CdTe layers have been grown on GaAs and Si substrates. Excellent thickness uniformities have been reported: 0.24% for the standard deviation of a 2-inch diameter CdTe layer grown on GaAs(100) and 2.3% for a 5-inch diameter CdTe grown on Si(100). (orig.).

  11. Relativistic M-subshell radiationless transition probabilities and energies for Zn, Cd and Hg

    International Nuclear Information System (INIS)

    Theoretical calculations of radiationless transition probabilities and energies for M-subshell vacancies in Zn, Cd, and Hg are tabulated using the Dirac–Fock method. Transition probabilities between an initial vacancy state and a final two-vacancies state are presented for each initial and final atomic angular momentum quantum number. Calculations were performed in the single configuration approach with the Breit interaction, self-energy and (Uehling) vacuum polarization corrections included in the self-consistent method. Higher-order retardation corrections and QED effects were also included as perturbations

  12. Levels Of Heavy Metals (Hg, Pb, Cd, And Cr) In Tissues Of Trachurus Trachurus

    OpenAIRE

    Enkeleda Ozuni; Luljeta Dhaskali; Jetmira Abeshi; Doriana Beqiraj

    2012-01-01

    The study was carried out to monitor the concentration level of mercury, lead, cadmium and chrome in different tissues of Trachurus trachurus (Horse mackerel). The concentration level of heavy metals was measured by using atomic absorption spectrophotometer (AAS). Concentrations of heavy metals in muscle tissue and liver of this animal ranged as follows: Hg 0.032-0.106; Cd nd-0.067 mg/kg wet weight; Pb and Cr resulted always below the detection level (nd) in all tissue samples. According to t...

  13. Electrical properties of modulation-doped HgTe-CdTe superlattices

    Science.gov (United States)

    Hwang, S.; Lansari, Y.; Yang, Z.; Cook, J. W.; Schetzina, J. F.

    1991-10-01

    Growth of modulation-doped HgTe-CdTe superlattices (SLs) at very low temperatures (140 °C) by photoassisted molecular beam epitaxy is reported. SL layer thicknesses were intentionally chosen such that most of the SLs studied are inverted-band semimetals or inverted-band semiconductors. Both p- and n-type samples were successsfully prepared and studied. The doped superlattices exhibit excellent electrical properties. Lack of carrier freeze-out at low temperatures provides convincing evidence that modulation-doping has been achieved.

  14. Technology for advanced focal plane arrays of HgCdTe and AIGaN

    CERN Document Server

    He, Li; Ni, Guoqiang

    2016-01-01

    This book introduces the basic framework of advanced focal plane technology based on the third-generation infrared focal plane concept. The essential concept, research advances, and future trends in advanced sensor arrays are comprehensively reviewed. Moreover, the book summarizes recent research advances in HgCdTe/AlGaN detectors for the infrared/ultraviolet waveband, with a particular focus on the numerical method of detector design, material epitaxial growth and processing, as well as Complementary Metal-Oxide-Semiconductor Transistor readout circuits. The book offers a unique resource for all graduate students and researchers interested in the technologies of focal plane arrays or electro-optical imaging sensors.

  15. Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Wen; Chang, Kai; /Beijing, Inst. Semiconductors; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    Spin Hall effect can be induced both by the extrinsic impurity scattering and by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe quantum well has a quantum phase transition where the electronic structure changes from normal to inverted. We show that the intrinsic spin Hall effect of the conduction band vanishes on the normal side, while it is finite on the inverted side. This difference gives a direct mechanism to experimentally distinguish the intrinsic spin Hall effect from the extrinsic one.

  16. Direct determination of Cd, Hg in liver and kidney by prompt gamma activation analysis

    International Nuclear Information System (INIS)

    The development of a method for in-vivo measurement of some elemental concentration in organs making use of prompt gamma activation analysis with the filtered neutron beam at the Dalat reactor is being carried out. In this paper we present primary results in research and development of an IVPGNAA facility at the Dalat reactor. Beside the description of experimental set-up, it consists of determination of thermal neutron flux distribution in phantom, and the evaluation of the detection limit and analytical sensitivity for Cd and Hg in the kidney and the liver. Discussions are given to improve the IVPGNAA facility in the future. (author)

  17. Finite size effects of helical edge states in HgTe/CdTe quantum wells

    OpenAIRE

    Zhou, Bin; Lu, Hai-Zhou; Chu, Rui-Lin; Shen, Shun-Qing; Niu, Qian

    2008-01-01

    The solutions for the helical edge states for an effective continuum model for the quantum spin Hall effect in HgTe/CdTe quantum wells are presented. For a sample of a large size, the solution gives the linear dispersion for the edge states. However, in a finite strip geometry, the edge states at two sides will couple with each other, which leads to a finite energy gap in the spectra. The gap decays in an exponential law of the width of sample. The magnetic field dependence of the edge states...

  18. HgTe/CdS/ZnS多壳层量子点的制备与表征%Synthesis and Characterization of HgTe/CdS/ZnS Multi-shell Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    胡军; 秦瑞飞; 金崇君

    2015-01-01

    采用一种简单的方法合成HgTe/CdS/ZnS多壳层量子点。首先,以1-硫代甘油为稳定剂,在水相溶液中制备出HgTe核量子点;然后,采用外延生长法依次在HgTe核量子点表面包覆CdS和ZnS壳层,合成出最终具有稳定近红外发光的HgTe/CdS/ZnS多壳层量子点。该合成方法仅需3个步骤,具有操作简单、成本低廉的优点。实验结果显示,当反应温度为90℃、反应溶液pH为11.0、反应加热回流时间为4 min时,HgTe/CdS/ZnS多壳层量子点具有最高荧光量子产率36%。%A simple method for HgTe/CdS/ZnS multi-shell quantum dots ( QDs) synthesizing was developed. Firstly, HgTe core QDs were synthesized in aqueous solution with 1-thioglycerol as the stabilizer. Then, CdS and ZnS shells were grown on the surface of HgTe core by epitaxial growth method . The resultant HgTe/CdS/ZnS multi-shell QDs have stable near-infrared light-emitting prop-erty . This synthetic method contains only three steps with the advantages of simple operation and low cost. The experimental results indicate that HgTe/CdS/ZnS multi-shell QDs can reach the highest fluorescence quantum yield of 36% as the reaction solution ( pH=11 . 0 ) is heated reflux for 4 min at 90 ℃.

  19. Magnetic field effects on edge and bulk states in topological insulators based on HgTe/CdHgTe quantum wells with strong natural interface inversion asymmetry

    OpenAIRE

    Durnev, M. V.; Tarasenko, S. A.

    2015-01-01

    We present a theory of the electron structure and the Zeeman effect for the helical edge states emerging in two-dimensional topological insulators based on HgTe/HgCdTe quantum wells with strong natural interface inversion asymmetry. The interface inversion asymmetry, reflecting the real atomistic structure of the quantum well, drastically modifies both bulk and edge states. For the in-plane magnetic field, this asymmetry leads to a strong anisotropy of the edge-state effective $g$-factor whic...

  20. (Hg, Sb)Ba2Ca2Cu3O8+δ thick films on YSZ substrates

    International Nuclear Information System (INIS)

    Superconducting thick films of (Hg, Sb)Ba2Ca2Cu3O8+δ have been fabricated on polycrystalline yttria-stabilized-zirconia substrates utilizing an Hg-free precursor film reacted with Hg vapour, released from a solid Hg source, in a sealed quartz tube. The resulting films have been studied by x-ray diffraction, scanning electron microscopy, ac susceptibility and resistance measurement techniques. A high quality Hg(Sb)-1223 superconducting thick film on YSZ can be fabricated by using a pre-melted Hg-free precursor film. The zero resistance superconducting transition temperature in the post-growth oxygenated thick film is in excess of 130 K and the transport critical current density for the film is 510 A cm-2 at 77 K. (author)

  1. Theory for electron and hole transport in HgTe-CdTe superlattices

    Science.gov (United States)

    Meyer, J. R.; Arnold, D. J.; Hoffman, C. A.; Bartoli, F. J.; Ram-Mohan, L. R.

    1991-10-01

    We present results of the first detailed theory for electron and hole transport in HgTe-CdTe superlattices. The calculations incorporates the superlattice band structure in full generality, and also treats multi-well scattering and screening processes which have been ignored in previous theories. It is predicted that whereas the electron and hole mobilities should be nearly equal at low temperatures, the hole mobility falls far below the electron value at somewhat higher temperatures due to the extreme nonparabolicity of the valence band. This prediction is entirely consistent with experimental results reported previously. Excellent quantitative agreement with the data over a broad temperature range is achieved if interface roughness scattering is considered in addition to ionized impurity scattering, acoustic and optical phonon scattering, and electron-hole scattering. It is pointed out that low-temperature electron mobilities for a number of thin-well HgTe-CdTe superlattices follow the d6W dependence expected for the interface roughness mechanism.

  2. Numerical Device Modeling, Analysis, and Optimization of Extended-SWIR HgCdTe Infrared Detectors

    Science.gov (United States)

    Schuster, J.; DeWames, R. E.; DeCuir, E. A.; Bellotti, E.; Dhar, N.; Wijewarnasuriya, P. S.

    2016-06-01

    Imaging in the extended short-wavelength infrared (eSWIR) spectral band (1.7-3.0 μm) for astronomy applications is an area of significant interest. However, these applications require infrared detectors with extremely low dark current (less than 0.01 electrons per pixel per second for certain applications). In these detectors, sources of dark current that may limit the overall system performance are fundamental and/or defect-related mechanisms. Non-optimized growth/device processing may present material point defects within the HgCdTe bandgap leading to Shockley-Read-Hall dominated dark current. While realizing contributions to the dark current from only fundamental mechanisms should be the goal for attaining optimal device performance, it may not be readily feasible with current technology and/or resources. In this regard, the U.S. Army Research Laboratory performed physics-based, two- and three-dimensional numerical modeling of HgCdTe photovoltaic infrared detectors designed for operation in the eSWIR spectral band. The underlying impetus for this capability and study originates with a desire to reach fundamental performance limits via intelligent device design.

  3. Subcellular localization of several heavy metals of Hg,Cd and Pb in human liver

    Institute of Scientific and Technical Information of China (English)

    CHEN Chunying; ZHANG Peiqun; CHAI Zhifang

    2005-01-01

    Liver, as an important metabolic and detoxicological organ of human body, can be used as a good bioindicator for evaluating body burden of environmental pollutants. Its elemental contents and their chemical forms are closely related to the status of human health and disease. In this paper, the liver samples collected from normal subjects were separated to different subcellular fractions of nuclei, mitochondria, lysosome, microsome and cytosol by differential centrifugation. Then their concentrations of heavy metals of As, Pb, Cd, and Hg were determined by atomic absorption and atomic fluorescent spectroscopy. Our results show no significant difference with literature ones when comparing their gross concentrations. In the case of their subcellular distribution, the Hg concentrations are higher in mitochondrial, microsomal and cytosolic fractions; the Cd concentrations are higher in cytosolic and mitochondrial fractions, while As highest in nuclear fraction. The highest concentration of Pb is found in microsomal fraction with similarity to Fe. Mercury in liver is mainly in the form of inorganic, and methylmercury ranged from 9% to 50% with the average value of 20.9%(13.3%. These results indicate that the cellular distribution and the accumulated target organelles are quite different among these heavy metals, which suggest their various pathways and toxic mechanism in vivo.

  4. Numerical Device Modeling, Analysis, and Optimization of Extended-SWIR HgCdTe Infrared Detectors

    Science.gov (United States)

    Schuster, J.; DeWames, R. E.; DeCuir, E. A.; Bellotti, E.; Dhar, N.; Wijewarnasuriya, P. S.

    2016-09-01

    Imaging in the extended short-wavelength infrared (eSWIR) spectral band (1.7-3.0 μm) for astronomy applications is an area of significant interest. However, these applications require infrared detectors with extremely low dark current (less than 0.01 electrons per pixel per second for certain applications). In these detectors, sources of dark current that may limit the overall system performance are fundamental and/or defect-related mechanisms. Non-optimized growth/device processing may present material point defects within the HgCdTe bandgap leading to Shockley-Read-Hall dominated dark current. While realizing contributions to the dark current from only fundamental mechanisms should be the goal for attaining optimal device performance, it may not be readily feasible with current technology and/or resources. In this regard, the U.S. Army Research Laboratory performed physics-based, two- and three-dimensional numerical modeling of HgCdTe photovoltaic infrared detectors designed for operation in the eSWIR spectral band. The underlying impetus for this capability and study originates with a desire to reach fundamental performance limits via intelligent device design.

  5. Design of HgCdTe heterojunction photodiodes on Si substrate

    Science.gov (United States)

    Zhang, P.; Ye, Z. H.; Chen, Y. Y.; Lin, C.; Hu, X. N.; Ding, R. J.; He, L.

    2014-05-01

    An innovative heterojunction photodiode structure in HgCdTe-on-Si long-wavelength (LW) infrared focal plane array (IRFPA) detector is investigated in this paper. The quantum efficiency and the photoresponse of devices have been numerically simulated, using Crosslight Technology Computer Aided Design (TCAD) software. Simulation results indicate that in contrast to the p+-on-n homojunction photodiode, the heterojunction photodiode effectively suppresses the crosstalk between adjacent pixels and interface recombination between HgCdTe active region and buffer layer on Si substrate. And in the range of the LW-band, the quantum efficiency of the heterojunction photodiode increases by 35.5%. Furthermore, the heterojunction photodiode acquires the narrow-band response spectrum desired in the application of the LW IRFPA detectors as the p+-on-n homojunction photodiode with the optical filter. Finally, the smaller bulk resistance of its heavily doped N-type layer ensures the uniformity of the pixel series resistance in the large format IRFPAs.

  6. The characteristic analysis and optimization design for HgCdTe TDI infrared detector array

    Science.gov (United States)

    Dong, Mei-feng; Chen, Xing; Qiu, Guang-yin; Xie, Xiao-hui

    2011-08-01

    Time Delay Integration (TDI) is an effective approach for high sensitive infrared detectors. According to the principle of the TDI, the central distance of pixel along the time delay integral direction is closely linked with the specific application requirements. So the optimization design, such as the area of pixels and their distance, plays an important role to improve the performance of TDI detectors. The crosstalk between pixels is a crucial factor that results in the decline of detector Modulation Transfer Function (MTF), and then affects the imaging quality. In this paper the optimization design rule for the arrangement of pixel has been investigated. The results show that the main method to appreciate it is reducing the crosstalk between pixels and enhancing detectivity. Chips of which pixel areas and edge intervals are different but with same distance were designed for the experiments. The optical and electrical measurements were carried out for these chips and the optimized structure was obtained. In addition, relationships between the crosstalk and parameters of material, pixel structure were analyzed based on the experiment data. According to the comprehensive analysis of the measurement data, we obtained the optimum design for specific HgCdTe TDI infrared detector. Meanwhile it is also a well reference for other HgCdTe TDI detector structure design.

  7. Thermal cycling reliability of indirect hybrid HgCdTe infrared detectors

    Science.gov (United States)

    Chen, Xing; He, Kai; Wang, Jian-xin; Zhang, Qin-yao

    2013-09-01

    Thermal cycling reliability is one of the most important issues whether the HgCdTe infrared focal plane array detectors can be applied to both military and civil fields. In this paper, a 3D finite element model for indirect hybrid HgCdTe infrared detectors is established. The thermal stress distribution and thermally induced warpage of the detector assembly as a function of the distance between the detector chip and Si-ROIC, the thickness and the materials properties of electrical lead board in cryogenic temperature are analyzed. The results show that all these parameters have influences on the thermal stress distribution and warpage of the detector assembly, especially the coefficient of thermal expansion(CTE) of electrical lead board. The thermal stress and warpage in the assembly can be avoided or minimized by choosing the appropriate electrical lead board. Additionally, the warpage of some indirect hybrid detectors assembly samples is measured in experiment. The experimental results are in good agreement with the simulation results, which verifies that the results are calculated by finite element method are reasonable.

  8. Comparison of Measured Dark Current Distributions with Calculated Damage Energy Distributions in HgCdTe

    Science.gov (United States)

    Marshall, C. J.; Marshall, P. W.; Howe, C. L.; Reed, R. A.; Weller, R. A.; Mendenhall, M.; Waczynski, A.; Ladbury, R.; Jordan, T. M.

    2007-01-01

    This paper presents a combined Monte Carlo and analytic approach to the calculation of the pixel-to-pixel distribution of proton-induced damage in a HgCdTe sensor array and compares the results to measured dark current distributions after damage by 63 MeV protons. The moments of the Coulombic, nuclear elastic and nuclear inelastic damage distributions were extracted from Monte Carlo simulations and combined to form a damage distribution using the analytic techniques first described in [1]. The calculations show that the high energy recoils from the nuclear inelastic reactions (calculated using the Monte Carlo code MCNPX [2]) produce a pronounced skewing of the damage energy distribution. While the nuclear elastic component (also calculated using the MCNPX) contributes only a small fraction of the total nonionizing damage energy, its inclusion in the shape of the damage across the array is significant. The Coulombic contribution was calculated using MRED [3-5], a Geant4 [4,6] application. The comparison with the dark current distribution strongly suggests that mechanisms which are not linearly correlated with nonionizing damage produced according to collision kinematics are responsible for the observed dark current increases. This has important implications for the process of predicting the on-orbit dark current response of the HgCdTe sensor array.

  9. 水溶性CdHgTe合金量子点的制备与表征%Synthesis and Characterization of Water-soluble CdHgTe Alloyed Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    王益林; 童张法; 陆建平; 黎建辉; 周立亚

    2011-01-01

    以巯基乙酸为稳定剂,在水溶液中加热CdCl2、HgCl2和NaHTe的混合物直接合成CdHgTe合金量子点.分别用荧光光谱、红外光谱、X射线衍射及透射电镜对其光谱性能、表面基团和结构形貌进行了表征.结果表明,合金量子点的发射波长在536到688 nm范围内连续可调,掺杂后量子点的发射光谱变宽,半高峰宽为70-90 nm;CdHgTe的荧光量子产率介于1.5%到6.7%之间;巯基与CdHgTe量子点表面的Cd2+离子发生键合,而使巯基乙酸结合于量子点表面;合金量子点具有闪锌矿结构;量子点分散性好,形貌呈颗粒状.%CdHgTe alloyed quantum dots (QDs) were directly synthesized in aqueous solution by heating a mixture of CdCl2, HgCl2 and NaHTe in the presence of thioglycolic acid as stabilizer. The obtained QDs were characterized by fluorescent spectroscope, fourier transform infrared spectroscope (FTIR), X-ray powder diffraction (XRD) and transmission electron microscope (TEM), respectively. The results show that the technique lead to the formation of CdHgTe alloyed QDs with broad fluorescence full-width at half-maximum (70-90 nm), moderate photoluminescence quantum yield (1.5%-6.7%), and a broad emission spectra tunable from 536 nm to 688 nm. The water-soluble alloyed QDs with thioglycolic acid modification for CdHgTe are of zinc-blended crystal structure in a sphere-like shape.

  10. Phase transition study in a [Cu2HgI4 : 0.AgI] mixed composite system

    Indian Academy of Sciences (India)

    Noorussaba; Afaq Ahmad

    2010-08-01

    A novel composite superionic system, [Cu2HgI4 : 0.AgI], ( = 0.2, 0.4, 0.6 mol wt.%), was prepared. A [Cu2HgI4] system was used as the host. Electrical conductivity was measured to study the transition behaviour at frequencies of 100 Hz, 120 Hz, 1 kHz and 10 kHz in the temperature range 90–170°C using a Gen Rad 1659 RLC Digibridge. Conductivity increased sharply during the – phase transition. Upon increasing the dopant-to-host ratio, the conductivity of the superionic system exhibited Arrhenius (thermally activated)-type behaviour. DTA, DTG, TGA and X-ray powder diffraction were performed to confirm doping effect and transition in the host. The phase transition temperature increased with an increase in the dopant concentration. Activation energies in eV for pre- and post-transition phase behaviour are also reported. Due to an interaction between [Cu2HgI4] and AgI, the addition of AgI to [Cu2HgI4] shifted the phase transition of the host [Cu2HgI4].

  11. Adsorption of Ag, Cu and Hg from aqueous solutions using expanded perlite

    International Nuclear Information System (INIS)

    The aim of the present work was to investigate the ability of expanded perlite (EP) to remove of silver, copper and mercury ions from aqueous solutions. Batch adsorption experiments were carried out and the effect of pH, adsorbent dosage, contact time and temperature of solution on the removal process has been investigated. The optimum pH for the adsorption was found to be 6.5. Adsorption of these metal ions reached their equilibrium concentration in 120, 240 and 180 min for Ag (I), Cu (II) and Hg (II) ions, respectively. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for these metal ions followed well pseudo-second-order kinetics. Using Langmuir isotherm model, maximum adsorption capacity of EP was found to be 8.46, 1.95 and 0.35 mg/g for Ag (I), Cu (II) and Hg (II) ions, respectively. Finally, the thermodynamic parameters including, the change of free energy (ΔGo), enthalpy (ΔHo) and entropy (ΔSo) of adsorption were calculated for each metal ion. The results showed that the adsorption of these metal ions on EP was feasible and exothermic at 20-50 deg. C.

  12. Microalloying with Cd of Antifriction Sn-Sb-Cu Alloys

    OpenAIRE

    Cinca Ionel Lupinca; Constantin Marta; Attila Szabo

    2012-01-01

    In the case of bimetallic sliding linings with superior technological characteristics, the use of an antifriction ally is imposed an alloy of the type Sn-Sb-Cu, which possesses a high adherence to the steel stand and a high durability in exploitation. For this reason we use the microalloying of the antifriction alloy with cadmium. The microalloying with Cd of antifriction alloys Sn-Sb-Cu determines an increase of the adhesion property of the antifriction alloy on the steel ...

  13. O K and Cu LIII edge study of itinerant holes in I2-, HgI2- and HgBr2- intercalated BSCCO(2212) single crystals

    International Nuclear Information System (INIS)

    Intercalation effect on BSCCO (2212) system, although it increases the interlayer distance and the c-axis remarkably, produces only a small change in the transition temperature. Thus, amongst other things, intercalation provides an effective method to investigate the influence of the interblock coupling. Electrons are transferred from the host Cu-O2 layers to the guest molecules I2, HgBr2, HgI2 leading to evolution of the Tc. For this we have made high resolution XANES study on the O K and Cu L3 edges to estimate the density of the doping holes. We attempt on basis of our and earlier results the evolution of Tc in these as also the much larger decrease produced in Tc for I2-intercalation for which the increase in basal spacing is the smallest of the three halides. (au)

  14. Epitaxial growth of HgCdTe 1.55-um avalanche photodiodes by molecular beam epitaxy

    Science.gov (United States)

    de Lyon, Terence J.; Baumgratz, B.; Chapman, G. R.; Gordon, E.; Hunter, Andrew T.; Jack, Michael D.; Jensen, John E.; Johnson, W.; Johs, Blaine D.; Kosai, K.; Larsen, W.; Olson, G. L.; Sen, M.; Walker, B.

    1999-04-01

    Separate absorption and multiplication avalanche photodiode (SAM-APD) device structures, operating in the 1.1 - 1.6 micrometer spectral range, have been fabricated in the HgCdTe material system by molecular-beam epitaxy. These HgCdTe device structures, which offer an alternative technology to existing III-V APD detectors, were grown on CdZnTe(211)B substrates using CdTe, Te, and Hg sources with in situ In and As doping. The alloy composition of the HgCdTe layers was adjusted to achieve both efficient absorption of IR radiation in the 1.1 - 1.6 micrometer spectral range and low excess-noise avalanche multiplication. To achieve resonant enhancement of hole impact ionization from the split-off valence band, the Hg(subscript 1-x)Cd(subscript x)Te alloy composition in the gain region of the device, x equals 0.73, was chosen to achieve equality between the bandgap energy and spin-orbit splitting. The appropriate value of this alloy composition was determined from analysis of the 300 K bandgap and spin-orbit splitting energies of a set of calibration layers, using a combination of IR transmission and spectroscopic ellipsometry measurements. MBE-grown APD epitaxial wafers were processed into passivated mesa-type discrete device structures and diode mini-arrays using conventional HgCdTe process technology. Device spectral response, dark current density, and avalanche gain measurements were performed on discrete diodes and diode mini- arrays on the processed wafers. Avalanche gains in the range of 30 - 40 at reverse bias of 85 - 90 V and array-median dark current density below 2 X 10(superscript -4) A/cm(superscript 2) at 40 V reverse bias have been demonstrated.

  15. 199mHg-derivatives of ascorbate oxidase and laccase: selective depletion and blocking of Cu-sites

    International Nuclear Information System (INIS)

    We report on the 199mHg nuclear quadrupole interaction (NQI) of Hg-derivatives of the blue oxidases ascorbate oxidase (AO) and laccase (LAC). For fully reconstituted enzymes, three different NQIs were observed. The assignment of these NQIs to the type-1, -2, and -3 Cu-sites is based on type-2 depleted AO, on blocking studies with inactive Hg prior to 199mHg/carrier reconstitution, and on the population ratio observed for fully reconstituted LAC. The NQIs for both enzymes are similar, suggesting similar Cu-sites. The type-2 site is preferentially reconstituted, contrary to expectations. Neither the blocking nor the depletion is as selective as expected. (orig.)

  16. Dislocation Reduction in HgCdTe Mesa Structures Formed on CdTe/Si

    Science.gov (United States)

    Simingalam, Sina; Pattison, James; Chen, Yuanping; Wijewarnasuriya, Priyalal; Rao, Mulpuri V.

    2016-04-01

    Mercury cadmium telluride (MCT) epilayers have been grown on CdTe/Si using molecular beam epitaxy and 8-μm-deep mesa structures formed using plasma etching. Following previous work done on etching mesas and subjecting material to thermal cycle annealing, we set out to determine the limits and underlying physics of dislocation reduction in mesa-etched and annealed MCT. This paper describes the dependence of dislocation reduction on anneal time, cycle annealing, temperature, and etch depth. We show dislocation density reduction below 3 × 105 cm-2 in 10-μm-wide, long-bar mesas along the [0bar{1}1] orientation with only a 5-min anneal at 400°C.

  17. Pressure dependence of the superconducting critical temperature of HgBa2Ca2Cu3O8+y and HgBa2Ca3Cu4O10+y up to 30 GPa

    International Nuclear Information System (INIS)

    By performing experiments on samples as pure as presently available, the origin of the reported pressure-induced Tc values well above 150 K in the mercury-based high-Tc superconductors has been investigated. For HgBa2Ca2Cu3O8+y (Hg-1223) maximum Tc values between 142 K and 146 K are obtained under pressure up to 30 GPa, while for HgBa2Ca3Cu4O10+y (Hg-1234) Tc never exceeds 121 K. To verify the reproducibility between different laboratories the pressure dependence of a sample from the same batch as the sample on which Nunez-Regueiro reported a Tc value of 157 K at 23.5 GPa has also been measured. Below 10 GPa the agreement with his results is rather good and a possible explanation for the disagreement above 10 GPa is given. It appears that the reported high Tc values in non-single-phase Hg-1223 samples are due to the presence of Hg-1234 phase impurities. Also some of the adopted definitions of Tc have led to somewhat optimistic values of Tc: The high-pressure results on Hg-1223 found in the literature are therefore reviewed and reanalyzed. copyright 1996 The American Physical Society

  18. Giant Tc shift in HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ superconductors due to Hg-Tl exchange

    International Nuclear Information System (INIS)

    The irreversibility lines of epitaxial thin films of HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ, whether deduced from field-induced magnetoresistive broadening or onset of nonhysteretic magnetization, were found to coincide when plotted against reduced temperature, showing the same exponential-decay temperature behavior for T/Tcc>0.8 (where Tc is zero-field, zero-resistivity critical temperature). These results indicate that replacing Tl with Hg has no noticeable effect on the anisotropy and suggests that Tc is not determined by anisotropy. copyright 1999 The American Physical Society

  19. High Performance MWIR and LWIR (Hg,Cd)Te Heterostructure Photodiodes

    Science.gov (United States)

    Vydyanath, H. R.; Ward, P. B.; Hampton, S. R.; Fishman, L.; Slawinski, J.; Devaney, C.; Ellsworth, J.; Krueger, T.

    1986-11-01

    (Hg,Cd)Te heterostructures have been grown liquid phase epitaxially from tellurium rich solutions on CdTe and (Cd,Zn)Te substrates. Both MWIR detectors sensitive in the 3-5 μm spectral region and LWIR detectors sensitive in the 8-14 µm spectral region have been fabricated in the heterostructures. Detectors with high RoA (low noise) and high quantum efficiency (high signal) have been fabricated. For the MWIR detectors, quantum efficiency in excess of 75 percent and RoA values in excess of 107 ohm cm2 at 80K have been demonstrated for λCo ~ 5.5 µm. For the LWIR detectors RoA values of ~ 106 ohm cm2 have been demonstrated at 40K for λCo ~ 11 μm. A correlation of the trap energies established via carrier lifetime and DLTS measurements with the depletion width - capacitance data indicates the p-n junction to be located at the heterostructure interface.

  20. The saturation boundary definition of solid components solution in cadmium-mercury-tellurium alloys of different compositions along CdTe-HgTe quasibinary cut

    International Nuclear Information System (INIS)

    The extent of solutions region during mixing is studied from the line of CdTe-HgTe cut both in the direction of Te excess and in the direction of metal sum (Cd+Hg) excess. The study was carried out by modelling the equilibrium of point defect ensemble in CdTe-HgTe solid solutions of different composition along the line of quasibinary cut of Cd-TeHg ternary system. The problem was solved in binary compounds - mercury and cadmium tellurides. The position of components solubility volume is determined for the first time. 12 refs.; 2 figs.; 2 tabs

  1. Sequencing Batch Reactor (SBR) for the removal of Hg2+ and Cd2+ from synthetic petrochemical factory wastewater

    International Nuclear Information System (INIS)

    Highlights: → We assessed SBR performances to treat synthetic wastewater containing Hg2+ and Cd2+. → SBR was able to remove 76-90% of Hg2+ and 96-98% of Cd2+. → COD removal efficiency and MLVSS was affected by Hg2+ and Cd2+ concentrations. → Removal was not only biological process but also by biosorption process of sludge. - Abstract: Petrochemical factories which manufacture vinyl chloride monomer and poly vinyl chloride (PVC) are among the largest industries which produce wastewater contains mercury and cadmium. The objective of this research is to evaluate the performance of a lab-scale Sequencing Batch Reactor (SBR) to treat a synthetic petrochemical wastewater containing mercury and cadmium. After acclimatization of the system which lasted 60 days, the SBR was introduced to mercury and cadmium in low concentrations which then was increased gradually to 9.03 ± 0.02 mg/L Hg and 15.52 ± 0.02 mg/L Cd until day 110. The SBR performance was assessed by measuring Chemical Oxygen Demand, Total and Volatile Suspended Solids as well as Sludge Volume Index. At maximum concentrations of the heavy metals, the SBR was able to remove 76-90% of Hg2+ and 96-98% of Cd2+. The COD removal efficiency and MLVSS (microorganism population) in the SBR was affected by mercury and cadmium concentrations in influent. Different species of microorganisms such as Rhodospirilium-like bacteria, Gomphonema-like algae, and sulfate reducing-like bacteria were identified in the system. While COD removal efficiency and MLVSS concentration declined during addition of heavy metals, the appreciable performance of SBR in removal of Hg2+ and Cd2+ implies that the removal in SBR was not only a biological process, but also by the biosorption process of the sludge.

  2. Molecular-beam epitaxy growth and in situ arsenic doping of p-on-n HgCdTe heterojunctions

    Science.gov (United States)

    Arias, Jose; Zandian, M.; Pasko, J. G.; Shin, S. H.; Bubulac, L. O.; DeWames, R. E.; Tennant, W. E.

    1991-02-01

    In this paper we present, results on the growth of in situ doped p-on-n heterojunctions on HgCdTe epilayers grown on (211)B GaAs substrates by molecular-beam epitaxy (MBE). Long wavelength infrared (LWIR) photodiodes made with these grown junctions are of high performance. The n-type MBE HgCdTe/GaAs alloy epilayer in these structures was grown at Ts=185 °C and it was doped with indium (high 1014 cm-3 range) atoms. This epilayer was directly followed by the growth, at Ts=165 °C, of an arsenic-doped (1017-1018 cm-3 ) HgTe/CdTe superlattice structure which was necessary to incorporate the arsenic atoms as acceptors. After the structure was grown, a Hg annealing step was needed to interdiffuse the superlattice and obtain the arsenic-doped p-type HgCdTe layer above the indium-doped layer. LWIR mesa diodes made with this material have 77 K R0A values of 5×103, 81, 8.5, and 1.1 Ω cm2 for cutoff wavelengths of 8.0, 10.2, 10.8, and 13.5 μm, respectively; the 77 K quantum efficiency values for these diodes were greater than 55%. These recent results represent a significant step toward the demonstration of MBE as a viable growth technique for the in situ fabrication of large area LWIR focal plane arrays.

  3. Thermoelectric properties of MBE-grown HgCdTe-based superlattices from 100K to 300K

    Science.gov (United States)

    Zhang, Kejia; Yadav, Abhishek; Shao, Lei; Bommena, Ramana; Zhao, Jun; Velicu, Silviu; Pipe, Kevin P.

    2016-07-01

    We report on the thermoelectric properties of long-period HgCdTe superlattices (MCT SLs) from cryogenic temperature to room temperature. We find that the thermal conductivity is lower than the alloy value especially at low temperatures, the electrical conductivity is similar to that of alloy films, and the Seebeck coefficient is comparable to other SLs. Calculations based on Rytov's elastic model show that the phonon group velocity is reduced due to folding by more than a factor of two relative to its value in bulk CdTe or HgTe. Thermal conductivity is found to be relatively constant over a wide range of temperatures.

  4. Quantitative damage depth profiles in arsenic implanted HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Lobre, C., E-mail: clement.lobre@cea.fr [CEA-Leti, MINATEC, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Jalabert, D. [CEA-INAC/UJF-Grenoble 1 UMR-E, MINATEC, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Vickridge, I.; Briand, E.; Benzeggouta, D. [Institut des NanoSciences de Paris, UMR 7588 du CNRS, Universite de Pierre et Marie Curie, Paris (France); Mollard, L. [CEA-Leti, MINATEC, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Jouneau, P.H. [CEA-INAC/UJF-Grenoble 1 UMR-E, MINATEC, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Ballet, P. [CEA-Leti, MINATEC, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France)

    2013-10-15

    Rutherford backscattering experiments under channeling conditions (RBS-c) have been carried out on Hg{sub 0.77}Cd{sub 0.23}Te (MCT) layers implanted with arsenic. Accurate damage profiles have been extracted through a simple formalism for implanted and annealed layers. Quantitative damage profiles are correlated with structural defects observed by bright-field scanning transmission electron microscopy (BF-STEM) and chemical composition measured by secondary ion mass spectrometry (SIMS). Evolution of damage for increasing ion implantation fluence has been investigated by these three complementary techniques. Evidence is found of irradiation induced annealing during implantation. A fast damage recovery has been observed for post-implantation thermal anneals. In the case of an implanted layer annealed during 1 h, the damage profile, associated with arsenic concentration measurements, indicates the presence of complexes involving arsenic.

  5. Surface energies for molecular beam epitaxy growth of HgTe and CdTe

    Science.gov (United States)

    Berding, M. A.; Krishnamurthy, Srinivasan; Sher, A.

    1991-10-01

    We present results for the surface binding energies for HgTe and CdTe that will serve as input for molecular beam epitaxy growth models. We have found that the surface binding energies are surface orientation dependent and are not simply proportional to the number of first-neighbor bonds being made to the underlying layer. Moreover, because of the possibility of charge transfer between cation and anion surface states, one may have large differences between the binding energy for the first and the last atom in a given layer, and these differences will be different for the narrow-gap, less ionic materials than for the wide gap, ionic materials. We also find that the surface states associated with an isolated surface atom or vacancy are extended in materials with small gaps and small effective masses, and thus call into question the modeling of surface binding by simple pair interactions.

  6. Numerical Simulation of the Modulation Transfer Function in HgCdTe Detector Arrays

    Science.gov (United States)

    Pinkie, Benjamin; Bellotti, Enrico

    2014-08-01

    In this work, we develop a method for simulating the modulation transfer function (MTF) of infrared detector arrays, which is based on numerical evaluation of the detector physics. The finite-difference time-domain and finite element methods are used to solve the electromagnetic and electrical equations for the device, respectively. We show how the total MTF can be deconvolved to examine the effects of specific physical processes. We introduce the MTF area difference and use it to quantify the effectiveness of several crosstalk mitigation techniques in improving the system MTF. We then apply our simulation methods to two-thirds generation mercury cadmium telluride (HgCdTe) detector architectures. The methodology is general, can be implemented with commercially available software, has experimentally realizable analogs, and is extendable to other material systems and device designs.

  7. Experimental determination of diffusion length in SWIR HgCdTe photodiodes

    Science.gov (United States)

    Jia, Jia; Chen, Guibin; Li, Xiangyang; Gong, Haimei

    2005-01-01

    Minority carrier diffusion length is a key parameter of material quality and gives an indication of diode performance. It is also one important parameter when considering the increase of the effective optical sensitive area caused by the lateral diffusion and the crosstalk between individual detectors on a focal plane array (FPA). In this paper, we perform diffusion length measurements with two methods on short wavelength infrared (SWIR) HgCdTe photovoltaic devices. One method is based on the different behaviors of electrons and holes in a variation magnetic field B and their effects on the saturation current density J0. The other method is an optical characterization technique called Laser Beam Induced Current (LBIC). The results were in good agreement with each other.

  8. Levels Of Heavy Metals (Hg, Pb, Cd, And Cr In Tissues Of Trachurus Trachurus

    Directory of Open Access Journals (Sweden)

    Enkeleda Ozuni

    2012-09-01

    Full Text Available The study was carried out to monitor the concentration level of mercury, lead, cadmium and chrome in different tissues of Trachurus trachurus (Horse mackerel. The concentration level of heavy metals was measured by using atomic absorption spectrophotometer (AAS. Concentrations of heavy metals in muscle tissue and liver of this animal ranged as follows: Hg 0.032-0.106; Cd nd-0.067 mg/kg wet weight; Pb and Cr resulted always below the detection level (nd in all tissue samples. According to the results the concentration levels of heavy metals measured in the muscle tissue was lower than the maximum permitted level for human consumption set by EC and Albanian regulation. The results obtained from the study indicate that heavy metal levels are in acceptable limits, so this product can be used as food for human consumption.

  9. Electronic structure and Compton profiles of CdO and HgO

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Gopal; Raykar, Veera [Department of Physics, Mewar University, Chittorgarh 312001, Rajasthan (India); Tiwari, Shailja; Dashora, Alpa; Ahuja, Babu Lal [Department of Physics, University College of Science, M. L. Sukhadia University, Udaipur 313002, Rajasthan (India)

    2011-01-15

    We present the first ever measured experimental electron momentum densities of CdO and HgO at an intermediate resolution using 20 Ci{sup 137}Cs Compton spectrometer. The measurements are compared with the theoretical Compton profiles using density functional theory (DFT) and hybridization of DFT with the Hartree-Fock as embodied in linear combination of atomic orbitals (LCAO) scheme. In addition, we have also calculated the energy bands and density of states using the full potential linearized augmented plane wave method and the LCAO schemes. It is seen that the hybridization scheme, which overestimates the band gap, gives a better agreement with the experimental profiles. A comparative nature of bonding is also discussed in terms of equal-valence-electron-density scaling of both the experimental profiles and valence charge densities. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Measured thermal diffusivity of Hg(1-x)Cd(x)Te solids and melts

    Science.gov (United States)

    Holland, L. R.; Taylor, R. E.

    1983-01-01

    The thermal diffusivity of Hg(1-x)Cd(x)Te melts is found to rise rapidly with temperature to values characteristic of metals. Solid and melt diffusivities for values of x from 0 to 0.3 and over a temperature range from 150 to 900 C have been determined by the laser flash method of Parker, Taylor, and Cowan. The diffusivity decreases from a maximum at x = 0 in both the solid and the liquid, with the values observed at x = 0.3 being about 40 percent of those for x = 0. The solid diffusivity for x = 0 is 1.7 sq mm/s at 150 C, decreasing to 0.7 sq mm/s at the melting point. The x = 0 liquid diffusivity increases from 0.7 sq mm/s at the melting point to 3.5 sq mm/s at 900 C.

  11. Quantitative damage depth profiles in arsenic implanted HgCdTe

    International Nuclear Information System (INIS)

    Rutherford backscattering experiments under channeling conditions (RBS-c) have been carried out on Hg0.77Cd0.23Te (MCT) layers implanted with arsenic. Accurate damage profiles have been extracted through a simple formalism for implanted and annealed layers. Quantitative damage profiles are correlated with structural defects observed by bright-field scanning transmission electron microscopy (BF-STEM) and chemical composition measured by secondary ion mass spectrometry (SIMS). Evolution of damage for increasing ion implantation fluence has been investigated by these three complementary techniques. Evidence is found of irradiation induced annealing during implantation. A fast damage recovery has been observed for post-implantation thermal anneals. In the case of an implanted layer annealed during 1 h, the damage profile, associated with arsenic concentration measurements, indicates the presence of complexes involving arsenic

  12. Investigation of trap levels in HgCdTe IR detectors through low frequency noise spectroscopy

    International Nuclear Information System (INIS)

    Low frequency noise spectroscopy is a valuable tool for studying narrow gap semiconductor materials and devices. In the paper, the method of traps investigation with low frequency noise spectroscopy was presented, together with quantitative analysis of the results obtained for high-operating-temperature, fast response, Hg1−xCdxTe mid-wavelength infrared detectors. The hole trap levels in these devices are Cd-content independent and take the value E T ≅ 140 meV or E T ≅ 40 meV. The level at E T ≅ 140 meV was found for almost all tested detectors. The level around E T = 40 meV was found in two samples. Apart from the hole traps, three electron traps were also found. Their energy levels follow the trend lines E T = 0.35E g(x) and E T = 0.75E g(x). All trap energies are consistent with the results reported in the literature for Hg1−xCdxTe devices. (paper)

  13. B+ Ion Implanted n+ on P HgCdTe Photovoltaic Arrays

    Science.gov (United States)

    Shi, Yanli

    2005-10-01

    B+ ion implantation technology has been utilized to fabricate n+ on P HgCdTe photovoltaic arrays with the HgCdTe epitaxial materials grown by the liquid phase epitaxial method. The effects of implanting energy and dose on doping profile and approximate junction depth were calculated in detail; the calculated results are well consistent with the measurement results by the second ion mass spectrum experimental technique (SIMS). The 10×10 photodiode arrays in which each pixel size is nominally 20×20 μm2 and the pitch is 30 μm were made to investigate the electro-optic performance of devices. The device characterization such as array uniformity and optical crosstalk was nondestructively investigated using a scanning laser microscope. The two-dimensional maps of laser beam induced current (LBIC) signal have shown good uniformity for the fabricated arrays, and there is no optical crosstalk between the arrays for the B+ ion implantation conditions used at the implanting energy of 130 KeV and the dose of 2×1014 cm2. The primary performance of photodiodes the zero bias dynamic resistance junction area product R0A, infrared response spectrum, and the detectivity D* have been measured, and the typical values for the test photodiodes with cutoff wavelength of 9.2 μm measured at 77°K are: R0A = 13.5'Ω.cm2, average blackbody detectivity D* = 7.18×1010 cm Hz1/2W-1. By further optimizing the implantation conditions and the quality of materials, excellent performances of photovoltaic detectors can be expected.

  14. Linear mode photon counting with the noiseless gain HgCdTe e-avalanche photodiode

    Science.gov (United States)

    Beck, Jeffrey D.; Scritchfield, Richard; Mitra, Pradip; Sullivan, William W.; Gleckler, Anthony D.; Strittmatter, Robert; Martin, Robert J.

    2014-08-01

    A linear mode photon counting focal plane array using HgCdTe mid-wave infrared (MWIR) cutoff electron initiated avalanche photodiodes (e-APDs) has been designed, fabricated, and characterized. The broad spectral range (0.4 to 4.3 μm) is unique among photon counters, making this a "first of its kind" system spanning the visible to the MWIR. The low excess noise [F(M)≈1] of the e-APDs allows for robust photon detection while operating at a stable linear avalanche gain in the range of 500-1000. The readout integrated circuit (ROIC) design included a very high gain-bandwidth product resistive transimpedance amplifier (3×1013 Ω-Hz) and a 4 ns output digital pulse width comparator. The ROIC had 16 high-bandwidth analogs and 16 low-voltage differential signaling digital outputs. The 2×8 array was integrated into an LN2 Dewar with a custom leadless chip carrier and daughter board design that preserved high-bandwidth analog and digital signal integrity. The 2×8 e-APD arrays were fabricated on 4.3 μm cutoff HgCdTe and operated at 84 K. The measured dark currents were approximately 1 pA at 13 V bias where the measured avalanche photodiode gain was 500. This translates to a predicted dark current induced dark count rate of less than 20 KHz. Single photon detection was achieved with a photon pulse signal-to-noise ratio of 13.7 above the amplifier noise floor. A photon detection efficiency of 50% was measured at a photon background limited false event rate of about 1 MHz. The measured jitter was in the range of 550-800 ps. The demonstrated minimum time between distinguishable events was less than 10 ns.

  15. Capacitance–voltage characteristics of metal–insulator–semiconductor structures based on graded-gap HgCdTe with various insulators

    International Nuclear Information System (INIS)

    Metal–insulator–semiconductor structures based on HgCdTe are grown by molecular-beam epitaxy. Near-surface graded-gap layers with a high CdTe content are inserted on both sides of the epitaxial HgCdTe film. The capacitance–voltage characteristics of these structures are studied experimentally. The main characteristics of these graded-gap HgCdTe structures are determined taking into account the effect of the non-uniform composition of the near-surface layers on the measured parameters. The capacitance–voltage characteristics of the graded-gap HgCdTe structures with various insulators are examined and the densities of surface states, densities of fixed and mobile charges are evaluated. The properties of the interface for CdTe grown in situ are found to be fairly good. We found that for structures based on HgCdTe–CdTe typical of very low density of mobile charges, the density of fixed charge does not exceed a 5.5 × 1010 cm−2. - Highlights: ► The metal–insulator–semiconductor structures based on HgCdTe were studied. ► A method is proposed for investigation of these graded-gap structures. ► The properties of the interface HgCdTe with some insulators were investigated. ► The properties of the interface for CdTe are found to be fairly good.

  16. Cu-doped CdS and its application in CdTe thin film solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Yi [School of Automation, Wuhan University of Technology, Wuhan, Hubei 430070 (China); College of Electronic and Information Engineering, Hankou University, Wuhan, Hubei 430212 (China); Yang, Jun; Yang, Ruilong; Shen, Kai; Wang, Dezhao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Deliang, E-mail: eedewang@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2016-01-15

    Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the V{sub Cd{sup −}} and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl{sub 2} annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

  17. Aging effect in (Hg,Cr)Sr2CuO4+δ superconductor

    International Nuclear Information System (INIS)

    The aging effect on the structural stability and superconducting properties of (Hg0.7Cr0.3)Sr2CuO4+δ was investigated, from the date of its preparation, and after every four months interval, by XRD, FT-IR and ac-susceptibility measurements. A slow degradation in diamagnetic signal was noted up to 8 months and the sample was non-superconducting at the end of 12 months. Although, XRD patterns were not altered much, but a considerable change in the a lattice parameter was noted for the aged samples suggesting a possible deterioration in the sample quality. This observation was well supported by FT-IR studies where a broad absorption band at ∼ 700 and ∼ 1450 cm-1 was clearly noticed in the case of non-superconducting samples owing to the formation of carbonate species. (author)

  18. Optical properties of thermochromic Cu2HgI4 thin films

    International Nuclear Information System (INIS)

    Cu2HgI4 powder has been prepared by precipitation from reactive chemical solutions. An electron beam gun evaporation system was used to deposit the prepared powder in a thin film form onto a Corning 7059 glass substrate. The x-ray diffraction study reveals that the as-deposited films are polycrystalline in nature and have a composition corresponding to the Cu2HgI4 single phase. The differential thermal analysis curve exhibits a strange endothermic peak located at a temperature of 355.5 K, corresponding to the phase change from the first-order phase to the fast ion-conducting phase. The phase change is accompanied by a colour change from bright-red (β-phase) to dark-brown (α-phase). The optical properties of as-deposited films have been calculated from the recorded transmission and reflection data in the spectral range 600-2500 nm. The refractive index of the as-deposited films was found to follow the two-term Cauchy dispersion relation and is adequately described by the effective-single-oscillator model. The refractive index-wavelength variation leads to the determination of the oscillator parameters Eo and Ed to be 3.113 and 9.883, respectively. The static refractive index, no(0), and static dielectric constant, εs, were also calculated as a result of the latter data and were found to be 2.043 and 4.175, respectively. The analysis of the optical absorption coefficient confirmed the presence of a direct optical transition with a band gap energy of 1.96 eV

  19. Optical properties of thermochromic Cu{sub 2}HgI{sub 4} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Salem, A M [Physics Division, National Research Center, Dokki, Cairo (Egypt); El-Gendy, Y A [Physics Department, Helwan University, Cairo (Egypt); Sakr, G B [Physics Division, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Soliman, W Z [Physics Division, National Research Center, Dokki, Cairo (Egypt)

    2008-01-21

    Cu{sub 2}HgI{sub 4} powder has been prepared by precipitation from reactive chemical solutions. An electron beam gun evaporation system was used to deposit the prepared powder in a thin film form onto a Corning 7059 glass substrate. The x-ray diffraction study reveals that the as-deposited films are polycrystalline in nature and have a composition corresponding to the Cu{sub 2}HgI{sub 4} single phase. The differential thermal analysis curve exhibits a strange endothermic peak located at a temperature of 355.5 K, corresponding to the phase change from the first-order phase to the fast ion-conducting phase. The phase change is accompanied by a colour change from bright-red ({beta}-phase) to dark-brown ({alpha}-phase). The optical properties of as-deposited films have been calculated from the recorded transmission and reflection data in the spectral range 600-2500 nm. The refractive index of the as-deposited films was found to follow the two-term Cauchy dispersion relation and is adequately described by the effective-single-oscillator model. The refractive index-wavelength variation leads to the determination of the oscillator parameters E{sub o} and E{sub d} to be 3.113 and 9.883, respectively. The static refractive index, n{sub o}(0), and static dielectric constant, {epsilon}{sub s}, were also calculated as a result of the latter data and were found to be 2.043 and 4.175, respectively. The analysis of the optical absorption coefficient confirmed the presence of a direct optical transition with a band gap energy of 1.96 eV.

  20. Growth and characterization of Hg1–CdTe epitaxial films by isothermal vapour phase epitaxy (ISOVPE)

    Indian Academy of Sciences (India)

    Manju Malhotra; Madhukar Gautam; J K Radhakrishnan; Vinod Kapoor; Sudeep Verma; Upendra Kumar; Anand Kumar; Garima Gupta; Anshu Goyal; S Sitharaman

    2005-04-01

    Growth of Hg1–CdTe epitaxial films by a new technique called asymmetric vapour phase epitaxy (ASVPE) has been carried out on CdTe and CZT substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition gradient and dislocation multiplication have been successfully solved. The epitaxial films have been electrically characterized by using the Hall effect and capacitance–voltage (–) measurements.

  1. Independently accessed back-to-back HgCdTe photodiodes: A new dual-band infrared detector

    Science.gov (United States)

    Reine, M. B.; Norton, P. W.; Starr, R.; Weiler, M. H.; Kestigian, M.; Musicant, B. L.; Mitra, P.; Schimert, T.; Case, F. C.; Bhat, Lb.; Ehsani, H.; Rao, V.

    1995-05-01

    We report the first data for a new two-color HgCdTe infrared detector for use in large dual-band infrared focal plane arrays (IRFPAs). Referred to as the independently accessed back-to-back photodiode structure, this novel dual-band HgCdTe detector provides independent electrical access to each of two spatially collocated back-to-back HgCdTe photodiodes so that true simultaneous and independent detection of medium wavelength (MW, 3-5 μm) and long wavelength (LW, 8-12 μm) infrared radiation can be accomplished. This new dual-band detector is directly compatible with standard backside-illuminated bump-interconnected hybrid HgCdTe IRFPA technology. It is capable of high fill factor, and allows high quantum efficiency and BLIP sensitivity to be realized in both the MW and LW photodiodes. We report data that demonstrate experimentally the key features of this new dual-band detector. These arrays have a unit cell size of 100 x 100 μm2, and were fabricated from a four-layer p-n-N-P HgCdTe film grown in situ by metalorganic chemical vapor deposition on a CdZnTe substrate. At 80K, the MW detector cutoff wavelength is 4.5 μm and the LW detector cutoff wavelength is 8.0 μm. Spectral crosstalk is less than 3%. Data confirm that the MW and LW photodiodes are electrically and radiometrically independent.

  2. Effect of bimetal Hg2+ and Cu2+on activity and conformation of papain%双金属Hg2+和Cu2+对木瓜蛋白酶活性与构象的影响

    Institute of Scientific and Technical Information of China (English)

    张存滢; 曾虹燕; 熊龙斌; 刘学英; Gohi A; 蔡西玲; 陈泽新

    2013-01-01

    The effect of the bimetal Hg2+ and Cu2+ on activity and conformation of papain was studied.The secondary structures of the papain treated by the bimetal ions were investigated by characterization using FT-IR,fluorescence emitting and ultraviolet-absorption spectra.The results show that there exists the dosage-response relationship between the metals and papain activity,which indicates that the bimetal ions have Hormesis effect on the activity known as “a low dose stimulation,high dose inhibition”.Under low concentration,the bimetal ions exhibit synergistic activation effect on papain activity,and Cu2+ shields Hg2+ inhibition on the activity at high concentration.On the one hand,when the concentrations of Hg2+ and Cu2+ are 10-6 and 10-8 mol/L respectively,the strongest activity effect of the bimetal ions on papain is obtained.The content of the nonrandom secondary structures (α-helix and β-sheet) of the treated papain is the highest with the secondary structures of papain being most stable,and enzymatic affinity strongest and papain activity being best.When the concentrations of Hg2+ and Cu2+ are 10-4mol/L,the ordered structure content and papain activity are the lowest.The bimetal ions unfold the enzymic protein and cause the destruction of the secondary structures.The order degree ofpapain conformation is correlated positively with the activity.%研究双金属Hg2+和Cu2+对木瓜蛋白酶活性与构象的影响.利用FT-IR、荧光发射以及紫外吸收光谱探讨Hg2+和Cu2+处理与木瓜蛋白酶二级结构变化的关系.研究结果表明:金属离子与木瓜蛋白酶活性之间存在剂量-效应关系,表现出低剂量促进,高剂量抑制的Hormesis现象.低浓度下,双金属Hg2+和Cu2+表现出协同激活效应;高浓度下,Cu2+的添加屏蔽了Hg2+的抑制作用.双金属离子浓度为10-6 mol/L Hg2+和10-8 mol/L Cu2+时,对酶的激活效应最大,其处理的木瓜蛋白酶的有序结构(α-螺旋和β-折叠)含量最高,二

  3. A simple Schiff base fluorescence probe for highly sensitive and selective detection of Hg(2+)and Cu(2.).

    Science.gov (United States)

    Zhang, Caihong; Gao, Baozhen; Zhang, Qingyan; Zhang, Guomei; Shuang, Shaomin; Dong, Chuan

    2016-07-01

    A new Schiff base fluorescent probe, 2-(4-(diphenylamine)benzylidene) thiosemicarbazide (DPBT), was synthesized and its sensing behavior to metal ions were studied by UV-vis and fluorescence spectra. The results show that DPBT can detect Hg(2+)sensitively and selectively in weakly acidic and neutral conditions, they form a complex with 2:1. The linear range was 0.095-1.14µM and the detection limit was 0.15nM. In weakly alkaline conditions, DPBT can interaction with Hg(2+)and Cu(2+)at the same time. We use "masking" reagent, NaBH4, to reduce Hg(2+)to Hg°, the detection of Cu(2+)were achieved. They formed 1:1 complex with the binding constant of 4×10(4)M(-1), a good linear relationship in 0.45-3.6µM and the detection limit of 0.17µM. The proposed method was used to determine Hg(2+)and Cu(2+)in tap water and waste water samples. PMID:27154675

  4. Cu-doped CdS and its application in CdTe thin film solar cell

    International Nuclear Information System (INIS)

    Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the VCd− and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl2 annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures

  5. Cu-doped CdS and its application in CdTe thin film solar cell

    Directory of Open Access Journals (Sweden)

    Yi Deng

    2016-01-01

    Full Text Available Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the VCd− and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl2 annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

  6. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    Science.gov (United States)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-09-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor /acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  7. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    Science.gov (United States)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-06-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor/acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  8. Visible laser discharge studies. Quarterly progress report, June 1, 1977--August 31, 1977. [CdHg vapors

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, B N; Jacob, J H; Mangano, J A

    1977-01-01

    In order to facilitate the development of metal vapor excimer lasers for inertial fusion, a theoretical study has been undertaken to identify the dominant discharge physics and kinetics for metal vapor excimers like cadmium-mercury (CdHg). Interest in such lasers have been heightened since the reported observation of gain in CdHg. An efficient method of pumping the first excited state of metal vapors is by secondary electrons created in a discharge. By discharge pumping it is possible to create mainly the lowest excited state, thereby minimizing highly excited electronic states that could photoabsorb. E-beam pumping may have difficulty in pumping metal vapor excimers due to photoabsorption by excited species. To obtain high efficiencies for CdHg system by discharge pumping three technical issues must be addressed: (1) inefficiencies in discharge pumping due to energy flow into excited states; (2) discharge stability; and (3) efficient discharge enhancement. The present effort is directed to the above issues through the development of a kinetics code that models the dominant kinetics of CdHg laser system. The bulk of the report is devoted to identification of inefficiencies in discharge pumping due to energy flow into excited states. The analysis can also be used to predict discharge stability and discharge enhancement.

  9. Characteristic of HgCdTe photoconductive detector in energy distribution measurement system of laser spot in far field

    Science.gov (United States)

    Zhang, Jianmin; Feng, Guobin; Zhao, Jun

    2008-02-01

    Detector is an important device for the far-field laser spot measuring apparatus in form of photoelectrical detector array, for it acts as an optical-to-electrical converter in measure. Two working parameters of n-type HgCdTe photoconductor are discussed in this paper. The fundamental electrical properties of n-type Hg 1-xCd xTe material are summarized and related to device performance parameters. It can be found that the dark resistance R d and the voltage responsivity R v are closely bound up with temperature T and the alloy composition x, and the normalized calculating R d-T and R v-T characteristic curves are in good agreement with experimental results at temperature below 20°C. And then the dynamic responses of a detector under laser irradiation are studied by utilizing 2-D transient heat transfer model and empirical formulas. Furthermore, experimental investigation on laser damage in PC-type HgCdTe devices is operated by a means named 1on1. Detectable change in performance parameters has not been found under the irradiation of in-band laser, at power density beyond the detector linear response zone, and time of 200s. When the power of irradiation strengthened, the dark resistance increased, and the responsivity reduced. By observing the surface morphology of HgCdTe wafers, calculating the compositions x from R d-T characteristic, the causes for performance changing has been analyzed.

  10. A modified hot wall epitaxy technique for the growth of CdTe and Hg sub 1-x Cd sub x epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Rogalski, A.; Piotrowski, J. (Inst. of Technical Physics, WAT, Warsaw (Poland)); Gronkowski, J. (Inst. of Experimental Physics, Warsaw Univ. (Poland))

    1990-10-15

    A modified hot wall epitaxy technique has been used for the growth of high quality CdTe epilayers on GaAs substrates. X-ray topographic analysis indicates that these epilayers have device quality crystalline structures. The possibility of growth of Hg{sub 1-x}Cd{sub x}Te epilayers in this deposition system has been demonstrated for the first time. (orig.).

  11. Structural and optical properties of Cd 0.7Hg 0.3Te-CdTe heterostructures grown by molecular beam epitaxy

    Science.gov (United States)

    Lentz, G.; Magnea, N.; Mariette, H.; Tuffigo, H.; Feuillet, G.; Fontenille, J.; Ligeon, E.; Saminadayar, K.

    1990-04-01

    Layers and single quantum wells of Cd xHg 1- xTe with x ⋍ 0.7 have been grown by molecular beam epitaxy. Structural analysis shows that growth free of defects (twins, dislocations) can be achieved on (111)Te Cd 0.96Zn 0.04Te substrates. The Photoluminescence analysis of the layers and the wells reveal that they are efficient light emittors in the 1.3-1.5 μm range.

  12. Water-Soluble N-Acetyl-L-cysteine-Capped CdTe Quantum Dots Application for Hg(II Detection

    Directory of Open Access Journals (Sweden)

    Tianming Yang

    2013-01-01

    Full Text Available A simple, rapid, and specific method for Hg(II detection has been proposed based on the fluorescence change of N-acetyl-L-cysteine-capped CdTe quantum dots (QDs. The presence of Hg(II ions could quench the fluorescence of QDs at 565 nm and meanwhile produce new peak in 700–860 nm wavelength range. The linear response range is 20–430 nM with the detection limit at 8.0 nM Hg(II. It was found that the position of the new peak was irrelevant to the size of QDs. Furthermore, the mechanism of the quenching of QDs fluorescence by Hg(II and the appearance of new peak in near-infrared area were also discussed and deduced through ultraviolet absorption spectrum, fluorescence spectrum, and X-ray photoelectron spectrum.

  13. Crystal growth and characterization of the model high-temperature superconductor HgBa2CuO4+δ

    International Nuclear Information System (INIS)

    Large, gram-sized single crystals of the model high-temperature superconductor HgBa2CuO4+δ are obtained and characterized. The results demonstrate the high quality of the obtained crystals and the feasibility of inelastic neutron scattering measurements. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  14. Muon spin rotation study of magnetism in multilayer HgBa2Ca4Cu5Oy superconductor

    International Nuclear Information System (INIS)

    Zero- and longitudinal-field muon-spin rotation (ZF-μSR and LF-μSR) measurements were carried out on a multi-layered HgBa2Ca4Cu5Oy (Hg-1245) superconductor with Tc of 108 K. With decreasing temperature, the observed ZF-μSR function changed from a Gaussian-type to an exponential-type below 60 K and zero field muon precession was also observed below 45 K. These μSR signals are attributed to the development of the antiferromagnetic ordering in inner CuO2 planes with a low carrier concentration. These results seem to indicate clear evidence that antiferromagnetism microscopically coexists with superconductivity in the Hg-1245 superconductor below 60 K

  15. Rhenium LIII-edge measurements on (Hg,Re)Sr2CuO4+δ system

    International Nuclear Information System (INIS)

    The nominal Hg1-xRexSr2CuO4+δ (x = 0.10 and 0.20) samples were synthesized at ∼ 920 degC in partial vacuum. From temperature dependent dc-magnetization, the x = 0.10 composition shows, Tconset of ∼ 54 K, while x = 0.20 sample is non-superconducting down to 5 K. The Re LIII-edge measurement on Hg1-xRexSr2CuO4+δ are reported here for the first time. The LIII-edge spectra of Re in 1201 phase clearly reveal Re in mixed valence (6+, 7+ predominant) state vis-a-vis 6+ in the reference ReO3. The presence of Re in mixed valence state seems to contribute to the paramagnetic effect observed in the x = 0.10, SC (Hg,Re)-1201 below 10 K in applied fields exceeding 1 kOe. (author)

  16. The growth of various buffer layer structures and their influence on the quality of (CdHg)Te epilayers

    Science.gov (United States)

    Gouws, G. J.; Muller, R. J.; Bowden, R. S.

    1993-05-01

    The suitability of various buffer layer structures on (100) GaAs for (CdHg)Te growth by organometallic vapour phase epitaxy (OMVPE) was investigated. The preferred epitaxial orientation of {(100)GaAs}/{(111)CdTe} was found to be unsuitable due to the formation of electrically active defects in the material. An intermediate ZnTe layer was used to select the (100) orientation and (100) CdTe layers were when deposited on this ZnTe layer. The quality of the resultant CdTe buffer was found to critically depend on the thickness of this intermediate ZnTe buffer, with a ZnTe thickness of approximately 500 Å producing the best CdTe buffer. (CdHg)Te epilayers grown on these {ZnTe}/{CdTe} buffers had improved electrical properties, but still suffered from a poor surface morphology. This surface morphology could be improved by using a lattice matched Cd 0.96Zn 0.04Te alloy as the final buffer layer, but the surface pyramids typical of the (100) orientation could never be completely eliminated.

  17. Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Weicheng [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China); National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Hu, Weida, E-mail: wdhu@mail.sitp.ac.cn; Lin, Tie; Yin, Fei; Zhang, Bo; Chen, Xiaoshuang; Lu, Wei [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Cheng, Xiang' ai, E-mail: xiang-ai-cheng@126.com; Wang, Rui [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China)

    2014-11-10

    In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B{sup +} ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.

  18. Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

    International Nuclear Information System (INIS)

    In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B+ ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays

  19. Structural characterization of Hg 0.78Cd 0.22Te/CdTe LPE heterostructures grown from Te solutions

    Science.gov (United States)

    Bernardi, S.; Bocchi, C.; Ferrari, C.; Franzosi, P.; Lazzarini, L.

    1991-08-01

    Hg 0.78Cd 0.22Te epilayers have been grown on CdTe substrates by slider liquid phase epitaxy. The crystal quality of the epitaxial material has been studied in as-grown structures and chemically or mechano-chemically prepared bevels using X-ray topography, double crystal diffractometry and transmission electron microscopy. It has been found that the bulk epilayers exhibit a very high crystal quality, as evidenced by the relatively low density of dislocations and the very narrow Bragg peaks. In contrast, a high dislocation and precipitate density and a broadening of the Bragg peak have been detected in the epilayer near the interface. Finally, a Hg decrease in the layer and a corresponding Hg increase in the substrate close to the interface have been observed.

  20. Assessment of HgCdTe and GaAs/GaAlAs technologies for LWIR infrared imagers

    Science.gov (United States)

    Dewames, Roger E.; Arias, Jose M.; Kozlowski, Lester J.; Williams, G. M.

    1992-12-01

    Imagery of long wavelength infrared HgCdTe and GaAs quantum well staring arrays in size 128 X 128 has been demonstrated. In this paper, we compare detector array performance characteristics, discuss the natural and technological limitations of both technologies and identify the improvements likely to be made in the near future. At this stage of feasibility demonstration in the spectral band 8 - 10 micrometers , the effective quantum efficiency in GaAs FPAs is 4% compared to 60% for HgCdTe and the responsivity is 0.08 A/W compared to 4.5 A/W. This value of 0.08 A/W is significantly below the value 2 A/W reported for single quantum well infrared photodetectors (QWIP) detectors. The peak detectivities and NE(Delta) T at 78 K are (5 X 10(superscript 9) cm (root)Hz/W, 0.037 K) and (2 X 10(superscript 11), 0.005 K) for QWIP and HgCdTe, respectively. The residual nonuniformities after two-point correction are Crosstalk is currently unsatisfactory in QWIP detector arrays, but design concepts can be used to reduce this effect. For terrestrial imaging, GaAs quantum well detector arrays most likely will need to operate at temperatures below 80 K from fundamental considerations; HgCdTe detector arrays are background limited at operating temperatures detector arrays with good yield, it is unlikely that HgCdTe will be displaced by this technology for terrestrial applications. For low background space applications at (phi) (subscript b) detectors at 40 K are background limited. This observation plus their radiation hard characteristics suggest a possible niche in strategic applications.

  1. p on n ion-implanted junctions in liquid phase epitaxy HgCdTe layers on CdTe substrates

    Science.gov (United States)

    Bubulac, L. O.; Lo, D. S.; Tennant, W. E.; Edwall, D. D.; Chen, J. C.

    1987-06-01

    The first demonstrated achievement of p-on-n activated junctions in HgCdTe material by As ion implantation is reported. The junctions were formed by treating the implant as a finite diffusion source in the postimplant anneals. The materials employed for this study were n-type In-impurity-doped LPE HgCdTe grown on CdTe. As was selected as the candidate acceptor impurity since it activated during postimplanted anneals in Hg vapor. The As concentration profile determined by secondary-ion mass spectroscopy showed that during postimplant anneal a complex diffusion mechanism redistributes the As. In the junction region the implant activation efficiency is about 50 percent. Junction depth can be controlled by varying As diffusion and background carrier concentration. Junction depths determined by the electron-beam-induced-current technique were consistent with the differential Hall electrical profiles. A p-on-n junction is shown with excellent rectification characteristics and high breakdown voltage (sharp at 2.5 V and 77 C). This was obtained from Hg(1-x)Cd(x)Te with x = 0.23.

  2. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    Science.gov (United States)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-06-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage (C-V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage (R-V) characteristics of variable-area photodiodes. The minority carrier lifetime, C-V characteristics, and R-V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  3. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    Science.gov (United States)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  4. High-Operating Temperature HgCdTe: A Vision for the Near Future

    Science.gov (United States)

    Lee, D.; Carmody, M.; Piquette, E.; Dreiske, P.; Chen, A.; Yulius, A.; Edwall, D.; Bhargava, S.; Zandian, M.; Tennant, W. E.

    2016-09-01

    We review recent advances in the HgCdTe material quality and detector performance achieved at Teledyne using molecular beam epitaxy growth and the double-layer planar hetero-junction (DLPH) detector architecture. By using an un-doped, fully depleted absorber, Teledyne's DLPH architecture can be extended for use in high operating temperatures and other applications. We assess the potential achievable performance for long wavelength infrared (LWIR) hetero-junction p-lightly-doped n or p-intrinsic- n (p-i-n) detectors based on recently reported results for 10.7 μm cutoff 1 K × 1 K focal plane arrays (FPAs) tested at temperatures down to 30 K. Variable temperature dark current measurements show that any Shockley-Read-Hall currents in the depletion region of these devices have lifetimes that are reproducibly greater than 100 ms. Under the assumption of comparable lifetimes at higher temperatures, it is predicted that fully-depleted background radiation-limited performance can be expected for 10- μm cutoff detectors from room temperature to well below liquid nitrogen temperatures, with room-temperature dark current nearly 400 times lower than predicted by Rule 07. The hetero-junction p-i-n diode is shown to have numerous other significant potential advantages including minimal or no passivation requirements for pBn-like processing, low 1/ f noise, compatibility with small pixel pitch while maintaining high modulation transfer function, low crosstalk and good quantum efficiency. By appropriate design of the FPA dewar shielding, analysis shows that dark current can theoretically be further reduced below the thermal equilibrium radiative limit. Modeling shows that background radiation-limited LWIR HgCdTe operating with f/1 optics has the potential to operate within √2 of background-limited performance at 215 K. By reducing the background radiation by 2/3 using novel shielding methods, operation with a single-stage thermo-electric-cooler may be possible. If the

  5. High-Operating Temperature HgCdTe: A Vision for the Near Future

    Science.gov (United States)

    Lee, D.; Carmody, M.; Piquette, E.; Dreiske, P.; Chen, A.; Yulius, A.; Edwall, D.; Bhargava, S.; Zandian, M.; Tennant, W. E.

    2016-05-01

    We review recent advances in the HgCdTe material quality and detector performance achieved at Teledyne using molecular beam epitaxy growth and the double-layer planar hetero-junction (DLPH) detector architecture. By using an un-doped, fully depleted absorber, Teledyne's DLPH architecture can be extended for use in high operating temperatures and other applications. We assess the potential achievable performance for long wavelength infrared (LWIR) hetero-junction p-lightly-doped n or p-intrinsic-n (p-i-n) detectors based on recently reported results for 10.7 μm cutoff 1 K × 1 K focal plane arrays (FPAs) tested at temperatures down to 30 K. Variable temperature dark current measurements show that any Shockley-Read-Hall currents in the depletion region of these devices have lifetimes that are reproducibly greater than 100 ms. Under the assumption of comparable lifetimes at higher temperatures, it is predicted that fully-depleted background radiation-limited performance can be expected for 10-μm cutoff detectors from room temperature to well below liquid nitrogen temperatures, with room-temperature dark current nearly 400 times lower than predicted by Rule 07. The hetero-junction p-i-n diode is shown to have numerous other significant potential advantages including minimal or no passivation requirements for pBn-like processing, low 1/f noise, compatibility with small pixel pitch while maintaining high modulation transfer function, low crosstalk and good quantum efficiency. By appropriate design of the FPA dewar shielding, analysis shows that dark current can theoretically be further reduced below the thermal equilibrium radiative limit. Modeling shows that background radiation-limited LWIR HgCdTe operating with f/1 optics has the potential to operate within √2 of background-limited performance at 215 K. By reducing the background radiation by 2/3 using novel shielding methods, operation with a single-stage thermo-electric-cooler may be possible. If the background

  6. Facile synthesis L-cysteine capped CdS:Eu quantum dots and their Hg2+ sensitive properties

    International Nuclear Information System (INIS)

    This paper described a facile aqueous route to prepare CdS: Eu quantum dots (QDs) with strong yellow emission using L-cysteine (L-Cys) as the capping ligands. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) confirm that the CdS:Eu QDs have a cubic structure with good crystallinity, the average diameter of the CdS:Eu QDs is about 8 nm. The traces of groups adsorbed on CdS:Eu QDs were confirmed via FT-IR spectra. In addition, the synthesis parameters including the concentration of doped Eu3+ ions, the pH value and the reaction time have influence on the optical properties of CdS:Eu QDs. The as-prepared L-Cys capped CdS:Eu QDs were used as a fluorescence probe to detect Hg2+ ions in aqueous media based on fluorescence quenching. The response of L-Cys capped CdS:Eu QDs as a fluorescence probe was linearly proportional to the concentration of Hg2+ ions in the range of 5 × 10−6 to 1 × 10−3 mol L−1 with a limit of detection of 2 × 10−6 mol L−1.

  7. 新型CdS/DNA纳米复合材料检测Hg^2+的研究%Study on New CdS/DNA Nanocomposites for Detection of Hg^2+

    Institute of Scientific and Technical Information of China (English)

    赵琎

    2011-01-01

    A new type of CdS/DNA nanocomposite was synthesized using DNA as a template. Cd^2+ and S^2- were absorbed alternately onto the negtively charged DNA backbone via electrostatic interaction. As a result, water -soluble and stable CdS wrapped DNA nanocomposi%采用模板法合成了一种新型的CdS/DNA纳米复合材料。由于DNA的磷酸骨架带负电,硫化镉过饱和溶液中Cd^2+和S^2-在DNA模板表面进行交替吸附,从而得到具有一定形貌的CdS/DNA纳米复合材料。该纳米复合材料具有良好的荧光特性和水溶性,在330nm处发射较强的荧光。利用Hg^2+对复合材料荧光猝灭的特性建立了灵敏检测废水样品中Hg^2+的方法。

  8. Cu and Cd Adsorption on Carbon Aerogel and Xerogel

    Directory of Open Access Journals (Sweden)

    Cotet L. C.

    2013-04-01

    Full Text Available Carbon aerogel (CA and xerogel (CX were proposed as new carbon adsorbent materials for Cu and Cd ions from contaminated water (synthetic water samples. These materials were prepared by a sol-gel process that involves a polycondensation of resorcinol and formaldehyde in Na2CO3 catalysis, followed by a drying step, either in supercritical conditions of CO2 to aerogel obtaining or in normal conditions to xerogel obtaining, and a pyrolytic step. Nitrogen adsorption, AFM, SEM, TEM and XRD were used for morpho-structural adsorbent investigation. Cu and Cd ions adsorption experiments were carried out in batch conditions under magnetic stirring. Adsorbent quantity and grain size influence over the adsorption efficiency were considered. Adsorption results expressed as adsorption capacities showed that prepared CA is a better adsorbent than CX. Adsorption capacities up to 14.2 mg g-1 and 8.5 mg g-1 were obtained for Cd2+ and Cu2+ adsorption on CA, respectively.

  9. Physical properties of electron beam evaporated CdTe and CdTe:Cu thin films

    International Nuclear Information System (INIS)

    In this paper, we report on physical properties of pure and Cu doped cadmium telluride (CdTe) films deposited onto corning 7059 microscopic glass substrates by electron beam evaporation technique. X-ray diffraction study showed that all the deposited films belong to amorphous nature. The average transmittance of the films is varied between 77% and 90%. The optical energy band gap of pure CdTe film is 1.57 eV and it decreased to 1.47 eV upon 4 wt. % of Cu addition, which may be due to the extension of localized states in the band structure. The refractive index of the films was calculated using Swanepoel method. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (Ed) parameters, dielectric constants, plasma frequency, and oscillator energy (Eo) of CdTe and CdTe:Cu films were calculated and discussed in detail with the light of possible mechanisms underlying the phenomena. The variation in intensity of photoluminescence band edge emission peak observed at 820 nm with Cu dopant is due to the change in surface state density. The observed trigonal lattice of Te peaks in the micro-Raman spectra confirms the p-type conductive nature of films, which was further corroborated by the Hall effect measurement. The lowest resistivity of 6.61 × 104 Ω cm was obtained for the CdTe:Cu (3 wt. %) film

  10. $^{111m}$Cd- and $^{199m}$Hg-derivatives of blue oxidases

    CERN Multimedia

    2002-01-01

    The rack-induced bonding concept (H.B.Gray & B.G.~Malmstroem, Comments Inorg. Chem, 2, 203, 1983) postulates that the bound metal ion in metalloproteins is forced to adopt a coordination geometry determined by the rigid peptide conformation of the protein. Alternatively, the metal ion could create its own favoured coordination geometry in a soft peptide conformation. In order to decide who is slave or master the changes of coordination and rigidity of metal sites in blue copper proteins due to metal and ligand exchange were studied by $^{111m}$Cd and $^{199m}$Hg $\\gamma$-$\\gamma$-perturbed angular correlation (PAC). To get a better understanding of the so called " Type 1 Copper Site " of the blue oxidases laccase (LAC) and ascorbate oxidase (AO) we concentrated our investigations on the small blue copper proteins azurin and plastocyanin. \\\\ \\\\In azurin~(Az), the metal ligand methionine 121~(M121) was replaced by several amino acids, e.g. asparagine~(N), glutamic acid~(E), via site directed mutagenesis. Di...

  11. Human biomonitoring for Cd, Hg and Pb in blood of inhabitants of the Sacco Valley (Italy

    Directory of Open Access Journals (Sweden)

    Sonia D'Ilio

    2013-03-01

    Full Text Available INTRODUCTION. The Sacco Valley (Lazio, Italy is characterized by high density population and several industrial chemical productions that during the time had led to a substantial amount of by-products. The result was a severe environmental pollution of the area and in particular of the river Sacco. In 1991, the analysis of water and soils samples of three industrial landfills revealed the presence of organochlorine compounds and heavy metals. A research project named "Health of residents living in Sacco Valley area", coordinated by the regional Department of Epidemiology, was undertaken and financed to evaluate the state of health of the population living near those polluted areas. MATERIALS AND METHODS. Cd, Hg and Pb were quantified in 246 blood samples of potentially exposed residents of the Sacco Valley by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS. RESULTS. Individuals who agreed to be sampled did not exhibit high levels of the elements. The distance from the river does not seem to be directly connected with the elements levels in blood. The contribution of these contaminants to the total intake due to ingestion of food was difficult to evaluate. The unclear trend of data would require a characterization of the polluted site with environmental sampling of different matrices.

  12. Temperature-dependent band structure of Hg1-xZnxTe-CdTe superlattices

    Science.gov (United States)

    Manassès, J.; Guldner, Y.; Vieren, J. P.; Voos, M.; Faurie, J. P.

    1991-12-01

    We present transport and far-infrared magneto-optical measurements in narrow-band-gap n-type Hg1-xZnxTe-CdTe superlattices. Hall and conductivity data obtained over a broad temperature range (1.5-300 K) show that these superlattices are semimetallic at low temperature and are degenerate intrinsic semiconductors for T>100 K, which constitutes an interesting situation in semiconductor-superlattice physics. The analysis of the data gives the Fermi energy as well as the temperature-dependent band gap, in good agreement with the calculated band structure, which predicts a semimetal-semiconductor transition induced by temperature in these heterostructures. We have measured the electron cyclotron resonances as a function of temperature with the magnetic field B applied parallel and perpendicular to the growth axis. The observed magneto-optical intraband transitions are in very satisfactory agreement with the calculated Landau levels and the Fermi energy. We show that the semimetal-semiconductor transition is characterized by an important reduction of the cyclotron mass measured with B perpendicular to the superlattice growth axis. The large variation of the conduction-band anisotropy calculated near the transition accounts for this effect.

  13. Electrical and optical characteristics of two color mid wave HgCdTe infrared detectors

    Science.gov (United States)

    Mason, Whitney; Waterman, J. R.

    1999-03-01

    Two-color mid wave triple-layer heterojunction HgCdTe detectors were studied using temperature-dependent current-voltage (I-V) measurements, temperature-dependent spectral response measurements, and temperature-dependent noise measurements. The reverse biased dark current shows diffusion-limited behavior for T>125 K. The same data show evidence for generation-recombination-type behavior for the longer wavelength junction at temperatures between 100 and 125 K. For temperatures less than 100 K, the measurements are background limited by photon flux, even though these measurements are performed at nominal zero background. The upper junction shows soft reverse breakdown voltages on the order of about 250 mV, while the bottom junction shows no breakdown for Vcrosstalk was less than 3%. At 80 K, the frequency-dependent noise of the shorter wavelength junction showed no dependence on bias, while for the longer wavelength junction, the noise at lower frequencies increased with bias. There is no difference in the noise characteristics when either the photon flux or the temperature is increased.

  14. Two-color HgCdTe infrared staring focal plane arrays

    Science.gov (United States)

    Smith, Edward P.; Pham, Le T.; Venzor, Gregory M.; Norton, Elyse; Newton, Michael; Goetz, Paul; Randall, Valerie; Pierce, Gregory; Patten, Elizabeth A.; Coussa, Raymond A.; Kosai, Ken; Radford, William A.; Edwards, John; Johnson, Scott M.; Baur, Stefan T.; Roth, John A.; Nosho, Brett; Jensen, John E.; Longshore, Randolph E.

    2003-12-01

    Raytheon Vision Systems (RVS) in collaboration with HRL Laboratories is contributing to the maturation and manufacturing readiness of third-generation two-color HgCdTe infrared staring focal plane arrays (FPAs). This paper will highlight data from the routine growth and fabrication of 256x256 30μm unit-cell staring FPAs that provide dual-color detection in the mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) spectral regions. FPAs configured for MWIR/MWIR, MWIR/LWIR and LWIR/LWIR detection are used for target identification, signature recognition and clutter rejection in a wide variety of space and ground-based applications. Optimized triple-layer-heterojunction (TLHJ) device designs and molecular beam epitaxy (MBE) growth using in-situ controls has contributed to individual bands in all two-color FPA configurations exhibiting high operability (>99%) and both performance and FPA functionality comparable to state-of-the-art single-color technology. The measured spectral cross talk from out-of-band radiation for either band is also typically less than 10%. An FPA architecture based on a single mesa, single indium bump, and sequential mode operation leverages current single-color processes in production while also providing compatibility with existing second-generation technologies.

  15. Assessment of Cu, Pb and Hg Contamination in Bottom Sediments Of Surface Water in XuZhou

    Institute of Scientific and Technical Information of China (English)

    王晓; 韩宝平; 朱雪强

    2004-01-01

    Pollution of heavy metals Cu,Pb and Hg is assessed using geo-accumulation index in this paper. The result shows that the bottom sediments of surface water in Xuzhou is polluted by these heavy metals to deferent degrees, of which the Jinma River is the most serious, and then the Kuihe River, the abandoned Yellow River, and the Jinghang Canal. The Yunlong Lake has also been polluted by Hg. The three kinds of heavy metals in the order of concentration is Hg>Cu>Pb. The pollution degree and the type of element is closely related with industrial structure in Xuzhou.

  16. Shubnikov-de Haas oscillations and quantum hall effect in modulation-doped HgTe-CdTe superlattices

    Science.gov (United States)

    Hoffman, C. A.; Meyer, J. R.; Arnold, D. J.; Bartoli, F. J.; Lansari, Y.; Cook, J. W.; Schetzina, J. F.

    1991-10-01

    We have investigated quantum oscillations in the magneto-transport properties of HgTe-CdTe superlattices grown by molecular-beam epitaxy. Modulation doping was achieved by incorporating either indium donors or arsenic acceptors into the CdTe barriers. In a p-type sample, quantized plateaus were observed in the Hall conductivity down to i=3 conduction channels. Since the structure contained 200 periods, this implies that the quantized holes populated only a small fraction of the total superlattice volume. A mixed conduction analysis of the nonoscillating component of magneto-transport data provided confirming evidence for the presence of a two-dimensional holes gas with the appropriate density in addition to the supperlattice holes. Previous reports of the quantum Hall effect in HgTe-CdTe also yielded i far less than the total number of superlattice wells. In contrast, an n-type sample from the present study displayed a single quantum Hall plateau at i≊140, indicating that in this case most of the 200 superlattice periods contributed to the conduction. We argue that this represents the first observation of the qunatum Hall effect associated with carriers distributed through the interior of a HgTe-CdTe superlattice.

  17. Receiver Performance of CO2 and CH4 Lidar with Low Noise HgCdTe Avalanche Photodiodes

    Science.gov (United States)

    Sun, X.; Abshire, J. B.

    2012-12-01

    NASA Goddard Space Flight Center (GSFC) is currently developing CO2 lidars at 1.57 μm wavelength for the Active Sensing of CO2 Emission over Days, Nights, and Seasons (ASCENDS) mission. One of the major technical challenges is the photodetectors that have to operate in short wave infrared (SWIR) wavelength region and sensitive to received laser pulses of only a few photons. We have been using InGaAs photocathode photomultiplier tubes (PMT) in our airborne simulator of the CO2 lidar that can detect single photon with up to 10% quantum efficiency at time with the PMTs. There may also be a lifetime limitation with the InGaAs photocathode PMT for a multi-year space mission. We have been developing HgCdTe avalanche photodiode (APD) SWIR detector systems with DRS Technologies, Reconnaissance, Surveillance and Target Acquisition (RSTA) Division as an alternative photodetector for our CO2 lidars. The new HgCdTe APDs have typically a >50% quantum efficiency, including the effect of fill-factor, from 0.9 to 4.5 μm wavelength. DRS RSTA will integrate a low noise read-out integrated circuit (ROIC) with the HgCdTe APD array into a low noise analog SWIR detector with near single photon sensitivity. The new HgCdTe APD SWIR detector assembly is expected to improve the receiver sensitivity of our CO2 lidar by at least a factor of two and provide a sufficient wide signal dynamic range. The new SWIR detector systems can also be used in the CH4 lidars at 1.65 μm wavelength currently being developed at GSFC. The near infrared PMTs have diminishing quantum efficiency as the wavelength exceeds 1.6 μm. InGaAs APDs have a high quantum efficiency but too high an excess noise factor to achieve near quantum limited performance. The new HgCdTe APDs is expected to give a much superior performance than the PMTs and the InGaAs APDs. In this paper, we will give a brief description of the new HgCdTe APD assembly and present a receiver performance analysis of our CO2 lidar and a CH4 lidar with

  18. Colloidal CdSe/Cu3P/CdSe nanocrystal heterostructures and their evolution upon thermal annealing.

    Science.gov (United States)

    De Trizio, Luca; De Donato, Francesco; Casu, Alberto; Genovese, Alessandro; Falqui, Andrea; Povia, Mauro; Manna, Liberato

    2013-05-28

    We report the synthesis of colloidal CdSe/Cu(3)P/CdSe nanocrystal heterostructures grown from hexagonal Cu(3)P platelets as templates. One type of heterostructure was a sort of "coral", formed by vertical pillars of CdSe grown preferentially on both basal facets of a Cu(3)P platelet and at its edges. Another type of heterostructure had a "sandwich" type of architecture, formed by two thick, epitaxial CdSe layers encasing the original Cu(3)P platelet. When the sandwiches were annealed under vacuum up to 450 °C, sublimation of P and Cd species with concomitant interdiffusion of Cu and Se species was observed by in situ HR- and EFTEM analyses. These processes transformed the starting sandwiches into Cu2Se nanoplatelets. Under the same conditions, both the pristine (uncoated) Cu(3)P platelets and a control sample made of isolated CdSe nanocrystals were stable. Therefore, the thermal instability of the sandwiches under vacuum might be explained by the diffusion of Cu species from Cu(3)P cores into CdSe domains, which triggered sublimation of Cd, as well as out-diffusion of P species and their partial sublimation, together with the overall transformation of the sandwiches into Cu(2)Se nanocrystals. A similar fate was followed by the coral-like structures. These CdSe/Cu(3)P/CdSe nanocrystals are therefore an example of a nanostructure that is thermally unstable, despite its separate components showing to be stable under the same conditions. PMID:23557168

  19. EXAFS in La2Cu1-xMxO4 (M = Cd,Ga)

    International Nuclear Information System (INIS)

    This paper reports on the local structure in La2Cu0.9Ga0.1O4 and La2cu0.9Cd0.1 that has been studied by Extended X-Ray Absorption Fine Structure (EXAFS) at the Cu, Ga and Cd K-edges. The results indicate that the Ga atoms, effective in suppressing Tc in La2CuO4 derived superconductors, induce structural distortions and seem not to be properly substituted at Cu sites. On the other hand, the Cd atoms, having a weak effect on Tc, substitute for Cu with small changes in the structure

  20. Nondestructive Characterization of Residual Threading Dislocation Density in HgCdTe Layers Grown on CdZnTe by Liquid-Phase Epitaxy

    Science.gov (United States)

    Fourreau, Y.; Pantzas, K.; Patriarche, G.; Destefanis, V.

    2016-05-01

    The performance of mercury cadmium telluride (MCT)-based infrared (IR) focal-plane arrays is closely related to the crystalline perfection of the HgCdTe thin film. In this work, Te-rich, (111)B-oriented HgCdTe epilayers grown by liquid-phase epitaxy on CdZnTe substrates have been studied. Surface atomic steps are shown on as-grown MCT materials using atomic force microscopy (AFM) and white-light interferometry (WLI), suggesting step-flow growth. Locally, quasiperfect surface spirals are also evidenced. A demonstration is given that these spirals are related to the emergence of almost pure screw threading dislocations. A nondestructive and quantitative technique to measure the threading dislocation density is proposed. The technique consists of counting the surface spirals on the as-grown MCT surface from images obtained by either AFM or WLI measurements. The benefits and drawbacks of both destructive—chemical etching of HgCdTe dislocations—and nondestructive surface imaging techniques are compared. The nature of defects is also discussed. Finally, state-of-the-art threading dislocation densities in the low 104 cm-2 range are evidenced by both etch pit density (EPD) and surface imaging measurements.

  1. Distribution of Cd, Pb, As and Hg in oyster (Crassostrea iredalei) tissues and sediment and water in Lingayen Gulf

    International Nuclear Information System (INIS)

    Philippine oysters are widely used for human consumption by local and international consumers thus safety of these organisms and the environment where they are grown is of primary concern. Oysters, sediments and water samples were collected from twelve (12) strategically located stations along Lingayen Gulf and its tributary waters. This study aims to establish baseline information on metal levels of Cd, Pb, As, and Hg in oyster tissues as they relate to concentrations in the water column and sediment of Lingayen Gulf. The metal levels were determined using Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma (ICP). Significant (pAs>Hg. Moreover, As, Pb and Hg levels present in all the samples were within the acceptable limits set by local and international standards. Possible sources of metal contaminations were temporal variations, physiological capability of oysters to bind with metal species and anthropogenic activities by local communities within the coastal areas of Lingayen Gulf. (author)

  2. The Strain Derivatives of $T_c$ in HgBa$_2$CuO$_{4+\\delta}$: CuO$_2$ Plane Alone is Not Enough

    OpenAIRE

    Wang, Shibing; Zhang, Jianbo; Yan, Jinyuan; Chen, Xiao-Jia; Struzhkin, Viktor; Tabis, Wojciech; Barišic, Neven; Chan, Mun; Dorow, Chelsey; Zhao, Xudong; Greven, Martin; Mao, Wendy L.; Geballe, Ted

    2013-01-01

    The strain derivatives of $T_c$ along the $a$ and $c$ axes have been determined for HgBa$_2$CuO$_{4+\\delta}$ (Hg1201), the simplest monolayer cuprate with the highest $T_c$ of all monolayer cuprates ($T_c$ = 97 K at optimal doping). The underdoped compound with the initial $T_c$ of 65 K has been studied as a function of pressure up to 20 GPa by magnetic susceptibility and X-ray diffraction (XRD). The observed linear increase in $T_c$ with pressure is the same as previously been found for the ...

  3. Vibrational properties of homopolar and heteropolar surfaces and interfaces of the CdTe/HgTe system

    International Nuclear Information System (INIS)

    We present results of calculations for the density of vibrational modes for (001) and (111) homopolar, as well as for (011) heteropolar free surfaces of CdTe and HgTe. A rigid-ion model with a dynamical matrix parametrization including force constants up to second neighbours is used. We report on the existence of highly localized surface resonant modes at the top of the acoustic branch for CdTe and the bottom of the optical branch for HgTe. A different behaviour in the three directions analysed is found. The interface atomic planes show themselves as phonon gapless layers. The contribution of in-plane and out-of-plane vibration is analysed for both the surface and interface cases. (author). 7 refs, 7 figs

  4. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  5. Determination of a natural valence-band offset - The case of HgTe and CdTe

    Science.gov (United States)

    Shih, C. K.; Spicer, W. E.

    1987-01-01

    A method to determine a natural valence-band offset (NVBO), i.e., the change in the valence-band maximum energy which is intrinsic to the bulk band structures of semiconductors is proposed. The HgTe-CdTe system is used as an example in which it is found that the valence-band maximum of HgTe lies 0.35 + or - 0.06 eV above that of CdTe. The NVBO of 0.35 eV is in good agreement with the X-ray photoemission spectroscopy measurement of the heterojunction offset. The procedure to determine the NVBO between semiconductors, and its implication on the heterojunction band lineup and the electronic structures of semiconductor alloys, are discussed.

  6. Effect of HgI2 intercalation on Bi2Sr2CaCu2Oy: Interlayer coupling effect

    International Nuclear Information System (INIS)

    By intercalating large HgI2 molecules between the Bi2O2 layers in Bi2Sr2CaCu2Oy, the distance between the CuO2 blocks was significantly extended up to 7.2 A. The superconducting properties of this system were measured in various magnetic fields applied perpendicular to the CuO2 planes. This system showed large positional fluctuation of the vortex even far below the transition temperature due to the reduction of dimensionality. The change of the thermodynamic parameters is well explained by the model of Josephson-coupled superconductivity. However, the interlayer coupling strength did not change the transition temperature drastically, which does not support the suggestion of Wheatley, Hsu, and Anderson of coherent hopping of the valence bond pair between the CuO2 layers. copyright 1996 The American Physical Society

  7. Photoluminescence Study of Enhanced Light Emission from HgCdTe Thin Films due to a Surface Pattern

    OpenAIRE

    Haugan, Espen Tunhøvd

    2015-01-01

    HgCdTe thin film samples with a CdTe passivation layer have been grown by molecular beam epitaxy, and photolithography has been used to etch a triangular pattern of holes into the passivation layer. The enhancement in light emission from the samples due to their surface pattern has been measured by means of photoluminescence spectroscopy (PL), giving values ranging from 31 % to 163 %. PL-measurements and simulations with both the transfer matrix method and the 3D finite-difference time d...

  8. Properties of PACE-I HgCdTe Detectors in Space - the NICMOS Warm-up Monitoring Program

    OpenAIRE

    Boeker, T.

    2000-01-01

    We summarize the results of a monitoring program which was executed following the cryogen exhaustion of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) onboard the Hubble Space Telescope. During the subsequent warm-up, detector parameters such as detective quantum efficiency, dark current, bias offsets, and saturation levels have been measured over the temperature range 62K to about 100K. The measurements provide a unique database of the characteristics of PACE-I HgCdTe detect...

  9. ACUTE TOXICITIES OF CD2+, CR+6, HG2+, NI2+, AND ZN2+ TO ESTUARINE MACROFAUNA

    Science.gov (United States)

    Static acute toxicity bioassays were conducted at 20 C and 20 o/oo salinity with CdCl2-2 and one half H2O, K2CrO4, HgCl2, NiCl2-6H2O, and ZnCl2 using adults of starfish, Asterias forbesi; sandworm, Nereis virens; hermit crab, Pagurus longicarpus; softshell clam, Mya arenaria; mud...

  10. The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector

    OpenAIRE

    Haoyang Cui; Yongpeng Xu; Junjie Yang; Naiyun Tang; Zhong Tang

    2013-01-01

    The transient photovoltaic (PV) characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This ...

  11. HgCdTe e-APD detector arrays with single photon sensitivity for space lidar applications

    Science.gov (United States)

    Sun, Xiaoli; Abshire, James B.; Beck, Jeffrey D.

    2014-05-01

    A multi-element HgCdTe electron initiated avalanche photodiode (e-APD) array has been developed for space lidar. The detector array was fabricated with 4.3μm cutoff HgCdTe with a spectral response from 0.4 to 4.3 μm. We have demonstrated a 4x4 e-APD array with 80 μm square elements followed by a custom cryogenic CMOS read-out integrated circuit (ROIC). The device operates at 77K inside a small closed-cycle cooler-Dewar with the support electronics integrated in a field programmable gate array. Measurements showed a unity gain quantum efficiency of about 90% at 1.5-1.6 μm wavelength. The bulk dark current of the HgCdTe e-APD at 77K was less than 50,000 input referred electrons/s at 12 V APD bias where the APD gain was 620 and the measured noise equivalent power (NEP) was 0.4 fW/Hz1/2. The electrical bandwidth of the device was about 6 MHz, mostly limited by the ROIC, but sufficient for the lidar application. Although the devices were designed for low bandwidth pulse detections, the high gain and low dark current enabled them to be used for single photon detections. Because the APD was biased below the break-down voltage, the output is linear to the input signal and there were no nonlinear effect such as dead-time and afterpulsing, and no need for gated operation. A new series of HgCdTe e-APDs have also been developed with a much wider bandwidth ROIC and higher APD gain, which is expected to give a much better performance in single photon detections.

  12. Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts

    Science.gov (United States)

    Su, Ching-Hua

    1986-01-01

    Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.

  13. BCS-like gap structure of HgBa{sub 2}CuO{sub 4+{delta}} tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J. [Argonne National Lab., IL (United States)]|[Yale Univ., New Haven, CT (United States); Zasadzinski, J.F.; Gray, K.E.; Wagner, J.L.; Hinks, D.G. [Argonne National Lab., IL (United States); Kouznetsov, K.; Coffey, L. [Illinois Inst. of Tech., Chicago, IL (United States)

    1994-12-01

    The authors report point-contact tunneling into polycrystalline HgBa{sub 2}CuO{sub 4+{delta}} superconductors with a T{sub c} onset of 97 K using a superconducting Nb counterelectrode. These SIS tunnel junctions are of unusually high quality for cuprate superconductors, exhibiting low and flat sub-gap conductances and sharp conductance peaks as expected from a BCS density of states. These features are obtained reproducibly and are consistent with earlier published SIN results using an Au counterelectrode. Use of experimental data to simulate the performance of a quasiparticle mixer indicates that HgBa{sub 2}CuO{sub 4+{delta}} may be suitable for use in low noise heterodyne receivers operating at a few THz.

  14. Advanced methods for preparation and characterization of infrared detector materials. [crystallization and phase diagrams of Hg sub 1-x Cd sub x Te

    Science.gov (United States)

    Lehoczy, S. L.

    1979-01-01

    Crystal growth of Hg sub 1-x Cd sub x Te and density measurements of ingot slices are discussed. Radial compositional variations are evaluated from the results of infrared transmission edge mapping. The pseudo-binary HgTe-CdTe phase diagram is examined with reference to differential thermal analysis measurements. The phase equilibria calculations, based on the 'regular association solution' theory (R.A.S.) are explained and, using the obtained R.A.S. parameters, the activities of Hg, Cd, and Te vapors and their partial pressures over the pseudo-binary melt are calculated.

  15. Charge-Transfer Excitations in the Model Superconductor HgBa$_2$CuO$_{\\bf 4+\\delta}$

    OpenAIRE

    L. Lu; Zhao, X.; Chabot-Couture, G.; Hancock, J. N.; Kaneko, N; Vajk, O. P.; Yu, G.; Grenier, S.; Kim, Y. J.; Casa, D.; Gog, T.; Greven, M.

    2005-01-01

    We report a Cu $K$-edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa$_2$CuO$_{4+\\delta}$ at optimal doping ($T_{\\rm c} = 96.5 $ K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly-dispersive ($ < 0.5$ eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the exi...

  16. Preliminary study of CdTe and CdTe:Cu thin films nanostructures deposited by using DC magnetron sputtering

    International Nuclear Information System (INIS)

    Growth and properties of CdTe and CdTe:Cu thin films nanostrucures deposited by using dc magnetron sputtering are reported. Scanning electron microscope (SEM) was used to observe the surface morphologies of the thin films. At growth conditions of 250 °C and 14 W, CdTe films did not yet evenly deposited. However, at growth temperature and plasma power of 325 °C and 43 W, both CdTe and CdTe:Cu(2%) have deposited on the substrates. In this condition, the morphology of the films indicate that the films have a grain-like nanostructures. Grain size diameter of about 200 nm begin to appear on top of the films. Energy Dispersive X-rays spectroscopy (EDX) was used to investigate chemical elements of the Cu doped CdTe film deposited. It was found that the film deposited consist of Cd, Te and Cu elements. XRD was used to investigate the full width at half maximum (FWHM) values of the thin films deposited. The results show that CdTe:Cu(2%) thin film has better crystallographic properties than CdTe thin film. The UV-Vis spectrometer was used to investigate the optical properties of thin films deposited. The transmittance spectra showed that transmittance of CdTe:Cu(2%) film is lower than CdTe film. It was found that the bandgap energy of CdTe and CdTe:Cu(2%) thin films of about 1.48 eV

  17. Demonstrating the Model Nature of the High-Temperature Superconductor HgBa2CuO4+d

    Energy Technology Data Exchange (ETDEWEB)

    Barisic, Neven; Li, Yuan; Zhao, Xudong; Cho, Yong-Chan; Chabot-Couture, Guillaume; Yu, Guichuan; Greven, Martin; /SLAC, SSRL /Boskovic Inst., Zagreb /Stanford U., Phys. Dept. /Jilin U. /Stanford U., Appl. Phys. Dept.

    2008-09-30

    The compound HgBa{sub 2}CuO{sub 4+{delta}} (Hg1201) exhibits a simple tetragonal crystal structure and the highest superconducting transition temperature (T{sub c}) among all single Cu-O layer cuprates, with T{sub c} = 97 K (onset) at optimal doping. Due to a lack of sizable single crystals, experimental work on this very attractive system has been significantly limited. Thanks to a recent breakthrough in crystal growth, such crystals have now become available. Here, we demonstrate that it is possible to identify suitable heat treatment conditions to systematically and uniformly tune the hole concentration of Hg1201 crystals over a wide range, from very underdoped (T{sub c} = 47 K, hole concentration p {approx} 0.08) to overdoped (T{sub c} = 64 K, p {approx} 0.22). We then present quantitative magnetic susceptibility and DC charge transport results that reveal the very high-quality nature of the studied crystals. Using XPS on cleaved samples, we furthermore demonstrate that it is possible to obtain large surfaces of good quality. These characterization measurements demonstrate that Hg1201 should be viewed as a model high-temperature superconductor, and they provide the foundation for extensive future experimental work.

  18. Synthesis of the Hg Ba2 Ca2 Cu3 O9+x superconductor ceramic: thermodynamic analysis

    International Nuclear Information System (INIS)

    Eh-pH diagrams of the systems Hg-H2O, Ba, H2O, Ca-H2 O at 25 deg C were constructed for selected activities of the species of interest and then from these diagrams have been extracted values of the couples (activity, pH) for the predominance limits of the species for the Eh-pH level corresponding to the equilibrium of the aqueous solution with an oxygen fugacity equal to 0.21 atm. With these extracted data, the corresponding pa-pH diagrams were constructed; therein being equal to Hg, Ba, Ca or Cu. The four pa-pH diagrams were then overlapped each other and analyzed in terms of the insight into the co-precipitation from an aqueous solution containing all of them. The conclusion taken is that at a pH > 11 and moderately high concentrations of the components it is possible to co-precipitate Hg O, Cu O and Ca (OH)2, but not the barium, once the barium hydroxide is extremely soluble. So, its co-precipitation is only possible by means of the use of ammonium (our sodium) carbonate or, alternatively, through complete evaporation of the solvent. Finally, it is discussed the need for the use of high fugacity of oxygen in order to keep as much as possible the stability of the Hg O, as well as the adversity born from the presence of barium and calcium carbon in the system. (author)

  19. Optical and magneto-optic properties of HgTe/CdTe superlattices in the inverted-band semiconducting regime

    Science.gov (United States)

    Yang, Z.; Yu, Z.; Lansari, Y.; Cook, J. W.; Schetzina, J. F.

    1991-10-01

    Low temperature infrared transmission and far-infrared magneto-optic transmission experiments were completed for a series of HgTe/CdTe superlattices (SLs). The SLs studied were grown with layer thickness intentionally chosen to make the samples inverted-band semimetals or inverted-band semiconductors, a new regime of the HgTe/CdTe SL which only recently has been predicted by theory. Cyclotron resonance of electrons in the first conduction subband H1 was observed in the far-infrared magneto-transmission experiments. From these measurements electron effective masses were calculated. The optical transition from the second heavy hole subband H2 to the second conduction subband E2 was observed in the infrared transmission experiments. The H2-E2 transition energy was observed to decrease with increasing SL well width Lz. In addition, the electron effective mass was found to increase as Lz increases. Both of these observations indicate that all of the SL samples are, indeed, inverted-band SLs. This in turn implies that the valence band offset between HgTe and CdTe must be large, ˜400 meV at 4.5 K.

  20. Comparison of NaI(Tl), CdTe, and HgI2 surgical probes: physical characterization.

    Science.gov (United States)

    Barber, H B; Barrett, H H; Hickernell, T S; Kwo, D P; Woolfenden, J M; Entine, G; Ortale Baccash, C

    1991-01-01

    The physical properties of three surgical probes containing different radiation detectors are compared: a NaI(Tl) scintillator with a flexible, fiber-optic light guide, and two semiconductor detectors that operate at room temperature, CdTe and HgI2. Also compared are spectra, energy resolutions, and counting efficiencies measured at a variety of gamma-ray energies between 30 and 1000 keV. The energy resolution of the NaI probe is substantially poorer than that of either semiconductor probe due in part to light losses in coupling the scintillator to the fiber optics. The semiconductor probes have complex spectral response due to charge-carrier trapping and K x-ray escape, and not all photoelectric interactions in these detectors contribute to the useful part of the photopeak. Above 120 keV the counting efficiency for the NaI probe is an order of magnitude higher than for the CdTe and HgI2 probes. Both energy resolution and counting efficiency are slightly better for the HgI2 probe than for the CdTe probe. PMID:1870478

  1. Investigation of MIS structures with high specific capacitance in InSb and HgCdTe semiconductors

    International Nuclear Information System (INIS)

    Electrophysical properties of metall-insulator-semiconductor (MIS) structures with high capacitance per unit area based on InSb and HgCdTe have been investigated. Ta2O5, Nb2O5 and TiO2 dielectric films have been deposited by the reactive magnetron sputtering on CdHgTe with anodic sulfide films (10-20 nm) and on InSb with anodic oxide films (10-25 nm). MIS-elements with capacitance (2,5-4,0) x 10-7 F x cm-2 at 293 K and 2 x 10-7 F x cm-2 at 77 K were made. For MIS-structures with Nb2O5 film as dielectric surface the state density was 1 x 1011 eV-1 x cm-2 for HgCdTe and 5 x 1011 eV-1 x cm-2 for InSb. 10 refs.; 2 figs.; 2 tabs

  2. Simultaneous cloud point extraction of low levels of Cd, Cr and Hg in seaweed species prior to neutron activation analysis

    International Nuclear Information System (INIS)

    A one-step preconcentration cloud point extraction (CPE) method has been developed for the simultaneous determination of Cd, Cr, and Hg using a mixture of 1-(2-pyridylazo)-2-naphthol (PAN) and 1-(2-thiazolylazo)-2-naphthol (TAN) chelating agents and polyoxyethylene nonylphenylether-20 (PONPE-20) surfactant. The pH concentration of PAN and TAN, concentration of PONPE-20, ionic strength and temperature affecting the separation were optimized. The recoveries of each of the elements under the optimum conditions of pH 8.6, (PAN/TAN) = 1 X 10-4 M, (PONPE-20) = 0.1 % (m/v), ionic strength = 0.05 M KNO3, and temperature of 41 0C were > 98%. The concentrations of the elements were determined by neutron activation analysis using the Dalhousie University Slowpoke-2 reactor (DUSR) facility. The detection limits of Cd, Cr and Hg were 6.0, 3.6 and 1.2 ng g-1 respectively, and precision and accuracy of measurements were evaluated. The method was successfully applied to the simultaneous determination of Cd, Cr and Hg in fifteen Ghanaian seaweed species. (au)

  3. The dependence of superconducting signal on the synthesis protocol of (Hg, Cr)Sr2CuO4+δ

    International Nuclear Information System (INIS)

    The dependence of synthesis procedures followed for making 1201 type (Hg, Cr)Sr2CuO4+δ samples, on their superconducting properties have been evaluated by ac-susceptibility and dc-magnetization measurements. It was found that a green sample in gold tube, shows remarkably improved diamagnetic signal and inter-grain coupling than bare sample placed in the quartz tube, during synthesis. (author)

  4. Chemical bath deposition of CdS thin films doped with Zn and Cu

    Indian Academy of Sciences (India)

    A I Oliva; J E Corona; R Patiño; A I Oliva-Avilés

    2014-04-01

    Zn- and Cu-doped CdS thin films were deposited onto glass substrates by the chemical bath technique. ZnCl2 and CuCl2 were incorporated as dopant agents into the conventional CdS chemical bath in order to promote the CdS doping process. The effect of the deposition time and the doping concentration on the physical properties of CdS films were investigated. The morphology, thickness, bandgap energy, crystalline structure and elemental composition of Zn- and Cu-doped CdS films were investigated and compared to the undoped CdS films properties. Both Zn- and Cu-doped CdS films presented a cubic crystalline structure with (1 1 1) as the preferential orientation. Lower values of the bandgap energy were observed for the doped CdS films as compared to those of the undoped CdS films. Zn-doped CdS films presented higher thickness and roughness values than those of Cu-doped CdS films. From the photoluminescence results, it is suggested that the inclusion of Zn and Cu into CdS crystalline structure promotes the formation of acceptor levels above the CdS valence band, resulting in lower bandgap energy values for the doped CdS films.

  5. HgCdTe Detectors for Space and Science Imaging: General Issues and Latest Achievements

    Science.gov (United States)

    Gravrand, O.; Rothman, J.; Cervera, C.; Baier, N.; Lobre, C.; Zanatta, J. P.; Boulade, O.; Moreau, V.; Fieque, B.

    2016-09-01

    HgCdTe (MCT) is a very versatile material system for infrared (IR) detection, suitable for high performance detection in a wide range of applications and spectral ranges. Indeed, the ability to tailor the cutoff frequency as close as possible to the needs makes it a perfect candidate for high performance detection. Moreover, the high quality material available today, grown either by molecular beam epitaxy or liquid phase epitaxy, allows for very low dark currents at low temperatures, suitable for low flux detection applications such as science imaging. MCT has also demonstrated robustness to the aggressive environment of space and faces, therefore, a large demand for space applications. A satellite may stare at the earth, in which case detection usually involves a lot of photons, called a high flux scenario. Alternatively, a satellite may stare at outer space for science purposes, in which case the detected photon number is very low, leading to low flux scenarios. This latter case induces very strong constraints onto the detector: low dark current, low noise, (very) large focal plane arrays. The classical structure used to fulfill those requirements are usually p/ n MCT photodiodes. This type of structure has been deeply investigated in our laboratory for different spectral bands, in collaboration with the CEA Astrophysics lab. However, another alternative may also be investigated with low excess noise: MCT n/ p avalanche photodiodes (APD). This paper reviews the latest achievements obtained on this matter at DEFIR (LETI and Sofradir common laboratory) from the short wave infrared (SWIR) band detection for classical astronomical needs, to long wave infrared (LWIR) band for exoplanet transit spectroscopy, up to very long wave infrared (VLWIR) bands. The different available diode architectures ( n/ p VHg or p/ n, or even APDs) are reviewed, including different available ROIC architectures for low flux detection.

  6. HgCdTe Detectors for Space and Science Imaging: General Issues and Latest Achievements

    Science.gov (United States)

    Gravrand, O.; Rothman, J.; Cervera, C.; Baier, N.; Lobre, C.; Zanatta, J. P.; Boulade, O.; Moreau, V.; Fieque, B.

    2016-05-01

    HgCdTe (MCT) is a very versatile material system for infrared (IR) detection, suitable for high performance detection in a wide range of applications and spectral ranges. Indeed, the ability to tailor the cutoff frequency as close as possible to the needs makes it a perfect candidate for high performance detection. Moreover, the high quality material available today, grown either by molecular beam epitaxy or liquid phase epitaxy, allows for very low dark currents at low temperatures, suitable for low flux detection applications such as science imaging. MCT has also demonstrated robustness to the aggressive environment of space and faces, therefore, a large demand for space applications. A satellite may stare at the earth, in which case detection usually involves a lot of photons, called a high flux scenario. Alternatively, a satellite may stare at outer space for science purposes, in which case the detected photon number is very low, leading to low flux scenarios. This latter case induces very strong constraints onto the detector: low dark current, low noise, (very) large focal plane arrays. The classical structure used to fulfill those requirements are usually p/n MCT photodiodes. This type of structure has been deeply investigated in our laboratory for different spectral bands, in collaboration with the CEA Astrophysics lab. However, another alternative may also be investigated with low excess noise: MCT n/p avalanche photodiodes (APD). This paper reviews the latest achievements obtained on this matter at DEFIR (LETI and Sofradir common laboratory) from the short wave infrared (SWIR) band detection for classical astronomical needs, to long wave infrared (LWIR) band for exoplanet transit spectroscopy, up to very long wave infrared (VLWIR) bands. The different available diode architectures (n/p VHg or p/n, or even APDs) are reviewed, including different available ROIC architectures for low flux detection.

  7. Microalloying with Cd of Antifriction Sn-Sb-Cu Alloys

    Directory of Open Access Journals (Sweden)

    Cinca Ionel Lupinca

    2012-09-01

    Full Text Available In the case of bimetallic sliding linings with superior technological characteristics, the use of an antifriction ally is imposed an alloy of the type Sn-Sb-Cu, which possesses a high adherence to the steel stand and a high durability in exploitation. For this reason we use the microalloying of the antifriction alloy with cadmium. The microalloying with Cd of antifriction alloys Sn-Sb-Cu determines an increase of the adhesion property of the antifriction alloy on the steel stand. The steel stand is previously subjected to a process of degreasing with ZnCl2 and washing so that is can later be subjected to a thermal-chemical treatment of tinning.

  8. Characterization of charged defects in Cd_xHg_(1-x)Te and CdTe crystals by electron beam induced current and scanning tunneling spectroscopy

    OpenAIRE

    Panin, G. N.; Diaz-Guerra, C.; Piqueras de Noriega, Javier

    1998-01-01

    A correlative study of the electrically active defects of CdxHg1-xTe and CdTe crystals has been carried out using a scanning electron microscope/scanning tunneling microscope (SEM/STM) combined system. Charged structural and compositional defects were revealed by the remote electron beam induced current (REBIC) mode of the scanning electron microscope. The electronic inhomogeneities of the samples were analyzed with nm resolution by current imaging tunneling spectroscopy (CITS) measurements, ...

  9. Chemical stabilization and high pressure synthesis of Ba-free Hg-based superconductors, (Hg,M)Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub y}(N=1{approximately}3)

    Energy Technology Data Exchange (ETDEWEB)

    Kishio, K. [Univ. of Tokyo (Japan)]|[Kyoto Univ. (Japan); Shimoyama, J.; Hahakura, S. [Univ. of Tokyo (Japan)] [and others

    1994-12-31

    A homologous series of new Hg-based HTSC compounds, (Hg,M)Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub y} with n=1 to 3, have been synthesized. The stabilization of the pure phases have been accomplished by chemical doping of third elements such as M=Cr, Mo and Re. While the Hg1201(n=1) phase was readily obtained in this way, it was necessary to simultaneously dope Y into the Ca site to stabilize the Hg1212(n=2) phase. On the other hand, single-phase Y-free Hg1212(n=2) and Hg1223(n=3) samples were synthesized only under a high pressure of 6 GPa. In sharp contrast to the Ba-containing compounds, all the samples prepared in the present study have been quite stable during the synthesis and no deterioration in air has been observed after the preparation.

  10. Label-free detection of Cu(2+ and Hg(2+ ions using reconstructed Cu(2+-specific DNAzyme and G-quadruplex DNAzyme.

    Directory of Open Access Journals (Sweden)

    Hui Li

    Full Text Available Label-free metal ion detection methods were developed. To achieve these, a reconstructed Cu(2+-specific DNA-cleaving DNAzyme (Cu(2+-specific DNAzyme with an intramolecular stem-loop structure was used. G-quadruplex-forming G-rich sequence(s, linked at the ends of double-helix stem of an intramolecular stem-loop structure, was partly caged in an intramolecular duplex or formed a split G-quadruplex. Cu(2+-triggered DNA cleavage at a specific site decreased the stability of the double-helix stem, resulting in the formation or destruction of G-quadruplex DNAzyme that can effectively catalyze the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS-H2O2 reaction. Based on these, two label-free, cost-effective and simple Cu(2+ sensors were designed. These two sensors followed different detection modes: 'turn-on' and 'turn-off'. As for the 'turn-on' sensor, the intramolecular stem-loop structure ensured a low background signal, and the co-amplification of detection signal by dual DNAzymes (Cu(2+-specific DNAzyme and G-quadruplex DNAzyme provided a high sensitivity. This sensor enabled the selective detection of aqueous Cu(2+ with a detection limit of 3.9 nM. Visual detection was possible. Although the 'turn-off' sensor gave lower detection sensitivity than the 'turn-on' one, the characteristics of cost-effectiveness and ease of operation made it an important implement to reduce the possibility of pseudo-positive or pseudo-negative results. Combining the ability of Hg(2+ ion to stabilize T-T base mismatch, above dual DNAzymes-based strategy was further used for Hg(2+ sensor design. The proposed sensor allowed the specific detection of Hg(2+ ion with a detection of 4.8 nM. Visual detection was also possible.

  11. Synthesis protocol and superconducting properties of (Hg,Cr)Sr{sub 2}CuO{sub 4+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Balamurugan, S [Superconducting Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Selvam, P [Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai, 400 076 (India)

    2005-03-01

    In this paper, we report the study of our results on the synthesis protocol and the superconducting properties of (Hg,Cr)Sr{sub 2}CuO{sub 4+{delta}}. We have used several distinct approaches for the synthesis of good quality (Hg, Cr)/Sr-1201 samples by varying the processing parameters such as starting materials, precursor and annealing treatments as well as the sample container. The (Hg, Cr)/Sr-1201 samples were synthesized in partial vacuum, and systematically characterized by powder XRD, {chi}-T, dc-electrical-resistance and dc-magnetization measurements. XRD data confirm that they are of tetragonal Hg/Ba-1201 type structure. Good quality (Hg, Cr)/Sr-1201 samples were obtained from the sample prepared using a strontium nitrate source with a maximum T{sub c}{sup onset} {approx} 60 K, which is higher than the samples prepared using a carbonate source T{sub c}{sup onset} {approx} 56 K). It is found that T{sub c} is not affected by the subsequent Ar or O{sub 2} annealing treatment. Remarkably, the annealed samples show significant improvement in the diamagnetic transition.

  12. Spatial distribution of Cd and Cu in soils in Shenyang Zhangshi Irrigation Area (SZIA), China

    Institute of Scientific and Technical Information of China (English)

    Lina SUN; Xiao-e YANG; Wen-qing WANG; Li MA; Su CHEN

    2008-01-01

    Heavy metal contamination of soils, derived from sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides, and so on, has been of wide concern in the last several decades. The Shenyang Zhangshi Irrigation Area (SZIA) in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years. This study investigated the spatial distribution and temporal variation of soil cadmium (Cd) and copper (Cu) contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd and Cu in soils was analyzed and then the spatial distribution and temporal variation of Cd and Cu in soils were modeled using Kriging methods. The results show that long-term sewage irrigation had caused serious Cd and Cu contamination in soils. The mean and the maximum of soil Cd are markedly higher than the levels in second grade standard soil (LSGSS) in China, and the maximum of soil Cu is close to the LSGSS in China in 2004 and is more than the LSGSS in China in 1990. The contamination magnitude of soil Cd and the soil extent of Cd con- tamination had evidently increased since sewage irrigation ceased in 1992. The contamination magnitude of soil Cu and the soil extent of Cu contamination had evidently increased in topsoil, but obviously decresed in subsoil. The soil contamination of Cd and Cu was mainly related to Cd and Cu reactivation of contaminated sediments in Shenyang Xi River and the import of Cd and Cu during irrigation. The eluviation of Cd and Cu in contaminated topsoil with rainfall and irrigation water was another factor of temporal-spatial variability of Cd and Cu contamination in soils.

  13. PENINGKATAN KUALITAS FILM TIPIS CdTe SEBAGAI ABSORBER SEL SURYA DENGAN MENGGUNAKAN DOPING TEMBAGA (Cu)

    OpenAIRE

    P. Marwoto; N.M. Darmaputra; Sugianto -; Othaman, Z.; E. Wibowo; S.Y. Astuti

    2012-01-01

    Film tipis CdTe dengan doping tembaga (Cu) berkonsenterasi 2% telah berhasil ditumbuhkan di atas substrat Indium Tin Oxide (ITO) dengan metode dc magnetron sputtering. Penelitian ini dilakukan untuk mengetahui pengaruh doping Cu(2%) terhadap struktur morfologi, struktur kristal, fotoluminisensi dan resistivitas listrik film CdTe. Citra morfologi Scanning Electron Microscopy (SEM) dan hasil analisis struktur dengan X-Ray Diffraction (XRD) menunjukkan bahwa film CdTe:Cu(2%) mempunyai citra perm...

  14. Novel M(II)-Hg(II) coordination polymers generated from metal-containing building blocks M(2-pyrazinecarboxylate) 2 · (H 2O) 2 (M=Cu, Ni, Co) and HgCl 2

    Science.gov (United States)

    Dong, Yu-Bin; Smith, Mark D.; zur Loye, Hans-Conrad

    2000-12-01

    A new class of M(II)-Hg(II) (M=Cu(II), Co(II), Ni(II)) mixed-metal coordination polymers, Cu(2-pyrazinecarboxylate) 2HgCl 2 ( 4), [Co(2-pyrazinecarboxylate) 2(HgCl 2) 2] · 0.61H 2O ( 5) and [Ni(2-pyrazinecarboxylate) 2(HgCl 2) 2] · 0.77H 2O ( 6), have been prepared by self assembly of metal-containing building blocks, M(2-pyrazinecarboxylate) 2 · (H 2O) 2 (M=Cu(II), Co(II), Ni(II)), with HgCl 2. Compounds 4- 6 were characterized fully by IR, elemental analysis and single crystal X-ray diffraction. Compound 4 crystallized in the monoclinic space group C2/ c, with a=17.916(5) Å, b=7.223(2) Å, c=13.335(4) Å, β=128.726(3)°, V=1346.2(6) Å 3, Z=4. It contains alternating Hg(II) and Cu(II) metal centers that are cross-linked by 2-pyrazinecarboxylate spacers and chlorine co-ligands to generate a unique three-dimensional Hg(II)-Cu(II) mixed metal framework. Compound 5 crystallized in the triclinic space group P1¯, with a=6.3879(7) Å, b=6.6626(8) Å, c=13.2286(15) Å, α=96.339(2)°, β=91.590(2)°, γ=113.462(2)°, V=511.71(10) Å 3, Z=1. Compound 6 also crystallized in the triclinic space group P1¯, with a=6.3543(8) Å, b=6.6194(8) Å, c=13.2801(16) Å, α=96.449(2)°, β=92.263(2)°, γ=113.541(2)°, V=506.67(11) Å 3, Z=1. Compounds 5 and 6 are isostructural and in the solid state the Hg(II)⋯M(II)⋯Hg(II) units are connected by Hg 2Cl 2 linkages to produce a novel M(II)-Hg(II) (MCo(II), Ni(II)) zigzag mixed-metal chain, in which a new type of M-M'-M'-M array was observed. The metal containing building blocks, M(2-pyrazinecarboxylate) 2 · (H 2O) 2 (MCu(II), Co(II), Ni(II)), exhibit different connectivities to HgCl 2 depending on the metal cation contained within them.

  15. Active Pixel HgCdTe Detectors With Built-in Dark Current Reduction for Near-Room Temperature Operation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High sensitivity HgCdTe infrared arrays operating at 77K can now be tailored in a wide range of wavelengths from 1 to 14 microns. However, due to the cooling...

  16. Active Pixel HgCdTe Detectors With Built-in Dark Current Reduction for Near-Room Temperature Operation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High sensitivity HgCdTe infrared arrays operating at 77K can now be tailored in a wide range of wavelengths from 1 to14 um. However, the cooling requirements make...

  17. Synthesis, structural parameters and superconducting properties of 1201-type (Hg,M)Sr2CuO4+δ (M = Cr, Mo or Re): an overview

    International Nuclear Information System (INIS)

    A brief overview of the current state of development of 1201-type, Ba-free, mercury cuprates, (Hg,M)Sr2CuO4+δ (M = Cr, Mo or Re), is presented. Our focus here is confined to synthesis methods, chemical stabilization, structural parameters and superconducting properties of this Hg/Sr 1201 system. (topical review)

  18. Synthesis, structural parameters and superconducting properties of 1201-type (Hg,M)Sr{sub 2}CuO{sub 4+{delta}} (M = Cr, Mo or Re): an overview

    Energy Technology Data Exchange (ETDEWEB)

    Balamurugan, S [Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076 (India); Prakash, Om [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076 (India); Padalia, B D [Department of Physics, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076 (India); Selvam, P [Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076 (India)

    2004-10-01

    A brief overview of the current state of development of 1201-type, Ba-free, mercury cuprates, (Hg,M)Sr{sub 2}CuO{sub 4+{delta}} (M = Cr, Mo or Re), is presented. Our focus here is confined to synthesis methods, chemical stabilization, structural parameters and superconducting properties of this Hg/Sr 1201 system. (topical review)

  19. A colorimetric and ratiometric turn-on BODIPY-based fluorescent probe for double-channel detection of Cu{sup 2+} and Hg{sup 2+}

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jinlong; Ma, Xiaowei; Liu, Bin; Cai, Libo; Li, Qi; Zhang, Yeqin [College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China); Jiang, Kezhi [Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Hangzhou 310036 (China); Yin, Shouchun, E-mail: yinsc@ustc.edu [College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China)

    2013-09-15

    A colorimetric and turn-on fluorescent chemosensor (RS1) for the detection of Hg{sup 2+} and Cu{sup 2+} based on BODIPY has been synthesized. RS1 selectively binds with Hg{sup 2+} and Cu{sup 2+} ions in CH{sub 3}CN among various metal ions. RS1 shows a significant red-shift in absorption spectra from 522 nm to 581 nm for Hg{sup 2+} and 600 nm for Cu{sup 2+}, which induces naked-eye color changes from pink to purple and blue. Upon excitation at 520 nm, RS1 upon interaction with Hg{sup 2+} ions shows the increase of the ratio of fluorescent intensities (I{sub 589}/I{sub 576}) from 0.84 to 1.87, while RS1 with Cu{sup 2+} exhibits a huge increase of I{sub 610}/I{sub 576} from 0.72 to 7.87. The binding stoichiometries of RS1 with Hg{sup 2+} or Cu{sup 2+} have been determined to be 1:1 by Job's plot and ESI. The binding of RS1 with Hg{sup 2+} is chemically reversible, while the sensing processing of RS1 in response to Cu{sup 2+} ions is irreversible. Highlights: • A new colorimetric and turn-on fluorescent chemosensor (RS1) was synthesized. • RS1 exhibits different fluorescence enhancement in the presence of Hg{sup 2+} and Cu{sup 2+} upon excitation at 520 nm in CH{sub 3}CN. • The remarkable and different naked-eye visible color changes also provide RS1 as a colorimetric senor for Hg{sup 2+} and Cu{sup 2+}.

  20. Assessment of Individual and Combined Toxicities of Four Non-Essential Metals (As, Cd, Hg and Pb in the Microtox Assay

    Directory of Open Access Journals (Sweden)

    Paul B. Tchounwou

    2006-03-01

    Full Text Available Although most researches with non-essential metals (NEMs have been done with single or individual metals, in reality, organisms are often exposed to multiple contaminants at the same time through the air, food and water. In this study, we tested the toxicity of four NEMs, As, Cd, Pb, and Hg, individually and as a composite mixture using the microtox bioassay. This assay uses the reduction of bioluminescence of the bacterium Vibrio fischeri as a measure of toxicity. The concentrations of each chemical in the mixture were based on multiples of their maximum contaminant levels (MCLs set by the U.S. EPA. The highest concentration of exposure was 20 times the MCL, which translated into 200, 100, 40 and 300 ppb for As, Cd, Hg and Pb, respectively. The ratio for the mixture from these concentrations was 10:5:2:15 for As, Cd, Hg and Pb, respectively. Among the individual metals tested, the ranking of toxicity was Hg>Pb>Cd>As based on the EC50 values of 109, 455, 508 and 768 ppb for Hg, Pb, Cd and As, respectively. The EC50 for the composite mixture was 495% MCL which translated into nominal concentrations of 49, 25, 10 and 74 ppb for As, Cd, Hg, and Pb, respectively. Overall, the EC50 value of each NEM within the mixture was lower than the EC50 of the individual chemical; an evidence of synergism for the mixture. The individual toxic units (TU were 0.06, 0.05, 0.09, and 0.16 for As, Cd Hg, and Pb, respectively and the summed toxic unit (TU was 0.37 (less than 1. This study provides needed scientific data necessary for carrying out complete risk assessment of As, Cd, Hg, and Pb mixtures of some priority compounds.

  1. Optical characterization of Hg1-xCdxTe/CdTe/GaAs multilayers grown by molecular beam epitaxy

    Science.gov (United States)

    Liu, Weijun; Liu, Pulin; Shi, Guo L.; Zhu, Jing-Bing; He, Li; Xie, Qin X.; Yuan, Shixin

    1991-11-01

    The IR transmission spectra for HgCdTe/CdTe/GaAs multilayers grown by molecular-beam epitaxy were measured in the wavenumber region of 600 cm-1 - 4000 cm-1 at 300 K and 77 K. The transmission spectra were calculated taking the thickness d1 of MCT layer and the thickness d2 of CdTe layer as fitting parameters in the energy range from 600 cm-1 to 300 cm-1 below the energy gap Eg assuming the existence of abrupt interfaces between the neighboring layers. The values of d1 and d2 obtained by fitting the IR transmission spectra are in good agreement with that by transmission electron microscopy (TEM) measurement. The accurate absorption coefficient spectra were obtained and discussed in the energy region equivalent to 0.9 Eg to 4000 cm-1 taking into account the interference effects.

  2. Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta).

    Science.gov (United States)

    Lu, L; Chabot-Couture, G; Zhao, X; Hancock, J N; Kaneko, N; Vajk, O P; Yu, G; Grenier, S; Kim, Y J; Casa, D; Gog, T; Greven, M

    2005-11-18

    We report a Cu -edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa(2)CuO(4+delta) at optimal doping (T(c)=96.5 K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La(2)CuO(4), demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section. PMID:16384172

  3. Charge-Transfer Excitations in the Model Superconductor HgBa2CuO4+δ

    Science.gov (United States)

    Lu, L.; Chabot-Couture, G.; Zhao, X.; Hancock, J. N.; Kaneko, N.; Vajk, O. P.; Yu, G.; Grenier, S.; Kim, Y. J.; Casa, D.; Gog, T.; Greven, M.

    2005-11-01

    We report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa2CuO4+δ at optimal doping (Tc=96.5K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La2CuO4, demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section.

  4. Influence of annealing conditions on impurity species in arsenic-doped HgCdTe grown by molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Yue Fang-Yu; Chen Lu; Li Ya-Wei; Hu Zhi-Gao; Sun Lin; Yang Ping-Xiong; Chu Jun-Hao

    2010-01-01

    Based on our previous work, the influence of annealing conditions on impurity species in in-situ arsenic (As)doped Hg1-x>Cdx>Te (x≈0.3) grown by molecular beam epitaxy has been systematically investigated by modulated photoluminescence spectra. The results show that (I) the doped-As acting as undesirable shallow/deep levels in as grown can be optimized under proper annealing conditions and the physical mechanism of the disadvantage of high activation temperature, commonly assumed to be more favourable for As activation, has been discussed as compared with the reports in the As-implanted HgCdTe epilayers (x≈0.39), (ii) the density of VHg> has an evident effect on the determination of bandgap (or composition) of epilayers and the excessive introduction of VHg will lead to a short wavelength shift of epilayers, and (iii) the VHg prefers forming the VHg-AsHg complex when the inactivated-As (AsHg>or related) coexists in a certain density, which makes it difficult to annihilate VHg in As-doped epilayers. As a result, the bandedge electronic structures of epilayers under different conditions have been drawn as a brief guideline for preparing extrinsic p-type epilayers or related devices.

  5. Doping dependence of the charge-density-wave order in HgBa2CuO4+δ

    Science.gov (United States)

    Yu, Biqiong

    Following the original discovery of short-range charge-density-wave (CDW) order in the orthorhombic double-layer cuprate YBa2Cu3O6+δ (YBCO) below optimal doping, resonant X-ray scattering measurements have revealed that the simple tetragonal single-layer compound HgBa2CuO4+δ (Hg1201; Tc = 71 K) exhibits short-range CDW order as well. Here we report on the doping dependence of the CDW order in Hg1201 and contrast our results with the extensive data available for YBCO. Work done in collaboration with: W. Tabis, G. Yu, M.J. Veit, N. BarisŬić, M.K. Chan, C.J. Dorow, X. Zhao, M. Greven (University of Minnesota); M. Bluschke, E. Weschke (BESSY, Berlin); T. Kolodziej, I. Bialo, A. Kozlowski (AGH, Krakow); M. Hepting, H. Gretarsson, M. Le Tacon, M. Minola, B. Keimer (MPI, Stuttgart); Ronny Sutarto (CLS, Saskatoon); Y. Li (PKU, Beijing); L. Braicovich, G. Dellea, G. Ghiringhelli (CNR-SPIN, Milano); A. Kreyssig, M. Ramazanoglu, A.I. Goldman (Iowa State University and Ames Lab); T. Schmitt (PSI, Switzerland). We acknowledge the support from US Department of Energy, Office of Basic Energy Sciences.

  6. Surface studies on bimetallic thiocyanate ligand based single crystals of MnHg(SCN) 4, CdHg(SCN) 4 and ZnCd(SCN) 4

    Science.gov (United States)

    Rajesh Kumar, T.; Jeyasekaran, R.; Ravi Kumar, S. M.; Vimalan, M.; Sagayaraj, P.

    2010-12-01

    Bimetallic SCN ligand based single crystals of manganese mercury thiocyanate (MMTC), cadmium mercury thiocyanate (CMTC) and zinc cadmium thiocyanate (ZCTC) are grown by slow solvent evaporation technique. The growth mechanism and surface features are investigated by optical microscopic techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM). The laser induced surface damage measurements were carried out using a Q-switched Nd:YAG laser at 1064 nm with laser beam of 1.0 Hz and pulse duration 25 ps. The laser damage threshold values of MMTC, CMTC and ZCTC are found to be 15.9, 22.9 and 19.7 GW/cm 2, respectively. The SEM analysis of MMTC reveals the formation of elongated dendrite growth pattern caused by the fluctuations of Mn and Hg metal ligands when thiocyanate (SCN) bridges them. The etching study indicates the occurrence of different types of etch pit patterns like terraced triangles, pillars, pyramids and rods. The AFM images confirm the formation of three major hillocks with cavities in MMTC. The measured roughness values for CMTC crystal are very much lower than that of MMTC.

  7. 63Cu-NMR study in high-Tc superconductor HgBa2Ca2Cu3O8+δ

    International Nuclear Information System (INIS)

    The 63Cu nuclear transverse relaxation rates have been measured in the normal state on both square and pyramidal CuO2 planes in HgBa2Ca2Cu3O8+δ with Tc=133 K. The Gaussian component of the spin-echo decay rate, 63(1/T2G), for both sites increases with decreasing temperature, followed by a peak around T*∼150 K, indicating that the spin correlation becomes stronger with decreasing temperature. Also, it is found that the magnitude of 63(1/T2G) for a square site is larger than that for a pyramidal one, suggesting that the spin correlation in the square plane is stronger than that in the pyramidal one. (orig.)

  8. Hole Transport in Arsenic-Doped Hg1-x Cd x Te with x ≥ 0.5

    Science.gov (United States)

    Umana-Membreno, G. A.; Kala, H.; Bains, S.; Akhavan, N. D.; Antoszewski, J.; Maxey, C. D.; Faraone, L.

    2016-04-01

    Hole transport in arsenic-doped p-type Hg1-x Cd x Te epitaxial layers with x ≥ 0.5 has been studied employing Hall-effect measurements and theoretical modeling of hole scattering mechanisms. The hole transport parameters extracted from four different Hg1-x Cd x Te films with x = 0.50, 0.56-0.58, 0.65, and 0.80, were analyzed using an iterative solution of Boltzmann's transport equation. Hole mobilities in the samples with x values of 0.5 and 0.56-0.58 were found to be predominantly limited by ionized impurity scattering, and exhibited relatively high impurity compensation ratios ≥2. The sample with x = 0.65 exhibited the highest hole mobility, a low compensation ratio of 1.05, and mobility characteristics were limited predominantly by polar optical phonon scattering at temperatures ≥200 K. Hole mobility in the sample with x = 0.80 was found to be limited by polar optical phonon scattering and ionized impurity scattering (compensation ratio 1.20-1.56). Although the sample temperatures employed were not sufficiently low to unambiguously discriminate the scattering strength of static strain and dislocations, the experimental hole mobility characteristics cannot be adequately modeled if these two mechanisms are neglected. The ionization energy of the arsenic acceptor impurities was found to exhibit a quadratic dependence on the CdTe mole fraction.

  9. Minority carrier lifetimes of metalorganic chemical vapor deposition long-wavelength infrared HgCdTe on GaAs

    Science.gov (United States)

    Zucca, R.; Edwall, D. D.; Chen, J. S.; Johnston, S. L.; Younger, C. R.

    1991-10-01

    Metalorganic chemical vapor deposition (MOCVD) growth of HgCdTe on GaAs is a promising technique that overcomes the size and crystal quality limitations of CdTe substrates. An important material parameter is the minority carrier liftetime, which determines the ultimate zero bias impedance and quantum efficiency of a photodiode. We present the first systematic study of the temperature and carrier concentration dependence of minority carrier lifetimes on n-type and p-type layers of MOCVD long-wavelength infrared HgCdTe grown on GaAs substrates. The temperature dependencies of the lifetime are compared with theoretical predictions based on Auger, radiative, and Shockley-Read recombination. Excellent fits are obtained over a broad temperature range, from 20 K to room temperature. The experimental lifetimes of n-type material reach the theoretical limit imposed by Auger+radiative recombination for carrier concentrations higher than 2×1015 cm-3. For lower carrier concentrations, the measured lifetimes are shorter than those predicted from Auguer+radiative recombination, and Shockley-Read recombination must be added to the calculations. The lifetimes of arsenic-doped and vacancy-doped p-type material are Shockley-Read limited. They are one order of magnitude longer than those previously observed on vacancy-doped liquid phase epitaxy material.

  10. Development of High-Performance eSWIR HgCdTe-Based Focal-Plane Arrays on Silicon Substrates

    Science.gov (United States)

    Park, J. H.; Pepping, J.; Mukhortova, A.; Ketharanathan, S.; Kodama, R.; Zhao, J.; Hansel, D.; Velicu, S.; Aqariden, F.

    2016-06-01

    We report the development of high-performance and low-cost extended short-wavelength infrared (eSWIR) focal-plane arrays (FPAs) fabricated from molecular beam epitaxial (MBE)-grown HgCdTe on Si-based substrates. High-quality n-type eSWIR HgCdTe (cutoff wavelength ˜2.68 μm at 77 K, electron carrier concentration 5.82 × 1015 cm-3) layers were grown on CdTe/Si substrates by MBE. High degrees of uniformity in composition and thickness were demonstrated over three-inch areas, and low surface defect densities (voids 9.56 × 101 cm-2, micro-defects 1.67 × 103 cm-2) were measured. This material was used to fabricate 320 × 256 format, 30 μm pitch FPAs with a planar device architecture using arsenic implantation to achieve p-type doping. The dark current density of test devices showed good uniformity between 190 K and room temperature, and high-quality eSWIR imaging from hybridized FPAs was obtained with a median dark current density of 2.63 × 10-7 A/cm2 at 193 K with a standard deviation of 1.67 × 10-7 A/cm2.

  11. Biomonitoring of heavy metals (Cd, Hg, and Pb) and metalloid (As) with the Portuguese common buzzard (Buteo buteo).

    Science.gov (United States)

    Carneiro, Manuela; Colaço, Bruno; Brandão, Ricardo; Ferreira, Carla; Santos, Nuno; Soeiro, Vanessa; Colaço, Aura; Pires, Maria João; Oliveira, Paula A; Lavín, Santiago

    2014-11-01

    The accumulation of heavy metals in the environment may have a wide range of health effects on animals and humans. Thus, in this study, the concentrations of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in the blood and tissues (liver and kidney) of Portuguese common buzzards (Buteo buteo) were determined by inductively coupled plasma-mass spectrometer (ICP-MS) in order to monitor environmental pollution to these elements. In general, Hg and As were the elements which appeared in the highest and lowest concentrations, respectively. A highest percentage of non-detected concentration was found for blood Cd (94.6 %) but, in turn, it was the only metal that was detected in all kidney samples. The kidney was the analyzed sample which showed the highest concentrations of each element evaluated. Statistically, significant differences among blood, liver, and kidney samples were observed for As and Cd (P < 0.05). Cd concentrations in kidney and liver varied significantly with age: Adults showed higher hepatic and renal Cd concentrations than juveniles. Blood Pb concentration seems to show an association with the hunting season. Although raptors are at the top of the food chain and are thus potentially exposed to any biomagnification processes that may occur in a food web, the individuals evaluated in this study generally had low levels of heavy metals in blood and tissues. However, chronic exposure to these metals was verified. The results presented here lend weight to arguments in favor of continuous biomonitoring of metals and metalloids, since heavy metals may accumulate to levels that will pose a risk to both human health and the environment. PMID:25074364

  12. Compound pollution of Cd, Pb, Cu, Zn, and As on lowland rice

    Institute of Scientific and Technical Information of China (English)

    WUYanyu; WANGXin

    1999-01-01

    Cd, Pb, Cu, Zn, and As are typical pollutants originated from Pb-Zn mine, smelting waste water discharge/irrigation and gas emission,and they were distributed widely in China. We studied the compound pollution of Cd, Pb,Cu, Zn, and As on rice.

  13. Studies of the levels of Cd, Hg, Mn, Se and Zn in Marine Fish Species commonly available and highly consumed in Ghana

    International Nuclear Information System (INIS)

    Marine fish is one of the main sources of dietary exposure to Hg and Cd. High levels of Hg and Cd are often reported in marine fishes, creating the impression that the mere consumption of marine fish exposes humans to the toxic effects of Cd and Hg. These reports often ignore the protective effects of Se against Hg toxicity. Mn and Zn also moderate the toxic effects of Cd. Consequently, the use of the levels of Hg and Cd alone without considering the levels of Se, Mn and Zn, and their antagonistic interaction is not appropriate and leads to misinformation. Antagonistic interaction between Se-Hg, Zn-Cd, and Mn-Cd, are essential factors in evaluating the health risk associated with dietary exposure to Cd and Hg due to fish consumption. the interacton depends on the concentratiions (µmol kg-1) of the elements and the molar ratios of the respective interacting pairs of elements. This study evaluated the antagonistic interaction [through estimation of concentration (µmol kg-1), molar ratios and the health benefit value (for selenium only)] between cadmium (Cd)- manganese(Mn), cadmium (Cd)- zinc (Zn) and selenium (Se)-mercury (Hg) in the nine (9) marine fish species. This fish species are Frigate tuna (Auxis thazard), African forktail snapper (Apsilus fuscus), Bigeye forstfish (Benthodesmus elongatus), Blue runner (Caranx crysos), Atlantic herrings (Clupea harengus), Smooth puffer (Lagocephalus laevigatusP, Brown shrimps (metapenaeus monoceros), Round sardinella (Sardinella aurita) and African moonfish (Selene dorsalis). This was achieved through the determination of the concerntrations(µg g-1) of Cd and Zn by flame atomic absorption spectrometry (FAAS), Se by hydride generation atomic absorption spectrometry (HG-AAS), and Mn by instrumental neutron activation analysis (INAA) in the lyophilized fish species. Hg in the lyophilized fish species was determined by HG-AAS after extraction of Hg in the fish species as the dithizonate using dithizonu as ligand and CHCL3 as

  14. Superconductivity of 132 K in HgBa2Ca2Cu3O8+δ thin films fabricated using a cation exchange method

    International Nuclear Information System (INIS)

    A cation exchange method was applied to convert epitaxial TlBa2Ca2Cu3O8 (Tl-1223) and Tl2Ba2Ca2Cu3O10 (Tl-2223) precursor superconducting thin films to epitaxial HgBa2Ca2Cu3O8+δ (Hg-1223) films on LaAlO3 (001) substrates. While the conversion of Tl-1223 to Hg-1223 was partially successful, high-quality epitaxial Hg-1223 films were obtained from Tl-2223 precursor films. A critical transition temperature Tc of up to 132 K has been demonstrated for the Hg-1223 films, which is close to the optimal value of 135 K reported on Hg-1223 bulk samples. The critical current density Jc of the Hg-1223 films was up to 0.25 MA cm−2 at 77 K and self-field. This work represents the first success in achieving the highest-Tc epitaxial Hg-1223 films using the cation exchange method, which are promising candidates for device applications with operational temperatures significantly above the temperature of liquid nitrogen. (paper)

  15. Hg, Bi, Cu and Zn distribution in human teeth treated by dental amalgam measured by synchrotron microprobe

    International Nuclear Information System (INIS)

    Human teeth restored with dental amalgam were analysed by a synchrotron microprobe to evaluate the diffusion of its major constituents, Cu, Zn and Hg, throughout the tooth structures. We measured the elemental distribution inside the tooth from the root to the enamel, specially the region around the amalgam, after its total removal. Hg is present only in restored teeth and concentration profiles show strongly increased levels of this element close to the amalgam region, reaching 500 μg g-1 in one or two cases, decreasing strongly to the inner part of the tooth. Pb concentration profiles do not seem to be affected by metallic amalgam. Very high concentrations of Bi were found in one of the restored teeth, reaching more than 2000 μg g-1, decreasing sharply to the outer regions. The distribution of Mn, Fe, Cu and Zn was also determined in order to evaluate elemental influences by amalgam components. No significant changes in elemental concentrations were detected for Mn and Fe between healthy and restored teeth. However, the levels of Zn and Cu are increased in restored teeth. An X-ray fluorescence set-up with microprobe capabilities, 100 μm of spatial resolution and an energy of 18 keV, installed at LURE synchrotron (France) was used

  16. Hg, Bi, Cu and Zn distribution in human teeth treated by dental amalgam measured by synchrotron microprobe

    Science.gov (United States)

    Carvalho, M. L.; Marques, J. P.; Brito, J.; Casaca, C.; Cunha, A. S.

    2002-11-01

    Human teeth restored with dental amalgam were analysed by a synchrotron microprobe to evaluate the diffusion of its major constituents, Cu, Zn and Hg, throughout the tooth structures. We measured the elemental distribution inside the tooth from the root to the enamel, specially the region around the amalgam, after its total removal. Hg is present only in restored teeth and concentration profiles show strongly increased levels of this element close to the amalgam region, reaching 500 μg g -1 in one or two cases, decreasing strongly to the inner part of the tooth. Pb concentration profiles do not seem to be affected by metallic amalgam. Very high concentrations of Bi were found in one of the restored teeth, reaching more than 2000 μg g -1, decreasing sharply to the outer regions. The distribution of Mn, Fe, Cu and Zn was also determined in order to evaluate elemental influences by amalgam components. No significant changes in elemental concentrations were detected for Mn and Fe between healthy and restored teeth. However, the levels of Zn and Cu are increased in restored teeth. An X-ray fluorescence set-up with microprobe capabilities, 100 μm of spatial resolution and an energy of 18 keV, installed at LURE synchrotron (France) was used.

  17. Hg, Bi, Cu and Zn distribution in human teeth treated by dental amalgam measured by synchrotron microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, M.L. E-mail: luisa@cii.fc.ul.pt; Marques, J.P.; Brito, J.; Casaca, C.; Cunha, A.S

    2002-11-01

    Human teeth restored with dental amalgam were analysed by a synchrotron microprobe to evaluate the diffusion of its major constituents, Cu, Zn and Hg, throughout the tooth structures. We measured the elemental distribution inside the tooth from the root to the enamel, specially the region around the amalgam, after its total removal. Hg is present only in restored teeth and concentration profiles show strongly increased levels of this element close to the amalgam region, reaching 500 {mu}g g{sup -1} in one or two cases, decreasing strongly to the inner part of the tooth. Pb concentration profiles do not seem to be affected by metallic amalgam. Very high concentrations of Bi were found in one of the restored teeth, reaching more than 2000 {mu}g g{sup -1}, decreasing sharply to the outer regions. The distribution of Mn, Fe, Cu and Zn was also determined in order to evaluate elemental influences by amalgam components. No significant changes in elemental concentrations were detected for Mn and Fe between healthy and restored teeth. However, the levels of Zn and Cu are increased in restored teeth. An X-ray fluorescence set-up with microprobe capabilities, 100 {mu}m of spatial resolution and an energy of 18 keV, installed at LURE synchrotron (France) was used.

  18. Cu{sub 2}S as ohmic back contact for CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Türck, Johannes; Siol, Sebastian; Mayer, Thomas; Klein, Andreas; Jaegermann, Wolfram, E-mail: jaegermann@surface.tu-darmstadt.de

    2015-05-01

    We prepared a back contact for CdTe solar cells with Cu{sub 2}S as primary contact. Cu{sub 2}S was evaporated on CdCl{sub 2} treated CdTe solar cells in superstrate configuration. The CdTe and CdS layers were deposited by Closed Space Sublimation. Direct interface studies with X-ray photoelectron spectroscopy have revealed a strongly reactive interface between CdTe and Cu{sub 2}S. A valence band offset of 0.4-0.6 eV has been determined. The performance of solar cells with Cu{sub 2}S back contacts was studied in comparison to cells with an Au contact that deposited onto a CdCl{sub 2}-treated CdTe surface that was chemically etched using a nitric-phosphoric etch. The solar cells were analyzed by current-voltage curves and external quantum efficiency measurements. After several post deposition annealing steps, 13% efficiency was reached with the Cu{sub 2}S back contact, which was significantly higher than the ones obtained for the NP-etched back contacts. - Highlights: • A new back contact for CdTe solar out of Cu{sub 2}S has been tested. • With a direct interface experiment the valence band offset was determined. • Post deposition heat treatment has been carried out for the solar cells. • 13% efficiency has been reached with the Cu{sub 2}S back contact.

  19. Cu2S as ohmic back contact for CdTe solar cells

    International Nuclear Information System (INIS)

    We prepared a back contact for CdTe solar cells with Cu2S as primary contact. Cu2S was evaporated on CdCl2 treated CdTe solar cells in superstrate configuration. The CdTe and CdS layers were deposited by Closed Space Sublimation. Direct interface studies with X-ray photoelectron spectroscopy have revealed a strongly reactive interface between CdTe and Cu2S. A valence band offset of 0.4-0.6 eV has been determined. The performance of solar cells with Cu2S back contacts was studied in comparison to cells with an Au contact that deposited onto a CdCl2-treated CdTe surface that was chemically etched using a nitric-phosphoric etch. The solar cells were analyzed by current-voltage curves and external quantum efficiency measurements. After several post deposition annealing steps, 13% efficiency was reached with the Cu2S back contact, which was significantly higher than the ones obtained for the NP-etched back contacts. - Highlights: • A new back contact for CdTe solar out of Cu2S has been tested. • With a direct interface experiment the valence band offset was determined. • Post deposition heat treatment has been carried out for the solar cells. • 13% efficiency has been reached with the Cu2S back contact

  20. Study on procedure for determination of Cr, As, Se, Cd, Hg, Pb in some kinds of herb products such as: kind of fungus, philamin... by ICP-MS

    International Nuclear Information System (INIS)

    The determination of Cr, As, Se, Cd, Hg, Pb in herb products such as: kind of fungus, philamin, etc by ICP-MS has been studied. The effects of the parameters of ICP-MS instrument, concentration of nitric acid and high concentration of some elements on the determination of Cr, As, Se, Cd, Hg, Pb by ICP-MS has been concerned. The study and choice the suitable internal standard for the accurate determination of Hg has been sold. The suitable parameters of the microwave, composition and content of the acid mixture for the complete decomposition of the sample have been studied. The recommended procedure has been applied to the determination of Cr, As, Se, Cd, Hg, Pb in the standard samples and real samples. The error of the results is acceptable. (author)

  1. Cu(N-N)2Cl2 and Cu(N-N-N)Cl2 and HgCl2 building blocks in the synthesis of coordination compounds-X-ray studies and magnetic properties

    International Nuclear Information System (INIS)

    A series of complexes containing Cu(N-N)2Cl2 (N-N=bis(pyrazol-1-yl)methane (bpzm), bis(3,5dimethylpyrazol-1-yl)methane (bdmpzm), 2,2-dipyridylamine (dpa), 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) and 2,2'-bipyridine (bipy)), Cu(N-N-N)Cl2 (N-N-N=2,2':6',2''-terpyridine (terpy)) and HgCl2 building blocks have been synthesized and structurally characterized. Increase in structural dimensionality is observed for [Cu(bpzm)2][HgCl4], [Cu(dpa)2][HgCl3]2 and [Cu(terpy)(μ-Cl)HgCl3] compounds. No coordination polymers have formed in the case of bis(3,5dimethylpyrazol-1-yl)methane, 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine and 2,2'-bipyridine. The [Cu(bpzm)2][HgCl4] and [Cu(terpy)(μ-Cl)HgCl3] complexes have been studied by magnetic measurements. - Graphical abstract: N-N: bis(3,5dimethylpyrazol-1-yl)methane (bdmpzm), 2,2-dipyridylamine (dpa), 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) and 2,2'-bipyridine (bipy), 6',2''-terpyridine (terpy).

  2. Magneto-optical transitions between subbands with different quantum numbers in narrow gap HgTe-CdTe superlattices

    Science.gov (United States)

    Luo, H.; Yang, G. L.; Furdyna, J. K.; Ram-Mohan, L. R.

    1991-10-01

    Magneto-optical transitions induced by the coupling between the conduction and the valence bands through the momentum matrix element, and by the coupling terms between light and heavy holes resulting from an applied magnetic field are studied theoretically in narrow gap HgTe-CdTe superlattices. Selection rules and transition probabilities for the above transitions are presented and compared with allowed transitions. The numerical results for the transition probabilities show that some of the interband transitions with ΔN=±1 are significant and have to be considered in the studies of interband magneto-optical spectra of narrow gap superlattices.

  3. Comment on ``Temperature-induced intraband transitions in the n-type HgTe/CdTe superlattice''

    Science.gov (United States)

    Meyer, J. R.; Hoffman, C. A.; Wagner, R. J.; Bartoli, F. J.

    1991-06-01

    On the basis of magneto-optical measurements on a HgTe-CdTe superlattice, Choi et al. [Phys. Rev. B 41, 10872 (1990)] have argued that the valence-band offset must be on the order of 40 meV. We show that rather than representing cyclotron resonance by electrons in the interior of the superlattice, the minima in their magnetotransmission spectra are more readily interpreted in terms of quasi-two-dimensional electrons residing near the interface of the superlattice with the substrate. When nonparabolicity is taken into account, the data are consistent with the large body of evidence favoring a large valence-band offset in this system.

  4. Tinjauan terhadap tailing mengandung unsur pencemar Arsen (As), Merkuri (Hg), Timbal (Pb), dan Kadmium (Cd) dari sisa pengolahan bijih logam

    OpenAIRE

    Danny Zulkifli Herman

    2014-01-01

    http://dx.doi.org/10.17014/ijog.vol1no1.20064aWhen tailing of a mining activity is discharged into either landscape or river body, the pollutan element wastes are possible to disperse within those areas and may cause pollution on environment. The environment pollution hazards of arsenic (As), mercury (Hg), lead (Pb) and cadmium (Cd) probably occurred if tailing with the content of those elements is not handled properly. Particularly in the tropical regions, higher rates of chemical weathering...

  5. Numerical simulation of crosstalk in reduced pitch HgCdTe photon-trapping structure pixel arrays.

    Science.gov (United States)

    Schuster, Jonathan; Bellotti, Enrico

    2013-06-17

    We have investigated crosstalk in HgCdTe photovoltaic pixel arrays employing a photon trapping (PT) structure realized with a periodic array of pillars intended to provide broadband operation. We have found that, compared to non-PT pixel arrays with similar geometry, the array employing the PT structure has a slightly higher optical crosstalk. However, when the total crosstalk is evaluated, the presence of the PT region drastically reduces the total crosstalk; making the use of the PT structure not only useful to obtain broadband operation, but also desirable for reducing crosstalk in small pitch detector arrays. PMID:23787659

  6. The new mineral species brodtkorbite, Cu2HgSe2, and the associated selenide assemblage from Tuminico, Sierra de Cacho, La Rioja, Argentina

    International Nuclear Information System (INIS)

    Brodtkorbite, ideally Cu2HgSe2, a new mineral species, occurs in a telethermal selenide vein-type assemblage at the Tuminico Ia selenium deposit, Sierra de Cacho (Sierra de Umango) district, La Rioja, Argentina. The selenide assemblage also contains berzelianite, bellidoite, cadmoselite (mercurian, cuprian), chameanite, crookesite, eskebornite, eucairite, ferroselite, hakite, klockmannite, a luanheite-type phase, trogtalite-krutaite, tiemannite, tyrrellite, umangite and uraninite. Minor constituents are undefined phases that belong to the Cd-(Cu)-Hg-Se and (Co,Ni,Cu)-As-Se systems. The selenides occur as veinlets, as impregnations and as massive ores in calcite veins, and are hosted by altered (hematite-stained) amphibolites of the Sierra de Pampeanas, the Precambrian basement of the Precordillera terrane. Brodtkorbite was observed as anhedral grains; they range in size from 10 X 20 up to 50 X 100 μm and as aggregates of composite grains up to 150 X 250 μm, commonly intergrown with berzelianite, tiemannite and (rarely) umangite and clausthalite. The mineral is dark grey, opaque, has a metallic luster, and a dark grey streak. VHN10 ranges from 91.4 to 131 (mean 118) kg/mm2, which corresponds to a calculated Mohs hardness of about 2 1/2 to 3. The density is 7.77 g/cm3 and was calculated for the ideal formula with Z = 2, In plane-polarized reflected light, the mineral is white, is weakly to moderately pleochroic from pinkish to bluish white, and lacks internal reflections. It has a weak to strong bireflectance; the anisotropy is weak to strong with rotation tints from mauve-grey to yellowish grey. The reflectance spectra and color values in air and in oil are tabulated. The chemical composition, which was obtained with an electron microprobe, shows very little variation within individual grains and between grains. The average composition is: Cu 26.2, Hg 40.7, Se 32.9, total 99.8 wt%. This leads to an empirical formula (total atoms = 5) of Cu2.00Hg0.98Se2

  7. Ordered state of magnetic charge in the pseudo-gap phase of a cuprate superconductor (HgBa2CuO(4+δ)).

    Science.gov (United States)

    Lovesey, S W; Khalyavin, D D

    2015-12-16

    A symmetry-based interpretation of published experimental results demonstrates that the pseudo-gap phase of underdoped HgBa2CuO(4+δ) (Hg1201) possesses an ordered state of magnetic charge epitomized by Cu magnetic monopoles. Magnetic properties of one-layer Hg1201 and two-layer YBa2Cu3O(6+x) (YBCO) cuprates have much in common, because their pseudo-gap phases possess the same magnetic space-group, e.g. both underdoped cuprates allow the magneto-electric (Kerr) effect. Differences in their properties stem from different Cu site symmetries, leaving Cu magnetic monopoles forbidden in YBCO. Resonant x-ray Bragg diffraction experiments can complement the wealth of information available from neutron diffraction experiments on five Hg1201 samples on which our findings are based. In the case of Hg1201 emergence of the pseudo-gap phase, with time-reversal violation, is accompanied by a reduction of Cu site symmetry that includes loss of a centre of inversion symmetry. In consequence, parity-odd x-ray absorption events herald the onset of the enigmatic phase, and we predict dependence of corresponding Bragg spots on magneto-electric multipoles, including the monopole, and the azimuthal angle (crystal rotation about the Bragg wavevector). PMID:26575373

  8. Anthropogenic and geogenic Cd, Hg, Pb and Se sources of contamination in a brackish aquifer below agricultural fields

    Science.gov (United States)

    Mastrocicco, Micòl; Colombani, Nicolò; Di Giuseppe, Dario; Faccini, Barbara; Ferretti, Giacomo; Coltorti, Massimo

    2015-04-01

    Groundwater quality is often threatened by industrial, agricultural and land use practices (anthropogenic input). In deltaic areas is however difficult to distinguish between geogenic and anthropogenic inorganic contaminants pollution, since these phenomena can influence each other and often display a seasonal cycling. The effect of geogenic groundwater ionic strength (>10 g/l) on the mobility of trace elements like Cd, Hg, Pb and Se was studied in combination with the anthropogenic sources of these elements (fertilizers) in a shallow aquifer. The site is located in the Po river plain (Northern Italy) in an agricultural field belonging to a reclaimed deltaic environment, near Codigoro town. It is 6 ha wide and is drained by a subsurface drainage system made of PVC tile drains with a slope of 3‰, which provides gravity drainage towards two ditches that in turn discharge in a main channel. The whole area has been intensively cultivated with cereal rotation since 1960, mainly using synthetic urea as nitrogen fertilizer at an average rate of 180 kg-N/ha/y and pig slurry at an average rate of 60 kg-N/ha/y. The sediments were analyzed for major and trace elements via XRF, while major ions in groundwater were analyzed via IC and trace elements via ICP-MS. Three monitoring wells, with an inner diameter of 2 cm and screened down to 4 m below ground level, were set up in the field and sampled every four month from 2012 to 2014. The use of intensive depth profiles with resolution of 0.5 m in three different locations, gave insights into groundwater and sediment matrix interactions. To characterize the anthropogenic inputs synthetic urea and pig slurry were analyzed for trace elements via ICP-MS. The synthetic urea is a weak source of Cd and Hg (~1 ppb), while Se and Pb are found below detection limits. The pig slurry is a much stronger source of Se (~19 ppb) and Pb (~23 ppb) and a weak source of Cd (~3 ppb) and Hg (~2 ppb). Although, the mass loading rate pig slurry is

  9. First-principles study of roles of Cu and Cl in polycrystalline CdTe

    International Nuclear Information System (INIS)

    Cu and Cl treatments are important processes to achieve high efficiency polycrystalline cadmium telluride (CdTe) solar cells, thus it will be beneficial to understand the roles they play in both bulk CdTe and CdTe grain boundaries (GBs). Using first-principles calculations, we systematically study Cu and Cl-related defects in bulk CdTe. We find that Cl has only a limited effect on improving p-type doping and too much Cl can induce deep traps in bulk CdTe, whereas Cu can enhance p-type doping of bulk CdTe. In the presence of GBs, we find that, in general, Cl and Cu will prefer to stay at GBs, especially for those with Te-Te wrong bonds, in agreement with experimental observations

  10. First-principles study of roles of Cu and Cl in polycrystalline CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ji-Hui; Park, Ji-Sang; Metzger, Wyatt [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Yin, Wan-Jian [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); College of Physics, Optoelectronics and Energy and Collaborative, Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Wei, Su-Huai, E-mail: suhuaiwei@csrc.ac.cn [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Beijing Computational Science Research Center, Beijing 100094 (China)

    2016-01-28

    Cu and Cl treatments are important processes to achieve high efficiency polycrystalline cadmium telluride (CdTe) solar cells, thus it will be beneficial to understand the roles they play in both bulk CdTe and CdTe grain boundaries (GBs). Using first-principles calculations, we systematically study Cu and Cl-related defects in bulk CdTe. We find that Cl has only a limited effect on improving p-type doping and too much Cl can induce deep traps in bulk CdTe, whereas Cu can enhance p-type doping of bulk CdTe. In the presence of GBs, we find that, in general, Cl and Cu will prefer to stay at GBs, especially for those with Te-Te wrong bonds, in agreement with experimental observations.

  11. First-principles study of roles of Cu and Cl in polycrystalline CdTe

    Science.gov (United States)

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Metzger, Wyatt; Wei, Su-Huai

    2016-01-01

    Cu and Cl treatments are important processes to achieve high efficiency polycrystalline cadmium telluride (CdTe) solar cells, thus it will be beneficial to understand the roles they play in both bulk CdTe and CdTe grain boundaries (GBs). Using first-principles calculations, we systematically study Cu and Cl-related defects in bulk CdTe. We find that Cl has only a limited effect on improving p-type doping and too much Cl can induce deep traps in bulk CdTe, whereas Cu can enhance p-type doping of bulk CdTe. In the presence of GBs, we find that, in general, Cl and Cu will prefer to stay at GBs, especially for those with Te-Te wrong bonds, in agreement with experimental observations.

  12. Adsorption of Cu(II), Hg(II), and Ni(II) ions by modified natural wool chelating fibers

    International Nuclear Information System (INIS)

    The graft copolymerization of ethyl acrylate (EA) onto natural wool fibers initiated by potassium persulphate and Mohr's salt redox initiator system in limited aqueous medium was carried out in heterogeneous media. Ester groups of the grafted copolymers were partially converted into hydrazide function groups followed by hydrazone formation through reaction with isatin. Also the application of the modified fibers for metal ion uptake was studied using Cu(II), Hg(II) and Ni(II). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

  13. Adsorption of Cu(II), Hg(II), and Ni(II) ions by modified natural wool chelating fibers

    Energy Technology Data Exchange (ETDEWEB)

    Monier, M., E-mail: monierchem@yahoo.com [Chemistry Department, Drexel University, Philadelphia, PA (United States); Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt); Ayad, D.M.; Sarhan, A.A. [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt)

    2010-04-15

    The graft copolymerization of ethyl acrylate (EA) onto natural wool fibers initiated by potassium persulphate and Mohr's salt redox initiator system in limited aqueous medium was carried out in heterogeneous media. Ester groups of the grafted copolymers were partially converted into hydrazide function groups followed by hydrazone formation through reaction with isatin. Also the application of the modified fibers for metal ion uptake was studied using Cu(II), Hg(II) and Ni(II). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

  14. Adsorption of Cu(II), Hg(II), and Ni(II) ions by modified natural wool chelating fibers.

    Science.gov (United States)

    Monier, M; Ayad, D M; Sarhan, A A

    2010-04-15

    The graft copolymerization of ethyl acrylate (EA) onto natural wool fibers initiated by potassium persulphate and Mohr's salt redox initiator system in limited aqueous medium was carried out in heterogeneous media. Ester groups of the grafted copolymers were partially converted into hydrazide function groups followed by hydrazone formation through reaction with isatin. Also the application of the modified fibers for metal ion uptake was studied using Cu(II), Hg(II) and Ni(II). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction. PMID:19962235

  15. The influence of precursor quality on the superconducting properties of (Hg,Cr)Sr2CuO4+δ

    International Nuclear Information System (INIS)

    We have investigated the superconducting properties of (Hg,Cr)Sr2Cu O4+δ prepared using different precursor routes. It was observed that the quality of the samples depends strongly on the precursor quality and the nature of starting materials. The samples were synthesized in partial vacuum and characterized by XRD, FT-IR, χ-T and dc-magnetization. Good quality samples with high Tc (60 K) was obtained for the sample prepared from strontium nitrate as compared to strontium carbonate source (Tc = 56 K). (author)

  16. Toward selective, sensitive, and discriminative detection of Hg(2+) and Cd(2+)via pH-modulated surface chemistry of glutathione-capped gold nanoclusters.

    Science.gov (United States)

    Huang, Pengcheng; Li, Sha; Gao, Nan; Wu, Fangying

    2015-11-01

    Heavy metal pollution can exert severe effects on the environment and human health. Simple, selective, and sensitive detection of heavy metal ions, especially two or more, using a single probe, is thereby of great importance. In this study, we report a new and facile strategy for discriminative detection of Hg(2+) and Cd(2+) with high selectivity and sensitivity via pH-modulated surface chemistry of the glutathione-capped gold NCs (GSH-Au NCs). By simply adjusting pH values of the colloidal solution of the NCs, Hg(2+) could specifically turn off the fluorescence under acidic pH, however, Cd(2+) could exclusively turn on the fluorescence under alkaline pH. This enables the NCs to serve as a dual fluorescent sensor for Hg(2+) and Cd(2+). We demonstrate that these two opposing sensing modes are presumably due to different interaction mechanisms: Hg(2+) induces aggregation by dissociating GSH from the Au surface via robust coordination and, Cd(2+) could passivate the Au surface by forming a Cd-GSH complex with a compact structure. Finally, the present strategy is successfully exploited to separately determine Hg(2+) and Cd(2+) in environmental water samples. PMID:26347906

  17. Bulk and Surface Nanoscale Hole Density Inhomogeneity in HgBa$_2$CuO$_{4+\\delta}$ and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\\delta}$ Cuprates

    OpenAIRE

    Chen, Wei; Sushkov, Oleg P.; Khaliullin, Giniyat

    2010-01-01

    It is well established that the hole density in the prototypical superconductor La$_{2-x}$Sr$_x$CuO$_4$ is very inhomogeneous due to Sr-dopant induced disorder. On the other hand, until recently it is widely believed that the hole distribution in HgBa$_2$CuO$_{4+\\delta}$ and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\\delta}$ doped by interstitial oxygen is much more uniform. Recent nuclear magnetic resonance measurements indicate, however, that the charge inhomogeneity in HgBa$_2$CuO$_{4+\\delta}$ is close to...

  18. Studies of the polynuclear complexes of labile ligands of vitamin B1 and Zn(II), Cd(II) and Hg(II) with Fe(III)

    International Nuclear Information System (INIS)

    The ligands (complex salts) of vitamin B/sub 1/ (H Vit.) and the chlorides of Zn, Cd and Hg with the general formula, [H Vit]/sup +2/ [MCl/sub 4/]/sup -2/ were prepared and their interactions with iron (III) investigated. It was found that the complex salts of Zn and Cd produced the dinuclear complexes and that of mercury produced a complex without the thiamine moiety. The possible reason for the absence of a Hg complex similar to those of Zn and Cd may be that large size of mercury ion. The complexes were characterized by elementary analyses, infrared and visible spectra, magnetic moment and conductivity measurements.(author)

  19. Perturbed angular correlations studies in the HgBa$_2$CaCu$_2$O$_{6+\\delta}$ high-T$_c$ superconductor

    CERN Document Server

    Mendonca, Tania Melo; Haas, Heinz; Odier, Philippe; Tavares, Pedro; SIlva, Manuel Ribeiro; Lopes, Armandina; Darie, Celine; Araujo, Joao Pedro

    2011-01-01

    The electric field gradients at $^{199m}$Hg nuclei have been measured via the perturbed angular correlation (PAC) technique, allowing a full characterization of the Hg neighborhood charge distribution at high oxygen doping on the Hg planes. The PAC technique has been applied to investigate the effect of high oxygen pressure during the measurement. Polycrystalline HgBa$_2$CaCu$_2$O$_{6+\\delta}$ (Hg-1212) samples have been annealed at 152 bar pressurized oxygen. The influence of oxygen pressure during the experiment was then investigated by measuring the samples at atmospheric pressure and under 152 bar oxygen pressure. The present set of PAC experiments shows that at high oxygen concentrations there is a non-uniform oxygen distribution. Moreover, the Hg environment is not free from oxygen and the results hint to a new type of ordering.

  20. High-pressure effect on Tc of HgBa2Ca3Cu4O10+δ up to 30 GPa

    International Nuclear Information System (INIS)

    In order to investigate the pressure dependence of Tc of the Hg-based cuprates, we performed the electrical resistance measurements of high purity HgBa2Ca2Cu3O10+δ (Hg-1234) synthesized under pressure. We used a diamond-anvil cell to generate high pressure up to 30 GPa. In this work, two Hg-1234 samples with different hole concentration (Tc = 125 K for optimaldoped sample and Tc = 124 K for underdoped one at ambient pressure) were measured. With applying pressure Tc of underdoped sample increased (dT/dP = +0.6 K/GPa) and passed through a peak with 143 K at ∼30 GPa and decreased drastically at higher pressure. This behavior was different from previous works for Hg-1234 and Hg-1223, in which the Tc saturates above the pressure giving the maximum Tc

  1. First-Principles Study on Cd Doping in Cu2ZnSnS4 and Cu2ZnSnSe4

    Science.gov (United States)

    Maeda, Tsuyoshi; Nakamura, Satoshi; Wada, Takahiro

    2012-10-01

    To quantitatively evaluate the substitution energies of Cd atom for Cu, Zn, or Sn atom in indium-free photovoltaic semiconductors Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe), first-principles pseudopotential calculations using plane-wave basis functions were performed. The substitution energies of Cd atom in kesterite-type CZTS and CZTSe were calculated in consideration of the atomic chemical potentials of the constituent elements of Cu, Zn, Sn, and the doping atom of Cd. During the chemical bath deposition (CBD) of the CdS layer on the CZTS or CZTSe layer, Cu, Zn, and Cd atoms dissolved in the ammonia aqueous solution and formed [Cu(NH3)2]+, [Zn(NH3)4]2+, and [Cd(NH3)4]2+ complex ions. Therefore, the chemical potentials of Cu, Zn, and Cd atoms in [Cu(NH3)2]+, [Zn(NH3)4]2+, and [Cd(NH3)4]2+ complex ions were calculated. We found that the substitution energies of n-type CdCu and charge-neutral CdZn in CZTS and CZTSe are smaller than that of p-type CdSn. The substitution energies of CdCu in CZTS and CZTSe are smaller than that in chalcopyrite-type CuInSe2 (CIS). However, the substitution energies of CdCu, CdZn, and CdSn are positive values. The formation energy of charge-neutral Cd doping with the Cu vacancy (CdCu + VCu) pair is a negative value and greatly smaller than those of donor-type CdCu and neutral CdZn in CZTS and CZTSe. These results indicate that the charge-neutral (CdCu + VCu) vacancy pair is easily formed during the CBD of the CdS layer on the CZTS or CZTSe layer. A small amount of n-type CdCu and neutral CdZn would also be formed.

  2. Advances in CuInSe sub 2 and CdTe thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Shafarmann, W.N.; Birkmire, R.W.; Farding, D.A.; McCandless, B.E.; Mondal, A.; Phillips, J.E.; Varrin, R.D. Jr. (Delaware Univ., Newark (USA). Inst. of Energy Conversion)

    1991-05-01

    Research on CuInSe{sub 2} and CdTe thin film solar cells is discussed. CuInSe{sub 2} was deposited by selenization of Cu/In layers and was used to make a 10% efficient CuInSe{sub 2}/(CdZn)S cell. Characterization of the reaction mechanisms is described. The open-circuit voltage V{sub oc} of CuInSe{sub 2}/(CdZn)S cells is dominated by recombination in the space charge region, so increassing the band gap or decreasing the width of this region should increase V{sub oc}. Increasing the band gap with a thin Cu(InGa)Se{sub 2} layer at the CuInSe{sub 2} surface has demonstrated increased V{sub oc} with collection out to the CuInSe{sub 2} band gap. A post-deposition treatment and contacting process for evaporated CdS/CdTe cells was developed and high efficiency cells were made. Several steps in the process, including a CdCl{sub 2} coating, a 400deg C heat treatment, and a contact containing copper are critical. ZnTe films were deposited from an aqueous solution as a contact to CdTe. (orig.).

  3. Application of the RHEED oscillation technique to the growth of II-VI compounds: CdTe, HgTe and their related alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, L.; Magnea, N.; Gentile, P. (Service de Physique, Dept. de Recherche Fondamentale, Centre d' Etudes Nucleaires de Grenoble, 38 (France)); Mariette, H. (Service de Physique, Dept. de Recherche Fondamentale, Centre d' Etudes Nucleaires de Grenoble, 38 (France) Lab. de Spectrometrie Physique, Univ. J. Fourier, 38 - Grenoble (France))

    1991-05-01

    The RHEED oscillation technique has been used to study the growth mechanism of (001) oriented CdTe, HgTe and Cd{sub x}Hg{sub 1-x}Te II-VI compounds. For Cd or Hg stabilized surfaces, the two-dimensional layer-by-layer growth provides intense oscillations. They are used to measure the influence of growth parameters (substrate temperature, flux ratio, growth interruption) on growth rate and alloy composition. It appears that the molecular beam epitaxy of these II-VI compounds is strongly affected by the non-unity sticking coefficient of Cd in a very wide temperature range (140-400degC) and that kinetic effects are important. (orig.).

  4. High operating temperature SWIR p+-n FPA based on MBE-grown HgCdTe/Si(0 1 3)

    Science.gov (United States)

    Bazovkin, V. M.; Dvoretsky, S. A.; Guzev, A. A.; Kovchavtsev, A. P.; Marin, D. V.; Polovinkin, V. G.; Sabinina, I. V.; Sidorov, G. Yu.; Tsarenko, A. V.; Vasil'ev, V. V.; Varavin, V. S.; Yakushev, M. V.

    2016-05-01

    The characteristics of SWIR (1.6-3 μm) 320 × 256 and 1024 × 1024 focal plane arrays (FPA's) based on n-type In-doped HgCdTe heteroepitaxial layers are reported. The HgCdTe layers were grown by molecular beam epitaxy on silicon substrates with ZnTe and CdTe buffer layers. p-n junctions were formed by arsenic ion implantation into HgCdTe film. Reverse current in the temperature range from 210 to 330 K was found to be limited by the diffusion mechanism. At the same time in the temperature range from 140 to 210 K the reverse current was dominated by the thermal generation of charge carriers through deep traps located in the middle of the band gap. At 170 K NETD was less than 40 mK.

  5. Effect of Cd, Zn and Hg complexes of barbituric acid and thiouracil on rat brain monoamine oxidase-B (in vitro).

    Science.gov (United States)

    Shaban, Nadia Z; Masoud, Mamdouh S; Awad, Doaa; Mawlawi, Mai A; Sadek, Omayma M

    2014-02-01

    Metal pyrimidine complexes (MPCs) including cadmium-barbiturate (Cd-BA), zinc-barbiturate (Zn-BA), cadmium-thiouracil (Cd-TU) and mercury-thiouracil (Hg-TU) were prepared and their analysis was carried out. These MPCs were evaluated as monoamine oxidase-B (MAO-B) inhibitors. Rat brain MAO-B was inhibited (in vitro) by Cd-BA, Zn-BA, Cd-TU and Hg-TU complexes. The inhibition of MAO-B by these complexes was time and concentration dependent. The values of IC50 of Zn-BA, Cd-BA, Hg-TU and Cd-TU were 10.2, 15.8, 16.2 and 20.4 nM, respectively. The effect of different substrate concentrations in the absence and in the presence of MPCs was determined. Lineweaver-Burk plots were plotted and the values of apparent Michaelis constant (Km), maximum velocity (Vmax), the dissociation constant of enzyme inhibitor complex (Ki) and the percent of inhibition (i%) were calculated. The data showed that the inhibition of MAO-B by all studied MPCs was the non-competitive type. The sequence of inhibition zone was: Zn-BA>Cd-BA and Hg-TU>Cd-TU affected by the chemistry of both the metal and the ligand. Otherwise, the results of the present study showed that the inhibition of MAO-B by all MPCs was fully reversible. The data showed that the presence of Cd-BA, Zn-BA, Cd-TU and Hg-TU complexes changed the optimum temperature and pH of MAO-B. PMID:24300193

  6. Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2

    Science.gov (United States)

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films. PMID:21673933

  7. Application of residual sludge: effects on soil nitrogen and retention of Cd, Cr, Hg and Zn by ray grass

    International Nuclear Information System (INIS)

    In pot studies on the application of urban sewage rich in organic matter as fertilizer (residual sludges from sewage purification stations), an investigation was made of the yield in dry matter and retention of Zn, Cd, Cr and Hg by ray grass, followed by an examination of the mineralization and organization of soil nitrogen or added nitrogen fertilizers. All the experiments described were conducted with tracers - radioactive in the case of Hg, Cd, Cr and Zn, and stable in the case of nitrogen. The main results obtained after six months' cultivation can be summarized as follows: (1) the suppressing effect produced immediately after application of a lime-treated sludge falls off rapidly (2-3 months), whereas the effect produced by straw persists even after six months. The sludges subsequently exert a positive effect on the yield of dry matter; (2) in the plant the transfer of the trace elements studied is not altered by adding residual sludges whereas the addition of 30 ppm of these elements to the soil in ionic form increases the plant content; (3) although the incorporation of straw into the soil considerably increases the organization of the nitrogen in the fertilizer applied, the changes are limited in the case of other forms of treatment. (author)

  8. The growth of CdHgTe on GaAs and fabrication of high-quality photodiodes

    International Nuclear Information System (INIS)

    The use of metal organic vapor phase epitaxy (MOVPE) for the growth of device quality CdHgTe (MCT) on GaAs has been studied extensively. This is the first report of diode formation by mercury diffusion in the MOVPE grown material. It is also the first report of medium-wavelength infrared (MWIR) photodiodes made in the material. The effect of altering the cadmium to tellurium alkyl ratios on the growth of a CdTe buffer on (100) and (111)GaAs was investigated. For every alkyl ratio used, it was possible to grow (111) or (100)CdTe on (100)GaAs. (100)CdTe/(100)GaAs samples exhibited very sharp, well-defined photoluminescence spectra and x-ray rocking curve full width half-maximum (FWHM) peaks of 2) over a large area (25x25 mm2). FWHMs of 80--90 arc s are routinely achieved for (100)MCT layers. Linear diode arrays have been fabricated with 77 K R0A values typically of 3x103 Ω cm2 for 7.5 μm cutoff. The detectivity of a 5.5 μm cutoff diode was 1.5x1011 cm Hz1/2 W-1 at 77 K, and 1.3x1010 cm Hz1/2 W-1 at 193 K. This is comparable to the performance obtained with the best traveling heater method devices

  9. Intrinsic Josephson properties in (Hg, Re)Ba2Ca3Cu4O10+δ single crystals

    International Nuclear Information System (INIS)

    We have investigated the I-V characteristics of intrinsic Josephson junctions (IJJs) in (Hg, Re)Ba2Ca3Cu4O10+δ [Hg(Re)1234]. Two types of inline junctions with different dimensions were fabricated using a focused Ga+ ion beam from Hg(Re)1234 single crystals grown by the flux method. In the I-V curves of the IJJs, multiple-branches with hysteresis structure similar to those of other HTS IJJs were successfully observed above 80 K. The IJJs with dimension of 1.2 x 0.65 μm2 showed almost step by step switching, while the other with larger size showed uniform-stack switching, which indicated that the switching dynamics in the IJJs were affected by the coupling between junctions. The critical current density, Jc, of both IJJs were high ∼320 kA/cm2 at 4.2 K due to its high Tc and relatively low anisotropy parameter γ=(mc*/mab*)1/2∼25

  10. Anthracene coupled thiourea as a colorimetric sensor for F{sup −}/Cu{sup 2+} and fluorescent sensor for Hg{sup 2+}/picric acid

    Energy Technology Data Exchange (ETDEWEB)

    Udhayakumari, Duraisamy [Organic and Polymer Synthesis Laboratory, Department of Chemistry, National Institute of Technology, Tiruchirappalli-620 015 (India); Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan, ROC (China); Velmathi, Sivan, E-mail: velmathis@nitt.edu [Organic and Polymer Synthesis Laboratory, Department of Chemistry, National Institute of Technology, Tiruchirappalli-620 015 (India); Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan, ROC (China); Venkatesan, Parthiban; Wu, Shu-Pao [Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan, ROC (China)

    2015-05-15

    A new dual chemosensor (Z)-2-(anthracen-9-ylmethylene)-N-phenylhydrazinecarbothioamide R1 was synthesized by incorporating a thiourea derivative as a binding unit and an anthracene group as a fluorescence signalling unit. R1 selectively binds with Cu{sup 2+} and Hg{sup 2+} ions in aqueous medium. R1 exhibits highly selective recognition towards F{sup −} ion and picric acid in organic medium. Fluorescence quenching was observed in case of R1 with Cu{sup 2+} and Hg{sup 2+} ions over commonly coexistent metal ions. Furthermore, fluorescence imaging experiments of Cu{sup 2+} and Hg{sup 2+} ions in living RAW 264.7 cells demonstrate its value of practical applications in biological systems. - Highlights: • R1 exhibited highly selective recognition towards Cu{sup 2+}, Hg{sup 2+} and F{sup −} ions. • The anion detection by R1 is further confirmed by {sup 1}H NMR titration method. • Detection of Cu{sup 2+} and Hg{sup 2+} ion in the living cell was achieved using fluorescence microscope. • R1 selectively sense picric acid over other nitroaromatics.

  11. Correlation between Tc and the structural parameters of the cation sublattice in the perovskite layer of HgBa2CuO4+δ and Tl2Ba2CuO4+δ

    International Nuclear Information System (INIS)

    Correlation between superconductivity transition temperature and interatomic distances in compounds HgBa2CuO4+δ and Tl2Ba2CuO4+δ was analyzed. Parabolic dependence of Tc on the value of Cu-Cu distances ratio along diagonal direction of CuO2-plane and Ba-Ba distances between Ba-cations planes was found. Factors determining the distances were discussed. The role of the structure of Ba-Cu perovskite layer cation sublattice of the phases in the appearance of high-temperature superconductivity was shown

  12. Development of electrodeposited ZnTe layers as window materials in ZnTe/CdTe/CdHgTe multi-layer solar cells

    International Nuclear Information System (INIS)

    Zinc telluride (ZnTe) thin films have been deposited on glass/conducting glass substrates using a low-cost electrodeposition method. The resulting films have been characterized using various techniques in order to optimize growth parameters. X-ray diffraction (XRD) has been used to identify the phases present in the films. Photoelectrochemical (PEC) cell and optical absorption measurements have been performed to determine the electrical conductivity type, and the bandgap of the layers, respectively. It has been confirmed by XRD measurement that the deposited layers mainly consist of ZnTe phases. The PEC measurements indicate that the ZnTe layers are p-type in electrical conduction and optical absorption measurements show that their bandgap is in the range 2.10-2.20 eV. p-Type ZnTe window materials have been used in CdTe based solar cell structures, following new designs of graded bandgap multi-layer solar cells. The structures of FTO/ZnTe/CdTe/metal and FTO/ZnTe/CdTe/CdHgTe/metal have been investigated. The results are presented in this paper using observed experimental data

  13. The impact of Cu on recombination in high voltage CdTe solar cells

    Science.gov (United States)

    Kuciauskas, Darius; Dippo, Pat; Kanevce, Ana; Zhao, Zhibo; Cheng, Long; Los, Andrei; Gloeckler, Markus; Metzger, Wyatt K.

    2015-12-01

    Using photoluminescence spectroscopy, we construct a recombination model for state-of-the-art CdTe solar cells doped with Cu. We observe that Cu on Cd sites form a dominant acceptor state about 150 meV from the valence band. Although it is intuitive that this state can increase hole density, we also find that this relatively shallow dopant can also limit lifetime. Consequently, CdTe solar cells doped with Cu could have a lifetime limitation inversely proportional to the hole concentration.

  14. TiO2-Cu[HgI4]纳米复合材料的制备及其热致变色性能%Preparation of TiO2-Cu[HgI4] Nanocomposite and Its Thermochromic Performance

    Institute of Scientific and Technical Information of China (English)

    陈晓丽; 林福华; 春燕; 苏秋成; 李新军

    2014-01-01

    以TiO2为载体制备了TiO2-Cu[HgI4]纳米复合材料,利用HRTEM、XRD、DSC、UV-Vis等方法对该材料的结构及其热致变色性能进行了研究。研究表明,TiO2-Cu[HgI4]纳米复合材料具有较好的热致变色性能,随着nTiO2/nCu[HgI4]摩尔比值的增大,其可见光吸收性能增强,相变温度也相应升高。%TiO2-Cu[HgI4] nanocomposite was synthesized by using TiO2 as carrier. HRTEM, XRD, DSC and UV-Vis were employed to characterize the structure and investigate the thermochromic performance of the nanocomposite. Results indicate that TiO2-Cu[HgI4] nanocomposite has good thermochromic performance. The visible light absorption is strengthened with the increase of nTiO2/nCu[HgI4] mole ratio, and the phase transition temperature rises accordingly.

  15. Novel signal inversion of laser beam induced current for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe

    International Nuclear Information System (INIS)

    In this paper, experimental results of temperature-dependent signal inversion of laser beam induced current (LBIC) for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe are reported. LBIC characterization shows that the traps induced by femtosecond laser drilling are sensitive to temperature. Theoretical models for trap-related p-n junction transformation are proposed and demonstrated using numerical simulations. The simulations are in good agreement with the experimental results. The effects of traps and mixed conduction are possibly the main reasons that result in the novel signal inversion of LBIC microscope at room temperature. The research results provide a theoretical guide for practical applications of large-scale array HgCdTe infrared photovoltaic detectors formed by femtosecond laser drilling, which may act as a potential new method for fabricating HgCdTe photodiodes.

  16. Photo-electric characteristics of HgCdTe tunnel MIS photo-detectors

    International Nuclear Information System (INIS)

    The photo-electric characteristics of tunnel MIS photo-detectors based on Hg1−xCdxTe for x ≈ 0.2 are presented. In order to reduce or eliminate Fermi level pinning, a passivation dielectric layer with thickness allowing for free carrier tunneling was grown on the metal–semiconductor interface. Dielectric layers composed of native oxides, native fluorides, SiO2 or Al2O3 were investigated. Values as high as 6.2 A W−1 for spectral responsivity and 5.3 × 1010 cm Hz1/2 W−1 for specific detectivity were obtained

  17. The isotypic family of the diarsenates MM'As{sub 2}O{sub 7} (M = Sr, Ba; M' = Cd, Hg)

    Energy Technology Data Exchange (ETDEWEB)

    Weil, Matthias [Technische Univ. Wien (Austria). Inst. for Chemical Technologies and Analytics

    2016-08-01

    The diarsenates MM'As{sub 2}O{sub 7} (M = Sr, Ba; M' = Cd, Hg) were prepared under hydrothermal conditions (∝200 C, autogenous pressure), starting from As{sub 2}O{sub 5} and the corresponding metal oxides or precursor compounds thereof in aqueous solutions. Structure analyses on the basis of single crystal X-ray data revealed the four structures to be isotypic. They are the first diarsenates to crystallize in the triclinic BaZnP{sub 2}O{sub 7} structure type (space group P anti 1, Z = 2, a ∼ 5.8 Aa, b ∼ 7.3 Aa, c ∼ 7.6 Aa, α ∼ 101 , β ∼ 91 , γ ∼ 98 ). All related MM'As{sub 2}O{sub 7} diarsenates reported so far (M = Sr, Ba, Pb; M' = Mg, Co, Cu, Zn) crystallize in the monoclinic α-Ca{sub 2}P{sub 2}O{sub 7} structure type (P2{sub 1}/n, Z = 4). Hence, the size of the divalent M' cation determines which of the two structure types is adopted.

  18. Sequencing Batch Reactor (SBR) for the removal of Hg{sup 2+} and Cd{sup 2+} from synthetic petrochemical factory wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Malakahmad, Amirhossein, E-mail: amirhossein@petronas.com.my [Faculty of Energy and Environmental Studies, Islamic Azad University, Science and Research branch, Hesarak, Tehran (Iran, Islamic Republic of); Civil Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak (Malaysia); Hasani, Amirhesam [Faculty of Energy and Environmental Studies, Islamic Azad University, Science and Research branch, Hesarak, Tehran (Iran, Islamic Republic of); Eisakhani, Mahdieh [School of Social, Development and the Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor (Malaysia); Isa, Mohamed Hasnain [Civil Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak (Malaysia)

    2011-07-15

    Highlights: {yields} We assessed SBR performances to treat synthetic wastewater containing Hg{sup 2+} and Cd{sup 2+}. {yields} SBR was able to remove 76-90% of Hg{sup 2+} and 96-98% of Cd{sup 2+}. {yields} COD removal efficiency and MLVSS was affected by Hg{sup 2+} and Cd{sup 2+} concentrations. {yields} Removal was not only biological process but also by biosorption process of sludge. - Abstract: Petrochemical factories which manufacture vinyl chloride monomer and poly vinyl chloride (PVC) are among the largest industries which produce wastewater contains mercury and cadmium. The objective of this research is to evaluate the performance of a lab-scale Sequencing Batch Reactor (SBR) to treat a synthetic petrochemical wastewater containing mercury and cadmium. After acclimatization of the system which lasted 60 days, the SBR was introduced to mercury and cadmium in low concentrations which then was increased gradually to 9.03 {+-} 0.02 mg/L Hg and 15.52 {+-} 0.02 mg/L Cd until day 110. The SBR performance was assessed by measuring Chemical Oxygen Demand, Total and Volatile Suspended Solids as well as Sludge Volume Index. At maximum concentrations of the heavy metals, the SBR was able to remove 76-90% of Hg{sup 2+} and 96-98% of Cd{sup 2+}. The COD removal efficiency and MLVSS (microorganism population) in the SBR was affected by mercury and cadmium concentrations in influent. Different species of microorganisms such as Rhodospirilium-like bacteria, Gomphonema-like algae, and sulfate reducing-like bacteria were identified in the system. While COD removal efficiency and MLVSS concentration declined during addition of heavy metals, the appreciable performance of SBR in removal of Hg{sup 2+} and Cd{sup 2+} implies that the removal in SBR was not only a biological process, but also by the biosorption process of the sludge.

  19. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    International Nuclear Information System (INIS)

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL−1 Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g−1 for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample

  20. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ni [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Jiang, Shiuh-Jen, E-mail: sjjiang@faculty.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Chen, Yen-Ling [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Sahayam, A.C. [National Centre for Compositional Characterisation of Materials (CCCM), Hyderabad (India)

    2015-02-20

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL{sup −1} Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g{sup −1} for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.

  1. Divalent Cu, Cd, and Pb Biosorption in Mixed Solvents

    Directory of Open Access Journals (Sweden)

    M. H. Al-Qunaibit

    2009-01-01

    Full Text Available Dead dried Chlorella vulgaris was studied in terms of its performance in binding divalent copper, cadmium, and lead ions from their aqueous or 50% v/v methanol, ethanol, and acetone solutions. The percentage uptake of cadmium ions exhibited a general decrease with decrease in dielectric constant values, while that of copper and lead ions showed a general decrease with increase in donor numbers. Uptake percentage becomes less sensitive to solvent properties the larger the atomic radius of the biosorbed ion, and uptake of copper was the most affected. FT-IR analyses revealed stability of the biomass in mixed solvents and a shift in vibrations of amide(I and (II, carboxylate, glucose ring, and metal oxygen upon metal binding in all media. ΔνCOO values (59–69 cm−1 confirmed bidentate metal coordination to carboxylate ligands. The value of νasCOO increased slightly upon Cu, Cd, and Pb biosorption from aqueous solutions indicating lowering of symmetry, while a general decrease was noticed in mixed solvents pointing to the opposite. M–O stretching frequencies increased unexpectedly with increase in atomic mass as a result of solvent effect on the nature of binding sites. Lowering polarity of the solvent permits variations in metal-alga bonds strengths; the smaller the metal ion, the more affected.

  2. Au/Cu2Te/CdTe/CdS/TCO/Glass Solar Cells with CdIn2O4 Obtained by Sol-Gel as TCO

    OpenAIRE

    Márquez Marín, J.; Torres Delgado, G.; M. A. Aguilar Frutis; Castanedo Pérez, R.; Zelaya Ángel, O.

    2014-01-01

    An Au/Cu2Te/CdTe/CdS/TCO/glass heterostructure based superstrate solar cells with 2.5 mm2 of area, where the CdTe layer was prepared by means of closed spaced sublimation (CSS) and the CdS by chemical bath, reached an efficiency η value of 12.1%. As transparent conductive oxide (TCO), a thin film of cadmium-indium oxide (CdIn2O4:CIO), obtained by sol-gel technique, was used. A systematic optimization of the thermal activation of the CdTe/CdS/CIO central part of the device with a CdCl2 vapor a...

  3. Study of some applications of residual sludges in agriculture using 15N, 32P, 65Zn, 109Cd and 203Hg

    International Nuclear Information System (INIS)

    Application of residual sludges increases dry matter production. This effect is due to the low C/N of these matters. The possible risks depend on the alteration of ions mobility as PO4---, Zn++, Hg++ and Cd++, which are often very strongly absorbed by soil particules. For these investigations, use of radioactive tracers is necessary. We have shown, with 65Zn++, that zinc of sludges is not available for ray-grass and, with 32PO4, that phosphorus mobility declines with lime-treated sludges. The use of isotopic dilution kinetics allows to shown that Hg++ and Cd++ are not absorbed in too acidic soils

  4. Broadening and shift of the intercombination spectral line of the second group elements (Hg, Cd and Zn) perturbed by inert gases

    International Nuclear Information System (INIS)

    The Van der Waals and Lennard - Jones potential parameters for the ground and exited states of the second group elements (Hg, Cd and Zn) perturbed by inert gases (Xe, Kr, Ar, Ne and He) have been calculated using coulomb approximation. The basis of the Lindholm -Foley impact theory and the calculated potential parameters are used for calculating the collision broadening and shift coefficients β and δ for the intercombination lines 253.7, 326.1 and 307.6 nm of Hg, Cd and Zn atoms respectively when they are colliding with inert gas atoms . The calculating coefficients of β and δ are compared with their corresponding experimental values, taken from literatures

  5. Accurate potential energy curves for the group 12 dimers Zn-2, Cd-2, and Hg-2

    NARCIS (Netherlands)

    Pahl, Elke; Figgen, Detlev; Borschevsky, Anastasia; Peterson, Kirk A.; Schwerdtfeger, Peter

    2011-01-01

    Potential energy curves of the electronic ground states of the group 12 dimers Zn-2 and Cd-2 were computed at the CCSD(T) level of theory, including full triple corrections Delta T in the coupled-cluster procedure, and spin-orbit (SO) contributions from four-component coupled-cluster calculations, e

  6. Vibrational spectroscopy of AII1-xMnxTe1-ySey (AII=Cd,Hg) alloys

    International Nuclear Information System (INIS)

    Far-infrared reflectivity spectra of Cd1-xMnxTe1-ySey (x=0.05, y=0.11; x=0.15, y=0.1) single crystals were measured in the 40-300 cm-1 spectral range at 80 K and 300 K. The analysis of the far-infrared spectra was carried out by a fitting procedure. We used a dielectric function that takes into account the existence of plasmon-LO phonon interaction. On that way the three optical modes frequencies (TO/LO pairs in cm-1) at ∝140/160, 170/190 and 205/210 were obtained, depending on composition and temperature. We discussed these results in the frame of the model which we previously applied on Hg1-xMnxTe1-ySey. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Nano-scale pattern formation on the surface of HgCdTe produced by ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, A.B.; Gudymenko, A.I.; Kladko, V.P.; Korchevyi, A.A.; Savkina, R.K.; Sizov, F.F.; Udovitska, R.S. [V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kiev (Ukraine)

    2015-08-15

    Presented in this work are the results concerning formation of nano-scale patterns on the surface of a ternary compound Hg{sub 1-x}Cd{sub x}Te (x ∝ 0.223). Modification of this ternary chalcogenide semiconductor compound was performed using the method of oblique-incidence ion bombardment with silver ions, which was followed by low-temperature treatment. The energy and dose of implanted ions were 140 keV and 4.8 x 10{sup 13} cm{sup -2}, respectively. Atomic force microscopy methods were used for the surface topography characterization. The structural properties of MCT-based structure was analyzed using double and triple crystal X-ray diffraction to monitor the disorder and strain of the implanted region as a function of processing conditions. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Comparing FDTD and Ray-Tracing Models in Numerical Simulation of HgCdTe LWIR Photodetectors

    Science.gov (United States)

    Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

    2016-09-01

    We present a simulation study of HgCdTe-based long-wavelength infrared detectors, focusing on methodological comparisons between the finite-difference time-domain (FDTD) and ray-tracing optical models. We performed three-dimensional simulations to determine the absorbed photon density distributions and the corresponding photocurrent and quantum efficiency spectra of isolated n-on- p uniform-composition pixels, systematically comparing the results obtained with FDTD and ray tracing. Since ray tracing is a classical optics approach, unable to describe interference effects, its applicability has been found to be strongly wavelength dependent, especially when reflections from metallic layers are relevant. Interesting cavity effects around the material cutoff wavelength are described, and the cases where ray tracing can be considered a viable approximation are discussed.

  9. The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector

    Directory of Open Access Journals (Sweden)

    Haoyang Cui

    2013-01-01

    Full Text Available The transient photovoltaic (PV characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction.

  10. First and second harmonic generation of the XAl2Se4 (X=Zn,Cd,Hg) defect chalcopyrite compounds

    International Nuclear Information System (INIS)

    The chemical bonding of the ZnAl2Se4, CdAl2Se4 and HgAl2Se4 defect chalcopyrites has been studied in the framework of the quantum theory of atoms in molecules (AIM). The GW quasi-particle approximation is used to correct the DFT-underestimation of energy gap, and as a consequence the linear and nonlinear optical properties are significantly enhanced. The second harmonic generation (SHG) displays certain dependence with the ionicity degree decrease through the dependency of the SHG on the band gap. The occurrence of the AIM saddle point is characterized and some clarifying features in relationship with the density topology are exposed, which enable to understand the relation with the second harmonic generation effect.

  11. Dynamic conductivity of the bulk states of n-type HgTe/CdTe quantum well topological insulator

    International Nuclear Information System (INIS)

    We theoretically studied the frequency-dependent current response of the bulk state of topological insulator HgTe/CdTe quantum well. The optical conductivity is mainly due to the inter-band process at high frequencies. At low frequencies, intra-band process dominates with a dramatic drop to near zero before the inter-band contribution takes over. The conductivity decreases with temperature at low temperature and increases with temperature at high temperature. The transport scattering rate has an opposite frequency dependence in the low and high temperature regime. The different frequency dependence is due to the interplay of the carrier-impurity scattering and carrier population near the Fermi surface

  12. Speciation of Aquatic Heavy Metals in Humic Substances by$^{111m}$Cd/$^{199m}$Hg-TDPAC

    CERN Multimedia

    2002-01-01

    Humic substances are ubiquitous in waters and soils and act as complexing agents for different heavy metals, e.g. Cd, Hg. Toxicity, reactivity, fixation and migration are therefore strongly influenced by the interactions between heavy metals and humic substances. Humic substances derive from postmortal materials such as rotten plants, have dark colours and usually a molecular weight between 500 and 10~000 Dalton. Complex formation studies with different heavy metal ions indicate at least two different kinds of metal sites. Usually, these studies are restricted to heavy metal concentrations 2 to 3 orders of magnitude higher than the natural heavy metal abundance (i.e. 10$^{-10}$ molar). This serious limitation can be overcome by the use of suitable radiosotope techniques capable of metal speciation at extreme sensitivity levels such as TDPAC (Time Differential Perturbed Angular Correlation of~$\\gamma$-rays). Thus, we studied the interaction of heavy metals with humic substances by monitoring the nuclear quadru...

  13. Speciation and behaviour of Cd, Pb and Cu in Zuari Estuary, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    George, M.D.

    Dissolved labile and nonlabile forms of Cd, Pb and Cu in Zuari Estuary, Goa, India measured for a period of 14 months showed lowest concentrations during the SW monsoon (June-September) while maximum concentrations were observed during...

  14. The growth and characterization of (211) and (133) Oriented (Hg,Cd)Te epilayers (211)B GaAs by organometallic vapor phase epitaxy

    Science.gov (United States)

    Gouws, G. J.; Muller, R. J.

    1995-09-01

    The growth of CdTe buffer layers on (211)B GaAs substrates by organometallic vapor phase epitaxy (OMVPE) was studied, and it was found that, depending on the growth conditions, either the (211) or (133) epitaxial orientation could be formed. In some cases, an epilayer showing a mixed (211) and (133) orientation was also observed. The influence of several growth parameters on the orientation of the CdTe layer was investigated, and it was found that the Te/Cd ratio, together with the growth temperature, have the most significant effect in determining the epilayer orientation. From these results, it was then possible to select nominally optimized growth conditions for CdTe buffer layers of both orientations. (Hg,Cd)Te layers of the same orientations could then be grown and characterized. Although double crystal x-ray diffraction measurements indicated a somewhat better crystalline perfection in the (133) (Hg,Cd)Te layers, these layers showed a poor surface morphology compared to the (211) orientation. Measurement of etch pit densities also indicated defect densities to be typically half an order of magnitude higher in the (133) orientation. Diodes were formed by ion implantation in both orientations and significantly better results were obtained on the (211) (Hg,Cd)Te layers.

  15. The vertical photoconductor: A novel device structure suitable for HgCdTe two-dimensional infrared focal plane arrays

    Science.gov (United States)

    Siliquini, J. F.; Faraone, L.

    1997-06-01

    A novel photoconductive device structure is proposed and described that has been designed specifically as a sensing element for high density two-dimensional infrared focal plane array (IRFPA) applications. Although the design concept can be applied to a variety of epitaxially grown HgCdTe material, optimum performance can be achieved using n-type HgCdTe semiconductor material consisting of epitaxially grown heterostructure layers in which a two-dimensional mosaic of vertical design photoconductors are fabricated. The heterostructure layers provide high performance devices at greatly reduced power dissipation levels, while the vertical design allows for the high density integration of photoconductors in a two-dimensional array geometry with high fill factor. The salient feature of the proposed device structure is that the bias field is applied in the vertical direction such that it is parallel to the impinging infrared radiation. A comprehensive one-dimensional model is presented for the vertical design photoconductor, which is subsequently used to determine the optimum design parameters in order to achieve maximum responsivity at the lowest possible power dissipation level. It is found that the proposed device structure has the potential to be used in the fabrication of long wavelength IRFPAs approaching 10 6 pixels using 25 × 25 μm 2 detector elements. Furthermore, this is achieved with individual device detectivities that are background limited and for a total array power dissipation of less than 0.1 W using a pulsed biasing scheme. Performance issues such as response uniformity, pixel yield, fill factor, crosstalk, power dissipation, detector impedance, array architecture, and maximum array size are discussed in relation to the suitability of the proposed vertical photoconductor structure for use in IRFPA modules. When considering IRFPA operability, it is found that in many cases the proposed technology has the potential to deliver significant advantages, such

  16. Large-scale numerical simulation of reduced-pitch HgCdTe infrared detector arrays

    Science.gov (United States)

    Pinkie, Benjamin; Bellotti, Enrico

    2013-06-01

    Numerical simulations play an important role in the development of large-format infrared detector array tech- nologies, especially when considering devices whose sizes are comparable to the wavelength of the radiation they are detecting. Computational models can be used to predict the optical and electrical response of such devices and evaluate designs prior to fabrication. We have developed a simulation framework which solves Maxwell's equations to determine the electromagnetic properties of a detector and subsequently uses a drift-diffusion ap- proach to asses the electrical response. We apply these techniques to gauge the effects of cathode placement on the inter- and intra-pixel attributes of compositionally graded and constant Hg1-xCdxTe mid-wavelength infrared detectors. In particular, the quantum efficiency, nearest-neighbor crosstalk, and modulation transfer function are evaluated for several device architectures.

  17. Influence of Cu2+ dopant in optical property of CdTe quantum dots and photoelectrochemical performance of CdTe:Cu2+/TiO2 nanotube arrays

    Science.gov (United States)

    Chen, Qian; Geng, Yue; Zhou, Chunyan; Song, Jiahui; Zhou, Liya

    2016-05-01

    A novel one-step synthesis process was used to prepare CdTe:Cu2+/TiO2 nanotube arrays (TNTAs). X-ray powder diffraction and high-resolution transmission electron microscopy analyses confirmed that the obtained CdTe:Cu2+ quantum dots (QDs) possess cubic structures, which are approximately spherical, and a small particle size (2.95 nm). The photoluminescent and UV-visible absorption spectra of CdTe:Cu2+ QDs also display an obvious redshift, which was attributed to the replacement of Cd2+ with Cu2+. Compared with that of the TNTAs and CdTe/TNTAs, the photoelectric conversion efficiency of CdTe:5% Cu2+/TNTAs increased by 785.7% and 103.3%, respectively. The incident photo-to-current conversion efficiency of CdTe:5% Cu2+/TNTAs was 50.6%, which indicated the potential use of QDs in photochemical solar cells.

  18. Periodicity of element and compounds in U,Bi,Pb,Hg,Pt,Sn,Zn,Cu,Ni,Fe deposits

    International Nuclear Information System (INIS)

    The analysis of succession of mineral formation of various types of endogene mineralization at U, Bi, Pb, Hg, Sn, Zn, Cu, Na, Co, Fe deposits is performed. It is shown that despite the difference in genetic types and physico-chemical conditions of formation in different type systems the regular succession in mineral formation exists. The main succession factors of mineral formation in all systems are charge, atomic masses and volume, electronic configuration, entropy and valent state of the element. In uranium deposits penta-element, sulphide-pitchblende, Ti-U-formations. In the above formation the following succession of mineral formation is established: 1) silicate-oxidic, association, 2) quartz-sulphide, 3) quartz-carbonate-pitchblende, 4) fluorite-arsenide, 5) quartz-hematite

  19. Cu(I), Ag(I), Cd(II), and Pb(II) binding to biomolecules studied by perturbed angular correlation of $\\gamma$-rays (PAC) spectroscopy

    CERN Multimedia

    Metal ions display diverse functions in biological systems and are essential components in both protein and nucleic acid structure and function, and in control of biochemical reaction paths and signalling. Similarly, metal ions may be used to control structure and function of synthetic biomolecules, and thus be a tool in the design of molecules with a desired function. In this project we address a variety of questions concerning both the function of metal ions in natural systems, in synthetic biomolecules, and the toxic effect of some metal ions. All projects involve other experimental techniques such as NMR, EXAFS, UV-Vis, fluorescence, and CD spectroscopies providing complementary data, as well as interpretation of the experimental data by quantum mechanical calculations of spectroscopic properties. The isotopes to be employed in the proposal are the following: $^{111m}$Cd, $^{111}$Ag, $^{199}$mHg, $^{204m}$Pb, $^{61}$Cu, $^{68m}$Cu

  20. Environmental pollution study by Hg, Pb, Cd, and Zn in Chetumal bay, Quintana Roo, Mexico

    International Nuclear Information System (INIS)

    The environmental pollution by heavy metals in Chetumal Bay was studied, quantifying mercury, lead, cadmium and zinc concentrations in mussels tissue (Mytilopsis sallei) and sea sediments by collecting samples in two seasons of the year (drought and rainy). Moreover, determining the motion of Cd, Pb and Zn in sediments using a BCR's sequential extraction scheme and identifying the different mineral phases by X-ray diffraction. From this study, it was observed that the Pb, Cd and Zn concentrations were lower in mussels than sediments. However the concentrations profiles for these metals are similar in mussels and sediments. Statistical correlations from the results are presented and discussed. The results obtained are in good agreement with published values for polluted sediments

  1. Effects of heat treatment on diffusion of Cu atoms into CdTe single crystals

    International Nuclear Information System (INIS)

    Angular dependence of x-ray fluorescence and x-ray absorption fine structure techniques have been used to study the diffusion of Cu atoms into the photovoltaic material CdTe. Depth profile, effective valency, and local structure of Cu atoms in a Cu-doped single crystal of CdTe were investigated before and after a second heat treatment. Enhanced Cu diffusion into the CdTe single crystal was observed as a result of heating at a moderate temperature around 200 degree sign C, resulting in a redistribution of the Cu impurities through a broader depth profile. Some of the Cu atoms are believed either to form small complexes with Te or occupy interstitial sites in the host but accompanied by a large local lattice distortion while others substitute for Cd on the cation sites. The results thus demonstrate that these nondestructive x-ray characterization methods are useful for probing microstructural changes in CdTe photovoltaic materials/devices in which some Cu-containing compounds are used as back contacts. (c) 2000 American Institute of Physics

  2. Oxygen ordering in the high-T$_c$ superconductor HgBa$_2$CaCu$_2$O$_{6+\\delta}$ as revealed by perturbed angular correlation

    CERN Document Server

    Mendonca, Tania Melo; Haas, Heinz; Odier, Philippe; Tavares, Pedro; Silva, Manuel Ribeiro; Lopes, Armandina; Pereira, Andre; Goncalves, Joao Nuno; Amaral, Joao; Darie, Celine; Araujo, Joao Pedro

    2011-01-01

    Lattice sites and collective ordering of oxygen atoms in HgBa$_2$CaCu$_2$O$_{6+\\delta}$ were studied using the perturbed angular correlation (PAC) technique at ISOLDE/CERN. The electric field gradients (EFG) at $^{199m}$Hg nuclei have been measured as functions of oxygen doping on the Hg planes, above and below T$_c$. In comparison with the results obtained for oxygen and fluorine doping in Hg-1201, the analysis shows a different oxygen ordering exhibited by Hg-1212. Moreover, for all studied cases, the experimental results show that at a local scale there is non-uniform oxygen distribution. A series of ab initio EFG calculations allowed to infer that at low concentrations, regions without oxygen coexist with regions where O$_{2\\delta}$ dumbbell molecules are located at the center of the Hg mesh. On the other side, at high concentrations, O$_{2\\delta}$ dumbbell molecules coexist with single O$_\\delta$ atoms occupying the center of the Hg mesh. The present results suggest that oxygen sits on the Hg planes in t...

  3. PENINGKATAN KUALITAS FILM TIPIS CdTe SEBAGAI ABSORBER SEL SURYA DENGAN MENGGUNAKAN DOPING TEMBAGA (Cu

    Directory of Open Access Journals (Sweden)

    P. Marwoto

    2012-12-01

    Full Text Available Film tipis CdTe dengan doping tembaga (Cu berkonsenterasi 2% telah berhasil ditumbuhkan di atas substrat Indium Tin Oxide (ITO dengan metode dc magnetron sputtering. Penelitian ini dilakukan untuk mengetahui pengaruh doping Cu(2% terhadap struktur morfologi, struktur kristal, fotoluminisensi dan resistivitas listrik film CdTe. Citra morfologi Scanning Electron Microscopy (SEM dan hasil analisis struktur dengan X-Ray Diffraction (XRD menunjukkan bahwa film CdTe:Cu(2% mempunyai citra permukaan dan struktur kristal yang lebih sempurna dibandingkan film CdTe tanpa doping. Hasil analisis spektrometer fotoluminisensi menunjukkan bahwa film CdTe dan CdTe(2% mempunyai puncak fotoluminisensi pada tiga panjang gelombang yang identik yaitu 685 nm (1,81 eV, 725 nm (1,71 eV dan 740 nm (1,67 eV. Film CdTe dengan doping Cu(2% memiliki intensitas puncak fotoluminisensi yang lebih tajam pada pita energi 1,81 eV dibandingkan dengan film CdTe tanpa doping. Pengukuran arus dan tegangan (I-V menunjukkan bahwa pemberian doping Cu(2% dapat menurunkan resistivitas film dari 8,40x109 Ωcm menjadi 6,92x105 Ωcm. Sebagai absorber sel surya, kualitas film tipis CdTe telah berhasil ditingkatkan dengan pemberian doping Cu(2%.CdTe:Cu(2% thin film has been successfully grown on Indium Tin Oxide (ITO substrates by using dc magnetron sputtering. This study was carried out in order to investigate the effect of Cu(2% doping on the morphologycal structure, crystal structure, photoluminesence, and resistivity of CdTe thin film. Scanning Electron Microscopy (SEM  images and X-Ray Diffraction (XRD results showed that CdTe:Cu(2% thin film has morphologycal and crystal structures more perfect than undoped CdTe film. Photoluminesence spectroscopy results showed that CdTe and CdTe:Cu(2% thin films have luminesence peak at three identical wevelength regions i.e. 685 nm (1.81 eV, 725 nm (1.71 eV and 740 nm (1.67 eV however CdTe:Cu(2% film shows sharper photoluminescence peak at band

  4. On characteristics of PVA/CdS and PVA/CdS:Cu nanocomposites for applications as LED

    Energy Technology Data Exchange (ETDEWEB)

    Kakati, Jumi, E-mail: jumikakati@gmail.com [Department of Electronics and Communication Technology, Gauhati University, Guwahati-781014, Assam (India); Datta, Pranayee [Department of Electronics and Communication Technology, Gauhati University, Guwahati-781014, Assam (India)

    2013-06-15

    We report the synthesis of poly vinyl alcohol/cadmium sulphide (PVA/CdS) and polyvinyl alcohol/cadmium sulphide:copper (PVA/CdS:Cu) nanocomposites by chemical route. Characterizations are done by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), ultra violet–visible (UV–VIS), photoluminescence (PL), energy dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). Sizes of the fabricated nanoparticles (NCs) obtained from XRD are in good agreement with those from TEM/HRTEM and confinement is found to be strong in some samples. The photoluminescence (PL) spectra show luminescence from band edge emission (481 nm) as well as from trap levels caused by sulpher vacancies (510 nm, 538 nm, 572 nm) and from defect states in case of doped sample (500 nm). The photoluminescence and electroluminescence (EL) spectra without as well as with applied (DC) bias are also studied using platinum electrodes in liquid samples. Results indicate that peak position remains same in both the cases of PL and EL and intensity is roughly an increasing function of excitation voltage. Encouraged by the results obtained so far, which indicates possible applications of the samples fabricated as LED, nano devices with ITO/N,N′-bis(3 methylphenyl)–N,N′-bis(phenyl)benzidine (TPD)/NC/Al have been fabricated to study the EL spectra. Operating voltages for PVA/CdS light emitting device (LED) is 0.2 V and for PVA/CdS:Cu light emitting device (LED) is 0.1 V. The emission dominantly belongs to CdS nanocrystals (NCs). Highest external quantum efficiency estimated for the PVA/CdS nanocomposites LED is 0.0024%. The highest external quantum efficiency gets increased upto 0.0027% after doping the PVA/CdS nanocomposites with Cu. -- Highlights: ► We synthesized CdS and CdS:Cu nanocrystals by chemical route method. ► PL and EL are found in the same position. ► Emission

  5. 碲镉汞的液相外延生长%Growth of HgCdTe by Liquid Phase Epitaxy

    Institute of Scientific and Technical Information of China (English)

    黄仕华; 何景福; 陈建才; 雷春红

    2001-01-01

    A novel graphite boat has been designed and an open-tube system for LPE growth with a mercury source been set up.With hydrogen as carrying gas,the mercury steam from a heating mercury source would compensate that volatilized from the growth liquid.Epitaxial films of HgCdTe with various values of x have been grown in Te-rich solution and on CdZnTe substrates using this system.By controlling the growth procedure,the morphology of HgCdTe epitaxial films is observed improved obviously,and remained melt on the surface of films has been reduced greatly.The constituent of epitaxial films is rather homogeneous with electrical characteristic improved obviously.The inter-diffusion between MCT epitaxial films and CdZnTe substrates is very little,and the crystal structure of MCT epitaxial films is perfect.%设计了一种使用良好的石墨舟,建立了一套能进行开管液相外延的系统,并利用此系统在CdZnTe衬底上和在富Te的生长条件下生长了不同x值的HgCdTe外延薄膜.通过对外延生长工艺的控制,外延薄膜的表面形貌有很大的改善,残留母液大为减少,外延薄膜的组分比较均匀,其电学性能得到较大改善,HgCdTe外延薄膜与CdZnTe衬底之间的互扩散非常少,外延膜的晶体结构也较完整.

  6. MBE growth of HgCdTe avalanche photodiode structures for low-noise 1.55 μm photodetection

    Science.gov (United States)

    de Lyon, T. J.; Baumgratz, B.; Chapman, G.; Gordon, E.; Hunter, A. T.; Jack, M.; Jensen, J. E.; Johnson, W.; Johs, B.; Kosai, K.; Larsen, W.; Olson, G. L.; Sen, M.; Walker, B.; Wu, O. K.

    1999-05-01

    Molecular-beam epitaxy (MBE) has been utilized to fabricate HgCdTe heterostructure separate absorption and multiplication avalanche photodiodes (SAM-APD) sensitive to infrared radiation in the 1.1-1.6 μm spectral range, as an alternative technology to existing III-V APD detectors. Device structures were grown on CdZnTe(211)B substrates using CdTe, Te, and Hg sources with in situ In and As doping. The composition of the HgCdTe alloy layers was adjusted to achieve both efficient absorption of IR radiation in the 1.1-1.6 μm spectral range and low excess-noise avalanche multiplication. The Hg 1- xCd xTe alloy composition in the gain region of the device, x=0.73, was selected to achieve equality between the bandgap energy and spin-orbit splitting to resonantly enhance the impact ionization of holes in the split-off valence band. The appropriate value of this alloy composition was determined from analysis of the 300 K bandgap and spin-orbit splitting energies of a set of calibration layers, using a combination of IR transmission and spectroscopic ellipsometry measurements. MBE-grown APD epitaxial wafers were processed into passivated mesa-type discrete device structures and diode mini-arrays using conventional HgCdTe process technology. Device spectral response, dark current density, and avalanche gain measurements were performed on the processed wafers. Avalanche gains in the range of 30-40 at reverse bias of 85-90 V and array-median dark current density below 2×10 -4 A/cm 2 at 40 V reverse bias have been demonstrated.

  7. Synthesis and characterization of aspartic acid-capped CdS/ZnS quantum dots in reverse micelles and its application to Hg(II) determination

    International Nuclear Information System (INIS)

    In this work, CdS/ZnS quantum dots (QDs) coated with aspartic acid (AsA) were synthesized in reverse micelles. The synthesized QDs were characterized by XRD, TEM, IR and photoluminescence (PL) spectroscopy. It was found that the intensity of CdS/ZnS QDs coated with AsA is much greater than CdS, and CdS/ZnS QDs. The interaction of some heavy metal ions with CdS/ZnS/AsA QDs was investigated at different buffering pH media. Based on the PL quenching of the QDs in the presence of each one of the metal ions, the feasibility of their determinations was examined according to the Stern–Volmer equation. The investigations showed that Hg(II) ions can be easily determined in contaminated atmospheric environments with the detection limit of 0.05 mg m−3. The results were satisfactorily confirmed by cold vapor atomic absorption spectrometric method. - Highlights: • A new CdS/ZnS quantum dot capped with aspartic acid (DDBA) was prepared. • The prepared QDs benefit from a favorable fluorescence. • Interaction of some metal ions with the QDs was examined according to the Stern–Volmer equation. • The determination of Hg(II) is feasible in the present of many co-existence metal ions. • The method benefits from a high-speed and considerable simplicity for Hg(II) determination

  8. Synthesis and characterization of aspartic acid-capped CdS/ZnS quantum dots in reverse micelles and its application to Hg(II) determination

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Mohammad Saeid, E-mail: mshosseini1336@yahoo.com; Kamali, Mohsen

    2015-11-15

    In this work, CdS/ZnS quantum dots (QDs) coated with aspartic acid (AsA) were synthesized in reverse micelles. The synthesized QDs were characterized by XRD, TEM, IR and photoluminescence (PL) spectroscopy. It was found that the intensity of CdS/ZnS QDs coated with AsA is much greater than CdS, and CdS/ZnS QDs. The interaction of some heavy metal ions with CdS/ZnS/AsA QDs was investigated at different buffering pH media. Based on the PL quenching of the QDs in the presence of each one of the metal ions, the feasibility of their determinations was examined according to the Stern–Volmer equation. The investigations showed that Hg(II) ions can be easily determined in contaminated atmospheric environments with the detection limit of 0.05 mg m{sup −3}. The results were satisfactorily confirmed by cold vapor atomic absorption spectrometric method. - Highlights: • A new CdS/ZnS quantum dot capped with aspartic acid (DDBA) was prepared. • The prepared QDs benefit from a favorable fluorescence. • Interaction of some metal ions with the QDs was examined according to the Stern–Volmer equation. • The determination of Hg(II) is feasible in the present of many co-existence metal ions. • The method benefits from a high-speed and considerable simplicity for Hg(II) determination.

  9. Numerical Simulation of Refractive-Microlensed HgCdTe Infrared Focal Plane Arrays Operating in Optical Systems

    Science.gov (United States)

    Li, Yang; Ye, Zhen-Hua; Hu, Wei-Da; Lei, Wen; Gao, Yan-Lin; He, Kai; Hua, Hua; Zhang, Peng; Chen, Yi-Yu; Lin, Chun; Hu, Xiao-Ning; Ding, Rui-Jun; He, Li

    2014-08-01

    The optoelectronic performance of the mid-wavelength HgCdTe infrared focal plane array (IRFPA) with refractive microlenses integrated on its CdZnTe substrate has been numerically simulated. A reduced light-distribution model based on scalar Kirchhoff diffraction theory was adopted to reveal the true behavior of IRFPAs operating in an optical system under imaging conditions. The pixel crosstalk obtained and the energy-gathering characteristics demonstrated that the microlenses can delay the rise in crosstalk when the image point shifts toward pixel boundaries, and can restrict the major optical absorption process in any case within a narrow region around the pixel center. The dependence of the microlenses' effects on the system's properties was also analyzed; this showed that intermediate relative aperture and small microlens radius are required for optimized device performance. Simulation results also indicated that for detectors farther from the center of the field of view, the efficacy of microlenses in crosstalk suppression and energy gathering is still maintained, except for a negligible difference in the lateral magnification from an ordinary array without microlenses.

  10. Photoelectrical characteristics of metal–insulator–semiconductor structures based on graded-gap HgCdTe grown by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Metal–insulator–semiconductor structures based on HgCdTe are grown by molecular-beam epitaxy. Near-surface graded-gap layers with high CdTe content are formed on both sides of the epitaxial HgCdTe film. Photoelectrical characteristics of these structures are studied experimentally and theoretically. For structures based on n-Hg1−xCdxTe (x = 0.21–0.23), the formation of a near-surface graded-gap layer leads to an increase in the differential resistance of the space charge region due to the suppression of tunneling. The temperature dependences of the differential resistance calculated with account to different mechanisms of generation of minority charge carriers are similar to the experimental dependences of the photoelectromotive force. - Highlights: • The metal–insulator–semiconductor structures based on HgCdTe were studied. • Photoelectrical properties of such structures were investigated. • Mechanisms of generation of minority carriers were studied. • Creation of near-surface graded-gap layers suppresses tunneling

  11. Selected trace metals (As, Cd and Hg) distribution and contamination in the coastal wetland sediment of the northern Beibu Gulf, South China Sea

    International Nuclear Information System (INIS)

    Highlights: ► Spatial and temporal distributions of As, Cd and Hg were presented. ► Mean sedimentation rates were 0.93–1.37 cm year−1 during 1920s to 2008. ► Metal content increased evidently in 1985–2008 due to anthropogenic impacts. ► Locally the surface sediments have potential ecological risk of As to benthos. -- Abstract: Contamination with As, Cd and Hg, their spatial and temporal distribution are reported from the coastal wetland sediments of the northern Beibu Gulf, South China Sea. The content of As, Cd, Hg and TOC in surface sediments is 8.1 ± 5.8 μg g−1, 0.08 ± 0.14 μg g−1, 0.034 ± 0.028 μg g−1 and 0.45 ± 0.39%, respectively. The mean sedimentation rates are 0.93–1.37 cm year−1 during 1920s to 2008 determined by 210Pb and 137Cs dating in three cores. The vertical profiles of As, Cd and Hg content in the cores retrieved from Qin and Nanliu River estuaries show increasing trends during 1985–2008 due to anthropogenic impact caused by local economic development. Locally the surface sediments have potential ecological risk of As to benthos according to the NOAA sediment quality guidelines

  12. Modification and characterization of PET fibers for fast removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions.

    Science.gov (United States)

    Monier, M; Abdel-Latif, D A

    2013-04-15

    A new chelating fiber (PET-TSC) was prepared with PET for fast removal of Hg(2+), Cu(2+) and Co(2+) from water. Elemental analysis, SEM, BET surface area, (13)C NMR, FTIR and X-ray diffraction spectra were used to characterize PET-TSC. The higher uptake capacity of the studied metal ions was observed at higher pH values. Kinetic study indicated that the adsorption of Hg(2+), Cu(2+) and Co(2+) followed the pseudo-second-order equation, suggesting chemical sorption as the rate-limiting step of the adsorption process. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 120.02, 96.81 and 78.08 mg/g for Hg(2+), Cu(2+) and Co(2+) ions, respectively. 1M HCl or 0.1M EDTA could be used as effective eluant to desorb the Hg(2+), Cu(2+) and Co(2+) adsorbed by PET-TSC, and the adsorption capacity of PET-TSC for the three heavy metal ions could still be maintained at about 90% level at the 5th cycle. Accordingly, it is expected that PET-TSC could be used as a promising adsorbent for fast removal of heavy metal ions from water, and the present work also might provide a simple and effective method to reuse the waste PET fibers. PMID:23435202

  13. Crystal structure of the Cu{sub 5.976}Hg{sub 0.972}SiSe{sub 6} compound

    Energy Technology Data Exchange (ETDEWEB)

    Gulay, L.D.; Parasyuk, O.V.; Romanyuk, Ya.E.; Olekseyuk, I.D

    2004-03-24

    The crystal structure of the quaternary phase Cu{sub 5.976}Hg{sub 0.972}SiSe{sub 6} was investigated using X-ray powder diffraction. This phase crystallizes in a cubic structure (space group F4-bar 3m, a=1.03013(2) nm) and is isostructural with Ag{sub 8}GeTe{sub 6}. The atomic parameters were refined in anisotropic approximation (R{sub I}=0.0604). The relation between Cu{sub 5.976}Hg{sub 0.972}SiSe{sub 6} and previously investigated compounds with approximate composition A{sub 6}{sup I}HgB{sup IV}X{sub 6} is described.

  14. Stability testing of ZnTe:N as a Cu-free back contact to CdTe/CdS solar cells

    Science.gov (United States)

    Simmons, D. A.

    2000-03-01

    Most CdTe/CdS solar cell devices use Cu as a back contact, but recent studies have suggested Cu may cause instabilities in the device under some extreme conditions. We have used rf-sputter deposited ZnTe:N as an alternative back contact to CdTe/CdS solar cells. Identical CdTe/CdS solar cells were back-contacted with ZnTe:N or a standard Cu/Au contact. Sets of both types of cells were subjected to either 3000 hours of baking at 100 C in the dark, or 3000 hours of light-soaking at 1 sun. While initial efficiencies of the Cu cells were slightly higher than the ZnTe:N cells, the ZnTe:N cells performed much better after baking and equally as well after light-soaking as the Cu cells.

  15. Effects of Different Doping Ratio of Cu Doped CdS on QDSCs Performance

    OpenAIRE

    Xiaojun Zhu; Xiaoping Zou; Hongquan Zhou

    2015-01-01

    We use the successive ionic layer adsorption and reaction (SILAR) method for the preparation of quantum dot sensitized solar cells, to improve the performance of solar cells by doping quantum dots. We tested the UV-Vis absorption spectrum of undoped CdS QDSCs and Cu doped CdS QDSCs with different doping ratios. The doping ratios of copper were 1 : 100, 1 : 500, and 1 : 1000, respectively. The experimental results show that, under the same SILAR cycle number, Cu doped CdS quantum dot sensitize...

  16. Modification and characterization of PET fibers for fast removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Monier, M., E-mail: monierchem@yahoo.com [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt); Abdel-Latif, D.A. [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt)

    2013-04-15

    Highlights: ► PET fibers were graft copolymerized with acrylonitrile. ► Further modification was carried out through the reaction with hydrazine hydrate and then potassium thiocyanate. ► The resulted chelating fibers were characterized by various instrumental methods. ► The fibers were applied to remove Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} from aqueous solutions. -- Abstract: A new chelating fiber (PET-TSC) was prepared with PET for fast removal of Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} from water. Elemental analysis, SEM, BET surface area, {sup 13}C NMR, FTIR and X-ray diffraction spectra were used to characterize PET-TSC. The higher uptake capacity of the studied metal ions was observed at higher pH values. Kinetic study indicated that the adsorption of Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} followed the pseudo-second-order equation, suggesting chemical sorption as the rate-limiting step of the adsorption process. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 120.02, 96.81 and 78.08 mg/g for Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} ions, respectively. 1 M HCl or 0.1 M EDTA could be used as effective eluant to desorb the Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} adsorbed by PET-TSC, and the adsorption capacity of PET-TSC for the three heavy metal ions could still be maintained at about 90% level at the 5th cycle. Accordingly, it is expected that PET-TSC could be used as a promising adsorbent for fast removal of heavy metal ions from water, and the present work also might provide a simple and effective method to reuse the waste PET fibers.

  17. Fabrication of CdS/CdTe solar cells with transparent p-type conductive BaCuSeF back contact

    Science.gov (United States)

    Yamamoto, Koichi; Sakakima, Hiroshi; Ogawa, Yohei; Hosono, Aikyo; Okamoto, Tamotsu; Wada, Takahiro

    2015-08-01

    BaCuSeF films were applied to CdS/CdTe solar cells as back electrodes. The interfaces between the CdTe and BaCuSeF layers in the CdS/CdTe solar cells with BaCuSeF back contact deposited at substrate temperatures (TS) of 200 and 300 °C were analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). We clearly observed many dislocations in the CdTe layer in the CdS/CdTe solar cell with the BaCuSeF layer deposited at TS = 300 °C. We also observed a reaction layer of Cu2.72Te2 between the BaCuSeF and CdTe layers in both solar cells. We concluded that (1) the substrate temperature for the pulsed laser deposition of the BaCuSeF layer and (2) the interface between the CdTe and BaCuSeF layers are important factors for the performance of the CdTe solar cells. We obtained high conversion efficiency of 8.31% for a solar cell with a BaCuSeF layer deposited at TS = 200 °C on a CdTe surface etched in a NH3 aqueous solution. The highest conversion efficiency of 9.91% was obtained for a solar cell with a CdTe surface etched in a bromide-bromate solution.

  18. Sputtered CdTe thin film solar cells with Cu2Te/Au back contact

    International Nuclear Information System (INIS)

    In this work, Cu2Te/Au back contact for CdTe thin film solar cells were prepared by vacuum evaporation. Influence of annealing temperature on the structure and electrical properties of Cu2Te films were investigated by field emission scanning electron microscope, X-ray diffraction, and Hall effect measurement. Also, CdS/CdTe thin film solar cells were fabricated by magnetron sputtering process, which is favorable for large area deposition and mass production, and the photovoltaic characteristics were studied. As the annealing temperature was increased, the crystal structure transformed from Cu2Te for as-deposited film to Cu2−xTe hexagonal phase, and the grains in the film became bigger. The electrical resistivity was slightly higher by the annealing. The cell efficiency was significantly improved by the heat treatment, and showed a maximum value of 9.14% at 180 °C. From these results, Cu2Te/Au contact acts as the proper pseudo-ohmic contact onto CdTe film. However, further increase of annealing temperature caused the deterioration of cell performance. - Highlights: • Annealing effects of the vacuum evaporated Cu2Te films were investigated. • The transformation from Cu2Te to Cu2−xTe hexagonal phase occurred by annealing. • The performance of the solar cell was highly increased by annealing at 180 °C. • Cu2Te/Au contact acts as the proper pseudo-ohmic contact onto CdTe film

  19. Hg/sub 1-x-y/Mn/sub x/Cd/sub y/Te alloys for 1.3-1.8 μm photodiode applications

    International Nuclear Information System (INIS)

    HgMnCdTe/CdTe photodiodes with responsivity cutoffs of up to 1.54 μm have been fabricated by liquid phase epitaxy (LPE). The mesa device structure consists of a boron-implanted mosaic fabricated on a p-type Hg/sub 1-x-y/Mn/sub x/Cd/sub y/Te layer grown on a CdTe substrate. A reverse breakdown voltage (V/sub B/) of 50 V and a leakage current density of 1.5 x 10/sup -4/ A/cm/sup 2/ at V = -10 V was measured at room temperature (295K). A 0.75 pF capacitance was also measured under a 5 V reverse bias at room temperature. This device performance based on the quaternary HgMnCdTe shows both theoretical and practical promise of superior performance for wavelengths in the range 1.3 to 1.8 μm for fiber optic applications

  20. Fabrication of Hg(Tl)-Ba-Ca-Cu-O high-Tc thin film RF-SQUID and its operation up to 121 K

    International Nuclear Information System (INIS)

    The development of high-Tc SQUID operating at temperatures higher than 77 K is very much desirable for reducing the cost of cryocoolers so that widespread field application of SQUID may become a reality. YBCO SQUID has been operated up to 87 K where as Bi (Pb) SrCaCuO and TlBaCaCuO high-Tc SQUID have shown SQUID modulation characteristics up to 101 K. The discovery of superconductivity in Hg-based high-Tc with maximum Tc ≅ 133 K at ambient pressure has generated hopes to develop high-Tc SQUID which can be operated at further higher temperatures. This paper reports fabrication of Hg(Tl)-Ba-Ca-Cu-O high-Tc thin film rf- SQUID using natural grain boundary junction and its operation; up to 121 K which is the highest temperature reported so far

  1. Pathways toward higher performance CdS/CdTe devices: Te exposure of CdTe surface before ZnTe:Cu/Ti contacting

    International Nuclear Information System (INIS)

    Many studies of thin-film CdS/CdTe photovoltaic devices have suggested that performance may be improved by reducing recombination due to Te-vacancy (VTe), Te antisite (TeCd), or Te-interstitial (Tei) defects. Although formation of these intrinsic defects is likely influenced by CdTe deposition parameters, it may be also coupled to the formation of beneficial cadmium vacancy (VCd) defects. In this study, we expose the CdTe surface to Te vapor prior to ZnTe:Cu/Ti contact-interface formation with the goal of reducing VTe without significantly reducing VCd. Initial results show that when this modified contact is used on a CdCl2-treated CdS/CdTe device, poorer device performance results. This suggests two things: First, the amount of free-Te available during contact formation (either from chemical etching or CuxTe or ZnTe deposition) may be a more important parameter to device performance than previously appreciated. Second, if processes have been used to reduce the effect of VTe (e.g., oxygen and chlorine additions), adding even a small amount of Te may produce detrimental defects. - Highlights: ► Te exposure of CdS/CdTe back contact reduces device performance. ► Field strength and minority carrier lifetime reduced. ► Calculations suggest formation of Te on Cd antisite defect

  2. Diffusion in CdS of Cd and S vacancies and Cu, Cd, Cl, S and Te interstitials studied with first-principles computations

    International Nuclear Information System (INIS)

    We present an ab initio study of the diffusion profiles in CdS of native, Cd and S vacancies, and interstitial adatoms Cd, S, Te, Cu, and Cl. The global minimum and saddle point positions in the bulk unit cell vary for different diffusing species. This results in a significant variation, in the bonding configurations and associated strain energies of different extrema positions along the diffusion paths for various defects. The rate-limiting diffusion barriers range from a low of 0.42 eV for an S interstitial to a high of 2.18 eV for a S vacancy. The rate-limiting barrier is 0.66 eV for Cu and Te interstitials, 0.76 eV for Cl interstitial, 0.87 eV for Cd interstitial and 1.09 eV for the Cd vacancy. The 0.66 eV barrier for a Cu interstitial is in good agreement with experimental values in the range of 0.58–0.96 eV reported in the literature. We report an electronic signature in the projected density of states for the s-and d-states of the Cu interstitial at the saddle point and global minimum energy position. In addition, we have examined the relative charge transfer experienced by the interstitials at the extrema positions through Bader analysis. (papers)

  3. Au/Cu2Te/CdTe/CdS/TCO/Glass Solar Cells with CdIn2O4 Obtained by Sol-Gel as TCO

    Directory of Open Access Journals (Sweden)

    J. Márquez Marín

    2014-01-01

    Full Text Available An Au/Cu2Te/CdTe/CdS/TCO/glass heterostructure based superstrate solar cells with 2.5 mm2 of area, where the CdTe layer was prepared by means of closed spaced sublimation (CSS and the CdS by chemical bath, reached an efficiency η value of 12.1%. As transparent conductive oxide (TCO, a thin film of cadmium-indium oxide (CdIn2O4:CIO, obtained by sol-gel technique, was used. A systematic optimization of the thermal activation of the CdTe/CdS/CIO central part of the device with a CdCl2 vapor ambient made the conversion efficiency of the Au/Cu2Te/CdTe/CdS/CIO/glass heterostructure reaches 9.94% for the CdTe layer with thickness of 1.8 μm. This efficiency was reached only through an open circuit voltage VOC optimization. A maximum η of 12.1% was reached with the established procedure of optimization and when the CdTe layer thickness was increased to 3.1 ± 0.05 μm. The substitution of CIO by commercial ITO provoked in the cell a decrease of η from 12.1% to 7.2%, both devices prepared under the same conditions. Starting from these results, we can say that CIO was a better TCO than commercial ITO in our solar cell, with the advantage that CIO was obtained by sol-gel, which is a simple and economical technique.

  4. Impact of the Cd2+ treatment on the electrical properties of Cu2ZnSnSe4 and Cu(In,Ga)Se-2 solar cells

    OpenAIRE

    Ben Messaoud, Khaled; Buffiere, Marie; Brammertz, Guy; ElAnzeery, Hossam; Oueslati, Souhaib; Hamon, Jonathan; Kniknie, Bas J.; MEURIS, Marc; Amlouk, Mosbah; Poortmans, Jef

    2015-01-01

    The present contribution aims at determining the impact of modifying the properties of the absorber/buffer layer interface on the electrical performance of Cu2ZnSnSe4 (CZTSe) thin-film solar cells, by using a Cd2+ partial electrolyte (Cd PE) treatment of the absorber before the buffer layer deposition. In this work, CZTSe/CdS solar cells with and without Cd PE treatment were compared with their respective Cu(In,Ga)Se-2 (CIGSe)/CdS references. The Cd PE treatment was performed in a chemical ba...

  5. [Concentration of Hg, Pb, Cd, Cr and As in liver Carcharhinus limbatus (Carcharhiniformes: Carcharhinidae) captured in Veracruz, Mexico].

    Science.gov (United States)

    Mendoza-Díaz, Fernando; Serrano, Arturo; Cuervo-López, Liliana; López-Jiménez, Alejandra; Galindo, José A; Basañez-Muñoz, Agustin

    2013-06-01

    Pollution by heavy metals in marine ecosystems in the Gulf of Mexico is one of the hardest conservation issues to solve. Sharks as top predators are bioindicators of the marine ecosystem health, since they tend to bioaccumulate and biomagnify contaminants; they also represent a food source for local consumption. Thus, the objective of this study was to study the possible presence of heavy metals and a metalloid in livers of Carcharhinus limbatus. For this, a total of 19 shark livers were taken from animals captured nearby Tamihua, Veracruz, Mexico from December 2007 to April 2008. 12 out of the 19 captured sharks were males, one was an adult female, three were juvenile males, and three juvenile females. Four heavy metals (Hg, Pb, Cd, and Cr) and one metaloid (As) were analyzed in shark livers using an atomic absorption spectrophotometry with flame and hydride generator. Our results showed that the maximum concentrations found were: Hg = 0.69 mg/kg, Cd = 0.43 mg/kg, As = 27.37 mg/kg, Cr = 0.70 mg/kg. The minimum concentrations found were: As = 14.91 mg/kg, Cr = 0.35 mg/kg. The Pb could not be determined because the samples did not have the spectrophotometer minimum detectable amount (0.1 mg/kg). None of the 19 samples analyzed showed above the permissible limits established by Mexican and American laws. There was a correlation between shark size and Cr and As concentration (Pearson test). The concentration of Cr and As was observed to be higher in bigger animals. There was not a significant difference in heavy metals concentration between juveniles and adults; however, there was a difference between males and females. A higher Cr concentration was found in females when compared to males. None of the samples exceed the maximum limit established by the laws of Mexico and the United States of America. Much longer studies are needed with C. limbatus and other species caught in the region, in order to determine the degree of contaminants exposure in aquatic ecosystems

  6. The future of large format HgCdTe arrays for astronomy

    Science.gov (United States)

    Vural, K.

    1994-01-01

    Rockwell has developed the 256 x 256 Near Infrared Camera and Multi-Object Spectrometer 3 (NICMOS3) FPA for the Hubble Space Telescope under funding from NASA through the University of Arizona. Since 1989, dozens of science grade devices have been delivered to astronomers throughout the world for ground based infrared observations. These devices have excellent sensitivity at 77 K with mean dark currents of 0.1 e(-)/s, noise of 25 e(-), and quantum efficiency of 55-70%. Pixel yields as high as 99.9% have been achieved. Our present plans are to develop a 1024 x 1024 focal plane array (FPA) with 2.5 micron cutoff and make it available to astronomers. Such large arrays are made possible by the advances in detector material size (3 in. diameter producible alternative to CdTe for epitaxy (PACE-I) wafers), multiplexer advances (ability to verify the design in detail and availability of advanced foundries), and novel hybridization and reliability approaches.

  7. Concentration of heavy metals (Cu, Pb, Cd, Hg) in feed mixtures, meat and liver of rabbits

    Czech Academy of Sciences Publication Activity Database

    Marounek, Milan; Skřivanová, V.; Tůmová, V.

    Athens : Agriculture University of Athens, 2002. s. 10. [Meeting of the working group 5 in "Meat and meat safety" /2./. 11.04.2002-14.04.2002, Athens] Institutional research plan: CEZ:AV0Z5045916 Keywords : meat * heavy metals Subject RIV: GH - Livestock Nutrition

  8. All Screen-Printed CdS/CuInSe2 Solar Cells

    Science.gov (United States)

    Kuhaimi, S. A. AL; Bahammam, S.

    1990-08-01

    Thick film technology offers advantages of low cost, product amenability and automation. This technology has been successful in the manufacture of solar cells using CdS/CdTe heterojunctions. It enables the use of the same equipment in various processes involved in manufacturing solar cells. In the present work, n-CdS/p-CuInSe2 solar cells are prepared by screen printing and sintering pastes which contain the semiconductors. An efficiency of 8.75% is achieved. Electron affinity difference, saturation current and diode quality factor are measured. They are 0.49 eV, (0.9--1.8)× 10-7 A, 1.5 respectively. Microstructure and electrical properties of sintered CdS films containing 10, 20, 30 and 40 wt% CdCl2 are investigated. Optimum results are obtained for the CdS films containing 10 wt% CdCl2.

  9. Light-stimulated carrier dynamics of CuInS2/CdS heterotetrapod nanocrystals

    Science.gov (United States)

    Sakamoto, Masanori; Inoue, Koki; Okano, Makoto; Saruyama, Masaki; Kim, Sungwon; So, Yeong-Gi; Kimoto, Koji; Kanemitsu, Yoshihiko; Teranishi, Toshiharu

    2016-05-01

    We synthesized a heterotetrapod composed of a chalcopyrite(ch)-CuInS2 core and wurtzite(w)-CdS arms and elucidated its optical properties and light-stimulated carrier dynamics using fs-laser flash photolysis. The CuInS2/CdS heterotetrapod possessed quasi-type II band alignment, which caused much longer-lived charge separation than that in the isolated CuInS2 nanocrystal.We synthesized a heterotetrapod composed of a chalcopyrite(ch)-CuInS2 core and wurtzite(w)-CdS arms and elucidated its optical properties and light-stimulated carrier dynamics using fs-laser flash photolysis. The CuInS2/CdS heterotetrapod possessed quasi-type II band alignment, which caused much longer-lived charge separation than that in the isolated CuInS2 nanocrystal. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01097k

  10. Band spectrum transformation and temperature dependences of thermoelectric power of Hg1-xRxBa2Ca2Cu3O8+δ system

    Directory of Open Access Journals (Sweden)

    M. Vasyuk

    2011-03-01

    Full Text Available Temperature dependences of thermoelectric power S(T at T>Tc of the Hg-based high temperature superconductors Hg1-xRxBa2Ca2Cu3O8+δ (R=Re, Pb have been analyzed with accounting for strong scattering of charge carriers. Transformation of parameters of a narrow conducting band in the region of the Fermi level was studied. The existence of correlation between the effective bandwidth and the temperature of a superconductive transition Tc is shown.

  11. Heavy metal levels (Pb, Cd, Cr and Hg) in the adult general population near an urban solid waste incinerator.

    Science.gov (United States)

    Zubero, Miren Begoña; Aurrekoetxea, Juan José; Ibarluzea, Jesús María; Arenaza, Maria Jesús; Rodríguez, Carlos; Sáenz, José Ramón

    2010-09-15

    In 2005 an urban solid waste incinerator (SWI) was commissioned in Bilbao (Basque Country, Spain). Serum and urine samples were collected from 95 and 107 volunteers in 2006 and 2008 respectively, of which 62 were repeats from the same individuals. Blood lead levels (BPb) were determined, as were the concentrations of cadmium (Cd), chromium (Cr) and mercury (Hg) in urine (UCd, UCr and UHg). The town of Alonsotegi and a borough of Bilbao (Altamira, Rekalde) were considered to be close, less than 2 km from the plant, and correspond to an urban environment with high traffic density. The areas of reference were a borough of Bilbao (Santutxu-Zurbaran), 5 km from the plant, also in an urban area with high traffic density, and a small town with little industrial activity and low traffic density (Balmaseda) 20 km from the plant; neither of these is downwind from the site with respect to prevailing winds. There was a significant correlation for BPb, r=0.63 (p0.05). Multiple linear regression models did not show increases over time of the levels of BPb, UCd, UCr and UHg in the areas close to the SWI compared to those of areas located further away, after adjusting for confounding variables. These results reinforce the hypothesis that populations near modern plants for solid waste incineration do not manifest increased levels of heavy metals. PMID:20659760

  12. Heavy metal levels (Pb, Cd, Cr and Hg) in the adult general population near an urban solid waste incinerator

    International Nuclear Information System (INIS)

    In 2005 an urban solid waste incinerator (SWI) was commissioned in Bilbao (Basque Country, Spain). Serum and urine samples were collected from 95 and 107 volunteers in 2006 and 2008 respectively, of which 62 were repeats from the same individuals. Blood lead levels (BPb) were determined, as were the concentrations of cadmium (Cd), chromium (Cr) and mercury (Hg) in urine (UCd, UCr and UHg). The town of Alonsotegi and a borough of Bilbao (Altamira, Rekalde) were considered to be close, less than 2 km from the plant, and correspond to an urban environment with high traffic density. The areas of reference were a borough of Bilbao (Santutxu-Zurbaran), 5 km from the plant, also in an urban area with high traffic density, and a small town with little industrial activity and low traffic density (Balmaseda) 20 km from the plant; neither of these is downwind from the site with respect to prevailing winds. There was a significant correlation for BPb, r = 0.63 (p 0.05). Multiple linear regression models did not show increases over time of the levels of BPb, UCd, UCr and UHg in the areas close to the SWI compared to those of areas located further away, after adjusting for confounding variables. These results reinforce the hypothesis that populations near modern plants for solid waste incineration do not manifest increased levels of heavy metals.

  13. Effect of surface fields on the dynamic resistance of planar HgCdTe mid-wavelength infrared photodiodes

    Science.gov (United States)

    He, Kai; Zhou, Song-Min; Li, Yang; Wang, Xi; Zhang, Peng; Chen, Yi-Yu; Xie, Xiao-Hui; Lin, Chun; Ye, Zhen-Hua; Wang, Jian-Xin; Zhang, Qin-Yao

    2015-05-01

    This work investigates the effect of surface fields on the dynamic resistance of a planar HgCdTe mid-wavelength infrared photodiode from both theoretical and experimental aspects, considering a gated n-on-p diode with the surface potential of its p-region modulated. Theoretical models of the surface leakage current are developed, where the surface tunnelling current in the case of accumulation is expressed by modifying the formulation of bulk tunnelling currents, and the surface channel current for strong inversion is simulated with a transmission line method. Experimental data from the fabricated devices show a flat-band voltage of V F B = - 5.7 V by capacitance-voltage measurement, and then the physical parameters for bulk properties are determined from the resistance-voltage characteristics of the diode working at a flat-band gate voltage. With proper values of the modeling parameters such as surface trap density and channel electron mobility, the theoretical R 0 A product and corresponding dark current calculated from the proposed model as functions of the gate voltage Vg demonstrate good consistency with the measured values. The R 0 A product remarkably degenerates when Vg is far below or above VFB because of the surface tunnelling current or channel current, respectively; and it attains the maximum value of 5.7 × 10 7 Ω . cm 2 around the transition between surface depletion and weak inversion when V g ≈ - 4 V , which might result from reduced generation-recombination current.

  14. Performance of the HgCdTe Detector for MOSFIRE, an Imager and Multi-Object Spectrometer for Keck Observatory

    CERN Document Server

    Kulas, Kristin R; Steidel, Charles C

    2012-01-01

    MOSFIRE is a new multi-object near-infrared spectrometer for the Keck 1 telescope with a spectral resolving power of R 3500 for a 0.7" slit (2.9 pixels). The detector is a substrate-removed 2K x 2K HAWAII 2-RG HgCdTe array from Teledyne Imaging Sensors with a cut-off wavelength of 2.5 {\\mu}m and an operational temperature of 77K. Spectroscopy of faint objects sets the requirement for low dark current and low noise. MOSFIRE is also an infrared camera with a 6.9' field of view projected onto the detector with 0.18" pixel sampling. Broad-band imaging drives the requirement for 32-channel readout and MOSFIREs fast camera optics implies the need for a very flat detector. In this paper we report the final performance of the detector selected for MOSFIRE. The array is operated using the SIDECAR ASIC chip inside the MOSFIRE dewar and v2.3 of the HxRG software. Dark current plus instrument background is measured at <0.008 e- s-1 pixel-1 on average. Multiple Correlated Double Sampling (MCDS) and Up-The-Ramp (UTR) sa...

  15. Resistance-area product of diodes in a long-wavelength infrared HgCdTe mosaic array

    Science.gov (United States)

    Gopal, Vishnu; Dhar, Vikram

    2002-02-01

    A long wavelength infrared (LWIR) 2D (mosaic) diode array has been studied by numerically solving the diffusion equation in terms of thermally generated carriers in a n +-on-p HgCdTe diode in an array environment. The results are presented in terms of the resistance-area ( RA) product, in the diffusion-limited case. The results are compared with analytical expressions in the limiting case of the infinite diode. For a finite diode, with a definite junction depth, and a diode size that is smaller than the pitch, the RA, obtained from quasi-3D calculations, is smaller than that expected for the infinite diode case, the deviation being greater for small diodes. Commonly in the literature, the theoretical values of the infinite (1D) diode - which are overestimates - are stated as experimental targets. In the present calculations, the volume of the diode is considered to consist of two parts: one that contributes to the lateral diffusion current that is collected by the four lateral faces of the diode junction, and another that is the `normal' diffusion current, collected by the planar part of the junction from the volume `under' the diode. For the infinite diode case, only the latter component exists. The effect of the perimeter-to-area ratio on the RA in an array environment has been studied. The effective diffusion length associated with the finite diode geometry in an array differs from the standard diffusion length.

  16. Simultaneous preconcentration of Cd, Cr and Hg in seaweeds by cloud point extraction using PAN/TAN and neutron activation

    International Nuclear Information System (INIS)

    A simple one-step green chemistry method for the simultaneous preconcentration of Cd, Cr, and Hg in seaweed samples has been developed. The method is based on the separation phenomenon of non-ionic surfactant polyoxyethylene nonyl ether (PONPE-20) in aqueous solutions after the formation of a complex with a mixture of two chelating agents, namely, 1-(2-pyridylazo)-2-naphthol (PAN) and 1-(2-thiazolylazo)-2-naphthol (TAN). The chemical variables affecting the separation phase were optimized. The recoveries of these elements under the optimum conditions, namely pH=8.5, (PAN/TAN)=1x10-4 M, (PONPE-20)=0.1% (wt) , ionic strength=0.05 M KNO3, T=40 deg C, and preconcentration of 20-30 mL of sample solutions, were found to be >98%. The samples were irradiated in the inner sites of the Dalhousie University SLOWPOKE-2 reactor (DUSR) facility at a thermal neutron flux of 2.5 x 1011 cm-2 s-1

  17. Dark conductivity and photoconductivity of amorphous Hg0.78Cd0.22Te thin films

    Institute of Scientific and Technical Information of China (English)

    Qiu Feng; Ji Rongbin; Xiang Jinzhong; Kong Jincheng; Yu Lianjie; Kong Lingde; Wang Guanghua; Li Xiongjun; Yang Lili; Li Cong

    2011-01-01

    This paper reports the dark conductivity and photoconductivity of amorphous Hg0.78Cd0.22 Te thin films deposited on an Al2O3 substrate by RF magnetron sputtering.It is determined that dark conduction activation energy is 0.417 eV for the as-grown sample.Thermal quenching is absent for the as-grown sample during the testing temperature zone,but the reverse is true for the polycrystalline sample.Photosensitivity shows the maximum at 240 K for amorphous thin films,while it is higher for the as-grown sample than for polycrystalline thin films in the range from 170 to 300 K.The recombination mechanism is the monomolecular recombination process at room temperature,which is different from the low temperature range.Theμτ-product is low in the range of 10-11-10-9 cm2/V,which indicates that some defect states exist in the amorphous thin films.

  18. 手性双修饰剂修饰的CdSe纳米晶的合成及选择性识别Hg(II)的研究%Synthesis of Chiral Dual-stabilizer Capped CdSe Nanocrystals and Its Application to Selective Detection of Hg(II)

    Institute of Scientific and Technical Information of China (English)

    陈帼敏; 俞英; 胡小刚; 曹玉娟; 吴建中

    2010-01-01

    以手性化合物D-青霉胺和L-半胱氨酸为双修饰剂在水相中合成了CdSe纳米晶, 痕量Hg(II)对其荧光强度有明显猝灭作用,基于此建立了定量测定痕量Hg(II)的新方法.在Cd2+, HSe-, D-Pen和L-Cys摩尔比为1: 0.25: 2: 1.2, pH=7.5的条件下,合成的纳米晶具有更好的发光强度和稳定性.TEM显示CdSe纳米晶为球形颗粒,粒径约为50和80 nm.在磷酸盐缓冲溶液(pH 7.38)中,CdSe纳米晶最大荧光峰为516 nm,对Hg(II)有高选择性响应.纳米晶的相对荧光强度与Hg(II)的浓度呈良好线性关系, 检出限为40 pmol/L.本方法测定不同水样中Hg(II)的浓度,回收率为96.7%~102.5%.

  19. CdS/ZnS core-shell quantum dots capped with mercaptoacetic acid as fluorescent probes for Hg(II) ions

    International Nuclear Information System (INIS)

    We have synthesised water soluble CdS/ZnS core-shell quantum dots (QDs) capped with mercaptoacetic acid (MAA). They were characterised by UV-vis absorption spectroscopy, fluorescence spectroscopy, FT-IR and transmission electron microscopy. Such QDs can be used as fluorescent probes for the determination of metal ions because they quench the fluorescence of the QDs. The QDs exhibit absorption and emission bands at 345 nm and 475 nm respectively, which is more longer wavelength compared to MAA-capped CdS QDs and obviously is the result of the larger particle size. The fluorescence intensity of CdS-based QDs is strongly enhanced by coating them with a shell of ZnS. In addition, such functionalised QDs are more sensitive to Hg(II) ions. Parameters such as pH, temperature and concentration of the QDs have been optimised. A high selectivity and sensitivity toward Hg(II) ions is obtained at pH 7.4 and a concentration of 12.0 mg of QDs per L. Under optimum conditions, the fluorescence intensity of CdS/ZnS QDs is linearly proportional to the concentration of Hg(II) in the range from 2.5 to 280 nM, with a detection limit of 2.2 nM. The effect of potentially interfering cations was examined and confirmed the high selectivity of this material. (author)

  20. The photoelectrical properties of MIS structures based on heteroepitaxial n-Hg1- xCd xTe ( x = 0.21-0.23)

    Science.gov (United States)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.; Vasil'ev, V. V.; Varavin, V. S.; Dvoretskii, S. A.; Mikhailov, N. N.; Sidorov, Yu. G.; Yakushev, M. V.

    2013-01-01

    The dependences of photo-emf of metal-insular-semiconductor structures based on n-Hg1- xCd xTe ( x = 0.21-0.23) on bias voltage, frequency, and temperature are experimentally studied. The photoelectrical characteristics of the metal-insulator-semiconductor structures based on epitaxial n-Hg1- xCd xTe ( x = 0.21-0.23), including those taking into account the presence of near-surface graded-gap layers having an increased content of CdTe at various temperatures are calculated. The calculated dependences are compared with experiment and it is shown that the differential resistance of the spatial charge region for the metal-insulatorsemiconductor structures based on n-Hg1- xCd xTe ( x = 0.21-0.23) without a graded-gap layer is restricted by tunneling through deep levels, whereas the differential resistance of the same structures with graded-gap layers - by the charge-carrier diffusion.

  1. 基于GSH-CdTe/CdS量子点的荧光变化研究hsDNA与盐酸洛美沙星-Cu(Ⅱ)配合物的相互作用%Interaction of Herring Sperm DNA with Lomefloxacin Hydrochloride-Cu(Ⅱ) Based on Changes in the Fluorescence Intensity of GSH-CdTe/CdS Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    沈益忠; 刘绍璞; 殷鹏飞; 何佑秋

    2013-01-01

    Glutathione (GSH)-capped CdTe/CdS quantum dots(GSH-CdTe/CdS QDs) were synthesized in aqueous solution.The particle sizes and morphological characteristics of GSH-CdTe/CdS QDs were investigated by transmission electron microscopy(TEM).The results exhibits that the particle size of as-prepared QDs has a narrow size distribution and good dispersivity.In Tris-HCl buffer medium (pH =7.6),lomefloxacin hydrochloride-Cu (Ⅱ) coordination compound(LMFH-Cu2+) was adsorbed to the surfaces of GSH-CdTe/CdS QDs through electrostatic attraction and formed ground state complex,which resulted in the quenching of the fluorescence of GSH-CdTe/CdS QDs.Adding herring sperm DNA (hsDNA) to GSH-CdTe/CdS QDs-LMFH-Cu(Ⅱ) system led to the fluorescence intensity of GSH-CdTe/CdS QDs recover,which can be explained by that the addition of hsDNA to the system induced LMFH-Cu(Ⅱ) to dissociate from the surface of GSH-CdTe/CdS QDs and embed into its double helix structure.According to the fluorescence quenching and restoration for GSH-CdTe/CdS QDs,fluorescence reversible control of GSH-CdTe/CdS QDs was realized.Compared with the interaction between GSH-CdTe/CdS QDs and LMFH,the interaction of GSH-CdTe/CdS QDs-LMFH-Cu (Ⅱ)-hsDNA was studied by fluorescence (FL),resonance Rayleigh scattering(RRS) and ultraviolet-visible absorption (UV-Vis) spectra.Meanwhile,the interaction mechanism was discussed and corresponding model of interaction was built.%采用水相法合成了谷胱甘肽(GSH)修饰的CdTe/CdS量子点(GSH-CdTe/CdS QDs).透射电子显微镜表征结果表明,GSH-CdTe/CdS QDs的粒径分布均匀,分散性好.在Tris-HCl(pH=7.6)缓冲液中,由于静电引力作用,带正电的盐酸洛美沙星(LMFH)-Cu(Ⅱ)配合物[LMFH-Cu(Ⅱ)]吸附到带负电的GSH-CdTe/CdSQDs表面形成基态复合物,导致GSH-CdTe/CdS QDs的荧光猝灭.随后,向GSH-CdTe/CdS QDs-LMFH-Ca(Ⅱ)配合物体系中加入鲱鱼精DNA(hsDNA),hsDNA可诱导LMFH-Cu(Ⅱ)配合物从GSH-CdTe/CdS QDs表面脱落而嵌

  2. Study of surfaces and interfaces in CdS-Cu2S and (Cd sub(x) Zn sub(1-x))S-Cu2S solar cells

    International Nuclear Information System (INIS)

    Auger microprobe was used for the analysis of interfaces and surfaces in several stages involved in the preparation of solar cells, in order to study the origin of adhesion problems and to study the formation of CdS-Cu2S barrier by the wet method. The detachment of the first CdS and (Cd sub(x) Zn sub(1-x))S films, during the dip process, was attributed to the contamination of Cr-Ag metallic substrates by existing chlorine from the environment next to the sea, due to long film stocking, by degasified species from the evaporating material and by the ejection of particles together with CdS vapour during deposition. The formation of conical mounds on the surface and of the CdS-Cu2S barrier at aproximatelly 3000 A depth in the dipped samples were observed. The migration of copper towards surface direction and the formation of a superficial thin layer of copper oxide after treatment in H2 plasma and air heating, were also verified. (C.L.B.)

  3. The Vein-type Zn-(Pb, Cu, As, Hg) mineralization at Fedj Hassene ore field, North-Western Tunisia: Mineralogy, Trace Elements, Sulfur Isotopes and Fluid Inclusions

    International Nuclear Information System (INIS)

    The Fedj Hassene district is localized at the edge of the Tuniso-Algerian border 10 km of Ghardimaou area. It consists of a Zn-Pb vein type with minor amounts of Cu-As-Hg. The total Zn reserves are about 370.000t. The mineralization occurs within sub parallel fractures to the Ain El Kohla ESE-WNW fault. Host rocks consist of limestones and marly limestones of the Middle Turonian. In the principal lode of Fedj Hassene, the mineralization occurs as vein filling of massive and brecciated brown sphalerite and minor galena ore with gangue. Other trace minerals are pyrite, chalcopyrite, orpiment, realgar, smithsonite and cerussite. LA-ICP-MS analyses in sphalerites show mean contents of 0,84 wt% Fe, 0,14 wt% Cd and 0,02 wt% Mn Ore. Fluid inclusions study in calcite and sphalerite reveals one mineralizing fluid characterized by an average salinity 23% wt NaCl with decreasing homogenisation temperature. In fact the temperature shows decrease from sphalerite to calcite. The fluid density that corresponds to trapping pressure ranges between 1.00 g/cm3 and 1.11 g/cm3 and pressure close to 200 bars. Micro thermometric data in fluid inclusion hosted by gangue mineral presented by calcite show an average temperature of formation around 194 degree centigrade. These inclusions homogenized to the liquid phase between 156 degree centigrade and 210 degree centigrade and salinities values ranging from 22 to 28 wt% NaCl and an average around 23% wt NaCl. The δ34S (VCDT) values of sphalerite are in the range of + 4,6% to 6,4% (average=5,6%). Thermochemical reduction of Triassic sulfate by reaction with hydro-carbons is the most probable source for the heavy and the narrow range of the dδ34S values. Mineralogical, geochemical of trace elements, fluid inclusions and sulfur isotopes studies allow to include the vein-type ore field of Fedj Hassene in the polymetallic (Pb-Zn-As-Hg) vein mineralization of the nappe zone in northern Tunisia and north eastern Algeria. (Author) 29 refs.

  4. Role of polycrystallinity in CdTe and CuInSe sub 2 photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Sites, J.R. (Colorado State Univ., Fort Collins, CO (United States))

    1991-01-01

    The polycrystalline nature of thin-film CdTe and CuInSe{sub 2} solar cells continues to be a major factor in several individual losses that limit overall cell efficiency. This report describes progress in the quantitative separation of these losses, including both measurement and analysis procedures. It also applies these techniques to several individual cells to help document the overall progress with CdTe and CuInSe{sub 2} cells. Notably, CdTe cells from Photon Energy have reduced window photocurrent losses to 1 mA/Cm{sup 2}; those from the University of South Florida have achieved a maximum power voltage of 693 mV; and CuInSe{sub 2} cells from International Solar Electric Technology have shown a hole density as high as 7 {times} 10{sup 16} cm{sup {minus}3}, implying a significant reduction in compensation. 9 refs.

  5. The urea combustion method in the preparation of precursors for high-TC single phase HgBa2Ca2Cu3O8+δ superconductors

    International Nuclear Information System (INIS)

    Urea appears as an alternative sol–gel agent to produce Ba–Ca–Cu–O precursor powders. The urea route allowed complete decarbonation in shorter times. This route does not need the use of special annealing atmospheres. Another advantage of this route is the much lower cost of the reactants. An alternative sol–gel route for synthesizing precursors of mercury based superconductors is presented. This route is based on urea as a combustion agent and has been applied in the synthesis of HgBa2Ca2Cu3O8+δ (Hg-1223). Moreover, the effects of the precursor preparation on the synthesis of Hg-1223 were studied. This method is further compared with other sol–gel routes used in the synthesis of this family of compounds.

  6. Investigation of surface potential in the V-defect region of MBE Cd{sub x}Hg{sub 1−x}Te film

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, V. A., E-mail: novikovvadim@mail.ru; Grigoryev, D. V. [Tomsk State University (Russian Federation)

    2015-03-15

    Atomic-force microscopy is used to investigate the distribution of the contact-potential difference (surface potential) in Cd{sub x}Hg{sub 1−x}Te epitaxial films grown by molecular-beam epitaxy. Modification of the solid-solution composition near the V-defect results in a variation in the contact-potential difference. It is shown that the solid-solution composition varies by ∼0.05 (2.5 at %) towards increasing mercury content in the V-defect region, and a region of mercury depletion by 0.36 at % is observed at the V-defect periphery. From analysis of the surface-potential distribution, it is shown that the Cd{sub x}Hg{sub 1−x}Te epitaxial film contains unform V-defects with a diameter less than 1 μm in addition to macroscopic V-defects.

  7. Impact of the nanosecond volume discharge in atmospheric pressure air on the distribution of the surface potential of epitaxial HgCdTe

    Science.gov (United States)

    Novikov, V. A.; Grigoryev, D. V.; Bezrodnyy, D. A.; Tarasenko, V. F.; Shulepov, M. A.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-03-01

    In this paper we present the results of our research of the impact of nanosecond volume discharge on the electronic properties of the near-surface region of epitaxial Hg1-x Cd x Te films. We show that the distribution of the surface potential and, as a consequence, the material composition of the individual crystal grains that form V-defects possess a complex structure and contain regions with elevated content of both mercury and cadmium. The volume discharge treatment of the film surface leads to a decrease of the mercury content in individual crystal grains compared to the bulk of Hg1-x Cd x Te epitaxial film. This indicates a higher mercury desorption rate from the V-defect region.

  8. Solvothermal synthesis of CdO and CuO nanocrystals

    OpenAIRE

    Ghosh, Moumita; Rao, CNR

    2004-01-01

    Nanocrystals of CdO have been obtained by the decomposition of the cupferron complex in the presence of tri-n-octylphosphine oxide (TOPO)under solvothermal conditions. The precursor:TOPO ratio plays an important role in determining the size of the nanocrystals. The nanocrystals have been characterized by electron microscopy, absorption spectroscopy and fluorescence spectroscopy, besides X-ray diffraction.The CdO nanocrystals are single crystalline and show evidence for quantum confinement. Cu...

  9. Commensurate antiferromagnetic excitations as a signature of the pseudogap in the tetragonal high-Tc cuprate HgBa2CuO4+δ

    Science.gov (United States)

    Chan, M. K.; Dorow, C. J.; Mangin-Thro, L.; Tang, Y.; Ge, Y.; Veit, M. J.; Yu, G.; Zhao, X.; Christianson, A. D.; Park, J. T.; Sidis, Y.; Steffens, P.; Abernathy, D. L.; Bourges, P.; Greven, M.

    2016-03-01

    Antiferromagnetic correlations have been argued to be the cause of the d-wave superconductivity and the pseudogap phenomena exhibited by the cuprates. Although the antiferromagnetic response in the pseudogap state has been reported for a number of compounds, there exists no information for structurally simple HgBa2CuO4+δ. Here we report neutron-scattering results for HgBa2CuO4+δ (superconducting transition temperature Tc~71 K, pseudogap temperature T*~305 K) that demonstrate the absence of the two most prominent features of the magnetic excitation spectrum of the cuprates: the X-shaped `hourglass' response and the resonance mode in the superconducting state. Instead, the response is Y-shaped, gapped and significantly enhanced below T*, and hence a prominent signature of the pseudogap state.

  10. Commensurate antiferromagnetic excitations as a signature of the pseudogap in the tetragonal high-Tc cuprate HgBa2CuO(4+δ).

    Science.gov (United States)

    Chan, M K; Dorow, C J; Mangin-Thro, L; Tang, Y; Ge, Y; Veit, M J; Yu, G; Zhao, X; Christianson, A D; Park, J T; Sidis, Y; Steffens, P; Abernathy, D L; Bourges, P; Greven, M

    2016-01-01

    Antiferromagnetic correlations have been argued to be the cause of the d-wave superconductivity and the pseudogap phenomena exhibited by the cuprates. Although the antiferromagnetic response in the pseudogap state has been reported for a number of compounds, there exists no information for structurally simple HgBa2CuO(4+δ). Here we report neutron-scattering results for HgBa2CuO(4+δ) (superconducting transition temperature Tc≈71 K, pseudogap temperature T*≈305 K) that demonstrate the absence of the two most prominent features of the magnetic excitation spectrum of the cuprates: the X-shaped 'hourglass' response and the resonance mode in the superconducting state. Instead, the response is Y-shaped, gapped and significantly enhanced below T*, and hence a prominent signature of the pseudogap state. PMID:26940332

  11. Spectrophotometric study of Co(II, Ni(II, Cu(II, Zn(II, Pd(II and Hg(II complexes with isatin- β-thiosemicarbazone

    Directory of Open Access Journals (Sweden)

    SANDRA S. KONSTANTINOVIC

    2007-10-01

    Full Text Available The composition and stability of the complexes of isatin-b-thiosemicarba­zone with Co(II, Ni(II, Cu(II, Zn(II, Pd(II and Hg(II have been investigated us­ing spectrophotometric method at 30 °C and constant ionic strength of 0.1 mol dm-3 (KNO3 in 70 % ethanol. Experimental results indicate the formation of MeL and MeL2 complexes for Ni(II and Co(II, and MeL for Cu(II, Zn(II, Pd(II and Hg(II complexes, whose stability constants, bn, have been calculated using a com­puteri­zed iterative method of successive approximation.

  12. Production and characterization of Cu/sub 2/S obtained by dipping from CdS chemically sprayed. Study of heat treatments of Cu/sub 2/S/CdS sprayed solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Marjan, M.

    1980-07-01

    The solar cell comprises a pyrex plate covered with a transparent electrode a layer of CdS + Al/sub 2/O/sub 3/ and a layer of CdS obtained by chemical spraying Cu/sub 2/S is obtained by treatment of CdS with a hot solution of CuCl(backwall structure). A p-n junction is obtained between CdS and Cusub(x)S. Thickness and stoichiometry of Cusub(x)S are studied. Photoelectrical properties are improved by annealing. Optical properties and structure of CuS are examined.

  13. Impact of water pollution by Hg, Cd and Pb on nutritional status of children in the North West of Morocco

    International Nuclear Information System (INIS)

    In this paper we describe and elucidate nutritional problems of the Gharb population of Morocco especially children relating to the environmental pollution. Indeed, the north west region of Morocco represent a zone where meet all sewages charged of heavy metals and other pollutants coming from different industries and human activities as well (agricultural, textiles, tanneries, paper-mills). We have chosen randomly about 400 children from 4 districts near downstream the Sebou river. Regarding the nutritional situation of the Gharb population, our survey indicated that stunting (27.9%), anaemia (28.7%), and weight deficiency (12.5%) are the most known nutritional problems. The main causes of these nutritional problems are poor nutritional intake as well as poor socio-economic situation. Otherwise, the objective of our study is to establish a relationship between these nutritional disorders and environmental pollution. This relationship deserves to be solved especially in this region. In this fact, we have studied the interaction between nutrition (micronutrients heavy metals: Fe, Zn, Cu) and toxic heavy metals such as Cd and Pb in blood and urine of children living in Gharb region of Morocco. A rapid and simple analytical procedure was used for the determination of Fe, Cu and Zn trace amounts in blood by total-reflection X-ray fluorescence technique. The accuracy of measurements has been investigated by using certified materials. Samples of blood and urines containing less than 50 ppb of heavy metals have been examined by atomic absorption spectrometry. The concentration of Cu in blood was found to be normal in all samples (at 1 ppm) which ruled out any interaction between this element and the others. On the other hand, amounts of Fe and Zn are very variables, suggesting an interaction between Fe and Zn. On the other hand, statistical treatment of data suggests that concentration of lead becomes important and interaction between this metal and iron can lead to

  14. Impact of a New Highly Sensitive HgCdTe Avalanche Photodiode Detector on Receiver Performance for the CO2 Sounder Lidar for the ASCENDS Mission

    Science.gov (United States)

    Sun, X.; Abshire, J. B.

    2013-12-01

    NASA Goddard Space Flight Center (GSFC) is currently developing a CO2 lidar as a candidate for the NASA's planned ASCENDS mission under the support of Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). As part of this work we have demonstrated new type of lower noise HgCdTe avalanche photodiode (APD) multi-element detector for the lidar receiver. This significantly improves the receiver sensitivity, lower the laser power, and reduce the receiver telescope size compared to InGaAs photomultiplier tubes (PMT) and APDs currently used. The HgCdTe APD arrays were designed and manufactured by DRS Technologies, Reconnaissance, Surveillance and Target Acquisition (RSTA) Division, which combines their mature HgCdTe APD detector in a hybrid package with a new custom cryogenic silicon preamplifier. The new detectors were specially designed for our airborne CO2 lidar and operate at ~ 77K inside a turn-key closed-cycle cooler. The detector has 80 μm square pixels in a 4x4 array, and >70% fill factor and was custom designed to match the optics of our airborne and eventually space-based CO2 lidar. The initial results of evaluating the detector at NASA GSFC showed the HgCdTe APD assembly has a quantum efficiency of ~90% near 1550-nm, >500 APD gain, 8-10 MHz electrical bandwidth, and an average noise equivalent power of Technology (ACT) program. DRS RSTA will use a new higher speed preamplifier and reduce the input capacitance to further reduce the noise and achieve linear mode photon counting performance.

  15. Preparation of cross-linked magnetic chitosan-phenylthiourea resin for adsorption of Hg(II), Cd(II) and Zn(II) ions from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Monier, M., E-mail: monierchem@yahoo.com [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt); Abdel-Latif, D.A. [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt)

    2012-03-30

    Highlights: Black-Right-Pointing-Pointer Chitosan was chemically modified through the reaction with phenylisothiocyanate. Black-Right-Pointing-Pointer The modified chitosan-phenylthiourea cross-linked with formaldehyde in presence of magnetite to produce modified magnetic resin. Black-Right-Pointing-Pointer The resulted resin characterized by various instrumental methods. Black-Right-Pointing-Pointer The resin was applied to remove Hg{sup 2+}, Cd{sup 2+} and Zn{sup 2+} from aqueous solutions. - Abstract: In this study, cross-linked magnetic chitosan-phenylthiourea (CSTU) resin were prepared and characterized by means of FTIR, {sup 1}H NMR, SEM high-angle X-ray diffraction (XRD), magnetic properties and thermogravimetric analysis (TGA). The prepared resin were used to investigate the adsorption properties of Hg(II), Cd(II) and Zn(II) metal ions in an aqueous solution. The extent of adsorption was investigated as a function of pH and the metal ion removal reached maximum at pH 5.0. Also, the kinetic and thermodynamic parameters of the adsorption process were estimated. These data indicated that the adsorption process is exothermic and followed the pseudo-second-order kinetics. Equilibrium studies showed that the data of Hg(II), Cd(II) and Zn(II) adsorption followed the Langmuir model. The maximum adsorption capacities for Hg(II), Cd(II) and Zn(II) were estimated to be 135 {+-} 3, 120 {+-} 1 and 52 {+-} 1 mg/g, which demonstrated the high adsorption efficiency of CSTU toward the studied metal ions.

  16. Preparation and characterization of Pyridoxine complexes of Fe(III), Mo(VI), Cd(II), Hg(II), and U(VI)

    International Nuclear Information System (INIS)

    Pyridoxine (vit B6) reacts with Fe(III), Mo(VI), Cd(II), Hg(II), and U(VI) in aqueous medium to produce solid stable compounds. The compound were characterized by using elemetal analysis data (C'H'N) and different spectroscopic techniques (IR and UV-visible). Condutance behaviour of aqueous solution and the thermal decomposition nature of the complexes were also studied

  17. Trace enrichment with activated carbon and determination of Ni, Hg, Sn and Cd using diethyldithiocarbamate as complexant by atomic emission spectrography (AES)

    International Nuclear Information System (INIS)

    A methods has been developed for the preconcentration and determination of trace amounts of Hg, Ni, Sn and Cd in aqueous solutions. The complexes of these elements with sodium diethyl dithiocarbamate were adsorbed on activated charcoal and determined by atomic emission spectrography d-c arc technique. Factors which affect the quantitative recovery of the microamounts of the elements were optimised. Pd was used as an internal standard. The detection limits ranged from 0.01 to 0.05 ppm. (author)

  18. Magnetotransmission of unpolarized infrared radiation in Hg1 - x Cd x Cr2Se4 (0 ≤ x ≤ 1) single crystals studied using the voigt geometry

    Science.gov (United States)

    Sukhorukov, Yu. P.; Telegin, A. V.; Bebenin, N. G.; Patrakov, E. I.; Naumov, S. V.; Fedorov, V. A.; Menshchikova, T. K.

    2013-11-01

    The features characterizing the behavior of magnetotransmission in Hg1 - x Cd x Cr2Se4 single crystals are studied using natural light in the infrared spectral range. The relation between the changes in the magneto-optical properties and in the electron band structure is found. It is shown that the most significant changes in the magnetotransmission spectrum and the band structure occur within the 0.1 < x < 0.25 range.

  19. Modeling of electron energy spectra and mobilities in semi-metallic Hg{sub 1−x}Cd{sub x}Te quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Melezhik, E. O., E-mail: emelezhik@gmail.com; Gumenjuk-Sichevska, J. V.; Sizov, F. F. [V.E. Lashkaryov Institute for Semiconductor Physics of NAS of Ukraine, Nauki 41 av., 03028 Kyiv (Ukraine)

    2015-11-21

    Electron mobility, energy spectra, and intrinsic carrier concentrations in the n-type Hg{sub 0.32}Cd{sub 0.68}Te/Hg{sub 1−x}Cd{sub x}Te/Hg{sub 0.32}Cd{sub 0.68}Te quantum well (QW) in semi-metallic state are numerically modeled. Energy spectra and wave functions were calculated in the framework of the 8-band k-p Hamiltonian. In our model, electron scattering on longitudinal optical phonons, charged impurities, and holes has been taken into account, and the mobility has been calculated by an iterative solution of the Boltzmann transport equation. Our results show that the increase of the electron concentration in the well enhances the screening of the 2D electron gas, decreases the hole concentration, and can ultimately lead to a high electron mobility at liquid nitrogen temperatures. The increase of the electron concentration in the QW could be achieved in situ by delta-doping of barriers or by applying the top-gate potential. Our modeling has shown that for low molar composition x the concentration of holes in the well is high in a wide range of electron concentrations; in this case, the purity of samples does not significantly influence the electron mobility. These results are important in the context of establishing optimal parameters for the fabrication of high-mobility Hg{sub 1−x}Cd{sub x}Te quantum wells able to operate at liquid nitrogen temperature and thus suitable for applications in terahertz detectors.

  20. Atomic ordering of the fluorine dopant in the $HgBa_{2}CuO_{4+\\delta}high-T_{c}$ superconductor

    CERN Document Server

    Correia, João Guilherme; Araújo, João Pedro; Bordet, P; Haas, Heinz; Le Floc'h, S; Lopes, A M L; Rita, E; Carvalho-Soares, João

    2005-01-01

    Lattice sites and collective ordering of fluorine atoms in oxygen- reduced samples of HgBa/sub 2/CuO/sub 4/ were investigated with the perturbed angular correlation technique by measuring the electric field gradients induced at /sup 199m/Hg nuclei. The experimental data were interpreted with the help of ab initio calculations of charge distributions for different fluorine configurations in Hg/sub m/Ba /sub 2m/Cu/sub m/O/sub 4m/F/sub n/, supercells. Internal parameters were allowed to relax, to cancel residual atomic forces due to the dopant. The experimental results show clearly that fluorine occupies only the center of the mercury mesh. For a fluorine content delta F>~0.35 the best agreement with theoretical data is obtained under the assumption that fluorine shows a tendency toward ordering along interstitial rows parallel to a, b. In conformity with experimental data from diffraction techniques the calculations show elongations of the O(2)-Hg-O(2) dumbbell and barium shifts towards the fluorine atoms as ef...

  1. A Carbazole-Attached NO{sub 2}S{sub 2}-Macrocycle Exhibiting Hg{sup 2+} and Cu{sup 2+} Selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seulgi; Kang, Eunju; Lee, Shimsung [Gyeongsang National Univ., Jinju (Korea, Republic of)

    2013-05-15

    A synthesis and cation-induced fluorescent behavior of the carbazole-attached NO{sub 2}S{sub 2}-macrocycle (L) is described and structurally characterized by single crystal X-ray analysis. The photoluminescence spectrum of L in 80% CH{sub 3}CN/CH{sub 2}Cl{sub 2} displays a peak maximum at 431 nm (blue emission). In the metal-induced fluorometric experiment, L showed a drastic chelation-enhanced fluorescence quenching (CHEQ) effect only with Hg{sup 2+} and Cu{sup 2+}. In ESI-mass study, a 1:1 stoichiometry for complexation of L with Hg{sup 2+} was confirmed, suggesting the unique sensing behavior of the proposed ligand L due to the selective complexation affinity for Hg{sup 2+}. The observed results indicate that L is a promising turn-off type fluoroionophore for Hg{sup 2+} and Cu{sup 2+} detections. Additionally, the Ag{sup +} complex of the precursor macrocycle was prepared and its solid structure was crystallographically characterized.

  2. Study of the analytic quality in the determinations of Cr, Fe, Mn, Cu, Zn, Pb and Hg through conventional and nuclear analytical techniques in mosses of the MATV

    International Nuclear Information System (INIS)

    To evaluate the environmental risks of air pollution and to facilitate the decision-making for control, is necessary to have the capacity to generate data with analytical quality. A comparison between nuclear (Neutron activation analysis and total reflection X-ray fluorescence spectrometry) and no nuclear analytical techniques (atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry) for simultaneous determination of metal content (Cr, Cu, Fe, Hg, Mn, Pb and Zn) in mosses from Metropolitan Area of the Toluca Valley (MATV) was performed. Epiphytic mosses (Fabriona ciliaris and Leskea angustata) were sampled in two campaigns, 16 sites (urban, transition and natural) and were prepared for each technique. The biological certified reference materials were used for the quality control and to evaluate accuracy, precision, linearity, detection and quantification limits. Results show that nuclear analytical techniques and no nuclear applied in chemical analysis of Cr, Cu, Fe, Hg, Mn, Pb and Zn in moss from MATV are comparable and therefore all of these can potentially be used for this purpose. However, if its considered both, the performance parameters and economic/operational characteristics is widely recommended inductively coupled plasma optical emission spectrometry, conventional analytical technique, which showed the highest analytical grade quality. Also were observed spatial and temporal variations in the concentrations of Cr, Cu, Fe, Hg, Mn, Pb and Zn in mosses from MATV and was discussed its potential origin. The urban sites had the highest concentration of anthropogenic elements as Cr, Cu, Fe, Hg, Pb and Zn because are strongly impacted by roads with high vehicle traffic. (Author)

  3. Simultaneous determination of Hg, Pb, As, Cu, Zn and Ni in natural waters (with humic material) by energy dispersive X-ray fluorescence

    International Nuclear Information System (INIS)

    Standardization of a method for simultaneous quantification of Hg, Pb, As, Cu, Zn and Ni in natural waters with humic acid contents was carried out. APDC for complexing free ions and silica gel as adsorber of metallic humates and further filtration were employed. X-ray fluorescence analysis was performed on filters. Good results were found for silica-gel as adsorber. Detection limits of 4 nanograms/milliliter were determined. (author)

  4. Influence of Cd impurity on the electronic properties of CuAlO2 delafossite: first-principles calculations

    International Nuclear Information System (INIS)

    We report on first-principles band-structure calculations of the semiconducting CuAlO2 delafossite compound in the pure form and also with Cd impurity occupying either a Cu or Al position. The computational tool was a full-potential linear augmented plane-wave method, with the generalized gradient approximation accounting for the exchange and correlation effects. The changes caused by the presence of Cd are studied by the analysis of the electronic structure and the electric field gradient (EFG) in both Cd-doped and pure CuAlO2 systems. Good agreement between the calculated and measured EFGs at Cd substituting for Cu or Al atoms in CuAlO2 indicates that the calculations were able to correctly describe the ground state of the system containing the impurity. It is shown that a specific hybridization scheme, involving Cu (and Cd) s and dz2 orbitals and neighbouring O pz orbitals, takes place at the Cu sites in CuAlO2 as proposed earlier. The results of the calculations indicate that the Cd-doped system changes its electrical properties when Cd replaces Cu atoms (producing an n-type semiconductor), but not when it substitutes for Al atoms. (author)

  5. CdS nanowires decorated with Cu2O nanospheres: Synthesis, formation process and enhanced photoactivity and stability

    International Nuclear Information System (INIS)

    Highlights: • Novel CdS/Cu2O heterostructural composites were synthesized by a two-step chemical method. • A formation process of CdS/Cu2O heterostructural composites. • The CdS/Cu2O heterostructural composites were found to have superior photocatalytic performance and stability. - Abstract: CdS/Cu2O heterostructural materials were successfully synthesized by a solvent-thermal process followed by a chemical bath deposition process. Structures and morphologies of the obtained CdS/Cu2O composites were characterized by XRD, SEM, and TEM; the experimental results indicate that the surface of CdS nanowires (NWs) is decorated with spherical Cu2O whose diameter ranges from 100 to 200 nm. Through crystal shape-evolution, the formation process of these hierarchical nanostructures was rationally proposed. Briefly, in the chemical bath deposition process, Cu(OH)2 colloids generate firstly, and then the colloids transform into nanobelts after adding ascorbic acid (AA). With the reaction time further increasing, nanobelts aggregate together to form the hierarchical nanospheres on the surface of CdS NWs. The photoactivity of CdS/Cu2O composite for methyl orange (MO) photodegradation was investigated in detail. The obtained high photocatalytic efficiency can be attributed to the heterojunction structure, which results in the efficient separation of photo-generated electrons and holes

  6. Opto-electronic Properties of Mid-Wavelength: n Type II InAs/InAs1- x Sb x and Hg1- x Cd x Te

    Science.gov (United States)

    De Wames, Roger E.

    2016-09-01

    There is significant interest in mid-wavelength type II strained layer superlattices (SLSs) and HgCdTe material systems for background limited performance, operating at significantly higher temperature, T ≥ 150 K, than InSb, T ≈ 80-90 K. A precise knowledge of the electronic and optical properties of these materials is desirable since they determine detector performance and are needed for input parameters in self-consistent physics-based predictive models. Recently, data on the optical absorption coefficient, and the hole minority carrier lifetime has become available, suggesting that in the extrinsic region the limiting recombination processes in mid-wavelength type II Ga-free SLSs are radiative and Shockley-Read-Hall (SRH). These findings provide the opportunity for comparisons with mid-wavelength HgCdTe. The comparisons show that the radiative recombination coefficients are similar; however, the SRH lifetime limited to 9 μs for the SLS implies that the dark current density is expected to be limited by bulk generation-recombination (G-R) SRH processes for temperatures below 160 K; hence requiring heterojunction designs to suppress the G-R dark currents and be diffusion limited. Mid-wavelength infrared HgCdTe photodiodes are shallow p+n photovoltaic devices and because of the very long SRH hole lifetime are diffusion radiatively limited photodiodes down to 80 K.

  7. Preparation of cross-linked magnetic chitosan-phenylthiourea resin for adsorption of Hg(II), Cd(II) and Zn(II) ions from aqueous solutions.

    Science.gov (United States)

    Monier, M; Abdel-Latif, D A

    2012-03-30

    In this study, cross-linked magnetic chitosan-phenylthiourea (CSTU) resin were prepared and characterized by means of FTIR, (1)H NMR, SEM high-angle X-ray diffraction (XRD), magnetic properties and thermogravimetric analysis (TGA). The prepared resin were used to investigate the adsorption properties of Hg(II), Cd(II) and Zn(II) metal ions in an aqueous solution. The extent of adsorption was investigated as a function of pH and the metal ion removal reached maximum at pH 5.0. Also, the kinetic and thermodynamic parameters of the adsorption process were estimated. These data indicated that the adsorption process is exothermic and followed the pseudo-second-order kinetics. Equilibrium studies showed that the data of Hg(II), Cd(II) and Zn(II) adsorption followed the Langmuir model. The maximum adsorption capacities for Hg(II), Cd(II) and Zn(II) were estimated to be 135 ± 3, 120 ± 1 and 52 ± 1 mg/g, which demonstrated the high adsorption efficiency of CSTU toward the studied metal ions. PMID:22277339

  8. Determination of charge-carrier diffusion length in the photosensing layer of HgCdTe n-on-p photovoltaic infrared focal plane array detectors

    International Nuclear Information System (INIS)

    In the present paper, we propose a method for evaluating the bulk diffusion length of minority charge carriers in the photosensing layer of photovoltaic focal plane array (FPA) photodetectors. The method is based on scanning a strip-shaped illumination spot with one of the detector diodes at a low level of photocurrents jph being registered; such scanning provides data for subsequent analysis of measured spot-scan profiles within a simple diffusion model. The asymptotic behavior of the effective (at jph ≠ 0) charge-carrier diffusion length ldeff as a function of jph for jph → 0 inferred from our experimental data proved to be consistent with the behavior of ldeff vs jph as predicted by the model, while the obtained values of the bulk diffusion length of minority carriers (electrons) in the p-HgCdTe film of investigated HgCdTe n-on-p FPA photodetectors were found to be in a good agreement with the previously reported carrier diffusion-length values for HgCdTe

  9. ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

    Directory of Open Access Journals (Sweden)

    Peter A. Ajibade

    2011-08-01

    Full Text Available The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm, 2.91 eV (426 nm and 4.27 eV (290 nm for the ZnS, CdS and HgS samples respectively.

  10. ZnS, CdS and HgS nanoparticles via alkyl-phenyl dithiocarbamate complexes as single source precursors.

    Science.gov (United States)

    Onwudiwe, Damian C; Ajibade, Peter A

    2011-01-01

    The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively. PMID:22016607

  11. Opto-electronic Properties of Mid-Wavelength: n Type II InAs/InAs1-x Sb x and Hg1-x Cd x Te

    Science.gov (United States)

    De Wames, Roger E.

    2016-06-01

    There is significant interest in mid-wavelength type II strained layer superlattices (SLSs) and HgCdTe material systems for background limited performance, operating at significantly higher temperature, T ≥ 150 K, than InSb, T ≈ 80-90 K. A precise knowledge of the electronic and optical properties of these materials is desirable since they determine detector performance and are needed for input parameters in self-consistent physics-based predictive models. Recently, data on the optical absorption coefficient, and the hole minority carrier lifetime has become available, suggesting that in the extrinsic region the limiting recombination processes in mid-wavelength type II Ga-free SLSs are radiative and Shockley-Read-Hall (SRH). These findings provide the opportunity for comparisons with mid-wavelength HgCdTe. The comparisons show that the radiative recombination coefficients are similar; however, the SRH lifetime limited to 9 μs for the SLS implies that the dark current density is expected to be limited by bulk generation-recombination (G-R) SRH processes for temperatures below 160 K; hence requiring heterojunction designs to suppress the G-R dark currents and be diffusion limited. Mid-wavelength infrared HgCdTe photodiodes are shallow p+n photovoltaic devices and because of the very long SRH hole lifetime are diffusion radiatively limited photodiodes down to 80 K.

  12. Growth, Characterization and Theoretical Study of a Novel Organometallic Nonlinear Optical Crystal: CdHg(SCN)4(C2H5NO)2

    Science.gov (United States)

    Liu, X. T.; Wang, X. Q.; Lin, X. J.; Sun, G. H.; Zhang, G. H.; Xu, D.

    2012-06-01

    A novel potentially useful second harmonic generation (SHG) organometallic nonlinear optical (NLO) crystal: cadmium mercury thiocyanate bis( N-methylformamide), CdHg(SCN)4(C2H5NO)2 (CMTN), has been prepared, and large high-optical-quality single crystals with dimensions up to 30 ×27×9 mm3 have been grown by the temperature-lowering method. Its structural, physicochemical and optical properties are characterized by elemental analyses, X-ray powder diffraction, Fourier transform infrared and Raman spectroscopy, thermal analysis, powder SHG measurements and UV/Vis/NIR transmission. The specific heat has been determined to be 515.5 J mol-1 K-1 at 300 K. CMTN possesses good physicochemical stability up to 128.5∘C, exhibits powder SHG efficiencies 0.8 times that of urea and its UV transparency cutoff is 358 nm. By the use of the DFT/B3LYP/6-31G(d) method, the microscopic second order NLO behavior of CMTN has been investigated by computing the first-order hyperpolarizability together with that of CdHg(SCN)4 (CMTC) and CdHg(SCN)4(C3H8O2) (CMTG) crystals. The results have been explained based on their crystal structures.

  13. Effects of Different Doping Ratio of Cu Doped CdS on QDSCs Performance

    Directory of Open Access Journals (Sweden)

    Xiaojun Zhu

    2015-01-01

    Full Text Available We use the successive ionic layer adsorption and reaction (SILAR method for the preparation of quantum dot sensitized solar cells, to improve the performance of solar cells by doping quantum dots. We tested the UV-Vis absorption spectrum of undoped CdS QDSCs and Cu doped CdS QDSCs with different doping ratios. The doping ratios of copper were 1 : 100, 1 : 500, and 1 : 1000, respectively. The experimental results show that, under the same SILAR cycle number, Cu doped CdS quantum dot sensitized solar cells have higher open circuit voltage, short circuit current density photoelectric conversion efficiency than undoped CdS quantum dots sensitized solar cells. Refinement of Cu doping ratio are 1 : 10, 1 : 100, 1 : 200, 1 : 500, and 1 : 1000. When the proportion of Cu and CdS is 1 : 10, all the parameters of the QDSCs reach the minimum value, and, with the decrease of the proportion, the short circuit current density, open circuit voltage, and the photoelectric conversion efficiency are all increased. When proportion is 1 : 500, all parameters reach the maximum values. While with further reduction of the doping ratio of Cu, the parameters of QDSCs have a decline tendency. The results showed that, in a certain range, the lower the doping ratio of Cu, the better the performance of quantum dot sensitized solar cell.

  14. Heavy metal levels (Pb, Cd, Cr and Hg) in the adult general population near an urban solid waste incinerator

    Energy Technology Data Exchange (ETDEWEB)

    Zubero, Miren Begona, E-mail: txitea@gmail.com [Research Unit, Cruces Hospital, Barakaldo, Bizkaia (Spain); Department of Preventative Medicine and Public Health, University of the Basque Country, Leioa, Bizkaia (Spain); Aurrekoetxea, Juan Jose, E-mail: jaurrekoetxea@ej-gv.es [Public Health Department, Dept. of Health, Basque Government, Gipuzkoa (Spain); Epidemiolgy and Public Health CIBER (CIBERESP) (Spain); Ibarluzea, Jesus Maria, E-mail: mambien3-san@ej-gv.es [Public Health Department, Dept. of Health, Basque Government, Gipuzkoa (Spain); Epidemiolgy and Public Health CIBER (CIBERESP) (Spain); Arenaza, Maria Jesus, E-mail: osalanrlhba@ej-gv.es [Basque Institute for Occupational Health and Safety, Barakaldo, Bizkaia (Spain); Rodriguez, Carlos, E-mail: carlos.rodriguez-andres@ehu.es [Department of Preventative Medicine and Public Health, University of the Basque Country, Leioa, Bizkaia (Spain); Saenz, Jose Ramon, E-mail: jrsaenz@chdo.osakidetza.net [Department of Preventative Medicine and Public Health, University of the Basque Country, Leioa, Bizkaia (Spain)

    2010-09-15

    In 2005 an urban solid waste incinerator (SWI) was commissioned in Bilbao (Basque Country, Spain). Serum and urine samples were collected from 95 and 107 volunteers in 2006 and 2008 respectively, of which 62 were repeats from the same individuals. Blood lead levels (BPb) were determined, as were the concentrations of cadmium (Cd), chromium (Cr) and mercury (Hg) in urine (UCd, UCr and UHg). The town of Alonsotegi and a borough of Bilbao (Altamira, Rekalde) were considered to be close, less than 2 km from the plant, and correspond to an urban environment with high traffic density. The areas of reference were a borough of Bilbao (Santutxu-Zurbaran), 5 km from the plant, also in an urban area with high traffic density, and a small town with little industrial activity and low traffic density (Balmaseda) 20 km from the plant; neither of these is downwind from the site with respect to prevailing winds. There was a significant correlation for BPb, r = 0.63 (p < 0.001), between the two surveys. However, there was no linear correlation for the other three metals (UCd, UCr and UHg), between the two sampling periods (p > 0.05). Multiple linear regression models did not show increases over time of the levels of BPb, UCd, UCr and UHg in the areas close to the SWI compared to those of areas located further away, after adjusting for confounding variables. These results reinforce the hypothesis that populations near modern plants for solid waste incineration do not manifest increased levels of heavy metals.

  15. Effect of surface fields on the dynamic resistance of planar HgCdTe mid-wavelength infrared photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    He, Kai; Wang, Xi; Zhang, Peng; Chen, Yi-Yu [Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhou, Song-Min; Xie, Xiao-Hui; Lin, Chun, E-mail: chun-lin@mail.sitp.ac.cn; Ye, Zhen-Hua; Wang, Jian-Xin; Zhang, Qin-Yao, E-mail: qinyao@mail.sitp.ac.cn [Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Li, Yang [Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2015-05-28

    This work investigates the effect of surface fields on the dynamic resistance of a planar HgCdTe mid-wavelength infrared photodiode from both theoretical and experimental aspects, considering a gated n-on-p diode with the surface potential of its p-region modulated. Theoretical models of the surface leakage current are developed, where the surface tunnelling current in the case of accumulation is expressed by modifying the formulation of bulk tunnelling currents, and the surface channel current for strong inversion is simulated with a transmission line method. Experimental data from the fabricated devices show a flat-band voltage of V{sub FB}=−5.7 V by capacitance-voltage measurement, and then the physical parameters for bulk properties are determined from the resistance-voltage characteristics of the diode working at a flat-band gate voltage. With proper values of the modeling parameters such as surface trap density and channel electron mobility, the theoretical R{sub 0}A product and corresponding dark current calculated from the proposed model as functions of the gate voltage V{sub g} demonstrate good consistency with the measured values. The R{sub 0}A product remarkably degenerates when V{sub g} is far below or above V{sub FB} because of the surface tunnelling current or channel current, respectively; and it attains the maximum value of 5.7×10{sup 7} Ω · cm{sup 2} around the transition between surface depletion and weak inversion when V{sub g}≈−4 V, which might result from reduced generation-recombination current.

  16. Miniaturized imaging spectrometer based on Fabry-Perot MOEMS filters and HgCdTe infrared focal plane arrays

    Science.gov (United States)

    Velicu, S.; Buurma, C.; Bergeson, J. D.; Kim, Tae Sung; Kubby, J.; Gupta, N.

    2014-05-01

    Imaging spectrometry can be utilized in the midwave infrared (MWIR) and long wave infrared (LWIR) bands to detect, identify and map complex chemical agents based on their rotational and vibrational emission spectra. Hyperspectral datasets are typically obtained using grating or Fourier transform spectrometers to separate the incoming light into spectral bands. At present, these spectrometers are large, cumbersome, slow and expensive, and their resolution is limited by bulky mechanical components such as mirrors and gratings. As such, low-cost, miniaturized imaging spectrometers are of great interest. Microfabrication of micro-electro-mechanicalsystems (MEMS)-based components opens the door for producing low-cost, reliable optical systems. We present here our work on developing a miniaturized IR imaging spectrometer by coupling a mercury cadmium telluride (HgCdTe)-based infrared focal plane array (FPA) with a MEMS-based Fabry-Perot filter (FPF). The two membranes are fabricated from silicon-oninsulator (SOI) wafers using bulk micromachining technology. The fixed membrane is a standard silicon membrane, fabricated using back etching processes. The movable membrane is implemented as an X-beam structure to improve mechanical stability. The geometries of the distributed Bragg reflector (DBR)-based tunable FPFs are modeled to achieve the desired spectral resolution and wavelength range. Additionally, acceptable fabrication tolerances are determined by modeling the spectral performance of the FPFs as a function of DBR surface roughness and membrane curvature. These fabrication non-idealities are then mitigated by developing an optimized DBR process flow yielding high-performance FPF cavities. Zinc Sulfide (ZnS) and Germanium (Ge) are chosen as the low and the high index materials, respectively, and are deposited using an electron beam process. Simulations are presented showing the impact of these changes and non-idealities in both a device and systems level.

  17. Effect of surface fields on the dynamic resistance of planar HgCdTe mid-wavelength infrared photodiodes

    International Nuclear Information System (INIS)

    This work investigates the effect of surface fields on the dynamic resistance of a planar HgCdTe mid-wavelength infrared photodiode from both theoretical and experimental aspects, considering a gated n-on-p diode with the surface potential of its p-region modulated. Theoretical models of the surface leakage current are developed, where the surface tunnelling current in the case of accumulation is expressed by modifying the formulation of bulk tunnelling currents, and the surface channel current for strong inversion is simulated with a transmission line method. Experimental data from the fabricated devices show a flat-band voltage of VFB=−5.7 V by capacitance-voltage measurement, and then the physical parameters for bulk properties are determined from the resistance-voltage characteristics of the diode working at a flat-band gate voltage. With proper values of the modeling parameters such as surface trap density and channel electron mobility, the theoretical R0A product and corresponding dark current calculated from the proposed model as functions of the gate voltage Vg demonstrate good consistency with the measured values. The R0A product remarkably degenerates when Vg is far below or above VFB because of the surface tunnelling current or channel current, respectively; and it attains the maximum value of 5.7×107 Ω · cm2 around the transition between surface depletion and weak inversion when Vg≈−4 V, which might result from reduced generation-recombination current

  18. Linear mode photon counting from visible to MWIR with HgCdTe avalanche photodiode focal plane arrays

    Science.gov (United States)

    Sullivan, William; Beck, Jeffrey; Scritchfield, Richard; Skokan, Mark; Mitra, Pradip; Sun, Xiaoli; Abshire, James; Carpenter, Darren; Lane, Barry

    2015-05-01

    Results of characterization data on linear mode photon counting (LMPC) HgCdTe electron-initiated avalanche photodiode (e-APD)focal plane arrays (FPA) are presented that reveal an improved understanding and the growing maturity of the technology. The first successful 2x8 LMPC FPA was fabricated in 2010 [1]. Since then a process validation lot of 2x8 arrays was fabricated. Five arrays from this lot were characterized that replicated the previous 2x8 LMPC array performance. In addition, it was unambiguously verified that readout integrated circuit (ROIC) glow was responsible for most of the false event rate (FER) of the 2010 array. The application of a single layer metal blocking layer between the ROIC and the detector array and optimization of the ROIC biases reduced the FER by an order of magnitude. Photon detection efficiencies (PDEs) of greater than 50% were routinely demonstrated across 5 arrays, with one array reaching a PDE of 70%. High resolution pixel-surface spot scans were performed and the junction diameters of the diodes were measured. The junction diameter was decreased from 31 μm to 25 μm resulting in a 2x increase in E-APD gain from 470 on the 2010 array to 1100 on one of the 2013 FPAs. Mean single photon signal to noise ratios of >12 were demonstrated at excess noise factors of 1.2-1.3. NASA Goddard Space Flight Center (GSFC) performed measurements on the delivered FPA that verified the PDE and FER data.

  19. Ectomycorrhizal Fungus-Induced Changes of Cu and Cd speciation in the rhizosphere of Chinese Pine Seedlings

    Institute of Scientific and Technical Information of China (English)

    HUANG Yi; LI Ting; HUANG Zhi-Ji; FEI Ying-Heng

    2008-01-01

    To understand the role of ectomycorrhizas in improving the tolerance of its host to excessive heavy metals in soil, this study was conducted to exam the patterns of four fractions (the exchangeable, the carbonate-bound, the Fe-Mn oxide-bound and the organically bound) of both Cu and Cd in the rhizosphere of Chinese pine (Pinus tabulaeformis) seedlings grown in excessive Cu and Cd environment. The results showed that the speciation of Cu and Cd in the rhizosphere was significantly influenced by inoculation of ectomycorrhizal fungus Boletus edulis. Compared to the rhizosphere, the content of exchangeable Cu slightly decreased in the mycorrhizosphere of the seedlings grown in 166 and 400 mg kg-1Cu contaminated soil, whereas the exchangeable Cd in the mycorrhizosphere decreased remarkably to only 33% and to 60% that of the rhizosphcre at 0.75 and 1.50 mg kg-1 Cd levels, respectively. These indicate the potential capacity of mycorrhizas to alleviate the damage of heavy metals to the host plants by reducing the bioavailability of heavy metals in soil. Distribution of the 4 tested fractions of Cu and Cd at different contamination levels showed that there was a strong tendency of changing from loosely associatcd fractions to strongly associated fractions in the mycorrhizosphere. The most stable Cd fraction, organically bound Cd, was significantly larger in the mycorrhizosphere than in the rhizosphere at different Cd contamination levels. This phenomenon was also observed for Cu but the difference was not statistically significant.

  20. A facile synthesis and spectral characterization of Cu2+ doped CdO/ZnS nanocomposite

    International Nuclear Information System (INIS)

    A facile two-step method is demonstrated for the preparation of Cu2+ doped CdO/ZnS nanocomposite. Systematic investigations like X-ray diffraction (XRD), Scanning electron microscopy (SEM) with EDS, transmission electron microscopy (TEM), FT-IR, electron paramagnetic resonance (EPR), optical absorption, photoluminescence (PL) and magnetic studies are carried out for the prepared material. From powder XRD, the nanocomposites are comprised for cubic phase of both CdO and ZnS in a close contact with each other. The ground state wave function of dopant ions has been estimated from EPR studies. Optical and EPR data confirm that doped Cu2+ions occupy rhombically distorted octahedral sites with the host material. Due to doping, band gap has been changed and blue shifts occurred in PL. Magnetic measurements indicate a possible ferromagnetic response, associated to the exchange interaction between local spin-polarized electrons of Cu2+ ions and conductive electrons. - Graphical abstract: M–H curve of Cu2+ doped CdO–ZnS nanocomposites. The magnetic properties of Cu2+ doped CdO/ZnS nanocomposite has been investigated using vibrating sample magnetometer given as magnetization and hysteresis (M–H) curve. The magnetization curve with noticeable coercivity of M–H loop clearly indicate the existence of ferromagnetic ordering in Cu2+ doped CdO/ZnS nanocomposite at room temperature. According to the Ruderman–Kittel–Kasuya–Yosida (RKKY) theory, the exchange interaction between local spin-polarized electrons (such as the electrons of Cu2+ ions) and conductive electrons is the main cause that leads to the ferromagnetism. Coercivity (Hc) of the field is about 98 Oe, saturation magnetization (Ms) and remnant magnetization (Mr) of present sample is estimated to be 15.8×10−3 and 1.43×10−3 emu/g respectively. The ferromagnetism observed in the prepared material is not commencing with other impurities but expected to be intrinsic. - Highlights: • Cu2+ doped Cd

  1. Fabrication and characterization of high-quality (Hg,Re)Ba sub 2 CaCu sub 2 O sub y thin films on LSAT substrates

    CERN Document Server

    Ogawa, A; Sugano, T; Adachi, S; Suzuki, K; Nakagaki, N; Enomoto, Y; Tanabe, K

    2002-01-01

    We have succeeded in fabricating high-quality (Hg,Re)Ba sub 2 CaCu sub 2 O sub y ((Hg,Re)-1212) thin films with a thickness of 300 nm on (LaAlO sub 3) sub 0 sub . sub 3 -(SrAl sub 0 sub . sub 5 Ta sub 0 sub . sub 5 O sub 3) sub 0 sub . sub 7 (LSAT) substrates. The films were fabricated by repeating the two-step process, which consists of the preparation of a precursor film and the heat treatment in Hg-vapour atmosphere. For the purpose of improving their crystal quality, the heat treatment in the final process was carried out in a lower Hg-vapour pressure for a longer time. The obtained films had a flat surface and no appreciable outgrowth. The films exhibited a T sub c value of 120 K and a J sub c value of 4.4 x 10 sup 6 A cm sup - sup 2 at 77 K in a self-field, which are substantially higher than those for the films fabricated in higher Hg-vapour atmosphere. Their electrical transport properties in magnetic fields up to 7 T were investigated. Their lower irreversibility fields at 77 K as well as the higher ...

  2. 广东贵屿土壤Cd、Hg潜在威胁评价%Potential Threat of Cd, Hg in Soil of Guiyu, Guangdong Province

    Institute of Scientific and Technical Information of China (English)

    罗杰; 温汉辉; 吴丽霞; 游远航; 欧阳春飞

    2012-01-01

    通过表层土壤、深层土壤、水稻样品及水样的采取与分析,结果表明,水俣病的元凶Hg在广东省贵屿镇土壤中具有极高的富集系数,易在酸性条件下向有效形态转化的弱有机结合态Hg占全Hg的17.74%;痛痛病的元凶Cd在部分土壤中的含量已超过环境承受的极限,且最易与生命体发生作用的水溶态Cd和离子交换态Cd占全Cd的比例高达16.2%.Hg、Cd的块金系数均大于70%,具明显的表层富集特征,与家电拆解作坊表层土壤重金属元素同源性较好,说明Cd、Hg的分布、富集受人类活动影响强烈,其对生态环境和居民健康存在极强的潜在威胁,在特定条件下有可能引发各类地方病.%Guiyu is located in the junction of Chaoyang, Puning and Jieyang. It is a famous "first town of e-lectronic-waste". Electronic-waste in the local has caused serious environmental pollution and damaged the health of residents. The research showed the Hg which is the main cause of Minamata disease has a high soil enrichment factor in the town. The weak organic-bound Cd which could easily transform to Hg under acidic conditions accounts for 17. 74% of the total content. Cd is the main cause of Itai-itai disease. The content of Cd in some soil has exceeded the environmental limit. The content of water-soluble Cd and ion-exchange Cd which can most easily influence living body accounts for 16. 2% of the total content. The nugget coefficient of Hg and Cd were more than 70%, which has a significant surface enrichment characteristics and has good homology with heavy metals in surface soil of dismantling workshops. This showed that the distribution and enrichment characteristics of Cd and Hg are affected by human activities significantly, and existence of a potential threat to environment and health of residents under certain conditions may lead to endemic diseases.

  3. Influences of Cu or Cd on the neurotoxicity induced by petroleum hydrocarbons in ragworm Perinereis aibuhitensis

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qianru; ZHOU Qixing; WANG Jing; SUN Shulan; HUA Tao; REN Liping

    2008-01-01

    The ecotoxicological effects of heavy metals and petroleum hydrocarbons (PHCs) on ragworms are still vague.The relationships between toxicological indices (mortality and acetylcholinesterase (ACHE) activity) and concentrations of toxicants (Cu,Cd,and PHCs)were examined in the estuary keystone species Perinereis aibuhitensis in laboratory conditions.The results of single toxicant indicated that three toxicants had potentially physiological toxicity to P.aibuhitensis.The estimated 4-d and 10-d LC50 for Cu,Cd,and PHCs was derived from the relationships between mortality and toxicants concentrations.Notable changes in the morphological signs and symptoms of P.aibuhitensis exposed to PHCs were observed.The ACHE activity of P.aibuhitensis was more sensitive to the toxicity of PHCs than the others.The results of combined toxicants implied that the combined toxicity of Cu or Cd and PHCs to P.aibuhitensis was related to the concentration combination of toxicants.Compared to single PHCs treatment,the addition of Cu or Cd significantly mitigated the neurotoxicity of PHCs to ACHE activity in P.aibuhitensis,which showed an antagonistic effect.

  4. Compositional Change of the Au-Cu2Te Contact for Thin-Film CdS/CdTe Solar Cells

    Science.gov (United States)

    Uda, Hiroshi; Ikegami, Seiji; Sonomura, Hajimu

    1990-03-01

    The stability of thin-film CdS/CdTe solar cells with evaporated Au-Cu2Te contacts to the CdTe film has been investigated. A decrease in conversion efficiency due to an increase in series resistance was observed in the solar cells stored in air at room temperature for 120 days. The increase in series resistance is caused by an increase in contact resistance resulting from the compositional change in the Au-Cu2Te contact to the CdTe film.

  5. Cu containing CdTe thin films deposited by two sources technique

    International Nuclear Information System (INIS)

    Cadmium Telluride (CdTe) thin films were deposited onto glass substrates by the two-source evaporation technique. Films were heated under vacuum at 500 degree C for 1 hour and dipped in Cu(No/sub 3/)/sub 2/-H/sub 2/O solution at room temperature These films were again heated under vacuum for 1 hour at 500 degree C to obtain maximum Cu diffusion. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optically by Lambda 900 UV/VIS/NIR spectrophotometer and electrically, i.e. DC electrical resistivity, by the Van der Pauw method at room temperature. The EDX results showed an increase of Cu content in the samples by increasing the immersion time of the CdTe films in the solution. (author)

  6. Linking biosensor responses to Cd, Cu and Zn partitioning in soils

    International Nuclear Information System (INIS)

    Soils bind heavy metals according to fundamental physico-chemical parameters. Bioassays, using bacterial biosensors, were performed in pore waters extracted from 19 contrasting soils individually amended with Cd, Cu and Zn concentrations related to the EU Sewage Sludge Directive. The biosensors were responsive to pore waters extracted from Zn amended soils but less so to those of Cu and showed no toxicity to pore water Cd at these environmentally relevant amended concentrations. Across the range of soils, the solid-solution heavy metal partitioning coefficient (K d) decreased (p d values. Gompertz functions of Cu and Zn, K d values against luminescence explained the relationship between heavy metals and biosensors. Consequently, biosensors provide a link between biologically defined hazard assessments of metals and standard soil-metal physico-chemical parameters for determining critical metal loadings in soils. - Biosensors link biological hazard assessments of metals in soils with physico-chemical partitioning

  7. Chemical behavior of Cu, Zn, Cd, and Pb in a eutrophic reservoir: speciation and complexation capacity.

    Science.gov (United States)

    Tonietto, Alessandra Emanuele; Lombardi, Ana Teresa; Choueri, Rodrigo Brasil; Vieira, Armando Augusto Henriques

    2015-10-01

    This research aimed at evaluating cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) speciation in water samples as well as determining water quality parameters (alkalinity, chlorophyll a, chloride, conductivity, dissolved organic carbon, dissolved oxygen, inorganic carbon, nitrate, pH, total suspended solids, and water temperature) in a eutrophic reservoir. This was performed through calculation of free metal ions using the chemical equilibrium software MINEQL+ 4.61, determination of labile, dissolved, and total metal concentrations via differential pulse anodic stripping voltammetry, and determination of complexed metal by the difference between the total concentration of dissolved and labile metal. Additionally, ligand complexation capacities (CC), such as the strength of the association of metals-ligands (logK'ML) and ligand concentrations (C L) were calculated via Ruzic's linearization method. Water samples were taken in winter and summer, and the results showed that for total and dissolved metals, Zn > Cu > Pb > Cd concentration. In general, higher concentrations of Cu and Zn remained complexed with the dissolved fraction, while Pb was mostly complexed with particulate materials. Chemical equilibrium modeling (MINEQL+) showed that Zn(2+) and Cd(2+) dominated the labile species, while Cu and Pb were complexed with carbonates. Zinc was a unique metal for which a direct relation between dissolved species with labile and complexed forms was obtained. The CC for ligands indicated a higher C L for Cu, followed by Pb, Zn, and Cd in decreasing amounts. Nevertheless, the strength of the association of all metals and their respective ligands was similar. Factor analysis with principal component analysis as the extraction procedure confirmed seasonal effects on water quality parameters and metal speciation. Total, dissolved, and complexed Cu and total, dissolved, complexed, and labile Pb species were all higher in winter, whereas in summer, Zn was mostly present in the

  8. A facile synthesis and spectral characterization of Cu2+ doped CdO/ZnS nanocomposite

    Science.gov (United States)

    Joyce Stella, R.; Thirumala Rao, G.; Babu, B.; Pushpa Manjari, V.; Reddy, Ch. Venkata; Shim, Jaesool; Ravikumar, R. V. S. S. N.

    2015-06-01

    A facile two-step method is demonstrated for the preparation of Cu2+ doped CdO/ZnS nanocomposite. Systematic investigations like X-ray diffraction (XRD), Scanning electron microscopy (SEM) with EDS, transmission electron microscopy (TEM), FT-IR, electron paramagnetic resonance (EPR), optical absorption, photoluminescence (PL) and magnetic studies are carried out for the prepared material. From powder XRD, the nanocomposites are comprised for cubic phase of both CdO and ZnS in a close contact with each other. The ground state wave function of dopant ions has been estimated from EPR studies. Optical and EPR data confirm that doped Cu2+ions occupy rhombically distorted octahedral sites with the host material. Due to doping, band gap has been changed and blue shifts occurred in PL. Magnetic measurements indicate a possible ferromagnetic response, associated to the exchange interaction between local spin-polarized electrons of Cu2+ ions and conductive electrons. The magnetic properties of Cu2+ doped CdO/ZnS nanocomposite has been investigated using vibrating sample magnetometer given as magnetization and hysteresis (M-H) curve. The magnetization curve with noticeable coercivity of M-H loop clearly indicate the existence of ferromagnetic ordering in Cu2+ doped CdO/ZnS nanocomposite at room temperature. According to the Ruderman-Kittel-Kasuya-Yosida (RKKY) theory, the exchange interaction between local spin-polarized electrons (such as the electrons of Cu2+ ions) and conductive electrons is the main cause that leads to the ferromagnetism. Coercivity (Hc) of the field is about 98 Oe, saturationmagnetization (Ms) and remnant magnetization (Mr) of present sample is estimated to be 15.8×10-3 and 1.43×10-3 emu/g respectively. The ferromagnetism observed in the prepared material is not commencing with other impurities but expected to be intrinsic.

  9. Estudio de la cinética de adsorción de Cu y Hg a partir de soluciones binarias usando quitosano

    Directory of Open Access Journals (Sweden)

    Martha Benavente

    2011-06-01

    Full Text Available In this work, the adsorption kinetic of Cu(II and Hg(II onto chitosan was studied from a binary solution at different initial concentration of metallic ions, at different particle sizes and agitation rate. Chitosan was obtained from shrimp shells. Solutions of 1 L of Cu(II and Hg(II were placed in contact with 2 g of chitosan and the mixture was agitated by 8 h. Afterwards, the samples were analysed by atomic absorption. The experimental data were tested by application of kinetic models of pseudo-first order and pseudo-second order. The results of adsorption process showed that in the most cases, both ions were effectively adsorbed by chitosan. The percentage of adsorption was 43-100 % and 94-100 % for Cu(II and Hg(II, respectively. The results also showed that at low concentrations, experimental data were better adjusted by pseudo-first order models; meanwhile, at high concentration, the data were well described by the pseudo-second model. Therefore, the rate-limiting step is the adsorption reaction and not mass transfer. Keywords: Adsorption kinetics; Binary solution; Chitosan; Kinetic models; Shrimp shell En este trabajo se estudió la cinética de adsorción de Cu(II y Hg(II en quitosano a partir de una solución binaria, a diferentes concentraciones iniciales de los iones metálicos, tamaño de partículas del adsorbente y velocidad de agitación. El quitosano fue extraído por métodos químicos de caparazón de camarón. Soluciones de 1 L de Cu(II y Hg(II fueron puestas en contacto con 2 g de quitosano y se agitaron por un período de 8 h. Al final del proceso, las muestras fueron analizadas en un espectrómetro de absorción atómica. Los datos experimentales fueron evaluados aplicando los modelos cinéticos de pseudo-primer orden y pseudo-segundo orden. Los resultados del proceso de adsorción de los iones metálicos Cu(II y Hg(II con quitosano, mostraron que en la mayoría de los casos, ambos iones fueron eficazmente adsorbidos por la

  10. Physiology and Ultrastructure of Azolla imbricata as Affected by Hg2+ and Cd2+ Toxicity%Hg2+和Cd2+胁迫对满江红生理和细胞超微结构的影响

    Institute of Scientific and Technical Information of China (English)

    施国新; 徐勤松; 解凯彬; 徐楠; 张小兰; 曾晓敏; 周红卫; 朱蕾

    2003-01-01

    The toxic effects of different gradient concentrations of Hg2+ and Cd2+ on chlorophyll content, chlorophyll a/b value, photosynthetic O2 evolution, respiration rate, anti-oxidase system (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD)) and ultrastructure of the cells of Azolla imbricata (Roxb.) Nakai were studied. The results showed that with Hg2+ and Cd2+ increase, chlorophyll content and chlorophyll a/b value, photosynthetic O2 evolution decreased drastically; respiration rate peaked at 2 mg/L pollutant and declined afterwards. The activities of SOD, CAT and POD increased first and decreased afterwards except the activity of POD, which decreased with the increasing of Cd2+ concentration. Ultrastructural observation showed that the extent of ultrastructural damage was much more serious with higher pollutant concentration and longer time of stress. This resulted in swelling of chloroplast, disruption and disappearance of chloroplast membrane and disintegration of chloroplasts; swelling of cristae of mitochondria, deformation and vacuolization of mitochondria; condensation of chromatin in nucleus, dispersion of nucleolus and disruption of nuclear membrane. The experimental results showed: (1) Hg2+ and Cd2+ pollution not only destroyed physiological activities, but also caused irreversible damage to its ultrastructure, thus leading the cells to death; (2) With increase in the stress of Hg2+ and Cd2+, ultrastructural damage was related to the changes of plant physiology; (3) The toxic symptoms of plant showed an evident correlation between dose and effect; (4) The toxicity of Cd2+ on A. imbricata is heavier than that of Hg2+ under the same treatment time and concentration. The lethal concentration of Hg2+ to A. imbricata ranged from 3.5 to 4 mg/L, and that of Cd2+ ranged from 3 to 3.5 mg/L. The damage of cell ultrastructure on Anabaena azollae Strasburger was observed. The results indicated that tolerance of Azolla imbricata for Hg2+ and Cd2+ was higher

  11. Geospatial Mapping of Pb, Cr, Cu, Zn, Cd, and Sb in Urban Soil, Cd. Juarez, Chihuahua, Mexico

    Science.gov (United States)

    Amaya, M. A.; Grimida, S. E.; Elkekli, A. R.; Aldouri, R. K.; Benedict, B. A.; Pingitore, N. E., Jr.

    2015-12-01

    Population-based random stratified sampling of the city of Cd. Juarez, Chihuahua, Mexico provided 500 city blocks for study. We collected soil from the public space (where present) in front of each house on a selected block; equal measured small volumes of these were combined to produce a composite sample for analysis. Such composite samples (1) decrease, by an order of magnitude, laboratory processing and analysis costs, and (2) smooth the data to represent blocks as averages of individual houses. Retention of the unanalyzed samples of the individual houses permits their later analysis should the composites suggest further study of individual houses on an anomalous block. Elemental analysis of 10 mg pressed powders was performed on a Panalytical Epsilon5 EDS-XRF, via 8 secondary targets and 12 USGS and NIST multi-element rock standards. The mean and (range) of concentration for Pb was 43 (13-550) ppm; for Cr, 31 (1.8-76); for Cu, 22 (6-550); for Zn 84 (42-415) ppm; for Cd, 1.9 (0.1-6.2); and for Sb, 5.9 (2.7-29). The old urban core of Cd. Juarez was marked by high levels of Pb, Cr, Cu, and Zn, and, to a smaller degree, of Cd and Sb. This pattern mirrors that of contiguous El Paso, Texas, USA, directly across the narrow Rio Grande. Businesses, industrial facilities, transportation (both railroads and highways), traditional "downtown" shopping, and old residential districts cluster in this urban core. A Pb-Cu-Zn smelter, which operated for more than a century until 1999, is present in the US adjacent to the Rio Grande, about two km away from downtown Cd. Juarez. Thus the city has been subject to both traditional metal sources (e.g., leaded gasoline, highway debris) and smelter emissions. The poplation of Cd. Juarez has exploded in the last few decades to some 1.5 million inhabitants due both to natural growth and in-migration from rural districts for economic opportunity. Most of this growth has been accommodated by radial expansion of the city into the surrounding

  12. Self-Assembled Templates of Aromatic Pentapeptides for Synthesis of CdS Quantum-Dots to Detect the Trace Amounts of Hg(2+) in Aqueous Solutions.

    Science.gov (United States)

    Meng, Min; Dou, Yingying; Xu, Wenlong; Hao, Jingcheng

    2016-05-01

    Molecular self-assembly has become a popular tool to prepare nanomaterials with potential applications, such as ion-responsive detection of Hg(2+) in aqueous solutions. In this study, FFACD aromatic pentapeptides, whose N-terminuses were protected by carboxyl (Ac-FFACD) or a 9-fluorenylmethoxycarbonyl group (Fmoc-FFACD), were chosen as building blocks to produce nanostructures in solutions. Based on the preliminary determination of the critical aggregation concentration (CAC) of Ac-FFACD and Fmoc-FFACD aromatic pentapeptides in water, the order of magnitude of which is 10(-5) mol·L(-1), self-assembled spiral and networked nanowires can be easily obtained over a range of concentrations. These nanowires were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The self-assembled spiral and networked nanowires were designed to be used as templates for preparing CdS quantum dots (QDs) in-situ at room temperature. The peptide-functionalized, nanowire-encapsulated CdS QDs can be used for rapid, sensitive, and selective detection of trace amounts of mercuric ions (Hg(2+)) in aqueous solutions. This method enables rapid, linear detection (the linear correlation coefficients are 0.9972 of ΔF = 257.09 + 3.58 cHg(2+) for Ac-FFACD and 0.9994 of ΔF = 48.13 + 32.96 cHg(2+) for Fmoc-FFACD) with the Hg(2+) limit of detection at 300.85 ng·L(-1) and 32.09 ng·L(-1) for Ac-FFACD and Fmoc-FFACD, respectively. The supramolecular, self-assembled nanowires, fabricated from the two aromatic pentapeptides and having encapsulated QDs, exhibit superior properties attributable to the large loading capacity and the coordination sites of these peptides with Hg(2+). These structures can serve as novel Hg(2+) sensors and have possible applications for detection of various targets in scientific and engineering systems. PMID:27086999

  13. ROIC with on-chip sigma-delta AD converter for HgCdTe e-APD FPA

    Science.gov (United States)

    Chen, Guoqiang; Zhang, Junling; Wang, Pan; Zhou, Jie; Gao, Lei; Ding, Ruijun

    2013-10-01

    HgCdTe electron injection avalanche photodiodes (e-APDs) work at linear mode. A weak optical current signal is amplified orders of magnitude due to the internal avalanche mechanism and it has been demonstrated to be one of the most promising methods to focal-plane arrays (FPAs) for low-flux like hyper-spectral imaging and high-speed applications such as active imaging. This paper presents the design of a column-shared ADC for cooled e-APDs FPA. Designing a digital FPA requires fulfilling very stringent requirements in terms of power consumption, silicon area and speed. Among the various ADC architectures sigma-delta conversion is a promising solution for high-performance and medium size FPA such as 128×128. The performance of Sigma-delta ADC rather relies on the modulator structure which set over-sampling and noise shaping characteristics than on critical analog circuits. This makes them quite robust and flexible. A multistage noise shaping (MASH) 2-1 single bit architecture sigma-delta conversion with switched-capacitor circuits is designed for column-shared ADC, which is implanted in the GLOBALFOUNDRIES 0.35um CMOS process with 4-poly and 4-metal on the basis of a 100um pixel pitch. It operates under 3.3V supply and the output range of the quantizer is 2V. A quantization noise subtraction circuit in modulator is designed to subtract the quantization noise of first-stage modulator. The quantization noise of the modulator is shaped by a high-pass filter. The silicon area and power consumption are mainly determined by the decimation low pass filter. A cascaded integrator-comb (CIC) filter is designed as the digital decimator filter. CIC filter requires no multipliers and use limited storage thereby leading to more economical hardware implementation. The register word length of the filter in each stage is carefully dimensioned in order to minimize the required hardware. Furthermore, the digital filters operate with a reduced supply voltage to 1.5V. Simulation

  14. Tinjauan terhadap tailing mengandung unsur pencemar Arsen (As, Merkuri (Hg, Timbal (Pb, dan Kadmium (Cd dari sisa pengolahan bijih logam

    Directory of Open Access Journals (Sweden)

    Danny Zulkifli Herman

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol1no1.20064aWhen tailing of a mining activity is discharged into either landscape or river body, the pollutan element wastes are possible to disperse within those areas and may cause pollution on environment. The environment pollution hazards of arsenic (As, mercury (Hg, lead (Pb and cadmium (Cd probably occurred if tailing with the content of those elements is not handled properly. Particularly in the tropical regions, higher rates of chemical weathering and bio-chemical activity will contribute a rapid mobilization of the most potentially toxic elements.One of adverse health effects from arsenic to human life is in the case of arsenic-contained drinking waters exceed the threshold limit value. As a result, it will create chronic symptoms of toxicity within the human body such as gastro-intestinal irritation, nerve damage and tissue wastage. Tailing originated from amalgamation processing of gold ore enables its mercury waste to disperse in the vicinity of mining area and may form environment pollution by either organic or inorganic mercury. The pollution would be more hazardous to human health if mercury element in the water body transform biochemically into a compound of methylmercury. There is a variety of mechanisms by micro-organism which can bring about the formation of the very toxic methylmercury species, particularly with regard to its uptake by fish. Effects to the human health from the organic mercury include the blood-brain barrier and upsetting the metabolism of the nervous system. Whilst the main toxic effect of inorganic mercury is disruption the functions of kidneys and liver within human body. Most mining activity of base metal may discharge tailing with a significant lead (Pb content. Lead is a cumulative poison, hence absorbing this element by human body with particularly exceeding its threshold limit value will bind strongly to a large number of molecules such as amino acids, haemoglobin

  15. Synthesis, crystal structure and photophysical properties of a series of metal complexes MI{sub 2}L{sub 2} (M = Zn, Cd, Hg) from an imidazole derivative

    Energy Technology Data Exchange (ETDEWEB)

    Fei, Wen-wen; Hu, Gui-ju; Li, Rui; Yang, Long-mei; Li, Sheng-li; Tian, Lei; Yang, Jia-xiang; Wu, Jie-ying [Department of Chemistry, Key Laboratory of Functional Inorganic Material Chemistry of Anhui Province, Anhui University, 230039 Hefei (China); Tian, Yu-peng, E-mail: yptian@ahu.edu.cn [Department of Chemistry, Key Laboratory of Functional Inorganic Material Chemistry of Anhui Province, Anhui University, 230039 Hefei (China); State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093 (China)

    2013-05-15

    A series of novel metal complexes, ZnL{sub 2}I{sub 2}, CdL{sub 2}I{sub 2}, and HgL{sub 2}I{sub 2} (L: 1-[Trans-4-(4-diethylaminostyryl) phenyl] imidazole), have been prepared and fully characterized. The structure of HgL{sub 2}I{sub 2} was confirmed by single crystal X-ray diffraction analysis, which exhibits that Hg atom is coordinated by two iodine atoms and two nitrogen atoms from the ligand to form a distorted tetrahedral environment. The variable temperature {sup 1}H NMR spectra proved that the metal complexes exhibit well stability in solution. Linear and nonlinear optical properties of them were described on the basis of density functional theory (DFT) calculations. Interestingly, we found that the complexation of the ligands with metal ion extends the electronic delocalization in the metal complexes, leading to dramatically enhanced two-photon absorption. - Highlights: ► Three d{sup 10}-metal complexes with two-photon absorption (TPA) are reported. ► The crystal structure of HgL{sub 2}I{sub 2} was determined. ► The complexes exhibit dramatically enhanced TPA related to its ligand. ► The connections between structure and properties for them were investigated.

  16. Crystal Growth And Characterization of the Model High-Temperature Superconductor HgBa{sub 2}CuO{sub 4+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xudong; Yu, Guichuan; Cho, Yong-Chan; Chabot-Couture, Guillaume; Barisic, Neven; Bourges, Philippe; Kaneko, Nobuhisa; Li, Yuan; Lu, Li; Motoyama, Eugene M.; Vajk,; Greven, Martin; /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Jilin U. /Stanford U., Phys. Dept. /Saclay /NIST, Wash., D.C.

    2007-03-16

    Since the discovery of high-transition-temperature (T{sub c}) superconductivity in La{sub 2-x}Ba{sub x}CuO{sub 4} in 1986, the study of the lamellar copper oxides has remained at the forefront of condensed matter physics. Apart from their unusually high values of T{sub c}, these materials also exhibit a variety of complex phenomena and phases. This rich behavior is a consequence of the lamellar crystal structures, formed of copper-oxygen sheets separated by charge reservoir layers, and of the strong electron-electron correlations in the copper-oxygen sheets. After two decades of intensive research, which has stimulated many valuable new insights into correlated electron systems in general, there remains a lack of consensus regarding the correct theory for high-T{sub c} superconductivity. The ultimate technological goal of room-temperature superconductivity might only be attained after the development of a deeper understanding of the mercury-based compounds HgBa{sub 2}Ca{sub n-1}Cu{sub n}OI{sub 2n+2+{delta}}, which currently exhibit the highest T{sub c}values. One very important issue in this regard is the role of electronic versus chemical and structural inhomogeneities in these materials, and the associated need to separate material-specific properties from those that are essential to superconductivity. Unfortunately, there has been remarkably little scientific work on the mercury-based compounds because sizable crystals have not been available; quantitative measurements of any kind would be invaluable benchmarks for testing the theories of high-T{sub c} superconductivity. The compounds HgBa{sub 2}Ca{sub n-1}Cu{sub n}OI{sub 2n+2+{delta}} can be viewed as model systems not only because of their record high-T{sub c} values, but also because of their high-symmetry crystal structures. Of particular interest is the simplest member of this materials family, HgBa{sub 2}CuO{sub 4+{delta}} (Hg1201), which possesses only one copper-oxygen sheet per unit cell (n = 1), as

  17. Synthesis and properties of superconducting HgBa2CuO4+x from a single-step low-temperature solid state reaction

    International Nuclear Information System (INIS)

    A novel technique based on a low-temperature single-step solid state reaction of stoichiometric quantities of HgO and Ba2CuO3 to produce superconducting HgBa2CuO4+x samples has been developed. The 'as-prepared' polycrystalline Hg-1201 samples had a Tc of 95 K, as obtained by the diamagnetic onset and resistivity measurements. The crystal symmetry was tetragonal with lattice parameters a = 3.876(1) AA, and c = 9.509(4) AA in agreement with literature data. Sample morphology consists of grains (average dimension 30 μ m) larger than in previously published works and of a needle-like structure embedding the whole sample. These results were highly reproducible over several batches. The resistive transition in magnetic field up to 8 T and a set of magnetic measurements is presented. From these measurements we obtain information about the irreversibility line, the critical current field dependence and the presence of weak links. (author)

  18. Interaction of Mg with heavy metals (Cu, Cd) in T. aestivum with special reference to oxidative and proline metabolism.

    Science.gov (United States)

    Singh, Vijeta; Tripathi, Bhumi Nath; Sharma, Vinay

    2016-05-01

    Little effort has been made to understand the influence of Mg on cellular processes of plant cell during Cu and Cd toxicities. The present work demonstrates the influence of magnesium (Mg) on copper (Cu) and cadmium (Cd) toxicity on Triticum aestivum (Wheat). We measured a range of parameters related to oxidative stress in wheat exposed to Cu or Cd toxicity in media with different concentrations of Mg. Decreasing Mg concentration significantly exacerbated Cu and Cd toxicity and optimum supply of Mg improved the growth and decreased the toxicity-induced oxidative stress (a substantial decline in the amount of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in root and shoot tissues). Activity of antioxidant enzymes-superoxide dismutase (SOD), ascorbae peroxidase (APX), catalase (CAT) was restored upon optimum Mg concentration in the presence of Cu and Cd toxicity. An increase in proline concentration in roots and shoots that was triggered by Cu and Cd exposure was partly reversed. This was due to decline in pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) activity and enhanced proline dehydrogenase (PDH) activity. In conclusion, decreasing supply of Mg effectively exacerbated the toxicities of Cu and Cd in wheat. PMID:26547559

  19. Thermally-restorable optical degradation and the mechanism of current transport in Cu2S-CdS photovoltaic cells

    Science.gov (United States)

    Fahrenbruch, A. L.; Bube, R. H.

    1974-01-01

    The photovoltaic properties of single-crystal Cu2S-CdS heterojunctions have been investigated as a function of heat treatment by detailed measurements of the dependence of short-circuit current on photon energy, temperature, and the state of optical degradation or enhancement. A coherent picture is formulated for the relationship between enhancement and optical degradation, and their effect on the transport of short-circuit photoexcited current and dark, forward-bias current in the cell. Optical degradation in the Cu2S-CdS cell is shown to be closely identical to optical degradation of lifetime in a homogeneous CdS:Cd:Cu crystal, indicating that the CdS:Cu layer near the junction interface controls carrier transport in the cell. It is proposed that both the photoexcited short-circuit current and the dark, forward-bias current are controlled by a tunneling-recombination process through interface states.

  20. Synthesis and enhanced photocatalytic property of feather-like Cd-doped CuO nanostructures by hydrothermal method

    Science.gov (United States)

    Wang, Yongqian; Jiang, Tingting; Meng, Dawei; Wang, Dagui; Yu, Meihua

    2015-11-01

    Feather-like Cd-doped CuO nanostructures were fabricated by a one-step hydrothermal method. X-ray diffraction pattern (XRD) and field emission scanning electron microscopy (FESEM) demonstrated that Cd2+ entered the crystal lattice of CuO and substituted Cu2+ without destroying crystal structures to form feather-like CuO nanostructures. The optical property of Cd-doped CuO was investigated by using UV-vis spectrophotometer. A slight blue-shift of optical band gap was observed because of quantum confinement effect. The doped samples exhibited obviously higher absorbance in UV light region and better photocatalytic activity for the photodegradation of methyl blue than the pure CuO nanosheets.