Enhanced room temperature ferromagnetism in Ni doped SnO2 nanoparticles: A comprehensive study

NASA Astrophysics Data System (ADS)

Ahmed, Ateeq; Ali, T.; Naseem Siddique, M.; Ahmad, Abid; Tripathi, P.

2017-08-01

We emphasized on a detailed investigation of the structural, optical, and magnetic properties of pure and Ni-doped SnO2 nanoparticles (NPs) synthesized by a sol-gel process. An extensive structural study has been carried out using various characterization techniques. The X-ray Diffraction (XRD) spectra show the formation of the single phase tetragonal structure of pure and Ni-doped SnO2 NPs without any noticeable impurity phase such as NiO. XRD results indicate that the crystallite size of SnO2 is found to be decreased with Ni doping, which has also been confirmed by the Field Emission Scanning Electron Microscopy study. X-ray Photoelectron Spectroscopy (XPS) measurements displayed a clear sign for Ni2+ ions occupying the lattice sites of Sn4+ in the SnO2 host which also gives clear evidence for the formation of single phase Sn1-xNixO2 NPs. The optical analysis shows a significant decrease in the energy gap of SnO2, i.e., (from 3.71 eV to 3.28 eV) as Ni concentration increases which may be correlated with the core level valence band XPS analysis. Photoluminescence studies show that Ni doping creates oxygen vacancies due to dissimilar ionic radii of Ni2+ and Sn4+. Superconducting quantum interference device measurements revealed that the Ni doped SnO2 NPs exhibit strong ferromagnetic behavior at room temperature and this analysis has been well fitted with a simple relationship to find out magnetic parameters proposed by Stearns and Cheng et al. Hence, our results demonstrate that Ni-doping has strong impact on the structural, optical, and magnetic properties.

Heterovalent Substitution to Enrich Electrical Conductivity in Cu2CdSn1-xGaxSe4 Series for High Thermoelectric Performances

PubMed Central

Wang, Bo; Li, Yu; Zheng, Jiaxin; Xu, Ming; Liu, Fusheng; Ao, Weiqing; Li, Junqing; Pan, Feng

2015-01-01

Serials of Ga doping on Sn sites as heterovalent substitution in Cu2CdSnSe4 are prepared by the melting method and the spark plasma sintering (SPS) technique to form Cu2CdSn1-xGaxSe4 (x = 0, 0.025, 0.05, 0.075, 0.01, and 0.125). Massive atomic vacancies are found at x = 0.10 by the heterovalent substitution, which contributes significantly to the increase of electrical conductivity and the decrease of lattice thermal conductivity. The electrical conductivity is increased by about ten times at 300 K after Ga doping. Moreover, the seebeck coefficient only decreases slightly from 310 to 226 μV/K at 723 K, and a significant increase of the power factor is obtained. As a result, a maxium value of 0.27 for the figure of merit (ZT) is obtained at x = 0.10 and at 723 K. Through an ab initio study of the Ga doping effect, we find that the Fermi level of Cu2CdSnSe4 is shifted downward to the valence band, thus improving the hole concentration and enhancing the electrical conductivity at low doping levels. Our experimental and theoretical studies show that a moderate Ga doping on Sn sites is an effective method to improve the thermoelectric performance of Cu2CdSnSe4. PMID:25791823

High Power Factor and Enhanced Thermoelectric Performance of SnTe-AgInTe2: Synergistic Effect of Resonance Level and Valence Band Convergence.

PubMed

Banik, Ananya; Shenoy, U Sandhya; Saha, Sujoy; Waghmare, Umesh V; Biswas, Kanishka

2016-10-05

Understanding the basis of electronic transport and developing ideas to improve thermoelectric power factor are essential for production of efficient thermoelectric materials. Here, we report a significantly large thermoelectric power factor of ∼31.4 μW/cm·K 2 at 856 K in Ag and In co-doped SnTe (i.e., SnAg x In x Te 1+2x ). This is the highest power factor so far reported for SnTe-based material, which arises from the synergistic effects of Ag and In on the electronic structure and the improved electrical transport properties of SnTe. In and Ag play different but complementary roles in modifying the valence band structure of SnTe. In-doping introduces resonance levels inside the valence bands, leading to a significant improvement in the Seebeck coefficient at room temperature. On the other hand, Ag-doping reduces the energy separation between light- and heavy-hole valence bands by widening the principal band gap, which also results in an improved Seebeck coefficient. Additionally, Ag-doping in SnTe enhances the p-type carrier mobility. Co-doping of In and Ag in SnTe yields synergistically enhanced Seebeck coefficient and power factor over a broad temperature range because of the synergy of the introduction of resonance states and convergence of valence bands, which have been confirmed by first-principles density functional theory-based electronic structure calculations. As a consequence, we have achieved an improved thermoelectric figure of merit, zT ≈ 1, in SnAg 0.025 In 0.025 Te 1.05 at 856 K.

Preparation of Ru-doped SnO2-supported Pt catalysts and their electrocatalytic properties for methanol oxidation.

PubMed

Pang, H L; Zhang, X H; Zhong, X X; Liu, B; Wei, X G; Kuang, Y F; Chen, J H

2008-03-01

Ru-doped SnO2 nanoparticles were prepared by chemical precipitation and calcinations at 823 K. Due to high stability in diluted acidic solution, Ru-doped SnO2 nanoparticles were selected as the catalyst support and second catalyst for methanol electrooxidation. The micrograph, elemental composition, and structure of the Ru-doped SnO2 nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, respectively. The electrocatalytic properties of the Ru-doped SnO2-supported Pt catalyst (Pt/Ru-doped SnO2) for methanol oxidation have been investigated by cyclic voltammetry. Under the same loading mass of Pt, the Pt/Ru-doped SnO2 catalyst shows better electrocatalytic performance than the Pt/SnO2 catalyst and the best atomic ratio of Ru to Sn in Ru-doped SnO2 is 1/75. Additionally, the Pt/Ru-doped SnO2 catalyst possesses good long-term cycle stability.

Stability and magnetic properties of SnSe monolayer doped by transition metal atom (Mn, Fe, and Co): a first-principles study

NASA Astrophysics Data System (ADS)

Tang, Chao; Li, Qinwen; Zhang, Chunxiao; He, Chaoyu; Li, Jin; Ouyang, Tao; Li, Hongxing; Zhong, Jianxin

2018-06-01

Two dimensional (2D) tin selenium (SnSe) is an intriguing material with desired thermal and electric properties in nanoelectronics. In this paper, we carry on a density functional theory study on the stability and dilute magnetism of the 3d TM (Mn, Fe, and Co) doped 2D SnSe. Both the adsorption and substitution are in consideration here. We find that all the defects are electrically active and the cation substitutional doping (TM@Sn) is energetically favorable. The TM@Sn prefers to act as accepters and exhibits high-spin state with nonzero magnetic moment. The magnetic moment is mainly contributed by the spin-polarized charge density of the TM impurities. The magnetism is determined by the arrangement of the TM-3d orbitals, which is the result of the crystal field splitting and spin exchange splitting under specific symmetry. The magnetic and electronic properties of the TM@Sn are effectively modulated by external electric field (Eext) and charge doping. The Eext shifts the TM impurities relative to the SnSe host and then modifies the crystal field splitting. In particular, the magnetic moment is sensitive to the Eext in the Fe@Sn because the Eext induces distinct structure transformation. Based on the formation energy, doping electrons is a viable way to modulate the magnetic moment of TM@Sn. Doping electrons shift the 3d states towards low energy level, which induces the occupation of more 3d states and then the reduction of magnetism. These results render SnSe monolayer a promising 2D material for applications in future spintronics.

Defect properties of Sn- and Ge-doped ZnTe: suitability for intermediate-band solar cells

NASA Astrophysics Data System (ADS)

Flores, Mauricio A.

2018-01-01

We investigate the electronic structure and defect properties of Sn- and Ge- doped ZnTe by first-principles calculations within the DFT+GW formalism. We find that ({{{Sn}}}{{Zn}}) and ({{{Ge}}}{{Zn}}) introduce isolated energy levels deep in the band gap of ZnTe, derived from Sn-5s and Ge-4s states, respectively. Moreover, the incorporation of Sn and Ge on the Zn site is favored in p-type ZnTe, in both Zn-rich and Te-rich environments. The optical absorption spectra obtained by solving the Bethe-Salpeter equation reveals that sub-bandgap absorptance is greatly enhanced due to the formation of the intermediate band. Our results suggest that Sn- and Ge-doped ZnTe would be a suitable material for the development of intermediate-band solar cells, which have the potential to achieve efficiencies beyond the single-junction limit.

Morphology, composition and electrical properties of SnO{sub 2}:Cl thin films grown by atomic layer deposition

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

Cheng, Hsyi-En, E-mail: sean@mail.stust.edu.tw; Wen, Chia-Hui; Hsu, Ching-Ming

2016-01-15

Chlorine doped SnO{sub 2} thin films were prepared using atomic layer deposition at temperatures between 300 and 450 °C using SnCl{sub 4} and H{sub 2}O as the reactants. Composition, structure, surface morphology, and electrical properties of the as-deposited films were examined. Results showed that the as-deposited SnO{sub 2} films all exhibited rutile structure with [O]/[Sn] ratios between 1.35 and 1.40. The electrical conductivity was found independent on [O]/[Sn] ratio but dependent on chlorine doping concentration, grain size, and surface morphology. The 300 °C-deposited film performed a higher electrical conductivity of 315 S/cm due to its higher chlorine doping level, larger grain size, andmore » smoother film surface. The existence of Sn{sup 2+} oxidation state was demonstrated to minimize the effects of chlorine on raising the electrical conductivity of films.« less

Stabilization of Fermi level via electronic excitation in Sn doped CdO thin films

NASA Astrophysics Data System (ADS)

Das, Arkaprava; Singh, Fouran

2018-04-01

Pure and Sn doped CdO sol-gel derived thin films were deposited on corning glass substrate and further irradiated by swift heavy ion (SHI) (Ag and O) with fluence upto 3×1013 ions/cm2. The observed tensile stress from X-ray diffraction pattern at higher fluence for Ag ions can be corroborated to the imbrications of cylindrical tracks due to multiple impacts. The anomalous band gap enhancement after irradiation may be attributed to the consolidated effect of Burstein-Moss shift (BMS) and impurity induced virtual gap states (ViGs). At higher excitation density as Fermi stabilization level (EFS) tends to coincide with charge neutrality level (CNL), band gap enhancement saturates as further creation of additional defects inside the lattice becomes unsustainable. Raman spectroscopy divulges an intensity enhancement of 478 cm-1 LO phonon mode with Sn doping and irradiation induces further asymmetric peak broadening due to damage and disordering inside the lattice. However for 3% Sn doped thin film irradiated with Ag ions having 3×1013 fluence shows a drastic change in structural properties and reduction in band gap which might be attributed to the generation of localized energy levels between conduction and valance band due to high density of defects.

Thermoelectric properties of Bi1-xSnxCuSeO solid solutions.

PubMed

Yang, Yuqing; Liu, Xiaocun; Liang, Xin

2017-02-21

We report the enhanced thermoelectric properties of p-type BiCuSeO by tin doping on bismuth sites. Powder X-ray diffraction analysis and Hall measurements indicated effective tin doping in all samples. We found that the doping efficiency of Sn is lower than expected, as seen from the measured carrier concentration. First-principles calculations indicate that the Sn lone pair modifies the band structure at the Fermi level, with the consequent effect observed in the electrical transport and Seebeck coefficient measurements. An enhanced thermoelectric power factor of ∼2.5 μW cm -1 K -2 was reached at 773 K. No significant effect of Sn doping on the thermal conductivity was found; a thermoelectric figure of merit value (ZT) of 0.3 at 773 K is achieved for Bi 0.9 Sn 0.1 CuSeO, which is more than twice that of the pristine BiCuSeO.

Synthesis and characterization of Sn-doped hematite as visible light photocatalyst

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

Cao, Zhiqin; School of Materials Science and Engineering, Pan Zhihua University, Pan Zhihua 617000; Qin, Mingli, E-mail: qinml@mater.ustb.edu.cn

2016-05-15

Highlights: • Sn-doped hematite nanoparticles are prepared by SCS in one step. • The Sn doping have the ability to inhibit particle growth of hematite. • Sn can enhance visible light harvesting and e{sup −}/h{sup +} separation. • Sn-doped hematite degrades MB under visible light effectively. • The products with 5 mol% Sn have the highest photocatalytic activity. - Abstract: Sn-doped hematite nanoparticles are prepared by solution combustion synthesis. The products are characterized with various analytical and spectroscopic techniques to determine their structural, morphological, light absorption and photocatalytic properties. The results reveal that all the samples consist of nanocrystalline hematitemore » with mesoporous structures, and Sn has the ability to inhibit the growth of hematite particle. Compared to pure hematite, the doped hematite samples with appropriate amount of Sn show better activities for degradation of methylene blue under visible light irradiation. The highest activity is observed for 5% Sn doped hematite and this product has long-term stability and no selectivity for dye degradation. The enhanced performance of 5% Sn doped hematite is ascribed to the smaller particle size, increased ability to absorb in visible light, efficient charge separation as well as improved e{sup −} transfer associated with the effects of appropriate amount of Sn doped sample.« less

Electronic and magnetic properties of SnS2 monolayer doped with 4d transition metals

NASA Astrophysics Data System (ADS)

Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Chen, Qiao; Wang, Ling-Ling

2017-09-01

We investigate the electronic structures and magnetic properties of SnS2 monolayers substitutionally doped with 4-d transition-metal through systematic first principles calculations. The doped complexes exhibit interesting electronic and magnetic behaviors, depending on the interplay between crystal field splitting, Hund's rule, and 4d levels. The system doped with Y is nonmagnetic metal. Both the Zr- and Pd-doped systems remain nonmagnetic semiconductors. Doping results in half-metallic states for Nb-, Ru-, Rh-, Ag, and Cd doped cases, and magnetic semiconductors for systems with Mo and Tc dopants. In particular, the Nb- and Mo-doped systems display long-ranged ferromagnetic ordering with Curie temperature above room temperature, which are primarily attributable to the double-exchange mechanism, and the p-d/p-p hybridizations, respectively. Moreover, The Mo-doped system has excellent energetic stability and flexible mechanical stability, and also possesses remarkable dynamic and thermal (500 K) stability. Our studies demonstrate that Nb- and Mo-doped SnS2 monolayers are promising candidates for preparing 2D diluted magnetic semiconductors, and hence will be a helpful clue for experimentalists.

Enhanced B doping in CVD-grown GeSn:B using B δ-doping layers

NASA Astrophysics Data System (ADS)

Kohen, David; Vohra, Anurag; Loo, Roger; Vandervorst, Wilfried; Bhargava, Nupur; Margetis, Joe; Tolle, John

2018-02-01

Highly doped GeSn material is interesting for both electronic and optical applications. GeSn:B is a candidate for source-drain material in future Ge pMOS device because Sn adds compressive strain with respect to pure Ge, and therefore can boost the Ge channel performances. A high B concentration is required to obtain low contact resistivity between the source-drain material and the metal contact. To achieve high performance, it is therefore highly desirable to maximize both the Sn content and the B concentration. However, it has been shown than CVD-grown GeSn:B shows a trade-off between the Sn incorporation and the B concentration (increasing B doping reduces Sn incorporation). Furthermore, the highest B concentration of CVD-grown GeSn:B process reported in the literature has been limited to below 1 × 1020 cm-3. Here, we demonstrate a CVD process where B δ-doping layers are inserted in the GeSn layer. We studied the influence of the thickness between each δ-doping layers and the δ-doping layers process conditions on the crystalline quality and the doping density of the GeSn:B layers. For the same Sn content, the δ-doping process results in a 4-times higher B doping than the co-flow process. In addition, a B doping concentration of 2 × 1021 cm-3 with an active concentration of 5 × 1020 cm-3 is achieved.

Morphology-controllable of Sn doped ZnO nanorods prepared by spray pyrolysis for transparent electrode application

NASA Astrophysics Data System (ADS)

Hameed, M. Shahul; Princice, J. Joseph; Babu, N. Ramesh; Zahirullah, S. Syed; Deshmukh, Sampat G.; Arunachalam, A.

2018-05-01

Transparent conductive Sn doped ZnO nanorods have been deposited at various doping level by spray pyrolysis technique on glass substrate. The structural, surface morphological and optical properties of these films have been investigated with the help of X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-Vis spectrophotometer respectively. XRD patterns revealed a successful high quality growth of single crystal ZnO nanorods with hexagonal wurtzite structure having (002) preferred orientation. The scanning electron microscope (SEM) image of the prepared films exposed the uniform distribution of Sn doped ZnO nanorod shaped grains. All these films were highly transparent in the visible region with average transmittance of 90%.

The Effect of Eu Doping on Microstructure, Morphology and Methanal-Sensing Performance of Highly Ordered SnO2 Nanorods Array

PubMed Central

Zhao, Yanping; Li, Yuehua; Ren, Xingping; Gao, Fan; Zhao, Heyun

2017-01-01

Layered Eu-doped SnO2 ordered nanoarrays constructed by nanorods with 10 nm diameters and several hundred nanometers length were synthesized by a substrate-free hydrothermal route using alcohol and water mixed solvent of sodium stannate and sodium hydroxide at 200 °C. The Eu dopant acted as a crystal growth inhibitor to prevent the SnO2 nanorods growth up, resulting in tenuous SnO2 nanorods ordered arrays. The X-ray diffraction (XRD) revealed the tetragonal rutile-type structure with a systematic average size reduction and unit cell volume tumescence, while enhancing the residual strain as the Eu-doped content increases. The surface defects that were caused by the incorporation of Eu ions within the surface oxide matrix were observed by high-resolution transmission electron microscope (HRTEM). The results of the response properties of sensors based on the different levels of Eu-doped SnO2 layered nanoarrays demonstrated that the 0.5 at % Eu-doped SnO2 layered nanorods arrays exhibited an excellent sensing response to methanal at 278 °C. The reasons of the enhanced sensing performance were discussed from the complicated defect surface structure, the large specific surface area, and the excellent catalytic properties of Eu dopant. PMID:29168796

Selenium doping NaCl-type superconductor: SnAs1-xSex (x=0-0.13)

NASA Astrophysics Data System (ADS)

He, Jianqiao; Zhang, Xian; Lai, Xiaofang; Huang, Fuqiang

2017-08-01

Selenium doped NaCl-type superconductor SnAs1-xSex (x=0-0.13) were made through solid state reaction. EDS results show that Se content increases with Se doping until over doped in SnAs0.9Se0.1 and SnAs0.87Se0.13 (around 2.7%). PXRD patterns confirmed the main phase of the six doped samples are SnAs. The cell parameters of doped SnAs were calculated using Rietveld refinements. Their cell parameters increase almost linearly with x until x reaches 13%. Single crystal diffraction measurement results show that there are no interstitial atom in doped SnAs. We conclude that Se atoms are substitutional atoms in SnAs. The superconducting onset temperatures (Tconset, under a magnetic field of 10 Oe) of SnAs increased from 3.8 K to 4.5 K by 10% Se doping. ρ-T curves of 1%, 5% and 10% Se doped samples show that all the three samples are metallic. Upper critical field Hc2(0) of 1%, 5% and 10% Se doped samples are 294 Oe, 649 Oe and 1011 Oe, respectively.

Electronic tuning of the transport properties of off-stoichiometric Pb{sub x}Sn{sub 1−x}Te thermoelectric alloys by Bi{sub 2}Te{sub 3} doping

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

Guttmann, Gilad M.; Dadon, David; Gelbstein, Yaniv

2015-08-14

The recent energy demands affected by the dilution of conventional energy resources and the growing awareness of environmental considerations had motivated many researchers to seek for novel renewable energy conversion methods. Thermoelectric direct conversion of thermal into electrical energies is such a method, in which common compositions include IV-VI semiconducting compounds (e.g., PbTe and SnTe) and their alloys. For approaching practical thermoelectric devices, the current research is focused on electronic optimization of off-stoichiometric p-type Pb{sub x}Sn{sub 1−x}Te alloys by tuning of Bi{sub 2}Te{sub 3} doping and/or SnTe alloying levels, while avoiding the less mechanically favorable Na dopant. It was shownmore » that upon such doping/alloying, higher ZTs, compared to those of previously reported undoped Pb{sub 0.5}Sn{sub 0.5}Te alloy, were obtained at temperatures lower than 210–340 °C, depending of the exact doping/alloying level. It was demonstrated that upon optimal grading of the carrier concentration, a maximal thermoelectric efficiency enhancement of ∼38%, compared to that of an undoped material, is expected.« less

n-type conversion of SnS by isovalent ion substitution: Geometrical doping as a new doping route

PubMed Central

Ran, Fan-Yong; Xiao, Zewen; Toda, Yoshitake; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

2015-01-01

Tin monosulfide (SnS) is a naturally p-type semiconductor with a layered crystal structure, but no reliable n-type SnS has been obtained by conventional aliovalent ion substitution. In this work, carrier polarity conversion to n-type was achieved by isovalent ion substitution for polycrystalline SnS thin films on glass substrates. Substituting Pb2+ for Sn2+ converted the majority carrier from hole to electron, and the free electron density ranged from 1012 to 1015 cm−3 with the largest electron mobility of 7.0 cm2/(Vs). The n-type conduction was confirmed further by the position of the Fermi level (EF) based on photoemission spectroscopy and electrical characteristics of pn heterojunctions. Density functional theory calculations reveal that the Pb substitution invokes a geometrical size effect that enlarges the interlayer distance and subsequently reduces the formation energies of Sn and Pb interstitials, which results in the electron doping. PMID:26020855

Nanocrystalline SnO2:F thin films for liquid petroleum gas sensors.

PubMed

Chaisitsak, Sutichai

2011-01-01

This paper reports the improvement in the sensing performance of nanocrystalline SnO(2)-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO(2) films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO(2) with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO(2):F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO(2) was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO(2):F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection.

Simultaneous thermal stability and phase change speed improvement of Sn15Sb85 thin film through erbium doping

NASA Astrophysics Data System (ADS)

Zou, Hua; Zhu, Xiaoqin; Hu, Yifeng; Sui, Yongxing; Sun, Yuemei; Zhang, Jianhao; Zheng, Long; Song, Zhitang

2016-12-01

In general, there is a trade off between the phase change speed and thermal stability in chalcogenide phase change materials, which leads to sacrifice the one in order to ensure the other. For improving the performance, doping is a widely applied technological process. Here, we fabricated Er doped Sn15Sb85 thin films by magnetron sputtering. Compared with the pure Sn15Sb85, we show that Er doped Sn15Sb85 thin films exhibit simultaneous improvement over the thermal stability and the phase change speed. Thus, our results suggest that Er doping provides the opportunity to solve the contradiction. The main reason for improvement of both thermal stability and crystallization speed is due to the existence of Er-Sb and Er-Sn bonds in Er doped Sn15Sb85 films. Hence, Er doped Sn15Sb85 thin films are promising candidates for the phase change memory application, and this method could be extended to other lanthanide-doped phase change materials.

Ex situ n+ doping of GeSn alloys via non-equilibrium processing

NASA Astrophysics Data System (ADS)

Prucnal, S.; Berencén, Y.; Wang, M.; Rebohle, L.; Böttger, R.; Fischer, I. A.; Augel, L.; Oehme, M.; Schulze, J.; Voelskow, M.; Helm, M.; Skorupa, W.; Zhou, S.

2018-06-01

Full integration of Ge-based alloys like GeSn with complementary-metal-oxide-semiconductor technology would require the fabrication of p- and n-type doped regions for both planar and tri-dimensional device architectures which is challenging using in situ doping techniques. In this work, we report on the influence of ex situ doping on the structural, electrical and optical properties of GeSn alloys. n-type doping is realized by P implantation into GeSn alloy layers grown by molecular beam epitaxy (MBE) followed by flash lamp annealing. We show that effective carrier concentration of up to 1 × 1019 cm‑3 can be achieved without affecting the Sn distribution. Sn segregation at the surface accompanied with an Sn diffusion towards the crystalline/amorphous GeSn interface is found at P fluences higher than 3 × 1015 cm‑2 and electron concentration of about 4 × 1019 cm‑3. The optical and structural properties of ion-implanted GeSn layers are comparable with the in situ doped MBE grown layers.

Surface oxidation and thermoelectric properties of indium-doped tin telluride nanowires.

PubMed

Li, Zhen; Xu, Enzhi; Losovyj, Yaroslav; Li, Nan; Chen, Aiping; Swartzentruber, Brian; Sinitsyn, Nikolai; Yoo, Jinkyoung; Jia, Quanxi; Zhang, Shixiong

2017-09-14

The recent discovery of excellent thermoelectric properties and topological surface states in SnTe-based compounds has attracted extensive attention in various research areas. Indium doped SnTe is of particular interest because, depending on the doping level, it can either generate resonant states in the bulk valence band leading to enhanced thermoelectric properties, or induce superconductivity that coexists with topological states. Here we report on the vapor deposition of In-doped SnTe nanowires and the study of their surface oxidation and thermoelectric properties. The nanowire growth is assisted by Au catalysts, and their morphologies vary as a function of substrate position and temperature. Transmission electron microscopy characterization reveals the formation of an amorphous surface in single crystalline nanowires. X-ray photoelectron spectroscopy studies suggest that the nanowire surface is composed of In 2 O 3 , SnO 2 , Te and TeO 2 which can be readily removed by argon ion sputtering. Exposure of the cleaned nanowires to atmosphere leads to rapid oxidation of the surface within only one minute. Characterization of electrical conductivity σ, thermopower S, and thermal conductivity κ was performed on the same In-doped nanowire which shows suppressed σ and κ but enhanced S yielding an improved thermoelectric figure of merit ZT compared to the undoped SnTe.

Ultrasonic synthesis of In-doped SnS nanoparticles and their physical properties

NASA Astrophysics Data System (ADS)

Jamali-Sheini, Farid; Cheraghizade, Mohsen; Yousefi, Ramin

2018-05-01

Indium (In)-doped Tin (II) Sulfide (SnS) nanoparticles (NPs) were synthesized by an ultra-sonication method and their optical, electrical, dielectric and photocatalytic properties were investigated. XRD patterns of the obtained NPs indicated formation of orthorhombic polycrystalline SnS. Field emission scanning electron microscopy exhibited flower-like NPs with particle sizes below 100 nm for both SnS and In-doped SnS samples. Optical analysis showed a decrease in energy band gap of SnS NPs upon In doping. In addition, electrical results demonstrated p-type nature of the synthesized SnS NPs and enhanced electrical conductivity of the NPs due to increased tin vacancy. Dielectric experiments on SnS NPs suggested an electronic polarizations effect to be responsible for changing dielectric properties of the particles, in terms of frequency. Finally, photocatalytic experiments revealed that high degradation power can be obtained using In-doped SnS NPs.

Influence of Fe ions on structural, optical and thermal properties of SnO{sub 2} nanoparticles

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

Ahmed, Ateeq, E-mail: ateeqamu124@gmail.com; Tripathi, P.; Khan, Wasi

2016-05-23

In the present work, Fe doped SnO{sub 2} nanoparticles with the composition Sn{sub 1-x}Fe{sub x}O{sub 2} (x = 0, 0.02, 0.04 and 0.06) have been successfully synthesized using sol-gel auto combustion technique. The samples are characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDAX), Ultraviolet (UV-Visible) absorption spectroscopy and thermal gravimetric analysis (TGA). The XRD study shows that all the samples have been found in tetragonal rutile structure without any extra phase and average crystallite size which lies in the range of 6-17 nm. The EDAX spectrum confirmed the doping of Fe ion into tin oxidemore » nanomaterial. The optical band gap of doped SnO{sub 2} is found to decrease with increasing Fe ion concentration, which is due to the formation of donor energy levels in the actual band gap of SnO{sub 2}.« less

Doped SnO₂ transparent conductive multilayer thin films explored by continuous composition spread.

PubMed

Lee, Jin Ju; Ha, Jong-Yoon; Choi, Won-Kook; Cho, Yong Soo; Choi, Ji-Won

2015-04-13

Mn-doped SnO₂ thin films were fabricated by a continuous composition spread (CCS) method on a glass substrate at room temperature to find optimized compositions. The fabricated materials were found to have a lower resistivity than pure SnO₂ thin films because of oxygen vacancies generated by Mn doping. As Mn content was increased, resistivity was found to decrease for limited doping concentrations. The minimum thin film resistivity was 0.29 Ω-cm for a composition of 2.59 wt % Mn-doped SnO₂. The Sn-O vibrational stretching frequency in FT-IR showed a blue shift, consistent with oxygen deficiency. Mn-doped SnO₂/Ag/Mn-doped SnO₂ multilayer structures were fabricated using this optimized composition deposited by an on-axis radio frequency (RF) sputter. The multilayer transparent conducting oxide film had a resistivity of 7.35 × 10⁻⁵ Ω-cm and an average transmittance above 86% in the 550 nm wavelength region.

Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors

PubMed Central

Chaisitsak, Sutichai

2011-01-01

This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

Reducing Hysteresis and Enhancing Performance of Perovskite Solar Cells Using Low-Temperature Processed Y-Doped SnO2 Nanosheets as Electron Selective Layers.

PubMed

Yang, Guang; Lei, Hongwei; Tao, Hong; Zheng, Xiaolu; Ma, Junjie; Liu, Qin; Ke, Weijun; Chen, Zhiliang; Xiong, Liangbin; Qin, Pingli; Chen, Zhao; Qin, Minchao; Lu, Xinhui; Yan, Yanfa; Fang, Guojia

2017-01-01

Despite the rapid increase of efficiency, perovskite solar cells (PSCs) still face some challenges, one of which is the current-voltage hysteresis. Herein, it is reported that yttrium-doped tin dioxide (Y-SnO 2 ) electron selective layer (ESL) synthesized by an in situ hydrothermal growth process at 95 °C can significantly reduce the hysteresis and improve the performance of PSCs. Comparison studies reveal two main effects of Y doping of SnO 2 ESLs: (1) it promotes the formation of well-aligned and more homogeneous distribution of SnO 2 nanosheet arrays (NSAs), which allows better perovskite infiltration, better contacts of perovskite with SnO 2 nanosheets, and improves electron transfer from perovskite to ESL; (2) it enlarges the band gap and upshifts the band energy levels, resulting in better energy level alignment with perovskite and reduced charge recombination at NSA/perovskite interfaces. As a result, PSCs using Y-SnO 2 NSA ESLs exhibit much less hysteresis and better performance compared with the cells using pristine SnO 2 NSA ESLs. The champion cell using Y-SnO 2 NSA ESL achieves a photovoltaic conversion efficiency of 17.29% (16.97%) when measured under reverse (forward) voltage scanning and a steady-state efficiency of 16.25%. The results suggest that low-temperature hydrothermal-synthesized Y-SnO 2 NSA is a promising ESL for fabricating efficient and hysteresis-less PSC. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ab initio study of thermoelectric properties of doped SnO{sub 2} superlattices

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

Borges, P.D., E-mail: pdborges@gmail.com; Silva, D.E.S.; Castro, N.S.

2015-11-15

Transparent conductive oxides, such as tin dioxide (SnO{sub 2}), have recently shown to be promising materials for thermoelectric applications. In this work we studied the thermoelectric properties of Fe-, Sb- and Zn-uniformly doping and co-doping SnO{sub 2}, as well as of Sb and Zn planar (or delta)-doped layers in SnO{sub 2} forming oxide superlattices (SLs). Based on the semiclassical Boltzmann transport equations (BTE) in conjunction with ab initio electronic structure calculations, the Seebeck coefficient (S) and figure of merit (ZT) are obtained for these systems, and are compared with available experimental data. The delta doping approach introduces a remarkable modificationmore » in the electronic structure of tin dioxide, when compared with the uniform doping, and colossal values for ZT are predicted for the delta-doped oxide SLs. This result is a consequence of the two-dimensional electronic confinement and the strong anisotropy introduced by the doped planes. In comparison with the uniformly doped systems, our predictions reveal a promising use of delta-doped SnO{sub 2} SLs for enhanced S and ZT, which emerge as potential candidates for thermoelectric applications. - Graphical abstract: Band structure and Figure of merit for SnO2:Sb superlattice along Z direction, P. D. Borges, D. E. S. Silva, N. S. Castro, C. R. Ferreira, F. G. Pinto, J. Tronto and L. Scolfaro, Ab initio study of thermoelectric properties of doped SnO2 superlattices. - Highlights: • Thermoelectric properties of SnO{sub 2}-based alloys and superlattices. • High figure of merit is predicted for planar-doped SnO{sub 2} superlattices. • Nanotechnology has an important role for the development of thermoelectric devices.« less

Codoping in SnTe: Enhancement of Thermoelectric Performance through Synergy of Resonance Levels and Band Convergence

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

Tan, Gangjian; Shi, Fengyuan; Hao, Shiqiang

2015-04-22

We report a significant enhancement of the thermoelectric performance of p-type SnTe over a broad temperature plateau with a peak ZT value of similar to 1.4 at 923 K through In/Cd codoping and a CdS nanostructuring approach. Indium and cadmium play different but complementary roles in modifying the valence band structure of SnTe. Specifically, In-doping introduces resonant levels inside the valence bands, leading to a considerably improved Seebeck coefficient at low temperature. Cd-doping, however, increases the Seebeck coefficient of SnTe remarkably in the mid- to high-temperature region via a convergence of the light and heavy hole bands and an enlargementmore » of the band gap. Combining the two dopants in SnTe yields enhanced Seebeck coefficient and power factor over a wide temperature range due to the synergy of resonance levels and valence band convergence, as demonstrated by the Pisarenko plot and supported by first-principles band structure calculations. Moreover, these codoped samples can be hierarchically structured on all scales (atomic point defects by doping, nanoscale precipitations by CdS nanostructuring, and mesoscale grains by SPS treatment) to achieve highly effective phonon scattering leading to strongly reduced thermal conductivities. In addition to the high maximum ZT the resultant large average ZT of similar to 0.8 between 300 and 923 K makes SnTe an attractive p-type material for high-temperature thermoelectric power generation.« less

Photocatalytic degradation of methylene blue on Sn-doped titania nanoparticles synthesized by solution combustion route

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

Bhange, P.D., E-mail: pallavi.ncl@gmail.com; Awate, S.V.; Gholap, R.S.

2016-04-15

Highlights: • Series of Sn-doped titania nanoparticles were prepared by solution combustion synthesis method. • Sn-doped titania nanoparticles were tested for degradation of MB under UV light irradiation. • The maximum Sn doping in the TiO{sub 2} lattice is found to be less than 10%. • The crystallite size decreases with increase in the Sn content. • The doping of Sn into TiO{sub 2} lattice hinders the recombination of electrons and holes thus enhance the photocatalytic activity. - Abstract: Series of tin-doped titania nanoparticles with varying tin content in the range 0–20 mol% have been prepared by solution combustion synthesismore » route using urea as a fuel. The structure, surface morphology and optical activity of Sn-doped TiO{sub 2} nanoparticles were investigated by various analytical techniques such as powder XRD, SEM, TEM, UV–vis and N{sub 2} adsorption study. The crystalline structures of the various phases were studied by rietveld refinement of the XRD data. The photocatalytic performance of Sn-doped titania nanoparticles were tested for degradation of MB under UV and visible light irradiation. The results reveal that the photocatalytic activity increases with increase in tin content which may be due to decrease in crystallite size with increase in surface area. The doping of Sn into TiO{sub 2} lattice hinders the recombination of electrons and holes thus enhance the quantum efficiency of photocatalytic reaction.« less

Structural and electrical properties of Si- and Ti-doped Cu{sub 2}SnSe{sub 3} bulks

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

Wubet, Walelign; Kuo, Dong-Hau, E-mail: dhkuo@mail.ntust.edu.tw

2015-07-15

Silicon-doped (Cu{sub 2}(Sn{sub 1−x}Si{sub x})Se{sub 3} and titanium-doped (Cu{sub 2}(Sn{sub 1−x}Ti{sub x})Se{sub 3} at x=0, 0.05, 0.1, 0.15, and 0.2 were prepared at 550 °C for 2 h with soluble sintering aids of volatile Sb{sub 2}S{sub 3} and Te. Defect chemistry was studied by measuring structural and electrical properties of Si-doped and Ti-doped Cu{sub 2}SnSe{sub 3} (CTSe) as a function of dopant concentration. Si-doped CTSe pellets show p-type at x=0 and 0.05 and n-type at x=0.1, 0.15, and 0.2, whereas Ti-doped CTSe pellets show p-type at x=0, 0.05 and 0.1 and n-type at x=0.15 and 0.2. The lowest hole concentrationmore » of 3.6×10{sup 17} cm{sup −3} and the highest mobility of 1525 cm{sup 2} V{sup −1} s{sup −1} were obtained for the Si-doped (Cu{sub 2}(Sn{sub 1−x}Si{sub x})Se{sub 3} bulks at x=0.1 (10% Si), while they were 3.1×10{sup 17} cm{sup −3} and 813 cm{sup 2} V{sup −1} s{sup −1} for the Ti-doped CTSe bulks at x=0.15 (15% Ti), as compared to 1.1×10{sup 18} cm{sup −3} and 209 cm{sup 2} V{sup −1} s{sup −1} for undoped one. The explanations based upon antisite defects of Si-to-Sn, Ti-to-Sn, Cu-to-Sn, and Sn-to-Cu for the changes in electrical property were declared. The study in bulk Si-doped and Ti-doped CTSe is based upon defect state and is consistent and supported by the data of electrical property and lattice parameter. - Graphical abstract: Cu{sub 2}SnSe{sub 3} (CTSe) semiconductor is interesting because of its adjustable electrical properties by extrinsic doping. Si and Ti doping in CTSe leads to high carrier mobility above 800 cm{sup 2} V{sup −1} s{sup −1}. - Highlights: • Cu{sub 2}SnSe{sub 3} (CTSe) is an interesting semiconductor because of its adjustable electrical properties. • Cu(In,Ga)Se{sub 2}, on the contrary, is difficult to change its electrical properties. • Si and Ti doping can change p-CTSe to n-CTSe. • The lowest electron concentration in doped CTSe had the highest mobility above 800 cm{sup 2} V{sup −1} s{sup −1}. • The defects of Si-to-Sn, Ti-to-Sn, Cu-to-Sn, and Sn-to-Cu in Si- and Ti-doped CTSe were proposed.« less

Different valence Sn doping - A simple way to detect oxygen concentration variation of ZnO quantum dots synthesized under ultrasonic irradiation.

PubMed

Yang, Weimin; Zhang, Bing; Zhang, Qitu; Wang, Lixi; Song, Bo; Wu, Fan; Wong, C P

2017-09-01

An ultrasonic method is employed to synthesize the Sn doped Zn 0.95 Sn 0.05 O quantum dots with green light emission. Sn 2+ and Sn 4+ ions are used to create different optical defects inside Zn 0.95 Sn 0.05 O quantum dots and the changing trend of oxygen concentration under different ultrasonic irradiation power are investigated. The photoluminescence spectra are employed to characterize the optical defects of Zn 0.95 Sn 0.05 O quantum dots. The UV-vis spectra are used to study the band gap of Zn 0.95 Sn 0.05 O quantum dots, which is influenced by their sizes. The results indicate that ultrasonic power would influence the size of Zn 0.95 Sn 0.05 O quantum dots as well as the type and quantity of defects in ZnO quantum dots. Changing trends in size of Sn 2+ and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots are quite similar with each other, while the changing trends in optical defects types and concentration of Sn 2+ and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots are different. The difference of the optical defects concentration changing between Sn 2+ doped Zn 0.95 Sn 0.05 O quantum dots (V O defects) and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots (O Zn and O i defects) shows that the formation process of ZnO under ultrasonic irradiation wiped oxygen out. Copyright © 2017 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

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

PubMed Central

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

2015-01-01

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

Study of Sn and Mg doping effects on TiO2/Ge stack structure by combinatorial synthesis

NASA Astrophysics Data System (ADS)

Nagata, Takahiro; Suzuki, Yoshihisa; Yamashita, Yoshiyuki; Ogura, Atsushi; Chikyow, Toyohiro

2018-04-01

The effects of Sn and Mg doping of a TiO2 film on a Ge substrate were investigated to improve leakage current properties and Ge diffusion into the TiO2 film. For systematic analysis, dopant-composition-spread TiO2 samples with dopant concentrations of up to 20.0 at. % were fabricated by RF sputtering and a combinatorial method. X-ray photoelectron spectroscopy revealed that the instability of Mg doping of TiO2 at dopant concentrations above 10.5 at. %. Both Sn and Mg dopants reduced Ge diffusion into TiO2. Sn doping enhanced the crystallization of the rutile phase, which is a high-dielectric-constant phase, although the Mg-doped TiO2 film indicated an amorphous structure. Sn-doping indicated systematic leakage current reduction with increasing dopant concentration. Doping at Sn concentrations higher than 16.8 at. % improved the leakage properties (˜10-7 A/cm2 at -3.0 V) and capacitance-voltage properties of metal-insulator-semiconductor (MIS) operation. The Sn doping of TiO2 may be useful for interface control and as a dielectric material for Ge-based MIS capacitors.

Improved Li storage performance in SnO 2 nanocrystals by a synergetic doping

DOE PAGES

Wan, Ning; Lu, Xia; Wang, Yuesheng; ...

2016-01-06

Tin dioxide (SnO 2) is a widely investigated lithium (Li) storage material because of its easy preparation, two-step storage mechanism and high specific capacity for lithium-ion batteries (LIBs). In this contribution, a phase-pure cobalt-doped SnO 2 (Co/SnO 2) and a cobalt and nitrogen co-doped SnO 2 (Co-N/SnO 2) nanocrystals are prepared to explore their Li storage behaviors. It is found that the morphology, specific surface area, and electrochemical properties could be largely modulated in the doped and co-doped SnO 2 nanocrystals. Gavalnostatic cycling results indicate that the Co-N/SnO 2 electrode delivers a specific capacity as high as 716 mAh gmore » –1 after 50 cycles, and the same outstanding rate performance can be observed in subsequent cycles due to the ionic/electronic conductivity enhancement by co-doping effect. Further, microstructure observation indicates the existence of intermediate phase of Li 3N with high ionic conductivity upon cycling, which probably accounts for the improvements of Co-N/SnO 2 electrodes. Furthermore, we find that the method of synergetic doping into SnO 2 with Co and N, with which the electrochemical performances is enhanced remarkably, undoubtedly, will have an important influence on the material itself and community of LIBs as well.« less

Ferromagnetism in two-dimensional hole-doped SnO

NASA Astrophysics Data System (ADS)

Houssa, M.; Iordanidou, K.; Pourtois, G.; Afanas'ev, V. V.; Stesmans, A.

2018-05-01

Hole-doped monolayer SnO has been recently predicted to be a ferromagnetic material, for a hole density typically above 5x1013/cm2. The possibility to induce a hole-doped stable ferromagnetic order in this two-dimensional material, either by intrinsic or extrinsic defects, is theoretically studied, using first-principles simulations. Sn vacancies and Sn vacancy-hydrogen complexes are predicted to be shallow acceptors, with relatively low formation energies in SnO monolayers grown under O-rich conditions. These defects produce spin-polarized gap states near the valence band-edge, potentially stabilizing the ferromagnetic order in 2D SnO. Hole-doping resulting from substitutional doping is also investigated. Among the considered possible dopants, As, substituting O, is predicted to produce shallow spin-polarized gap states near the valence band edge, also potentially resulting in a stable ferromagnetic order in SnO monolayers.

The electrical, optical, structural and thermoelectrical characterization of n- and p-type cobalt-doped SnO 2 transparent semiconducting films prepared by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Bagheri-Mohagheghi, Mohammad-Mehdi; Shokooh-Saremi, Mehrdad

2010-10-01

The electrical, optical and structural properties of Cobalt (Co) doped SnO 2 transparent semiconducting thin films, deposited by the spray pyrolysis technique, have been studied. The SnO 2:Co films, with different Co-content, were deposited on glass substrates using an aqueous-ethanol solution consisting of tin and cobalt chlorides. X-ray diffraction studies showed that the SnO 2:Co films were polycrystalline only with tin oxide phases and preferential orientations along (1 1 0) and (2 1 1) planes and grain sizes in the range 19-82 nm. Optical transmittance spectra of the films showed high transparency ∼75-90% in the visible region, decreasing with increase in Co-doping. The optical absorption edge for undoped SnO 2 films was found to be 3.76 eV, while for higher Co-doped films shifted toward higher energies (shorter wavelengths) in the range 3.76-4.04 eV and then slowly decreased again to 4.03 eV. A change in sign of the Hall voltage and Seebeck coefficient was observed for a specific acceptor dopant level ∼11.4 at% in film and interpreted as a conversion from n-type to p-type conductivity. The thermoelectric electro-motive force (e.m.f.) of the films was measured in the temperature range 300-500 K and Seebeck coefficients were found in the range from -62 to +499 μVK -1 for various Co-doped SnO 2 films.

Roles of cobalt doping on ethanol-sensing mechanisms of flame-spray-made SnO2 nanoparticles-electrolytically exfoliated graphene interfaces

NASA Astrophysics Data System (ADS)

Punginsang, Matawee; Wisitsoraat, Anurat; Sriprachuabwong, Chakrit; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Phanichphant, Sukon; Liewhiran, Chaikarn

2017-12-01

In this work, the roles of cobalt (Co) and electrolytically exfoliated graphene additives on ethanol gas-sensing properties of flame-spray-made SnO2 nanoparticles were systematically studied. Structural characterizations indicated that Co dopants formed solid solution with SnO2 nanoparticles while multilayer graphene sheets were well dispersed within the Co-doped SnO2 matrix at low graphene loading contents. The sensing films were fabricated by a spin coating process and tested towards 50-1000 ppm ethanol at 150-400 °C. It was found that the response to 1000 ppm ethanol at the optimal working temperature of 350 °C was enhanced from 91 to 292 and to 803 by 0.5 wt% graphene loading and 0.5 wt% Co-doping, respectively. The combination of Co-doping and graphene loading with the same concentration of 0.5 wt% led to a synergistic enhancement of ethanol response to 2147 at 1000 ppm with a short response time of ∼0.9 s and fast recovery stabilization at 350 °C, proving the significance of dopant on the gas-sensing performances of graphene/SnO2 composites. Furthermore, the optimal sensor exhibited high ethanol selectivity against C3H6O, NO2, H2S, H2, CH4 and humidity. The mechanisms for the ethanol response enhancement were proposed on the basis of combinative effects of catalytic substitutional p-type Co dopants and active graphene-Co-doped SnO2 M-S junctions with highly accessible surface area of micropores and mesopores in the composites. Therefore, the graphene loaded Co-doped SnO2 sensor is highly potential for responsive and selective detection of ethanol vapor at ppm levels and may be practically useful for drunken driving applications.

Synthesis, structural and paramagnetic properties of SnO{sub 2} doped NiO nanoparticles

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

Islam, I., E-mail: ishtihadahislam@gmail.com; Dwivedi, Sonam; Dar, Hilal A.

2016-05-06

In this work, Sn doped NiO nanoparticles were synthesized by co-precipitation route to explore the impact of doping on lattice structure, dielectric constant and magnetization. X-ray diffraction analysis confirmed cubic (Fd-3m) structure of Sn doped NiO. Average crystallite size decreases from 78.2 nm (Ni{sub 0.95}Sn{sub 0.05}O) to 64.23 nm (Ni{sub 0.8}Sn{sub 0.2}O). Scanning electron microscopy images confirm that nanocrystals have agglomerated spherical morphology. The Raman spectrum exhibits a strong, broad peak at 410 cm{sup -1} and is attributed to the Ni-O stretching mode and doped samples show a blue shift. The dielectric constants at about 1 Hz are measured to be about 1.795,more » 1.030, 0.442, and 0.302 × 10{sup 3} Ni{sub 1-x}Sn{sub x}O (x = 0.05, 0.1, 0.15, 0.2), respectively. The dielectric constant in nanoparticles of doped Ni{sub 1-x}Sn{sub x}O is three orders of magnitude higher as compared to pure NiO ceramics. The nature of magnetization - applied field (M-H) infers paramagnetic behaviour for Sn doped NiO nanoparticles.« less

Structural, Optical and Ethanol Sensing Properties of Dy-Doped SnO2 Nanoparticles

NASA Astrophysics Data System (ADS)

Shaikh, F. I.; Chikhale, L. P.; Nadargi, D. Y.; Mulla, I. S.; Suryavanshi, S. S.

2018-04-01

We report a facile co-precipitation synthesis of dysprosium (Dy3+) doped tin oxide (SnO2) thick films and their use as gas sensors. The doping percentage (Dy3+) was varied from 1 mol.% to 4 mol.% with the step of 1 mol.%. As-produced material with varying doping levels were sintered in air; and by using a screen printing technique, their thick films were developed. Prior to sensing performance investigations, the films were examined for structural, morphological and compositional properties using x-ray diffraction, a field emission scanning electron microscope, a transmission electron microscope, selected area electron diffraction, energy dispersive analysis by x-rays, Fourier transform infrared spectroscopy and Raman spectroscopic techniques. The structural analyses revealed formation of single phase nanocrystalline material with tetragonal rutile structure of SnO2. The morphological analyses confirmed the nanocrystalline porous morphology of as-developed material. Elemental analysis defined the composition of material in accordance with the doping concentration. The produced sensor material exhibited good response towards different reducing gases (acetone, ethanol, LPG, and ammonia) at different operating temperatures. The present study confirms that the Dy3+ doping in SnO2 enhances the response towards ethanol with reduction in operating temperature. Particularly, 3 mol.% Dy3+ doped sensor exhibited the highest response (˜ 92%) at an operating temperature of 300°C with better selectivity, fast response (˜ 13 s) and recovery (˜ 22 s) towards ethanol.

Electrochemically synthesis and optoelectronic properties of Pb- and Zn-doped nanostructured SnSe films

NASA Astrophysics Data System (ADS)

Jamali-Sheini, Farid; Cheraghizade, Mohsen; Yousefi, Ramin

2018-06-01

In this study, electrodeposition technique was applied to deposit un-, lead (Pb), and zinc (Zn)-doped SnSe films. X-ray diffraction (XRD) patterns of the films showed a polycrystalline SnSe phase with orthorhombic crystalline lattice. SEM images revealed ball-shaped, rod-shaped, and wire-shaped morphologies for SnSe films. Moreover, optical measurements indicated incorporation of dopant in the crystalline lattice of films by varying the optical energy band gap. Electrical characterization of Pb- and Zn-doped SnSe films showed their p-type nature. Finally, the solar cell device fabricated using the Zn-doped SnSe films reveal a higher efficiency because of their higher carrier concentration.

The effect of simultaneous substitution on the electronic band structure and thermoelectric properties of Se-doped Co3SnInS2 with the Kagome lattice

NASA Astrophysics Data System (ADS)

Fujioka, Masaya; Shibuya, Taizo; Nakai, Junya; Yoshiyasu, Keigo; Sakai, Yuki; Takano, Yoshihiko; Kamihara, Yoichi; Matoba, Masanori

2014-12-01

The thermoelectric properties and electronic band structures for Se-doped Co3SnInS2 were examined. The parent compound of this material (Co3Sn2S2) has two kinds of Sn sites (Sn1 and Sn2 sites). The density functional theory (DFT) calculations show that the indium substitution at the Sn2 site induces a metallic band structure, on the other hand, a semiconducting band structure is obtained from substitution at the Sn1 site. However, according to the previous reports, since the indium atom prefers to replace the tin atom at the Sn1 site rather than the Sn2 site, the resistivity of Co3SnInS2 shows semiconducting-like behavior. In this study we have demonstrated that metallic behavior and a decrease in resistivity for Se-doped Co3SnInS2 occurs without suppression of the Seebeck coefficient. From the DFT calculations, when the selenium content is above 0.5, the total crystallographic energy shows that a higher indium occupancy at Sn2 site is more stable. Therefore, it is suggested that the selenium doping suppress the site preference for indium substitution. This is one of the possible explanations for the metallic conductivity observed in Se-doped Co3SnInS2

Novel Carbon Dioxide Microsensor Based on Tin Oxide Nanomaterial Doped With Copper Oxide

NASA Technical Reports Server (NTRS)

Xu, Jennifer C.; Hunter, Gary W.; Lukco, Dorothy; Liu, Chung-Chiun; Ward, Benjamin J.

2008-01-01

Carbon dioxide (CO2) is one of the major indicators of fire and therefore its measurement is very important for low-false-alarm fire detection and emissions monitoring. However, only a limited number of CO2 sensing materials exist due to the high chemical stability of CO2. In this work, a novel CO2 microsensor based on nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been successfully demonstrated. The CuO-SnO2 based CO2 microsensors are fabricated by means of microelectromechanical systems (MEMS) technology and sol-gel nanomaterial-synthesis processes. At a doping level of CuO: SnO2 = 1:8 (molar ratio), the resistance of the sensor has a linear response to CO2 concentrations for the range of 1 to 4 percent CO2 in air at 450 C. This approach has demonstrated the use of SnO2, typically used for the detection of reducing gases, in the detection of an oxidizing gas.

An insight into the origin of room-temperature ferromagnetism in SnO2 and Mn-doped SnO2 quantum dots: an experimental and DFT approach.

PubMed

Manikandan, Dhamodaran; Boukhvalov, D W; Amirthapandian, S; Zhidkov, I S; Kukharenko, A I; Cholakh, S O; Kurmaev, E Z; Murugan, Ramaswamy

2018-02-28

SnO 2 and Mn-doped SnO 2 single-phase tetragonal crystal structure quantum dots (QDs) of uniform size with control over dopant composition and microstructure were synthesized using the high pressure microwave synthesis technique. On a broader vision, we systematically investigated the influence of dilute Mn ions in SnO 2 under the strong quantum confinement regime through various experimental techniques and density functional theoretical (DFT) calculations to disclose the physical mechanism governing the observed ferromagnetism. DFT calculations revealed that the formation of the stable (001) surface was much more energetically favorable than that of the (100) surface, and the formation energy of the oxygen vacancies in the stable (001) surface was comparatively higher in the undoped SnO 2 QDs. X-ray photoelectron spectroscopy (XPS) and first-principles modeling of doped QDs revealed that the lower doping concentration of Mn favored the formation of MnO-like (Mn 2+ ) structures in defect-rich areas and the higher doping concentration of Mn led to the formation of multiple configurations of Mn (Mn 2+ and Mn 3+ ) in the stable surfaces of SnO 2 QDs. Electronic absorption spectra indicated the characteristic spin allowed ligand field transitions of Mn 2+ and Mn 3+ and the red shift in the band gap. DFT calculations clearly indicated that only the substitutional dopant antiferromagnetic configurations were more energetically favorable. The gradual increase of magnetization at a low level of Mn-doping could be explained by the prevalence of antiferromagnetic manganese-vacancy pairs. Higher concentrations of Mn led to the appearance of ferromagnetic interactions between manganese and oxygen vacancies. The increase in the concentration of metallic dopants caused not just an increase in the total magnetic moment of the system but also changed the magnetic interactions between the magnetic moments on the metal ions and oxygen. The present study provides new insight into the fundamental understanding of the origin of ferromagnetism in transition metal-doped QDs.

Structural, electrical and optical properties of indium tin oxide thin film grown by metal organic chemical vapor deposition with tetramethyltin-precursor

NASA Astrophysics Data System (ADS)

Zhuo, Yi; Chen, Zimin; Tu, Wenbin; Ma, Xuejin; Wang, Gang

2018-01-01

Tin-doped indium oxide (ITO) is grown by metal organic chemical vapor deposition (MOCVD) using tetramethyltin (TDMASn) as tin precursor. The as-grown ITO films are polycrystalline with (111) and (100) textures. A gradual transition of crystallographic orientation from (111) preferred to (100) preferred is observed as the composition of tin changes. By precisely controlling the Sn doping, the ITO thin films present promising optical and electrical performances at either near-infrared-visible or visible-near-ultraviolet ranges. At low Sn doping level, the as-grown ITO possesses high electron mobility of 48.8 cm2 V-1 s-1, which results in high near-infrared transmittance and low resistivity. At higher Sn doping level, high carrier concentration (8.9 × 1020 cm-3) and low resistivity (3 × 10-4 Ω cm) are achieved. The transmittance is 97.8, 99.1, and 82.3% at the wavelength of 550, 365, and 320 nm, respectively. The results strongly suggest that MOCVD with TDMASn as tin precursor is an effective method to fabricate high quality ITO thin film for near-infrared, visible light, and near-ultraviolet application.

Metal to insulator transition in Sb doped SnO2 monocrystalline nanowires thin films

NASA Astrophysics Data System (ADS)

Costa, I. M.; Bernardo, E. P.; Marangoni, B. S.; Leite, E. R.; Chiquito, A. J.

2016-12-01

We report on the growth and transport properties of single crystalline Sb doped SnO2 wires grown from chemical vapour deposition. While undoped samples presented semiconducting behaviour, doped ones clearly undergo a transition from an insulating state ( d R /d T <0 ) to a metallic one ( d R /d T >0 ) around 130 -150 K depending on the doping level. Data analysis in the framework of the metal-to-insulator transition theories allowed us to investigate the underlying physics: electron-electron and electron-phonon interactions were identified as the scattering mechanisms present in the metallic phase, while the conduction mechanism of the semiconducting phase (undoped sample) was characterized by thermal activation and variable range hopping mechanisms.

Superconductivity, pairing symmetry, and disorder in the doped topological insulator Sn1 -xInxTe for x ≥0.10

NASA Astrophysics Data System (ADS)

Smylie, M. P.; Claus, H.; Kwok, W.-K.; Louden, E. R.; Eskildsen, M. R.; Sefat, A. S.; Zhong, R. D.; Schneeloch, J.; Gu, G. D.; Bokari, E.; Niraula, P. M.; Kayani, A.; Dewhurst, C. D.; Snezhko, A.; Welp, U.

2018-01-01

The temperature dependence of the London penetration depth Δ λ (T ) in the superconducting doped topological crystalline insulator Sn1 -xInxTe was measured down to 450 mK for two different doping levels, x ≈0.45 (optimally doped) and x ≈0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. The introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance Tc, indicating that ferroelectric interactions do not compete with superconductivity.

Revealing Surface States in In-Doped SnTe Nanoplates with Low Bulk Mobility.

PubMed

Shen, Jie; Xie, Yujun; Cha, Judy J

2015-06-10

Indium (In) doping in topological crystalline insulator SnTe induces superconductivity, making In-doped SnTe a candidate for a topological superconductor. SnTe nanostructures offer well-defined nanoscale morphology and high surface-to-volume ratios to enhance surface effects. Here, we study In-doped SnTe nanoplates, In(x)Sn(1-x)Te, with x ranging from 0 to 0.1 and show they superconduct. More importantly, we show that In doping reduces the bulk mobility of In(x)Sn(1-x)Te such that the surface states are revealed in magnetotransport despite the high bulk carrier density. This is manifested by two-dimensional linear magnetoresistance in high magnetic fields, which is independent of temperature up to 10 K. Aging experiments show that the linear magnetoresistance is sensitive to ambient conditions, further confirming its surface origin. We also show that the weak antilocalization observed in In(x)Sn(1-x)Te nanoplates is a bulk effect. Thus, we show that nanostructures and reducing the bulk mobility are effective strategies to reveal the surface states and test for topological superconductors.

Pure and Sn-doped ZnO films produced by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Holmelund, E.; Schou, J.; Tougaard, S.; Larsen, N. B.

2002-09-01

A new technique, metronome doping, has been used for doping of films during pulsed laser deposition (PLD). This technique makes it possible to dope continuously during film growth with different concentrations of a dopant in one deposition sequence. Films of pure and doped ZnO have been produced with Sn concentrations up to 16%. The specific resistivity is found to increase and the transmission of visible light to decrease with increasing Sn concentration.

Epitaxial Growth and Electronic Structure of Half Heuslers Co1-xNixTiSb (001), Ni1-xCoxTiSn, and PtLuSb

DTIC Science & Technology

2016-01-09

studied in detail using scanning tunneling microscopy and angle resolved photoemission. For the doping levels achieved in cobalt titanium antimony, the...angle resolved photoemission. For the doping levels achieved in cobalt titanium antimony, the electron mobility at room temperature was comparable...scanning tunneling microscopy and angle resolved photoemission. For the doping levels achieved in cobalt titanium antimony, the electron mobility at room

Structural and optical characterization of p-type highly Fe-doped SnO2 thin films and tunneling transport on SnO2:Fe/p-Si heterojunction

NASA Astrophysics Data System (ADS)

Ben Haj Othmen, Walid; Ben Hamed, Zied; Sieber, Brigitte; Addad, Ahmed; Elhouichet, Habib; Boukherroub, Rabah

2018-03-01

Nanocrystalline highly Fe-doped SnO2 thin films were prepared using a new simple sol-gel method with iron amounts of 5, 10, 15 and 20%. The obtained gel offers a long durability and high quality allowing to reach a sub-5 nm nanocrystalline size with a good crystallinity. The films were structurally characterized through X-ray diffraction (XRD) that confirms the formation of rutile SnO2. High Resolution Transmission Electron Microscopy (HRTEM) images reveals the good crystallinity of the nanoparticles. Raman spectroscopy shows that the SnO2 rutile structure is maintained even for high iron concentration. The variation of the PL intensity with Fe concentration reveals that iron influences the distribution of oxygen vacancies in tin oxide. The optical transmittance results indicate a redshift of the SnO2 band gap when iron concentration increases. The above optical results lead us to assume the presence of a compensation phenomenon between oxygen vacancies and introduced holes following Fe doping. From current-voltage measurements, an inversion of the conduction type from n to p is strongly predicted to follow the iron addition. Electrical characterizations of SnO2:Fe/p-Si and SnO2:Fe/n-Si heterojunctions seem to be in accordance with this deduction. The quantum tunneling mechanism is expected to be important at high Fe doping level, which was confirmed by current-voltage measurements at different temperatures. Both optical and electrical properties of the elaborated films present a particularity for the same iron concentration and adopt similar tendencies with Fe amount, which strongly correlate the experimental observations. In order to evaluate the applicability of the elaborated films, we proceed to the fabrication of the SnO2:Fe/SnO2 homojunction for which we note a good rectifying behavior.

Morphology-modulation of SnO2 Hierarchical Architectures by Zn Doping for Glycol Gas Sensing and Photocatalytic Applications

NASA Astrophysics Data System (ADS)

Zhao, Qinqin; Ju, Dianxing; Deng, Xiaolong; Huang, Jinzhao; Cao, Bingqiang; Xu, Xijin

2015-01-01

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively).

Morphology-modulation of SnO2 Hierarchical Architectures by Zn Doping for Glycol Gas Sensing and Photocatalytic Applications

PubMed Central

Zhao, Qinqin; Ju, Dianxing; Deng, Xiaolong; Huang, Jinzhao; Cao, Bingqiang; Xu, Xijin

2015-01-01

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively). PMID:25597269

Formation and evolution of oxygen-vacancy clusters in lead and tin doped silicon

NASA Astrophysics Data System (ADS)

Londos, C. A.; Aliprantis, D.; Sgourou, E. N.; Chroneos, A.; Pochet, P.

2012-06-01

Infrared spectroscopy (IR) measurements were used to investigate the effect of lead (Pb), tin (Sn), and (Pb, Sn) codoping on electron radiation-induced defects in silicon (Si). The study was mainly focused on oxygen-vacancy (VOn) clusters and in particular their formation and evolution upon annealing. It was determined that Pb causes a larger reduction in the production of the VO defect than Sn. In (Pb, Sn) co-doped Si isochronal anneals revealed that the evolution of VO increases substantially at ˜170 °C. This is attributed to the release of V from the SnV pair. Interestingly, in the corresponding evolution curves of VO in the Sn- and the Pb-doped samples, this inverse annealing stage is also present for the former while it is not present for the latter. This is attributed to the formation of PbV pairs that do not dissociate below 280 °C. The partial capture of V by Sn in co-doped samples is rationalized through the higher compressive local strain around Pb atoms that leads to a retardation of vacancy diffusion. The conversion of VO to the VO2 defect is substantially reduced in the Pb-doped sample. The evolution curves of VO and VO2 clusters in the isovalent doped Si samples hint the production of VO2 from other mechanisms (i.e., besides VO + Oi → VO2). For larger VOn clusters (n = 3,4), the signals are very weak in the Pb-doped sample, whereas for n ≥ 5, they are not present in the spectra. Conversely, bands related with the VO5 and VOnCs defects are present in the spectra of the Sn-doped and (Pb, Sn) codoped Si.

Research update: Prediction of high figure of merit plateau in SnS and solid solution of (Pb,Sn)S

DOE PAGES

Hao, Shiqiang; Dravid, Vinayak P.; Kanatzidis, Mercouri G.; ...

2016-10-17

Direct conversion between thermal and electrical energy can be achieved by thermoelectric materials, which provide a viable route for power generation and solid state refrigeration. Here, we use a combination of energetic, electronic, and vibrational first-principles based results to predict the figure of merit performance in hole doped single crystals of SnS and (Pb,Sn)S. We find high ZT values for both materials, specifically for (Pb,Sn)S along the b-axis. Both SnS and (Pb,Sn)S have excellent power factors when doped, due to a combination of increased electrical conductivity (due to doping) and a significantly enhanced Seebeck coefficient obtained by a doping-induced multibandmore » effect. Anharmonic phonon calculations combined with a Debye-Calloway model show that the lattice thermal conductivity of both compounds is low, due to intrinsic anharmonicity, and is lowered further by the random, solid solution nature of the cation sublattice of (Pb,Sn)S. (Pb,Sn)S exhibits a high ZT plateau ranging from 1.3 at 300 K to 1.9 at 800 K. Finally, the overall ZT of the hole doped (Pb,Sn)S crystals is predicted to outperform most of the current state-of-the-art thermoelectric sulfide materials.« less

Research update: Prediction of high figure of merit plateau in SnS and solid solution of (Pb,Sn)S

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

Hao, Shiqiang; Dravid, Vinayak P.; Kanatzidis, Mercouri G.

Direct conversion between thermal and electrical energy can be achieved by thermoelectric materials, which provide a viable route for power generation and solid state refrigeration. Here, we use a combination of energetic, electronic, and vibrational first-principles based results to predict the figure of merit performance in hole doped single crystals of SnS and (Pb,Sn)S. We find high ZT values for both materials, specifically for (Pb,Sn)S along the b-axis. Both SnS and (Pb,Sn)S have excellent power factors when doped, due to a combination of increased electrical conductivity (due to doping) and a significantly enhanced Seebeck coefficient obtained by a doping-induced multibandmore » effect. Anharmonic phonon calculations combined with a Debye-Calloway model show that the lattice thermal conductivity of both compounds is low, due to intrinsic anharmonicity, and is lowered further by the random, solid solution nature of the cation sublattice of (Pb,Sn)S. (Pb,Sn)S exhibits a high ZT plateau ranging from 1.3 at 300 K to 1.9 at 800 K. Finally, the overall ZT of the hole doped (Pb,Sn)S crystals is predicted to outperform most of the current state-of-the-art thermoelectric sulfide materials.« less

Role of Cu in engineering the optical properties of SnO2 nanostructures: Structural, morphological and spectroscopic studies

NASA Astrophysics Data System (ADS)

Kumar, Virender; Singh, Kulwinder; Jain, Megha; Manju; Kumar, Akshay; Sharma, Jeewan; Vij, Ankush; Thakur, Anup

2018-06-01

We have carried out a systematic study to investigate the effect of Cu doping on the optical properties of SnO2 nanostructures synthesized by chemical route. Synthesized nanostructures were characterized using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), High resolution transmission electron microscopy (HR-TEM), Energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, UV-visible and Photoluminescence (PL) spectroscopy. The Rietveld refinement analysis of XRD patterns of Cu-doped SnO2 samples confirmed the formation of single phase tetragonal rutile structure, however some localized distortion was observed for 5 mol% Cu-doped SnO2. Crystallite size was found to decrease with increase in dopant concentration. FE-SEM images indicated change in morphology of samples with doping. HR-TEM images revealed that synthesized nanostructures were nearly spherical and average crystallite size was in the range 12-21 nm. Structural defects, crystallinity and size effects on doping were investigated by Raman spectroscopy and results were complemented by FTIR spectroscopy. Optical band gap of samples was estimated from reflectance spectra. We have shown that band gap of SnO2 can be engineered from 3.62 to 3.82 eV by Cu doping. PL emission intensity increased as the doping concentration increased, which can be attributed to the development of defect states in the forbidden transition region of band gap of SnO2 with doping. We have also proposed a band model owing to defect states in SnO2 to explain the observed PL in Cu doped SnO2 nanostructures.

Electronic and magnetic properties of SnS2 monolayer doped with non-magnetic elements

NASA Astrophysics Data System (ADS)

Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Wang, Ling-Ling

2018-05-01

We performed a systematic study of the electronic structures and magnetic properties of SnS2 monolayer doped with non-magnetic elements in groups IA, IIA and IIIA based on the first-principles methods. The doped systems exhibit half-metallic and metallic natures depending on the doping elements. The formation of magnetic moment is attributable to the cooperative effect of the Hund's rule coupling and hole concentration. The spin polarization can be stabilized and enhanced through confining the delocalized impurity states by biaxial tensile strain in hole-doped SnS2 monolayer. Both the double-exchange and p-p exchange mechanisms are simultaneously responsible for the ferromagnetic ground state in those hole-doped materials. Our results demonstrate that spin polarization can be induced and controlled in SnS2 monolayers by non-magnetic doping and tensile strain.

Influence of defects on the thermoelectricity in SnSe: A comprehensive theoretical study

NASA Astrophysics Data System (ADS)

Zhou, Yecheng; Li, Wei; Wu, Minghui; Zhao, Li-Dong; He, Jiaqing; Wei, Su-Huai; Huang, Li

2018-06-01

SnSe has emerged as an efficient and fascinating thermoelectric material. A fundamental understanding of the effects and nature of intrinsic defects and dopants in SnSe is crucial to optimize its thermoelectric performance. In this paper, we perform first-principles calculations to examine the native and extrinsic point-defect properties in SnSe. We show that the easy formation of acceptorlike Sn vacancy (VSn) is responsible for the p -type conductivity in intrinsic SnSe. We also propose a mechanism and explain the anomalous temperature dependence of the carrier concentration in intrinsic SnSe crystals. Concerning the extrinsic defects, we focus on the dopants used in experiments. We find that Na (Ag) substitution on Sn site, NaSn (AgSn), acts as acceptor, whereas, substitutional BrSe, ISe, and BiSn dopants act as donor. It is shown that for Ag doping, its carrier concentration will be saturated with increasing doping concentration due to the coexistence of compensated defects (Agi and AgSn). Furthermore, we analyze how this doping introduced carrier impact on their thermoelectric characteristics. It is found that the more efficient doping of Na, Br, and I can realize higher Z T .

Structure and Electronic Properties of Crystalline and Amorphous Zinc Indium Tin Oxide Thin Films

NASA Astrophysics Data System (ADS)

Proffit, Diana Elizabeth

The local structures and surface electronic properties of crystalline (c-) and amorphous (a-) Zn and Sn codoped In2O3 (ZITO) films were studied. X-ray absorption spectroscopy (XAS) measurements confirm that Zn and Sn dopants occupy In sites in the bixbyite structure of c-ZITO. Also, Zn dopants are generally under-coordinated and some compensated Sn dopants are over-coordinated, as demonstrated by the trend in coordination numbers (CN) of CNSn>CNIn>CNZn. Aliovalent Sn dopants form Frank-Kostlin clusters, (2Sn•InO'' i)x , which can act as donors when reduced. XAS and anomalous X-ray scattering studies on a-ZITO show that the local structure in a-ZITO is somewhat different than that in c-ZITO, particularly around Zn. The Zn-O bond length is significantly smaller than in c-ZITO and Zn is 4-fold coordinated. The smaller coordination numbers in a-ZITO follow the same trend as in c-ZITO. Unlike in c-ZITO, variations in the Sn/Zn ratio do not alter the electrical properties of a-ZITO, although variations in deposition oxygen pressure do. The 3-D geometrical arrangement linking local structure units seems to play a key role in charge balancing ZITO. As measured by in situ grazing incidence wide angle X-ray scattering, ZITO crystallizes at a higher temperature than In2 O3 and Sn-doped In2O3. The difference is attributed to a higher activation energy, which may result from the unique structure around Zn in a-ZITO. Increasing the codoping level consistently increases crystallization temperature. For a given codoping level, the crystallization temperature during deposition is lower than that during post-deposition annealing. X-ray and ultraviolet photoelectron spectroscopy measurements show that a-ZITO and c-ZITO thin films have similar surface electronic properties. In situ a-ZITO and c-ZITO films have low ionization potentials that are similar to In2O3. However, dry-air-annealed in situ films, ex situ films, and bulk ceramics have higher ionization potentials that are similar to ITO and match well with previous results on air-exposed surfaces. Lastly, a parallelogram plot of work function versus Fermi level shows that a wider range of work functions is achievable in ZITO materials than in Sb-doped SnO2, Al-doped ZnO, and Sn-doped In2O3.

Ultraviolet/visible photodiode of nanostructure Sn-doped ZnO/Si heterojunction

NASA Astrophysics Data System (ADS)

Kheirandish, N.; Mortezaali, A.

2013-05-01

Sn doped ZnO nanostructures deposited on Si substrate with (100) orientation by spray pyrolysis method at temperature 450 °C. Sn/Zn atomic ratio varies from 0% to 5%. The scanning electron microscope measurements showed that size of particles reduce with increasing the doping concentration. The X-ray diffraction analysis revealed formation of the wurtzite phase of ZnO. I-V curves of Sn doped ZnO/Si were investigated in dark and shows diode-like rectifying behavior. Among doped ZnO/Si, sample with atomic ratio of Sn/Zn = 5% is a good candidate to study photodiode properties in UV/visible range. Photoelectric effects have been observed under illumination monochromatic laser light with a wavelength of 325 nm and halogen lamp. Measurements demonstrate that the photodiode has high sensitivity and reproducibility to halogen light respect to laser light.

Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb 1$-$xSn x)1 $-$yInyTe: Topological and Superconducting Properties

DOE PAGES

Zhong, Ruidan; Schneeloch, John; Li, Qiang; ...

2017-02-16

Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb 1-xSn x) 1-yIn yTe. For samples with a tin concentration x ≤ 50% , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ~2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with `6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels,more » superconductivity was observed, with a transition temperature, T c , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,Sn)Te, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems.« less

Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb 1$-$xSn x)1 $-$yInyTe: Topological and Superconducting Properties

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

Zhong, Ruidan; Schneeloch, John; Li, Qiang

Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb 1-xSn x) 1-yIn yTe. For samples with a tin concentration x ≤ 50% , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ~2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with `6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels,more » superconductivity was observed, with a transition temperature, T c , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,Sn)Te, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems.« less

A detailed study on Sn4+ doped ZnO for enhanced photocatalytic degradation

NASA Astrophysics Data System (ADS)

Beura, Rosalin; Pachaiappan, R.; Thangadurai, P.

2018-03-01

The samples of Sn4+ doped (1, 5, 10, 15, 20 & 30%) ZnO nanostructures were synthesized by a low temperature hydrothermal method. Structural analysis by XRD and Raman spectroscopy showed the hexagonal wurtzite phase of ZnO and the formation of a secondary phase Zn2SnO4 beyond 10% doping of Sn4+. Microstructural analysis by TEM also confirmed the wurtzite ZnO with rod as well as particle like structure. Presence of various functional groups (sbnd OH, sbnd CH, Znsbnd O) were confirmed by FTIR. Optical properties were studied by UV-vis absorption, photoluminescence emission spectroscopies and lifetime measurement. Band gap of the undoped and Sn4+ doped ZnO were analyzed by Tauc plot and it was observed that the band gap of the materials had slightly decreased from 3.2 to 3.16 eV and again increased to 3.23 eV with respect to the increase in the doping concentration from 1 to 30%. A significant change was also noticed in the photoluminescence emission properties of ZnO i.e. increase in the intensity of NBE emission and decrease in DLE, on subject to Sn4+ doping. Average PL lifetime had increased from 29.45 ns for ZnO to 30.62 ns upon 1% Sn ion doping in ZnO. Electrical properties studied by solid state impedance spectroscopy showed that the conductivity had increased by one order of magnitude (from 7.48×10-8 to 2.21×10-7 S/cm) on Sn4+ doping. Photocatalytic experiments were performed on methyl orange (MO) as a model industrial dye under UV light irradiation for different irradiation times. The optimum Sn4+ content in order to achieve highest photocatalytic activity was found to be 1% Sn 4+ doping. The enhancement was achieved due to a decrease in the band gap favoring the generation of electron-hole pairs and the enhanced PL life time that delays the recombination of these charge carrier formation. The third reason was that the increased electrical conductivity that indicated the faster charge transfer in this material to enhance the photocatalytic activity. The Sn doped ZnO was found to be more photostable than pure ZnO.

Superconductivity, pairing symmetry, and disorder in the doped topological insulator Sn 1 - x In x Te for x ≥ 0.10

DOE PAGES

Smylie, M. P.; Claus, H.; Kwok, W. -K.; ...

2018-01-19

The temperature dependence of the London penetration depth Δλ(T) in the superconducting doped topological crystalline insulator Sn 1-xIn x Te was measured down to 450 mK for two different doping levels, x ≈ 0.45 (optimally doped) and x ≈ 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. The introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T c, indicating that ferroelectric interactionsmore » do not compete with superconductivity.« less

Superconductivity, pairing symmetry, and disorder in the doped topological insulator Sn 1 - x In x Te for x ≥ 0.10

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

Smylie, M. P.; Claus, H.; Kwok, W. -K.

The temperature dependence of the London penetration depth Δλ(T) in the superconducting doped topological crystalline insulator Sn 1-xIn x Te was measured down to 450 mK for two different doping levels, x ≈ 0.45 (optimally doped) and x ≈ 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. The introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T c, indicating that ferroelectric interactionsmore » do not compete with superconductivity.« less

Superconductivity, Pairing Symmetry, and Disorder in the Doped Topological Insulator Sn 1-xIn xTe for x >= 0.10.

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

Smylie, M. P.; Claus, H.; Kwok, W. -K.

The temperature dependence of the London penetration depth Delta lambda(T) in the superconducting doped topological crystalline insulator Sn1-xInxTe was measured down to 450 mK for two different doping levels, x approximate to 0.45 (optimally doped) and x approximate to 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. The introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T-c, indicating that ferroelectric interactions domore » not compete with superconductivity.« less

Carbon-doped SnS2 nanostructure as a high-efficiency solar fuel catalyst under visible light.

PubMed

Shown, Indrajit; Samireddi, Satyanarayana; Chang, Yu-Chung; Putikam, Raghunath; Chang, Po-Han; Sabbah, Amr; Fu, Fang-Yu; Chen, Wei-Fu; Wu, Chih-I; Yu, Tsyr-Yan; Chung, Po-Wen; Lin, M C; Chen, Li-Chyong; Chen, Kuei-Hsien

2018-01-12

Photocatalytic formation of hydrocarbons using solar energy via artificial photosynthesis is a highly desirable renewable-energy source for replacing conventional fossil fuels. Using an L-cysteine-based hydrothermal process, here we synthesize a carbon-doped SnS 2 (SnS 2 -C) metal dichalcogenide nanostructure, which exhibits a highly active and selective photocatalytic conversion of CO 2 to hydrocarbons under visible-light. The interstitial carbon doping induced microstrain in the SnS 2 lattice, resulting in different photophysical properties as compared with undoped SnS 2 . This SnS 2 -C photocatalyst significantly enhances the CO 2 reduction activity under visible light, attaining a photochemical quantum efficiency of above 0.7%. The SnS 2 -C photocatalyst represents an important contribution towards high quantum efficiency artificial photosynthesis based on gas phase photocatalytic CO 2 reduction under visible light, where the in situ carbon-doped SnS 2 nanostructure improves the stability and the light harvesting and charge separation efficiency, and significantly enhances the photocatalytic activity.

Cr:SnO2 thin films-synthesis and characterization

NASA Astrophysics Data System (ADS)

Varghese, Anitta Rose; B. Bhadrapriya, C.; Amarendra, G.; Hussain, Shamima

2018-04-01

Thin films of pure and Chromium doped SnO2 were synthesized using sol-gel method by spin coating technique. XRD studies confirmed the formation of tetragonal structure for SnO2 thin films. Variations in peak width and position were identified with doping. The optical band gap of the undoped films was found to be 3.8eV and varied with doping. Raman spectrum gave signature peaks of Sn-O and Cr-O bonds for undoped and doped films. The uniformity of the samples and formation of aggregates were observed from FESEM analysis.

CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO

NASA Technical Reports Server (NTRS)

Xu, Jennifer C.; Hunter, Gary W.; Liu, Chung Chiun; Ward, Benjamin J.

2008-01-01

Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases. Prototype CO2 sensors based on CuO-doped SnO2 have been fabricated by means of semiconductor-microfabrication and sol-gel nanomaterial-synthesis batch processes that are amendable to inexpensive implementation in mass production.

Ethanol chemiresistor with enhanced discriminative ability from acetone based on Sr-doped SnO2 nanofibers.

PubMed

Jiang, Ziqiao; Jiang, Tingting; Wang, Jinfeng; Wang, Zhaojie; Xu, Xiuru; Wang, Zongxin; Zhao, Rui; Li, Zhenyu; Wang, Ce

2015-01-01

We demonstrated a new metal oxides based chemiresistor (MOC), which exhibits fast response/recovery behavior, large sensitivity, and good selectivity to ethanol, enabled by Sr-doped SnO2 nanofibers via simple electrospinning and followed by calcination. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS) were carefully used to characterize their morphology, structure, and composition. The ethanol sensing performances based on Sr-doped SnO2 nanofibers were investigated. Comparing with the pristine SnO2 nanofibers, enhanced ethanol sensing performances (more rapid response/recovery behavior and larger response values) have been achieved owing to the basic SnO2 surface caused by Sr-doping, whereas the acetone sensing performances have been weakened. Thus, good discriminative ability to ethanol from acetone has been realized. Additionally, Sr-doped SnO2 nanofibers also exhibit good selectivity. Copyright © 2014 Elsevier Inc. All rights reserved.

Co-precipitation synthesis of nanostructured Cu3SbSe4 and its Sn-doped sample with high thermoelectric performance.

PubMed

Li, Di; Li, Rui; Qin, Xiao-Ying; Song, Chun-Jun; Xin, Hong-Xing; Wang, Ling; Zhang, Jian; Guo, Guang-lei; Zou, Tian-Hua; Liu, Yong-Fei; Zhu, Xiao-Guang

2014-01-28

Large-scale fabrication of nanostructured Cu3SbSe4 and its Sn-doped sample Cu3Sb0.98Sn0.02Se4 through a low-temperature co-precipitation route is reported. The effects of hot-pressing temperatures, time and Sn doping on the thermoelectric properties of Cu3SbSe4 are explored. The maximum figure of merit ZTmax obtained here reaches 0.62 for the un-doped Cu3SbSe4, which is three times as large as that of Cu3SbSe4 synthesized by the fusion method. Due to the ameliorated power factor by optimized carrier concentration and the reduced lattice thermal conductivity by enhanced phonon scattering at grain interfaces, Sn doping leads to an improvement of thermoelectric performance as compared to Cu3SbSe4. The maximum ZT for Cu3Sb0.98Sn0.02Se4 is 1.05 in this work, which is 50% larger than the largest value reported.

Scintillation and optical properties of Sn-doped Ga2O3 single crystals

NASA Astrophysics Data System (ADS)

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

2018-06-01

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

Defect phase diagram for doping of Ga2O3

NASA Astrophysics Data System (ADS)

Lany, Stephan

2018-04-01

For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2) conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

Sn-doped β-Ga2O3 nanowires deposited by radio frequency powder sputtering

NASA Astrophysics Data System (ADS)

Lee, Su Yong; Kang, Hyon Chol

2018-01-01

We report the synthesis and characterization of Sn-doped β-Ga2O3 nanowires (NWs) deposited using radio frequency powder sputtering. The growth sequence of Sn-doped β-Ga2O3 NWs is similar to that of the undoped β-Ga2O3 NWs. Self-assembled Ga clusters act as seeds for initiating the growth of Sn-doped β-Ga2O3 NWs through a vapor-liquid-solid process, while Sn atoms are incorporated into the trunk of NWs uniformly. Different from the straight shape of undoped NWs, the conical shape of NWs is observed, which is attributed to the change in supersaturation conditions and the diffusion of the catalyst tip and reaction species.

A study of structural, electrical, and optical properties of p-type Zn-doped SnO2 films versus deposition and annealing temperature

NASA Astrophysics Data System (ADS)

Le, Tran; Phuc Dang, Huu; Luc, Quang Ho; Hieu Le, Van

2017-04-01

This study presents a detailed investigation of the structural, electrical, and optical properties of p-type Zn-doped SnO2 versus the deposition and annealing temperature. Using a direct-current (DC) magnetron sputtering method, p-type transparent conductive Zn-doped SnO2 (ZTO) films were deposited on quartz glass substrates. Zn dopants incorporated into the SnO2 host lattice formed the preferred dominant SnO2 (1 0 1) and (2 1 1) planes. X-ray photoelectron spectroscopy (XPS) was used for identifying the valence state of Zn in the ZTO film. The electrical property of ZTO films changed from n-type to p-type at the threshold temperature of 400 °C, and the films achieved extremely high conductivity at the optimum annealing temperature of 600 °C after annealing for 2 h. The best conductive property of the film was obtained on a 10 wt% ZnO-doped SnO2 target with a resistivity, hole concentration, and hole mobility of 0.22 Ω · cm, 7.19  ×  1018 cm-3, and 3.95 cm2 V-1 s-1, respectively. Besides, the average transmission of films was  >84%. The surface morphology of films was examined using scanning electron microscopy (SEM). Moreover, the acceptor level of Zn2+ was identified using photoluminescence spectra at room temperature. Current-voltage (I-V) characteristics revealed the behavior of a p-ZTO/n-Si heterojunction diode.

Metallic conduction induced by direct anion site doping in layered SnSe2

PubMed Central

Kim, Sang Il; Hwang, Sungwoo; Kim, Se Yun; Lee, Woo-Jin; Jung, Doh Won; Moon, Kyoung-Seok; Park, Hee Jung; Cho, Young-Jin; Cho, Yong-Hee; Kim, Jung-Hwa; Yun, Dong-Jin; Lee, Kyu Hyoung; Han, In-taek; Lee, Kimoon; Sohn, Yoonchul

2016-01-01

The emergence of metallic conduction in layered dichalcogenide semiconductor materials by chemical doping is one of key issues for two-dimensional (2D) materials engineering. At present, doping methods for layered dichalcogenide materials have been limited to an ion intercalation between layer units or electrostatic carrier doping by electrical bias owing to the absence of appropriate substitutional dopant for increasing the carrier concentration. Here, we report the occurrence of metallic conduction in the layered dichalcogenide of SnSe2 by the direct Se-site doping with Cl as a shallow electron donor. The total carrier concentration up to ~1020 cm−3 is achieved by Cl substitutional doping, resulting in the improved conductivity value of ~170 S·cm−1 from ~1.7 S·cm−1 for non-doped SnSe2. When the carrier concentration exceeds ~1019 cm−3, the conduction mechanism is changed from hopping to degenerate conduction, exhibiting metal-insulator transition behavior. Detailed band structure calculation reveals that the hybridized s-p orbital from Sn 5s and Se 4p states is responsible for the degenerate metallic conduction in electron-doped SnSe2. PMID:26792630

Metallic conduction induced by direct anion site doping in layered SnSe2.

PubMed

Kim, Sang Il; Hwang, Sungwoo; Kim, Se Yun; Lee, Woo-Jin; Jung, Doh Won; Moon, Kyoung-Seok; Park, Hee Jung; Cho, Young-Jin; Cho, Yong-Hee; Kim, Jung-Hwa; Yun, Dong-Jin; Lee, Kyu Hyoung; Han, In-taek; Lee, Kimoon; Sohn, Yoonchul

2016-01-21

The emergence of metallic conduction in layered dichalcogenide semiconductor materials by chemical doping is one of key issues for two-dimensional (2D) materials engineering. At present, doping methods for layered dichalcogenide materials have been limited to an ion intercalation between layer units or electrostatic carrier doping by electrical bias owing to the absence of appropriate substitutional dopant for increasing the carrier concentration. Here, we report the occurrence of metallic conduction in the layered dichalcogenide of SnSe2 by the direct Se-site doping with Cl as a shallow electron donor. The total carrier concentration up to ~10(20) cm(-3) is achieved by Cl substitutional doping, resulting in the improved conductivity value of ~170 S · cm(-1) from ~1.7 S · cm(-1) for non-doped SnSe2. When the carrier concentration exceeds ~10(19) cm(-3), the conduction mechanism is changed from hopping to degenerate conduction, exhibiting metal-insulator transition behavior. Detailed band structure calculation reveals that the hybridized s-p orbital from Sn 5s and Se 4p states is responsible for the degenerate metallic conduction in electron-doped SnSe2.

Electrochemical capacitance of nanostructured ruthenium-doped tin oxide Sn1- x Ru x O2 by the microemulsion method

NASA Astrophysics Data System (ADS)

Saraswathy, Ramanathan

2017-12-01

Synthesis of nanostructured Ru-doped SnO2 was successfully carried out using the reverse microemulsion method. The phase purity and the crystallite size were analyzed by XRD. The surface morphology and the microstructure of synthesized nanoparticles were analyzed by SEM and TEM. The vibration mode of nanoparticles was investigated using FTIR and Raman studies. The electrochemical behavior of the Ru-doped SnO2 electrode was evaluated in a 0.1 mol/L Na2SO4 solution using cyclic voltammetry. The 5% Ru-doped SnO2 electrode exhibited a high specific capacitance of 535.6 F/g at a scan rate 20 mV/s, possessing good conductivity as well as the electrocycling stability. The Ru-doped SnO2 composite shows excellent electrochemical properties, suggesting that this composite is a promising material for supercapacitors.

Investigation of Hydrogen-Like Muonium States in Nb-Doped SnO2 Films

NASA Astrophysics Data System (ADS)

Rabis, Annett; Prokscha, Thomas; Fabbri, Emiliana; Salman, Zaher; Schmidt, Thomas; Suter, Andreas

Little is known about the characteristics of hydrogen states in thin films of SnO2 and Nb doped SnO2 (NTO) and its influence on the electrical properties in these materials, which are promising candidates for metal-oxide supports in polymer electrolyte fuel cells. Here, we used low-energy muon spin rotation/relaxation (LE-μSR) to study hydrogen-like muonium (Mu) states between 5 and 300 K in undoped and Nb doped SnO2 films with Nb doping levels of 0.1 and 2%, respectively. The films were prepared by reactive DC magnetron sputtering on undoped Si substrates. Film thicknesses varied between 75 and 200 nm, and muons were implanted close to the surface at a mean depth of 10 nm, in the center of the films, and in some cases close to the NTO/Si interface. Our results of transverse-field and longitudinal-field μSR show striking similarities to recent bulk μSR measurements on various zirconia systems [Vieira et al., Phys. Rev. B 94, 115207 (2016)]. This suggests that in the NTO systems the same Mu configurations exist which are the interstitial site with a deep, isotropic atomic Mu state, and, as the dominant fraction, the oxygen bound configuration with polaronic character.

Zr-doped SnO2 thin films synthesized by spray pyrolysis technique for barrier layers in solar cells

NASA Astrophysics Data System (ADS)

Reddy, N. Nanda Kumar; Akkera, Harish Sharma; Sekhar, M. Chandra; Park, Si-Hyun

2017-12-01

In the present work, we investigated the effect of Zr doping (0-6 at%) on the structural, electrical, and optical properties of tin oxide (SnO2) thin films deposited onto glass substrates using a spray pyrolysis technique. The room-temperature X-ray diffraction pattern shows that all deposited films exhibit polycrystalline tetragonal structure. The pure SnO2 film is grown along a preferred (200) direction, whereas Zr-doped SnO2 (Zr:SnO2) films started growing along the (220) orientation along with a high intensity peak of (200). Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed that the grains of the films are spherical in structure, and the grain size decreased with increasing of Zr concentration. The optical transmission spectra of deposited films as a function of wavelength confirm that the average optical transmittance is > 85% for Zr:SnO2 films. The value of the optical bandgap is significantly decreased from 3.94 to 3.68 eV with increasing Zr concentration. Furthermore, the electrical measurements found that the sheet resistance ( R sh) and resistivity ( ρ) values are decreased with increasing of Zr doping. The lowest values of R sh = 6.82 Ω and ρ = 0.4 × 10- 3 Ω cm are found in 6-at% Zr-doped SnO2 film. In addition, a good efficiency value of the figure of merit ( ɸ = 3.35 × 10- 3 Ω-1) is observed in 6-at% Zr-doped SnO2 film. These outstanding properties of Zr-doped SnO2 films make them useful for several optoelectronic device applications.

Dopant controlled photoinduced hydrophilicity and photocatalytic activity of SnO2 thin films

NASA Astrophysics Data System (ADS)

Talinungsang; Dhar Purkayastha, Debarun; Krishna, M. Ghanashyam

2018-07-01

The influence of Fe and Ni (1 wt.%) doping on the wettability and photocatalytic activity of sol-gel derived SnO2 films is reported. X-ray diffraction studies revealed the presence of tetragonal phase for both pure and doped SnO2 thin films. The crystallite size was of the order of 8 nm indicating the nanocrystalline nature of the films. The pure SnO2 films which were hydrophilic with a contact angle of 11.8° showed increase in contact angle with doping (38.7° for Fe and 48.6° for Ni). This is accompanied by decrease in surface energy and root mean square roughness, with doping of SnO2 film. In order to further increase the water contact angle, the film surfaces were modified using a layer of stearic acid. As a consequence, the water contact angles increased to 108°, 110° and 111° for the pure, Fe and Ni doped SnO2 films respectively, rendering them hydrophobic. Significantly, the unmodified surfaces that did not exhibit any change under UV irradiation showed photoinduced hydrophilicity on modification with stearic acid. There was a red-shift in the optical band gap of SnO2 films from 3.8 to 3.5 eV with doping, indicating the possibility of dopant controlled photocatalytic activity. This was confirmed by observing the photocatalytic degradation of an aqueous solution of methylene blue under UV irradiation. There was, indeed, significant improvement in the photocatalytic efficiency of the metal doped SnO2 thin film in comparison to undoped film. The current work, thus, demonstrates a simple method to chemically engineer the wettability and photocatalytic activity of SnO2 thin film surfaces.

Hydrogen sensor based on Sm-doped SnO{sub 2} nanostructures

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

Singh, Gurpreet; Hastir, Anita; Singh, Ravi Chand, E-mail: ravichand.singh@gmail.com

2016-05-23

In this paper the effect of samarium doping on the structural and hydrogen gas sensing properties of SnO{sub 2} nanoparticles has been reported. X-ray Diffraction (XRD) results revealed tetragonal rutile structure of both undoped and Sm-doped SnO{sub 2} nanoparticles. It has been observed that doping with samarium led to reduction in crystallite size of SnO{sub 2} nanoparticles which was confirmed from XRD analysis. Shifting and broadening of Raman peaks in case of doped nanoparticles has been explained by well-known phonon confinement model. The optimum operable temperature of both the sensors was found to 400 °C and the sensor response towardsmore » hydrogen gas has been improved after doping with samarium which was attributed to increase in sensing sites for the gas adsorption.« less

Dopant activation in Sn-doped Ga2O3 investigated by X-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Siah, S. C.; Brandt, R. E.; Lim, K.; Schelhas, L. T.; Jaramillo, R.; Heinemann, M. D.; Chua, D.; Wright, J.; Perkins, J. D.; Segre, C. U.; Gordon, R. G.; Toney, M. F.; Buonassisi, T.

2015-12-01

Doping activity in both beta-phase (β-) and amorphous (a-) Sn-doped gallium oxide (Ga2O3:Sn) is investigated by X-ray absorption spectroscopy (XAS). A single crystal of β-Ga2O3:Sn grown using edge-defined film-fed growth at 1725 °C is compared with amorphous Ga2O3:Sn films deposited at low temperature (<300 °C). Our XAS analyses indicate that activated Sn dopant atoms in conductive single crystal β-Ga2O3:Sn are present as Sn4+, preferentially substituting for Ga at the octahedral site, as predicted by theoretical calculations. In contrast, inactive Sn atoms in resistive a-Ga2O3:Sn are present in either +2 or +4 charge states depending on growth conditions. These observations suggest the importance of growing Ga2O3:Sn at high temperature to obtain a crystalline phase and controlling the oxidation state of Sn during growth to achieve dopant activation.

Photonic Nanoparticle Doped Architectures for Enhanced Solar to Fuel Photocatalytic Conversion 154060

DTIC Science & Technology

2016-12-09

coverage of the ZIS shell. We are also exploring the use of nanoshells coated with tin oxide (SnO2) rather than silica (SiO2) and coating the GS-NSs with...exploring the use of nanoshells coated with tin oxide (SnO2) rather than silica (SiO2) and coating the GS-NSs with zinc- and antimony-doped SnO2...to the preparation of GS-NS@SiO2 particles, we are also exploring the GS-NS coated with tin oxide (SnO2) and doped SnO2. Nanoshells with other

Microscopic study of thermoelectric In-doped SnTe

NASA Astrophysics Data System (ADS)

Nan, Pengfei; Liu, Ruibin; Chang, Yunjie; Wu, Hongbo; Wang, Yumei; Yu, Richeng; Shen, Jun; Guo, Wei; Ge, Binghui

2018-06-01

SnTe is a p-type thermoelectric material that is isostructural with PbTe, for which it is a potential environmentally friendly replacement. By doping the SnTe lattice with In, the thermal conductivity of SnTe can be significantly reduced and the thermoelectric conversion efficiency improved. A large number of precipitates were present in the In-doped SnTe samples; based on atomic-resolution high-angle annular dark-field images and electron energy loss spectra, these precipitates were identified as the zinc-blende phase of In2Te3. Through geometry phase analysis, a new phonon scattering mechanism is discussed.

Spectroscopic ellipsometry characterization of ZnO:Sn thin films with various Sn composition deposited by remote-plasma reactive sputtering

NASA Astrophysics Data System (ADS)

Janicek, Petr; Niang, Kham M.; Mistrik, Jan; Palka, Karel; Flewitt, Andrew J.

2017-11-01

ZnO:Sn thin films were deposited onto thermally oxidized silicon substrates using a remote plasma reactive sputtering. Their optical constants (refractive index n and extinction coefficient k) were determined from ellipsometric data recorded over a wide spectral range (0.05-6 eV). Parametrization of ZnO:Sn complex dielectric permittivity consists of a parameterized semiconductor oscillator function describing the short wavelength absorption edge, a Drude oscillator describing free carrier absorption in near-infrared part of spectra and a Lorentz oscillator describing the long wavelength absorption edge and intra-band absorption in the ultra-violet part of the spectra. Using a Mott-Davis model, the increase in local disorder with increasing Sn doping is quantified from the short wavelength absorption edge onset. Using the Wemple-DiDomenico single oscillator model for the transparent part of the optical constants spectra, an increase in the centroid distance of the valence and conduction bands with increasing Sn doping is shown and only slight increase in intensity of the inter-band optical transition due to Sn doping occurs. The Drude model applied in the near-infrared part of the spectra revealed the free carrier concentration and mobility of ZnO:Sn. Results show that the range of transparency of prepared ZnO:Sn layers is not dramatically affected by Sn doping whereas electrical conductivity could be controlled by Sn doping. Refractive index in the transparent part is comparable with amorphous Indium Gallium Zinc Oxide allowing utilization of prepared ZnO:Sn layers as an indium-free alternative.

Multisource Synergistic Electrocatalytic Oxidation Effect of Strongly Coupled PdM (M = Sn, Pb)/N-doped Graphene Nanocomposite on Small Organic Molecules

PubMed Central

Wu, Peng; Huang, Yiyin; Kang, Longtian; Wu, Maoxiang; Wang, Yaobing

2015-01-01

A series of palladium-based catalysts of metal alloying (Sn, Pb) and/or (N-doped) graphene support with regular enhanced electrocatalytic activity were investigated. The peak current density (118.05 mA cm−2) of PdSn/NG is higher than the sum current density (45.63 + 47.59 mA cm−2) of Pd/NG and PdSn/G. It reveals a synergistic electrocatalytic oxidation effect in PdSn/N-doped graphene Nanocomposite. Extend experiments show this multisource synergetic catalytic effect of metal alloying and N-doped graphene support in one catalyst on small organic molecule (methanol, ethanol and Ethylene glycol) oxidation is universal in PdM(M = Sn, Pb)/NG catalysts. Further, The high dispersion of small nanoparticles, the altered electron structure and Pd(0)/Pd(II) ratio of Pd in catalysts induced by strong coupled the metal alloying and N-doped graphene are responsible for the multisource synergistic catalytic effect in PdM(M = Sn, Pb) /NG catalysts. Finally, the catalytic durability and stability are also greatly improved. PMID:26434949

Experimental and Theoretical Investigations on Intermediate Band in Doped Nano-SnS2

NASA Astrophysics Data System (ADS)

Heiba, Zein K.; Mohamed, Mohamed Bakr; Abdel Kader, M. H.

2018-03-01

Nano-SnS2 and Sn0.75 X 0.25S2 (X = Cr, Fe, Y) have been prepared by thermolysis method. Phase analysis of x-ray diffraction data confirmed the single-phase nature of all prepared samples, with some residual carbon contributing to the background. Rietveld refinement revealed high anisotropy in crystallite size, signifying a cylindrical structure for the particle shape, as confirmed by transmission electron microscopy. The refined occupancies obtained for the doped cations were found to be smaller than the nominal target doping ratio (25%). Fourier-transform infrared spectra showed presence of Sn-S bond in all samples. The energy was found to be 3.42 eV, 3.33 eV, 2.1 eV and 3.14 eV, and 3.62 eV for undoped SnS2 and when doped with Cr, Fe, and Y, respectively. Density functional theory calculations illustrated that Fe-doped SnS2 has two bandgaps [normal and intermediate (IB) bands]. Meanwhile, Sn0.75Fe0.25S2 sample showed anti-Stokes and an extra photoluminescence peak related to the newly created intermediate band (IB) inside the energy gap. On the other hand, pure SnS2 and Sn0.75 X 0.25S2 (X = Cr, Y) samples emitted four photoluminescence subspectra in ultraviolet, violet, and blue regions.

Superconductivity, pairing symmetry, and disorder in the doped topological insulator Sn 1 - x In x Te for x ≥ 0.10

DOE PAGES

Smylie, M. P.; Claus, H.; Kwok, W. -K.; ...

2018-01-19

In this paper, the temperature dependence of the London penetration depth Δλ(T) in the superconducting doped topological crystalline insulator Sn 1-xIn xTe was measured down to 450 mK for two different doping levels, x ≈ 0.45 (optimally doped) and x ≈ 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. Finally, the introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T c, indicatingmore » that ferroelectric interactions do not compete with superconductivity.« less

Superconductivity, pairing symmetry, and disorder in the doped topological insulator Sn 1 - x In x Te for x ≥ 0.10

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

Smylie, M. P.; Claus, H.; Kwok, W. -K.

In this paper, the temperature dependence of the London penetration depth Δλ(T) in the superconducting doped topological crystalline insulator Sn 1-xIn xTe was measured down to 450 mK for two different doping levels, x ≈ 0.45 (optimally doped) and x ≈ 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. Finally, the introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T c, indicatingmore » that ferroelectric interactions do not compete with superconductivity.« less

Incorporation of heterostructured Sn/SnO nanoparticles in crumpled nitrogen-doped graphene nanosheets for application as anodes in lithium-ion batteries.

PubMed

Du, Fei-Hu; Liu, Yu-Si; Long, Jie; Zhu, Qian-Cheng; Wang, Kai-Xue; Wei, Xiao; Chen, Jie-Sheng

2014-09-07

Sn/SnO nanoparticles are incorporated in crumpled nitrogen-doped graphene nanosheets by a simple melting diffusion method. The resulting composite exhibits large specific capacity, excellent cycling stability and high rate capability as an anode for lithium-ion batteries.

Structural characterizations of pure SnS and In-doped SnS thin films using isotropic and anisotropic models

NASA Astrophysics Data System (ADS)

Kafashan, Hosein

2018-04-01

An electrochemical route has been employed to prepare pure SnS and indium-doped SnS thin films. Six samples including undoped SnS and In-doped SnS thin films deposited on the fluorine-doped tin oxide (FTO) glass substrates. An aqueous solution having SnCl2 and Na2S2O3 used as the primary electrolyte. Different In-doped SnS samples were prepared by adding a different amount of 1 mM InCl3 solution into the first electrolyte. The applied potential (E), time of deposition (t), pH and bath temperature (T) were kept at ‑1 V, 30 min, 2.1 and 60 °C, respectively. For all samples, except the In-dopant concentration, all the deposition parameters are the same. After preparation, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with an energy dispersive X-ray analyzer (EDX) attachment, atomic force microscopy (AFM), and transmission electron microscopy (TEM) were used to determine structural properties of as-deposited films. XRD patterns revealed that the synthesized undoped- and In-doped SnS thin films were crystallized in the orthorhombic structure. The shape of SnS crystals was spherical in the TEM image. X-ray peak broadening studies was done by applying Scherrer’s method, Williamson-Hall (W–H) models (including uniform deformation model (UDM), uniform strain deformation model (UDSM), and uniform deformation energy density model (UDEDM)), and size-strain plot (SSP) method. Using these techniques, the crystallite size and the lattice strains have been predicted. There was a good agreement in the particle size achieved by W–H- and SSP methods with TEM image.

Studying Structural, Optical, Electrical, and Sensing Properties of Nanocrystalline SnO2:Cu Films Prepared by Sol-Gel Method for CO Gas Sensor Application at Low Temperature

NASA Astrophysics Data System (ADS)

Al-Jawad, Selma M. H.; Elttayf, Abdulhussain K.; Saber, Amel S.

Nanocrystalline SnO2 and SnO2:Cu thin films derived from SnCl2ṡ2H2O precursors have been prepared on glass substrates using sol-gel dip-coating technique. The deposited film was 300±20nm thick and the films were annealed in air at 500∘C for 1h. Structural, optical and sensing properties of the films were studied under different preparation conditions, such as Cu-doping concentration of 2%, 4% and 6wt.%. X-ray diffraction studies show the polycrystalline nature with tetragonal rutile structure of SnO2 and Cu:SnO2 thin films. The films have highly preferred orientation along (110). The crystallite size of the prepared samples reduced with increasing Cu-doping concentrations and the addition of Cu as dopants changed the structural properties of the thin films. Surface morphology was determined through scanning electron microscopy and atomic force microscopy. Results show that the particle size decreased as doping concentration increased. The films have moderate optical transmission (up to 82.4% at 800nm), and the transmittance, absorption coefficient and energy gap at different Cu-doping concentration were measured and calculated. Results show that Cu-doping decreased the transmittance and energy gap whereas it increased the absorption coefficient. Two peaks were noted with Cu-doping concentration of 0-6wt.%; the first peak was positioned exactly at 320nm ultraviolet emission and the second was positioned at 430-480nm. Moreover, emission bands were noticed in the photoluminescence spectra of Cu:SnO2. The electrical properties of SnO2 films include DC electrical conductivity, showing that the films have two activation energies, namely, Ea1 and Ea2, which increase as Cu-doping concentration increases. Cudoped nanocrystalline SnO2 gas-sensing material has better sensitivity to CO gas compared with pure SnO2.

Mo-doped SnO2 mesoporous hollow structured spheres as anode materials for high-performance lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Xuekun; Li, Zhaoqiang; Zhang, Zhiwei; Li, Qun; Guo, Enyan; Wang, Chengxiang; Yin, Longwei

2015-02-01

We designed a facile infiltration route to synthesize mesoporous hollow structured Mo doped SnO2 using silica spheres as templates. It is observed that Mo is uniformly incorporated into SnO2 lattice in the form of Mo6+. The as-prepared mesoporous Mo-doped SnO2 LIBs anodes exhibit a significantly improved electrochemical performance with good cycling stability, high specific capacity and high rate capability. The mesoporous hollow Mo-doped SnO2 sample with 14 at% Mo doping content displays a specific capacity of 801 mA h g-1 after 60 cycles at a current density of 100 mA g-1, about 1.66 times higher than that of the pure SnO2 hollow sample. In addition, even if the current density is as high as 1600 mA g-1 after 60 cycles, it could still retain a stable specific capacity of 530 mA h g-1, exhibiting an extraordinary rate capability. The greatly improved electrochemical performance of the Mo-doped mesoporous hollow SnO2 sample could be attributed to the following factors. The large surface area and hollow structure can significantly enhance structural integrity by acting as mechanical buffer, effectively alleviating the volume changes generated during the lithiation/delithiation process. The incorporation of Mo into the lattice of SnO2 improves charge transfer kinetics and results in a faster Li+ diffusion rate during the charge-discharge process.

Effect of Sn doping on structural, mechanical, optical and electrical properties of ZnO nanoarrays prepared by sol-gel and hydrothermal process

NASA Astrophysics Data System (ADS)

Agarwal, Manish Baboo; Sharma, Akash; Malaidurai, M.; Thangavel, R.

2018-05-01

Undoped and Sn doped Zinc oxide nanorods were prepared by two step process: initially growth of seed layers by sol-gel spin coating technique and then zinc oxide nanorods by hydrothermal process using the precursors zinc nitrate hexahydrate, hexamine and tin chloride. The effects on the electrical, optical, mechanical and structural properties for various Sn concentrations were studied. The crystalline phase determination from X-ray diffraction (XRD) confirms that Sn doped ZnO nanorods have hexagonal wurtzite structure. The variations of stress and strain with different doping concentration of Sn in ZnO nanorods were studied. The doping effect on electrical properties and optical bandgap is estimated by current voltage characteristics and absorbance spectra respectively. The surface morphology was studied with field emission scanning electron microscope (FESEM), which shows that the formation of hexagonal nanorods arrays with increasing Sn concentration. The calculated value of Young's modulus of elasticity (Y) for all the samples remains same. These results can be used in optoelectronic devices.

Morphology and Doping Engineering of Sn-Doped Hematite Nanowire Photoanodes.

PubMed

Li, Mingyang; Yang, Yi; Ling, Yichuan; Qiu, Weitao; Wang, Fuxin; Liu, Tianyu; Song, Yu; Liu, Xiaoxia; Fang, Pingping; Tong, Yexiang; Li, Yat

2017-04-12

High-temperature activation has been commonly used to boost the photoelectrochemical (PEC) performance of hematite nanowires for water oxidation, by inducing Sn diffusion from fluorine-doped tin oxide (FTO) substrate into hematite. Yet, hematite nanowires thermally annealed at high temperature suffer from two major drawbacks that negatively affect their performance. First, the structural deformation reduces light absorption capability of nanowire. Second, this "passive" doping method leads to nonuniform distribution of Sn dopant in nanowire and limits the Sn doping concentration. Both factors impair the electrochemical properties of hematite nanowire. Here we demonstrate a silica encapsulation method that is able to simultaneously retain the hematite nanowire morphology even after high-temperature calcination at 800 °C and improve the concentration and uniformity of dopant distribution along the nanowire growth axis. The capability of retaining nanowire morphology allows tuning the nanowire length for optimal light absorption. Uniform distribution of Sn doping enhances the donor density and charge transport of hematite nanowire. The morphology and doping engineered hematite nanowire photoanode decorated with a cobalt oxide-based oxygen evolution reaction (OER) catalyst achieves an outstanding photocurrent density of 2.2 mA cm -2 at 0.23 V vs Ag/AgCl. This work provides important insights on how the morphology and doping uniformity of hematite photoanodes affect their PEC performance.

Significant enhancement of compositional and superconducting homogeneity in Ti rather than Ta-doped Nb 3Sn

DOE PAGES

Tarantini, C.; Sung, Z. -H.; Lee, P. J.; ...

2016-01-25

Nb 3Sn wires are now very close to their final optimization but despite its classical nature, detailed understanding of the role of Ta and Ti doping in the A15 is not fully understood. Long thought to be essentially equivalent in their influence on H c2, they were interchangeably applied. Here we show that Ti produces significantly more homogeneous chemical and superconducting properties. Despite Ta-doped samples having a slightly higher T c onset in zero-field, they always have a wider Tc-distribution. In particular, whereas the Ta-doped A15 has a T c-distribution extending from 18 down to 5-6 K (the lowest expectedmore » Tc for the binary A15 phase), the Ti-doped samples have no A15 phase with T c below ~12 K. The much narrower T c distribution in the Ti-doped samples has a positive effect on their in-field T c-distribution too, leading to an extrapolated μ0H c2(0) 2 Tesla larger than the Ta-doped one. Ti-doping also appears to be very homogeneous even when the Sn content is reduced in order to inhibit breakdown of the diffusion barriers in very high Jc conductors. As a result, the enhanced homogeneity of the Ti-doped samples appears to result from its assistance of rapid diffusion of Sn into the filaments and by its incorporation into the A15 phase interchangeably with Sn on the Sn sites of the A15 phase.« less

Superparamagnetic behavior of Fe-doped SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y.

2014-02-01

SnO2 is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO2 nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO2 nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO2, were investigated. The particle size (1.8-16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO2 single-phase structure for samples annealed at 1073-1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO2 is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system.

Influence of Sn ion doping on the photocatalytic performance of V2O5 nanorods prepared by hydrothermal method

NASA Astrophysics Data System (ADS)

Rajeshwari, S.; Santhosh Kumar, J.; Rajendrakumar, R. T.; Ponpandian, N.; Thangadurai, P.

2018-02-01

Pure and different concentrations of Sn4+ doped V2O5 (Sn:V2O5) nanorods were synthesized by hydrothermal method. The Sn:V2O5 nanorods obtained were orthorhombic in structure. No secondary phase was observed up to 10% of Sn doping, but beyond that, there evolved a secondary phase of SnO2. Microstructural analysis revealed the morphology of V2O5 as nanorods and platelets like structure. Presence of V, O and Sn elements in the samples was confirmed by energy dispersive spectroscopy. The V2O5 nanorods have shown a strong absorption in the visible region and the band gap energy was obtained to be varying from 2.21 to 2.26 eV as a function of Sn ion doping. Photocatalytic studies on methylene blue (MB) under visible light irradiation showed that the 3% Sn:V2O5 had effectively degraded MB up to a maximum degradation of 96% and further increase in Sn content had decreased the photodegradation due to higher recombination rate of photogenerated electrons. The mechanism of photodegradation was completely understood and the OH· radicals have played a dominant role in the photodegradation of the organic dyes.

Extrinsic doping of the half-Heusler compounds

NASA Astrophysics Data System (ADS)

Stern, Robin; Dongre, Bonny; Madsen, Georg K. H.

2016-08-01

Controlling the p- and n-type doping is a key tool to improve the power-factor of thermoelectric materials. In the present work we provide a detailed understanding of the defect thermochemistry in half-Heusler compounds. We calculate the formation energies of intrinsic and extrinsic defects in state of the art n-type TiNiSn and p-type TiCoSb thermoelectric materials. It is shown how the incorporation of online repositories can reduce the workload in these calculations. In TiNiSn we find that Ni- and Ti-interstitial defects play a crucial role in the carrier concentration of TiNiSn. Furthermore, we find that extrinsic doping with Sb can substantially enhance the carrier concentration, in agreement with experiment. In case of TiCoSb, we find ScTi, FeCo and SnSb being possible p-type dopants. While experimental work has mainly focussed on Sn-doping of the Sb site, the present result underlines the possibility to p-dope TiCoSb on all lattice sites.

Ultra-low specific contact resistivity (1.4 × 10-9 Ω.cm2) for metal contacts on in-situ Ga-doped Ge0.95Sn0.05 film

NASA Astrophysics Data System (ADS)

Wu, Ying; Luo, Sheng; Wang, Wei; Masudy-Panah, Saeid; Lei, Dian; Liang, Gengchiau; Gong, Xiao; Yeo, Yee-Chia

2017-12-01

A heavily Ga-doped Ge0.95Sn0.05 layer was grown on the Ge (100) substrate by molecular beam epitaxy (MBE), achieving an active doping concentration of 1.6 × 1020 cm-3 without the use of ion implantation and high temperature annealing that could cause Sn precipitation or surface segregation. An advanced nano-scale transfer length method was used to extract the specific contact resistivity ρc between the metal and the heavily doped p-Ge0.95Sn0.05 layer. By incorporating Sn into Ge and in-situ Ga doping during the MBE growth, an ultra-low ρc of 1.4 × 10-9 Ω.cm2 was achieved, which is 50% lower than the ρc of p+-Ge control and is also the lowest value obtained for metal/p-type semiconductor contacts.

A Rapid Method for Deposition of Sn-Doped GaN Thin Films on Glass and Polyethylene Terephthalate Substrates

NASA Astrophysics Data System (ADS)

Pat, Suat; Özen, Soner; Korkmaz, Şadan

2018-01-01

We report the influence of Sn doping on microstructure, surface, and optical properties of GaN thin films deposited on glass and polyethylene terephthalate (PET) substrate. Sn-doped GaN thin films have been deposited by thermionic vacuum arc (TVA) at low temperature. TVA is a rapid deposition technology for thin film growth. Surface and optical properties of the thin films were presented. Grain size, height distribution, roughness values were determined. Grain sizes were calculated as 20 nm and 13 nm for glass and PET substrates, respectively. Nano crystalline forms were shown by field emission scanning electron microscopy. Optical band gap values were determined by optical methods and photoluminescence measurement. The optical band gap values of Sn doped GaN on glass and PET were determined to be approximately ˜3.40 eV and ˜3.47 eV, respectively. As a result, TVA is a rapid and low temperature deposition technology for the Sn doped GaN deposited on glass and PET substrate.

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

Mariammal, R. N.; Ramachandran, K.

Cu{sub 1-x}Sn{sub x}O(x = 0.00, 0.03, and 0.05) nanoflakes were synthesized by a simple wet chemical method and X-Ray diffraction (XRD) result confirms the monoclinic structure of CuO with no secondary phases due to Sn doping. The scanning electron microscopic images indicate the formation of nanoflakes. The fundamental Raman modes were observed at 273, 318, 610, and 1084 cm{sup -1} for undoped CuO sample and theses modes were slightly shifted towards lower frequency side for Sn-doped samples, which indicates the inclusion of Sn in CuO. In addition, XRD and Raman studies infer the decrease of crystallinity in doped samples, whichmore » is reflected in the sensitivity towards ethanol. The ethanol sensitivity (resistivity measurement) increases with ethanol gas concentration and decreases with Sn-doping in CuO nanoflakes.« less

Dopant activation in Sn-doped Ga{sub 2}O{sub 3} investigated by X-ray absorption spectroscopy

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

Siah, S. C., E-mail: sincheng@alum.mit.edu; Brandt, R. E.; Jaramillo, R.

2015-12-21

Doping activity in both beta-phase (β-) and amorphous (a-) Sn-doped gallium oxide (Ga{sub 2}O{sub 3}:Sn) is investigated by X-ray absorption spectroscopy (XAS). A single crystal of β-Ga{sub 2}O{sub 3}:Sn grown using edge-defined film-fed growth at 1725 °C is compared with amorphous Ga{sub 2}O{sub 3}:Sn films deposited at low temperature (<300 °C). Our XAS analyses indicate that activated Sn dopant atoms in conductive single crystal β-Ga{sub 2}O{sub 3}:Sn are present as Sn{sup 4+}, preferentially substituting for Ga at the octahedral site, as predicted by theoretical calculations. In contrast, inactive Sn atoms in resistive a-Ga{sub 2}O{sub 3}:Sn are present in either +2 or +4more » charge states depending on growth conditions. These observations suggest the importance of growing Ga{sub 2}O{sub 3}:Sn at high temperature to obtain a crystalline phase and controlling the oxidation state of Sn during growth to achieve dopant activation.« less

Limits of carrier mobility in Sb-doped SnO{sub 2} conducting films deposited by reactive sputtering

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

Bissig, B., E-mail: Benjamin.bissig@empa.ch; Jäger, T.; Tiwari, A. N.

2015-06-01

Electron transport in Sb-doped SnO{sub 2} (ATO) films is studied to unveil the limited carrier mobility observed in sputtered films as compared to other deposition methods. Transparent and conductive ATO layers are deposited from metallic tin targets alloyed with antimony in oxygen atmosphere optimized for reactive sputtering. The carrier mobility decreases from 24 cm{sup 2} V{sup −1} s{sup −1} to 6 cm{sup 2} V{sup −1} s{sup −1} when increasing the doping level from 0 to 7 at. %, and the lowest resistivity of 1.8 × 10{sup −3} Ω cm corresponding to the mobility of 12 cm{sup 2} V{sup −1} s{sup −1}more » which is obtained for the 3 at. % Sb-doped ATO. Temperature-dependent Hall effect measurements and near-infrared reflectance measurements reveal that the carrier mobility in sputtered ATO is limited by ingrain scattering. In contrast, the mobility of unintentionally doped SnO{sub 2} films is determined mostly by the grain boundary scattering. Both limitations should arise from the sputtering process itself, which suffers from the high-energy-ion bombardment and yields polycrystalline films with small grain size.« less

In-situ sulfuration synthesis of sandwiched spherical tin sulfide/sulfur-doped graphene composite with ultra-low sulfur content

NASA Astrophysics Data System (ADS)

Zhao, Bing; Yang, Yaqing; Wang, Zhixuan; Huang, Shoushuang; Wang, Yanyan; Wang, Shanshan; Chen, Zhiwen; Jiang, Yong

2018-02-01

SnS is widely studied as anode materials since of its superior structural stability and physicochemical property comparing with other Sn-based composites. Nevertheless, the inconvenience of phase morphology control and excessive consumption of sulfur sources during synthesis hinder the scalable application of SnS nanocomposites. Herein, we report a facile in-situ sulfuration strategy to synthesize sandwiched spherical SnS/sulfur-doped graphene (SnS/S-SG) composite. An ultra-low sulfur content with approximately stoichiometric ratio of Sn:S can effectively promote the sulfuration reaction of SnO2 to SnS and simultaneous sulfur-doping of graphene. The as-prepared SnS/S-SG composite shows a three-dimensional interconnected spherical structure as a whole, in which SnS nanoparticles are sandwiched between the multilayers of graphene sheets forming a hollow sphere. The sandwiched sphere structure and high S doping amount can improve the binding force between SnS and graphene, as well as the structural stability and electrical conductivity of the composite. Thus, a high reversibility of conversion reaction, promising specific capacity (772 mAh g-1 after 100 cycles at 0.1 C) and excellent rate performance (705 and 411 mAh g-1 at 1 C and 10 C, respectively) are exhibited in the SnS/S-SG electrode, which are much higher than that of the SnS/spherical graphene synthesized by traditional post-sulfuration method.

On Defect Cluster Aggregation and Non-Reducibilty in Tin-Doped Indium Oxide

NASA Astrophysics Data System (ADS)

Warschkow, Oliver; Ellis, Donald E.; Gonzalez, Gabriela; Mason, Thomas O.

2003-03-01

The conductivity of tin-doped indium oxide (ITO), a transparent conductor, is critically dependent on the amount of tin-doping and oxygen partial pressure during preparation and annealing. Frank and Kostlin (Appl. Phys. A 27 (1982) 197-206) rationalized the carrier concentration dependence by postulating the formation of two types of neutral defect clusters at medium tin-doping levels: "Reducible" and "non-reducible" defect clusters; so named to indicate their ability to create carriers under reduction. According to Frank and Kostlin, both are composed of a single oxygen interstitial and two tin atoms substituting for indium, positioned in non-nearest and nearest coordination, respectively. This present work, seeking to distinguish reducible and non-reducible clusters by use of an atomistic model, finds only a weak correlation of oxygen interstitial binding energies with the relative positioning of dopants. Instead, the number of tin-dopants in the vicinity of the interstitial has a much larger effect on how strongly it is bound, a simple consequence of Coulomb interactions. We postulate that oxygen interstitials become non-reducible when clustered with three or more Sn_In. This occurs at higher doping levels as reducible clusters aggregate and share tin atoms. A simple probabilistic model, estimating the average number of clusters so aggregated, provides a qualitatively correct description of the carrier density in reduced ITO as a function of Sn doping level.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Compensating vacancy defects in Sn- and Mg-doped In2O3

NASA Astrophysics Data System (ADS)

Korhonen, E.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; Galazka, Z.

2014-12-01

MBE-grown Sn- and Mg-doped epitaxial In2O3 thin-film samples with varying doping concentrations have been measured using positron Doppler spectroscopy and compared to a bulk crystal reference. Samples were subjected to oxygen or vacuum annealing and the effect on vacancy type defects was studied. Results indicate that after oxygen annealing the samples are dominated by cation vacancies, the concentration of which changes with the amount of doping. In highly Sn-doped In2O3 , however, these vacancies are not the main compensating acceptor. Vacuum annealing increases the size of vacancies in all samples, possibly by clustering them with oxygen vacancies.

Defect phase diagram for doping of Ga 2O 3

DOE PAGES

Lany, Stephan

2018-04-01

For the case of n-type doping of β-Ga 2O 3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO 2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association ofmore » dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO 2) conditions. Considering further the stability constraints due to sublimation of molecular Ga 2O, specific predictions of optimized pO 2 and Si dopant concentrations are given. To conclude, the incomplete passivation of dopant-defect complexes in β-Ga 2O 3 suggests a design rule for metastable doping above the solubility limit.« less

Defect phase diagram for doping of Ga 2O 3

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

Lany, Stephan

For the case of n-type doping of β-Ga 2O 3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO 2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association ofmore » dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO 2) conditions. Considering further the stability constraints due to sublimation of molecular Ga 2O, specific predictions of optimized pO 2 and Si dopant concentrations are given. To conclude, the incomplete passivation of dopant-defect complexes in β-Ga 2O 3 suggests a design rule for metastable doping above the solubility limit.« less

Ni doping effect on the electronic and sensing properties of 2D SnO2

NASA Astrophysics Data System (ADS)

Patel, Anjali; Roondhe, Basant; Jha, Prafulla K.

2018-05-01

In the present work using state of art first principles calculations under the frame work of density functional theory the effect of Nickel (Ni) doping on electronic as well as sensing properties of most stable two dimensional (2D) T-SnO2 phase towards ethanol (C2H5OH) has been observed. It has been found that Ni atom when dope on T-SnO2 causes prominent decrement in the band gap from 2.26 eV to 1.48 eV and improves the sensing phenomena of pristine T-SnO2 towards C2H5OH by increasing the binding energy from -0.18eV to -0.93eV. The comparative analysis of binding energy shows that Ni improves the binding of C2H5OH by 5.16 times the values for pristine T-SnO2. The doping of Ni into 2D T-SnO2 reduces the band gap through lowering of the conduction band minimum, thereby increasing the electron affinity which increases the sensing performance of T-SnO2. The variation in the electronic properties after and before the exposure of ethanol reinforced to use Ni:SnO2 nano structure for sensing applications. The results indicate that the Ni doped T-SnO2 can be utilized in improved optoelectronic as well as sensor devices in the future.

Electrochemical synthesis of nanostructured Se-doped SnS: Effect of Se-dopant on surface characterizations

NASA Astrophysics Data System (ADS)

Kafashan, Hosein; Azizieh, Mahdi; Balak, Zohre

2017-07-01

SnS1-xSex nanostructures with different Se-dopant concentrations were deposited on fluorine doped tin oxide (FTO) substrate through cathodic electrodeposition technique. The pH, temperature, applied potential (E), and deposition time remained were 2.1, 60 °C, -1 V, and 30 min, respectively. SnS1-xSex nanostructures were characterized using X-ray diffraction (XRD), field emission scanning electron microcopy (FESEM), energy dispersive X-ray spectroscopy (EDX), room temperature photoluminescence (PL), and UV-vis spectroscopy. The XRD patterns revealed that the SnS1-xSex nanostructures were polycrystalline with orthorhombic structure. FESEM showed various kinds of morphologies in SnS1-xSex nanostructures due to Se-doping. PL and UV-vis spectroscopy were used to evaluate the optical properties of SnS1-xSex thin films. The PL spectra of SnS1-xSex nanostructures displayed four emission peaks, those are a blue, a green, an orange, and a red emission. UV-vis spectra showed that the optical band gap energy (Eg) of SnS1-xSex nanostructures varied between 1.22-1.65 eV, due to Se-doping.

Role of oxygen defects on the magnetic properties of ultra-small Sn1-xFexO2 nanoparticles

NASA Astrophysics Data System (ADS)

Dodge, Kelsey; Chess, Jordan; Eixenberger, Josh; Alanko, Gordon; Hanna, Charles B.; Punnoose, Alex

2013-05-01

Although the role of oxygen defects in the magnetism of metal oxide semiconductors has been widely discussed, it is been difficult to directly measure the oxygen defect concentration of samples to verify this. This work demonstrates a direct correlation between the photocatalytic activity of Sn1-xFexO2 nanoparticles and their magnetic properties. For this, a series of ˜2.6 nm sized, well characterized, single-phase Sn1-xFexO2 crystallites with x = 0-0.20 were synthesized using tin acetate, urea, and appropriate amounts of iron acetate. X-ray photoelectron spectroscopy confirmed the concentration and 3+ oxidation state of the doped Fe ions. The maximum magnetic moment/Fe ion, μ, of 1.6 × 10-4 μB observed for the 0.1% Fe doped sample is smaller than the expected spin-only contribution from either high or low spin Fe3+ ions, and μ decreases with increasing Fe concentration. This behavior cannot be explained by the existing models of magnetic exchange. Photocatalytic studies of pure and Fe-doped SnO2 were used to understand the roles of doped Fe3+ ions and of the oxygen vacancies and defects. The photocatalytic rate constant k also showed an increase when SnO2 nanoparticles were doped with low concentrations of Fe3+, reaching a maximum at 0.1% Fe, followed by a rapid decrease of k for further increase in Fe%. Fe doping presumably increases the concentration of oxygen vacancies, and both Fe3+ ions and oxygen vacancies act as electron acceptors to reduce e--h+ recombination and promote transfer of electrons (and/or holes) to the nanoparticle surface, where they participate in redox reactions. This electron transfer from the Fe3+ ions to local defect density of states at the nanoparticle surface could develop a magnetic moment at the surface states and leads to spontaneous ferromagnetic ordering of the surface shell under favorable conditions. However, at higher doping levels, the same Fe3+ ions might act as recombination centers causing a decrease of both k and magnetic moment μ.

Molecular approaches to p- and n-nanoscale doping of Ge 1-ySn y semiconductors: Structural, electrical and transport properties

NASA Astrophysics Data System (ADS)

Xie, Junqi; Tolle, J.; D'Costa, V. R.; Weng, C.; Chizmeshya, A. V. G.; Menendez, J.; Kouvetakis, J.

2009-08-01

We report the development of practical doping protocols via designer molecular sources to create n- and p-type doped Ge 1-ySn y layers grown directly upon Si(1 0 0). These materials will have applications in the fabrication of advanced PIN devices that are intended to extend the infrared optical response beyond that of Ge by utilizing the Sn composition as an additional design parameter. Highly controlled and efficient n-doping of single-layer structures is achieved using custom built P(GeH 3) 3 and As(GeH 3) 3, precursors containing preformed Ge-As and Ge-P near-tetrahedral bonding arrangements compatible with the structure of the host Ge-Sn lattice. Facile substitution and complete activation of the P and As atoms at levels ˜10 17-10 19 cm -3 is obtained via in situ depositions at low temperatures (350 °C). Acceptor doping is readily achieved using conventional diborane yielding carrier concentrations between 10 17-10 19 cm -3 under similar growth conditions. Full activation of the as-grown dopant concentrations is demonstrated by combined SIMS and Hall experiments, and corroborated using a contactless spectroscopic ellipsometry approach. RTA processing of the samples leads to a significant increase in carrier mobility comparable to that of bulk Ge containing similar doping levels. The alloy scattering contribution appears to be negligible for electron carrier concentrations beyond 10 19 cm -3 in n-type samples and hole concentrations beyond 10 18 cm -3 in p-type samples. A comparative study using the classical lower-order hydrides PH 3 and AsH 3 produced n-doped films with carrier densities (up to 9 × 10 19 cm -3) similar to those afforded by P(GeH 3) 3 and As(GeH 3) 3. However, early results indicate that the simpler PH 3 and AsH 3 sources yield materials with inferior morphology and microstructure. Calculations of surface energetics using bond enthalpies suggest that the latter massive compounds bind to the surface via strong Ge-Ge bonds and likely act as "retardants" that moderate surface diffusion of the reactions species, thereby promoting layer-by-layer growth leading to thick, atomically smooth films, particularly in the case of P(GeH 3) 3. Furthermore, the intact incorporation of the Ge 3P and Ge 3As molecular cores results in highly uniform compositional, strain and doping profiles at the atomic level.

Microstructural, Optical and Dielectric Properties of Al-Incorporated SnO2 Nanoparticles

NASA Astrophysics Data System (ADS)

Ahmed, Ateeq; Tripathi, P.; Naseem Siddique, M.; Ali, Tinku

2017-08-01

In this work, Pure SnO2 and Al doped SnO2 nanoparticles with the composition Sn1-xAlxO2 (x = 0, and 0.05) have been successfully prepared using sol-gel technique. The effect of Al dopant on microstructural, optical and dielectric properties has been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Ultraviolet (UV-Visible) absorption spectroscopy andImpedance spectroscopy (LCR meter)respectively. The XRD patterns indicated tetragonal rutile structure with single phase without any detectable impurity for all samples and incorporation of Al ions into the SnO2 lattice. Crystalline size decreased with aluminum content. The results of SEM confirm nanoparticles size decreases with Al dopant. UV-Visible results showed that optical band also decreases when Al is doped into pure SnO2 lattice. Frequency dependent dielectric properties of pure and doped SnO2 nanoparticles have been also studied.

X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates

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

Botez, Cristian E.; Martinez, Heber; Morris, Joshua L.

2017-08-01

Laboratory and synchrotron x-ray powder diffraction were used to investigate the structural modifications that occur upon indium doping of tin pyrophosphate. The data collected under air, vacuum, and inert gas sample environments at temperatures (T) from 50 °C to 300 °C show that regardless of the In-doping level (0 ≤ x ≤ 0.18) all InxSn1-xP2O7 samples are isomorphic (have the same P a -3 cubic crystal structure) at all temperatures and under all the conditions investigated. The cubic lattice parameter (a) increases linearly with T at all doping levels, but the “a vs. x|T“ isotherms exhibit a robust peak atmore » x = 0.1 when data are collected on samples measured in air. On the other hand, Rietveld refinements against data collected on InxSn1-xP2O7 samples yield values of OO bond lengths and POP bond angles that show no major changes at x = 0.1 at any temperature. This is significant, as the Sn0.9In0.1P2O7 (x = 0.1) compound is known to exhibit the highest proton conductivity within the series, but the microscopic details responsible for the increased proton conductivity are not understood. Finally, the peak observed in the “a vs. x|T“ curves vanishes if the measurements are taken on samples kept either under vacuum or in an inert gas environment. This is a remarkable behavior as it lends further support to our hypothesis that a key microscopic feature responsible for the large proton conductivity of the Sn0.9In0.1P2O7 compound is the enlargement of the lattice constant at x = 0.1.« less

Facile fabrication of a well-ordered porous Cu-doped SnO2 thin film for H2S sensing.

PubMed

Zhang, Shumin; Zhang, Pingping; Wang, Yun; Ma, Yanyun; Zhong, Jun; Sun, Xuhui

2014-09-10

Well-ordered Cu-doped and undoped SnO2 porous thin films with large specific surface areas have been fabricated on a desired substrate using a self-assembled soft template combined with simple physical cosputtering deposition. The Cu-doped SnO2 porous film gas sensor shows a significant enhancement in its sensing performance, including a high sensitivity, selectivity, and a fast response and recovery time. The sensitivity of the Cu-doped SnO2 porous sensor is 1 order of magnitude higher than that of the undoped SnO2 sensor, with average response and recovery times to 100 ppm of H2S of ∼ 10.1 and ∼ 42.4 s, respectively, at the optimal operating temperature of 180 °C. The well-defined porous sensors fabricated by the method also exhibit high reproducibility because of the accurately controlled fabrication process. The facile process can be easily extended to the fabrication of other semiconductor oxide gas sensors with easy doping and multilayer porous nanostructure for practical sensing applications.

Tuning optical properties of transparent conducting barium stannate by dimensional reduction

DOE PAGES

Li, Yuwei; Zhang, Lijun; Ma, Yanming; ...

2015-01-30

We report calculations of the electronic structure and optical properties of doped n-type perovskite BaSnO 3 and layered perovskites. While doped BaSnO 3 retains its transparency for energies below the valence to conduction band onset, the doped layered compounds exhibit below band edge optical conductivity due to transitions from the lowest conduction band. This gives absorption in the visible for Ba 2SnO 4. It is important to minimize this phase in transparent conducting oxide (TCO) films. Ba 3Sn 2O 7 and Ba 4Sn 3O 10 have strong transitions only in the red and infrared, respectively. Thus, there may be opportunitiesmore » for using these as wavelength filtering TCO.« less

Nitrogen anion doping as a strategy to suppress negative gate-bias illumination instability of ZnSnO thin film transistor

NASA Astrophysics Data System (ADS)

Li, Jun; Fu, Yi-Zhou; Huang, Chuan-Xin; Zhang, Jian-Hua; Jiang, Xue-Yin; Zhang, Zhi-Lin

2016-04-01

This work presents a strategy of nitrogen anion doping to suppress negative gate-bias illumination instability. The electrical performance and negative gate-bias illumination stability of the ZnSnON thin film transistors (TFTs) are investigated. Compared with ZnSnO-TFT, ZnSnON-TFT has a 53% decrease in the threshold voltage shift under negative bias illumination stress and electrical performance also progresses obviously. The stability improvement of ZnSnON-TFT is attributed to the reduction in ionized oxygen vacancy defects and the photodesorption of oxygen-related molecules. It suggests that anion doping can provide an effective solution to the adverse tradeoff between field effect mobility and negative bias illumination stability.

Selective Detection of Formaldehyde Gas Using a Cd-Doped TiO2-SnO2 Sensor

PubMed Central

Zeng, Wen; Liu, Tianmo; Wang, Zhongchang; Tsukimoto, Susumu; Saito, Mitsuhiro; Ikuhara, Yuichi

2009-01-01

We report the microstructure and gas-sensing properties of a nonequilibrium TiO2-SnO2 solid solution prepared by the sol-gel method. In particular, we focus on the effect of Cd doping on the sensing behavior of the TiO2-SnO2 sensor. Of all volatile organic compound gases examined, the sensor with Cd doping exhibits exclusive selectivity as well as high sensitivity to formaldehyde, a main harmful indoor gas. The key gas-sensing quantities, maximum sensitivity, optimal working temperature, and response and recovery time, are found to meet the basic industrial needs. This makes the Cd-doped TiO2-SnO2 composite a promising sensor material for detecting the formaldehyde gas. PMID:22291551

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

Lin, Tengda; Li, Xiuling; Jang, Jin, E-mail: jjang@khu.ac.kr

Major obstacles towards power efficient complementary electronics employing oxide thin-film transistors (TFTs) lie in the lack of equivalent well performing p-channel devices. Here, we report a significant performance enhancement of solution-processed p-type nickel oxide (NiO{sub x}) TFTs by introducing Sn dopant. The Sn-doped NiO{sub x} (Sn-NiO{sub x}) TFTs annealed at 280 °C demonstrate substantially improved electrical performances with the increase in the on/off current ratio (I{sub on}/I{sub off}) by ∼100 times, field-effect mobility (μ{sub lin}) by ∼3 times, and the decrease in subthreshold swing by half, comparing with those of pristine NiO{sub x} TFTs. X-ray photoelectron spectroscopy and X-ray diffraction resultsmore » confirm that Sn atoms tend to substitute Ni sites and induce more amorphous phase. A decrease in density of states in the gap of NiO{sub x} by Sn doping and the shift of Fermi level (E{sub F}) into the midgap lead to the improvements of TFT performances. As a result, Sn-NiO{sub x} can be a promising material for the next-generation, oxide-based electronics.« less

Analysis of SnS2 hyperdoped with V proposed as efficient absorber material.

PubMed

Seminovski, Yohanna; Palacios, Pablo; Wahnón, Perla

2014-10-01

Intermediate-band materials can improve the photovoltaic efficiency of solar cells through the absorption of two subband-gap photons that allow extra electron-hole pair formations. Previous theoretical and experimental findings support the proposal that the layered SnS2 compound, with a band-gap of around 2 eV, is a candidate for an intermediate-band material when it is doped with a specific transition-metal. In this work we characterize vanadium doped SnS2 using density functional theory at the dilution level experimentally found and including a dispersion correction combined with the site-occupancy-disorder method. In order to analyze the electronic characteristics that depend on geometry, two SnS2 polytypes partially substituted with vanadium in symmetry-adapted non-equivalent configurations were studied. In addition the magnetic configurations of vanadium in a SnS2 2H-polytype and its comparison with a 4H-polytype were also characterized. We demonstrate that a narrow intermediate-band is formed, when these dopant atoms are located in different layers. Our theoretical predictions confirm the recent experimental findings in which a paramagnetic intermediate-band material in a SnS2 2H-polytype with 10% vanadium concentration is obtained.

Electro-caloric effect in lead-free Sn doped BaTiO{sub 3} ceramics at room temperature and low applied fields

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

Upadhyay, Sanjay Kumar; Reddy, V. Raghavendra, E-mail: varimalla@yahoo.com, E-mail: vrreddy@csr.res.in; Bag, Pallab

2014-09-15

Structural, dielectric, ferroelectric (FE), {sup 119}Sn Mössbauer, and specific heat measurements of polycrystalline BaTi{sub 1–x}Sn{sub x}O{sub 3} (x = 0% to 15%) ceramics are reported. Phase purity and homogeneous phase formation with Sn doping is confirmed from x-ray diffraction and {sup 119}Sn Mössbauer measurements. With Sn doping, the microstructure is found to change significantly. Better ferroelectric properties at room temperature, i.e., increased remnant polarization (38% more) and very low field switchability (225% less) are observed for x = 5% sample as compared to other samples and the results are explained in terms of grain size effects. With Sn doping, merging of all the phasemore » transitions into a single one is observed for x ≥ 10% and for x = 5%, the tetragonal to orthorhombic transition temperature is found close to room temperature. As a consequence better electro-caloric effects are observed for x = 5% sample and therefore is expected to satisfy the requirements for non-toxic, low energy (field) and room temperature based applications.« less

Influence of Sn doping on structural, optical and electrical properties of ZnO thin films prepared by cost effective sol-gel process.

PubMed

Vishwas, M; Narasimha Rao, K; Arjuna Gowda, K V; Chakradhar, R P S

2012-09-01

Tin (Sn) doped zinc oxide (ZnO) thin films were synthesized by sol-gel spin coating method using zinc acetate di-hydrate and tin chloride di-hydrate as the precursor materials. The films were deposited on glass and silicon substrates and annealed at different temperatures in air ambient. The agglomeration of grains was observed by the addition of Sn in ZnO film with an average grain size of 60 nm. The optical properties of the films were studied using UV-VIS-NIR spectrophotometer. The optical band gap energies were estimated at different concentrations of Sn. The MOS capacitors were fabricated using Sn doped ZnO films. The capacitance-voltage (C-V), dissipation vs. voltage (D-V) and current-voltage (I-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated. The porosity and surface area of the films were increased with the doping of Sn which makes these films suitable for opto-electronic applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Sb:SnO2 thin films-synthesis and characterization

NASA Astrophysics Data System (ADS)

Bhadrapriya B., C.; Varghese, Anitta Rose; Amarendra, G.; Hussain, Shamima

2018-04-01

Transparent thin films of antimony doped SnO2 have been synthesized and characterized using optical spectroscopy, XRD, RAMAN and FESEM. The band gap of Sb doped tin oxide thin film samples were found to vary from 3.26 eV to 3.7 eV. The XRD peaks showed prominent rutile SnO2 peaks with diminished intensity due to antimony doping. A wide band in the range 550-580 cm-1 was observed in raman spectra and is a feature of nano-sized SnO2. SEM images showed flower-like structures on thin film surface, a characteristic feature of antimony.

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

Tarantini, C.; Sung, Z. -H.; Lee, P. J.

Nb 3Sn wires are now very close to their final optimization but despite its classical nature, detailed understanding of the role of Ta and Ti doping in the A15 is not fully understood. Long thought to be essentially equivalent in their influence on H c2, they were interchangeably applied. Here we show that Ti produces significantly more homogeneous chemical and superconducting properties. Despite Ta-doped samples having a slightly higher T c onset in zero-field, they always have a wider Tc-distribution. In particular, whereas the Ta-doped A15 has a T c-distribution extending from 18 down to 5-6 K (the lowest expectedmore » Tc for the binary A15 phase), the Ti-doped samples have no A15 phase with T c below ~12 K. The much narrower T c distribution in the Ti-doped samples has a positive effect on their in-field T c-distribution too, leading to an extrapolated μ0H c2(0) 2 Tesla larger than the Ta-doped one. Ti-doping also appears to be very homogeneous even when the Sn content is reduced in order to inhibit breakdown of the diffusion barriers in very high Jc conductors. As a result, the enhanced homogeneity of the Ti-doped samples appears to result from its assistance of rapid diffusion of Sn into the filaments and by its incorporation into the A15 phase interchangeably with Sn on the Sn sites of the A15 phase.« less

Mg2Sn heterostructures on Si(111) substrate

NASA Astrophysics Data System (ADS)

Dózsa, L.; Galkin, N. G.; Pécz, B.; Osváth, Z.; Zolnai, Zs.; Németh, A.; Galkin, K. N.; Chernev, I. M.; Dotsenko, S. A.

2017-05-01

Thin un-doped and Al doped polycrystalline Mg-stannide films consisting mainly of Mg2Sn semiconductor phase have been grown by deposition of Sn-Mg multilayers on Si(111) p-type wafers at room temperature and annealing at 150 °C. Rutherford backscattering measurement spectroscopy (RBS) were used to determine the amount of Mg and Sn in the structures. Raman spectroscopy has shown the layers contain Mg2Sn phase. Cross sectional transmission electron microscopy (XTEM) measurements have identified Mg2Sn nanocrystallites in hexagonal and cubic phases without epitaxial orientation with respect to the Si(111) substrate. Significant oxygen concentration was found in the layer both by RBS and TEM. The electrical measurements have shown laterally homogeneous conductivity in the grown layer. The undoped Mg2Sn layers show increasing resistivity with increasing temperature indicating the scattering process dominates the resistance of the layers, i.e. large concentration of point defects was generated in the layer during the growth process. The Al doped layer shows increase of the resistance at low temperature caused by freeze out of free carriers in the Al doped Mg2Sn layer. The measurements indicate the necessity of protective layer grown over the Mg2Sn layers, and a short time delay between sample preparation and cross sectionalTEM analysis, since the unprotected layer is degraded by the interaction with the ambient.

Synthesis, Characterization and Photocatalytic Activity of Ag+ - and Sn2+ -Doped KTi0.5 Te1.5 O6.

PubMed

Guje, Ravinder; Gundeboina, Ravi; Reddy, Jitta Raju; Veldurthi, Naveen Kumar; Kurra, Sreenu; Vithal, Muga

2016-03-01

In this study, the photocatalytic dye degradation efficiency of KTi 0.5 Te 1.5 O 6 synthesized through solid-state method was enhanced by cation (Ag + /Sn +2 ) doping at potassium site via ion exchange method. As prepared materials were characterized by XRD, SEM-EDS, IR, TGA and UV-Vis Diffuse reflectance spectroscopic (DRS) techniques. All the compounds were crystallized in cubic lattice with Fd3¯m space group. The bandgap energies of parent, Ag + - and Sn +2 -doped KTi 0.5 Te 1.5 O 6 materials obtained from DRS profiles were found to be 2.96, 2.55 and 2.40 eV, respectively. Photocatalytic efficiency of parent, Ag + - and Sn +2 -doped materials was evaluated against the degradation of methylene blue (MB) and methyl violet (MV) dyes under visible light irradiation. The Sn +2 -doped KTi 0.5 Te 1.5 O 6 showed higher activity toward the degradation of both MB and MV dyes and its higher activity is ascribed to the lower bandgap energy compared to the parent and Ag + -doped KTi 0.5 Te 1.5 O 6 . The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of Sn 2+ -doped KTi 0.5 Te 1.5 O 6 . Quenching experiments were performed to know the participation of holes, super oxide and hydroxyl radicals in the dye degradation process. The stability and reusability of the catalysts were studied. © 2015 The American Society of Photobiology.

Structural and magnetic properties of Ni-doped SnO{sub 2}

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

Dwivedi, Sonam, E-mail: vdinesh33@rediffmail.com, E-mail: sonam.dwivedi88@gmail.com; Kumar, Ashwini; Dar, Mashkoor A.

2015-06-24

Samples of Ni doped SnO{sub 2} nanocrystalline were successfully prepared by chemical co-precipitation method. X-ray diffraction pattern infers that Sn{sub 1-x}Ni{sub x}O{sub 2} (x=0.00, 0.10, 0.15 and 0.20) samples are in single phase with tetragonal structure (P4{sub 2}/mnm). Raman spectroscopy reveals the observed phonon modes of SnO{sub 2} are at about 387-397, and 559 - 572 cm{sup −1}. For Sn{sub 0.9}Ni{sub 0.1}O{sub 2}, these peaks are shifted to higher wave numbers, while to that for Sn{sub 0.85}Ni{sub 0.15}O{sub 2} and Sn{sub 0.8}Ni{sub 0.2}O{sub 2}, peaks are shifted to the lower wave numbers. The frequency dependent dielectric constant decreases with the increasemore » in the frequency and becomes constant at high frequencies for all compositions of Ni substituted SnO{sub 2}. The magnetization curve confirms the paramagnetic nature of all Ni doped SnO{sub 2} samples.« less

Vacancy-induced brittle to ductile transition of W-M co-doped Al3Ti (M=Si, Ge, Sn and Pb).

PubMed

Zhu, Mingke; Wu, Ping; Li, Qiulin; Xu, Ben

2017-10-25

We investigated the effect of vacancy formation on brittle (D0 22 ) to ductile (L1 2 -like) transition in Al 3 Ti using DFT calculations. The well-known pseudogap on the density of states of Al 3 Ti migrates towards its Fermi level from far above, via a W - M co-doping strategy, where M is Si, Ge, Sn or Pb respectively. In particular, by a W - M co-doping the underline electronic structure of the pseudogap approaches an octahedral (L1 2 : t 2g , e g ) from the tetragonal (D0 22 : e g , b 2g , a 1g , b 1g ) crystal field. Our calculations demonstrated that (1) a W-doping is responsible for the close up of the energy gap between a 1g and b 1g so that they tend to merge into an e g symmetry, and (2) all M-doping lead to a narrower gap between e g and b 2g (moving towards a t 2g symmetry). Thus, a brittle to ductile transition in Al 3 Ti is possible by adopting this W - M co-doping strategy. We further recommend the use of W-Pb co-doped Al 3 Ti to replace the less anodic Al electrode in Al-battery, due to its improved ductility and high Al diffusivity. Finally this study opens a new field in physics to tailor mechanical properties by manipulating electron energy level(s) towards higher symmetry via vacancy optimization.

Colossal dielectric permittivity in (Al + Nb) co-doped rutile SnO2 ceramics with low loss at room temperature

NASA Astrophysics Data System (ADS)

Song, Yongli; Wang, Xianjie; Zhang, Xingquan; Qi, Xudong; Liu, Zhiguo; Zhang, Lingli; Zhang, Yu; Wang, Yang; Sui, Yu; Song, Bo

2016-10-01

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Al + Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 103) and low dielectric losses (0.015 < tan δ < 0.1) in a wide range of frequencies and at temperatures from 140 to 400 K. Al doping can effectively modulate the dielectric behavior by increasing the grain and grain boundary resistances. The large differences in the resistance and conductive activation energy of the grains and grain boundaries suggest that the CP in co-doped SnO2 ceramics can be attributed to the internal barrier layer capacitor effect.

Enhanced thermoelectric property of oxygen deficient nickel doped SnO2 for high temperature application

NASA Astrophysics Data System (ADS)

Paulson, Anju; Sabeer, N. A. Muhammad; Pradyumnan, P. P.

2018-04-01

Motivated by the detailed investigation on the thermoelectric performance of oxide materials our work concentrated on the influence of acceptor dopants and defect density in the lattice plane for the enhancement of thermoelectric power. The series of Sn1‑x Nix O2 (0.01 ≤ x ≤ 0.05) compositions were prepared by solid state reaction mechanism and found that 3 atomic percentage Ni doped SnO2 can be considered as a good candidate due to its promising electrical and transport properties. Defect lattices were introduced in the sample and the deviation from oxygen stochiometry was ensured using photoluminescence measurement. High power factor was obtained for the 3 atomic percentage nickel doped SnO2 due to the effective number of charge carrier concentration and the depletion of oxygen rich layers. Defect centered and acceptor doped SnO2 lattice opens a new door for energy harvesting at higher temperatures.

Evaluation of high specific-heat ceramic for regenerator use at temperatures between 2-30 K

NASA Technical Reports Server (NTRS)

Lawless, W. N.

1979-01-01

Specific heat, thermal conductivity (both in the range 2-30 K), and microhardness data were measured on the ceramics labelled LS-8, LS-8A, and LS-8A doped with CsI, SnCl2, and AgCl. A work hardened sample of LS-8A was also studied in an effort to determine the feasibility of using these types of LS-8 materials to replace Pb spheres in the regenerator of the JPL cryocooler. The LS-8A materials are all more than an order of magnitude harder than Pb, and the dopants do not significantly improve the hardness. However, the SnCl2 dopant has a remarkable effect in improving the specific heat and thermal conductivity of LS-8A. The SnCl2 doping level which maximized the regenerator enthalpy change in going from an unloaded to a loaded condition was found to be 0.2 percent SnCl2 in LS-8A. It was also found that the enthalpy change for a regenerator employing the LS-8A material is more than three times larger than for the Pb spheres case. The use of rods, rather than spheres, of optimally doped LS-8A in regenerators is discussed.

Synthesis of SnO2versus Sn crystals within N-doped porous carbon nanofibers via electrospinning towards high-performance lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Hongkang; Lu, Xuan; Li, Longchao; Li, Beibei; Cao, Daxian; Wu, Qizhen; Li, Zhihui; Yang, Guang; Guo, Baolin; Niu, Chunming

2016-03-01

The design of tin-based anode materials (SnO2 or Sn) has become a major concern for lithium ion batteries (LIBs) owing to their different inherent characteristics. Herein, particulate SnO2 or Sn crystals coupled with porous N-doped carbon nanofibers (denoted as SnO2/PCNFs and Sn/PCNFs, respectively) are fabricated via the electrospinning method. The electrochemical behaviors of both SnO2/PCNFs and Sn/PCNFs are systematically investigated as anodes for LIBs. When coupled with porous carbon nanofibers, both SnO2 nanoparticles and Sn micro/nanoparticles display superior cycling and rate performances. SnO2/PCNFs and Sn/PCNFs deliver discharge capacities of 998 and 710 mA h g-1 after 140 cycles (at 100, 200, 500 and 1000 mA g-1 each for 10 cycles and then 100 cycles at 100 mA g-1), respectively. However, the Sn/PCNF electrodes show better cycling stability at higher current densities, delivering higher discharge capacities of 700 and 550 mA h g-1 than that of SnO2/PCNFs (685 and 424 mA h g-1) after 160 cycles at 200 and 500 mA g-1, respectively. The different superior electrochemical performance is attributed to the introduction of porous N-doped carbon nanofibers and their self-constructed networks, which, on the one hand, greatly decrease the charge-transfer resistance due to the high conductivity of N-doped carbon fibers; on the other hand, the porous carbon nanofibers with numerous voids and flexible one-dimensional (1D) structures efficiently alleviate the volume changes of SnO2 and Sn during the Li-Sn alloying-dealloying processes. Moreover, the discussion of the electrochemical behaviors of SnO2vs. Sn would provide new insights into the design of tin-based anode materials for practical applications, and the current strategy demonstrates great potential in the rational design of metallic tin-based anode materials.The design of tin-based anode materials (SnO2 or Sn) has become a major concern for lithium ion batteries (LIBs) owing to their different inherent characteristics. Herein, particulate SnO2 or Sn crystals coupled with porous N-doped carbon nanofibers (denoted as SnO2/PCNFs and Sn/PCNFs, respectively) are fabricated via the electrospinning method. The electrochemical behaviors of both SnO2/PCNFs and Sn/PCNFs are systematically investigated as anodes for LIBs. When coupled with porous carbon nanofibers, both SnO2 nanoparticles and Sn micro/nanoparticles display superior cycling and rate performances. SnO2/PCNFs and Sn/PCNFs deliver discharge capacities of 998 and 710 mA h g-1 after 140 cycles (at 100, 200, 500 and 1000 mA g-1 each for 10 cycles and then 100 cycles at 100 mA g-1), respectively. However, the Sn/PCNF electrodes show better cycling stability at higher current densities, delivering higher discharge capacities of 700 and 550 mA h g-1 than that of SnO2/PCNFs (685 and 424 mA h g-1) after 160 cycles at 200 and 500 mA g-1, respectively. The different superior electrochemical performance is attributed to the introduction of porous N-doped carbon nanofibers and their self-constructed networks, which, on the one hand, greatly decrease the charge-transfer resistance due to the high conductivity of N-doped carbon fibers; on the other hand, the porous carbon nanofibers with numerous voids and flexible one-dimensional (1D) structures efficiently alleviate the volume changes of SnO2 and Sn during the Li-Sn alloying-dealloying processes. Moreover, the discussion of the electrochemical behaviors of SnO2vs. Sn would provide new insights into the design of tin-based anode materials for practical applications, and the current strategy demonstrates great potential in the rational design of metallic tin-based anode materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09305h

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

NASA Astrophysics Data System (ADS)

Sinha, Sudip Kumar; Ghosh, Saptarshi

2016-10-01

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

Thermoelectric performance of co-doped SnTe with resonant levels

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

Zhou, Min; Han, Yemao; Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com

2016-07-25

Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n{sub H}) and extrinsic dopant concentration (N{sub I}, N{sub Ag}) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n{sub H}.more » Upon substituting extrinsic dopants beyond a certain amount, the n{sub H} changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials.« less

Oxidation of Sn doped Cu cluster: A first principle study

NASA Astrophysics Data System (ADS)

Parida, Ganesh; Majumder, Chiranjib

2017-05-01

Bimetallic clusters have immense potential to exhibit tunable properties in the emerging field of nano catalysis. Using plane wave based pseudopotential approach we have investigated the oxidation behavior of pure and Sn doped Cu13 clusters. The results showed significant modification of the cluster geometry upon interaction with oxygen molecule. The interaction of oxygen with Cu13, Cu12Sn1 and Cu11Sn2 clusters show dissociative chemisorption is more favorable than molecular adsorption. In addition, the adsorption energy is found to decrease with the increase in Sn concentration.

Qualitative and quantitative analysis of an additive element in metal oxide nanometer film using laser induced breakdown spectroscopy.

PubMed

Xiu, Junshan; Liu, Shiming; Sun, Meiling; Dong, Lili

2018-01-20

The photoelectric performance of metal ion-doped TiO 2 film will be improved with the changing of the compositions and concentrations of additive elements. In this work, the TiO 2 films doped with different Sn concentrations were obtained with the hydrothermal method. Qualitative and quantitative analysis of the Sn element in TiO 2 film was achieved with laser induced breakdown spectroscopy (LIBS) with the calibration curves plotted accordingly. The photoelectric characteristics of TiO 2 films doped with different Sn content were observed with UV visible absorption spectra and J-V curves. All results showed that Sn doping could improve the optical absorption to be red-shifted and advance the photoelectric properties of the TiO 2 films. We had obtained that when the concentration of Sn doping in TiO 2 films was 11.89  mmol/L, which was calculated by the LIBS calibration curves, the current density of the film was the largest, which indicated the best photoelectric performance. It indicated that LIBS was a potential and feasible measured method, which was applied to qualitative and quantitative analysis of the additive element in metal oxide nanometer film.

Alkaline earth metal doped tin oxide as a novel oxygen storage material

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

Dong, Qiang, E-mail: dong@tagen.tohoku.ac.jp; Yin, Shu; Yoshida, Mizuki

2015-09-15

Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tinmore » oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.« less

Thermoelectric Properties of Bi2Te2Se Compensated by Native Defects and Sn Doping

NASA Astrophysics Data System (ADS)

Fuccillo, M. K.; Jia, Shuang; Charles, M. E.; Cava, R. J.

2013-06-01

In Bi2Te2Se the defect chemistry involves native defects that compete such that they can either exchange dominance or else significantly compensate each other. Here we show how the net carrier concentration, n - p, which depends on the relative amounts of these defects and is readily obtained from Hall data, can be used as a fundamental materials parameter to describe the varied behavior of the thermoelectric properties as a function of compensation. We report the effects of tuning this parameter over multiple orders of magnitude by hole-doping the n-type material Bi2Te2Se0.995, which is already significantly compensated because of its Se deficiency. Crystals with different levels of hole doping were achieved by two separate approaches, namely by selecting pieces from different locations in an undoped crystal in which a systematic carrier concentration gradient had been induced by its growth conditions, and alternatively by doping with Sn for Bi. The thermoelectric power factors for Bi2- x Sn x Te2Se0.995 for x = 0, 0.002, 0.005, 0.010, and 0.040 are reported, and the dependence of the transport properties on the extent of compensation is discussed.

Probing cation and vacancy ordering in the dry and hydrated yttrium-substituted BaSnO3 perovskite by NMR spectroscopy and first principles calculations: implications for proton mobility.

PubMed

Buannic, Lucienne; Blanc, Frédéric; Middlemiss, Derek S; Grey, Clare P

2012-09-05

Hydrated BaSn(1-x)Y(x)O(3-x/2) is a protonic conductor that, unlike many other related perovskites, shows high conductivity even at high substitution levels. A joint multinuclear NMR spectroscopy and density functional theory (total energy and GIPAW NMR calculations) investigation of BaSn(1-x)Y(x)O(3-x/2) (0.10 ≤ x ≤ 0.50) was performed to investigate cation ordering and the location of the oxygen vacancies in the dry material. The DFT energetics show that Y doping on the Sn site is favored over doping on the Ba site. The (119)Sn chemical shifts are sensitive to the number of neighboring Sn and Y cations, an experimental observation that is supported by the GIPAW calculations and that allows clustering to be monitored: Y substitution on the Sn sublattice is close to random up to x = 0.20, while at higher substitution levels, Y-O-Y linkages are avoided, leading, at x = 0.50, to strict Y-O-Sn alternation of B-site cations. These results are confirmed by the absence of a "Y-O-Y" (17)O resonance and supported by the (17)O NMR shift calculations. Although resonances due to six-coordinate Y cations were observed by (89)Y NMR, the agreement between the experimental and calculated shifts was poor. Five-coordinate Sn and Y sites (i.e., sites next to the vacancy) were observed by (119)Sn and (89)Y NMR, respectively, these sites disappearing on hydration. More five-coordinated Sn than five-coordinated Y sites are seen, even at x = 0.50, which is ascribed to the presence of residual Sn-O-Sn defects in the cation-ordered material and their ability to accommodate O vacancies. High-temperature (119)Sn NMR reveals that the O ions are mobile above 400 °C, oxygen mobility being required to hydrate these materials. The high protonic mobility, even in the high Y-content materials, is ascribed to the Y-O-Sn cation ordering, which prevents proton trapping on the more basic Y-O-Y sites.

Trade-off between Zr Passivation and Sn Doping on Hematite Nanorod Photoanodes for Efficient Solar Water Oxidation: Effects of a ZrO2 Underlayer and FTO Deformation.

PubMed

Subramanian, Arunprabaharan; Annamalai, Alagappan; Lee, Hyun Hwi; Choi, Sun Hee; Ryu, Jungho; Park, Jung Hee; Jang, Jum Suk

2016-08-03

Herein we report the influence of a ZrO2 underlayer on the PEC (photoelectrochemical) behavior of hematite nanorod photoanodes for efficient solar water splitting. Particular attention was given to the cathodic shift in onset potential and photocurrent enhancement. Akaganite (β-FeOOH) nanorods were grown on ZrO2-coated FTO (fluorine-doped tin oxide) substrates. Sintering at 800 °C transformed akaganite to the hematite (α-Fe2O3) phase and induced Sn diffusion into the crystal structure of hematite nanorods from the FTO substrates and surface migration, shallow doping of Zr atoms from the ZrO2 underlayer. The ZrO2 underlayer-treated photoanode showed better water oxidation performance compared to the pristine (α-Fe2O3) photoanode. A cathodic shift in the onset potential and photocurrent enhancement was achieved by surface passivation and shallow doping of Zr from the ZrO2 underlayer, along with Sn doping from the FTO substrate to the crystal lattice of hematite nanorods. The Zr based hematite nanorod photoanode achieved 1 mA/cm(2) at 1.23 VRHE with a low turn-on voltage of 0.80 VRHE. Sn doping and Zr passivation, as well as shallow doping, were confirmed by XPS, Iph, and M-S plot analyses. Electrochemical impedance spectroscopy revealed that the presence of a ZrO2 underlayer decreased the deformation of FTO substrate, improved electron transfer at the hematite/FTO interface and increased charge-transfer resistance at the electrolyte/hematite interface. This is the first systematic investigation of the effects of Zr passivation, shallow doping, and Sn doping on hematite nanorod photoanodes through application of a ZrO2 underlayer on the FTO substrate.

Free-standing anode of N-doped carbon nanofibers containing SnO{sub x} for high-performance lithium batteries

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

Zou, Mingzhong; Li, Jiaxin, E-mail: ljx3012982@yahoo.com; Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002

2014-12-15

Highlights: • Self-standing SnO{sub x} N-CNF electrodes were synthesized by electrospinning. • The SnO{sub x} N-CNFs anode exhibits high capacity, good cyclic stability, and excellent rate performance for lithium ion batteries. • The enhanced performance is ascribed to the synergetic effects between N-CNFs and SnO{sub x} nanoparticles. - Abstract: Free-standing paper of N-doped carbon nanofibers (NCNFs) containing SnO{sub x} was prepared by electrospinning. The structure and morphology of the sample were analyzed by XRD, XPS, SEM, and TEM. The results show that nitrogen atoms were successfully doped into CNFs. The SnO{sub x} were homogenously embedded in the N-doped CNFs viamore » annealing treatment. Subsequently, the SnO{sub x} NCNF paper was cut into disks and used as anodes for lithium ion batteries (LIBs). The anodes of SnO{sub x} NCNFs exhibit excellent cycling stability and show high capacity of 520 mA h g{sup −1} tested at a 200 mA g{sup −1} after 100 cycles. More importantly, at a high current density of 500 mA g{sup −1}, a large reversible capacity of 430 mA h g{sup −1} after 100 cycles can still be obtained. The good electrochemical performance should be attributed to the good electronic conductivity from the NCNFs and the synergistic effects from NCNFs and SnO{sub x} materials.« less

Nanostructured SnSe: Synthesis, doping, and thermoelectric properties

NASA Astrophysics Data System (ADS)

Liu, Shuhao; Sun, Naikun; Liu, Mei; Sucharitakul, Sukrit; Gao, Xuan P. A.

2018-03-01

IV-VI monochalcogenide SnSe or SnS has recently been proposed as a promising two-dimensional (2D) material for valleytronics and thermoelectrics. We report the synthesis of SnSe nanoflakes and nanostructured thin films with chemical vapor deposition method and their thermoelectric properties. As grown SnSe nanostructures are found to be intrinsically p-type and the single SnSe nanoflake field effect transistor was fabricated. By Ag doping, the power factor of SnSe nanostructured thin films can be improved by up to one order of magnitude compared to the "intrinsic" as grown materials. Our work provides an initial step in the pursuit of IV-VI monochalcogenides as novel 2D semiconductors for electronics and thermoelectrics.

Thermoelectric properties of Sn doped BiCuSeO

NASA Astrophysics Data System (ADS)

Das, Sayan; Chetty, Raju; Wojciechowski, Krzysztof; Suwas, Satyam; Mallik, Ramesh Chandra

2017-10-01

BiCuSeO and Bi1-xSnxCuSeO (x = 0.02, 0.04, 0.06, 0.08) were prepared by a two-step solid state synthesis. The phase purity and the crystal structure were investigated by the X-Ray Diffraction (XRD) and confirmed by Energy Dispersive Spectroscopy (EDS). The volatilization of Bi and Bi2O3 lead to off-stoichiometry of the main phase and the formation of CuSe2 secondary phase in the undoped sample. SnO2 secondary phases were found in the doped samples. Both the Seebeck coefficient and the electrical resistivity, measured from the room temperature to 773 K linearly increases with the temperature, which indicates that the sample have metallic like behavior. The origin of such a behavior is due to high hole concentration originating from the Bi and the O vacancies. The Sn +4 valence state was confirmed from the X-Ray Photoelectron Spectroscopy (XPS) and from the reduction of lattice parameter 'a' with doping. The substitution of Sn+4 in the place of Bi+3 leads to the higher Seebeck coefficient and electrical resistivity in the doped samples. Highest power-factor (∼1 mW/m-K2 at 773 K), was obtained for the undoped sample and the 4% Sn doped sample (Bi0.96Sn0.04CuSeO). The lowest thermal conductivity was obtained for the undoped sample, from the room temperature to 773 K. The presence of thermally-conducting SnO2 secondary phases in the doped samples increases the thermal conductivity in comparison with the undoped sample. The zTs of the doped samples were lower compared to the undoped sample, owing to their higher thermal conductivity. The oxygen vacancies as well as the all-length scale phonon scattering, lowers the thermal conductivity of the undoped sample and, as a result, a maximum zT of 1.09 was achieved at 773 K.

Ethanol Sensitivity of Cu1-xSnxO (x = 0.00, 0.03, and 0.05) Nanoflakes

NASA Astrophysics Data System (ADS)

Mariammal, R. N.; Ramachandran, K.

2011-07-01

Cu1-xSnxO (x = 0.00, 0.03, and 0.05) nanoflakes were synthesized by a simple wet chemical method and X-Ray diffraction (XRD) result confirms the monoclinic structure of CuO with no secondary phases due to Sn doping. The scanning electron microscopic images indicate the formation of nanoflakes. The fundamental Raman modes were observed at 273, 318, 610, and 1084 cm-1 for undoped CuO sample and theses modes were slightly shifted towards lower frequency side for Sn-doped samples, which indicates the inclusion of Sn in CuO. In addition, XRD and Raman studies infer the decrease of crystallinity in doped samples, which is reflected in the sensitivity towards ethanol. The ethanol sensitivity (resistivity measurement) increases with ethanol gas concentration and decreases with Sn-doping in CuO nanoflakes.

Anatase phase stability and doping concentration dependent refractivity in codoped transparent conducting TiO2 films

NASA Astrophysics Data System (ADS)

Chen, T. L.; Furubayashi, Y.; Hirose, Y.; Hitosugi, T.; Shimada, T.; Hasegawa, T.

2007-10-01

Nb0.06SnxTi0.94-xO2 (x <= 0.3) thin films were grown by a pulsed-laser deposition method with varying Sn concentration. Through a combinatorial technique, we find that Sn concentration can reach a maximum of about x = 0.3 while maintaining the stable anatase phase and epitaxy. A doping concentration dependence of the refractivity is revealed, in which refractivity reduction at a wavelength of λ = 500 nm is estimated to be 12.4% for Nb0.06Sn0.3 Ti0.64O2 thin film. Sn doping induced band-gap blue shift can be contributed to the mixing of extended Sn 5s orbitals with the conduction band of TiO2. Low resistivity on the order of 10-4 Ω cm at room temperature and high internal transmittance of more than 95% in the visible light region are exhibited for Nb0.06Snx Ti0.94-xO2 thin films (x <= 0.2). Optical and transport analyses demonstrate that doping Sn into Nb0.06 Ti0.94O2 can reduce the refractivity while maintaining low resistivity and high transparency.

Segregation of chlorine in n-type tin monosulfide ceramics: Actual chlorine concentration for carrier-type conversion

NASA Astrophysics Data System (ADS)

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

2018-05-01

Tin monosulfide (SnS) is an attractive material for photovoltaic cells because of its suitable band-gap energy, high absorption coefficient, and non-toxic and abundant constituent elements. The primary drawback of this material is the lack of n-type SnS. We recently demonstrated n-type SnS by doping with Cl. However, the Cl-doped n-type SnS bulk ceramics exhibited an odd behavior in which carrier-type conversion but not electron carrier concentration depended on the Cl concentration. In this study, the electron probe microanalysis (EPMA) elemental mapping of Cl-doped SnS revealed continuous homogeneous regions with a relatively low Cl concentration along with the islands of high Cl concentration in which Sn/S is far from unity. The difference between the Cl concentration in the homogeneous region (determined by EPMA) and the bulk Cl concentration (determined by wavelength-dispersive X-ray fluorescence spectroscopy) increased with the increasing Cl doping amount. The carrier concentration and the Hall coefficient clearly depended on the Cl concentration in the homogeneous region. Carrier-type conversion was observed at the Cl concentration of 0.26 at. % (in the homogeneous region).

Refinement of the β-Sn Grains in Ni-Doped Sn-3.0Ag-0.5Cu Solder Joints with Cu-Based and Ni-Based Substrates

NASA Astrophysics Data System (ADS)

Chou, Tzu-Ting; Chen, Wei-Yu; Fleshman, Collin Jordon; Duh, Jenq-Gong

2018-03-01

A fine-grain structure with random orientations of lead-free solder joints was successfully obtained in this study. The Sn-Ag-Cu solder alloys doped with minor Ni were reflowed with Ni-based or Cu-based substrates to fabricate the joints containing different Ni content. Adding 0.1 wt.% Ni into the solder effectively promoted the formation of fine Sn grains, and reflowing with Ni-based substrates further enhanced the effects of β-Sn grain refinement. The crystallographic characteristics and the microstructures were analyzed to identify the solidification mechanism of different types of microstructure in the joints. The phase precipitating order in the joint altered as the solder composition were modified by elemental doping and changing substrate, which significantly affected the efficiency of grain refinement and the final grain structure. The formation mechanism of fine β-Sn grains in the Ni-doped joint with a Ni-based substrate is attributable to the heterogeneous nucleation by Ni, whereas the Ni in the joint using ChouCu-based substrate is consumed to form an intermetallic compound and thus retard the effect of grain refining.

Ferroelectricity of Sn-doped SrTiO3 perovskites with tin at both A and B sites

NASA Astrophysics Data System (ADS)

Suzuki, Shoichiro; Honda, Atsushi; Iwaji, Naoki; Higai, Shin'ichi; Ando, Akira; Takagi, Hiroshi; Kasatani, Hirofumi; Deguchi, Kiyoshi

2012-08-01

We successfully obtained Sn-doped SrTiO3 (SSTO) perovskites, and clarified their ferroelectricity and structural properties by using first-principles theoretical calculations. The ferroelectricity of SSTO was confirmed by the appearance of a dielectric permittivity maximum and a clear hysteresis loop of the relationship between the external electric field and the electric flux density below 180 K. X-ray diffraction and Raman spectra revealed the structural phase transition of SSTO at approximately 200 K. We directly observed by spherical aberration corrected scanning transmission electron microscopy with energy-dispersive x-ray spectroscopy that Sn ions are doped into both Sr and Ti sites (SnA and SnB), and that SnA is located at an off-centered position. We also performed theoretical analyses of SSTO and related perovskites, and found that SnA is preferentially located in an off-centered position and that SnA and the O6 octahedron, which includes SnB in its center, oscillate along the antiphase direction in the soft mode. Thus, we propose that the ferroelectricity of SSTO originates from the antiphase off-centering, which induces ferroelectric nanoregions in paraelectric SrTiO3.

Synthesis and Gas Sensing Properties of Single La-Doped SnO2 Nanobelts

PubMed Central

Wu, Yuemei; Zhang, Heng; Liu, Yingkai; Chen, Weiwu; Ma, Jiang; Li, Shuanghui; Qin, Zhaojun

2015-01-01

Single crystal SnO2 nanobelts (SnO2 NBs) and La-SnO2 nanobelts (La-SnO2 NBs) were synthesized by thermal evaporation. Both a single SnO2 NB sensor and a single La-SnO2 NB sensor were developed and their sensing properties were investigated. It is found that the single La-SnO2 NB sensor had a high sensitivity of 8.76 to ethanediol at a concentration of 100 ppm at 230 °C, which is the highest sensitivity of a single SnO2 NB to ethanediol among three kinds of volatile organic (VOC) liquids studied, including ethanediol, ethanol, and acetone. The La-SnO2 NBs sensor also exhibits a high sensitivity, good selectivity and long-term stability with prompt response time to ethanediol. The mechanism behind the enhanced sensing performance of La-doped SnO2 nanobelts is discussed. PMID:26087374

Metal-Organic Frameworks Derived Okra-like SnO2 Encapsulated in Nitrogen-Doped Graphene for Lithium Ion Battery.

PubMed

Zhou, Xiangyang; Chen, Sanmei; Yang, Juan; Bai, Tao; Ren, Yongpeng; Tian, Hangyu

2017-04-26

A facile process is developed to prepare SnO 2 -based composites through using metal-organic frameworks (MOFs) as precursors. The nitrogen-doped graphene wrapped okra-like SnO 2 composites (SnO 2 @N-RGO) are successfully synthesized for the first time by using Sn-based metal-organic frameworks (Sn-MOF) as precursors. When utilized as an anode material for lithium-ion batteries, the SnO 2 @N-RGO composites possess a remarkably superior reversible capacity of 1041 mA h g -1 at a constant current of 200 mA g -1 after 180 charge-discharge processes and excellent rate capability. The excellent performance can be primarily ascribed to the unique structure of 1D okra-like SnO 2 in SnO 2 @N-RGO which are actually composed of a great number of SnO 2 primary crystallites and numerous well-defined internal voids, can effectively alleviate the huge volume change of SnO 2 , and facilitate the transport and storage of lithium ions. Besides, the structural stability acquires further improvement when the okra-like SnO 2 are wrapped by N-doped graphene. Similarly, this synthetic strategy can be employed to synthesize other high-capacity metal-oxide-based composites starting from various metal-organic frameworks, exhibiting promising application in novel electrode material field of lithium-ion batteries.

Enhanced electron mobility at the two-dimensional metallic surface of BaSnO3 electric-double-layer transistor at low temperatures

NASA Astrophysics Data System (ADS)

Fujiwara, Kohei; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi

2017-05-01

Wide-bandgap oxides exhibiting high electron mobility hold promise for the development of useful electronic and optoelectronic devices as well as for basic research on two-dimensional electron transport phenomena. A perovskite-type tin oxide, BaSnO3, is currently one of such targets owing to distinctly high mobility at room temperature. The challenge to overcome towards the use of BaSnO3 thin films in applications is suppression of dislocation scattering, which is one of the dominant scattering origins for electron transport. Here, we show that the mobility of the BaSnO3 electric-double-layer transistor reaches 300 cm2 V-1 s-1 at 50 K. The improved mobility indicates that charged dislocation scattering is effectively screened by electrostatically doped high-density charge carriers. We also observed metallic conduction persisting down to 2 K, which is attributed to the transition to the degenerate semiconductor. The experimental verification of bulk-level mobility at the densely accumulated surface sheds more light on the importance of suppression of dislocation scattering by interface engineering in doped BaSnO3 thin films for transparent electrode applications.

Structural, morphological and gas sensing study of zinc doped tin oxide nanoparticles synthesized via hydrothermal technique

NASA Astrophysics Data System (ADS)

Singh, Davender; Kundu, Virender Singh; Maan, A. S.

2016-07-01

The pure and Zn-doped SnO2 nanoparticles were prepared successfully by hydrothermal route on large scale having different doping concentration of zinc from 0 to 0.20%. The calcined nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) for structural and morphological studies. XRD analyses reveal that the nanoparticles of these doping concentrations are polycrystalline in nature and existed as tetragonal rutile structure, SEM study of images confirms the existence of very small, homogeneously distributed, and spherical nanoparticles. The particles size of the nanoparticles was calculated by Scherrer formula and was found in the range of 9-21 nm. The presence of dopant (i.e. zinc) and formation of Sn-O phase and hydrous nature of Zn-doped SnO2 nanoparticles are confirmed by EDX and FTIR study. The gas sensing properties of pure and Zn-doped SnO2 nanoparticles were investigated for various concentrations of methanol, ethanol and acetone at different operating temperatures and it has been found that with doping concentration of zinc (x = 0.20%) shows the maximum response 78% to methanol, 65% to ethanol and 62% to acetone respectively at different operating temperature within the measurement limit for a concentration of 100 ppm of each gases.

Growth and Characterization of Sn Doped β-Ga2O3 Thin Films and Enhanced Performance in a Solar-Blind Photodetector

NASA Astrophysics Data System (ADS)

Zhao, Xiaolong; Cui, Wei; Wu, Zhenping; Guo, Daoyou; Li, Peigang; An, Yuehua; Li, Linghong; Tang, Weihua

2017-04-01

Ga2- x Sn x O3 thin films were deposited on c-plane Al2O3 (0001) substrates with different Sn content by laser molecular beam epitaxy technology (L-MBE). The Sn content x was varied from 0 to 1.0. (bar{2}01) oriented β-phase Ga2- x Sn x O3 thin films were obtained at the substrate temperature of 850°C in the vacuum pressure of 5 × 10-5 Pa. The crystal lattice expanded and the energy band-gap decreased with the increase of Sn content for Sn4+ ions incorporated into the Ga site. The n-type conductivity was generated effectively through doping Sn4+ ions in the Ga2O3 lattice in the oxygen-poor conditions. The solar-blind (SB) photodetectors (PDs) based on Ga2- x Sn x O3 ( x = 0, 0.2) thin films were fabricated. The current intensity and responsivity almost increased by one order of magnitude and the relaxation time constants became shorter for x = 0.2. Our work suggests that the performance of PD can be improved by doping Sn4+ ions in Ga2O3 thin films.

A comparative study of the magnetization in transition metal ion doped CeO2, TiO2 and SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

2018-05-01

Using the microscopic s-d model taking into account anharmonic spin-phonon interactions we have studied the magnetic properties of Co and Cu ion doped CeO2 and TiO2 nanoparticles and compared them with those of SnO2. By Co-doping there is a maximum in the magnetization M(x) curve for all nanoparticles observed in the most transition metal doped ones. The s-d interaction plays an important role by the decrease of M at higher dopant concentration. We have discussed the magnetization in dependence of different model parameters. By small Cu-ion doping there are some differences. In CeO2M decreases with the Cu-concentration, whereas in TiO2 and SnO2M increases. For higher Cu dopant concentrations M(X) decreases in TiO2 nanoparticles. We obtain room temperature ferromagnetism also in Zn doped CeO2, TiO2 and SnO2 nanoparticles, i.e. in non-transition metal ion doped ones. The different behavior of M in Co and Cu doped nanoparticles is due to a combination effect of multivalent metal ions, oxygen vacancies, different radius of cation dopants, connection between lattice and magnetism, as well as competition between the s-d and d-d ferromagnetic or antiferromagnetic interactions.

Selection Rule of Preferred Doping Site for n-Type Oxides

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

Li, C.; Li, J.; Li, S. S.

2012-06-25

Using first-principles calculations and analysis, we show that to create shallow n-type dopants in oxides, anion site doping is preferred for more covalent oxides such as SnO{sub 2} and cation site doping is preferred for more ionic oxides such as ZnO. This is because for more ionic oxides, the conduction band minimum (CBM) state actually contains a considerable amount of O 3s orbitals, thus anion site doping can cause large perturbation on the CBM and consequently produces deeper donor levels. We also show that whether it is cation site doping or anion site doping, the oxygen-poor condition should always bemore » used.« less

Magnetic phase change in Mn-doped ZnSnAs2 thin films depending on Mn concentration

NASA Astrophysics Data System (ADS)

Uchitomi, Naotaka; Hidaka, Shiro; Saito, Shin; Asubar, Joel T.; Toyota, Hideyuki

2018-04-01

The relationship between Mn concentration and Curie temperature (TC) is studied for Mn-doped ZnSnAs2 ferromagnetic semiconductors, epitaxially grown on InP substrates by molecular beam epitaxy. In the ferromagnetic phase, Mn distributions in a (Zn,Mn,Sn)As2 thin film with 7.2 cation percent (cat. %) Mn are investigated using three-dimensional atom probe tomography. The results indicate an inhomogeneous distribution which spreads to a relatively high Mn concentration of 9.0 at. % (at. %). In the paramagnetic phase, it is found that the paramagnetic to ferromagnetic transition takes place sharply with a TC of 334 K when the Mn doping concentration increases to about 4 cat. % Mn, which corresponds to a magnetic percolation threshold for ferromagnetism in (Zn,Mn,Sn)As2. An effective Curie temperature ⟨TC⟩ is considered to bridge the Curie temperatures obtained experimentally to those calculated theoretically in inhomogeneous magnetic semiconductors. The behavior of magnetism in Mn-doped ZnSnAs2 can be explained by three different phases within the present framework.

High-performance tin oxide-nitrogen doped graphene aerogel hybrids as anode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Tan, Chunhui; Cao, Jing; Khattak, Abdul Muqsit; Cai, Feipeng; Jiang, Bo; Yang, Gai; Hu, Suqin

2014-12-01

Tin dioxide nanoparticles on nitrogen doped graphene aerogel (SnO2-NGA) hybrid are synthesized by one-step hydrothermal method and successfully applied in lithium-ion batteries as a free-standing anode. The electrochemical performance of SnO2-NGA hybrid is investigated by galvanostatic charge-discharge cycling, rate capability test, cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the SnO2-NGA hybrid with freestanding spongy-like structure exhibit remarkable lithium storage capacity (1100 mAh g-1 after 100 cycles), good cycling stability and high rate capability. The outstanding performance is attributed to the uniform SnO2 nanoparticles, unique spongy-like structure and N doping defect for Li+ diffusion.

Origins of n -type doping difficulties in perovskite stannates

NASA Astrophysics Data System (ADS)

Weston, L.; Bjaalie, L.; Krishnaswamy, K.; Van de Walle, C. G.

2018-02-01

The perovskite stannates (A SnO3 ; A = Ba, Sr, Ca) are promising for oxide electronics, but control of n -type doping has proved challenging. Using first-principles hybrid density functional calculations, we investigate La dopants and explore the formation of compensating acceptor defects. We find that La on the A site always behaves as a shallow donor, but incorporation of La on the Sn site can lead to self-compensation. At low La concentrations and in O-poor conditions, oxygen vacancies form in BaSnO3. A -site cation vacancies are found to be dominant among the native compensating centers. Compared to BaSnO3, charge compensation is a larger problem for the wider-band-gap stannates, SrSnO3 and CaSnO3, a trend we can explain based on conduction-band alignments. The formation of compensating acceptor defects can be inhibited by choosing oxygen-poor (cation-rich) growth or annealing conditions, thus providing a pathway for improved n -type doping.

The role of Tin Oxide Concentration on The X-ray Diffraction, Morphology and Optical Properties of In2O3:SnO2 Thin Films

NASA Astrophysics Data System (ADS)

Hasan, Bushra A.; Abdallah, Rusul M.

2018-05-01

Alloys were performed from In2O3 doped SnO2 with different doping ratio by quenching from the melt technique. Pulsed Laser Deposition PLD was used to deposit thin films of different doping ratio In2O3 : SnO2 (0, 1, 3, 5, 7 and 9 % wt.) on glass substrate at ambient temperature under vacuum of 10-3 bar thickness of ∼100nm. The structural type,grain size and morphology of the prepared alloys compounds and thin films were examined using X-ray diffraction and atomic force microscopy. The results showed that all alloys have polycrystalline structures and the peaks belonged to the preferred plane for crystal growth were identical with the ITO (Indium – Tin –Oxide) standard cards also another peaks were observed belonged to SnO2 phase. The structures of thin films was also polycrystalline, and the predominate peaks are identical with standard cards ITO. On the other side the prepared thin films declared decrease a reduction of degree of crystallinity with the increase of doping ratio. Atomic Force Microscopy AFM measurements showed the average grain size and average surface roughness exhibit to change in systematic manner with the increase of doping ratio with tin oxide. The optical measurements show that the In2O3:SnO2 thin films have a direct energy gap Eg opt in the first stage decreases with the increase of doping ratio and then get to increase with further increase of doping ration, whereas reverse to that the optical constants such as refractive index (n), extinction coefficient (k) and dielectric constant (εr, εi) have a regular increase with the doping ratio by tin oxide and then decreases.

Iron doped SnO2/Co3O4 nanocomposites synthesized by sol-gel and precipitation method for metronidazole antibiotic degradation.

PubMed

Agarwal, Shilpi; Tyagi, Inderjeet; Gupta, Vinod Kumar; Sohrabi, Maryam; Mohammadi, Sanaz; Golikand, Ahmad Nozad; Fakhri, Ali

2017-01-01

Sol-gel and precipitation reaction methods were used to synthesize Un-doped and Fe-doped SnO 2 /Co 3 O 4 nanocomposites under UV light; the synthesized nanocomposites were applied for the photocatalytic degradation of metronidazole antibiotic. The developed photo catalyst was well characterized using energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FE-SEM), UV-Visible and photoluminescence (PL) spectroscopy. Effective parameters such as pH, photocatalyst dose and contact time was optimized and well investigated. From the obtained facts it is clear that the 98.3% of MTZ was degraded with in 15min, pH6 and 0.1g catalyst when the Fe molar ratio was 1:1 at %. As compared to results obtained from un-doped SnO 2 /Co 3 O 4 nanocomposites Fe doped SnO 2 /Co 3 O 4 nanocomposites possess greater photocatalytic efficiency. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation and Characterization of Nanosized Bi-Doped SnO₂/Reduced Graphene Oxide 3D Hybrids for Visible-Light-Driven Photocatalysis.

PubMed

Wu, Xiang-Feng; Zhang, Chen-Xu; Sun, Yang; Fu, Shi-Da; Li, Hui; Wang, Yi-Jin; Zhang, Jia-Rui; Su, Jun-Zhang; Wang, Yi-Wei; Wang, Kai-Yuan

2018-07-01

The nanosized Bi-doped SnO2/reduced graphene oxide 3D hybrids have been synthesized via one-step hydrothermal method. The structures, morphologies, photocatalytic activities of the as-prepared samples were discussed, respectively. The formation mechanism of the as-prepared hybrids was also proposed. Experimental results indicated that the usage amount of Bi2Sn2O7 obviously affected the photocatalytic performance of the as-prepared products. When it was 450 mg, the as-prepared sample possessed the band gap energy of 1.9 eV and the photocatalytic efficiency of 90% in 210 min for degradation of rhodamine B solution. In addition, triethylene tetramine and the as-prepared carbon hydrogel could act as reductant to synergistically reduce Bi2Sn2O7 into Bi-doped SnO2 particles during the formation of the hybrids.

Specific heat and magnetic susceptibility of CeNiSn doped with Rh.

PubMed

Slebarski, A; Maple, M B; Fijałkowski, M; Goraus, J

2010-04-28

CeNiSn is known as a semimetallic system with a small pseudogap at the Fermi energy. We investigate the effect of Rh doping on the Kondo insulator CeNiSn by means of measurements of ac magnetic susceptibility and specific heat. We show that the formation of the Kondo insulator narrow gap in CeNi(1 - x)Rh(x)Sn is associated with disorder-induced f-electron localization. For doped CeNiSn with x ≤ 0.06, the electrical resistivity data follow an activation and variable range hopping behaviour at low T, consistent with weak disorder and localization, while C/T is large, which is not a common feature of Kondo insulators. For x > 0.06, the system is metallic and exhibits non-Fermi liquid behaviour with magnetic susceptibility χ ∼ T( - n) with n ∼ 0.4 and electrical resistivity ρ ∼ T.

Defect physics in intermediate-band materials: Insights from an optimized hybrid functional

NASA Astrophysics Data System (ADS)

Han, Miaomiao; Zeng, Zhi; Frauenheim, Thomas; Deák, Peter

2017-10-01

Despite the efforts to implement the idea of a deep level impurity intermediate band (IB) into bulk solar cell materials, a breakthrough in efficiency increase has not yet been achieved. Taking Sn-doped CuGaS2 as an example, we investigate the problem here from the perspective of defect physics, considering all possible charge states of the dopant and its interaction with native defects. Using an optimized hybrid functional, we find that SnGa has not only a donor-type (+/0), but also an acceptor-type (0 /- ) charge transition level. We estimate the probability of the optical transition of an electron from/to the neutral defect to/from the conduction-band edge to be about equal, therefore, the lifetimes of the excited carriers are probably quite short, limiting the enhancement of the photocurrent. In addition, we find that doping with SnGa leads to the spontaneous formation of the intrinsic acceptor CuGa defects which passivate the donor SnGa and pin the Fermi level to a position (1.4 eV above the valence-band edge) where both defects are ionized. As a result, the possibility of absorption in the middle of the visible range gets lost. These two recombination and passivation mechanisms appear to be quite likely the case for other donors and other similar host materials as well, explaining some of the experimental bottlenecks with IB solar cells based on deep level impurities.

Preparation and electrical properties of electrospun tin-doped indium oxide nanowires

NASA Astrophysics Data System (ADS)

Lin, Dandan; Wu, Hui; Zhang, Rui; Pan, Wei

2007-11-01

Well-aligned tin-doped indium (ITO) nanowires have been prepared using the electrospinning process. The Sn doping mechanism and microstructure have been characterized by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Devices for I-V measurement and field-effect transistors (FETs) were assembled using ITO nanowires with top contact configurations. The effect of Sn doping on the electrical conductivity was significant in that it enhanced the conductance by over 107 times, up to ~1 S cm-1 for ITO nanowires with an Sn content of 17.5 at.%. The nanowire FETs were operated in the depletion mode with an electron mobility of up to 0.45 cm2 V-1 s-1 and an on/off ratio of 103.

Growth of SnO2 Nanoflowers on N-doped Carbon Nanofibers as Anode for Li- and Na-ion Batteries

NASA Astrophysics Data System (ADS)

Liang, Jiaojiao; Yuan, Chaochun; Li, Huanhuan; Fan, Kai; Wei, Zengxi; Sun, Hanqi; Ma, Jianmin

2018-06-01

It is urgent to solve the problems of the dramatic volume expansion and pulverization of SnO2 anodes during cycling process in battery systems. To address this issue, we design a hybrid structure of N-doped carbon fibers@SnO2 nanoflowers (NC@SnO2) to overcome it in this work. The hybrid NC@SnO2 is synthesized through the hydrothermal growth of SnO2 nanoflowers on the surface of N-doped carbon fibers obtained by electrospinning. The NC is introduced not only to provide a support framework in guiding the growth of the SnO2 nanoflowers and prevent the flower-like structures from agglomeration, but also serve as a conductive network to accelerate electronic transmission along one-dimensional structure effectively. When the hybrid NC@SnO2 was served as anode, it exhibits a high discharge capacity of 750 mAh g-1 at 1 A g-1 after 100 cycles in Li-ion battery and 270 mAh g-1 at 100 mA g-1 for 100 cycles in Na-ion battery, respectively.[Figure not available: see fulltext.

Long range superhyperfine interactions in polycrystalline vanadium doped SnO 2 investigated by CW and pulsed ENDOR spectroscopy

NASA Astrophysics Data System (ADS)

Murphy, Damien M.; Farley, Robert D.; Marshall, Joanne; Willock, David J.

2004-06-01

CW and pulsed ENDOR was used to probe the electron nuclear superhyperfine interactions between V 4+ ions and distant Sn nuclei in vanadium doped tin oxide (V/SnO 2). Whilst interactions with two sets of nearest neighbour Sn nuclei (with a V-Sn distance of 3.185 and 3.708 Å respectively) are observed by EPR, superhyperfine couplings to two remote sets of tins (with a V-Sn distance of 6.370 and ˜7.42 Å) are detected by ENDOR. The interaction was found to be largely isotropic and largest along the crystal c axis. Small differences in the remote tin environments were also detected by ENDOR.

The effect of electron and hole doping on the thermoelectric properties of shandite-type Co3Sn2S2

NASA Astrophysics Data System (ADS)

Mangelis, Panagiotis; Vaqueiro, Paz; Jumas, Jean-Claude; da Silva, Ivan; Smith, Ronald I.; Powell, Anthony V.

2017-07-01

Electron and hole doping in Co3Sn2S2, through chemical substitution of cobalt by the neighbouring elements, nickel and iron, affects both the structure and thermoelectric properties. Electron doping to form Co3-xNixSn2S2 (0≤x≤3) results in an expansion of the kagome layer and materials become increasingly metallic as cobalt is substituted. Conversely, hole doping in Co3-xFexSn2S2 (0≤x≤0.6) leads to a transition from metallic to n-type semiconducting behaviour at x=0.5. Iron substitution induces a small increase in the separation between the kagome layers and improves the thermoelectric performance. Neutron diffraction data reveal that substitution occurs at the Co 9(d) site in a disordered fashion. Mössbauer spectroscopy reveals two iron environments with very different isomer shifts, which may be indicative of a mixed-valence state, while Sn exhibits an oxidation state close to zero in both series. Co2.6Fe0.4Sn2S2 exhibits a maximum figure-of-merit, ZT=0.2 at 523 K while Co2.4Fe0.6Sn2S2 reaches a power factor of 10.3 μW cm-1 K-2 close to room temperature.

Microstructural analysis and thermoelectric properties of Sn-Al co-doped ZnO ceramics

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

Hoemke, Joshua, E-mail: jhoemke@sigma.t.u-tokyo.ac.jp; Tochigi, Eita; Shibata, Naoya

2016-08-26

Sn-Al co-doped polycrystalline ZnO ceramics were prepared by sintering in air. Phase and microstructure analysis was performed by X-ray diffraction and SEM-EDS and thermoelectric properties were measured. XRD analysis showed a ZnO primary phase as well as secondary phase peaks due to the formation of a Zn{sub 2}SnO{sub 4} spinel phase or SnO{sub 2}(ZnO:Sn-Al){sub m} intergrowth phase. SEM analysis revealed a dense microstructure with a small number of nanometric pores, consistent with the measured density of 5.48 g/cm{sup 3}. An activated electrical conductivity characteristic of a semiconducting material was observed as well as a negative Seebeck coefficient with both valuesmore » increasing in absolute value from RT to 730 °C. The power factor had a maximum value of 3.73×10{sup −4} W m{sup −1} K{sup −2} at 730 °C. Thermal conductivity measurements showed a significant reduction over the measured temperature range compared to undoped ZnO. This could be attributed to grain size reduction, the formation of a nanoscale secondary phase or a reduction in crystallinity caused by Sn-Al co-doping. A maximum ZT of 0.06 was obtained at 750 °C for the Sn-Al co-doped ZnO ceramics.« less

Band offset and electron affinity of MBE-grown SnSe2

NASA Astrophysics Data System (ADS)

Zhang, Qin; Li, Mingda Oscar; Lochocki, Edward B.; Vishwanath, Suresh; Liu, Xinyu; Yan, Rusen; Lien, Huai-Hsun; Dobrowolska, Malgorzata; Furdyna, Jacek; Shen, Kyle M.; Cheng, Guangjun; Hight Walker, Angela R.; Gundlach, David J.; Xing, Huili G.; Nguyen, N. V.

2018-01-01

SnSe2 is currently considered a potential two-dimensional material that can form a near-broken gap heterojunction in a tunnel field-effect transistor due to its large electron affinity which is experimentally confirmed in this letter. With the results from internal photoemission and angle-resolved photoemission spectroscopy performed on Al/Al2O3/SnSe2/GaAs and SnSe2/GaAs test structures where SnSe2 is grown on GaAs by molecular beam epitaxy, we ascertain a (5.2 ± 0.1) eV electron affinity of SnSe2. The band offset from the SnSe2 Fermi level to the Al2O3 conduction band minimum is found to be (3.3 ± 0.05) eV and SnSe2 is seen to have a high level of intrinsic electron (n-type) doping with the Fermi level positioned at about 0.2 eV above its conduction band minimum. It is concluded that the electron affinity of SnSe2 is larger than that of most semiconductors and can be combined with other appropriate semiconductors to form near broken-gap heterojunctions for the tunnel field-effect transistor that can potentially achieve high on-currents.

Cathodoluminescence Studies of the Inhomogeneities in Sn-doped Ga2O3 Nanowires

DTIC Science & Technology

2009-01-01

Cathodoluminescence Studies of the Inhomogeneities in Sn-doped Ga2O3 Nanowires S. I. Maximenko, L. Mazeina, Y. N. Picard, J. A. Freitas, Jr., V. M...color imaging and spectroscopy were employed to study the properties of Ga2O3 nanowires grown with different Sn/Ga ratios. The structures grown under...green to red emission correlates with a phase transition of β- Ga2O3 to polycrystalline SnO2. The origin of the green emission band is discussed based

Using a double-doping strategy to improve physical properties of nanostructured CdO films

NASA Astrophysics Data System (ADS)

Aydin, R.; Sahin, B.

2018-06-01

In this present study nanostructured dually doped samples of Cd1‑x‑yMgxMyO (M: Sn, Pb, Bi) are synthesized by SILAR method. The effects of the mono and dual doping on the structural, morphological and optoelectronic characteristics of CdO nanoparticles are examined. The SEM images verify that deposited CdO films are nano-sized. Also the SEM computations demonstrated that the morphological surface structures of the films were influenced from the Mg mono doping and (Mg, Sn), (Mg, Pb) and (Mg, Bi) dual doping. The XRD designs specified that all the CdO samples have polycrystalline structure exhibiting cubic crystal form with dominant peaks of (111) and (220). The results display that Mg and (Mg, Sn), (Mg, Pb) and (Mg, Bi) ions were successfully doped into CdO film matrix. The UV spectroscopy results show that the optical energy band gap of the CdO films, ranging from 2.21 to 2.66 eV, altered with the dopant materials.

Structural, electrical and magnetic properties of (Fe, Co) co-doped SnO2 diluted magnetic semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Mehraj, Sumaira; Ansari, M. Shahnawaze; Alimuddin

2015-01-01

Nanostructures (NSs) of basic composition Sn1-xFex/2Cox/2O2 with x=0.00, 0.04, 0.06, 0.08 and 0.1 were synthesized by citrate-gel route and characterized to understand their structural, electrical and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase rutile type tetragonal structure. The crystallite sizes calculated by using Williamson Hall were found to decrease with increasing doping level. In addition to the fundamental Raman peaks of rutile SnO2, the other three weak Raman peaks at about 505, 537 and 688 cm-1 were also observed. Field emission scanning electron microscopy studies showed the emergence of structural transformation. Electric properties such as dc electrical resistivity as a function of temperature and ac conductivity as a function of frequency were also studied. The variation of dielectric properties with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general. Hysteresis loops were clearly observed in M-H curves of Fe and Co co-doped SnO2 NSs. However, pure SnO2 nanoparticles (NPs) showed paramagnetic behaviour which vanished at higher values of magnetic field. The grain and grain boundary contribution in the conduction process is estimated through complex impedance plot fitted with non-linear least square (NLLS) approach which shows that the role of grain boundaries increases rapidly as compared to the grain volume with the increase of Fe and Co ions in to system.

Enhanced Thermoelectric Properties of Polycrystalline SnSe via LaCl₃ Doping.

PubMed

Li, Fu; Wang, Wenting; Ge, Zhen-Hua; Zheng, Zhuanghao; Luo, Jingting; Fan, Ping; Li, Bo

2018-01-28

LaCl₃ doped polycrystalline SnSe was synthesized by combining mechanical alloying (MA) process with spark plasma sintering (SPS). It is found that the electrical conductivity is enhanced after doping due to the increased carrier concentration and carrier mobility, resulting in optimization of the power factor at 750 K combing with a large Seebeck coefficient over 300 Μvk -1 . Meanwhile, all the samples exhibit lower thermal conductivity below 1.0 W/mK in the whole measured temperature. The lattice thermal conductivity for the doped samples was reduced, which effectively suppressed the increscent of the total thermal conductivity because of the improved electrical conductivity. As a result, a ZT value of 0.55 has been achieved for the composition of SnSe-1.0 wt % LaCl₃ at 750 K, which is nearly four times higher than the undoped one and reveals that rare earth element is an effective dopant for optimization of the thermoelectric properties of SnSe.

Co-precipitation synthesis and characterization of tin-doped α-Fe2O3 nanoparticles with enhanced photocatalytic activities

NASA Astrophysics Data System (ADS)

Mansour, Houda; Bargougui, Radhouane; Autret-Lambert, Cécile; Gadri, Abdellatif; Ammar, Salah

2018-03-01

In this study, Sn-doped hematite (α-Fe2O3) nanoparticles with various dopant concentrations ranging from 1 to 6 mol% were prepared successfully using a simple co-precipitation technique. The effects of Sn doping on the structural, morphological, optical, and magnetic properties were determined using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy, and a superconducting quantum interference device. XRD analysis showed that all of the samples had a typical hematite-type hexagonal structure of Fe2O3 without any additional peaks due to spurious phases. The cell parameters a and c decreased monotonically as the Sn content increased, thereby indicating that Sn ions were substituted into the α-Fe2O3 lattice. These results and the TEM analyses showed that the size of the nanoparticles decreased to 10 nm as the Sn doping concentration increased. UV-visible absorption measurements showed that the decrease in particle size was accompanied by a decrease in the band gap value from 2.07 eV for α-Fe2O3 to 1.87 eV with 6 mol% Sn doping. Furthermore, the magnetic properties demonstrated that all of the samples exhibited ferromagnetic behavior at room temperature. The photocatalytic activities of the samples were studied based on the degradation of methylene blue as a model compound, where the results showed that an appropriate amount of Sn dopant could greatly increase the amount of hydroxyl radicals generated by α-Fe2O3 nanoparticles, which were responsible for the obvious increase in the photocatalytic activity.

Transition-metal-doped group-IV monochalcogenides: a combination of two-dimensional triferroics and diluted magnetic semiconductors

NASA Astrophysics Data System (ADS)

Yang, Liu; Wu, Menghao; Yao, Kailun

2018-05-01

We report the first-principles evidence of a series of two-dimensional triferroics (ferromagnetic + ferroelectric + ferroelastic), which can be obtained by doping transition-metal ions in group-IV monochalcogenide (SnS, SnSe, GeS, GeSe) monolayers, noting that a ferromagnetic Fe-doped SnS2 monolayer has recently been realized (Li B et al 2017 Nat. Commun. 8 1958). The ferroelectricity, ferroelasticity and ferromagnetism can be coupled and the magnetization direction may be switched upon ferroelectric/ferroelastic switching, rendering electrical writing + magnetic reading possible. They can be also two-dimensional half-metals or diluted magnetic semiconductors, where p/n channels or even multiferroic tunneling junctions can be designed by variation in doping and incorporated into a monolayer wafer.

Transition-metal-doped group-IV monochalcogenides: a combination of two-dimensional triferroics and diluted magnetic semiconductors.

PubMed

Yang, Liu; Wu, Menghao; Yao, Kailun

2018-05-25

We report the first-principles evidence of a series of two-dimensional triferroics (ferromagnetic + ferroelectric + ferroelastic), which can be obtained by doping transition-metal ions in group-IV monochalcogenide (SnS, SnSe, GeS, GeSe) monolayers, noting that a ferromagnetic Fe-doped SnS 2 monolayer has recently been realized (Li B et al 2017 Nat. Commun. 8 1958). The ferroelectricity, ferroelasticity and ferromagnetism can be coupled and the magnetization direction may be switched upon ferroelectric/ferroelastic switching, rendering electrical writing + magnetic reading possible. They can be also two-dimensional half-metals or diluted magnetic semiconductors, where p/n channels or even multiferroic tunneling junctions can be designed by variation in doping and incorporated into a monolayer wafer.

Structural and dielectric studies of Ce doped BaSnO3 perovskite nanostructures

NASA Astrophysics Data System (ADS)

Angel, S. Lilly; Deepa, K.; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2018-04-01

Undoped and Cerium (Ce) doped BaSnO3(BSO) nanostructures were synthesized by co-precipitation method. The cubic structure and perovskite phase were confirmed by X-ray diffraction (XRD). The crystallite size of BSO is 41nm and when Ce ion concentration is increased, the crystallite sizesdecreased. The nanocube, nanocuboids and nanorods are observed from SEM analysis. The purity of the undoped and doped samples are confirmed by EDS spectrum. For larger defects, wide band gap was obtained from UV-Vis and PL spectrum. The dielectric constants are increased at low frequencies when Ce impurities are introduced in the BSO matrix at Sn site.

Enhancement of Thermoelectric Performances in a Topological Crystal Insulator Pb0.7Sn0.3Se via Weak Perturbation of the Topological State and Chemical Potential Tuning by Chlorine Doping.

PubMed

Lin, Chan-Chieh; Kim, Gareoung; Ginting, Dianta; Ahn, Kyunghan; Rhyee, Jong-Soo

2018-04-04

Topological insulators generally share commonalities with good thermoelectric (TE) materials because of their narrow band gaps and heavy constituent elements. Here, we propose that a topological crystalline insulator (TCI) could exhibit a high TE performance by breaking its crystalline symmetry and tuning the chemical potential by elemental doping. As a candidate material, we investigate the TE properties of the Cl-doped TCI Pb 0.7 Sn 0.3 Se. The infrared absorption spectra reveal that the band gap is increased from 0.055 eV for Pb 0.7 Sn 0.3 Se to 0.075 eV for Pb 0.7 Sn 0.3 Se 0.99 Cl 0.01 , confirming that the Cl doping can break the crystalline mirror symmetry of a TCI Pb 0.7 Sn 0.3 Se and thereby enlarge its bulk electronic band gap. The topological band inversion is confirmed by the extended X-ray absorption fine structure spectroscopy, which shows that the TCI state is weakened in a chlorine x = 0.05-doped compound. The small gap opening and partial linear band dispersion with massless and massive bands may have a high power factor (PF) for high electrical conductivity with an enhancement of the Seebeck coefficient. As a result, Pb 0.7 Sn 0.3 Se 0.99 Cl 0.01 shows a considerably enhanced ZT of 0.64 at 823 K, which is about 1200% enhancement in ZT compared with that of the undoped Pb 0.7 Sn 0.3 Se. This work demonstrates that the optimal n-type Cl doping tunes the chemical potential together with breaking the state of the TCI, suppresses the bipolar conduction at high temperatures, and thereby enables the Seebeck coefficient to increase up to 823 K, resulting in a significantly enhanced PF at high temperatures. In addition, the bipolar contribution to thermal conductivity is effectively suppressed for the Cl-doped samples of Pb 0.7 Sn 0.3 Se 1- x Cl x ( x ≥ 0.01). We propose that breaking the crystalline mirror symmetry in TCIs could be a new research direction for exploring high-performance TE materials.

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

DOE PAGES

Kumar, E. Senthil; Mohammadbeigi, F.; Boatner, Lynn A.; ...

2016-01-01

Here, Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-dopants. We present high-resolution photoluminescence spectroscopy studies of unintentionally doped and Sn doped ZnO single crystals grown by the chemical vapor transport method. Doped samples showed greatly increased emission from the I10 bound exciton transition which was recently proven to be related to the incorporation of Sn impurities based on radio-isotope studies. PL linewidths are exceptionally sharp for these samples, enabling clear identification of several donor species. Temperature dependent PL measurements of the I10 line emission energy and intensity dependence reveal a behavior similar tomore » other shallow donors in ZnO. Ionized donor bound exciton and two electron satellite transitions of the I10 transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Sn-related donor bound exciton follows a linear relationship with donor binding energy (Haynes rule), confirming the shallow nature of this defect center, which we attribute to a SnZn double donor compensated by an unknown single acceptor.« less

Effective properties of undoped and Indium3+-doped tin manganese telluride (Sn1 - xMnxTe) nanoparticles via using a chemical bath deposition route

NASA Astrophysics Data System (ADS)

Boon-on, Patsorn; Tubtimtae, Auttasit; Vailikhit, Veeramol; Teesetsopon, Pichanan; Choopun, Supab

2017-06-01

Tin manganese telluride nanoparticles (Sn1-xMnxTe NPs) were first synthesized on a niobium pentoxide (Nb2O5) film using a chemical bath deposition (CBD) route. An individual particle size before and after indium (In3+) doping of ∼70-150 nm was investigated with stoichiometric formation of the SnMnTe phase. Furthermore, a cubic or rocksalt structure of the Sn0.938Mn0.062Te phase was also kept incorporated in the structure. The plotted energy band gaps for undoped and In3+-doped samples were 2.17 and 1.83 eV, respectively. The reduction of photoluminescence (PL) spectra after In3+ doping, while the indium dopant acted as a trap state incorporated in Sn1-xMnxTe NPs, showed enhanced charge separation and reduced charge recombination, which resulted in a higher charge density trapped in the conduction band of Nb2O5 and was also confirmed by the result of anodic peaks in the cyclic voltammetry. These results suggest new possibilities in optoelectronic and electrochemical devices.

Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles.

PubMed

Lavanya, N; Radhakrishnan, S; Sekar, C

2012-01-01

Ni doped SnO(2) nanoparticles (0-5 wt%) have been prepared by a simple microwave irradiation (2.45 GHz) method. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirmed the formation of rutile structure with space group (P(42)/mnm) and nanocrystalline nature of the products with spherical morphology. Direct electrochemistry of horseradish peroxidase (HRP)/nano-SnO(2) composite has been studied. The immobilized enzyme retained its bioactivity, exhibited a surface confined, reversible one-proton and one-electron transfer reaction, and had good stability, activity and a fast heterogeneous electron transfer rate. A significant enzyme loading (3.374×10(-10) mol cm(-2)) has been obtained on nano-Ni doped SnO(2) as compared to the bare glassy carbon (GC) and nano-SnO(2) modified surfaces. This HRP/nano-Ni-SnO(2) film has been used for sensitive detection of H(2)O(2) by differential pulse voltammetry (DPV), which exhibited a wider linearity range from 1.0×10(-7) to 3.0×10(-4)M (R=0.9897) with a detection limit of 43 nM. The apparent Michaelis-Menten constant (K(M)(app)) of HRP on the nano-Ni-SnO(2) was estimated as 0.221 mM. This excellent performance of the fabricated biosensor is attributed to large surface-to-volume ratio and Ni doping into SnO(2) which facilitate the direct electron transfer between the redox enzyme and the surface of electrode. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis, electrochemical investigation and structural analysis of doped Li[Ni0.6Mn0.2Co0.2-xMx]O2 (x = 0, 0.05; M = Al, Fe, Sn) cathode materials

NASA Astrophysics Data System (ADS)

Eilers-Rethwisch, Matthias; Winter, Martin; Schappacher, Falko Mark

2018-05-01

Layered Ni-rich Li[Ni0.6Mn0.2Co0.2-xMx]O2 cathode materials (x = 0, 0.05; M = Al, Fe, Sn) are synthesized via a co-precipitation synthesis route and the effect of dopants on the structure and electrochemical performance is investigated. All synthesized materials show a well-defined layered structure of the hexagonal α-NaFeO2 phase investigated by X-ray diffraction (XRD). Undoped LiNi0.6Mn0.2Co0.2O2 exhibits a discharge capacity of 170 mAh g-1 in Li-metal 2032 coin-type cells. Doped materials reach lower capacities between 145 mAh g-1 for Al and 160 mAh g-1 for Sn. However, all doped materials prolong the cycle life by up to 20%. Changes of the lattice parameter before and after delithiation yield information about structural stability. A smaller repulsion of the transition metal layer during delithiation in the Sn-doped material leads to a smaller expansion of the unit cell, which results in enhanced structural stability of the material. The improved structural stability of Sn-doped NMC cathode active material is proven by thermal investigations with the help of Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA).

Synthesis and superconductivity of In-doped SnTe nanostructures

DOE PAGES

Kumaravadivel, Piranavan; Pan, Grace A.; Zhou, Yu; ...

2017-07-01

In xSn 1-xTe is a time-reversal invariant candidate 3D topological superconductor derived from doping the topological crystalline insulator SnTe with indium. The ability to synthesize low-dimensional nanostructures of indium-doped SnTe is key for realizing the promise they hold in future spintronic and quantum information processing applications. But hitherto only bulk synthesized crystals and nanoplates have been used to study the superconducting properties. Here for the first time we synthesize In xSn 1-xTe nanostructures including nanowires and nanoribbons, which show superconducting transitions. In some of the lower dimensional morphologies, we observe signs of more than one superconducting transition and the absencemore » of complete superconductivity. We propose that material inhomogeneity, such as indium inhomogeneity and possible impurities from the metal catalyst, is amplified in the transport characteristics of the smaller nanostructures and is responsible for this mixed behavior. Our work represents the first demonstration of In xSn 1-xTe nanowires with the onset of superconductivity, and points to the need for improving the material quality for future applications« less

Synthesis and superconductivity of In-doped SnTe nanostructures

NASA Astrophysics Data System (ADS)

Kumaravadivel, Piranavan; Pan, Grace A.; Zhou, Yu; Xie, Yujun; Liu, Pengzi; Cha, Judy J.

2017-07-01

InxSn1-xTe is a time-reversal invariant candidate 3D topological superconductor derived from doping the topological crystalline insulator SnTe with indium. The ability to synthesize low-dimensional nanostructures of indium-doped SnTe is key for realizing the promise they hold in future spintronic and quantum information processing applications. But hitherto only bulk synthesized crystals and nanoplates have been used to study the superconducting properties. Here for the first time we synthesize InxSn1-xTe nanostructures including nanowires and nanoribbons, which show superconducting transitions. In some of the lower dimensional morphologies, we observe signs of more than one superconducting transition and the absence of complete superconductivity. We propose that material inhomogeneity, such as indium inhomogeneity and possible impurities from the metal catalyst, is amplified in the transport characteristics of the smaller nanostructures and is responsible for this mixed behavior. Our work represents the first demonstration of InxSn1-xTe nanowires with the onset of superconductivity, and points to the need for improving the material quality for future applications.

Influence of Sodium Chloride Doping on Thermoelectric Properties of p-type SnSe

NASA Astrophysics Data System (ADS)

Yang, Shi Dan; Nutor, Raymond Kwesi; Chen, Zi Jie; Zheng, Hao; Wu, Hai Fei; Si, Jian Xiao

2017-11-01

We investigated the effect of NaCl doping on the thermoelectric properties of p-type Sn 1- x Na x SeCl x ( x = 0, 0.005, 0.01, 0.02, 0.03 and 0.04) prepared by a method which combines rapid induction melting and rapid hot pressing. After introducing the NaCl into the SnSe system, the carrier concentration of SnSe is significantly increased from ˜4.55 × 1017 cm-3 to ˜3.95 × 1019 cm-3 at 300 K. An electrical conductivity of ˜102.5 S cm-1 was obtained at 473 K by addition of 2 mol.% NaCl. It was found that Cl was effective in reducing the thermal conductivity by inducing abundant defects. A maximum ZT value of 0.84 was achieved in the Na0.005Sn0.995SeCl0.005 sample at 810 K. This suggests that doping with NaCl is a facile and cost-effective method in optimizing the thermoelectric properties of SnSe materials.

XPS and 31P NMR inquiry of Eu3+-induced structural modification in SnO-containing phosphate glass

NASA Astrophysics Data System (ADS)

Jiménez, José A.; Fachini, Esteban Rosim; Zhao, Chunqing

2018-07-01

The influence of Eu3+ doping on the structural properties of SnO-containing phosphate glass has been investigated by X-ray photoelectron spectroscopy (XPS) and 31P nuclear magnetic resonance (NMR) spectroscopy. Oxygen 1s XPS data indicates that the Eu3+ doping results in a higher concentration of non-bridging oxygens in the glass matrix, whereas 31P NMR shows an increase in the terminal phosphate chain tetrahedral units, i.e. the amount of Q1 sites with only one bridging oxygen. Accordingly, both techniques agree with a depolymerization effect induced by the Eu3+ ions. Further, XPS reveals that together with the Eu3+ doping, the presence of Sn4+ is supported while the presence of Eu2+ is also indicated. The structural changes are then indicated to be a consequence of redox chemistry between Sn2+ and Eu3+ promoting a transition of tin from Sn2+ with a role as network former to Sn4+ acting as network modifier in the glass system.

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

PubMed

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

2018-06-05

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

Enhanced thermoelectric performance of Pb doped Cu2SnSe3 synthesized employing spark plasma sintering

NASA Astrophysics Data System (ADS)

Shyam Prasad, K.; Rao, Ashok; Tyagi, Kriti; Singh Chauhan, Nagendra; Gahtori, Bhasker; Bathula, Sivaiah; Dhar, Ajay

2017-05-01

We report an enhancement in the thermoelectric performance of Cu2SnSe3 alloy on Pb doping, owing to a sharp increase in its power factor. The powder XRD pattern of all samples of Cu2Sn1-xPbxSe3 (0≤x≤0.03), prepared using solid state reaction, exhibited a cubic structure with a space group of F 4 ̅ 3 m . The results show that temperature dependent electrical resistivity, ρ(T) increases with increasing temperature thereby demonstrating that the samples display heavily doped semiconducting nature, which could be satisfactorily described by small polaron hopping model in the whole temperature range of measurement for all the samples. Both the resistivity and the Seebeck coefficient are reduced with 2 vol% Pb doping. The thermal conductivity of all the samples reduces with increasing temperature. Despite a decrease in Seebeck coefficient the power factor shows an increase on Pb doping, owing to a sharp surge in the electrical conductivity which results in an enhanced ZTmax 0.64 at 700 K for an optimized composition of Cu2Sn0.98Pb0.02Se3, which is nearly twice the value of the corresponding undoped counterpart.

Effect of oxygen impurities on properties of the ternary superconductor SnMo/sub 6/S/sub 8/: Extended x-ray-absorption fine-structure determination of bond distances and local-density cluster calculations

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

Guenzburger, D.; Ellis, D.E.; Montano, P.A.

1985-10-01

Electronic structure calculations were performed for clusters representing the Chevrel-phase SnMo/sub 6/S/sub 8/, with and without oxygen doping. In order to obtain the local structure around the Sn atom, extended x-ray-absorption fine-structure (EXAFS) measurements were made with synchro- tron radiation. The interatomic distances obtained experimentally were used in the calculations. The effect of oxygen doping on the Moessbauer isomer shift and quadrupole splitting values of /sup 119/Sn was investigated theoretically and compared with reported experimental values. The effect of oxygen substitution on the density of states at the Fermi energy of the (Mo/sub 6/S/sub 8/)/sup 2 -/ cluster was alsomore » studied. The results suggest that oxygen doping does not alter significantly the electronic structure of SnMo/sub 6/S/sub 8/.« less

Simultaneous enhancement of magnetic and mechanical properties in Ni-Mn-Sn alloy by Fe doping

PubMed Central

Tan, Changlong; Tai, Zhipeng; Zhang, Kun; Tian, Xiaohua; Cai, Wei

2017-01-01

Both magnetic-field-induced reverse martensitic transformation (MFIRMT) and mechanical properties are crucial for application of Ni-Mn-Sn magnetic shape memory alloys. Here, we demonstrate that substitution of Fe for Ni can simultaneously enhance the MFIRMT and mechanical properties of Ni-Mn-Sn, which are advantageous for its applications. The austenite in Ni44Fe6Mn39Sn11 shows the typical ferromagnetic magnetization with the highest saturation magnetization of 69 emu/g at 223 K. The result shows that an appropriate amount of Fe substitution can really enhance the ferromagnetism of Ni50Mn39Sn11 alloy in austenite, which directly leads to the enhancement of MFIRMT. Meanwhile, the mechanical property significantly improves with Fe doping. When there is 4 at.% Fe added, the compressive and maximum strain reach the maximum value (approximately 725.4 MPa and 9.3%). Furthermore, using first-principles calculations, we clarify the origin of Fe doping on martensitic transformation and magnetic properties. PMID:28230152

The Structural Changes of the Sn(y)OX Thin Films Under Influence of Heat Treament

NASA Astrophysics Data System (ADS)

Vong, V.

2001-04-01

Composite oxide Sn(y) Ox made by thermal oxidation of the Sn(y)-bimetal thin films, in which y is the doped-materials as well as Sb, Ag or Pd. The Sn(y)-bimetal thin films have been made by evaporation in high vacuum onto NaCl-monocrystall and optical glass substrates. In the work the tin and the doped material (y) were put on two different boats and then both the boats were simultaniously heated to evaporate. The Sn(y)Ox thin films were annealed at the differential temperatures. The structural changes of its have been investigated by using X-ray diffraction and transmission electron microscope.

Fabrication of a transparent ultraviolet detector by using n-type Ga2O3 and p-type Ga-doped SnO2 core-shell nanowires.

PubMed

Hsu, Cheng-Liang; Lu, Ying-Ching

2012-09-21

This study investigates the feasibility of synthesizing high-density transparent Ga(2)O(3)/SnO(2):Ga core-shell nanowires on a sapphire substrate at 1000 °C by VLS. The doping Ga concentrations are 0.46, 1.07, 2.30 and 17.53 atomic%. The XRD spectrum and HR-TEM reveal Ga(2)O(3) and SnO(2) as having monoclinic and tetragonal rutile structures, respectively. Experimental results indicate that the XRD peak shift of SnO(2) to a larger angle increases with the increasing amount of Ga doping. According to the CL spectrum, SnO(2) and Ga(2)O(3) peak at approximately 528-568 nm and 422-424 nm, respectively. The maximum quantum efficiency of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 0.362%. The UV light on-off current contrast ratio of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 1066.7 at a bias of 5 V. Moreover, the dynamic response of Ga(2)O(3)/SnO(2):Ga core-shell nanowires has an on-off current contrast ratio of around 16. Furthermore, the Ga(2)O(3) region functions similar to a capacitor and continues to accumulate SnO(2):Ga excited electrons under UV light exposure.

3D Porous Nanoarchitectures Derived from SnS/S-Doped Graphene Hybrid Nanosheets for Flexible All-Solid-State Supercapacitors.

PubMed

Liu, Chunyan; Zhao, Shulin; Lu, Yanan; Chang, Yingxue; Xu, Dongdong; Wang, Qi; Dai, Zhihui; Bao, Jianchun; Han, Min

2017-03-01

3D porous nanoarchitectures derived from SnS/S-doped graphene hybrid nanosheets are successfully prepared by controllable thermal conversion of oleylamine-capped mixed-phase SnS 2 -SnS nanodisks precursors, and employed as electroactive material to fabricate flexible, symmetric, all-solid-state supercapacitors. The fabricated solid devices exhibit very high areal specific capacitance (2.98 mF cm -2 ), good cycling stability (99% for 10 000 cycles), excellent flexibility, and desirable mechanical stability. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A first-principles study of group IV and VI atoms doped blue phosphorene

NASA Astrophysics Data System (ADS)

Bai, Ruimin; Chen, Zheng; Gou, Manman; Zhang, Yixin

2018-02-01

Using first-principles calculations, we have systematically investigated the structural, electronic and magnetic properties of blue phosphorene doped by group IV and VI atoms, including C, Si, Ge, Sn, O, S, Se and Te. All the doped systems are energetically stable. Only C, Si, Ge and O-substituted systems show the characteristics of spin polarization and the magnetic moments are all 1.0 μB. Moreover, we found that C, Si, Ge and O doped systems are indirect bandgap semiconductors, while Sn, S, Se and Te doped systems present metallic property. These results show that blue phosphorene can be used prospectively in optoelectronic and spintronic devices.

Correlations of charge neutrality level with electronic structure and p-d hybridization

PubMed Central

Das, Arkaprava; Gautam, Subodh K.; Shukla, D. K.; Singh, Fouran

2017-01-01

The formation of charge neutrality level (CNL) in highly conducting Cadmium oxide (CdO) thin films is demonstarted by the observed variation in the band gap upon annealing and doping. It may be explained by the observation that Tin (Sn) doping breaks the perfect periodicity of CdO cubic crystal structure and creates virtual gap states (ViGS). The level of local CNL resides at the branch point of ViGS, making the energy at which native defect’s character changes from predominantly donor-like below CNL to predominantly acceptor-like above the CNL and a schematic band diagram is developed to substantiate the same. Further investigations using soft x-ray absorption spectroscopy (SXAS) at Oxygen and Cadmium edges show the reduction of Sn4+ to Sn2+. The analysis of the spectral features has revealed an evidence of p-d interaction between O 2p and Cd 4d orbitals that pushes the valence band minima at higher energies which is symmetry forbidden at г point and causing a positive valance band dispersion away from the zone centre in the г ~ L, K direction. Thus, origin of the CNL is attributed to the high density of the Oxygen vacancies as confirmed by the change in the local electronic structure and p-d hybridization of orbitals. PMID:28102312

Correlations of charge neutrality level with electronic structure and p-d hybridization

NASA Astrophysics Data System (ADS)

Das, Arkaprava; Gautam, Subodh K.; Shukla, D. K.; Singh, Fouran

2017-01-01

The formation of charge neutrality level (CNL) in highly conducting Cadmium oxide (CdO) thin films is demonstarted by the observed variation in the band gap upon annealing and doping. It may be explained by the observation that Tin (Sn) doping breaks the perfect periodicity of CdO cubic crystal structure and creates virtual gap states (ViGS). The level of local CNL resides at the branch point of ViGS, making the energy at which native defect’s character changes from predominantly donor-like below CNL to predominantly acceptor-like above the CNL and a schematic band diagram is developed to substantiate the same. Further investigations using soft x-ray absorption spectroscopy (SXAS) at Oxygen and Cadmium edges show the reduction of Sn4+ to Sn2+. The analysis of the spectral features has revealed an evidence of p-d interaction between O 2p and Cd 4d orbitals that pushes the valence band minima at higher energies which is symmetry forbidden at г point and causing a positive valance band dispersion away from the zone centre in the г ~ L, K direction. Thus, origin of the CNL is attributed to the high density of the Oxygen vacancies as confirmed by the change in the local electronic structure and p-d hybridization of orbitals.

Impact of Sodium Contamination in Tin Sulfide Thin-Film Solar Cells

DOE PAGES

Steinmann, Vera; Brandt, Riley E.; Chakraborty, Rupak; ...

2016-02-12

Empirical observations show that sodium(Na) is a benign contaminant in some thin-filmsolar cells. Here, we intentionally contaminate thermally evaporated tin sulfide (SnS)thin-films with sodium and measure the SnS absorber properties and solar cellcharacteristics. The carrier concentration increases from 2 × 10 16 cm -3 to 4.3 × 10 17 cm -3 in Na-doped SnSthin-films, when using a 13 nm NaCl seed layer, which is detrimental for SnS photovoltaic applications but could make Na-doped SnS an attractive candidate in thermoelectrics. We observed trends in carrier concentration and found that it is in good agreement with density functional theory calculations, which predictmore » an acceptor-type NaSn defect with low formation energy.« less

Highly sensitive ethanol chemical sensor based on Ni-doped SnO₂ nanostructure materials.

PubMed

Rahman, Mohammed M; Jamal, Aslam; Khan, Sher Bahadar; Faisal, M

2011-10-15

Due to potential applications of semiconductor transition doped nanostructure materials and the important advantages of synthesis in cost-effective and environmental concerns, a significant effort has been consummated for improvement of Ni-doped SnO(2) nanomaterials using hydrothermal technique at room conditions. The structural and optical properties of the low-dimensional (average diameter, 52.4 nm) Ni-doped SnO(2) nanostructures were demonstrated using various conventional techniques such as UV/visible spectroscopy, FT-IR spectroscopy, X-ray powder diffraction (XRD), and Field-emission scanning electron microscopy (FE-SEM). The calcined doped material is an attractive semiconductor nanoparticle for accomplishment in chemical sensing by simple I-V technique, where toxic chemical (ethanol) is used as a target chemical. Thin-film of Ni-doped SnO(2) nanostructure materials with conducting coating agents on silver electrodes (AgE, surface area, 0.0216 cm(2)) revealed higher sensitivity and repeatability. The calibration plot is linear (R, 0.8440) over the large dynamic range (1.0 nM-1.0 mM), where the sensitivity is approximately 2.3148 μA cm(-2) mM(-1) with a detection limit of 0.6 nM, based on signal/noise ratio in short response time. Consequently on the basis of the sensitive communication among structures, morphologies, and properties, it is exemplified that the morphologies and the optical characteristics can be extended to a large scale in doping nanomaterials and proficient chemical sensors applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Dehydroxyl effect of Sn-doped silicon oxide resistance random access memory with supercritical CO2 fluid treatment

NASA Astrophysics Data System (ADS)

Tsai, Tsung-Ming; Chang, Kuan-Chang; Chang, Ting-Chang; Syu, Yong-En; Liao, Kuo-Hsiao; Tseng, Bae-Heng; Sze, Simon M.

2012-09-01

The tin-doped can supply conduction path to induce resistance switching behavior. However, the defect of tin-doped silicon oxide (Sn:SiOx) increased the extra leakage path lead to power consumption and joule heating degradation. In the study, supercritical CO2 fluids treatment was used to improve resistive switching property. The current conduction of high resistant state in post-treated Sn:SiOx film was transferred to Schottky emission from Frenkel-Poole due to the passivation effect. The molecular reaction model is proposed that the defect was passivated through dehydroxyl effect of supercritical fluid technology, verified by material analyses of x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.

Thermoelectric Properties of Topological Crystalline Insulator Nanowires

NASA Astrophysics Data System (ADS)

Xu, Enzhi

Bulk lead telluride (PbTe) and its alloy compounds are well-known thermoelectric materials for electric power generation. Tin telluride (SnTe) which has the same rock-salt crystalline structure as PbTe has recently been demonstrated to host unique topological surface states that may favor improved thermoelectric properties. In this thesis work, we studied the thermoelectric properties of single-crystalline nanowires of the SnTe family compounds, i.e. undoped SnTe, PbTe, (Sn,Pb)Te alloy, and In-doped SnTe, all of which were grown by a vapor transport approach. We measured the thermopower S, electrical conductivity sigma and thermal conductivity kappa on each individual nanowire over a temperature range of 25 - 300 K, from which the thermoelectric figures of merit ZTs were determined. In comparison to PbTe nanowires, SnTe and (Sn,Pb)Te has lower thermopower but significantly higher electrical conductivity. Both SnTe and (Sn,Pb)Te nanowires showed enhanced thermopower and suppressed thermal conductivity, compared to their bulk counterparts. The enhancement of thermopower may result from the existence of topological surface states, while the suppression of thermal conductivity may relate to the increased phonon-surface scattering in nanowires. Moreover, indium doping suppresses both electrical and thermal conductivities but enhances thermopower, yielding an improved figure of merit ZT. Our results highlight nanostructuring in combination with alloying or doping as an important approach to enhancing thermoelectric properties. In spite of excellent thermoelectric properties and robust topological surface states, we found that the nanowire surface is subject to fast oxidation. In particular, we demonstrated that exposure of In-doped SnTe nanowires to air leads to surface oxidation within only one minute. Transmission electron microscopy characterization suggests the amorphous nature of the surface, and X-ray photoelectron spectroscopy studies identify the oxide species on nanowire surface. We further developed an effective approach to removing surface oxides by means of argon ion sputtering.

Effective Targeted Gene Delivery to Dendritic Cells via Synergetic Interaction of Mannosylated Lipid with DOPE and BCAT

PubMed Central

Kim, Hee-Kwon; Wei, Huiling; Kulkarni, Aditya; Pogranichniy, Roman M.; Thompson, David H.

2012-01-01

The efficient delivery of plasmids encoding antigenic determinants into dendritic cells (DCs) that control immune response is a promising strategy for rapid development of new vaccines. In this study, we prepared a series of targeted cationic lipoplex based on two synthetic lipid components, mannose-poly(ethylene glycol, MW3000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (Mannose-PEG3000-DSPE) and O-(2R-1,2-di-O-(1'Z,9'Z-octadecadienyl)-glycerol)-3-N-(bis-2-aminoethyl)-carbamate (BCAT), that were formulated with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) for evaluation as non-viral vectors for transgene expression in DCs. First, we optimized the N:P ratio for maximum transfection and then screened the effects of mannose targeting for further enhancement of transfection levels. Our results indicate that efficient delivery of gWIZ GFP plasmid into DCs was observed for mannose compositions of ~10%, whereas low transfection efficiencies were observed with non-targeted formulations. Mannose-targeted lipofectamine complexes also showed high GFP expression levels in DCs relative to non-targeted lipofectamine controls. The best transfection performance was observed using 10 mol % Mannose-PEG3000-DSPE, 60 mol% BCAT, and 30 mol % DOPE, indicating that the most efficient delivery into DCs occurs via synergistic interaction between mannose targeting and acid-labile, fusogenic BCAT:DOPE formulations. Our data suggest that mannose-PEG3000-DSPE:BCAT:DOPE formulations may be effective gene delivery vehicles for the development of DC-based vaccines. PMID:22229467

Facile synthesis of antimony-doped tin oxide nanoparticles by a polymer-pyrolysis method

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

Li, Yuan-Qing, E-mail: yqli@mail.ipc.ac.cn; Wang, Jian-Lei; Fu, Shao-Yun, E-mail: syfu@mail.ipc.ac.cn

2010-06-15

In this article, antimony-doped tin oxide (ATO) nanoparticles was synthesized by a facile polymer-pyrolysis method. The pyrolysis behaviors of the polymer precursors prepared via in situ polymerization of metal salts and acrylic acid were analyzed by simultaneous thermogravimetric and differential scanning calorimetry (TG-DSC). The structural and morphological characteristics of the products were studied by powder X-ray diffraction (XRD) and transmission electron microscope (TEM). The results reveal that the ATO nanoparticles calcined at 600 {sup o}C show good crystallinity with the cassiterite structure and cubic-spherical like morphology. The average particle size of ATO decreases from 200 to 15 nm as themore » Sb doping content increases from 5 mol% to 15 mol%. Electrical resistivity measurement shows that the resistivity for the 10-13 mol% Sb-doped SnO{sub 2} nanoparticles is reduced by more than three orders compared with the pure SnO{sub 2} nanoparticles. In addition, due to its versatility this polymer-pyrolysis method can be extended to facile synthesis of other doped n-type semiconductor, such as In, Ga, Al doped ZnO, Sn doped In{sub 2}O{sub 3}.« less

Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

DOE PAGES

Si, W.; Zhang, C.; Wu, L.; ...

2015-09-01

Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF2 crystalline substrates respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk.more » With large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.« less

Bio-green synthesis of Fe doped SnO2 nanoparticle thin film

NASA Astrophysics Data System (ADS)

Gattu, Ketan P.; Ghule, Kalyani; Huse, Nanasaheb P.; Dive, Avinash S.; Bagul, Sagar B.; Digraskar, Renuka V.; Sharma, Ramphal; Ghule, Anil V.

2017-05-01

Herein Fe doped SnO2 nanoparticles have been synthesized using simple, cost effective and ecofriendly biosynthesis method, in which remnant water (ideally kitchen waste) collected from soaked Bengal gram beans (Cicer arietinum L.) was used. This extract consists of different bio-molecules which acted as complexing as well as capping agents for synthesis of Fe-doped SnO2 nanoparticles. The X-ray powder diffraction (XRD) and Field-emission scanning electron microscopy (FE-SEM) revealed uniform size distribution with the average size of 6 nm and confirmed the formation of rutile structure with space group (P42/mnm) and nanocrystalline nature of the products with spherical morphology. Further, the gas sensing properties of the materials have been studied in comparison with other gases. The reported gas sensing results are promising, which suggest that the Fe-dopant is a promising noble metal additives to fabricate low cost SnO2 based sensor.

Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

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

Si, Weidong, E-mail: wds@bnl.gov, E-mail: qiangli@bnl.gov; Zhang, Cheng; Wu, Lijun

2015-08-31

Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF{sub 2} crystalline substrates, respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk. Withmore » large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.« less

High thermoelectric figure of merit by resonant dopant in half-Heusler alloys

NASA Astrophysics Data System (ADS)

Chen, Long; Liu, Yamei; He, Jian; Tritt, Terry M.; Poon, S. Joseph

2017-06-01

Half-Heusler alloys have been one of the benchmark high temperature thermoelectric materials owing to their thermal stability and promising figure of merit ZT. Simonson et al. early showed that small amounts of vanadium doped in Hf0.75Zr0.25NiSn enhanced the Seebeck coefficient and correlated the change with the increased density of states near the Fermi level. We herein report a systematic study on the role of vanadium (V), niobium (Nb), and tantalum (Ta) as prospective resonant dopants in enhancing the ZT of n-type half-Heusler alloys based on Hf0.6Zr0.4NiSn0.995Sb0.005. The V doping was found to increase the Seebeck coefficient in the temperature range 300-1000 K, consistent with a resonant doping scheme. In contrast, Nb and Ta act as normal n-type dopants, as evident by the systematic decrease in electrical resistivity and Seebeck coefficient. The combination of enhanced Seebeck coefficient due to the presence of V resonant states and the reduced thermal conductivity has led to a state-of-the-art ZT of 1.3 near 850 K in n-type (Hf0.6Zr0.4)0.99V0.01NiSn0.995Sb0.005 alloys.

The Gadolinium (Gd3+) and Tin (Sn4+) Co-doped BiFeO3 Nanoparticles as New Solar Light Active Photocatalyst

PubMed Central

Irfan, Syed; Rizwan, Syed; Shen, Yang; Li, Liangliang; Asfandiyar, A; Butt, Sajid; Nan, Ce-Wen

2017-01-01

The process of photocatalysis is appealing to huge interest motivated by the great promise of addressing current energy and environmental issues through converting solar light directly into chemical energy. However, an efficient solar energy harvesting for photocatalysis remains a critical challenge. Here, we reported a new full solar spectrum driven photocatalyst by co-doping of Gd3+ and Sn4+ into A and B-sites of BiFeO3 simultaneously. The co-doping of Gd3+ and Sn4+ played a key role in hampering the recombination of electron-hole pairs and shifted the band-gap of BiFeO3 from 2.10 eV to 2.03 eV. The Brunauer-Emmett-Teller (BET) measurement confirmed that the co-doping of Gd3+ and Sn4+ into BiFeO3 increased the surface area and porosity, and thus the photocatalytic activity of the Bi0.90Gd0.10Fe0.95Sn0.05O3 system was significantly improved. Our work proposed a new photocatalyst that could degrade various organic dyes like Congo red, Methylene blue, and Methyl violet under irradiation with different light wavelengths and gave guidance for designing more efficient photocatalysts. PMID:28195198

Developing the photovoltaic performance of dye-sensitized solar cells (DSSCs) using a SnO2-doped graphene oxide hybrid nanocomposite as a photo-anode

NASA Astrophysics Data System (ADS)

Sasikumar, Ragu; Chen, Tse-Wei; Chen, Shen-Ming; Rwei, Syang-Peng; Ramaraj, Sayee Kannan

2018-05-01

Tin(IV) oxide nanoparticles (SnO2 NPs) doped on the surface of graphene oxide (GO) sheets for application in Dye-Sensitized Solar Cells (DSSCs). The effective incorporation of SnO2 on the surface of GO sheets were confirmed by powder X-ray diffraction (PXRD), Fourier transform infra-red spectroscopy (FT-IR), thermogravimetric analysis (TGA), electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. The morphology of the GO/SnO2 hybrid nanocomposite was confirmed by field emission scanning electron microscopy (FE-SEM) analysis. This current study involvement with the effect of different photo-anodes such as GO, SnO2, and GO/SnO2 hybrid nanocomposite on the power conversion efficiency (PCE) of the triiodide electrolyte based DSSCs. Remarkably, GO/SnO2 hybrid nanocomposite based photo-anode for DSSC observed PCE of 8.3% and it is about 12% higher than that of un-doped TiO2 photo-anode. The equivalent short-circuit photocurrent density (Jsc) of 16.67 mA cm-2, open circuit voltage (Voc) of 0.77 V, and fill factor (FF) of 0.65 respectively. The achieved results propose that the hybrid nanocomposite is an appropriate photo-anodic material for DSSCs applications.

Enhancement of the catalytic activity of Pt nanoparticles toward methanol electro-oxidation using doped-SnO2 supporting materials

NASA Astrophysics Data System (ADS)

Merati, Zohreh; Basiri Parsa, Jalal

2018-03-01

Catalyst supports play important role in governing overall catalyst activity and durability. In this study metal oxides (SnO2, Sb and Nb doped SnO2) were electrochemically deposited on titanium substrate (Ti) as a new support material for Pt catalyst in order to electro-oxidation of methanol. Afterward platinum nanoparticles were deposited on metal oxide film via electro reduction of platinum salt in an acidic solution. The surface morphology of modified electrodes were evaluated by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX) techniques. The electro-catalytic activities of prepared electrodes for methanol oxidation reaction (MOR) and oxidation of carbon monoxide (CO) absorbed on Pt was considered with cyclic voltammetry. The results showed high catalytic activity for Pt/Nb-SnO2/Ti electrode. The electrochemical surface area (ECSA) of a platinum electro-catalyst was determined by hydrogen adsorption. Pt/Nb-SnO2/Ti electrode has highest ECSA compared to other electrode resulting in high activity toward methanol electro-oxidation and CO stripping experiments. The doping of SnO2 with Sb and Nb improved ECSA and MOR activity, which act as electronic donors to increase electronic conductivity.

New insights into organic-inorganic hybrid perovskite CH₃NH₃PbI₃ nanoparticles. An experimental and theoretical study of doping in Pb²⁺ sites with Sn²⁺, Sr²⁺, Cd²⁺ and Ca²⁺.

PubMed

Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Hernández, Norge Cruz; Piñero, Jose Carlos; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; De los Santos, Desireé M; Aguilar, Teresa; Martín-Calleja, Joaquín

2015-04-14

This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb(2+) position with Sn(2+), Sr(2+), Cd(2+) and Ca(2+). The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn(2+), Sr(2+) and Cd(2+) did not modify the normal tetragonal phase. When doping with Ca(2+), the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr(2+) < Cd(2+) < Ca(2+) < CH3NH3PbI3 ≈ Sn(2+). The biggest decrease was generated by Sr(2+), which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn(2+) ≈ Pb(2+) > Cd(2+) > Sr(2+) for the tetragonal structure and Pb(2+) > Ca(2+) for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn(2+)-doped tetragonal structures, which were different from those doped with Sr(2+) and Cd(2+). Furthermore, when Cd(2+) was incorporated, the Cd-I interaction was strengthened. For Ca(2+) doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.

Novel preparation of N-doped SnO 2 nanoparticles via laser-assisted pyrolysis: Demonstration of exceptional lithium storage properties

DOE PAGES

Wang, Luyuan Paul; Leconte, Yann; Feng, Zhenxing; ...

2016-12-05

Here, laser pyrolyzed SnO 2 nanoparticles with an option of nitrogen (N) doping are prepared using a cost-effective method. The electrochemical performance of N-doped samples is tested for the first time in Li-ion batteries where the sample with 3% of N-dopant exhibits optimum performance with a capacity of 522 mAh g active material –1 that can be obtained at 10 A g –1 (6.7C).

Highly conducting and crystalline doubly doped tin oxide films fabricated using a low-cost and simplified spray technique

NASA Astrophysics Data System (ADS)

Ravichandran, K.; Muruganantham, G.; Sakthivel, B.

2009-11-01

Doubly doped (simultaneous doping of antimony and fluorine) tin oxide films (SnO 2:Sb:F) have been fabricated by employing an inexpensive and simplified spray technique using perfume atomizer from aqueous solution of SnCl 2 precursor. The structural studies revealed that the films are highly crystalline in nature with preferential orientation along the (2 0 0) plane. It is found that the size of the crystallites of the doubly doped tin oxide films is larger (69 nm) than that (27 nm) of their undoped counterparts. The dislocation density of the doubly doped film is lesser (2.08×10 14 lines/m 2) when compared with that of the undoped film (13.2×10 14 lines/m 2), indicating the higher degree of crystallinity of the doubly doped films. The SEM images depict that the films are homogeneous and uniform. The optical transmittance in the visible range and the optical band gap of the doubly doped films are 71% and 3.56 eV respectively. The sheet resistance (4.13 Ω/□) attained for the doubly doped film in this study is lower than the values reported for spray deposited fluorine or antimony doped tin oxide films prepared from aqueous solution of SnCl 2 precursor (without using methanol or ethanol).

Synthesis and thermoelectric properties of tantalum-doped ZrNiSn half-Heusler alloys

NASA Astrophysics Data System (ADS)

Zhao, Degang; Zuo, Min; Wang, Zhenqing; Teng, Xinying; Geng, Haoran

2014-04-01

The Ta-doped ZrNiSn half-Heusler alloys, Zr1-xTaxNiSn, were synthesized by arc melting and hot-press sintering. Microstructure of Zr1-xTaxNiSn compounds were analyzed and the thermoelectric (TE) properties of Zr1-xTaxNiSn compounds were measured from room temperature to 823 K. The electrical conductivity increased with increasing Ta content. The Seebeck coefficient of Zr1-xTaxNiSn compounds was sharply decreased with increasing Ta content. The Hall mobility was proportional to T-1.5 above 673 K, indicating that the acoustic phonon scattering was predominant in the temperature range. The thermal conductivity was effectively depressed by introducing Ta substitution. The figure of merit of ZrNiSn compounds was improved due to the decreased thermal conductivity and increased electrical conductivity. The maximum ZT value of 0.60 was achieved for Zr0.97Ta0.03NiSn sample at 823 K.

Electrical and optical properties of nitrogen doped SnO{sub 2} thin films deposited on flexible substrates by magnetron sputtering

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

Fang, Feng, E-mail: fangfeng@seu.edu.cn; Zhang, Yeyu; Wu, Xiaoqin

2015-08-15

Graphical abstract: The best SnO{sub 2}:N TCO film: about 80% transmittance and 9.1 × 10{sup −4} Ω cm. - Highlights: • Nitrogen-doped tin oxide film was deposited on PET by RF-magnetron sputtering. • Effects of oxygen partial pressure on the properties of thin films were investigated. • For SnO{sub 2}:N film, visible light transmittance was 80% and electrical resistivity was 9.1 × 10{sup −4} Ω cm. - Abstract: Nitrogen-doped tin oxide (SnO{sub 2}:N) thin films were deposited on flexible polyethylene terephthalate (PET) substrates at room temperature by RF-magnetron sputtering. Effects of oxygen partial pressure (0–4%) on electrical and optical propertiesmore » of thin films were investigated. Experimental results showed that SnO{sub 2}:N films were amorphous state, and O/Sn ratios of SnO{sub 2}:N films were deviated from the standard stoichiometry 2:1. Optical band gap of SnO{sub 2}:N films increased from approximately 3.10 eV to 3.42 eV as oxygen partial pressure increased from 0% to 4%. For SnO{sub 2}:N thin films deposited on PET, transmittance was about 80% in the visible light region. The best transparent conductive oxide (TCO) deposited on flexible PET substrates was SnO{sub 2}:N thin films preparing at 2% oxygen partial pressure, the transmittance was about 80% and electrical conductivity was about 9.1 × 10{sup −4} Ω cm.« less

Effect of both deposition temperature and indium doping on the properties of sol-gel dip-coated SnO2 films

NASA Astrophysics Data System (ADS)

Caglar, Mujdat; Atar, Kadir Cemil

2012-10-01

Using indium chloride as an In source, In-doped SnO2 films were fabricated by sol-gel method through dip-coating on borofloat glass substrates. The undoped SnO2 films were deposited in air between 400 and 600 °C to get optimum deposition temperature in terms of crystal quality and hence In-doped SnO2 films were deposited in air at 600 °C. The effect of both deposition temperature and In content on structural, morphological, optical and electrical properties was investigated. The crystalline structure and orientation of the films were investigated by X-ray diffraction (XRD) and surface morphology was studied by a field emission scanning electron microscope (FESEM). The compositional analysis of the films was confirmed by energy dispersive X-ray spectrometer (EDS). The absorption band edge of the SnO2 films shifted from 3.88 to 3.66 eV with In content. The van der Pauw method was used to measure the sheet resistance of the films. The sheet resistance was affected significantly by deposition temperature and In content.

Fully gapped superconductivity in In-doped topological crystalline insulator Pb 0.5Sn 0.5Te

DOE PAGES

Du, Guan; Gu, G. D.; Du, Zengyi; ...

2015-07-27

In this study, superconductors derived from topological insulators and topological crystalline insulators by chemical doping have long been considered to be candidates as topological superconductors. Pb 0.5Sn 0.5Te is a topological crystalline insulator with mirror symmetry protected surface states on (001)-, (011)-, and (111)-oriented surfaces. The superconductor (Pb 0.5Sn 0.5) 0.7In 0.3Te is produced by In doping in Pb 0.5Sn 0.5Te, and is thought to be a topological superconductor. Here we report scanning tunneling spectroscopy measurements of the superconducting state as well as the superconducting energy gap in (Pb 0.5Sn 0.5) 0.7In 0.3Te on a (001)-oriented surface. The spectrum canmore » be well fitted by an anisotropic s-wave gap function of Δ = 0.72 + 0.18cos4θ meV using Dynes model. The results show that the superconductor seems to be a fully gapped one without any in-gap states, in contradiction with the expectation of a topological superconductor.« less

Divacancy-tin related defects in irradiated germanium

NASA Astrophysics Data System (ADS)

Khirunenko, L. I.; Sosnin, M. G.; Duvanskii, A. V.; Abrosimov, N. V.; Riemann, H.

2018-04-01

A new absorption spectrum has been detected in the region of 770-805 cm-1 following the annealing of low temperature irradiated Sn-doped Ge. The spectrum develops simultaneously with the disappearance of the V2-related absorption band. The new spectra arise both in p- (doping with gallium) and n- (doping with antimony) type samples and are completely identical to the absorption spectrum of the corresponding dopants. The studies have shown that the defects responsible for the registered spectra have hydrogen-like excited states similar to those observed for hydrogen-like group-III acceptors and group-V donors in Ge. The defects are identified as SnV2Ga and SnV2Sb. The formation of the revealed complexes consists of two stages. During the first stage, the defects are created as a result of the direct interaction of SnV2 diffusing upon the annealing with atoms Ga or Sb. The second stage arises, apparently, due to the participation of SnV2 in the formation of intermediate defects that are optically inactive and transform into the revealed defects at annealing temperatures Tann. > 243 K.

Electrical properties of tin-doped zinc oxide nanostructures doped at different dopant concentrations

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

Nasir, M. F., E-mail: babaibaik2002@yahoo.com; Zainol, M. N., E-mail: nizarzainol@yahoo.com; Hannas, M., E-mail: mhannas@gmail.com

This project has been focused on the electrical and optical properties respectively on the effect of Tin doped zinc oxide (ZnO) thin films at different dopant concentrations. These thin films were doped with different Sn dopant concentrations at 1 at%, 2 at%, 3 at%, 4 at% and 5 at% was selected as the parameter to optimize the thin films quality while the annealing temperature is fixed 500 °C. Sn doped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thinmore » films were characterized using Current Voltage (I-V) measurement and ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (Perkin Elmer Lambda 750) for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 4 at% Sn doping concentration with the value 3.08 × 10{sup 3} Ωcm{sup −1}. The absorption coefficient spectrum obtained shows all films exhibit very low absorption in the visible (400-800 nm) and near infrared (NIR) (>800 nm) range but exhibit high absorption in the UV range.« less

Effect of tetravalent dopants on hematite nanostructure for enhanced photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Subramanian, Arunprabaharan; Gracia-Espino, Eduardo; Annamalai, Alagappan; Lee, Hyun Hwi; Lee, Su Yong; Choi, Sun Hee; Jang, Jum Suk

2018-01-01

In this paper, the influence of tetravalent dopants such as Si4+, Sn4+, Ti4+, and Zr4+ on the hematite (α-Fe2O3) nanostructure for enhanced photoelectrochemical (PEC) water splitting are reported. The tetravalent doping was performed on hydrothermally grown akaganeite (β-FeOOH) nanorods on FTO (fluorine-doped tin-oxide) substrates via a simple dipping method for which the respective metal-precursor solution was used, followed by a high-temperature (800° C) sintering in a box furnace. The photocurrent density for the pristine (hematite) photoanode is ∼0.81 mA/cm2 at 1.23 VRHE, with an onset potential of 0.72 VRHE; however, the tetravalent dopants on the hematite nanostructures alter the properties of the pristine photoanode. The Si4+-doped hematite photoanode showed a slight photocurrent increment without a changing of the onset potential of the pristine photoanode. The Sn4+- and Ti4+-doped hematite photoanodes, however, showed an anodic shift of the onset potential with the photocurrent increment at a higher applied potential. Interestingly, the Zr4+-doped hematite photoanode exhibited an onset potential that is similar to those of the pristine and Si4+-doped hematite, but a larger photocurrent density that is similar to those of the Sn4+- and Ti4+-doped photoanodes was recorded. The photoactivity of the doped photoanodes at 1.23 VRHE follows the order Zr > Sn > Ti > Si. The onset-potential shifts of the doped photoanodes were investigated using the Ab initio calculations that are well correlated with the experimental data. X-ray diffraction (XRD) and scanning-electron microscopy (FESEM) revealed that both the crystalline phase of the hematite and the nanorod morphology were preserved after the doping procedure. X-ray photoelectron spectroscopy (XPS) confirmed the presence of the tetravalent dopants on the hematite nanostructure. The charge-transfer resistance at the various interfaces of the doped photoanodes was studied using impedance spectroscopy. The doping on the hematite photoanodes was confirmed using the Mott-Schottky (MS) analysis.

Charge-transport in tin-iodide perovskite CH3NH3SnI3: origin of high conductivity.

PubMed

Takahashi, Yukari; Obara, Rena; Lin, Zheng-Zhong; Takahashi, Yukihiro; Naito, Toshio; Inabe, Tamotsu; Ishibashi, Shoji; Terakura, Kiyoyuki

2011-05-28

The structural and electrical properties of a metal-halide cubic perovskite, CH(3)NH(3)SnI(3), have been examined. The band structure, obtained using first-principles calculation, reveals a well-defined band gap at the Fermi level. However, the temperature dependence of the single-crystal electrical conductivity shows metallic behavior down to low temperatures. The temperature dependence of the thermoelectric power is also metallic over the whole temperature range, and the large positive value indicates that charge transport occurs with a low concentration of hole carriers. The metallic properties of this as-grown crystal are thus suggested to result from spontaneous hole-doping in the crystallization process, rather than the semi-metal electronic structure. The present study shows that artificial hole doping indeed enhances the conductivity.

Highly enhanced ultraviolet photosensitivity and recovery speed in electrospun Ni-doped SnO2 nanobelts

NASA Astrophysics Data System (ADS)

Huang, Siya; Matsubara, Kohei; Cheng, Jing; Li, Heping; Pan, Wei

2013-09-01

Precisely controlled Ni-doped SnO2 (NSO) nanobelt arrays are synthesized and assembled via electrospinning. In comparison to pristine SnO2 nanobelts, enhanced photosensitivity (˜103) as well as recovery speed (˜1 s) is obtained in NSO nanobelts. The mechanism is clarified by the compensation effect of acceptor impurity Ni, which not only promotes the oxygen-surface interaction but also introduces trapping centers in SnO2 matrix. The reduced grain size (˜4 nm) along with increased depletion layer thickness also benefits the photosensitivity of NSO nanobelts. These improved photoresponse properties make the NSO nanobelt a promising candidate for high-performance ultraviolet detectors.

Electronic structure and magnetic properties of Ni-doped SnO2 thin films

NASA Astrophysics Data System (ADS)

Sharma, Mayuri; Kumar, Shalendra; Alvi, P. A.

2018-05-01

This paper reports the electronic structure and magnetic properties of Ni-doped SnO2 thin film which were grown on Si (100) substrate by PLD (pulse laser deposition) technique under oxygen partial pressure (PO2). For getting electronic structure and magnetic behavior, the films were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DC magnetization measurements. The NEXAFS study at Ni L3,2 edge has been done to understand the local environment of Ni and Sn ions within SnO2 lattice. DC magnetization measurement shows that the saturation magnetization increases with the increase in substitution of Ni2+ ions in the system.

Formation and characterization of Ni/Al Ohmic contact on n+-type GeSn

NASA Astrophysics Data System (ADS)

Zhang, Xu; Zhang, Dongliang; Zheng, Jun; Liu, Zhi; He, Chao; Xue, Chunlai; Zhang, Guangze; Li, Chuanbo; Cheng, Buwen; Wang, Qiming

2015-12-01

In this study, a Ni/Al Ohmic contact on a highly doped n-type GeSn has been investigated. A specific contact resistivity as low as (2.26 ± 0.11) × 10-4 Ω cm2 was obtained with the GeSn sample annealed at a temperature of 450 °C for 30 s. The linear Ohmic behavior was attributed to the low resistance of the Ni(GeSn) phase; this behavior was determined using glancing-angle X-ray diffraction, and the quantum tunneling current through the Schottky barrier narrowed because of high doping; this phenomenon was confirmed from the contact resistance characteristics at different temperatures from 45 to 205 K.

Moss-Burstein shift in La-doped BaSnO3; A novel electron transport layer material for hybrid halide perovskite solar cells

NASA Astrophysics Data System (ADS)

Taya, Ankur; Rani, Priti; Kashyap, Manish K.

2018-04-01

Highly efficient hybrid (organic-inorganic) halide perovskite solar cells (PSCs) employ TiO2 as electron transport layer (ETL) but it impedes the device stability under solar illumination. Therefore, there is an imperative need to study the materials that can be the ideal replacement for TiO2 as ETL. With its growth at mild conditions recently by Shin et al. [Science, 356, 167 (2017)], La-doped BaSnO3 (LBSO) emerges out as an efficient candidate for ETL in PSCs. In this direction, we represent first-principles electronic properties and optical response of pristine and La-doped BaSnO3 using full potential linear augmented plane wave (FPLAPW) method within time efficient orbital independent modified Becke Johnson (mBJ) approach. Post La-doping, Moss-Burtsein shift is observed in BaSnO3 that establishes it as an excellent n-type transparent conducting oxide. The optical absorption spectra of LBSO has been analyzed to prove almost full transmittivity for energy ≤ 4eV which affirms LBSO as an ideal material for ETL in various PSCs.

Enhanced magnetism of perovskite oxides, Sr(Sn,Fe)O3- δ , by substitution of nonmagnetic Ca and Ti ions

NASA Astrophysics Data System (ADS)

Nomura, Kiyoshi; Suzuki, Shigeyo; Mizunuma, Tomoya; Koike, Yuya; Okazawa, Atsushi

2017-11-01

Magnetic properties of perovskite oxides, SrSn1- x Fe x O3- δ ( x ≤ 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (Sr1- y Ca y )(Sn1- x Fe x )O3- δ and Sr(Sn1- x- y Fe x Ti y )O3- δ . The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O3- δ showed small saturation magnetizations as compared with non-Ti substituted one, the magnetization increased a little with Ti doping rates up to 15%. On the other hand, all Ca-substituted Sr(Sn, Fe)O3- δ showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe3+ and a doublet of Fe4+ were observed in Mössbauer spectra of Ca-substituted Sr(Sn, Fe)O3- δ with weak ferromagnetism, and two sextets of high spin Fe3+ were additionally observed in Mössbauer spectra of Ca-doped Sr(Sn, Fe)O3- δ with relatively strong ferromagnetism. When Sr(Sn, Fe)O3- δ were further codoped with Ca and Ti ions, they showed the stable and enhanced ferromagnetic properties. It is considered that magnetic polarons among high spin Fe3+ species are overlapped by shrinking or deforming the crystal structure of perovskite oxides. That is the magnetism induced by a chemical pressure of perovskite oxides.

Effects of hydrogen on acceptor activation in ternary nitride semiconductors

DOE PAGES

Fioretti, Angela N.; Stokes, Adam; Young, Matthew R.; ...

2017-02-09

Doping control is necessary to unlock the scientific and technological potential of many materials, including ternary II-IV-nitride semiconductors, which are closely related to binary GaN. In particular, ZnSnN 2 has been reported to have degenerate doping density, despite bandgap energies that are well suited for solar energy conversion. Here, we show that annealing Zn-rich Zn 1+xSn 1-xN 2 grown with added hydrogen reduces its free electron density by orders of magnitude, down to 4 x 10 16 cm -3. This experimental observation can be explained by hydrogen passivation of acceptors in Zn 1+xSn 1-xN 2 during growth, lowering the drivingmore » force for unintentional donor formation. Lastly, these results indicate that the doping control principles used in GaN can be translated to ZnSnN 2, suggesting that other strategies used in binary III-Vs can be applied to accelerate the technological development of ternary II-IV-N 2 materials.« less

Hollow SnO2 nanospheres with oxygen vacancies entrapped by a N-doped graphene network as robust anode materials for lithium-ion batteries.

PubMed

Wu, Naiteng; Du, Wuzhou; Gao, Xu; Zhao, Liang; Liu, Guilong; Liu, Xianming; Wu, Hao; He, Yan-Bing

2018-06-21

The practical application of tin dioxide (SnO2) in lithium-ion batteries has been greatly hindered by its large volumetric expansion and low conductivity. Thus, a rational design of the size, geometry and the pore structure of SnO2-based nanomaterials is still a dire demand. To this end, herein we report an effective approach for engineering hollow-structured SnO2 nanospheres with adequate surface oxygen vacancies simultaneously wrapped by a nitrogen-doped graphene network (SnO2-x/N-rGO) through an electrostatic adsorption-induced self-assembly together with a thermal reduction process. The close electrostatic attraction achieved a tight and uniform combination of positively charged SnO2 nanospheres with negatively charged graphene oxide (GO), which can alleviate the aggregation and volume expansion of the entrapped SnO2 nanospheres. Subsequent thermal treatment not only ensures a significant reduction of the GO sheets accompanying nitrogen-doping, but also induces the generation of oxygen vacancies on the surface of the SnO2 hollow nanospheres, together building up a long-range and bicontinuous transfer channel for rapid electron and ion transport. Because of these structural merits, the as-built SnO2-x/N-rGO composite used as the anode material exhibits excellent robust cycling stability (∼912 mA h g-1 after 500 cycles at 0.5 A g-1 and 652 mA h g-1 after 200 cycles at 1 A g-1) and superior rate capability (309 mA h g-1 at 10 A g-1). This facile fabrication strategy may pave the way for the construction of high performance SnO2-based anode materials for potential application in advanced lithium-ion batteries.

An analysis of point defects induced by In, Al, Ni, and Sn dopants in Bridgman-grown CdZnTe detectors and their influence on trapping of charge carriers

DOE PAGES

Gul, R.; Roy, U. N.; James, R. B.

2017-03-15

In this paper, we studied point defects induced in Bridgman-grown CdZnTe detectors doped with Indium (In), Aluminium (Al), Nickel (Ni), and Tin (Sn). Point defects associated with different dopants were observed, and these defects were analyzed in detail for their contributions to electron/hole (e/h) trapping. We also explored the correlations between the nature and abundance of the point defects with their influence on the resistivity, electron mobility-lifetime (μτ e) product, and electron trapping time. We used current-deep level transient spectroscopy to determine the energy, capture cross-section, and concentration of each trap. Furthermore, we used the data to determine the trappingmore » and de-trapping times for the charge carriers. In In-doped CdZnTe detectors, uncompensated Cd vacancies (V Cd -) were identified as a dominant trap. The V Cd - were almost compensated in detectors doped with Al, Ni, and Sn, in addition to co-doping with In. Dominant traps related to the dopant were found at E v + 0.36 eV and E v + 1.1 eV, E c + 76 meV and E v + 0.61 eV, E v + 36 meV and E v + 0.86 eV, E v + 0.52 eV and E c + 0.83 eV in CZT:In, CZT:In + Al, CZT:In + Ni, and CZT:In + Sn, respectively. Results indicate that the addition of other dopants with In affects the type, nature, concentration (N t), and capture cross-section (σ) and hence trapping (t t) and de-trapping (t dt) times. Finally, the dopant-induced traps, their corresponding concentrations, and charge capture cross-section play an important role in the performance of radiation detectors, especially for devices that rely solely on electron transport.« less

An analysis of point defects induced by In, Al, Ni, and Sn dopants in Bridgman-grown CdZnTe detectors and their influence on trapping of charge carriers

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

Gul, R.; Roy, U. N.; James, R. B.

In this paper, we studied point defects induced in Bridgman-grown CdZnTe detectors doped with Indium (In), Aluminium (Al), Nickel (Ni), and Tin (Sn). Point defects associated with different dopants were observed, and these defects were analyzed in detail for their contributions to electron/hole (e/h) trapping. We also explored the correlations between the nature and abundance of the point defects with their influence on the resistivity, electron mobility-lifetime (μτ e) product, and electron trapping time. We used current-deep level transient spectroscopy to determine the energy, capture cross-section, and concentration of each trap. Furthermore, we used the data to determine the trappingmore » and de-trapping times for the charge carriers. In In-doped CdZnTe detectors, uncompensated Cd vacancies (V Cd -) were identified as a dominant trap. The V Cd - were almost compensated in detectors doped with Al, Ni, and Sn, in addition to co-doping with In. Dominant traps related to the dopant were found at E v + 0.36 eV and E v + 1.1 eV, E c + 76 meV and E v + 0.61 eV, E v + 36 meV and E v + 0.86 eV, E v + 0.52 eV and E c + 0.83 eV in CZT:In, CZT:In + Al, CZT:In + Ni, and CZT:In + Sn, respectively. Results indicate that the addition of other dopants with In affects the type, nature, concentration (N t), and capture cross-section (σ) and hence trapping (t t) and de-trapping (t dt) times. Finally, the dopant-induced traps, their corresponding concentrations, and charge capture cross-section play an important role in the performance of radiation detectors, especially for devices that rely solely on electron transport.« less

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

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

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

2016-05-09

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

Multiscale microstructures and improved thermoelectric performance of Mg2(Si0.4Sn0.6)Sbx solid solutions

NASA Astrophysics Data System (ADS)

Zhang, Xin; Liu, Hongliang; Li, Songhao; Zhang, Feipeng; Lu, Qingmei; Li, Jingfeng

2014-03-01

A series of Sb-doped Mg2(Si0.4Sn0.6)Sbx (0 ≤ x ≤ 0.025) solid solutions were prepared by an induction melting, Melt Spinning (MS) and Spark Plasma Sintering (SPS) method, namely the non-equilibrium technique MS-SPS, using bulks of Magnesium, Silicon, Tin, and Antimony as raw materials. The non-equilibrium technique generates the unique multiscale microstructures of samples containing micronscale grains and nanoscale precipitates, the multiscale microstructures remarkably make the lattice thermal conductivities decreased, particularly for samples with the nanoscale precipitates having the size of 10-20 nm. Meanwhile, Sb-doping greatly increased the electrical performance of samples. Consequently, the Sb-doping combined with the multiscale microstructures strategy remarkably improves the overall thermoelectric (TE) performance of Sb doped samples, and a high dimensionless figure of merit (ZT) value of up to 1.25 at 723 K is obtained with Mg2(Si0.4Sn0.6)Sb0.02 sample in a relatively wide temperature range.

P-type field effect transistor based on Na-doped BaSnO3

NASA Astrophysics Data System (ADS)

Jang, Yeaju; Hong, Sungyun; Park, Jisung; Char, Kookrin

We fabricated field effect transistors (FET) based on the p-type Na-doped BaSnO3 (BNSO) channel layer. The properties of epitaxial BNSO channel layer were controlled by the doping rate. In order to modulate the p-type FET, we used amorphous HfOx and epitaxial BaHfO3 (BHO) gate oxides, both of which have high dielectric constants. HfOx was deposited by atomic-layer-deposition and BHO was epitaxially grown by pulsed laser deposition. The pulsed laser deposited SrRuO3 (SRO) was used as the source and the drain contacts. Indium-tin oxide and La-doped BaSnO3 were used as the gate electrodes on top of the HfOx and the BHO gate oxides, respectively. We will analyze and present the performances of the BNSO field effect transistor such as the IDS-VDS, the IDS-VGS, the Ion/Ioff ratio, and the field effect mobility. Samsung Science and Technology Foundation.

Luminescence properties of Sm3+-doped alkaline earth ortho-stannates

NASA Astrophysics Data System (ADS)

Stanulis, Andrius; Katelnikovas, Artūras; Enseling, David; Dutczak, Danuta; Šakirzanovas, Simas; Bael, Marlies Van; Hardy, An; Kareiva, Aivaras; Jüstel, Thomas

2014-05-01

A series of Sm3+ doped M2SnO4 (M = Ca, Sr and Ba) samples were prepared by a conventional high temperature solid-state reaction route. All samples were characterized by powder X-ray diffraction (XRD) analysis, photoluminescence (PL), photoluminescence thermal quenching (TQ) and fluorescence lifetime (FL) measurements. The morphology of synthesized phosphor powders was examined by scanning electron microscopy (SEM). Moreover, luminous efficacies (LE) and color points of the CIE 1931 color space diagram were calculated and discussed. Synthesized powders showed bright orange-red emission under UV excitation. Based on the results obtained we demonstrate that Sm3+ ions occupy Ca and Sr sites in the Ca2SnO4 and Sr2SnO4 ortho-stannate structures, respectively. In contrast, Sm3+ substitutes Sn in the barium ortho-stannate Ba2SnO4 structure.

Structural and optical properties of ITO and Cu doped ITO thin films

NASA Astrophysics Data System (ADS)

Chakraborty, Deepannita; Kaleemulla, S.; Rao, N. Madhusudhana; Subbaravamma, K.; Rao, G. Venugopal

2018-04-01

(In0.95Sn0.05)2O3 and (In0.90Cu0.05Sn0.05)2O3 thin films were coated onto glass substrate by electron beam evaporation technique. The structural and optical properties of ITO and Cu doped ITO thin films have been studied by X-ray diffractometer (XRD) and UV-Vis-NIR spectrophotometer. The crystallite size obtained for ITO and Cu doped ITO thin films was in the range of 24 nm to 22 nm. The optical band gap of 4 eV for ITO thin film sample has been observed. The optical band gap decreases to 3.85 eV by doping Cu in ITO.

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

DOE PAGES

Chen, K.; Strigari, F.; Sundermann, M.; ...

2018-01-17

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Fluorine-doped SnO2 nanoparticles anchored on reduced graphene oxide as a high-performance lithium ion battery anode

NASA Astrophysics Data System (ADS)

Cui, Dongming; Zheng, Zhong; Peng, Xue; Li, Teng; Sun, Tingting; Yuan, Liangjie

2017-09-01

The composite of fluorine-doped SnO2 anchored on reduced graphene oxide (F-SnO2/rGO) has been synthesized through a hydrothermal method. F-SnO2 particles with average size of 8 nm were uniformly anchored on the surfaces of rGO sheets and the resulting composite had a high loading of F-SnO2 (ca. 90%). Benefiting from the remarkably improved electrical conductivity and Li-ion diffusion in the electrode by F doping and rGO incorporation, the composite material exhibited high reversible capacity, excellent long-term cycling stability and superior rate capability. The electrode delivered a large reversible capacity of 1037 mAh g-1 after 150 cycles at 100 mA g-1 and high rate capacities of 860 and 770 mAh g-1 at 1 and 2 A g-1, respectively. Moreover, the electrode could maintain a high reversible capacities of 733 mAh g-1 even after 250 cycles at 500 mA g-1. The outstanding electrochemical performance of the as-synthesized composite make it a promising anode material for high-energy lithium ion batteries.

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

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

Chen, K.; Strigari, F.; Sundermann, M.

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Effect of both deposition temperature and indium doping on the properties of sol-gel dip-coated SnO2 films.

PubMed

Caglar, Mujdat; Atar, Kadir Cemil

2012-10-01

Using indium chloride as an In source, In-doped SnO(2) films were fabricated by sol-gel method through dip-coating on borofloat glass substrates. The undoped SnO(2) films were deposited in air between 400 and 600 °C to get optimum deposition temperature in terms of crystal quality and hence In-doped SnO(2) films were deposited in air at 600 °C. The effect of both deposition temperature and In content on structural, morphological, optical and electrical properties was investigated. The crystalline structure and orientation of the films were investigated by X-ray diffraction (XRD) and surface morphology was studied by a field emission scanning electron microscope (FESEM). The compositional analysis of the films was confirmed by energy dispersive X-ray spectrometer (EDS). The absorption band edge of the SnO(2) films shifted from 3.88 to 3.66 eV with In content. The van der Pauw method was used to measure the sheet resistance of the films. The sheet resistance was affected significantly by deposition temperature and In content. Copyright © 2012 Elsevier B.V. All rights reserved.

Extracting dielectric fixed charge density on highly doped crystalline-silicon surfaces using photoconductance measurements

NASA Astrophysics Data System (ADS)

To, A.; Hoex, B.

2017-11-01

A novel method for the extraction of fixed interface charge, Qf, and the surface recombination parameters, Sn0 and Sp0, from the injection-level dependent effective minority carrier lifetime measurements is presented. Unlike conventional capacitance-voltage measurements, this technique can be applied to highly doped surfaces provided the surface carrier concentration transitions into strong depletion or inversion with increased carrier injection. By simulating the injection level dependent Auger-corrected inverse lifetime curve of symmetrically passivated and diffused samples after sequential annealing and corona charging, it was revealed that Qf, Sn0, and Sp0 have unique signatures. Therefore, these important electronic parameters, in some instances, can independently be resolved. Furthermore, it was shown that this non-linear lifetime behaviour is exhibited on both p-type and n-type diffused inverted surfaces, by demonstrating the approach with phosphorous diffused n+pn+ structures and boron diffused p+np+ structures passivated with aluminium oxide (AlOx) and silicon nitride, respectively (SiNx). The results show that the approximation of a mid-gap Shockley-Read-Hall defect level with equal capture cross sections is able to, in the samples studied in this work, reproduce the observed injection level dependent lifetime behaviour.

Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

NASA Astrophysics Data System (ADS)

Vignesh, K.; Hariharan, R.; Rajarajan, M.; Suganthi, A.

2013-07-01

Visible light active Ag doped SnO2 nanoparticles modified with curcumin (Cur-Ag-SnO2) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV-visible diffuse reflectance spectra (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO2, the surface modified photocatalysts (Ag-SnO2 and Cur-Ag-SnO2) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur-Ag-SnO2 shows better photocatalytic activity than that of Ag-SnO2 and SnO2. The superior photocatalytic activity of Cur-Ag-SnO2 could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur-Ag-SnO2 were tested.

Infrared absorption and visible transparency in heavily doped p-type BaSnO 3

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

Li, Yuwei; Sun, Jifeng; Singh, David J.

2017-01-30

The recent experimental work shows that perovskite BaSnO 3 can be heavily doped by K to become a stable p-type semiconductor. Here, we find that p-type perovskite BaSnO 3 retains transparency for visible light while absorbing strongly in the infrared below 1.5 eV. The origin of the remarkable optical transparency even with heavy doping is that the interband transitions that are enabled by empty states at the top of the valence band are concentrated mainly in the energy range from 0.5 to 1.5 eV, i.e., not extending past the near IR. In contrast to n-type, the Burstein-Moss shift is slightlymore » negative, but very small reflecting the heavier valence bands relative to the conduction bands.« less

Structural and photocatalytic studies on pure and Sn ion doped ZnO-graphene nanocomposites

NASA Astrophysics Data System (ADS)

Beura, Rosalin; Thangadurai, P.

2016-05-01

Graphene based metal oxide nanocomposites have been widely used as a photocatalyst for the treatment of water pollutants. This work demonstrates the synthesis of graphene composite with pure and Sn ion doped-ZnO and their photocatalytic properties are reported. Structural studies were carried out by X-ray diffraction and Raman spectroscopy to confirm the formation of the nanocomposites. Microstructure was characterized by scanning electron microscopy showing rod shaped ZnO and the layer structured graphene in the ZnO-graphene composite. In comparison with the undoped ZnO-graphene composite, the Sn ion doped ZnO-graphene composite have shown better degradation of methyl orange dye that is about 99% of degradation. Band gap of the composite materials was calculated to be 3.36 eV from the UV-Vis result.

Structural and photocatalytic studies on pure and Sn ion doped ZnO-graphene nanocomposites

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

Beura, Rosalin; Thangadurai, P., E-mail: thangaduraip.nst@pondiuni.edu.in

2016-05-23

Graphene based metal oxide nanocomposites have been widely used as a photocatalyst for the treatment of water pollutants. This work demonstrates the synthesis of graphene composite with pure and Sn ion doped-ZnO and their photocatalytic properties are reported. Structural studies were carried out by X-ray diffraction and Raman spectroscopy to confirm the formation of the nanocomposites. Microstructure was characterized by scanning electron microscopy showing rod shaped ZnO and the layer structured graphene in the ZnO-graphene composite. In comparison with the undoped ZnO-graphene composite, the Sn ion doped ZnO-graphene composite have shown better degradation of methyl orange dye that is aboutmore » 99% of degradation. Band gap of the composite materials was calculated to be 3.36 eV from the UV-Vis result.« less

An investigation of the Nb doping effect on structural, morphological, electrical and optical properties of spray deposited F doped SnO2 films

NASA Astrophysics Data System (ADS)

Turgut, G.; Keskenler, E. F.; Aydın, S.; Yılmaz, M.; Doǧan, S.; Düzgün, B.

2013-03-01

F and Nb + F co-doped SnO2 thin films were deposited on glass substrates by the spray pyrolysis method. The microstructural, morphological, electrical and optical properties of the 10 wt% F doped SnO2 (FTO) thin films were investigated specifically for niobium (Nb) doping in the range of 0-4 at.% with 1 at.% steps. As shown by the x-ray diffraction patterns, the films exhibited a tetragonal cassiterite structure with (200) preferential orientation. It was observed that grain sizes of the films for (200) and (301) peaks depended on the Nb doping concentration and varied in the range of 25.11-32.19 and 100.6-183.7 nm, respectively. The scanning electron microscope (SEM) micrographs showed that the FTO films were made of small pyramidal grains, while doubly doped films were made of small pyramidal grains and big polyhedron grains. From electrical studies, although 1 at.% Nb doped FTO films have the lowest sheet resistance and resistivity values, the highest figure-of-merit and optical band gap values obtained for FTO films were 16.2 × 10-2 Ω-1 and 4.21 eV, respectively. Also, infrared reflectivity values of the films were in the range of 97.39-98.98%. These results strongly suggest that these films are an attractive candidate for various optoelectronic applications and for photothermal conversion of solar energy.

Ca(2+)-mediated anionic lipid-plasmid DNA lipoplexes. Electrochemical, structural, and biochemical studies.

PubMed

Barrán-Berdón, Ana L; Yélamos, Belén; Malfois, Marc; Aicart, Emilio; Junquera, Elena

2014-10-07

Several experimental methods, such as zeta potential, gel electrophoresis, small-angle X-ray scattering, gene transfection, fluorescence microscopy, flow cytometry, and cell viability/cytotoxicity assays, have been used to analyze the potential of anionic lipids (AL) as effective nontoxic and nonviral DNA vectors, assisted by divalent cations. The lipoplexes studied are those comprised of the green fluorescent protein-encoding plasmid DNA pEGFP-C3, an anionic lipid as 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) or 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS), and a zwitterionic lipid, the 1,2-dioleoyl-sn -glycero-3-phosphatidylethanolamine (DOPE, not charged at physiological pH). The studies have been carried on at different liposome and lipoplex compositions and in the presence of a variety of [Ca2+]. Electrochemical experiments reveal that DOPG/DOPE and DOPS/DOPE anionic liposomes may compact more effectively pDNA at low molar fractions (with an excess of DOPE) and at AL/pDNA ratios ≈20. Calcium concentrations around 15-20 mM are needed to yield lipoplexes neutral or slightly positive. From a structural standpoint, DOPG/DOPE-Ca2+-pDNA lipoplexes are self-assembled into a HIIc phase (inverted cylindrical micelles in hexagonal ordering with plasmid supercoils inside the cylinders), while DOPS/DOPE-Ca2+-pDNA lipoplexes show two phases in coexistence: one classical HIIc phase which contains pDNA supercoils and one Lα phase without pDNA among the lamellae, i.e., a lamellar stack of lipidic bilayers held together by Ca2+ bridges. Transfection and cell viability studies were done with HEK293T and HeLa cells in the presence of serum. Lipoplexes herein studied show moderate-to-low transfection levels combined with moderate-to-high cell viability, comparable to those yield by Lipofectamine2000*, which is a cationic lipid (CL) standard formulation, but none of them improve the output of typical CL gen vectors, mostly if they are gemini or dendritic. This fact would be indicating that, nowadays, lipofection via anionic lipids and divalent cations as mediators still needs to enhance transfection levels in order to be considered as a real and plausible alternative to lipofection through improved CLs-based lipoplexes.

On the tin impurity in the thermoelectric compound ZnSb: Charge-carrier generation and compensation

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

Prokofieva, L. V., E-mail: lprokofieva496@gmail.com; Konstantinov, P. P.; Shabaldin, A. A.

2016-06-15

The technique for measuring the Hall coefficient and electrical conductivity in the thermal cycling mode is used to study the effect of the Sn impurity on the microstructure and properties of pressed ZnSb samples. Tin was introduced as an excess component (0.1 and 0.2 at %) and as a substitutional impurity for Zn and Sb atoms in a concentration of (2–2.5) at % The temperature dependences of the parameters of lightly doped samples are fundamentally like similar curves for ZnSb with 0.1 at % of Cu. The highest Hall concentration, 1.4 × 10{sup 19} cm{sup –3} at 300 K, ismore » obtained upon the introduction of 0.1 at % of Sn; the dimensionless thermoelectric figure of merit attains its maximum value of 0.85 at 660 K. The experimental data are discussed under the assumption of two doping mechanisms, which are effective in different temperature ranges, with zinc vacancies playing the decisive role of acceptor centers. In two ZnSb samples with SnSb and ZnSn additives, the charge-carrier compensation effect is observed; this effect depends on temperature and markedly changes with doping type. As in p-type A{sup IV}–B{sup VI} materials with a low Sn content, hole compensation can be attributed to atomic recharging Sn{sup 2+} → Sn{sup 4+}. Types of compensating complexes are considered.« less

Hall and Seebeck measurements estimate the thickness of a (buried) carrier system: Identifying interface electrons in In-doped SnO{sub 2} films

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

Papadogianni, Alexandra; Bierwagen, Oliver; White, Mark E.

2015-12-21

We propose a simple method based on the combination of Hall and Seebeck measurements to estimate the thickness of a carrier system within a semiconductor film. As an example, this method can distinguish “bulk” carriers, with homogeneous depth distribution, from “sheet” carriers, that are accumulated within a thin layer. The thickness of the carrier system is calculated as the ratio of the integral sheet carrier concentration, extracted from Hall measurements, to the volume carrier concentration, derived from the measured Seebeck coefficient of the same sample. For rutile SnO{sub 2}, the necessary relation of Seebeck coefficient to volume electron concentration inmore » the range of 3 × 10{sup 17} to 3 × 10{sup 20 }cm{sup −3} has been experimentally obtained from a set of single crystalline thin films doped with varying Sb-doping concentrations and unintentionally doped bulk samples, and is given as a “calibration curve.” Using this calibration curve, our method demonstrates the presence of interface electrons in homogeneously deep-acceptor (In) doped SnO{sub 2} films on sapphire substrates.« less

Effect of Sn doping on the structural, optical and electrical properties of TiO2 films prepared by spray pyrolysis

NASA Astrophysics Data System (ADS)

Arunachalam, A.; Dhanapandian, S.; Manoharan, C.

2016-02-01

In this work, highly oriented pure and Tin-doped Titanium dioxide (Sn-doped TiO2) with porous nature photoelectrodes were deposited on ITO glass plates using spray pyrolysis technique. The XRD pattern revealed the formation of anatase TiO2 with the maximum intensity of (101) plane while doping 6 at% of Sn. The morphological studies depicted the porous nature with the uniform arrangement of small-sized grains. The presence of tin confirmed with the EDX spectra. The size of particles of 13 nm was observed from High Resolution Transmission Electron Microscopy (HR-TEM) analysis. The average transmittance was about 85% for the doped photoelectrode and was observed for the photoelectrode deposited with 6 at% of tin, with decreased energy band gap. The PL study showed the emission peak at 391 nm. The maximum carrier concentration and Hall mobility was observed for the photoelectrode deposited with 6 at% of tin. With these studies, the DSSCs were prepared separately with the dye extracted from Hibiscus Rosasinesis and Hibiscus Surttasinesis and their efficiency was maximum for the DSSC prepared with 6 at% of tin.

Eu 3+-doped wide band gap Zn 2SnO 4 semiconductor nanoparticles: Structure and luminescence

DOE PAGES

Dimitrievska, Mirjana; Ivetić, Tamara B.; Litvinchuk, Alexander P.; ...

2016-08-03

Nanocrystalline Zn 2SnO 4 powders doped with Eu 3+ ions were synthesized via a mechanochemical solid-state reaction method followed by postannealing in air at 1200 °C. X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Raman and photoluminescence (PL) spectroscopies provide convincing evidence for the incorporation of Eu 3+ ions into the host matrix on noncentrosymmetric sites of the cubic inverse spinel lattice. Microstructural analysis shows that the crystalline grain size decreases with the addition of Eu 3+. Formation of a nanocrystalline Eu 2Sn 2O 7 secondary phase is also observed. Luminescence spectra of Eu 3+-doped samples show several emissions, including narrow-bandmore » magnetic dipole emission at 595 nm and electric dipole emission at 615 nm of the Eu 3+ ions. Excitation spectra and lifetime measurements suggest that Eu 3+ ions are incorporated at only one symmetry site. According to the crystal field theory, it is assumed that Eu 3+ ions participate at octahedral sites of Zn 2+ or Sn 4+ under a weak crystal field, rather than at the tetrahedral sites of Zn2+, because of the high octahedral stabilization energy for Eu 3+. Activation of symmetry forbidden (IR-active and silent) modes is observed in the Raman scattering spectra of both pure and doped samples, indicating a disorder of the cation sublattice of Zn 2SnO 4 nanocrystallites. These results were further supported by the first principle lattice dynamics calculations. The spinel-type Zn 2SnO 4 shows effectiveness in hosting Eu 3+ ions, which could be used as a prospective green/red emitter. As a result, this work also illustrates how sustainable and simple preparation methods could be used for effective engineering of material properties.« less

Structural, optical, and improved field-emission properties of tetrapod-shaped Sn-doped ZnO nanostructures synthesized via thermal evaporation.

PubMed

Zhou, Xiongtu; Lin, Tihang; Liu, Yuhui; Wu, Chaoxing; Zeng, Xiangyao; Jiang, Dong; Zhang, Yong-ai; Guo, Tailiang

2013-10-23

High-quality tetrapod-shaped Sn-doped ZnO (T-SZO) nanostructures have been successfully synthesized via the thermal evaporation of mixed Zn and Sn powder. The effects of the Sn dopant on the morphology, microstructure, optical, and field-emission (FE) properties of T-SZO were investigated. It was found that the growth direction of the legs of T-SZO is parallel to the [0001] crystal c-axis direction and that the incorporation of Sn in the ZnO matrix increases the aspect ratio of the tetrapods, leads to blue shift in the UV region, and considerably improves the FE performance. The results also show that tetrapod cathodes with around a 0.84 atom % Sn dosage have the best FE properties, with a turn-on field of 1.95 V/μm, a current density of 950 μA/cm2 at a field of 4.5 V/μm, and a field-enhancement factor as high as 9556.

A novel flexible room temperature ethanol gas sensor based on SnO2 doped poly-diallyldimethylammonium chloride.

PubMed

Zhan, Shuang; Li, Dongmei; Liang, Shengfa; Chen, Xin; Li, Xia

2013-04-02

A novel flexible room temperature ethanol gas sensor was fabricated and demonstrated in this paper. The polyimide (PI) substrate-based sensor was formed by depositing a mixture of SnO2 nanopowder and poly-diallyldimethylammonium chloride (PDDAC) on as-patterned interdigitated electrodes. PDDAC acted both as the binder, promoting the adhesion between SnO2 and the flexible PI substrate, and the dopant. We found that the response of SnO2-PDDAC sensor is significantly higher than that of SnO2 alone, indicating that the doping with PDDAC effectively improved the sensor performance. The SnO2-PDDAC sensor has a detection limit of 10 ppm at room temperature and shows good selectivity to ethanol, making it very suitable for monitoring drunken driving. The microstructures of the samples were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared spectra (FT-IR), and the sensing mechanism is also discussed in detail.

Thermoelectric Properties of Self Assembled TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 W/mK2 at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Thermoelectric Properties of Self Assemble TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 (mu)W/m sq K at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Superparamagnetic behavior in Sn0.95Mg0.05O2 nanoparticles

NASA Astrophysics Data System (ADS)

Ahmed, Ateeq; Siddique, M. Naseem; Ali, Tinku; Tripathi, P.

2018-04-01

We have studied structural, optical and magnetic properties of Sn0.95Mg0.05O2 nanoparticles synthesized by sol-gel process. Single phase tetragonal structure of Mg doped SnO2 nanoparticles (NPs) have been inferred by X-ray diffraction, which involves Rietveld refinement analysis and average crystallite size is found to be 20.4 nm. Energy dispersive X -ray analysis confirmed the presence of Mg into host SnO2 lattice. The energy band gap is found to be wider (Eg = 3.73 eV) compared to the bulk (3.6 eV) which is due to the quantum confinement effect. The observed defects due to oxygen vacancies are studied by the photoluminescence study. The SQUID magnetometer measurements shows superparamagnetic behavior of Mg-doped SnO2 NPs at room temperature and they are single domain NPs. Our results suggest that it is possible to control the superparamagnetic properties through chemical composition.

The effect of sub-oxide phases on the transparency of tin-doped gallium oxide

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

Lim, K.; Schelhas, L. T.; Siah, S. C.

2016-10-03

There have been a number of studies on the fabrication of Sn-doped gallium oxide (Ga 2O 3:Sn) films with both conductive and transparent properties using a variety of deposition methods. However, often, synthesis results in films that are not transparent. In this paper, we examine the mechanisms underlying these results in Ga 2O 3:Sn thin films prepared at various growth temperatures, Sn concentrations, and oxygen partial pressures. With X-ray absorption spectroscopy, transmission electron microscopy and energy dispersive spectroscopy, we find that when films are grown under the oxygen deficient conditions there are Ga sub-oxide and SnOx phases in the Gamore » 2O 3:Sn thin film. These Ga sub-oxide phases are only found in non-transparent films, and so we infer that the Ga sub-oxide is responsible for the non-transparency. These observations suggest that to obtain transparent Ga 2O 3:Sn, films deposition or subsequent annealing must be carefully controlled in both temperature and oxygen partial pressure to avoid the formation of Ga sub-oxide phases.« less

The effect of sub-oxide phases on the transparency of tin-doped gallium oxide

DOE PAGES

Lim, K.; Schelhas, L. T.; Siah, S. C.; ...

2016-10-07

There have been a number of studies on the fabrication of Sn-doped gallium oxide (Ga 2O 3:Sn) films with both conductive and transparent properties using a variety of deposition methods. However, often, synthesis results in films that are not transparent. In this paper, we examine the mechanisms underlying these results in Ga 2O 3:Sn thin films prepared at various growth temperatures, Sn concentrations, and oxygen partial pressures. With X-ray absorption spectroscopy, transmission electron microscopy and energy dispersive spectroscopy, we find that when films are grown under the oxygen deficient conditions there are Ga sub-oxide and SnO x phases in themore » Ga 2O 3:Sn thin film. These Ga sub-oxide phases are only found in non-transparent films, and so we infer that the Ga sub-oxide is responsible for the non-transparency. Furthermore, these observations suggest that to obtain transparent Ga 2O 3:Sn, films deposition or subsequent annealing must be carefully controlled in both temperature and oxygen partial pressure to avoid the formation of Ga sub-oxide phases.« less

Theory for n-type doped, tensile-strained Ge-Si(x)Ge(y)Sn1-x-y quantum-well lasers at telecom wavelength.

PubMed

Chang, Guo-En; Chang, Shu-Wei; Chuang, Shun Lien

2009-07-06

We propose and develop a theoretical gain model for an n-doped, tensile-strained Ge-Si(x)Ge(y)Sn(1-x-y) quantum-well laser. Tensile strain and n doping in Ge active layers can help achieve population inversion in the direct conduction band and provide optical gain. We show our theoretical model for the bandgap structure, the polarization-dependent optical gain spectrum, and the free-carrier absorption of the n-type doped, tensile-strained Ge quantum-well laser. Despite the free-carrier absorption due to the n-type doping, a significant net gain can be obtained from the direct transition. We also present our waveguide design and calculate the optical confinement factors to estimate the modal gain and predict the threshold carrier density.

Enhanced Thermoelectric Properties of Cu 2ZnSnSe 4 with Ga-doping

DOE PAGES

Wei, Kaya; Beauchemin, Laura; Wang, Hsin; ...

2015-08-10

Gallium doped Cu 2ZnSnSe 4 quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S 2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are partmore » of the continuing effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.« less

Electronic structure and p-type doping of ZnSnN2

NASA Astrophysics Data System (ADS)

Wang, Tianshi; Janotti, Anderson; Ni, Chaoying

ZnSnN2 is a promising solar-cell absorber material composed of earth abundant elements. Little is known about doping, defects, and how the valence and conduction bands in this material align with the bands in other semiconductors. Using density functional theory with the the Heyd-Scuseria-Ernzerhof hybrid functional (HSE06), we investigate the electronic structure of ZnSnN2, its band alignment to other semiconductors, such as GaN and ZnO, the possibility of p-type doping, and the possible causes of the observed unintentional n-type conductivity. We find that the position of the valence-band maximum of ZnSnN2 is 0.55 eV higher than that of GaN, yet the conduction-band minimum is close to that in ZnO. As possible p-type dopants, we explore Li, Na, and K substituting on the Zn site. Finally, we discuss the cause of unintentional n-type conductivity by analyzing the position of the conduction-band minimum with respect to that of GaN and ZnO.

A Fast Responsive Ultraviolet Sensor from mSILAR-Processed Sn-ZnO

NASA Astrophysics Data System (ADS)

Thomas, Deepu; Vijayalakshmi, K. A.; Sadasivuni, Kishor Kumar; Thomas, Ajith; Ponnamma, Deepalekshmi; Cabibihan, John-John

2017-11-01

Microwave-assisted successive ionic layer adsorption and reaction was employed to synthesize Sn-ZnO (tin-doped zinc oxide), and its sensitivity to ultraviolet radiation is compared with zinc oxide (ZnO). The sensing films were made by the dip-coated method on an indium titanium oxide glass substrate, and the sensing performance was monitored using the 300-700 nm wavelength of UV-Vis light. Excellent sensitivity and recovery were observed for the Sn-doped ZnO sensor device, especially at 380 nm wavelength of ultraviolet (UV) light (response and recovery time 2.26 s and 8.63 s, respectively, at 5 V bias voltage). The variation in photocurrent with respect to dark and light illumination atmosphere was well illustrated based on the Schottky and inter-particle network effects. Doping of Sn on ZnO nanoparticles varied the surface roughness and crystallite size as observed from scanning electron microscopic and x-ray diffraction studies. Here, we demonstrate a simple and economical fabrication technique for designing a high-performance UV light sensor. The developed device works at room temperature with high durability and stability.

Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping

NASA Astrophysics Data System (ADS)

Chen, K.; Strigari, F.; Sundermann, M.; Hu, Z.; Fisk, Z.; Bauer, E. D.; Rosa, P. F. S.; Sarrao, J. L.; Thompson, J. D.; Herrero-Martin, J.; Pellegrin, E.; Betto, D.; Kummer, K.; Tanaka, A.; Wirth, S.; Severing, A.

2018-01-01

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M4 ,5 edges of Cd- and Sn-doped CeCoIn5. The 4 f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In1-xCdx) 5 suggests that the 4 f -conduction-electron (c f ) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In1-ySny) 5 compresses the 4 f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4 f and conduction electrons, even conveying information about direction dependencies.

Local symmetry breaking in SnO2 nanocrystals with cobalt doping and its effect on optical properties.

PubMed

Roy, S; Joshi, Amish G; Chatterjee, S; Ghosh, Anup K

2018-06-07

X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to study the structural and morphological characteristics of cobalt doped tin(iv) oxide (Sn1-xCoxO2; 0 ≤ x ≤ 0.04) nanocrystals synthesized by a chemical co-precipitation technique. Electronic structure analysis using X-ray photoemission spectroscopy (XPS) shows the formation of tin interstitials (Sni) and reduction of oxygen vacancies (VO) in the host lattice on Co doping and that the doped Co exists in mixed valence states of +2 and +3. Using XRD, the preferential position of the Sni and doped Co in the unit cell of the nanocrystals have been estimated. Rietveld refinement of XRD data shows that samples are of single phase and variation of lattice constants follows Vegard's law. XRD and TEM measurements show that the crystallite size of the nanocrystals decrease with increase in Co doping concentration. SAED patterns confirm the monocrystalline nature of the samples. The study of the lattice dynamics using Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy shows the existence of many disorder activated forbidden optical phonon modes, along with the corresponding classical modes, signifying Co induced local symmetry breaking in the nanocrystals. UV-Vis spectroscopy shows that the optical band gap has red shifted with increase in doping concentration. The study of Urbach energy confirms the increase in disorder in the nanocrystals with Co doping. Local symmetry breaking induced UV emission along with violet, blue and green luminescence has been observed from the PL study. The spectral contribution of UV emission decreases and green luminescence increases with increase in doping. Using PL, in conjunction with Raman spectroscopy, the type of oxygen vacancy induced in the nanocrystals on Co doping has been confirmed and the position of the defect levels in the forbidden zone (w.r.t. the optical band gap) has been studied.

Effect of hafnium doping on density of states in dual-target magnetron co-sputtering HfZnSnO thin film transistors

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

Huang, Chuan-Xin; Li, Jun, E-mail: SHUniverjunli@163.com; Fu, Yi-Zhou

2015-11-23

This study investigates the effect of hafnium doping on the density of states (DOSs) in HfZnSnO thin film transistors fabricated by dual-target magnetron co-sputtering system. The DOSs is extracted by temperature-dependent field-effect measurements, and they decrease from 1.1 × 10{sup 17} to 4.6 × 10{sup 16 }eV/cm{sup 3} with increasing the hafnium concentrations. The behavior of DOSs for the increasing hafnium concentration HfZnSnO thin film transistors can be confirmed by both the reduction of ΔV{sub T} under bias stress and the trapping charges calculated by capacitance voltage measurements. It suggests that the reduction in DOSs due to the hafnium doping is closely related with themore » bias stability and thermal stability.« less

Transport properties in magnetic field of Pb1-xSnxTe alloys doped with Indium

NASA Astrophysics Data System (ADS)

Jovovic, V.; Joottu-Thiagaraj, S.; West, J.; Heremans, J. P.; Khokhlov, D.

2007-03-01

The galvanomagnetic and thermomagnetic transport properties of single-crystal In-doped Pb1-xSnxTe are presented as a function of Sn (10 to 30%) and In (0 to 10%) concentrations. The concept is that the In level might pin the Fermi energy in a position with and enhanced density of states, which might increase the thermoelectric figure of merit. The transport properties were measured in a transverse magnetic field and at temperatures varying from 80 to 380K. Depending on the Sn concentrations, the prepared samples are p and n type semiconductors. The measurements of the electrical conductivity, Hall, Seebeck and transverse Nernst-Ettingshausen effects yield the carrier density and mobility, the density of states effective mass, and the scattering exponent, following the method of the four coefficients. The transport properties are interpreted in terms of hybridization of the In levels and density of state of the host alloy and observations are discussed in terms of Mahan-Sofo theory. The model provides an explanation for unexpected variation in thermoelectric and thermomagnetic properties of these alloys.

Plasmonic transparent conducting metal oxide nanoparticles and films for optical sensing applications

DOEpatents

Ohodnicki, Jr., Paul R; Wang, Congjun; Andio, Mark A

2014-01-28

The disclosure relates to a method of detecting a change in a chemical composition by contacting a doped oxide material with a monitored stream, illuminating the doped oxide material with incident light, collecting exiting light, monitoring an optical signal based on a comparison of the incident light and the exiting light, and detecting a shift in the optical signal. The doped metal oxide has a carrier concentration of at least 10.sup.18/cm.sup.3, a bandgap of at least 2 eV, and an electronic conductivity of at least 10.sup.1 S/cm, where parameters are specified at a temperature of 25.degree. C. The optical response of the doped oxide materials results from the high carrier concentration of the doped metal oxide, and the resulting impact of changing gas atmospheres on that relatively high carrier concentration. These changes in effective carrier densities of conducting metal oxide nanoparticles are postulated to be responsible for the change in measured optical absorption associated with free carriers. Exemplary doped metal oxides include but are not limited to Al-doped ZnO, Sn-doped In.sub.2O.sub.3, Nb-doped TiO.sub.2, and F-doped SnO.sub.2.

Correlation of Hall and Shubnikov-de Haas Oscillations and Impurity States in Sn- and I- Doped Single Crystals p-Bi 2 Te 3

NASA Astrophysics Data System (ADS)

Tahar, M. Z.; Popov, D. I.; Nemov, S. A.

2018-03-01

Oscillations of the Hall coefficient and Shubnikov-de Haas (SdH) were observed in p-Bi2Te3 crystals doped with Sn (acceptor) and with I (donor) in magnetic fields up to 9 T parallel to the C3 trigonal axis at low temperatures (2 K < T < 20K), which is an evidence of the spatial homogeneity of carriers in complex solid solutions. This supports the existence of a narrow band of Sn states (partially filled) against the background of the valence band acting as a reservoir with high density of states partially filled with electrons. Previously, in these systems in which the Fermi level was in the light-hole valence band, both large Hall and SdH oscillations were observed, with ∼π phase shift between them, whereas when the Fermi level was in the heavy-hole valence band (larger acceptor content), no quantum oscillations were observed. It was concluded that the observed low amplitude quantum oscillations may be attributed to the shifting of the reservoir from the light-hole band to the heavy-hole, and the observed phase shift in the range 0 - π/2 between Hall and SdH oscillations may be attributed to filling factor of the reservoir with electrons, which varies with I content. Experimental results along with theoretical explanation of these correlations are presented.

A novel precursor system and its application to produce tin doped indium oxide.

PubMed

Veith, M; Bubel, C; Zimmer, M

2011-06-14

A new type of precursor has been developed by molecular design and synthesised to produce tin doped indium oxide (ITO). The precursor consists of a newly developed bimetallic indium tin alkoxide, Me(2)In(O(t)Bu)(3)Sn (Me = CH(3), O(t)Bu = OC(CH(3))(3)), which is in equilibrium with an excess of Me(2)In(O(t)Bu). This quasi single-source precursor is applied in a sol-gel process to produce powders and coatings of ITO using a one-step heat treatment process under an inert atmosphere. The main advantage of this system is the simple heat treatment that leads to the disproportionation of the bivalent Sn(II) precursor into Sn(IV) and metallic tin, resulting in an overall reduced state of the metal in the final tin doped indium oxide (ITO) material, hence avoiding the usually necessary reduction step. Solid state (119)Sn-NMR measurements of powder samples confirm the appearance of Sn(II) in an amorphous gel state and of metallic tin after annealing under nitrogen. The corresponding preparation of ITO coatings by spin coating on glass leads to transparent conductive layers with a high transmittance of visible light and a low electrical resistivity without the necessity of a reduction step.

Lifshitz topological transitions, induced by doping and deformation in single-crystal bismuth wires

NASA Astrophysics Data System (ADS)

Nikolaeva, A. A.; Konopko, L. A.; Huber, T. E.; Kobylianskaya, A. K.; Para, Gh. I.

2017-02-01

The features associated with the manifestation of Lifshitz electron topological transitions (ETT) in glass-insulated bismuth wires upon qualitative changes to the topology of the Fermi surface are investigated. The variation of the energy spectrum parameters was implemented by doping Bi with an acceptor impurity Sn and using elastic strain of up to 2%, relative to the elongation in the weakly-doped p-type Bi wires. Pure and doped glass-insulated single-crystal bismuth with different diameters and (1011) orientations along the axis were prepared by the Ulitovsky liquid phase casting method. For the first time, ETT-induced anomalies are observed along the temperature dependences of the thermoemf α(T) as triple-changes of the α sign (given heavy doping of Bi wires with an acceptor impurity Sn). The concentration and energy position of the Σ-band given a high degree of bismuth doping with Sn was assessed using the Shubnikov-de Haas effect oscillations, which were detected both from L-electrons and from T-holes in magnetic fields of up to 14 T. It is shown that the Lifshitz electron-topological transitions with elastic deformation of weakly-doped p-type Bi wires are accompanied by anomalies along the deformation dependences of the thermoemf at low temperatures. The effect is interpreted in terms of the formation of a selective scattering channel of L-carriers into the T-band with a high density of states, which is in good agreement with existing theoretical ETT models.

Color tunable emission through energy transfer from Yb3+ co-doped SrSnO3: Ho3+ perovskite nano-phosphor

NASA Astrophysics Data System (ADS)

Jain, Neha; Singh, Rajan Kr.; Sinha, Shriya; Singh, R. A.; Singh, Jai

2018-04-01

First time color tunable lighting observed from Ho3+ and Yb3+ co-doped SrSnO3 perovskite. Down-conversion and up-conversion (UC) photoluminescence emission spectra were recorded to understand the whole mechanism of energy migration between Ho3+ and Yb3+ ions. The intensity of green and red emission varies with Yb3+ doping which causes multicolour emissions from nano-phosphor. The intensity of UC red emission (654 nm) obtained from 1 at.% Ho3+ and 3 at.% Yb3+ co-doped nano-phosphor is nine times higher than from 1 at.% Ho3+ doped SrSnO3 nano-phosphor. Enhanced brightness of 654 nm in UC process belongs in biological transparency window so that it might be a promising phosphor in the bio-medical field. Moreover, for the other Yb3+ co-doped nano-phosphor, Commission Internationale de l'Éclairage chromaticity co-ordinates were found near the white region and their CCT values lie in the range 4900-5100 K indicating cool white. Decay time was measured for 545 nm emission of Ho3+ ion found in 7.652 and 8.734 µs at 355 nm excitation. The variation in lifetime was observed in ascending order with increasing Yb3+ concentration which supports PL emission spectra observation that with increasing Yb3+ concentration, rate of transition has changed. These studies reveal that Ho3+ and Yb3+ co-doped phosphor is useful for fabrication of white LEDs.

The role of Sb in solar cell material Cu 2ZnSnS 4

DOE PAGES

Zhang, Xiaoli; Han, Miaomiao; Zeng, Zhi; ...

2017-03-03

In this paper, based on first-principles calculations we report a possible mechanism of the efficiency improvement of the Sb-doped Cu 2ZnSnS 4 (CZTS) solar cells from the Sb-related defect point of view. Different from Sb in CuInSe 2 which substituted the Cu atomic site and acted as group-13 elements on the Cu-poor growth condition, we find out that Sb prefers to substitute Sn atomic site and acts as group-14 elements on the Cu-poor growth condition in CZTS. At low Sb concentration, Sb Sn produces a deep defect level which is detrimental for the solar cell application. At high Sb concentration,more » Sb 5s states form an isolated half-filled intermediate band at 0.5 eV above the valence band maximum which will increase the photocurrent as well as the solar cell efficiency.« less

Structure and optical band gaps of (Ba,Sr)SnO{sub 3} films grown by molecular beam epitaxy

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

Schumann, Timo; Raghavan, Santosh; Ahadi, Kaveh

2016-09-15

Epitaxial growth of (Ba{sub x}Sr{sub 1−x})SnO{sub 3} films with 0 ≤ x ≤ 1 using molecular beam epitaxy is reported. It is shown that SrSnO{sub 3} films can be grown coherently strained on closely lattice and symmetry matched PrScO{sub 3} substrates. The evolution of the optical band gap as a function of composition is determined by spectroscopic ellipsometry. The direct band gap monotonously decreases with x from to 4.46 eV (x = 0) to 3.36 eV (x = 1). A large Burnstein-Moss shift is observed with La-doping of BaSnO{sub 3} films. The shift corresponds approximately to the increase in Fermi level and is consistent with the low conduction band mass.

Hybrid of Co(3)Sn(2)@Co nanoparticles and nitrogen-doped graphene as a lithium ion battery anode.

PubMed

Mahmood, Nasir; Zhang, Chenzhen; Liu, Fei; Zhu, Jinghan; Hou, Yanglong

2013-11-26

A facile strategy was designed for the fabrication of hybrid of Co3Sn2@Co nanoparticles (NPs) and nitrogen-doped graphene (NG) sheets through a hydrothermal synthesis, followed by annealing process. Core-shell architecture of Co3Sn2@Co pin on NG is designed for the dual encapsulation of Co3Sn2 with adaptable ensembles of Co and NG to address the structural and interfacial stability concerns facing tin-based anodes. In the resulted unique architecture of Co3Sn2@Co-NG hybrid, the sealed cobalt cover prevents the direct exposer of Sn with electrolyte because of encapsulated structure and keeps the structural and interfacial integrity of Co3Sn2. However, the elastically strong, flexible and conductive NG overcoat accommodates the volume changes and therefore brings the structural and electrical stabilization of Co3Sn2@Co NPs. As a result, Co3Sn2@Co-NG hybrid exhibits extraordinary reversible capacity of 1615 mAh/g at 250 mA/g after 100 cycles with excellent capacity retention of 102%. The hybrid bears superior rate capability with reversible capacity of 793.9 mAh/g at 2500 mA/g and Coulombic efficiency nearly 100%.

High mobility La-doped BaSnO3 on non-perovskite MgO substrate

NASA Astrophysics Data System (ADS)

Kim, Youjung; Shin, Juyeon; Kim, Young Mo; Char, Kookrin

(Ba,La)SnO3 is a transparent perovskite oxide with high electron mobility and excellent oxygen stability. Field effect device with (Ba,La)SnO3 channel was reported to show good output characteristics on STO substrate. Here, we fabricated (Ba,La)SnO3\\ films and field effect devices with (Ba,La)SnO3 channel on non-perovskite MgO substrates, which are available in large size wafers. X-ray diffraction and transmission electron microscope (TEM) images of (Ba,La)SnO3\\ films on MgO substrates show that the films are epitaxial with many threading dislocations. (Ba,La)SnO3 exhibits the high mobility with 97.2 cm2/Vs at 2 % La doping on top of 150 nm thick BaSnO3 buffer layer. Excellent carrier modulation was observed in field effect devices. FET performances on MgO substrates are slightly better than those on SrTiO3 substrates in spite of the higher dislocation density on MgO than on SrTiO3 substrates. These high mobility BaSnO3 thin films and transistors on MgO substrates will accelerate development for applications in high temperature and high power electronics. Samsung Science and Technology Foundation.

Multi-phase structures of boron-doped copper tin sulfide nanoparticles synthesized by chemical bath deposition for optoelectronic devices

NASA Astrophysics Data System (ADS)

Rakspun, Jariya; Kantip, Nathakan; Vailikhit, Veeramol; Choopun, Supab; Tubtimtae, Auttasit

2018-04-01

We investigated the influence of boron doping on the structural, optical, and electrical properties of copper tin sulfide (CTS) nanoparticles coated on a WO3 surface and synthesized using chemical bath deposition. Boron doping at concentrations of 0.5, 1.0, 1.5, and 2.0 wt% was investigated. The X-ray diffraction pattern of CTS showed the presence of monoclinic Cu2Sn3S7, cubic Cu2SnS3, and orthorhombic Cu4SnS4. Boron doping influenced the preferred orientation of the nanoparticles for all phase structures and produced a lattice strain effect and changes in the dislocation density. Increasing the concentration of boron in CTS from 0.5 wt% to 2.0 wt% reduced the band gap for all phases of CTS from 1.46 to 1.29 eV and reduced the optical transmittance. Optical constants, such as the refractive index, extinction coefficient, and dissipation factor, were also obtained for B-doped CTS. The dispersion behavior of the refractive index was investigated in terms of a single oscillator model and the physical parameters were determined. Fourier transform infrared spectroscopy confirmed the successful synthesis of CTS nanoparticles. Cyclic voltammetry indicated that optimum boron doping (<1.5 wt% for all phases) resulted in desirable p-n junction behavior for optoelectronic applications.

Vanadium doped tin dioxide as a novel sulfur dioxide sensor.

PubMed

Das, S; Chakraborty, S; Parkash, O; Kumar, D; Bandyopadhyay, S; Samudrala, S K; Sen, A; Maiti, H S

2008-04-15

Considering the short-term exposure limit of SO2 to be 5 ppm, we first time report that semiconductor sensors based on vanadium doped SnO2 can be used for SO2 leak detection because of their good sensitivity towards SO2 at concentrations down to 5 ppm. Such sensors are quite selective in presence of other gases like carbon monoxide, methane and butane. The high sensitivity of vanadium doped tin dioxide towards SO2 may be understood by considering the oxidation of sulfur dioxide to sulfur trioxide on SnO2 surface through redox cycles of vanadium-sulfur-oxygen adsorbed species.

Thermoelectric properties and chlorine doping effect of In4Pb0.01Sn0.03Se2.9Clx polycrystalline compounds.

PubMed

Hee Kim, Jin; Jae Kim, Min; Oh, Suekyung; Rhyee, Jong-Soo; Park, Su-Dong; Ahn, Docheon

2015-02-21

We investigated the thermoelectric properties of Cl-doped polycrystalline compounds In4Pb0.01Sn0.03Se2.9Clx (x = 0.02, 0.04, and 0.06). X-ray diffraction measurement shows a gradual change in lattice volume for x ≤ 0.04 without any impurity phases indicating a systemic change in Cl doping. The Cl doping in the compounds has the effect of increasing carrier concentration and the effective mass of carriers, resulting in an increase in power factor at a high temperature (∼700 K). Because of the increased electrical conductivity at a high temperature, the dimensionless thermoelectric figure of merit ZT reaches 1.25 at 723 K for the x = 0.04 Cl-doped compound, which is a relatively high value for n-type polycrystalline materials.

Spatially controlled doping of two-dimensional SnS 2 through intercalation for electronics

DOE PAGES

Gong, Yongji; Yuan, Hongtao; Wu, Chun-Lan; ...

2018-02-26

Doped semiconductors are the most important building elements for modern electronic devices. In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development10. Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturallymore » grown n-type S-vacancy SnS 2, Cu intercalated bilayer SnS 2 obtained by this technique displays a hole field-effect mobility of ~40 cm 2 V -1 s -1, and the obtained Co-SnS 2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene. Combining this intercalation technique with lithography, an atomically seamless p–n–metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.« less

Thermal conductivity of bulk and thin film β-Ga2O3 measured by the 3ω technique

NASA Astrophysics Data System (ADS)

Blumenschein, N.; Slomski, M.; Paskov, P. P.; Kaess, F.; Breckenridge, M. H.; Muth, J. F.; Paskova, T.

2018-02-01

Thermal conductivity of undoped and Sn-doped β-Ga2O3 bulk and single-crystalline thin films have been measured by the 3ω technique. The bulk samples were grown by edge-defined film-field growth (EFG) method, while the thin films were grown on c-plane sapphire by pulsed-laser deposition (PLD). All samples were with (-201) surface orientation. Thermal conductivity of bulk samples was calculated along the in-plane and cross-plane crystallographic directions, yielding a maximum value of 29 W/m-K in the [010] direction at room temperature. A slight thermal conductivity decrease was observed in the Sn-doped bulk samples, which was attributed to enhanced phonon-impurity scattering. The differential 3ω method was used for β-Ga2O3 thin film samples due to the small film thickness. Results show that both undoped and Sndoped films have a much lower thermal conductivity than that of the bulk samples, which is consistent with previous reports in the literature showing a linear relationship between thermal conductivity and film thickness. Similarly to bulk samples, Sn-doped thin films have exhibited a thermal conductivity decrease. However, this decrease was found to be much greater in thin film samples, and increased with Sn doping concentration. A correlation between thermal conductivity and defect/dislocation density was made for the undoped thin films.

Spatially controlled doping of two-dimensional SnS 2 through intercalation for electronics

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

Gong, Yongji; Yuan, Hongtao; Wu, Chun-Lan

Doped semiconductors are the most important building elements for modern electronic devices. In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development10. Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturallymore » grown n-type S-vacancy SnS 2, Cu intercalated bilayer SnS 2 obtained by this technique displays a hole field-effect mobility of ~40 cm 2 V -1 s -1, and the obtained Co-SnS 2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene. Combining this intercalation technique with lithography, an atomically seamless p–n–metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.« less

Spatially controlled doping of two-dimensional SnS2 through intercalation for electronics

NASA Astrophysics Data System (ADS)

Gong, Yongji; Yuan, Hongtao; Wu, Chun-Lan; Tang, Peizhe; Yang, Shi-Ze; Yang, Ankun; Li, Guodong; Liu, Bofei; van de Groep, Jorik; Brongersma, Mark L.; Chisholm, Matthew F.; Zhang, Shou-Cheng; Zhou, Wu; Cui, Yi

2018-04-01

Doped semiconductors are the most important building elements for modern electronic devices1. In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface2,3. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits4-9. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development10. Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturally grown n-type S-vacancy SnS2, Cu intercalated bilayer SnS2 obtained by this technique displays a hole field-effect mobility of 40 cm2 V-1 s-1, and the obtained Co-SnS2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene5. Combining this intercalation technique with lithography, an atomically seamless p-n-metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.

Thermoelectric properties of IV–VI-based heterostructures and superlattices

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

Borges, P.D., E-mail: pabloborges@ufv.br; Department of Physics, Texas State University, San Marcos, TX 78666; Petersen, J.E.

2015-07-15

Doping in a manner that introduces anisotropy in order to reduce thermal conductivity is a significant focus in thermoelectric research today. By solving the semiclassical Boltzmann transport equations in the constant scattering time (τ) approximation, in conjunction with ab initio electronic structure calculations, within Density Functional Theory, we compare the Seebeck coefficient (S) and figure of merit (ZT) of bulk PbTe to PbTe/SnTe/PbTe heterostructures and PbTe doping superlattices (SLs) with periodically doped planes. Bismuth and Thallium were used as the n- and p-type impurities, respectively. The effects of carrier concentration are considered via chemical potential variation in a rigid bandmore » approximation. The impurity bands near the Fermi level in the electronic structure of PbTe SLs are of Tl s- and Bi p-character, and this feature is independent of the doping concentration or the distance between impurity planes. We observe the impurity bands to have a metallic nature in the directions perpendicular to the doping planes, yet no improvement on the values of ZT is found when compared to bulk PbTe. For the PbTe/SnTe/PbTe heterostructures, the calculated S presents good agreement with recent experimental data, and an anisotropic behavior is observed for low carrier concentrations (n<10{sup 18} cm{sup −3}). A large value of ZT{sub ||} (parallel to the growth direction) of 3.0 is predicted for n=4.7×10{sup 18} cm{sup −3} and T=700 K, whereas ZT{sub p} (perpendicular to the growth direction) is found to peak at 1.5 for n=1.7×10{sup 17} cm{sup −3}. Both electrical conductivity enhancement and thermal conductivity reduction are analyzed. - Graphical abstract: Figure of merit for PbTe/SnTe/PbTe heterostructure along the [0 0 1] direction, P.D. Borges, J.E. Petersen, L. Scolfaro, H.W. Leite Alves, T.H. Myers, Improved thermoelectric properties of IV–VI-based heterostructures and superlattices. - Highlights: • Thermoelectric properties of IV–VI-based heterostructures and superlattices. • High figure of merit is predicted for the PbTe/SnTe/PbTe heterostructure. • Nanotechnology has an important role for the development of thermoelectric devices.« less

Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics.

PubMed

Ferluccio, Daniella A; Smith, Ronald I; Buckman, Jim; Bos, Jan-Willem G

2018-02-07

The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo 1+y Sn 1-z Sb z (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (∼18.25) for the NbCo 1+y Sn 1-z Sb z samples (z > 0). Mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m -1 K -1 (z = 0) to 4.5 W m -1 K -1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S 2 /ρ = 2.5-3 mW m -1 K -2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K -1 for 20% Zr at 773 K. However, the electrical resistivity, ρ 323K = 27-35 mΩ cm, remains too large for these materials to be considered useful p-type materials.

P-type hole mobility measurement in Na-doped BaSnO3

NASA Astrophysics Data System (ADS)

Hong, Sungyun; Jang, Yeaju; Park, Jisung; Char, Kookrin

P-type doping in oxide materials has been a difficult task because of the oxygen vacancies. Taking advantage of the excellent oxygen stability in BaSnO3 (BSO), we replaced Ba with Na in BSO to achieve p-type doping. Ba1-xNaxSnO3 (BNSO) films with varying dopant ratios were epitaxially grown by the pulsed laser deposition technique. We confirmed that the BNSO films were properly grown and determined their lattice constants with respect to the dopant ratio by x-ray diffraction. Due to the high resistance of the films at room temperature, we measured the transport properties of the BNSO films at temperatures ranging from 200 C to 400 C. Hall resistance measurements in a +/- 5 kG magnetic field were performed to confirm that the films are indeed p-type. As the temperature increased, the hole carrier concentration of the films increased while the film resistance decreased. The hole mobility values, in the tens of cm2/Vsec range, were found to decrease with the temperature. We will present the complete doping rate and temperature dependence of the hole mobility and compare their behavior with those of n-type La-doped BSO. Samsung science and technology foundation.

Fabrication of textured SnO2 transparent conductive films using self-assembled Sn nanospheres

NASA Astrophysics Data System (ADS)

Fukumoto, Michitaka; Nakao, Shoichiro; Hirose, Yasushi; Hasegawa, Tetsuya

2018-06-01

We present a novel method to fabricate textured surfaces on transparent conductive SnO2 films by processing substrates through a bottom-up technique with potential for industrially scalable production. The substrate processing consists of three steps: deposition of precursor Sn films on glass substrates, formation of a self-assembled Sn nanosphere layer with reductive annealing, and conversion of Sn to SnO2 by oxidative annealing. Ta-doped SnO2 films conformally deposited on the self-assembled nanospherical SnO2 templates exhibited attractive optical and electrical properties, namely, enhanced haze values and low sheet resistances, for applications as transparent electrodes in photovoltaics.

Nanosized thin SnO₂ layers doped with Te and TeO₂ as room temperature humidity sensors.

PubMed

Georgieva, Biliana; Podolesheva, Irena; Spasov, Georgy; Pirov, Jordan

2014-05-21

In this paper the humidity sensing properties of layers prepared by a new method for obtaining doped tin oxide are studied. Different techniques-SEM, EDS in SEM, TEM, SAED, AES and electrical measurements-are used for detailed characterization of the thin layers. The as-deposited layers are amorphous with great specific area and low density. They are built up of a fine grained matrix, consisting of Sn- and Te-oxides, and a nanosized dispersed phase of Te, Sn and/or SnTe. The chemical composition of both the matrix and the nanosized particles depends on the ratio R(Sn/Te) and the evaporation conditions. It is shown that as-deposited layers with R(Sn/Te) ranging from 0.4 to 0.9 exhibit excellent characteristics as humidity sensors operating at room temperature-very high sensitivity, good selectivity, fast response and short recovery period. Ageing tests have shown that the layers possess good long-term stability. Results obtained regarding the type of the water adsorption on the layers' surface help better understand the relation between preparation conditions, structure, composition and humidity sensing properties.

Identification of metal s states in Sn-doped anatase by polarisation dependent hard X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Regoutz, A.; Oropeza, F. E.; Poll, C. G.; Payne, D. J.; Palgrave, R. G.; Panaccione, G.; Borgatti, F.; Agrestini, S.; Utsumi, Y.; Tsuei, K. D.; Liao, Y. F.; Watson, G. W.; Egdell, R. G.

2016-03-01

The contributions of Sn 5s and Ti 4s states to the valence band electronic structure of Sn-doped anatase have been identified by hard X-ray photoelectron spectroscopy. The metal s state intensity is strongly enhanced relative to that of O 2p states at high photon energies due to matrix element effects when electrons are detected parallel to the direction of the polarisation vector of the synchrotron beam, but becomes negligible in the perpendicular direction. The experimental spectra in both polarisations are in good agreement with cross section and asymmetry parameter weighted partial densities of states derived from density functional theory calculations.

Conduction band edge effective mass of La-doped BaSnO{sub 3}

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

James Allen, S., E-mail: allen@itst.ucsb.edu; Law, Ka-Ming; Raghavan, Santosh

2016-06-20

BaSnO{sub 3} has attracted attention as a promising material for applications requiring wide band gap, high electron mobility semiconductors, and moreover possesses the same perovskite crystal structure as many functional oxides. A key parameter for these applications and for the interpretation of its properties is the conduction band effective mass. We measure the plasma frequency of La-doped BaSnO{sub 3} thin films by glancing incidence, parallel-polarized resonant reflectivity. Using the known optical dielectric constant and measured electron density, the resonant frequency determines the band edge electron mass to be 0.19 ± 0.01. The results allow for testing band structure calculations and transport models.

Possibility of Flat-Band Ferromagnetism in Hole-Doped Pyrochlore Oxides Sn2 Nb2 O7 and Sn2 Ta2 O7

NASA Astrophysics Data System (ADS)

Hase, I.; Yanagisawa, T.; Aiura, Y.; Kawashima, K.

2018-05-01

Quantum mechanics tells us that the hopping integral between local orbitals makes the energy band dispersive. In a lattice with geometric frustration, however, dispersionless flat bands may appear due to quantum interference. Several models possessing flat bands have been proposed theoretically, and many attracting magnetic and electronic properties are predicted. However, despite many attempts to realize these models experimentally, compounds that are appropriately described by this model have not been found so far. Here we show that pyrochlore oxides Sn2 Nb2 O7 and Sn2Ta2O7 are such examples, by performing first-principles band calculation and several tight-binding analyses. Moreover, spin-polarized band calculation shows that the hole-doped systems Sn2 Nb2 O6 N and Sn2 Ta2 O6 N have complete spin polarization, and their magnetic moments are mostly carried by Sn-s and N-p orbitals, which are usually nonmagnetic. These compounds are not only candidates for ferromagnets without a magnetic element, but also will provide an experimental platform for a flat-band model which shows a wide range of physical properties.

Overcoming Short-Circuit in Lead-Free CH3NH3SnI3 Perovskite Solar Cells via Kinetically Controlled Gas-Solid Reaction Film Fabrication Process.

PubMed

Yokoyama, Takamichi; Cao, Duyen H; Stoumpos, Constantinos C; Song, Tze-Bin; Sato, Yoshiharu; Aramaki, Shinji; Kanatzidis, Mercouri G

2016-03-03

The development of Sn-based perovskite solar cells has been challenging because devices often show short-circuit behavior due to poor morphologies and undesired electrical properties of the thin films. A low-temperature vapor-assisted solution process (LT-VASP) has been employed as a novel kinetically controlled gas-solid reaction film fabrication method to prepare lead-free CH3NH3SnI3 thin films. We show that the solid SnI2 substrate temperature is the key parameter in achieving perovskite films with high surface coverage and excellent uniformity. The resulting high-quality CH3NH3SnI3 films allow the successful fabrication of solar cells with drastically improved reproducibility, reaching an efficiency of 1.86%. Furthermore, our Kelvin probe studies show the VASP films have a doping level lower than that of films prepared from the conventional one-step method, effectively lowering the film conductivity. Above all, with (LT)-VASP, the short-circuit behavior often obtained from the conventional one-step-fabricated Sn-based perovskite devices has been overcome. This study facilitates the path to more successful Sn-perovskite photovoltaic research.

Exceptional thermoelectric performance of a "star-like" SnSe nanotube with ultra-low thermal conductivity and a high power factor.

PubMed

Lin, Chensheng; Cheng, Wendan; Guo, Zhengxiao; Chai, Guoliang; Zhang, Hao

2017-08-30

Efficient thermoelectric energy conversion is both crucial and challenging, and requires new material candidates by design. From first principles simulations, we identify that a "star-like" SnSe nanotube - with alternating dense and loose rings along the tube direction - gives rise to an ultra-low lattice thermal conductivity, 0.18 W m -1 K -1 at 750 K, and a large Seebeck coefficient, compared with single crystal SnSe. The power factor of the p-type SnSe nanotube reaches its maximum value of 235 μW cm -1 K -2 at a moderate doping level of around 10 20 -10 21 cm -3 . The p-type nanotube shows better thermoelectric properties than the n-type one. The phonon anharmonic scattering rate of the SnSe nanotube is larger than that of the SnSe crystal. All of these factors lead to an exceptional figure-of-merit (ZT) value of 3.5-4.6 under the optimal conditions, compared to 0.6-2.6 for crystalline SnSe. Such a large ZT value should lead to a six-fold increase in the energy conversion efficiency to about 30%.

Synthesis and enhanced acetone gas-sensing performance of ZnSnO3/SnO2 hollow urchin nanostructures

NASA Astrophysics Data System (ADS)

Lian, Dandan; Shi, Bing; Dai, Rongrong; Jia, Xiaohua; Wu, Xiangyang

2017-12-01

A kind of novel ZnSnO3/SnO2 hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption techniques. The results revealed that many tiny needle-like SnO2 nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO3 hollow microspheres and the ZnSnO3/SnO2 hollow urchin nanostructures with different SnO2 content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO3/SnO2 hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO3/SnO2 hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO3/SnO2 hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO2.

n-type dopants in (001) β-Ga2O3 grown on (001) β-Ga2O3 substrates by plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Han, Sang-Heon; Mauze, Akhil; Ahmadi, Elaheh; Mates, Tom; Oshima, Yuichi; Speck, James S.

2018-04-01

Ge and Sn as n-type dopants in (001) β-Ga2O3 films were investigated using plasma-assisted molecular beam epitaxy. The Ge concentration showed a strong dependence on the growth temperature, whereas the Sn concentration remains independent of the growth temperature. The maximum growth temperature at which a wide range of Ge concentrations (from 1017 to 1020 cm-3) could be achieved was 675 °C while the same range of Sn concentration could be achieved at growth temperature of 750 °C. Atomic force microscopy results revealed that higher growth temperature shows better surface morphology. Therefore, our study reveals a tradeoff between higher Ge doping concentration and high quality surface morphology on (001) β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy. The Ge doped films had an electron mobility of 26.3 cm2 V-1 s-1 at the electron concentration of 6.7 × 1017 cm-3 whereas the Sn doped films had an electron mobility of 25.3 cm2 V-1 s-1 at the electron concentration of 1.1 × 1018 cm-3.

Band alignment and p -type doping of ZnSnN2

NASA Astrophysics Data System (ADS)

Wang, Tianshi; Ni, Chaoying; Janotti, Anderson

2017-05-01

Composed of earth-abundant elements, ZnSnN2 is a promising semiconductor for photovoltaic and photoelectrochemical applications. However, basic properties such as the precise value of the band gap and the band alignment to other semiconductors are still unresolved. For instance, reported values for the band gap vary from 1.4 to 2.0 eV. In addition, doping in ZnSnN2 remains largely unexplored. Using density functional theory with the Heyd-Scuseria-Ernzerhof hybrid functional, we investigate the electronic structure of ZnSnN2, its band alignment to GaN and ZnO, and the possibility of p -type doping. We find that the position of the valence-band maximum of ZnSnN2 is 0.39 eV higher than that in GaN, yet the conduction-band minimum is close to that in ZnO, which suggests that achieving p -type conductivity is likely as in GaN, yet it may be difficult to control unintentional n -type conductivity as in ZnO. Among possible p -type dopants, we explore Li, Na, and K substituting on the Zn site. We show that while LiZn is a shallow acceptor, NaZn and KZn are deep acceptors, which we trace back to large local relaxations around the Na and K impurities due to the atomic size mismatches.

Luminescence of Ga2O3 Crystals Excited with a Runaway Electron Beam

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Molecular beam epitaxy and characterization of stannic oxide

NASA Astrophysics Data System (ADS)

White, Mark Earl

Wide bandgap oxides such as tin-doped indium oxide (ITO), zinc oxide (ZnO), and tin oxide (SnO2) are currently used in a variety of technologically important applications, including gas sensors and transparent conducting films for devices such as flat panel displays and photovoltaics. Due to the focus on industrial applications, prior research did not investigate the basic material properties of SnO2 films due to unoptimized growth methods such as RF sputtering and pulsed laser deposition which produced low resistance, polycrystalline films. Beyond these applications, few attempts to enhance and control the fundamental SnO2 properties for semiconducting applications have been reported. This work develops the heteroepitaxy of SnO2 thin films on r-plane Al2O3 by plasma-assisted molecular beam epitaxy (PA-MBE) and demonstrates control of the electrical transport of those films. Phase-pure, epitaxial single crystalline films were controllably and reproducibly grown. X-ray diffraction measurements indicated that these films exhibited the highest structural quality reported. Depending on the epitaxial conditions, tin- and oxygen-rich growth regimes were observed. An unexpected growth rate decrease in the tin-rich regime was determined to be caused by volatile suboxide formation. Excellent transport properties for naturally n-type SnO2 were achieved: the electron mobility, mu, was 103 cm2/V s at a concentration, n, of 2.7 x 1017 cm-3. To control the bulk electron density, antimony was used as an intentional n-type dopant. Antimony-doped film properties showed the highest reported mobilities for doped films (mu = 36 cm2/V s for n = 2.8 x 10 20 cm-3). Films doped with indium had resistivities over five orders-of-magnitude greater than undoped films. These highly resistive films provided a method to control the electrical transport properties. Further research will facilitate detailed studies of the fundamental properties of SnO2 and its development as an oxide with full semiconducting properties.

Effect of charge and composition on the structural fluxionality and stability of nine atom tin-bismuth Zintl analogues.

PubMed

Gupta, Ujjwal; Reber, Arthur C; Clayborne, Penee A; Melko, Joshua J; Khanna, Shiv N; Castleman, A W

2008-12-01

Synergistic studies of bismuth doped tin clusters combining photoelectron spectra with first principles theoretical investigations establish that highly charged Zintl ions, observed in the condensed phase, can be stabilized as isolated gas phase clusters through atomic substitution that preserves the overall electron count but reduces the net charge and thereby avoids instability because of coulomb repulsion. Mass spectrometry studies reveal that Sn(8)Bi(-), Sn(7)Bi(2)(-), and Sn(6)Bi(3)(-) exhibit higher abundances than neighboring species, and photoelectron spectroscopy show that all of these heteroatomic gas phase Zintl analogues (GPZAs) have high adiabatic electron detachment energies. Sn(6)Bi(3)(-) is found to be a particularly stable cluster, having a large highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap. Theoretical calculations demonstrate that the Sn(6)Bi(3)(-) cluster is isoelectronic with the well know Sn(9)(-4) Zintl ion; however, the fluxionality reported for Sn(9)(-4) is suppressed by substituting Sn atoms with Bi atoms. Thus, while the electronic stability of the clusters is dominated by electron count, the size and position of the atoms affects the dynamics of the cluster as well. Substitution with Bi enlarges the cage compared with Sn(9)(-4) making it favorable for endohedral doping, findings which suggest that these cages may find use for building blocks of cluster assembled materials.

Sn-doped Bi1.1Sb0.9Te2S: An ideal bulk topological insulator

NASA Astrophysics Data System (ADS)

Kushwaha, Sk; Pletikosic, I.; Liang, T.; Gyenis, A.; Lapidus, Sh; Tian, Y.; Zhao, H.; Burch, Ks; Lin, J.; Wang, W.; Ji, H.; Fedorov, Av; Yazdani, A.; Ong, Np; Valla, T.; Cava, Rj

In the recent decade the topological insulators have been of significant importance for the condensed matter community. However, so far no real materials could fulfill all the requirements. Here, we present the Bridgman growth of slightly Sn-doped Bi1.1Sb0.9Te2S (with bulk band gap of 350) single crystals and characterization by electronic transport, STM and ARPES. The results on the crystals exhibit an intrinsic semiconducting behavior with the Fermi level and Dirac energies lie in bulk gap and high quality 2D surface states are detangled from the bulk states, and it fulfils all the requirements to be an ideal topological insulator. ARO MURI W911NF-12-1-0461; ARO W911NF-12-1-0461; MRSEC NSF-DMR-1420541; LBNL & BNL DE-AC02-05CH11231 & DE-SC0012704; DOE Office of Science DE-AC02-06CH11357; NSF DMR-1410846.

SN-EXCHANGED HYDROTALCITES AS CATALYSTS FOR CLEAN AND SELECTIVE BAEYER-VILLIGER OXIDATION OF KETONES USING HYDROGEN PEROXIDE

EPA Science Inventory

A Sn-doped hydrotalcite (Sn/HT) catalyst prepared by ion-exchange is found to be an active and selective catalyst for the liquid phase Baeyer-Villiger (BV) oxidation of cyclic ketones in acetonitrile using hydrogen peroxide (H2O2) as oxidant. Different reaction perameters such as...

Thermoelectric study of Ag doped SnSe-Sb2Se3 based alloy

NASA Astrophysics Data System (ADS)

Das, Anish; Talukdar, M.; Kumar, Aparabal; Sarkar, Kalyan Jyoti; Dhama, P.; Banerji, P.

2018-05-01

In this article we have synthesized p-type alloy of SnSe and Sb2Se3 (10 atomic %) to study the thermoelectric transport properties. The alloy was prepared by melt grown technique followed by spark plasma sintering and latter doped with 2 atomic % Ag to compensate the carrier density in order to achieve higher electrical conductivity (σ). Out of these, the doped sample resulted in the maximum figure of merit, ZT˜0.7 at 773 K due to the existence of the secondary phase AgSbSe2 and reduced lattice thermal conductivity (0.61 W m-1 K-1 at 300 K). The fitted lattice thermal conductivity shows that point defect and Umklapp scattering are the primary process of phonon scattering for all the samples whereas the fitted mobility data confirms acoustic phonon scattering along with point defect and grain boundary scattering to be the main carrier scattering mechanism. More over room temperature carrier density and electrical conductivity are found to increase for the doped sample which further corroborate (90%)SnSe-(10%)Sb2Se3:2%Ag to be a potential candidate for highly efficient thermoelectric materials.

Green and Selective Fluorescent Sensor for Detection of Sn (IV) and Mo (VI) Based on Boron and Nitrogen-Co-Doped Carbon Dots.

PubMed

Tabaraki, Reza; Abdi, Omran; Yousefipour, Sedigheh

2017-03-01

A green and simple microwave-assisted method was used to synthesis water-soluble boron and nitrogen-co-doped carbon dots (B-N-CDs). These B-N-CDs were successfully used for the fluorescent determination of Sn 4+ and Mo 6+ ions. This probe had a fast response time at pH = 4 with high sensitivity and selectivity. Linear correlation between F 0 /F and the concentration was seen in the range of 0.2-18 μM and 0.2-25 μM for Sn 4+ and Mo 6+ , respectively. Under optimum condition, the limit of detection (LOD) for Sn 4+ and Mo 6+ were 150 nM and 132 nM, respectively. The performance of the sensor was evaluated by different real samples such as tap, river and mineral water, canned fish sample and tomato samples.

Study of Ce3+, Dy3+ and Eu3+ activated SrSnO3 for white LEDs

NASA Astrophysics Data System (ADS)

Jain, Neha; Pandey, Deepak Kumar; Singh, Rajan Kumar; Singh, Jai; Singh, R. A.

2018-05-01

Herein, Eu3+- Dy3+-Ce3+ tri-doped SrSnO3 have been prepared by conventional sol-gel method. XRD analysis confirmed its orthorhombic phase with Pnma (62) space group symmetry. The morphology of the sample is flake like which has examined by SEM. SrSnO3 consists of several vibrational modes due to Sn-O bond which was analysed by Fourier transform Infrared (FTIR) spectra. Photoluminescence (PL) emission and excitation spectra have been recorded for optical analysis. It consist characteristic emission peaks of Ce3+, Dy3+ and Eu3. The intensity of 590 nm emission increases with increasing Eu3+ concentration and it is maximum for 3 at% Eu3+ co-doped sample. The CIE chromaticity co-ordinates are found near white region so it would be a promising phosphor for white LEDs.

Layered Lithium-Rich Oxide Nanoparticles Doped with Spinel Phase: Acidic Sucrose-Assistant Synthesis and Excellent Performance as Cathode of Lithium Ion Battery.

PubMed

Chen, Min; Chen, Dongrui; Liao, Youhao; Zhong, Xiaoxin; Li, Weishan; Zhang, Yuegang

2016-02-01

Nanolayered lithium-rich oxide doped with spinel phase is synthesized by acidic sucrose-assistant sol-gel combustion and evaluated as the cathode of a high-energy-density lithium ion battery. Physical characterizations indicate that the as-synthesized oxide (LR-SN) is composed of uniform and separated nanoparticles of about 200 nm, which are doped with about 7% spinel phase, compared to the large aggregated ones of the product (LR) synthesized under the same condition but without any assistance. Charge/discharge demonstrates that LR-SN exhibits excellent rate capability and cyclic stability: delivering an average discharge capacity of 246 mAh g(-1) at 0.2 C (1C = 250 mA g(-1)) and earning a capacity retention of 92% after 100 cycles at 4 C in the lithium anode-based half cell, compared to the 227 mA g(-1) and the 63% of LR, respectively. Even in the graphite anode-based full cell, LR-SN still delivers a capacity of as high as 253 mAh g(-1) at 0.1 C, corresponding to a specific energy density of 801 Wh kg(-1), which are the best among those that have been reported in the literature. The separated nanoparticles of the LR-SN provide large sites for charge transfer, while the spinel phase doped in the nanoparticles facilitates lithium ion diffusion and maintains the stability of the layered structure during cycling.

Modulation doping at BaSnO3LaInO3

NASA Astrophysics Data System (ADS)

Char, Kookrin; Shin, Juyeon; Kim, Young Mo; Kim, Youjung

We recently reported on the conductance enhancement at the interface between two band insulators: LaInO3 (LIO) and BaSnO3 (BSO). These two-dimensional electron gas-like (2DEG) states at the LIO/Ba1-xLaxSnO3 (BLSO) polar interface display the stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. Search for the origin of enhanced conductance at the interface has been carried out, and one of the findings is that the doping level of BSO is a critical parameter for the polar charge contribution . We have also investigated a new modulated heterostructure by inserting an undoped BSO spacer layer at the LIO/BLSO interface. As increasing the thickness of the spacer layer, the carrier concentration and the mobility continually decreased. We attribute the results to the modified band bending as the thickness of the spacer layer varies and to the dislocation-limited transport. However, when we controlled the band bending by field effect, improved mobility was observed in these modulated heterostructures. This new modulated heterostructures of the LIO/BSO polar interface look promising not only for higher electron mobility devices but also for elucidating the mechanism of the 2DEG-like behavior. Samsung science and technology foundation.

PbSnTe:In compound: Electron capture levels, galvanomagnetic properties, and THz sensitivity

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

Ishchenko, D. V., E-mail: miracle4348@gmail.com; Klimov, A. E.; Shumsky, V. N.

A model of the Pb{sub 1–x}Sn{sub x}Te:In compound, based on concepts of the theory of disordered systems is considered. The temperature dependences of the Fermi-level position and carrier concentration are calculated depending on the indium doping level and are compared with experimental data. The transient current–voltage characteristics are calculated in the mode of injection from the contact and current limitation by space charge at various voltage-variation rates. The data obtained are compared with the experiments. It is demonstrated that the shape of the characteristics is controlled by the parameters of electron capture at localized states. Photocurrent relaxation in a magneticmore » field is studied, and the mechanism of such relaxation is discussed under the assumption of the magnetic freezing of carriers.« less

Investigation of the structural, optical and electrical transport properties of n-doped CdSe thin films

NASA Astrophysics Data System (ADS)

Ali, H. M.; Abd El-Ghanny, H. A.

2008-04-01

Thin films of (CdSe)90(In2O3)10, (CdSe)90(SnO2)10 and (CdSe)90(ZnO)10 have been grown on glass substrates by the electron beam evaporation technique. It has been found that undoped and Sn or In doped CdSe films have two direct transitions corresponding to the energy gaps Eg and Eg+Δ due to spin-orbit splitting of the valence band. The electrical resistivity for n-doped CdSe thin films as a function of light exposure time has been studied. The influence of doping on the structural, optical and electrical characteristics of In doped CdSe films has been investigated in detail. The lattice parameters, grain size and dislocation were determined from x-ray diffraction patterns. The optical transmittance and band gap of these films were determined using a double beam spectrophotometer. The DC conductivity of the films was measured in vacuum using a two-probe technique.

Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping

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

Ming, Fangfei; Mulugeta Amare, Daniel; Tu, Weisong

Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Itsmore » formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.« less

Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping

DOE PAGES

Ming, Fangfei; Mulugeta Amare, Daniel; Tu, Weisong; ...

2017-03-07

Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Itsmore » formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.« less

Antimony-Doped Tin Oxide Thin Films Grown by Home Made Spray Pyrolysis Technique

NASA Astrophysics Data System (ADS)

Yusuf, Gbadebo; Babatola, Babatunde Keji; Ishola, Abdulahi Dimeji; Awodugba, Ayodeji O.; Solar cell Collaboration

2016-03-01

Transparent conducting antimony-doped tin oxide (ATO) films have been deposited on glass substrates by home made spray pyrolysis technique. The structural, electrical and optical properties of the ATO films have been investigated as a function of Sb-doping level and annealing temperature. The optimum target composition for high conductivity and low resistivity was found to be 20 wt. % SnSb2 + 90 wt. ATO. Under optimized deposition conditions of 450oC annealing temperature, electrical resistivity of 5.2×10-4 Ω -cm, sheet resistance of 16.4 Ω/sq, average optical transmittance of 86% in the visible range, and average optical band-gap of 3.34eV were obtained. The film deposited at lower annealing temperature shows a relatively rough, loosely bound slightly porous surface morphology while the film deposited at higher annealing temperature shows uniformly distributed grains of greater size. Keywords: Annealing, Doping, Homemade spray pyrolysis, Tin oxide, Resistivity

pn junctions based on a single transparent perovskite semiconductor BaSnO3

NASA Astrophysics Data System (ADS)

Kim, Hoon Min; Kim, Useong; Park, Chulkwon; Kwon, Hyukwoo; Lee, Woongjae; Kim, Tai Hoon; Kim, Kee Hoon; Char, Kookrin; Mdpl, Department Of Physics; Astronomy Team; Censcmr, Department Of Physics; Astronomy Team

2014-03-01

Successful p doping of transparent oxide semiconductor will further increase its potential, especially in the area of optoelectronic applications. We will report our efforts to dope the BaSnO3 (BSO) with K by pulsed laser deposition. Although the K doped BSO exhibits rather high resistivity at room temperature, its conductivity increases dramatically at higher temperatures. Furthermore, the conductivity decreases when a small amount of oxygen was removed from the film, consistent with the behavior of p type doped oxides. We have fabricated pn junctions by using K doped BSO as a p type and La doped BSO as an n type material. I_V characteristics of these devices show the typical rectifying behavior of pn junctions. We will present the analysis of the junction properties from the temperature dependent measurement of their electrical properties, which shows that the I_V characteristics are consistent with the material parameters such as the carrier concentration, the mobility, and the bandgap. Our demonstration of pn junctions based on a single transparent perovskite semiconductor further enhances the potential of BSO system with high mobility and stability.

Synergetic effect of Zn substitution on the electron and phonon transport in Mg2Si0.5Sn0.5-based thermoelectric materials.

PubMed

Gao, Hongli; Zhu, Tiejun; Zhao, Xinbing; Deng, Yuan

2014-10-07

Mg2Si1-xSnx alloys are a prospective material for thermoelectric generators at moderate temperatures. The thermoelectric properties of Mg2Si0.5Sn0.5-based thermoelectric materials with only Zn substitution or Zn/Sb co-doping were investigated. Isoelectronic Zn substitution did not affect the carrier concentration, but improved the carrier mobility. Zn atoms incorporated into a Sb-doped Mg2Si0.5Sn0.5 matrix simultaneously boosted the power factor and suppressed the lattice thermal conductivity, leading to an enhancement of the thermoelectric figure of merit ZT of the resulting bulk materials. The interplay between the electron and phonon transport of Mg2Si0.5Sn0.49Sb0.01 substituted with Zn at Mg sites results in an enhancement of the ZT by 25% at ∼730 K, from ZT≈ 0.8 in Mg2Si0.5Sn0.49Sb0.01 to ZT≈ 1.0 in Mg1.98Zn0.02Si0.5Sn0.49Sb0.01. Solid solutions in the Mg2Si-Mg2Sn system appear to be more promising for thermoelectric applications.

Synthesis and evaluation of optical and antimicrobial properties of Ag-SnO2 nanocomposites

NASA Astrophysics Data System (ADS)

Kumar Nair, Kishore; Kumar, Promod; Kumar, Vinod; Harris, R. A.; Kroon, R. E.; Viljoen, Bennie; Shumbula, P. M.; Mlambo, M.; Swart, H. C.

2018-04-01

We report on the sol-gel based room temperature synthesis of undoped SnO2 and Ag-SnO2 nanostructures. The synthesized nanostructures were characterized by Fourier transform infrared spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, High-resolution transmission electron microscopy (HR-TEM) and UV-visible spectroscopy. The XRD pattern confirmed that the obtained nanostructures have a tetragonally rutile structure. No extra phase changes were observed after Ag doping. UV-visible spectroscopy measurements indicated that the band gap of 3.59 eV for pure SnO2 nanostructures, decreased to 3.39 eV after doping. TEM analysis showed that no regular shape morphology existed and some rod-shaped particles were also detected in the nanostructures. The antibacterial activity of the nanostructures against E. coli was evaluated and a continuous decrease of microbial count was observed. The microbial population decreased from 6 × 105 cfu/ml to 7 × 104 cfu/ml and 5 × 104 cfu/ml on SnO2 and Ag-SnO2 treatments, respectively. Thus, the nanostructures can be used for the biorational management of E. coli for waste water treatment before discharge.

Preparation of ZnO/SnO2 Composite Nanometer Photocatalyst and Photocatalytic Treatment of Marine Diesel Pollution

NASA Astrophysics Data System (ADS)

Zhang, J.; Yu, X. C.; Nie, Z. W.; Guo, M. C.; Liu, J. H.; Wang, L. P.

2017-12-01

The ZnO/SnO2 composite nanophotocatalyst studied in this paper was prepared by a chemical precipitation method, which were characterized by XRD and SEM. The results show that the prepared samples were rutile SnO2 particles and the average grain size is 8.41 nm. In this paper, the factors for the degradation efficiency of marine diesel oil degraded by ZnO/SnO2 composite nanophotocatalyst are the catalysts’ doping ratio, the initial concentration of oil, the pH value of seawater, the dosage of catalyst and the dosage of hydrogen peroxide. The results show that the ZnO/SnO2 composite nanophotocatalyst can effectively degrade seawater diesel oil under UV light. When the doping ratio of ZnO and SnO2 is 0.35, the reaction time is 2.5 hours, the pH value of seawater with oil is 7, The concentration of diesel oil is 0.1g/L, the dosage of catalyst is 0.3g/L and the dosage of hydrogen peroxide is 0.1 g/L, the highest degradation rate is 91.54%.

First-principles study of the atomic and electronic properties of (1 0 0) stacking faults in BaSnO3 crystal

NASA Astrophysics Data System (ADS)

Xue, Yuanbin; Wang, Wenyuan; Guo, Yao

2018-02-01

We investigated the atomic and electronic properties of (1 0 0) stacking fault (SF) in undoped and La-doped BaSnO3 by first-principles calculations. It was found that 1/2[1 1 1] (1 0 0) SF is energetically favorable when Ba atoms occupy the interface while 1/2 (1 0 0) [1 0 1] SF becomes the most stable when the SF interface is occupied by Sn atoms. SF influences the distribution of La dopant and the electric properties of the system. In the presence of SF, electronic states near the Fermi level decrease and the bandgap expands by about 0.6 eV. Our results suggest that SF is one of the possible origins for the performance degradation.

Control of conduction type in ferromagnetic (Zn,Sn,Mn)As2 thin films by changing Mn content and effect of annealing on thin films with n-type conduction

NASA Astrophysics Data System (ADS)

Minamizawa, Yuto; Kitazawa, Tomohiro; Hidaka, Shiro; Toyota, Hideyuki; Nakamura, Shin-ichi; Uchitomi, Naotaka

2018-04-01

The conduction type in (Zn,Sn,Mn)As2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (MnI) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 °C, the magnetic properties of the thin films remain stable. This suggests that a MnI complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As2 thin films may be suitable for application as n-type spin-polarized injectors.

Structural and physical properties of transparent conducting, amorphous Zn-doped SnO2 films

NASA Astrophysics Data System (ADS)

Zhu, Q.; Ma, Q.; Buchholz, D. B.; Chang, R. P. H.; Bedzyk, M. J.; Mason, T. O.

2014-01-01

The structural and physical properties of conducting amorphous Zn-doped SnO2 (a-ZTO) films, prepared by pulsed laser deposition, were investigated as functions of oxygen deposition pressure (pO2), composition, and thermal annealing. X-ray scattering and X-ray absorption spectroscopy measurements reveal that at higher pO2, the a-ZTO films are highly transparent and have a structural framework similar to that found in crystalline (c-), rutile SnO2 in which the Sn4+ ion is octahedrally coordinated by 6 O2- ions. The Sn4+ ion in these films however has a coordination number (CN) smaller by 2%-3% than that in c-SnO2, indicating the presence of oxygen vacancies, which are the likely source of charge carriers. At lower pO2, the a-ZTO films show a brownish tint and contain some 4-fold coordinated Sn2+ ions. Under no circumstances is the CN around the Zn2+ ion larger than 4, and the Zn-O bond is shorter than the Sn-O bond by 0.07 Å. The addition of Zn has no impact on the electroneutrality but improves significantly the thermal stability of the films. Structural changes due to pO2, composition, and thermal annealing account well for the changes in the physical properties of a-ZTO films.

Combinatorial development of Cu2SnS3 as an earth abundant photovoltaic absorber

NASA Astrophysics Data System (ADS)

Baranowski, Lauryn L.

The development of high efficiency, earth abundant photovoltaic absorbers is critical if photovoltaics are to be implemented on the TW scale. Although traditional thin films absorbers such as Cu(In,Ga)Se2 and CdTe have achieved over 20% device efficiencies, the ultimately scalability of these devices may be limited by elemental scarcity and toxicity issues. To date, the most successful earth abundant thin film absorber is Cu2ZnSn(S,Se) 4, which has achieved 12.6% efficiency as of 2014. However, chemical complexity and disorder issues with this material have made the path to higher efficiency CZTSSe devices unclear. As a result, many researchers are now exploring alternative earth abundant absorber materials. In this thesis, we apply our "rapid development" methodology to the exploration of alternative photovoltaic absorbers. The rapid development (RD) methodology, consisting of exploration, research, and development stages, uses complementary theory and experiment to assess candidate materials and down-select in each stage. The overall result is that, in the time span of ~2-3 years, we are able to rapidly go from tens of possible absorber materials to 1-2 working PV device prototypes. Here, we demonstrate the RD approach as applied to the Cu-Sn-S system. We begin our investigation of the Cu-Sn-S system by evaluating the thermodynamic stability, electrical transport, electronic structure, and optical and defect properties of candidate materials using complementary theory and experiment. We find that Cu2SnS3 is the most promising absorber candidate because of its strong optical absorption, tunable doping, and wide stability range. Our other candidate compounds suffer from serious flaws that preclude them from being successful photovoltaic absorbers, including too high experimental conductivity (Cu4SnS4), or poor hole transport and low absorption coefficient (Cu4Sn7S16). Next, we investigate the doping and defect physics of Cu2SnS 3. We identify the origins of the changes in doping in sputtered cubic Cu2SnS3 thin films using combinatorial experiments and first-principles theory. High S chemical potential during deposition decreases the enthalpy of formation of Cu vacancies, which are the dominant acceptor defect in Cu2SnS3. Unexpectedly, under Cu-rich conditions, alloying with an isostructural (cubic) metallic Cu3SnS4 phase occurs, causing high levels of p-type doping. Both of these effects lead to undesirably high electrical conductivity, thus Cu2SnS 3 films must be grown both S- and Cu-poor in order to achieve moderate hole concentrations. To understand the effects of structural disorder on the transport properties in Cu2SnS3 we develop synthetic techniques to control this disorder, and observe improvements in the majority carrier (hole) transport. However, when the minority carrier (electron) transport was investigated, minimal differences were observed between the ordered and disordered Cu 2SnS3. By combining these results with first-principles and Monte Carlo theoretical calculations, we are able to conclude that even ostensibly "ordered" Cu2SnS3 displays minority carrier transport properties corresponding to the disordered structure. The presence of extended planar defects in all samples, observed in TEM imaging, suggests that disorder is present even when it is not detectable using traditional structural characterization methods. Lastly, we attempt to integrate our Cu2SnS3 films into photovoltaic devices, which requires translating our growth techniques to conductive substrates. We survey a wide range of possible conductive substrates, but are not able to find a suitable back contact for Cu2SnS 3 device integration, due to issues such as secondary phase formation and delamination. From a survey of successful Cu2SnS3 device literature, we are able to conclude that the issue may lie with our binary sputtering method in which the ternary compound formation and the film growth occur simultaneously. At the conclusion of this study, we eliminated Cu2SnS as an absorber candidate for future development. However, the two main issues we encountered (eliminating structural disorder and difficulty growing on conductive back contacts) may both be related to our binary sputtering technique. We expect that interest in Cu2SnS3-based photovoltaics will continue to grow, and that further scientific understanding may shed light on our particular difficulties. In the future, the RD methodology has the potential to greatly accelerate the discovery and development of non-traditional thin film absorbers, and may enable high impact material breakthroughs.

Photocatalytic Antibacterial Performance of Glass Fibers Thin Film Coated with N-Doped SnO 2 /TiO 2

PubMed Central

Sikong, Lek; Niyomwas, Sutham; Rachpech, Vishnu

2014-01-01

Both N-doped and undoped thin films of 3SnO2/TiO2 composite were prepared, by sol-gel and dip-coating methods, and then calcined at 600°C for 2 hours. The films were characterized by FTIR, XRD, UV-Vis, SEM, and XPS, and their photocatalytic activities to degrade methylene blue in solution were determined, expecting these activities to correlate with the inactivation of bacteria, which was confirmed. The doped and undoped films were tested for activities against Gram-negative Escherichia coli (E. coli) and Salmonella typhi (S. typhi), and Gram-positive Staphylococcus aureus (S. aureus). The effects of doping on these composite films included reduced energy band gap, high crystallinity of anatase phase, and small crystallite size as well as increased photocatalytic activity and water disinfection efficiency. PMID:24693250

Structural and Optoelectronic Properties of SnO2 Thin Films Doped by Group-Ia Elements

NASA Astrophysics Data System (ADS)

Benhebal, Hadj; Benrabah, Bedhiaf; Ammari, Aek; Madoune, Yacine; Lambert, Stéphanie D.

This paper presents the results of an experimental work devoted to the synthesis and the characterization of tin dioxide (SnO2) thin layers doped with group-IA elements (Li, Na and K). The materials were synthesized by the sol-gel method and deposited by dip-coating, using tin (II) chloride dihydrate as a source of tin and absolute ethyl alcohol as solvent. Thin films prepared were characterized by several techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), visible and ultraviolet spectroscopy and complex impedance method. The results obtained show that the materials kept their tetragonal rutile structure with preferred orientation of (101), whereas doping leads to a reduction of their energy band gap. The complex impedance analysis suggests that the different processes occurring at the electrode interface are modeled by an electrical circuit not affected by the doping.

N-doped amorphous carbon coated Fe3O4/SnO2 coaxial nanofibers as a binder-free self-supported electrode for lithium ion batteries.

PubMed

Xie, Wenhe; Li, Suyuan; Wang, Suiyan; Xue, Song; Liu, Zhengjiao; Jiang, Xinyu; He, Deyan

2014-11-26

N-doped amorphous carbon coated Fe3O4/SnO2 coaxial nanofibers were prepared via a facile approach. The core composite nanofibers were first made by electrospinning technology, then the shells were conformally coated using the chemical bath deposition and subsequent carbonization with polydopamine as a carbon source. When applied as a binder-free self-supported anode for lithium ion batteries, the coaxial nanofibers displayed an enhanced electrochemical storage capacity and excellent rate performance. The morphology of the interwoven nanofibers was maintained even after the rate cycle test. The superior electrochemical performance originates in the structural stability of the N-doped amorphous carbon shells formed by carbonizing polydopamine.

Engineering Group-IV Monochalcogenides by Doping and Alloying

NASA Astrophysics Data System (ADS)

Sirikumara, Hansika; Fitzpatrick, Trevor; Jayasekera, Thushari

Group-IV monochalcogenides, MX (M=Sn,Ge and X=S,Se) have shown to be promising materials for thermoelectric and photovoltaic applications. These properties can be further engineered by substitutional doping and alloying. Using the results from ab initio Density Functional Theory calculations, we identified a series of new class of monochalcogenide alloys in the form Ge(1-x)SnxS, Ge(1-x)SnxSe, GeSxSe(1- x), SnSxSe(1-x). Stability of their two-dimensional counterparts will also be discussed in this presentation.

Defect-driven localization crossovers in MBE-grown La-doped SrSn O3 films

NASA Astrophysics Data System (ADS)

Wang, Tianqi; Thoutam, Laxman Raju; Prakash, Abhinav; Nunn, William; Haugstad, Greg; Jalan, Bharat

2017-11-01

Through systematic control of cation stoichiometry using a hybrid molecular beam epitaxy method, we show a crossover from weak to strong localization of electronic carriers in La-doped SrSn O3 films on LaAl O3 (001). We demonstrate that substrate-induced dislocations in these films can have a strong influence on the electron phase coherence length resulting in two-dimensional to three-dimensional weak localization crossover. We discuss the correlation between electronic transport, and defects associated with nonstoichiometry and dislocations.

Vacancy defects and optoelectrical properties for fluorine tin oxide thin films with various SnF2 contents

NASA Astrophysics Data System (ADS)

Zhou, Yawei; Xu, Wenwu; Li, Jingjing; Yin, Chongshan; Liu, Yong; Zhao, Bin; Chen, Zhiquan; He, Chunqing; Mao, Wenfeng; Ito, Kenji

2018-01-01

Fluorine doped tin oxide (FTO) thin films were deposited on glass substrates by e-beam evaporation. Much higher carrier concentration, broader optical band gap, and average transmittance over 80% were obtained with SnF2 doped SnO2 thin films. Positron annihilation results showed that there are two kinds of vacancy clusters with different sizes existing in the annealed FTO thin films, and the concentration of the larger vacancy clusters of VSnO in the thin films increases with increasing SnF2 contents. Meanwhile, photoluminescence spectra results indicated that the better electrical and optical properties of the FTO thin films are attributed to FO substitutions and oxygen vacancies with higher concentration, which are supported by positron annihilation Doppler broadening results and confirmed by X-ray photoelectron spectroscopy. The results showed that widening of the optical band gap of the FTO thin films strongly depends on the carrier concentration, which is interpreted for the Burstein-Moss effect and is associated with the formation of FO and oxygen vacancies with increasing SnF2 content.

High quality, giant crystalline-Ge stripes on insulating substrate by rapid-thermal-annealing of Sn-doped amorphous-Ge in solid-liquid coexisting region

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

Matsumura, Ryo; JSPS Research Fellow, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, 102-0083; Kai, Yuki

Formation of large-grain (≥30 μm) Ge crystals on insulating substrates is strongly desired to achieve high-speed thin-film transistors. For this purpose, we propose the methods of Sn-doping into amorphous-Ge combined with rapid-thermal-annealing (RTA) in the solid-liquid coexisting temperature region for the Ge-Sn alloy system. The densities of micro-crystal-nuclei formed in this temperature region become low by tuning the RTA temperature close to the liquidus curve, which enhances the lateral growth of GeSn. Thanks to the very small segregation coefficient of Sn, almost all Sn atoms segregate toward edges of the stripes during growth. Agglomeration of GeSn degrades the surface morphologies;more » however, it is significantly improved by lowering the initial Sn concentration. As a result, pure Ge with large crystal grains (∼40 μm) with smooth surface are obtained by optimizing the initial Sn concentration as low as 3 ∼ 5%. Lateral growth lengths are further increased through decreasing the number of nuclei in stripes by narrowing stripe width. In this way, high-crystallinity giant Ge crystals (∼200 μm) are obtained for the stripe width of 3 μm. This “Si-seed free” technique for formation of large-grain pure Ge crystals is very useful to realize high-performance thin-film devices on insulator.« less

Overcoming Short-Circuit in Lead-Free CH 3 NH 3 SnI 3 Perovskite Solar Cells via Kinetically Controlled Gas–Solid Reaction Film Fabrication Process

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

Yokoyama, Takamichi; Cao, Duyen H.; Stoumpos, Constantinos C.

2016-02-17

The development of Sn-based perovskite solar cells has been challenging because devices often show short-circuit behavior due to poor morphologies and undesired electrical properties of the thin films. A low-temperature vapor-assisted solution process (LT-VASP) has been employed as a novel kinetically controlled gas–solid reaction film fabrication method to prepare lead-free CH3NH3SnI3 thin films. We show that the solid SnI2 substrate temperature is the key parameter in achieving perovskite films with high surface coverage and excellent uniformity. The resulting high-quality CH3NH3SnI3 films allow the successful fabrication of solar cells with drastically improved reproducibility, reaching an efficiency of 1.86%. Furthermore, our Kelvinmore » probe studies show the VASP films have a doping level lower than that of films prepared from the conventional one-step method, effectively lowering the film conductivity. Above all, with (LT)-VASP, the short-circuit behavior often obtained from the conventional one-step-fabricated Sn-based perovskite devices has been overcome. This study facilitates the path to more successful Sn-perovskite photovoltaic research.« less

Features of the band structure and conduction mechanisms of n-HfNiSn semiconductor heavily Lu-doped

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

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua; Rogl, P.; Romaka, V. V.

2015-03-15

The crystal and electronic structures, energy, kinetic, and magnetic characteristics of n-HfNiSn semiconductor heavily doped with a Lu acceptor impurity in the ranges T = 80–400 K and N{sub A}{sup Lu} ≈ 1.9 × 10{sup 20}−1.9 × 10{sup 21} cm{sup −3} (x = 0.01–0.10) at H ≤ 10 kG is studied. The nature of the structural-defect generation mechanism leading to changes in the band gap and the degree of semiconductor compensation is determined. Its essence is the simultaneous reduction and elimination of donor-type structural defects due to the displacement of ∼1% of Ni atoms from the Hf (4a) site, themore » generation of acceptor-type structural defects by substituting Ni atoms with Lu atoms at the 4c site, and the generation of donor-type defects such as vacancies at the Sn (4b) site. The results of calculations of the electronic structure of Hf{sub 1−x}Lu{sub x}NiSn are in agreement with experimental data. The results are discussed within the model of a heavily doped and compensated Shklovskii-Efros semiconductor.« less

Effect of solvent volume on the physical properties of undoped and fluorine doped tin oxide films deposited using a low-cost spray technique

NASA Astrophysics Data System (ADS)

Muruganantham, G.; Ravichandran, K.; Saravanakumar, K.; Ravichandran, A. T.; Sakthivel, B.

2011-12-01

Undoped and fluorine doped tin oxide films were deposited from starting solutions having different values of solvent volume (10-50 ml) by employing a low cost and simplified spray technique using perfume atomizer. X-ray diffraction studies showed that there was a change in the preferential orientation from (2 1 1) plane to (1 1 0) plane as the volume of the solvent was increased. The sheet resistance ( Rsh) of undoped SnO 2 film was found to be minimum (13.58 KΩ/□) when the solvent volume was lesser (10 ml) and there was a sharp increase in Rsh for higher values of solvent volume. Interestingly, it was observed that while the Rsh increases sharply with the increase in solvent volume for undoped SnO 2 films, it decreases gradually in the case of fluorine doped SnO 2 films. The quantitative analysis of EDAX confirmed that the electrical resistivity of the sprayed tin oxide film was mainly governed by the number of oxygen vacancies and the interstitial incorporation of Sn atoms which in turn was governed by the impinging flux on the hot substrate. The films were found to have good optical characteristics suitable for opto-electronic devices.

n-type doping and morphology of GaAs nanowires in Aerotaxy

DOE PAGES

Metaferia, Wondwosen; Sivakumar, Sudhakar; Persson, Axel R.; ...

2018-05-10

Controlled doping in semiconductor nanowires modifies their electrical and optical properties, which are important for high efficiency optoelectronic devices. We have grown n-type (Sn) doped GaAs nanowires in Aerotaxy, a new continuous gas phase mass production technique. The morphology of Sn doped nanowires is found to be a strong function of dopant, tetraethyltin to trimethylgallium flow ratio, Au-Ga-Sn alloying, and nanowire growth temperatures. High temperature and high flow ratios result in low morphological quality nanowires and in parasitic growth on the wire base and surface. Alloying and growth temperatures of 400 and 530 degrees C, respectively, resulted in good morphologicalmore » quality nanowires for a flow ratio of TESn to TMGa up to 2.25 x 10 -3. The wires are pure Zinc-blende for all investigated growth conditions, whereas nanowires grown by MOVPE with the same growth conditions are usually mainly Wurtzite. The growth rate of the doped wires is found to be dependent more on the TESn flow fraction than on alloying and nanowire growth temperatures. Our photoluminescence measurements, supported by four-point probe resistivity measurements, reveal that the carrier concentration in the doped wires varies only slightly (1- 3) x 10 19 cm -3 with TESn flow fraction and both alloying and growth temperatures, indicating that good morphological quality wires with high carrier density can be grown with low TESn flow. Carrier concentrations lower than 1019 cm-3 can be grown by further reducing the flow fraction of TESn, which may give better morphology wires.« less

n-type doping and morphology of GaAs nanowires in Aerotaxy

NASA Astrophysics Data System (ADS)

Metaferia, Wondwosen; Sivakumar, Sudhakar; Persson, Axel R.; Geijselaers, Irene; Reine Wallenberg, L.; Deppert, Knut; Samuelson, Lars; Magnusson, Martin H.

2018-07-01

Controlled doping in semiconductor nanowires modifies their electrical and optical properties, which are important for high efficiency optoelectronic devices. We have grown n-type (Sn) doped GaAs nanowires in Aerotaxy, a new continuous gas phase mass production technique. The morphology of Sn doped nanowires is found to be a strong function of dopant, tetraethyltin to trimethylgallium flow ratio, Au–Ga–Sn alloying, and nanowire growth temperatures. High temperature and high flow ratios result in low morphological quality nanowires and in parasitic growth on the wire base and surface. Alloying and growth temperatures of 400 °C and 530 °C, respectively, resulted in good morphological quality nanowires for a flow ratio of TESn to TMGa up to 2.25 × 10‑3. The wires are pure zinc-blende for all investigated growth conditions, whereas nanowires grown by metal-organic vapor phase epitaxy with the same growth conditions are usually mainly Wurtzite. The growth rate of the doped wires is found to be dependent more on the TESn flow fraction than on alloying and nanowire growth temperatures. Our photoluminescence measurements, supported by four-point probe resistivity measurements, reveal that the carrier concentration in the doped wires varies only slightly (1–3) × 1019 cm‑3 with TESn flow fraction and both alloying and growth temperatures, indicating that good morphological quality wires with high carrier density can be grown with low TESn flow. Carrier concentrations lower than 1019 cm‑3 can be grown by further reducing the flow fraction of TESn, which may give better morphology wires.

n-type doping and morphology of GaAs nanowires in Aerotaxy

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

Metaferia, Wondwosen; sivakumar, sudhakar; R. Persson, Axel

2018-04-17

Controlled doping in semiconductor nanowires modifies their electrical and optical properties, which are important for high efficiency optoelectronic devices. We have grown n-type (Sn) doped GaAs nanowires in Aerotaxy, a new continuous gas phase mass production technique. The morphology of Sn doped nanowires is found to be a strong function of dopant, tetraethyltin to trimethylgallium flow ratio, Au-Ga-Sn alloying, and nanowire growth temperatures. High temperature and high flow ratios result in low morphological quality nanowires and in parasitic growth on the wire base and surface. Alloying and growth temperatures of 400 and 530 degrees C, respectively, resulted in good morphologicalmore » quality nanowires for a flow ratio of TESn to TMGa up to 2.25 x 10-3. The wires are pure Zinc-blende for all investigated growth conditions, whereas nanowires grown by MOVPE with the same growth conditions are usually mainly Wurtzite. The growth rate of the doped wires is found to be dependent more on the TESn flow fraction than on alloying and nanowire growth temperatures. Our photoluminescence measurements, supported by four-point probe resistivity measurements, reveal that the carrier concentration in the doped wires varies only slightly (1- 3) x 1019 cm-3 with TESn flow fraction and both alloying and growth temperatures, indicating that good morphological quality wires with high carrier density can be grown with low TESn flow. Carrier concentrations lower than 1019 cm-3 can be grown by further reducing the flow fraction of TESn, which may give better morphology wires.« less

n-type doping and morphology of GaAs nanowires in Aerotaxy.

PubMed

Metaferia, Wondwosen; Sivakumar, Sudhakar; Persson, Axel R; Geijselaers, Irene; Wallenberg, L Reine; Deppert, Knut; Samuelson, Lars; Magnusson, Martin H

2018-04-17

Controlled doping in semiconductor nanowires modifies their electrical and optical properties, which are important for high efficiency optoelectronic devices. We have grown n-type (Sn) doped GaAs nanowires in Aerotaxy, a new continuous gas phase mass production technique. The morphology of Sn doped nanowires is found to be a strong function of dopant, tetraethyltin to trimethylgallium flow ratio, Au-Ga-Sn alloying, and nanowire growth temperatures. High temperature and high flow ratios result in low morphological quality nanowires and in parasitic growth on the wire base and surface. Alloying and growth temperatures of 400 °C and 530 °C, respectively, resulted in good morphological quality nanowires for a flow ratio of TESn to TMGa up to 2.25 × 10 -3 . The wires are pure zinc-blende for all investigated growth conditions, whereas nanowires grown by metal-organic vapor phase epitaxy with the same growth conditions are usually mainly Wurtzite. The growth rate of the doped wires is found to be dependent more on the TESn flow fraction than on alloying and nanowire growth temperatures. Our photoluminescence measurements, supported by four-point probe resistivity measurements, reveal that the carrier concentration in the doped wires varies only slightly (1-3) × 10 19 cm -3 with TESn flow fraction and both alloying and growth temperatures, indicating that good morphological quality wires with high carrier density can be grown with low TESn flow. Carrier concentrations lower than 10 19 cm -3 can be grown by further reducing the flow fraction of TESn, which may give better morphology wires.

n-type doping and morphology of GaAs nanowires in Aerotaxy

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

Metaferia, Wondwosen; Sivakumar, Sudhakar; Persson, Axel R.

Controlled doping in semiconductor nanowires modifies their electrical and optical properties, which are important for high efficiency optoelectronic devices. We have grown n-type (Sn) doped GaAs nanowires in Aerotaxy, a new continuous gas phase mass production technique. The morphology of Sn doped nanowires is found to be a strong function of dopant, tetraethyltin to trimethylgallium flow ratio, Au-Ga-Sn alloying, and nanowire growth temperatures. High temperature and high flow ratios result in low morphological quality nanowires and in parasitic growth on the wire base and surface. Alloying and growth temperatures of 400 and 530 degrees C, respectively, resulted in good morphologicalmore » quality nanowires for a flow ratio of TESn to TMGa up to 2.25 x 10 -3. The wires are pure Zinc-blende for all investigated growth conditions, whereas nanowires grown by MOVPE with the same growth conditions are usually mainly Wurtzite. The growth rate of the doped wires is found to be dependent more on the TESn flow fraction than on alloying and nanowire growth temperatures. Our photoluminescence measurements, supported by four-point probe resistivity measurements, reveal that the carrier concentration in the doped wires varies only slightly (1- 3) x 10 19 cm -3 with TESn flow fraction and both alloying and growth temperatures, indicating that good morphological quality wires with high carrier density can be grown with low TESn flow. Carrier concentrations lower than 1019 cm-3 can be grown by further reducing the flow fraction of TESn, which may give better morphology wires.« less

Cu doping concentration effect on the physical properties of CdS thin films obtained by the CBD technique

NASA Astrophysics Data System (ADS)

Albor Aguilera, M. L.; Flores Márquez, J. M.; Remolina Millan, A.; Matsumoto Kuwabara, Y.; González Trujillo, M. A.; Hernández Vásquez, C.; Aguilar Hernandez, J. R.; Hernández Pérez, M. A.; Courel-Piedrahita, M.; Madeira, H. T. Yee

2017-08-01

Cu(In, Ga)Se2 (CIGS) and Cu2ZnSnS4 (CZTS) semiconductors are direct band gap materials; when these types of material are used in solar cells, they provide efficiencies of 22.1% and 12.6%, respectively. Most traditional fabrication methods involve expensive vacuum processes including co-evaporation and sputtering techniques, where films and doping are conducted separately. On the other hand, the chemical bath deposition (CBD) technique allows an in situ process. Cu-doped CdS thin films working as a buffer layer on solar cells provide good performing devices and they may be deposited by low cost techniques such as chemical methods. In this work, Cu-doped CdS thin films were deposited using the CBD technique on SnO2:F (FTO) substrates. The elemental analysis and mapping reconstruction were conducted by EDXS. Morphological, optical and electrical properties were studied, and they revealed that Cu doping modified the CdS structure, band-gap value and the electrical properties. Cu-doped CdS films show high resistivity compared to the non-doped CdS. The appropriate parameters of Cu-doped CdS films were determined to obtain an adequate window or buffer layer on CIGS and CZTS photovoltaic solar cells.

High-field transport properties of a P-doped BaFe2As2 film on technical substrate

PubMed Central

Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

2017-01-01

High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport Jc of 105 A/cm2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E − J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis. PMID:28079117

High-field transport properties of a P-doped BaFe2As2 film on technical substrate

NASA Astrophysics Data System (ADS)

Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

2017-01-01

High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport Jc of 105 A/cm2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E - J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.

Recent developments in the formation and structure of tin-iron oxides by laser pyrolysis

NASA Astrophysics Data System (ADS)

Alexandrescu, R.; Morjan, I.; Dumitrache, F.; Birjega, R.; Fleaca, C.; Soare, I.; Gavrila, L.; Luculescu, C.; Prodan, G.; Kuncser, V.; Filoti, G.

2011-04-01

Complex oxides demonstrate specific electric and magnetic properties which make them suitable for a wide variety of applications, including dilute magnetic semiconductors for spin electronics. A tin-iron oxide Sn 1- xFe xO 2 nanoparticulate material has been successfully synthesized by using the laser pyrolysis of tetramethyl tin-iron pentacarbonyl-air mixtures. Fe doping of SnO 2 nanoparticles has been varied systematically in the 3-10 at% range. As determined by EDAX, the Fe/Sn ratio (in at%) in powders varied between 0.14 and 0.64. XRD studies of Sn 1- xFe xO 2 nanoscale powders, revealed only structurally modified SnO 2 due to the incorporation of Fe into the lattice mainly by substitutional changes. The substitution of Fe 3+ in the Sn 4+ positions (Fe 3+ has smaller ionic radius as compared to the ionic radius of 0.69 Å for Sn 4+) with the formation of a mixed oxide Sn 1- xFe xO 2 is suggested. A lattice contraction consistent with the determined Fe/Sn atomic ratios was observed. The nanoparticle size decreases with the Fe doping (about 7 nm for the highest Fe content). Temperature dependent 57Fe Mössbauer spectroscopy data point to the additional presence of defected Fe 3+-based oxide nanoclusters with blocking temperatures below 60 K. A new Fe phase presenting magnetic order at substantially higher temperatures was evidenced and assigned to a new type of magnetism relating to the dispersed Fe ions into the SnO 2 matrix.

Fluorescence properties of Yb3+-Er3+ co-doped phosphate glasses containing silver nanoparticles

NASA Astrophysics Data System (ADS)

Martínez Gámez, Ma A.; Vallejo H, Miguel A.; Kiryanov, A. V.; Licea-Jiménez, L.; Lucio M, J. L.; Pérez-García, S. A.

2018-04-01

Er3+-Yb3+ co-doped phosphate glasses containing silver nitrate (SN), were fabricated. Transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) analyses were used to evidence the nucleation and presence of silver nanoparticles (SNP). The basic parameters of the glasses were inspected by means of absorption and fluorescence spectra, and fluorescence lifetimes under excitation at 916 nm (in-band of Yb3+), and at 406 nm (in-band of surface plasmon resonance given by the presence of SNP). The spectra as well as estimates for the basic parameters defining the lasing/amplifying potential of the glasses were studied as a function of SN concentration. The experimental results indicate that by increasing the SN content an enhancement of Er3+/Yb3+ fluorescence takes place.

Enhanced gas sensing correlated with structural and optical properties of Cs-loaded SnO2 nanofilms

NASA Astrophysics Data System (ADS)

Elia Raine, P. J.; Arun George, P.; Balasundaram, O. N.; Varghese, T.

2016-09-01

The Cs-loaded SnO2 thin films were prepared by the spray pyrolysis technique and were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, impedance spectroscopy and conductometric method. Investigations based on the structural, optical and electrical properties confirm an enhanced gas sensing potential of cesium-loaded tin oxide films. It is found that the tin oxide thin film doped with 4% Cs with a mean grain size of 20 nm at a deposition temperature of 350 ° C show a maximum sensor response of 97.5% for LPG consistently. It is also observed that the sensor response of Cs-doped SnO2 thin films depends on the dopant concentration and the deposition temperature of the film.

Chromium-induced ferromagnetism with perpendicular anisotropy in topological crystalline insulator SnTe (111) thin films

NASA Astrophysics Data System (ADS)

Wang, Fei; Zhang, Hongrui; Jiang, Jue; Zhao, Yi-Fan; Yu, Jia; Liu, Wei; Li, Da; Chan, Moses H. W.; Sun, Jirong; Zhang, Zhidong; Chang, Cui-Zu

2018-03-01

Topological crystalline insulator is a recently discovered topological phase of matter. It possesses multiple Dirac surface states, which are protected by the crystal symmetry. This is in contrast to the time-reversal symmetry that is operative in the well-known topological insulators. In the presence of a Zeeman field and/or strain, the multiple Dirac surface states are gapped. The high-Chern-number quantum anomalous Hall (QAH) state is predicted to emerge if the chemical potential resides in all the Zeeman gaps. Here, we use molecular-beam epitaxy to grow 12 double-layer (DL) pure and Cr-doped SnTe (111) thin film on heat-treated SrTi O3 (111) substrate using a quintuple layer of insulating (Bi0.2Sb0.8 ) 2T e3 topological insulator as a buffer film. The Hall traces of Cr-doped SnTe film at low temperatures display square hysteresis loops indicating long-range ferromagnetic order with perpendicular anisotropy. The Curie temperature of the 12 DL S n0.9C r0.1Te film is ˜110 K. Due to the chemical potential crossing the bulk valence bands, the anomalous Hall resistance of 12 DL S n0.9C r0.1Te film is substantially lower than the predicted quantized value (˜1 /4 h /e2 ). It is possible that with systematic tuning the chemical potential via chemical doping and electrical gating, the high-Chern-number QAH state can be realized in the Cr-doped SnTe (111) thin film.

What is the origin of concentration quenching of Cu+ luminescence in glass?

NASA Astrophysics Data System (ADS)

Jiménez, José A.

2016-10-01

Monovalent copper-doped luminescent glasses are attractive materials for white light-emitting devices, photonic waveguides, and solar spectral conversion in photovoltaic cells. However, the occurrence of concentration quenching in such is not fully understood at present. In this work, calcium-phosphate glasses with high concentrations of luminescent Cu+ ions have been prepared by a simple melt-quench method via CuO and SnO co-doping. The aim is to elucidate the origin of concentration quenching of Cu+ light emission. A spectroscopic characterization was carried out by optical absorption and photoluminescence (PL) spectroscopy including emission decay dynamics. The concentrations of both CuO and SnO dopants were varied as 5, 10 and 15 mol%. Monovalent copper content is estimated in the CuO/SnO-containing glasses following the assessment of the concentration dependence of Cu2+ absorption in the visible for CuO singly-doped glasses. Contrary to the conventionally acknowledged direct Cu+→Cu2+ transfer, the data supports a Cu+-Cu+ energy migration channel at the origin of the PL quenching.

Effect of atomic disorder and Ce doping on superconductivity of Ca 3 Rh 4 Sn 13 : Electric transport properties under high pressure

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

Ślebarski, Andrzej; Goraus, Jerzy; Maśka, Maciej M.

2016-06-13

Here, we report the observation of a superconducting state below ~8 K coexistent with a spin-glass state caused by atomic disorder in Ce substituted Ca 3Rh 4Sn 13. Measurements of specific heat, resistivity, and magnetism reveal the existence of inhomogeneous superconductivity in samples doped with Ce with superconducting critical temperatures T c higher than those observed in the parent compound. For Ca 3Rh 4Sn 13, the negative value of the change in resistivity ρ with pressure P, dρ/dP correlates well with the calculated decrease in the density of states (DOS) at the Fermi energy with P. In conclusion, based onmore » band-structure calculations performed under pressure, we demonstrate how the change in DOS would affect T c of Ca 3Rh 4Sn 13 under negative lattice pressure in samples that are strongly defected by quenching.« less

Smart chemical sensors using ZnO semiconducting thin films for freshness detection of foods and beverages

NASA Astrophysics Data System (ADS)

Nanto, Hidehito; Kobayashi, Toshiki; Dougami, Naganori; Habara, Masaaki; Yamamoto, Hajime; Kusano, Eiji; Kinbara, Akira; Douguchi, Yoshiteru

1998-07-01

The sensitivity of the chemical sensor, based on the resistance change of Al2O3-doped and SnO2-doped ZnO (ZnO:Al and ZnO:SnO2) thin film, is studied for exposure to various gases. It is found that the ZnO:Al and ZnO:Sn thin film chemical sensor has a high sensitivity and excellent selectivity for amine (TMA and DMA) gas and ethanol gas, respectively. The ZnO:Al (5.0 wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to odors from rotten sea foods, such as salmon, sea bream, oyster, squid and sardine, responds to the freshness change of these sea foods. The ZnO:SnO2 (78 wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to aroma from alcohols, such as wine, Japanese sake, and whisky, responds to the freshness change of these alcohols.

First-principles study of ZnSnAs2-based dilute magnetic semiconductors

NASA Astrophysics Data System (ADS)

Kizaki, Hidetoshi; Morikawa, Yoshitada

2018-02-01

The electronic structure and magnetic properties of chalcopyrite Zn(Sn,TM)As2 and (Zn,TM)SnAs2 have been investigated by the Korringa-Kohn-Rostoker method combined with the coherent potential approximation within the local spin density approximation, where TM denotes a 3d transition metal element. We find that the half-metallic and high-spin ferromagnetic state can be obtained in Zn(Sn,V)As2, Zn(Sn,Cr)As2, Zn(Sn,Mn)As2, (Zn,V)SnAs2, and (Zn,Cr)SnAs2. The calculated result of Zn(Sn,Mn)As2 is in good agreement with the experimentally observed room-temperature ferromagnetism if we can control selective Mn doping at Sn sites. In addition, (Zn,V)SnAs2 and (Zn,Cr)SnAs2 are predicted to exhibit high-Curie-temperature ferromagnetism.

Pressure effects on topological crystalline insulator SnTe and derived superconductor Sn{sub 0.5}In{sub 0.5}Te

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

Maurya, V. K.; Shruti,; Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in

2016-05-23

We are reporting decrease in superconducting transition temperature accompanied by increased metallicity in indium doped SnTe superconductor. SnTe is a topological crystalline insulator and superconductivity is achieved by indium substitution in place of tin. With application of hydrostatic pressure we find negative dT{sub c}/dP of ~ -0.6K/GPa upto 2.5 GPa. The overall phenomenon is ascribed to unconventional superconductivity. Decrease in resistivity is also seen in single crystal SnTe with application of pressure but no evidence of superconductivity is observed.

Effect of dilute magnetic ions on the optical, dielectric and ferroelectric properties of PZT at morphotopic phase boundary

NASA Astrophysics Data System (ADS)

Rao, T. Lakshmana; Pradhan, M. K.; Ramakrishna, P. V.; Dash, S.

2018-05-01

Modified-PZT ceramics with a formula Pb0.9Ni0.1[(Zr0.52Ti0.48)]1-xSnxO3 located near the morphotropic phase boundary (MPB) were prepared by conventional solid state process to investigate effects of dilute doping of Ni and Sn in different sites of PZT. The single phase structure of the series of samples has been identified by x-ray diffraction technique. The optical band gap has been obtained from the UV-Vis spectra and found to be shrinkage with doping. The detail dielectric and impedance studies are being carried out to investigate the conduction mechanism of the samples. A significant enhancement in the electric polarization is observed for the maximum Sn doping in a modified PZT.

Thermal Studies of New Precursors to Indium-tin Oxides for Use as Sensor Materials in the Detection of NO(x)

NASA Technical Reports Server (NTRS)

Goldsby, J. C.; Kacik, T.; Hockensmith, C. M.

1999-01-01

Control of combustion product emissions in both sub and super-sonic jet engines can be facilitated by measurement of NO(x) levels with metal oxide sensors, In2O3, metal-doped SnO2, and SnO, (as well as other materials) show resistivity changes in the presence of NO(x), but often their sensitivity, stability, and selectivity are low. This study was designed to develop new synthetic pathways to precursors that produce high purity, two phase In2O3-SnO2. The precursors were formed by complexation of tin with any oxide ligands to give the ammonium salt (NH4). Thermal studies of these precursors were carried out by thermal gravimetry (TG) and differential scanning calorimetry (DSC). Further studies by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) were also conducted.

Sn-doped ZnO nanopetal networks for efficient photocatalytic degradation of dye and gas sensing applications

NASA Astrophysics Data System (ADS)

Bhatia, Sonik; Verma, Neha; Bedi, R. K.

2017-06-01

Nowadays, tremendous increase in environmental issue is an alarming threat to the ecosystem. This paper reports, rapid synthesis and characterization for tin doped ZnO nanoparticles prepared by simple combustion method and doctor blade technique. The prepared nanoparticles were characterized by several techniques in terms of their morphological, structural, compositional, optical, photocatalytic and gas sensing properties. These detailed characterization confirmed that all the synthesized nanoparticles are well crystalline and having good optoelectronic properties. Herein, different concentrations of Sn (0.5 at. wt%, 1.0 at. wt%, 2.0 at. wt%, 3.0 at. wt%) were used as dopants (SZ1-SZ4). The morphology of synthesized technique confirmed that the petal-shaped nanoparticles has high surface area and are well crystalline. In order to develop smart and functional nano-device, the prepared powder was coated on glass substrate by doctor blade technique and fabricated device was sensed for ethanol and acetone gas at different operating temperatures (300-500̊C). It is noteworthy that morphology of the nanoparticles of the sensitive layer is maintained after different concentration of Sn. High sensitivity is the main cause of high surface area and tin doping. PL intensity near 598 nm of SZ3 is greater than other Sn-doped ZnO which indicates more oxygen vacancies of SZ3 is responsible for enhanced gas sensitivity and photocatalytic activity. The sensing performance showed 5% volume of ethanol and acetone and gases could be detected with sensitivity of 86.80% and 84.40% respectively. The mechanism for the improvement in the sensing properties can be explained with the surface adsorption theory. Sn-ZnO was used as photocatalyst for degradation of DR-31 dye. Optimum concentration of prepared nanoparticles (2.0 at. wt%) exhibits complete degradation of dye only in 60 min under UV irradiation.

Role of different chelating agent in synthesis of copper doped tin oxide (Cu-SnO2) nanoparticles

NASA Astrophysics Data System (ADS)

Saravanakumar, B.; Anusiya, A.; Rani, B. Jansi; Ravi, G.; Yuvakkumar, R.

2018-05-01

An attempt was made to synthesis the copper doped tin oxide (Cu-SnO2) nanoparticles by adopting different chelating agents (NaOH, KOH and C2H2O4) by Sol-gel process. The synthesized products were characterized by XRD, Photoluminescence (PL), Infra- Red (FTIR) and SEM analysis. The XRD confirms the formation of Cu-SnO2 shows the maximum peak at 33.8° with lattice plane (101). The PL peak at 361 and 382 nm due to the recombination of electron in conduction band to valence band infers the optical properties. The IR spectra correspond to the peak at 551 and 620 cm-1 attributed to the characteristics peak for Cu-SnO2 nanoparticles. The SEM images for all three Cu-SnO2 nanoparticles formed by three chelating agent (NaOH, KOH and C2H2O4) facilitates the formation mechanism and the chelating agent Oxalic acid results in formation of nano flowers with diverse layers orientated in random direction. Further SEM studies reveal that, the Cu-SnO2 nanoparticles formed by oxalic acid could posses high surface area with large number layered structured enables the better electrochemical properties and its applications.

Combinatorial Platform for Discovery of Nanocrystal-Ink Based Earth Abundant Element PV with Efficiency Greater than 20%

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

Hillhouse, Hugh W.

(1) We successfully developed an ultrasonic spray coating system that can be used to deposit thin chalcogenide films with composition gradients. 4 publications under the contract have been published with the instrument. The instrument was used to reveal the effects of intrinsic composition and examine the effects of 25 different dopant elements. Surprisingly, doping with most elements had little to no effect on the quasi-Fermi level splitting of bare films. Ge and Li were explored in depth, and our best devices utilize lithium doping. (2) We developed a new model of absorption coefficients, that when combined with absolute intensity photoluminescence,more » yield the steady-state quasi-Fermi level splitting and a way to quantify the sub-bandgap absorption. This has resulted in 2 publications on the method, with another in preparation. This is a significant development that should impact other PV technologies. (3) We found that lithium doping has several beneficial effects on CZTSSe. It improves the open-circuit voltage, short circuit current, fill factor, and shunt resistance. By using scanning Kelvin probe microscopy (SKPM) and conductive AFM (along with device measurements, DLPC, and XPS), we discovered that lithium acts to increase the p-type doping in both the grain and grain boundaries (GBs). The effect is stronger in the GBs and changes the direction of the electric field at the GB. In lithium doped devices, an electric field repels minority carrier electrons away from the GB. This resulted in a publication and the fabrication of 11.8% efficient devices from a DMSO-thiourea molecular ink. The mechanism of action is most likely due to the formation of LiCu, which inhibits the formation of the donor defect ZnCu. This reduces compensation and increases the net p-type doping. (4) By alloying with germanium, we have fabricated CZTGSSe devices with the best open-circuit voltage (relative the maximum theoretical open-circuit voltage for the bandgap) for any kesterite solar cell. The Voc/Voc,max is 63%, compared to 58% for the record efficiency cell from hydrazine. The origin of the increased voltage efficiency appears to be related to the conduction band off-set and the suppression of a deep defect (~0.8 eV), most likely due to CuSn, but SnZn or SnCu are also possible. All milestones and go/no-go metrics were met with exception of the device efficiency milestone (15% then 20%). However, under the contract, hydrazine-free CZTSSe device efficiencies increased from 7.2% at the start of the contract to 11.8% upon completion.« less

Achieving deep-red-to-near-infrared emissions in Sn-doped Cu-In-S/ZnS quantum dots for red-enhanced white LEDs and near-infrared LEDs.

PubMed

Chen, Jixin; Li, Ye; Wang, Le; Zhou, Tianliang; Xie, Rong-Jun

2018-05-16

Semiconductor quantum dots (QDs) are promising luminescent materials for use in lighting, display and bio-imaging, and the color tuning is a necessity for such applications. In this work, we report tunable colors and deep-red or near infrared (NIR) emissions in Cu-In-S and Cu-In-S/ZnS QDs by incorporating Sn. These QDs (with a size of 5 nm) with varying Sn concentrations and/or Cu/In ratios were synthesized by a non-injection method, and characterized by a variety of analytical techniques (i.e., XRD, TEM, XPS, absorption, photoluminescence, decay time, etc.). The Cu-Sn-In-S and Cu-Sn-In-S/ZnS QDs with Cu/In = 1/2 show the emission maximum in the ranges of 701-894 nm and 628-785 nm, respectively. The red-shift in emission is ascribed to the decrease of the band gap with the Sn doping. The highest quantum yield of 75% is achieved in Cu-Sn-In-S/ZnS with 0.1 mmol Sn and Cu/In = 1/2. Both the white and NIR LEDs were fabricated by using Cu-Sn-In-S/ZnS QDs and a 365 nm LED chip. The white LED exhibits superhigh color rendering indices of Ra = 97.2 and R9 = 91 and a warm color temperature of 2700 K. And the NIR LED shows an interesting broadband near-infrared emission centered at 741 nm, allowing for applications in optical communication, sensing and medical devices.

Investigation of electronic structures and optical properties of β -Si3N4 doped with IV A elements: A first-principles simulation

NASA Astrophysics Data System (ADS)

Lu, Xuefeng; Gao, Xu; Ren, Junqiang; Li, Cuixia; Guo, Xin; Wei, Yupeng; La, Peiqing

2018-04-01

Based on first-principles simulations with the generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) functional, we studied the electronic structures and optical properties of hexagonal silicon nitride (β-Si3N4) doped with IV A elements, C, Ge, Sn and Pb. It was found that the Ge-doped system is characterized by a more stable structure with a lower formation energy of 2.584 eV compared with those of the C-, Sn- and Pb-doped systems of 3.877 eV, 5.249 eV and 7.672 eV, respectively. The band gap (EG) of the Pb-doped system was the lowest at 1.6 eV, displaying semiconducting characteristics. Additionally, there was a transition from a direct band gap to an indirect band gap in the C-doped system. Charge difference density analysis showed that the covalent property of the C-N bonds was enhanced by expansion of the electron-free region and the larger Mulliken population values of 0.71 and 0.86. Furthermore, lower absorption and reflectivity peaks at 11.30 eV were observed for the C-doped system, demonstrating its broader potential for application in photoelectric and microelectronic devices.

Tuning Phase Composition of TiO2 by Sn(4+) Doping for Efficient Photocatalytic Hydrogen Generation.

PubMed

Wang, Fenglong; Ho, Jie Hui; Jiang, Yijiao; Amal, Rose

2015-11-04

The anatase-rutile mixed-phase photocatalysts have attracted extensive research interest because of the superior activity compared to their single phase counterparts. In this study, doping of Sn(4+) ions into the lattice of TiO2 facilitates the phase transformation from anatase to rutile at a lower temperature while maintaining the same crystal sizes compared to the conventional annealling approach. The mass ratios between anatase and rutile phases can be easily manipulated by varying the Sn-dopant content. Characterization results reveal that the Sn(4+) ions entered into the lattice of TiO2 by substituting some of the Ti(4+) ions and distributed evenly in the matrix of TiO2. The substitution induced the distortion of the lattice structure, which realized the phase transformation from anatase to rutile at a lower temperature and the close-contact phase junctions were consequently formed between anatase and rutile, accounting for the efficient charge separations. The mixed-phase catalysts prepared by doping Sn(4+) ions into the TiO2 exhibit superior activity for photocatalytic hydrogen generation in the presence of Au nanoparticles, relatively to their counterparts prepared by the conventional annealling at higher temperatures. The band allignment between anatase and rutile phases is established based on the valence band X-ray photoelectron spectra and diffuse reflectance spectra to understand the spatial charge separation process at the heterojunction between the two phases. The study provides a new route for the synthesis of mixed-phase TiO2 catalysts for photocatalytic applications and advances the understanding on the enhanced photocatalytic properties of anatase-rutile mixtures.

Radiative transitions in highly doped and compensated chalcopyrites and kesterites: The case of Cu2ZnSnS4

NASA Astrophysics Data System (ADS)

Teixeira, J. P.; Sousa, R. A.; Sousa, M. G.; da Cunha, A. F.; Fernandes, P. A.; Salomé, P. M. P.; Leitão, J. P.

2014-12-01

The theoretical models of radiative recombinations in both CuIn1 -xGaxSe2 chalcopyrite and Cu2ZnSnS4 kesterite, and related compounds, were revised. For heavily doped materials, electrons are free or bound to large donor agglomerates which hinders the involvement of single donors in the radiative recombination channels. In this work, we investigated the temperature and excitation power dependencies of the photoluminescence of Cu2ZnSnS4-based solar cells in which the absorber layer was grown through sulphurization of multiperiod structures of precursor layers. For both samples the luminescence is dominated by an asymmetric band with peak energy at ˜1.22 eV, which is influenced by fluctuating potentials in both conduction and valence bands. A value of ˜60 meV was estimated for the root-mean-square depth of the tails in the conduction band. The radiative transitions involve the recombination of electrons captured by localized states in tails of the conduction band with holes localized in neighboring acceptors that follow the fluctuations in the valence band. The same acceptor level with an ionization energy of ˜280 meV was identified in both absorber layers. The influence of fluctuating potentials in the electrical performance of the solar cells was discussed.

Si-Based Germanium Tin Semiconductor Lasers for Optoelectronic Applications

NASA Astrophysics Data System (ADS)

Al-Kabi, Sattar H. Sweilim

Silicon-based materials and optoelectronic devices are of great interest as they could be monolithically integrated in the current Si complementary metal-oxide-semiconductor (CMOS) processes. The integration of optoelectronic components on the CMOS platform has long been limited due to the unavailability of Si-based laser sources. A Si-based monolithic laser is highly desirable for full integration of Si photonics chip. In this work, Si-based germanium-tin (GeSn) lasers have been demonstrated as direct bandgap group-IV laser sources. This opens a completely new avenue from the traditional III-V integration approach. In this work, the material and optical properties of GeSn alloys were comprehensively studied. The GeSn films were grown on Ge-buffered Si substrates in a reduced pressure chemical vapor deposition system with low-cost SnCl4 and GeH4 precursors. A systematic study was done for thin GeSn films (thickness 400 nm) with Sn composition 5 to 17.5%. The room temperature photoluminescence (PL) spectra were measured that showed a gradual shift of emission peaks towards longer wavelength as Sn composition increases. Strong PL intensity and low defect density indicated high material quality. Moreover, the PL study of n-doped samples showed bandgap narrowing compared to the unintentionally p-doped (boron) thin films with similar Sn compositions. Finally, optically pumped GeSn lasers on Si with broad wavelength coverage from 2 to 3 mum were demonstrated using high-quality GeSn films with Sn compositions up to 17.5%. The achieved maximum Sn composition of 17.5% broke the acknowledged Sn incorporation limit using similar deposition chemistry. The highest lasing temperature was measured at 180 K with an active layer thickness as thin as 270 nm. The unprecedented lasing performance is due to the achievement of high material quality and a robust fabrication process. The results reported in this work show a major advancement towards Si-based electrically pumped mid-infrared laser sources for integrated photonics.

Low-temperature thermoelectric properties of Pb doped Cu2SnSe3

NASA Astrophysics Data System (ADS)

Prasad K, Shyam; Rao, Ashok; Gahtori, Bhasker; Bathula, Sivaiah; Dhar, Ajay; Chang, Chia-Chi; Kuo, Yung-Kang

2017-09-01

A series of Cu2Sn1-xPbxSe3 (0 ≤ x ≤ 0.04) compounds was prepared by solid state synthesis technique. The electrical resistivity (ρ) decreased with increase in Pb content up to x = 0.01, thereafter it increased with further increase in x (till x = 0.03). However, the lowest value of electrical resistivity is observed for Cu2Sn0.96Pb0.04Se3. Analysis of electrical resistivity of all the samples suggests that small poloron hoping model is operative in the high temperature regime while variable range hopping is effective in the low temperature regime. The positive Seebeck coefficient (S) for pristine and doped samples in the entire temperature range indicates that the majority charge carriers are holes. The electronic thermal conductivity (κe) of the Cu2Sn1-xPbxSe3 compounds was estimated by the Wiedemann-Franz law and found that the contribution from κe is less than 1% of the total thermal conductivity (κ). The highest ZT 0.013 was achieved at 400 K for the sample Cu2Sn0.98Pb0.02Se3, about 30% enhancement as compared to the pristine sample.

The structural properties of Sn-doped zinc oxide synthesized by hot-tube thermal evaporation

NASA Astrophysics Data System (ADS)

Suhaimi, Syahida; Sakrani, Samsudi; Yatim, Nadhrah Md.; Hashim, Mohd Azman

2018-06-01

The growth of Sn:ZnO nanowires on a silicon substrate using a low thermal evaporation method is reported. A horizontal quartz tube with controlled supply of O2 gas were used to fabricate the samples where Zn and Sn metal powders were previously mixed and heated at 500°C. This allows the reactant vapours to deposit onto the substrate, which placed at a certain distance from the source materials. The samples were characterized using FESEM, EDX and HRTEM measurements. Randomly oriented nanowires were formed with varying dopant concentrations from 3 to 15 at%. It was observed that from FESEM images, when the dopant concentrations were increased, a hexagonal rod with a wire extended at its end was clearly formed and the best images of nanowires were shown at the highest concentration of 15 at% measuring between 26 to 35 nm and roughly 500 nm in diameter and length respectively. The doping process played an important role in order to alter the morphological properties of Sn:ZnO nanowires. Sn:ZnO nanowires have large potential in many applications such as in selected sensor technology including gaseous sensors, liquid sensors and others.

Nitrogen-Doped Carbon-Encapsulated SnO2@Sn Nanoparticles Uniformly Grafted on Three-Dimensional Graphene-like Networks as Anode for High-Performance Lithium-Ion Batteries.

PubMed

Li, Yunyong; Zhang, Haiyan; Chen, Yiming; Shi, Zhicong; Cao, Xiaoguo; Guo, Zaiping; Shen, Pei Kang

2016-01-13

A peculiar nanostructure consisting of nitrogen-doped, carbon-encapsulated (N-C) SnO2@Sn nanoparticles grafted on three-dimensional (3D) graphene-like networks (designated as N-C@SnO2@Sn/3D-GNs) has been fabricated via a low-cost and scalable method, namely an in situ hydrolysis of Sn salts and immobilization of SnO2 nanoparticles on the surface of 3D-GNs, followed by an in situ polymerization of dopamine on the surface of the SnO2/3D-GNs, and finally a carbonization. In the composites, three-layer core-shell N-C@SnO2@Sn nanoparticles were uniformly grafted onto the surfaces of 3D-GNs, which promotes highly efficient insertion/extraction of Li(+). In addition, the outermost N-C layer with graphene-like structure of the N-C@SnO2@Sn nanoparticles can effectively buffer the large volume changes, enhance electronic conductivity, and prevent SnO2/Sn aggregation and pulverization during discharge/charge. The middle SnO2 layer can be changed into active Sn and nano-Li2O during discharge, as described by SnO2 + Li(+) → Sn + Li2O, whereas the thus-formed nano-Li2O can provide a facile environment for the alloying process and facilitate good cycling behavior, so as to further improve the cycling performance of the composite. The inner Sn layer with large theoretical capacity can guarantee high lithium storage in the composite. The 3D-GNs, with high electrical conductivity (1.50 × 10(3) S m(-1)), large surface area (1143 m(2) g(-1)), and high mechanical flexibility, tightly pin the core-shell structure of the N-C@SnO2@Sn nanoparticles and thus lead to remarkably enhanced electrical conductivity and structural integrity of the overall electrode. Consequently, this novel hybrid anode exhibits highly stable capacity of up to 901 mAh g(-1), with ∼89.3% capacity retention after 200 cycles at 0.1 A g(-1) and superior high rate performance, as well as a long lifetime of 500 cycles with 84.0% retention at 1.0 A g(-1). Importantly, this unique hybrid design is expected to be extended to other alloy-type anode materials such as silicon, germanium, etc.

The Material Properties of CsSnBr3 and CsBr:Sn-1% and Their Potential as Scintillator Detector Material

DTIC Science & Technology

2010-03-01

Iodide or Cesium Iodide are the benchmarks for ease of use and quick identification of isotope species. This research aims to explore Cesium Bromide doped...oxidation states of 3+, 4+, 5+ and 6+ were used to identify the Pu pollution in the Rocky Flats area. The identification of the Pu4+ oxidation state...point was causing the normalization of the spectra to be much higher than what it should be. The XANES structures lineup showing the Sn in the CsSnBr3

Distribution of impurity states and charge transport in Zr{sub 0.25}Hf{sub 0.75}Ni{sub 1+x}Sn{sub 1−y}Sb{sub y} nanocomposites

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

Liu, Yuanfeng; Makongo, Julien P.A.; Page, Alexander

Energy filtering of charge carriers in a semiconducting matrix using atomically coherent nanostructures can lead to a significant improvement of the thermoelectric figure of merit of the resulting composite. In this work, several half-Heusler/full-Heusler (HH/FH) nanocomposites with general compositions Zr{sub 0.25}Hf{sub 0.75}Ni{sub 1+x}Sn{sub 1−y}Sb{sub y} (0≤x≤0.15 and y=0.005, 0.01 and 0.025) were synthesized in order to investigate the behavior of extrinsic carriers at the HH/FH interfaces. Electronic transport data showed that energy filtering of carriers at the HH/FH interfaces in Zr{sub 0.25}Hf{sub 0.75}Ni{sub 1+x}Sn{sub 1−y}Sb{sub y} samples strongly depends on the doping level (y value) as well as the energymore » levels occupied by impurity states in the samples. For example, it was found that carrier filtering at HH/FH interfaces is negligible in Zr{sub 0.25}Hf{sub 0.75}Ni{sub 1+x}Sn{sub 1−y}Sb{sub y} (y=0.01 and 0.025) composites where donor states originating from Sb dopant dominate electronic conduction. However, we observed a drastic decrease in the effective carrier density upon introduction of HH/FH interfaces for the mechanically alloyed Zr{sub 0.25}Hf{sub 0.75}Ni{sub 1+x}Sn{sub 0.995}Sb{sub 0.005} samples where donor states from unintentional Fe impurities contribute the largest fraction of conduction electrons. This work demonstrates the ability to synergistically integrate the concepts of doping and energy filtering through nanostructuring for the optimization of electronic transport in semiconductors. - Graphical abstract: Electronic transport in semiconducting half-Heusler (HH) matrices containing full-Heusler (FH) nanoinclusions strongly depends on the energy distribution of impurity states within the HH matrix with respect to the magnitude of the potential energy barrier at the HH/FH interfaces. - Highlights: • Coherent nanostructures enhanced thermoelectric behavior of half-Heusler alloys. • Nanostructures act as energy filter of carriers at the HH/FH interfaces. • Carrier filtering depends on the energy levels of impurity states in the samples.« less

Structural, electrical and optical properties of Al-Sn codoped ZnO transparent conducting layer deposited by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Bedia, A.; Bedia, F. Z.; Aillerie, M.; Maloufi, N.

2017-11-01

Low cost Al-Sn codoped ZnO (ATZO) Transparent Conductive Oxide films were deposited by spray pyrolysis on glass substrate. The influence of Al-Sn codoping on the structural, optical and electrical properties of ZnO thin films was studied by comparing the same properties obtained in undoped ZnO, Al doped ZnO (AZO) and Sn doped ZnO (TZO) thin films. The so-obtained films crystallized in hexagonal wurtzite structure. The morphology and structural defects have been investigated by both High resolution Field Effect Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy at 532 nm excitation source. In the visible region, the undoped and doped films show an average transmittance of the order of 85%, while for ATZO thin film, it is of the order of 72%, which points out a degradation of the optical properties due to the co-doping. The optical band gap of ATZO thin film achieves 3.31eV and this shift, compared to the referred samples is attributed to the Burstein-Moss (BM) and band gap narrowing (BGN) opposite effects which is due to the increase of the carrier concentration in degenerate semiconductors. Within all the samples, the ATZO thin film exhibits the lowest electrical resistivity of 4.56 × 10-3 Ωcm with a Hall mobility equal to 2.13 cm2 V-1s-1, and the highest carrier concentration of 6.41 × 1020 cm-3. The performance of ATZO transparent conductive oxide film are determined by its figure of merit (φTC), found equal to 1.69 10-4 Ω-1, which is a suitable value for potentially high-performance solar cell applications.

Atomic and electronic structure of doped Si (111 ) (2 √{3 }×2 √{3 }) R 30∘ -Sn interfaces

NASA Astrophysics Data System (ADS)

Yi, Seho; Ming, Fangfei; Huang, Ying-Tzu; Smith, Tyler S.; Peng, Xiyou; Tu, Weisong; Mulugeta, Daniel; Diehl, Renee D.; Snijders, Paul C.; Cho, Jun-Hyung; Weitering, Hanno H.

2018-05-01

The hole-doped Si (111 ) (2 √ 3 ×2 √ 3 ) R 30∘ -Sn interface exhibits a symmetry-breaking insulator-insulator transition below 100 K that appears to be triggered by electron tunneling into the empty surface-state bands. No such transition is seen in electron-doped systems. To elucidate the nature and driving force of this phenomenon, the structure of the interface must be resolved. Here we report on an extensive experimental and theoretical study, including scanning tunneling microscopy and spectroscopy (STM/STS), dynamical low-energy electron diffraction (LEED) analysis, and density functional theory (DFT) calculations, to elucidate the structure of this interface. We consider six different structure models, three of which have been proposed before, and conclude that only two of them can account for the majority of experimental data. One of them is the model according to Törnevik et al. [C. Törnevik et al., Phys. Rev. B 44, 13144 (1991), 10.1103/PhysRevB.44.13144] with a total Sn coverage of 14/12 monolayers (ML). The other is the "revised trimer model" with a total Sn coverage of 13/12 ML, introduced in this work. These two models are very difficult to discriminate on the basis of DFT or LEED alone, but STS data clearly point toward the Törnevik model as the most viable candidate among the models considered here. The STS data also provide additional insights regarding the electron-injection-driven phase transformation. Similar processes may occur at other metal/semiconductor interfaces, provided they are nonmetallic and can be doped. This could open up a new pathway toward the creation of novel surface phases with potentially very interesting and desirable electronic properties.

Long-Term Stability of Oxide Nanowire Sensors via Heavily Doped Oxide Contact.

PubMed

Zeng, Hao; Takahashi, Tsunaki; Kanai, Masaki; Zhang, Guozhu; He, Yong; Nagashima, Kazuki; Yanagida, Takeshi

2017-12-22

Long-term stability of a chemical sensor is an essential quality for long-term collection of data related to exhaled breath, environmental air, and other sources in the Internet of things (IoT) era. Although an oxide nanowire sensor has shown great potential as a chemical sensor, the long-term stability of sensitivity has not been realized yet due to electrical degradation under harsh sensing conditions. Here, we report a rational concept to accomplish long-term electrical stability of metal oxide nanowire sensors via introduction of a heavily doped metal oxide contact layer. Antimony-doped SnO 2 (ATO) contacts on SnO 2 nanowires show much more stable and lower electrical contact resistance than conventional Ti contacts for high temperature (200 °C) conditions, which are required to operate chemical sensors. The stable and low contact resistance of ATO was confirmed for at least 1960 h under 200 °C in open air. This heavily doped oxide contact enables us to realize the long-term stability of SnO 2 nanowire sensors while maintaining the sensitivity for both NO 2 gas and light (photo) detections. The applicability of our method is confirmed for sensors on a flexible polyethylene naphthalate (PEN) substrate. Since the proposed fundamental concept can be applied to various oxide nanostructures, it will give a foundation for designing long-term stable oxide nanomaterial-based IoT sensors.

High-field transport properties of a P-doped BaFe2As2 film on technical substrate.

PubMed

Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

2017-01-12

High temperature (high-T c ) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-T c Nb 3 Sn due probably to cost and processing issues. The recent discovery of a second class of high-T c materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe 2 As 2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, H c2 , moderate H c2 anisotropy, and intermediate T c . Here we report on in-field transport properties of P-doped BaFe 2 As 2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport J c of 10 5  A/cm 2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field J c over MgB 2 and NbTi, and a comparable level to Nb 3 Sn above 20 T. By analysing the E - J curves for determining J c , a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.

MgO Nanoparticle Modified Anode for Highly Efficient SnO2-Based Planar Perovskite Solar Cells.

PubMed

Ma, Junjie; Yang, Guang; Qin, Minchao; Zheng, Xiaolu; Lei, Hongwei; Chen, Cong; Chen, Zhiliang; Guo, Yaxiong; Han, Hongwei; Zhao, Xingzhong; Fang, Guojia

2017-09-01

Reducing the energy loss and retarding the carrier recombination at the interface are crucial to improve the performance of the perovskite solar cell (PSCs). However, little is known about the recombination mechanism at the interface of anode and SnO 2 electron transfer layer (ETL). In this work, an ultrathin wide bandgap dielectric MgO nanolayer is incorporated between SnO 2 :F (FTO) electrode and SnO 2 ETL of planar PSCs, realizing enhanced electron transporting and hole blocking properties. With the use of this electrode modifier, a power conversion efficiency of 18.23% is demonstrated, an 11% increment compared with that without MgO modifier. These improvements are attributed to the better properties of MgO-modified FTO/SnO 2 as compared to FTO/SnO 2 , such as smoother surface, less FTO surface defects due to MgO passivation, and suppressed electron-hole recombinations. Also, MgO nanolayer with lower valance band minimum level played a better role in hole blocking. When FTO is replaced with Sn-doped In 2 O 3 (ITO), a higher power conversion efficiency of 18.82% is demonstrated. As a result, the device with the MgO hole-blocking layer exhibits a remarkable improvement of all J-V parameters. This work presents a new direction to improve the performance of the PSCs based on SnO 2 ETL by transparent conductive electrode surface modification.

Ternary semiconductors NiZrSn and CoZrBi with half-Heusler structure: A first-principles study

NASA Astrophysics Data System (ADS)

Fiedler, Gregor; Kratzer, Peter

2016-08-01

The ternary semiconductors NiZrSn and CoZrBi with C 1b crystal structure are introduced by calculating their basic structural, electronic, and phononic properties using density functional theory. Both the gradient-corrected PBE functional and the hybrid functional HSE06 are employed. While NiZrSn is found to be a small-band-gap semiconductor (Eg=0.46 eV in PBE and 0.60 eV in HSE06), CoZrBi has a band gap of 1.01 eV in PBE (1.34 eV in HSE06). Moreover, effective masses and deformation potentials are reported. In both materials A B C , the intrinsic point defects introduced by species A (Ni or Co) are calculated. The Co-induced defects in CoZrBi are found to have a higher formation energy compared to Ni-induced defects in NiZrSn. The interstitial Ni atom (Nii) as well as the VNiNii complex introduce defect states in the band gap, whereas the Ni vacancy (VNi) only reduces the size of the band gap. While Nii is electrically active and may act as a donor, the other two types of defects may compensate extrinsic doping. In CoZrBi, only the VCoCoi complex introduces a defect state in the band gap. Motivated by the reported use of NiZrSn for thermoelectric applications, the Seebeck coefficient of both materials, both in the p -type and the n -type regimes, is calculated. We find that CoZrBi displays a rather large thermopower of up to 500 μ V /K when p doped, whereas NiZrSn possesses its maximum thermopower in the n -type regime. The reported difficulties in achieving p -type doping in NiZrSn could be rationalized by the unintended formation of Nii2 + in conjunction with extrinsic acceptors, resulting in their compensation. Moreover, it is found that all types of defects considered, when present in concentrations as large as 3%, tend to reduce the thermopower compared to ideal bulk crystals at T =600 K. For NiZrSn, the calculated thermodynamic data suggest that additional Ni impurities could be removed by annealing, leading to precipitation of a metallic Ni2ZrSn phase.

Features of the band structure and conduction mechanisms of n-HfNiSn heavily doped with Y

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

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua; Rogl, P.; Romaka, V. V.

The crystalline and electronic structures, energy, kinetic, and magnetic characteristics of n-HfNiSn semiconductor heavily doped with Y acceptor impurity are studied in the ranges: T = 80–400 K, N{sub A}{sup Y} ≈ 1.9 × 10{sup 20}–5.7 × 10{sup 21} cm{sup –3} (x = 0.01–0.30), and H ≤ 10 kG. The nature of the mechanism of structural defect generation is determined, which leads to a change in the band gap and the degree of semiconductor compensation, the essence of which is the simultaneous reduction and elimination of structural donor-type defects as a result of the displacement of ~1% of Ni atomsmore » from the Hf (4a) site, and the generation of structural acceptor-type defects by substituting Hf atoms with Y atoms at the 4a site. The results of calculations of the electronic structure of Hf{sub 1–x}Y{sub x}NiSn are in agreement with the experimental data. The discussion is performed within the Shklovskii–Efros model of a heavily doped and compensated semiconductor.« less

Cd in SnO: Probing structural effects on the electronic structure of doped oxide semiconductors through the electric field gradient at the Cd nucleus

NASA Astrophysics Data System (ADS)

Errico, Leonardo A.; Rentería, Mario; Petrilli, Helena M.

2007-04-01

We perform an ab initio study of the electric field gradient (EFG) at the nucleus of Cd impurities at substitutional Sn sites in crystalline SnO. The full-potential linearized-augmented plane wave and the projector augmented wave methods used here allow us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host in a fully self-consistent way using a supercell approach in a state-of-the-art way. Effects of the impurity charge state on the electronic and structural properties are also discussed. Since the EFG is a very subtle quantity, its determination is very useful to probe ground-state properties such as the charge density. We show that the EFG is very sensitive to structural relaxations induced by the impurity. Our theoretical predictions are compared with available experimental results.

Eco-friendly p-type Cu2SnS3 thermoelectric material: crystal structure and transport properties

PubMed Central

Shen, Yawei; Li, Chao; Huang, Rong; Tian, Ruoming; Ye, Yang; Pan, Lin; Koumoto, Kunihito; Zhang, Ruizhi; Wan, Chunlei; Wang, Yifeng

2016-01-01

As a new eco-friendly thermoelectric material, copper tin sulfide (Cu2SnS3) ceramics were experimentally studied by Zn-doping. Excellent electrical transport properties were obtained by virtue of 3-dimensionally conductive network for holes, which are less affected by the coexistence of cubic and tetragonal phases that formed upon Zn subsitition for Sn; a highest power factors ~0.84 mW m−1 K−2 at 723 K was achieved in the 20% doped sample. Moreover, an ultralow lattice thermal conductivity close to theoretical minimum was observed in these samples, which could be related to the disordering of atoms in the coexisting cubic and tetragonal phases and the interfaces. Thanks to the phonon-glass-electron-crystal features, a maximum ZT ~ 0.58 was obtained at 723 K, which stands among the tops for sulfide thermoelectrics at the same temperature. PMID:27666524

Tin-Doped Inorganic Amorphous Films for Use as Transparent Monolithic Phosphors.

PubMed

Masai, Hirokazu; Miyata, Hiroki; Yamada, Yasuhiro; Okumura, Shun; Yanagida, Takayuki; Kanemitsu, Yoshihiko

2015-06-10

Although inorganic crystalline phosphors can exhibit high quantum efficiency, their use in phosphor films has been limited by a reliance on organic binders that have poor durability when exposed to high-power and/or high excitation energy light sources. To address this problem, Sn(2+)-doped transparent phosphate films measuring several micrometers in thickness have been successfully prepared through heat treatment and a subsequent single dip-coating process. The resulting monolithic inorganic amorphous film exhibited an internal quantum efficiency of over 60% and can potentially utilize transmitted light. Analysis of the film's emissivity revealed that its color can be tuned by changing the amount of Mn and Sn added to influence the energy transfer from Sn(2+) to Mn(2+). It is therefore concluded that amorphous films containing such emission centers can provide a novel and viable alternative to conventional amorphous films containing crystalline phosphors in light-emitting devices.

Tin-Doped Inorganic Amorphous Films for Use as Transparent Monolithic Phosphors

PubMed Central

Masai, Hirokazu; Miyata, Hiroki; Yamada, Yasuhiro; Okumura, Shun; Yanagida, Takayuki; Kanemitsu, Yoshihiko

2015-01-01

Although inorganic crystalline phosphors can exhibit high quantum efficiency, their use in phosphor films has been limited by a reliance on organic binders that have poor durability when exposed to high-power and/or high excitation energy light sources. To address this problem, Sn2+ -doped transparent phosphate films measuring several micrometers in thickness have been successfully prepared through heat treatment and a subsequent single dip-coating process. The resulting monolithic inorganic amorphous film exhibited an internal quantum efficiency of over 60% and can potentially utilize transmitted light. Analysis of the film’s emissivity revealed that its color can be tuned by changing the amount of Mn and Sn added to influence the energy transfer from Sn2+ to Mn2+. It is therefore concluded that amorphous films containing such emission centers can provide a novel and viable alternative to conventional amorphous films containing crystalline phosphors in light-emitting devices. PMID:26061744

Effects of La-doped BaSnO3epitaxial electrode on the ferroelectric properties of BaTiO3

NASA Astrophysics Data System (ADS)

Lee, Hahoon; Kim, Young Mo; Kim, Youjung; Shin, Juyeon; Char, Kookrin

In order to integrate the newly discovered high-mobility perovskite semiconductor BaSnO3 with a ferroelectric perovskite, we have grown epitaxial ferroelectric BaTiO3 (BTO) on top of the 4 % La-doped BaSnO3 (BLSO). X-ray diffraction measurement suggests that the BTO film on top of BLSO electrode is tensilely strained due to the larger lattice constant of BLSO. An all epitaxial sandwich structure of BLSO/BTO/BLSO was fabricated in order to measure the ferroelectric properties of the BTO under tensile strain. The polarization-electric field (P-E) hysteresis curve will be discussed from the viewpoint of the tensile strain. In addition, the breakdown field will be measured to evaluate the potential of BTO for a gate oxide on top of BLSO. Samsung science and technology foundation.

Fluorescence and afterglow of Ca2Sn2Al2O9:Mn2+

NASA Astrophysics Data System (ADS)

Takemoto, Minoru; Iseki, Takahiro

2018-03-01

By using a polymerized complex method, we synthesized manganese (Mn)-doped Ca2Sn2Al2O9, which exhibits yellow fluorescence and afterglow at room temperature when excited by UV radiation. The material emits a broad, featureless fluorescence band centered at 564 nm, which we attribute to the presence of Mn2+ ions. The afterglow decay is well fit by a power-law function, rather than an exponential function. In addition, thermoluminescence analyses demonstrate that two different types of electron traps form in this material. Based on experimental results, we conclude that the fluorescence and afterglow both result from thermally assisted tunneling, in which trapped electrons are thermally excited to higher-level traps and subsequently tunnel to recombination centers.

Synthesis and magnetic properties of tin spinel ferrites doped manganese

NASA Astrophysics Data System (ADS)

El Moussaoui, H.; Mahfoud, T.; Habouti, S.; El Maalam, K.; Ben Ali, M.; Hamedoun, M.; Mounkachi, O.; Masrour, R.; Hlil, E. K.; Benyoussef, A.

2016-05-01

In this work we report the synthesis, the microstructural characterization and the magnetic properties of tin spinel ferrites doped manganese (Sn1-xMnxFe2O4 with x=0.25, 0.5, 0.75, and 1) nanoparticles prepared by co-precipitation method. The effect of annealing temperature on the structure, morphology and magnetic properties of Sn0.5Mn0.5Fe2O4 has been investigated. The synthesized nanoparticle sizes have been controlled between 4 and 9 nm, with uniform spherical morphology as confirmed by transmission electron microscopy (TEM). All the samples prepared possess single domain magnetic. The nanoparticles of Sn0.5Mn0.5Fe2O4 with 4 nm in diameter have a blocking temperature close to 100 K. In addition, the cation distribution obtained from the X-ray diffraction of this sample was confirmed by magnetic measurement. For the Sn1-xMnxFe2O4; (0≤x≤1) samples, the magnetization and coercive fields increase when the augmentation of Mn content increases. For x=0.5, such parameters decrease when the calcination temperature increases.

Low effective mass and carrier concentration optimization for high performance p-type Mg2(1-x)Li2xSi0.3Sn0.7 solid solutions.

PubMed

Zhang, Qiang; Cheng, Long; Liu, Wei; Zheng, Yun; Su, Xianli; Chi, Hang; Liu, Huijun; Yan, Yonggao; Tang, Xinfeng; Uher, Ctirad

2014-11-21

Mg2Si1-xSnx solid solutions are promising thermoelectric materials for power generation applications in the 500-800 K range. Outstanding n-type forms of these solid solutions have been developed in the past few years with the thermoelectric figure of merit ZT as high as 1.4. Unfortunately, no comparable performance has been achieved so far with p-type forms of the structure. In this work, we use Li doping on Mg sites in an attempt to enhance and control the concentration of hole carriers. We show that Li as well as Ga is a far more effective p-type dopant in comparison to Na or K. With the increasing content of Li, the electrical conductivity rises rapidly on account of a significantly enhanced density of holes. While the Seebeck coefficient decreases concomitantly, the power factor retains robust values supported by a rather high mobility of holes. Theoretical calculations indicate that Mg2Si0.3Sn0.7 intrinsically possesses the almost convergent double valence band structure (the light and heavy band), and Li doping retains a low density of states (DOS) on the top of the valence band, contrary to the Ga doping at the sites of Si/Sn. Low temperature specific heat capacity studies attest to a low DOS effective mass in Li-doped samples and consequently their larger hole mobility. The overall effect is a large power factor of Li-doped solid solutions. Although the thermal conductivity increases as more Li is incorporated in the structure, the enhanced carrier density effectively shifts the onset of intrinsic excitations (bipolar effect) to higher temperatures, and the beneficial role of phonon Umklapp processes as the primary limiting factor to the lattice thermal conductivity is thus extended. The final outcome is the figure of merit ZT ∼ 0.5 at 750 K for x = 0.07. This represents a 30% improvement in the figure of merit of p-type Mg2Si1-xSnx solid solutions over the literature values. Hence, designing low DOS near Fermi level EF for given carrier pockets can serve as an effective approach to optimize the PF and thus ZT value.

Doping-induced quantum crossover in Er2Ti2 -xSnxO7

NASA Astrophysics Data System (ADS)

Shirai, M.; Freitas, R. S.; Lago, J.; Bramwell, S. T.; Ritter, C.; Živković, I.

2017-11-01

We present the results of the investigation of magnetic properties of the Er2Ti2 -xSnxO7 series. For small doping values, the ordering temperature decreases linearly with x , while the moment configuration remains the same as in the x =0 parent compound. Around x =1.7 doping level, we observe a change in the behavior, where the ordering temperature starts to increase and new magnetic Bragg peaks appear. For the first time, we present evidence of a long-range order (LRO) in Er2Sn2O7 (x =2.0 ) below TN=130 mK. It is revealed that the moment configuration corresponds to a Palmer-Chalker type with a value of the magnetic moment significantly renormalized compared to x =0 . We discuss our results in the framework of a possible quantum phase transition occurring close to x =1.7 .

Electrochemical oxidation of hydrolyzed poly oxymethylene-dimethyl ether by PtRu catalysts on Nb-doped SnO(2-δ) supports for direct oxidation fuel cells.

PubMed

Kakinuma, Katsuyoshi; Kim, In-Tae; Senoo, Yuichi; Yano, Hiroshi; Watanabe, Masahiro; Uchida, Makoto

2014-12-24

We synthesized Pt and PtRu catalysts supported on Nb-doped SnO(2-δ) (Pt/Sn0.99Nb0.01O(2-δ), PtRu/Sn0.99Nb0.01O(2-δ)) for direct oxidation fuel cells (DOFCs) using poly oxymethylene-dimethyl ether (POMMn, n = 2, 3) as a fuel. The onset potential for the oxidation of simulated fuels of POMMn (methanol-formaldehyde mixtures; n = 2, 3) for Pt/Sn0.99Nb0.01O(2-δ) and PtRu/Sn0.99Nb0.01O(2-δ) was less than 0.3 V vs RHE, which was much lower than those of two commercial catalysts (PtRu black and Pt2Ru3/carbon black). In particular, the onset potential of the oxidation reaction of simulated fuels of POMMn (n = 2, 3) for PtRu/Sn0.99Nb0.01O(2-δ) sintered at 800 °C in nitrogen atmosphere was less than 0.1 V vs RHE and is thus considered to be a promising anode catalyst for DOFCs. The mass activity (MA) of PtRu/Sn0.99Nb0.01O(2-δ) sintered at 800 °C was more than five times larger than those of the commercial catalysts in the measurement temperature range from 25 to 80 °C. Even though the MA for the methanol oxidation reaction was of the same order as those of the commercial catalysts, the MA for the formaldehyde oxidation reaction was more than five times larger than those of the commercial catalysts. Sn from the Sn0.99Nb0.01O(2-δ) support was found to have diffused into the Pt catalyst during the sintering process. The Sn on the top surface of the Pt catalyst accelerated the oxidation of carbon monoxide by a bifunctional mechanism, similar to that for Pt-Ru catalysts.

Band structure modification of the thermoelectric Heusler-phase TiFe2Sn via Mn substitution.

PubMed

Zou, Tianhua; Jia, Tiantian; Xie, Wenjie; Zhang, Yongsheng; Widenmeyer, Marc; Xiao, Xingxing; Weidenkaff, Anke

2017-07-19

Doping (or substitution)-induced modification of the electronic structure to increase the electronic density of states (eDOS) near the Fermi level is considered as an effective strategy to enhance the Seebeck coefficient, and may consequently boost the thermoelectric performance. Through density-functional theory calculations of Mn-substituted TiFe 2-x Mn x Sn compounds, we demonstrate that the d-states of the substituted Mn atoms induce a strong resonant level near the Fermi energy. Our experimental results are in good agreement with the calculations. They show that Mn substitution results in a large increase of the Seebeck coefficient, arising from an enhanced eDOS in Heusler compounds. The results prove that a proper substitution position and element selection can increase the eDOS, leading to a higher Seebeck coefficient and thermoelectric performance of ecofriendly materials.

Enhancement of green long lasting phosphorescence in CaSnO3:Tb3+ by addition of alkali ions

NASA Astrophysics Data System (ADS)

Liang, Zuoqiu; Zhang, Jinsu; Sun, Jiashi; Li, Xiangping; Cheng, Lihong; Zhong, Haiyang; Fu, Shaobo; Tian, Yue; Chen, Baojiu

2013-03-01

Long lasting phosphors of CaSnO3:Tb3+ added alkali ions (Li+, Na+, K+) were prepared by solid-state reaction. The phosphorescence of samples consists of a group of green emission lines originating from 5D4→7FJ transitions of Tb3+. The afterglow spectra and concentration quenching behaviors of fluorescence were investigated in the Tb3+ mono-doped sample. The result shows the optimal doping concentration of Tb3+ is 0.3 mol%. In the co-doped samples, the doping concentrations of Tb3+ and alkali ions are both at 0.3 mol%. It is found from the afterglow decay curves that the introduction of alkali ions can prolong the phosphorescent lasting time and the sample of incorporating Na+ shows the best result. Tb3+ and alkali ions can substitute Ca2+ ions, acting as hole and electron traps, respectively. The thermoluminescence (TL) spectra are also investigated. The depths of traps for the mono- and co-doped samples are calculated to be 0.622, 0.541, 0.529 and 0.538 eV, respectively. Moreover, the possible mechanism of the green long lasting phosphorescence is proposed based on the experiment results.

Investigation of thermoelectricity in KScSn half-Heusler compound

NASA Astrophysics Data System (ADS)

Shrivastava, Deepika; Acharya, Nikita; Sanyal, Sankar P.

2018-05-01

The electronic and transport properties of KScSn half-Heusler (HH) compound have been investigated using first-principles density functional theory and semi classical Boltzmann transport theory. The electronic band structure and density of states (total and partial) show semiconducting nature of KScSn with band gap 0.48 eV which agree well with previously reported results. The transport coefficient such as electrical conductivity, Seebeck coefficient, electronic thermal conductivity and power factor as a function of chemical potential are evaluated. KScSn has high power factor for p-type doping and is a potential candidate for thermoelectric applications.

Synthesis and study of photovoltaic performance on various photoelectrode materials for DSSCs: Optimization of compact layer on nanometer thickness

NASA Astrophysics Data System (ADS)

Surya, Subramanian; Thangamuthu, Rangasamy; Senthil Kumar, Sakkarapalayam Murugesan; Murugadoss, Govindhasamy

2017-02-01

Dye-sensitized solar cells (DSSCs) have gained widespread attention in recent years because of their low production costs, ease of fabrication process and tuneable optical properties, such as colour and transparency. In this work, we explored a strategy wherein nanoparticles of pure TiO2, TiO2sbnd SnO2 nanocomposite, Sn (10%) doped TiO2 and SnO2 synthesized by the simple chemical precipitation method were employed as photoelectrodes to enhance the photovoltaic conversion efficiency of solar cells. The nanoparticles were characterized by different characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM with EDX), transmission electron microscopy (TEM), high resolution electron microscopy (HR-TEM), UV-Visible absorbance (UV-vis), photoluminescence (PL), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) measurements. Moreover, we also demonstrated the effect of thin compact layer in DSSCs by architecture with various precursor materials of different concentrations. We found that the optimized compact layer material TDIP (titanium diisopropoxide) with a concentration of 0.3 M % is produced the highest efficiency of 2.25% for Sn (10%) doped TiO2 electron transport material (ETM) and 4.38% was achieved for pure TiO2 ETM using SnCl2 compact layer with 0.1 M concentrations.

Electrodeposition of Ni on Bi2Te3 and Interfacial Reaction Between Sn and Ni-Coated Bi2Te3

NASA Astrophysics Data System (ADS)

Tseng, Yu-Chen; Lee, Hsuan; Hau, Nga Yu; Feng, Shien-Ping; Chen, Chih-Ming

2018-01-01

Bismuth-telluride (Bi2Te3)-based compounds are common thermoelectric materials used for low-temperature applications, and nickel (Ni) is usually deposited on the Bi2Te3 substrates as a diffusion barrier. Deposition of Ni on the p-type (Sb-doped) and n-type (Se-doped) Bi2Te3 substrates using electroplating and interfacial reactions between Sn and Ni-coated Bi2Te3 substrates are investigated. Electrodeposition of Ni on different Bi2Te3 substrates is characterized based on cyclic voltammetry and Tafel measurements. Microstructural characterizations of the Ni deposition and the Sn/Ni/Bi2Te3 interfacial reactions are performed using scanning electron microscopy. A faster growth rate is observed for the Ni deposition on the n-type Bi2Te3 substrate which is attributed to a lower activation energy of reduction due to a higher density of free electrons in the n-type Bi2Te3 material. The common Ni3Sn4 phase is formed at the Sn/Ni interfaces on both the p-type and n-type Bi2Te3 substrates, while the NiTe phase is formed at a faster rate at the interface between Ni and n-type Bi2Te3 substrates.

Energy band alignment of antiferroelectric (Pb,La)(Zr,Sn,Ti)O3

NASA Astrophysics Data System (ADS)

Klein, Andreas; Lohaus, Christian; Reiser, Patrick; Dimesso, Lucangelo; Wang, Xiucai; Yang, Tongqing

2017-06-01

The energy band alignment of antiferroelectric (Pb,La)(Zr,Sn,Ti)O3 is studied with photoelectron spectroscopy using interfaces with high work function RuO2 and low work function Sn-doped In2O3 (ITO). It is demonstrated how spectral deconvolution can be used to determine absolute Schottky barrier heights for insulating materials with a high accuracy. Using this approach it is found that the valence band maximum energy of (Pb,La)(Zr,Sn,Ti)O3 is found to be comparable to that of Pb- and Bi-containing ferroelectric materials, which is ∼1 eV higher than that of BaTiO3. The results provide additional evidence for the occupation of the 6s orbitals as origin of the higher valence band maximum, which is directly related to the electrical properties of such compounds. The results also verify that the energy band alignment determined by photoelectron spectroscopy of as-deposited electrodes is not influenced by polarisation. The electronic structure of (Pb,La)(Zr,Sn,Ti)O3 should enable doping of the material without strongly modifying its insulating properties, which is crucial for high energy density capacitors. Moreover, the position of the energy bands should result in a great freedom of selecting electrode materials in terms of avoiding charge injection.

Band gap and mobility of epitaxial perovskite BaSn1 -xHfxO3 thin films

NASA Astrophysics Data System (ADS)

Shin, Juyeon; Lim, Jinyoung; Ha, Taewoo; Kim, Young Mo; Park, Chulkwon; Yu, Jaejun; Kim, Jae Hoon; Char, Kookrin

2018-02-01

A wide band-gap perovskite oxide BaSn O3 is attracting much attention due to its high electron mobility and oxygen stability. On the other hand, BaHf O3 was recently reported to be an effective high-k gate oxide. Here, we investigate the band gap and mobility of solid solutions of BaS n1 -xH fxO3 (x =0 -1 ) (BSHO) as a basis to build advanced perovskite oxide heterostructures. All the films were epitaxially grown on MgO substrates using pulsed laser deposition. Density functional theory calculations confirmed that Hf substitution does not create midgap states while increasing the band gap. From x-ray diffraction and optical transmittance measurements, the lattice constants and the band-gap values are significantly modified by Hf substitution. We also measured the transport properties of n -type La-doped BSHO films [(Ba ,La ) (Sn ,Hf ) O3 ] , investigating the feasibility of modulation doping in the BaSn O3/BSHO heterostructures. The Hall measurement data revealed that, as the Hf content increases, the activation rate of the La dopant decreases and the scattering rate of the electrons sharply increases. These properties of BSHO films may be useful for applications in various heterostructures based on the BaSn O3 system.

a Facile Synthesis of Fully Porous Tazo Composite and its Remarkable Gas Sensitive Performance

NASA Astrophysics Data System (ADS)

Liang, Dongdong; Liu, Shimin; Wang, Zhinuo; Guo, Yu; Jiang, Weiwei; Liu, Chaoqian; Ding, Wanyu; Wang, Hualin; Wang, Nan; Zhang, Zhihua

The composite of a nanocrystalline SnO2 thick film deposited on an Al-doped ZnO ceramic substrate was firstly proposed. This study also provided a simple, fast and cost effective method to prepare SnO2 thick film and Al-doped ZnO ceramic as well as the final composite. The crystal structure, morphology, composition, pore size distribution and gas sensitivity of the composite were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Barrett-Joyner-Halenda analysis and gas sensitive measurement system. Results indicated that the composite was fully porous consisted of SnO2, ZnO and ZnAl2O4 crystal phases. The macrosized pores generated in the composite could enhance the gas infiltration into the sensing layers effectively. In this way, combining a high gas-transporting-capability and a nanocrystalline SnO2 thick film, the composite showed very impressive performance. The gas sensitivity of the composite was high enough for ethanol vapor with different concentrations, which was comparable to other kinds of reported SnO2 gas sensors, while showing two straight lines with a turning point at 1000ppm. Finally, the gas sensitive mechanism was proposed based on the microstructure and composition of the composite.

Near infrared group IV optoelectronics and novel pre-cursors for CVD epitaxy

NASA Astrophysics Data System (ADS)

Hazbun, Ramsey Michael

Near infrared and mid infrared optoelectronic devices have become increasingly important for the telecommunications, security, and medical imaging industries. The addition of nitrogen to III-V alloys has been widely studied as a method of modifying the band gap for mid infrared (IR) applications. In xGa1-xSb1-y Ny/InAs strained-layer superlattices with type-II (staggered) energy offsets on GaSb substrates, were modeled using eight-band k˙p simulations to analyze the superlattice miniband energies. Three different zero-stress strain balance conditions are reported: fixed superlattice period thickness, fixed InAs well thickness, and fixed InxGa1-xSb 1-yNy barrier thickness. Optoelectronics have traditionally been the realm of III-V semiconductors due to their direct band gap, while integrated circuit chips have been the realm of Group IV semiconductors such as silicon because of its relative abundance and ease of use. Recently the alloying of Sn with Ge and Si has been shown to allow direct band-gap light emission. This presents the exciting prospect of integrating optoelectronics into current Group IV chip fabrication facilities. However, new approaches for low temperature growth are needed to realize these new SiGeSn alloys. Silicon-germanium epitaxy via ultra-high vacuum chemical vapor deposition has the advantage of allowing low process temperatures. Deposition processes are sensitive to substrate surface preparation and the time delay between oxide removal and epitaxial growth. A new monitoring process utilizing doped substrates and defect decoration etching is demonstrated to have controllable and unique sensitivity to interfacial contaminants. Doped substrates were prepared and subjected to various loading conditions prior to the growth of typical Si/SiGe bilayers. The defect densities were correlated to the concentration of interfacial oxygen suggesting this monitoring process may be an effective complement to monitoring via secondary ion mass spectrometry measurements. The deposition of silicon using tetrasilane as a vapor pre-cursor is described for an ultra-high vacuum chemical vapor deposition tool. The growth rates and morphology of the Si epitaxial layers over a range of temperatures and pressures are presented. In order to understand the suitability of tetrasilane for the growth of SiGe and SiGeSn alloys, the layers were characterized using transmission electron microscopy, x-ray diffraction, spectroscopic ellipsometry, atomic force microscopy, and secondary ion mass spectrometry. To date no n-type doping has been demonstrated in GeSn alloys grown via MBE. A GaP decomposition source was used to grow n-type phosphorus doped GeSn layers on p- Ge substrates. Doping concentrations were calibrated using SIMS measurements. GeSn/Ge heterojunction diodes were grown and fabricated into mesa devices. Diode parameters were extracted from current-voltage measurements. The effects of P and Sn concentrations, metallization, and mesa geometry on device performance are all discussed.

Structural and dielectric studies on Ag doped nano ZnSnO3

NASA Astrophysics Data System (ADS)

Deepa, K.; Angel, S. Lilly; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2018-04-01

Undoped and Ag-doped nano Zinc Stannate (ZSO) ternary oxide were prepared by co-precipitation method. The crystallographic, morphological and optical properties of the synthesized nanoparticles were studied using X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis) and Scanning electron microscopy (SEM). The electrical properties of the synthesized samples were studied by dielectric measurements. Higher concentration Ag doped ZSO nanoparticles exhibit higher dielectric constant at low frequency.

Indium oxide co-doped with tin and zinc: A simple route to highly conducting high density targets for TCO thin-film fabrication

NASA Astrophysics Data System (ADS)

Saadeddin, I.; Hilal, H. S.; Decourt, R.; Campet, G.; Pecquenard, B.

2012-07-01

Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (˜ 92% of In2O3 theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In2O3 only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In2O3 forming a solid-solution. A very low value of electrical resistivity is obtained for [In2O3:Sn0.10]:Zn0.10 (1.7 × 10-3 Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.

Enhanced bactericidal potency of nanoliposomes by modification of the fusion activity between liposomes and bacterium.

PubMed

Ma, Yufan; Wang, Zhao; Zhao, Wen; Lu, Tingli; Wang, Rutao; Mei, Qibing; Chen, Tao

2013-01-01

Pseudomonas aeruginosa represents a good model of antibiotic resistance. These organisms have an outer membrane with a low level of permeability to drugs that is often combined with multidrug efflux pumps, enzymatic inactivation of the drug, or alteration of its molecular target. The acute and growing problem of antibiotic resistance of Pseudomonas to conventional antibiotics made it imperative to develop new liposome formulations to overcome these mechanisms, and investigate the fusion between liposome and bacterium. The rigidity, stability and charge properties of phospholipid vesicles were modified by varying the cholesterol, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE), and negatively charged lipids 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol sodium salt (DMPG), 1,2-dimyristoyl-sn-glycero-3-phopho-L-serine sodium salt (DMPS), 1,2-dimyristoyl-sn-glycero-3-phosphate monosodium salt (DMPA), nature phosphatidylserine sodium salt from brain and nature phosphatidylinositol sodium salt from soybean concentrations in liposomes. Liposomal fusion with intact bacteria was monitored using a lipid-mixing assay. It was discovered that the fluid liposomes-bacterium fusion is not dependent on liposomal size and lamellarity. A similar degree of fusion was observed for liposomes with a particle size from 100 to 800 nm. The fluidity of liposomes is an essential pre-request for liposomes fusion with bacteria. Fusion was almost completely inhibited by incorporation of cholesterol into fluid liposomes. The increase in the amount of negative charges in fluid liposomes reduces fluid liposomes-bacteria fusion when tested without calcium cations due to electric repulsion, but addition of calcium cations brings the fusion level of fluid liposomes to similar or higher levels. Among the negative phospholipids examined, DMPA gave the highest degree of fusion, DMPS and DMPG had intermediate fusion levels, and PI resulted in the lowest degree of fusion. Furthermore, the fluid liposomal encapsulated tobramycin was prepared, and the bactericidal effect occurred more quickly when bacteria were cultured with liposomal encapsulated tobramycin. The bactericidal potency of fluid liposomes is dramatically enhanced with respect to fusion ability when the fusogenic lipid, DOPE, is included. Regardless of changes in liposome composition, fluid liposomes-bacterium fusion is universally enhanced by calcium ions. The information obtained in this study will increase our understanding of fluid liposomal action mechanisms, and help in optimizing the new generation of fluid liposomal formulations for the treatment of pulmonary bacterial infections.

Enhanced bactericidal potency of nanoliposomes by modification of the fusion activity between liposomes and bacterium

PubMed Central

Ma, Yufan; Wang, Zhao; Zhao, Wen; Lu, Tingli; Wang, Rutao; Mei, Qibing; Chen, Tao

2013-01-01

Background Pseudomonas aeruginosa represents a good model of antibiotic resistance. These organisms have an outer membrane with a low level of permeability to drugs that is often combined with multidrug efflux pumps, enzymatic inactivation of the drug, or alteration of its molecular target. The acute and growing problem of antibiotic resistance of Pseudomonas to conventional antibiotics made it imperative to develop new liposome formulations to overcome these mechanisms, and investigate the fusion between liposome and bacterium. Methods The rigidity, stability and charge properties of phospholipid vesicles were modified by varying the cholesterol, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE), and negatively charged lipids 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol sodium salt (DMPG), 1,2-dimyristoyl-sn-glycero-3-phopho-L-serine sodium salt (DMPS), 1,2-dimyristoyl-sn-glycero-3-phosphate monosodium salt (DMPA), nature phosphatidylserine sodium salt from brain and nature phosphatidylinositol sodium salt from soybean concentrations in liposomes. Liposomal fusion with intact bacteria was monitored using a lipid-mixing assay. Results It was discovered that the fluid liposomes-bacterium fusion is not dependent on liposomal size and lamellarity. A similar degree of fusion was observed for liposomes with a particle size from 100 to 800 nm. The fluidity of liposomes is an essential pre-request for liposomes fusion with bacteria. Fusion was almost completely inhibited by incorporation of cholesterol into fluid liposomes. The increase in the amount of negative charges in fluid liposomes reduces fluid liposomes-bacteria fusion when tested without calcium cations due to electric repulsion, but addition of calcium cations brings the fusion level of fluid liposomes to similar or higher levels. Among the negative phospholipids examined, DMPA gave the highest degree of fusion, DMPS and DMPG had intermediate fusion levels, and PI resulted in the lowest degree of fusion. Furthermore, the fluid liposomal encapsulated tobramycin was prepared, and the bactericidal effect occurred more quickly when bacteria were cultured with liposomal encapsulated tobramycin. Conclusion The bactericidal potency of fluid liposomes is dramatically enhanced with respect to fusion ability when the fusogenic lipid, DOPE, is included. Regardless of changes in liposome composition, fluid liposomes-bacterium fusion is universally enhanced by calcium ions. The information obtained in this study will increase our understanding of fluid liposomal action mechanisms, and help in optimizing the new generation of fluid liposomal formulations for the treatment of pulmonary bacterial infections. PMID:23847417

Defect engineering of the oxygen-vacancy clusters formation in electron irradiated silicon by isovalent doping: An infrared perspective

NASA Astrophysics Data System (ADS)

Londos, C. A.; Sgourou, E. N.; Chroneos, A.

2012-12-01

Infrared spectroscopy was used to study the production and evolution of oxygen-vacancy (VOn for n = 1, 2, 3 and VmO for m = 1, 2, 3) clusters, in electron-irradiated Czochralski silicon (Cz-Si) samples, doped with isovalent dopants. It was determined that the production of the VO pair is enhanced in Ge-doped Si but is suppressed in Sn and Pb-doped Si. The phenomenon is discussed in terms of the competition between isovalent dopants and oxygen atoms in capturing vacancies in the course of irradiation. In the case of Ge, only transient GeV pairs form, leading finally to an increase of the VO production. Conversely, for Sn and Pb the corresponding pairs with vacancies are stable, having an opposite impact on the formation of VO pairs. Regarding V2O and V3O clusters, our measurements indicate that Ge doping enhances their formation, although Sn and Pb dopants suppress it. Similar arguments as those for the VO pair could be put forward, based on the effect of isovalent impurities on the availability of vacancies. Additionally, it was found that the conversion ratio of VO to VO2 decreases as the covalent radius of the isovalent dopant increases. These results are discussed in terms of the local strains introduced by the isovalent dopants in the Si lattice. These local strains affect the balance of the intrinsic defects created as a result of irradiation, as well as the balance between the two main reactions (VO + Oi → VO2 and VO + SiI → Oi) participating in the VO annealing, leading finally to a decrease of the VO2 production. The larger the covalent radius of the isovalent dopant (rGe < rSn < rPb), the larger the introduced strains in the lattice and then the less the VO2 formation in accordance with our experimental results. Interestingly, an opposite trend was observed for the conversion ratio of VO2 to VO3. The phenomenon is attributed to the enhanced diffusivity of oxygen impurity as a result of the presence of isovalent dopants, leading to an enhanced formation of the VO3 cluster. The results indicate that isovalent doping of Si is an effective way to control the formation of the deleterious oxygen-vacancy clustering that can affect Si-based devices.

Progress in the Development of Superconducting RF

NASA Astrophysics Data System (ADS)

Martinello, Martina

2016-03-01

The R &D of superconducting radiofrequency (SRF) cavities is focused on lowering the power dissipation, i.e. increasing the Q factor, during their operation in accelerators. Nitrogen doping is the innovative high Q SRF technology currently implemented in the LCLS-II cavity production. Of crucial importance is the understanding on how high Q factors can be maintained from the cavity vertical test to the cryomodule operation. One of the major issue of SRF cavity operation is the remnant magnetic field which will always be present during the cool down through the critical temperature, jeopardizing the cavity performance. Research is ongoing both to reduce the remnant field levels and to avoid magnetic field trapping during the SC transition. In addition, fundamental studies allowed us to define the best nitrogen doping treatment needed to lower the sensitivity to trapped flux. Recent developments on the preparation of Nb3Sn coatings for SRF cavities will be also presented. This alternative technology has been demonstrated to allow high Q operation even at 4.2 K. In addition, the maximum field limit of Nb3Sn is predicted to be twice that of niobium, potentially providing a significant decrease in the required length of an accelerator to reach a given energy.

Effect of iron doping on structural and microstructural properties of nanocrystalline ZnSnO3 thin films prepared by spray pyrolysis techniques

NASA Astrophysics Data System (ADS)

Pathan, Idris G.; Suryawanshi, Dinesh N.; Bari, Anil R.; Patil, Lalchand A.

2018-05-01

This work presents the effect of iron doping having different volume ratios (1 ml, 2.5 ml and 5 ml) on the structural, microstructural and electrical properties of zinc stannate thin films, prepared by spray pyrolysis method. These properties were characterized with X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). In our study, XRD pattern indicates that ZnSnO3 has a perovskite phase with face exposed hexahedron structure. The electron diffraction fringes observed are in consistent with the peak observed in XRD patterns. Moreover the sensor reported in our study is cost-effective, user friendly and easy to fabricate.

Wetting reaction of Sn-Ag based solder systems on Cu substrates plated with Au and/or Pd layer

NASA Astrophysics Data System (ADS)

Liu, C. Y.; Li, Jian; Vandentop, G. J.; Choi, W. J.; Tu, K. N.

2001-05-01

The wetting behavior of SnAg based Pb-free solders on Cu and Cu substrates plated with Au, Pd, and Au/Pd thin films have been studied. The wetting angle and kinetics of interfacial reaction were measured. The Au-plated substrates exhibit better wetting than the Pd-plated substrates. In the case of SnAg on Pd-plated Cu, SEM observation revealed that the solder cap was surrounded by an innerring of Cu-Sn compound and an outer ring of Pd-Sn compound. This implies that the molten SnAg solder had removed the Pd and wetted the Cu directly in the equilibrium state. The effects of pre-doping Cu in the SnAg solder on wetting behavior were also investigated. We found that wettability decreases with increasing Cu content in the solder. We also observed that the SnAgCu solders have a lower Cu consumption rate than the SnAg solder.

AgI alloying in SnTe boosts the thermoelectric performance via simultaneous valence band convergence and carrier concentration optimization

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

Banik, Ananya; Biswas, Kanishka, E-mail: kanishka@jncasr.ac.in

SnTe, a Pb-free analogue of PbTe, was earlier assumed to be a poor thermoelectric material due to excess p-type carrier concentration and large energy separation between light and heavy hole valence bands. Here, we report the enhancement of the thermoelectric performance of p-type SnTe by Ag and I co-doping. AgI (1–6 mol%) alloying in SnTe modulates its electronic structure by increasing the band gap of SnTe, which results in decrease in the energy separation between its light and heavy hole valence bands, thereby giving rise to valence band convergence. Additionally, iodine doping in the Te sublattice of SnTe decreases themore » excess p-type carrier concentration. Due to significant decrease in hole concentration and reduction of the energy separation between light and heavy hole valence bands, significant enhancement in Seebeck coefficient was achieved at the temperature range of 600–900 K for Sn{sub 1−x}Ag{sub x}Te{sub 1−x}I{sub x} samples. A maximum thermoelectric figure of merit, zT, of ~1.05 was achieved at 860 K in high quality crystalline ingot of p-type Sn{sub 0.95}Ag{sub 0.05}Te{sub 0.95}I{sub 0.05}. - Graphical abstract: Significant decrease in hole concentration and reduction of the energy separation between light and heavy hole valence bands resulted in a maximum thermoelectric figure of merit, zT, of ~1.05 at 860 K in high quality crystalline ingot of p-type Sn{sub 0.95}Ag{sub 0.05}Te{sub 0.95}I{sub 0.05}. - Highlights: • AgI alloying in SnTe increases the principle band gap. • Hole concentration reduction and valence band convergence enhances thermopower of SnTe-AgI. • A maximum zT of ~1.05 was achieved at 860 K in p-type Sn{sub 0.95}Ag{sub 0.05}Te{sub 0.95}I{sub 0.05}.« less

Influence of annealing temperature and Sn doping on the optical properties of hematite thin films determined by spectroscopic ellipsometry

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

Souza, Lígia P. de; Chaves, Rodrigo O. G.; Malachias, Angelo

2016-06-28

Hematite (α-Fe{sub 2}O{sub 3}) thin films were prepared by sol-gel route and investigated for application in H{sub 2} generation by photo-assisted water splitting. The photoelectrochemical (PEC) performance was shown to increase significantly for films deposited on SnO{sub 2}:F/glass subjected to high temperature (T) annealing (>750 °C). Strong correlation was found between photogenerated current, donor concentration, and Sn concentration as determined by Mott-Schottky analysis and X-ray photoelectron spectroscopy. The effects of thermal annealing and Sn addition in the resulting microstructure and optical properties of hematite films deposited on fused silica substrates were determined by a combination of structural characterization techniques and spectroscopicmore » ellipsometry. Thermal annealing (>600 °C) induces a higher optical absorption that is associated directly to film densification and grain growth; however, it promotes no changes in the energy positions of the main Fe{sub 2}O{sub 3} electronic transitions. The band gap energy was found to be 2.21 eV and independent of microstructure and of Sn concentration for all studied films. On the other hand, Sn can be incorporated in the Fe{sub 2}O{sub 3} lattice for concentration up to Sn/Fe ∼2%, leading to an increase in energy split of the main absorption peak, attributed to a distortion of the Fe{sub 2}O{sub 3} lattice. For higher concentrations, Sn incorporation leads to a reduction in absorption, associated with higher porosity and the formation of a secondary Sn-rich phase. In summary, the variation in the optical properties induced by thermal annealing and Sn addition cannot account for the order of magnitude increase of the current density generated by photoanodes annealed at high T (>750 °C); thus, it is concluded that the major contribution for the enhanced PEC performance comes from improved electronic properties induced by the n-type doping caused by Sn diffusion from the SnO{sub 2}:F substrate.« less

Degradation of organic pollutants by Ag, Cu and Sn doped waste non-metallic printed circuit boards.

PubMed

Ramaswamy, Kadari; Radha, Velchuri; Malathi, M; Vithal, Muga; Munirathnam, Nagegownivari R

2017-02-01

The disposal and reuse of waste printed circuit boards have been the major global concerns. Printed circuit boards, a form of Electronic waste (hereafter e-waste), have been chemically processed, doped with Ag + , Cu 2+ and Sn 2+ , and used as visible light photocatalysts against the degradation of methylene blue and methyl violet. The elemental analyses of pristine and metal doped printed circuit board were obtained using energy dispersive X-ray fluorescence (EDXRF) spectra and inductively coupled plasma optical emission spectroscopy (ICP-OES). The morphology of parent and doped printed circuit board was obtained from scanning electron microscopy (SEM) measurements. The photocatalytic activity of parent and metal doped samples was carried out for the decomposition of organic pollutants, methylene blue and methyl violet, under visible light irradiation. Metal doped waste printed circuit boards (WPCBs) have shown higher photocatalytic activity against the degradation of methyl violet and methylene blue under visible light irradiation. Scavenger experiments were performed to identify the reactive intermediates responsible for the degradation of methylene blue and methyl violet. The reactive species responsible for the degradation of MV and MB were found to be holes and hydroxyl radicals. A possible mechanism of degradation of methylene blue and methyl violet is given. The stability and reusability of the catalysts are also investigated. Copyright © 2016. Published by Elsevier Ltd.

Dopant behavior in heavily doped polycrystalline Ge1- x Sn x layers prepared with pulsed laser annealing in water

NASA Astrophysics Data System (ADS)

Takahashi, Kouta; Kurosawa, Masashi; Ikenoue, Hiroshi; Sakashita, Mitsuo; Nakatsuka, Osamu; Zaima, Shigeaki

2018-04-01

A low-temperature process for the formation of heavily doped polycrystalline Ge (poly-Ge) layers on insulators is required to realize next-generation electronic devices. In this study, we have systematically investigated pulsed laser annealing (PLA) in flowing water for heavily doped amorphous Ge1- x Sn x layers (x ≈ 0.02) with various dopants such as B, Al, Ga, In, P, As, and Sb on SiO2. It is found that the dopant density after PLA with a high laser energy is reduced when the oxidized dopant has a lower oxygen chemical potential than H2O. As a result, for the p-type doping of B, Al, Ga, and In, we obtained a high Hall hole density of 5 × 1019 cm-3 for PLA with a low energy. Consequently, the Hall hole mobility is limited to as low as 10 cm2 V-1 s-1. In contrast, for As and Sb doping, because the density of substitutional dopants does not decrease even after PLA with a high energy, we achieved a high Hall electron density of 6 × 1019 cm-3 and a high Hall electron mobility simultaneously. These results indicate that preventing the oxidation of dopant atoms by water is an important factor for achieving heavy doping using PLA in water.

Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO2 thin films annealed under magnetic field

PubMed Central

2014-01-01

Co-doped SnO2 thin films were grown by sputtering technique on SiO2/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (HTT) were performed in vacuum at 600°C for 20 min. HTT was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μB/Co at. is obtained when HTT is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co+2 from 0.06 to 0.42 μB/Co at. for the sample on which HTT was applied perpendicular to the surface. The FM order is attributed to the coupling of Co+2 ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO2 nanocrystals, which is proposed to be the easy magnetization axis. PMID:25489286

Effect of defects on the small polaron formation and transport properties of hematite from first-principles calculations

NASA Astrophysics Data System (ADS)

Smart, Tyler J.; Ping, Yuan

2017-10-01

Hematite (α-Fe2O3) is a promising candidate as a photoanode material for solar-to-fuel conversion due to its favorable band gap for visible light absorption, its stability in an aqueous environment and its relatively low cost in comparison to other prospective materials. However, the small polaron transport nature in α-Fe2O3 results in low carrier mobility and conductivity, significantly lowering its efficiency from the theoretical limit. Experimentally, it has been found that the incorporation of oxygen vacancies and other dopants, such as Sn, into the material appreciably enhances its photo-to-current efficiency. Yet no quantitative explanation has been provided to understand the role of oxygen vacancy or Sn-doping in hematite. We employed density functional theory to probe the small polaron formation in oxygen deficient hematite, N-doped as well as Sn-doped hematite. We computed the charged defect formation energies, the small polaron formation energy and hopping activation energies to understand the effect of defects on carrier concentration and mobility. This work provides us with a fundamental understanding regarding the role of defects on small polaron formation and transport properties in hematite, offering key insights into the design of new dopants to further improve the efficiency of transition metal oxides for solar-to-fuel conversion.

Highly electrically conductive layered carbon derived from polydopamine and its functions in SnO2-based lithium ion battery anodes.

PubMed

Kong, Junhua; Yee, Wu Aik; Yang, Liping; Wei, Yuefan; Phua, Si Lei; Ong, Hock Guan; Ang, Jia Ming; Li, Xu; Lu, Xuehong

2012-10-25

Thin carbonized polydopamine (C-PDA) coatings are found to have similar structures and electrical conductivities to those of multilayered graphene doped with heteroatoms. Greatly enhanced electrochemical properties are achieved with C-PDA-coated SnO(2) nanoparticles where the coating functions as a mechanical buffer layer and conducting bridge.

Nanosized Thin SnO2 Layers Doped with Te and TeO2 as Room Temperature Humidity Sensors

PubMed Central

Georgieva, Biliana; Podolesheva, Irena; Spasov, Georgy; Pirov, Jordan

2014-01-01

In this paper the humidity sensing properties of layers prepared by a new method for obtaining doped tin oxide are studied. Different techniques—SEM, EDS in SEM, TEM, SAED, AES and electrical measurements—are used for detailed characterization of the thin layers. The as-deposited layers are amorphous with great specific area and low density. They are built up of a fine grained matrix, consisting of Sn- and Te-oxides, and a nanosized dispersed phase of Te, Sn and/or SnTe. The chemical composition of both the matrix and the nanosized particles depends on the ratio RSn/Te and the evaporation conditions. It is shown that as-deposited layers with RSn/Te ranging from 0.4 to 0.9 exhibit excellent characteristics as humidity sensors operating at room temperature—very high sensitivity, good selectivity, fast response and short recovery period. Ageing tests have shown that the layers possess good long-term stability. Results obtained regarding the type of the water adsorption on the layers' surface help better understand the relation between preparation conditions, structure, composition and humidity sensing properties. PMID:24854359

A Top-Down Strategy toward SnSb In-Plane Nanoconfined 3D N-Doped Porous Graphene Composite Microspheres for High Performance Na-Ion Battery Anode.

PubMed

Qin, Jian; Wang, Tianshuai; Liu, Dongye; Liu, Enzuo; Zhao, Naiqin; Shi, Chunsheng; He, Fang; Ma, Liying; He, Chunnian

2018-03-01

Engineering of 3D graphene/metal composites with ultrasmall sized metal and robust metal-graphene interfacial interaction for energy storage application is still a challenge and rarely reported. In this work, a facile top-down strategy is developed for the preparation of SnSb-in-plane nanoconfined 3D N-doped porous graphene networks for sodium ion battery anodes, which are composed of several tens of interconnected empty N-graphene boxes in-plane firmly embedded with ultrasmall SnSb nanocrystals. The all-around encapsulation (plane-to-plane contact) architecture that provides a large interface between N-graphene and SnSb nanocrystal not only effectively enhances the electron conductivity and structural integrity of the overall electrode, but also offers excess interfacial sodium storage, thus leading to much enhanced high-rate sodium storage capacity and stability, which has been proven by both experimental results and first-principles simulations. Moreover, this top-down strategy can enable new paths to the low-cost and high-yield synthesis of 3D graphene/metal composites for applications in energy-related fields and beyond. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of different compositions from magnetic and nonmagnetic dopants on structural and electrical properties of ZnO nanoparticles-based varistor ceramics

NASA Astrophysics Data System (ADS)

Sendi, Rabab Khalid

2018-03-01

In the current study, 20 nm zinc oxide (ZnO) nanoparticles were used to manufacture high-density ZnO discs doped with Mn and Sn via the conventional ceramic processing method, and their properties were characterized. Results show that the dopants were found to have significant effects on the ZnO varistors, especially on the shape and size of grains, which are significantly different for both dopants. The strong solid-state reaction in the varistor from the 20 nm ZnO powder during the sintering process may be attributed to the high surface area of the 20 nm ZnO nanoparticles. Although Mn and Sn do not affect the well-known peaks related to the wurtzite structure of ZnO ceramics, a few of the additional peaks could be formed at high doping content (≥2.0) due to the formation of other unknown phases during the sintering process. Both additives also significantly affect the electrical properties of the varistor, with a marked changed in the breakdown voltage from 415 V to 460 V for Sn and from 400 V to 950 V for Mn. Interestingly, the electrical behaviors of the varistors, such as breakdown voltage, nonlinear coefficient, and barrier height, are higher for Mn- than Sn-doping samples, and the opposite behaviors hold for hardness, leakage currents, and electrical conductivities. Results show that the magnetic moment and valence state of the two additive dopants are responsible for all demonstrated differences in the electrical characteristics between the two dopants.

Tailoring band structure and band filling in a simple cubic (IV, III)-VI superconductor

NASA Astrophysics Data System (ADS)

Kriener, M.; Kamitani, M.; Koretsune, T.; Arita, R.; Taguchi, Y.; Tokura, Y.

2018-04-01

Superconductivity and its underlying mechanisms are one of the most active research fields in condensed-matter physics. An important question is how to enhance the transition temperature Tc of a superconductor. In this respect, the possibly positive role of valence-skipping elements in the pairing mechanism has been attracting considerable interest. Here we follow this pathway and successfully enhance Tc up to almost 6 K in the simple chalcogenide SnTe known as a topological crystalline insulator by doping the valence-skipping element In substitutionally for the Sn site and codoping Se for the Te site. A high-pressure synthesis method enabled us to form single-phase solid solutions Sn1 -xInxTe1 -ySey over a wide composition range while keeping the cubic structure necessary for the superconductivity. Our experimental results are supported by density-functional theory calculations which suggest that even higher Tc values would be possible if the required doping range was experimentally accessible.

Sn-doped Bi 1.1Sb 0.9Te 2S bulk crystal topological insulator with excellent properties

DOE PAGES

S. K. Kushwaha; Pletikosic, I.; Liang, T.; ...

2016-04-27

A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons, and be growable as large, high quality bulk single crystals. Here we show that this materials obstacle is overcome by bulk crystals of lightly Sn-doped Bi 1.1Sb 0.9Te 2S grown by the Vertical Bridgeman method.more » We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunneling microscopy, transport studies, X-ray diffraction, and Raman scattering. We present this material as a high quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states.« less

Contribution of tin in electrochemical properties of zinc antimonate nanostructures: An electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Balasubramaniam, M.; Balakumar, S.

2018-04-01

Tin (Sn) doped ZnSb2O6 nanostructures was synthesized by chemical precipitation method and was used as an electrode material for supercapacitors to explore its electrochemical stability and potentiality as energy storage materials. Their characteristic structural, morphological and compositional features were investigated through XRD, FESEM and XPS analysis. Results showed that the nanostructures have well ordered crystalline features with spherical particle morphology. As the size and morphology are the vital parameters in exhibiting better electrochemical properties, the prepared nanostructures exhibited a significant specific capacitance of 222 F/g at a current density of 0.5 A/g respectively. While charging and discharging for 1000 cycles, the capacitance retention was enhanced to 105.0% which depicts the stability and activeness of electrochemical sites present in the Sn doped ZnSb2O6 nanostructures even after cycling. Hence, the inclusion of Sn into ZnSb2O6 has contributed in improving the electrochemical properties thereby it represents itself as a potential electrode material for supercapacitors.

Effect of (Ag, Sn) Doping on the Structure and Optical Properties of Au Nanocluster

NASA Astrophysics Data System (ADS)

Balu, Radhakrishnan; Karna, Shashi

2014-03-01

Noble metal nanoclusters (NCs) consisting of a few to 35 atoms in size in the sub 2 nm range dimension are considered to be nontoxic as opposed to nanoparticles that are cytotoxic. Also, due to the quantum confinement of electrons, these NCs exhibit atom-like energy spectrum and display fluorescent properties useful in a wide range of applications, including medical diagnosis. The unique features of NCs such as size-tunable optical properties, intense fluorescence in the visible, and biocompatibility have stimulated an active area of investigation of noble metal NCs comprised of Au, Ag, Cu, and Pt. Furthermore, the electronic properties of nanoclusters can be modified by combining them with other elements. In this study, we consider the space-filled configuration of Au32 NC and investigate the effects of Ag and Sn atom incorporation on geometry and electronic spectrum. Our study suggests that Ag and Sn doping of Au32 NC red-shifts the absorption maximum and also reduces the oscillator strength.

High efficiency Cu2ZnSn(S,Se)4 solar cells by applying a double In2S3/CdS emitter.

PubMed

Kim, Jeehwan; Hiroi, Homare; Todorov, Teodor K; Gunawan, Oki; Kuwahara, Masaru; Gokmen, Tayfun; Nair, Dhruv; Hopstaken, Marinus; Shin, Byungha; Lee, Yun Seog; Wang, Wei; Sugimoto, Hiroki; Mitzi, David B

2014-11-26

High-efficiency Cu2ZnSn(S,Se)4 solar cells are reported by applying In2S3/CdS double emitters. This new structure offers a high doping concentration within the Cu2ZnSn(S,Se)4 solar cells, resulting in a substantial enhancement in open-circuit voltage. The 12.4% device is obtained with a record open-circuit voltage deficit of 593 mV. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intermediate Band Material of Titanium-Doped Tin Disulfide for Wide Spectrum Solar Absorption.

PubMed

Hu, Keyan; Wang, Dong; Zhao, Wei; Gu, Yuhao; Bu, Kejun; Pan, Jie; Qin, Peng; Zhang, Xian; Huang, Fuqiang

2018-04-02

Intermediate band (IB) materials are of great significance due to their superior solar absorption properties. Here, two IBs peaking at 0.88 and 1.33 eV are reported to be present in the forbidden gap of semiconducting SnS 2 ( E g = 2.21 eV) by doping titanium up to 6 atom % into the Sn site via a solid-state reaction at 923 K. The solid solution of Sn 1- x Ti x S 2 is able to be formed, which is attributed to the isostructural structure of SnS 2 and TiS 2 . These two IBs were detected in the UV-vis-NIR absorption spectra with the appearance of two additional absorption responses at the respective regions, which in good agreement with the conclusion of first-principles calculations. The valence band maximum (VBM) consists mostly of the S 3p state, and the conduction band minimum (CBM) is the hybrid state composing of Ti 3d (e g ), S 3p, and Sn 5s, and the IBs are mainly the nondegenerate t 2g states of Ti 3d orbitals. The electronic states of Ti 3d reveal a good ability to transfer electrons between metal and S atoms. These wide-spectrum absorption IBs bring about more solar energy utilization to enhance solar thermal collection and photocatalytic degradation of methyl orange.

Bulk crystal growth of Ga2O3

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Tin Selenide (SnSe): Growth, Properties, and Applications

PubMed Central

Shi, Weiran; Gao, Minxuan; Wei, Jinping; Gao, Jianfeng; Fan, Chenwei; Ashalley, Eric; Wang, Zhiming

2018-01-01

Abstract The indirect bandgap semiconductor tin selenide (SnSe) has been a research hotspot in the thermoelectric fields since a ZT (figure of merit) value of 2.6 at 923 K in SnSe single crystals along the b‐axis is reported. SnSe has also been extensively studied in the photovoltaic (PV) application for its extraordinary advantages including excellent optoelectronic properties, absence of toxicity, cheap raw materials, and relative abundance. Moreover, the thermoelectric and optoelectronic properties of SnSe can be regulated by the structural transformation and appropriate doping. Here, the studies in SnSe research, from its evolution to till now, are reviewed. The growth, characterization, and recent developments in SnSe research are discussed. The most popular growth techniques that have been used to prepare SnSe materials are discussed in detail with their recent progress. Important phenomena in the growth of SnSe as well as the problems remaining for future study are discussed. The applications of SnSe in the PV fields, Li‐ion batteries, and other emerging fields are also discussed. PMID:29721411

Tin Selenide (SnSe): Growth, Properties, and Applications.

PubMed

Shi, Weiran; Gao, Minxuan; Wei, Jinping; Gao, Jianfeng; Fan, Chenwei; Ashalley, Eric; Li, Handong; Wang, Zhiming

2018-04-01

The indirect bandgap semiconductor tin selenide (SnSe) has been a research hotspot in the thermoelectric fields since a ZT (figure of merit) value of 2.6 at 923 K in SnSe single crystals along the b -axis is reported. SnSe has also been extensively studied in the photovoltaic (PV) application for its extraordinary advantages including excellent optoelectronic properties, absence of toxicity, cheap raw materials, and relative abundance. Moreover, the thermoelectric and optoelectronic properties of SnSe can be regulated by the structural transformation and appropriate doping. Here, the studies in SnSe research, from its evolution to till now, are reviewed. The growth, characterization, and recent developments in SnSe research are discussed. The most popular growth techniques that have been used to prepare SnSe materials are discussed in detail with their recent progress. Important phenomena in the growth of SnSe as well as the problems remaining for future study are discussed. The applications of SnSe in the PV fields, Li-ion batteries, and other emerging fields are also discussed.

Band Degeneracy, Low Thermal Conductivity, and High Thermoelectric Figure of Merit in SnTe-CaTe Alloys

NASA Astrophysics Data System (ADS)

Al Rahal Al Orabi, R.; Mecholsky, N.; Hwang, J. P.; Kim, W.; Rhyee, J. S.; Wee, D.; Fornari, M.

Pure lead-free SnTe has limited thermoelectric potentials because of the low Seebeck coeffcients and the relatively large thermal conductivity. In this study, we provide experimental evidence and theoretical understanding that alloying SnTe with Ca greatly improves the transport properties leading to ZT of 1.35 at 873 K, the highest ZT value so far reported for singly doped SnTe materials. The introduction of Ca (0-9%) in SnTe induces multiple effects: (1) Ca replaces Sn and reduces the hole concentration due to Sn vacancies, (2) the energy gap increases limiting the bipolar transport, (3) several bands with larger effective masses become active in transport, and (4) the lattice thermal conductivity is reduced of about 70% due to the contribution of concomitant scattering terms associated with the alloy disorder and the presence of nanoscale precipitates. An effciency of 10% (for ΔT = 400 K) was predicted for high temperature thermoelectric power generation using SnTe-based n- and p-type materials.

Cation/Anion Substitution in Cu2ZnSnS4 for Improved Photovoltaic Performance

PubMed Central

Ananthoju, Balakrishna; Mohapatra, Jeotikanta; Jangid, Manoj K.; Bahadur, D.; Medhekar, N. V.; Aslam, M.

2016-01-01

Cations and anions are replaced with Fe, Mn, and Se in CZTS in order to control the formations of the secondary phase, the band gap, and the micro structure of Cu2ZnSnS4. We demonstrate a simplified synthesis strategy for a range of quaternary chalcogenide nanoparticles such as Cu2ZnSnS4 (CZTS), Cu2FeSnS4 (CFTS), Cu2MnSnS4 (CMTS), Cu2ZnSnSe4 (CZTSe), and Cu2ZnSn(S0.5Se0.5)4 (CZTSSe) by thermolysis of metal chloride precursors using long chain amine molecules. It is observed that the crystal structure, band gap and micro structure of the CZTS thin films are affected by the substitution of anion/cations. Moreover, secondary phases are not observed and grain sizes are enhanced significantly with selenium doping (grain size ~1 μm). The earth-abundant Cu2MSnS4/Se4 (M = Zn, Mn and Fe) nanoparticles have band gaps in the range of 1.04–1.51 eV with high optical-absorption coefficients (~104 cm−1) in the visible region. The power conversion efficiency of a CZTS solar cell is enhanced significantly, from 0.4% to 7.4% with selenium doping, within an active area of 1.1 ± 0.1 cm2. The observed changes in the device performance parameters might be ascribed to the variation of optical band gap and microstructure of the thin films. The performance of the device is at par with sputtered fabricated films, at similar scales. PMID:27748406

S/N dual-doped carbon nanosheets decorated with Co x O y nanoparticles as high-performance anodes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, XiaoFei; Zhu, Yong; Zhu, Sheng; Fan, JinChen; Xu, QunJie; Min, YuLin

2018-03-01

In this work, we have successfully synthesized the S/N dual-doped carbon nanosheets which are strongly coupled with Co x O y nanoparticles (SNCC) by calcinating cobalt/dithizone complex precursor following KOH activation. The SNCC as anode shows the wonderful charge capacity of 1200 mAh g-1 after 400th cycles at 1000 mA g-1 for Li-ion storage. The superior electrochemical properties illustrate that the SNCC can be a candidate for high-performance anode material of lithium-ion batteries (LIBs) because of the facile preparation method and excellent performance. Significantly, we also discuss the mechanism for the SNCC from the strong synergistic effect perspective.

Biaxial tensile strain modulates magnetic properties of the 3d transition metal doped stanene

NASA Astrophysics Data System (ADS)

Dai, Xian-Qi; Zhao, Ming-Yu; Zhao, Ru-Meng; Li, Wei

2017-06-01

Utilizing first-principle calculations, the biaxial tensile strain modulating magnetic states and electronic structures of transition metal (TM) (i.e., Mn, Fe, Sc, Ni and Ti) atoms doped in stanene are investigated. It shows that Mn and Fe doped stanene systems are magnetic, while the Sc, Ti and Ni doped stanene systems are nonmagnetic. When the biaxial tensile strain increases, a weaker antiferromagnetic coupling between the nearest neighbor (NN) Sn atoms and Mn (Fe, Ti) atom is observed. For Sc and Ni doped stanene systems, the biaxial strain doesn't introduce spin polarization for the TM atoms. In a word, the TM atoms doped stanene systems may manifest potential applications in nanoelectronics, spintronics and magnetic storage devices.

Unraveling the Origin of Magnetism in Mesoporous Cu-Doped SnO₂ Magnetic Semiconductors.

PubMed

Fan, Junpeng; Menéndez, Enric; Guerrero, Miguel; Quintana, Alberto; Weschke, Eugen; Pellicer, Eva; Sort, Jordi

2017-10-25

The origin of magnetism in wide-gap semiconductors doped with non-ferromagnetic 3d transition metals still remains intriguing. In this article, insights in the magnetic properties of ordered mesoporous Cu-doped SnO₂ powders, prepared by hard-templating, have been unraveled. Whereas, both oxygen vacancies and Fe-based impurity phases could be a plausible explanation for the observed room temperature ferromagnetism, the low temperature magnetism is mainly and unambiguously arising from the nanoscale nature of the formed antiferromagnetic CuO, which results in a net magnetization that is reminiscent of ferromagnetic behavior. This is ascribed to uncompensated spins and shape-mediated spin canting effects. The reduced blocking temperature, which resides between 30 and 5 K, and traces of vertical shifts in the hysteresis loops confirm size effects in CuO. The mesoporous nature of the system with a large surface-to-volume ratio likely promotes the occurrence of uncompensated spins, spin canting, and spin frustration, offering new prospects in the use of magnetic semiconductors for energy-efficient spintronics.

Proximity-induced superconductivity in all-silicon superconductor /normal-metal junctions

NASA Astrophysics Data System (ADS)

Chiodi, F.; Duvauchelle, J.-E.; Marcenat, C.; Débarre, D.; Lefloch, F.

2017-07-01

We have realized laser-doped all-silicon superconducting (S)/normal metal (N) bilayers of tunable thickness and dopant concentration. We observed a strong reduction of the bilayers' critical temperature when increasing the normal metal thickness, a signature of the highly transparent S/N interface associated to the epitaxial sharp laser doping profile. We extracted the interface resistance by fitting with the linearized Usadel equations, demonstrating a reduction of 1 order of magnitude from previous superconductor/doped Si interfaces. In this well-controlled crystalline system we exploited the low-resistance S/N interfaces to elaborate all-silicon lateral SNS junctions with long-range proximity effect. Their dc transport properties, such as the critical and retrapping currents, could be well understood in the diffusive regime. Furthermore, this work led to the estimation of important parameters in ultradoped superconducting Si, such as the Fermi velocity, the coherence length, or the electron-phonon coupling constant, fundamental to conceive all-silicon superconducting electronics.

Color stable manganese-doped phosphors

DOEpatents

Lyons, Robert Joseph [Burnt Hills, NY; Setlur, Anant Achyut [Niskayuna, NY; Deshpande, Anirudha Rajendra [Twinsburg, OH; Grigorov, Ljudmil Slavchev [Sofia, BG

2012-08-28

A process for preparing color stable Mn.sup.+4 doped phosphors includes providing a phosphor of formula I; A.sub.x[MF.sub.y]:Mn.sup.+4 I and contacting the phosphor in particulate form with a saturated solution of a composition of formula II in aqueous hydrofluoric acid; A.sub.x[MF.sub.y]; II wherein A is Li, Na, K, Rb, Cs, NR.sub.4 or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, lower alkyl, or a combination thereof; x is the absolute value of the charge of the [MF.sub.y] ion; and y is 5, 6 or 7. In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof. A lighting apparatus capable of emitting white light includes a semiconductor light source; and a phosphor composition radiationally coupled to the light source, and which includes a color stable Mn.sup.+4 doped phosphor.

The Longwave Silicon Chip - Integrated Plasma-Photonics in Group IV And III-V Semiconductors

DTIC Science & Technology

2013-10-01

infrared applications; SiGeSn heterostructure photonics; group IV plasmonics with silicides , germanicides, doped Si, Ge or GeSn; Franz-Keldysh...SPP waveguide in which localized silicide or germanicide “conductors” are introduced to give local plasmonic confinement. Therefore, guided-wave...reconfigurable integrated optoelectronics, electro-optical logic in silicon, silicides for group IV plasmonics, reviews of third-order nonlinear optical

SnO 2 nanowires decorated with forsythia-like TiO 2 for photoenergy conversion

DOE PAGES

Park, Ik Jae; Park, Sangbaek; Kim, Dong Hoe; ...

2017-05-17

Here, we report forsythia-like TiO 2-decorated SnO 2 nanowires on fluorine-doped SnO 2 electrode as a photoelectrode of dye-sensitized solar cells. When SnO 2 nanowires grown via vapor-liquid-solid reaction were soaked in TiCl 4 solution, leaf-shaped rutile TiO 2 was grown onto the surface of the nanowires. The TiO 2 decoration increases the short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) of dye-sensitized solar cells. Further, electron lifetime increased by employing an atomic-layer-deposited TiO 2 nanoshell between the TiO 2 leaves and the SnO 2 nanowire, due to preventing charge recombination at the nanowire/electrolytemore » interface.« less

SnO 2 nanowires decorated with forsythia-like TiO 2 for photoenergy conversion

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

Park, Ik Jae; Park, Sangbaek; Kim, Dong Hoe

Here, we report forsythia-like TiO 2-decorated SnO 2 nanowires on fluorine-doped SnO 2 electrode as a photoelectrode of dye-sensitized solar cells. When SnO 2 nanowires grown via vapor-liquid-solid reaction were soaked in TiCl 4 solution, leaf-shaped rutile TiO 2 was grown onto the surface of the nanowires. The TiO 2 decoration increases the short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) of dye-sensitized solar cells. Further, electron lifetime increased by employing an atomic-layer-deposited TiO 2 nanoshell between the TiO 2 leaves and the SnO 2 nanowire, due to preventing charge recombination at the nanowire/electrolytemore » interface.« less

Physical and photoelectrochemical properties of Sb-doped SnO2 thin films deposited by chemical vapor deposition: application to chromate reduction under solar light

NASA Astrophysics Data System (ADS)

Outemzabet, R.; Doulache, M.; Trari, M.

2015-05-01

Sb-doped SnO2 thin films (Sb-SnO2) are prepared by chemical vapor deposition. The X-ray diffraction indicates a rutile phase, and the SEM analysis shows pyramidal grains whose size extends up to 200 nm. The variation of the film thickness shows that the elaboration technique needs to be optimized to give reproducible layers. The films are transparent over the visible region. The dispersion of the optical indices is evaluated by fitting the diffuse reflectance data with the Drude-Lorentz model. The refractive index ( n) and absorption coefficient ( k) depend on both the conditions of preparation and of the doping concentration and vary between 1.4 and 2.0 and 0.2 and 0.01, respectively. Tin oxide is nominally non-stoichiometric, and the conduction is dominated by thermally electrons jump with an electron mobility of 12 cm2 V-1 s-1 for Sb-SnO2 (1 %). The ( C 2- V) characteristic in aqueous electrolyte exhibits a linear behavior from which an electrons density of 4.15 × 1018 cm-3 and a flat-band potential of -0.83 V SCE are determined. The electrochemical impedance spectroscopy shows a semicircle attributed to a capacitive behavior with a low density of surface states. The center lies below the real axis with a depletion angle (12°), due to a constant phase element, i.e., a deviation from a pure capacitive behavior, presumably attributed to the roughness and porosity of the film. The straight line at low frequencies is attributed to the Warburg diffusion. The energy diagram reveals the photocatalytic feasibility of Sb-SnO2. As application, 90 % of the chromate concentration (20 mg L-1, pH ~3) disappears after 6 h of exposure to solar light.

Structural differences existing in bulk and nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}: Investigated by experimental and theoretical methods

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

Nigam, Sandeep, E-mail: snigam@barc.gov.in; Sudarsan, V., E-mail: vsudar@barc.gov.in; Majumder, C.

Present manuscript deals with the structural changes associated with transformation of bulk Y{sub 2}Sn{sub 2}O{sub 7} into nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}. Nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7} both undoped and Eu{sup 3+} doped, were prepared at a relatively low temperature (700 °C) and investigated for their structural and luminescence properties and compared them with that of bulk Y{sub 2}Sn{sub 2}O{sub 7} sample prepared by the solid-state method at 1300 °C. Significant distortion in geometry and electron density distribution around Y{sup 3+}/Eu{sup 3+} ions in nanoparticles are confirmed from the Rietveld refinement of the powder X-ray diffraction patterns andmore » theoretical calculations based on the density functional theory (DFT). The SnO{sub 6} octahedron in Y{sub 2}Sn{sub 2}O{sub 7} is more expanded in nanoparticles compared to bulk. Iso-surface density distribution reveals that while bulk sample shows typical ionic feature in Y/Eu--O bonds, nanoparticle sample shows sharing of electron density along bond axis pertaining to covalent character. These inferences are further supported by the doped Eu{sup 3+} luminescence and calculated Ω{sub 2} and Ω{sub 4} parameters. - Graphical abstract: YO{sub 8} scalenohedron present in bulk and nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}.Variation of the electron density around Y{sup 3+} ions in YO{sub 8} polyhedron is also shown in bulk and nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7}. The difference in the extent of ionic/covalent nature of the Y--O bond is clearly seen the contour plot of electron density. Highlights: ► YO{sub 8} scalenohedron is axially and equatorially distorted in Y{sub 2}Sn{sub 2}O{sub 7} nanoparticles. ► Enlargement of SnO{sub 6} octahedron in nanoparticles of Y{sub 2}Sn{sub 2}O{sub 7} compared to bulk. ► Less symmetric charge distribution around Y{sup 3+} ions in Y{sub 2}Sn{sub 2}O{sub 7} nanoparticles.« less

Exploiting nonlinear properties of pure and Sn-doped Bi2Te2Se for passive Q-switching of all-polarization maintaining ytterbium- and erbium-doped fiber lasers.

PubMed

Bogusławski, Jakub; Kowalczyk, Maciej; Iwanowski, Przemysław; Hruban, Andrzej; Diduszko, Ryszard; Piotrowski, Kazimierz; Dybko, Krzysztof; Wojciechowski, Tomasz; Aleszkiewicz, Marta; Sotor, Jarosław

2017-08-07

Due to their broadband nonlinear optical properties, low-dimensional materials are widely used for pulse generation in fiber and solid-state lasers. Here we demonstrate novel materials, Bi 2 Te 2 Se (BTS) and Sn-doped Bi 2 Te 2 Se (BSTS), which can be used as a universal saturable absorbers for distinct spectral regimes. The material was mechanically exfoliated from a bulk single-crystal and deposited onto a side-polished fiber. We have performed characterization of the fabricated devices and employed them in polarization-maintaining ytterbium- and erbium-doped fiber lasers. This enabled us to obtain self-starting passively Q-switched regime at 1 µm and 1.56 µm. The oscillators emitted stable, linearly polarized radiation with the highest single pulse energy approaching 692 nJ. Both lasers are characterized by the best performance observed in all-polarization maintaining Q-switched fiber lasers with recently investigated new saturable absorbers, which was enabled by a very high damage threshold of the devices. This demonstrates the great potential of the investigated materials for the ultrafast photonics community.

A high performance lithium ion capacitor achieved by the integration of a Sn-C anode and a biomass-derived microporous activated carbon cathode

NASA Astrophysics Data System (ADS)

Sun, Fei; Gao, Jihui; Zhu, Yuwen; Pi, Xinxin; Wang, Lijie; Liu, Xin; Qin, Yukun

2017-02-01

Hybridizing battery and capacitor materials to construct lithium ion capacitors (LICs) has been regarded as a promising avenue to bridge the gap between high-energy lithium ion batteries and high-power supercapacitors. One of the key difficulties in developing advanced LICs is the imbalance in the power capability and charge storage capacity between anode and cathode. Herein, we design a new LIC system by integrating a rationally designed Sn-C anode with a biomass-derived activated carbon cathode. The Sn-C nanocomposite obtained by a facile confined growth strategy possesses multiple structural merits including well-confined Sn nanoparticles, homogeneous distribution and interconnected carbon framework with ultra-high N doping level, synergically enabling the fabricated anode with high Li storage capacity and excellent rate capability. A new type of biomass-derived activated carbon featuring both high surface area and high carbon purity is also prepared to achieve high capacity for cathode. The assembled LIC (Sn-C//PAC) device delivers high energy densities of 195.7 Wh kg-1 and 84.6 Wh kg-1 at power densities of 731.25 W kg-1 and 24375 W kg-1, respectively. This work offers a new strategy for designing high-performance hybrid system by tailoring the nanostructures of Li insertion anode and ion adsorption cathode.

A high performance lithium ion capacitor achieved by the integration of a Sn-C anode and a biomass-derived microporous activated carbon cathode.

PubMed

Sun, Fei; Gao, Jihui; Zhu, Yuwen; Pi, Xinxin; Wang, Lijie; Liu, Xin; Qin, Yukun

2017-02-03

Hybridizing battery and capacitor materials to construct lithium ion capacitors (LICs) has been regarded as a promising avenue to bridge the gap between high-energy lithium ion batteries and high-power supercapacitors. One of the key difficulties in developing advanced LICs is the imbalance in the power capability and charge storage capacity between anode and cathode. Herein, we design a new LIC system by integrating a rationally designed Sn-C anode with a biomass-derived activated carbon cathode. The Sn-C nanocomposite obtained by a facile confined growth strategy possesses multiple structural merits including well-confined Sn nanoparticles, homogeneous distribution and interconnected carbon framework with ultra-high N doping level, synergically enabling the fabricated anode with high Li storage capacity and excellent rate capability. A new type of biomass-derived activated carbon featuring both high surface area and high carbon purity is also prepared to achieve high capacity for cathode. The assembled LIC (Sn-C//PAC) device delivers high energy densities of 195.7 Wh kg -1 and 84.6 Wh kg -1 at power densities of 731.25 W kg -1 and 24375 W kg -1 , respectively. This work offers a new strategy for designing high-performance hybrid system by tailoring the nanostructures of Li insertion anode and ion adsorption cathode.

A high performance lithium ion capacitor achieved by the integration of a Sn-C anode and a biomass-derived microporous activated carbon cathode

PubMed Central

Sun, Fei; Gao, Jihui; Zhu, Yuwen; Pi, Xinxin; Wang, Lijie; Liu, Xin; Qin, Yukun

2017-01-01

Hybridizing battery and capacitor materials to construct lithium ion capacitors (LICs) has been regarded as a promising avenue to bridge the gap between high-energy lithium ion batteries and high-power supercapacitors. One of the key difficulties in developing advanced LICs is the imbalance in the power capability and charge storage capacity between anode and cathode. Herein, we design a new LIC system by integrating a rationally designed Sn-C anode with a biomass-derived activated carbon cathode. The Sn-C nanocomposite obtained by a facile confined growth strategy possesses multiple structural merits including well-confined Sn nanoparticles, homogeneous distribution and interconnected carbon framework with ultra-high N doping level, synergically enabling the fabricated anode with high Li storage capacity and excellent rate capability. A new type of biomass-derived activated carbon featuring both high surface area and high carbon purity is also prepared to achieve high capacity for cathode. The assembled LIC (Sn-C//PAC) device delivers high energy densities of 195.7 Wh kg−1 and 84.6 Wh kg−1 at power densities of 731.25 W kg−1 and 24375 W kg−1, respectively. This work offers a new strategy for designing high-performance hybrid system by tailoring the nanostructures of Li insertion anode and ion adsorption cathode. PMID:28155853

Sn 1-x VxOy thin films deposited by pulsed laser ablation for gas sensing devices

NASA Astrophysics Data System (ADS)

Duhalde, Stella; Vignolo, M. F.; Quintana, G.; Mercader, R.; Lamagna, Antonino

2000-02-01

Polycrystalline pure and V-doped SnO2 thin films have been prepare by pulsed laser deposition (PLD) on Si substrates, with a Si3Ni4 buffered layer. PLD technique, under proper conditions, has probed to produce nanocrystalline-structured materials, which are suitable for gas sensing. In this work we analyze the role of V doping in the structural properties and in the electrical conductivity of the films. The deposition temperature was fixed at 600 degrees C and the films were grown in oxygen atmosphere. The films resulted nanocrystalline with 50 to 120 nm average grain size connected by necks with high surface areas. The microstructural and electronic properties of all the films were analyzed using scanning-electron microscopy, x-ray diffraction and conversion electron Moessbauer spectroscopy. Electrical conductance in a dynamic regime in dry synthetic air has been evaluated as a function of temperature. Moessbauer spectra reveal the presence of 15 percent of Sn2+ in the 5at. percent V-doped films. At about 340 degrees C, a strong increase in the conductivity of the films occurs. Possible explanations are that thermal energy could excite electrons from the vanadium ions into the crystal's conduction band or promotes the diffusion of surface oxygen vacancies towards the bulk, increasing strongly the conductivity of the film.

Oxygen deficiency and Sn doping of amorphous Ga{sub 2}O{sub 3}

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

Heinemann, M. D.; Unold, T.; Berry, J.

2016-01-11

The potential of effectively n-type doping Ga{sub 2}O{sub 3} considering its large band gap has made it an attractive target for integration into transistors and solar cells. As a result amorphous GaO{sub x} is now attracting interest as an electron transport layer in solar cells despite little information on its opto-electrical properties. Here we present the opto-electronic properties, including optical band gap, electron affinity, and charge carrier density, for amorphous GaO{sub x} thin films deposited by pulsed laser deposition. These properties are strongly dependent on the deposition temperature during the deposition process. The deposition temperature has no significant influence onmore » the general structural properties but produces significant changes in the oxygen stoichiometry of the films. The density of the oxygen vacancies is found to be related to the optical band gap of the GaO{sub x} layer. It is proposed that the oxygen deficiency leads to defect band below the conduction band minimum that increases the electron affinity. These properties facilitate the use of amorphous GaO{sub x} as an electron transport layer in Cu(In,Ga)Se{sub 2} and in Cu{sub 2}O solar cells. Further it is shown that at low deposition temperatures, extrinsic doping with Sn is effective at low Sn concentrations.« less

Computational design of materials for solar hydrogen generation

NASA Astrophysics Data System (ADS)

Umezawa, Naoto

Photocatalysis has a great potential for the production of hydrogen from aquerous solution under solar light. In this talk, two different approaches toward the computational materials desing for solar hydrogen generation will be presented. Tin (Sn), which has two major oxidation states, Sn2+ and Sn4+, is abundant on the earth's crust. Recently, visible-light responsive photocatalytc H2 evolution reaction was identified over a mixed valence tin oxide Sn3O4. We have carried out crystal structure prediction for mixed valence tin oxides in different atomic compositions under ambient pressure condition using advanced computational methods based on the evolutionary crystal-structure search and density-functional theory. The predicted novel crystal structures realize the desirable band gaps and band edge positions for H2 evolution under visible light irradiation. It is concluded that multivalent tin oxides have a great potential as an abundant, cheap and environmentally-benign solar-energy conversion photofunctional materials. Transition metal doping is effective for sensitizing SrTiO3 under visible light. We have theoretically investigated the roles of the doped Cr in STO based on hybrid density-functional calculations. Cr atoms are preferably substituting for Ti under any equilibrium growth conditions. The lower oxidation state Cr3+, which is stabilized under an n-type condition of STO, is found to be advantageous for the photocatalytic performance. It is firther predicted that lanthanum is the best codopant for stabilizing the favorable oxidation state, Cr3+. The prediction was validated by our experiments that La and Cr co-doped STO shows the best performance among examined samples. This work was supported by the Japan Science and Technology Agency (JST) Precursory Research for Embryonic Science and Technology (PRESTO) and International Research Fellow program of Japan Society for the Promotion of Science (JSPS) through project P14207.

Application of pristine and doped SnO2 nanoparticles as a matrix for agro-hazardous material (organophosphate) detection

NASA Astrophysics Data System (ADS)

Khan, Naushad; Athar, Taimur; Fouad, H.; Umar, Ahmad; Ansari, Z. A.; Ansari, S. G.

2017-02-01

With an increasing focus on applied research, series of single/composite materials are being investigated for device development to detect several hazardous, dangerous, and toxic molecules. Here, we report a preliminary attempt of an electrochemical sensor fabricated using pristine Ni and Cr-doped nano tin oxide material (SnO2) as a tool to detect agro-hazardous material, i.e. Organophosphate (OP, chlorpyrifos). The nanomaterial was synthesized using the solution method. Nickel and chromium were used as dopant during synthesis. The synthesized material was calcined at 1000 °C and characterized for morphological, structural, and elemental analysis that showed the formation of agglomerated nanosized particles of crystalline nature. Screen-printed films of powder obtained were used as a matrix for working electrodes in a cyclic voltammogram (CV) at various concentrations of organophosphates (0.01 to 100 ppm). The CV curves were obtained before and after the immobilization of acetylcholinesterase (AChE) on the nanomaterial matrix. An interference study was also conducted with hydroquinone to ascertain the selectivity. The preliminary study indicated that such material can be used as suitable matrix for a device that can easily detect OP to a level of 10 ppb and thus contributes to progress in terms of desired device technology for the food and agricultural-industries.

Pressure-induced topological insulator-to-metal transition and superconductivity in Sn-doped B i1.1S b0.9T e2S

NASA Astrophysics Data System (ADS)

An, Chao; Chen, Xuliang; Wu, Bin; Zhou, Yonghui; Zhou, Ying; Zhang, Ranran; Park, Changyong; Song, Fengqi; Yang, Zhaorong

2018-05-01

Tetradymite-type topological insulator Sn-doped B i1.1S b0.9T e2S (Sn-BSTS), with a surface state Dirac point energy well isolated from the bulk valence and conduction bands, is an ideal platform for studying the topological transport phenomena. Here, we present high-pressure transport studies on single-crystal Sn-BSTS, combined with Raman scattering and synchrotron x-ray diffraction measurements. Over the studied pressure range of 0.7-37.2 GPa, three critical pressure points can be observed: (i) At ˜9 GPa, a pressure-induced topological insulator-to-metal transition is revealed due to closure of the bulk band gap, which is accompanied by changes in slope of the Raman frequencies and a minimum in c /a within the pristine rhombohedral structure (R -3 m ); (ii) at ˜13 GPa, superconductivity is observed to emerge, along with the R -3 m to a C 2 /c (monoclinic) structural transition; (iii) at ˜24 GPa, the superconducting transition onset temperature TC reaches a maximum of ˜12 K , accompanied by a second structural transition from the C 2 /c to a body-centered cubic I m -3 m phase.

Cytoplasmic Delivery of Liposomal Contents Mediated by an Acid-Labile Cholesterol-Vinyl Ether-PEG Conjugate

PubMed Central

Boomer, Jeremy A.; Qualls, Marquita M.; Inerowicz, H. Dorota; Haynes, Robert H.; Patri, G.V. Srilaksmi; Kim, Jong-Mok; Thompson, David H.

2009-01-01

An acid-cleavable PEG lipid, 1′-(4′-cholesteryloxy-3′-butenyl)-ω-methoxy-polyethylene[112] glycolate (CVEP), has been developed that produces stable liposomes when dispersed as a minor component (0.5–5 mol%) in 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Cleavage of CVEP at mildly acidic pH’s results in dePEGylation of the latently fusogenic DOPE liposomes, thereby triggering the onset of contents release. This paper describes the synthesis of CVEP via a six step sequence starting from the readily available precursors 1,4-butanediol, cholesterol, and mPEG acid. The hydrolysis rates and release kinetics from CVEP:DOPE liposome dispersions as a function of CVEP loading, as well as the cryogenic transmission electron microscopy and pH-dependent monolayer properties of 9:91 CVEP:DOPE mixtures, also are reported. When folate-receptor positive KB cells were exposed to calcein-loaded 5:95 CVEP:DOPE liposomes containing 0.1 mol% folate-modified 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-polyethylene[76] glycolamide (folate-PEG-DSPE), efficient delivery of the calcein cargo to the cytoplasm of the cells was observed as determined by fluorescence microscopy and flow cytometry. Fluorescence resonance energy transfer analysis of lipid mixing in these cells was consistent with membrane-membrane fusion between the liposome and endosomal membranes. PMID:19072698

A room temperature ethanol sensor made from p-type Sb-doped SnO2 nanowires.

PubMed

Wu, Jyh Ming

2010-06-11

A p-type ethanol sensor with a response time of approximately 8.3 s at room temperature was produced by SnO(2):Sb nanowires. The electrical properties of p-type SnO(2) nanowires are stable with a hole concentration of 1.544 x 10(17) cm(-3) and a field-effect mobility of 22 cm(2) V(-2) S(-1). X-ray photoelectron spectroscopy (XPS) and Hall measurement revealed that as-synthesized nanowires exhibit p-type behavior. A comprehensive investigation of the p-type sensing mechanism is reported.

Composition dependence of structural and optical properties in epitaxial Sr(Sn1-xTix)O3 films

NASA Astrophysics Data System (ADS)

Liu, Qinzhuang; Li, Bing; Li, Hong; Dai, Kai; Zhu, Guangping; Wang, Wei; Zhang, Yongxing; Gao, Guanyin; Dai, Jianming

2015-03-01

Epitaxial Sr(Sn1-xTix)O3 (SSTO, x = 0-1) thin films were grown on MgO substrates by a pulsed laser deposition technique. The effects of composition on the structural and optical properties of SSTO films were investigated. X-ray diffraction studies show that the lattice parameter decreases from 4.041 to 3.919 Å gradually with increasing Ti content from 0 to 1 in SSTO films. Optical spectra analysis reveals that the band gap energy Eg decreases continuously from 4.44 to 3.78 eV over the entire doping range, which is explained by the decreasing degree of octahedral tilting distortion and thus the increasing tolerance factor caused by the increasing small-Ti-ion doping concentration.

THz characterization and demonstration of visible-transparent/terahertz-functional electromagnetic structures in ultra-conductive La-doped BaSnO3 Films.

PubMed

Arezoomandan, Sara; Prakash, Abhinav; Chanana, Ashish; Yue, Jin; Mao, Jieying; Blair, Steve; Nahata, Ajay; Jalan, Bharat; Sensale-Rodriguez, Berardi

2018-02-23

We report on terahertz characterization of La-doped BaSnO 3 (BSO) thin-films. BSO is a transparent complex oxide material, which has attracted substantial interest due to its large electrical conductivity and wide bandgap. The complex refractive index of these films is extracted in the 0.3 to 1.5 THz frequency range, which shows a metal-like response across this broad frequency window. The large optical conductivity found in these films at terahertz wavelengths makes this material an interesting platform for developing electromagnetic structures having a strong response at terahertz wavelengths, i.e. terahertz-functional, while being transparent at visible and near-IR wavelengths. As an example of such application, we demonstrate a visible-transparent terahertz polarizer.

Surface-state-dominated transport in crystals of the topological crystalline insulator In-doped Pb 1-xSn xTe

DOE PAGES

Zhong, Ruidan; He, Xugang; Schneeloch, J. A.; ...

2015-05-29

Three-dimensional topological insulators and topological crystalline insulators represent new quantum states of matter, which are predicted to have insulating bulk states and spin-momentum-locked gapless surface states. Experimentally, it has proven difficult to achieve the high bulk resistivity that would allow surface states to dominate the transport properties over a substantial temperature range. Here we report a series of indium-doped Pb 1-xSn xTe compounds that manifest huge bulk resistivities together with evidence consistent with the topological character of the surface states for x ≳ 0.35, based on thickness-dependent transport studies and magnetoresistance measurements. For these bulk-insulating materials, the surface states determinemore » the resistivity for temperatures beyond 20 K.« less

Characterization of SnO2 Film with Al-Zn Doping Using Sol-Gel Dip Coating Techniques

NASA Astrophysics Data System (ADS)

Doyan, A.; Susilawati; Ikraman, N.; Taufik, M.

2018-04-01

Sn1-2x AlxZnxO2 film has been developed using sol-gel dip coating technique. The materials SnCl2.2H2O, AlCl3 and ZnCl2 dissolved in water and ethanol with 5:95 volume ratio. Variations dopant concentration x = 0.000, 0.005, 0.0025, and 0.050. The film was grown with sol concentration 0.4 M, the withdrawal speed of 12 cm/min and sintering at 600 °C for 30 minutes. The characteristics Sn1-2x AlxZnxO2 films with various doping concentration phase were characterized by XRD. The morphological characteristics and the composition of the constituent elements of the film were characterized by SEM-EDX. The characteristics of the shape, structure, and size of the particles were characterized by TEM. The XRD results show that all films have a tetragonal SnO2 rutile phase without any secondary phase with an average particle size in the range 5.14 – 2.09 nm. The SEM results show that the film grown has a smooth morphology with a striped texture (x = 0.00), and there is a crack (x = 0.050). The EDX results show that the composition and distribution of the constituent elements of the film are uniformly distributed. TEM results show that the particle films has tetragonal rutile structure, orthorhombic and amorphous with a spherical shape.

Gas-sensing enhancement methods for hydrothermal synthesized SnO2-based sensors

NASA Astrophysics Data System (ADS)

Zhao, Yalei; Zhang, Wenlong; Yang, Bin; Liu, Jingquan; Chen, Xiang; Wang, Xiaolin; Yang, Chunsheng

2017-11-01

Gas sensing for hydrothermal synthesized SnO2-based gas sensors can be enhanced in three ways: structural improvement, composition optimization, and processing improvement. There have been zero-dimensional, one-dimensional, and three-dimensional structures reported in the literature. Controllable synthesis of different structures has been deployed to increase specific surface area. Change of composition would intensively tailor the SnO2 structure, which affected the gas-sensing performance. Furthermore, doping and compounding methods have been adopted to promote gas-sensing performance by adjusting surface conditions of SnO2 crystals and constructing heterojunctions. As for processing area, it is very important to find the optimal reaction time and temperature. In this paper, a gas-solid reaction rate constant was proposed to evaluate gas-sensing properties and find an excellent hydrothermal synthesized SnO2-based gas sensor.

Influence of Sn doping in BaSnxTi1-xO3 ceramics on microstructural and dielectric properties

NASA Astrophysics Data System (ADS)

Ansari, Mohd. Azaj; Sreenivas, K.

2018-05-01

BaSnxTi1-x O3 solid solutions with varying Sn content (x = 0.00, 0.05, 0.15, 0.25) prepared by solid state reaction method have been studied for their structural and dielectric properties. X-ray diffraction and Raman spectroscopic analysis show composition induced modifications in the crystallographic structure, and with increasing Sn content the structure changes from tetragonal to cubic structure. The tetragonal distortion decreases with increasing Sn, and the structure becomes purely cubic for x =0.25. Changes in the structure are reflected in the temperature dependent dielectric properties. For increasing Sn content the peak dielectric constant is found to increase and the phase transition temperature (Tc) decreases to lower temperature. The purely cubic structure with x=0.25 shows a diffused phased transition.

Electrical and Plasmonic Properties of Ligand-Free Sn(4+) -Doped In2 O3 (ITO) Nanocrystals.

PubMed

Jagadeeswararao, Metikoti; Pal, Somnath; Nag, Angshuman; Sarma, D D

2016-03-03

Sn(4+) -doped In2 O3 (ITO) is a benchmark transparent conducting oxide material. We prepared ligand-free but colloidal ITO (8 nm, 10 % Sn(4+) ) nanocrystals (NCs) by using a post-synthesis surface-modification reaction. (CH3 )3 OBF4 removes the native oleylamine ligand from NC surfaces to give ligand-free, positively charged NCs that form a colloidal dispersion in polar solvents. Both oleylamine-capped and ligand-free ITO NCs exhibit intense absorption peaks, due to localized surface plasmon resonance (LSPR) at around λ=1950 nm. Compared with oleylamine-capped NCs, the electrical resistivity of ligand-free ITO NCs is lower by an order of magnitude (≈35 mΩ cm(-1) ). Resistivity over a wide range of temperatures can be consistently described as a composite of metallic ITO grains embedded in an insulating matrix by using a simple equivalent circuit, which provides an insight into the conduction mechanism in these systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermoelectric performance and the role of anti-site disorder in the 24-electron Heusler TiFe2Sn.

PubMed

Buffon, Malinda L C; Laurita, Geneva; Lamontagne, Leo; Levin, Emily E; Mooraj, Shahryar; Lloyd, Demetrious L; White, Natalie; Pollock, Tresa M; Seshadri, Ram

2017-10-11

Heusler compounds XY 2 Z with 24 valence electrons per formula unit are potential thermoelectric materials, given their thermal and chemical stability and their relatively earth-abundant constituent elements. We present results on the 24-electron compound TiFe 2 Sn here. First principles calculations on this compound suggest semiconducting behavior. A relatively flat conduction band that could be associated with a high Seebeck coefficient upon electron doping is found. A series of compounds have been prepared and characterized using a combination of synchrotron x-ray and neutron diffraction studies to understand the effects of site order/disorder phenomena and n-type doping. Samples fabricated by a three step processing approach were subjected to high temperature Seebeck and electrical resistivity measurements. Ti:Fe anti-site disorder is present in the stoichiometric compound and these defects are reduced when starting Ti-rich compositions are employed. Additionally, we investigate control of the Seebeck coefficient through the introduction of carriers through the substitution of Sb on the Sn site in these intrinsically p-type materials.

Synthesis and characterization of indium doped La{sub 3}Co{sub 4}Sn{sub 13} skutterudite superconductor

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

Neha, P.; Srivastava, P.; Shruti,

2016-05-06

We report the synthesis and characterization of a novel superconductor La{sub 3}Co{sub 4}Sn{sub 12.35}In{sub 0.65} by Indium doping at Tin site in parent compound La{sub 3}Co{sub 4}Sn{sub 13}. We observe enhanced T{sub c} along with improved superconducting properties as onset compared to parent compound. By transport measurements we get superconducting transition with T{sub c}{sup onset} = 4.7 K and T{sub c}{sup zero} = 3.2 K. In magnetization measurements (ZFC-FC) superconducting transition is observed at 5.1 K. Upper critical field (H{sub c2}) and lower critical field (H{sub c1}) calculated by magneto resistance and M-H loop measurement are found to be 1.65more » T and 0.0026 T respectively. Hall measurement shows the majority charge carrier as electrons with carrier density of the order of 10{sup 19} cm{sup −3}. TEP measurement also support the Hall data as the Seebeck coefficient is negative over whole temperature range of measurement.« less

A novel method for photodegradation of high-chroma dye wastewater via electrochemical pre-oxidation.

PubMed

Zhao, Kunjiao; Zhao, Guohua; Li, Peiqiang; Gao, Junxia; Lv, Baoying; Li, Dongming

2010-06-01

A new two-step process involving the electrocatalytic (EC) pre-oxidation and the following photoelectrocatalytic synergistic (PEC) oxidation is proposed to treat the high concentration and high-chroma methyl orange dye wastewater, which cannot be degraded by photocatalytic oxidation (PC) directly. The SnO(2)/TiO(2)-NTs/Ti electrode simultaneously possessing the outstanding PC oxidation properties of TiO(2)-NTs and the excellent EC oxidation abilities of the Sb doped SnO(2) was synthesized by impregnating Sb doped SnO(2) nanoparticles into TiO(2)-NTs. In the pre-oxidation process as the first stage, the high-color dye wastewater is decolorized with electrochemical method to some extent. Then, the wastewater becomes a light transmission system. It provides a suitable condition for PC oxidation reaction in the second stage. The synergistic effects of PC and EC oxidation led to the high PEC efficiency and the complete mineralization of dye wastewater is achieved. This two-step process is fast and efficient, which is worthy to study and explore in the practical environmental treatment.

The Effect of Copper Addition on the Properties of Sn-0.7Cu Solder Paste

NASA Astrophysics Data System (ADS)

Said, R. M.; Mohamad Johari, F. H.; Salleh, M. A. A. Mohd; Sandu, A. V.

2018-03-01

The effect of copper addition on the properties of Sn-Cu based solder paste were investigate through this study. The Sn-0.7Cu solder paste doped with different concentration of Cu were prepared using solder paste mixture. The bulk solder microstructure of assolidified solder paste was studied. Besides that, intermetallic compound (IMC) formation on Cu substrate and hardness of all solder paste also being investigated. Results shows that increasing Cu concentration cause formation of large Cu6Sn5 IMC at bulk solder and the size of the IMC grew larger at high temperature. In addition, β-Sn area reduce when Cu concentration was high. The IMC morphology for all solder paste almost remain unchanged. However, there are large Cu6Sn5 IMC form near the interfacial IMC in Sn-Cu solder paste with high amount of Cu (Sn-10Cu). The hardness value was decrease when processing temperature at 250 °C due to present of small void in the microstructure while hardness of solder material increased at high temperature.

Melt growth and properties of bulk BaSnO3 single crystals

NASA Astrophysics Data System (ADS)

Galazka, Z.; Uecker, R.; Irmscher, K.; Klimm, D.; Bertram, R.; Kwasniewski, A.; Naumann, M.; Schewski, R.; Pietsch, M.; Juda, U.; Fiedler, A.; Albrecht, M.; Ganschow, S.; Markurt, T.; Guguschev, C.; Bickermann, M.

2017-02-01

We present the first-time growth of bulk BaSnO3 single crystals from the melt by direct solidification, their basic electrical and optical properties as well as their structural quality. Our measurement of the melting point (MP) of BaSnO3 amounts to 1855 °C  ±  25 K. At this temperature an intensive decomposition and non-stoichiometric evaporation takes place as the partial pressure of SnO(g) is about 90 times higher than that of BaO(g). X ray powder diffraction identified only the BaSnO3 perovskite phase, while narrow rocking curves having a full width at half maximum of 26 arcsec and etch pit densities below 106 cm-2 confirm a high degree of structural perfection of the single crystals. In this respect they surpass the structural properties of those single crystals that were reported in the literature. The electrical conductivity of nominally undoped crystals depends on the growth conditions and ranges from insulating to medium n-type conductivity. After post-growth annealing in an oxidizing atmosphere undoped crystals are generally insulating. Doping the crystals with lanthanum during growth results in a high n-type conductivity. For a La doping concentration of 0.123 wt.% we measured an electron concentration of 3.3  ×  1019 cm-3 and an electron mobility of 219 cm2 V-1 s-1. Based on optical absorption measurements we determined an energy of 3.17  ±  0.04 eV at 5 K and of 2.99  ±  0.04 eV at 297 K for the indirect band gap of BaSnO3.

Theoretical Investigation of the Thermodynamic Properties of η'-(Cu, Co)6Sn5 Alloys

NASA Astrophysics Data System (ADS)

Wu, Heng; Zhang, Xuechao; Zheng, Bing; Zhao, Xiuchen; Liu, Ying; Li, Hong; Cheng, Jingwei

2018-02-01

We perform theoretical investigations on the structures of η'-Cu6Sn5-based intermetallic compounds (IMCs) with different Co doping concentration (0-12.2 wt.%) based on density functional theory (DFT). The variations of the structural, elastic and thermodynamic properties of (Cu, Co)6Sn5 IMCs with pressure (0-18 GPa) and temperature (0-500 K) are obtained with the application of quasi-harmonic Debye model for the non-equilibrium Gibbs free energy. It is found that the volume of (Cu, Co)6Sn5 shrinks with Co concentration increasing in the range of imposed pressure and temperature. At the same time, the bulk modulus of Cu4Co2Sn5 is the largest among those of Cu6Sn5, Cu5Co1Sn5 and Cu4Co2Sn5. By calculating the Debye temperature of Cu6Sn5, we find that it is higher than that of Cu5Co1Sn5 and Cu4Co2Sn5 when the pressure is higher than 2 GPa. Meanwhile, heat capacities of all three Cu6Sn5, Cu5Co1Sn5, and Cu4Co2Sn5 converge to a near-constant value at about 1090 J/mol K in the range of the imposed pressures.

Thermally evaporated mechanically hard tin oxide thin films for opto-electronic apllications

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

Tripathy, Sumanta K.; Rajeswari, V. P.

2014-01-28

Tungsten doped tin oxide (WTO) and Molybdenum doped tin oxide (MoTO) thin film were deposited on corn glass by thermal evaporation method. The films were annealed at 350°C for one hour. Structural analysis using Xray diffraction data shows both the films are polycrystalline in nature with monoclinic structure of tin oxide, Sn{sub 3}O{sub 4}, corresponding to JCPDS card number 01-078-6064. SEM photograph showed that both the films have spherical grains with size in the range of 20–30 nm. Compositional analysis was carried out using EDS which reveals the presence of Sn, O and the dopant Mo/W only thereby indicating themore » absence of any secondary phase in the films. The films are found to contain nearly 6 wt% of Mo, 8 wt% of W as dopants respectively. The transmission pattern for both the films in the spectral range 200 – 2000 nm shows that W doping gives a transparency of nearly 80% from 380 nm onwards while Mo doping has less transparency of 39% at 380nm. Film hardness measurement using Triboscope shows a film hardness of about 9–10 GPa for both the films. It indicates that W or M doping in tin oxide provides the films the added advantage of withstanding the mechanical wear and tear due to environmental fluctuations By optimizing the optical and electrical properties, W/Mo doped tin oxide films may be explored as window layers in opto-electronic applications such as solar cells.« less

Pressure-induced enhancement in the thermoelectric properties of monolayer and bilayer SnSe2

NASA Astrophysics Data System (ADS)

Zou, Daifeng; Yu, Chuanbin; Li, Yuhao; Ou, Yun; Gao, Yongyi

2018-03-01

The electronic structures of monolayer and bilayer SnSe2 under pressure were investigated by using first-principles calculations including van der Waals interactions. For monolayer SnSe2, the variation of electronic structure under pressure is controlled by pressure-dependent lattice parameters. For bilayer SnSe2, the changes in electronic structure under pressure are dominated by intralayer and interlayer atomic interactions. The n-type thermoelectric properties of monolayer and bilayer SnSe2 under pressure were calculated on the basis of the semi-classical Boltzmann transport theory. It was found that the electrical conductivity of monolayer and bilayer SnSe2 can be enhanced under pressure, and such dependence can be attributed to the pressure-induced changes of the Se-Sn antibonding states in conduction band. Finally, the doping dependence of power factors of n-type monolayer and bilayer SnSe2 at three different pressures were estimated, and the results unveiled that thermoelectric performance of n-type monolayer and bilayer SnSe2 can be improved by applying external pressure. This study benefits to understand the nature of the transport properties for monolayer and bilayer SnSe2 under pressure, and it offers valuable insight for designing high-performance thermoelectric few-layered SnSe2 through strain engineering induced by external pressure.

Pressure-induced enhancement in the thermoelectric properties of monolayer and bilayer SnSe2.

PubMed

Zou, Daifeng; Yu, Chuanbin; Li, Yuhao; Ou, Yun; Gao, Yongyi

2018-03-01

The electronic structures of monolayer and bilayer SnSe 2 under pressure were investigated by using first-principles calculations including van der Waals interactions. For monolayer SnSe 2 , the variation of electronic structure under pressure is controlled by pressure-dependent lattice parameters. For bilayer SnSe 2 , the changes in electronic structure under pressure are dominated by intralayer and interlayer atomic interactions. The n -type thermoelectric properties of monolayer and bilayer SnSe 2 under pressure were calculated on the basis of the semi-classical Boltzmann transport theory. It was found that the electrical conductivity of monolayer and bilayer SnSe 2 can be enhanced under pressure, and such dependence can be attributed to the pressure-induced changes of the Se-Sn antibonding states in conduction band. Finally, the doping dependence of power factors of n -type monolayer and bilayer SnSe 2 at three different pressures were estimated, and the results unveiled that thermoelectric performance of n -type monolayer and bilayer SnSe 2 can be improved by applying external pressure. This study benefits to understand the nature of the transport properties for monolayer and bilayer SnSe 2 under pressure, and it offers valuable insight for designing high-performance thermoelectric few-layered SnSe 2 through strain engineering induced by external pressure.

Electronically conducting metal oxide nanoparticles and films for optical sensing applications

DOEpatents

Ohodnicki, Jr., Paul R.; Wang, Congjun; Andio, Mark A

2014-09-16

The disclosure relates to a method of detecting a change in a chemical composition by contacting a conducting oxide material with a monitored stream, illuminating the conducting oxide material with incident light, collecting exiting light, monitoring an optical signal based on a comparison of the incident light and the exiting light, and detecting a shift in the optical signal. The conducting metal oxide has a carrier concentration of at least 10.sup.17/cm.sup.3, a bandgap of at least 2 eV, and an electronic conductivity of at least 10.sup.-1 S/cm, where parameters are specified at the gas stream temperature. The optical response of the conducting oxide materials is proposed to result from the high carrier concentration and electronic conductivity of the conducting metal oxide, and the resulting impact of changing gas atmospheres on that relatively high carrier concentration and electronic conductivity. These changes in effective carrier densities and electronic conductivity of conducting metal oxide films and nanoparticles are postulated to be responsible for the change in measured optical absorption associated with free carriers. Exemplary conducting metal oxides include but are not limited to Al-doped ZnO, Sn-doped In.sub.2O.sub.3, Nb-doped TiO.sub.2, and F-doped SnO.sub.2.

Multivalent Mn-doped TiO2 thin films

NASA Astrophysics Data System (ADS)

Lin, C. Y. W.; Channei, D.; Koshy, P.; Nakaruk, A.; Sorrell, C. C.

2012-07-01

Thin films of TiO2 doped with Mn were deposited on F-doped SnO2-coated glass using spin coating. The concentration of the dopant was in the range 0-7 wt% Mn (metal basis). The films were examined in terms of the structural, chemical, and optical properties. Glancing angle X-ray diffraction data show that the films consisted of the anatase polymorph of TiO2, without any contaminant phases. The X-ray photoelectron spectroscopy data indicate the presence of Mn3+ and Mn4+ in the doped films as well as atomic disorder and associated structural distortion. Ultraviolet-visible spectrophotometry data show that the optical indirect band gap of the films decreased significantly with increasing manganese doping, from 3.32 eV for the undoped composition to 2.90 eV for that doped with 7 wt% Mn.

ROS mediated malignancy cure performance of morphological, optical, and electrically tuned Sn doped CeO2 nanostructures

NASA Astrophysics Data System (ADS)

Abbas, Fazal; Iqbal, Javed; Maqbool, Qaisar; Jan, Tariq; Ullah, Muhammad Obaid; Nawaz, Bushra; Nazar, Mudassar; Naqvi, M. S. Hussain; Ahmad, Ishaq

2017-09-01

To grapple with cancer, implementation of differentially cytotoxic nanomedicines have gained prime attention of the researchers across the globe. Now, ceria (CeO2) at nanoscale has emerged as a cut out therapeutic agent for malignancy treatment. Keeping this in view, we have fabricated SnxCe1-xO2 nanostructures by facile, eco-friendly, and biocompatible hydrothermal method. Structural examinations via XRD and FT-IR spectroscopy have revealed single phase cubic-fluorite morphology while SEM analysis has depicted particle size ranging 30-50nm for pristine and doped nanostructures. UV-Vis spectroscopy investigation explored that Sn doping significantly tuned the band gap (eV) energies of SnxCe1-xO2 nanostructures which set up the base for tremendous cellular reactive oxygen species (ROS) generations involved in cancer cells' death. To observe cytotoxicity, synthesized nanostructures were found selectively more toxic to neuroblastoma cell lines as compared to HEK-293 healthy cells. This study anticipates that SnxCe1-xO2 nanostructures, in future, might be used as nanomedicine for safer cancer therapy.

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

Moto, Kenta; Sadoh, Taizoh; Miyao, Masanobu, E-mail: miyao@ed.kyushu-u.ac.jp

Crystalline GeSn-on-insulator structures with high Sn concentration (>8%), which exceeds thermal equilibrium solid-solubility (∼2%) of Sn in Ge, are essential to achieve high-speed thin film transistors and high-efficiency optical devices. We investigate non-thermal equilibrium growth of Ge{sub 1−x}Sn{sub x} (0 ≤ x ≤ 0.2) on quartz substrates by using pulsed laser annealing (PLA). The window of laser fluence enabling complete crystallization without film ablation is drastically expanded (∼5 times) by Sn doping above 5% into Ge. Substitutional Sn concentration in grown layers is found to be increased with decreasing irradiation pulse number. This phenomenon can be explained on the basis of significant thermal non-equilibriummore » growth achieved by higher cooling rate after PLA with a lower pulse number. As a result, GeSn crystals with substitutional Sn concentration of ∼12% are realized at pulse irradiation of single shot for the samples with the initial Sn concentration of 15%. Raman spectroscopy and electron microscopy measurements reveal the high quality of the grown layer. This technique will be useful to fabricate high-speed thin film transistors and high-efficiency optical devices on insulating substrates.« less

Effect of Sn Composition in Ge1- x Sn x Layers Grown by Using Rapid Thermal Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Kil, Yeon-Ho; Kang, Sukill; Jeong, Tae Soo; Shim, Kyu-Hwan; Kim, Dae-Jung; Choi, Yong-Dae; Kim, Mi Joung; Kim, Taek Sung

2018-05-01

The Ge1- x Sn x layers were grown by using rapid thermal chemical-vapor deposition (RTCVD) on boron-doped p-type Si (100) substrates with Sn compositions up to x = 0.83%. In order to obtain effect of the Sn composition on the structural and the optical characteristics, we utilized highresolution X-ray diffraction (HR-XRD), etch pit density (EPD), atomic force microscopy (AFM), Raman spectroscopy, and photocurrent (PC) spectra. The Sn compositions in the Ge1- x Sn x layers were found to be of x = 0.00%, 0.51%, 0.65%, and 0.83%. The root-mean-square (RMS) of the surface roughness of the Ge1- x Sn x layer increased from 2.02 nm to 3.40 nm as the Sn composition was increased from 0.51% to 0.83%, and EPD was on the order of 108 cm-2. The Raman spectra consist of only one strong peak near 300 cm-1, which is assigned to the Ge-Ge LO peaks and the Raman peaks shift to the wave number with increasing Sn composition. Photocurrent spectra show near energy band gap peaks and their peak energies decrease with increasing Sn composition due to band-gap bowing in the Ge1- x Sn x layer. An increase in the band gap bowing parameter was observed with increasing Sn composition.

Structural, optical and dielectric properties of Sn0.97Ce0.03O2 nanostructures

NASA Astrophysics Data System (ADS)

Ahmed, Ateeq; Siddique, M. Naseem; Ali, Tinku; Tripathi, P.

2018-05-01

In present work, 3% cerium doped SnO2 (Sn0.97Ce0.03O2) nanoparticles (NPs) have been synthesized by sol-gel method. The prepared sample has been characterized by using various techniques such as XRD, UV-visible absorption spectroscopy and LCR meter measurements. Structural Rietveld refinement of XRD data reveals that (Sn0.97Ce0.03O2) sample has a pure single phase tetragonal structure with space group (P42/mnm) without creating any impurity phase such as cerium oxide. UV-visible spectroscopy determines band gap value 3.47 eV for (Sn0.97Ce0.03O2) NPs using Tauc's relation. Dielectric constant and loss decreased with increase in frequency while ac conductivity was found to increase with increase in frequency. The observed dielectric results has been explained in the light of Maxwell-Wagner model.

Self-catalytic crystal growth, formation mechanism, and optical properties of indium tin oxide nanostructures

NASA Astrophysics Data System (ADS)

Liang, Yuan-Chang; Zhong, Hua

2013-08-01

In-Sn-O nanostructures with rectangular cross-sectional rod-like, sword-like, and bowling pin-like morphologies were successfully synthesized through self-catalytic growth. Mixed metallic In and Sn powders were used as source materials, and no catalyst layer was pre-coated on the substrates. The distance between the substrate and the source materials affected the size of the Sn-rich alloy particles during crystal growth in a quartz tube. This caused In-Sn-O nanostructures with various morphologies to form. An X-ray photoelectron spectroscope and a transmittance electron microscope with an energy-dispersive X-ray spectrometer were used to investigate the elemental binding states and compositions of the as-synthesized nanostructures. The Sn doping and oxygen vacancies in the In2O3 crystals corresponded to the blue-green and yellow-orange emission bands of the nanostructures, respectively.

EPR investigation of local structure for [Mn(H 2O) 6] 2+ cluster in [M(H 2O) 6]XCl 6:Mn 2+ (M = Zn, Mg, Cd, Ca; X = Pt, Sn) systems at different temperatures

NASA Astrophysics Data System (ADS)

Tian, Wen-Yan; Kuang, Xiao-Yu; Li, Hui-Fang; Li, Yan-Fang; Ying-Li

2009-01-01

A theoretical method for studying the inter-relation between the local structure and EPR spectra is established by diagonalizing the complete energy matrices. For [M(H 2O) 6]XCl 6:Mn 2+ (M = Zn, Mg, Cd, Ca; X = Pt, Sn) systems, the calculated results demonstrate that the local structures around the octahedral Mn 2+ centers in the doped systems are very similar despite of the host crystals being different. Furthermore, it is shown that the EPR zero-field parameter D depends simultaneously on the local structure parameters R and θ while ( a - F) depends mainly on R, whether the doped systems are at liquid-nitrogen temperature or room temperature.

Mössbauer study of oxide films of Fe-, Sn-, Cr- doped zirconium alloys during corrosion in autoclave

NASA Astrophysics Data System (ADS)

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.

2016-12-01

Mössbauer investigations were used to compare iron atom states in oxide films of binary Zr-Fe, ternary Zr-Fe-Cu and quaternary Zr-Fe-Cr-Sn alloys. Oxide films are received in an autoclave at a temperature of 350-360 °C and at pressure of 16.8 MPa. The corrosion process decomposes the intermetallic precipitates in alloys and forms metallic iron with inclusions of chromium atoms α-Fe(Cr), α-Fe(Cu), α-Fe 2O3 and Fe 3O4 compounds. Some iron ions are formed in divalent and in trivalent paramagnetic states. The additional doping influences on corrosion kinetics and concentration of iron compounds and phases formed in oxide films. It was shown the correlation between concentration of iron in different chemical states and corrosion resistance of alloys.

The effects of additives to SnAgCu alloys on microstructure and drop impact reliability of solder joints

NASA Astrophysics Data System (ADS)

Liu, Weiping; Lee, Ning-Cheng

2007-07-01

The impact reliability of solder joints in electronic packages is critical to the lifetime of electronic products, especially those portable devices using area array packages such as ball-grid array (BGA) and chip-scale packages (CSP). Currently, SnAgCu (SAC) solders are most widely used for lead-free applications. However, BGA and CSP solder joints using SAC alloys are fragile and prone to premature interfacial failure, especially under shock loading. To further enhance impact reliability, a family of SAC alloys doped with a small amount of additives such as Mn, Ce, Ti, Bi, and Y was developed. The effects of doping elements on drop test performance, creep resistance, and microstructure of the solder joints were investigated, and the solder joints made with the modified alloys exhibited significantly higher impact reliability.

Transparent CH{sub 3}NH{sub 3}SnCl{sub 3}/Al-ZnO p-n heterojunction diode

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

Kumar, Sunil, E-mail: skbgudha@gmail.com; Ansari, Mohd Zubair; Khare, Neeraj

2016-05-23

A p-type Organic inorganic tin chloride (CH{sub 3}NH{sub 3}SnCl{sub 3}) perovskite thin film has been synthesized by solution method. An n-type 1% Al doped ZnO (AZO) film has been deposited on FTO substrate by ultrasonic assisted chemical vapor deposition technique. A transparent CH{sub 3}NH{sub 3}SnCl{sub 3}/AZO p-n heterojunction diode has been fabricated by spin coating technique. CH{sub 3}NH{sub 3}SnCl{sub 3}/AZO p-n heterojunction shows 75% transparency in the visible region. I-V characteristic of CH{sub 3}NH{sub 3}SnCl{sub 3}/AZO p-n heterojunction shows rectifying behavior of the diode. The diode parameters calculated as ideality factor η=2.754 and barrier height Φ= 0.76 eV. The resultmore » demonstrates the potentiality of CH{sub 3}NH{sub 3}SnCl{sub 3}/AZO p-n heterojunction for transparent electronics.« less

Experimental Study of Acid Treatment Toward Characterization of Structural, Optical, and Morphological Properties of TiO2-SnO2 Composite Thin Film

NASA Astrophysics Data System (ADS)

Fajar, M. N.; Hidayat, R.; Triwikantoro; Endarko

2018-04-01

The TiO2-SnO2 thin film with single and double-layer structure has successfully synthesized on FTO (Fluorine-doped Tin Oxide) substrate using the screen printing technique. The structural, optical, and morphological properties of the film were investigated by XRD, UV-Vis, and SEM, respectively. The results showed that the single and double-layer structure of TiO2-SnO2 thin film has mixed phase with a strong formation of casseritte phase. The acid treatment effect on TiO2-SnO2 thin film decreases the peak intensity of anatase phase formation and thin film’s absorbance values. The morphological study is also revealed that the single layer TiO2-SnO2 thin film had a more porous nature and decreased particle size distribution after acid treatment, while the double-layer TiO2-SnO2 thin film Eroded due to acid treatment.

Room-temperature processed tin oxide thin film as effective hole blocking layer for planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Tao, Hong; Ma, Zhibin; Yang, Guang; Wang, Haoning; Long, Hao; Zhao, Hongyang; Qin, Pingli; Fang, Guojia

2018-03-01

Tin oxide (SnO2) film with high mobility and good transmittance has been reported as a promising semiconductor material for high performance perovskite solar cells (PSCs). In this study, ultrathin SnO2 film synthesized by radio frequency magnetron sputtering (RFMS) method at room temperature was employed as hole blocking layer for planar PSCs. The room-temperature sputtered SnO2 film not only shows favourable energy band structure but also improves the surface topography of fluorine doped SnO2 (FTO) substrate and perovskite (CH3NH3PbI3) layer. Thus, this SnO2 hole blocking layer can efficiently promote electron transport and suppress carrier recombination. Furthermore, the best efficiency of 13.68% was obtained for planar PSC with SnO2 hole blocking layer prepared at room temperature. This research highlights the room-temperature preparation process of hole blocking layer in PSC and has a certain reference significance for the usage of flexible and low-cost substrates.

Crystal phase analysis of SnO{sub 2}-based varistor ceramic using the Rietveld method

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

Moreira, M.L.; Pianaro, S.A.; Andrade, A.V.C.

2006-09-15

A second addition of l mol% of CoO to a pre calcined SnO{sub 2}-based ceramic doped with 1.0 mol% of CoO, 0.05 mol% of Nb{sub 2}O{sub 5} and 0.05 mol% of Cr{sub 2}O{sub 3} promotes the appearance of a secondary phase, Co{sub 2}SnO{sub 4}, besides the SnO{sub 2} cassiterite phase, when the ceramic was sintered at 1350 deg. C/2 h. This was observed using X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray techniques. Rietveld refinement was carried out to quantify the phases present in the ceramic system. The results of the quantitative analysis were 97 wt.% SnO{sub 2}more » and 3 wt.% Co{sub 2}SnO{sub 4}. The microstructural analysis showed that a certain amount of cobalt ion remains into cassiterite grains.« less

Effect of replacing Sn4+ ions by Zn2+ ions on structural, optical and magnetic properties of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Selvi, E. Thamarai; Sundar, S. Meenakshi

2017-05-01

This paper highlights on the consequence of replacing tetravalent Sn4+ ions of the SnO2 by divalent Zn2+ ions on their structural, optical, and magnetic properties. Samples of Sn1- x Zn x O2 with x = 0, 0.01, 0.02, 0.03, and 0.04 were synthesized using microwave irradiated solvothermal process. The X-ray powder diffraction patterns reveal the rutile tetragonal phase of all doped SnO2 samples with no secondary phases. The transmission electron microscopy results show the formation of spherical nanoparticles of size 10-30 nm. Morphological changes were observed by scanning electron microscopy. The functional groups were investigated using Fourier transform infrared spectroscopy studies. Optical studies were carried by UV-Vis spectroscopy and fluorescence spectroscopy. Electron paramagnetic resonance was used to calculate the Lande splitting factor ` g'. The magnetic properties using vibrating sample magnetometer exhibit room temperature ferromagnetism for all the samples.

High Thermoelectric Performance of In4Se3-Based Materials and the Influencing Factors.

PubMed

Yin, Xin; Liu, Jing-Yuan; Chen, Ling; Wu, Li-Ming

2018-02-20

Materials that can directly convert electricity into heat, i.e., thermoelectric materials, have attracted renewed attention globally for sustainable energy applications. As one of the state-of-the-art thermoelectric materials, In 4 Se 3 features an interesting crystal structure of quasi-two-dimensional sheets comprising In/Se chains that provide a platform to achieve a Peierls distortion and support a charge density wave instability. Single-crystal In 4 Se 3-δ (δ = 0.65) shows strong anisotropy in its thermoelectric properties with a very high ZT of 1.48 at 705 K in the b-c plane (one of the highest values for an n-type thermoelectric material to date) but a much lower ZT of approximately 0.5 in the a-b plane. Because of the random dispersion of grains and the grain boundary effect, the electrical transport properties of polycrystalline In 4 Se 3 are poor, which is the main impediment to improve their performance. The In4-site in the In 4 Se 3 unit cell is substitutional for dopants such as Pb, which increases the carrier concentration by 2 orders of magnitude and the electrical conductivity to 143 S/cm. Furthermore, the electrical conductivity markedly increases to approximately 160 S/cm when Cu is doped into the interstitial site but remains as low as 30 S/cm with In1/In2/In3-site dopants, e.g., Ni, Zn, Ga, and Sn. In particular, the In4-site dopant ytterbium introduces a pinning level that highly localizes the charge carriers; thus, the electrical conductivity is maintained within an order of magnitude of 30 S/cm. Meanwhile, ytterbium also creates resonance states around the Fermi level that increase the Seebeck coefficient to -350 μV/K, the highest value at the ZT peak. However, the maximum solubility of the dopant may be limited by the Se-vacancy concentration. In addition, a Se vacancy also destroys the regular lattice vibrations and weakens phonon transport. Finally, nanoinclusions can effectively scatter the middle wavelength phonons, resulting in a decrease in the lattice thermal conductivity. Because of the multiple-dopant strategy, polycrystalline materials are competitive with single crystals regarding ZT values; for instance, Pb/Sn-co-doped In 4 Pb 0.01 Sn 0.04 Se 3 has ZT = 1.4 at 733 K, whereas In 4 Se 2.95 (CuI) 0.01 has ZT = 1.34 at 723 K. These properties illustrate the promise of polycrystalline In 4 Se 3 -based materials for various applications. Finally, the ZT values of all single crystalline and polycrystalline In 4 Se 3 materials have been summarized as a function of the doping strategy applied at the different lattice sites. Additionally, the correlations between the electrical conductivity and the Seebeck coefficient of all the polycrystalline materials are presented. These insights may provide new ideas in the search for and selection of new thermoelectric compounds in the In/Se and related In/Te, Sn/Se, and Sn/Te systems.

Effect of heterovalent substitutions in yttrium chromite on the hyperfine interactions of {sup 119}Sn{sup 4+} studied by Mössbauer spectroscopy

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

Fabritchnyi, Pavel B., E-mail: pf_1404@yahoo.fr; Afanasov, Mikhail I.; Mezhuev, Evgeny M.

2016-03-15

In order to develop the {sup 119}Sn Mössbauer spectroscopic probe technique to study magnetically ordered materials, three Ca-substituted yttrium chromites, i.e. Y{sub 0.9}Ca{sub 0.1}CrO{sub 3}, Y{sub 0.9}Ca{sub 0.1}Cr{sub 0.9}Ti{sub 0.1}O{sub 3} and Y{sub 0.8}Ca{sub 0.2}Cr{sub 0.8}Ti{sub 0.2}O{sub 3}, doped with 0.3 atom-% Sn{sup 4+}, were for the first time investigated. {sup 119}Sn Mössbauer spectra, recorded at 4.2 K, have allowed, through analysis of the magnetic hyperfine field values, probed by {sup 119}Sn nuclei, to gain insight into the local magnetically active surrounding of different Sn{sup 4+} ions. In all of these compounds, partial segregation of Sn{sup 4+} ions is revealed.more » In the case of Y{sub 0.9}Ca{sub 0.1}CrO{sub 3}, neither highly oxidized Cr{sup 4+} nor Cr{sup 6+} species, expected to compensate for the Ca{sup 2+} positive charge deficit, is found in the vicinity of the {sup 119}Sn{sup 4+} probe. In the case of both studied Ti-containing chromites, {sup 119}Sn Mössbauer spectra have provided the original indirect evidence for the statistical distribution of Cr{sup 3+} and Ti{sup 4+} ions over the octahedral sites and permitted characterization of the occurring associates of Sn{sup 4+}. - Graphical abstract: Two kinds of Sn{sup 4+} associates allowing {sup 119}Sn Mössbauer spectra of tin-doped Y{sub 0.9}Ca{sub 0.1}Cr{sub 0.9}Ti{sub 0.1}O{sub 3} and Y{sub 0.8}Ca{sub 0.2}Cr{sub 0.8}Ti{sub 0.2}O{sub 3} to be accounted for. - Highlights: • {sup 119}Sn probe is tested as a source of information on the B-sublattice of AF perovskites. • Neither Cr{sup 3+} nor Cr{sup 6+} is detected nearby {sup 119}Sn{sup 4+} ions in Y{sub 0.9}Ca{sub 0.1}CrO{sub 3}. • Cr{sup 3+} and Ti{sup 4+} are found to be randomly distributed in Y{sub 1−x}Ca{sub x}Cr{sub 1−x}Ti{sub x}O{sub 3} (x=0.1 or 0.2). • Sn{sup 4+} dopant segregations are revealed in all of the studied materials.« less

The interaction between divacancies and shallow dopants in irradiated Ge:Sn

NASA Astrophysics Data System (ADS)

Khirunenko, L. I.; Pomozov, Yu. V.; Sosnin, M. G.; Abrosimov, N. V.; Riemann, H.

2014-02-01

It has been found that upon annealing of irradiated Ge doped with gallium and Sn simultaneously with disappearance of divacancies V20 the appearance of the new absorption spectrum consisting of sharp lines was observed. The spectrum is identical to the absorption spectrum of gallium. It is shown that the defect, to which the new spectrum corresponds, has hydrogen-like properties. The distances between the lines in the spectrum are in good agreement with those predicted by effective-mass theory. The appearance of Fano resonance in the continuum region in addition to intracenter transitions of the defect was detected. The defect found is identified as SnV20Ga. The binding energy for the ground state of the SnV20Ga centers has been estimated.

Development of a detection sensor for lethal H2S gas.

PubMed

Park, Young-Ho; Kim, Yong-Jae; Lee, Chang-Seop

2012-07-01

The gas which may be lethal to human body with short-term exposure in common industrial fields or workplaces in LAB may paralyze the olfactory sense and impose severe damages to central nervous system and lung. This study is concerned with the gas sensor which allows individuals to avoid the toxic gas that may be generated in the space with residues of organic wastes under 50 degrees C or above. This study investigates response and selectivity of the sensor to hydrogen sulfide gas with operating temperatures and catalysts. The thick-film semiconductor sensor for hydrogen sulfide gas detection was fabricated WO3/SnO2 prepared by sol-gel and precipitation methods. The nanosized SnO2 powder mixed with the various metal oxides (WO3, TiO2, and ZnO) and doped with transition metals (Au, Ru, Pd Ag and In). Particle sizes, specific surface areas and phases of sensor materials were investigated by SEM, BET and XRD analyses. The metal-WO3/SnO2 thick films were prepared by screen-printing method. The measured response to hydrogen sulfide gas is defined as the ratio (Ra/R,) of the resistance of WO3ISnO2 film in air to the resistance of WO3/SnO2 film in a hydrogen sulfide gas. It was shown that the highest response and selectivity of the sensor for hydrogen sulfide by doping with 1 wt% Ru and 10 wt% WO3 to SnO2 at the optimum operating temperature of 200 degrees C.

One-step growth of thin film SnS with large grains using MOCVD.

PubMed

Clayton, Andrew J; Charbonneau, Cecile M E; Tsoi, Wing C; Siderfin, Peter J; Irvine, Stuart J C

2018-01-01

Thin film tin sulphide (SnS) films were produced with grain sizes greater than 1 μm using a one-step metal organic chemical vapour deposition process. Tin-doped indium oxide (ITO) was used as the substrate, having a similar work function to molybdenum typically used as the back contact, but with potential use of its transparency for bifacial illumination. Tetraethyltin and ditertiarybutylsulphide were used as precursors with process temperatures 430-470 °C to promote film growth with large grains. The film stoichiometry was controlled by varying the precursor partial pressure ratios and characterised with energy dispersive X-ray spectroscopy to optimise the SnS composition. X-ray diffraction and Raman spectroscopy were used to determine the phases that were present in the film and revealed that small amounts of ottemannite Sn 2 S 3 was present when SnS was deposited on to the ITO using optimised growth parameters. Interaction at the SnS/ITO interface to form Sn 2 S 3 was deduced to have resulted for all growth conditions.

Hybrid quantum dot-tin disulfide field-effect transistors with improved photocurrent and spectral responsivity

DOE PAGES

Cotlet, Mircea; Huang, Yuan Zang; Chen, Jia -Shiang; ...

2016-03-24

We report an improved photosensitivity in few-layer tin disulfide (SnS 2) field-effect transistors(FETs) following doping with CdSe/ZnS core/shell quantum dots(QDs). The hybrid QD-SnS 2 FET devices achieve more than 500% increase in the photocurrent response compared with the starting SnS 2-only FET device and a spectral responsivity reaching over 650 A/W at 400 nm wavelength. The negligible electrical conductance in a control QD-only FET device suggests that the energy transfer between QDs and SnS 2 is the main mechanism responsible for the sensitization effect, which is consistent with the strong spectral overlap between QDphotoluminescence and SnS 2 optical absorption asmore » well as the large nominal donor-acceptor interspacing between QD core and SnS 2. Furthermore, we also find enhanced charge carrier mobility in hybrid QD-SnS 2 FETs which we attribute to a reduced contact Schottky barrier width due to an elevated background charge carrier density.« less

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

Lim, K.; Schelhas, L. T.; Siah, S. C.

There have been a number of studies on the fabrication of Sn-doped gallium oxide (Ga 2O 3:Sn) films with both conductive and transparent properties using a variety of deposition methods. However, often, synthesis results in films that are not transparent. In this paper, we examine the mechanisms underlying these results in Ga 2O 3:Sn thin films prepared at various growth temperatures, Sn concentrations, and oxygen partial pressures. With X-ray absorption spectroscopy, transmission electron microscopy and energy dispersive spectroscopy, we find that when films are grown under the oxygen deficient conditions there are Ga sub-oxide and SnO x phases in themore » Ga 2O 3:Sn thin film. These Ga sub-oxide phases are only found in non-transparent films, and so we infer that the Ga sub-oxide is responsible for the non-transparency. Furthermore, these observations suggest that to obtain transparent Ga 2O 3:Sn, films deposition or subsequent annealing must be carefully controlled in both temperature and oxygen partial pressure to avoid the formation of Ga sub-oxide phases.« less

Kinetics of photo-activated charge carriers in Sn:CdS

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

Patidar, Manju Mishra, E-mail: manjumishra.iuc@gmail.com; Gorli, V. R.; Gangrade, Mohan

2016-05-23

Kinetics of the photo-activated charge carriers has been investigated in Tin substituted Cadmium Sulphide, Cd{sub 1-x}Sn{sub x}S (x=0, 0.05, 0.10 and 0.15), thin films prepared by spray pyrolysis. X-Ray Diffraction shows an increase in strain that resulted in the decreased crystallite size upon Sn substitution. At the first sight, the photo current characteristics show a quenching effect on Sn substitution. However, survival of persistent photocurrents is seen even up to 15% of Sn substitution. Transient photo current decay could be explained with a 2τ relaxation model. CdS normally has an n-type character and the Sn doping expected to inject holemore » carriers. The two fold increase in τ{sub 1}, increase in activation energy and the decrease in photocurrents upon Sn substitution point towards a band gap cleaning scenario that include compensation and associated carrier injection dynamics. In addition Atomic Force Microscopy shows a drastic change in microstructure that modulates the carrier dynamics as a whole.« less

Two-step fabrication of single-layer rectangular SnSe flakes

NASA Astrophysics Data System (ADS)

Jiang, Jizhou; Wong, Calvin Pei Yu; Zou, Jing; Li, Shisheng; Wang, Qixing; Chen, Jianyi; Qi, Dianyu; Wang, Hongyu; Eda, Goki; Chua, Daniel H. C.; Shi, Yumeng; Zhang, Wenjing; Thye Shen Wee, Andrew

2017-06-01

Recent findings about ultrahigh thermoelectric performances in SnSe single crystals have stimulated research on this binary semiconductor material. Furthermore, single-layer SnSe is an interesting analogue of phosphorene, with potential applications in two-dimensional (2D) nanoelectronics. Although significant advances in the synthesis of SnSe nanocrystals have been made, fabrication of well-defined large-sized single-layer SnSe flakes in a facile way still remains a challenge. The growth of single-layer rectangular SnSe flakes with a thickness of ~6.8 Å and lateral dimensions of about 30 µm  ×  50 µm is demonstrated by a two-step synthesis method, where bulk rectangular SnSe flakes were synthesized first by a vapor transport deposition method followed by a nitrogen etching technique to fabricate single-layer rectangular SnSe flakes in an atmospheric pressure system. The as-obtained rectangular SnSe flakes exhibited a pure crystalline phase oriented along the a-axis direction. Field-effect transistor devices fabricated on individual single-layer rectangular SnSe flakes using gold electrodes exhibited p-doped ambipolar behavior and a hole mobility of about 0.16 cm2 V-1 s-1. This two-step fabrication method can be helpful for growing other similar 2D large-sized single-layer materials.

Synthesis of phthalocyanine doped sol-gel materials

NASA Technical Reports Server (NTRS)

Dunn, Bruce

1993-01-01

The synthesis of sol-gel silica materials doped with three different types of metallophthalocyanines has been studied. Homogeneous materials of good optical quality were prepared and the first optical limiting measurements of dyes in sol-gel hosts were carried out. The properties of these solid state limiters are similar to limiters based on phthalocyanine (Pc) in solution. Sol-gel silica materials containing copper, tin and germanium phthalocyanines were investigated. The initial step in all cases was to prepare silica sols by the sonogel method using tetramethoxy silane (TMOS), HCl and distilled water. Thereafter, the synthesis depended upon the specific Pc and its solubility characteristics. Copper phthalocyanine tetrasulfonic acid tetra sodium salt (CuPc4S) is soluble in water and various doping levels (1 x 10 (exp -4) M to 1 x 10 (exp -5) M) were added to the sol. The group IV Pc's, SnPc(OSi(n-hexyl)3)2 and GePc(OSi(n-hexyl)3)2, are insoluble in water and the process was changed accordingly. In these cases, the compounds were dissolved in THF and then added to the sol. The Pc concentration in the sol was 2 x 10(exp -5)M. The samples were then aged and dried in the standard method of making xerogel monoliths. Comparative nanosecond optical limiting experiments were performed on silica xerogels that were doped with the different metallophthalocyanines. The ratio of the net excited state absorption cross section (sigma(sub e)) to the ground state cross section (sigma(sub g)) is an important figure of merit that is used to characterize these materials. By this standard the SnPc sample exhibits the best limiting for the Pc doped sol-gel materials. Its cross section ratio of 19 compares favorably with the value of 22 that was measured in toluene. The GePc materials appear to not be as useful as those containing SnPc. The GePc doped solids exhibit a higher onset energy (2.5 mj and lower cross section ratio, 7. The CuPc4S sol-gel material has a still lower cross section ratio, 4, however, the tetrasulfonate groups make the dye soluble in water which greatly facilitates its incorporation into the sol-gel matrix. The nonlinear transmission of CuPc4S in a pH 2 buffer solution and in a silica xerogel were compared. It is evident that the CuPc4S preserves its optical limiting behavior in the sol-gel matrix, indicating that the fundamental excited state absorption process is essentially the same for a molecule in solution or in the solid state. Although the spectroscopic details of energy level lifetimes are unknown, the significance is that passive optical limiting has been achieved in the solid state via incorporation of a dye into an inorganic host. The only compromise occurs at the extremely high energy regime where photobleaching is observed. This is a result of the limited mobility of the dye molecules in the solid silica host relative to a liquid host. The effects of photodegradation in the xerogel are additive, whereas the solution provides a supply of fresh molecules that are free to enter the active volume between pulses.

Enhancing electrical conductivity of room temperature deposited Sn-doped In2O3 thin films by hematite seed layers

NASA Astrophysics Data System (ADS)

Lohaus, Christian; Steinert, Céline; Deyu, Getnet; Brötz, Joachim; Jaegermann, Wolfram; Klein, Andreas

2018-04-01

Hematite Fe2O3 seed layers are shown to constitute a pathway to prepare highly conductive transparent tin-doped indium oxide thin films by room temperature magnetron sputtering. Conductivities of up to σ = 3300 S/cm are observed. The improved conductivity is not restricted to the interface but related to an enhanced crystallization of the films, which proceeds in the rhombohedral phase.