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Sample records for nanocrystalline zns thin

  1. Study of Microstructure and Optical Properties of Pva-Capped ZnS: cu Nanocrystalline Thin Films

    NASA Astrophysics Data System (ADS)

    Thi, Tran Minh; van, Bui Hong; Ben, Pham Van

    A study has been carried out on the Cu doping and PVA capping induced optical property changes in ZnS : Cu nanocrystalline powders and thin film. For this study, ZnS : Cu nanopowders with Cu concentrations of 0.1%, 0.15%, 0.2%, 0.3% and 0.4% are synthesized by the wet chemical method. The polyvinyl alcohol (PVA)-capped ZnS thin film with 0.2% Cu concentration and various PVA concentrations are prepared by the spin-coating method. The microstructures of the samples are investigated by the X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM). The results show that the prepared samples belong to the wurtzite structure with the average particle size of about 3-7 nm. The optical properties of samples are studied by measuring absorption and photoluminescence (PL) spectra in the wavelength range from 300 nm to 900 nm at 300 K. It is shown that the luminescent intensity of ZnS : Cu nanopowders reaches the highest intensity for optimal Cu concentration of 0.2% with the corresponding values of its direct band gap estimated to be about 3.90 eV. While the PVA coating does not affect the microstructure of ZnS nanometerials, the PL spectra of the samples are found to be affected by the PVA concentration as well as the exciting power density. The influence of the polymer coating on the optical properties can be explained by the quantum confinement effect of ZnS nanoparticles in the PVA matrix.

  2. Characterization of ZnS thin films synthesized through a non-toxic precursors chemical bath

    SciTech Connect

    Rodríguez, C.A.; Sandoval-Paz, M.G.; Cabello, G.; Flores, M.; Fernández, H.; Carrasco, C.

    2014-12-15

    Highlights: • High quality ZnS thin films have been deposited by chemical bath deposition technique from a non-toxic precursor’s solution. • Nanocrystalline ZnS thin films with large band gap energy were synthesized without using ammonia. • Evidence that the growing of the thin films is carried out by means of hydroxide mechanism was found. • The properties of these ZnS thin films are similar and in some cases better than the corresponding ones produced using toxic precursors such as ammonia. - Abstract: In solar cells, ZnS window layer deposited by chemical bath technique can reach the highest conversion efficiency; however, precursors used in the process normally are materials highly volatile, toxic and harmful to the environment and health (typically ammonia and hydrazine). In this work the characterization of ZnS thin films deposited by chemical bath in a non-toxic alkaline solution is reported. The effect of deposition technique (growth in several times) on the properties of the ZnS thin film was studied. The films exhibited a high percentage of optical transmission (greater than 80%); as the deposition time increased a decreasing in the band gap values from 3.83 eV to 3.71 eV was observed. From chemical analysis, the presence of ZnS and Zn(OH){sub 2} was identified and X-ray diffraction patterns exhibited a clear peak corresponding to ZnS hexagonal phase (1 0 3) plane, which was confirmed by electron diffraction patterns. From morphological studies, compact samples with well-defined particles, low roughness, homogeneous and pinhole-free in the surface were observed. From obtained results, it is evident that deposits of ZnS–CBD using a non-toxic solution are suitable as window layer for TFSC.

  3. Nonlinear optical characterization of ZnS thin film synthesized by chemical spray pyrolysis method

    NASA Astrophysics Data System (ADS)

    G, Sreeja V.; V, Sabitha P.; Anila, E. I.; R, Reshmi; John, Manu Punnan; Radhakrishnan, P.

    2014-10-01

    ZnS thin film was prepared by Chemical Spray Pyrolysis (CSP) method. The sample was characterized by X-ray diffraction method and Z scan technique. XRD pattern showed that ZnS thin film has hexagonal structure with an average size of about 5.6nm. The nonlinear optical properties of ZnS thin film was studied by open aperture Z-Scan technique using Q-switched Nd-Yag Laser at 532nm. The Z-scan plot showed that the investigated ZnS thin film has saturable absorption behavior. The nonlinear absorption coefficient and saturation intensity were also estimated.

  4. Nonlinear optical characterization of ZnS thin film synthesized by chemical spray pyrolysis method

    SciTech Connect

    G, Sreeja V; Anila, E. I. R, Reshmi John, Manu Punnan; V, Sabitha P; Radhakrishnan, P.

    2014-10-15

    ZnS thin film was prepared by Chemical Spray Pyrolysis (CSP) method. The sample was characterized by X-ray diffraction method and Z scan technique. XRD pattern showed that ZnS thin film has hexagonal structure with an average size of about 5.6nm. The nonlinear optical properties of ZnS thin film was studied by open aperture Z-Scan technique using Q-switched Nd-Yag Laser at 532nm. The Z-scan plot showed that the investigated ZnS thin film has saturable absorption behavior. The nonlinear absorption coefficient and saturation intensity were also estimated.

  5. Nanocrystalline silicon based thin film solar cells

    NASA Astrophysics Data System (ADS)

    Ray, Swati

    2012-06-01

    Amorphous silicon solar cells and panels on glass and flexible substrate are commercially available. Since last few years nanocrystalline silicon thin film has attracted remarkable attention due to its stability under light and ability to absorb longer wavelength portion of solar spectrum. For amorphous silicon/ nanocrystalline silicon double junction solar cell 14.7% efficiency has been achieved in small area and 13.5% for large area modules internationally. The device quality nanocrystalline silicon films have been fabricated by RF and VHF PECVD methods at IACS. Detailed characterizations of the materials have been done. Nanocrystalline films with low defect density and high stability have been developed and used as absorber layer of solar cells.

  6. Influence of the Ultrasonic Vibration on Chemical Bath Deposition of ZnS Thin Films

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Mao, Guobing

    Chemical bath deposition (CBD) and ultrasonic chemical bath deposition (US-CBD) of ZnS thin films from NH4OH/SC(NH2)2/ZnSO4 solutions have been studied. The influence of the ultrasonic vibration on properties of ZnS thin films has been investigated. The growth rate, structure, and properties of ZnS thin film deposited by different CBD techniques were studied using X-ray diffractometer (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM). The results show that the growth rate of US-CBD is slower than that of CBD. The XRD analysis of as-deposited ZnS films shows that the films are both cubic ZnS structure and the crystallinity of US-CBD ZnS film is higher than that of CBD ZnS film. SEM studies indicate that adhesion particles on the US-CBD ZnS surface are fewer than that on the CBD ZnS surface. Moreover, the film prepared by US-CBD is homogeneous and with high compactness. The rms roughness (Rrms) value of CBD ZnS film is higher than that of US-CBD. Transmission measurement shows that the optical transmittance of US-CBD ZnS is higher than that of CBD ZnS, and the optical transmittance is above 90% when the wavelength is over 470 nm. The band gap (Eg) values of the films deposited by CBD and US-CBD are 3.50 and 3.67 eV, respectively.

  7. Microstructural characterization of textured ZnS thin films

    SciTech Connect

    Kryshtab, T. . E-mail: tkrysh@esfm.ipn.mx; Andraca-Adame, J.A.; Kryvko, A.

    2007-08-15

    During thin film growth texture formation is controlled by several kinetic parameters that determine the grain structural evolution. For highly textured thin films, i.e. only one strong peak can be obtained from X-ray diffraction pattern, it is impossible to separate the effect of grain size and residual strains based on peak broadening. We propose an original method for evaluating residual strains, eliminating their contribution in peak breadth and determining the domain size. A two-axes diffractometer with a Ge monochromator and a K {sub {alpha}}{sub 1,2} doublet was used for this study. The measurements of 2{theta} scans were carried out in the grazing geometry for the incident beam. ZnS thin films as-deposited and annealed were studied. Structural analysis was carried out using a one-axis diffractometer for a {theta}-2{theta} scan in the standard symmetric geometry. Surface morphology was explored by atomic force microscopy. The specification of the proposed method and its application in microstructural characterization are introduced.

  8. Microstructural characterization in nanocrystalline ceramic thin films

    NASA Astrophysics Data System (ADS)

    Kim, Hakkwan

    The primary objective of this research is to investigate the effects of process variables on microstructure in several fluoride and oxide thin films prepared by vapor deposition, in order to predict the properties and behaviors of nanocrystalline thin film materials. There are three distinct stages of this research. The first stage focuses on measuring of the porosity in polycrystalline thin films of a variety of fluorides as a function of the substrate temperature during deposition, and discussing the mechanism by which the porosity varies as a function of the process variables. We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF 2) and calcium fluoride (CaF2) using an atomic force microscope (AFM) and a quartz crystal thickness monitor. The porosity is very sensitive to the substrate temperature and decreases as the substrate temperature increases. Consistent behavior is observed among all of the materials in this study. The second stage is to understand the film microstructure including grain growth and texture development, because these factors are known to influence the behavior and stability of polycrystalline thin films. This study focuses on grain growth and texture development in polycrystalline lithium fluoride thin films using dark field (DF) transmission electron microscopy (TEM). It is demonstrated that we can isolate the size distribution of <111> surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction (XRD) and AFM, respectively. The grain size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to the {111}-oriented grains which do not grow significantly, while

  9. Post-annealing effects on ZnS thin films grown by using the CBD method

    NASA Astrophysics Data System (ADS)

    Ahn, Heejin; Um, Youngho

    2015-09-01

    Herein, the structural, morphological, and optical properties of zinc sulfide (ZnS) thin films deposited via the chemical bath deposition method are reported. These films were deposited on soda-lime glass (SLG) substrates by using ZnSO4, thiourea, and 25% ammonia at 90 °C. The effect of changing the annealing temperature from 100 °C to 300 °C on the properties of the ZnS thin films was investigated. X-ray diffraction (XRD) patterns showed that the ZnS thin film annealed at 100 °C had an amorphous structure; however, as the annealing temperature was increased, the crystalline quality of the thin film was enhanced. Moreover, transmission measurements showed that the optical transmittance was about 80% for wavelengths above 500 nm. The band gap energy (E g ) value of the film annealed at 300 °C was decreased to about 3.82 eV.

  10. Preparation and optical properties of chemical bath deposited ZnS thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoli; Qin, Juan; Chen, Zhenyi; Zhang, Min; Li, Jirong; Shi, Weimin; Wang, Linjun

    2011-02-01

    In this paper we study chemical bath deposition of ZnS thin films on glass slides with two different kinds of systems, that is, hydrazine hydrate system (N2H4•H2O/NH3•H2O/SC(NH2)2/ZnSO4) and citric acid system (C6H8O7/NH3•H2O/ SC(NH2)2/ZnSO4) in aqueous solution. The properties of ZnS thin films are characterized by X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy. The optical band gap is calculated from transmission spectra. The results show that ZnS thin films in citric acid system have better crystallization, higher transmittance and much lesser white spots which might be colloidal particles sedimentation mixed with ZnS, indicating that ZnS thin films prepared using citric acid system being more suitable for the buffer layer of CIGS solar cells.

  11. Preparation and optical properties of chemical bath deposited ZnS thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoli; Qin, Juan; Chen, Zhenyi; Zhang, Min; Li, Jirong; Shi, Weimin; Wang, Linjun

    2010-10-01

    In this paper we study chemical bath deposition of ZnS thin films on glass slides with two different kinds of systems, that is, hydrazine hydrate system (N2H4•H2O/NH3•H2O/SC(NH2)2/ZnSO4) and citric acid system (C6H8O7/NH3•H2O/ SC(NH2)2/ZnSO4) in aqueous solution. The properties of ZnS thin films are characterized by X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy. The optical band gap is calculated from transmission spectra. The results show that ZnS thin films in citric acid system have better crystallization, higher transmittance and much lesser white spots which might be colloidal particles sedimentation mixed with ZnS, indicating that ZnS thin films prepared using citric acid system being more suitable for the buffer layer of CIGS solar cells.

  12. ZnS thin films deposition by thermal evaporation for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Benyahia, K.; Benhaya, A.; Aida, M. S.

    2015-10-01

    ZnS thin films were deposited on glass substrates by thermal evaporation from millimetric crystals of ZnS. The structural, compositional and optical properties of the films are studied by X-ray diffraction, SEM microscopy, and UV-VIS spectroscopy. The obtained results show that the films are pin hole free and have a cubic zinc blend structure with (111) preferential orientation. The estimated optical band gap is 3.5 eV and the refractive index in the visible wavelength ranges from 2.5 to 1.8. The good cubic structure obtained for thin layers enabled us to conclude that the prepared ZnS films may have application as buffer layer in replacement of the harmful CdS in CIGS thin film solar cells or as an antireflection coating in silicon-based solar cells.

  13. Process and film characterization of chemical-bath-deposited ZnS thin films

    SciTech Connect

    Dona, J.M.; Herrero, J.

    1994-01-01

    Chemical-bath deposition of ZnS thin films from NH{sub 3}/NH{sub 2}-NH{sub 2}/SC(NH{sub 2}){sub 2}/ZnSO{sub 4} solutions has been studied. The effect of various process parameters on the growth and the film quality is presented. A first approach to a mechanistic interpretation of the chemical process is reported. The structural, optical, chemical, and electrical properties of the ZNS thin films deposited by this method have been studied. The electron diffraction (EDS) analysis shows that the films are microcrystalline with a cubic structure. EDS analysis has demonstrated that the films are highly stoichiometric. Scanning electron microscopy studies of the ZnS thin films deposited by this method show that the films are continuous and homogeneous. Electrical conductivity measurements have shown the highly resistivity nature of these films ({sigma} = 10{sup {minus}9} S/cm).

  14. Optical Characteristics of La-Doped ZnS Thin Films Prepared by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Xie, Hai-Qing; Chen, Yuan; Huang, Wei-Qing; Huang, Gui-Fang; Peng, Ping; Peng, Li; Wang, Tai-Hong; Zeng, Yun

    2011-02-01

    Undoped and La-doped ZnS thin films are prepared by chemical bath deposition (CBD) process through the co-precipitation reaction of inorganic precursors zinc sulfate, thiosulfate ammonia and La2O3. Composition of the films is analyzed using an energy-dispersive x-ray spectroscopy (EDS). Absorption spectra and spectral transmittances of the films are measured using a double beam UV-VIS spectrophotometer (TU-1901). It is found that significant red shifts in absorption spectra and decrease in absorptivity are obtained with increasing lanthanum. Moreover, optical transmittance is increased as La is doped, with a transmittance of more than 80% for wavelength above 360 nm in La-doped ZnS thin films. Compared to pure ZnS, the band gap decreases and flat-band potential positively shifts to quasi-metal for the La-doped ZnS. These results indicate that La-doped ZnS thin films could be valuably adopted as transparent electrodes.

  15. Nanocrystalline silicon thin films for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Queen, Daniel; Jugdersuren, Battogtokh; Culberston, Jim; Wang, Qi; Nemeth, William; Metcalf, Tom; Liu, Xiao

    2014-03-01

    Recent advances in thermoelectric materials have come from reductions in thermal conductivity by manipulating both chemical composition and nanostructure to limit the phonon mean free path. However, wide spread applications for some of these materials may be limited due to high raw material and integration costs. In this talk we will discuss our recent results on nanocrystalline silicon thin films deposited by both hot-wire and plasma enhanced chemical vapor deposition where the nanocrystal size and crystalline volume fraction are varied by dilution of the silane precursor gas with hydrogen. Nanocyrstalline silicon is an established material technology used in multijunction amorphous silicon solar cells and has the potential to be a low cost and scalable material for use in thermoelectric devices. This work supported by the Office of Naval Research and the National Research Council.

  16. Influence of Deposition Time on ZnS Thin Films Performance with Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Zhou, Limei; Tang, Nan; Wu, Sumei; Hu, Xiaofei; Xue, Yuzhi

    ZnS thin films had been deposited by chemical bath deposition method onto glass substrates in alkaline liquor. The reaction solution is made of ZnSO4, NH4OH and SC(NH2)2. Different deposition times (1 h, 1.5 h, 2 h, 2.5 h and 3 h) were selected to study the performance of ZnS thin films. As the results, the ZnS films' thickness were about 50-207 nm. XRD results showed an amorphous structure. Through comparing the surface morphology before and after annealing, it could be seen that annealing made some particles grow up and the surface smooth and even. The transmittance decreased with the increase of deposition time in the range of 300-800 nm. The transmittance of annealed ZnS film was lower than that of deposited one in the range of 300-800 nm. The ZnS band gap values were calculated in the range of 3.72-3.9 eV.

  17. Preparation and characterization of ZnS thin films by the chemical bath deposition method (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ando, Shizutoshi; Iwashita, Taisuke

    2017-06-01

    Nowadays, the conversion efficiency of Cu(In・Ga)Se2 (CIGS)-based solar cell already reached over 20%. CdS thin films prepared by chemical bath deposition (CBD) method are used for CIGS-based thin film solar cells as the buffer layer. Over the past several years, a considerable number of studies have been conducted on ZnS buffer layer prepared by CBD in order to improve in conversion efficiency of CIGS-based solar cells. In addition, application to CIGS-based solar cell of ZnS buffer layer is expected as an eco-friendly solar cell by cadmium-free. However, it was found that ZnS thin films prepared by CBD included ZnO or Zn(OH)2 as different phase [1]. Nakata et. al reported that the conversion efficiency of CIGS-based solar cell using ZnS buffer layer (CBD-ZnS/CIGS) reached over 18% [2]. The problem which we have to consider next is improvement in crystallinity of ZnS thin films prepared by CBD. In this work, we prepared ZnS thin films on quarts (Si02) and SnO2/glass substrates by CBD with the self-catalysis growth process in order to improve crystallinity and quality of CBD-ZnS thin films. The solution to use for CBD were prepared by mixture of 0.2M ZnI2 or ZnSO4, 0.6M (NH2)2CS and 8.0M NH3 aq. In the first, we prepared the particles of ZnS on Si02 or SnO2/glass substrates by CBD at 80° for 20 min as initial nucleus (1st step ). After that, the particles of ZnS on Si02 or SnO2/glass substrates grew up to be ZnS thin films by CBD method at 80° for 40 min again (2nd step). We found that the surface of ZnS thin films by CBD with the self-catalyst growth process was flat and smooth. Consequently, we concluded that the CBD technique with self-catalyst growth process in order to prepare the particles of ZnS as initial nucleus layer was useful for improvement of crystallinity of ZnS thin films on SnO2/glass. [1] J.Vidal et,al., Thin Solid Films 419 (2002) 118. [2] T.Nakata et.al., Jpn. J. Appl. Phys. 41(2B), L165-L167 (2002)

  18. Structural and optical properties of ZnS thin films deposited by RF magnetron sputtering

    PubMed Central

    2012-01-01

    Zinc sulfide [ZnS] thin films were deposited on glass substrates using radio frequency magnetron sputtering. The substrate temperature was varied in the range of 100°C to 400°C. The structural and optical properties of ZnS thin films were characterized with X-ray diffraction [XRD], field emission scanning electron microscopy [FESEM], energy dispersive analysis of X-rays and UV-visible transmission spectra. The XRD analyses indicate that ZnS films have zinc blende structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM data also reveal that the films have nano-size grains with a grain size of approximately 69 nm. The films grown at 350°C exhibit a relatively high transmittance of 80% in the visible region, with an energy band gap of 3.79 eV. These results show that ZnS films are suitable for use as the buffer layer of the Cu(In, Ga)Se2 solar cells. PMID:22221917

  19. Effect of [Zn]/[S] ratios on the properties of chemical bath deposited zinc sulfide thin films

    NASA Astrophysics Data System (ADS)

    Li, Z. Q.; Shi, J. H.; Liu, Q. Q.; Wang, Z. A.; Sun, Z.; Huang, S. M.

    2010-10-01

    ZnS thin films have been prepared by chemical bath deposition (CBD) technique onto glass substrates deposited at about 80 °C using aqueous solution of zinc sulfate hepta-hydrate, ammonium sulfate, thiourea, ammonia and hydrazine hydrate. Ammonia and hydrazine hydrate were used as complexing agents. The influence of the ratio of [Zn]/[S] on formation and properties of ZnS thin films has been investigated. The ratio of [Zn]/[S] was changed from 3:1 to 1:9 by varying volumes and/or concentrations of zinc sulfate hepta-hydrate and thiourea in the deposition solution. The structural and morphological characteristics of films have been investigated by X-ray diffraction (XRD), scanning electron microscope and UV-vis spectroscopic analysis. ZnS films were obtained with the [Zn]/[S] ratio ranged from1:1 to 1:6. In the cases of [Zn]/[S] ratio ≥ 3:1 or ≤1:9, no deposition was found. Transparent and polycrystalline ZnS film was obtained with pure-wurtzite structure at the [S]/[Zn] ratio of 1:6. The related formation mechanisms of CBD ZnS are discussed. The deposited ZnS films show good optical transmission (80-90%) in the visible region and the band gap is found to be in the range of 3.65-3.74 eV. The result is useful to further develop the CBD ZnS technology.

  20. Effects of zinc salts on the structural and optical properties of acidic chemical bath deposited ZnS thin films

    SciTech Connect

    Cao, Meng; Zhang, Bin Lei; Li, Liang; Huang, Jian; Zhao, Shou Ren; Cao, Hong; Jiang, Jin Chun; Sun, Yan; Shen, Yue

    2013-02-15

    Graphical abstract: XRD patterns of annealed ZnS films from different zinc salts. Curves a, b, c, d correspond to the annealed ZnS–C1, ZnS–S{sub 3}, ZnS–Cl{sub 2}, ZnS–N{sub 2} thin films. Display Omitted Highlights: ► ZnS thin films were deposited using different zinc salts. ► The grain sizes of deposited ZnS thin films are about 12.5 15.5 nm. ► The band gaps of deposited ZnS thin films were in the range of 3.66–3.83 eV. -- Abstract: ZnS thin films were deposited from different zinc salts by chemical bath deposition (CBD). Structural, morphological and optical characterizations were performed using different methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectra. The particle sizes of as-deposited ZnS thin films were calculated to be about 12.5–15.5 nm and the crystal qualities were improved after annealed at 500 °C in Ar/H{sub 2}S (5%) atmosphere. Optical absorption measurements indicated that the band gaps of ZnS thin films were in the range of 3.66–3.83 eV and they decreased with the increasing of particle sizes. ZnCl{sub 2} was found to the best precursor due to the higher crystal quality and compact surface of deposited ZnS thin films.

  1. Protein-modified nanocrystalline diamond thin films for biosensor applications

    NASA Astrophysics Data System (ADS)

    Härtl, Andreas; Schmich, Evelyn; Garrido, Jose A.; Hernando, Jorge; Catharino, Silvia C. R.; Walter, Stefan; Feulner, Peter; Kromka, Alexander; Steinmüller, Doris; Stutzmann, Martin

    2004-10-01

    Diamond exhibits several special properties, for example good biocompatibility and a large electrochemical potential window, that make it particularly suitable for biofunctionalization and biosensing. Here we show that proteins can be attached covalently to nanocrystalline diamond thin films. Moreover, we show that, although the biomolecules are immobilized at the surface, they are still fully functional and active. Hydrogen-terminated nanocrystalline diamond films were modified by using a photochemical process to generate a surface layer of amino groups, to which proteins were covalently attached. We used green fluorescent protein to reveal the successful coupling directly. After functionalization of nanocrystalline diamond electrodes with the enzyme catalase, a direct electron transfer between the enzyme's redox centre and the diamond electrode was detected. Moreover, the modified electrode was found to be sensitive to hydrogen peroxide. Because of its dual role as a substrate for biofunctionalization and as an electrode, nanocrystalline diamond is a very promising candidate for future biosensor applications.

  2. Biomolecularly capped uniformly sized nanocrystalline materials: glutathione-capped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Torres-Martínez, Claudia L.; Nguyen, Liem; Kho, Richard; Bae, Weon; Bozhilov, Krassimir; Klimov, Victor; Mehra, Rajesh K.

    1999-09-01

    Micro-organisms such as bacteria and yeasts form CdS to detoxify toxic cadmium ions. Frequently, CdS particles formed in yeasts and bacteria were found to be associated with specific biomolecules. It was later determined that these biomolecules were present at the surface of CdS. This coating caused a restriction in the growth of CdS particles and resulted in the formation of nanometre-sized semiconductors (NCs) that exhibited typical quantum confinement properties. Glutathione and related phytochelatin peptides were shown to be the biomolecules that capped CdS nanocrystallites synthesized by yeasts Candida glabrata and Schizosaccharomyces pombe. Although early studies showed the existence of specific biochemical pathways for the synthesis of biomolecularly capped CdS NCs, these NCs could be formed in vitro under appropriate conditions. We have recently shown that cysteine and cysteine-containing peptides such as glutathione and phytochelatins can be used in vitro to dictate the formation of discrete sizes of CdS and ZnS nanocrystals. We have evolved protocols for the synthesis of ZnS or CdS nanocrystals within a narrow size distribution range. These procedures involve three steps: (1) formation of metallo-complexes of cysteine or cysteine-containing peptides, (2) introduction of stoichiometric amounts of inorganic sulfide into the metallo-complexes to initiate the formation of nanocrystallites and finally (3) size-selective precipitation of NCs with ethanol in the presence of Na+. The resulting NCs were characterized by optical spectroscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction and electron diffraction. HRTEM showed that the diameter of the ZnS-glutathione nanocrystals was 3.45+/-0.5 nm. X-ray diffraction and electron diffraction analyses indicated ZnS-glutathione to be hexagonal. Photocatalytic studies suggest that glutathione-capped ZnS nanocrystals prepared by our procedure are highly efficient in degrading a test model

  3. Scalable production of microbially-mediated ZnS nanoparticles and application to functional thin films

    SciTech Connect

    Moon, Ji Won; Ivanov, Ilia N; Joshi, Pooran C; Armstrong, Beth L; Wang, Wei; Jung, Hyunsung; Rondinone, Adam Justin; Jellison Jr, Gerald Earle; Meyer III, Harry M; Jang, Gyoung Gug; Meisner, Roberta; Duty, Chad E; Phelps, Tommy Joe

    2014-01-01

    A series of semiconducting zinc sulfide (ZnS) nanoparticles were scalably, reproducibly, controllably, and economically synthesized with anaerobic metal-reducing Thermoanaerobacter species. They reduced partially oxidized sulfur sources to sulfides that extracellularly and thermodynamically incorporated with zinc ions to produce sparingly soluble ZnS nanoparticles with ~5 nm crystallites at yields of ~5 g l 1 month 1. A predominant sphalerite formation was facilitated by rapid precipitation kinetics, low cation/anion ratio, higher zinc concentration, water stabilization, or some combination of the four. The sphalerite ZnS nanoparticles exhibited narrow size distribution, high emission intensity, and few native defects. Scale-up and emission tunability using copper-doping were confirmed spectroscopically. Surface characterization was determined using Fourier transform infrared and X-ray photoelectron spectroscopies, which confirmed amine and carboxylic acid not only maintaining a nano-dimensional average crystallite size, but also increasing aggregation. Application of ZnS nanoparticle ink to a functional thin film was successfully tested for potential future applications.

  4. Electroluminescence spectra of rare-earth-doped ZnS 1-XSe X thin films

    NASA Astrophysics Data System (ADS)

    Miura, Noboru; Ogawa, Kiyoshi; Kobayashi, Shuko; Matsumoto, Hironaga; Nakano, Ryotaro

    1994-04-01

    Electroluminescence has been measured for ZnS 1- XSe X thin films doped with rare-earth ions. As X increases the band-gap energy of the host decreases. The emission levels of trivalent rare-earth ions are not observed when the band-gap energy is narrower than the excitation levels. This is because of the energy transfer between the host and the emission center.

  5. ZnS nanostructured thin-films deposited by successive ionic layer adsorption and reaction

    NASA Astrophysics Data System (ADS)

    Deshmukh, S. G.; Jariwala, Akshay; Agarwal, Anubha; Patel, Chetna; Panchal, A. K.; Kheraj, Vipul

    2016-04-01

    ZnS thin films were grown on glass substrate using successive ionic layer adsorption and reaction (SILAR) technique at room temperature. Aqueous solutions of ZnCl2 and Na2S were used as precursors. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy and optical absorption measurements were applied to study the structural, surface morphology and optical properties of as-deposited ZnS thin films. The X-ray diffraction profiles revealed that ZnS thin films consist of crystalline grains with cubic phase. Spherical nano grains of random size and well covered on the glass substrate were observed from FESEM. The average grain size were found to be 77 nm, 100 nm and 124 nm for 20 cycles, 40 cycles and 60 cycles samples respectively. For 60 cycle sample, Raman spectra show two prominent peaks at 554 cm-1 and 1094 cm-1. The optical band gap values were found to be 3.76 eV, 3.72 eV and 3.67 eV for 20 cycle, 40 cycle and 60 cycle samples respectively.

  6. ZnS nanostructured thin-films deposited by successive ionic layer adsorption and reaction

    SciTech Connect

    Deshmukh, S. G. Jariwala, Akshay; Agarwal, Anubha; Patel, Chetna; Kheraj, Vipul; Panchal, A. K.

    2016-04-13

    ZnS thin films were grown on glass substrate using successive ionic layer adsorption and reaction (SILAR) technique at room temperature. Aqueous solutions of ZnCl{sub 2} and Na{sub 2}S were used as precursors. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy and optical absorption measurements were applied to study the structural, surface morphology and optical properties of as-deposited ZnS thin films. The X-ray diffraction profiles revealed that ZnS thin films consist of crystalline grains with cubic phase. Spherical nano grains of random size and well covered on the glass substrate were observed from FESEM. The average grain size were found to be 77 nm, 100 nm and 124 nm for 20 cycles, 40 cycles and 60 cycles samples respectively. For 60 cycle sample, Raman spectra show two prominent peaks at 554 cm{sup −1} and 1094 cm{sup −1}. The optical band gap values were found to be 3.76 eV, 3.72 eV and 3.67 eV for 20 cycle, 40 cycle and 60 cycle samples respectively.

  7. Effect of anionic concentration on the structural and optical properties of nanostructured ZnS thin films

    NASA Astrophysics Data System (ADS)

    Safeera, T. A.; Johns, N.; Anila, E. I.

    2016-08-01

    Nanostructured Zinc Sulfide (ZnS) thin films with wurtzite structure were prepared by chemical spray pyrolysis method at low temperature. The effect of sulfur concentration on the structural and optical properties of ZnS thin films was studied. The films were analysed by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and photoluminescence (PL). Nano grain formation of ZnS was observed from XRD and SEM. Variation in band gap of different films is in agreement with size effects. But there is a red shift in the band gap of these films compared to bulk ZnS. This is due to band tailing effect experienced by the films due to the presence of large number of defects which was verified by PL spectrum. The overall emission was blue in colour for all the films and it was confirmed by Commission International d'Eclairage (CIE) diagram.

  8. Growth and characterization studies of ZnS thin films prepared by single source evaporation technique

    NASA Astrophysics Data System (ADS)

    Maligi, Anantha Sunil; Jampana, Nagaraju; Gowravaram, Mohan Rao

    2017-05-01

    Zinc sulfide thin films are deposited on glass substrates using thermal evaporation technique. Effect of thickness on the properties of as-deposited ZnS films is studied. ZnS films exhibited cubic structure with preferential orientation along (111) plane. All the films exhibited n-type conductivity with resistivity ranging in the order of 105 to 106 Ω-cm. The transmittance in the visible region is in the range of 80 to 89% and the band gap of the material varied from 3.65 to 3.52 eV. The as-deposited films can be used as window layer for fabrication of hetero-junction solar cell.

  9. Effects of pH on the characteristics of ZnS thin films grown by using the CBD method

    NASA Astrophysics Data System (ADS)

    Ahn, Heejin; Lee, Dongchan; Park, Sujung; Um, Youngho

    In CIGS-based thin film solar cells, a chemically deposited ZnS buffer layer with high resistivity is generally used between the absorber layer and transparent conducting oxide layer. In this work, we report a chemical process to prepare ZnS films by the CBD technique based on the typical bath deposition. The influences of ammonia (NH4OH) and Na2EDTA (Na2C10H16N2O8) as complexing agents on structural, morphological, and optical properties of ZnS thin films are investigated ranging pH concentration from 5 to 10. To investigate effects of pH on the characteristics of ZnS thin films, by using UV-visible transmittance, atomic force microscopy, and optical absorption were investigated. With changing the pH range, the ZnS thin films demonstrate high transmittance of 75~80% in the visible region, indicating the films are potentially useful in photovoltaic applications. The results will be presented in detail. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (2011-0024709).

  10. Thermal Conductivity in Nanocrystalline Ceria Thin Films

    SciTech Connect

    Marat Khafizov; In-Wook Park; Aleksandr Chernatynskiy; Lingfeng He; Jianliang Lin; John J. Moore; David Swank; Thomas Lillo; Simon R. Phillpot; Anter El-Azab; David H. Hurley

    2014-02-01

    The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser-based modulated thermoreflectance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO2. A variety of microstructure imaging techniques including X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries.

  11. Unprecedented coloration of rutile titanium dioxide nanocrystalline thin films.

    PubMed

    Mane, Rajaram S; Joo, Oh-Shim; Lee, Won Joo; Han, Sung-Hwan

    2007-01-01

    In this communication, TiO2 nanocrystalline thin films synthesized by a room temperature (27 degrees C) chemical dip process. To our knowledge, this is first report of the preparation of nanoscale rutile TiO2 particles from common inorganic salt at such low temperature. Interestingly, unprecedented dynamic color change accompanies with titanium dioxide grain size, which can be seen with the naked eye that generated curiosity in our mind to check UV-vis absorption, where significant changes were observed. The room temperature synthesized thin films of rutile titanium dioxide make it a potential candidate for high-compatibility material, which can be used in artificial heart valves.

  12. Electrical characterization of nanocrystalline zinc selenide thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Jeewan; Shikha, Deep; Tripathi, Surya Kant

    2012-08-01

    In the present paper, we have studied the effect of photo-illumination on electrical properties of nanocrystalline ZnSe thin films. The ZnSe thin films with different grain sizes (coherently diffracting domains) have been prepared. The semiconducting material with the composition Zn25Se75 has been prepared using melt-quenching technique. Thermal evaporation technique has been used to prepare nanocrystalline ZnSe thin films on highly cleaned glass substrates at different partial pressures of Ar gas. The grain size has been controlled by the partial pressure of inert gas. The grain size has been calculated using X-ray diffraction plots. Mobility activation has been studied from the photocurrent decay curves. The effective density of states ( N eff), frequency factor ( S), and trap depth ( E) have been calculated for all the films having different grain sizes. Three different types of trap levels have been found in these films. There is a linear distribution of traps having different energies below the conduction band. The increase in photoconductivity is explained in terms of built in potential barriers ( ϕ b) at the grain boundaries.

  13. Metal Chalcogenide Nanocrystalline Solid Thin Films

    NASA Astrophysics Data System (ADS)

    Deo, Soumya R.; Singh, Ajaya K.; Deshmukh, Lata; Abu Bin Hasan Susan, Md.

    2015-11-01

    Over the past decades, chemical bath deposition (CBD) has proven its suitability and has established itself as one of the prominent techniques for depositing different metal chalcogenide semiconductor thin films via ion-by-ion or by adsorption of colloidal particles from the chemical bath on the substrate. It is a simple, cost-effective and convenient method for large-scale deposition and has recently received a surge of interest. This article reviews the research progress in various methods or techniques including CBD for the preparation and study of the properties of metal chalcogenides. Various parameters for efficient preparation and variation in structural, morphological, compositional, optical properties, etc. are also briefly discussed.

  14. Study of structural and optical properties of ZnS zigzag nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Rahchamani, Seyyed Zabihollah; Rezagholipour Dizaji, Hamid; Ehsani, Mohammad Hossein

    2015-11-01

    Zinc sulfide (ZnS) nanostructured thin films of different thicknesses with zigzag shapes have been deposited on glass substrates by glancing angle deposition (GLAD) technique. Employing a homemade accessory attached to the substrate holder enabled the authors to control the substrate temperature and substrate angle. The prepared samples were subjected to X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and UV-VIS. spectroscopy techniques. The structural studies revealed that the film deposited at room temperature crystallized in cubic structure. The FESEM images of the samples confirmed the formation of zigzag nano-columnar shape with mean diameter about 60-80 nm. By using the data obtained from optical studies, the real part of the refractive index (n), the absorption coefficient (α) and the band gap (Eg) of the samples were calculated. The results show that the refractive indices of the prepared films are very sensitive to deposition conditions.

  15. Photochemical Deposition of ZnS Thin Films by Intermittent Illumination

    NASA Astrophysics Data System (ADS)

    Ichimura, Masaya; Kobayashi, Ryohei; Miyawaki, Tetsuya

    2004-09-01

    We prepared ZnS thin films by photochemical deposition (PCD) using continuous and intermittent illumination. The aqueous solution used for the deposition contains ZnSO4 and Na2S2O3, and H2SO4 for pH adjustment. The solution is illuminated with light from an ultrahigh-pressure mercury arc lamp. When the illumination is continuous, the deposited film is black and not transparent because of excess zinc in the film. When the illumination is turned on and off periodically by a mechanical shutter, the deposited film becomes gradually transparent with increasing “off” time. The film deposited by the intermittent illumination has an optical absorption edge near 350 nm and shows photoconductivity.

  16. Stacking faults-mediated ultrastrong nanocrystalline Ti thin films.

    PubMed

    Wu, Kai; Zhang, Jinyu; Li, Gen; Wang, Yaqiang; Cui, Junchao; Liu, Gang; Sun, Jun

    2017-08-25

    In this work, we prepared nanocrystalline (NC) Ti thin films with abundant stacking faults (SFs), which are created via partial dislocations emitted from grain boundaries and insensitive to grain sizes. By employing the nanoindentation test, we investigated the effects of SFs and grain sizes on the strength of NC Ti films at room temperature. The high density of SFs significantly strengthens NC Ti films via dislocation-SF interactions associated with the reported highest Hall-Petch slope of ~20 GPa•nm1/2 to ultrahigh strength of ~4.4 GPa, approaching ~50% of its ideal strength. © 2017 IOP Publishing Ltd.

  17. Study of the morphology of ZnS thin films deposited on different substrates via chemical bath deposition.

    PubMed

    Gómez-Gutiérrez, Claudia M; Luque, P A; Castro-Beltran, A; Vilchis-Nestor, A R; Lugo-Medina, Eder; Carrillo-Castillo, A; Quevedo-Lopez, M A; Olivas, A

    2015-01-01

    In this work, the influence of substrate on the morphology of ZnS thin films by chemical bath deposition is studied. The materials used were zinc acetate, tri-sodium citrate, thiourea, and ammonium hydroxide/ammonium chloride solution. The growth of ZnS thin films on different substrates showed a large variation on the surface, presenting a poor growth on SiO2 and HfO2 substrates. The thin films on ITO substrate presented a uniform and compact growth without pinholes. The optical properties showed a transmittance of about 85% in the visible range of 300-800 nm with band gap of 3.7 eV. © Wiley Periodicals, Inc.

  18. Morphological, luminescence and structural properties of nanocrystalline silicon thin films

    SciTech Connect

    Ali, Atif Mossad; Kobayashi, Hikaru; Inokuma, Takao; Al-Hajry, Ali

    2013-03-15

    Highlights: ► The PL spectra showed two stronger peaks and one weaker peak. ► The PL peak energies and optical band-gap values were found higher than 1.12 eV. ► The structural change from an amorphous to nanocrystalline with increasing [SiH{sub 4}]. - Abstract: Nanocrystalline silicon (nc-Si) thin films deposited by plasma-enhanced chemical vapor deposition at various silane flow rates ([SiH{sub 4}]) are studied. The characterization of these films by high-resolution transmission electron microscopy, Raman spectroscopy and X-ray diffraction reveals that no film and very thin film is deposited at [SiH{sub 4}] = 0.0 and 0.1 sccm, respectively. In addition, the structural change from an amorphous to a nanocrystalline phase occurs at around [SiH{sub 4}] = 0.2 sccm. In this study, the importance of arriving species at surfaces and precursors is clearly demonstrated by the effect of a small addition of SiH{sub 4} on the frequency and width of a Raman peak and the structure of the grown film. The infrared spectroscopic analysis shows no hydrogen incorporation in the nc-Si film deposited at the low value of [SiH{sub 4}]. However, the intensity of the peak around 2100 cm{sup −1} due to SiH decreases with increasing [SiH{sub 4}]. All fabricated films give photoluminescence in the range between 1.7 and 2.4 eV at room temperature, indicating enlargement of the band-gap energy. The presence of very small crystallites leads to the appearance of quantum confinement effects. The variations of the photoluminescence energy and spectral width are well correlated with the structural properties of the films such as crystallite size, crystalline volume fraction, and the density of Si-H bonds.

  19. Low temperature oxidation mechanisms of nanocrystalline magnetite thin film

    SciTech Connect

    Bourgeois, F.; Gergaud, P.; Feuillet, G.; Renevier, H.; Leclere, C.

    2013-01-07

    A detailed investigation of the mechanisms related to the low temperature oxidation of nanocrystalline magnetite thin films into maghemite is presented. Despite strong differences in the functional properties of these two phases, structural similarities make it difficult to distinguish between them, and to quantify the oxidation process, particularly in the case of nanostructured polycrystalline layers. Contrary to the case of bulk materials or monocrystalline films and particles, the oxidation processes in nanocrystalline thin film have only scarcely been studied. In this work, structural and optical techniques, including X-ray diffraction (XRD), EXAFS/X-ray absorption near edge structure, FTIR, and Raman scattering, have been used to estimate the oxidation rate of magnetite. The overall oxidation reaction rates are discussed in the framework of two limiting cases corresponding to intra grain diffusion and to grain boundary diffusion. SIMS profiling and electrical measurements were also carried out to better assess the oxidation quantification in order to conclude on the predominant oxidation mechanisms in this heterogeneous material. We propose a qualitative model for the structure, in terms of insulating zone distribution, for partially oxidized films.

  20. The radiation response of mesoporous nanocrystalline zirconia thin films

    NASA Astrophysics Data System (ADS)

    Manzini, Ayelén M.; Alurralde, Martin A.; Giménez, Gustavo; Luca, Vittorio

    2016-12-01

    The next generation of nuclear systems will require materials capable of withstanding hostile chemical, physical and radiation environments over long time-frames. Aside from its chemical and physical stability, crystalline zirconia is one of the most radiation tolerant materials known. Here we report the first ever study of the radiation response of nanocrystalline and mesoporous zirconia and Ce3+-stabilized nanocrystalline zirconia (Ce0.1Zr0.9O2) thin films supported on silicon wafers. Zirconia films prepared using the block copolymer Brij-58 as the template had a thickness of around 60-80 nm. In the absence of a stabilizing trivalent cation they consisted of monoclinic and tetragonal zirconia nanocrystals with diameters in the range 8-10 nm. Films stabilized with Ce3+ contained only the tetragonal phase. The thin films were irradiated with iodine ions of energies of 70 MeV and 132 keV at low fluences (1013 - 1014 cm-2) corresponding to doses of 0.002 and 1.73 dpa respectively, and at 180 keV and high fluences (2 × 1016 cm-2) corresponding to 82.4 dpa. The influence of heavy ion irradiation on the nanocrystalline structure was monitored through Rietveld analysis of grazing incidence X-ray diffraction (GIXRD) patterns recorded at angles close to the critical angle to ensure minimum contribution to the diffraction pattern from the substrate. Irradiation of the mesoporous nanocrystalline zirconia thin films with 70 MeV iodine ions, for which electronic energy loss is dominant, resulted in slight changes in phase composition and virtually no change in crystallographic parameters as determined by Rietveld analysis. Iodine ion bombardment in the nuclear energy loss regime (132-180 keV) at low fluences did not provoke significant changes in phase composition or crystallographic parameters. However, at 180 keV and high fluences the monoclinic phase was totally eliminated from the GIXRD pattern of films prepared at both 350 and 500 °C implying either a monoclinic

  1. Investigation of thermally evaporated nanocrystalline thin cobalt films

    NASA Astrophysics Data System (ADS)

    Kozłowski, W.; Balcerski, J.; Kowalczyk, P. J.; Cichomski, M.; Szmaja, W.

    2017-03-01

    In this paper, a study has been made of nanocrystalline thin cobalt films with thicknesses in the range from 10 to 60 nm. The films were thermally evaporated at incidence angle of 0° in a vacuum of about 10- 5 mbar. The morphological structure of the films consists of nanocrystalline grains regular in shape and densely packed. As the film thickness is increased from 10 to 60 nm, the average grain size increases from 22.0 to 28.9 nm. The films crystallize mainly in the hexagonal close-packed phase of cobalt. The magnetic structure is composed of domains. In films with thicknesses in the range from 10 to 40 nm, the domains are magnetized in the plane of the film, while films with thicknesses of 50 and 60 nm possess both inplane and perpendicular magnetization components. The domains with inplane magnetization are irregular in shape and typically from a few to 10 mm in size, whereas the domains with perpendicular magnetization form a fine maze stripe pattern of the order of 100 nm in width.

  2. Substrate dependent structural, optical and electrical properties of ZnS thin films grown by RF sputtering

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok K.; Kumar, Vinod; Purohit, L. P.; Swart, H. C.; Kroon, R. E.

    2016-10-01

    Zinc sulphide (ZnS) films are of great importance for applications in various optoelectronic devices. ZnS thin films were grown on glass, indium tin oxide (ITO) and Corning glass substrates by radio-frequency magnetron sputtering at a temperature of 373 K and a comparative study of the structural, optical and electrical properties was performed using X-ray diffraction (XRD), scanning electron microscopy, optical and current-voltage (I-V) measurements. The XRD patterns showed that the sputtered thin films exhibited good crystallinity with the (111) peak around 2θ=28.3° indicating preferential orientation of the cubic structure. The maximum strain and most densely packed grains were obtained for the Corning glass substrate. The transmittance spectra of the films were measured in the wavelength range from 200 to 800 nm, showing that the films are about 77% transparent in the visible region. A slight change of 3.50 eV to 3.54 eV was found for the bandgap of the films deposited on different substrates. The ZnS thin films deposited on Corning glass show better crystallinity, morphology and I-V characteristics than that deposited on ordinary glass and ITO substrates.

  3. Structural, Optical, and Magnetic Properties of Solution-Processed Co-Doped ZnS Thin Films

    NASA Astrophysics Data System (ADS)

    Goktas, A.; Mutlu, İ. H.

    2016-11-01

    Co-doped ZnS thin films have been grown on glass substrates using solution-processing and dip-coating techniques, and the impact of the Co doping level (0% to 5%) and film thickness on certain characteristics examined. X-ray diffraction study revealed that all the films possessed hexagonal crystal structure. Energy-dispersive x-ray analysis confirmed presence of Zn, Co, and S in the samples. Scanning electron microscopy showed that the film surface was homogeneous and dense with some cracks and spots. X-ray photoelectron spectroscopy confirmed introduction and integration of Co2+ ions into the ZnS thin films. Compared with undoped ZnS, optical studies indicated a reduction in optical bandgap energy ( E g) while the refractive index ( n), extinction coefficient ( k), and dielectric constants ( ɛ 1, ɛ 2) increased with film thickness ( t) and Co doping level (except for 5%). Photoluminescence spectra showed enhanced luminescence intensity as the Co concentration was increased, while the dependence on t showed an initial increase followed by a decrease. The origin of the observed low-temperature (5 K and 100 K) ferromagnetic order may be related to point defects such as zinc vacancies, zinc interstitials, and sulfide vacancies or to the grain-boundary effect.

  4. Growth of MPS-capped ZnS quantum dots in self-assembled thin films: Influence of heat treatment

    NASA Astrophysics Data System (ADS)

    Koç, Kenan; Tepehan, Fatma Zehra; Tepehan, Galip Gültekin

    2015-12-01

    The colloidal ZnS quantum dots (QDs) were prepared using 3-mercaptopropyltrimethoxysilane (MPS) molecules. Sol-gel spin coating method was used to deposit the colloidal nanoparticles on a glass substrate. Several features of the MPS were made use to produce self assembled thin films of ZnS quantum dots in a SiO2 network. Produced films were heat treated in between 225 °C and 325 °C to investigate their growth kinetics. The result showed that their size changed approximately from 3 nm to 4 nm and the first excitation peak position changed from 4.6 eV to 4.1 eV in this temperature interval. The activation energy of the nanoparticles for the Ostwald ripening process was found to be 59 kJ/mol.

  5. Nanocrystalline silicon quantum dots thin films prepared by magnetron reaction sputtering

    NASA Astrophysics Data System (ADS)

    Zhao, Weiping; Deng, Jinxiang; Yang, Bing; Yu, Zhenrui; Aceves, Mariano

    2009-07-01

    Silicon is a kind of excellent semiconductor material and is one of the core material of microelectronics. But it is not a fine luminescent material. The photoluminescence(PL) will be obtained by excitation only when the size of silicon partials reduced to a certain value. Nanocrystalline silicon films have special structure and many excellent optoelectronic properties and are supposed to be applied in optoelectronic devices and large scale integrated circuits. In this paper, Nanocrystalline silicon films was deposited on silicon substrate by RF magnetron sputtering with pure Si target. And the working gas is the mixture of oxygen and argon .The content of O2 in working gas (O2/ O2 + Ar) and the power of sputtering were changed separately .However, the substrate temperature, working gas pressure and other conditions were definite. After annealing in the stove, we got the Nanocrystalline silicon particles in the thin films. Fourier transform infrared(FTIR) transmittance measurement was carried out to characterized Nanocrystalline silicon films. X-ray photoelectron spectroscopy (XPS) measurement was also performed to estimate the atom ratio of the Nanocrystalline silicon films. Raman scattering measurements was also taken in to characterize the Nanocrystalline silicon films. The formation of Nanocrystalline silicon filmswere depended partly on the parameters of experiment. The annealed silicon films were researched that the size of the Nanocrystalline silicon particles proved to be largely impacted by the annealing temperature in the thin film

  6. Experimental evidence of tunable space-charge-layer-induced electrical properties of nanocrystalline ceria thin films.

    PubMed

    Lee, Kyung-Ryul; Lee, Jong-Ho; Yoo, Han-Ill

    2013-10-07

    Fully dense nanocrystalline ceria films were successfully deposited on a MgO single crystal by pulsed laser deposition (PLD). The electrical conductivity of the nanocrystalline thin film was 20 times higher than that of the bulk sample. The activation energy of bulk ceria was 2.3 eV, whereas the activation energy of the nanocrystalline sample was only 1.2 eV. After post-annealing at 1273 K in which the grain size of the nanocrystalline thin film increased to ~400 nm, the electrical conductivity and activation energy of the film were changed similar to those of bulk. These unique electrical properties of the nano-crystalline thin-film can be attributed to the grain size effect, or more specifically, to the space charge layer (SCL) effect. Furthermore, the electrical conductivity of the nanocrystalline thin film became similar to that of the bulk in an extremely reducing atmosphere because of the unusual dependence of the SCL effect on the oxygen partial pressure.

  7. Characterization of nanocrystalline anatase TiO(2) thin films.

    PubMed

    Huber, Bernd; Gnaser, Hubert; Ziegler, Christiane

    2003-04-01

    Nanoporous thin films were deposited onto glass substrates by painting with a solution of nanocrystalline anatase TiO(2) particles (with a size of either 6 nm or 16 nm) suspended in an organic solvent. Upon drying in air for about 1 day, the films were tempered at 450 degrees C in air for 1 h. This procedure results in stoichiometric TiO(2) films with a thickness of several micro m and a milky whitish appearance. Scanning force microscopy of the surface revealed that the nanoparticles of the films agglomerated into structures with lateral dimensions of some 100 nm. Transmission electron microscopy was utilized to investigate the structural arrangement of the crystallites in the films. High-resolution electron diffraction and X-ray diffraction analyses demonstrated, furthermore, that the material consists exclusively of a single TiO(2) phase, namely anatase, and that the films do not exhibit any preferential texture. The elemental stoichiometry and the possible presence of impurities were monitored throughout the films by means of secondary-ion mass spectrometry depth profiling. Electrical measurements have been carried out as a function of both the sample temperature T and the ambient oxygen partial pressure p(O(2)). From these data the electrical conductivity sigma of the porous films was determined in dependence of those parameters.

  8. Structure and Optical Properties of Nanocrystalline Hafnium Oxide Thin Films (PostPrint)

    DTIC Science & Technology

    2014-09-01

    AFRL-RX-WP-JA-2014-0214 STRUCTURE AND OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) Neil R. Murphy AFRL...OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...publication is available at http://dx.doi.org/10.1016/j.optmat.2014.08.005 14. ABSTRACT Hafnium oxide (HfO2) films were grown by sputter-deposition by

  9. Electrodeposited ZnS Precursor Layer with Improved Electrooptical Properties for Efficient Cu2ZnSnS4 Thin-Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Mkawi, E. M.; Ibrahim, K.; Ali, M. K. M.; Farrukh, M. A.; Mohamed, A. S.

    2015-10-01

    Zinc sulfide (ZnS) thin films were prepared on indium tin oxide-coated glass by electrodeposition using aqueous zinc sulfate, thiourea, and ammonia solutions at 80°C. The effects of sulfurization at temperatures of 350°C, 400°C, 450°C, and 500°C on the morphological, structural, optical, and electrical properties of the ZnS thin films were investigated. X-ray diffraction analysis showed that the ZnS thin films exhibited cubic zincblende structure with preferred (111) orientation. The film crystallization improved with increasing annealing temperature. Field-emission scanning electron microscopy images showed that the film morphology became more compact and uniform with increasing annealing temperature. The percentage of sulfur in the ZnS thin films increased after sulfurization until a stoichiometric S/Zn ratio was achieved at 500°C. The annealed films showed good adhesion to the glass substrates, with moderate transmittance (85%) in the visible region. Based on absorption measurements, the direct bandgap increased from 3.71 eV to 3.79 eV with annealing temperature, which is attributed to the change of the buffer material composition and suitable crystal surface properties for effective p- n junction formation. The ZnS thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu2ZnSnS4/ZnS/ZnO/Al grid. The best solar cell efficiency was 1.86%.

  10. Investigating the role of hydrogen in ultra-nanocrystalline diamond thin film growth

    NASA Astrophysics Data System (ADS)

    Birrell, James; Gerbi, J. E.; Auciello, O. A.; Carlisle, J. A.

    2006-08-01

    Hydrogen has long been known to be critical for the growth of high-quality microcrystalline diamond thin films as well as homoepitaxial single-crystal diamond. A hydrogen-poor growth process that results in ultra-nanocrystalline diamond thin films has also been developed, and it has been theorized that diamond growth with this gas chemistry can occur in the absence of hydrogen. This study investigates the role of hydrogen in the growth of ultra-nanocrystalline diamond thin films in two different regimes. First, we add hydrogen to the gas phase during growth, and observe that there seems to be a competitive growth process occurring between microcrystalline diamond and ultra-nanocrystalline diamond, rather than a simple increase in the grain size of ultra-nanocrystalline diamond. Second, we remove hydrogen from the plasma by changing the hydrocarbon precursor from methane to acetylene and observe that there does seem to be some sort of lower limit to the amount of hydrogen that can sustain ultra-nanocrystalline diamond growth. We speculate that this is due to the amount of hydrogen needed to stabilize the surface of the growing diamond nanocrystals.

  11. Structural characterization of PVA capped ZnS nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Barman, Bijoy; Sarma, Kanak C.

    2012-08-01

    ZnS nanoparticles within the range 3-6 nm have been synthesized by simple chemical method using polyvinyl alcohol as matrix. X-ray diffraction has been used for determining structures of ZnS nanocrystals along with high resolution transmission electron microscopy. For all deposited films the preferential orientation is along (111) direction with some other planes (220) and (311). The grain sizes of the particles have been calculated using both Scherrer's formula and Williamson-Hall plot. The lattice constant `a' have been obtained using Nelson-Riley plot. The average internal stress, microstrain, dislocation density and degree of preferred orientation in the films are calculated and correlated with molarities of the films.

  12. Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

    2017-05-01

    In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

  13. Subtractive Plasma-Assisted-Etch Process for Developing High Performance Nanocrystalline Zinc-Oxide Thin-Film-Transistors

    DTIC Science & Technology

    2015-03-26

    SUBTRACTIVE PLASMA -ASSISTED- ETCH PROCESS FOR DEVELOPING HIGH PERFORMANCE NANOCRYSTALLINE ZINC-OXIDE...Government and is not subject to copyright protection in the United States. AFIT-ENG-MS-15-M-027 SUBTRACTIVE PLASMA -ASSISTED- ETCH PROCESS FOR...15-M-027 SUBTRACTIVE PLASMA -ASSISTED- ETCH PROCESS FOR DEVELOPING HIGH PERFORMANCE NANOCRYSTALLINE ZINC-OXIDE THIN-FILM-TRANSISTORS Thomas

  14. Ultrasensitive, Real-time and Discriminative Detection of Improvised Explosives by Chemiresistive Thin-film Sensory Array of Mn2+ Tailored Hierarchical ZnS

    PubMed Central

    Zhou, Chaoyu; Wu, Zhaofeng; Guo, Yanan; Li, Yushu; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

    2016-01-01

    A simple method combing Mn2+ doping with a hierarchical structure was developed for the improvement of thin-film sensors and efficient detection of the explosives relevant to improvised explosive devices (IEDs). ZnS hierarchical nanospheres (HNs) were prepared via a solution-based route and their sensing performances were manipulated by Mn2+ doping. The responses of the sensors based on ZnS HNs towards 8 explosives generally increase firstly and then decrease with the increase of the doped Mn2+ concentration, reaching the climate at 5% Mn2+. Furthermore, the sensory array based on ZnS HNs with different doping levels achieved the sensitive and discriminative detection of 6 analytes relevant to IEDs and 2 military explosives in less than 5 s at room temperature. Importantly, the superior sensing performances make ZnS HNs material interesting in the field of chemiresistive sensors, and this simple method could be a very promising strategy to put the sensors based on thin-films of one-dimensional (1D) nanostructures into practical IEDs detection. PMID:27161193

  15. Ultrasensitive, Real-time and Discriminative Detection of Improvised Explosives by Chemiresistive Thin-film Sensory Array of Mn2+ Tailored Hierarchical ZnS

    NASA Astrophysics Data System (ADS)

    Zhou, Chaoyu; Wu, Zhaofeng; Guo, Yanan; Li, Yushu; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

    2016-05-01

    A simple method combing Mn2+ doping with a hierarchical structure was developed for the improvement of thin-film sensors and efficient detection of the explosives relevant to improvised explosive devices (IEDs). ZnS hierarchical nanospheres (HNs) were prepared via a solution-based route and their sensing performances were manipulated by Mn2+ doping. The responses of the sensors based on ZnS HNs towards 8 explosives generally increase firstly and then decrease with the increase of the doped Mn2+ concentration, reaching the climate at 5% Mn2+. Furthermore, the sensory array based on ZnS HNs with different doping levels achieved the sensitive and discriminative detection of 6 analytes relevant to IEDs and 2 military explosives in less than 5 s at room temperature. Importantly, the superior sensing performances make ZnS HNs material interesting in the field of chemiresistive sensors, and this simple method could be a very promising strategy to put the sensors based on thin-films of one-dimensional (1D) nanostructures into practical IEDs detection.

  16. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    PubMed Central

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  17. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    NASA Astrophysics Data System (ADS)

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-07-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

  18. Method for the preparation of nanocrystalline diamond thin films

    DOEpatents

    Gruen, Dieter M.; Krauss, Alan R.

    1998-01-01

    A method and system for manufacturing nanocrystalline diamond film on a substrate such as field emission tips. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrocarbon and possibly hydrogen, and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous vapor and deposition of a diamond film on the field emission tip.

  19. Method for the preparation of nanocrystalline diamond thin films

    DOEpatents

    Gruen, D.M.; Krauss, A.R.

    1998-06-30

    A method and system are disclosed for manufacturing nanocrystalline diamond film on a substrate such as field emission tips. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrocarbon and possibly hydrogen, and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous vapor and deposition of a diamond film on the field emission tip. 40 figs.

  20. Photoluminescence studies of chemically bath deposited nanocrystalline lead sulphide (PbS) thin films

    NASA Astrophysics Data System (ADS)

    Singh, L. Rajen; Singh, S. Bobby; London, R. K.; Sharma, H. B.; Rahman, A.

    2012-07-01

    Nanocrystalline lead sulphide (PbS) films have been deposited on glass substrates by chemical bath deposition (CBD) method. Lead acetate [Pb(CH3COOH)2] and thiourea [(NH2)2CS] were used as starting materials for deposition of PbS thin films. The as-deposited thin films were found to be crystalline having cubic phase structure with the strongest diffraction intensity along (200) plane. The grain sizes calculated from XRD spectra were found to decrease from 17 to 15 nm with the decrease in molar concentration of the precursor solutions. The structural, optical and photoluminescence properties of the PbS nanocrystalline thin film with different molar concentration were studied.

  1. Enhanced superconductivity and superconductor to insulator transition in nano-crystalline molybdenum thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Shilpam; Amaladass, E. P.; Sharma, Neha; Harimohan, V.; Amirthapandian, S.; Mani, Awadhesh

    2017-06-01

    Disorder driven superconductor to insulator transition via intermediate metallic regime is reported in nano-crystalline thin films of molybdenum. The nano-structured thin films have been deposited at room temperature using DC magnetron sputtering at different argon pressures. The grain size has been tuned using deposition pressure as the sole control parameter. A variation of particle sizes, room temperature resistivity and superconducting transition has been studied as a function of deposition pressure. The nano-crystalline molybdenum thin films are found to have large carrier concentration but very low mobility and electronic mean free path. Hall and conductivity measurements have been used to understand the effect of disorder on the carrier density and mobilities. Ioffe-Regel parameter is shown to correlate with the continuous metal-insulator transition in our samples.

  2. Fabrication of Cu2O nanocrystalline thin films photosensor prepared by RF sputtering technique

    NASA Astrophysics Data System (ADS)

    Selman, Abbas M.; Mahdi, M. A.; Hassan, Z.

    2017-10-01

    Cuprous oxide (Cu2O) nanocrystalline thin films were prepared on two types of substrates known as crystalline silicon and amorphous glass, by radio frequency reactive magnetron sputtering method. Scanning electron microscopy images confirmed that Cu2O particles covered the entire surface of both substrates with smoothing distribution. The root mean square surface roughness for the prepared Cu2O thin films on glass and Si (111) substrates is 4.16, and 3.36 nm, respectively. Meanwhile, X-ray diffraction results demonstrated that the two phases of Cu2O and CuO were produced on Si (111) and glass substrates. The optical bandgap of Cu2O thin films synthesised on glass substrate is 2.42 eV. Furthermore, the prepared Cu2O nanocrystalline thin films have showed low reflectance value in the visible spectrum. Metal-Semiconductor-Metal photodetector based Cu2O nanocrystalline thin films deposited onto Si (111) was fabricated using aluminium and platinum, with the current-voltage and photoresponse characteristic investigated under various applied bias voltages. The fabricated Metal-Semiconductor-Metal (M-S-M) photodetector had shown 126% sensitivity in the presence of 10 mW/cm2 of 490 nm light with 1.0 V bias, displaying 90 and 100 ms response and recovery times, respectively. These findings have demonstrated the suitability of M-S-M Cu2O photodetector as an affordable photosensor in the future.

  3. Effect of deposition variables on properties of CBD ZnS thin films prepared in chemical bath of ZnSO4/SC(NH2)2/Na3C3H5O7/NH4OH

    NASA Astrophysics Data System (ADS)

    Liu, Wei-Long; Yang, Chang-Siao; Hsieh, Shu-Huei; Chen, Wen-Jauh; Fern, Chi-Lon

    2013-01-01

    The CBD ZnS thin films were prepared on substrates of soda lime glass in chemical bath. The effect of deposition variables including zinc sulfate, thiourea, tri-sodium citrate, ammoina water, bath temperature, and deposition time on the properties of CBD ZnS thin films were comprehensively studied. The CBD ZnS thin films were characterized by a field emission scanning electron microscope (FESEM) for the surface and cross section morphologies and thicknesses, an energy dispersive spectrometer equipped in FESEM for the atomic% of Zn and S, an ultraviolet-visible spectrometer (300-800 nm) for the transmittance and energy gap, and an atomic force microscope for the surface roughness. The results showed that the CBD ZnS thin films have a transmittance for ultraviolet-visible rays (300-800 nm) from 70.8 to 87.8%. The CBD ZnS thin films prepared in bath 5 have an energy gap from 3.881 to 3.980 eV. The CBD ZnS thin films prepared in bath 6 have a growth rate from 1.8 to 3.2 nm/min and activation energy of 59.8 kJ/mol for their growth.

  4. Effect of dopent on the structural and optical properties of ZnS thin film as a buffer layer in solar cell application

    SciTech Connect

    Vashistha, Indu B. Sharma, S. K.; Sharma, Mahesh C.; Sharma, Ramphal

    2015-08-28

    In order to find the suitable alternative of toxic CdS buffer layer, deposition of pure ZnS and doped with Al by chemical bath deposition method have been reported. Further as grown pure and doped thin films have been annealed at 150°C. The structural and surface morphological properties have been characterized by X-Ray diffraction (XRD) and Atomic Force Microscope (AFM).The XRD analysis shows that annealed thin film has been polycrystalline in nature with sphalerite cubic crystal structure and AFM images indicate increment in grain size as well as growth of crystals after annealing. Optical measurement data give band gap of 3.5 eV which is ideal band gap for buffer layer for solar cell suggesting that the obtained ZnS buffer layer is suitable in a low-cost solar cell.

  5. Preparation and characterization of nanocrystalline SnO 2 thin films by PECVD

    NASA Astrophysics Data System (ADS)

    Huang, Hui; Tan, O. K.; Lee, Y. C.; Tse, M. S.

    2006-02-01

    Nanocrystalline SnO 2 thin films were deposited by RF inductively coupled plasma enhanced chemical vapor deposition (PECVD) using dibutyltin diacetate as precursor. The effects of substrate-nozzle distance ( Dsn), RF power and deposition time on the phase and morphologies of the SnO 2 thin films have been studied. The as-deposited SnO 2 thin films were well crystallized even without additional substrate heating and post-annealing. The grain size and film thickness decreased continuously with the increase of Dsn and RF power while increased with increasing deposition time. The deposition parameters showed notable effects on the microstructure of the SnO 2 thin films, thus it was possible to optimize the microstructure of the SnO 2 thin films by adjusting deposition parameters to achieve high-performance SnO 2-based thin film gas sensors.

  6. Coexistence of colossal stress and texture gradients in sputter deposited nanocrystalline ultra-thin metal films

    SciTech Connect

    Kuru, Yener; Welzel, Udo; Mittemeijer, Eric J.

    2014-12-01

    This paper demonstrates experimentally that ultra-thin, nanocrystalline films can exhibit coexisting colossal stress and texture depth gradients. Their quantitative determination is possible by X-ray diffraction experiments. Whereas a uniform texture by itself is known to generally cause curvature in so-called sin{sup 2}ψ plots, it is shown that the combined action of texture and stress gradients provides a separate source of curvature in sin{sup 2}ψ plots (i.e., even in cases where a uniform texture does not induce such curvature). On this basis, the texture and stress depth profiles of a nanocrystalline, ultra-thin (50 nm) tungsten film could be determined.

  7. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    NASA Technical Reports Server (NTRS)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-01-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  8. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    NASA Technical Reports Server (NTRS)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-01-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  9. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    NASA Astrophysics Data System (ADS)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-03-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  10. Nanocrystalline Domain Formation as a Strain Relaxation Mechanism in Ultra-Thin Metallic Films

    NASA Astrophysics Data System (ADS)

    Gungor, M. Rauf; Maroudas, Dimitrios

    2006-03-01

    In this presentation, we report results for the atomistic mechanisms of strain relaxation over a wide range of applied biaxial tensile strain (up to 17%) in free standing Cu thin films based on isothermal-isostrain molecular-dynamics simulations. After an elastic response at low strain (< 2%), plastic deformation occurs through ductile void growth accompanied by emission of screw dislocations from the void surface, as well as emission of threading dislocation loops from the film's surface. At strain levels below 8%, expansion of the plastic zone around the void during void growth is the major strain relaxation mechanism. At higher levels of applied strain (> 8%), a practically uniform distribution of dislocations is generated in the metallic thin film, which mediates the transformation of the initially single-crystalline film structure to a nanocrystalline one. Furthermore, void growth is inhibited as the dislocations emitted from the void surface are pinned by the simultaneously generated network of defects in the nanocrystalline material.

  11. Thermal transport properties of nanocrystalline Bi-Sb-Te thin films prepared by sputter deposition

    SciTech Connect

    Liao, C.-N.; Wang, Y.-C.; Chu, H.-S.

    2008-11-15

    Grain-size dependent thermal conductivity of sputtered nanocrystalline Bi-Sb-Te thin films was measured by a 3{omega} method. By changing deposition temperature from 100 deg. C to room temperature, the mean grain size of the Bi-Sb-Te films decreased from 83 to 26 nm and the lattice thermal conductivity reduced from 0.79 to 0.45 W/mK proportionally. The effect of grain boundary on lattice thermal conductivity can be described by an effective thermal boundary resistance that was determined in the range of 0.56-1.8x10{sup -8} m{sup 2}K/W for the nanocrystalline Bi-Sb-Te thin films studied.

  12. Stress-driven surface topography evolution in nanocrystalline A1 thin films.

    SciTech Connect

    Gianola, D. S.; Eberl, C.; Cheng, X.; Hemker, K. J.; X-Ray Science Division; Johns Hopkins Univ.; Inst for Materials Research II

    2008-01-01

    Stress-assisted grain growth at room temperature is identified as a plastic deformation mechanism in nanocrystalline thin films. Unique surface relief is attributed to the direct application of stress-coupled grain boundary migration theory. The figure shows a false-color SEM image of surface topography and an AFM height profile as a result of stress-assisted grain growth. A strategy for tailoring the mechanical properties of nanostructured metals is shown.

  13. Stress-driven surface topography evolution in nanocrystalline A1 thin films.

    SciTech Connect

    Gianola, D. S.; Eberl, C.; Cheng, X. M.; Hemker, K. J.; X-Ray Science Division; Johns Hopkins Univ.

    2008-01-01

    Stress-assisted grain growth at room temperature is identified as a plastic deformation mechanism in nanocrystalline thin films. Unique surface relief is attributed to the direct application of stress-coupled grain boundary migration theory. A figure shows a false-color SEM image of surface topography and an AFM height profile as a result of stress-assisted grain growth. A strategy for tailoring the mechanical properties of nanostructured metals is shown.

  14. Surface Energy in Nanocrystalline Carbon Thin Films: Effect of Size Dependence and Atmospheric Exposure.

    PubMed

    Kumar, Manish; Javid, Amjed; Han, Jeon Geon

    2017-03-14

    Surface energy (SE) is the most sensitive and fundamental parameter for governing the interfacial interactions in nanoscale carbon materials. However, on account of the complexities involved of hybridization states and surface bonds, achieved SE values are often less in comparison with their theoretical counterparts and strongly influenced by stability aspects. Here, an advanced facing-target pulsed dc unbalanced magnetron-sputtering process is presented for the synthesis of undoped and H/N-doped nanocrystalline carbon thin films. The time-dependent surface properties of the undoped and H/N-doped nanocrystalline carbon thin films are systematically studied. The advanced plasma process induced the dominant deposition of high-energy neutral carbon species, consequently controlling the intercolumnar spacing of nanodomain morphology and surface anisotropy of electron density. As a result, significantly higher SE values (maximum = 79.24 mJ/m(2)) are achieved, with a possible window of 79.24-66.5 mJ/m(2) by controlling the experimental conditions. The intrinsic (size effects and functionality) and extrinsic factors (atmospheric exposure) are resolved and explained on the basis of size-dependent cohesive energy model and long-range van der Waals interactions between hydrocarbon molecules and the carbon surface. The findings anticipate the enhanced functionality of nanocrystalline carbon thin films in terms of selectivity, sensitivity, and stability.

  15. Dye-Sensitization Of Nanocrystalline ZnO Thin Films

    SciTech Connect

    Ajimsha, R. S.; Tyagi, M.; Das, A. K.; Misra, P.; Kukreja, L. M.

    2010-12-01

    Nannocrystalline and nanoporus thin films of ZnO were synthesized on glass substrates by using wet chemical drop casting method. X-ray diffraction measurements on these samples confirmed the formation of ZnO nanocrystallites in hexagonal wurtzite phase with mean size of {approx}20 nm. Photo sensitization of these nanostructured ZnO thin films was carried out using three types of dyes Rhodamine 6 G, Chlorophyll and cocktail of Rhodamine 6 G and Chlorophyll in 1:1 ratio. Dye sensitized ZnO thin films showed enhanced optical absorption in visible spectral region compared to the pristine ZnO thin films.

  16. Fabrication and Characterization of Amorphous/Nanocrystalline Thin Film Composite

    NASA Astrophysics Data System (ADS)

    Newton, Benjamin S.

    Combining the absorption abilities of amorphous silicon and the electron transport capabilities of crystalline silicon would be a great advantage to not only solar cells but other semiconductor devices. In this work composite films were created using molecular beam epitaxy and electron beam deposition interchangeably as a method to create metallic precursors. Aluminum induced crystallization techniques were used to convert an amorphous silicon film with a capping layer of aluminum nanodots into a film composed of a mixture of amorphous silicon and nanocrystalline silicon. This layer was grown into the amorphous layer by cannibalizing a portion of the amorphous silicon material during the aluminum induced crystallization. Characterization was performed on films and metallic precursors utilizing SEM, TEM, ellipsometry and spectrophotometer.

  17. Enhanced optical constants of nanocrystalline yttrium oxide thin films

    SciTech Connect

    Ramana, C. V.; Mudavakkat, V. H.; Bharathi, K. Kamala; Atuchin, V. V.; Pokrovsky, L. D.; Kruchinin, V. N.

    2011-01-17

    Yttrium oxide (Y{sub 2}O{sub 3}) films with an average crystallite-size (L) ranging from 5 to 40 nm were grown by sputter-deposition onto Si(100) substrates. The optical properties of grown Y{sub 2}O{sub 3} films were evaluated using spectroscopic ellipsometry measurements. The size-effects were significant on the optical constants and their dispersion profiles of Y{sub 2}O{sub 3} films. A significant enhancement in the index of refraction (n) is observed in well-defined Y{sub 2}O{sub 3} nanocrystalline films compared to that of amorphous Y{sub 2}O{sub 3}. A direct, linear L-n relationship found for Y{sub 2}O{sub 3} films suggests that tuning optical properties for desired applications can be achieved by controlling the size at the nanoscale dimensions.

  18. Microstructural evolution of nanocrystalline nickel thin films due to high-energy heavy-ion irradiation

    SciTech Connect

    Rajasekhara, S.; Ferreira, P. J.; Hattar, K.

    2013-04-19

    This initial feasibility study demonstrates that recent advancements in precession electron diffraction microscopy can be applied to nanostructured metals exposed to high displacement damage from a Tandem accelerator. In this study, high purity, nanocrystalline, free-standing nickel thin films produced by pulsed laser deposition were irradiated with approximately 3 Multiplication-Sign 10{sup 14} ions/cm{sup 2} of 35 MeV Ni{sup 6+} ions resulting in an approximately uniform damage profile to approximately 16 dpa. Pristine and ionirradiated regions of the nanocrystalline Ni films were characterized by conventional transmission electron microscopy and precession electron diffraction microscopy. Precession electron diffraction microscopy provided additional insight into the texture, phase, and grain boundary distribution resulting from the displacement damage that could not be obtained from traditional electron microscopy techniques. For the nanocrystalline nickel film studied, this included the growth in number and percentage of a metastable hexagonal closed packed phase grains and the formation of large <001> textured face centered cubic grains. The application of precession electron diffraction microscopy to characterize other nanocrystalline metals, which are being considered for radiation tolerant applications, will permit a comparison of materials that goes beyond the dominant length scale to consider the effects of local phase, texture, and grain boundary or interface information.

  19. Microstructural evolution of nanocrystalline nickel thin films due to high-energy heavy-ion irradiation

    NASA Astrophysics Data System (ADS)

    Rajasekhara, S.; Ferreira, P. J.; Hattar, K.

    2013-04-01

    This initial feasibility study demonstrates that recent advancements in precession electron diffraction microscopy can be applied to nanostructured metals exposed to high displacement damage from a Tandem accelerator. In this study, high purity, nanocrystalline, free-standing nickel thin films produced by pulsed laser deposition were irradiated with approximately 3 × 1014 ions/cm2 of 35 MeV Ni6+ ions resulting in an approximately uniform damage profile to approximately 16 dpa. Pristine and ionirradiated regions of the nanocrystalline Ni films were characterized by conventional transmission electron microscopy and precession electron diffraction microscopy. Precession electron diffraction microscopy provided additional insight into the texture, phase, and grain boundary distribution resulting from the displacement damage that could not be obtained from traditional electron microscopy techniques. For the nanocrystalline nickel film studied, this included the growth in number and percentage of a metastable hexagonal closed packed phase grains and the formation of large <001> textured face centered cubic grains. The application of precession electron diffraction microscopy to characterize other nanocrystalline metals, which are being considered for radiation tolerant applications, will permit a comparison of materials that goes beyond the dominant length scale to consider the effects of local phase, texture, and grain boundary or interface information.

  20. New Numerical Simulation of the Optical Behavior of Nanocrystalline Silicon Thin Films

    NASA Astrophysics Data System (ADS)

    Besahraoui, F.; Bouizem, Y.; Chahed, L.; Sib, J. D.

    2009-11-01

    The absorption enhancement observed on the CPM spectra of nanotextured silicon thin films should be attributed to light scattering effects. A detailed numerical simulation based on Monte Carlo method is presented to calculate the absorption spectra of hydrogenated nanocrystalline silicon films according to the CPM setup. The calculated spectra of apparent optical absorption coefficient depend mainly on the characteristic parameters of nano-Si:H thin film, denoted crystalline/amorphous fraction which favors bulk light scattering phenomena and the film thickness which leads to the light scattering at the rough surface.

  1. Low-temperature Amorphous and Nanocrystalline Silicon Materials and Thin-film Transistors

    NASA Astrophysics Data System (ADS)

    Sazonov, Andrei; Striakhilev, Denis; Nathan, Arokia

    Low-temperature processing and characterization of amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si) materials and devices are reviewed. An overview of silicon-based low-temperature thin-film dielectrics is given in the context of thin-film transistor (TFT) device operation. The low-temperature growth and synthesis of these materials are also presented and compared to conventionally fabricated high-temperature processed devices. The effect of using nc-Si contacts on a-Si:H TFTs and the stability of nc-Si TFTs is reviewed.

  2. The influence of substrate temperature on the structural and optical properties of ZnS thin films

    SciTech Connect

    Ashraf, M.; Akhtar, S. M. J.; Ali, Z.; Qayyum, A.

    2011-05-15

    Thin films of ZnS were deposited on soda lime glass substrates by a modified close-space sublimation technique. The change in optical and structural properties of the films deposited at various substrate temperatures (150-450 Degree-Sign C) was investigated. X-ray diffraction spectra showed that films were polycrystalline in nature having cubic structure oriented only along (111) plan. The crystallinity of films increased with the substrate temperature up to 250 Degree-Sign C. However, crystallinity decreased with further increase of substrate temperature and films became amorphous at 450 Degree-Sign C. The atomic force microscopy data revealed that the films become more uniform and dense with the increase of substrate temperature. Optical properties of the films were determined from the transmittance data using Swanepoel model. It was observed that the energy band gap is increased from 3.52 to 3.65 eV and refractive index of the films are decreased with the increase of substrate temperature. Moreover, considerable improvement in blue response of the films was noticed with increasing substrate temperature.

  3. Intrinsic Doping in Electrodeposited ZnS Thin Films for Application in Large-Area Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Madugu, Mohammad Lamido; Olusola, Olajide Ibukun-Olu; Echendu, Obi Kingsley; Kadem, Burak; Dharmadasa, Imyhamy Mudiy

    2016-06-01

    Zinc sulphide (ZnS) thin films with both n- and p-type electrical conductivity were grown on glass/fluorine-doped tin oxide-conducting substrates from acidic and aqueous solution containing ZnSO4 and (NH4)2S2O3 by simply changing the deposition potential in a two-electrode cell configuration. After deposition, the films were characterised using various analytical techniques. X-ray diffraction analysis reveals that the materials are amorphous even after heat treatment. Optical properties (transmittance, absorbance and optical bandgap) of the films were studied. The bandgaps of the films were found to be in the range (3.68-3.86) eV depending on the growth voltage. Photoelectrochemical cell measurements show both n- and p-type electrical conductivity for the films depending on the growth voltage. Scanning electron microscopy shows material clusters on the surface with no significant change after heat treatment at different temperatures. Atomic force microscopy shows that the surface roughness of these materials remain fairly constant reducing only from 18 nm to 17 nm after heat treatment. Thickness estimation of the films was also carried out using theoretical and experimental methods. Direct current conductivity measurements on both as-deposited and annealed films show that resistivity increased after heat treatment.

  4. Electron Filtering by an Intervening ZnS Thin Film in the Au Nanoparticle-loaded CdS Plasmonic Photocatalyst.

    PubMed

    Takayama, Kouichi; Fujiwara, Keigo; Kume, Takahiro; Naya, Shin-Ichi; Tada, Hiroaki

    2016-12-12

    In the gold nanoparticle (Au NP)-loaded CdS film on fluorine-doped tin oxide electrode (Au/CdS/FTO), the localized plasmonic resonance excitation-induced electron injection from Au NP to CdS has been proved by photoelectrochemical measurements. Formation of ZnS thin films between the Au NP and CdS film leads to a drastic increase of the photocurrent under visible-light irradiation ( > 610 nm) in a 0.1 M NaClO4 aqueous electrolyte solution due to the electron filtering effect. The photocurrent strongly depends on the thickness of the ZnS film, and the maximum value is obtained at the thickness of as thin as 2.1 nm. Further, the ZnS overlayer significantly stabilizes the photocurrent of the CdS/FTO electrode in a polysulfide/sulfide electrolyte solution even under the excitation of CdS ( > 430 nm). This work presents important information about the design for the new plasmonic photocatalysts consisting of plasmonic metal NP and chalcogenide semiconductors with high conduction band edge.

  5. Electron Filtering by an Intervening ZnS Thin Film in the Gold Nanoparticle-Loaded CdS Plasmonic Photocatalyst.

    PubMed

    Takayama, Kouichi; Fujiwara, Keigo; Kume, Takahiro; Naya, Shin-Ichi; Tada, Hiroaki

    2017-01-05

    In the gold nanoparticle (Au NP)-loaded CdS film on fluorine-doped tin oxide electrode (Au/CdS/FTO), the localized plasmonic resonance excitation-induced electron injection from Au NP to CdS has been proven by photoelectrochemical measurements. Formation of ZnS thin films between the Au NP and CdS film leads to a drastic increase of the photocurrent under visible-light irradiation (λ > 610 nm) in a 0.1 M NaClO4 aqueous electrolyte solution due to the electron filtering effect. The photocurrent strongly depends on the thickness of the ZnS film, and the maximum value is obtained at a thickness as thin as 2.1 nm. Furthermore, the ZnS overlayer significantly stabilizes the photocurrent of the CdS/FTO electrode in a polysulfide/sulfide electrolyte solution even under the excitation of CdS (λ > 430 nm). This work presents important information about the design for new plasmonic photocatalysts consisting of plasmonic metal NPs and chalcogenide semiconductors with high conduction band edge.

  6. Statistical and fractal features of nanocrystalline AZO thin films

    NASA Astrophysics Data System (ADS)

    Hosseinabadi, S.; Abrinaei, F.; Shirazi, M.

    2017-09-01

    In this paper, We investigate the morphology effect of Aluminum-doped zinc oxide (AZO) thin films on the physical properties such as conductivity and grain size. The AZO thin films are prepared by spray pyrolysis at different thicknesses in the range 100-400 nm. Height fluctuations obtained from atomic force microscopy (AFM) analysis are applied to the statistical and fractal analysis of thin films. We show that the conductivity of thin films is proportional to the roughness parameter as σ ∼Wm which m = 6 . 42 ± 0 . 50. Calculating the nonlinear measures (skewness and kurtosis) of height fluctuations demonstrates the isotropic nature of AZO rough surfaces. Fractal analysis of the mentioned thin films using two dimensional multifractal detrended fluctuation analysis illustrates the multifractality scaling and the strength of multifractality increases with thickness. Our results show that the reason for the multi-affinity is the existence of different correlations in the height fluctuations of the thin films. Calculating the contour loops features of the height fluctuations reveals that the radius, length, and area of loops increase with thickness enhancement and the radius of contour loops is introduced as a new statistical parameter which is linearly related to the grain size and could be useful to calculate it.

  7. DNA-modified nanocrystalline diamond thin-films as stable, biologically active substrates

    NASA Astrophysics Data System (ADS)

    Yang, Wensha; Auciello, Orlando; Butler, James E.; Cai, Wei; Carlisle, John A.; Gerbi, Jennifer E.; Gruen, Dieter M.; Knickerbocker, Tanya; Lasseter, Tami L.; Russell, John N.; Smith, Lloyd M.; Hamers, Robert J.

    2002-12-01

    Diamond, because of its electrical and chemical properties, may be a suitable material for integrated sensing and signal processing. But methods to control chemical or biological modifications on diamond surfaces have not been established. Here, we show that nanocrystalline diamond thin-films covalently modified with DNA oligonucleotides provide an extremely stable, highly selective platform in subsequent surface hybridization processes. We used a photochemical modification scheme to chemically modify clean, H-terminated nanocrystalline diamond surfaces grown on silicon substrates, producing a homogeneous layer of amine groups that serve as sites for DNA attachment. After linking DNA to the amine groups, hybridization reactions with fluorescently tagged complementary and non-complementary oligonucleotides showed no detectable non-specific adsorption, with extremely good selectivity between matched and mismatched sequences. Comparison of DNA-modified ultra-nanocrystalline diamond films with other commonly used surfaces for biological modification, such as gold, silicon, glass and glassy carbon, showed that diamond is unique in its ability to achieve very high stability and sensitivity while also being compatible with microelectronics processing technologies. These results suggest that diamond thin-films may be a nearly ideal substrate for integration of microelectronics with biological modification and sensing.

  8. Thermoelectric properties of n-type nanocrystalline bismuth-telluride-based thin films deposited by flash evaporation

    NASA Astrophysics Data System (ADS)

    Takashiri, M.; Takiishi, M.; Tanaka, S.; Miyazaki, K.; Tsukamoto, H.

    2007-04-01

    The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3ω method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 °C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W/m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT =0.7. As compared with a sintered bulk sample with average grain size of 30 μm and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% reduction in the thermal conductivity, but the electrical conductivity also falls 40%. The reduced thermal and electrical conductivities are attributed to increased carrier trapping and scattering in the nanocrystalline film.

  9. Synthesis and characterization of nanocrystalline MoBi2Te5 thin films for photoelectrode applications

    NASA Astrophysics Data System (ADS)

    Salunkhe, M. M.; Kharade, R. R.; Mane, R. M.; Bhosale, P. N.

    2012-10-01

    Molybdenum bismuth telluride thin films have been prepared on clean glass substrate using arrested precipitation technique which is based on self-organized growth process. As deposited MoBi2Te5 thin films were dried in constant temperature oven at 110°C and further characterized for their optical, structural, morphological, compositional, and electrical analysis. Optical absorption spectra recorded in the wavelength range 300-800 nm showed band gap (E g) 1.44 eV. X-ray diffraction pattern and scanning electron microscopic images showed that MoBi2Te5 thin films are granular, nanocrystalline having rhombohedral structure. The compositional analysis showed close agreements in theoretical and experimental atomic percentages of Mo4+, Bi3+, and Te2- suggest that chemical formula MoBi2Te5 assigned to as deposited molybdenum bismuth telluride new material is confirmed. The electrical conductivity and thermoelectric power measurement showed that the films are semiconducting with n-type conduction. The fill factor and conversion efficiency was characterized by photoelectrochemical (PEC) technique. In this article, we report the optostructural, morphological, compositional, and electrical characteristics of nanocrystalline MoBi2Te5 thin films to check its suitability as photoelectrode in PEC cell.

  10. Stress and morphological development of CdS and ZnS thin films during the SILAR growth on (1 0 0)GaAs

    NASA Astrophysics Data System (ADS)

    Laukaitis, Giedrius; Lindroos, Seppo; Tamulevičius, Sigitas; Leskelä, Markku

    2001-12-01

    Cadmium sulfide and zinc sulfide films were grown on (1 0 0)GaAs substrate by successive ionic layer adsorption and reaction (SILAR) technique from aqueous precursor solutions at room temperature and normal pressure. The stress development of the thin films was characterized by laser interferometry as a function of the thickness of the films. The morphology and roughness of the films were monitored by atomic force microscopy. Additionally the crystallinity and crystallite size were analyzed by X-ray diffraction and composition by electron spectroscopy for chemical analysis. The CdS thin films had significantly higher stress level and also better crystallinity compared with ZnS thin films. Both films were polycrystalline and cubic, but the CdS thin films followed the substrate (1 0 0) orientation, whereas the ZnS films were (1 1 1) orientated. The roughness vs. film thickness curves of both films followed each other in shape, but the CdS films consisted of smaller particles.

  11. Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

    NASA Astrophysics Data System (ADS)

    Wienkes, Lee Raymond

    Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

  12. Photoconductivity on nanocrystalline ZnO/TiO2 thin films obtained by sol-gel

    NASA Astrophysics Data System (ADS)

    Valverde-Aguilar, G.; García-Macedo, J. A.; Juárez-Arenas, R.

    2008-08-01

    In this paper we report results on the synthesis, characterization and photoconductivity behaviour of amorphous and nanocrystalline ZnO/TiO2 thin films. They were produced by the sol-gel process at room temperature by using the spin-coating method and deposited on glass substrates. The ZnO/TiO2 films were synthesized by using tetrabutyl orthotitanate and zinc nitrate hexahydrate as the inorganic precursors. The samples were sintered at 520°C for 1 hour. The obtained films were characterized by X-ray diffraction (XRD), optical absorption (OA), infrared spectroscopy (IR) and scanning electronic microscopy (SEM) studies. Photoconductivity studies were performed on amorphous and nanocrystalline (anatase phase) films to determine the charge transport parameters. The experimental data were fitted with straight lines at darkness and under illumination at 310 nm, 439 nm and 633 nm. This indicates an ohmic behavior. The Φμτ and Φl0 parameters were fitted by least-squares with straight lines (nanocrystalline films) and polynomial fits (amorphous films).

  13. Correlation between surface chemistry, density and band gap in nanocrystalline WO3 thin films

    SciTech Connect

    Vemuri, Venkata Rama Ses; Engelhard, Mark H.; Ramana, C.V.

    2012-03-01

    Nanocrystalline WO3 thin films were produced by sputter-deposition by varying the ratio of argon to oxygen in the reactive gas mixture during deposition. The surface chemistry, physical characteristics, and optical properties of nanocrystalline WO3 films were evaluated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray reflectivity (XRR), and spectrophotometric measurements. The effect of ultra-microstructure was significant on the optical properties of WO3 films. The XPS analyses indicate the formation of stoichiometric WO3 with tungsten existing in fully oxidized valence state (W6+). However, WO3 films grown at high oxygen concentration (>60%) in the sputtering gas mixture were over stoichiometric with excess oxygen. XRR simulations, which are based on isotropic WO3 film - SiO2 interface - Si substrate model, indicate that the density of WO3 films is sensitive to the oxygen content in the sputtering gas. The spectral transmission of the films increased with the increasing oxygen. The band gap of these films increases from 2.78 eV to 3.25 eV with increasing oxygen. A direct correlation between the film-density and band gap in nanocrystalline WO3 films is established based on the observed results.

  14. Structural, optical and photo-catalytic activity of nanocrystalline NiO thin films

    SciTech Connect

    Al-Ghamdi, Attieh A.; Abdel-wahab, M. Sh.; Farghali, A.A.; Hasan, P.M.Z.

    2016-03-15

    Highlights: • Synthesis of nanocrystalline NiO thin films with different thicknesses using DC magnetron sputtering technique. • Effect of film thickness and particle size on photo-catalytic degradation of methyl green dye under UV light was studied. • The deposited NiO thin films are efficient, stable and possess high photo-catalytic activity upon reuse. - Abstract: Physical deposition of nanocrystalline nickel oxide (NiO) thin films with different thickness 30, 50 and 80 nm have been done on glass substrate by DC magnetron sputtering technique and varying the deposition time from 600, 900 to 1200 s. The results of surface morphology and optical characterization of these films obtained using different characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), photoluminescence (PL) and UV–vis spectrophotometry provide important information like formation of distinct nanostructures in different films and its effect on their optical band gap which has decreased from 3.74 to 3.37 eV as the film thickness increases. Most importantly these films have shown very high stability and a specialty to be recycled without much loss of their photo-catalytic activity, when tested as photo-catalysts for the degradation of methyl green dye (MG) from the wastewater under the exposure of 18 W energy of UV lamp.

  15. Room-temperature deposition of nanocrystalline PbWO 4 thin films by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Ryu, J. H.; Yoon, J.-W.; Shim, K. B.; Koshizaki, N.

    2006-07-01

    Pulsed laser ablation (PLA) was applied to synthesize nanocrystalline PbWO4 thin films onto glass substrates. The effects of Ar background gas pressure on phase evolution, microstructures and optical characteristics of PbWO4 thin films were investigated in detail. The PLA processes were carried out at room temperature without substrate heating or post-annealing treatment. XRD and HR-TEM results revealed that the PbWO4 thin films are composed of nanocrystalline and amorphous phases. Moreover, the films contained a high density of lattice defects such as twin boundaries and edge dislocations. The crystallite size and crystallinity increased, which were associated with a change in surface morphology as the Ar pressure increased. Reduced tungsten states W5+ or W4+ induced by oxygen vacancies were observed at 10 Pa and the atomic concentration of all constituent element was almost stoichiometric, especially the [Pb]/[W] ratio, which was nearly unity above 50 Pa. The optical energy band-gap was 3.03 eV at 50 Pa and increased to 3.35 eV at 100 Pa, which are narrower than the reported value (4.20 eV). This optical band-gap narrowing could be attributed to localized band-tail states and new energy levels induced by the amorphous structure and inherent lattice defects.

  16. Fabrication of high quality nanocrystalline Cd(1-x)ZnxS thin films for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Verma, Urvashi; Thakur, Vikas; Rajaram, P.; Shrivastava, A. K.

    2013-02-01

    Nanocrystalline Cd(1-x)ZnxS thin films were prepared by spray pyrolysis technique. XRD studies showed that the films are polycrystalline and possess the hexagonal structure. The preferred crystallographic orientation of crystallites changes gradually from (002) to (101) with the increase in Zn composition. The AFM studies showed that the surface of the film is highly smooth and uniformly covered with the CdZnS nanoparticles. UV-VIS studies confirm the high quality of films. The band edge of these films is blue-shifted with the increase in Zn composition.

  17. Magnetic atomistic modelling and simulation of nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Agudelo-Giraldo, J. D.; Ortiz-Álvarez, H. H.; Restrepo, J.; Restrepo-Parra, E.

    2017-05-01

    In this study, a methodology, for polycrystalline magnetic thin films construction composed by nano-grains, was developed. The size and shape of grains and samples under scale considerations of magnetic materials were developed, taking into account periodic boundary conditions. A comparative analysis of results obtained with experimental grains' distribution is presented. Lognormal distribution was proposed as a function of number of atoms per grain that agrees with experimental reports. A test of the magnetization as a function of the temperature was obtained by the parallelized Monte Carlo method dividing the sample in cells. The Hamiltonian considered variations of the exchange constant with atomic distance from RKKY approximation and a cubic magneto-crystalline anisotropy as a function of the temperature also was implemented. Results showed changes over critical behavior and different values for magnetization of saturation at low temperatures. Critical temperature is affected by the increments of disorder into the sample when grain size is reduced. A reduction of magnetization is correlated with mono-domain regimen in the sample for most of grains. These states are favored during the cooling process by the disorder in grain boundaries.

  18. Evaluation of Specific Heat, Sound Velocity and Lattice Thermal Conductivity of Strained Nanocrystalline Bismuth Antimony Telluride Thin Films

    NASA Astrophysics Data System (ADS)

    Zheng, D.; Tanaka, S.; Miyazaki, K.; Takashiri, M.

    2015-06-01

    To investigate the effect of strain on specific heat, sound velocity and lattice thermal conductivity of nanocrystalline bismuth antimony telluride thin films, we performed both experimental study and modeling. The nanocrystalline thin films had mostly preferred crystal orientation along c-axis, and strains in the both directions of c-axis and a- b-axis. It was found that the thermal conductivity of nanocrystalline thin films decreased greatly as compared with that of bulk alloys. To gain insight into the thermal transport in the strained nanocrystalline thin films, we estimated the lattice thermal conductivity based on the phonon transport model of full distribution of mean free paths accounting for the effects of grain size and strain which was influenced to both the sound velocity and the specific heat. As a result, the lattice thermal conductivity was increased when the strain was shifted from compressive to tensile direction. We also confirmed that the strain was influenced by the lattice thermal conductivity but the reduction of the lattice thermal conductivity of thin films can be mainly attributed to the nano-size effect rather than the strain effect. Finally, it was found that the measured lattice thermal conductivities were in good agreement with modeling.

  19. Chemical synthesis of p-type nanocrystalline copper selenide thin films for heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Ambade, Swapnil B.; Mane, R. S.; Kale, S. S.; Sonawane, S. H.; Shaikh, Arif V.; Han, Sung-Hwan

    2006-12-01

    Nanocrystalline thin films of copper selenide have been grown on glass and tin doped-indium oxide substrates using chemical method. At ambient temperature, golden films have been synthesized and annealed at 200 °C for 1 h and were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy and UV-vis spectrophotometry techniques, respectively. Cu 2- xSe phase was confirmed by XRD pattern and spherical grains of 30 ± 4 - 40 ± 4 nm in size aggregated over about 130 ± 10 nm islands were seen by SEM images. Effect of annealing on crystallinity improvement, band edge shift and photoelectrochemical performance (under 80 mW/cm 2 light intensity and in lithium iodide electrolyte) has been studied and reported. Observed p-type electrical conductivity in copper selenide thin films make it a suitable candidate for heterojunction solar cells.

  20. Effect of texture and grain size on the residual stress of nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Cao, Lei; Sengupta, Arkaprabha; Pantuso, Daniel; Koslowski, Marisol

    2017-10-01

    Residual stresses develop in thin film interconnects mainly as a result of deposition conditions and multiple thermal loading cycles during the manufacturing flow. Understanding the relation between the distribution of residual stress and the interconnect microstructure is of key importance to manage the nucleation and growth of defects that can lead to failure under reliability testing and use conditions. Dislocation dynamics simulations are performed in nanocrystalline copper subjected to cyclic loading to quantify the distribution of residual stresses as a function of grain misorientation and grain size distribution. The outcomes of this work help to evaluate the effect of microstructure in thin films failure by identifying potential voiding sites. Furthermore, the simulations show how dislocation structures are influenced by texture and grain size distribution that affect the residual stress. For example, when dislocation loops reach the opposite grain boundary during loading, these dislocations remain locked during unloading.

  1. Room temperature ferromagnetism in Co defused CdTe nanocrystalline thin films

    SciTech Connect

    Rao, N. Madhusudhana; Kaleemulla, S.; Begam, M. Rigana

    2014-04-24

    Nanocrystalline Co defused CdTe thin films were prepared using electron beam evaporation technique by depositing CdTe/Co/CdTe stacked layers with different Co thickness onto glass substrate at 373 K followed by annealing at 573K for 2 hrs. Structural, morphological and magnetic properties of of all the Co defused CdTe thin films has been investigated. XRD pattern of all the films exhibited zinc blende structure with <111> preferential orientation without changing the crystal structure of the films. The grain size of the films increased from 31.5 nm to 48.1 nm with the increase of Co layer thickness from 25nm to 100nm. The morphological studies showed that uniform texture of the films and the presence of Co was confirmed by EDAX. Room temperature magnetization curves indicated an improved ferromagnetic behavior in the films with increase of the Co thickness.

  2. Control of crystalline volume and nano crystal grain size in nanocrystalline silicon thin film deposited by PECVD

    NASA Astrophysics Data System (ADS)

    Bui, Thanh Tung; Chien Dang, Mau

    2014-11-01

    Application of the radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique was studied to fabricate amorphous and nanocrystalline silicon (a-Si and nc-Si) thin films for photovoltaic devices at substrate temperature of 200 °C. Amorphous-crystalline transition of silicon thin films in working conditions of PECVD system was shown as a function of deposition parameters, i.e., dilution ratio of silane (SiH4) in hydrogen, total gas pressure during deposition and RF excitation power density. The crystalline volume as well as grain size of nanocrystalline silicon films could be successfully controlled by tuning those deposition parameters. Micro Raman scattering spectroscopy and spectroscopic ellipsometry (SE) methods were used to characterize the structure and crystallization of the deposited silicon thin films. We could make nc-Si thin films with various crystalline volumes. Nc-Si grain size was also controlled and was in the range of 3-5 nm.

  3. Influence of number of pitches and substrate on the nanostructure and optical properties of ZnS helical sculptured thin films

    NASA Astrophysics Data System (ADS)

    Abdi, Fateme; Savaloni, Hadi; Placido, Frank

    2016-12-01

    ZnS helical sculptured thin films with different number of pitches were produced on glass (microscope slides) and pre-deposited 7 nm ZnS on glass substrate. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) were used for structural analyses. Crystallographic structure of samples was obtained using x-ray diffraction (XRD) method which confirmed the formation of ZnS films on the substrates. Optical spectra of the samples were measured using a single beam spectrophotometer for both s- and p-polarized light and at different incident light angles. Optical results showed a strong dependence on the structural void fraction and number of pitches and, due to anisotropy of the helical structure, a dependence on the incident light angle. It is shown that by controlling the growth of these structures the optical spectra can be controlled. The reversed homogenization theory was used to calculate the complex refractive index of these structures and the percentage of the void fraction in the produced samples. This investigation showed that both real and imaginary parts of the refractive index are dependent on the structural void fraction; structures with larger grains and higher percentage of void fraction having larger real and imaginary parts of the refractive index. Band gap calculations showed that structures with larger grains and higher void fraction have smaller band gaps. A correlation is obtained between the band gap energies and the nano-strain developed in the structure of the produced films; band gap energy decreases with nano-strain.

  4. Microstructure evolution and photoluminescence in nanocrystalline Mg(x)Zn(1 - x)O thin films.

    PubMed

    Sahaym, U; Norton, M G; Huso, J; Morrison, J L; Che, H; Bergman, L

    2011-10-21

    The effects of Mg concentration and annealing temperature on the characteristics of nanocrystalline Mg(x)Zn(1 - x)O thin films (where x = 0-0.4) were studied using electron microscopy and photoluminescence. The films were prepared by a sol-gel method. The solid solubility limit of MgO in ZnO for the sol-gel-derived Mg(x)Zn(1 - x)O films in the present study was determined to be ∼ 20 at.%. Microstructural characterization of the films showed that the wurtzite crystallites decrease in size with increase in Mg concentration up to the solubility limit. Increasing Mg concentration beyond the solubility limit resulted in a decrease in crystallinity of the films. The bandgap energy was found to increase with Mg concentration whereas the linewidth first increased and then decreased when the Mg concentration was increased beyond the solubility limit. Photoluminescence properties have been correlated to the microstructure of the films. A growth mechanism for Mg(x)Zn(1 - x)O nanocrystalline films under the present processing conditions has also been proposed.

  5. Structural and nanomechanical properties of nanocrystalline carbon thin films for photodetection

    SciTech Connect

    Rawal, Ishpal; Panwar, Omvir Singh Tripathi, Ravi Kant; Chockalingam, Sreekumar; Srivastava, Avanish Kumar; Kumar, Mahesh

    2015-05-15

    This paper reports the effect of helium gas pressure upon the structural, nanomechanical, and photoconductive properties of nanocrystalline carbon thin (NCT) films deposited by the filtered cathodic jet carbon arc technique. High-resolution transmission electron microscopy images confirm the nanocrystalline nature of the deposited films with different crystallite sizes (3–7 nm). The chemical structure of the deposited films is further analyzed by x-ray photoelectron spectroscopy and Raman spectroscopy, which suggest that the deposited films change from graphitelike to diamondlike, increasing in sp{sup 3} content, with a minor change in the dilution of the inert gas (helium). The graphitic character is regained upon higher dilution of the helium gas, whereupon the films exhibit an increase in sp{sup 2} content. The nanomechanical measurements show that the film deposited at a helium partial pressure of 2.2 × 10{sup −4} has the highest value of hardness (37.39 GPa) and elastic modulus (320.50 GPa). At a light intensity of 100 mW/cm{sup 2}, the NCT films deposited at 2.2 × 10{sup −4} and 0.1 mbar partial pressures of helium gas exhibit good photoresponses of 2.2% and 3.6%, respectively.

  6. Study of the electron field emission and microstructure correlation in nanocrystalline carbon thin films

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Weiss, B. L.; Weiner, B. R.; Morell, G.

    2001-05-01

    Nanocrystalline carbon thin films were deposited by hot-filament chemical vapor deposition using a 2% concentration of methane in hydrogen. The films were deposited on molybdenum substrates under various substrate biasing conditions. A positive bias produced a continuous flow of electrons from the filament onto the substrate, while a negative bias caused the substrate to be bombarded with positive ions. Films were also grown under no bias, for comparison. Differences in the electron field emission properties (turn-on fields and emitted currents) of these films were characterized. Correspondingly, microstructural differences were also studied, as characterized with atomic force microscopy and Raman spectroscopy. Films grown under electron bombardment showed lower turn-on fields, smoother surfaces, and smaller grains than those grown under ion bombardment or no bias. A correlation between the enhanced emission properties and the nanocrystalline carbon material produced by the low-energy particle bombardment was found through the parameters obtained using spectroscopic ellipsometry modeling. The results confirm the significant role of defects on the electron field emission mechanism.

  7. Multifunctional nature of UV-irradiated nanocrystalline anatase thin films for biomedical applications.

    PubMed

    Rupp, F; Haupt, M; Klostermann, H; Kim, H-S; Eichler, M; Peetsch, A; Scheideler, L; Doering, C; Oehr, C; Wendel, H P; Sinn, S; Decker, E; von Ohle, C; Geis-Gerstorfer, J

    2010-12-01

    Anatase is known to decompose organic material by photocatalysis and to enhance surface wettability once irradiated by ultraviolet (UV) light. In this study, pulse magnetron-sputtered anatase thin films were investigated for their suitability with respect to specific biomedical applications, namely superhydrophilic and biofilm degrading implant surfaces. UV-induced hydrophilicity was quantified by static and dynamic contact angle analysis. Photocatalytic protein decomposition was analyzed by quartz crystal microbalance with dissipation. The surfaces were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The radical formation on anatase, responsible for photocatalytic effects, was analyzed by electron spin resonance spectroscopy. Results have shown that the nanocrystalline anatase films, in contrast to reference titanium surfaces, were sensitive to UV irradiation and showed rapid switching towards superhydrophilicity. The observed decrease in carbon adsorbents and the increase in the fraction of surface hydroxyl groups upon UV irradiation might contribute to this hydrophilic behavior. UV irradiation of anatase pre-conditioned with albumin protein layers induces the photocatalytic decomposition of these model biofilms. The observed degradation is mainly caused by hydroxyl radicals. It is concluded that nanocrystalline anatase films offer different functions at implant interfaces, e.g. bedside hydrophilization of anatase-coated implants for improved osseointegration or the in situ decomposition of conditioning films forming the basal layer of biofilms in the oral cavity.

  8. Room temperature atomic layerlike deposition of ZnS on organic thin films: Role of substrate functional groups and precursors

    SciTech Connect

    Shi, Zhiwei; Walker, Amy V.

    2015-09-15

    The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H{sub 2}S as reactants. Depositions on SAMs with three different terminal groups, –CH{sub 3,} –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH{sub 3} terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate on –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H{sub 2}S with the Zn-surface adduct may be incomplete.

  9. Structural evolution of nanocrystalline silicon thin films synthesized in high-density, low-temperature reactive plasmas.

    PubMed

    Cheng, Qijin; Xu, Shuyan; Ostrikov, Kostya Ken

    2009-05-27

    Silicon thin films with a variable content of nanocrystalline phase were deposited on single-crystal silicon and glass substrates by inductively coupled plasma-assisted chemical vapor deposition using a silane precursor without any hydrogen dilution in the low substrate temperature range from 100 to 300 degrees C. The structural and optical properties of the deposited films are systematically investigated by Raman spectroscopy, x-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/vis spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy. It is shown that the structure of the silicon thin films evolves from the purely amorphous phase to the nanocrystalline phase when the substrate temperature is increased from 100 to 150 degrees C. It is found that the variations of the crystalline fraction f(c), bonded hydrogen content C(H), optical bandgap E(Tauc), film microstructure and growth rate R(d) are closely related to the substrate temperature. In particular, at a substrate temperature of 300 degrees C, the nanocrystalline Si thin films of our interest feature a high growth rate of 1.63 nm s(-1), a low hydrogen content of 4.0 at.%, a high crystalline fraction of 69.1%, a low optical bandgap of 1.55 eV and an almost vertically aligned columnar structure with a mean grain size of approximately 10 nm. It is also shown that the low-temperature synthesis of nanocrystalline Si thin films without any hydrogen dilution is attributed to the outstanding dissociation ability of the high-density inductively coupled plasmas and effective plasma-surface interactions during the growth process. Our results offer a highly effective yet simple and environmentally friendly technique to synthesize high-quality nanocrystalline Si films, vitally needed for the development of new-generation solar cells and other emerging nanotechnologies.

  10. Synthesis and optical characterization of nanocrystalline CdTe thin films

    NASA Astrophysics Data System (ADS)

    Al-Ghamdi, A. A.; Khan, Shamshad A.; Nagat, A.; Abd El-Sadek, M. S.

    2010-11-01

    From several years the study of binary compounds has been intensified in order to find new materials for solar photocells. The development of thin film solar cells is an active area of research at this time. Much attention has been paid to the development of low cost, high efficiency thin film solar cells. CdTe is one of the suitable candidates for the production of thin film solar cells due to its ideal band gap, high absorption coefficient. The present work deals with thickness dependent study of CdTe thin films. Nanocrystalline CdTe bulk powder was synthesized by wet chemical route at pH≈11.2 using cadmium chloride and potassium telluride as starting materials. The product sample was characterized by transmission electron microscope, X-ray diffraction and scanning electron microscope. The structural characteristics studied by X-ray diffraction showed that the films are polycrystalline in nature. CdTe thin films with thickness 40, 60, 80 and 100 nm were prepared on glass substrates by using thermal evaporation onto glass substrate under a vacuum of 10 -6 Torr. The optical constants (absorption coefficient, optical band gap, refractive index, extinction coefficient, real and imaginary part of dielectric constant) of CdTe thin films was studied as a function of photon energy in the wavelength region 400-2000 nm. Analysis of the optical absorption data shows that the rule of direct transitions predominates. It has been found that the absorption coefficient, refractive index ( n) and extinction coefficient ( k) decreases while the values of optical band gap increase with an increase in thickness from 40 to 100 nm, which can be explained qualitatively by a thickness dependence of the grain size through decrease in grain boundary barrier height with grain size.

  11. Determination of dispersive optical constants of nanocrystalline CdSe (nc-CdSe) thin films

    SciTech Connect

    Sharma, Kriti; Al-Kabbi, Alaa S.; Saini, G.S.S.; Tripathi, S.K.

    2012-06-15

    Highlights: ► nc-CdSe thin films are prepared by thermal vacuum evaporation technique. ► TEM analysis shows NCs are spherical in shape. ► XRD reveals the hexagonal (wurtzite) crystal structure of nc-CdSe thin films. ► The direct optical bandgap of nc-CdSe is 2.25 eV in contrast to bulk (1.7 eV). ► Dispersion of refractive index is discussed in terms of Wemple–DiDomenico single oscillator model. -- Abstract: The nanocrystalline thin films of CdSe are prepared by thermal evaporation technique at room temperature. These thin films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). The transmission spectra are recorded in the transmission range 400–3300 nm for nc-CdSe thin films. Transmittance measurements are used to calculate the refractive index (n) and absorption coefficient (α) using Swanepoel's method. The optical band gap (E{sub g}{sup opt}) has been determined from the absorption coefficient values using Tauc's procedure. The optical constants such as extinction coefficient (k), real (ε{sub 1}) and imaginary (ε{sub 2}) dielectric constants, dielectric loss (tan δ), optical conductivity (σ{sub opt}), Urbach energy (E{sub u}) and steepness parameter (σ) are also calculated for nc-CdSe thin films. The normal dispersion of refractive index is described using Wemple–DiDomenico single-oscillator model. Refractive index dispersion is further analysed to calculate lattice dielectric constant (ε{sub L}).

  12. Optical and mechanical properties of nanocrystalline ZrC thin films grown by pulsed laser deposition.

    DOE PAGES

    Craciun, D.; Socol, G.; Lambers, E.; ...

    2015-01-17

    Thin ZrC films (<500 nm) were grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under different CH4 pressures. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies found out films were very dense and exhibited a smooth surface morphology. Optical spectroscopy data shows that the films have high reflectivity (>90%) in the infrared region, characteristic of metallic behavior. Nanoindentation results indicated that films deposited under lower CH4 pressures exhibited slightly higher nanohardness and Young modulus values than films deposited undermore » higher pressures. As a result, tribological characterization revealed that these films exhibited relatively high wear resistance and steady-state friction coefficients on the order of μ = 0.4.« less

  13. Dip coated nanocrystalline CdZnS thin films for solar cell application

    NASA Astrophysics Data System (ADS)

    Dongre, J. K.; Chaturvedi, Mahim; Patil, Yuvraj; Sharma, Sandhya; Jain, U. K.

    2015-07-01

    Nanocrystalline cadmium sulfide (CdS) and zinc cadmium sulfide (ZnCdS) thin films have been grown via simple and low cost dip coating technique. The prepared films are characterized by X-ray diffraction (XRD), atomic force microscopic (AFM) and UV-VIS spectrophotometer techniques to reveal their structural, morphological and optical properties. XRD shows that both samples grown have zinc blende structure. The grain size is calculated as 6.2 and 8 nm using Scherrer's formula. The band gap value of CdS and CdZnS film is estimated to be 2.58 and 2.69 eV respectively by UV-vis spectroscopy. Photoelectrochemical (PEC) investigations are carried out using cell configuration as n-CdZnS/(1M NaOH + 1M Na2S + 1M S)/C. The photovoltaic output characteristic is used to calculate fill-factor (FF) and solar conversion efficiency (η).

  14. Optical and mechanical properties of nanocrystalline ZrC thin films grown by pulsed laser deposition.

    SciTech Connect

    Craciun, D.; Socol, G.; Lambers, E.; McCumiskey, E. J.; Taylor, C. R.; Martin, C.; Argibay, Nicolas; Craciun, V.; Tanner, D. B.

    2015-01-17

    Thin ZrC films (<500 nm) were grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under different CH4 pressures. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies found out films were very dense and exhibited a smooth surface morphology. Optical spectroscopy data shows that the films have high reflectivity (>90%) in the infrared region, characteristic of metallic behavior. Nanoindentation results indicated that films deposited under lower CH4 pressures exhibited slightly higher nanohardness and Young modulus values than films deposited under higher pressures. As a result, tribological characterization revealed that these films exhibited relatively high wear resistance and steady-state friction coefficients on the order of μ = 0.4.

  15. Low-voltage driving phototransistor based on dye-sensitized nanocrystalline titanium dioxide thin films

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoqi; Xu, Jia; Liu, Zhiyong; Lu, Yuming; Cai, Chuanbing

    2012-01-01

    Photo-gated transistors based on dye-sensitized nanocrystalline titanium dioxide thin film are established. A transistor-like transport behavior characterized by the linear increase, saturated plateau, and breakdown-like increase in the voltage-current curve is achievable with a low driven bias for the present device. The response current exhibits a linear dependence on the intensity of gated light, and the measured maximum photosensitivity is approximately 0.1 A/W. The dynamic responses for various light frequencies and their dependences on the load resistances are investigated as well. The cut-off frequency of ~50 Hz is abstracted, indicating the potential application for economical and efficient light switch or optical communication unit. The dc photo-gated response is explained by the energy level diagram, and is numerically simulated by an equivalent circuit model, suggesting a clear correlation between photovoltaic and photoconductive behaviors as well as their optical responses.

  16. 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

  17. 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.

  18. Morphology and electron emission properties of nanocrystalline CVD diamond thin films.

    SciTech Connect

    Krauss, A. R.; Gruen, D. M.; Zhou, D.; McCauley, T. G.; Qin, L. C.; Corrigan, T.; Auciello, O.; Chang, R. P. H.

    1998-01-30

    Nanocrystalline diamond thin films have been produced by microwave plasma-enhanced chemical vapor deposition (MPECVD) using C{sub 60}/Ar/H{sub 2} or CH{sub 4}/Ar/H{sub 2} plasmas. Films grown with H{sub 2} concentration {le} 20% are nanocrystalline, with atomically abrupt grain boundaries and without observable graphitic or amorphous carbon phases. The growth and morphology of these films are controlled via a high nucleation rate resulting from low hydrogen concentration in the plasma. Initial growth is in the form of diamond, which is the thermodynamic equilibrium phase for grains {le}5 nm in diameter. Once formed, the diamond phase persists for grains up to at least 15-20 nm in diameter. The renucleation rate in the near-absence of atomic hydrogen is very high ({approximately} 10{sup 10} cm{sup {minus}2} sec{sup {minus}1}), limiting the average grain size to a nearly constant value as the film thickness increases, although the average grain size increases as hydrogen is added to the plasma. For hydrogen concentrations less than {approximately}20%, the growth species is believed to be the carbon dimer, C{sub 2}, rather than the CH{sub 3}* growth species associated with diamond film growth at higher hydrogen concentrations. For very thin films grown from the C{sub 60} precursor, the threshold field (2 to {approximately}60 volts/micron) for cold cathode electron emission depends on the electrical conductivity and on the surface topography, which in turn depends on the hydrogen concentration in the plasma. A model of electron emission, based on quantum well effects at the grain boundaries is presented. This model predicts promotion of the electrons at the grain boundary to the conduction band of diamond for a grain boundary width {approximately} 3--4 {angstrom}, a value within the range observed by TEM.

  19. Simultaneous Optimization of Nanocrystalline SnO2 Thin Film Deposition Using Multiple Linear Regressions

    PubMed Central

    Ebrahimiasl, Saeideh; Zakaria, Azmi

    2014-01-01

    A nanocrystalline SnO2 thin film was synthesized by a chemical bath method. The parameters affecting the energy band gap and surface morphology of the deposited SnO2 thin film were optimized using a semi-empirical method. Four parameters, including deposition time, pH, bath temperature and tin chloride (SnCl2·2H2O) concentration were optimized by a factorial method. The factorial used a Taguchi OA (TOA) design method to estimate certain interactions and obtain the actual responses. Statistical evidences in analysis of variance including high F-value (4,112.2 and 20.27), very low P-value (<0.012 and 0.0478), non-significant lack of fit, the determination coefficient (R2 equal to 0.978 and 0.977) and the adequate precision (170.96 and 12.57) validated the suggested model. The optima of the suggested model were verified in the laboratory and results were quite close to the predicted values, indicating that the model successfully simulated the optimum conditions of SnO2 thin film synthesis. PMID:24509767

  20. Influence of nanocrystalline size on optical band gap in CdSe thin films prepared by DC sputtering

    NASA Astrophysics Data System (ADS)

    Khalaf, Mohammed Khammass; ALhilli, Baha A. M.; Khudiar, Ausama I.; Alzahra, Anwar Abd

    2016-01-01

    Cadmium selenide CdSe thin films have been deposited on glass substrate by using plasma sputtering at room temperature with different times of sputtering. The CdSe thin films are characterized using XRD. The crystallite size of the film is calculated from XRD data, which is found as 12.65 nm as-deposited. It is also found that crystallite size of CdSe thin films increased with thin films thickness. The optical properties concerning the absorption spectra were studied for the prepared thin films. The energy band gaps were found to be in the range of 2.21 eV to 1.8 eV. On varying the film thickness in the range of 350 nm to 600 nm, it was found that the optical band gap increased due to the nanocrystalline size of the CdSe thin films decreased.

  1. Synthesis and characterization of pure anatase phase nanocrystalline TiO2 thin film by magnetron sputtering method

    NASA Astrophysics Data System (ADS)

    Pawar, Nimisha; Bhargava, Ankita; Dayal, Saurabh; Kumar, C. Sasi

    2016-05-01

    In present work, our focus is to deposit anatase phase nanocrystalline TiO2 thin films. In order to prepare Titanium oxide films we first deposited Titanium thin films using DC magnetron sputtering and then the substrates were annealed in a muffle furnace at different temperatures. Further the samples were characterized for analysis of phase, morphology and optical properties using XRD, SEM, AFM and photoluminescence spectroscopy respectively. XRD shows the formation of tetragonal phase TiO2 with lattice parameters values a= 3.8 Å and c=9.6 Å. The surface roughness value of the films were found to vary from 1.6 nm to 15.9 nm. The grain size as estimated from AFM varies from 48 nm to 125 nm at different temperatures. Thus, the results revealed the formation of ultra-smooth anatase phase pure nanocrystalline TiO2 spherical particles.

  2. Nanocrystalline ZnO thin film deposition on flexible substrate by low-temperature sputtering process for plastic displays.

    PubMed

    Banerjee, Arghya Narayan; Joo, Sang Woo; Min, Bong-Ki

    2014-10-01

    A low temperature sputter deposition process is adopted to fabricate nanocrystalline ZnO thin films on plastic (polyethylene terepthalate) substrate. Very good crystalline films are synthesized at a substrate temperature around 120 degrees C. Structural and microstructural analyses confirm the proper phase formation of the nanomaterial with an average nanoparticle size around 5-10 nm. Optical transmission analysis of the film deposited on plastic substrate depicts nearly 90% visible transmittance with a direct bandgap around 3.56 eV. This cost-effective, low-temperature fabrication of nanocrystalline thin film with very good structural and optical properties will find important applications in plastic display technology. Also the process is a vacuum-based clean process, which is compatible to CMOS-IC fabrication techniques and therefore, can easily be integrated with modern solid state device fabrication processes for diverse device applications.

  3. Defect engineered d{sup 0} ferromagnetism in tin-doped indium oxide nanostructures and nanocrystalline thin-films

    SciTech Connect

    Khan, Gobinda Gopal E-mail: sghoshphysics@gmail.com; Sarkar, Ayan; Ghosh, Shyamsundar E-mail: sghoshphysics@gmail.com; Mandal, Guruprasad; Mukherjee, Goutam Dev; Manju, Unnikrishnan; Banu, Nasrin; Dev, Bhupendra Nath

    2015-08-21

    Origin of unexpected defect engineered room-temperature ferromagnetism observed in tin-doped indium oxide (ITO) nanostructures (Nanowires, Nano-combs) and nanocrystalline thin films fabricated by pulsed laser deposition has been investigated. It is found that the ITO nanostructures prepared under argon environment exhibit strongest ferromagnetic signature as compared to that nanocrystalline thin films grown at oxygen. The evidence of singly ionized oxygen vacancy (V{sub 0}{sup +}) defects, obtained from various spectroscopic measurements, suggests that such V{sub 0}{sup +} defects are mainly responsible for the intrinsic ferromagnetic ordering. The exchange interaction of the defects provides extensive opportunity to tune the room-temperature d{sup 0} ferromagnetism and optical properties of ITOs.

  4. The Structural, optical and electrical properties of nanocrystalline ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Benhaoua, Boubaker; Rahal, Achour; Benramache, Said

    2014-04-01

    The Al doped ZnO thin films were deposited by ultrasonic spray technique. The influence of Al doping on structural, optical and electrical properties of the ZnO thin films was studied. A set of Al doped ZnO (0-3.5 wt.%) were deposited at 350 °C. Nanocrystalline films with a hexagonal wurtzite structure with a strong (0 0 2) preferred orientation were observed after Al doping. The maximum value of grain size (33.28 nm) is attained with Al doped ZnO at 3 wt.%. Texture coefficient TC(h k l) of the four major peaks where evaluated. Optically, in visible region the transmissions spectra T(λ) show that the whole doped films exhibit lower values than the non doped one which has as transmittance more than 80%; whereas in the same region the optical transmissions of the doped films are affected by the doping ration. The band gap (Eg) increased after doping from 3.267 to 3.325 eV with increasing concentration of doping from 0 to 2.75 wt.%, respectively, according to the Burstein-Moss effect (blue shift of Eg) then beyond 3 wt.% in doping the band gap exhibit a slight decreasing due to the coexistence of Roth and Burstein-Moss effect. The electrical resistivity of the films decreased from 20 to 5.26 (Ω cm). The best results are achieved with 2.75 wt.% Al doped ZnO film.

  5. Tailoring the morphology of mesoporous titania thin films through biotemplating with nanocrystalline cellulose.

    PubMed

    Ivanova, Alesja; Fattakhova-Rohlfing, Dina; Kayaalp, Bugra Eymer; Rathouský, Jiri; Bein, Thomas

    2014-04-23

    The tunable porosity of titania thin films is a key factor for successful applications in photovoltaics, sensing, and photocatalysis. Here, we report on nanocrystalline cellulose (NCC) as a novel shape-persistent templating agent enabling the straightforward synthesis of mesoporous titania thin films. The obtained structures are highly porous anatase morphologies having well-defined, narrow pore size distributions. By varying the titania-to-template ratio, it is possible to tune the surface area, pore size, pore anisotropy, and dimensions of titania crystallites in the films. Moreover, a post-treatment at high humidity and subsequent slow template removal can be used to achieve pore widening; this treatment is also beneficial for the multilayer deposition of thick films. The resulting homogeneous transparent films can be directly spin- or dip- coated on glass, silicon, and transparent conducting oxide (TCO) substrates. The mesoporous titania films show very high activity in the photocatalytic NO conversion and in the degradation of 4-chlorophenol. Furthermore, the films can be successfully applied as anodes in dye-sensitized solar cells.

  6. Preparation of large-pore mesoporous nanocrystalline TiO2 thin films with tailored pore diameters.

    PubMed

    Liu, Kesong; Fu, Honggang; Shi, Keying; Xiao, Fengshou; Jing, Liqiang; Xin, Baifu

    2005-10-13

    A novel and facile synthesis route to large-pore mesoporous nanocrystalline anatase thin films with tunable pore diameters in narrow distribution of sizes ranging from 8.3 to 14 nm is reported, using triblock copolymer as the template and Ti(OBu(n))4 as the inorganic precursor. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. A reasonable formation mechanism is also presented in this work.

  7. Synthesis and characterization of nanocrystalline CdS thin films for highly photosensitive self-powered photodetector

    NASA Astrophysics Data System (ADS)

    Husham, Mohammed; Hassan, Zainuriah; Selman, Abass M.

    2016-04-01

    A self-powered highly photosensitive photodetector based on a nanocrystalline CdS thin film was fabricated using a microwave-assisted chemical bath deposition. In this study, highly uniform nanocrystalline CdS thin films were grown on Si(1 0 0) substrates from aqueous solutions of cadmium chloride (CdCl2) and thiourea [SC(NH2)2], which served as cadmium Cd2+ and sulfur S2- ions sources, respectively. Structural, morphological and optical analysis revealed that good-quality nanocrystalline CdS thin films were synthesized. Current-voltage (I-V) measurements of the fabricated photodetector showed a significant sensitivity to visible light at zero applied voltage, indicating that the fabricated device is a self-powered photodetector. The device was highly photosensitive to low-power visible light; it showed a sensitivity of 97.2 × 103 to (1.20 mW/cm2) 500-nm light, without an external bias. Photoresponse measurements demonstrated the highly reproducible characteristics of the fabricated photodetector with rapid response and baseline recovery time. This work introduces a simple and low-cost method for fabricating a rapid-response, highly photosensitive photodetector with zero power consumption. The mechanism of self-powered photodetectors is discussed.

  8. Facile Synthesis of Cu2ZnSnS4 Photovoltaic Absorber Thin Films via Sulfurization of Cu2SnS3/ZnS Layers

    NASA Astrophysics Data System (ADS)

    Kahraman, Süleyman; Podlogar, Mateja; Bernik, Slavko; Güder, Hüsnü Salih

    2014-04-01

    Copper zinc tin sulfide (Cu2ZnSnS4) has been receiving a lot of attention in recent years as a new, alternative absorber for the production of cheap thin film solar cells owing to the high natural abundance of all the constituents, its tunable direct-band-gap energy, and its large optical absorption coefficient. In addition, to overcome the problem of expensive vacuum-based methods, solution-based approaches are being developed for Cu2ZnSnS4 deposition. In this study, Cu2ZnSnS4 thin films were grown on soda lime glass substrates via the sulfurization of solution grown Cu2SnS3/ZnS stacked sulfide layers. A new facile route to overcome the difficulty of depositing Cu2ZnSnS4 thin film with a desired stoichiometric composition in a single cation solution has been presented. The influences of deposition cycles of layers on the morphological, compositional, structural, and optical properties of the samples were investigated. It was observed from scanning electron microscopy (SEM) images that the films were continuous and composed of homogenously distributed large grains. Possible chemical formulations of the best samples were predicted to be Cu1.99Zn1.25Sn1.00S3.76 and Cu1.97Zn1.03Sn1.29S3.71 via energy-dispersive X-ray spectroscopy (EDXS) results. The X-ray diffraction (XRD) patterns of the samples matched very well with the reference values. The Raman-scattering analysis of the films proved the phase purity of the CZTS samples. The optical absorption coefficient of the films was found to be about 104 cm-1 based on absorbance spectroscopy. The optical band gaps of the films were estimated to be between 1.36 and 1.50 eV. From these we are able to conclude that CZTS thin films can be effectively obtained via the vacuum-atmosphere sulfurization of Cu2SnS3/ZnS stacked sulfide layers.

  9. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    PubMed Central

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-01-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency. PMID:27194181

  10. Effect of fluorine doping on highly transparent conductive spray deposited nanocrystalline tin oxide thin films

    NASA Astrophysics Data System (ADS)

    Moholkar, A. V.; Pawar, S. M.; Rajpure, K. Y.; Bhosale, C. H.; Kim, J. H.

    2009-09-01

    The undoped and fluorine doped thin films are synthesized by using cost-effective spray pyrolysis technique. The dependence of optical, structural and electrical properties of SnO 2 films, on the concentration of fluorine is reported. Optical absorption, X-ray diffraction, scanning electron microscope (SEM) and Hall effect studies have been performed on SnO 2:F (FTO) films coated on glass substrates. The film thickness varies from 800 to 1572 nm. X-ray diffraction pattern reveals the presence of cassiterite structure with (2 0 0) preferential orientation for FTO films. The crystallite size varies from 35 to 66 nm. SEM and AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The 20 wt% F doped film has a minimum resistivity of 3.8 × 10 -4 Ω cm, carrier density of 24.9 × 10 20 cm -3 and mobility of 6.59 cm 2 V -1 s -1. The sprayed FTO film having minimum resistance of 3.42 Ω/cm 2, highest figure of merit of 6.18 × 10 -2 Ω -1 at 550 nm and 96% IR reflectivity suggest, these films are useful as conducting layers in electrochromic and photovoltaic devices and also as the passive counter electrode.

  11. Dip coated nanocrystalline CdZnS thin films for solar cell application

    SciTech Connect

    Dongre, J. K. Chaturvedi, Mahim; Patil, Yuvraj; Sharma, Sandhya; Jain, U. K.

    2015-07-31

    Nanocrystalline cadmium sulfide (CdS) and zinc cadmium sulfide (ZnCdS) thin films have been grown via simple and low cost dip coating technique. The prepared films are characterized by X-ray diffraction (XRD), atomic force microscopic (AFM) and UV-VIS spectrophotometer techniques to reveal their structural, morphological and optical properties. XRD shows that both samples grown have zinc blende structure. The grain size is calculated as 6.2 and 8 nm using Scherrer’s formula. The band gap value of CdS and CdZnS film is estimated to be 2.58 and 2.69 eV respectively by UV-vis spectroscopy. Photoelectrochemical (PEC) investigations are carried out using cell configuration as n-CdZnS/(1M NaOH + 1M Na2S + 1M S)/C. The photovoltaic output characteristic is used to calculate fill-factor (FF) and solar conversion efficiency (η)

  12. Electrochemical Evaluation of Nanocrystalline Diamond Thin Films on Ti-6Al-4V Implant Alloy

    NASA Astrophysics Data System (ADS)

    Fries, Marc; Venugopalan, Ramakrishna; Vohra, Yogesh

    2002-03-01

    Some 186,000 hip replacement surgeries are peformed every year in the United States alone. About 10surgeries are revision operations to replace an implant that has most likely failed through mechanical-electrochemical interactions resulting in implant wear. The ability to enhance the resistance to such mechanical-electrochemical interaction and thereby reduce wear could result in significantly increased device lifespan. Nanocrystalline diamond (NCD) thin films were deposited on Ti-6Al-4V disk samples (processed per ASTM F86 standard for medical implant surface conditions) using microwave plasma chemical vapor deposition (MPCVD). As a first step, these samples (n=3/test per group) were subjected to electrochemical evaluation in inorganic neutral salt solution at 37 C. The electrochemical evaluation involved both impedence spectroscopy (per ASTM G106) and polarization testing (per ASTM G5). The impedence spectroscopy data indicated a significantly higher charge transfer resistance at the interface due to the protective NCD as compared to the bare or uncoated substrate. The polarization test data confirmed that this increased charge transfer resistance resulted in a decreased current density measurement. This decreased current density measurement resulted in an order of magnitude lower calculated static corrosion rate from the NCD coated samples as opposed to the uncoated controls. Future studies will focus on investigations that will facilitate transfer of these static electrochemical resistance results to a more relevant mechanical-electrochemical interaction milieu.

  13. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    NASA Astrophysics Data System (ADS)

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-05-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency.

  14. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    SciTech Connect

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300 deg. C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300 deg. C are found to be 0.0178 and 0.0279 mV/ deg. C, respectively.

  15. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    NASA Astrophysics Data System (ADS)

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300°C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300°C are found to be 0.0178 and 0.0279mV/°C, respectively.

  16. Nanocrystalline-CdS thin films grown on flexible PET-substrates by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rosales, K.; Quiñones-Galván, J. G.; Guillén-Cervantes, A.; Campos-González, E.; Santos-Cruz, J.; Mayén-Hernández, S. A.; Arias-Cerón, J. S.; Olvera, M. de la L.; Zelaya-Angel, O.; Hernández-Hernández, L. A.; Contreras-Puente, G.; de Moure-Flores, F.

    2017-07-01

    CdS thin films were grown on flexible PET and PET/ITO substrates by chemical bath deposition varying the deposition time. The structural analysis indicates that CdS films are composed of nano-crystalline and amorphous material. CdS films grown on PET substrates have hexagonal phase, while those grown on PET/ITO substrates have a cubic phase. The bandgap values of CdS films grown on PET substrates are in the range 2.31-2.45 eV, and the E g of CdS films grown on PET/ITO substrates are 2.18-2.42 eV. A strong green photoluminescence emission was observed in all the samples, which is associated to near band edge transitions. CdS films grown on PET/ITO substrates have an additional emission at 2.80 eV, which can be attributed to the presence of nano-crystals, in agreement with TEM analyses.

  17. Ultrananocrystalline and nanocrystalline diamond thin films for NEMS/MEMS applications.

    SciTech Connect

    Sumant, A. V.; Auciello, O.; Carpick, R. W.; Srinivasan, S.; Butler, J. E.

    2010-04-01

    There has been a tireless quest by the designers of micro- and nanoelectro mechanical systems (MEMS/NEMS) to find a suitable material alternative to conventional silicon. This is needed to develop robust, reliable, and long-endurance MEMS/NEMS with capabilities for working under demanding conditions, including harsh environments, high stresses, or with contacting and sliding surfaces. Diamond is one of the most promising candidates for this because of its superior physical, chemical, and tribomechanical properties. Ultrananocrystalline diamond (UNCD) and nanocrystalline diamond (NCD) thin films, the two most studied forms of diamond films in the last decade, have distinct growth processes and nanostructures but complementary properties. This article reviews the fundamental and applied science performed to understand key aspects of UNCD and NCD films, including the nucleation and growth, tribomechanical properties, electronic properties, and applied studies on integration with piezoelectric materials and CMOS technology. Several emerging diamond-based MEMS/NEMS applications, including high-frequency resonators, radio frequency MEMS and photonic switches, and the first commercial diamond MEMS product - monolithic diamond atomic force microscopy probes - are discussed.

  18. Power-law photoconductivity time decay in nanocrystalline TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Comedi, D.; Heluani, S. P.; Villafuerte, M.; Arce, R. D.; Koropecki, R. R.

    2007-12-01

    The sub-band-gap excited photoconductivity (PC) time decay and the film structure of rf-sputter deposited nanocrystalline TiO2 thin films have been studied. Atomic force microscopy and x-ray diffraction measurements were used to assess roughness, crystalline structure and mean grain size of the films. Samples fabricated under different deposition conditions exhibit different microstructures and absolute PC, but similar persistent PC behaviour after switching off the light source. The very slow PC decay can be well represented by a function that is nearly constant for short times and decreases as a power law for times longer than about 100 s. This function is shown to be consistent with a rate equation characterized by a relaxation time that increases linearly with time. This behaviour, in turn, agrees with predictions of a previously reported model that assumes electron-hole recombination limited by carrier-density-dependent potential barriers associated with inhomogeneities. These results may have important implications on attempts to determine distributions of trap energies from PC decay curves in TiO2.

  19. Selective Growth of Nanocrystalline 3C-SiC Thin Films on Si

    NASA Astrophysics Data System (ADS)

    Beke, D.; Pongrácz, A.; Battistig, G.; Josepovits, K.; Pécz, B.

    2010-11-01

    Epitaxial formation of SiC nanocrystals has been investigated on single crystal silicon surfaces. A simple and cheap method using reactive annealing in CO has been developed and patented by our group (BME AFT and MTA MFA). By this technique epitaxial 3C-SiC nanocrystals can be grown at the Si side of a SiO2/Si interface without void formation at the SiC/Si interface. CO diffusion and SiC nanocrystal formation on different silicon based systems (SiO2/Si, Si3N4/3Si and SiO2/LPCVD poly-Si) after CO treatment at 105 Pa at elevated temperatures (T>1000° C) will be presented. By optimizing the annealing time a thin continuous nanocrystalline SiC layer has been formed. Applying a patterned Si3N4 capping layer as a barrier layer against CO diffusion, SiC nanocrystal formation at the Si3N4/Si interface is inhibited. We will present the selective growth of SiC nanocrystals using the before mentioned technique.

  20. Structure, Morphology, and Optical Properties of Amorphous and Nanocrystalline Gallium Oxide Thin Films

    SciTech Connect

    Kumar, S. Sampath; Rubio, E. J.; Noor-A-Alam, M.; Martinez, G.; Manandhar, Sandeep; Shutthanandan, V.; Thevuthasan, Suntharampillai; Ramana, C.V.

    2013-02-15

    Ga2O3 thin films were produced by sputter deposition by varying the substrate temperature (Ts) in a wide range (Ts=25-800 oC). The structural characteristics and optical properties of Ga2O3 films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga2O3 films. XRD and SEM analyses indicate that the Ga2O3 films grown at lower temperatures were amorphous while those grown at Ts≥500 oC were nanocrystalline. RBS measurements indicate the well-maintained stoichiometry of Ga2O3 films at Ts=300-700 oC. The spectral transmission of the films increased with increasing temperature. The band gap of the films varied from 4.96 eV to 5.17 eV for a variation in Ts in the range 25-800 oC. A relationship between microstructure and optical property is discussed.

  1. Direct-Coated Photoconducting Nanocrystalline PbS Thin Films with Tunable Band Gap

    NASA Astrophysics Data System (ADS)

    Vankhade, Dhaval; Kothari, Anjana; Chaudhuri, Tapas K.

    2016-06-01

    Nanocrystalline PbS thin films are deposited on glass by direct coating from a precursor solution of lead acetate and thiourea in methanol. A single coating has a thickness of 50 nm and greater thicknesses are obtained from layer by layer deposition. The films are smooth and shiny with roughness (rms) of about 1.5 nm. X-ray diffraction studies show that films are cubic PbS with crystallite size about 10 nm. The films are p-type with dark electrical conductivities in the range of 0.4-0.5 S/cm. These films are basically photoconducting. Photoconductivity monotonically increases with increase in thickness. The band gap of the films strongly depends on the thickness of the films. The band gap decreases from 2.4 eV to 1.6 eV as the thickness is increased from 50 nm to 450 nm. The tunability of the band gap is useful for technical applications, such as solar cells and photodetectors.

  2. Thermal conductivity of self-ion irradiated nanocrystalline zirconium thin films

    DOE PAGES

    Pulavarthy, Raghu; Wang, Baoming; Hattar, Khalid; ...

    2017-07-15

    Thermomechanical stability and high thermal conductivity are important for nuclear cladding material performance and reliability, which degrade over time under irradiation. The literature suggests nanocrystalline materials as radiation tolerant, but little or no evidence is present from thermal transport perspective. In this study, we irradiated 10 nm grain size zirconium thin films with 800 keV Zr+ beam from a 6 MV HVE Tandem accelerator to achieve various doses of 3 × 1010 to 3.26 × 1014 ions/cm2, corresponding to displacement per atom (dpa) of 2.1 × 10–4 to 2.28. Transmission electron microscopy showed significant grain growth, texture evolution and oxidationmore » in addition to the creation of displacement defects due to the irradiation. The specimens were co-fabricated with micro-heaters to establish thermal gradients that were mapped using infrared thermometry. An energy balance approach was used to estimate the thermal conductivity of the specimens, as function of irradiation dosage. As a result, up to 32% reduction of thermal conductivity was measured for the sample exposed to a dose of 2.1 dpa (3 × 1014 ions/cm2).« less

  3. Reactive Radiofrequency Sputtering-Deposited Nanocrystalline ZnO Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Li, Shao-Juan; He, Xin; Han, De-Dong; Sun, Lei; Wang, Yi; Han, Ru-Qi; Chan, Man-Sun; Zhang, Sheng-Dong

    2012-01-01

    The structural and electrical properties of ZnO films deposited by reactive radiofrequency sputtering with a metallic zinc target are systematically investigated. While the as-deposited ZnO film is in a poly-crystalline structure when the partial pressure of oxygen (pO2) is low, the grain size abruptly decreases to a few nanometers as pO2 increases to a critical value, and then becomes almost unchanged with a further increase in pO2. In addition, the resistivity of the ZnO films shows a non-monotonic dependence on pO2, including an abrupt transition of about seven orders of magnitude at the critical pO2. Thin-film transistors (TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 107, an off-current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2cm2/(V·s). The results show that radiofrequency sputtered ZnO with a zinc target is a promising candidate for high-performance ZnO TFTs.

  4. Biocompatible nanocrystalline octacalcium phosphate thin films obtained by pulsed laser deposition.

    PubMed

    Socol, G; Torricelli, P; Bracci, B; Iliescu, M; Miroiu, F; Bigi, A; Werckmann, J; Mihailescu, I N

    2004-06-01

    We extended for the first time pulsed laser ablation to the deposition of octacalcium phosphate Ca8H2(PO4)6.5H2O (OCP) thin films. The depositions were performed with a pulsed UV laser source (lambda=248 nm, tau> or =20 ns) in a flux of hot water vapors. The targets were sintered from crystalline OCP powder and the laser ablation fluence was set at values of 1.5-2 J/cm2. During depositions the collectors, Si or Ti substrates, were maintained at a constant temperature within the range 20-200 degrees C. The resulting structures were submitted to heat treatment in hot water vapors for up to 6 h. The best results were obtained at a substrate temperature of 150 degrees C during both deposition and post-deposition treatment. High-resolution electron microscopy and XRD at grazing incidence indicated that the coatings obtained were made of nanocrystalline OCP. Cross-section TEM investigations showed that the coatings contained droplets stacked on Ti substrates as well as distributed across the entire thickness of the arborescence-like structure layers. The results of WST-1 assay, cell adherence, DNA replication, and caspase-1 activity confirmed the good biocompatibility of the coatings.

  5. Nanocrystalline CsPbBr3 thin films: a grain boundary opto-electronic study

    NASA Astrophysics Data System (ADS)

    Conte, G.; Somma, F.; Nikl, M.

    2005-01-01

    CsPbBr3 thin films with nanocrystalline morphology were studied by using optoelectronic techniques to infer the grain boundary region in respect of the crystallite's interior performance. Co-evaporation of puri-fied powders or crushed Bridgman single crystals were used to deposit materials and compare recombina-tion mechanism and dielectric relaxation processes within them. Nanosecond photoconduction decay was observed on both materials as well as activated hopping transport. An asymmetric Debye-like peak was evaluated from impedance spectroscopy with a FWHM value, which remains constant for 1.25 +/- 0.02 deca-des, addressing the presence of a tight conductivity relaxation times distribution. The evaluated activation energy, equal to 0.72 +/- 0.05 eV, similar to that estimated by DC measurements, is well smaller then that expected for an intrinsic material with exciton absorption at 2.36 eV. A simple model based on Voigt's elements was used to model the electronic characteristics of these nanostructured materials, to discuss observed results and define the role played by grain boundaries.

  6. Optical Properties of Ar Ions Irradiated Nanocrystalline ZrC and ZrN Thin Films

    NASA Technical Reports Server (NTRS)

    Martin, C.; Miller, K. H.; Makino, H.; Craciun, D.; Simeone, D.; Craciun, V.

    2016-01-01

    Thin nanocrystalline ZrC and ZrN films (less than 400 nanometers), grown on (100) Si substrates at a substrate temperature of 500 degrees Centigrade by the pulsed laser deposition (PLD) technique, were irradiated by 800 kiloelectronvolts Ar ion irradiation with fluences from 1 times 10(sup 14) atoms per square centimeter up to 2 times 10(sup 15) atoms per square centimeter. Optical reflectance data, acquired from as-deposited and irradiated films, in the range of 500-50000 per centimeter (0.06–6 electronvolts), was used to assess the effect of irradiation on the optical and electronic properties. Both in ZrC and ZrN films we observed that irradiation affects the optical properties of the films mostly at low frequencies, which is dominated by the free carriers response. In both materials, we found a significant reduction in the free carriers scattering rate, i.e. possible increase in mobility, at higher irradiation flux. This is consistent with our previous findings that irradiation affects the crystallite size and the micro-strain, but it does not induce major structural changes.

  7. Molecular dynamics study of deformation and fracture in a tantalum nano-crystalline thin film

    NASA Astrophysics Data System (ADS)

    Smith, Laura; Zimmerman, Jonathan A.; Hale, Lucas M.; Farkas, Diana

    2014-06-01

    We present results from molecular dynamics simulations of two nano-crystalline tantalum thin films that illuminate the variety of atomic-scale mechanisms of incipient plasticity. Sample 1 contains approximately 500 K atoms and 3 grains, chosen to facilitate study at 105 s-1 strain rate; sample 2 has 4.6 M atoms and 30 grains. The samples are loaded in uniaxial tension at deformation rates of 105-109 s-1, and display phenomena including emission of perfect 1/2<1 1 1>-type dislocations and the formation and migration of twin boundaries. It was found that screw dislocation emission is the first deformation mechanism activated at strain rates below 108 s-1. Deformation twins emerge as a deformation mechanism at higher strains, with twins observed to cross grain boundaries as larger strains are reached. At high strain rates atoms are displaced with the characteristic twin vector at a ratio of 3 : 1 (108 s-1) or 4 : 1 (109 s-1) to characteristic dislocation vectors. Fracture is nucleated through a nano-void growth process. Grain boundary sliding does not scale with increasing strain rate. Detailed analysis of nano-scale deformation using these tools enhances our understanding of deformation mechanisms in tantalum.

  8. Study of nanocrystalline thin cobalt films with perpendicular magnetic anisotropy obtained by thermal evaporation

    NASA Astrophysics Data System (ADS)

    Kozłowski, Witold; Balcerski, Józef; Szmaja, Witold

    2017-02-01

    We have performed a detailed investigation of the morphological and magnetic domain structures of nanocrystalline thin cobalt films with perpendicular magnetic anisotropy. The films were thermally evaporated at an incidence angle of 0° in a vacuum of about 10-5 mbar and possessed thicknesses in the range from 60 nm to 100 nm. The films were studied by X-ray photoelectron spectroscopy (XPS), electron diffraction of transmission electron microscopy (TEM), atomic force microscopy (AFM), magnetic force microscopy (MFM) and the Fresnel mode of TEM. The films are polycrystalline and consist of very densely packed grains with sizes at the nanometer range. The grains are roundish in shape and generally exhibit no geometric alignment. The films are mainly composed of the hexagonal close-packed (HCP) phase of cobalt and possess preferential orientation of the cobalt grains with the hexagonal axis perpendicular to the film surface. 70 nm thick films and thicker have fully perpendicular magnetization, while 60 nm thick films possess clearly dominating perpendicular magnetization component. The magnetic domain structure is in the form of stripe domains forming a maze pattern. When the film thickness increases from 60 nm to 100 nm, the average grain size increases from 28.9 nm to 31.5 nm and the average domain width increases from 79.4 nm to 98.7 nm.

  9. Investigation on structural, optical, morphological and electrical properties of thermally deposited lead selenide (PbSe) nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Shyju, T. S.; Anandhi, S.; Sivakumar, R.; Garg, S. K.; Gopalakrishnan, R.

    2012-08-01

    In this paper, we report the substrate temperature induced changes in physical properties of thermal evaporated lead selenide (PbSe) thin films from the chemically synthesized nanocrystalline PbSe powders. As the first step, nanocrystalline lead selenide was synthesized by simple chemical method at 80 °C using lead nitrate [Pb(NO3)2] and sodium selenosulphate [Na2SeSO3] in the aqueous alkaline media. Ethylene Diamine Tetra acetic acid (0.1 M) was used as a complexing agent to form stable complexes with metal ions. Later on, the lead selenide thin films were deposited on the degreased glass substrates under a vacuum of 10-5 Torr at various substrate temperatures by thermal evaporation technique using the pre-synthesized nanocrystalline PbSe powders. X-ray diffraction results show the synthesized powders and the deposited PbSe films belong to cubic structure. A gradual reduction in optical bandgap of films was observed with increasing substrate temperatures, which revealed the crystallization of the films. These observations are corroborated by photoluminescence spectroscopy study. Changes in surface morphology of the films with respect to substrate temperature were studied by high resolution scanning electron microscopy and atomic force microscopy. Electrical study infers the deposited films are of p-type semiconducting nature.

  10. Effect of aging heat time and annealing temperature on the properties of nanocrystalline tin dioxide thin films

    NASA Astrophysics Data System (ADS)

    Kadhim, Imad H.; Abu Hassan, H.

    2017-04-01

    Nanocrystalline tin dioxide (SnO2) thin films have been successfully prepared by sol-gel spin-coating technique on p-type Si (100) substrates. A stable solution was prepared by mixing tin(II) chloride dihydrate, pure ethanol, and glycerin. Temperature affects the properties of SnO2 thin films, particularly the crystallite size where the crystallization of SnO2 with tetragonal rutile structure is achieved when thin films that prepared under different aging heat times are annealed at 400∘C. By increasing aging heat time in the presence of annealing temperatures the FESEM images indicated that the thickness of the fabricated film was directly proportional to solution viscosity, increasing from approximately 380 nm to 744 nm, as well as the crystallization of the thin films improved and reduced defects.

  11. Optical and Surface Characteristics of Mg-Doped GaAs Nanocrystalline Thin Film Deposited by Thermionic Vacuum Arc Technique

    NASA Astrophysics Data System (ADS)

    Pat, Suat; Özen, Soner; Şenay, Volkan; Korkmaz, Şadan

    2017-01-01

    Magnesium (Mg) is the most promising p-type dopant for gallium arsenide (GaAs) semiconductor technology. Mg-doped GaAs nanocrystalline thin film has been deposited at room temperature by the thermionic vacuum arc technique, a rapid deposition method for production of doped GaAs material. The microstructure and surface and optical properties of the deposited sample were investigated by x-ray diffraction analysis, scanning electron microscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, ultraviolet-visible spectrophotometry, and interferometry. The crystalline direction of the deposited sample was determined to be (220) plane and (331) plane at 44.53° and 72.30°, respectively. The Mg-doped GaAs nanocrystalline sample showed high transmittance.

  12. Luminescence characteristics of impurities-activated ZnS nanocrystals prepared in microemulsion with hydrothermal treatment

    NASA Astrophysics Data System (ADS)

    Xu, S. J.; Chua, S. J.; Liu, B.; Gan, L. M.; Chew, C. H.; Xu, G. Q.

    1998-07-01

    Cu-, Eu-, or Mn-doped ZnS nanocrystalline phosphors were prepared at room temperature using a chemical synthesis method. Transmission electron microscopy observation shows that the size of the ZnS clusters is in the 3-18 nm range. New luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the doped ZnS nanocrystals at room temperature. These results strongly suggest that impurities, especially transition metals and rare-earth metals-activated ZnS nanoclusters form a new class of luminescent materials.

  13. Microstructure evolution of metallic nanocrystalline thin-films under ion-beam irradiation

    NASA Astrophysics Data System (ADS)

    Kaoumi, Djamel

    The microstructural evolution of nanocrystalline metallic thin-films under ion irradiation, especially grain growth and second-phase precipitation, was studied with detailed in situ experiments, and a theoretical model was developed to explain the results of grain-growth. Free-standing Zr, Pt, Cu and Au, Cu-Fe, and Zr-Fe nanocrystalline thin films prepared by sputter deposition were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Ar and Kr ions to fluences in excess of 1016 ion/cm2 at temperatures ranging from 20 to 773 K. The microstructural evolution of the thin-films was followed in situ by systematically recording bright field images and diffraction patterns at successive ion-irradiation doses. Grain growth was observed as a result of irradiation in all samples at all irradiation temperatures. The results suggest the existence of three regimes with increasing irradiating temperature: a low temperature regime (below about 0.15 to 0.22 Tm) where grain-growth does not depend on the irradiation temperature, a thermally assisted regime where both the grain-growth rate and the final grain size increase with increasing irradiation temperature, and a thermal regime where thermal effects dominate ion beam effects. Similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type: Dn-Dn0=KF with n˜3 in the low temperature regime. The effect of solute addition on grain-growth was investigated using Zr(Fe) and Cu(Fe) supersaturated solid-solutions. In the case of Zr-Fe, Zr2Fe precipitates formed during irradiation (with the dose-to-precipitation of Zr2Fe decreasing with increasing irradiation temperature), whereas Cu-Fe remained as a solid-solution. The grain-growth rate and final size decreased in both alloys with respect to the pure metallic films as a result of second-phase particle pinning (Zener drag) (Zr-Fe), and solute drag (Cu-Fe). The grain

  14. Cobalt and nickel macrocycles anchored to nanocrystalline titanium dioxide thin films: Sensitization, catalysis, and ligand association

    NASA Astrophysics Data System (ADS)

    Achey, Darren Craig

    The global demand for renewable, clean electricity and fuel has compelled efforts to utilize the immense power incident upon the Earth from the Sun. Photovoltaic systems could power the planet's electrical demands with only moderate efficiencies. However, mitigation of fossil fuels used for transportation and night-time electricity requires the storage of photon energy, for example, in the form of chemical bonds. Mesoporous, nanocrystalline TiO2 thin films provide a manifold for anchoring molecular species that absorb and utilize photons to catalyze fuel-generating reactions. The overarching theme of this thesis is to improve understanding of the semiconductor/molecule interface utilizing earth abundant first-row transition metal coordination compounds. Chapter 2 presents the non-ideal redox behavior of cobalt porphyrins anchored to semiconductor surfaces. Additionally, CoI porphyrins were utilized as photocatalysts for the 2e- reduction of organobromides to yield a CoIII-R intermediate. The cobalt-carbon bond of CoIII-R was photodissociated with visible light to yield Co II and R·. The organic radical dimerized to form R-R. Light excitation of CoI compounds was found to result in electron transfer to TiO2, Chapter 3. Cobalt porphyrins, phthalocyanines, glyoximes, and corrins were all observed to exhibit this behavior. Electron transfer was demonstrated to primarily occur via excitation into the large extinction coefficient metal-to-ligand charge transfer absorption bands of CoI complexes. Chapter 4 focuses on the unique coordination chemistry of cobalt porphyrins anchored to a TiO2 thin film. Notably, pyridine axially ligated a CoII porphyrin following excited-state electron transfer of the CoI porphyrin to the TiO2. The rate constant for recombination of an electron in the TiO2 with CoII was observed to decrease with increasing pyridine concentration, behavior attributed primarily to a negative shift of the CoII/I potential in the presence of pyridine. Finally

  15. Enhanced violet photoemission of nanocrystalline fluorine doped zinc oxide (FZO) thin films

    NASA Astrophysics Data System (ADS)

    Anusha, Muthukumar; Arivuoli, D.; Manikandan, E.; Jayachandran, M.

    2015-09-01

    Highly stable fluorine doped nanocrystalline zinc oxide thin films were prepared on corning glass substrates by aerosol assisted chemical vapor deposition (AACVD) at variable deposition temperature of 360 °C, 380 °C and 420 °C. Especially, the optimum deposition temperature was investigated for high intense violet emission. The film crystallinity improved with the increasing deposition temperature and highly textured film was obtained at 420 °C. The films exhibited surface morphology variation from spherical to platelets due to deposition temperature effect, analyzed by field emission scanning electron microscope (FE-SEM). Higher growth rate observed at 420 °C which leads larger grains and lowest resistivity of ∼5.77 Ω cm among the deposited films which may be due to reduction in zinc vacancies and grain boundary area. Zinc vacancies are acts as electron killer centres. UV-visible spectra indicated higher transmittance (83-90%) in the visible region. Red shift of optical absorption edges associated with the increase in particle size consistent well with the XRD results. Reduced E2(high) intensity was observed in Raman spectra, for the film deposited at 380 °C which indicates decreased oxygen incorporation confirmed by PL spectra. Especially, enhanced violet emission observed at 3.06 eV for the films deposited at 380 °C due to electronic transition from the defect level of zinc vacancies to the conduction band, probably attributed to enhanced incorporation of 'F' into 'O' sites associated with increased Zn vacancies and also decreased oxygen incorporation consistent with the electrical and Raman analyses.

  16. Effect of film thickness on NO2 gas sensing properties of sprayed orthorhombic nanocrystalline V2O5 thin films

    NASA Astrophysics Data System (ADS)

    Mane, A. A.; Moholkar, A. V.

    2017-09-01

    The nanocrystalline V2O5 thin films with different thicknesses have been grown onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD study shows that the films exhibit an orthorhombic crystal structure. The narrow scan X-ray photoelectron spectrum of V-2p core level doublet gives the binding energy difference of 7.3 eV, indicating that the V5+ oxidation state of vanadium. The FE-SEM micrographs show the formation of nanorods-like morphology. The AFM micrographs show the high surface area to volume ratio of nanocrystalline V2O5 thin films. The optical study gives the band gap energy values of 2.41 eV, 2.44 eV, 2.47 eV and 2.38 eV for V2O5 thin films deposited with the thicknesses of 423 nm, 559 nm, 694 nm and 730 nm, respectively. The V2O5 film of thickness 559 nm shows the NO2 gas response of 41% for 100 ppm concentration at operating temperature of 200 °C with response and recovery times of 20 s and 150 s, respectively. Further, it shows the rapid response and reproducibility towards 10 ppm NO2 gas concentration at 200 °C. Finally, NO2 gas sensing mechanism based on chemisorption process is discussed.

  17. Swift heavy ion induced optical and structural modifications in RF sputtered nanocrystalline ZnO thin film

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Singhal, R.; Vishnoi, R.; Kumar, V. V. S.; Kulariya, P. K.

    2017-01-01

    In the present study, 100 MeV Ag7+ ion beam-induced structural and optical modifications of nanocrystalline ZnO thin films are investigated. The nanocrystalline ZnO thin films are grown using radio frequency magnetron sputtering and irradiated at fluences of 3 × 1012, 1 × 1013 and 3 × 1013 ions/cm2. The incident swift heavy ions induced change in the crystallinity together with the preferential growth of crystallite size along the c axis (002) orientation. The average crystallite size is found to be increased from 10.8 ± 0.7 to 20.5 ± 0.3 nm with increasing the ion fluence. The Atomic force microscopy analysis confirms the variation in the surface roughness by varying the incident ion fluences. The UV-visible spectroscopy shows the decrement in transmittance of the film with ion irradiation. The micro-Raman spectra of ZnO thin films are investigated to observe ion-induced modifications which support the increased lattice defects with higher fluence. The variation in crystallinity indicates that ZnO-based devices can be used in piezoelectric transduction mechanism.

  18. Swift heavy ion induced optical and structural modifications in RF sputtered nanocrystalline ZnO thin film

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Singhal, R.; Vishnoi, R.; Kumar, V. V. S.; Kulariya, P. K.

    2017-05-01

    In the present study, 100 MeV Ag7+ ion beam-induced structural and optical modifications of nanocrystalline ZnO thin films are investigated. The nanocrystalline ZnO thin films are grown using radio frequency magnetron sputtering and irradiated at fluences of 3 × 1012, 1 × 1013 and 3 × 1013 ions/cm2. The incident swift heavy ions induced change in the crystallinity together with the preferential growth of crystallite size along the c axis (002) orientation. The average crystallite size is found to be increased from 10.8 ± 0.7 to 20.5 ± 0.3 nm with increasing the ion fluence. The Atomic force microscopy analysis confirms the variation in the surface roughness by varying the incident ion fluences. The UV-visible spectroscopy shows the decrement in transmittance of the film with ion irradiation. The micro-Raman spectra of ZnO thin films are investigated to observe ion-induced modifications which support the increased lattice defects with higher fluence. The variation in crystallinity indicates that ZnO-based devices can be used in piezoelectric transduction mechanism.

  19. Microstructure factor and mechanical and electronic properties of hydrogenated amorphous and nanocrystalline silicon thin-films for microelectromechanical systems applications

    SciTech Connect

    Mouro, J.; Gualdino, A.; Chu, V.; Conde, J. P.

    2013-11-14

    Thin-film silicon allows the fabrication of MEMS devices at low processing temperatures, compatible with monolithic integration in advanced electronic circuits, on large-area, low-cost, and flexible substrates. The most relevant thin-film properties for applications as MEMS structural layers are the deposition rate, electrical conductivity, and mechanical stress. In this work, n{sup +}-type doped hydrogenated amorphous and nanocrystalline silicon thin-films were deposited by RF-PECVD, and the influence of the hydrogen dilution in the reactive mixture, the RF-power coupled to the plasma, the substrate temperature, and the deposition pressure on the structural, electrical, and mechanical properties of the films was studied. Three different types of silicon films were identified, corresponding to three internal structures: (i) porous amorphous silicon, deposited at high rates and presenting tensile mechanical stress and low electrical conductivity, (ii) dense amorphous silicon, deposited at intermediate rates and presenting compressive mechanical stress and higher values of electrical conductivity, and (iii) nanocrystalline silicon, deposited at very low rates and presenting the highest compressive mechanical stress and electrical conductivity. These results show the combinations of electromechanical material properties available in silicon thin-films and thus allow the optimized selection of a thin silicon film for a given MEMS application. Four representative silicon thin-films were chosen to be used as structural material of electrostatically actuated MEMS microresonators fabricated by surface micromachining. The effect of the mechanical stress of the structural layer was observed to have a great impact on the device resonance frequency, quality factor, and actuation force.

  20. Enhancement of photo sensor properties of nanocrystalline ZnO thin film by swift heavy ion irradiation

    SciTech Connect

    Mahajan, S. V.; Upadhye, D. S.; Bagul, S. B.; Shaikh, S. U.; Birajadar, R. B.; Siddiqui, F. Y.; Huse, N. P.; Sharma, R. B. E-mail: rps.phy@gmail.com

    2015-06-24

    Nanocrystalline Zinc Oxide (ZnO) thin film prepared by Low cost Successive Ionic Layer Adsorption and Reaction (SILAR) method. This film was irradiated by 120 MeV Ni{sup 7+} ions with the fluence of 5x10{sup 12}ions/cm{sup 2}. The X-ray diffraction study was shows polycrystalline nature with wurtzite structure. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Photo Sensor nature was calculated by I-V characteristics with different sources of light 40W, 60W and 100W.

  1. Magnetic domain structure in nanocrystalline Ni-Zn-Co spinel ferrite thin films using off-axis electron holography

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Ray, N. M.; Petuskey, W. T.; Smith, D. J.; McCartney, M. R.

    2014-08-01

    We report a study of the magnetic domain structure of nanocrystalline thin films of nickel-zinc ferrite. The ferrite films were synthesized using aqueous spin-spray coating at low temperature (˜90 °C) and showed high complex permeability in the GHz range. Electron microscopy and microanalysis revealed that the films consisted of columnar grains with uniform chemical composition. Off-axis electron holography combined with magnetic force microscopy indicated a multi-grain domain structure with in-plane magnetization. The correlation between the magnetic domain morphology and crystal structure is briefly discussed.

  2. Magnetic domain structure in nanocrystalline Ni-Zn-Co spinel ferrite thin films using off-axis electron holography

    SciTech Connect

    Zhang, D.; Ray, N. M.; Petuskey, W. T.; Smith, D. J.; McCartney, M. R.

    2014-08-28

    We report a study of the magnetic domain structure of nanocrystalline thin films of nickel-zinc ferrite. The ferrite films were synthesized using aqueous spin-spray coating at low temperature (∼90 °C) and showed high complex permeability in the GHz range. Electron microscopy and microanalysis revealed that the films consisted of columnar grains with uniform chemical composition. Off-axis electron holography combined with magnetic force microscopy indicated a multi-grain domain structure with in-plane magnetization. The correlation between the magnetic domain morphology and crystal structure is briefly discussed.

  3. Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD.

    PubMed

    Pedersen, Joachim D; Esposito, Heather J; Teh, Kwok Siong

    2011-10-31

    We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion.PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz.

  4. Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

    PubMed Central

    2011-01-01

    We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion. PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz. PMID:22040295

  5. Structural changes in nanocrystalline Bi2Te3/Bi2Se3 multilayer thin films caused by thermal annealing

    NASA Astrophysics Data System (ADS)

    Hamada, Jun; Takashiri, Masayuki

    2017-06-01

    To assess the performance of thermoelectric devices with nanostructured materials at high operating temperatures, we investigated the effects of structural changes on the thermoelectric properties of nanocrystalline bismuth telluride (Bi2Te3)/bismuth selenide (Bi2Se3) multilayer thin films caused by thermal annealing. Multilayer thin films with 12 and 48 layers were fabricated by radio-frequency magnetron sputtering. These thin films were then thermally annealed at temperatures ranging from 250 to 350 °C. As the annealing temperature increased, flake-like nanocrystals were grown in the 12- and 48-layer thin films. X-ray diffraction peaks from three alloys, which were determined to be Bi2Te3, Bi2Se3, and (Bi2Te3)0.4(Bi2Se3)0.6, were observed in the thin films. This indicates that Bi2Te3 and Bi2Se3 layers were not completely diffused mutually in this range of annealing temperature. The 12- and 48-layer thin films exhibited increases in both the electrical conductivity and the absolute value of the Seebeck coefficient at the annealing temperature of 300 °C. One possible explanation for this improvement is that the band structure is tuned by inducing strain during the variation of atomic composition in the multilayer thin films. As a result, the power factor was significantly improved by the thermal annealing. In particular, the maximum power factor reached 13.7 μW/(cm K2) in the 12-layer thin film at the annealing temperature of 350 °C. Therefore, we may conclude that if the multilayer thin films undergo structural changes at higher operating temperature (≈350 °C), thermoelectric devices composed of multilayer thin films are expected to exhibit suitable thermoelectric performance.

  6. Structural and thermoelectric power properties of Na-doped V2O5·nH2O nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    El-Desoky, M. M.; Al-Assiri, M. S.; Bahgat, A. A.

    2014-08-01

    X-ray diffraction (XRD), thermoelectric power (S) and at room temperature electrical conductivity (σ) of Na+1-doped V2O5·nH2O nanocrystalline thin films fabricated by sol gel technique (colloid route) were studied. XRD showed that the Na2O-V2O5·nH2O thin films are highly oriented nanocrystals. The average value of particle size was found to be about 7.5 nm. The thermoelectric power showed that the thermoelectric power for all present nanocrystalline thin films samples decreased with increasing Na+1 content. However, the electrical conductivity increased with increasing Na+1 content. There is evidence that small polarons are responsible for determining the transport properties of the Na+1 doped V2O5·nH2O nanocrystalline thin films samples. The high value of electrical conductivity and small value of thermoelectric power is ideal for device applications, where device to device variation of the thermoelectric power must be small. This preparation technique was demonstrated to fabricate high quality Na2O-V2O5·nH2O nanocrystalline thin films for thermoelectric device applications. However, this may be further used for deposition with an ink-jet printer.

  7. Structural and morphological characterization of ternary nanocrystalline Cu-In-S thin films prepared by laser ablation

    NASA Astrophysics Data System (ADS)

    Bineva, I.; Pejova, B.; Mihailov, V.; Dinescu, A.; Danila, M.; Karatodorov, S.

    2017-01-01

    Thin nanocrystalline Cu-In-S films are prepared by pulsed laser ablation in vacuum with Nd:YAG laser operating at 1064 nm on Si (100) substrates. As a target, a CuInS2 quantum dots powder, synthesized by sonochemical template-free colloidal approach and pressed to form a pellet is used. The structure and morphology of the deposited films were studied employing X-ray diffraction, scanning electron microscopy, and atomic force microscopy techniques. The analysis of the deposited thin films revealed predominant cubic Cu1.7In0.05S phase. It has been found that deposited films were nanocrystalline. The effect of laser pulse energy and deposition time on the structure and morphology of as-prepared films is studied. Slight mean diameter increase from 8 nm to 13 nm with deposition time and applied power was observed, as the time dependence is more pronounced. On the contrary, six fold increase from 7.4 to 44.3 nm of the surface root mean square roughness was estimated with augmentation of the applied laser pulse energy.

  8. Photoluminescence of dense nanocrystalline titanium dioxide thin films: effect of doping and thickness and relation to gas sensing.

    PubMed

    Mercado, Candy; Seeley, Zachary; Bandyopadhyay, Amit; Bose, Susmita; McHale, Jeanne L

    2011-07-01

    The photoluminescence (PL) of dense nanocrystalline (anatase) TiO(2) thin films is reported as a function of calcination temperature, thickness, and tungsten and nickel doping. The dependence of the optical absorption, Raman spectra, and PL spectra on heat treatment and dopants reveals the role of oxygen vacancies, crystallinity, and phase transformation in the performance of TiO(2) films used as gas sensors. The broad visible PL from defect states of compact and undoped TiO(2) films is found to be much brighter and less sensitive to the presence of oxygen than that of mesoporous films. The dense nanocrystalline grains and the nanoparticles comprising the mesoporous film are comparable in size, demonstrating the importance of film morphology and carrier transport in determining the intensity of defect photoluminescence. At higher calcination temperatures, the transformation to rutile results in the appearance of a dominant near-infrared peak. This characteristic change in the shape of the PL spectra demonstrates efficient capture of conduction band electrons by the emerging rutile phase. The W-doped samples show diminished PL with quenching on the red side of the emission spectrum occurring at lower concentration and eventual disappearance of the PL at higher W concentration. The results are discussed within the context of the performance of the TiO(2) thin films as CO gas sensors and the chemical nature of luminescent defects.

  9. Modeling and simulation of boron-doped nanocrystalline silicon carbide thin film by a field theory.

    PubMed

    Xiong, Liming; Chen, Youping; Lee, James D

    2009-02-01

    This paper presents the application of a multiscale field theory in modeling and simulation of boron-doped nanocrystalline silicon carbide (B-SiC). The multiscale field theory was briefly introduced. Based on the field theory, numerical simulations show that intergranular glassy amorphous films (IGFs) and nano-sized pores exist in triple junctions of the grains for nanocrystalline B-SiC. Residual tensile stress in the SiC grains and compressive stress on the grain boundaries (GBs) were observed. Under tensile loading, it has been found that mechanical response of 5 wt% boron-SiC exhibits five characteristic regimes. Deformation mechanism at atomic scale has been revealed. Tensile strength and Young's modulus of nanocrystalline SiC were accurately reproduced.

  10. A study of structural transition in nanocrystalline titania thin films by X-ray diffraction Rietveld method

    SciTech Connect

    Murugesan, S.; Padhy, N.; Kuppusami, P.; Mudali, U. Kamachi; Mohandas, E.

    2010-12-15

    Structural and microstructural analyses of nanocrystalline titania thin films prepared by pulsed laser deposition have been carried out. At lower oxygen partial pressures ({<=}10{sup -4} mbar), rutile films were formed, whereas at 1.2 x 10{sup -3} mbar of oxygen partial pressure, the thin films contained both rutile and anatase phases. At 0.04 and 0.05 mbar of oxygen partial pressure, the film was purely anatase. Addition of oxygen has also shown a profound influence on the surface morphology of the as deposited titania films. Modified Rietveld method has been used to determine crystallite size, root mean square strain and fractional coordinates of oxygen of the anatase films. The influence of crystallite size and strain on the rutile to anatase phase transition is investigated.

  11. Effect of substrate temperature on structural, optical and electrical properties of sputtered NiO-Ag nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Ashok Kumar Reddy, Y.; Ajitha, B.; Sreedhara Reddy, P.; Siva Pratap Reddy, M.; Lee, Jung-Hee

    2014-09-01

    NiO-Ag thin films were deposited on Corning 7059 glass substrates by DC reactive magnetron sputtering technique and investigated the substrate temperature ( T s ) dependent properties of NiO-Ag thin films. X-ray diffraction results showed that crystalline films can be obtained at high T s and all films have a preferred crystal growth texture with face centered cubic ( f cc ) structure and was also confirmed by Raman studies. The grain size, transmittance, band gap, mobility and carrier concentrations were increased with T s . Room temperature deposited films have an average roughness around 6.9 nm where as increment of T s resulted in increased roughness up to 14 nm with nanocrystalline morphology. The optimum substrate temperature to obtain NiO-Ag films was found to be 200°C. It was found that with increasing the T s , resistivity of the films was significantly decreased.

  12. Cu2ZnSnS4 thin films obtained by sulfurization of evaporated Cu2SnS3 and ZnS layers: Influence of the ternary precursor features

    NASA Astrophysics Data System (ADS)

    Robles, V.; Guillén, C.; Trigo, J. F.; Herrero, J.

    2017-04-01

    Cu2ZnSnS4 (CZTS) thin films have been grown by sulfurization of Cu2SnS3 (CTS) and ZnS layers evaporated on glass substrates. Four CTS precursor films have been tested, with two different atomic compositions (Cu/Sn = 1.7 and Cu/Sn = 2.1) and substrate temperatures (350 and 450 °C), together with analogous ZnS layers deposited by maintaining the substrate at 200 °C. The sulfurization of the CTS and ZnS stacked layers was performed at 500 °C during 1 h. The evolution of the crystalline structure, morphology, optical and electrical properties from each CTS precursor to the CZTS compound has been studied, especially the influence of the ternary precursor features on the quaternary film characteristics. The kesterite structure has been identified after sulfurization of the various samples, with main (112) orientation and mean crystallite sizes S112 = 40-56 nm, being higher for the Cu-poor compositions. The CZTS average roughness has varied in a wide interval Ra = 8-66 nm, being directly related to the CTS precursor layer, which becomes rougher for a higher deposition temperature or Cu content. Besides, the band gap energy and the electrical resistivity of the CZTS films have changed in the ranges Eg = 1.54-1.64 eV and ρ = 0.2-40 Ωcm, both decreasing when the Cu content and/or the surface roughness increase.

  13. Tailoring the mechanical behavior of nanocrystalline thin films with alloying and heat treatments

    NASA Astrophysics Data System (ADS)

    Dasgupta, Suman

    Metals and alloys with grain sizes below a hundred nanometers exhibit very different mechanical and physical properties compared to their coarse grained counterparts. Unique nanoscale deformation mechanisms are triggered by the ubiquitous nature of grain boundaries in nanocrystalline (NC) materials. Microstructural instabilities can develop in NC materials during deformation due to stress-coupled grain boundary migration and global stress-driven grain growth. The presence or absence of these mechanisms can dramatically affect the attendant mechanical response of the material. The ability to control these grain boundary instabilities with impurity doping might make it possible to engineer nanostructured materials with desired properties. Motivated by this prospect, a collaborative effort was launched with scientists from The University of Pennsylvania, The University of Sydney and The Johns Hopkins University. This dissertation, in particular, describes efforts to tailor mechanical behavior of NC alloy systems by controlling global stress-driven grain growth through alloying and annealing treatments. NC aluminum and nickel, which have been shown to exhibit stress-assisted grain growth, were chosen as the parent materials for this study. NC aluminum was doped with oxygen, and NC nickel with phosphorus, to assess the role of grain boundary solutes in stabilizing grains against stress-assisted grain growth. Confocal co-sputtering techniques were employed to fabricate alloy thin films with precise control over chemistry and microstructure. Tensile properties were measured through microtensile testing and microstructural evolution associated with deformation was characterized using ex-situ and in-situ precession-assisted crystal orientation mapping in TEM. The critical global solute concentrations required to stabilize grain boundaries against applied stresses were identified. Local grain boundary pinning imparted mechanical stability to the microstructure and resulted

  14. X-ray microstructural analysis of nanocrystalline TiZrN thin films by diffraction pattern modeling

    SciTech Connect

    Escobar, D.; Ospina, R.; Gómez, A.G.; Restrepo-Parra, E.; Arango, P.J.

    2014-02-15

    A detailed microstructural characterization of nanocrystalline TiZrN thin films grown at different substrate temperatures (T{sub S}) was carried out by X-ray diffraction (XRD). Total diffraction pattern modeling based on more meaningful microstructural parameters, such as crystallite size distribution and dislocation density, was performed to describe the microstructure of the thin films more precisely. This diffraction modeling has been implemented and used mostly to characterize powders, but the technique can be very useful to study hard thin films by taking certain considerations into account. Nanocrystalline films were grown by using the cathodic pulsed vacuum arc technique on stainless steel 316L substrates, varying the temperature from room temperature to 200 °C. Further surface morphology analysis was performed to study the dependence of grain size on substrate temperature using atomic force microscopy (AFM). The crystallite and surface grain sizes obtained and the high density of dislocations observed indicate that the films underwent nanostructured growth. Variations in these microstructural parameters as a function of T{sub S} during deposition revealed a competition between adatom mobility and desorption processes, resulting in a specific microstructure. These films also showed slight anisotropy in their microstructure, and this was incorporated into the diffraction pattern modeling. The resulting model allowed for the films' microstructure during synthesis to be better understood according to the experimental results obtained. - Highlights: • Mobility and desorption competition generates a critical temperature. • A microstructure anisotropy related to the local strain was observed in thin films. • Adatom mobility and desorption influence grain size and microstrain.

  15. Synthesis of Mn-doped ZnS thin films by chemical bath deposition: Optical properties in the visible region

    NASA Astrophysics Data System (ADS)

    Erken, Ozge; Gunes, Mustafa; Gumus, Cebrail

    2017-04-01

    Transparent ZnS:Mn thin films were produced by chemical bath deposition (CBD) technique at 80 °C for 4h, 6h and 8h durations. The optical properties such as optical transmittance (T %), reflectance (R %), extinction coefficient (k) and refractive index (n) were deeply investigated in terms of contribution ratio, wavelength and film thickness. The optical properties of ZnS:Mn thin films were determined by UV/vis spectrophotometer transmittance measurements in the range of λ=300-1100 nm. Optical transmittances of the films were found from 12% to 92% in the visible region. The refractive index (n) values for visible region were calculated as 1.34-5.09. However, film thicknesses were calculated between 50 and 901 nm by gravimetric analysis.

  16. Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

    PubMed

    Zhang, Ming-Jian; Lin, Qinxian; Yang, Xiaoyang; Mei, Zongwei; Liang, Jun; Lin, Yuan; Pan, Feng

    2016-02-10

    Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

  17. Characterization of Zns-GaP Naon-composites

    SciTech Connect

    Voiles, Todd

    1993-12-09

    It proved possible to produce consistent, high-quality nanocrystalline ZnS powders with grain sizes as small as 8 nm. These powders are nano-porous and are readily impregnated with GaP precursor, although inconsistently. Both crystal structure and small grain size of the ZnS can be maintained through the use of GaP. Heat treatment of the impregnated powders results in a ZnS-GaP composite structure where the grain sizes of the phases are on the order of 10--20 nm. Conventional powder processing should be able to produce optically dense ceramic compacts with improved mechanical properties and suitable IR transmission.

  18. Room temperature tunable blue-green luminescence in nanocrystalline (Pb1-xSrx)TiO3 thin film grown on yttrium-doped zirconia substrate

    NASA Astrophysics Data System (ADS)

    Luo, L.; Ren, H. Z.; Tang, X. G.; Ding, C. R.; Wang, H. Z.; Chen, X. M.; Jia, J. K.; Hu, Z. F.

    2008-08-01

    Room temperature tunable blue-green photoluminescence was observed in nanocrystalline (Pb1-xSrx)TiO3 thin film under UV excitation. Its emission energy increases from 2.42 (at x =0.6) to 2.76 eV (at x =0.4), while the band gap decreases from 3.6 to 3.3 eV. Thin films of (Pb1-xSrx)TiO3 were prepared on yttrium-doped zirconia substrate by a simple sol-gel technique with spinning-coating process. Atom force microscope micrographs and crystallographic studies revealed the polycrystalline perovskite-type structure of the thin films. The observed optical properties are attributed to distorted octahedral due to different cation substitutions. The work shows that this kind of wide band gap and low cost nanocrystalline thin films is a very promising material for flat panel display applications and integrated light emission devices.

  19. Correlation between surface phonon mode and luminescence in nanocrystalline CdS thin films: An effect of ion beam irradiation

    SciTech Connect

    Kumar, Pragati Agarwal, Avinash; Saxena, Nupur; Singh, Fouran; Gupta, Vinay

    2014-07-28

    The influence of swift heavy ion irradiation (SHII) on surface phonon mode (SPM) and green emission in nanocrystalline CdS thin films grown by chemical bath deposition is studied. The SHII of nanocrystalline CdS thin films is carried out using 70 MeV Ni ions. The micro Raman analysis shows that asymmetry and broadening in fundamental longitudinal optical (LO) phonon mode increases systematically with increasing ion fluence. To analyze the role of phonon confinement, spatial correlation model (SCM) is fitted to the experimental data. The observed deviation of SCM to the experimental data is further investigated by fitting the micro Raman spectra using two Lorentzian line shapes. It is found that two Lorentzian functions (LFs) provide better fitting than SCM fitting and facilitate to identify the contribution of SPM in the observed distortion of LO mode. The behavior of SPM as a function of ion fluence is studied to correlate the observed asymmetry (Γ{sub a}/Γ{sub b}) and full width at half maximum of LO phonon mode and to understand the SHII induced enhancement of SPM. The ion beam induced interstitial and surface state defects in thin films, as observed by photoluminescence (PL) spectroscopy studies, may be the underlying reason for enhancement in SPM. PL studies also show enhancement in green luminescence with increase in ion fluence. PL analysis reveals that the variation in population density of surface state defects after SHII is similar to that of SPM. The correlation between SPM and luminescence and their dependence on ion irradiation fluence is explained with the help of thermal spike model.

  20. ZnS thin films grown by atomic layer deposition on GaAs and HgCdTe substrates at very low temperature

    NASA Astrophysics Data System (ADS)

    Sun, C. H.; Zhang, P.; Zhang, T. N.; Chen, X.; Chen, Y. Y.; Ye, Z. H.

    2017-09-01

    ZnS films grown on GaAs and HgCdTe substrates by atomic layer deposition (ALD) under very low temperature were investigated in this work. ZnS films were grown under several temperatures lower than 140 °C. The properties of the films were investigated with high-resolution X-ray diffraction (HRXRD), scanning electron microscope (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed the ZnS films were polycrystalline. The growth rate monotonically decreased with temperature, as well as the root mean square (r.m.s) roughness measured by AFM. XPS measurement revealed the films were stoichiometric in Zn and S.

  1. Thickness-dependent photocatalytic performance of nanocrystalline TiO2 thin films prepared by sol-gel spin coating

    NASA Astrophysics Data System (ADS)

    Wu, Chung-Yi; Lee, Yuan-Ling; Lo, Yu-Shiu; Lin, Chen-Jui; Wu, Chien-Hou

    2013-09-01

    TiO2 nanocrystalline thin films on soda lime glass have been prepared by sol-gel spin coating. The thin films were characterized for surface morphology, crystal structure, chemical composition, thickness, and transparency by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ellipsometry, and UV-vis spectrophotometry. The films prepared by titanium tetraisopropoxide (TTIP) as the precursor under pH of 3.5 ± 0.5 and with calcination temperature of 450 ̊C for 3 h exhibited superior homogeneous aggregation, good optical transparency, superhydrophilicity, and reliable thickness. The effect of film thickness on the photocatalytic degradation of acid yellow 17 was investigated under UV irradiation. The photocatalytic activity was strongly correlated with the number of coatings and followed Langmuir-type kinetics. Under the same film thickness, TiO2 thin films prepared by 0.1 M TTIP exhibited more efficient photocatalytic activity than those prepared by 0.3 M TTIP. For thin films prepared by 0.1 M TTIP, the maximum specific photocatalytic activity occurred at 5 coatings with thickness of 93 ± 1 nm. A model was proposed to rationalize the dependence of the film thickness on the photocatalytic activity, which predicts the existence of an optimum film thickness.

  2. Novel aspect in grain size control of nanocrystalline diamond film for thin film waveguide mode resonance sensor application.

    PubMed

    Lee, Hak-Joo; Lee, Kyeong-Seok; Cho, Jung-Min; Lee, Taek-Sung; Kim, Inho; Jeong, Doo Seok; Lee, Wook-Seong

    2013-11-27

    Nanocrystalline diamond (NCD) thin film growth was systematically investigated for application for the thin film waveguide mode resonance sensor. The NCD thin film was grown on the Si wafer or on the SiO2-coated sapphire substrate using the hot filament chemical vapor deposition (HFCVD). The structural/optical properties of the samples were characterized by the high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), near edge X-ray absorption fine structure (NEXAFS), X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. The waveguide modes of the NCD layer were studied by prism coupler technique using laser (wavelength: 632.8 nm) with varying incident angle. A novel aspect was disclosed in the grain size dependence on the growth temperature at the relatively low methane concentration in the precursor gas, which was important for optical property: the grain size increased with decreasing growth temperature, which was contrary to the conventional knowledge prevailing in the microcrystalline diamond (MCD) domain. We have provided discussions to reconcile such observation. An optical waveguide mode resonance was demonstrated in the visible region using the microstructure-controlled transparent NCD thin film waveguide, which provided a strong potential for the waveguide mode resonance sensor applications.

  3. Anisotropic optical response of nanocrystalline V2O5 thin films and effects of oxygen vacancy formation

    NASA Astrophysics Data System (ADS)

    Kang, T. D.; Chung, J.-S.; Yoon, Jong-Gul

    2014-03-01

    We report a high sensitivity to oxygen vacancy formation as well as the temperature dependence of anisotropic optical properties of a nanocrystalline V2O5 thin film. Spectroscopic ellipsometry data show that the film has a uniaxial optical anisotropy due to a highly ordered nanocrystalline layer structure. The anisotropic optical properties of the film begin to change at ˜400 K in a high vacuum and can be linked to the changes in the electronic structure of the film upon reduction. An increase in the refractive indices, anisotropic changes of the optical conductivities, and a decrease in film thickness are observed after vacuum heating and are recovered to original values by heating in air up to 480 K. The experimental results are supported by the previous theoretical studies on the stability of reduced V2O5 surface through the formation of oxygen vacancies. We discuss the formation of oxygen vacancies, vacancy-induced structural relaxations, and changes in the electronic structure of V2O5 in conjunction with the experimental results.

  4. Band gap bowing of nanocrystalline Zn(1-x)CaxO thin films for blue and ultraviolet optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Narayanan, Nripasree; Deepak, N. K.

    2017-09-01

    Alloying materials having different band gaps is a tool to tailor the optical energy gaps of semiconducting materials. In the present study, the effect of alloying ZnO with CaO was investigated. Thin films of Zn(1-x)CaxO (0 ≤ x ≤ 0.20) were deposited on glass substrates by spray pyrolysis technique. All the films possessed nanocrystalline grains and crystallinity deteriorated with increase in Ca2+ substitution level. Elemental composition analysis confirmed the presence of Ca in the samples. Films showed good optical transmission in the visible and near infrared region and the absorption edge blue-shifted with Ca2+ substitution. Optical energy gap enhanced by 9.89% upon 20% Ca2+ substitution. Photoluminescence analysis also confirmed band gap broadening with mesovalent cation substitution.

  5. Synthesis of nanocrystalline Cu2ZnSnS4 thin films grown by the spray-pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Chandel, Tarun; Singh, Joginder; Rajaram, P.

    2015-08-01

    Spray pyrolysis was used to deposit Cu2ZnSnS4 (CZTS) thin films on soda lime glass substrates at 300 °C. Aqueous solutions of copper chloride, zinc chloride, stannous chloride and thiourea were mixed together to form the spray liquid. The sprayed films were annealed under vacuum at 350 °C, 400 °C and 450 °C. Structural and optical characterization was performed on the CZTS films using X-ray diffraction (XRD) and UV-VIS spectrophotometry. XRD results indicate that the films are single phase nanocrystalline CZTS. Optical studies show that the optical gap values are 1.44 eV for the as-grown film and 1.46 eV, 1.48 eV and 1.49 eV for the films annealed at 350 °C, 400 °C and 450 °C, respectively.

  6. Solution assisted growth mechanism and characterization of ZnS microspheres

    NASA Astrophysics Data System (ADS)

    Ghoderao, Karuna P.; Jamble, Shweta N.; Sawant, Jitendra P.; Kale, Rohidas B.

    2017-02-01

    The ZnS microspheres were synthesized via simple, efficient and cost-effective hydrothermal method. The x-ray diffraction study revealed nanocrystalline nature of the synthesized ZnS with the cubic crystal structure. Scanning and transmission electron microscopy observations revealed the formation of 3D microspheres that consist of numerous ZnS nanocrystals. The grown microspheres are also interconnected with each other by driving force of attachment. The obtained product has excellent elemental stoichiometric proportion as evidenced by the EDS technique. The electron diffraction pattern reveals the polycrystalline nature of obtained ZnS product. The band gap was measured from UV–Vis spectroscopic study and found to be blue shifted from the bulk band gap value. The PL study exhibits negligibly weak band edge emission and dominant, widespread defect-related green emission. The nucleation of a ZnS nanocrystals and subsequent growth into the microspheres is also discussed.

  7. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    PubMed Central

    Ibupoto, Zafar Hussain; Khun, Kimleang; Liu, Xianjie; Willander, Magnus

    2013-01-01

    Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  8. Sn-doped ZnO nanocrystalline thin films with enhanced linear and nonlinear optical properties for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Ganesh, V.; Yahia, I. S.; AlFaify, S.; Shkir, Mohd.

    2017-01-01

    In the current work, nanocrystalline undoped and Sn doped ZnO thin films with different doping concentrations (1, 3, 5, 7 at%) have been deposited on glass substrate by low cost spin coating technique. The strong effect of Sn doping on structural, morphological, optical, nonlinear properties have been observed. X-ray diffraction study revealed that all the thin films are preferentially grown along (002) plane. The crystallite size is found to be increased with increasing the concentration of Sn, similar behavior was observed by atomic force microscopy analysis. Optical study shows that the prepared thin films are highly transparent. The direct optical band gap was calculate and found to be 3.16, 3.20, 3.22, 3.34, 3.18 eV for pure and doped films respectively. The refractive index, linear susceptibility, nonlinear absorption coefficient, nonlinear susceptibility and nonlinear refractive index were calculated. Furthermore, the third order nonlinear optical properties are investigated using Z-scan technique and their values are found to be -3.75×10-8 cm2/W, -3.76×10-3 cm/W and 0.65×10-3 esu for 7% Sn doped ZnO, respectively. There is a good correlation between theoretical and experimental third order nonlinear properties and higher values shows that the deposited films are may be applied in nonlinear optical applications.

  9. Boosting the mobility and bias stability of oxide-based thin-film transistors with ultra-thin nanocrystalline InSnO:Zr layer

    NASA Astrophysics Data System (ADS)

    Raja, Jayapal; Jang, Kyungsoo; Hussain, Shahzada Qamar; Balaji, Nagarajan; Chatterjee, Somenath; Velumani, S.; Yi, Junsin

    2015-01-01

    Extensive attention on high-definition flat panel displays is the driving force to fabricate high-performance thin-film transistors (TFTs). A hybrid oxide TFTs fabricated using an interfacial layer of nanocrystalline Zr-doped InSnO (nc-ITO:Zr) and an amorphous InSnZnO films as an active channel is reported here. Due to the presence of nc-ITO:Zr layer, an improvement of the field-effect mobility (86.4 cm2/V.s) and threshold voltage (0.43 V) values for TFTs are observed. Positive gate bias stress study indicates the role of nc-ITO:Zr layer in fabricated TFTs through the suppression of charge trapping capability between the channel and insulating layer.

  10. Intensity-dependent relaxation of photoconductivity in nanocrystalline titania thin films

    NASA Astrophysics Data System (ADS)

    Xie, Z.; Burlakov, V. M.; Henry, B. M.; Kirov, K. R.; Smith, H. E.; Grovenor, C. R. M.; Assender, H. E.; Briggs, G. A. D.; Kano, Mitsuru; Tsukahara, Yusuke

    2006-03-01

    We have discovered that the initial rate of the post-illumination decay of photoconductivity in nanocrystalline TiO2 depends on the intensity of the illumination. The phenomenon is described by hole detrapping processes affected by electrostatic interactions between the trapped holes, and screening of these interactions by free electrons. The analysis allows determination of both the electron concentration and the electron mobility. In our materials, the value of electron mobility μ≈10-6cm2V-1s-1 , in good agreement with results obtained by other methods.

  11. Characterizing the phase purity of nanocrystalline Fe3O4 thin films using Verwey transition

    NASA Astrophysics Data System (ADS)

    Bohra, Murtaza; Prasad, K. Eswar; Bollina, Ravi; Sahoo, S. C.; Kumar, Naresh

    2016-11-01

    We have employed Verwey transition as a probe to check phase purity of nanocrystalline Fe3O4 films grown at different substrate temperatures (Ts) by means of magnetization study. The drop in magnetization at temperatures other than Verwey transition temperature Tv (120 K), in the low and high Ts films indicates the presence of antiferromagnetic (α-Fe2O3/FeO) impurity phases. After wet H2 reduction treatment on these films, a vibrant appearance of Verwey transition is observed which confirms Fe3O4 phase at all Ts. However, high Ts films exhibit low Tv value with distribution, Tv±ΔTv=112+25 K emanating from residual magnetic phases, which were not traced by XRD studies. Interestingly, these nanocrystalline Fe3O4 films exhibit anisotropic magnetic behaviors above Tv, similar to the single crystal Fe3O4. Below the saturation field, the easy (111) and relatively hard (110) axis of magnetizations align along their texture planes.

  12. Deformation-induced grain growth and twinning in nanocrystalline palladium thin films

    PubMed Central

    Lohmiller, Jochen; Schäfer, Jonathan; Kerber, Michael; Castrup, Anna; Kashiwar, Ankush; Gruber, Patric A; Albe, Karsten; Hahn, Horst

    2013-01-01

    Summary The microstructure and mechanical properties of nanocrystalline Pd films prepared by magnetron sputtering have been investigated as a function of strain. The films were deposited onto polyimide substrates and tested in tensile mode. In order to follow the deformation processes in the material, several samples were strained to defined straining states, up to a maximum engineering strain of 10%, and prepared for post-mortem analysis. The nanocrystalline structure was investigated by quantitative automated crystal orientation mapping (ACOM) in a transmission electron microscope (TEM), identifying grain growth and twinning/detwinning resulting from dislocation activity as two of the mechanisms contributing to the macroscopic deformation. Depending on the initial twin density, the samples behaved differently. For low initial twin densities, an increasing twin density was found during straining. On the other hand, starting from a higher twin density, the twins were depleted with increasing strain. The findings from ACOM-TEM were confirmed by results from molecular dynamics (MD) simulations and from conventional and in-situ synchrotron X-ray diffraction (CXRD, SXRD) experiments. PMID:24205451

  13. Electron diffraction based analysis of phase fractions and texture in nanocrystalline thin films, part II: implementation.

    PubMed

    Lábár, János L

    2009-02-01

    This series of articles describes a method that performs (semi)quantitative phase analysis for nanocrystalline transmission electron microscope samples from selected area electron diffraction (SAED) patterns. Volume fractions of phases and their textures are obtained separately in the method. First, the two-dimensional SAED pattern is converted into an X-ray diffraction-like one-dimensional distribution. Volume fractions of the nanocrystalline components are determined by fitting the spectral components, calculated for the previously identified phases with a priori known structures. Blackman correction is also applied to take into account dynamic effects for medium grain sizes. Peak shapes and experimental parameters (camera length, etc.) are refined during the fitting iterations. Parameter space is explored with the help of the Downhill-SIMPLEX algorithm. Part I presented the principles, while Part II now elaborates current implementation, and Part III will demonstrate its usage by examples. The method is implemented in a computer program that runs under the Windows operating system on IBM PC compatible machines.

  14. Deformation-induced grain growth and twinning in nanocrystalline palladium thin films.

    PubMed

    Kobler, Aaron; Lohmiller, Jochen; Schäfer, Jonathan; Kerber, Michael; Castrup, Anna; Kashiwar, Ankush; Gruber, Patric A; Albe, Karsten; Hahn, Horst; Kübel, Christian

    2013-01-01

    The microstructure and mechanical properties of nanocrystalline Pd films prepared by magnetron sputtering have been investigated as a function of strain. The films were deposited onto polyimide substrates and tested in tensile mode. In order to follow the deformation processes in the material, several samples were strained to defined straining states, up to a maximum engineering strain of 10%, and prepared for post-mortem analysis. The nanocrystalline structure was investigated by quantitative automated crystal orientation mapping (ACOM) in a transmission electron microscope (TEM), identifying grain growth and twinning/detwinning resulting from dislocation activity as two of the mechanisms contributing to the macroscopic deformation. Depending on the initial twin density, the samples behaved differently. For low initial twin densities, an increasing twin density was found during straining. On the other hand, starting from a higher twin density, the twins were depleted with increasing strain. The findings from ACOM-TEM were confirmed by results from molecular dynamics (MD) simulations and from conventional and in-situ synchrotron X-ray diffraction (CXRD, SXRD) experiments.

  15. Determining the Thermal Conductivity of Nanocrystalline Bismuth Telluride Thin Films Using the Differential 3 ω Method While Accounting for Thermal Contact Resistance

    NASA Astrophysics Data System (ADS)

    Kudo, S.; Hagino, H.; Tanaka, S.; Miyazaki, K.; Takashiri, M.

    2015-06-01

    We have estimated the thermal conductivity of nanocrystalline bismuth telluride thin films using the differential 3 ω method, taking into account the thermal contact resistance (TCR) between the substrate and thin-film layers. The thin films were prepared on alumina substrates by radio-frequency (RF) magnetron sputtering at temperature of 200°C. Film thickness varied between 0.8 μm and 3.1 μm. The structural properties of the films were analyzed using x-ray diffraction analysis. Their electrical conductivity, Seebeck coefficient, and power factor were evaluated. For measurement of thermal properties by the differential 3 ω method, SiO2 thin films were deposited onto the samples, to act as insulating layers. Thin aluminum wire was then patterned onto the SiO2 layer. The observed variations in temperature amplitude as a function of film thickness indicated that the TCR contribution was very small and could therefore be neglected when estimating the thermal conductivity of the thin films. The thermal conductivity of the nanocrystalline bismuth telluride thin films with thickness of 0.8 μm and 2.1 μm were determined to be 0.55 W/(m K) and 0.48 W/(m K), respectively.

  16. Thin Film Nanocrystalline TiO2 Electrodes: Dependence of Flat Band Potential on pH and Anion Adsorption.

    PubMed

    Minella, M; Maurino, V; Minero, C; Pelizzetti, E

    2015-05-01

    Thin nanocrystalline TiO2 films were produced on ITO conductive glass by dip-coating of a sol-gel TiO2 precursor. The transparent films were characterized from the optical and structural point of view with UV-Vis, Spectroscopic Ellipsometry, Raman and X-ray photoelectron spectroscopies, the roughness of the coating by AFM. The changes in the electrochemical properties features of ITO/TiO2 electrodes were evaluated in the presence of different electrolytes (KCI, Na2SO4 and phosphate buffer) with the aim to clarify the role of the ion adsorption on the structure of the electrical double layer. Electrochemical tests (Cyclic Voltammetry, CV, and Impedance Electrochemical Spectroscopy, EIS) showed a strong influence of the electrolyte properties on the semiconductor band edge position in the electrochemical scale and on band bending. The CV profiles recorded can be explained by considering that the interface capacity is due to the charging of surface states (e.g., Ti(IV) surface sites coordinated by oxygen atoms, ≡Ti-OH or Ti-O-Ti). The surface charge is strongly affected also by the density and nature of adsorbed ions and by dissociation of surficial OH. Of interest the fact that for the produced nanocrystalline electrodes the flat band potential, measured from the Mott-Schottky analysis of the space charge layer capacity obtained with EIS, showed a non Nernstian behavior with the pH probably caused by a change in the surface acidity as a consequence of specific anion adsorption. The modulation of flat band potential with adsorbed ions is of interest for many applications, in particular for photocatalysis (change in the redox potential of photogenerated carriers) and for photovoltaic applications like DSSC (change in the photopotentials).

  17. Structural evolution of TiO{sub 2} nanocrystalline thin films by thermal annealing and swift heavy ion irradiation

    SciTech Connect

    Rath, H.; Dash, P.; Mishra, N. C.; Som, T.; Satyam, P. V.; Singh, U. P.; Kulriya, P. K.; Kanjilal, D.; Avasthi, D. K.

    2009-04-01

    The present study probes into the transition from anatase to rutile phase of TiO{sub 2} in 100 nm thick nanocrystalline thin films under thermal annealing and swift heavy ion (SHI) irradiation. The films were prepared using sol-gel and spin coating techniques on silicon (100) substrates. The as-deposited films are found to be amorphous by glancing angle x-ray diffraction and Raman spectroscopy. Though thermal annealing is known to cause transformation from anatase to rutile phase of TiO{sub 2} in a temperature interval of 700-900 deg. C, in nanoparticle thin films, we found that a sizable volume fraction of anatase still remains even after annealing at 1000 deg. C. Irradiations by 200 MeV Ag ions on the other hand suppressed the anatase phase and almost phase pure rutile TiO{sub 2} could be obtained at a fluence of 3x10{sup 12} ions cm{sup -2}. A mechanism based on the competing effect of grain growth and conversion of anatase to rutile at the grain boundary of the anatase on annealing and conversion of anatase to rutile in the grains of the anatase due to SHI induced thermal spike is proposed to explain the observed result.

  18. Structural, morphological and optical properties of sprayed nanocrystalline thin films of Cd1-xZnxS solid solution

    NASA Astrophysics Data System (ADS)

    Verma, Urvashi; Thakur, Vikas; Rajaram, Poolla; Shrivastava, A. K.

    2015-01-01

    A series of nanocrystalline thin films of cadmium zinc sulphide (Cd1-xZnxS) solid solution were deposited on glass substrates using spray pyrolysis. Cadmium chloride (CdCl2), zinc chloride (ZnCl2) and thiourea (NH2CSNH2) were used as the sources of Cd, Zn and S respectively. The films were characterized using structural, morphological and optical techniques. X-ray diffraction (XRD) studies show that the films of Cd1-xZnxS are polycrystalline and single phase having the wurtzite structure. The crystallites in the thin films of pure CdS possess preferred crystallographic orientation along the <002> direction. The preferred orientation of crystallites in the Cd1-xZnxS films changes from <002> to <101> with increase in Zn concentration. The lattice parameters of Cd1-xZnxS decrease with increase in Zn concentration. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show that the surfaces of the films are smooth and are uniformly covered with nanoparticles. Energy dispersive analysis of xrays (EDAX) results reveal that the grown films have good stoichiometry. Optical transmission spectra confirm the good quality of the Cd1-xZnxS films.

  19. A light-trapping strategy for nanocrystalline silicon thin-film solar cells using three-dimensionally assembled nanoparticle structures.

    PubMed

    Ha, Kyungyeon; Jang, Eunseok; Jang, Segeun; Lee, Jong-Kwon; Jang, Min Seok; Choi, Hoseop; Cho, Jun-Sik; Choi, Mansoo

    2016-02-05

    We report three-dimensionally assembled nanoparticle structures inducing multiple plasmon resonances for broadband light harvesting in nanocrystalline silicon (nc-Si:H) thin-film solar cells. A three-dimensional multiscale (3DM) assembly of nanoparticles generated using a multi-pin spark discharge method has been accomplished over a large area under atmospheric conditions via ion-assisted aerosol lithography. The multiscale features of the sophisticated 3DM structures exhibit surface plasmon resonances at multiple frequencies, which increase light scattering and absorption efficiency over a wide spectral range from 350-1100 nm. The multiple plasmon resonances, together with the antireflection functionality arising from the conformally deposited top surface of the 3D solar cell, lead to a 22% and an 11% improvement in power conversion efficiency of the nc-Si:H thin-film solar cells compared to flat cells and cells employing nanoparticle clusters, respectively. Finite-difference time-domain simulations were also carried out to confirm that the improved device performance mainly originates from the multiple plasmon resonances generated from three-dimensionally assembled nanoparticle structures.

  20. Microwave Plasma Source for Fabrication of Micro- and Nano-Crystalline Diamond Thin Films for Electronic Devices

    NASA Astrophysics Data System (ADS)

    Paosawatyanyong, Boonchoat; Rujisamphan, Nopporn; Bhanthumnavin, Worawan

    2013-01-01

    The design and utilization of an affordable compact-size high-density plasma reactor for micro- and nano-crystalline diamond (MCD/NCD) thin film deposition is presented. The system is based on a 2.45 GHz domestic microwave oven magnetron. A switching power supply module, which yields a low-voltage high-current AC filament feeding and a high-voltage low-current DC cathode bias, is constructed to serve as the magnetron power source. With a high stability of the power module combined with the usage of water cooling gaskets, over 100 h of plasma processing time was achieved without overheating or causing any damage to the magnetron. Depositions of well-faceted MCD/NCD thin films, with distinct diamond Raman characteristics, were obtained using H2-CH4 discharge with 1-5% CH4. Metal-semiconductor diode structures were fabricated using gold and aluminum as ohmic and rectifying contacts, respectively, and their responses to DC signals revealed a high rectification ratio of up to 106 in the intrinsic MCD/NCD devices.

  1. Investigation of nanocrystalline thin cobalt films thermally evaporated on Si(100) substrates

    NASA Astrophysics Data System (ADS)

    Kozłowski, W.; Balcerski, J.; Szmaja, W.; Piwoński, I.; Batory, D.; Miękoś, E.; Cichomski, M.

    2017-03-01

    We have made a quantitative study of the morphological and magnetic domain structures of 100 nm thick nanocrystalline cobalt films thermally evaporated on naturally oxidized Si(100) substrates. The morphological structure is composed of densely packed grains with the average grain size (35.6±0.8) nm. The grains exhibit no geometric alignment and no preferred elongation on the film surface. In the direction perpendicular to the film surface, the grains are aligned in columns. The films crystallize mainly in the hexagonal close-packed phase of cobalt and possess a crystallographic texture with the hexagonal axis perpendicular to the film surface. The magnetic domain structure consists of domains forming a maze stripe pattern with the average domain size (102±6) nm. The domains have their magnetizations oriented almost perpendicularly to the film surface. The domain wall energy, the domain wall thickness and the critical diameter for single-domain particle were determined.

  2. Nonlinear optical parameters of nanocrystalline AZO thin film measured at different substrate temperatures

    NASA Astrophysics Data System (ADS)

    Jilani, Asim; Abdel-wahab, M. Sh; Al-ghamdi, Attieh A.; Dahlan, Ammar sadik; Yahia, I. S.

    2016-01-01

    The 2.2 wt% of aluminum (Al)-doped zinc oxide (AZO) transparent and preferential c-axis oriented thin films were prepared by using radio frequency (DC/RF) magnetron sputtering at different substrate temperature ranging from room temperature to 200 °C. For structural analysis, X-ray Diffraction (XRD) and Atomic Force Electron Microscope (AFM) was used for morphological studies. The optical parameters such as, optical energy gap, refractive index, extinction coefficient, dielectric loss, tangent loss, first and third order nonlinear optical properties of transparent films were investigated. High transmittance above 90% and highly homogeneous surface were observed in all samples. The substrate temperature plays an important role to get the best transparent conductive oxide thin films. The substrate temperature at 150 °C showed the growth of highly transparent AZO thin film. Energy gap increased with the increased in substrate temperature of Al doped thin films. Dielectric constant and loss were found to be photon energy dependent with substrate temperature. The change in substrate temperature of Al doped thin films also affect the non-liner optical properties of thin films. The value of χ(3) was found to be changed with the grain size of the thin films that directly affected by the substrate temperature of the pure and Al doped ZnO thin films.

  3. Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

    NASA Astrophysics Data System (ADS)

    Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

    2016-10-01

    In this work, Pd:NiFe2O4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe2O4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost.

  4. Fabrication and photoelectrocatalytic properties of nanocrystalline monoclinic BiVO4 thin-film electrode.

    PubMed

    Zhou, Bin; Qu, Jiuhui; Zhao, Xu; Liu, Huijuan

    2011-01-01

    Monoclinic bismuth vanadate (BiVO4) thin film was fabricated on indium-tin oxide glass from an amorphous heteronuclear complex via dip-coating. After annealation at 400, 500, and 600 degrees C, the thin films were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry. The BiVO4 particles on the ITO glass surface had a monoclinic structure. The UV-Visible diffuse reflection spectra showed the BiVO4 thin film had photoabsorption properties, with a band gap around 2.5 eV. In addition, the thin film showed high visible photocatalytic activities towards 2,4-dichlorophenol and Bisphenol A degradation under visible light irradiation (lambda > 420 nm). Over 90% of the two organic pollutants were removed in 5 hr. A possible degradation mechanism of 2,4-dichlorophenol were also studied.

  5. Band gap states in nanocrystalline WO3 thin films studied by soft x-ray spectroscopy and optical spectrophotometry

    NASA Astrophysics Data System (ADS)

    Johansson, M. B.; Kristiansen, P. T.; Duda, L.; Niklasson, G. A.; Österlund, L.

    2016-11-01

    Nanocrystalline tungsten trioxide (WO3) thin films prepared by DC magnetron sputtering have been studied using soft x-ray spectroscopy and optical spectrophotometry. Resonant inelastic x-ray scattering (RIXS) measurements reveal band gap states in sub-stoichiometric γ-WO3-x with x  =  0.001-0.005. The energy positions of these states are in good agreement with recently reported density functional calculations. The results were compared with optical absorption measurements in the near infrared spectral region. An optical absorption peak at 0.74 eV is assigned to intervalence transfer of polarons between W sites. A less prominent peak at energies between 0.96 and 1.16 eV is assigned to electron excitation of oxygen vacancies. The latter results are supported by RIXS measurements, where an energy loss in this energy range was observed, and this suggests that electron transfer processes involving transitions from oxygen vacancy states can be observed in RIXS. Our results have implications for the interpretation of optical properties of WO3, and the optical transitions close to the band gap, which are important in photocatalytic and photoelectrochemical applications.

  6. Determination of the five parameter grain boundary character distribution of nanocrystalline alpha-zirconium thin films using transmission electron microscopy

    DOE PAGES

    Ghamarian, I.; Colorado School of Mines, Golden, CO; Samani, P.; ...

    2017-03-24

    Grain boundary engineering and other fundamental materials science problems (e.g., phase transformations and physical properties) require an improvement in the understanding of the type and population of grain boundaries in a given system – yet, databases are limited in number and spare in detail, including for hcp crystals such as zirconium. One way to rapidly obtain databases to analyze is to use small-grained materials and high spatial resolution orientation microscopy techniques, such as ASTAR™/precession electron diffraction. To demonstrate this, a study of grain boundary character distributions was conducted for α-zirconium deposited at room temperature on fused silica substrates using physicalmore » vapor deposition. The orientation maps of the nanocrystalline thin films were acquired by the ASTARα/precession electron diffraction technique, a new transmission electron microscope based orientation microscopy method. The reconstructed grain boundaries were classified as pure tilt, pure twist, 180°-twist and 180°-tilt grain boundaries based on the distribution of grain boundary planes with respect to the angle/axis of misorientation associated with grain boundaries. The results of the current study were compared to the results of a similar study on α-titanium and the molecular dynamics results of grain boundary energy for α-titanium.« less

  7. RETRACTED: Ammonia-free method for synthesis of CdS nanocrystalline thin films through chemical bath deposition technique

    NASA Astrophysics Data System (ADS)

    Karimi, M.; Rabiee, M.; Moztarzadeh, F.; Bodaghi, M.; Tahriri, M.

    2009-11-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief of Solid State Communications as the authors have plagiarized part of a paper that has also appeared in Current Applied Physics: Controlled synthesis, characterization and optical properties of CdS nanocrystalline thin films via chemical bath deposition (CBD) route Meysam Karimi, Mohammad Rabiee, Fathollah Moztarzadeh, Mohammadreza Tahriri and Masoud Bodaghi; Curr. Appl. Phys., 9 (2009) 1263-1268, doi: 10.1016/j.cap.2009.02.006. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  8. Effect of thickness on structural, optical, electrical and morphological properties of nanocrystalline CdSe thin films for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Purohit, Anuradha; Chander, S.; Nehra, S. P.; Lal, C.; Dhaka, M. S.

    2015-09-01

    This paper presents effect of thickness on the physical properties of thermally evaporated cadmium selenide thin films. The films of thickness 445 nm, 631 nm and 810 nm were deposited employing thermal evaporation technique on glass and ITO coated glass substrates followed by thermal annealing in air atmosphere at temperature 300 °C. The as-deposited and annealed films were subjected to the XRD, UV-Vis spectrophotometer, source meter, SEM and EDS to find the structural, optical, electrical, morphological and compositional analysis respectively. The structural analysis shows that the films have cubic phase with preferred orientation (1 1 1) and nanocrystalline nature. The structural parameters like inter-planner spacing, lattice constant, grain size, number of crystallites per unit area, internal strain, dislocation density and texture coefficient are calculated. The optical band gap is found in the range 1.69-1.84 eV and observed to decrease with thickness. The electrical resistivity is found to increase with thickness for as-deposited films and decrease for annealed films. The morphological studies show that the as-deposited and annealed films are homogeneous, smooth, fully covered and free from crystal defects like pin holes and voids. The grains in the as-deposited films are densely packed, well defined and found to be increased with thickness.

  9. Rapid growth of nanocrystalline CuInS 2 thin films in alkaline medium at room temperature

    NASA Astrophysics Data System (ADS)

    Roh, Seung Jae; Mane, Rajaram S.; Pathan, Habib M.; Joo, Oh-Shim; Han, Sung-Hwan

    2005-12-01

    Layer-by-layer (LbL) deposition of CuInS 2 (CIS) thin films at room temperature (25 °C) from alkaline CuSO 4 + In 2(SO 4) 3 and Na 2S precursor solutions was reported. The method allowed self-limited growth of CIS films with nanocrystalline structure and composed of densely packed nanometer-sized grains. The as-deposited CIS film was 250 nm thick and composed of closely packed particles of 20-30 nm in diameter. The alkaline cationic precursor solution was obtained by dissolving CuSO 4 and InSO 4 in deionized water with a appropriate amount of hydrazine monohydrate (H-H) and 2,2',2″-nitrilotriethanol (TEA). CIS films were annealed at 200 °C for 2 h and effect of annealing on structural, optical, and surface morphological properties was thoroughly investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis spectrometer, C-V, and water contact angle techniques, respectively.

  10. Nano-environment effects on the luminescence properties of Eu3+-doped nanocrystalline SnO2 thin films

    NASA Astrophysics Data System (ADS)

    Bazargan, Samad; Leung, K. T.

    2012-11-01

    Nanocrystalline tin (IV) oxide thin films doped with Eu3+ ions are synthesized using a simple spin-coating method followed by postannealing in an O2 flow at 700 °C. Transmission electron microscopy and x-ray photoelectron spectroscopy studies illustrate the incorporation of Eu3+ ions in the films with a high atomic percentage of 2.7%-7.7%, which is found to be linearly dependent on the initial concentration of Eu3+ in the precursor solution. Glancing incidence x-ray diffraction results show that the crystalline grain sizes decrease with increasing the Eu3+ concentration and decreasing the postannealing temperature with the emergence of the Eu2Sn2O7 phase at high Eu3+ concentrations (≥5.3 at.%). Luminescence spectra of these doped samples show the characteristic narrow-band magnetic dipole emission at 593 nm and electric dipole emission at 614 nm of the Eu3+ ions, arising from UV absorption at the SnO2 band-edge followed by energy transfer to the emission centers. Manipulating the crystallite size, composition, and defect density of the samples greatly affects the absorption edge, energy transfer, and therefore the emission spectra. These modifications in the environment of the Eu3+ ions allow the emission to be tuned from pure orange characteristic Eu3+ emission to the broadband emission corresponding to the combination of strong characteristic Eu3+ emission with the intense defect emissions.

  11. Mechanical response of nanocrystalline platinum via molecular dynamics: size effects in bulk versus thin-film samples

    NASA Astrophysics Data System (ADS)

    Kim, Hojin; Strachan, Alejandro

    2015-09-01

    We use large-scale molecular dynamics simulations to characterize the mechanical responses of nanocrystalline bulk and thin-film samples with average grain size ranging from 5 to 40 nm and at two strain rates. Our simulations show Hall-Petch maxima for both yield and flow stresses and for both sets of specimens. We find that the presence of free surface decreases both the yield and flow stresses and, interestingly, the Hall-Petch maximum for slabs occur at a larger grain size than for the bulk samples. A quantitative analysis of plastic slip on grain interiors and boundaries reveals that the shift in the maximum results from a combination of higher intergranular slip and weaker size dependence of dislocation activity in the slabs as compared with the bulk. Finally, increasing strain rate increases both yield and flow stresses and this rate effect is dominated by the plasticity involving full dislocations; plastic slip by partial dislocations and grain boundary processes exhibit weaker size effects.

  12. Effect of RF power density on micro- and macro-structural properties of PECVD grown hydrogenated nanocrystalline silicon thin films

    SciTech Connect

    Gokdogan, Gozde Kahriman; Anutgan, Tamila

    2016-03-25

    This contribution provides the comparison between micro- and macro-structure of hydrogenated nanocrystalline silicon (nc-Si:H) thin films grown by plasma enhanced chemical vapor deposition (PECVD) technique under different RF power densities (P{sub RF}: 100−444 mW/cm{sup 2}). Micro-structure is assessed through grazing angle X-ray diffraction (GAXRD), while macro-structure is followed by surface and cross-sectional morphology via field emission scanning electron microscopy (FE-SEM). The nanocrystallite size (∼5 nm) and FE-SEM surface conglomerate size (∼40 nm) decreases with increasing P{sub RF}, crystalline volume fraction reaches maximum at 162 mW/cm{sup 2}, FE-SEM cross-sectional structure is columnar except for the film grown at 162 mW/cm{sup 2}. The dependence of previously determined ‘oxygen content–refractive index’ correlation on obtained macro-structure is investigated. Also, the effect of P{sub RF} is discussed in the light of plasma parameters during film deposition process and nc-Si:H film growth models.

  13. Structural, optical and electrical characterization of vacuum-evaporated nanocrystalline CdSe thin films for photosensor applications

    NASA Astrophysics Data System (ADS)

    Kumar, Vipin; Sharma, D. K.; Sharma, Kapil; Dwivedi, D. K.

    2016-11-01

    II-VI nanocrystalline semiconductors offer a wide range of applications in electronics, optoelectronics and photonics. Thin films of CdSe were deposited onto ultra-clean glass substrates by vacuum evaporation method. The as-deposited films were annealed in vacuum at 350 K. The structural, elemental, morphological, optical and electrical investigations of annealed films were carried out. The X-ray diffraction pattern of the films shows that films were polycrystalline in nature having hexagonal structure with preferential orientation of grains along (002) plane. SEM image indicates that the films were uniform and well covered to the glass substrate. EDAX analysis confirms the stoichiometric composition of the film. Raman spectra were used to observe the characteristic vibrational modes of CdSe. The energy band gap of these films was obtained by absorption spectra. The films were found to have a direct type of transition of band gap occurring at 1.75 eV. The dark electrical conductivity and photoconductivity reveals that the films were semiconducting in nature indicating the suitability of these films for photosensor applications. The Hall effect measurement reveals that the films have n-type electrical conductivity.

  14. Investigations of the drift mobility of carriers and density of states in nanocrystalline CdS thin films

    NASA Astrophysics Data System (ADS)

    Singh, Baljinder; Singh, Janpreet; Kaur, Jagdish; Moudgil, R. K.; Tripathi, S. K.

    2016-06-01

    Nanocrystalline Cadmium Sulfide (nc-CdS) thin films have been prepared on well-cleaned glass substrate at room temperature (300 K) by thermal evaporation technique using inert gas condensation (IGC) method. X-ray diffraction (XRD) analysis reveals that the films crystallize in hexagonal structure with preferred orientation along [002] direction. Scanning electron microscope (SEM) and Transmission electron microscope (TEM) studies reveal that grains are spherical in shape and uniformly distributed over the glass substrates. The optical band gap of the film is estimated from the transmittance spectra. Electrical parameters such as Hall coefficient, carrier type, carrier concentration, resistivity and mobility are determined using Hall measurements at 300 K. Transit time and mobility are estimated from Time of Flight (TOF) transient photocurrent technique in gap cell configuration. The measured values of electron drift mobility from TOF and Hall measurements are of the same order. Constant Photocurrent Method in ac-mode (ac-CPM) is used to measure the absorption spectra in low absorption region. By applying derivative method, we have converted the measured absorption data into a density of states (DOS) distribution in the lower part of the energy gap. The value of Urbach energy, steepness parameter and density of defect states have been calculated from the absorption and DOS spectra.

  15. Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

    SciTech Connect

    Vargas, Mirella; Murphy, N. R.; Ramana, C. V.

    2014-03-10

    Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s} = 25–700 °C). HfO{sub 2} films grown at T{sub s} < 200 °C were amorphous, while those grown at T{sub s} ≥ 200 °C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (ρ) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (λ)} = 550 nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-ρ-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and the microstructure of HfO{sub 2} films.

  16. Microarray of neuroblastoma cells on the selectively functionalized nanocrystalline diamond thin film surface

    NASA Astrophysics Data System (ADS)

    Park, Young-Sang; Son, Hyeong-Guk; Kim, Dae-Hoon; Oh, Hong-Gi; Lee, Da-Som; Kim, Min-Hye; Lim, Ki-Moo; Song, Kwang-Soup

    2016-01-01

    Nanocrystalline diamond (NCD) film surfaces were modified with fluorine or oxygen by plasma treatment in an O2 or C3F8 gas environment in order to induce wettability. The oxygenated-NCD (O-NCD) film surface was hydrophilic and the fluorinated-NCD (F-NCD) surface was hydrophobic. The efficiency of early cell adhesion, which is dependent on the wettability of the cell culture plate and necessary for the growth and proliferation of cells, was 89.62 ± 3.92% on the O-NCD film and 7.78 ± 0.77% on the F-NCD film surface after 3 h of cell culture. The wettability of the NCD film surface was artificially modified using a metal mask and plasma treatment to fabricate a micro-pattern. Four types of micro-patterns were fabricated (line, circle, mesh, and word) on the NCD film surface. We precisely arrayed the neuroblastoma cells on the micro-patterned NCD film surfaces by controlling the surface wettability and cell seeding density. The neuroblastoma cells adhered and proliferated along the O-NCD film surface.

  17. Synthesis of colloidal Mn2+:ZnO quantum dots and high-TC ferromagnetic nanocrystalline thin films.

    PubMed

    Norberg, Nick S; Kittilstved, Kevin R; Amonette, James E; Kukkadapu, Ravi K; Schwartz, Dana A; Gamelin, Daniel R

    2004-08-04

    We report the synthesis of colloidal Mn(2+)-doped ZnO (Mn(2+):ZnO) quantum dots and the preparation of room-temperature ferromagnetic nanocrystalline thin films. Mn(2+):ZnO nanocrystals were prepared by a hydrolysis and condensation reaction in DMSO under atmospheric conditions. Synthesis was monitored by electronic absorption and electron paramagnetic resonance (EPR) spectroscopies. Zn(OAc)(2) was found to strongly inhibit oxidation of Mn(2+) by O(2), allowing the synthesis of Mn(2+):ZnO to be performed aerobically. Mn(2+) ions were removed from the surfaces of as-prepared nanocrystals using dodecylamine to yield high-quality internally doped Mn(2+):ZnO colloids of nearly spherical shape and uniform diameter (6.1 +/- 0.7 nm). Simulations of the highly resolved X- and Q-band nanocrystal EPR spectra, combined with quantitative analysis of magnetic susceptibilities, confirmed that the manganese is substitutionally incorporated into the ZnO nanocrystals as Mn(2+) with very homogeneous speciation, differing from bulk Mn(2+):ZnO only in the magnitude of D-strain. Robust ferromagnetism was observed in spin-coated thin films of the nanocrystals, with 300 K saturation moments as large as 1.35 micro(B)/Mn(2+) and T(C) > 350 K. A distinct ferromagnetic resonance signal was observed in the EPR spectra of the ferromagnetic films. The occurrence of ferromagnetism in Mn(2+):ZnO and its dependence on synthetic variables are discussed in the context of these and previous theoretical and experimental results.

  18. Dielectric, optical and electric studies on nanocrystalline Ba5Nb4O15 thin films deposited by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Anil Kumar, C.; Pamu, D.

    2015-06-01

    We report the fabrication of nanocrystalline Ag/BNO/Pt/Ti/SiO2/Si thin film capacitors by RF magnetron sputtering with different film thicknesses. The effect of Ba5Nb4O15 (BNO) thickness on structural, microstructural, electrical, optical and dielectric properties is investigated for the first time. BNO sputtering target prepared is by mechanochemical synthesis method to eliminate the subordinate phases. As deposited thin films were X-ray amorphous and crystallinity is induced after annealing at 700 °C. Upon annealing, refractive indices of the films enhanced whereas the bandgap is decreased and are in the range of 1.89-2.16 and 4.07-4.24, respectively. With an increase in thickness, the dielectric properties improved substantially, which is described by the representation of a dead layer connected in series with a bulk region of the BNO film. The extracted values of thickness and dielectric constant for the dead layer found to be 15.21 nm and 37.03, correspondingly. The activation energy of the mobile charge carriers obtained using the Arrhenius relation are found to be 0.254, 0.036 and 0.027 eV, for the films with 150, 250 and 450 nm, respectively. The leakage current density found to decrease with thickness and found to be 2.5 × 10-6 A/cm2 at applied voltage of 50 kV/cm. The J-E characteristics of the BNO films show a combined response of grain, grain boundaries and film-electrode interfaces. It is interesting to note that in the negative electric field region, conduction is ohmic in nature whereas in the positive field region BNO films exhibit both ohmic and the space charge-limited current mechanisms. The achieved dielectric, electrical and optical properties make these films suitable for MIC, CMOS and optoelectronic applications.

  19. The influence of Cd doping on the microstructure and optical properties of nanocrystalline copper ferrite thin films

    SciTech Connect

    El-Hagary, M.; Matar, A.; Shaaban, E.R.; Emam-Ismail, M.

    2013-06-01

    Highlights: ► The structural and optical properties of Cu{sub 1−x}Cd{sub x}Fe{sub 2}O{sub 4} thin films were studied. ► The micro structural parameters of the films have been determined. ► The room temperature reflectance and transmittance data are analyzed. ► The refractive index and energy gap are determined. ► The single oscillator parameters were calculated. - Abstract: Nanocrystalline thin films of mixed Cu–Cd ferrites, Cu{sub 1−x}Cd{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.2, 0.3, 0.5, 0.7, 0.8, 0.9 and 1), were deposited by electron beam evaporation technique. The films were annealed at 450 °C for 1 h. The effect of Cd doping on the structural and optical properties of the deposited films has been investigated by using X-ray diffraction (XRD) and optical spectrophotometry. XRD patterns of the annealed films show spinal cubic structure. The lattice parameter was found to increase with the increase of cadmium concentration. The crystallite size of the films was found to vary from 8 nm to 30 nm. The optical transition was found to be direct and indirect transitions with energy gaps decrease from 2.466 (x = 0) to 2.00 (x = 1) eV and from 2.148 (x = 0) to 1.824 (x = 1) eV, respectively. The refractive index dispersion of the films was found to increase with Cd content and discussed in terms of the Wemple–DiDomenico single oscillator model.

  20. Ag Nanodots Emitters Embedded in a Nanocrystalline Thin Film Deposited on Crystalline Si Solar Cells.

    PubMed

    Park, Seungil; Ryu, Sel Gi; Ji, HyungYong; Kim, Myeong Jun; Peck, Jong Hyeon; Kim, Keunjoo

    2016-06-01

    We fabricated crystalline Si solar cells with the inclusion of various Ag nanodots into the additional emitters of nanocrystallite Si thin films. The fabricated process was carried out on the emitter surface of p-n junction for the textured p-type wafer. The Ag thin films were deposited on emitter surfaces and annealed at various temperatures. The amorphous Si layers were also deposited on the Ag annealed surfaces by hot-wire chemical vapor deposition and then the deposited layers were doped by the second n-type doping process to form an additional emitter. From the characterization, both the Ag nanodots and the deposited amorphous Si thin films strongly reduce photo-reflectances in a spectral region between 200-400 nm. After embedding Ag nanodots in nanocrystallite Si thin films, a conversion efficiency of the sample with added emitter was achieved to 15.1%, which is higher than the 14.1% of the reference sample and the 14.7% of the de-posited sample with a-Si:H thin film after the Ag annealing process. The additional nanocrystallite emitter on crystalline Si with Ag nanodots enhances cell properties.

  1. Anomalous hopping conduction in nanocrystalline/amorphous composites and amorphous semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Kakalios, James; Bodurtha, Kent

    Composite nanostructured materials consisting of nanocrystals (nc) embedded within a thin film amorphous matrix can exhibit novel opto-electronic properties. Composite films are synthesized in a dual-chamber co-deposition PECVD system capable of producing nanocrystals of material A and embedding then within a thin film matrix of material B. Electronic conduction in composite thin films of hydrogenated amorphous silicon (a-Si:H) containing nc-germanium or nc-silicon inclusions, as well as in undoped a-Si:H, does not follow an Arrhenius temperature dependence, but rather is better described by an anomalous hopping expression (exp[-(To/T)3/4) , as determined from the ``reduced activation energy'' proposed by Zabrodskii and Shlimak. This temperature dependence has been observed in other thin film resistive materials, such as ultra-thin disordered films of Ag, Bi, Pb and Pd; carbon-black polymer composites; and weakly coupled Au and ZnO quantum dot arrays. There is presently no accepted theoretical understanding of this expression. The concept of a mobility edge, accepted for over four decades, appears to not be necessary to account for charge transport in amorphous semiconductors. Supported by NSF-DMR and the Minnesota Nano Center.

  2. Effect of pH on the properties of nanocrystalline CuO thin films deposited by sol-gel process

    NASA Astrophysics Data System (ADS)

    Saadat Niavol, S.; Ghodsi, F. E.

    2013-01-01

    Nanocrystalline cupric oxide thin films were prepared using the sol-gel method. Three sols with different pH were performed in order to evaluate the pH effect on the morphology and optical properties of the films. XRD pattern confirmed the nanocrystalline monoclinic CuO phase formation. The influences of pH on surface morphology of films were investigated by scanning electron microscopy (SEM). It was observed that grains size increases by increasing the pH of the sol. UV-Vis spectrum measurement showed low transparency of the films in the visible region. Optical constants such as extinction coefficient, refractive index and optical band gap were evaluated from these spectra by using the Pointwise Unconstrained Minimization Approach (PUMA). The band gap of the films varies from 2.20 to 1.98 eV for various pH of sol.

  3. Structural and Mechanical Characterization of Nanocrystalline Tungsten and Tungsten-Based Alloy Thin Films for Extreme Environment Applications

    NASA Astrophysics Data System (ADS)

    Martinez, Gustavo

    Extreme environments associated with nuclear applications often results in degradation of the physical, mechanical and thermo-mechanical properties of the materials. Tungsten (W) exhibits unique physical and mechanical properties, which makes tungsten a good candidate for nuclear applications; however, intrinsic W exhibits low fracture toughness at all temperatures in addition to a high ductile to brittle transition. In the present work, nanocrystalline W, W-Y and W-Mo alloys were nanoengineered for nuclear applications. Nanocrystalline tungsten coatings with a thickness of 1 microm were deposited onto Silicon (100) and Sapphire (C-plane) using RF and DC sputtering techniques under various growth conditions. Yttrium content in W-Y alloys has been varied to enhance the irradiation tolerance under optimum concentration. The W, W-Y coatings were characterized to understand the structure and morphology and to establish a mapping of conditions to obtain phase and size controlled materials. The samples were then subjected to depth-controlled irradiation by neutrons and Au3+ ions. Solid solution strengthening was achieved by doping molybdenum (Mo) solute atoms to W matrix under varied sputtering pressures and temperatures with the intention of creating interstitial point defects in the crystals that impede dislocation motion, increasing the hardness and young modulus of the material. The effect of PAr (3-19 mTorr) was also investigated and associated microstructure are significant on the mechanical characteristics; the hardness (H) and modulus of elasticity (Er) of the nc W-Mo thin films were higher at lower pressures but decreases continuously with increasing PAr. Using nano-indentation and nano-scratch technique, mechanical characterization testing was performed before and after irradiation. The structure, mechanics and irradiation stability of the W and W-Y coatings will be presented and discussed to demonstrate that Y-addition coupled with nano-scale features

  4. Post-annealing-free, room temperature processed nanocrystalline indium tin oxide thin films for plastic electronics

    NASA Astrophysics Data System (ADS)

    Nyoung Jang, Jin; Jong Lee, You; Jang, YunSung; Yun, JangWon; Yi, Seungjun; Hong, MunPyo

    2016-06-01

    In this study, we confirm that bombardment by high energy negative oxygen ions (NOIs) is the key origin of electro-optical property degradations in indium tin oxide (ITO) thin films formed by conventional plasma sputtering processes. To minimize the bombardment effect of NOIs, which are generated on the surface of the ITO targets and accelerated by the cathode sheath potential on the magnetron sputter gun (MSG), we introduce a magnetic field shielded sputtering (MFSS) system composed of a permanent magnetic array between the MSG and the substrate holder to block the arrival of energetic NOIs. The MFSS processed ITO thin films reveal a novel nanocrystal imbedded polymorphous structure, and present not only superior electro-optical characteristics but also higher gas diffusion barrier properties. To the best of our knowledge, no gas diffusion barrier composed of a single inorganic thin film formed by conventional plasma sputtering processes achieves such a low moisture permeability.

  5. Monte Carlo Simulation of the Optical Absorption of Hydrogenated Nanocrystalline Silicon Thin Films

    NASA Astrophysics Data System (ADS)

    Besahraoui, Fatiha; Sib, Jamal Dine; Bouizem, Yahia; Chahed, Larbi

    2008-05-01

    The optical absorption coefficient measured by Constant Photocurrent Method (CPM) for nanotextured silicon thin films is apparent affected by light scattering produced in these heterogeneous materials. A detailed Monte Carlo simulation of the absorption spectra and the random optical paths traveled by the scattered photons is presented for the case of nano-Si:H layers. The calculated values of apparent absorption coefficient and the mean optical path depend mainly on the variation of the included nanocrystallites fraction, which favors bulk light scattering phenomena. The particular structure of these materials is a key characteristic of efficient thin films solar cells.

  6. Cyclic compression response of micropillars extracted from textured nanocrystalline NiTi thin-walled tubes

    DOE PAGES

    Ghassemi-Armaki, Hassan; Leff, Asher C.; Taheri, Mitra L.; ...

    2017-06-22

    Compression-compression cyclic deformation of nanocrystalline NiTi tubes intended for medical stents and with an outer diameter of 1 mm and wall thickness of 70 μm was studied using micropillars produced by FIB with the loading axis orthogonal to the tube axis. These micropillars were cycled in a displacement-controlled mode using a nanoindenter equipped with a flat punch to strain levels of 4, 6 and 8% in each cycle and specimens were subjected to several hundred cycles. Furthermore, the cyclic response of two NiTi tubes, one with Af of 17 °C and the other with an Af of -5 °C ismore » compared. The texture of the tube with the Af of -5 °C was measured at the microscopic level using transmission electron microscopy and at the macroscopic level by X-ray diffraction and good agreement was noted. Characteristics such as i) a reduction in the forward transformation stress, ii) increase in maximum stress for a given displacement amplitude, and iii) a reduction in the hysteresis loop area, all with increasing number of cycles, observed typically during cyclic deformation of conventional macroscopic specimens, were captured in the micropillar cyclic tests. Our observations lead to the conclusion that micropillar compression testing in a cyclic mode can enable characterizing the orientation-dependent response in such small dimension components that see complex loading in service, and additionally provide an opportunity for calibrating constitutive equations in micromechanical models.« less

  7. Study of Photo-Conductivity in Nano-Crystalline Cadmium Telluride Thin Films

    SciTech Connect

    Mahesha, M. G.; Bangera, Kasturi V.; Shivakumar, G. K.

    2011-07-15

    Nano crystallite thin films of Cadmium Telluride have been grown on glass substrates by thermal evaporation under vacuum. The growth conditions to get stoichiometric films of the compound have been optimized. The effect of substrate temperature and annealing on photosensitivity has been investigated. Also the effect of deposition parameters and post deposition annealing on rise time and decay time have been studied in detail.

  8. Liquid-Phase Epitaxial Growth of ZnS, ZnSe and Their Mixed Compounds Using Te as Solvent

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroshi; Aoki, Masaharu

    1981-01-01

    Epitaxial layers of ZnS, ZnSe and their mixed compounds were grown on ZnS substrates by the liquid-phase epitaxial growth (LPE) method using Te as the solvent. The open-tube slide-boat technique was used, and a suitable starting temperature for growth was found to be 850°C for ZnS and 700-800°C for ZnSe. The ZnS epitaxial layers grown on {111}A and {111}B oriented ZnS substrates were thin (˜1 μm) and smooth, had low, uniform Te concentrations (˜0.1 at.%) and were highly luminescent. The ZnSe epitaxial layers were relatively thick (10-30 μm) and had fairly high Te concentrations (a few at.%). Various mixed compound ZnS1-xSex were also grown on ZnS substrates.

  9. Synthesis and Characterization of Nanocrystalline CdZnS Thin Films

    NASA Astrophysics Data System (ADS)

    Verma, Urvashi; Thakur, Vikas; Yadav, Preeti; Shrivastava, A. K.

    2011-07-01

    CdZnS thin films have been grown on the glass substrate using Chemical Bath Deposition (CBD) technique. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) studies were performed in order to investigate the structural, surface morphology and elemental composition properties of the films. X-ray diffraction studies show polycrystalline nature of CdZnS films. SEM micrographs show that the grains of CdZnS thin films possess flake like morphology or nanosheet morphology. It has also been observed that the doping concentration of Zn do not affect the morphology of CdZnS film. SEM studies also show that particle size decreases with annealing.

  10. Nanocrystalline CuInSSe thin films by chemical bath deposition technique

    SciTech Connect

    Shrotriya, Vipin Rajaram, P.

    2016-05-06

    Crystalline CuInSSe thin films have been deposited on glass substrate by chemical bath deposition technique. The CuCl{sub 2}, InCl{sub 3}, thiourea and SeO{sub 2} were used as source materials for the Cu{sup 2+}, In{sup 3+}, S{sup 2−} and Se{sup 2−} ions and the Cu/In ratio was kept at 1.0. EDC was used as a complexing agent. The XRD, Scanning Electron Microscope (SEM), Energy Dispersive Analysis of X-Ray (EDAX) and Optical transmission studies were used for structural analysis, surface morphology, elemental analysis and optical band gap, of the grown thin films respectively. The deposition parameters such as pH, deposition temperature and deposition time were optimized.

  11. Nanocrystalline CuInSSe thin films by chemical bath deposition technique

    NASA Astrophysics Data System (ADS)

    Shrotriya, Vipin; Rajaram, P.

    2016-05-01

    Crystalline CuInSSe thin films have been deposited on glass substrate by chemical bath deposition technique. The CuCl2, InCl3, thiourea and SeO2 were used as source materials for the Cu2+, In3+, S2- and Se2- ions and the Cu/In ratio was kept at 1.0. EDC was used as a complexing agent. The XRD, Scanning Electron Microscope (SEM), Energy Dispersive Analysis of X-Ray (EDAX) and Optical transmission studies were used for structural analysis, surface morphology, elemental analysis and optical band gap, of the grown thin films respectively. The deposition parameters such as pH, deposition temperature and deposition time were optimized.

  12. Thermo-electrical properties of composite semiconductor thin films composed of nanocrystalline graphene-vanadium oxides.

    PubMed

    Jung, Hye-Mi; Um, Sukkee

    2014-12-01

    This paper presents an experimental comparative study involving the characterization of the thermo-electrical and structural properties of graphene-based vanadium oxide (graphene-VOx) composite thin films on insulating and conducting surfaces (i.e., fused quartz and acrylic resin-impregnated graphite) produced by a sol-gel process via dipping-pyrolysis. A combination of FE-SEM and XPS analyses revealed that the graphene-VOx composite thin films (coated onto fused quartz) exhibiting the microstructure of 2-graded nanowire arrays with a diameter of 40-80 nm were composed of graphene, a few residual oxygen-containing functional groups (i.e., C-O and C=O), and the VO2 Magnéli phase. The temperature-dependent electrical resistance measured on the as-deposited thin films clearly demonstrated that the graphene-VOx composite nanowire arrays thermally grown on fused quartz act as a semiconductor switch, with a transition temperature of 64.7 degrees C in the temperature range of -20 degrees C to 140 degrees C, resulting from the contributions of graphene and graphene oxides. In contrast, the graphene-VOx composite thin films deposited onto acrylic resin-impregnated graphite exhibit a superlinear semiconducting property of extremely low electrical resistance with negative temperature coefficients (i.e., approximately four orders of magnitude lower than that of the fused quartz), despite the similar microstructural and morphological characteristics. This difference is attributed to the synergistic effects of the paramagnetic metal feature of the tightly stacked nanowire arrays consisting of hexagonal V2O3 on the intrinsic electrical properties of the acrylic resin-impregnated graphite substrate, as revealed by FE-SEM, EDX, AFM, and XRD measurements. Although the thermo-sensitive electrical properties of the graphene-VOx composite thin films are very substrate specific, the applicability of graphene sheets can be considerably effective in the formation of highly planar arrays

  13. Synthesis and characterization of Eu(3+), Ti(4+) @ ZnO organosols and nanocrystalline c-ZnTiO3 thin films aiming at high transparency and luminescence.

    PubMed

    Aubert, Tangi; Grasset, Fabien; Potel, Michel; Nazabal, Virginie; Cardinal, Thierry; Pechev, Stanislav; Saito, Noriko; Ohashi, Naoki; Haneda, Hajime

    2010-08-01

    By exploiting colloidal properties, such as transparency, rheology and versatile chemistry, we propose to synthesize new photonic nanomaterials based on colloidal solutions and thin films. This contribution highlights our efforts to elaborate and to characterize nanostructures based on the ZnO-TiO2 system. Using a recently developed sol-gel route to synthesize new Ti(4+)@ZnO organosols, we were able to prepare, at relatively low temperature (400 °C) and short annealing time (15 min), highly transparent, luminescent, nanocrystalline Eu(3+) doped c-ZnTiO3 thin films. The organosols and thin films were characterized with UV-visible-near infrared absorption, ellipsometry, photoluminescence spectroscopy, dynamic light scattering, x-ray diffraction and scanning electron microscopy.

  14. Synthesis and characterization of Eu3+, Ti4+ @ ZnO organosols and nanocrystalline c-ZnTiO3 thin films aiming at high transparency and luminescence

    PubMed Central

    Aubert, Tangi; Grasset, Fabien; Potel, Michel; Nazabal, Virginie; Cardinal, Thierry; Pechev, Stanislav; Saito, Noriko; Ohashi, Naoki; Haneda, Hajime

    2010-01-01

    By exploiting colloidal properties, such as transparency, rheology and versatile chemistry, we propose to synthesize new photonic nanomaterials based on colloidal solutions and thin films. This contribution highlights our efforts to elaborate and to characterize nanostructures based on the ZnO–TiO2 system. Using a recently developed sol–gel route to synthesize new Ti4+@ZnO organosols, we were able to prepare, at relatively low temperature (400 °C) and short annealing time (15 min), highly transparent, luminescent, nanocrystalline Eu3+ doped c-ZnTiO3 thin films. The organosols and thin films were characterized with UV-visible-near infrared absorption, ellipsometry, photoluminescence spectroscopy, dynamic light scattering, x-ray diffraction and scanning electron microscopy. PMID:27877348

  15. Synthesis and characterization of Eu3+,Ti4+@ZnO organosols and nanocrystalline c-ZnTiO3 thin films aiming at high transparency and luminescence

    NASA Astrophysics Data System (ADS)

    Aubert, Tangi; Grasset, Fabien; Potel, Michel; Nazabal, Virginie; Cardinal, Thierry; Pechev, Stanislav; Saito, Noriko; Ohashi, Naoki; Haneda, Hajime

    2010-08-01

    By exploiting colloidal properties, such as transparency, rheology and versatile chemistry, we propose to synthesize new photonic nanomaterials based on colloidal solutions and thin films. This contribution highlights our efforts to elaborate and to characterize nanostructures based on the ZnO-TiO2 system. Using a recently developed sol-gel route to synthesize new Ti4+@ZnO organosols, we were able to prepare, at relatively low temperature (400 °C) and short annealing time (15 min), highly transparent, luminescent, nanocrystalline Eu3+ doped c-ZnTiO3 thin films. The organosols and thin films were characterized with UV-visible-near infrared absorption, ellipsometry, photoluminescence spectroscopy, dynamic light scattering, x-ray diffraction and scanning electron microscopy.

  16. Pulsed laser-deposited nanocrystalline GdB6 thin films on W and Re as field emitters

    NASA Astrophysics Data System (ADS)

    Suryawanshi, Sachin R.; Singh, Anil K.; Phase, Deodatta M.; Late, Dattatray J.; Sinha, Sucharita; More, Mahendra A.

    2016-10-01

    Gadolinium hexaboride (GdB6) nanocrystalline thin films were grown on tungsten (W), rhenium (Re) tips and foil substrates using optimized pulsed laser deposition (PLD) technique. The X-ray diffraction analysis reveals formation of pure, crystalline cubic phase of GdB6 on W and Re substrates, under the prevailing PLD conditions. The field emission (FE) studies of GdB6/W and GdB6/Re emitters were performed in a planar diode configuration at the base pressure ~10-8 mbar. The GdB6/W and GdB6/Re tip emitters deliver high emission current densities of ~1.4 and 0.811 mA/cm2 at an applied field of ~6.0 and 7.0 V/µm, respectively. The Fowler-Nordheim ( F- N) plots were found to be nearly linear showing metallic nature of the emitters. The noticeably high values of field enhancement factor ( β) estimated using the slopes of the F- N plots indicate that the PLD GdB6 coating on W and Re substrates comprises of high-aspect-ratio nanostructures. Interestingly, the GdB6/W and GdB6/Re planar emitters exhibit excellent current stability at the preset values over a long-term operation, as compared to the tip emitters. Furthermore, the values of workfunction of the GdB6/W and GdB6/Re emitters, experimentally measured using ultraviolet photoelectron spectroscopy, are found to be same, ~1.6 ± 0.1 eV. Despite possessing same workfunction value, the FE characteristics of the GdB6/W emitter are markedly different from that of GdB6/Re emitter, which can be attributed to the growth of GdB6 films on W and Re substrates.

  17. Structural, optical and electrical properties of yttrium-doped hafnium oxide nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Kongu, Abhilash

    Hafnium oxide (HfO2) has emerged as the most promising high-k dielectric for Metal-Oxide-Semiconductor (MOS) devices and has been highlighted as the most suitable dielectric materials to replace silicon oxide because of its comprehensive performance. In the present research, yttrium-doped HfO2 (YDH) thin films were fabricated using RF magnetron sputter deposition onto Si (100) and quartz with a variable thickness. Cross-sectional scanning electron microscopy coupled with Filmetrics revealed that film thickness values range from 700 A° to 7500 A°. Electrical properties such as AC Resistivity and current-voltage (I-V) characteristics of YDH films were studied. YDH films that were relatively thin (<1500 A°) crystallized in monoclinic phase while thicker films crystallized in cubic phase. The band gap (Eg) of the films was calculated from the optical measurements. The band gap was found to be ˜5.60 eV for monoclinic while it is ˜6.05 eV for cubic phase of YDH films. Frequency dependence of the electrical resistivity (rhoac) and the total conductivity of the films were measured. Resistivity decreased (by three orders of magnitude) with increasing frequency from 100 Hz to 1 MHz, attributed due to the hopping mechanism in YDH films. Whereas, while rhoac˜1O-m at low frequencies (100 Hz), it decreased to ˜ 104 O-cm at higher frequencies (1 MHz). Aluminum (Al) metal electrodes were deposited to fabricate a thin film capacitor with YDH layer as dielectric film thereby employing Al-YDH-Si capacitor structure. The results indicate that the capacitance of the films decrease with increasing film thickness. A detailed analysis of the electrical characteristics of YDH films is presented.

  18. Molecular dynamics simulations of grain boundaries in thin nanocrystalline silicon films

    SciTech Connect

    Berman, G.P.; Doolen, G.D.; Mainieri, R.; Campbell, D.K.; Luchnikov, V.A. |

    1997-10-01

    Using molecular dynamics simulations, the grain boundaries in thin polycrystalline silicon films (considered as promising material for future nanoelectronic devices) are investigated. It is shown that in polysilicon film with randomly oriented grains the majority of grain boundaries are disordered. However, some grains with small mutual orientation differences can form extended crystalline patterns. The structure of the grain boundaries satisfies the thermodynamical criterion. The majority of atoms in the grain boundaries are tetrahedrally coordinated with the nearest neighbors, even though the grain boundaries are disordered. The grain boundary matter is characterized as an amorphous phase with a characteristic tetragonality value.

  19. Photoinduced charge, ion & energy transfer processes at transition-metal coordination compounds anchored to mesoporous, nanocrystalline metal-oxide thin films

    NASA Astrophysics Data System (ADS)

    Ardo, Shane

    Photovoltaics provide a direct means of converting photons into useful, electric power; however traditional silicon-based technologies are too expensive for global commercialization. Dye-sensitized mesoporous semiconducting thin films, when utilized in regenerative photoelectrochemical cells, are one category of next generation photovoltaics that could eventually circumvent this issue. In fact, their architecture also affords a clear platform for implementation of a direct, solar fuel-forming system. The mechanisms involved in the myriad of molecular processes that occur in these molecular--solid-state hybrid materials are poorly understood. Thus, the overriding goal of this dissertation was to evaluate sensitized mesoporous, nanocrystalline metal-oxide thin films critically so as to elucidate mechanistic phenomena. Using transient and steady-state absorption and emission spectroscopies as well as (photo)electrochemistry, various previously unobserved processes have been identified. Chapter 2 demonstrates for the first time that the electric fields emanating from these charged thin films affect surface-anchored molecular sensitizers via a Stark effect. In most cases, further, but incomplete, ionic screening of the charged nanoparticles from the sensitizers, as non-Faradaic electrolyte redistribution, was spectroscopically inferred after rapid semiconductor charging. Chapter 3 highlights the reactivity of Co(I) coordination-compound catalysts anchored to anatase TiO2 thin-film electrodes. Visible-light excitation resulted in prompt excited-state electron injection into TiO2 while introduction of benzylbromide into the fluid solution surrounding the thin film led to a 2e--transfer, oxidative-addition reaction to Co1 forming a stable Co--benzyl product. Subsequent visible-light excitation initiated a photocatalytic cycle for C--C bond formation. Unique to the nanocrystalline thin films employed here, Chapter 4 demonstrates that traditional time-resolved polarization

  20. Nano-Crystalline Thermally Evaporated Bi2Se3 Thin Films Synthesized from Mechanically Milled Powder

    NASA Astrophysics Data System (ADS)

    Amara, A.; Abdennouri, N.; Drici, A.; Abdelkader, D.; Bououdina, M.; Chaffar Akkari, F.; Khemiri, N.; Kanzari, M.; Bernède, J. C.

    2017-08-01

    Bi2Se3 powder has been successfully synthesized via mechanical ball milling of bismuth and selenium as starting materials. X-ray diffraction characterization revealed the formation of the rhombohedral and orthorhombic phases of Bi2Se3 material belonging to systems with space groups R\\bar{3}m and Pbnm, respectively. The advantageous last finding is confirmed by the Rietveld refinement of the x-ray diffraction data. Furthermore, the analysis of the x-ray data of thermally deposited thin films revealed that both orthorhombic and rhombohedral phases are coexisting in the layer. The morphology of the ball milled powder was studied by scanning electron microscopy. The phase formation of the material is confirmed by Raman spectroscopy. M-H (Magnetization versus Magnetic field) curve indicates that Bi2Se3 powder has a ferromagnetic behavior. Additionally, absorbance and transmittance measurements were carried out on the obtained thermally evaporated thin films and yielded a band gap of 1.33 eV supporting the potential application of the heterogeneous rhombohedral/orthorhombic Bi2Se3 material in photovoltaics.

  1. Non-toxic novel route synthesis and characterization of nanocrystalline ZnS{sub x}Se{sub 1−x} thin films with tunable band gap characteristics

    SciTech Connect

    Agawane, G.L.; Shin, Seung Wook; Vanalakar, S.A.; Moholkar, A.V.; Gurav, K.V.; Suryawanshi, M.P.; Lee, Jeong Yong; Yun, Jae Ho; Kim, Jin Hyeok

    2014-07-01

    Highlights: • A simple, inexpensive, and non-toxic CBD route is used to deposit ZnS thin films. • The ZnS{sub x}Se{sub 1−x} thin films formation takes place via annealing of ZnS thin films in Se atmosphere. • S/(S + Se) ratio found to be temperature dependent and easy tuning of band gap has been done by Se atom deposition. - Abstract: An environmentally benign chemical bath deposition (CBD) route was employed to deposit zinc sulfide (ZnS) thin films. The CBD-ZnS thin films were further selenized in a furnace at various temperatures viz. 200, 300, 400, and 500 °C and the S/(S + Se) ratio was found to be dependent on the annealing temperature. The effects of S/(S + Se) ratio on the structural, compositional and optical properties of the ZnS{sub x}Se{sub 1−x} (ZnSSe) thin films were investigated. EDS analysis showed that the S/(S + Se) ratio decreased from 0.8 to 0.6 when the film annealing temperature increased from 200 to 500 °C. The field emission scanning electron microscopy and atomic force microscopy studies showed that all the films were uniform, pin hole free, smooth, and adhered well to the glass substrate. The X-ray diffraction study on the ZnSSe thin films showed the formation of the cubic phase, except for the unannealed ZnSSe thin film, which showed an amorphous phase. The X-ray photoelectron spectroscopy revealed Zn-S, Zn-Se, and insignificant Zn-OH bonds formation from the Zn 2p{sub 3/2}, S 2p, Se 3d{sub 5/2}, and O 1s atomic states, respectively. The ultraviolet–visible spectroscopy study showed ∼80% transmittance in the visible region for all the ZnSSe thin films having various absorption edges. The tuning of the band gap energy of the ZnSSe thin films was carried out by selenizing CBD-ZnS thin films, and as the S/(S + Se) ratio decreased from 0.8 to 0.6, the band gap energy decreased from 3.20 to 3.12 eV.

  2. Basal-plane thermal conductivity of nanocrystalline and amorphized thin germanane

    SciTech Connect

    Coloyan, Gabriella; Cultrara, Nicholas D.; Katre, Ankita; Carrete, Jesús; Heine, Matt; Ou, Eric; Kim, Jaehyun; Jiang, Shishi; Lindsay, Lucas; Mingo, Natalio; Broido, David; Heremans, Joseph P.; Goldberger, Joshua; Shi, Li

    2016-09-30

    Recently, we synthesized Germanane (GeH), a hydrogen-terminated layered germanium structure. We employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. Furthermore, the obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53± 0.03 W m-1 K-1, which is close to the value calculated for 3.3 nm grain size, to 0.29± 0.02 W m-1 K-1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.

  3. Growth and characterization of nanocrystalline PbS:Li thin films

    NASA Astrophysics Data System (ADS)

    Portillo, M. Chávez; Mathew, X.; Juárez Santiesteban, H.; Pacio Castillo, M.; Portillo Moreno, O.

    2016-10-01

    The structural, electrical and opto-electronic properties of PbS thin films doped with Li+ ion were investigated. The crystallite size showed a strong dependence on Li doping, the crystal size changed from 36 nm to 12 nm due to Li incorporation in PbS. Optical band gap showed a shift in the range ∼1.5-2.3 eV with Li incorporation. Urbach tailing in the band gap was observed and the Urbach energy has a dependence on the amount of incorporated Li. SEM images showed a notable change in grain size with Li doping, however the morphology changes from large grains to agglomerations of smaller grains when doped with Li. The electric conductivity of the films showed a dependence on Li doping, reached a maximum value and later decreased for higher Li containing films. The doped samples showed better photosensitivity.

  4. Basal-plane thermal conductivity of nanocrystalline and amorphized thin germanane

    DOE PAGES

    Coloyan, Gabriella; Cultrara, Nicholas D.; Katre, Ankita; ...

    2016-09-30

    Recently, we synthesized Germanane (GeH), a hydrogen-terminated layered germanium structure. We employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. Furthermore, the obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53± 0.03 W m-1 K-1, which is close to the value calculated for 3.3 nm grain size, to 0.29± 0.02 W m-1more » K-1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.« less

  5. Basal-plane thermal conductivity of nanocrystalline and amorphized thin germanane

    SciTech Connect

    Coloyan, Gabriella; Cultrara, Nicholas D.; Katre, Ankita; Carrete, Jesús; Heine, Matt; Ou, Eric; Kim, Jaehyun; Jiang, Shishi; Lindsay, Lucas; Mingo, Natalio; Broido, David; Heremans, Joseph P.; Goldberger, Joshua; Shi, Li

    2016-09-30

    Recently, we synthesized Germanane (GeH), a hydrogen-terminated layered germanium structure. We employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. Furthermore, the obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53± 0.03 W m-1 K-1, which is close to the value calculated for 3.3 nm grain size, to 0.29± 0.02 W m-1 K-1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.

  6. Electronic transport in nanocrystalline germanium/hydrogenated amorphous silicon composite thin films

    NASA Astrophysics Data System (ADS)

    Bodurtha, Kent Edward

    Recent interest in composite materials based on hydrogenated amorphous silicon (a-Si:H) stems in part from its potential for technical applications in thin film transistors and solar cells. Previous reports have shown promising results for films of a-Si:H with embedded silicon nanocrystals, with the goal of combining the low cost, large area benefits of hydrogenated amorphous silicon with the superior electronic characteristics of crystalline material. These materials are fabricated in a dual-chamber plasma-enhanced chemical vapor deposition system in which the nanocrystals are produced separately from the amorphous film, providing the flexibility to independently tune the growth parameters of each phase; however, electronic transport through these and other similar materials is not well understood. This thesis reports the synthesis and characterization of thin films composed of germanium nanocrystals embedded in a-Si:H. The results presented here describe detailed measurements of the conductivity, photoconductivity and thermopower which reveal a transition from conduction through the a-Si:H for samples with few germanium nanocrystals, to conduction through the nanocrystal phase as the germanium crystal fraction XGe is increased. These films display reduced photosensitivity as XGe is increased, but an unexpected increase in the dark conductivity is found in samples with X Ge > 5% after long light exposures. Detailed studies of the conductivity temperature dependence in these samples exposes a subtle but consistent deviation from the standard Arrhenius expression; the same departure is found in samples of pure a-Si:H; a theoretical model is presented which accurately describes the actual conductivity temperature dependence.

  7. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    NASA Astrophysics Data System (ADS)

    Argibay, N.; Mogonye, J. E.; Michael, J. R.; Goeke, R. S.; Kotula, P. G.; Scharf, T. W.; Dugger, M. T.; Prasad, S. V.

    2015-04-01

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situ electrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea = 21.6 kJ/mol and Ao = 2.3 × 10-17 m2/s for Au-1 vol. % ZnO and Ea = 12.7 kJ/mol and Ao = 3.1 × 10-18 m2/s for Au-2 vol. % ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. The proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.

  8. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    DOE PAGES

    Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; ...

    2015-04-08

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilizedmore » grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea = 21.6 kJ/mol and Ao = 2.3 × 10-17 m2/s for Au-1 vol. % ZnO and Ea =12.7 kJ/mol and Ao = 3.1 × 10-18 m2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.« less

  9. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    SciTech Connect

    Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; Goeke, Ronald S.; Kotula, Paul G.; Scharf, T. W.; Dugger, Michael Thomas; Prasad, Somuri V.

    2015-04-08

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea = 21.6 kJ/mol and Ao = 2.3 × 10-17 m2/s for Au-1 vol. % ZnO and Ea =12.7 kJ/mol and Ao = 3.1 × 10-18 m2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.

  10. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    SciTech Connect

    Argibay, N. Mogonye, J. E.; Michael, J. R.; Goeke, R. S.; Kotula, P. G.; Scharf, T. W.; Dugger, M. T.; Prasad, S. V.

    2015-04-14

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situ electrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of E{sub a} = 21.6 kJ/mol and A{sub o} = 2.3 × 10{sup −17} m{sup 2}/s for Au-1 vol. % ZnO and E{sub a} = 12.7 kJ/mol and A{sub o} = 3.1 × 10{sup −18} m{sup 2}/s for Au-2 vol. % ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. The proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.

  11. Determination of the Origin of Crystal Orientation for Nanocrystalline Bismuth Telluride-Based Thin Films Prepared by Use of the Flash Evaporation Method

    NASA Astrophysics Data System (ADS)

    Takashiri, M.; Tanaka, S.; Miyazaki, K.

    2014-06-01

    We have investigated the origin of crystal orientation for nanocrystalline bismuth telluride-based thin films. Thin films of p-type bismuth telluride antimony (Bi-Te-Sb) and n-type bismuth telluride selenide (Bi-Te-Se) were fabricated by a flash evaporation method, with exactly the same deposition conditions except for the elemental composition of the starting powders. For p-type Bi-Te-Sb thin films the main x-ray diffraction (XRD) peaks were from the c-axis (Σ{00l}/Σ{ hkl} = 0.88) whereas n-type Bi-Te-Se thin films were randomly oriented (Σ{00l}/Σ{ hkl} = 0.40). Crystal orientation, crystallinity, and crystallite size were improved for both types of thin film by sintering. For p-type Bi-Te-Sb thin films, especially, high-quality structures were obtained compared with those of n-type Bi-Te-Se thin films. We also estimated the thermoelectric properties of the as-grown and sintered thin films. The power factor was enhanced by sintering; maximum values were 34.9 μW/cm K2 for p-type Bi-Te-Sb thin films at a sintering temperature of 300°C and 23.9 μW/cm K2 for n-type Bi-Te-Se thin films at a sintering temperature of 350°C. The exact mechanisms of film growth are not yet clear but we deduce the crystal orientation originates from the size of nano-clusters generated on the tungsten boat during flash evaporation.

  12. Vertically self-ordered orientation of nanocrystalline hexagonal boron nitride thin films for enhanced thermal characteristics.

    PubMed

    Cometto, Olivier; Sun, Bo; Tsang, Siu Hon; Huang, Xi; Koh, Yee Kan; Teo, Edwin Hang Tong

    2015-12-07

    Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm(-2). Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m(-1) K(-1). The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature growth could outperform SiO2 in high power density electronic applications.

  13. Highly ordered, accessible and nanocrystalline mesoporous TiO₂ thin films on transparent conductive substrates.

    PubMed

    Violi, Ianina L; Perez, M Dolores; Fuertes, M Cecilia; Soler-Illia, Galo J A A

    2012-08-01

    Highly porous (V(mesopore) = 25-50%) and ordered mesoporous titania thin films (MTTF) were prepared on ITO (indium tin oxide)-covered glass by a fast two-step method. The effects of substrate surface modification and thermal treatment on pore order, accessibility and crystallinity of the MTTF were systematically studied for MTTF deposited onto bare and titania-modified ITO. MTTF exposed briefly to 550 °C resulted in highly ordered films with grid-like structures, enlarged pore size, and increased accessible pore volume when prepared onto the modified ITO substrate. Mesostructure collapse and no significant change in pore volume were observed for MTTF deposited on bare ITO substrates. Highly crystalline anatase was obtained for MTTF prepared on the modified-ITO treated at high temperatures, establishing the relationship between grid-like structures and titania crystallization. Photocatalytic activity was maximized for samples with increased crystallization and high accessible pore volume. In this manner, a simple way of designing materials with optimized characteristics for optoelectronic applications was achieved through the modification of the ITO surface and a controlled thermal treatment.

  14. Photoelectrocatalytic production of active chlorine on nanocrystalline titanium dioxide thin-film electrodes.

    PubMed

    Zanoni, Maria Valnice B; Sene, Jeosadaque J; Selcuk, Huseyin; Anderson, Marc A

    2004-06-01

    The production of chlorine and hypochlorite is of great economical and technological interest due to their large-scale use in many kinds of commercial applications. Yet, the current processes are not without problems such as inevitable side reactions and the high cost of production. This work reports the photoelectrocatalytic oxidation of chloride ions to free chlorine as it has been investigated by using titanium dioxide (TiO2) and several metal-doped titanium dioxide (M-TiO2) material electrodes. An average concentration of 800 mg L(-1) of free chlorine was obtained in an open-air reactor using a TiO2 thin-film electrode biased at +1.0 V (SCE) and illuminated by UV light. The M-doped electrodes have performed poorly compared with the pure TiO2 counterpart. Test solutions containing 0.05 mol L(-1) NaCl pH 2.0-4.0 were found to be the best conditions for fast production of free chlorine. A complete investigation of all parameters that influence the global process of chlorine production by the photo electrocatalytic method such as applied potential, concentration of NaCl, pH solution, and time is presented in detail. In addition, photocurrent vs potential curves and the reaction order are also discussed.

  15. Microstructure and optical properties of nanocrystalline Cu2O thin films prepared by electrodeposition

    PubMed Central

    2014-01-01

    Cuprous oxide (Cu2O) thin films were prepared by using electrodeposition technique at different applied potentials (−0.1, −0.3, −0.5, −0.7, and −0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV–vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission. PMID:24872805

  16. Influence of terbium on structure and luminescence of nanocrystalline TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Wojcieszak, Damian; Kaczmarek, Danuta; Domaradzki, Jaroslaw; Lukowiak, Anna; Strek, Wieslaw

    2013-02-01

    In this work analysis of the structural and optical properties of TiO2 thin films doped with terbium has been described. Samples were prepared by a high energy reactive magnetron sputtering process under low pressure of oxygen plasma. X-ray diffraction results have shown that different TiO2 crystal forms have been produced, depending on the amount of Tb dopant. The undoped matrix had rutile structure with crystallites with a size of 8.7 nm, while incorporation of 0.4 at. % of Tb into the film during the sputtering process resulted in anatase structure with bigger crystallites (11.7 nm). Increasing the amount of terbium up to 2 at. % and 2.6 at. % gave rutile structure with crystallites with a size of 6.6 nm for both films. However, Raman spectroscopy has revealed that in the case of TiO2:(2 at. % Tb), except for the rutile form, the presence of fine-crystalline anatase was observed. Moreover, the lack of Raman peaks shift attests to the lack of stress in the titania lattice of all of the TiO2:Tb films. This fact indicates localization of Tb3+ ions on the surface of TiO2 nanocrystals. In the case of optical investigation, results have shown that doping with terbium has a significant influence on the properties of TiO2, but it does not decrease the high transparency of the matrix. The observed changes of the transmission characteristics were produced only due to modification of the TiO2:Tb structure. Photoluminescence measurements have shown that emission of light from TiO2:Tb films occurs when the amount of terbium is 2.6 at. %. Based on the obtained results a scheme of direct energy transfer from titanium dioxide matrix (with rutile structure) to Tb3+ ions has been proposed.

  17. Thermal and photochemical reactions of methanol on nanocrystalline anatase TiO2 thin films.

    PubMed

    Bennett, David A; Cargnello, Matteo; Gordon, Thomas R; Murray, Christopher B; Vohs, John M

    2015-07-14

    The catalytic and photo-catalytic activity of well-defined anatase TiO2 nanocrystals for the partial oxidation of methanol was investigated using temperature-programmed desorption (TPD) in ultra-high vacuum in order to determine how crystallite size and shape affect reactivity. The TiO2 films used in this study were prepared from well-defined TiO2 nanocrystals synthesized by colloidal methods. These nanocrystals had a truncated bi-pyramidal shape which exposes primarily (101) and to a lesser extent (001) surfaces and ranged in size from 10 to 25 nm. Two distinct regimes of reactivity were investigated, namely in the dark and under UV light illumination. In the dark, methanol adsorbed dissociatively on the (001) planes and only molecularly on the (101) surfaces. Dissociated methoxy groups on the (001) surfaces coupled to produce dimethyl ether, suggesting the presence of fourfold coordinate Ti cations. Under UV light illumination, the nanocrystals were additionally found to be active for the photo-catalytic oxidation of methanol to methyl formate. On the (101) surfaces, this reaction proceeded in a stepwise photocatalytic pathway involving dehydrogenation of methanol to form methoxy groups and then formaldehyde, followed by coupling of these latter two species to form methyl formate. The (001) surfaces were also found to be photo-catalytically active but surface methoxy groups could be produced thermally and the reaction proceeds only to formaldehyde in the absence of molecularly adsorbed methanol. The overall photocatalytic activity of the nanocrystals was also was found to increase with increasing crystallite size. The results of this study show that thin films of well-defined nanocrystals are excellent model systems that can be used to help bridge the materials gap between studies of single crystal surfaces and high surface area polycrystalline catalysts.

  18. Structure and properties of ZnSxSe1-x thin films deposited by thermal evaporation of ZnS and ZnSe powder mixtures

    NASA Astrophysics Data System (ADS)

    Valeev, R. G.; Romanov, E. A.; Vorobiev, V. L.; Mukhgalin, V. V.; Kriventsov, V. V.; Chukavin, A. I.; Robouch, B. V.

    2015-02-01

    Interest to ZnSxSe1-x alloys is due to their band-gap tunability varying S and Se content. Films of ZnSxSe1-x were grown evaporating ZnS and ZnSe powder mixtures onto SiO2, NaCl, Si and ITO substrates using an original low-cost method. X-ray diffraction patterns and Raman spectroscopy, show that the lattice structure of these films is cubic ZnSe-like, as S atoms replace Se and film compositions have their initial S/Se ratio. Optical absorption spectra show that band gap values increase from 2.25 to 3 eV as x increases, in agreement with the literature. Because S atomic radii are smaller than Se, EXAFS spectra confirm that bond distances and Se coordination numbers decrease as the Se content decreases. The strong deviation from linearity of ZnSe coordination numbers in the ZnSxSe1-x indicate that within this ordered crystal structure strong site occupation preferences occur in the distribution of Se and S ions. The behavior is quantitatively confirmed by the strong deviation from the random Bernoulli distribution of the three sight occupation preference coefficients of the strained tetrahedron model. Actually, the ternary ZnSxSe1-x system is a bi-binary (ZnS+ZnSe) alloy with evanescent formation of ternary configurations throughout the x-range.

  19. Hydrogen plasma treatment of very thin p-type nanocrystalline Si films grown by RF-PECVD in the presence of B(CH3)3

    PubMed Central

    Filonovich, Sergej Alexandrovich; Águas, Hugo; Busani, Tito; Vicente, António; Araújo, Andreia; Gaspar, Diana; Vilarigues, Marcia; Leitão, Joaquim; Fortunato, Elvira; Martins, Rodrigo

    2012-01-01

    We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (∼20 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film. PMID:27877504

  20. Atomic layer deposited nanocrystalline tungsten carbides thin films as a metal gate and diffusion barrier for Cu metallization

    SciTech Connect

    Kim, Jun Beom; Kim, Soo-Hyun; Han, Won Seok; Lee, Do-Joong

    2016-07-15

    Tungsten carbides (WC{sub x}) thin films were deposited on thermally grown SiO{sub 2} substrates by atomic layer deposition (ALD) using a fluorine- and nitrogen-free W metallorganic precursor, tungsten tris(3-hexyne) carbonyl [W(CO)(CH{sub 3}CH{sub 2}C ≡ CCH{sub 2}CH{sub 3}){sub 3}], and N{sub 2} + H{sub 2} plasma as the reactant at deposition temperatures between 150 and 350 °C. The present ALD-WC{sub x} system showed an ALD temperature window between 200 and 250 °C, where the growth rate was independent of the deposition temperature. Typical ALD characteristics, such as self-limited film growth and a linear dependency of the film grown on the number of ALD cycles, were observed, with a growth rate of 0.052 nm/cycle at a deposition temperature of 250 °C. The ALD-WC{sub x} films formed a nanocrystalline structure with grains, ∼2 nm in size, which consisted of hexagonal W{sub 2}C, WC, and nonstoichiometric cubic β-WC{sub 1−x} phase. Under typical deposition conditions at 250 °C, an ALD-WC{sub x} film with a resistivity of ∼510 μΩ cm was deposited and the resistivity of the ALD-WC{sub x} film could be reduced even further to ∼285 μΩ cm by further optimizing the reactant pulsing conditions, such as the plasma power. The step coverage of ALD-WC{sub x} film was ∼80% on very small sized and dual trenched structures (bottom width of 15 nm and aspect ratio of ∼6.3). From ultraviolet photoelectron spectroscopy, the work function of the ALD-WC{sub x} film was determined to be 4.63 eV. Finally, the ultrathin (∼5 nm) ALD-WC{sub x} film blocked the diffusion of Cu, even up to 600 °C, which makes it a promising a diffusion barrier material for Cu interconnects.

  1. Formation of nanocrystalline SiGe in Polycrystalline-Ge/Si thin film without any metal induced crystallization

    NASA Astrophysics Data System (ADS)

    Tah, Twisha; Singh, Ch. Kishan; Madapu, K. K.; Polaki, S. R.; Ilango, S.; David, C.; Dash, S.; Panigrahi, B. K.

    2017-05-01

    The formation of nanocrystalline SiGe without the aid of metal induced crystallization is reported. Re-crystallization of the as-deposited poly-Ge film (deposited at 450 °C) leads to development of regions with depleted Ge concentration upon annealing at 500 °C. Clusters with crystalline facet containing both nanocrystalline SiGe and crystalline Ge phase starts appearing at 600 °C. The structural phase characteristics were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The stoichiometry of the SiGe phase was estimated from the positions of the Raman spectral peaks.

  2. A size-dependent structural evolution of ZnS nanoparticles

    PubMed Central

    Khalkhali, Mohammad; Liu, Qingxia; Zeng, Hongbo; Zhang, Hao

    2015-01-01

    Recently, ZnS quantum dots have attracted a lot of attention since they can be a suitable alternative for cadmium-based quantum dots, which are known to be highly carcinogenic for living systems. However, the structural stability of nanocrystalline ZnS seems to be a challenging issue since ZnS nanoparticles have the potential to undergo uncontrolled structural change at room temperature. Using the molecular dynamics technique, we have studied the structural evolution of 1 to 5 nm freestanding ZnS nanoparticles with zinc-blende and wurtzite crystal structures. Simulation results revealed that relaxed configurations of ZnS nanoparticles larger than 3 nm consist of three regions: a) a crystalline core, b) a distorted network of 4-coordinated atoms environing the crystalline core, and c) a surface structure made entirely of 3-coordinated atoms. Decreasing the size of ZnS nanoparticle to 2 nm will cause the crystalline core to disappear. Further reducing the size will cause all of the atoms to become 3-coordinated. Dipole moments of zinc-blende and wurtzite nanoparticles are in the same range when the nanoparticles are smaller than 3 nm. Increasing the size makes dipole moments converge to the bulk values. This makes zinc-blende and wurtzite nanoparticles less and more polar, respectively. PMID:26381583

  3. Phase Evolution of Cubic ZnS Annealed in Mild Oxidizing Atmosphere

    NASA Astrophysics Data System (ADS)

    Xue, Shu-Wen; Zhang, Jun; Shao, Le-Xi

    2012-03-01

    ZnS thin films are prepared by thermal evaporation of high-purity ZnS powder on quartz glass substrates. The samples were annealed in floating argon at temperatures from 300°C to 900°C. The effects of annealing temperature on the structural and optical properties were investigated by x-ray diffraction (XRD), scanning electron microscope (SEM) and optical absorption. The results show that annealing below 500°C is beneficial to improve the quality of ZnS films. When the annealing temperature exceeds 500°C, ZnS is gradually oxidized into ZnSO4, which has evident influences on the structural and optical properties of ZnS films.

  4. Photodriven spin change of Fe(II) benzimidazole compounds anchored to nanocrystalline TiO(2) thin films.

    PubMed

    Xia, Hai-Long; Ardo, Shane; Narducci Sarjeant, Amy A; Huang, Sunxiang; Meyer, Gerald J

    2009-12-01

    Ferrous tris-chelate compounds based on 2-(2'-pyridyl)benzimidazole (pybzim) have been prepared and characterized for studies of spin equilibria in fluid solution and when anchored to the surface of mesoporous nanocrystalline (anatase) TiO(2) and colloidal ZrO(2) thin films. The solid state structure of Fe(pybzim)(3)(ClO(4))(2).CH(3)CN.H(2)O was determined by single-crystal X-ray diffraction at 110 K to be triclinic, P-1, a = 11.6873(18), b = 12.2318(12), c = 14.723(4) A, alpha = 89.864(13) degrees , beta = 71.430(17) degrees , gamma = 73.788(11) degrees , V = 1907.1(6) A(3), Z = 2, and R = 0.0491. The iron compound has a meridional FeN(6) distorted octahedral geometry with bond lengths expected for a low-spin iron center at 110 K. The visible absorption spectra of Fe(pybzim)(3)(2+) and Fe(pymbA)(3)(2+), where pymbA is 4-(2-pyridin-2-yl-benzimidazol-1-ylmethyl)-benzoic acid, in methanol solution were dominated by metal-to-ligand charge-transfer (MLCT) bands. Variable-temperature UV-visible absorption spectroscopy revealed dramatic changes in the extinction coefficient consistent with a high-spin ((1)A) left harpoon over right harpoon low-spin ((5)T) equilibrium. Thermodynamic parameters for the temperature-dependent spin equilibrium of Fe(pymbA)(3)(2+) in methanol were determined to be DeltaH(HL) = 3270 +/- 210 cm(-1) and DeltaS(HL) = 13.3 +/- 0.8 cm(-1) K(-1). The corresponding values for Fe(pybzimEE)(3)(2+), where pybzimEE is (2-pyridin-2-yl-benzimidazol-1-yl)-acetic acid ethyl ester, in acetonitrile solution were determined to be 3072 +/- 34 cm(-1)and 10.5 +/- 0.1 cm(-1) K(-1). The temperature-dependent effective magnetic moments of Fe(pybzimEE)(3)(2+) in acetonitrile solution were also quantified by the Evans method. Pulsed 532 nm light excitation of Fe(pybzim)(3)(2+) or Fe(pymbA)(3)(2+) in solution resulted in an immediate bleach of the MLCT absorption bands. Relaxation back to the equilibrium state followed a first-order reaction mechanism. Arrhenius analysis

  5. Characteristics of radio frequency-sputtered ZnS on the flexible polyethylene terephthalate (PET) substrate.

    PubMed

    Yoo, Dongjun; Choi, Moon-Suk; Chung, Chulwon; Heo, Seung Chan; Kim, Dohyung; Choi, Changhwan

    2013-12-01

    Zinc sulfide (ZnS) thin film was deposited on the flexible polyethylene-terephtalate (PET) polymer substrate by radio frequency (RF) magnetron sputtering system. ZnS film has a critical thickness range affecting crystal structure where it shows preferred orientation with intensity peak of X-ray diffractometer at 28.4 degrees for ZnS thinner than 200 nm while hexagonal wurtzite and cubic zinc-blend (101) are co-existed for film thicker than 200 nm. Optical band gap energy (Eg) decreases with increasing RF-powers, resulting from increase in film thickness. Eg of ZnS films on PET is 3.68-3.86 eV, which is lower than that of ZnS on the rigid substrate by 0.27-0.28 eV. This is attributed to amount of incorporated oxygen to ZnS material as well as residual strain and disorder of grain boundary. Transmittance of ZnS on PET degrades due to surface defects and complex internal structure. Energy dispersive spectroscopy reveals out that ZnS film does not have a unity of Zn to S ratio, but it is close to stoichiometric composition with increasing thickness.

  6. Optical and impedance studies of pure and Ba-doped ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Firdous, Arfat; Baba, M. Aslam; Singh, D.; Bhat, Abdul Hamid

    2015-02-01

    Chemical precipitation method using a high-boiling solvent is used to synthesize ZnS and Ba-doped ZnS quantum dots. The presence of organic ligands in the prepared nanostructures is verified using Fourier transform infra-red spectroscopic studies. The samples have been analysed using X-ray diffraction analysis confirming nanocrystallinity of the as-prepared quantum dots (QD). The mean crystal size obtained by full width half maxima analysis is 3.2 nm for ZnS and 3.9, 4.2 nm for ZnS:Ba (2, 4 mM). TEM micrographs also reveal nanosized particles of ZnS and Ba-doped ZnS. An optical absorption study conducted in UV-Vis range 150-600 nm reveals the transparency of these quantum dots in entire visible range but not in ultraviolet range. The results based on optical analysis yield band gap values as 4.88 eV for ZnS and 4.69, 4.43 eV for ZnS:Ba (2, 4 mM) quantum dots. Impedance analysis of the samples was carried out to reveal the variation of impedance with frequency at room temperature. These results show the capacitive admittance associated with the quantum dots and hence nanostructure ZnS and Ba-doped ZnS can have potential applications in electronics as nano-tuned devices in which resonant frequency can be adjusted by controlling the size and shape of the quantum dots.

  7. Defect-driven magnetism in luminescent n/p-type pristine and Gd-substituted SnO2 nanocrystalline thin films.

    PubMed

    Ghosh, S; Khan, Gobinda Gopal; Mandal, K

    2012-04-01

    The effects of rare-earth-element Gd doping on the intrinsic magnetic ordering, photoluminescence, and electrical-conducting properties of the pristine SnO(2) nanocrystalline thin films fabricated by radio-frequency (RF) sputtering are investigated. The pristine SnO(2) thin film exhibits significant ferromagnetism while Gd doping results in an absence of intrinsic ferromagnetism. The presence of large amounts of singly ionized oxygen vacancies (V(O)(+)) is traced by photoluminescence spectroscopic analysis and they are found to be responsible for the observed ferromagnetism in pristine SnO(2) thin films. A significant reduction of oxygen vacancies is observed after Gd doping, and that might be insufficient to mediate long-range ferromagnetic ordering between V(O)(+) defects in a Gd-doped SnO(2) system. Although the associated magnetic moment is increased by 1 order of magnitude, because of the insertion of Gd(3+) ions, which have localized f-shell paramagnetic moment, there is no intrinsic FM ordering. Hall measurement reveals that the pure SnO(2) exhibits n-type behavior whereas Gd-doped SnO(2) films show the p-type conductivity with higher resistivity. The studies demonstrate that only structural defects such as V(O)(+) defects, not magnetic ions such as Gd(3+), are responsible for inducing ferromagnetism in SnO(2) thin films.

  8. Length Scale Discontinuities Between Non-Crystalline And Nano-Crystalline Thin Films: Chemical Bonding Self-Organization, Broken Constraints And Reductions of Macroscopic Strain

    SciTech Connect

    Lucovsky, G.; Phillips, J.C.

    2009-05-19

    This paper identifies different length scales, {lambda}{sub s}, for strain-reducing chemical bonding self-organizations in non-crystalline and nano-crystalline thin films. Length scales have been identified through spectroscopic studies, thermal heat flow measurements, and are analyzed by semi-empirical bond-constraint theory (SE-BCT) and symmetry adapted linear combinations (SALC) of atomic states. In both instances, strain-reducing self-organizations result in reduced defect densities that are minimized and enabling for device applications. The length scale for non-crystalline solids extends to at most 1 nm, and more generally to 0.5-0.8 nm; however, there are two different length scales for nano-crystalline films: one is <2.5 nm and is characterized by suppression of longer range ordering required for complex unit cells based on more than one primitive unit cell and the second is >3-3.5 nm and defines a regime where complex unit cells, comprised of two or more primitive unit cells are stabilized and the electronic structure is changed.

  9. Electron diffraction based analysis of phase fractions and texture in nanocrystalline thin films, part III: application examples.

    PubMed

    Lábár, J L; Adamik, M; Barna, B P; Czigány, Zs; Fogarassy, Zs; Horváth, Z E; Geszti, O; Misják, F; Morgiel, J; Radnóczi, G; Sáfrán, G; Székely, L; Szüts, T

    2012-04-01

    In this series of articles, a method is presented that performs (semi)quantitative phase analysis for nanocrystalline transmission electron microscope samples from selected area electron diffraction (SAED) patterns. Volume fractions and degree of fiber texture are determined for the nanocrystalline components. The effect of the amorphous component is minimized by empirical background interpolation. First, the two-dimensional SAED pattern is converted into a one-dimensional distribution similar to X-ray diffraction. Volume fractions of the nanocrystalline components are determined by fitting the spectral components, calculated for the previously identified phases with a priori known structures. These Markers are calculated not only for kinematic conditions, but the Blackwell correction is also applied to take into account dynamic effects for medium thicknesses. Peak shapes and experimental parameters (camera length, etc.) are refined during the fitting iterations. Parameter space is explored with the help of the Downhill-SIMPLEX. The method is implemented in a computer program that runs under the Windows operating system. Part I presented the principles, while part II elaborated current implementation. The present part III demonstrates the usage and efficiency of the computer program by numerous examples. The suggested experimental protocol should be of benefit in experiments aimed at phase analysis using electron diffraction methods.

  10. Nanocrystalline silicon thin films from SiH4 plasma diluted by H2 and He in RF-PECVD

    NASA Astrophysics Data System (ADS)

    Samanta, Subhashis; Das, Debajyoti

    2017-06-01

    Systematic changes in structural, optical and electrical properties of nanocrystalline silicon (nc-Si:H) films prepared at 250 °C in capacitively-coupled RF-PECVD operated at 200 W of RF (13.56 MHz) power have been investigated as an effect of gas pressure variation in SiH4 plasma diluted by equal amount of H2 and He. Considering nanocrystallites with <220> crystallographic orientation arising due to thermodynamically preferred grain growth, an optimum pressure, p 0.6 Torr has been identified at which the maximum ultra-nanocrystalline component fraction of crystallinity in the network with corresponding silicon di-hydride components mostly in clusters control the growth. The H2-dilution in the plasma maintains a good crystallinity while enhancement of secondary electron emission coefficient induced by He-ions has been attributed to contribute a high growth-rate. The Si:H films at the onset of nanocrystallinity prepared at a high deposition rate in the SiH4-depleted plasma condition at p 1.5 Torr, appears promising in the fabrication of efficient solar-cells.

  11. Synthesis of nanocrystalline Cu{sub 2}ZnSnS{sub 4} thin films grown by the spray-pyrolysis technique

    SciTech Connect

    Chandel, Tarun Singh, Joginder; Rajaram, P.

    2015-08-28

    Spray pyrolysis was used to deposit Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films on soda lime glass substrates at 300 °C. Aqueous solutions of copper chloride, zinc chloride, stannous chloride and thiourea were mixed together to form the spray liquid. The sprayed films were annealed under vacuum at 350 °C, 400 °C and 450 °C. Structural and optical characterization was performed on the CZTS films using X-ray diffraction (XRD) and UV-VIS spectrophotometry. XRD results indicate that the films are single phase nanocrystalline CZTS. Optical studies show that the optical gap values are 1.44 eV for the as-grown film and 1.46 eV, 1.48 eV and 1.49 eV for the films annealed at 350 °C, 400 °C and 450 °C, respectively.

  12. Galvanic deposition of nanocrystalline ZnO thin films from a ZnO-Zn(OH)(2) mixed phase precursor on p-Si substrate.

    PubMed

    Mukherjee, N; Bhattacharyya, P; Banerjee, M; Mondal, A; Gettens, Robert T T; Ghosh, P K; Saha, H

    2006-05-28

    A galvanic technique for the deposition of ZnO thin films is reported. The depositions were carried out on p-type single-crystal silicon substrates at room temperature, from a solution of ZnSO(4), where the Zn rod acted as a sacrificing anode and p-Si was the cathode. The deposition of ZnO by this method is pH sensitive, and a pH between 4 and 5 is found to be optimum for film deposition. This deposition technique is simple, inexpensive and can be carried out at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies revealed the nanocrystalline structure of the films. The resistivity of the annealed ZnO films was determined by the Van der Pauw measurement technique.

  13. Galvanic deposition of nanocrystalline ZnO thin films from a ZnO Zn(OH)2 mixed phase precursor on p-Si substrate

    NASA Astrophysics Data System (ADS)

    Mukherjee, N.; Bhattacharyya, P.; Banerjee, M.; Mondal, A.; Gettens, Robert T. T.; Ghosh, P. K.; Saha, H.

    2006-05-01

    A galvanic technique for the deposition of ZnO thin films is reported. The depositions were carried out on p-type single-crystal silicon substrates at room temperature, from a solution of ZnSO4, where the Zn rod acted as a sacrificing anode and p-Si was the cathode. The deposition of ZnO by this method is pH sensitive, and a pH between 4 and 5 is found to be optimum for film deposition. This deposition technique is simple, inexpensive and can be carried out at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies revealed the nanocrystalline structure of the films. The resistivity of the annealed ZnO films was determined by the Van der Pauw measurement technique.

  14. Deposition of nanocrystalline thin TiO2 films for MOS capacitors using Sol-Gel spin method with Pt and Al top electrodes

    NASA Astrophysics Data System (ADS)

    Rathee, Davinder; Kumar, Mukesh; Arya, Sandeep K.

    2012-10-01

    Nanocrystalline titanium dioxide (TiO2) films were deposited by Sol-Gel spin coating method on well clean P<1 0 0> Si substrate. Titanium isoproxide Ti(OC3H7O2)4 (TIP) was used as the Titania precursor. The thickness, composition, and surface morphology of the thin films were characterized using Stylus profilometer, X-ray diffraction (XRD), Field-Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM). The crystallite sizes of the TiO2 grains were measured from the typical diffraction peaks and were found to be approximately 23-54 nm. The XRD pattern and Raman spectrum analysis of the deposited film confirmed the polymorphism nature of TiO2 thin films. After annealing at high temperature; the phase transition, improvement in crystallinity, structure and property of the films were being observed. The six Raman peaks were analyzed at 145 cm-1, 199 cm-1, 397 cm-1, 516 cm-1 (doublet) and 637 cm-1 corresponding to active mode of anatase phase. Capacitance-Voltage (C-V) measurement analysis was performed to obtain various devices and process parameters. Metal Oxide Semiconductor (MOS) capacitors with Pt and Al as the top electrode were fabricated to explore electrical characteristics. The refractive index by ellipsometry was found 2.36 and dielectric constant was calculated as 58. In this study, the comparison of the leakage current for TiO2 thin films fabricated by various methods has also been reported.

  15. Thin Layer Electrochemical Studies of ZnS, ZnSe, and ZnTe Formation by Electrochemical Atomic Layer Epitaxy (ECALE)

    DTIC Science & Technology

    1997-10-16

    Thin-layer electrochemical studies of the underpotential deposition (UPD) of Zn, Te, Se, and S on polycrystalline Au substrates have been performed...was scanned. Sulfur atomic layers were spontaneously deposited below -0.6 V from a sulfide solution. Thermodynamic effects are clearly evident during...the first monolayer of deposition . Zinc deposition onto Te, Se, and S coated electrodes occurs at progressively more positive potentials as the

  16. Some physical investigations on ZnS 1- xSe x films obtained by selenization of ZnS sprayed films using the Boubaker polynomials expansion scheme

    NASA Astrophysics Data System (ADS)

    Fridjine, S.; Touihri, S.; Boubaker, K.; Amlouk, M.

    2010-01-01

    ZnS 1- xSe x thin films have been grown by selenization process, applied to ZnS sprayed thin films deposited on Pyrex glass substrates at 550 °C. The crystal structure and surface morphology were investigated by the XRD technique and by the atomic force microscopy. This structural study shows that selenium-free ( x=0) ZnS thin films, prepared at substrate temperature TS=450 °C, were well crystallized in cubic structure and oriented preferentially along (1 1 1) direction. The thermal and mechanical properties were also investigated using a photothermal protocol along with Vickers hardness measurements. On the other hand, the analyze of the transmittance T( λ) and the reflectance R( λ), optical measurements of these films depicts a decrease in the band gap energy value Eg with an increase in Se content ( x). Indeed, Eg values vary from 3.6 to 3.1 eV.

  17. Synthesis and characterization of mesoporous ZnS with narrow size distribution of small pores

    NASA Astrophysics Data System (ADS)

    Nistor, L. C.; Mateescu, C. D.; Birjega, R.; Nistor, S. V.

    2008-08-01

    Pure, nanocrystalline cubic ZnS forming a stable mesoporous structure was synthesized at room temperature by a non-toxic surfactant-assisted liquid liquid reaction, in the 9.5 10.5 pH range of values. The appearance of an X-ray diffraction (XRD) peak in the region of very small angles (˜ 2°) reveals the presence of a porous material with a narrow pore size distribution, but with an irregular arrangement of the pores, a so-called worm hole or sponge-like material. The analysis of the wide angle XRD diffractograms shows the building blocks to be ZnS nanocrystals with cubic structure and average diameter of 2 nm. Transmission electron microscopy (TEM) investigations confirm the XRD results; ZnS crystallites of 2.5 nm with cubic (blende) structure are the building blocks of the pore walls with pore sizes from 1.9 to 2.5 nm, and a broader size distribution for samples with smaller pores. Textural measurements (N2 adsorption desorption isotherms) confirm the presence of mesoporous ZnS with a narrow range of small pore sizes. The relatively lower surface area of around 100 m2/g is attributed to some remaining organic molecules, which are filling the smallest pores. Their presence, confirmed by IR spectroscopy, seems to be responsible for the high stability of the resulting mesoporous ZnS as well.

  18. Properties of Al-doped ZnS Films Grown by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Nagamani, K.; Prathap, P.; Lingappa, Y.; Miles, R. W.; Reddy, K. T. R.

    Zinc sulphide (ZnS) buffer layers are a cadmium free, wider energy band gap, alternative to the cadmium sulphide (CdS) buffer layers commonly used in copper indium gallium diselenide (CuInGaSe2)-based solar cells. However extrinsic doping of the ZnS is important to lower the resistivity of the layers and to improve flexibility of device design. In this work, Al-doped ZnS nanocrystalline films have been produced on glass substrates using a chemical bath deposition (CBD) method. The Al- concentration was varied from 0 at. % to 10 at. %, keeping other deposition parameters constant. The elemental composition of a typical sample with 6 at. % 'Al' in ZnS was Zn=44.9 at. %, S=49.8 at. % and Al=5.3 at.%. The X-ray diffraction data taken on these samples showed a broad peak corresponding to the (111) plane of ZnS while the crystallite size varied in the range, 8 - 15 nm, depending on the concentration of Al in the layers. The films with a Al-doping content of 6 at. % had an optical transmittance of 75% in the visible range and the energy band gap evaluated from the data was 3.66 eV. The films n-type electrical conductivities and the electrical resistivity varied in the range, 107-103 Ωcm, it decreasing with an increase of the Al-concentration in the solution.

  19. High-efficiency cadmium-free Cu(In,Ga)Se{sub 2} thin-film solar cells with chemically deposited ZnS buffer layers

    SciTech Connect

    Nakada, Tokio; Furumi, Keisuke; Kunioka, Akio

    1999-10-01

    Cadmium-free Cu(In,Ga)Se{sub 2} (CIGS) thin-film solar cells with a MgF{sub 2}/ZnO:Al/CBD-ZnS/CIGS/Mo/SLG structure have been fabricated using chemical bath deposition (CBD)-ZnS buffer layers and high-quality CIGS absorber layers grown using molecular beam epitaxy (MBE) system. The use of CBD-ZnS, which is a wider band gap material than CBD-CdS, improved the quantum efficiency of fabricated cells at short wavelengths, leading to an increase in the short-circuit current. The best cell at present yielded an active area efficiency of 16.9% which is the highest value reported previously for Cd-free CIGS thin-film solar cells. The as-fabricated solar cells exhibited a reversible light-soaking effect under AM 1.5, 100 mW/cm{sup 2} illumination. This paper also presents a discussion of the issues relating to the use of the CBD-ZnS buffer material for improving device performance.

  20. The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

    NASA Astrophysics Data System (ADS)

    Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

    2016-04-01

    Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

  1. Study of electronic characteristics of heterojunction with intrinsic thin-layer devices and defect density profile of nanocrystalline silicon germanium devices

    NASA Astrophysics Data System (ADS)

    Mulder, Watson

    Heterojunction with Intrinsic Thin-layer (HIT) solar cells are an important photovoltaic technology, recently reaching record power conversion efficiencies. HIT cells hold advantages over the conventional crystalline Si solar cells, such as their fabrication at lower temperatures and their shorter fabrication time. It is important to understand the electronic characteristics and transport properties of HIT cells to continue to improve their efficiencies. The fundamental measurements of a HIT solar cell with an innovative n+/p/p+ structure are presented. We also report on a series of these HIT cells fabricated on wafers with different doping concentrations, observing the relationship between doping concentration and characteristics such as open-circuit voltage and diffusion length. Nanocrystalline Silicon-Germanium (nc-SiGe) is a useful material for photovoltaic devices and photodetectors. The material features good absorption extending to the infrared region even in thin layers. Its bandgap can be adjusted between that of Si (˜1.1 eV) and Ge (˜0.7 eV) by varying the alloy composition ratio during deposition. However, there has been very little previous work to measure and understand the defect density spectrum of nc-SiGe. Defects are responsible for controlling the recombination and thus the performance of solar cell devices. Capacitance-Frequency measurements at various temperatures are used in order to estimate the trap density profile within the bandgap of nc-SiGe.

  2. Influence of surfactant and annealing temperature on optical properties of sol-gel derived nano-crystalline TiO2 thin films.

    PubMed

    Vishwas, M; Sharma, Sudhir Kumar; Rao, K Narasimha; Mohan, S; Gowda, K V Arjuna; Chakradhar, R P S

    2010-03-01

    Titanium dioxide thin films have been synthesized by sol-gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 degrees C. The influence of surfactant and annealing temperature on optical properties of TiO(2) thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO(2) films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO(2) films was estimated by Tauc's method at different annealing temperature.

  3. Enhanced Cu emission in ZnS : Cu,Cl/ZnS core-shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Corrado, Carley; Hawker, Morgan; Livingston, Grant; Medling, Scott; Bridges, Frank; Zhang, Jin Z.

    2010-07-01

    ZnS : Cu,Cl/ZnS core-shell nanocrystals (NCs) have been synthesized via a facile aqueous synthesis method. The shell growth of the NCs was observed via a red-shift in the UV-Vis absorption spectra with increasing NC size. The Cu photoluminescence (PL) emission was enhanced by capping with a thin ZnS shell. The ZnS : Cu (0.2%) and ZnS : Cu (0.5%) show a more pronounced red-shift in the apparent PL peak position as well as a 37% and 67% increase in emission intensity, respectively, in comparison to the undoped NCs. The observed red-shift is mainly due to an increase in intensity of the Cu PL emission. The 1% Cu-doped NCs exhibit very little red-shift because the observed emission is dominated by the Cu-dopant and thus nearly independent of the size of the NCs. The increase in Cu emission is evidence that Cu atoms occupying non-emissive surface sites in doped ZnS NCs were encapsulated by the ZnS shell. Extended X-Ray Absorption Fine Structure (EXAFS) data also suggests that the Cu had slightly more neighbors upon growth of a ZnS shell, indicating its encapsulation into the core of the NCs. The EXAFS Zn edge data also indicate greater disorder in the ZnS structure when the shell is grown, which may be attributed to the ZnS shell being more amorphous than the core NCs. This study demonstrates that core-shell structures can be used as a simple and yet powerful strategy to enhance PL properties of doped semiconductor NCs.

  4. Optical and electrical properties of copper-incorporated ZnS films applicable as solar cell absorbers

    NASA Astrophysics Data System (ADS)

    Mehrabian, M.; Esteki, Z.; Shokrvash, H.; Kavei, G.

    2016-10-01

    Un-doped and Cu-doped ZnS (ZnS:Cu) thin films were synthesized by Successive Ion Layer Absorption and Reaction (SILAR) method. The UV-visible absorption studies have been used to calculate the band gap values of the fabricated ZnS:Cu thin films. It was observed that by increasing the concentration of Cu2+ ions, the Fermi level moves toward the edge of the valence band of ZnS. Photoluminescence spectra of un-doped and Cu-doped ZnS thin films was recorded under 355 nm. The emission spectrum of samples has a blue emission band at 436 nm. The peak positions of the luminescence showed a red shift as the Cu2+ ion concentration was increased, which indicates that the acceptor level (of Cu2+) is getting close to the valence band of ZnS.

  5. Magnetism in undoped ZnS studied from density functional theory

    SciTech Connect

    Xiao, Wen-Zhi E-mail: llwang@hun.edu.cn; Rong, Qing-Yan; Xiao, Gang; Wang, Ling-ling E-mail: llwang@hun.edu.cn; Meng, Bo

    2014-06-07

    The magnetic property induced by the native defects in ZnS bulk, thin film, and quantum dots are investigated comprehensively based on density functional theory within the generalized gradient approximation + Hubbard U (GGA + U) approach. We find the origin of magnetism is closely related to the introduction of hole into ZnS systems. The relative localization of S-3p orbitals is another key to resulting in unpaired p-electron, due to Hund's rule. For almost all the ZnS systems under study, the magnetic moment arises from the S-dangling bonds generated by Zn vacancies. The charge-neutral Zn vacancy, Zn vacancy in 1− charge sate, and S vacancy in the 1+ charge sate produce a local magnetic moment of 2.0, 1.0, and 1.0 μ{sub B}, respectively. The Zn vacancy in the neutral and 1− charge sates are the important cause for the ferromagnetism in ZnS bulk, with a Curie temperature (T{sub C}) above room temperature. For ZnS thin film with clean (111) surfaces, the spins on each surface are ferromagnetically coupled but antiferromagnetically coupled between two surfaces, which is attributable to the internal electric field between the two polar (111) surfaces of the thin film. Only surface Zn vacancies can yield local magnetic moment for ZnS thin film and quantum dot, which is ascribed to the surface effect. Interactions between magnetic moments on S-3p states induced by hole-doping are responsible for the ferromagnetism observed experimentally in various ZnS samples.

  6. Effect of the nanocrystalline structure type on the optical properties of TiO2:Nd (1 at.%) thin films

    NASA Astrophysics Data System (ADS)

    Mazur, Michal; Wojcieszak, Damian; Kaczmarek, Danuta; Domaradzki, Jaroslaw; Zatryb, Grzegorz; Misiewicz, Jan; Morgiel, Jerzy

    2015-04-01

    Titanium dioxide thin films, each doped with the same amount of neodymium (1 at.%) were deposited by Low Pressure Hot Target Reactive Sputtering and High Energy Reactive Magnetron Sputtering processes in order to obtain anatase and rutile thin film structures respectively. The microstructure and phase composition were analyzed using the transmission electron microscopy method including high resolution electron microscopy imaging. The measurements of the optical properties showed, that both prepared thin films were transparent in the visible light range and had a low extinction coefficient of ca. 3 ṡ 10-3. The thin film with the anatase structure had a lower cut-off wavelength and refractive index and a higher value of optical energy band gap as-compared to the TiO2:Nd coating with the rutile structure. Simultaneously, more efficient photoluminescence emission was observed for the rutile thin films.

  7. Remediation of arsenic and lead with nanocrystalline zinc sulfide

    NASA Astrophysics Data System (ADS)

    Piquette, Alan; Cannon, Cody; Apblett, Allen W.

    2012-07-01

    Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m2 g-1 was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As5+, As3+, and Pb2+. The reaction of the nanocrystalline ZnS with Pb2+ proceeds as a replacement reaction where solid PbS is formed and Zn2+ is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb2+ are included in this study. Unlike the instance of lead, both As5+ and As3+ adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g-1 for the removal of As5+ is possible. The uptake of As3+ appears to proceed by a slower process than that of the As5+ with a capacity of nearly 20 mg g-1. The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.

  8. Synthesis and photoluminescent properties of nanocrystalline CaMoO4 thin film via chemical solution processing.

    PubMed

    Yu, Ping; Hu, Guo-Bing; Tian, Yun-Fei; Xiao, Ding-Quan; Liu, Yang; Guo, Qing-Wu

    2008-05-01

    Stoichiometric CaMoO4 thin film was successfully fabricated based on chemical solution processing. The thin films were deposited on Si(100) substrates by means of the spin-coating technique. X-ray diffraction reveals that the CaMoO4 thin film prepared are pure and well crystalline thin films. Atom Force Microscope photographs indicate that the film prepared possesses a homogeneous and dense surface morphology. The average grain size of the films was 40-50 nm, and the root-mean-square (RMS) of the surface roughness and the average surface roughness of the film measured were 2.161 nm and 1.726 nm respectively. The photoluminescent properties of calcium molybdate thin film under ultraviolet light excitation were systematically measured from 12 K to room temperature and a green emission band of the films were observed. The results of present work confirm that the chemical solution processing is a promising technology on the fabrication of CaMoO4 thin film.

  9. Evaluation of undoped ZnS single crystal materials for x-ray imaging applications

    NASA Astrophysics Data System (ADS)

    Saleh, Muad; Lynn, Kelvin G.; McCloy, John S.

    2017-05-01

    ZnS-based materials have a long history of use as x-ray luminescent materials. ZnS was one of the first discovered scintillators and is reported to have one of the highest scintillator efficiencies. The use of ZnS for high energy luminescence has been thus far limited to thin powder screens, such as ZnS:Ag which is used for detecting alpha radiation, due to opacity to its scintillation light, primarily due to scattering. ZnS in bulk form (chemical vapor deposited, powder processed, and single crystal) has high transmission and low scattering compared to powder screens. In this paper, the performance of single crystalline ZnS is evaluated for low energy x-ray (<10 keV) imaging. For these applications, a scintillator needs to be thick enough to absorb the incoming x-rays and to provide sufficient gain, but thin enough to allow for a good spatial resolution. The scintillators also need to have a good radiation hardness, a fast decay time, and low levels of afterglow. We present a trade study which compares the calculated scintillation gain and absolute efficiency for low energy x-rays (<10 keV) comparing thin (<100 μm) ZnS to CsI:Tl, Bi4Ge3O12 (BGO), and Y3Al5O12:Ce (YAG:Ce). The study also gives insight into the spatial resolution of these scintillators. Further, photoluminescence (PL) and PL excitation (PLE) of several undoped ZnS single crystals is compared to their Radioluminescence (RL) spectra. It was found that the ZnS emission wavelength varies on the excitation source energy.

  10. Microscopic model for exchange bias from grain-boundary disorder in a ferromagnet/antiferromagnet thin film with a nanocrystalline microstructure

    SciTech Connect

    Cortie, D. L.; Biternas, A. G.; Chantrell, R. W.; Wang, X. L.; Klose, F.

    2014-07-21

    Monte Carlo spin simulations were coupled to a Voronoi microstructure-generator to predict the magnitude and behavior of exchange bias in a ferromagnet/antiferromagnet (AF) thin film bilayer with a nanocrystalline microstructure. Our model accounts for the effects of irregular grain-shapes, finite-sized particles, and the possible presence of local random-fields originating from the antiferromagnet's grain-boundary regions. As the grain-boundary represents a crystal-structure distortion, we model the local effect on the exchange constants in the Gaussian approximation which can cause regions resembling a spin glass confined to an unusual 2D topology. Although an ensemble of completely disconnected AF grains isolated by non-magnetic barriers provides a small exchange bias, the introduction of a spin-glass network at the boundaries causes a four-fold enhancement in the magnitude of the loop-shift. This implies the importance of local grain-boundary behavior in defect-engineered antiferromagnets.

  11. Evidence of quantum correction to conductivity and variable range hopping conduction in nano-crystalline Cu{sub 3}N thin film

    SciTech Connect

    Sahoo, Guruprasad Jain, Mahaveer K.

    2015-10-15

    We have investigated the temperature dependent carrier transport properties of nano-crystalline copper nitride thin films synthesized by modified activated reactive evaporation. The films, prepared in a Cu-rich growth condition are found to be highly disordered and the carrier transport in these films is mainly attributed to the impurity band conduction. We have observed that no single conduction mechanism is appropriate to elucidate the carrier transport in the entire temperature range of 20 – 300 K. Therefore, we have employed different conduction mechanisms in different temperature regimes. The carrier transport of the films in the low temperature regime (20 – 150 K) has been interpreted by implementing quantum correction to the conductivity. In the high temperature regime (200 – 300 K), the conduction mechanism has been successfully analyzed on the basis of Mott’s variable range hopping mechanism. Furthermore, it can be predicted that copper ions present at the surface of the crystallites are responsible for the hopping conduction mechanism.

  12. Catastrophic vs gradual collapse of thin-walled nanocrystalline Ni hollow cylinders as building blocks of microlattice structures.

    PubMed

    Lian, Jie; Jang, Dongchan; Valdevit, Lorenzo; Schaedler, Tobias A; Jacobsen, Alan J; B Carter, William; Greer, Julia R

    2011-10-12

    Lightweight yet stiff and strong lattice structures are attractive for various engineering applications, such as cores of sandwich shells and components designed for impact mitigation. Recent breakthroughs in manufacturing enable efficient fabrication of hierarchically architected microlattices, with dimensional control spanning seven orders of magnitude in length scale. These materials have the potential to exploit desirable nanoscale-size effects in a macroscopic structure, as long as their mechanical behavior at each appropriate scale - nano, micro, and macro levels - is properly understood. In this letter, we report the nanomechanical response of individual microlattice members. We show that hollow nanocrystalline Ni cylinders differing only in wall thicknesses, 500 and 150 nm, exhibit strikingly different collapse modes: the 500 nm sample collapses in a brittle manner, via a single strain burst, while the 150 nm sample shows a gradual collapse, via a series of small and discrete strain bursts. Further, compressive strength in 150 nm sample is 99.2% lower than predicted by shell buckling theory, likely due to localized buckling and fracture events observed during in situ compression experiments. We attribute this difference to the size-induced transition in deformation behavior, unique to nanoscale, and discuss it in the framework of "size effects" in crystalline strength.

  13. Effect of doping on the surface modification of nebulizer sprayed Ba x Zn1-x O nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Gopala Krishnan, V.; Elango, P.; Ragavendar, M.; Sathish, P.; Gowrisankar, G.

    2017-03-01

    The influence of Ba doped zinc oxide films were investigated by nebulizer spray pyrolysis technique at 673 K. X-ray diffraction reveals the polycrystalline hexagonal (wurtzite) crystal structure with (0 0 2) preferential orientation. Energy dispersive spectroscopy confirms the presence of Ba, Zn and O elements in the films. Field emission scanning electron microscopy shows that the surface morphology of the nanocrystalline films were changed from spherical shape structure to flake net-like shape and sprout like spherical structure with average grain size is ~100 nm due to the critical doping concentration. PL spectra prominent peaks corresponding to near band edge UV emission and intrinsic defect of the visible blue light region and defect related deep level green emission regions were discussed. The films are highly transparent in the visible region with a transmittance higher than 74%, and have an optical band gap energy values are increased from 3.22 eV to 4.02 eV depending on the Ba doping concentration. Interparticle like grains, grain boundary effect of deposited films is studied by complex impedance spectroscopy.

  14. Infrared optical properties of amorphous and nanocrystalline Ta{sub 2}O{sub 5} thin films

    SciTech Connect

    Bright, T. J.; Watjen, J. I.; Zhang, Z. M.; Muratore, C.; Voevodin, A. A.; Koukis, D. I.; Tanner, D. B.; Arenas, D. J.

    2013-08-28

    The optical constants of tantalum pentoxide (Ta{sub 2}O{sub 5}) are determined in a broad spectral region from the visible to the far infrared. Ta{sub 2}O{sub 5} films of various thicknesses from approximately 170 to 1600 nm are deposited using reactive magnetron sputtering on Si substrates. X-ray diffraction shows that the as-deposited films are amorphous, and annealing in air at 800 °C results in the formation of nanocrystalline Ta{sub 2}O{sub 5}. Ellipsometry is used to obtain the dispersion in the visible and near-infrared. Two Fourier-transform infrared spectrometers are used to measure the transmittance and reflectance at wavelengths from 1 to 1000 μm. The surface topography and microstructure of the samples are examined using atomic force microscopy, confocal microscopy, and scanning electron microscopy. Classical Lorentz oscillators are employed to model the absorption bands due to phonons and impurities. A simple model is introduced to account for light scattering in the annealed films, which contain micro-cracks. For the unannealed samples, an effective-medium approximation is used to take into account the adsorbed moisture in the film and a Drude free-electron term is also added to model the broad background absorption.

  15. An investigation on the effect of high partial pressure of hydrogen on the nanocrystalline structure of silicon carbide thin films prepared by radio-frequency magnetron sputtering.

    PubMed

    Daouahi, Mohsen; Omri, Mourad; Kerm, Abdul Ghani Yousseph; Al-Agel, Faisal Abdulaziz; Rekik, Najeh

    2015-02-05

    The aim of the study reported in this paper is to investigate the role of the high partial pressure of hydrogen introduced during the growth of nanocrystalline silicon carbide thin films (nc-SiC:H). For this purpose, we report the preparation as well as spectroscopic studies of four series of nc-SiC:H obtained by radio-frequency magnetron sputtering at high partial pressure of hydrogen by varying the percentage of H2 in the gas mixture from 70% to 100% at common substrate temperature (TS=500°C). The effects of the dilution on the structural changes and the chemical bonding of the different series have been studied using Fourier transform infrared and Raman spectroscopy. For this range of hydrogen dilution, two groups of films were obtained. The first group is characterized by the dominance of the crystalline phase and the second by a dominance of the amorphous phase. This result confirms the multiphase structure of the grown nc-SiC:H thin films by the coexistence of the SiC network, carbon-like and silicon-like clusters. Furthermore, infrared results show that the SiC bond is the dominant absorption peak and the carbon atom is preferentially bonded to silicon. The maximum value obtained of the crystalline fraction is about 77%, which is relatively important compared to other results obtained by other techniques. In addition, the concentration of CHn bonds was found to be lower than that of SiHn for all series. Raman measurements revealed that the crystallization occurs in all series even at 100% H2 dilution suggesting that high partial pressure of hydrogen favors the formation of silicon nanocrystallites (nc-Si). The absence of both the longitudinal acoustic band and the transverse optical band indicate that the crystalline phase is dominant.

  16. Optical properties of ZnS and Cu2+ doped ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Sarkar, A.; Chakrabarty, N.; Bera, S.; Chakraborty, A. K.

    2015-06-01

    Flower like ZnS and ZnS:Cu2+ nanostructures are developed by simple chemical route. Structural, morphological and optical characterizations are carried out by XRD, FESEM, UV-Visible absorption spectroscopy and FTIR. Analysis indicates successful incorporation of Cu2+ ions into ZnS lattice. Optical studies show that the copper doped ZnS enhances the optical property of pristine ZnS by harvesting more visible light.

  17. Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing.

    PubMed

    Takashiri, Masayuki; Asai, Yuki; Yamauchi, Kazuki

    2016-08-19

    We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment). We employed Williamson-Hall analysis for separating the strain contribution from the crystallite domain contribution in the x-ray diffraction data of the films. We found that strain was induced in the thin films by EB irradiation and was relieved by thermal annealing. The crystal orientation along c-axis was significantly enhanced by the two-step treatment. Scanning electron microscopy indicated the melting and aggregation of nano-sized grains on the film surface by the two-step treatment. Optical analysis indicated that the interband transition of all the thin films was possibly of the indirect type, and that thermal annealing and two-step treatment methods increased the band gap of the films due to relaxation of the strain. Thermoelectric performance was significantly improved by the two-step treatment. The power factor reached a value of 17.2 μW (cm(-1) K(-2)), approximately 10 times higher than that of the as-deposited thin films. We conclude that improving the crystal orientation and relaxing the strain resulted in enhanced thermoelectric performance.

  18. Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing

    NASA Astrophysics Data System (ADS)

    Takashiri, Masayuki; Asai, Yuki; Yamauchi, Kazuki

    2016-08-01

    We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment). We employed Williamson-Hall analysis for separating the strain contribution from the crystallite domain contribution in the x-ray diffraction data of the films. We found that strain was induced in the thin films by EB irradiation and was relieved by thermal annealing. The crystal orientation along c-axis was significantly enhanced by the two-step treatment. Scanning electron microscopy indicated the melting and aggregation of nano-sized grains on the film surface by the two-step treatment. Optical analysis indicated that the interband transition of all the thin films was possibly of the indirect type, and that thermal annealing and two-step treatment methods increased the band gap of the films due to relaxation of the strain. Thermoelectric performance was significantly improved by the two-step treatment. The power factor reached a value of 17.2 μW (cm-1 K-2), approximately 10 times higher than that of the as-deposited thin films. We conclude that improving the crystal orientation and relaxing the strain resulted in enhanced thermoelectric performance.

  19. Transition from a nanocrystalline phase to an amorphous phase in In-Si-O thin films: The correlation between the microstructure and the optical properties

    SciTech Connect

    Park, Jun-Woo; So, Hyeon Seob; Lee, Hosun; Lee, Hye-Min; Kim, Hyo-Joong; Kim, Han-Ki

    2015-04-21

    We investigated the structural and optical properties of In-Si-O thin films as the phase abruptly changes from nanocrystalline (nc) to amorphous (a) with increasing Si content. In-Si-O thin films were deposited on Si substrate using a co-sputtering deposition method. The RF power of the In{sub 2}O{sub 3} target was fixed at 100 W, while the power applied to the SiO{sub 2} target was varied between 0 W and 60 W. At the Si = 2.8 at. %, i.e., at the onset of amorphous phase, the optical properties, including the dielectric functions, optical gap energies, and phonon modes, changed abruptly which were triggered by changes in the crystallinity and surface morphology. X-ray diffraction (XRD) spectra showed crystalline (c-) In{sub 2}O{sub 3}-like peaks below Si = 2.2%. Additionally, a broad peak associated with an amorphous (a-) In{sub 2}O{sub 3} phase appeared above 2.8%. However, the Raman spectra of In-Si-O showed very weak peaks associated with c-In{sub 2}O{sub 3} below 2.2%, and then showed a strong Raman peak associated with a-In-Si-O above 2.8%. X-ray photoelectron spectroscopy measurements showed that oxygen vacancy-related peak intensities increased abruptly above Si = 2.8%. The contrasting results of XRD and Raman measurements can be explained as follows: first, the large enhancement in Drude tails in the a-In-Si-O phase was caused by Si-induced amorphization and a large increase in the density of oxygen vacancies in the In-Si-O thin films. Second, the apparently drastic increase of the Raman peak intensity near 364 cm{sup −1} (for amorphous phase, i.e., above Si = 2.8%) is attributed to a disorder-activated infrared mode caused by both the amorphization and the increase in the oxygen vacancy density in In-Si-O thin films.

  20. P-Type Transparent Cu-Alloyed ZnS Deposited at Room Temperature

    SciTech Connect

    Woods-Robinson, Rachel; Cooper, Jason K.; Xu, Xiaojie; Schelhas, Laura T.; Pool, Vanessa L.; Faghaninia, Alireza; Lo, Cynthia S.; Toney, Michael F.; Sharp, Ian D.; Ager, Joel W.

    2016-03-16

    All transparent conducting materials (TCMs) of technological practicality are n-type; the inferior conductivity of p-type TCMs has limited their adoption. Additionally, many relatively high-performing p-type TCMs require synthesis temperatures > 400 °C. Here, room-temperature pulsed laser deposition of copper-alloyed zinc sulfide (Cu x Zn 1- x S) thin films (0 ≤ x ≤ 0.75) is reported. For 0.09 ≤ x ≤ 0.35, Cu x Zn 1- x S has high p-type conductivity, up to 42 S cm -1 at x = 0.30, with an optical band gap tunable from ≈3.0–3.3 eV and transparency, averaged over the visible, of 50%–71% for 200–250 nm thick films. In this range, synchrotron X-ray and electron diffraction reveal a nanocrystalline ZnS structure. Secondary crystalline Cu y S phases are not observed, and at higher Cu concentrations, x > 0.45, films are amorphous and poorly conducting. Furthermore, within the TCM regime, the conductivity is temperature independent, indicating degenerate hole conduction. A decrease in lattice parameter with Cu content suggests that the hole conduction is due to substitutional incorporation of Cu onto Zn sites. This hole-conducting phase is embedded in a less conducting amorphous Cu y S, which dominates at higher Cu concentrations. Finally, the combination of high hole conductivity and optical transparency for the peak conductivity Cu x Zn 1- x S films is among the best reported to date for a room temperature deposited p-type TCM.

  1. P-Type Transparent Cu-Alloyed ZnS Deposited at Room Temperature

    DOE PAGES

    Woods-Robinson, Rachel; Cooper, Jason K.; Xu, Xiaojie; ...

    2016-03-16

    All transparent conducting materials (TCMs) of technological practicality are n-type; the inferior conductivity of p-type TCMs has limited their adoption. Additionally, many relatively high-performing p-type TCMs require synthesis temperatures > 400 °C. Here, room-temperature pulsed laser deposition of copper-alloyed zinc sulfide (Cu x Zn 1- x S) thin films (0 ≤ x ≤ 0.75) is reported. For 0.09 ≤ x ≤ 0.35, Cu x Zn 1- x S has high p-type conductivity, up to 42 S cm -1 at x = 0.30, with an optical band gap tunable from ≈3.0–3.3 eV and transparency, averaged over the visible, of 50%–71% formore » 200–250 nm thick films. In this range, synchrotron X-ray and electron diffraction reveal a nanocrystalline ZnS structure. Secondary crystalline Cu y S phases are not observed, and at higher Cu concentrations, x > 0.45, films are amorphous and poorly conducting. Furthermore, within the TCM regime, the conductivity is temperature independent, indicating degenerate hole conduction. A decrease in lattice parameter with Cu content suggests that the hole conduction is due to substitutional incorporation of Cu onto Zn sites. This hole-conducting phase is embedded in a less conducting amorphous Cu y S, which dominates at higher Cu concentrations. Finally, the combination of high hole conductivity and optical transparency for the peak conductivity Cu x Zn 1- x S films is among the best reported to date for a room temperature deposited p-type TCM.« less

  2. Influencing the structural, microstructural and optical properties of PbS nanocrystalline thin films by Mg2+ doping

    NASA Astrophysics Data System (ADS)

    Gassoumi, Abdelaziz; Alleg, Safia; Kamoun-Turki, Najoua

    2016-07-01

    The aim of the current work is study the effect of Mg2+ doping (0-4%) on lead sulfide (PbS) thin films prepared using a simplest and cost effective chemical bath deposition (CBD) technique on glass substrates at ambient temperature and pressure. The effect of Mg2+ content on structural, morphological and optical properties of PbS thin films was studied. Powder X-ray diffraction and Atomic Force Microscopic results showed that all the deposited thin films exhibits both nanostructured and polycrystalline nature with cubic structure. The remarkable effect on optical transmittance and band gap was observed due to Mg2+ doping for all the films. The optical energy band gap values were found to enhance with increasing the Mg2+ content in PbS thin films. Further, the refractive index was calculated and a relationship with energy band gap was investigated and also the high frequency dielectric constant (ε∞) was determined using the energy band gap values as a function of the Mg2+ content.

  3. Enhanced growth and osteogenic differentiation of human osteoblast-like cells on boron-doped nanocrystalline diamond thin films.

    PubMed

    Grausova, Lubica; Kromka, Alexander; Burdikova, Zuzana; Eckhardt, Adam; Rezek, Bohuslav; Vacik, Jiri; Haenen, Ken; Lisa, Vera; Bacakova, Lucie

    2011-01-01

    Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH(4):H(2) gas mixture, the B∶C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000 ± 14,000 and 152,000 ± 10,000 cells/cm(2), respectively, compared to 113,000 ± 10,000 cells/cm(2) on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells.

  4. Enhanced Growth and Osteogenic Differentiation of Human Osteoblast-Like Cells on Boron-Doped Nanocrystalline Diamond Thin Films

    PubMed Central

    Grausova, Lubica; Kromka, Alexander; Burdikova, Zuzana; Eckhardt, Adam; Rezek, Bohuslav; Vacik, Jiri; Haenen, Ken; Lisa, Vera; Bacakova, Lucie

    2011-01-01

    Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH4:H2 gas mixture, the B∶C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000±14,000 and 152,000±10,000 cells/cm2, respectively, compared to 113,000±10,000 cells/cm2 on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells. PMID:21695172

  5. Anomalous behavior of B{sub 1g} mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO) thin films

    SciTech Connect

    Gautam, Subodh K. E-mail: fouran@gmail.com; Ojha, S.; Singh, Fouran E-mail: fouran@gmail.com; Gautam, Naina; Singh, R. G.; Shukla, D. K.

    2015-12-15

    The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO) thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO{sub 2} lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb{sup +5} in the TiO{sub 2} lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Raman (MR) spectra of films with small size crystallites shows stiffening of about 4 cm{sup −1} for the E{sub g(1)} mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B{sub 1g} mode exhibits a large anomalous softening of 20 cm{sup −1} with asymmetrical broadening; which was not reported for the case of pure TiO{sub 2} crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb{sup 5+} doping induced reduction of Ti{sup 4+} ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS) and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.

  6. Highly transparent and reproducible nanocrystalline ZnO and AZO thin films grown by room temperature pulsed-laser deposition on flexible Zeonor plastic substrates

    NASA Astrophysics Data System (ADS)

    Inguva, Saikumar; Vijayaraghavan, Rajani K.; McGlynn, Enda; Mosnier, Jean-Paul

    2015-09-01

    Zeonor plastics are highly versatile due to exceptional optical and mechanical properties which make them the choice material in many novel applications. For potential use in flexible transparent optoelectronic applications, we have investigated Zeonor plastics as flexible substrates for the deposition of highly transparent ZnO and AZO thin films. Films were prepared by pulsed laser deposition at room temperature in oxygen ambient pressures of 75, 150 and 300 mTorr. The growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of as-grown films with thicknesses ˜65-420 nm were recorded for the three oxygen pressures. The growth rates were found to be highly linear both as a function of film thickness and oxygen pressure, indicating high reproducibility. All the films were optically smooth, hydrophobic and nanostructured with lateral grain shapes of ˜150 nm wide. This was found compatible with the deposition of condensed nanoclusters, formed in the ablation plume, on a cold and amorphous substrate. Films were nanocrystalline (wurtzite structure), c-axis oriented, with average crystallite size ˜22 nm for ZnO and ˜16 nm for AZO. In-plane compressive stress values of 2-3 GPa for ZnO films and 0.5 GPa for AZO films were found. Films also displayed high transmission greater than 95% in some cases, in the 400-800 nm wavelength range. The low temperature photoluminescence spectra of all the ZnO and AZO films showed intense near band edge emission. A considerable spread from semi-insulating to n-type conductive was observed for the films, with resistivity ˜103 Ω cm and Hall mobility in 4-14 cm2 V-1 s-1 range, showing marked dependences on film thickness and oxygen pressure. Applications in the fields of microfluidic devices and flexible electronics for these ZnO and AZO films are suggested.

  7. One-step synthesis of nanocrystalline transition metal oxides on thin sheets of disordered graphitic carbon by oxidation of MXenes.

    PubMed

    Naguib, Michael; Mashtalir, Olha; Lukatskaya, Maria R; Dyatkin, Boris; Zhang, Chuanfang; Presser, Volker; Gogotsi, Yury; Barsoum, Michel W

    2014-07-18

    Herein we show that heating 2D Ti3C2 in air results in TiO2 nanocrystals enmeshed in thin sheets of disordered graphitic carbon structures that can handle extremely high cycling rates when tested as anodes in lithium ion batteries. Oxidation of 2D Ti3C2 in either CO2 or pressurized water also resulted in TiO2-C hybrid structures. Similarly, other hybrids can be produced, as we show here for Nb2O5/C from 2D Nb2C.

  8. The role of the domain size and titanium dopant in nanocrystalline hematite thin films for water photolysis

    NASA Astrophysics Data System (ADS)

    Yan, Danhua; Tao, Jing; Kisslinger, Kim; Cen, Jiajie; Wu, Qiyuan; Orlov, Alexander; Liu, Mingzhao

    2015-11-01

    Here we develop a novel technique for preparing high quality Ti-doped hematite thin films for photoelectrochemical (PEC) water splitting, through sputtering deposition of metallic iron films from an iron target embedded with titanium (dopants) pellets, followed by a thermal oxidation step that turns the metal films into doped hematite. It is found that the hematite domain size can be tuned from ~10 nm to over 100 nm by adjusting the sputtering atmosphere from more oxidative to mostly inert. The better crystallinity at a larger domain size ensures excellent PEC water splitting performance, leading to record high photocurrent from pure planar hematite thin films on FTO substrates. Titanium doping further enhances the PEC performance of hematite photoanodes. The photocurrent is improved by 50%, with a titanium dopant concentration as low as 0.5 atom%. It is also found that the role of the titanium dopant in improving the PEC performance is not apparently related to the films' electrical conductivity which had been widely believed, but is more likely due to the passivation of surface defects by the titanium dopants.Here we develop a novel technique for preparing high quality Ti-doped hematite thin films for photoelectrochemical (PEC) water splitting, through sputtering deposition of metallic iron films from an iron target embedded with titanium (dopants) pellets, followed by a thermal oxidation step that turns the metal films into doped hematite. It is found that the hematite domain size can be tuned from ~10 nm to over 100 nm by adjusting the sputtering atmosphere from more oxidative to mostly inert. The better crystallinity at a larger domain size ensures excellent PEC water splitting performance, leading to record high photocurrent from pure planar hematite thin films on FTO substrates. Titanium doping further enhances the PEC performance of hematite photoanodes. The photocurrent is improved by 50%, with a titanium dopant concentration as low as 0.5 atom%. It is

  9. Structure and magnetic properties of hcp and fcc nanocrystalline thin Ni films and nanoparticles produced by radio frequency magnetron sputtering.

    PubMed

    Kapaklis, Vassilios; Pappas, Spiridon D; Poulopoulos, Panagiotis; Trachylis, Dimitrios; Schweiss, Peter; Politis, Constantin

    2010-09-01

    We report on the growth of thin Ni films by radio frequency magnetron sputtering in Ar-plasma. The growth temperature was about 350 K and the films were deposited on various substrates such as glass, silicon, sapphire and alumina. The thickness of the thinnest films was estimated by the appearance of Kiessig fringes up to about 2theta = 8 degrees in the small-angle X-ray diffraction pattern, as expected for high-quality atomically-flat thin films. With the help of this, a quartz balance system was calibrated and used for measuring the thickness of thicker samples with an accuracy of better than 5%. Structural characterization via X-ray diffraction and high resolution transmission electron microscopy revealed an Ar-gas pressure window, where single phase hcp Ni films may be grown. The magnetic response of the Ni films was checked at room temperature via a newly established and fully automatic polar magneto-optic Kerr effect magnetometer. The hcp films show no magnetic response. Interestingly, the magnetic saturation field of fcc films deposited at low Ar pressure is comparable to the one of bulk Ni, while the one of fcc films deposited at high Ar pressures is decreased, revealing the presence of residual strain in the films. Finally, it is shown that it is possible to form films which contain magnetic Ni fcc nanoparticles in a non-magnetic hcp matrix, i.e., a system interesting for technological applications demanding a single Ni target for its production.

  10. Unravelling a simple method for the low temperature synthesis of silicon nanocrystals and monolithic nanocrystalline thin films

    NASA Astrophysics Data System (ADS)

    Kim, Ka-Hyun; Johnson, Erik V.; Kazanskii, Andrey G.; Khenkin, Mark V.; Roca I Cabarrocas, Pere

    2017-01-01

    In this work, we present new results on the plasma processing and structure of hydrogenated polymorphous silicon (pm-Si:H) thin films. pm-Si:H thin films consist of a low volume fraction of silicon nanocrystals embedded in a silicon matrix with medium range order, and they possess this morphology as a significant contribution to their growth comes from the impact on the substrate of silicon clusters and nanocrystals synthesized in the plasma. Quadrupole mass spectrometry, ion flux measurements, and material characterization by transmission electron microscopy (TEM) and atomic force microscopy all provide insight on the contribution to the growth by silicon nanocrystals during PECVD deposition. In particular, cross-section TEM measurements show for the first time that the silicon nanocrystals are uniformly distributed across the thickness of the pm-Si:H film. Moreover, parametric studies indicate that the best pm-Si:H material is obtained at the conditions after the transition between a pristine plasma and one containing nanocrystals, namely a total gas pressure around 2 Torr and a silane to hydrogen ratio between 0.05 to 0.1. From a practical point of view these conditions also correspond to the highest deposition rate achievable for a given RF power and silane flow rate.

  11. The role of the domain size and titanium dopant in nanocrystalline hematite thin films for water photolysis

    SciTech Connect

    Yan, Danhua; Tao, Jing; Kisslinger, Kim; Cen, Jiajie; Wu, Qiyuan; Orlov, Alexander; Liu, Mingzhao

    2015-10-13

    In this study, we develop a novel technique for preparing high quality Ti-doped hematite thin films for photoelectrochemical (PEC) water splitting, through sputtering deposition of metallic iron films from an iron target embedded with titanium (dopants) pellets, followed by a thermal oxidation step that turns the metal films into doped hematite. It is found that the hematite domain size can be tuned from ~10 nm to over 100 nm by adjusting the sputtering atmosphere from more oxidative to mostly inert. The better crystallinity at a larger domain size ensures excellent PEC water splitting performance, leading to record high photocurrent from pure planar hematite thin films on FTO substrates. Titanium doping further enhances the PEC performance of hematite photoanodes. The photocurrent is improved by 50%, with a titanium dopant concentration as low as 0.5 atom%. It is also found that the role of the titanium dopant in improving the PEC performance is not apparently related to the films’ electrical conductivity which had been widely believed, but is more likely due to the passivation of surface defects by the titanium dopants.

  12. The role of the domain size and titanium dopant in nanocrystalline hematite thin films for water photolysis

    DOE PAGES

    Yan, Danhua; Tao, Jing; Kisslinger, Kim; ...

    2015-10-13

    Here we develop a novel technique for preparing high quality Ti-doped hematite thin films for photoelectrochemical (PEC) water splitting, through sputtering deposition of metallic iron films from an iron target embedded with titanium (dopants) pellets, followed by a thermal oxidation step that turns the metal films into doped hematite. It is found that the hematite domain size can be tuned from ~10 nm to over 100 nm by adjusting the sputtering atmosphere from more oxidative to mostly inert. The better crystallinity at a larger domain size ensures excellent PEC water splitting performance, leading to record high photocurrent from pure planarmore » hematite thin films on FTO substrates. Titanium doping further enhances the PEC performance of hematite photoanodes. The photocurrent is improved by 50%, with a titanium dopant concentration as low as 0.5 atom%. As a result, it is also found that the role of the titanium dopant in improving the PEC performance is not apparently related to the films’ electrical conductivity which had been widely believed, but is more likely due to the passivation of surface defects by the titanium dopants.« less

  13. Unravelling a simple method for the low temperature synthesis of silicon nanocrystals and monolithic nanocrystalline thin films

    PubMed Central

    Kim, Ka-Hyun; Johnson, Erik V.; Kazanskii, Andrey G.; Khenkin, Mark V.; Roca i Cabarrocas, Pere

    2017-01-01

    In this work, we present new results on the plasma processing and structure of hydrogenated polymorphous silicon (pm-Si:H) thin films. pm-Si:H thin films consist of a low volume fraction of silicon nanocrystals embedded in a silicon matrix with medium range order, and they possess this morphology as a significant contribution to their growth comes from the impact on the substrate of silicon clusters and nanocrystals synthesized in the plasma. Quadrupole mass spectrometry, ion flux measurements, and material characterization by transmission electron microscopy (TEM) and atomic force microscopy all provide insight on the contribution to the growth by silicon nanocrystals during PECVD deposition. In particular, cross-section TEM measurements show for the first time that the silicon nanocrystals are uniformly distributed across the thickness of the pm-Si:H film. Moreover, parametric studies indicate that the best pm-Si:H material is obtained at the conditions after the transition between a pristine plasma and one containing nanocrystals, namely a total gas pressure around 2 Torr and a silane to hydrogen ratio between 0.05 to 0.1. From a practical point of view these conditions also correspond to the highest deposition rate achievable for a given RF power and silane flow rate. PMID:28091562

  14. Study of creep/relaxation mechanisms in thin freestanding nanocrystalline palladium films through the lab-on-chip technology

    NASA Astrophysics Data System (ADS)

    Guisbiers, G.; Colla, M.-S.; Coulombier, M.; Raskin, J.-P.; Pardoen, T.

    2013-01-01

    A nanomechanical lab-on-chip set-up has been used to study the creep/relaxation response of thin palladium films with temperature. The basic idea is to use residual stresses present in a silicon nitride thin beam to load the test film after etching the underneath sacrificial layer. The main advantage of this experimental method is that we can simultaneously perform thousands of creep/relaxation tests without monopolizing any external actuating/loading equipment and without using any time consuming calibration procedures. A signature of the dominant relaxation mechanism is given by the activation volume which has been determined for different levels of plastic deformation and different temperatures. The activation volume is equal to ˜15-40 b3 at room temperature and tends to decrease with increasing plastic deformation. The activation volume decreases when relaxation takes place at 50 °C down to ˜7-20 b3. These variations of the activation volume indicate the competition between two different thermally activated deformation mechanisms in the temperature range between 20 °C and 50 °C.

  15. Synthesis, phase to phase deposition and characterization of rutile nanocrystalline titanium dioxide (TiO2) thin films

    NASA Astrophysics Data System (ADS)

    Gupta, Sanjeev K.; Singh, Jitendra; Anbalagan, K.; Kothari, Prateek; Bhatia, Ravi Raj; Mishra, Pratima K.; Manjuladevi, V.; Gupta, Raj K.; Akhtar, J.

    2013-01-01

    In this work the preparation, deposition and structural properties of titanium oxide (TiO2) thin films were investigated. The films were deposited by means of the e-beam physical vapor deposition (EBPVD) method in high vacuum (10-7 Torr). A controlled deposition rate in the range of 0.1-0.3 Å/s was monitored in situ employing quartz crystal. The films were deposited on the oxidized Si (1 0 0) wafer, glass micro slides. These films were analyzed using Grazing Angle X-ray diffraction (GA-XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RAMAN), Atomic Force Microscopy (AFM) and UV-visible Spectroscopy (UV-vis). Structural characterization results showed mainly presence of the crystalline rutile phase, however an interfacial SiO2 layer between TiO2 and the substrate and the minor anatase crystalline phase of TiO2 was also identified in FTIR analysis. Grain size was found to be in the range of 100-125 nm while grain boundary was estimated to be 20 nm. Direct and indirect optical band gap was estimated to be 3.64 and 3.04 eV, respectively. A process induced self annealing of deposited film shows a strong effect on the structural, morphological and optical properties. Furthermore, low deposition rate and high vacuum allows rutile to rutile phase transformation from indigenously prepared TiO2 target to thin film.

  16. Nanocrystalline Cu2ZnSnSe4 thin films for solar cells application: Microdiffraction and structural characterization

    NASA Astrophysics Data System (ADS)

    Quiroz, Heiddy P.; Dussan, A.

    2016-08-01

    This work presents a study of the structural characterization of Cu2ZnSnSe4 (CZTSe) thin films by X-ray diffraction (XRD) and microdiffraction measurements. Samples were deposited varying both mass (MX) and substrate temperature (TS) at which the Cu and ZnSe composites were evaporated. CZTSe samples were deposited by co-evaporation method in three stages. From XRD measurements, it was possible to establish, with increased Ts, the presence of binary phases associated with the quaternary composite during the material's growth process. A stannite-type structure in Cu2ZnSnSe4 thin films and sizes of the crystallites varying between 30 and 40 nm were obtained. X-ray microdiffraction was used to investigate interface orientations and strain distributions when deposition parameters were varied. It was found that around the main peak, 2ϴ = 27.1°, the Cu1.8Se and ZnSe binary phases predominate, which are formed during the subsequent material selenization stage. A Raman spectroscopy study revealed Raman shifts associated with the binary composites observed via XRD.

  17. Effect of annealing on the properties of nanocrystalline CuInSSe thin films deposited by spray pyrolysis

    SciTech Connect

    Shrotriya, Vipin Rajaram, P.

    2015-08-28

    The effect of annealing CuInSSe thin films, which were grown on glass substrates using the spray pyrolysis technique from spray solutions having S/Se ionic ratio 0.6, were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical transmission measurements. The CuInSSe films were co-deposited from an aqueous solution containing CuCl{sub 2}, InCl{sub 3}, thiourea and SeO{sub 2}. EDC was used as a complexing agent and films were deposited at the constant temperature 300°C. Post annealing (at 350°C) was used to improve the structural, morphological and optical properties of CuInSSe thin films. From the results, it is found that the films are single phase, p-type in conductivity having the chalcopyrite structure. From the Scherrer formula the average size of the films was found to be in the range (15-28) nm. Optical studies show that the optical band gap value increases slightly from 1.35 eV to 1.37 eV with annealing for films grown from spray solutions having S/Se ionic ratio 0.6.

  18. Effect of annealing on the properties of nanocrystalline CuInSSe thin films deposited by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Shrotriya, Vipin; Rajaram, P.

    2015-08-01

    The effect of annealing CuInSSe thin films, which were grown on glass substrates using the spray pyrolysis technique from spray solutions having S/Se ionic ratio 0.6, were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical transmission measurements. The CuInSSe films were co-deposited from an aqueous solution containing CuCl2, InCl3, thiourea and SeO2. EDC was used as a complexing agent and films were deposited at the constant temperature 300°C. Post annealing (at 350°C) was used to improve the structural, morphological and optical properties of CuInSSe thin films. From the results, it is found that the films are single phase, p-type in conductivity having the chalcopyrite structure. From the Scherrer formula the average size of the films was found to be in the range (15-28) nm. Optical studies show that the optical band gap value increases slightly from 1.35 eV to 1.37 eV with annealing for films grown from spray solutions having S/Se ionic ratio 0.6.

  19. Nanocrystalline diamond thin films on titanium-6 aluminum-4 vanadium alloy temporomandibular joint prosthesis simulants by microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Fries, Marc Douglas

    A course of research has been performed to assess the suitability of nanocrystal-line diamond (NCD) films on Ti-6Al-4V alloy as wear-resistant coatings in biomedical implant use. A series of temporomandibular (TMJ) joint condyle simulants were polished and acid-passivated as per ASTM F86 standard for surface preparation of implants. A 3-mum-thick coating of NCD film was deposited by microwave plasma chemical vapor deposition (MPCVD) over the hemispherical articulation surfaces of the simulants. Plasma chemistry conditions were measured and monitored by optical emission spectroscopy (OES), using hydrogen as a relative standard. The films consist of diamond grains around 20 nm in diameter embedded in an amorphous carbon matrix, free of any detectable film stress gradient. Hardness averages 65 GPa and modulus measures 600 GPa at a depth of 250 nm into the film surface. A diffuse film/substrate boundary produces a minimal film adhesion toughness (GammaC) of 158 J/m2. The mean RMS roughness is 14.6 +/- 4.2 nm, with an average peak roughness of 82.6 +/- 65.9 nm. Examination of the surface morphology reveals a porous, dendritic surface. Wear testing resulted in two failed condylar coatings out of three tests. No macroscopic delamination was found on any sample, but micron-scale film pieces broke away, exposing the substrate. Electrochemical corrosion testing shows a seven-fold reduction in corrosion rate with the application of an NCD coating as opposed to polished, passivated Ti-6Al-4V, producing a corrosion rate comparable to wrought Co-Cr-Mo. In vivo biocompatibility testing indicates that implanted NCD films did not elicit an immune response in the rabbit model, and osteointegration was apparent for both compact and trabecular bone on both NCD film and bare Ti-6Al-4V. Overall, NCD thin film material is reasonably smooth, biocompatible, and very well adhered. Wear testing indicates that this material is unacceptable for use in demanding TMJ applications without

  20. Electrodepostion of nanocrystalline cobalt iron and cobalt iron nickel soft magnetic thin films from citrate-added baths

    NASA Astrophysics Data System (ADS)

    Zhang, Yahui

    2005-11-01

    With increasing storage density of hard-disk-drives, the need for recording heads to write on high-coercivity media has raised new requirements for the write-head core material that cannot be met by traditionally employed permalloy (Ni80Fe20). Therefore, new soft magnetic materials with higher saturation flux density Bs (>>1 Tesla) such as CoFe alloys, CoFeNi alloys, and other CoFe-based alloys have been developed during the past decades. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes are being employed in the fabrication of thin-film recording heads. Conventional CoFe or CoFeNi alloy plating baths, which employ low pH levels (typically 2.0-3.0), suffer from several problems that can limit commercialization. These include poor stability, i.e., precipitation occurs in plating baths rapidly with time, low current density efficiency and voids in deposited films due to the electrodeposition of hydrogen. The voids present in deposits will degenerate film uniformity and magnetic properties. Therefore, the development of stable baths with relatively high pH levels is crucial for commercial fabrication of CoFe and CoFeNi thin films with optimal soft magnetic properties. In this study, stable electrolytes, with the introduction of ammonium citrate as a complexing agent and bath stabilizer and relatively high pH levels (natural pH), have been developed for the electrodeposition of CoFe or CoFeNi alloys. Citrate can effectively improve the stability of CoFe and CoFeNi plating baths. Denser and more uniform deposits can be plated out from the citrate-added baths because of the higher pH levels. CoFe and CoFeNi thin films with preferred composition, mixed fcc-bcc phases, and 10-20nm grain sizes, which are necessary for achieving optimal soft magnetic properties, have been electroplated from the citrate-added baths. So far, the saturation magnetizations of CoFe and CoFeNi films plated from citrate-added baths can

  1. Surface/interface analysis and optical properties of RF sputter-deposited nanocrystalline titanium nitride thin films

    NASA Astrophysics Data System (ADS)

    White, N.; Campbell, A. L.; Grant, J. T.; Pachter, R.; Eyink, K.; Jakubiak, R.; Martinez, G.; Ramana, C. V.

    2014-02-01

    Titanium nitride (TiNx) thin films were grown by radio-frequency (RF) magnetron sputter deposition by varying the nitrogen content in the reactive gas mixture over a wide range. The effect of nitrogen gas flow rate on the surface and interface morphology, chemical composition and optical properties of TiN thin films was studied employing atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Analysis of the optical properties probed with SE has shown that films deposited at low (0-5 sccm) nitrogen flow rates have the highest absorption at energies <2 eV. It was also shown that Lorentz oscillators with energy positions lower than 2 eV can be distinguished from the Drude oscillator function during parameter fitting. AFM imaging analysis indicates that the roughness decreases and plateaus at approximately 1.5 nm with the introduction of a small N2 flow rate, remaining consistent thereafter. SEM cross-sectional imaging analysis indicates the dense, columnar structure for the films grown at lower nitrogen flow rates. XPS analysis of atomic composition and the chemical states indicate that the atomic composition remained nearly constant while the chemical states varied significantly among the samples as a function of N2 flow rate. XPS analyses confirm the presence of TiNx, TiO2 and TiOxNy. These process-property relationships derived could be useful for defining and expanding the range of optical and electronic applications of titanium nitrides and (oxy)nitrides.

  2. Influence of sputtering power on structural, mechanical and photoluminescence properties of nanocrystalline SiC thin films

    SciTech Connect

    Singh, Narendra; Kaur, Davinder

    2016-05-06

    In the present study, SiC thin films were deposited on Si (100) substrate by magnetron sputtering using a 4N purity commercial SiC target in argon atmosphere. The effect of sputtering RF power (140-170W) on structural, mechanical and photoluminescence properties were systematically studied by X-ray diffraction, field emission scanning electron microscopy, Nanoindentation and Spectrophotometer respectively. X-ray diffraction shows polycrystalline 4H-SiC phase with (105) preferred orientation and an enhancement in crystallite size with increasing power was also observed. The decrement in hardness and Young’s modulus with increment in RF power was ascribed to Hall-Petch relation. The maximum hardness and Young’s modulus were found to be 32 GPa and 232 GPa respectively. The photoluminescence spectra show peaks at 384 nm (3.22 eV) which corresponds to bandgap of 4H-SiC (phonon assisted band to band recombination) and 416 nm (2.99 eV) may be attributed to defect states and intensity of both peaks decreases as power increases.

  3. Tune-Ability of Physical Properties of Nanocrystalline Cu x Zn1- x Se Thin Films with Copper Concentration

    NASA Astrophysics Data System (ADS)

    Arslan, M.; Zakria, M.; Naz, Nazir A.; Muhammad, R.; Mahmood, A.; Raza, Q.

    2015-12-01

    Thin films of Cu x Zn1- x Se (0 ≤ x ≤ 0.20) have been prepared on glass substrates at room temperature by closed space sublimation. The effect of copper (Cu) concentration on the structural, optical and electrical properties of the prepared films has been investigated using x-ray diffraction (XRD), Raman spectroscopy (RS), spectrophotometery and Hall effect measurements. XRD spectra show that all the films are cubic with (111) preferred orientation. The lattice constants, crystallite size, strain, and dislocation density were calculated from the XRD spectra. The structural analysis shows that crystallite size and crystallinity increase while strain and dislocation density decrease up to 10% Cu addition. However, an opposite trend has been observed beyond 10% Cu concentration. RS was carried out to investigate different phonon bands and crystalline phases. The strong reflection corresponding to the (111) texture in the XRD and the observed longitudinal optical (LO) phonon bands at 251 cm-1 and 497 cm-1 in the Raman spectra reveal the formation of single phase zinc-blende structure. The band gap energy decreases from 2.67 eV to 2.24 eV as the Cu concentration is increased from 0% to 20%. Hall effect measurements shows that electrical resistivity ( ρ) is decreased by about three orders of magnitude from 10.4 × 10-03 Ω-cm to 47.9 × 10-03 Ω-cm while, carrier concentration and mobility ( μ) is increased with Cu addition.

  4. Synthesis of nanocrystalline thin films of gold on the surface of GaSb by swift heavy ion

    SciTech Connect

    Jadhav, Vidya; Dubey, S. K.; Yadav, A. D.; Singh, A.

    2013-02-05

    Thin films of gold ({approx}100 nm thick) were deposited on p-type GaSb substrates. These samples were irradiated with 100 MeV Fe{sup 7+}ions for the fluence of 1 Multiplication-Sign 10{sup 13} and 1 Multiplication-Sign 10{sup 14} ions cm{sup -2}. After irradiation, samples were characterized using AFM, UV-VIS -NIR, X-Ray Diffraction techniques. AFM studies showed the presence of clusters on the surface of GaSb. R.M.S. roughness of the sample was found to increase w.r.t ion fluence. Absorption coefficient obtained from the Ultra violet - Visible NIR (UV-VIS -NIR) spectra of the samples irradiated with various fluences compared with non irradiated GaSb. The annealing experiment showed a significant improvement in the absorption coefficient after rapid thermal annealing at temperature of 400 Degree-Sign C. X-Ray Diffraction study reveals different orientations of Au film.

  5. Influence of annealing temperature on structural and optical properties of nanocrystalline Platinum octaethylporphyrin (PtOEP) thin films

    NASA Astrophysics Data System (ADS)

    Abuelwafa, A. A.; El-Denglawey, A.; Dongol, M.; El-Nahass, M. M.; Soga, T.

    2015-11-01

    Thermal evaporation technique was used to prepare the Platinum octaethylporphyrin (PtOEP) thin films at room temperature. The deposited films were studied before and after thermal annealing at 373 and 473 K for 3 h under vacuum (10-3 Pa). The film structure, surface morphologies and molecular structure were investigated as a function of annealing temperature by X-ray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM) and Fourier-transform infrared techniques (FT-IR) respectively. The results confirmed that the as-deposited and annealed films have nanostructural features. Optical constants of the as-deposited and annealed films have been obtained in the wavelength range 200-1100 nm by using spectrophotometric measurements. Analysis of the spectra of absorption coefficient showed indirect allowed transition and optical energy gap found to decrease with increase in annealing temperature. The dispersion of refractive index at the normal dispersion (λ > 600 nm) was discussed in terms of single oscillator model of Wemple-Didomenico. Based on generalized Miller's rule the third order non-linear susceptibility, χ(3) and nonlinear refractive index, n2 were estimated and studied at lower photon energy and showing lower value for the annealed film.

  6. Microstructural and Morphological Properties of Nanocrystalline Cu2ZnSnSe4 Thin Films: Identification New Phase on Structure

    NASA Astrophysics Data System (ADS)

    Quiroz, Heiddy P.; Seña, N. J.; Dussan, A.

    2014-04-01

    This paper presents a study of the structural and morphological properties of thin films of compound Cu2ZnSnSe4. Mass (MX) and temperature of the substrate (TS(Cu)) of compound copper (Cu), were varied. All samples were deposited by co-evaporation method in three stages. From measurements of X-ray diffraction it was possible to establish with TS increasing the presence of associated binary phases quaternary compound during the growth process of the material. It was found that the main peak around, 2θ= 27.1°, predominate binary phases Cu1.8Se and ZnSe. Measurements of X-ray diffraction were performed to pure binary compounds, showing a peak corresponding to the main peak found around the compound. Raman shifts showed associated binary compounds with the observed by XRD. In this work, we report for the first time the binary phase identification Cu1.8Se and ZnSe as part of the structure of the stannite CZTSe. Since the Scherrer equation was found that the crystallite sizes ranged between 30 and 40 nm. A correlation between structure and topography superficial is presented.

  7. Optical properties of nanocrystalline Y2O3 thin films grown on quartz substrates by electron beam deposition

    NASA Astrophysics Data System (ADS)

    Wiktorczyk, Tadeusz; Biegański, Piotr; Serafińczuk, Jarosław

    2016-09-01

    Yttrium oxide thin films of a thickness 221-341 nm were formed onto quartz substrates by reactive physical vapor deposition in an oxygen atmosphere. An electron beam gun was applied as a deposition source. The effect of substrate temperature during film deposition (in the range of 323-673 K) on film structure, surface morphology and optical properties was investigated. The surface morphology studies (with atomic force microscopy and diffuse spectra reflectivity) show that the film surface was relatively smooth with RMS surface roughness in the range of 1.7-3.8 nm. XRD analysis has revealed that all diffraction lines belong to a cubic Y2O3 structure. The films consisted of small nanocrystals. Their average grain size increases from 1.6 nm to 22 nm, with substrate temperature rising from 323 K to 673 K. Optical examinations of transmittance and reflectance were performed in the spectral range of 0.2-2.5 μm. Optical constants and their dispersion curves were determined. Values of the refractive index of the films were in the range of n = 1.79-1.90 (at 0.55 μm) for substrate temperature during film deposition of 323-673 K. The changes in the refractive index upon substrate temperature correspond very well with the increase in the nanocrystals grain diameter and with film porosity.

  8. Electrical properties of point defects in CdS and ZnS

    NASA Astrophysics Data System (ADS)

    Varley, J. B.; Lordi, V.

    2013-09-01

    We investigate native point defects in CdS and ZnS, which are conventional n-type buffer layers used in thin-film solar cells. Using hybrid functional calculations, we characterize the electrical behavior of these defects and also consider common impurities such as O, H, and their complexes. We find cation vacancies are the dominant compensating acceptors and recombination centers, and their effects are more dramatic in ZnS than in CdS. We also determine the band alignment for conventional Cu(In,Ga)Se2-based solar cells, giving insight into why CdS outperforms ZnS and why Zn oxysulfides are promising due to their improved conduction band offsets.

  9. Photocatalytic decolorization of methylene blue in the presence of TiO2/ZnS nanocomposites.

    PubMed

    Franco, A; Neves, M C; Carrott, M M L Ribeiro; Mendonça, M H; Pereira, M I; Monteiro, O C

    2009-01-15

    The synthesis of distinct nanocrystalline TiO2 capped ZnS samples was carried out using a chemical deposition method. The materials characterization showed that the presence of ZnS onto TiO2 surface results in a red shift of the material band edge when compared with the initial semiconductor. The photocatalytic activity of the prepared nanocomposites was tested on the decolorization of methylene blue (MB) aqueous solutions. The dye photodecolorization process was studied considering the influence of experimental parameters such as catalyst concentration, TiO2/ZnS ratio, pH and methylene blue adsorption rate. The material with the best catalytic activity towards the methylene blue photodecolorization was the TiO2 doped with 0.2% of ZnS. The complete photodecolorization of a 20ppm methylene blue solution, at natural pH was achieved in less than 20min, nearly 70min faster than the TiO2 photoassisted process.

  10. Nanocrystalline ceramic materials

    DOEpatents

    Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

    1994-01-01

    A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

  11. Light-soaking effects and capacitance profiling in Cu(In,Ga)Se2 thin-film solar cells with chemical-bath-deposited ZnS buffer layers.

    PubMed

    Yu, Hye-Jung; Lee, Woo-Jung; Wi, Jae-Hyung; Cho, Dae-Hyung; Han, Won Seok; Chung, Yong-Duck; Kim, Tae-Soo; Song, Jung-Hoon

    2016-12-07

    We fabricated Cu(In,Ga)Se2 (CIGS) solar cells with chemical-bath deposited (CBD) ZnS buffer layers with different deposition times. The conversion efficiency and the fill factor of the CIGS solar cells reveal a strong dependence on the deposition time of CBD-ZnS films. In order to understand the detailed relationship between the heterojunction structure and the electronic properties of CIGS solar cells with different deposition times of CBD-ZnS films, capacitance-voltage (C-V) profiling measurements with additional laser illumination were performed. The light-soaking effects on CIGS solar cells with a CBD-ZnS buffer layer were investigated in detail using current density-voltage (J-V) and C-V measurements with several different lasers with different emission wavelengths. After light-soaking, the conversion efficiency changed significantly and the double diode feature in J-V curves disappeared. We explain that the major reason for the improvement of efficiency by light-soaking is due to the fact that negatively charged and highly defective vacancies in the CIGS absorber near the interface of CBD-ZnS/CIGS were formed and became neutral due to carriers generated by ultra-violet absorption in the buffer layer.

  12. Photo-electrochemical studies of chemically deposited nanocrystalline meso-porous n-type TiO2 thin films for dye-sensitized solar cell (DSSC) using simple synthesized azo dye

    NASA Astrophysics Data System (ADS)

    Ezema, C. G.; Nwanya, A. C.; Ezema, B. E.; Patil, B. H.; Bulakhe, R. N.; Ukoha, P. O.; Lokhande, C. D.; Maaza, Malik; Ezema, Fabian I.

    2016-04-01

    Nanocrystalline titanium dioxide (TiO2) thin films were deposited by successive ionic layer adsorption and reaction method onto fluorine doped tin oxide coated glass substrate at room temperature (300 K). Titanium trichloride and sodium hydroxide were used as cationic and anionic sources, respectively. The as-deposited and annealed films were characterized for structural, morphological, optical, electrical and wettability properties. The photoelectrochemical study of TiO2 sensitized with a laboratory synthesized organic dye (azo) was evaluated in the polyiodide electrolyte at 40 mW cm-2 light illumination intensity. The photovoltaic characteristics show a fill factor of 0.24 and solar conversion efficiency value of 0.032 % for a TiO2 thickness of 0.96 µm as compared to efficiency of 0.014 % for rose Bengal of the same thickness.

  13. Room temperature fabrication of dielectric Bragg reflectors composed of a CaF2/ZnS multilayered coating.

    PubMed

    Muallem, Merav; Palatnik, Alex; Nessim, Gilbert D; Tischler, Yaakov R

    2015-01-14

    We describe the design, fabrication, and characterization of mechanically stable, reproducible, and highly reflecting distributed Bragg reflectors (DBR) composed of thermally evaporated thin films of calcium fluoride (CaF2) and zinc sulfide (ZnS). CaF2 and ZnS were chosen as the low and high refractive index components of the multilayer DBR structures, with n = 1.43 and n = 2.38 respectively, because neither material requires substrate heating during the deposition process in order to produce optical quality thin films. DBRs consisting of seven pairs of CaF2 and ZnS layers, were fabricated with thicknesses of 96 and 58 nm, respectively, as characterized by high-resolution scanning electron microscopy (HR-SEM), and exhibited a center wavelength of λc = 550 nm and peak reflectance exceeding 99%. The layers showed good adhesion to each other and to the glass substrate, resulting in mechanically stable DBR coatings. Complete optical microcavities consisting of two such DBR coatings and a CaF2 spacer layer between them could be fabricated in a single deposition run. Optically, these structures exhibited a resonator quality factor of Q > 160. When a CaF2/ZnS DBR was grown, without heating the substrate during deposition, on top of a thin film containing the fluorescent dye Rhodamine 6G, the fluorescence intensity showed no degradation compared to an uncoated film, in contrast to a MgF2/ZnS DBR coating grown with substrate heating which showed a 92% reduction in signal. The ability to fabricate optical quality CaF2/ZnS DBRs without substrate heating, as introduced here, can therefore enable formation of low-loss high-reflectivity coatings on top of more delicate heat-sensitive materials such as organics and other nanostructured emitters, and hence facilitate the development of nanoemitter-based microcavity device applications.

  14. Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

    SciTech Connect

    Sugimura, K.; Miyajima, Y.; Sonehara, M.; Sato, T.; Hayashi, F.; Zettsu, N.; Teshima, K.; Mizusaki, H.

    2016-05-15

    This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO{sub 2}) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC{sub 2}H{sub 5}){sub 4}). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

  15. Biomolecule-mediated synthesis of nanocrystalline semiconductors

    NASA Astrophysics Data System (ADS)

    Bae, Weon

    CdS and ZnS nanocrystalline semiconductors (NCs) were prepared by titrating inorganic sulfide into preformed Cd(II)- or Zn(II)-complexes of phytochelatins, glutathione or cysteine. This strategy resulted in the formation NCs capped by the chosen biomolecule. The range of sizes and their distributions depended primarily on the quantity of sulfide titrated and the biomolecule chosen for the initial metallo-complex. The processes of NC formation were studied by absorption and fluorescence spectrophotometry. The size distribution was analyzed by gel permeation chromatography. Ethanol precipitation of NCs under aqueous conditions was used to isolate nanoparticles within a very narrow size-range. Reduction of selected dyes was also studied on the surfaces of NCs. Glutathione-capped CdS nanoparticles exhibited significant size heterogeneity even at a single sulfide titration. In contrast, phytochelatins showed much less dispersion in size at a given sulfide titration. Phytochelatins could replace glutathione without changing the size of glutathione-capped CdS nanoparticles. Cysteine appeared to be intermediate between glutathione and phytochelatins in the formation of CdS nanoparticles. The calculated radii, using an effective mass approximation method, were 10.8-17.3, 10.6-11.8, and 13.5-15.5A for glutathione-, phytochelatin-, and cysteine-capped CdS nanoparticles, respectively. Cysteine-capped ZnS showed narrower size distribution than glutathione-capped ZnS. However, elevated temperatures were necessary to accomplish optimal yields of cysteine-capped ZnS NCs. An additional control over the size distribution of NCs was achieved by size-selective precipitation with ethanol. These procedures led to the isolation of nanoparticles that were more uniform in size and chemical compositions as determined by spectroscopic and chemical analyses of size-fractionated samples. Precipitation also allowed preparation of large quantities of powdered nanoparticles that could be

  16. Nanocrystalline ceramic materials

    DOEpatents

    Siegel, R.W.; Nieman, G.W.; Weertman, J.R.

    1994-06-14

    A method is disclosed for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material. 19 figs.

  17. Optical Properties of ZnO-Alloyed Nanocrystalline Films

    DOE PAGES

    Che, Hui; Huso, Jesse; Morrison, John L.; ...

    2012-01-01

    ZnO is emore » merging as one of the materials of choice for UV applications. It has a deep excitonic energy level and a direct bandgap of ~3.4 eV. Alloying ZnO with certain atomic constituents adds new optical and electronic functionalities to ZnO. This paper presents research on M g x Z n 1 − x O and Z n S 1 − x O x nanocrystalline flexible films, which enable tunable optical properties in the deep-UV and in the visible range. The ZnO and Mg 0 .3 Zn 0 .7 O films were found to have bandgaps at 3.35 and 4.02 eV, respectively. The photoluminescence of the Mg 0 .3 Zn 0 .7 O exhibited a bandedge emission at 3.95 eV, and at lower energy 3.38 eV due to the limited solubility inherent to these alloys. ZnS 0 .76 O 0 .24 and ZnS 0 .16 O 0 .84 were found to have bandgaps at 3.21 and 2.65 eV, respectively. The effect of nitrogen doping on ZnS 0 .16 O 0 .84 is discussed in terms of the highly lattice mismatched nature of these alloys and the resulting valence-band modification.« less

  18. Fabrication of micro hole array on the surface of CVD ZnS by scanning ultrafast pulse laser for antireflection

    NASA Astrophysics Data System (ADS)

    Li, Yangping; Zhang, Tianhui; Fan, Siling; Cheng, Guanghua

    2017-04-01

    Chemical vapor deposited (CVD) ZnS is a promising long-wave infrared (8-12 μm) window material. Yet antireflection is necessary since Fresnel reflection from its surface is high due to the high refractive index of ZnS. Sub-wavelength structured surface of micro hole array was fabricated on CVD ZnS by scanning ultrafast pulse laser ablation. The effects of beam profile, pulse width and beam power on the radius and morphology of the holes were studied. Gaussian beam can cause severe melted-resolidified layers around the hole, yet Bessel beam only resulted in thin ribbon around the hole. The picosecond Bessel laser is more suitable than femtosecond laser for ablating holes on ZnS. The radius of the holes increases with increasing the Bessel beam pulse width and the beam power. But larger power may cause circle grooves around the central holes. Ordered hole array was fabricated on single side of CVD ZnS and antireflection was realized.

  19. Structure and magnetism of nanocrystalline and epitaxial (Mn,Zn,Fe)3O4 thin films

    SciTech Connect

    Alaan, U. S.; Wong, F. J.; Grutter, A. J.; Iwata-Harms, J. M.; Mehta, V. V.; Arenholz, E.; Suzuki, Y.

    2012-02-21

    We study nanocrystalline (NC) textured Mn0.5Zn0.6Fe1.9O4 (MZFO) films, grown at room temperature on both isostructural and non-isostructural substrates, that show magnetization values significantly suppressed from epitaxial MZFO films. X-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements indicate larger ratios of Fe3+ to Fe2+ ions on the tetrahedral sites in the NC films compared to the epitaxialfilms. The magnetization loops of the NC films are shifted by 200-400 Oe at low temperatures. No such effect is observed in the epitaxialfilms. In conclusion, we hypothesize that the presence of a more structurally disordered, possibly magnetically frustrated, matrix exchange biases the crystalline regions.

  20. Surface plasmon resonance in nanostructured Ag incorporated ZnS films

    NASA Astrophysics Data System (ADS)

    Chalana, S. R.; Ganesan, V.; Mahadevan Pillai, V. P.

    2015-10-01

    Silver incorporated zinc sulfide thin films are prepared by RF magnetron sputtering technique and the influence of silver incorporation on the structural, optical and luminescence properties is analyzed using techniques like grazing incidence X-Ray diffraction (GIXRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), micro-Raman spectroscopy, UV-Vis spectroscopy and laser photoluminescence spectroscopy. XRD analysis presents hexagonal wurtzite structure for the films. A reduction of crystallinity of the films is observed due to Ag incorporation. The Raman spectral analysis confirms the reduction of crystallinity and increase of strain due to the Ag incorporation. AFM analysis reveals a rough surface morphology for the undoped film and Ag incorporation makes the films uniform, dense and smooth. A blue shift of band gap energy with increase in Ag incorporation is observed due to quantum confinement effect. An absorption band (450-650 nm region) due to surface plasmon resonance of the Ag clusters present in the ZnS matrix is observed for the samples with higher Ag incorporation. The complex dielectric constant, loss factor and distribution of volume and surface energy loss of the ZnS thin films are calculated. Laser photoluminescence measurements gives an intense bluish green emission from the ZnS films and a quenching of the PL emission is observed which can be due to the metal plasmonic absorption and non-radiative energy transfer due to Ag incorporation.

  1. Surface plasmon resonance in nanostructured Ag incorporated ZnS films

    SciTech Connect

    Chalana, S. R.; Mahadevan Pillai, V. P.; Ganesan, V.

    2015-10-15

    Silver incorporated zinc sulfide thin films are prepared by RF magnetron sputtering technique and the influence of silver incorporation on the structural, optical and luminescence properties is analyzed using techniques like grazing incidence X-Ray diffraction (GIXRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), micro-Raman spectroscopy, UV-Vis spectroscopy and laser photoluminescence spectroscopy. XRD analysis presents hexagonal wurtzite structure for the films. A reduction of crystallinity of the films is observed due to Ag incorporation. The Raman spectral analysis confirms the reduction of crystallinity and increase of strain due to the Ag incorporation. AFM analysis reveals a rough surface morphology for the undoped film and Ag incorporation makes the films uniform, dense and smooth. A blue shift of band gap energy with increase in Ag incorporation is observed due to quantum confinement effect. An absorption band (450-650 nm region) due to surface plasmon resonance of the Ag clusters present in the ZnS matrix is observed for the samples with higher Ag incorporation. The complex dielectric constant, loss factor and distribution of volume and surface energy loss of the ZnS thin films are calculated. Laser photoluminescence measurements gives an intense bluish green emission from the ZnS films and a quenching of the PL emission is observed which can be due to the metal plasmonic absorption and non-radiative energy transfer due to Ag incorporation.

  2. Modeling and performance analysis dataset of a CIGS solar cell with ZnS buffer layer.

    PubMed

    Hosen, Md Billal; Bahar, Ali Newaz; Ali, Md Karamot; Asaduzzaman, Md

    2017-10-01

    This article represents the baseline data of the several semiconductor materials used in the model of a CIGS thin film solar cell with an inclusion of ZnS buffer layer. As well, input parameters, contact layer data and operating conditions for CIGS solar cell simulation with ZnS buffer layer have been described. The schematic diagram of photovoltaic solar cell has been depicted. Moreover, the most important performance measurement graph, J-V characteristic curve, resulting from CIGS solar cell simulation has been analyzed to estimate the optimum values of fill factor and cell efficiency. These optimum results have been obtained from the open circuit voltage, short circuit current density, and the maximum points of voltage and current density generated from the cell.

  3. Synthesis and Luminescent Properties of GaN and GaN-Mn Blue Nanocrystalline Thin-film Phosphor for FED

    SciTech Connect

    Bondar, V D; Felter, T E; Hunt, C E; Kucharsky, I Y; Chakhovskoi, A G

    2003-04-09

    The technologies of fabrication of thin film phosphors based on gallium nitride using rf-magnetron sputtering are developed and structural properties of films are studied. Luminescence and electron spin resonance (ESR) spectra of GaN and GaN-Mn thin films have been studied. The correlation between cathodoluminescence intensity and conductivity of GaN films has been found. The nature of emission centers in GaN and GaN-Mn thin films is discussed as well as mechanism of luminescence in these films is proposed.

  4. Effect of substrate baking temperature on zinc sulfide and germanium thin films optical parameters

    NASA Astrophysics Data System (ADS)

    Liu, Fang; Gao, Jiaobo; Yang, Chongmin; Zhang, Jianfu; Liu, Yongqiang; Liu, Qinglong; Wang, Songlin; Mi, Gaoyuan; Wang, Huina

    2016-10-01

    ZnS and Ge are very normal optical thin film materials in Infrared wave. Studying the influence of different substrate baking temperature to refractive index and actual deposition rates is very important to promote optical thin film quality. In the same vacuum level, monitoring thickness and evaporation rate, we use hot evaporation to deposit ZnS thin film materials and use ion-assisted electron beam to deposit Ge thin film materials with different baking temperature. We measure the spectral transmittance with the spectrophotometer and calculate the actual deposition rates and the refractive index in different temperature. With the higher and higher temperature in a particular range, ZnS and Ge refractive index become higher and actual deposition rates become smaller. The refractive index of Ge film material change with baking temperature is more sensitive than ZnS. However, ZnS film actual deposition rates change with baking temperature is more sensitive than Ge.

  5. Thermally Stable Nanocrystalline Steel

    NASA Astrophysics Data System (ADS)

    Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

    2017-10-01

    Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

  6. Nano-crystalline thin and nano-particulate thick TiO{sub 2} layer: Cost effective sequential deposition and study on dye sensitized solar cell characteristics

    SciTech Connect

    Das, P.; Sengupta, D.; Kasinadhuni, U.; Mondal, B.; Mukherjee, K.

    2015-06-15

    Highlights: • Thin TiO{sub 2} layer is deposited on conducting substrate using sol–gel based dip coating. • TiO{sub 2} nano-particles are synthesized using hydrothermal route. • Thick TiO{sub 2} particulate layer is deposited on prepared thin layer. • Dye sensitized solar cells are made using thin and thick layer based photo-anode. • Introduction of thin layer in particulate photo-anode improves the cell efficiency. - Abstract: A compact thin TiO{sub 2} passivation layer is introduced between the mesoporous TiO{sub 2} nano-particulate layer and the conducting glass substrate to prepare photo-anode for dye-sensitized solar cell (DSSC). In order to understand the effect of passivation layer, other two DSSCs are also developed separately using TiO{sub 2} nano-particulate and compact thin film based photo-anodes. Nano-particles are prepared using hydrothermal synthesis route and the compact passivation layer is prepared by simply dip coating the precursor sol prepared through wet chemical route. The TiO{sub 2} compact layer and the nano-particles are characterised in terms of their micro-structural features and phase formation behavior. It is found that introduction of a compact TiO{sub 2} layer in between the mesoporous TiO{sub 2} nano-particulate layer and the conducting substrate improves the solar to electric conversion efficiency of the fabricated cell. The dense thin passivation layer is supposed to enhance the photo-excited electron transfer and prevent the recombination of photo-excited electrons.

  7. Synthesis of fibrous reticulate nanocrystalline n-type MoBi{sub 2}(Se{sub 1−x}Te{sub x}){sub 5} thin films: Thermocooling applications

    SciTech Connect

    Salunkhe, Manauti M.; Kharade, Rohini R.; Kharade, Suvarta D.; Mali, Sawanta S.; Patil, P.S.; Bhosale, P.N.

    2012-11-15

    Graphical abstract: Ostwald ripening: If small nucleus is close to a larger crystal, ions formed by particle dissolution of smaller crystal incorporated into larger crystal, and film formation takes place by ion by ion condensation. Display Omitted Highlights: ► Arrested Precipitation Technique is applied to deposit MoBi{sub 2}(Se{sub 1−x}Te{sub x}){sub 5}. ► X-ray diffraction confirms the proper phase formation of material. ► MoBi{sub 2}(Se{sub 1−x}Te{sub x}){sub 5} exhibits an n-type semiconducting behavior. ► Good thermoelectric performance suggests future fantasy. -- Abstract: In the present investigation n-type MoBi{sub 2}(Se{sub 1−x}Te{sub x}){sub 5} nanocrystalline thin films with various compositions of Se and Te were successfully deposited on ultrasonically cleaned glass substrates using recently developed Arrested Precipitation Technique (APT). The effect of composition on optical, morphological, structural, electrical and thermocooling properties of MoBi{sub 2}(Se{sub 1−x}Te{sub x}){sub 5} were investigated using UV–vis–NIR Spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometer, thermoelectric power and thermocooling measurements. Thermoelectric properties including electrical conductivity (σ), Seeback coefficient (S) and figure of merit (ZT) were measured at 300 K. Our aim is to investigate thermocooling behavior in respect of variation in composition of Se and Te in MoBi{sub 2}(Se{sub 1−x}Te{sub x}){sub 5} thin films along with optostructural and optoelectric properties.

  8. Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Das, N. S.; Chattopadhyay, K. K.

    2014-07-01

    BiVO4 thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO4 target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO4 target material was prepared through solid-state reaction method by heating Bi2O3 and V2O5 mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV-Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO4 thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO4 thin films have been investigated in detail. Dielectric properties of the BiVO4 thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO4 thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO4.

  9. Creating bulk nanocrystalline metal.

    SciTech Connect

    Fredenburg, D. Anthony; Saldana, Christopher J.; Gill, David D.; Hall, Aaron Christopher; Roemer, Timothy John; Vogler, Tracy John; Yang, Pin

    2008-10-01

    Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

  10. In situ spectroelectrochemical and theoretical study on the oxidation of a 4H-imidazole-ruthenium dye adsorbed on nanocrystalline TiO2 thin film electrodes.

    PubMed

    Zhang, Ying; Kupfer, Stephan; Zedler, Linda; Schindler, Julian; Bocklitz, Thomas; Guthmuller, Julien; Rau, Sven; Dietzek, Benjamin

    2015-11-28

    Terpyridine 4H-imidazole-ruthenium(II) complexes are considered promising candidates for use as sensitizers in dye sensitized solar cells (DSSCs) by displaying broad absorption in the visible range, where the dominant absorption features are due to metal-to-ligand charge transfer (MLCT) transitions. The ruthenium(III) intermediates resulting from photoinduced MLCT transitions are essential intermediates in the photoredox-cycle of the DSSC. However, their photophysics is much less studied compared to the ruthenium(II) parent systems. To this end, the structural alterations accompanying one-electron oxidation of the RuIm dye series (including a non-carboxylic RuIm precursor, and, carboxylic RuImCOO in solution and anchored to a nanocrystalline TiO2 film) are investigated via in situ experimental and theoretical UV-Vis absorption and resonance Raman (RR) spectroelectrochemistry. The excellent agreement between the experimental and the TDDFT spectra derived in this work allows for an in-depth assignment of UV-Vis and RR spectral features of the dyes. A concordant pronounced wavelength dependence with respect to the charge transfer character has been observed for the model system RuIm, and both RuImCOO in solution and attached on the TiO2 surface. Excitation at long wavelengths leads to the population of ligand-to-metal charge transfer states, i.e. photoreduction of the central ruthenium(III) ion, while high-energy excitation features an intra-ligand charge transfer state localized on the 4H-imidazole moiety. Therefore, these 4H-imidazole ruthenium complexes investigated here are potential multi-photoelectron donors. One electron is donated from MLCT states, and additionally, the 4H-imidazole ligand reveals electron-donating character with a significant contribution to the excited states of the ruthenium(III) complexes upon blue-light irradiation.

  11. Efficient preparation of nanocrystalline anatase TiO{sub 2} and V/TiO{sub 2} thin layers using microwave drying and/or microwave calcination technique

    SciTech Connect

    Zabova, H.; Sobek, J.; Cirkva, V.; Solcova, O.; Kment, S.; Hajek, M.

    2009-12-15

    This study has demonstrated that the synthesis of TiO{sub 2} and V/TiO{sub 2} thin layers may be significantly improved and extended if microwave energy is employed during the drying and/or calcination step. Thin nanoparticulate titania layers were prepared via the sol-gel method using titanium n-butoxide as a precursor. As prepared films were then analyzed by means of various characterization techniques (Raman spectroscopy, UV/Vis, AFM, XPS) in order to determine their functional properties. The photocatalytic activities of prepared layers were quantified by the decoloring rate of Rhodamine B. All thermal treatments in microwave field were done in the same manner, by using an IR pyrometer in the microwave oven and monitoring the temperature of the heating. Nevertheless the microwave and thermally prepared materials were different. This in turn may lead to differences in their functional and also photocatalytic properties. - Graphical abstract: This study has demonstrated that the synthesis of thin layers may be improved and extended if microwave energy is employed during the preparation process. Microwave processing has the potential to reduce the time, cost and energy input for the production of thin layers.

  12. Luminescent Processes Elucidated by Simple Experiments on ZnS.

    ERIC Educational Resources Information Center

    Schwankner, R.; And Others

    1981-01-01

    Describes some impurity-related optical properties of semiconductors, with special emphasis on the luminescence of zinc sulfide (ZnS). Presents and interprets five experiments using a ZnS screen, ultraviolet lamp, transparent Dewar liquid nitrogen, and a helium/neon gas base. Includes application of luminescence measurements to archaeology. (SK)

  13. Luminescent Processes Elucidated by Simple Experiments on ZnS.

    ERIC Educational Resources Information Center

    Schwankner, R.; And Others

    1981-01-01

    Describes some impurity-related optical properties of semiconductors, with special emphasis on the luminescence of zinc sulfide (ZnS). Presents and interprets five experiments using a ZnS screen, ultraviolet lamp, transparent Dewar liquid nitrogen, and a helium/neon gas base. Includes application of luminescence measurements to archaeology. (SK)

  14. Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes--an improved model for nanocrystalline thin films and a review of experimental data.

    PubMed

    Korte, C; Keppner, J; Peters, A; Schichtel, N; Aydin, H; Janek, J

    2014-11-28

    A phenomenological and analytical model for the influence of strain effects on atomic transport in columnar thin films is presented. A model system consisting of two types of crystalline thin films with coherent interfaces is assumed. Biaxial mechanical strain ε0 is caused by lattice misfit of the two phases. The conjoined films consist of columnar crystallites with a small diameter l. Strain relaxation by local elastic deformation, parallel to the hetero-interface, is possible along the columnar grain boundaries. The spatial extent δ0 of the strained hetero-interface regions can be calculated, assuming an exponential decay of the deformation-forces. The effect of the strain field on the local ionic transport in a thin film is then calculated by using the thermodynamic relation between (isostatic) pressure and free activation enthalpy ΔG(#). An expression describing the total ionic transport relative to bulk transport of a thin film or a multilayer as a function of the layer thickness is obtained as an integral average over strained and unstrained regions. The expression depends only on known material constants such as Young modulus Y, Poisson ratio ν and activation volume ΔV(#), which can be combined as dimensionless parameters. The model is successfully used to describe own experimental data from conductivity and diffusion studies. In the second part of the paper a comprehensive literature overview of experimental studies on (fast) ion transport in thin films and multilayers along solid-solid hetero-interfaces is presented. By comparing and reviewing the data the observed interface effects can be classified into three groups: (i) transport along interfaces between extrinsic ionic conductors (and insulator), (ii) transport along an open surface of an extrinsic ionic conductor and (iii) transport along interfaces between intrinsic ionic conductors. The observed effects in these groups differ by about five orders of magnitude in a very consistent way. The

  15. Efficient preparation of nanocrystalline anatase TiO 2 and V/TiO 2 thin layers using microwave drying and/or microwave calcination technique

    NASA Astrophysics Data System (ADS)

    Žabová, H.; Sobek, J.; Církva, V.; Šolcová, O.; Kment, Š.; Hájek, M.

    2009-12-01

    This study has demonstrated that the synthesis of TiO 2 and V/TiO 2 thin layers may be significantly improved and extended if microwave energy is employed during the drying and/or calcination step. Thin nanoparticulate titania layers were prepared via the sol-gel method using titanium n-butoxide as a precursor. As prepared films were then analyzed by means of various characterization techniques (Raman spectroscopy, UV/Vis, AFM, XPS) in order to determine their functional properties. The photocatalytic activities of prepared layers were quantified by the decoloring rate of Rhodamine B. All thermal treatments in microwave field were done in the same manner, by using an IR pyrometer in the microwave oven and monitoring the temperature of the heating. Nevertheless the microwave and thermally prepared materials were different. This in turn may lead to differences in their functional and also photocatalytic properties.

  16. Growth of Zn1- x Cd x O nanocrystalline thin films by sol-gel method and their characterization for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Munirah; Khan, Ziaul Raza; Khan, Mohd. Shahid; Aziz, Anver

    2014-12-01

    This paper describes the growth of Cd doped ZnO thin films on a glass substrate via sol-gel spin coating technique. The effect of Cd doping on ZnO thin films was investigated using X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence spectroscopy, I-V characteristics and field emission scanning electron microscopy (FESEM). X-ray diffraction patterns showed that the films have preferred orientation along (002) plane with hexagonal wurtzite structure. The average crystallite sizes decreased from 24 nm to 9 nm, upon increasing of Cd doping. The films transmittance was found to be very high (92 to 95 %) in the visible region of solar spectrum. The optical band gap of ZnO and Cd doped ZnO thin films was calculated using the transmittance spectra and was found to be in the range of 3.30 to 2.77 eV. On increasing Cd concentration in ZnO binary system, the absorption edge of the films showed the red shifting. Photoluminescence spectra of the films showed the characteristic band edge emission centred over 377 to 448 nm. Electrical characterization revealed that the films had semiconducting and light sensitive behaviour.

  17. Highly efficient nanocrystalline ZnO thin films prepared by a novel method and their application in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Bahadur, Lal; Kushwaha, Suman

    2012-11-01

    Nanostructured ZnO aggregates are synthesized under controlled conditions using zinc acetate dihydrate and 1-butanol as the starting materials and triethylamine as precipitating agent. Thin films were formed by a doctor-blade technique. The phase and morphology were investigated by using SEM and XRD. These films, derivatized by N719 dye, (Bu4N)2[Ru(dcbpyH)2(NCS)2], were used to construct sandwich-type dye-sensitized solar cells (DSSCs) and their photoelectrochemical characteristics were determined. The photocurrent, photovoltage and power conversion efficiency characteristics for the DSSCs were measured under illumination by light of varied irradiance power. With a typical cell, V OC=0.518 V, J SC=11.1 mA cm-2, fill factor (FF)=0.50, overall conversion efficiency ( η)=0.69 % and incident photon to current conversion efficiency (IPCE)=35 % were achieved under full light illumination (430 mW cm-2) and V OC=0.516 V, J SC=8.72 mA cm-2, fill factor 0.54 and overall conversion efficiency η=0.64 % were achieved under visible light illumination (380 mW cm-2). With the use of a thin ZnO film prepared during the present work, improved results have been achieved than many of the earlier reported ones. The good structural quality (crystallinity, densely packed spherical grains, lack of voids, nanometer-size crystallites etc.) of our thin films is mainly responsible for their better photoactivity.

  18. Structural properties of single step electrochemically deposited ZnS nanofibers

    NASA Astrophysics Data System (ADS)

    Bhalerao, Anuradha B.; Wagh, B. G.; Lokhande, C. D.

    2013-06-01

    ZnS thin films are prepared by electro deposition technique over stainless steel substrates in potentiostatic mode from an aqueous acidic bath containing ZnSo4 and Na2S2O3. The growth kinetics of the film was studied and the deposition parameters such as electrolyte bath concentration, deposition time, deposition potential and pH of electrolyte bath are optimized. The X-ray diffraction (XRD) analysis of the deposited film showed presence of polycrystalline nature. The surface morphology studied by scanning electron microscope (SEM) shows fibrous morphology with well adherence and uniform distribution of nanosized fibers over the surface of substrate.

  19. Measurements of grain boundary properties in nanocrystalline ceramics

    SciTech Connect

    Chiang, Y.M.; Smyth, I.P.; Terwilliger, C.D. . Dept. of Materials Science and Engineering); Petuskey, W.T. . Dept. of Chemistry); Eastman, J.A. )

    1990-11-01

    The advent of nanocrystalline ceramics prepared by a variety of solution-chemical and vapor deposition methods offers a unique opportunity for the determination grain boundary properties by bulk'' thermodynamic methods. In this paper we discuss results from two types of measurements on model nanocrystalline ceramics. The first is a solution thermodynamic measurement of the activity of nanocrystalline SiC in polycarbosilane-derived silicon carbide fibers (Nicalon). Structural studies have shown that Nicalon consists of well-ordered cubic ({beta} or 3C polytype) SiC grains separated by a very thin grain boundary layer (<1 nm thick) containing the oxygen. The physical properties and chemical reactivity of these fibers are distinctly different from that of bulk silicon carbide. Direct measurement of the alloy composition and analysis of the microstructure has allowed the dissolution reaction to be identified and a lower limit for the SiC activity in the nanocrystalline form to be determined. A second method of measuring grain boundary properties we have investigated for nanocrystalline Si and TiO{sub 2} is high temperature calorimetry. In appropriate samples the grain boundary enthalpy can be measured through the heat evolved during grain growth. Preliminary results on nanocrystalline Si prepared by the recrystallization of amorphous evaporated films and on TiO{sub 2} condensed from the vapor phase are discussed. 29 refs., 3 figs., 1 tab.

  20. Nanocrystalline Cu{sub 2}ZnSnSe{sub 4} thin films for solar cells application: Microdiffraction and structural characterization

    SciTech Connect

    Quiroz, Heiddy P. Dussan, A.

    2016-08-07

    This work presents a study of the structural characterization of Cu{sub 2}ZnSnSe{sub 4} (CZTSe) thin films by X-ray diffraction (XRD) and microdiffraction measurements. Samples were deposited varying both mass (M{sub X}) and substrate temperature (T{sub S}) at which the Cu and ZnSe composites were evaporated. CZTSe samples were deposited by co-evaporation method in three stages. From XRD measurements, it was possible to establish, with increased Ts, the presence of binary phases associated with the quaternary composite during the material's growth process. A stannite-type structure in Cu{sub 2}ZnSnSe{sub 4} thin films and sizes of the crystallites varying between 30 and 40 nm were obtained. X-ray microdiffraction was used to investigate interface orientations and strain distributions when deposition parameters were varied. It was found that around the main peak, 2ϴ = 27.1°, the Cu{sub 1.8}Se and ZnSe binary phases predominate, which are formed during the subsequent material selenization stage. A Raman spectroscopy study revealed Raman shifts associated with the binary composites observed via XRD.

  1. Optimization of the ZnS Buffer Layer by Chemical Bath Deposition for Cu(In,Ga)Se2 Solar Cells.

    PubMed

    Jeon, Dong-Hwan; Hwang, Dae-Kue; Kim, Dae-Hwan; Kang, Jin-Kyu; Lee, Chang-Seop

    2016-05-01

    We evaluated a ZnS buffer layer prepared using a chemical bath deposition (CBD) process for application in cadmium-free Cu(In,Ga)Se2 (CIGS) solar cells. The ZnS buffer layer showed good transmittance (above 90%) in the spectral range from 300 to 800 nm and was non-toxic compared with the CdS buffer layers normally used in CIGS solar cells. The CBD process was affected by several deposition conditions. The deposition rate was dependent on the ammonia concentration (complexing agent). When the ammonia concentration was either too high or low, a decrease in the deposition rate was observed. In addition, post heat treatments at high temperatures had detrimental influences on the ZnS buffer layers because portions of the ZnS thin films were transformed into ZnO. With optimized deposition conditions, a CIGS solar cell with a ZnS buffer layer showed an efficiency of 14.18% with a 0.23 cm2 active area under 100 mW/cm2 illumination.

  2. New route to the fabrication of nanocrystalline diamond films

    SciTech Connect

    Varshney, Deepak Morell, Gerardo; Palomino, Javier; Resto, Oscar; Gil, Jennifer; Weiner, Brad R.

    2014-02-07

    Nanocrystalline diamond (NCD) thin films offer applications in various fields, but the existing synthetic approaches are cumbersome and destructive. A major breakthrough has been achieved by our group in the direction of a non-destructive, scalable, and economic process of NCD thin-film fabrication. Here, we report a cheap precursor for the growth of nanocrystalline diamond in the form of paraffin wax. We show that NCD thin films can be fabricated on a copper support by using simple, commonplace paraffin wax under reaction conditions of Hot Filament Chemical Vapor Deposition (HFCVD). Surprisingly, even the presence of any catalyst or seeding that has been conventionally used in the state-of-the-art is not required. The structure of the obtained films was analyzed by scanning electron microscopy and transmission electron microscopy. Raman spectroscopy and electron energy-loss spectroscopy recorded at the carbon K-edge region confirm the presence of nanocrystalline diamond. The process is a significant step towards cost-effective and non-cumbersome fabrication of nanocrystalline diamond thin films for commercial production.

  3. New route to the fabrication of nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Varshney, Deepak; Palomino, Javier; Gil, Jennifer; Resto, Oscar; Weiner, Brad R.; Morell, Gerardo

    2014-02-01

    Nanocrystalline diamond (NCD) thin films offer applications in various fields, but the existing synthetic approaches are cumbersome and destructive. A major breakthrough has been achieved by our group in the direction of a non-destructive, scalable, and economic process of NCD thin-film fabrication. Here, we report a cheap precursor for the growth of nanocrystalline diamond in the form of paraffin wax. We show that NCD thin films can be fabricated on a copper support by using simple, commonplace paraffin wax under reaction conditions of Hot Filament Chemical Vapor Deposition (HFCVD). Surprisingly, even the presence of any catalyst or seeding that has been conventionally used in the state-of-the-art is not required. The structure of the obtained films was analyzed by scanning electron microscopy and transmission electron microscopy. Raman spectroscopy and electron energy-loss spectroscopy recorded at the carbon K-edge region confirm the presence of nanocrystalline diamond. The process is a significant step towards cost-effective and non-cumbersome fabrication of nanocrystalline diamond thin films for commercial production.

  4. Effect of solvent volume on the physical properties of aluminium doped nanocrystalline zinc oxide thin films deposited using a simplified spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Jabena Begum, N.; Mohan, R.; Ravichandran, K.

    2013-01-01

    Aluminium doped zinc oxide (AZO) thin films were deposited by employing a low cost and simplified spray technique using a perfume atomizer from starting solutions having different volumes (10, 20, … , 50 mL) of solvent. The effect of solvent volume on the structural, electrical, optical, photoluminescence (PL) and surface morphological properties was studied. The electrical resistivity of the AZO films is remarkably influenced by the variation in the solvent volume. The X-ray diffraction profiles clearly showed that all the films have preferential orientation along the (0 0 2) plane irrespective of the solvent volume. The crystallite size was found to be in the nano range of 35-46 nm. The optical transmittance in the visible region is desirably high (>85%). The AFM images show columnar morphology with varying grain size. The PL studies revealed that the AZO film deposited from 50 mL of solvent volume has good quality with lesser defect density.

  5. High durability antireflection coatings for silicon and multispectral ZnS

    NASA Astrophysics Data System (ADS)

    Joseph, Shay; Marcovitch, Orna; Yadin, Ygal; Klaiman, Dror; Koren, Nitzan; Zipin, Hedva

    2007-04-01

    In the current complex battle field, military platforms are required to operate on land, at sea and in the air in all weather conditions both day and night. In order to achieve such capabilities, advanced electro-optical systems are being constantly developed and improved. These systems such as missile seeker heads, reconnaissance and target acquisition pods and tracking, monitoring and alert systems have external optical components (window or dome) which must remain operational even at extreme environmental conditions. Depending on the intended use of the system, there are a few choices of window and dome materials. Amongst the more common materials one can point out sapphire, ZnS, germanium and silicon. Other materials such as spinel, ALON and yittria may also be considered. Most infrared materials have high indices of refraction and therefore they reflect a large part of radiation. To minimize the reflection and increase the transmission, antireflection (AR) coatings are the most common choice. Since these systems operate at different environments and weather conditions, the coatings must be made durable to withstand these extreme conditions. In cases where the window or dome is made of relatively soft materials such as multispectral ZnS, the coating may also serve as protection for the window or dome. In this work, several antireflection coatings have been designed and manufactured for silicon and multispectral ZnS. The coating materials were chosen to be either oxides or fluorides which are known to have high durability. Ellipsometry measurements were used to characterize the optical constants of the thin films. The effects of the deposition conditions on the optical constants of the deposited thin films and durability of the coatings will be discussed. The coatings were tested according to MIL-STD-810E and were also subjected to rain erosion tests at the University of Dayton Research Institute (UDRI) whirling arm apparatus in which one of the coatings showed

  6. Synthesis and optical characterization of n-ZnO and p-Cu2ZnSnS4 nanocrystalline thin films for low cost solar cells

    NASA Astrophysics Data System (ADS)

    Abdel-Galil, A.; Balboul, M. R.

    2016-12-01

    High quality ZnO/Cu2ZnSnS4 thin films as a window/absorber layers were successfully synthesized via spin coating the sol-gel precursor of each composition without using any vacuum facilities. In this study, the impact of annealing temperature (400 °C, 3 h) on the ZnO window layer and different thickness (3 and 5 layers) of the Cu2ZnSnS4 (CZTS) absorber layer were investigated. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM) and UV-vis-NIR spectroscopy were used for the structural, compositional, morphological and optical absorption analysis of each layer. ZnO exhibits wurtzite hexagonal crystal structure with particle size equals to 8.60 and 28.59 nm for fresh and annealed films, respectively. Micro-strain and dislocations density decreased with the annealing temperature. X-ray diffraction patterns for CZTS films show small peak at (112) according to the kesterite structure with particle size in nano-scale for the two thicknesses. ZnO films demonstrated direct optical band gap of 3.23 and 3.21 eV for fresh and annealed films, respectively. CZTS films (3 and 5 layers) also have direct optical band with optimum value (1.51 eV) for thickness of 5 layers. The J-V characteristics of the CZTS-based thin film solar cells (CZTS/ZnO/ZnO:Ag) were measured under air mass AM 1.5 and 100 mW/cm2 illumination. The values of the short circuit current (Jsc), open circuit voltage (Voc) and fill factor (FF) also have been obtained.

  7. Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputtering

    SciTech Connect

    Abadias, G.; Tse, Y.Y.; Guerin, Ph.; Pelosin, V.

    2006-06-01

    To clarify the underlying mechanisms that cause the preferred orientation in TiN films, we investigated the evolution with the thickness of the texture, surface morphology, and residual stress in TiN thin films deposited by dual ion beam sputtering. The films, with thickness h ranging from 50 to 300 nm, were grown on oxidized Si substrates using a primary Ar ion beam accelerated under 1.2 kV and different voltages V{sub a} of the (Ar+N{sub 2}) assistance beam: 25, 50, and 150 V. The influence of temperature was also investigated by varying the substrate temperature T{sub s} (25-300 deg. C) during growth or by performing a postdeposition annealing. X-ray diffraction (XRD) as well as transmission electron microscopy were used to study the microstructure and changes of texture with thickness h, while x-ray reflectivity and atomic force microscopy measurements were performed to determine the surface roughness. Residual stresses were measured by XRD and analyzed using a triaxial stress model. The crystallite group method was used for a strain determination of crystallites having different fiber axis directions, i.e., when a mixed texture exists. The surface roughness is found to increase with V{sub a} and T{sub s} due to the resputtering effect of the film surface. XRD reveals that for a small thickness (h{approx}50 nm) the TiN films exhibit a strong (002) texture independent of V{sub a}. For a larger thickness (100

  8. Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputtering

    NASA Astrophysics Data System (ADS)

    Abadias, G.; Tse, Y. Y.; Guérin, Ph.; Pelosin, V.

    2006-06-01

    To clarify the underlying mechanisms that cause the preferred orientation in TiN films, we investigated the evolution with the thickness of the texture, surface morphology, and residual stress in TiN thin films deposited by dual ion beam sputtering. The films, with thickness h ranging from 50 to 300 nm, were grown on oxidized Si substrates using a primary Ar ion beam accelerated under 1.2 kV and different voltages Va of the (Ar+N2) assistance beam: 25, 50, and 150 V. The influence of temperature was also investigated by varying the substrate temperature Ts (25-300 °C) during growth or by performing a postdeposition annealing. X-ray diffraction (XRD) as well as transmission electron microscopy were used to study the microstructure and changes of texture with thickness h, while x-ray reflectivity and atomic force microscopy measurements were performed to determine the surface roughness. Residual stresses were measured by XRD and analyzed using a triaxial stress model. The crystallite group method was used for a strain determination of crystallites having different fiber axis directions, i.e., when a mixed texture exists. The surface roughness is found to increase with Va and Ts due to the resputtering effect of the film surface. XRD reveals that for a small thickness (h~50 nm) the TiN films exhibit a strong (002) texture independent of Va. For a larger thickness (100

  9. 3-D solar cells by electrochemical-deposited Se layer as extremely-thin absorber and hole conducting layer on nanocrystalline TiO2 electrode

    NASA Astrophysics Data System (ADS)

    Nguyen, Duy-Cuong; Tanaka, Souichirou; Nishino, Hitoshi; Manabe, Kyohei; Ito, Seigo

    2013-01-01

    A three-dimensional selenium solar cell with the structure of Au/Se/porous TiO2/compact TiO2/fluorine-doped tin oxide-coated glass plates was fabricated by an electrochemical deposition method of selenium, which can work for the extremely thin light absorber and the hole-conducting layer. The effect of experimental conditions, such as HCl and H2SeO3 in an electrochemical solution and TiO2 particle size of porous layers, was optimized. This kind of solar cell did not use any buffer layer between an n-type electrode (porous TiO2) and a p-type absorber layer (selenium). The crystallinity of the selenium after annealing at 200°C for 3 min in the air was significantly improved. The cells with a selenium layer deposited at concentrations of HCl = 11.5 mM and H2SeO3 = 20 mM showed the best performance, resulting in 1- to 2-nm thickness of the Se layer, short-circuit photocurrent density of 8.7 mA/cm2, open-circuit voltage of 0.65 V, fill factor of 0.53, and conversion efficiency of 3.0%.

  10. 3-D solar cells by electrochemical-deposited Se layer as extremely-thin absorber and hole conducting layer on nanocrystalline TiO2 electrode.

    PubMed

    Nguyen, Duy-Cuong; Tanaka, Souichirou; Nishino, Hitoshi; Manabe, Kyohei; Ito, Seigo

    2013-01-03

    A three-dimensional selenium solar cell with the structure of Au/Se/porous TiO2/compact TiO2/fluorine-doped tin oxide-coated glass plates was fabricated by an electrochemical deposition method of selenium, which can work for the extremely thin light absorber and the hole-conducting layer. The effect of experimental conditions, such as HCl and H2SeO3 in an electrochemical solution and TiO2 particle size of porous layers, was optimized. This kind of solar cell did not use any buffer layer between an n-type electrode (porous TiO2) and a p-type absorber layer (selenium). The crystallinity of the selenium after annealing at 200°C for 3 min in the air was significantly improved. The cells with a selenium layer deposited at concentrations of HCl = 11.5 mM and H2SeO3 = 20 mM showed the best performance, resulting in 1- to 2-nm thickness of the Se layer, short-circuit photocurrent density of 8.7 mA/cm2, open-circuit voltage of 0.65 V, fill factor of 0.53, and conversion efficiency of 3.0%.

  11. Influence of RF excitation during pulsed laser deposition in oxygen atmosphere on the structural properties and luminescence of nanocrystalline ZnO:Al thin films

    SciTech Connect

    Meljanac, Daniel Plodinec, Milivoj; Siketić, Zdravko; Gracin, Davor; Juraić, Krunoslav; Bernstorff, Sigrid

    2016-03-15

    Thin ZnO:Al layers were deposited by pulsed laser deposition in vacuum and in oxygen atmosphere at gas pressures between 10 and 70 Pa and by applying radio-frequency (RF) plasma. Grazing incidence small angle x-ray scattering and grazing incidence x-ray diffraction (GIXRD) data showed that an increase in the oxygen pressure leads to an increase in the roughness, a decrease in the sample density, and changes in the size distribution of nanovoids. The nanocrystal sizes estimated from GIXRD were around 20 nm, while the sizes of the nanovoids increased from 1 to 2 nm with the oxygen pressure. The RF plasma mainly influenced the nanostructural properties and point defects dynamics. The photoluminescence consisted of three contributions, ultraviolet (UV), blue emission due to Zn vacancies, and red emission, which are related to an excess of oxygen. The RF excitation lowered the defect level related to blue emission and narrowed the UV luminescence peak, which indicates an improvement of the structural ordering. The observed influence of the deposition conditions on the film properties is discussed as a consequence of two main effects: the variation of the energy transfer from the laser plume to the growing film and changes in the growth chemistry.

  12. Effect of Ni and Au ion irradiations on structural and optical properties of nanocrystalline Sb-doped SnO2 thin films

    NASA Astrophysics Data System (ADS)

    Mir, Feroz A.; Batoo, Khalid Mujasam

    2016-04-01

    The effect of shift heavy ion irradiations on the structural and optical properties of 6 % Sb-doped SnO2 thin films deposited on quartz substrate by electron beam evaporation technique is presented. Two ion species Ni and Au with energy 120 MeV and fluence of 1 × 1013 ion/cm2 were used. These films were characterized by X-ray diffraction, atomic force microscope, UV-visible and micro-Raman spectroscopy. From structural analysis, these films exhibit tetragonal rutile structure and retain it even after irradiation. The ion irradiations have shown improvement in the structural properties, such as increase in grain size and decrease in the lattice strain. Raman study also indicates enhancement in quality of crystal structure after irradiations. The grain growth after ion interaction is also observed by atomic force microscope study. Further, a variation in optical band gap and reduction in disorder is observed after irradiation. Other parameters such as Urbach tails energy and steepness parameter are obtained from optical data. The overall observed physical properties show a significant improvement after irradiation. A good correspondence between structures with its various properties can be seen.

  13. ZnO nanorods decorated with ZnS nanoparticles

    SciTech Connect

    Joicy, S.; Sivakumar, P.; Thangadurai, P.; Ponpandian, N.

    2015-06-24

    In this study, ZnO nanorods (NRs) and ZnS nanoparticles decorated ZnO-NRs were prepared by a combination of hydrothermal and hydrolysis method. Structural and optical properties of the samples were studied by XRD, FE-SEM, UV-Vis DRS and photoluminescence spectroscopy. Microscopy analysis revealed that the diameter of ZnO-NRs was ∼500 nm and the length was ranging from a few hundred nm to several micrometers and their surface was decorated with ZnS nanoparticles. UV-Vis DRS showed the absorption of ZnS decorated ZnO-NRs was blue shifted with respect to pure ZnO-NRs which enhanced the separation of electron-hole pairs. PL spectrum of ZnS decorated ZnO-NRs showed a decrease in intensity of UV and green emissions with the appearance of blue emission at 436 nm.

  14. Magnetism in undoped ZnS nanotetrapods.

    PubMed

    Shan, Aixian; Liu, Wei; Wang, Rongming; Chen, Chinping

    2013-02-21

    The magnetism of undoped ZnS nanotetrapods, synthesized by a solvothermal method, has been investigated by magnetization measurements and first principle numerical calculations. The background magnetic impurity concentrations of Fe, Co and Ni were determined at ppm level by inductively coupled plasma mass spectrometry (ICP-MS). Hysteresis loops of weak ferromagnetism were observed, attributable to the magnetic impurities. However, the total magnetic moments analyzed from the paramagnetism are far beyond the explanations from the presence of these magnetic impurities, by about two orders of magnitude larger. It implies a different origin of the magnetic moments. Electron microscopy analysis reveals that there are defects in the sample. Numerical simulations indicate that the excessive magnetic moments might arise from the local band structure of polarized electrons associated with the defects of cation deficiency. This study elaborates on the understanding of magnetic properties in the non-magnetic II-VI semiconductor nanomaterials.

  15. Nanocrystalline heterojunction materials

    DOEpatents

    Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

    2003-07-15

    Mesoporous nanocrystalline titanium dioxide heterojunction materials are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

  16. Nanocrystalline Heterojunction Materials

    DOEpatents

    Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

    2004-02-03

    Mesoporous nanocrystalline titanium dioxide heterojunction materials and methods of making the same are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

  17. Nanocrystalline coatings properties forecasting

    NASA Astrophysics Data System (ADS)

    Eremin, E. N.; Yurov, V. M.; Guchenko, S. A.; Laurynas, V. Ch

    2017-06-01

    The paper considers various properties of nanocrystalline coatings. The methods of determining the surface tension of the deposited coating on the basis of the size dependence of their physical properties. It is shown that predict the mechanical properties of the coatings, their melting point, heat resistance, wear resistance, corrosion resistance, etc. It can be based on a theoretical evaluation of the surface tension.

  18. Optical properties of nanocrystalline WO{sub 3} and WO{sub 3-x} thin films prepared by DC magnetron sputtering

    SciTech Connect

    Johansson, Malin B. Niklasson, Gunnar A.; Österlund, Lars; Zietz, Burkhard

    2014-06-07

    The optical properties of tungsten trioxide thin films prepared by DC magnetron sputtering, with different oxygen vacancy (V{sub o}) concentration, have been studied by spectrophotometry and photoluminescence (PL) emission spectroscopy. Absorption and PL spectra show that the films exhibit similar band gap energies, E{sub g} ≈ 2.9 eV. The absorption spectra of the films show two pronounced absorption bands in the near-infrared region. One peak (P1) is located at approximately 0.7 eV, independent of V{sub o} concentration. A second peak (P2) shifts from 0.96 eV to 1.16 eV with decreasing V{sub o} concentration. Peak P1 is assigned to polaron absorption due to transitions between tungsten sites (W{sup 5+} → W{sup 6+}), or an optical transition from a neutral vacancy state to the conduction band, V{sub o}{sup 0} → W{sup 6+}. The origin of peak P2 is more uncertain but may involve +1 and +2 charged vacancy sites. The PL spectra show several emission bands in the range 2.07 to 3.10 eV in the more sub-stoichiometric and 2.40 to 3.02 eV in the less sub-stoichiometric films. The low energy emission bands agree well with calculated optical transition energies of oxygen vacancy sites, with dominant contribution from neutral and singly charged vacancies in the less sub-stoichiometric films, and additional contributions from doubly charged vacancy sites in the more sub-stoichiometric films.

  19. Novel microwave assisted synthesis of ZnS nanomaterials.

    PubMed

    Synnott, Damian W; Seery, Michael K; Hinder, Steven J; Colreavy, John; Pillai, Suresh C

    2013-02-01

    A novel ambient pressure microwave assisted technique is developed in which silver and indium-modified ZnS is synthesized. The as-prepared ZnS is characterized by x-ray diffraction, UV-vis spectroscopy, x-ray photoelectron spectroscopy and luminescence spectroscopy. This procedure produced crystalline materials with particle sizes below 10 nm. The synthesis technique leads to defects in the crystal which induce mid-energy levels in the band gap and lead to indoor light photocatalytic activity. Increasing the amount of silver causes a phase transition from cubic blende to hexagonal phase ZnS. In a comparative study, when the ZnS cubic blende is heated in a conventional chamber furnace, it is completely converted to ZnO at 600 °C. Both cubic blende and hexagonal ZnS show excellent photocatalytic activity under irradiation from a 60 W light bulb. These ZnS samples also show significantly higher photocatalytic activity than the commercially available TiO(2) (Evonik-Degussa P-25).

  20. Novel microwave assisted synthesis of ZnS nanomaterials

    NASA Astrophysics Data System (ADS)

    Synnott, Damian W.; Seery, Michael K.; Hinder, Steven J.; Colreavy, John; Pillai, Suresh C.

    2013-02-01

    A novel ambient pressure microwave assisted technique is developed in which silver and indium-modified ZnS is synthesized. The as-prepared ZnS is characterized by x-ray diffraction, UV-vis spectroscopy, x-ray photoelectron spectroscopy and luminescence spectroscopy. This procedure produced crystalline materials with particle sizes below 10 nm. The synthesis technique leads to defects in the crystal which induce mid-energy levels in the band gap and lead to indoor light photocatalytic activity. Increasing the amount of silver causes a phase transition from cubic blende to hexagonal phase ZnS. In a comparative study, when the ZnS cubic blende is heated in a conventional chamber furnace, it is completely converted to ZnO at 600 °C. Both cubic blende and hexagonal ZnS show excellent photocatalytic activity under irradiation from a 60 W light bulb. These ZnS samples also show significantly higher photocatalytic activity than the commercially available TiO2 (Evonik-Degussa P-25).

  1. Ultrasonic Emission from Nanocrystalline Porous Silicon

    NASA Astrophysics Data System (ADS)

    Shinoda, Hiroyuki; Koshida, Nobuyoshi

    A simple layer structure composed of a metal thin film and a porous silicon layer on a silicon substrate generates intense and wide-band airborne ultrasounds. The large-bandwidth and the fidelity of the sound reproduction are leveraged in applications varying from sound-based measurement to a scientific study of animal ecology. This chapter describes the basic principle of the ultrasound generation. The macroscopic properties of the low thermal conductivity and the small heat capacity of nanocrystalline porous silicon thermally induce ultrasonic emission. The state-of-the-art of the achievable sound pressure and sound signal properties is introduced, with the technological and scientific applications of the devices.

  2. Near unity photon-to-electron conversion efficiency of photoelectrochemical cells built on cationic water-soluble porphyrins electrostatically decorated onto thin-film nanocrystalline SnO₂ surface.

    PubMed

    Subbaiyan, Navaneetha K; Maligaspe, Eranda; D'Souza, Francis

    2011-07-01

    Thin transparent SnO(2) films have been surface modified with cationic water-soluble porphyrins for photoelectrochemical investigations. Free-base and zinc(II) derivatives of three types of cationic water-soluble porphyrins, (P)M, viz., tetrakis(N-methylpyridyl)porphyrin chloride, (TMPyP)M, tetrakis(trimethylanilinium)porphyrin chloride, (TAP)M, and tetrakis(4'-N-methylimidazolyl-phenyl)porphyrin iodide, (TMIP)M, (M = 2H or Zn) are employed. The negative surface charge and the porous structure of SnO(2) facilitated binding of positively charged porphyrins via electrostatic interactions, in addition to strong electronic interactions in the case of (TMPyP)M binding to nanocrystalline SnO(2). The SnO(2)-porphyrin binding in solution was probed by absorption spectroscopy which yielded apparent binding constants in the range of 1.5-2.6 × 10(4) M(-1). Both steady-state and time-resolved fluorescence studies revealed quenching of porphyrin emission upon binding to SnO(2) in water suggesting electron injection from singlet excited porphyrin to SnO(2) conduction band. Addition of LiClO(4) weakened the ion-paired porphyrin-SnO(2) binding as revealed by reversible emission changes. Over 80% of the quenched fluorescence was recovered in the case of (TMPyP)M and (TAP)M compounds but not for (TMIP)M suggesting stronger binding of the latter to SnO(2) surface. Photoelectrochemical studies performed on FTO/SnO(2)/(P)M electrodes revealed incident photon-to-current conversion efficiencies (IPCE) up to 91% at the peak maxima for the SnO(2)-dye modified electrodes, with very good on-off switchability. The high IPCE values have been attributed to the strong electrostatic and electronic interactions between the dye, (TMPyP)M and SnO(2) nanoparticles that would facilitate better charge injection from the excited porphyrin to the conduction band of the semiconductor. Electrochemical impedance spectral measurements of electron recombination resistance calculations were supportive of this

  3. Single-material multilayer ZnS as anti-reflective coating for solar cell applications

    NASA Astrophysics Data System (ADS)

    Salih, Ammar T.; Najim, Aus A.; Muhi, Malek A. H.; Gbashi, Kadhim R.

    2017-04-01

    Multilayer Zinc Sulfide (ZnS) is a promising low cost antireflective coating for solar cell applications, in this work; thin films with novel structure containing cubic and hexagonal phases were successfully deposited by thermal evaporation technique with three different layers. XRD analysis confirms the existence of both phases and high specific surface area. AFM analysis reveals that films with three layers have lower roughness and average grain size than other films. The optical measurements obtained by UV-vis, the calculated values of refractive index and reflectivity using some well known refractive index-band gap relations indicate that thin films with triple layer TL-ZnS have lower refractive index and reflectivity than other films, empirical equations were suggested and show the quantum confinement effects on band gap and reflectivity.

  4. Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

    2017-08-01

    Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

  5. Optical characteristics of nanocrystalline Al{sub x}Ga{sub 1−x}N thin films deposited by hollow cathode plasma-assisted atomic layer deposition

    SciTech Connect

    Goldenberg, Eda; Ozgit-Akgun, Cagla; Biyikli, Necmi; Kemal Okyay, Ali

    2014-05-15

    Gallium nitride (GaN), aluminum nitride (AlN), and Al{sub x}Ga{sub 1−x}N films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200 °C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al{sub x}Ga{sub 1−x}N films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2 nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4 nm when the annealing duration increased from 30 min to 2 h (800 °C). For all films, the average optical transmission was ∼85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and Al{sub x}Ga{sub 1−x}N were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (λ = 550 nm) with the increased Al content x (0 ≤ x ≤ 1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400 nm). Postdeposition annealing at 900 °C for 2 h considerably lowered the refractive index value of GaN films (2.33–1.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95 eV, and it decreased to 3.90 eV for films annealed at 800 °C for 30 min and 2 h. On the other hand, this value increased to 4.1 eV for GaN films annealed at 900 °C for 2 h. This might be caused by Ga{sub 2}O{sub 3} formation and following phase change. The optical bandgap value of as-deposited Al{sub x}Ga{sub 1−x}N films decreased from 5.75 to 5.25 eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not

  6. In situ observation of deformation processes in nanocrystalline face-centered cubic metals.

    PubMed

    Kobler, Aaron; Brandl, Christian; Hahn, Horst; Kübel, Christian

    2016-01-01

    The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline Pd x Au1- x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin-twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains.

  7. In situ observation of deformation processes in nanocrystalline face-centered cubic metals

    PubMed Central

    Kobler, Aaron; Brandl, Christian; Hahn, Horst

    2016-01-01

    Summary The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline PdxAu1− x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin–twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains. PMID:27335747

  8. Enhanced charge separation at 2D MoS2/ZnS heterojunction: KPFM based study of interface photovoltage

    NASA Astrophysics Data System (ADS)

    Sharma, Intu; Mehta, B. R.

    2017-02-01

    Two dimensional (2D) MoS2/ZnS heterojunctions with MoS2 thickness varying from monolayer to bulk have been prepared by sulfurization of a controlled thickness of Mo deposited on the ZnS thin films. Kelvin probe force microscopy measurements on MoS2/ZnS junction having varying thicknesses of MoS2 layers are carried out in the surface and junction modes, under white light exposure. Differences in the surface potential values of the surface and junction modes represent interface photovoltages at heterojunctions. Enhanced interface photovoltage is observed in junctions having the mono and few layer MoS2 in comparison to bulk MoS2 layer. This suggests the active participation of 2D MoS2 layer in photon absorption and charge separation processes taking place close to the junction. The present study is an effort towards the integration of 2D layered materials with 3D semiconductors, which may be advantageous for the development of 2D material based optoelectronic devices.

  9. Role of ZnS shell on stability, cytotoxicity, and photocytotoxicity of water-soluble CdSe semiconductor quantum dots surface modified with glutathione

    NASA Astrophysics Data System (ADS)

    Ibrahim, Salwa Ali; Ahmed, Wafaa; Youssef, Tareq

    2014-09-01

    Biomedical applications of quantum dots (QDs) have become a subject of a considerable concern in the past few decades. The present study examines the stability and cytotoxicity of two QDs systems in cell culture medium in the presence and absence of a thin layer of ZnS shell. The two systems were built from core, CdSe QDs, surface modified with glutathione (GSH), named CdSe˜GSH and CdSe/ZnS˜GSH. Our results demonstrated that 0.7 nm layer of ZnS shell played a significant role in the stability of CdSe/ZnS~GSH QDs in supplemented cell culture medium (RPMI). Also, a significant improvement in the physicochemical properties of the core CdSe QDs was shown by maintaining their spectroscopic characteristics in RPMI medium due to the wide band gap of ZnS shell. Both systems showed insignificant reduction in cell viability of HFB-4 or MCF-7 cell lines in the dark which was attributed to the effective GSH coating. Following photoirradiation with low laser power (irradiance 10 mW cm-2), CdSe~GSH QDs showed a significant decrease in cell viability after 60 min irradiation which may result from detachment of GSH molecules. Under the same irradiation condition, CdSe/ZnS~GSH QDs showed insignificant decrease in cell viability or after 2 h incubation from laser irradiation which was attributed to the strong binding between ZnS and GSH coatings. It can be concluded that the stability of CdSe core QDs was significantly improved in cell culture medium by encapsulation with a thin layer of ZnS shell whereas their cytotoxicity and photo-cytotoxicity are highly dependent on surface modification.

  10. Photocatalytic studies of capped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdeep; Sharma, Manoj; Pandey, O. P.

    2013-06-01

    In this work, we report on the synthesis of ZnS semiconductor nanoparticles stabilized with sodium hexa meta phosphate (SHMP). Capped ZnS nanoparticles were synthesized by a chemical route. The as obtained nanoparticles were characterized by X-ray diffraction (XRD), uv-vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. The average particle size was found to be 2-3 nm. UV-Vis optical spectra showed a blue shift with respect to the bulk counterpart. The room temperature photoluminescence spectra of the nanoparticles showed emission peaks in the range of 363 - 446 nm at excitation wavelength of 325 nm for different concentrations of SHMP. Photocatalytic degradation of bromophenol blue dye was done using capped ZnS nanoparticles. It took about 3.5 hours to degrade the dye completely under uv irradiation.

  11. Luminescence from ZnS: Bulk vs nano

    NASA Astrophysics Data System (ADS)

    Mishra, R. K.; Kamal, Satya; Patel, D. K.; Rao, K. Ramachandra; Sudarsan, V.; Vatsa, R. K.

    2015-06-01

    Based on the detailed luminescence studies on bulk and nanoparticles of ZnS, it is inferred that the defect emission due to zinc (VZn) and sulfur (VS) vacancies in ZnS, significantly change in terms of line shape and peak position, when bulk form is converted to nanoparticles. From the XRD studies, this has been explained in terms of difference in the crystalline modifications of ZnS, namely the wurtzite and cubic forms. Copper doping in the sample quenches the luminescence and stabilize the cubic phase. Bright blue electro luminescence (efficiency of around 1.5 %) with CIE coordinates (0.18. 0.11) could be seen from bulk ZnS:Cu sample. Unlike this the nanoparticles did not give any emission due to the quenching of charge carriers/excitons. Lifetime values further supported these inferences.

  12. Effect of UV irradiation on evaporated ZnS films

    NASA Technical Reports Server (NTRS)

    Hass, G.; Heaney, J. B.; Hunter, W. R.; Angel, D. W.

    1980-01-01

    Evaporated ZnS films used as a component in reflectance enhancing or decreasing multilayer coatings for mirrors, transparent optical materials, and vacuum UV reflecting optics, are investigated with reference to the reflectance loss under UV irradiation and the formation of ZnO as a result of the decomposition of ZnS in the presence of oxygen. Reflectance measurements over a broad wavelength range reveal that the UV induced reflectance losses are generally restricted to wavelengths shorter than 4000 A and are most severe in the vacuum UV region. After 134 hr of UV exposure initially polycrystalline film of 150-200 A thick is completely converted to amorphous ZnO. The results demonstrate that caution should be exercised in employing ZnS as the outer layer in an optical coating system designed for use in the UV and vacuum UV regions.

  13. Research of annular polishing asymmetric ZnS plane window

    NASA Astrophysics Data System (ADS)

    Guo, Weijin; Tong, Yi; Jin, Yuzhu; Lin, Nana

    2016-10-01

    Due the annular polishing technology for planar optical components do not have the sharp selectivity, annular polishing technology is a very import process to fabricate irregular planar elements which with high precision surface shape and low surface roughness. According to the characteristics of annular polishing, the zns asymmetric plane window annular polishing process and key technical parameters control was researched. In this paper, one pair of asymmetric planar ZnS window parts were machined which diagonal length is 147mm, through technology experiments, obtained process test samples. The surface figures of the plane zns window are measured by a Zygo interferometer and the reflect wavefront P-V value is better than 1.5λ, the reflect wavefront local error rms value is better than 0.05λ (λ=632.8nm). Experiments results demonstrate the effectiveness of annular processing technology was used to manufacture zinc sulfide asymmetric shape plane window.

  14. ZnS micro-Fresnel lens and its uses.

    PubMed

    Hosokawa, H; Yamashita, T

    1990-12-01

    A micro-Fresnel lens replication method by inorganic material deposition has been developed. A ZnS micro-Fresnel lens and a completely flat micro-Fresnel lens have been made by this method. The ZnS microFresnel lens stability characteristics are improved for temperature, humidity, and focusing. Furthermore, higher resolution in electron-beam lithography is made possible by lens thickness reduction. The completely flat micro-Fresnel lens is a new device and improves integration performance. This lens can be applied to stacked planar optics devices for use in the construction of 3-D optical circuits.

  15. Scanning near-field optical microscope working with a CdSe /ZnS quantum dot based optical detector

    NASA Astrophysics Data System (ADS)

    Aigouy, L.; Samson, B.; Julié, G.; Mathet, V.; Lequeux, N.; Nı. Allen, C.; Diaf, H.; Dubertret, B.

    2006-06-01

    We have developed a scanning near-field optical microscope that uses a subwavelength-sized silica sphere covered with CdSe /ZnS quantum dots as a fluorescent optical detector. Due to the good photostability of these semiconducting particles, we are routinely able to perform several successive scans without a noticeable decrease of fluorescence signals. As an example, we will show some images of the light immediately transmitted through 300nm wide slits made in a thin gold film. We will also discuss the advantages of such fluorescent probes compared to other near-field optical techniques.

  16. Magnetism in nanocrystalline gold.

    PubMed

    Tuboltsev, Vladimir; Savin, Alexander; Pirojenko, Alexandre; Räisänen, Jyrki

    2013-08-27

    While bulk gold is well known to be diamagnetic, there is a growing body of convincing experimental and theoretical work indicating that nanostructured gold can be imparted with unconventional magnetic properties. Bridging the current gap in experimental study of magnetism in bare gold nanomaterials, we report here on magnetism in gold nanocrystalline films produced by cluster deposition in the aggregate form that can be considered as a crossover state between a nanocluster and a continuous film. We demonstrate ferromagnetic-like hysteretic magnetization with temperature dependence indicative of spin-glass-like behavior and find this to be consistent with theoretical predictions, available in the literature, based on first-principles calculations.

  17. Starch-assisted synthesis and optical properties of ZnS nanoparticles

    SciTech Connect

    Tian, Xiuying Wen, Jin; Wang, Shumei; Hu, Jilin; Li, Jing; Peng, Hongxia

    2016-05-15

    Highlights: • ZnS spherical nanostructure was prepared via starch-assisted method. • The crystalline lattice structure, morphologies, chemical and optical properties of ZnS nanoparticles. • The forming mechanism of ZnS nanoparticles. • ZnS spherical nano-structure can show blue emission at 460–500 nm. - Abstract: ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130 nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2 μm. The band gap value of ZnS is 3.97 eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.

  18. Effect of Cr doping on structural and magnetic properties of ZnS nanoparticles

    SciTech Connect

    Virpal,; Singh, Jasvir; Sharma, Sandeep; Singh, Ravi Chand

    2016-05-23

    The structural, optical and magnetic properties of pure and Cr doped ZnS nanoparticles were studied at room temperature. X-ray diffraction analysis confirmed the absence of any mixed phase and the cubic structure of ZnS in pure and Cr doped ZnS nanoparticles. Fourier transfer infrared spectra confirmed the Zn-S stretching bond at 664 cm{sup −1} of ZnS in all prepared nanoparticles. The UV-Visible absorption spectra showed blue shift which became even more pronounced in Cr doped ZnS nanoparticles. However, at relatively higher Cr concentrations a slower red shift was shown by the doped nanoparticles. This phenomenon is attributed to sp-d exchange interaction that becomes prevalent at higher doping concentrations. Further, magnetic hysteresis measurements showed that Cr doped ZnS nanoparticles exhibited ferromagnetic behavior at room temperature.

  19. ZnS nanostructure arrays: a developing material star.

    PubMed

    Fang, Xiaosheng; Wu, Limin; Hu, Linfeng

    2011-02-01

    Semiconductor nanostructure arrays are of great scientific and technical interest because of the strong non-linear and electro-optic effects that occur due to carrier confinement in three dimensions. The use of such nanostructure arrays with tailored geometry, array density, and length-diameter-ratio as building blocks are expected to play a crucial role in future nanoscale devices. With the unique properties of a direct wide-bandgap semiconductor, such as the presence of polar surfaces, excellent transport properties, good thermal stability, and high electronic mobility, ZnS nanostructure arrays has been a developing material star. The research on ZnS nanostructure arrays has seen remarkable progress over the last five years due to the unique properties and important potential applications of nanostructure arrays, which are summarized here. Firstly, a survey of various methods to the synthesis of ZnS nanostructure arrays will be introduced. Next recent efforts on exploiting the unique properties and applications of ZnS nanostructure arrays are discussed. Potential future directions of this research field are also highlighted.

  20. A review on ZnS phosphor degradation

    NASA Astrophysics Data System (ADS)

    Swart, H. C.

    2004-08-01

    Standard ZnS cathodoluminescent phosphors normally lose brightness upon bombardment with electron beams. The main reason for the degradation is the formation of a non-luminescent dead layer on the surface due to the electron stimulated surface chemical reaction (ESSCR) mechanism. The decrease in luminance was found to be a result of the growth of the dead layer. Calculations showed that the thickness of the oxide layer that formed during electron bombardment, cannot completely explain the magnitude of the decline of the CL intensity. Iso-electronic point defects due to the presence of oxygen that diffuse into the ZnS matrix at the interface further contribute to the degradation. When the ZnS phosphor powder was exposed to the electron beam in a water-rich O2 ambient, a chemically-limited ZnO layer was formed on the surface. A layer of ZnSO4 was formed on the surface during the electron beam degradation of the ZnS phosphor powder in a dry O2 ambient.

  1. Texture evolution in nanocrystalline iron films deposited using biased magnetron sputtering

    SciTech Connect

    Vetterick, G.; Taheri, M. L.; Baldwin, J. K.; Misra, A.

    2014-12-21

    Fe thin films were deposited on sodium chloride (NaCl) substrates using magnetron sputtering to investigate means of texture control in free standing metal films. The Fe thin films were studied using transmission electron microscopy equipped with automated crystallographic orientation microscopy. Using this technique, the microstructure of each film was characterized in order to elucidate the effects of altering deposition parameters. The natural tendency for Fe films grown on (100) NaCl is to form a randomly oriented nanocrystalline microstructure. By careful selection of substrate and deposition conditions, it is possible to drive the texture of the film toward a single (100) orientation while retaining the nanocrystalline microstructure.

  2. A new approach to grain boundary engineering for nanocrystalline materials

    PubMed Central

    Tsurekawa, Sadahiro; Watanabe, Tadao

    2016-01-01

    A new approach to grain boundary engineering (GBE) for high performance nanocrystalline materials, especially those produced by electrodeposition and sputtering, is discussed on the basis of some important findings from recently available results on GBE for nanocrystalline materials. In order to optimize their utility, the beneficial effects of grain boundary microstructures have been seriously considered according to the almost established approach to GBE. This approach has been increasingly recognized for the development of high performance nanocrystalline materials with an extremely high density of grain boundaries and triple junctions. The effectiveness of precisely controlled grain boundary microstructures (quantitatively characterized by the grain boundary character distribution (GBCD) and grain boundary connectivity associated with triple junctions) has been revealed for recent achievements in the enhancement of grain boundary strengthening, hardness, and the control of segregation-induced intergranular brittleness and intergranular fatigue fracture in electrodeposited nickel and nickel alloys with initial submicrometer-grained structure. A new approach to GBE based on fractal analysis of grain boundary connectivity is proposed to produce high performance nanocrystalline or submicrometer-grained materials with desirable mechanical properties such as enhanced fracture resistance. Finally, the potential power of GBE is demonstrated for high performance functional materials like gold thin films through precise control of electrical resistance based on the fractal analysis of the grain boundary microstructure. PMID:28144533

  3. A new approach to grain boundary engineering for nanocrystalline materials.

    PubMed

    Kobayashi, Shigeaki; Tsurekawa, Sadahiro; Watanabe, Tadao

    2016-01-01

    A new approach to grain boundary engineering (GBE) for high performance nanocrystalline materials, especially those produced by electrodeposition and sputtering, is discussed on the basis of some important findings from recently available results on GBE for nanocrystalline materials. In order to optimize their utility, the beneficial effects of grain boundary microstructures have been seriously considered according to the almost established approach to GBE. This approach has been increasingly recognized for the development of high performance nanocrystalline materials with an extremely high density of grain boundaries and triple junctions. The effectiveness of precisely controlled grain boundary microstructures (quantitatively characterized by the grain boundary character distribution (GBCD) and grain boundary connectivity associated with triple junctions) has been revealed for recent achievements in the enhancement of grain boundary strengthening, hardness, and the control of segregation-induced intergranular brittleness and intergranular fatigue fracture in electrodeposited nickel and nickel alloys with initial submicrometer-grained structure. A new approach to GBE based on fractal analysis of grain boundary connectivity is proposed to produce high performance nanocrystalline or submicrometer-grained materials with desirable mechanical properties such as enhanced fracture resistance. Finally, the potential power of GBE is demonstrated for high performance functional materials like gold thin films through precise control of electrical resistance based on the fractal analysis of the grain boundary microstructure.

  4. Probing nanocrystalline grain dynamics in nanodevices

    PubMed Central

    Yeh, Sheng-Shiuan; Chang, Wen-Yao; Lin, Juhn-Jong

    2017-01-01

    Dynamical structural defects exist naturally in a wide variety of solids. They fluctuate temporally and hence can deteriorate the performance of many electronic devices. Thus far, the entities of these dynamic objects have been identified to be individual atoms. On the other hand, it is a long-standing question whether a nanocrystalline grain constituted of a large number of atoms can switch, as a whole, reversibly like a dynamical atomic defect (that is, a two-level system). This is an emergent issue considering the current development of nanodevices with ultralow electrical noise, qubits with long quantum coherence time, and nanoelectromechanical system sensors with ultrahigh resolution. We demonstrate experimental observations of dynamic nanocrystalline grains that repeatedly switch between two or more metastable coordinate states. We study temporal resistance fluctuations in thin ruthenium dioxide (RuO2) metal nanowires and extract microscopic parameters, including relaxation time scales, mobile grain sizes, and the bonding strengths of nanograin boundaries. These material parameters are not obtainable by other experimental approaches. When combined with previous in situ high-resolution transmission electron microscopy, our electrical method can be used to infer rich information about the structural dynamics of a wide variety of nanodevices and new two-dimensional materials. PMID:28691094

  5. Silver nanowire composite thin films as transparent electrodes for Cu(In,Ga)Se₂/ZnS thin film solar cells.

    PubMed

    Tan, Xiao-Hui; Chen, Yu; Liu, Ye-Xiang

    2014-05-20

    Solution processed silver nanowire indium-tin oxide nanoparticle (AgNW-ITONP) composite thin films were successfully applied as the transparent electrodes for Cu(In,Ga)Se₂ (CIGS) thin film solar cells with ZnS buffer layers. Properties of the AgNW-ITONP thin film and its effects on performance of CIGS/ZnS thin film solar cells were studied. Compared with the traditional sputtered ITO electrodes, the AgNW-ITONP thin films show comparable optical transmittance and electrical conductivity. Furthermore, the AgNW-ITONP thin film causes no physical damage to the adjacent surface layer and does not need high temperature annealing, which makes it very suitable to use as transparent conductive layers for heat or sputtering damage-sensitive optoelectronic devices. By using AgNW-ITONP electrodes, the required thickness of the ZnS buffer layers for CIGS thin film solar cells was greatly decreased.

  6. A Facile Method for the Synthesis Fluorescent Zinc Chalcogenide (ZnO, ZnS and ZnSe) Nanoparticles in PS and PMMA Polymer Matrix.

    PubMed

    Hariharan, P S; Subhashini, N; Vasanthalakshmi, J; Anthony, Savarimuthu Philip

    2016-03-01

    A simple method for the synthesis of fluorescent zinc chalcogenide (ZnO, ZnS and ZnSe) nanoparticles directly in the transparent PMMA and PS polymer matrices were reported. Highly dispersed small spherical ZnO nanoparticles (3-5 nm) was obtained by hydrothermal reaction of PMMA/PS-Zn(acac)2H2O in toluene. ZnS and ZnSe nanoparticles were prepared by heterogeneous stirring of PMMA/PS-Zn(acac)2H2O in toluene with aqueous solution of thiourea or NaHSe. Interestingly, ZnO and ZnS-PMMA thin film showed strong fluorescence quenching upon exposure to ammonia.

  7. Optical and photocatalytic properties of Corymbia citriodora leaf extract synthesized ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Jinfeng; Hu, Binjie; Zhi, Jinhu

    2016-05-01

    ZnS nanoparticles were biosynthesized via a green and simple method using Corymbia citriodora leaf extract as reducing and stabilizing agent. The biosynthesized ZnS nanoparticles were in the size range of 45 nm with a surface plasmon resonance band at 325 nm. XRD analysis revealed that the nanoparticles were in the sphalerite phase. Quantum confinement effects of biosynthesized ZnS nanoparticles were observed using photoluminescence spectroscopy. The photocatalytic activity of the ZnS nanoparticles has been investigated by degradation methylene blue under UV light irradiation. Due to the smaller size and excellent dispersicity, the biosynthesized ZnS nanoparticles showed a superior photocatalytic performance compared with that of chemical synthesize ZnS nanoparticles.

  8. Synthesis and enhanced humidity detection response of nanoscale Au-particle-decorated ZnS spheres

    PubMed Central

    2014-01-01

    We successfully prepared Au-nanoparticle-decorated ZnS (ZnS-Au) spheres by sputtering Au ultrathin films on surfaces of hydrothermally synthesized ZnS spheres and subsequently postannealed the samples in a high-vacuum atmosphere. The Au nanoparticles were distributed on ZnS surfaces without substantial aggregation. The Au nanoparticle diameter range was 5 to 10 nm. Structural information showed that the surface of the annealed ZnS-Au spheres became more irregular and rough. A humidity sensor constructed using the Au-nanoparticle-decorated ZnS spheres demonstrated a substantially improved response to the cyclic change in humidity from 11% relative humidity (RH) to 33% to 95% RH at room temperature. The improved response was associated with the enhanced efficiency of water molecule adsorption onto the surfaces of the ZnS because of the surface modification of the ZnS spheres through noble-metal nanoparticle decoration. PMID:25520595

  9. Ferromagnetic properties of Cu-doped ZnS: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Yan, Huiyu; Li, Yuqi; Guo, Yanrui; Song, Qinggong; Chen, Yifei

    2011-02-01

    Using plane-wave pseudopotential (PWPP) method, the magnetism and spin-resolved electronic properties of Cu-doped ZnS system are studied. Our calculations indicate that ferromagnetic (FM) state is ground state in Cu-doped ZnS. The FM coupling strength in ZnS doping with Cu fluctuates with the variation of distance between two dopants and the fluctuation gets larger with increase in distance. Room temperature ferromagnetism can be observed in Cu-doped ZnS with high dopant concentration. Formation energy calculation implies that the clustering effect is not obvious in Cu-doped ZnS. Thus, Cu-doped ZnS can be a promising dilute magnetic semiconductor (DMS), which promises to be free of magnetic precipitates.

  10. Photoluminescence study of ZnS and ZnS:Pb nanoparticles

    SciTech Connect

    Virpal, Hastir, Anita; Kaur, Jasmeet; Singh, Gurpreet; Singh, Ravi Chand

    2015-05-15

    Photoluminescence (PL) study of pure and 5wt. % lead doped ZnS prepared by co-precipitation method was conducted at room temperature. The prepared nanoparticles were characterized by X-ray Diffraction (XRD), UV-Visible (UV-Vis) spectrophotometer, Photoluminescence (PL) and Raman spectroscopy. XRD patterns confirm cubic structure of ZnS and PbS in doped sample. The band gap energy value increased in case of Pb doped ZnS nanoparticles. The PL spectrum of pure ZnS was de-convoluted into two peaks centered at 399nm and 441nm which were attributed to defect states of ZnS. In doped sample, a shoulder peak at 389nm and a broad peak centered at 505nm were observed. This broad green emission peak originated due to Pb activated ZnS states.

  11. Effect of ZnS nanoparticles on the photoluminescence of Sm3+ ions in methanol

    NASA Astrophysics Data System (ADS)

    Kakoti, D.; Rajkonwar, N.; Dehingia, N.; Boruah, A.; Gogoi, P.; Dutta, P.

    2016-10-01

    ZnS nanoparticles co-doped with Sm3+ ions were prepared in methanol medium for fixed Sm3+ and varying ZnS concentrations. Enhancements in absorption as well as photoluminescence efficiency of the co-doped samples were observed. This enhanced efficiency is attributed to the effective increase in oscillator strengths of the Sm3+ transitions because of the addition of ZnS nanoparticles.

  12. Laser-induced refractive index changes in nanocrystalline diamond membranes.

    PubMed

    Preclíková, Jana; Kromka, Alexander; Rezek, Bohuslav; Malý, Petr

    2010-02-15

    We have observed what we believe to be a new phenomenon in nanocrystalline diamond membranes. The optical thickness of the membrane is changed under laser irradiation, which leads to a spectral shift of interference fringes in the transmission and photoluminescence spectra of high-quality thin self-supporting nanocrystalline membranes. The direction of the spectral shift (red/blue) can be tuned by the ambient air pressure. The effect is reversible and is accompanied by changes in photoluminescence intensity. We interpret the results in terms of the changes in the index of refraction caused by the photoinduced adsorption/desorption of air molecules that subsequently affect the properties of subgap energy states related to the surface and the grain boundaries of the nanocrystals.

  13. Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

    SciTech Connect

    Vukoje, Ivana D.; Tomašević-Ilić, Tijana D.; Zarubica, Aleksandra R.; Dimitrijević, Suzana; Budimir, Milica D.; Vranješ, Mila R.; Šaponjić, Zoran V.; Nedeljković, Jovan M.

    2014-12-15

    Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical and morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.

  14. CTAB-Assisted Solvothermal Growth and Optical Characterization of Flower-Like ZnS Structures

    NASA Astrophysics Data System (ADS)

    Roy, J. S.; Pal Majumder, T.

    2016-08-01

    Flower-like ZnS structures have been prepared by solvothermal method with the assistance of cetyl trimethyl ammonium bromide (CTAB). The effects of different experimental conditions on the morphology of ZnS structure have been investigated. The performances of ZnS structures have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), room temperature photoluminescence (PL), and UV-visible absorption spectroscopy. The XRD patterns indicate that the prepared ZnS structures are highly crystallized, which are of hexagonal phase. The SEM images indicate that the main role of CTAB is to assemble the ZnS flakes together to form the flower-like structures, and the reaction time affects the morphology of ZnS. The growth mechanism for the formation of flower-like ZnS structure is also described. The absorption and emission bands gradually shift towards longer wavelength due to the transformation of flower-like ZnS nanoflowers from ZnS flakes.

  15. Synthesis and spectroscopic investigations of Cu- and Pb-doped colloidal ZnS nanocrystals.

    PubMed

    Ehlert, Oliver; Osvet, Andres; Batentschuk, Miroslaw; Winnacker, Albrecht; Nann, Thomas

    2006-11-23

    A novel organometallic synthesis method for the preparation of colloidal ZnS nanoparticles is presented. This method enables the synthesis of undoped ZnS nanocrystals as well as doping with Cu, Pb, or both. The particles can be covered with an undoped layer of ZnS, forming core/shell-type particles with the ZnS:Pb, ZnS:Cu, or ZnS:Cu,Pb cores. The particles were characterized via TEM, XRD, dynamic light scattering, and optical spectroscopy. We investigated the extrinsic surface defects and their coverage with an additional ZnS layer in detail by temperature-dependent luminescence and luminescence lifetime spectroscopy.

  16. Comparison of crystal growth and thermoelectric properties of n-type Bi-Se-Te and p-type Bi-Sb-Te nanocrystalline thin films: Effects of homogeneous irradiation with an electron beam

    SciTech Connect

    Takashiri, Masayuki Imai, Kazuo; Uyama, Masato; Nishi, Yoshitake; Hagino, Harutoshi; Miyazaki, Koji; Tanaka, Saburo

    2014-06-07

    The effects of homogenous electron beam (EB) irradiation on the crystal growth and thermoelectric properties of n-type Bi-Se-Te and p-type Bi-Sb-Te thin films were investigated. Both types of thin films were prepared by flash evaporation, after which homogeneous EB irradiation was performed at an acceleration voltage of 0.17 MeV. For the n-type thin films, nanodots with a diameter of less than 10 nm were observed on the surface of rice-like nanostructures, and crystallization and crystal orientation were improved by EB irradiation. The resulting enhancement of mobility led to increased electrical conductivity and thermoelectric power factor for the n-type thin films. In contrast, the crystallization and crystal orientation of the p-type thin films were not influenced by EB irradiation. The carrier concentration increased and mobility decreased with increased EB irradiation dose, possibly because of the generation of defects. As a result, the thermoelectric power factor of p-type thin films was not improved by EB irradiation. The different crystallization behavior of the n-type and p-type thin films is attributed to atomic rearrangement during EB irradiation. Selenium in the n-type thin films is more likely to undergo atomic rearrangement than the other atoms present, so only the crystallinity of the n-type Bi-Se-Te thin films was enhanced.

  17. Formation of ZnS nanorods by simple evaporation technique

    NASA Astrophysics Data System (ADS)

    Velumani, S.; Ascencio, J. A.

    Semiconductor nanocrystals and nanorods whose properties are largely determined by the quantum confinement effect are currently being intensively studied by materials scientists, physicists and chemists. Zinc sulphide (ZnS), a II-VI group semiconductor material possessing a direct band gap of 3.66 eV, has recently been extensively investigated due to its multifaceted applications. We report the synthesis of ZnS nanorods by a simple physical vapor deposition method and an in-detail surface analysis for device applications. Our interest in this material mainly lies behind its use as an n-window layer for our investigations on different window layers for CdTe- and CIS (Copper Indium diselenide) based solar cells and for photocatalytic production of hydrogen from water using the photocatalysts CdS/ZnS. ZnS films are deposited onto well-cleaned glass substrates at a vacuum of 5×10-5 Torr and various parameters are determined. The distance between the substrate and the source was maintained at 0.15 cm. The deposition time was about 20 min at a constant rate of evaporation and the substrates were maintained at room temperature. Structural analysis reveals the cubic nature of the crystallites, which is confirmed from atomic force microscopy (AFM) analysis. The AFM analysis reveals the formation of nanorods due to coalescence, which is substantiated from sectional analysis. A further analysis reveals the preferential growth of the nanorods and the coalescence limited by the energy in the (002) face. The composition was analyzed using an energy-dispersive X-ray method (EDX) and the film was found to possess excess sulfur. The band gap of the vacuum-deposited ZnS film was found to be 3.6 eV.

  18. Microstructural Properties of Chemically Synthesized Cubic ZnS Nanocrystals

    NASA Astrophysics Data System (ADS)

    Deka, Kuldeep; Kalita, M. P. C.

    2015-02-01

    In this paper we present microstructural properties of chemically synthesized cubic zinc sulfide (ZnS) nanocrystals, investigated by X-ray diffraction (XRD) line profile analysis applying classical Williamson-Hall (WH) and modified Williamson-Hall (MWH) methods, and transmission electron microscopy (TEM) observations. ZnS nanocrystals are synthesized using 1:1 M ratio of Zn and S precursors with 25, 50, and 75 mM, 2-mercaptoethanol as capping agent. WH analyses show that the average crystallite sizes (lattice strain) are 3.98 nm (2.22 × 10-2), 2.69 nm (1.99 × 10-2), and 2.58 nm (2.65 × 10-2). Dislocation contrast factors of ZnS crystals required for the MWH method are calculated from their elastic stiffness constants for various proportions of screw and edge dislocations. The best fit to MWH equation is found to be for dislocation contrast factors corresponding to 100 % edge dislocations and thereby suggesting edge dislocations are main contributors to strain. MWH analyses show dislocation density of 3.65, 2.69, and 2.47 nm crystallites are 3.19 × 1018 m-2, 2.58 × 1018 m-2, and 4.62 × 1018 m-2 , respectively. The crystallite sizes as estimated from the WH, MWH, and TEM studies are found to be intercorrelated. Presence of edge dislocations, as suggested by the MWH analysis, is confirmed by high resolution TEM (HRTEM) studies.

  19. Frozen ZnS Aqueous Suspension Nonlinear Optical Properties

    NASA Astrophysics Data System (ADS)

    Ehrlich, H.; Kudryavtseva, A.; Lisichkin, G.; Savranskii, V.; Tcherniega, N.; Zemskov, K.; Zhilenko, M.

    2015-11-01

    The study of nonlinear effects, caused by nanosecond laser pulses' impact on the frozen ZnS nanoparticles' suspension, is presented. Laser pulses excite strong nanoparticles' coherent vibrations in the near-terahertz range which lead to different nonlinear effects: X-ray emission, stimulated low-frequency Raman scattering, and luminescence. X-ray emission was observed as bright spots on the special X-ray film. This provides evidence that an X-ray propagates with narrow beams. Stimulated low-frequency Raman scattering is a result of light scattering by acoustic vibrations of nanoparticles. Its frequency shift corresponds to the nanoparticles' eigenvibration frequencies and depends on the sample material and particle's dimension. It was measured with the help of a Fabri-Perot interferometer in the range of dispersion 16.67 {cm}^{-1}. For ZnS, the first Stokes component frequency shift is equal to 465 GHz. Under excitation by 20 ns ruby laser pulses, the luminescence of the frozen ZnS nanoparticles' suspension was observed in two bands located at 480 nm and 510 nm. Its duration was more than 3 s.

  20. Multicolor electroluminescent devices using doped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Manzoor, K.; Vadera, S. R.; Kumar, N.; Kutty, T. R. N.

    2004-01-01

    Alternate-current electroluminescent (ac EL) devices based on doped ZnS nanocrystals emitting blue, green, and orange-red colors are reported. ZnS nanocrystals doped with Cu+-Al3+ and Cu+-Al3+-Mn2+ combinations were synthesized by wet chemical method at room temperature. The ZnS:Cu+, Al3+ nanocrystals show blue (462 nm) and green (530 nm) EL emissions depending upon the presence and absence of sulphur vacancies, respectively. The orange EL emission (590 nm) is realized from ZnS:Cu+, Al3+, Mn2+ nanoparticles by way of nonradiative energy transfer from AlZn-CuZn pairs to MnZn. The EL devices show low turn-on voltage of ˜10 V ac @100 Hz. The mechanism of ac EL in ZnS nanocrystals has been explained wherein the excitation is attributed to the electric-field-assisted injection of electron-hole pairs from the surface regions into the interiors and their subsequent recombination therein causes emission.

  1. Heterogeneous ZnS hollow urchin-like hierarchical nanostructures and their structure-enhanced photocatalytic properties.

    PubMed

    Liu, Jun; Guo, Zaiping; Wang, Wenjun; Huang, Qingsong; Zhu, Kaixing; Chen, Xiaolong

    2011-04-01

    Hexagonal wurtzite ZnS nanowires radially arrayed on cubic zinc-blende ZnS hollow spheres have been successfully achieved for the first time, and such novel heterogeneous ZnS hollow urchin-like hierarchical nanostructures show greatly enhanced photocatalytic properties due to their two-phase enhanced light-harvesting and high surface-to-volume ratio.

  2. Laser Compression of Nanocrystalline Metals

    NASA Astrophysics Data System (ADS)

    Meyers, M. A.; Jarmakani, H. N.; Bringa, E. M.; Earhart, P.; Remington, B. A.; Vo, N. Q.; Wang, Y. M.

    2009-12-01

    Shock compression in nanocrystalline nickel is simulated over a range of pressures (10-80 GPa) and compared with experimental results. Laser compression carried out at Omega and Janus yields new information on the deformation mechanisms of nanocrystalline Ni. Although conventional deformation does not produce hardening, the extreme regime imparted by laser compression generates an increase in hardness, attributed to the residual dislocations observed in the structure by TEM. An analytical model is applied to predict the critical pressure for the onset of twinning in nanocrystalline nickel. The slip-twinning transition pressure is shifted from 20 GPa, for polycrystalline Ni, to 80 GPa, for Ni with g. s. of 10 nm. Contributions to the net strain from the different mechanisms of plastic deformation (partials, perfect dislocations, twinning, and grain boundary shear) were quantified in the nanocrystalline samples through MD calculations. The effect of release, a phenomenon often neglected in MD simulations, on dislocation behavior was established. A large fraction of the dislocations generated at the front are annihilated.

  3. Phase transformation and optical properties of Cu-doped ZnS nanorods

    SciTech Connect

    Datta, Anuja Panda, Subhendu K.; Chaudhuri, Subhadra

    2008-09-15

    ZnS nanorods doped with 0-15 mol% of Cu have been prepared by simple solvothermal process. With gradual increase in the Cu concentration, phase transformation of the doped ZnS nanorods from wurtzite to cubic was observed. Twins and stacking faults were developed due to atomic rearrangement in the heavily doped ZnS nanorods during phase transformation. UV-vis-NIR absorbance spectroscopy ruled out the presence of any impure Cu-S phase. The doped ZnS nanorods showed luminescence over a wide range from UV to near IR with peaks at 370, 492-498, 565 and 730 nm. The UV region peak is due to the near-band-edge transition, whereas, the green peak can be related to emission from elementary sulfur species on the surfaces of the nanorods. The orange emission at 565 nm may be linked to the recombination of electrons at deep defect levels and the Cu(t{sub 2}) states present near the valence band of ZnS. The near IR emission possibly originated from transitions due to deep-level defects. - Graphical abstract: ZnS nanorods doped with 0-15 mol% of Cu has been prepared by simple solvothermal route. Interestingly, phase transformation of the doped ZnS nanorods from wurtzite to cubic was observed with gradual increase in the Cu concentration. Doped ZnS nanorods showed luminescence over a wide range from UV to near IR, which is also a rare observation.

  4. Quantification of Grain Boundary Mediated Plasticity Mechanisms in Nanocrystalline Metals

    NASA Astrophysics Data System (ADS)

    Panzarino, Jason F.

    of nanocrystalline Ni-W thin films. These experiments track the development of a surface grain growth layer which evolves through grain boundary mediated plasticity and we are able to make direct connections between this evolution and that which was observed in our simulation work. All of the findings of this thesis are a direct result of the dynamic and collective nature by which nanocrystalline materials deform.

  5. Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications.

    PubMed

    Sajan, P; Jayasree, R S; Agouram, S; Bushiri, M Junaid

    2016-03-01

    Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo-hydrothermal (S-H) method using water-acetonitrile-ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform (FT)-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380-580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm(-1). Cytotoxicity and haemocompatibility investigations of these ZnS microspheres revealed its biocompatibility. ZnS microspheres, along with biological cell lines, were giving visible light emission and could be used for bioimaging applications.

  6. Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles.

    PubMed

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2013-09-01

    Fe doped ZnS nanoparticles (Zn1-xFexS; where x=0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

  7. Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2013-09-01

    Fe doped ZnS nanoparticles (Zn1-xFexS; where x = 0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

  8. Efficient photoelectric converters of ultraviolet radiation based on ZnS and CdS with low-resistivity surface layers

    SciTech Connect

    Bobrenko, Yu. N.; Pavelets, S. Yu. Pavelets, A. M.; Kiselyuk, M. P.; Yaroshenko, N. V.

    2010-08-15

    The formation of thin high- and low-resistivity layers in the space-charge region of Cu{sub 1.8}S-CdS and Cu{sub 1.8}S-ZnS surface-barrier photoconverter structures leads to a considerable increase in photosensitivity and a reduction in the dark tunneling-recombination currents. Highly efficient and stable ultraviolet photoconverters based on CdS and ZnS were obtained, and their electrical and photoelectrical properties were studied. The main operational parameters of the photoconverters are reported.

  9. Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition.

    PubMed

    Walock, Michael J; Rahil, Issam; Zou, Yujiao; Imhoff, Luc; Catledge, Shane A; Nouveau, Corinne; Stanishevsky, Andrei V

    2012-06-01

    Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.

  10. Reduction of 4-Nitrophenol using electrocatalytic ZnS nanoparticles for counter electrode application in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Subalakshmi, K.; Kumar, K. Ashok; Senthilselvan, J.

    2017-05-01

    Polycrystalline ZnS nanoparticles of c.a 5 nm were synthesized by simple hydrothermal method. X-ray diffraction analysis confirms the formation of cubic zinc blende phase of ZnS. HRSEM image reveals the sample is composed of agglomerated trigonal flake shaped ZnS nanoparticulates. UV-Visible absorption spectrum of ZnS ensures the absorption maximum at 340 nm and its band gap energy is found to be reduced (3.2 eV) owing to its surface light scattering effect. Nyquist plot of ZnS nanoparticles show decrease in electrical resistance with increasing the applied potential resulting in increased conductivity. The fast reduction process of n-nitrophenol (4-NP) into n-aminophenol (4-AP) reveals a high catalytic behavior of ZnS. Hence, the prepared ZnS nanoparticles with high electrical conductivity and catalytic activity can be useful for counter electrode application in DSSC.

  11. Electrical properties of Cu4ZnSnS2/ZnS heterojunction prepared by ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Guitouni, S.; Khammar, M.; Messaoudi, M.; Attaf, N.; Aida, M. S.

    2016-12-01

    Cu2ZnSnS4 (CZTS)/ZnS heterojunctions have been prepared by a successive deposition of ZnS and CZTS thin films by ultrasonic spray pyrolysis technique on glass substrates. The cupric chloride concentration has been varied in the starting solution in order to investigate its influence on device properties. CZTS/ZnS heterojunctions were characterized by recording their current-voltage characteristics at different temperatures. The obtained results exhibit a good rectifying behavior of the realized heterojunction. Analysis of these results yields saturation current, series resistance and ideality factor determination. From the activation energy of saturation current we inferred that the thermal emission through the barrier height is the dominant mechanism of the reverse current rather than the defects contribution.

  12. Single crystalline wurtzite ZnO/zinc blende ZnS coaxial heterojunctions and hollow zinc blende ZnS nanotubes: synthesis, structural characterization and optical properties

    NASA Astrophysics Data System (ADS)

    Huang, Xing; Willinger, Marc-Georg; Fan, Hua; Xie, Zai-Lai; Wang, Lei; Klein-Hoffmann, Achim; Girgsdies, Frank; Lee, Chun-Sing; Meng, Xiang-Min

    2014-07-01

    Synthesis of ZnO/ZnS heterostructures under thermodynamic conditions generally results in the wurtzite (WZ) structure of the ZnS component because its WZ phase is thermodynamically more stable than its zinc blende (ZB) phase. In this report, we demonstrate for the first time the preparation of ZnO/ZnS coaxial nanocables composed of single crystalline ZB structured ZnS epitaxially grown on WZ ZnO via a two-step thermal evaporation method. The deposition temperature is believed to play a crucial role in determining the crystalline phase of ZnS. Through a systematic structural analysis, the ZnO core and the ZnS shell are found to have an orientation relationship of (0002)ZnOWZ//(002)ZnSZB and [01-10]ZnOWZ//[2-20]ZnSZB. Observation of the coaxial nanocables in cross-section reveals the formation of voids between the ZnO core and the ZnS shell during the coating process, which is probably associated with the nanoscale Kirkendall effect known to result in porosity. Furthermore, by immersing the ZnO/ZnS nanocable heterojunctions in an acetic acid solution to etch away the inner ZnO cores, single crystalline ZnS nanotubes orientated along the [001] direction of the ZB structure were also achieved for the first time. Finally, optical properties of the hollow ZnS tubes were investigated and discussed in detail. We believe that our study could provide some insights into the controlled fabrication of one dimensional (1D) semiconductors with desired morphology, structure and composition at the nanoscale, and the synthesized WZ ZnO/ZB ZnS nanocables as well as ZB ZnS nanotubes could be ideal candidates for the study of optoelectronics based on II-VI semiconductors.Synthesis of ZnO/ZnS heterostructures under thermodynamic conditions generally results in the wurtzite (WZ) structure of the ZnS component because its WZ phase is thermodynamically more stable than its zinc blende (ZB) phase. In this report, we demonstrate for the first time the preparation of ZnO/ZnS coaxial

  13. Structural, magnetic and optical properties of ZnO nanostructures converted from ZnS nanoparticles

    SciTech Connect

    Patel, Prayas Chandra; Ghosh, Surajit; Srivastava, P.C.

    2016-09-15

    Graphical abstract: The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. - Highlights: • Phase change of cubic ZnS to hexagonal ZnO via heat treatment. • Band gap was found to decrease with increasing calcinations temperature. • ZnO samples have higher magnetic moment than ZnS. • Blocking Temperature of the samples is well above room temperature. • Maximum negative%MR with saturation value ∼38% was found for sample calcined at 600° C. - Abstract: The present work concentrates on the synthesis of cubic ZnS and hexagonal ZnO semiconducting nanoparticle from same precursor via co-precipitation method. The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. From the analysis of influence of calcination temperature on the structural, optical and vibrational properties of the samples, an optimum temperature was found for the total conversion of ZnS nanoparticles to ZnO. Role of quantum confinement due to finite size is evident from the blue shift of the fundamental absorption in UV–vis spectra only in the ZnS nanoparticles. The semiconducting nature of the prepared samples is confirmed from the UV–vis, PL study and transport study. From the magnetic and transport studies, pure ZnO phase was found to be more prone to magnetic field.

  14. Low-temperature phase transition of ZnS: The critical role of ZnO

    SciTech Connect

    Lin, Po-Chang; Hua, Chi Chung; Lee, Tai-Chou

    2012-10-15

    Wurtzite zinc sulfide (WZ-ZnS) is a valuable wide-band-gap semiconductor. However, it is difficult to synthesize due to its high transition temperature (1020 Degree-Sign C). This study investigates the formation of WZ-ZnS particles using a ZnO template. Various phase structures of ZnS with the same size but different levels of ZnO content are generated during the annealing process. The transition temperature can be lowered significantly to below 350 Degree-Sign C. Furthermore, when the powders of ZnO and zinc-blende ZnS are mixed, large ZnS particles are not induced by ZnO to transform into WZ-ZnS. The results strongly suggest that grain size is an essential but not sufficient factor in the formation of WZ-ZnS at lower temperatures. - Graphical abstract: By controlling pH of the precursor, wurtzite ZnS particles can be generated at {approx}350 Degree-Sign C. The ZnO-template mechanism was proposed and discussed. Highlights: Black-Right-Pointing-Pointer Wurtzite ZnS particles were prepared by using simple wet chemistry. Black-Right-Pointing-Pointer pH of the precursor solution was adjusted to decrease the phase transition temperature of ZnS. Black-Right-Pointing-Pointer ZnO-template-inducing mechanism of ZnS phase transition was proposed and discussed.

  15. Wurtzite-type ZnS nanoparticles by pulsed electric discharge.

    PubMed

    Omurzak, Emil; Mashimo, Tsutomu; Sulaimankulova, Saadat; Takebe, Shintaro; Chen, Liliang; Abdullaeva, Zhypargul; Iwamoto, Chihiro; Oishi, Yudai; Ihara, Hirotaka; Okudera, Hiroki; Yoshiasa, Akira

    2011-09-07

    The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

  16. Semi-empirical scattering model for Chemical Vapor Deposited ZnS

    SciTech Connect

    McCloy, John S.

    2009-10-06

    A model has been created based on scattering from internal surfaces of different refractive index that describes the λ-2 dependence of the extinction in bulk samples of CVD ZnS. The model hinges on the lamellar nanostructure composed of alternating layers of thickness on the order of 10 to 100 nm. A family of solutions is generated which depend on both the difference in refractive index (Δn) and the layer thickness. Reasonable layer thicknesses require Δn for CVD ZnS with higher values than can be explained solely by the Δn between sphalerite and wurtzite phases of ZnS. Other evidence suggests a substantial oxygen component in CVD ZnS that could result in the lower refractive index Zn(O,S) necessary for the model. Differences in transmission for CVD ZnS, elemental ZnS, and multispectral ZnS can be explained simply by a different magnitude of Δn between the layers. Absolute transmission is modeled satisfactorily from the band edge to 10 μm using this approach.

  17. Effect of structure, size and copper doping on the luminescence properties of ZnS

    SciTech Connect

    Kamal, Ch. Satya; Mishra, R.K.; Patel, Dinesh K.; Rao, K. Ramachandra; Sudarsan, V.; Vatsa, R.K.

    2016-09-15

    Highlights: • Blue and green emission intensity form ZnS is sensitive to crystallographic form. • For ZnS nanoparticles, emission characteristics are not affected by copper doping. • Cu solubility poor in ZnS nanoparticles compared to corresponding bulk. - Abstract: Luminescence properties of wurtzite and cubic forms of bulk ZnS have been investigated in detail and compared with that of ZnS nanoparticles. Blue emission observed in both hexagonal and cubic forms of undoped bulk ZnS is explained based on electron–hole recombination involving electron in conduction band and hole trapped in Zn{sup 2+} vacancies where as green emission arises due to electron hole recombination from Zn{sup 2+} and S{sup 2−} vacancies. Conversion of wurtzite form to cubic form is associated with relative increase in intensity of green emission due to increased defect concentration brought about by high temperature heat treatment. Copper doping in ZnS, initially leads to formation of both Cu{sub Zn} and Cu{sub i} (interstitial copper) centers, and latter to mainly Cu{sub Zn} centers as revealed by variation in relative intensities of blue and green emission from the samples.

  18. Wurtzite-type ZnS nanoparticles by pulsed electric discharge

    NASA Astrophysics Data System (ADS)

    Omurzak, Emil; Mashimo, Tsutomu; Sulaimankulova, Saadat; Takebe, Shintaro; Chen, Liliang; Abdullaeva, Zhypargul; Iwamoto, Chihiro; Oishi, Yudai; Ihara, Hirotaka; Okudera, Hiroki; Yoshiasa, Akira

    2011-09-01

    The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

  19. Ionic Conduction in Nanocrystalline Materials

    DTIC Science & Technology

    2000-02-10

    photo- largely due to oxygen desorption from particle voltaic cells and as the photocatalyst in water surfaces. The latter interpretation...and Tuller [22] prepared dense (-95%) temperature, where bulk reduction was observed. At compacts of TiO2 with the anatase phase. The lower... TiO2 , evidence preparation. is mixed. Nanocrystalline rutile appears to exhibit higher ionic conductivity than single crystal rutile while

  20. Laser Compression of Nanocrystalline Metals

    NASA Astrophysics Data System (ADS)

    Meyers, Marc

    2009-06-01

    Laser compression carried out at the Omega and Janus yields new information on the deformation mechanisms of nanocrystalline Ni. Although conventional deformation does not produce hardening, the extreme regime imparted by laser compression generates an increase in hardness, attributed to the residual dislocations observed in the structure by TEM. An analytical model is applied to predict the critical pressures for the cell-stacking-faults transition in single-crystalline nickel and the onset twinning in nanocrystalline nickel. The slip-twinning transition pressure is shifted from 20 GPa, for polycrystalline Ni, to 80 GPa, for Ni with g. s. of 10 nm. Contributions to the net strain from the mechanisms of plastic deformation (partials, perfect dislocations, twinning, and gb shear) were quantified in the nanocrystalline samples through MD calculations. The effect of release, a phenomenon often neglected in MD simulations, on dislocation behavior was established. A large fraction of the dislocations generated at the front are annihilated.[4pt] In collaboration with Hussam Jarmakani, University of California, San Diego; Eduardo Bringa, U. Nacional de Cuyo; Bruce Remington, Lawrence Livermore National Laboratory; V. Nhon, University of Illinois; P. Earhart and Morris Wang, Lawrence Livermore National Laboratory.

  1. Alloying ZnS in the hexagonal phase to create high-performing transparent conducting materials.

    PubMed

    Faghaninia, Alireza; Bhatt, Kunal Rajesh; Lo, Cynthia S

    2016-08-10

    Alloyed zinc sulfide (ZnS) has shown promise as a relatively inexpensive and earth-abundant transparent conducting material (TCM). Though Cu-doped ZnS has been identified as a high-performing p-type TCM, the corresponding n-doped ZnS has, to date, been challenging to synthesize in a controlled manner; this is because the dopant atoms compete with hole-inducing zinc vacancies near the conduction band minimum as the most thermodynamically stable intrinsic point defects. We thus aim to identify the most promising n-type ZnS-based TCM, with the optimal combination of physical stability, transparency, and electrical conductivity. Using a relatively new method for calculating the free energy of both the sphalerite (cubic) and wurtzite (hexagonal) phases of undoped and doped ZnS, we find that doped ZnS is more stable in the hexagonal structure. This, for the first time, fundamentally explains previous experimental observations of the coexistence of both phases in doped ZnS; hence, it profoundly impacts future work on sulfide TCMs. We also employ hybrid density functional theory calculations and a new carrier transport model, AMSET (ab initio model for mobility and Seebeck coefficient using the Boltzmann transport equation), to analyze the defect physics and electron mobility of the different cation- (B, Al, Ga, In) and anion-doped (F, Cl, Br, I) ZnS, in both the cubic and hexagonal phases, at various dopant compositions, temperatures, and carrier concentrations. Among all doped ZnS candidates, Al-doped ZnS (AZS) exhibits the highest dopant solubility, largest electronic band gap, and highest electrical conductivity of 3830, 1905, and 321 S cm(-1), corresponding to the possible carrier concentrations of n = 10(21), 10(20), and 10(19) cm(-3), respectively, at the optimal 6.25% dopant concentration of Al and the temperature of 300 K.

  2. NH3 and PH3 adsorption through single walled ZnS nanotube: First principle insight

    NASA Astrophysics Data System (ADS)

    Khan, Md. Shahzad; Srivastava, Anurag; Chaurasiya, Rajneesh; Khan, Mohd. Shahid; Dua, Piyush

    2015-09-01

    The density functional theory (DFT) based adsorption analysis of NH3 and PH3 gas molecule has been made for confirming the sensing behaviour of ZnS nanotube. For a particular orientation of XH3 (X = N or P), the ZnS nanotube is found to be a good sensor with Zn as interactive site, discussed in terms of chemisorption and physisorption. Partial density of state (PDOS) analysis reveals strong interaction between few selected fragments from XH3 and ZnS nanotube. The quality of interaction for most favourable orientation is further scrutinized using charge decomposition analysis (CDA) analysis and sensing ability through current-voltage (I-V) characteristics.

  3. Photoinduced stiffening and photoplastic effect of ZnS individual nanobelt in nanoindentation

    SciTech Connect

    Zheng, X. J.; Yu, G. C.; Chen, Y. Q.; Mao, S. X.; Zhang, T.

    2010-11-15

    The photoinduced stiffening (PIS) and photoplastic effect (PPE) of ZnS individual nanobelt (NB) were observed by using a nanoindenter in conjunction with an incident ultraviolet (UV) light source system. The results show that the elastic modulus and hardness of ZnS individual NB under UV illumination are at least 32% and 20% larger than those in darkness. The mechanisms of PIS and PPE are interpreted by the increase in electronic strain and Peierls barrier due to the photogeneration of free carriers in ZnS individual NB. The research may offer useful guidelines to the application of optoelectronic devices based on individual nanostructures.

  4. Nanocrystalline films for gas-reactive applications

    DOEpatents

    Eastman, Jeffrey A.; Thompson, Loren J.

    2004-02-17

    A gas sensor for detection of oxidizing and reducing gases, including O.sub.2, CO.sub.2, CO, and H.sub.2, monitors the partial pressure of a gas to be detected by measuring the temperature rise of an oxide-thin-film-coated metallic line in response to an applied electrical current. For a fixed input power, the temperature rise of the metallic line is inversely proportional to the thermal conductivity of the oxide coating. The oxide coating contains multi-valent cation species that change their valence, and hence the oxygen stoichiometry of the coating, in response to changes in the partial pressure of the detected gas. Since the thermal conductivity of the coating is dependent on its oxygen stoichiometry, the temperature rise of the metallic line depends on the partial pressure of the detected gas. Nanocrystalline (<100 nm grain size) oxide coatings yield faster sensor response times than conventional larger-grained coatings due to faster oxygen diffusion along grain boundaries rather than through grain interiors.

  5. Rheology of nanocrystalline cellulose aqueous suspensions.

    PubMed

    Shafiei-Sabet, Sadaf; Hamad, Wadood Y; Hatzikiriakos, Savvas G

    2012-12-11

    The rheological properties and microstructure of nanocrystalline cellulose (NCC) aqueous suspensions have been investigated at different concentrations. The suspension is isotropic up to 3 wt %, and phase separates to liquid crystalline and isotropic domains at higher concentrations where the samples exhibit a fingerprint texture and the viscosity profile shows a three-region behavior, typical of liquid crystals. The suspension behaves as a rheological gel at even higher concentrations where the viscosity profile shows a single shear thinning behavior over the whole range of shear rates investigated. The effects of ultrasound energy and temperature on the rheological properties and structure of these suspensions were studied using polarized optical microscopy and rheometry. Our results indicate that the amount of applied ultrasound energy affects the microstructure of the suspensions and the pitch of the chiral nematic domains. The viscosity profile is changed significantly at low shear rates, whereas the viscosity of biphasic suspensions at intermediate and high shear rates decreased with increasing temperature. This suggests that, between 30 and 40 °C, structural rearrangement takes place. At higher concentrations of about 10 wt %, the temperature has no significant effect on viscosity; however, a marked increase in viscosity has been observed at around 50 °C. Finally, the Cox-Merz rule was found to fail after a critical concentration, thereby implying significant structural formation. This critical concentration is much higher for sonicated compared to unsonicated suspensions.

  6. Composite Thin Films

    SciTech Connect

    Martin, Peter M.

    2003-02-01

    Composites are one of more versatile types of materials, and can be characterized as multicomponent, or multiphase, mixtures. They can have unique structural, optical, electrical and magnetic properties not possible with a simple single component material. One of the best known composite materials is fiberglass, which is composed of glass fibers in a polymer matrix. This family of materials and thin films is highly disordered and inhomogeneous on a microstructural scale. Nanocrystalline and nanoclusters are now actively being investigated. The inhomogeneities can be fibers, clusters of atoms or molecules, grains with different crystalline phases (nanocrystalline clusters), inclusions with different electrical and magnetic properties. Note that the particles can have the same composition as the host material, but will have a different structural geometry. Carbon-carbon composites are a good example, where carbon fibers or threads are incorporated into carbonaceous resin

  7. Method of making nanocrystalline alpha alumina

    DOEpatents

    Siegel, Richard W.; Hahn, Horst; Eastman, Jeffrey A.

    1992-01-01

    Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.

  8. Plastic deformation mechanisms in nanocrystalline metallic materials

    NASA Astrophysics Data System (ADS)

    Ovid'ko, Ilya A.

    2013-11-01

    This article discusses the experiments, computer simulations, and theoretical models addressing the conventional and specific mechanisms of plastic deformation in nanocrystalline metallic materials. Particular attention is devoted to the competition between lattice dislocation slip and specific deformation mechanisms mediated by grain boundaries as well as its sensitivity to grain size and other parameters of nanocrystalline metallic structures.

  9. Semiconducting Nanocrystals in Mesostructured Thin Films for Optical and Opto-Electronic Device Applications

    DTIC Science & Technology

    2007-03-01

    nanocrystals……………………………………… 7 ZnSe and ZnS nanowires and nanorods, ZnO…………..……………………………… 9 Conjugated polymers in nanostructured composite materials...treatments and nanocrystal size. Compared to nanocrystalline Group II-VI compounds CdSe and CdS, Group III-V semiconductors, such as InP, GaP, InN, or...molecular level are being used to facilitate their integration into host matrices and devices. ZnSe and ZnS nanowires and nanorods, ZnO

  10. Micro-emulsion-assisted synthesis of ZnS nanospheres and their photocatalytic activity

    SciTech Connect

    Li Yao; He Xiaoyan; Cao Minhua

    2008-11-03

    ZnS nanospheres with rough surface were synthesized by using a micro-emulsion-assisted solvothemal process. The molar ratio of [water]/[surfactant] played an important role in controlling the size of the ZnS nanospheres. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscope (FE-SEM), and selected area electron diffraction (SAED) were used for the characterization of the resulting ZnS nanospheres. A possible formation mechanism was proposed. These ZnS nanospheres exhibited a good photocatalytic activity for degradation of an aqueous p-nitrophenol solution and the total organic carbon (TOC) of the degradation product has also been investigated.

  11. Facile fabrication of porous ZnO microspheres by thermal treatment of ZnS microspheres.

    PubMed

    Wu, Xiao; Li, KunWei; Wang, Hao

    2010-02-15

    Porous ZnO microspheres with an average size of around 500 nm had been synthesized by thermal treatment of ZnS microspheres in an air atmosphere. The ZnS spheres had been synthesized at a low temperature of 100 degrees C by using L-cysteine (an ordinary amino acid) as a sulfur source with the assist of gelatin. By combining the results of X-ray diffraction (XRD), transmission electron microscope (TEM), field-emission scanning electron microscopy (FE-SEM), and Fourier transformation infrared spectra (FTIR), a structural and morphological characterization of the products was performed. The photocatalytic activity of ZnS microspheres and porous ZnO microspheres have been tested by degradation of Rhodamine-B (RB) under UV light, indicating that the porous ZnO microspheres showed enhanced photocatalytic performance compared to ZnS microspheres and commercial Degussa P25 TiO(2).

  12. First-principles prediction of half-metallic ferromagnetism in Cu-doped ZnS

    NASA Astrophysics Data System (ADS)

    Zhang, Chang-wen; Yan, Shi-shen

    2010-02-01

    The spin-polarized full potential linearized augmented plane wave method in the generalized gradient approximation is carried out for investigation on the magnetism and electronic structures of Cu-doped ZnS. We find that the Cu-doped ZnS supercell shows half-metallic ferromagnetic character with a total magnetic moment of 1.0μB per Cu. The long-range ferromagnetism in Cu-doped ZnS can be explained in terms of p-d like hybridization chain, and the Curie temperature higher than around 350 K is predicted. These results suggest that Cu-doped ZnS may be a promising half-metallic ferromagnetic material for applications in spintronics.

  13. Self-assembled ZnS nanowire arrays: synthesis, in situ Cu doping and field emission

    NASA Astrophysics Data System (ADS)

    Liu, Baodan; Bando, Yoshio; Jiang, Xin; Li, Chun; Fang, Xiaosheng; Zeng, Haibo; Terao, Takeshi; Tang, Chengchun; Mitome, Masanori; Golberg, Dmitri

    2010-09-01

    Well-aligned single-crystalline ZnS nanowire arrays have been grown on highly conductive Cu substrates through controlling the morphology evolution of self-patterned ZnS nanoparticles. The ZnS nanowires have sharp tips with an average size of ~ 30 nm and a length of ~ 3 µm. Field emission measurements demonstrated that the aligned ZnS nanowires grown on Cu substrates are excellent field emitters having a turn-on field as low as 2.92 V µm - 1 and a field-enhancement factor as high as 3400. The use of highly conductive metal substrate may promote the commercial applications of ZnS-based emitters in flat panel displays and other optoelectronic devices.

  14. Structural, compositional and Raman studies of ZnS: Ce, Cu co-doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Harish, G. S.; Reddy, P. Sreedhara

    2013-06-01

    In this present work, Ce, Cu co-doped ZnS nanoparticles were prepared at room temperature using chemical precipitation method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy dispersive analysis of X-rays (EDAX) and High Resolution Raman spectroscopic techniques. X-ray diffraction studies show that the diameter of the particles is 2-4 nm. Broadened XRD peaks confirmed the formation of nanoparticles with face centered cubic (FCC) structure. SEM attached with EDS gave the size, morphology and compositional analysis of as-prepared material. The Raman spectra of unplanted and Cu, Ce ions implanted samples of nano structured ZnS showed LO mode and TO mode. Compared with the Raman modes (276 and 351 cm-1) of undoped ZnS nanoparticles, the Raman modes of Ce, Cu co-doped ZnS nanoparticles are slightly shifted towards lower frequency side.

  15. Low temperature synthesis, photoluminescence, magnetic properties of the transition metal doped wurtzite ZnS nanowires

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Han, Donglai; Wang, Bingji; Fan, Lin; Fu, Hao; Wei, Maobin; Feng, Bo; Liu, Xiaoyan; Yang, Jinghai

    2013-04-01

    In this paper, we synthesized the transition metal ions (Mn, Cu, Fe) doped and co-doped ZnS nanowires (NWs) by a one-step hydrothermal method. The results showed that the solid solubility of the Fe2+ ions in the ZnS NWs was about two times larger than that of the Mn2+ or Cu2+ ions in the ZnS NWs. There was no phase transformation from hexagonal to cubic even in a large quantity transition metal ions introduced for all the samples. The Mn2+/Cu2+/Fe2+ related emission peaks can be observed in the Mn2+,Cu2+ and Fe2+ doped ZnS NWs. The ferromagnetic properties of the co-doped samples were investigated at room temperature.

  16. Influence of Cu ion implantation on the microstructure and cathodoluminescence of ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Shang, L. Y.; Zhang, D.; Liu, B. Y.

    2016-07-01

    The microstructure and optical properties of as-synthesized and Cu ion implanted ZnS nanostructures with branched edges are studied by using high-resolution transmission electron microscope (TEM) and spatially-resolved cathodoluminescence measurement. Obvious crystalline deterioration has been observed in Cu-doped ZnS nanostructures due to the invasion of Cu ions into ZnS lattice. It was found that the optical emissions of ZnS nanostructures can be selectively modified through the control of Cu ion dose and subsequent heat treatment. An increase of Cu dopant content will lead to an apparent red-shift of the intrinsic band-gap emission in the UV range and the broadening of defect-related emission in visible range. The influences of Cu ion implantation on the microstructure and related optical properties were discussed.

  17. Thin films for micro solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Beckel, D.; Bieberle-Hütter, A.; Harvey, A.; Infortuna, A.; Muecke, U. P.; Prestat, M.; Rupp, J. L. M.; Gauckler, L. J.

    Thin film deposition as applied to micro solid oxide fuel cell (μSOFC) fabrication is an emerging and highly active field of research that is attracting greater attention. This paper reviews thin film (thickness ≤1 μm) deposition techniques and components relevant to SOFCs including current research on nanocrystalline thin film electrolyte and thin-film-based model electrodes. Calculations showing the geometric limits of μSOFCs and first results towards fabrication of μSOFCs are also discussed.

  18. Photo-Seebeck effect in ZnS

    NASA Astrophysics Data System (ADS)

    Shiraishi, Yuuka; Okazaki, Ryuji; Taniguchi, Hiroki; Terasaki, Ichiro

    2015-03-01

    To explore the thermoelectric transport nature of photo-excited carriers, the electrical conductivity and the Seebeck coefficient are measured under ultraviolet illumination in the wide-gap semiconductor ZnS near room temperature. The conductivity increases linearly as against the photon flux density with little dependence on temperature, indicating the conduction under illumination is mostly governed by the photo-doped carriers. We have found that, in high contrast to the temperature-insensitive photoconductivity, the temperature dependence of the Seebeck coefficient is dramatically varied by illumination, which is unexplained from a simple photo-doping effect for one majority carrier. Such a distinct difference in the transport quantities is rather understood within a two-carrier model, in which only the Seebeck coefficient is strongly affected by photo-excited minority carriers. The present result is also compared with earlier reports of the photo-Hall experiments to discuss the underlying photo-transport mechanism.

  19. Synthesis and different property of yttrium doped ZnS nanoparticles

    SciTech Connect

    Khawal, H. A.; Raskar, N. D.; Gawai, U. P.; Dole, B. N.

    2016-05-06

    Yttrium doped ZnS samples Zn{sub 1-x}Y{sub x}S with nominal compositions (x = 0.00, 0.04 and 0.06) were synthesized by a chemical co - precipitation route at room temperature. The synthesized Zn{sub 1-x}Y{sub x}S nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV–VIS spectrometer. XRD patterns revealed that entire peaks corresponding to the various planes of cubic zinc blend structure with no segregation of Y. The lattice parameters were calculated for the Y doped ZnS using XRD data and it found to be slightly smaller than pure ZnS, which indicate substitution of Y in to ZnS lattice. The average crystallite size was calculated using Debye - Scherrer’s formula for pure and Y doped ZnS samples. It is observed that grain size is in the range 30 to 12 nm. Band gap of Y doped ZnS nanoparticles has been calculated using UV-Vis spectrometer. It is found that the band gap decreases as content of Y increases, It may be due the smaller average grain size or ionic radii. The functional groups and chemical interactions of Y substituted Zinc sulfide samples were detected peaks using FTIR spectra and observed the presence of functional groups in the samples. It outlines the formation of ZnS with the stretching vibrational mode around at 511 cm{sup −1}. It is evidently confirmed from FTIR spectra that yttrium substitutes into ZnS lattice.

  20. Optical properties of colloidal CdS and ZnS quantum dots nanoparticles

    NASA Astrophysics Data System (ADS)

    Amran, Afiqah Shafify; Shamsudin, Siti Aisyah

    2016-11-01

    CdS and ZnS nanoparticles are luminescent semiconductors with great properties to be used in biosensors. Both semiconducting nanoparticles were synthesized in distilled water by using the simple colloidal method. Thioglycolic acid (TGA) was used as a stabilizer and Polyethyleneimine (PEI) was used as a surface modifier. The chemical composition and optical properties of the CdS and ZnS nanoparticles were investigated using Ultra Violet (UV) lamp, UV Spectroscopy and Photoluminescence (PL) Spectroscopy.

  1. Manufacturing optimal nanocrystalline microtruss materials

    NASA Astrophysics Data System (ADS)

    Lausic, Ante Tony

    Fabrication of optimal ultra-lightweight hybrid cellular materials via a two-step synthesis method of rapid prototyping followed by electrodeposition was accomplished in three distinct stages: modelling, fabrication, and validation. For the first stage, a baseline microtruss architecture with multiple geometric and material degrees of freedom was optimized with relation to the expected failure mechanisms. An intrinsic link between material selection and architectural variables was discovered and quantified. For a given electrodeposited polycrystalline Ni/polymer microtruss that has already been optimized for maximum load carrying capacity with minimal mass, substituting a nanocrystalline coating shifts the location of optimal design. It is possible through the redistribution of metal and polymer in this nanocrystalline microtruss to further decrease the total beam mass by a factor of three, showcasing this material-geometry dependency. The second stage hinged on developing a novel processing technique to deposit metal coatings on the as-printed polymer parts. The critical step of adhesion was solved using an 18~M sulphuric acid wash to preferentially smoothen the inherent 0.6~mm roughness on the samples. Finally, the models were validated through the testing of as-printed and coated rods and microtrusses. Nanocrystalline microtrusses showed a 60x increase in peak flexural strength with only a 6x increase in density. Further optimization can more than halve the final density while maintaining the same load carrying capacity by removing the sacrificial polymer core using the same sulphuric acid wash. The experimental values fit very well to those predicted in stage one for varying slenderness ratios, scales, and material systems.

  2. Laser compression of nanocrystalline tantalum

    NASA Astrophysics Data System (ADS)

    Lu, Chia-Hui; Maddox, Brian; Remington, B.; Bringa, Eduardo M.; Kawasaki, Megumi; Langdon, Terence; Park, Hye-Sook; Kad, Bimal; Meyers, Marc

    2012-03-01

    Nanocrystalline tantalum was prepared by high pressure torsion from monocrystalline [100] stock, yielding a grain size of 70nm. It was subjected to laser driven compression at energy levels of ~ 350 J to ~ 850 J in the Omega facility (LLE, U. of Rochester) with corresponding pressures as high as ~ 170 GPa. The laser beam created a crater of significant depth (~ 100 µm). Transmission electron microscopy (TEM) revealed dislocations in the grains but no twins in contrast with monocrystalline tantalum. Hardness measurements were conducted and show the same trend as single crystalline tantalum. The grain size was found to increase close to the energy deposition surface due to the thermomechanical excursion.

  3. Nanocrystalline high performance permanent magnets

    NASA Astrophysics Data System (ADS)

    Gutfleisch, O.; Bollero, A.; Handstein, A.; Hinz, D.; Kirchner, A.; Yan, A.; Müller, K.-H.; Schultz, L.

    2002-04-01

    Recent developments in nanocrystalline rare earth-transition metal magnets are reviewed and emphasis is placed on research work at IFW Dresden. Principal synthesis methods include high energy ball milling, melt spinning and hydrogen assisted methods such as reactive milling and hydrogenation-disproportionation-desorption-recombination. These techniques are applied to NdFeB-, PrFeB- and SmCo-type systems with the aim to produce high remanence magnets with high coercivity. Concepts of maximizing the energy density in nanostructured magnets by either inducing a texture via anisotropic HDDR or hot deformation or enhancing the remanence via magnetic exchange coupling are evaluated.

  4. Microwave-assisted low temperature synthesis of wurtzite ZnS quantum dots

    SciTech Connect

    Shahid, Robina; Toprak, Muhammet S.; Muhammed, Mamoun

    2012-03-15

    In this work we report, for the first time, on microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) in controlled reaction at temperature as low as 150 Degree-Sign C. The synthesis can be done in different microwave absorbing solvents with multisource or single source precursors. The QDs are less than 3 nm in size as characterized by transmission electron microscopy (TEM) using selected area electron diffraction (SAED) patterns to confirm the wurtzite phase of ZnS QDs. The optical properties were investigated by UV-Vis absorption which shows blue shift in absorption compared to bulk wurtzite ZnS due to quantum confinement effects. The photoluminescence (PL) spectra of QDs reveal point defects related emission of ZnS QDs. - Graphical abstract: Microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) have been achieved in controlled reaction at temperature as low as 150 Degree-Sign C. The synthesis was performed in different microwave absorbing solvents with multisource or single source precursors for very short reaction periods due to effective heating with microwaves. Highlights: Black-Right-Pointing-Pointer Wurtzite a high temperature phase of ZnS was synthesized at low temperature. Black-Right-Pointing-Pointer Low temperature synthesis was possible because of the use of microwave absorbing solvents. Black-Right-Pointing-Pointer Capping agent was used to control the size of Quantum Dots. Black-Right-Pointing-Pointer Two different systems were developed using single molecular precursor and multisource precursors.

  5. Photoluminescence study of Mn doped ZnS nanoparticles prepared by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Deshpande, M. P.; Patel, Kamakshi; Gujarati, Vivek P.; Chaki, S. H.

    2016-05-01

    ZnS nanoparticles co-doped with different concentration (5,10,15%) of Mn were synthesized using polyvinylpyrrolidone (PVP) as a capping agent under microwave irradiation. We confirmed doping of Mn in the host ZnS by EDAX whereas powder X-ray diffractogram showed the cubic zinc blende structure of all these samples. TEM images did showed agglomeration of particles and SAED pattern obtained indicated polycrystalline nature. From SAED pattern we calculated lattice parameter of the samples which have close resemblance from that obtained from XRD pattern. The band gap values of pure and doped ZnS nanoparticles were calculated from UV-Visible absorption spectra. ZnS itself is a luminescence material but when we dope it with transition metal ion such as Mn, Co, and Cu they exhibits strong and intense luminescence in the particular region. The photoluminescence spectra of pure ZnS nanoparticles showed an emission at 421 and 485nm which is blue emission which was originated from the defect sites of ZnS itself and also sulfur deficiency and when doped with Mn2+ an extra peak with high intensity was observed at 530nm which is nearly yellow-orange emission which isrelated to the presence of Mn in the host lattice.

  6. ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

    NASA Astrophysics Data System (ADS)

    Tian, Xiuying; Wen, Jin; Hu, Jilin; Chen, Zhanjun; Wang, Shumei; Peng, Hongxia; Li, Jing

    2016-09-01

    ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450-750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.

  7. Hepatotoxicity assessment of Mn-doped ZnS quantum dots after repeated administration in mice

    PubMed Central

    Yang, Yanjie; Lv, Shuang-Yu; Yu, Bianfei; Xu, Shuang; Shen, Jianmin; Zhao, Tong; Zhang, Haixia

    2015-01-01

    Doped ZnS quantum dots (QDs) have a longer dopant emission lifetime and potentially lower cytotoxicity compared to other doped QDs. The liver is the key organ for clearance and detoxification of xenobiotics by phagocytosis and metabolism. The present study was designed to synthesize and evaluate the hepatotoxicity of Mn-doped ZnS QDs and their polyethylene glycol-coated counterparts (1 mg/kg and 5 mg/kg) in mice. The results demonstrated that daily injection of Mn-doped ZnS QDs and polyethylene glycol-coated QDs via tail vein for 7 days did not influence body weight, relative liver weight, serum aminotransferases (alanine aminotransferase and aspartate aminotransferase), the levels of antioxidant enzymes (catalase, glutathione peroxidase, and superoxide dismutase), or malondialdehyde in the liver. Analysis of hepatocyte ultrastructure showed that Mn-doped ZnS QDs and polyethylene glycol-coated QDs mainly accumulated in mitochondria at 24 hours after repeated intravenous injection. No damage to cell nuclei or mitochondria was observed with either of the QDs. Our results indicate that Mn-doped ZnS QDs did not cause obvious damage to the liver. This study will assist in the development of Mn-doped ZnS QDs-based bioimaging and biomedical applications in the future. PMID:26396512

  8. Photoluminescence study of Mn doped ZnS nanoparticles prepared by co-precipitation method

    SciTech Connect

    Deshpande, M. P. Patel, Kamakshi Gujarati, Vivek P.; Chaki, S. H.

    2016-05-06

    ZnS nanoparticles co-doped with different concentration (5,10,15%) of Mn were synthesized using polyvinylpyrrolidone (PVP) as a capping agent under microwave irradiation. We confirmed doping of Mn in the host ZnS by EDAX whereas powder X-ray diffractogram showed the cubic zinc blende structure of all these samples. TEM images did showed agglomeration of particles and SAED pattern obtained indicated polycrystalline nature. From SAED pattern we calculated lattice parameter of the samples which have close resemblance from that obtained from XRD pattern. The band gap values of pure and doped ZnS nanoparticles were calculated from UV-Visible absorption spectra. ZnS itself is a luminescence material but when we dope it with transition metal ion such as Mn, Co, and Cu they exhibits strong and intense luminescence in the particular region. The photoluminescence spectra of pure ZnS nanoparticles showed an emission at 421 and 485nm which is blue emission which was originated from the defect sites of ZnS itself and also sulfur deficiency and when doped with Mn{sup 2+} an extra peak with high intensity was observed at 530nm which is nearly yellow-orange emission which isrelated to the presence of Mn in the host lattice.

  9. Synthesis and self-assembly of photonic materials from nanocrystalline titania sheets.

    PubMed

    Zhu, Jian; Wang, Jinguo; Lv, Fujian; Xiao, Shengxiong; Nuckolls, Colin; Li, Hexing

    2013-03-27

    We describe the use of benzyl alcohols in a solvothermal/alcoholysis reaction to form nanocrystalline sheets of anatase titania. By tuning the reaction conditions, we adjust the size of the nanosheets. The type and density of benzyl groups that decorate the basal plane of the titania sheets control the self-assembly into layered structures. These layered materials can be grown from solid substrates to create iridescent thin films that reflect specific wavelengths of visible light.

  10. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  11. Laser Compression of Nanocrystalline Tantalum

    NASA Astrophysics Data System (ADS)

    Lu, Chia-Hui; Remington, Bruce; Maddox, Brian; Kad, Bimal; Park, Hye-Sook; Kawasaki, Megumi; Langdon, Terence; Meyers, Marc

    2013-06-01

    Nanocrystalline tantalum (g.s. ~70 nm) prepared by severe plastic deformation (HPT) from monocrystalline [100] stock was subjected to high energy laser driven shock compression (up to ~850 J), generating a pressure pulse with initial duration of ~3 ns and amplitude of up to ~145 GPa. TEM revealed few dislocations within the grains and an absence of twins at the highest shock strengths, in contrast with monocrystalline tantalum, which exhibited twinning at P > ~45 GPa. Hardness measurements were conducted and show a rise as the energy deposition surface is approached, evidence of shock-induced defects. The grain size was found to increase at a distance of 100 μm from the energy deposition surface as a result of thermally induced grain growth. Calculations using the Hu-Rath analysis are consistent with the experimental results. The experimentally measured dislocation densities and threshold stress for twinning are compared with predictions using analyses based on physically-based constitutive models. The predicted threshold stress for twinning increases from ~45 GPa for the monocrystalline to ~165 GPa for the nanocrystalline tantalum.

  12. Multifunctionality of nanocrystalline lanthanum ferrite

    SciTech Connect

    Rai, Atma; Thakur, Awalendra K.

    2016-05-06

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  13. Micromechanics Modeling of Fracture in Nanocrystalline Metals

    NASA Technical Reports Server (NTRS)

    Glaessgen, E. H.; Piascik, R. S.; Raju, I. S.; Harris, C. E.

    2002-01-01

    Nanocrystalline metals have very high theoretical strength, but suffer from a lack of ductility and toughness. Therefore, it is critical to understand the mechanisms of deformation and fracture of these materials before their full potential can be achieved. Because classical fracture mechanics is based on the comparison of computed fracture parameters, such as stress intlmsity factors, to their empirically determined critical values, it does not adequately describe the fundamental physics of fracture required to predict the behavior of nanocrystalline metals. Thus, micromechanics-based techniques must be considered to quanti@ the physical processes of deformation and fracture within nanocrystalline metals. This paper discusses hndamental physicsbased modeling strategies that may be useful for the prediction Iof deformation, crack formation and crack growth within nanocrystalline metals.

  14. Eu(2)(+) -induced enhancement of defect luminescence of ZnS.

    PubMed

    Xiao-Bo, Zhang; Fu-Xiang, Wei

    2016-12-01

    The Eu(2)(+) -induced enhancement of defect luminescence of ZnS was studied in this work. While photoluminescence (PL) spectra exhibited 460 nm and 520 nm emissions in both ZnS and ZnS:Eu nanophosphors, different excitation characteristics were shown in their photoluminescence excitation (PLE) spectra. In ZnS nanophosphors, there was no excitation signal in the PLE spectra at the excitation wavelength λex  > 337 nm (the bandgap energy 3.68 eV of ZnS); while in ZnS:Eu nanophosphors, two excitation bands appeared that were centered at 365 nm and 410 nm. Compared with ZnS nanophosphors, the 520 nm emission in the PL spectra was relatively enhanced in ZnS:Eu nanophosphors and, furthermore, in ZnS:Eu nanophosphors the 460 nm and 520 nm emissions increased more than 10 times in intensity. The reasons for these differences were analyzed. It is believed that the absorption of Eu(2)(+) intra-ion transition and subsequent energy transfer to sulfur vacancy, led to the relative enhancement of the 520 nm emission in ZnS:Eu nanophosphors. In addition, more importantly, Eu(2)(+) acceptor-bound excitons are formed in ZnS:Eu nanophosphors and their excited levels serve as the intermediate state of electronic relaxation, which decreases non-radiative electronic relaxation and thus increases the intensity of the 460 nm and 520 nm emission dramatically. In summary, the results in this work indicate a new mechanism for the enhancement of defect luminescence of ZnS in Eu(2)(+) -doped ZnS nanophosphors. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  15. An experimental and theoretical investigation on the optical and photocatalytic properties of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    La Porta, F. A.; Nogueira, A. E.; Gracia, Lourdes; Pereira, W. S.; Botelho, G.; Mulinari, T. A.; Andrés, Juan; Longo, E.

    2017-04-01

    From the viewpoints of materials chemistry and physical chemistry, crystal structure directly determines the electronic structure and furthermore their optical and photocatalytic properties. Zinc sulfide (ZnS) nanoparticles (NPs) with tunable photoluminescence (PL) emission and high photocatalytic activity have been obtained by means of a microwave-assisted solvothermal (MAS) method using different precursors (i.e., zinc nitrate (ZN), zinc chloride (ZC), or zinc acetate (ZA)). The morphologies, optical properties, and electronic structures of the as-synthesized ZnS NPs were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) isotherms for N2 adsorption/desorption processes, diffuse reflectance spectroscopy (DRS), PL measurements and theoretical calculations. Density functional theory calculations were used to determine the geometries and electronic properties of bulk wurtzite (WZ) ZnS NPs and their (0001), (101 ̅0), (112 ̅0), (101 ̅1), and (101 ̅2) surfaces. The dependence of the PL emission behavior of ZnS NPs on the precursor was elucidated by examining the energy band structure and density of states. The method for degradation of Rhodamine B (RhB) was used as a probe reaction to investigate the photocatalytic activity of the as-Synthesised ZnS NPs under UV light irradiation. The PL behavior as well as photocatalytic activities of ZnS NPs were attributed to specific features of the structural and electronic structures. Increased photocatalytic degradation was observed for samples synthesized using different precursors in the following order: ZAZnS NPs were also briefly discussed.

  16. Improving the ductility of nanocrystalline bcc metals.

    PubMed

    Farkas, Diana; Hyde, Brian

    2005-12-01

    Nanocrystalline metals present extremely high yield strengths but limited ductility. Using atomistic simulations, we show that the fracture resistance of bcc nanocrystalline materials increases with decreasing grain size below a critical grain size. There appears to be a "most brittle" grain size corresponding to the "strongest size" that has been postulated. Impurities that strengthen the grain boundaries can improve ductility significantly for the relatively larger grain sizes, whereas ductility decreases for the smallest grain sizes.

  17. Enhancement of efficiency by embedding ZnS and Mn-doped ZnS nanoparticles in P3HT:PCBM hybrid solid state solar cells

    NASA Astrophysics Data System (ADS)

    Jabeen, Uzma; Adhikari, Tham; Shah, Syed Mujtaba; Nunzi, Jean-Michel; Badshah, Amin; Ahmad, Iqbal

    2017-06-01

    Zinc sulphide (ZnS) and Mn-doped ZnS nanoparticles were synthesized by wet chemical method. The synthesized nanoparticles were characterized by UV-visible, fluorescence, X-ray diffraction (XRD), fourier transform infra-red (FTIR) spectrometer, field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). Scanning electron microscope (SEM) was used to find particle size while chemical composition of the synthesized materials was investigated by EDAX. UV-visible absorption spectrum of Mn-doped ZnS was slightly shifted to lower wavelength with respect to the un-doped zinc sulphide with decrease in the size of nanoparticles. Consequently, the band gap was tuned from 3.04 to 3.13 eV. The photoluminescence (PL) emission positioned at 597 nm was ascribed to 4T1 → 6A1 transition within the 3d shell of Mn2+. X-ray diffraction (XRD) analysis revealed that the synthesized nanomaterials existed in cubic crystalline state. The effect of embedding un-doped and doped ZnS nanoparticles in the active layer and changing the ratio of PCBM ([6, 6]-phenyl-C61-butyric acid methyl ester) to nanoparticles on the performance of hybrid solar cell was studied. The device with active layer consisting of poly(3-hexylthiophene) (P3HT), [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM), and un-doped ZnS nanoparticles combined in the ratio of (1:0.5:0.5) attained an efficiency of 2.42% which was found 71% higher than the reference device under the same conditions but not containing nanoparticles. Replacing ZnS nanoparticles with Mn-doped ZnS had a little effect on the enhancement of efficiency. The packing behavior and morphology of blend of nanoparticles with P3HT:PCBM were examined using atomic force microscope (AFM) and XRD. Contribution to the topical issue "Materials for Energy harvesting, conversion and storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  18. Greener synthesis of nanocrystalline ZSM-5

    NASA Astrophysics Data System (ADS)

    Nada, Majid Hameed

    Nanocrystalline ZSM-5 zeolite, which is a well-known catalyst used in a variety of applications in industry, environment, and medicine, can be synthesized using different methods. However, a big challenge in synthesizing nanocrsytalline ZSM-5 is the use of an organic template such as TPAOH, which is very expensive. The template is required to facilitate the growth of the nanocrsytalline ZSM-5 during the synthesis. However, to use the nanocrsytalline ZSM-5, the template has to be removed by a calcination process to open the pores and reveal the active surface of the nanocrystalline ZSM-5. The calcination process requires a high temperature for a long time to remove the organic template. Consequently, synthesizing nanocrystalline ZSM-5 by using a templated method is considered to be time, energy, and materials inefficient. In addition, the production of CO2 from the calcination process is a negative impact on the environment. Therefore, finding another method to synthesize nanocrystalline ZSM-5 without using an organic template would be beneficial. Here, nanocrystalline ZSM-5 was synthesized successfully in high yield and quality by using a seed-assisted method and without using the organic template. In addition, the effect of synthesis temperature, synthesis time, basic environment, amount of seeds, size of seeds, aging time, and use of calcined and uncalcined seeds are investigated in this study. The synthesized nanocrystalline ZSM-5 materials were characterized by using X-ray diffraction (XRD), gas adsorption isotherm (BET/BJH), and transmission electron microscopy (TEM).

  19. Investigation of thioglycerol stabilized ZnS quantum dots in electroluminescent device performance

    SciTech Connect

    Ethiraj, Anita Sagadevan; Rhen, Dani; Kang, Dae Joon; Lee, D. H.; Kulkarni, S. K.

    2016-05-06

    The present work is focused on the investigation of thioglycerol (TG) stabilized Zinc Sulfide Quantum dots (ZnS QDs) in the hybrid electroluminescence (EL) device. Optical absorption spectroscopy clearly indicates the formation of narrow size distributed ZnS in the quantum confinement regime. X-ray Diffraction (XRD), Photoluminescence (PL), Energy Dispersive X-ray Spectroscopy (EDS) data supports the same. The hybrid EL device with structure of ITO (indium tin oxide)//PEDOT:PSS ((poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)//HTL (α NPD- N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-phenyl)-4,4′-diamine// PVK:ZnS QDs//ETL(PBD- 2-tert-butylphenyl- 5-biphenyl-1,3,4-oxadiazole)//LiF:Al (Device 1) was fabricated. Reference device without the ZnS QDs were also prepared (Device 2). The results show that the ZnS QDs based device exhibited bright electroluminescence emission of 24 cd/m{sup 2} at a driving voltage of 16 Volts under the forward bias conditions as compared to the reference device without the ZnS QDs, which showed 6 cd/m{sup 2} at ∼22 Volts.

  20. Optical properties of Mn-doped ZnS semiconductor nanoclusters synthesized by a hydrothermal process

    NASA Astrophysics Data System (ADS)

    Hoa, Tran Thi Quynh; The, Ngo Duc; McVitie, Stephen; Nam, Nguyen Hoang; Vu, Le Van; Canh, Ta Dinh; Long, Nguyen Ngoc

    2011-01-01

    Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant a = 5.408 ± 0.011 Ǻ. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn2+ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn2+ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn2+ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour.

  1. Effect of nickel doping on structural and optical properties of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Sanjeev Kumar, R.; Veeravazhuthi, V.; Muthukumarasamy, N.; Thambidurai, M.; Vishnu Shankar, D.

    2015-10-01

    In the present work, solution based simple chemical precipitation method has been used to prepare undoped and Ni-doped ZnS nanoparticles. Zinc acetate, sodium sulfide, and nickel nitrate have been used as precursors for the preparation of Ni-doped ZnS nanoparticles. The X-ray diffraction results revealed that the undoped and Ni-doped ZnS nanoparticles exhibit hexagonal Structure. The average grain size of the prepared nanoparticles was found to lie in the range of 2.6-4.2 nm. The SEM images show that the particles have smooth surface and the formation of agglomerated nanoparticles. The compositional analysis results confirm the presence of Ni, Zn and S in the prepared samples. The optical properties of undoped and Ni-doped ZnS quantum dots have been studied using absorption spectra. HRTEM results show that undoped and Ni-doped ZnS nanoparticles exhibit a uniform size distribution with average grain size lying in the range of 2.3-3.6 nm. The synthesized nanoparticles exhibited an emission peak centered at around 612 nm in the PL spectrum.

  2. Scintillation and luminescence in transparent colorless single and polycrystalline bulk ceramic ZnS

    SciTech Connect

    McCloy, John S.; Bliss, Mary; Miller, Brian W.; Wang, Zheming; Stave, Sean C.

    2015-01-01

    ZnS:Ag is a well-known extremely bright scintillator used in powder form for α-particle detection and, mixed with powdered LiF, for thermal neutron detection. Recently, we discovered some commercial bulk colorless and transparent, single-crystal and polycrystalline (chemical vapor-deposited) ZnS forms that scintillate in response to α-particles. The scintillation light transmits through the sample thickness (mm), challenging the commonly held assumption that ZnS is opaque to its own scintillation light. Individual α-particle events were imaged in space and time using a charged-particle camera originally developed for medical imaging applications. Photoluminescence (PL) and PL excitation show that scintillating bulk ZnS likely depends on different electronic defects than commercial ZnS powder scintillators. These defects, associated with copper and oxygen, are discussed in relation to PL results and extensive literature assessment. Commercial transparent ZnS is routinely produced by chemical vapor deposition to sizes larger than square meters, enabling potentially novel radiation detection applications requiring large, thick apertures.

  3. Synthesis and influence of ultrasonic treatment on luminescence of Mn incorporated ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Cadis, A.-I.; Muresan, L. E.; Perhaita, I.; Munteanu, V.; Karabulut, Y.; Garcia Guinea, J.; Canimoglu, A.; Ayvacikli, M.; Can, N.

    2017-10-01

    Manganese (Mn) doping of ZnS phosphors was achieved by precipitation method using different ultrasound (US) maturation times. The structural and luminescence properties of the samples were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), photoluminescence (PL), and cathodoluminescence (CL). The real amount of manganese incorporated in ZnS lattice was calculated based on ICP-OES results. According with XRD patterns, the phase structure of ZnS:Mn samples is cubic. EDS spectra reveal deviations of the Mn dopant concentration from the target composition. Both 300 K PL and CL emission spectra of the Mn doped ZnS phosphors display intense orange emission at 590 and 600 nm, respectively, which is characteristic emission of Mn ion corresponding to a 4T1→6A1 transition. Both PL and CL spectra confirmed manganese is substitutionally incorporated into the ZnS host as Mn2+. However, it is suggested that the origin of broad blue emission around 400 nm appeared in CL is due to the radiative recombination at deep level defect states in the ZnS. The ultrasound treatment at first enhances the luminescent intensity by ∼3 times in comparison with samples prepared by classical way. This study gives rise to an optimization guideline, which is extremely demanded for the development of new luminescent materials.

  4. Investigation of thioglycerol stabilized ZnS quantum dots in electroluminescent device performance

    NASA Astrophysics Data System (ADS)

    Ethiraj, Anita Sagadevan; Rhen, Dani; Lee, D. H.; Kang, Dae Joon; Kulkarni, S. K.

    2016-05-01

    The present work is focused on the investigation of thioglycerol (TG) stabilized Zinc Sulfide Quantum dots (ZnS QDs) in the hybrid electroluminescence (EL) device. Optical absorption spectroscopy clearly indicates the formation of narrow size distributed ZnS in the quantum confinement regime. X-ray Diffraction (XRD), Photoluminescence (PL), Energy Dispersive X-ray Spectroscopy (EDS) data supports the same. The hybrid EL device with structure of ITO (indium tin oxide)//PEDOT:PSS ((poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)//HTL (α NPD- N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-phenyl)-4,4'-diamine// PVK:ZnS QDs//ETL(PBD- 2-tert-butylphenyl- 5-biphenyl-1,3,4-oxadiazole)//LiF:Al (Device 1) was fabricated. Reference device without the ZnS QDs were also prepared (Device 2). The results show that the ZnS QDs based device exhibited bright electroluminescence emission of 24 cd/m2 at a driving voltage of 16 Volts under the forward bias conditions as compared to the reference device without the ZnS QDs, which showed 6 cd/m2 at ˜22 Volts.

  5. Quasi-particle energies and optical excitations of ZnS monolayer honeycomb structure

    NASA Astrophysics Data System (ADS)

    Shahrokhi, Masoud

    2016-12-01

    Using ab-initio density functional theory calculations combined with many-body perturbation formalism we carried out the electronic structure and optical properties of 2D graphene-like ZnS structure. The electronic properties were analyzed at three levels of many-body GW approach (G0W0, GW0 and GW) constructed over a Generalized Gradient Approximation functional. Our results indicate that ZnS sheet has a direct band gap at the Γ-point. Also it is seen that inclusion of electron-electron interaction does not change the sort of direct semiconducting band gap in ZnS sheet. The optical properties and excitonic effects of these materials are investigated using the Bethe-Salpeter equation (BSE) approach. The formation of first exciton peaks at 3.86, 4.26, and 4.57 eV with large binding energy of 0.36, 0.49 and 0.73 eV using G0W0 + BSE, GW0 + BSE and GW + BSE, respectively, was observed. We show that the optical absorption spectrum of 2D ZnS structure is dominated by strongly bound Frenkel excitons. The enhanced excitonic effects in the ZnS monolayer sheet can be useful in designing optoelectronic applications.

  6. Mechanochemistry of Chitosan-Coated Zinc Sulfide (ZnS) Nanocrystals for Bio-imaging Applications

    NASA Astrophysics Data System (ADS)

    Bujňáková, Zdenka; Dutková, Erika; Kello, Martin; Mojžiš, Ján; Baláž, Matej; Baláž, Peter; Shpotyuk, Oleh

    2017-05-01

    The ZnS nanocrystals were prepared in chitosan solution (0.1 wt.%) using a wet ultra-fine milling. The obtained suspension was stable and reached high value of zeta potential (+57 mV). The changes in FTIR spectrum confirmed the successful surface coating of ZnS nanoparticles by chitosan. The prepared ZnS nanocrystals possessed interesting optical properties verified in vitro. Four cancer cells were selected (CaCo-2, HCT116, HeLa, and MCF-7), and after their treatment with the nanosuspension, the distribution of ZnS in the cells was studied using a fluorescence microscope. The particles were clearly seen; they passed through the cell membrane and accumulated in cytosol. The biological activity of the cells was not influenced by nanoparticles, they did not cause cell death, and only the granularity of cells was increased as a consequence of cellular uptake. These results confirm the potential of ZnS nanocrystals using in bio-imaging applications.

  7. The Combustion Synthesis Zns Doped Materials to Create Ultra-Electroluminscent Materials in Microgravity

    NASA Astrophysics Data System (ADS)

    Castillo, Martin; Steinberg, Theodore

    2012-07-01

    Self-propagating high temperature synthesis (SHS) utilises a rapid exothermic process involving high energy and nonlinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials. ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there have been no advancements in refining this structure to create ultra-electroluminescent materials. Utilising this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the SHS of ZnS and will re-examine the work performed in both normal gravity and in reduced gravity within the Queensland University of Technology Drop Tower Facility. Quantifications in the lattice parameters, crystal structures, and phases produced are presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

  8. Cytotoxicity tests of water soluble ZnS and CdS quantum dots.

    PubMed

    Li, Hui; Li, Mengyan; Shih, Wan Y; Lelkes, Peter I; Shih, Wei-Heng

    2011-04-01

    Cytotoxicity tests of zinc sulfide (ZnS) and cadmium sulfide (CdS) quantum dots (QDs) synthesized via all-aqueous process with various surface conditions were carried out with human endothelial cells (EA hy926) using two independent viability assays, i.e., by cell counting following Trypan blue staining and by measuring Alamar Blue (AB) fluorescence. The ZnS QDs with all four distinct types of surface conditions were nontoxic at both 1 microM and 10 microM concentrations for at least 6 days. On the other hand, the CdS QDs were nontoxic only at 1 microM, and showed significant cytotoxicity at 10 microM after 3 days in the cell counting assay and after 4 days in the AB fluorescence assay. The CdS QDs with (3-mercaptopropyl)trimethoxysilane (MPS)-replacement plus silica capping were less cytotoxic than those with 3-mercaptopropionic acid (MPA) capping and those with MPS-replacement capping. Comparing the results of ZnS and CdS QDs with the same particle size, surface condition and concentration, it is indicated that the cytotoxicity of CdS QDs and the lack of it in ZnS QDs were probably due to the presence and absence of the toxic Cd element, respectively. The nontoxicity of the aqueous ZnS QDs makes them favorable for in vivo imaging applications.

  9. Grain boundaries and mechanical properties of nanocrystalline diamond films.

    SciTech Connect

    Busmann, H.-G.; Pageler, A.; Gruen, D. M.

    1999-08-06

    Phase-pure nanocrystalline diamond thin films grown from plasmas of a hydrogen-poor carbon argon gas mixture have been analyzed regarding their hardness and elastic moduli by means of a microindentor and a scanning acoustic microscope.The films are superhard and the moduli rival single crystal diamond. In addition, Raman spectroscopy with an excitation wavelength of 1064 nm shows a peak at 1438 l/cm and no peak above 1500 l/cm, and X-ray photoelectron spectroscopy a shake-up loss at 4.2 eV. This gives strong evidence for the existence of solitary double bonds in the films. The hardness and elasticity of the films then are explained by the assumption, that the solitary double bonds interconnect the nanocrystals in the films, leading to an intergrain boundary adhesion of similar strength as the intragrain diamond cohesion. The results are in good agreement with recent simulations of high-energy grain boundaries.

  10. Mesoporous nanocrystalline film architecture for capacitive storage devices

    DOEpatents

    Dunn, Bruce S.; Tolbert, Sarah H.; Wang, John; Brezesinski, Torsten; Gruner, George

    2017-05-16

    A mesoporous, nanocrystalline, metal oxide construct particularly suited for capacitive energy storage that has an architecture with short diffusion path lengths and large surface areas and a method for production are provided. Energy density is substantially increased without compromising the capacitive charge storage kinetics and electrode demonstrates long term cycling stability. Charge storage devices with electrodes using the construct can use three different charge storage mechanisms immersed in an electrolyte: (1) cations can be stored in a thin double layer at the electrode/electrolyte interface (non-faradaic mechanism); (2) cations can interact with the bulk of an electroactive material which then undergoes a redox reaction or phase change, as in conventional batteries (faradaic mechanism); or (3) cations can electrochemically adsorb onto the surface of a material through charge transfer processes (faradaic mechanism).

  11. Strong adhesion in nanocrystalline diamond films on silicon substrates

    NASA Astrophysics Data System (ADS)

    Sharda, T.; Umeno, M.; Soga, T.; Jimbo, T.

    2001-05-01

    Strong adhesion is shown to be achieved in the growth of smooth nanocrystalline diamond (NCD) thin films on silicon substrates at 600 °C using biased enhanced growth in microwave plasma chemical vapor deposition. The strong adhesion is evident from the films sustaining compressive stress, which may be as high as 85 GPa. The substrates are bent spherically after deposition, however, films are not peeled off, in spite of having enormous in-plane stress. The strong adhesion may be a result of implanted carbon below the substrate surface with an optimized ion flux density in the initial stages of growth. The compressive stress in the films is shown to be generating from the graphitic and other nondiamond carbon impurities in the films. It was observed that the NCD grain size decreases with biasing hence increasing grain boundary area in the films accommodating more graphitic impurities, which in turn results in an increase in compressive stress in the films.

  12. Vapor deposition of thin films

    DOEpatents

    Smith, David C.; Pattillo, Stevan G.; Laia, Jr., Joseph R.; Sattelberger, Alfred P.

    1992-01-01

    A highly pure thin metal film having a nanocrystalline structure and a process of preparing such highly pure thin metal films of, e.g., rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium by plasma assisted chemical vapor deposition of, e.g., rhodium(allyl).sub.3, iridium(allyl).sub.3, molybdenum(allyl).sub.4, tungsten(allyl).sub.4, rhenium(allyl).sub.4, platinum(allyl).sub.2, or palladium(allyl).sub.2 are disclosed. Additionally, a general process of reducing the carbon content of a metallic film prepared from one or more organometallic precursor compounds by plasma assisted chemical vapor deposition is disclosed.

  13. Nanocrystalline cellulose from coir fiber: preparation, properties, and applications

    USDA-ARS?s Scientific Manuscript database

    Nanocrystalline cellulose derived from various botanical sources offers unique and potentially useful characteristics. In principle, any cellulosic material can be considered as a potential source of a nanocrystalline material, including crops, crop residues, and agroindustrial wastes. Because of t...

  14. Enhanced photocatalytic activity of ZnS nanoparticles loaded with MoS2 nanoflakes by self-assembly approach

    NASA Astrophysics Data System (ADS)

    Vattikuti, S. V. Prabhakar; Byon, Chan; Jeon, Sora

    2016-12-01

    A hybrid consisting of ZnS nanoparticles supported on layered MoS2-ZnS was synthesized by a hydrothermal method based on self-assembly technique without using a template. XRD, SEM-EDX, TEM, HR-TEM, TG-DTA, XPS, N2 adsorption-desorption, and UV-Vis spectroscopies were used to characterize the structural features, morphology, and composition of the MoS2-ZnS hybrid. The results show that the MoS2-ZnS hybrid is mainly ZnS nanoparticles on layered MoS2 with a thickness of ca. 5-20 nm. The combination of the MoS2 and ZnS hybrid structure is beneficial for enhancing the photocatalytic degradation of rhodamine B (RhB) under visible light irradiation. A possible photoreaction mechanism of the MoS2-ZnS hybrid in the degradation is proposed. The photoexcited electrons from the ZnS could easily transfer to the conduction band of MoS2, thus decreasing the recombination of photoinduced carriers and enabling the degradation of RhB under visible light irradiation.

  15. Optical, phonon and efficient visible and infrared photocatalytic activity of Cu doped ZnS micro crystals

    NASA Astrophysics Data System (ADS)

    Prasad, Neena; Balasubramanian, Karthikeyan

    2017-02-01

    We report, the enhanced photocatalytic behaviour of Cu doped ZnS micro crystals. ZnS and different concentrations of Cu doped ZnS microcrystals were prepared. X-ray diffraction confirms the crystalline and phase of the particles. Morphology and sizes were studied using Scanning Electron Microscopy (SEM). Recorded optical absorption spectra show a band for around 365 nm for pure ZnS, but there is a broad band in the near infrared regime for the Cu-doped ZnS microcrystals which are attributed to the d-d transitions of Cu2 + ions. Phonon properties of as-prepared samples were investigated using Raman spectroscopy. Present work we investigate the potential of ZnS and Cu doped ZnS as a photocatalyst. For this from the degradation of methylene blue dye in aqueous media the photocatalytic activity of pure and highest doped ZnS samples with the irradiation of white light and infrared, enhanced photocatalytic activity were observed. Mechanism of white light an IR light based photocatalytic activity is explained based on the electron-hole pair production.

  16. Characterization and Application of Colloidal Nanocrystalline Materials for Advanced Photovoltaics

    NASA Astrophysics Data System (ADS)

    Bhandari, Khagendra P.

    Solar energy is Earth's primary source of renewable energy and photovoltaic solar cells enable the direct conversion of sunlight into electricity. Crystalline silicon solar cells and modules have dominated photovoltaic technology from the beginning and they now constitute more than 90% of the PV market. Thin film (CdTe and CIGS) solar cells and modules come in second position in market share. Some organic, dye-sensitized and perovskite solar cells are emerging in the market but are not yet in full commercial scale. Solar cells made from colloidal nanocrystalline materials may eventually provide both low cost and high efficiency because of their promising properties such as high absorption coefficient, size tunable band gap, and quantum confinement effect. It is also expected that the greenhouse gas emission and energy payback time from nanocrystalline solar PV systems will also be least compared to all other types of PV systems mainly due to the least embodied energy throughout their life time. The two well-known junction architectures for the fabrication of quantum dot based photovoltaic devices are the Schottky junction and heterojunction. In Schottky junction cells, a heteropartner semiconducting material is not required. A low work function metal is used as the back contact, a transparent conducting layer is used as the front contact, and the layer of electronically-coupled quantum dots is placed between these two materials. Schottky junction solar cells explain the usefulness of nanocrystalline materials for high efficiency heterojunction solar cells. For heterojunction devices, n-type semiconducting materials such as ZnO , CdS or TiO2 have been used as suitable heteropartners. Here, PbS quantum dot solar cells were fabricated using ZnO and CdS semiconductor films as window layers. Both of the heteropartners are sputter-deposited onto TCO coated glass substrates; ZnO was deposited with the substrate held at room temperature and for CdS the substrate was at 250

  17. Atomic structure relaxation in nanocrystalline NiO studied by EXAFS spectroscopy: Role of nickel vacancies

    NASA Astrophysics Data System (ADS)

    Anspoks, A.; Kalinko, A.; Kalendarev, R.; Kuzmin, A.

    2012-11-01

    Nanocrystalline NiO samples have been studied using the Ni K-edge extended x-ray absorption fine structure (EXAFS) spectroscopy and recently developed modeling technique, combining classical molecular dynamics with ab initio multiple-scattering EXAFS calculations (MD-EXAFS). Conventional analysis of the EXAFS signals from the first two coordination shells of nickel revealed that (i) the second shell average distance R(Ni-Ni2) expands in nanocrystalline NiO compared to microcrystalline NiO, in agreement with overall unit cell volume expansion observed by x-ray diffraction; (ii) on the contrary, the first shell average distance R(Ni-O1) in nanocrystalline NiO shrinks compared to microcrystalline NiO; (iii) the thermal contribution into the mean-square relative displacement σ2 is close in both microcrystalline and nanocrystalline NiO and can be described by the Debye model; (iv) the static disorder is additionally present in nanocrystalline NiO in both the first Ni-O1 and second Ni-Ni2 shells due to nanocrystal structure relaxation. Within the MD-EXAFS method, the force-field potential models have been developed for nanosized NiO using as a criterion the agreement between the experimental and theoretical EXAFS spectra. The best solutions have been obtained for the 3D cubic-shaped nanoparticle models with nonzero Ni vacancy concentration Cvac: Cvac≈0.4-1.2% for NiO nanoparticles having the cube size of L≈3.6-4.2 nm and Cvac≈1.6-2.0% for NiO thin film composed of cubic nanograins with a size of L≈1.3-2.1 nm. Thus our results show that the Ni vacancies in nanosized NiO play important role in its atomic structure relaxation along with the size reduction effect.

  18. One-pot process in scalable anoxic vessels for water-dispersed ZnS nanocrystals with the tailored size

    SciTech Connect

    Jung, Hyunsung; Phelps, Tommy Joe; Rondinone, Adam Justin; Jellison Jr, Gerald Earle; Duty, Chad E; Han, Kee Sung; Moon, Ji Won

    2017-01-01

    Well-dispersed ZnS nanocrystals with tailored size in aqueous solutions were synthesized by employing cysteine-sulfur (Cys-S) complexes with low molecular weight in a scalable anoxic vessel. High yield production of water-dispersed ZnS nanocrystals on a 10-L scale was demonstrated in an aqueous solution process. The average crystallite size of ZnS was controlled by changing the ratio of the cysteine to sulfide in the applied Cys-S complexes. A decrease in the crystallite size of ZnS likely resulted in both the blue shift of peak positions and the relative variation of peak intensities in the photoluminescence properties. Additionally, the pH-dependent stability against aggregation of ZnS nanocrystals was investigated to reduce agglomeration.

  19. One-Pot Process in Scalable Bath for Water-Dispersed ZnS Nanocrystals with the Tailored Size

    DOE PAGES

    Jung, Hyunsung; Phelps, Tommy J.; Rondinone, Adam J.; ...

    2017-05-01

    Well-dispersed ZnS nanocrystals with tailored size in aqueous solutions were synthesized by employing cysteine-sulfur (Cys-S) complexes with low molecular weight in a scalable anoxic vessel. High yield production of water-dispersed ZnS nanocrystals on a 10-L scale was demonstrated in an aqueous solution process. The average crystallite size of ZnS was controlled by changing the ratio of the cysteine to sulfide in the applied Cys-S complexes. A decrease in the crystallite size of ZnS likely resulted in both the blue shift of peak positions and the relative variation of peak intensities in the photoluminescence properties. In addition, the pH-dependent stability againstmore » aggregation of ZnS nanocrystals was investigated to reduce agglomeration.« less

  20. Enhanced dielectric permittivity and photoluminescence in Cr doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Virpal; Kumar, Jitender; Thangaraj, R.; Sharma, Sandeep; Singh, Ravi Chand

    2017-09-01

    The effect of Cr doping on dielectric and optical properties of ZnS nanoparticles was systematically investigated at room temperature. Structural analysis confirmed that dopant occupy the regular lattice and interstitial sites in host lattice. Experimental data revealed exceptionally large, low frequency dielectric constant (ɛ‧ ≈ 106) and enhanced photoluminescence emission in Cr doped ZnS nanoparticles. It is argued that larger value of the dielectric constant in doped nanoparticles originate due to combined effect of Maxwell-Wagner phenomenon and microscopic spontaneous polarization, when larger ionic radius Zn2+ (0.74 Å) ions are replaced by smaller ionic radius Cr3+(0.63 Å) ions. The huge enhancement in the value of dielectric constant and emission intensity justify the use of doped ZnS nanostructures for various technological applications.