bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time Evolution of Nanoscale Surface Topography of Tungsten Carbide Coatings on “Hot” Silicon Carbide Electronics Devices
Authors: Muntele Claudin , Walker Daniel , Elsamadicy Abdalla , Ila Daryush 
Published: April 2011

ABSTRACTWe are reporting here on the current status of our investigations on the time evolution of nanoscale surface morphology of thermally evaporated tungsten carbide coatings on silicon carbide substrates. The purpose of the study is to develop a recipe for creating thermally and chemically stable electrical contacts on silicon carbide electronic devices able to work at elevated temperatures (up to 800 °C) in oxidizing environments. We used thermal evaporation and tungsten carbide (WC) powder as a starting material to produce the thin layer deposition on semi-insulating silicon carbide (6H). Our intended applications are for devices working at 800 °C; therefore, our investigations are carried out at 1 hr intervals of time the samples spent at this temperature, in air at atmospheric pressure. We used Rutherford Backscattering Spectrometry (RBS) for measuring the stoichiometry and depth profile, and Atomic Force Microscopy (AFM) to monitor the surface morphology change.
Electroless Deposition of Gold Nanoparticles Over Silicon-based Substrates
Authors: Borteh Hassan , Ferrell Nick , Butler Randall , Olesik Susan , Hansford Derek 
Published: April 2011

ABSTRACTThe use of proteins and peptides to deposit and pattern metallic nanoparticles is becoming increasingly important. This method provides an inexpensive procedure to produced patterned and continuous metallic nanoparticles on variety of substrates such as silicon dioxide, silicon nitride, and polyimide. In this work, we explore the use of proteins and peptides for patterning and depositing gold nanoparticles. We used two different peptides or proteins for this experiment. One is 3XFLAG peptide from Sigma-Aldrich and the other one is bovine serum albumin (BSA). To pattern the peptides on the substrates we used two different methods, photolithography and micro-transfer molding. In photolithography, S1813 photoresist was patterned on the substrates through clean room process. In the micro-transfer molding process, a PDMS mold was made out of photoresist pattern. Polypropylmethacrylate (PPMA) was spin coated on the PDMS mold and stamped on the substrate in a high temperature. The proteins were adsorbed on the surface either physically or covalently. To deposit gold nanoparticles, the substrates with adsorbed proteins were covered with aqueous HAuCl4 solution. The proteins catalyze gold nanoparticles reduction from the solution. To characterize nanoparticles we used SEM and Electron Beam Induced Current (EBIC).
ITO-Channel Ferroelectric-Gate Thin Film Transistor with Large On/off Current Ratio
Authors: Tokumitsu Eisuke , Senoo Masaru , Shin Etsu , Fujimura Tomofumi 
Published: April 2011

AbstractIndium tin oxide (ITO)-channel ferroelectric-gate thin film transistor (TFT) with large on/off current ratio is demonstrated by using mechanical polishing process to planarize the surface of ferroelectric bottom gate insulator (Bi,La)4Ti3O12 (BLT). It is shown that the mechanical polishing of the sol-gel derived polycrystalline ferroelectric BLT films causes no degradation in electrical properties. ITO channel layer was then deposited on the planarized BLT gate insulator to fabricate ferroelectric-gate TFTs. The off-current of the ITO/BLT TFT fabricated with the polishing process is drastically reduced to around 10−12 A, which is four orders of magnitude lower than that of the TFT fabricated without the polishing process. The obtained on/off current ratio is more than 107. In addition, a subthreshold voltage swing as small as 200 mV/decade was obtained.
Composition Control in the Deposition of Cu(InGa)(SeS)2Thin Films
Authors: Shafarman William , Hanket Gregory , Nishiwaki Shiro 
Published: April 2011

AbstractThe pentenary chalcopyrite compound Cu(InGa)(SeS)2provides several potential advantages over Cu(InGa)Se2as the absorber layer in thin film solar cells, especially with wide bandgap alloys. The effects of S addition to the quaternary alloy are investigated with films deposited by elemental thermal co-evaporation and by the reaction of metallic precursors in hydride gases. With co-evaporated films the addition of S complicates the control of composition through the film. The incorporation of the chalcogen species Se and S depend on the relative Cu in the film and, for films with excess Cu, on the relative group III composition. For the precursor reaction process the addition of S by the inclusion of H2S gas in the reaction enables control of the relative Ga concentration and bandgap of the film. With both processes the incorporation of S during deposition also effects the morphology and grain size. The co-evaporated films have smaller grains with S while the reacted films have larger grains which may be due to the higher TSS the S reaction enables.
Fabrication of (Cu,Ag)InSe2 Thin films by a Combination of Mechanochemical and Screen Printing/Sintering Processes
Authors: Nomura Syuusuke , Matsuo Yoshihiro , Wada Takahiro 
Published: April 2011

AbstractWe successfully prepared (Cu1-XAgx)InSe2 solid solution with 0 ¡Ü x ¡Ü 1.0 by a mechanochemical process without any additional heating. The obtained fine powder was suitable for screen-printing. Particulate precursors were deposited in a thin layer by a screen-printing technique and then the porous precursor layer was sintered into a dense polycrystalline film by atmospheric-pressure firing. The crystal structures of the powder and the film were analyzed by x-ray diffraction and the microstructure of the film was observed in an SEM. For the (Cu1-XAgx)InSe2 films with x ¡Ü 0.2, the (Cu,Ag)InSe2 films had a good microstructure for the solar cell absorbers.
All-CSS processing of CdS/CdTe thin-film solar cells with thin CdS layers
Authors: Davies Alan , Sites J. R. , Enzenroth R. A. , Sampath W. S. , Barth K. L. 
Published: April 2011

AbstractCadmium Sulfide/Cadmium Telluride (CdS/CdTe) thin-film solar cells were fabricated by an in-line, close-space-sublimation (CSS) process at Colorado State University. Source temperature control was used to reduce the deposited CdS thickness. Quantum efficiency (QE) showed CdS thicknesses that varied over a range from 250 to 10 nm. Current-Voltage (J-V) measurements showed increased Jsc as CdS was thinned. Thin CdS resulted in reduced voltage (800 mV to 350 mV) and fill factor, which offset gains in current, and caused efficiencies to drop from 12.6% for thick CdS layers to 4.5% for devices with the thinnest CdS. These performance trends are consistent with calculations assuming parallel junctions of CdS/CdTe and SnO2/CdTe. Localized weak-junction formation was characterized by high-resolution laser-beam-induced current (LBIC) mapping. Greater incidence of spatial non-uniformities in photocurrent response accompanied thinning of the CdS layer, with 638-nm spectral response varying spatially by 4.5% for thin CdS devices compared to variations less than 1% for devices with thicker CdS. Non-uniformities of cells with thin CdS are highly sensitive to voltage bias and are likely indicative of parallel p-n and Schottky-type junctions.
Formation of Cu2ZnSnS4 and Cu2ZnSnS4-CuInS2 Thin Films Investigated by In-Situ Energy Dispersive X-Ray Diffraction
Authors: Weber Alfons , Kötschau Immo , Schorr Susan , Schock Hans-Werner 
Published: April 2011

AbstractChalcopyrite CuInS2 and the structurally related kesterite Cu2ZnSnS4 are known as photovoltaic absorber materials. In this study different precursor thin films of the quaternary Cu-Zn-Sn-S system (stacking: Mo/CuS/ZnS-SnS) and of the pentenary Cu-In-Zn-Sn-S system (stacking: Mo/CuIn/ZnS-SnS) were annealed in sulfur atmosphere. The predominant crystalline phases were detected by in-situ energy dispersive X-ray diffraction (EDXRD). Additionally the X-ray fluorescence signals of the film components were recorded to detect diffusion effects. For the quaternary system we found ZnS, CuS, Cu2-xS, Sn2S3 and SnS as main binary phases during annealing. The Sn2S3-SnS phase transition had a significant impact on the later formation of ternary/quaternary phases. A high diffusivity of copper can explain the little influence of the precursor stacking on the reaction path and may also be responsible for the poor adhesion of the films. For annealing temperatures above 450°C Cu2ZnSnS4 can be identified clearly by XRD. The incorporation of indium in the system leads to new diffraction peaks which can be explained by the formation of solid solutions in the system CuInS2-Cu2ZnSnS4.
Characterisation of Thin Films CuIn1-xAlxSe2 Prepared by Selenisation of Magnetron Sputtered Metallic Precursors
Authors: Zoppi Guillaume , Forbes Ian , Nasikkar Paresh , Miles Robert W. 
Published: April 2011

AbstractThin films of CuIn1-xAlxSe2 have been produced by the selenisation of magnetron sputtered Cu/In/Al precursor layers using elemental selenium and the chemical and physical properties of the layers have been determined for different conditions of synthesis. For optimum conditions of synthesis it was found possible to produce single phase films with the chalcopyrite structure. These films were pinhole free, had good adhesion and were conformal to the substrate. The films had uniform depth profiles as determined using the MiniSIMS. The layers were highly photoactive, indicating that they have the potential to be used to fabricate thin film photovoltaic solar cell devices.
Optical Properties of Strained Polycrystalline CuInS2 Layers
Authors: Eberhardt Jens , Metzner Heinrich , Goldhahn Rüdiger , Hudert Florian , Schulz Kristian , Reislöhner Udo , Hahn Thomas , Cieslak Janko , Witthuhn Wolfgang 
Published: April 2011

AbstractUsing molecular beams, polycrystalline thin CuInS2 (CIS) films of different thicknesses were grown on Si substrates covered with a sputtered Mo-buffer layer. Systematic photoluminescence and photoreflectance measurements were performed to investigate the influence of strain - introduced during growth - on the optical properties. The transition energy of the free A-exciton (FXA) decreases with increasing tensile strain caused by (i) increasing thickness of the Mo buffer layer and (ii) decreasing thickness of the CIS layer. Furthermore, the energetic splittings between FXA, FXB, and FXC increase with increasing tensile strain. When combined with X-ray diffraction data, the oscillator strengths of the excitonic transitions yield information on the strain distribution within the films.
SnS Thin Films in Chemically Deposited Solar Cell Structures
Authors: Avellaneda David , Nair M. T. S. , Nair P. K. 
Published: April 2011

AbstractWe report photovoltaic cell structures on SnO2:F (TCO) coated glass substrates. Thin films of CdS, SnS, and CuS or PbS were deposited sequentially from chemical baths to produce the solar cell structures: SnO2:F-CdS- SnS (A)-CuS-Ag; SnO2:F-CdS- SnS (A)-PbS-Ag; and SnO2:F-CdS- SnS (B)-PbS-Ag. Heating SnS-CuS films results in the formation of Cu2SnS3, and sequential depositions of SnS and PbS to obtain solar cells produce stratified layers as required for solar cells. The photovoltaic characteristics, Voc 340 mV and Jsc 6 mA/cm2 in these structures suggest that absorber thin films based on tin sulfide are worth investigating as a relatively abundant and non-toxic material for solar cells.
Revisiting CdS-PbS Solar Cell Structure
Authors: Garcia Harumi Moreno , Gómez-Daza O. , Campos J. , Nair M. T. S. , Nair P. K. 
Published: April 2011

AbstractCdS and PbS are well known semiconductor materials. Starting in 1969 and into 1970's CdS-PbS cells were reported with open circuit voltage (Voc) up to 450 mV and short circuit current density (Jsc) < 1 mA/cm2. However, further reports are scarce. These two materials are also the most investigated by chemical deposition technique. In this work we revisit this type of photovoltaic junctions and present the photovoltaic behavior of distinct type of cell structures prepared by chemical deposition: glass/CdS/PbS/Ag, SnO2:F/CdS/PbS/Ag, and SnO2:F/CdS/(Bi2S3 or/and CdSe)/PbS/Ag. Depending on the cell type, Voc of > 500 mV or Jsc of > 3 mA/cm2 could be obtained under illumination of 1-3 kW/m2. This work opens up possibilities for developing simple solar cell structures by sequential chemical deposition of semiconductors.
Tailoring the Work Function of Chalcopyrite Thin Films with Self-Assembled Monolayers of Thiols
Authors: Lehmann Sebastian , Fuertes Marrón David , Bär Marcus , Lauermann Iver , Mönig Harry , Lux-Steiner Martha Ch. 
Published: April 2011

AbstractSelf-assembled monolayers of fluorinated thiols have been used as a means of surface conditioning to modify the work function of polycrystalline, wide-gap, chalcopyrite thin films. The molecular dipole, characteristic of such polar molecules, could be transferred to the surface of the semiconductor. Self-arrangement and orientation of the molecules upon adsorption ensured a net dipole contribution that was observed by means of ultra-violet photoemission spectroscopy. Such an approach offers a simple way for interface engineering, with a potential impact on the design of compound-specific band alignments of chalcopyrite-based devices. Molecular mechanics calculations of the expected molecular geometries complemented this work.
Imaging Cellular and Viral Materials with Small Cantilevers Developed for High Speed Atomic Force Microscopy
Authors: Fantner Georg , Ivanov Tzvetan , Ivanova Katerina , Gray David , Rangelow Ivo W , Hansma Paul K , Belcher Angela M 
Published: April 2011

AbstractHigh speed atomic force microscopy (AFM) holds the promise of investigating dynamic systems in real time with single molecule resolution. With the big push towards understanding more complex systems such as cell mechanics or cell-cell and cell-virus interactions, a tool is required that can extract information about these processes in real time in a physiological environment. Atomic force microscopy has been successfully used for investigations of many biological systems and materials in real life conditions, but taking AFM images takes too long to follow many biologically relevant processes. Therefore, attempts have been made to develop high speed AFM by reengineering all the components of an AFM system and much progress has been made. To be useful for investigations of biological systems however, it is often essential to keep imaging forces low in order to get good image quality and not to damage the sample. In this paper we will discuss new small AFM cantilevers we've developed to combine high resonance frequencies for faster imaging with low spring constants for gentle imaging.
Effect of Relative Humidity on Chemical Heterogeneity Imaging with Atomic Force Microscopy
Authors: Gu Xiaohong , Chen Lijiang , Xu Chang , Julthongpiput Duangrut , Fasolka Michael , Nguyen Tinh 
Published: April 2011

AbstractIn this study, a well-controlled humidity system is used to enhance the sensitivity of AFM for characterizing surface chemical heterogeneity of patterned self-assembled monolayers (SAMs) and hydrophilic-hydrophobic polymeric brush specimens. Dependence of the AFM friction contrasts on the surface energy differences between the hydrophilic regions and hydrophobic regions of the chemically heterogeneous samples has been investigated as a function of relative humidity (RH). Effects of RH and surface chemistry on tip-sample adhesion are also investigated. Both AFM image contrast and tip-sample adhesion forces between the hydrophilic and hydrophobic regions significantly depend on RH and follow the similar trend as a function of RH. The results clearly demonstrate that, by using proper RH at the tip-sample environment, chemically heterogeneous regions can be distinguished with the AFM.
The Effect of Composition on the Properties of Semiconducting Transition Metal Nitrides
Authors: Moreno-Armenta Maria G. , Armando Reyes-Serrato , Gerardo Soto H. 
Published: April 2011

AbstractUsing the full potential linearized augmented plane wave (FP-LAPW) method, we investigate the bulk structural and electronic properties in the scandium-, yttrium-, and copper-nitrides over a wide range of nitrogen concentrations. The N atom was gradually incorporated into metal matrix with and without metal vacancies. The ground state properties like densities of states (DOS) and formation energies are determined for each calculated alloy. We have found that the semi-conducting state in copper nitride have a tinny compositional margin. Any deviation of the ideal stoichiometry will produce a metallic character. What is more, the stabilities of the conductive phases are very close to the stability of the semi conducting phase, with a little margin favorable to the conducting phases. The calculations of scandium- and yttrium nitrides show, that for very low nitrogen incorporations, the hexagonal and fcc phases may coexist. However, for high nitrogen concentration the cubic phases are favored. For non-stoichiometric nitrogen content, the materials behave as metal, whereas at stoichiometric composition the DOS becomes zero at Fermi level (EF), confirming in this way the semiconductor character of these nitrides.
Structure of Isolated Oxygen Impurity States in InN
Authors: Alexandrov Dimiter , Butcher Scott , Dietz Nikolaus , Yu Hang 
Published: April 2011

AbstractThe electron state structure of isolated interstitial O atoms in real InN (containing clusters of InN, clusters of InON and clusters of non-stoichiometric InN:In) is the subject of investigation in this paper. It is shown that for the interstitial O atoms the corresponding symmetry is equivalent to that of an O atom in vacuum if the dielectric permittivity of InN is considered, and therefore the hydrogen like impurity atom analysis can be applied for isolated interstitial O atoms hosted in a real InN lattice. It is found that: i) If the O atom is interstitially incorporated in a cluster of pure InN the impurity state has an energy of -5.11 eV, which acts as a donor level with ionization energy +0.06 eV, and also this state is a donor level with an ionization energy of -0.02 eV for a cluster of InON if this cluster occurs at a distance of less than 30 Angstroms; ii) The impurity state has energy -5.15 eV if the O atom is interstitially incorporated in a cluster of InON, which acts as a donor level with ionization energy +0.02 eV, and also this state is a donor level with ionization energy +0.10 eV for a cluster of InN if this cluster occurs on a distance less than 60 Angstroms from the O atom. iii) If the O atom is interstitially incorporated in cluster of non-stoichiometric InN:In the impurity state has energy -5.38 eV, which is in the valence band of this cluster. However this state acts as donor level for both cluster of InN and cluster of InON if they are on distance less that 59 Angstroms from the O atom. The donor ionization energy for the first cluster is +0.33 eV, and for the second cluster it is +0.25 eV.
Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications
Authors: Rodak L. E. , Kuchibhatla Sridhar , Famouri P. , Liu Ting , Korakakis D. 
Published: April 2011

AbstractAluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nano-electromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro- channels for fuel cell applications, and micromechanical resonators.This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.
Application of XRF and AMS Techniques to Textiles in the Mongol Empire
Authors: Katayama Tomoko , Ide-Ektessabi Ari , Funahashi Kazuki , Nishimura Ryoichi 
Published: April 2011

AbstractX-ray fluorescence (XRF) and Accelerator Mass Spectrometry (AMS) techniques were applied to four pieces of ancient Mongolian textiles in order to assist cultural studies of the most significant era of medieval western Asian culture. Radiocarbon dating using Accelerator Mass Spectrometry (AMS) was performed in order to determine the historical age of these pieces. Then, X-ray fluorescence analysis using Synchrotron Radiation (SR-XRF) was carried out in order to obtain elemental maps as well as investigate their constituent elements. Results showed that the textiles were produced between13th and 14th century, and possessed elements such as Au, Cu, Fe and Ti were traced in these pieces whereas Au was used to make gold threads. Cu, Fe and Ti are well known as metallic mordant. In addition, high resolution images were obtained using Scanning Electron Microscope (SEM) to observe the textile structure and their weaving conditions. The whole collected data can assist in bringing into light and facilitate a deeper understanding of the medieval Mongolian cultures, the textile technology, staining techniques, material process technology of the Mongolian Empire and their relations with the neighboring east and central Asian cultures, such as Persia, India and China.
Analysis of Modern and Ancient Artifacts for the Presence of Corn Beer; Dynamic Headspace Testing of Pottery Sherds from Mexico and New Mexico
Authors: Borek Theodore , Mowry Curtis , Dean Glenna 
Published: April 2011

AbstractA large volume-headspace apparatus that permits the heating of pottery fragments for direct analysis by gas chromatography/mass spectrometry is described here. A series of fermented-corn beverages were produced in modern clay pots and the pots were sampled to develop organic-species profiles for comparison with fragments of ancient pottery. Brewing pots from the Tarahumara of northern Mexico, a tribe that regularly uses corn kernels to ferment a weak beer, were also examined for volatile residues and organic-species profiles were generated. Finally, organic species were generated from ancient potsherds from an archaeological site and compared with the modern spectra. The datasets yielded similar organic species, many of which were identified by computer matching of the resulting mass spectra with the NIST mass spectral library. Additional analyses are now underway to highlight patterns of organic species common to all the spectra. This presentation demonstrates the utility of GC/MS for detecting fermentation residues in the fabric of unglazed archaeological ceramics after centuries of burial. This, in turn, opens unexpected new doors for understanding the human past by means of GC/MS analyses.