bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ferromagnetic Ge1-xMx (M = Mn, Co, and Fe) Nanowires
Authors: Cho Yong Jae , Kim chang hyun , Park jeunghee 
Published: April 2011

AbstractWe synthesized Ge and Ge1-xMx (M = Mn, Co, and Fe, x ≤ 0.2) nanowires using thermal vapour transport method. All nanowires consisted of single-crystalline Ge nanocrystals grown uniformly with the [111] direction. High-resolution X-ray diffraction pattern shows no cluster formation for all Ge1-xMx nanowires. The Mn and Fe doping decreases the lattice constant, but not Co doping. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurement revealed that the Mn2+ and Fe2+ ions preferentially occupy the tetrahedral sites, substituting for Ge. We suggest that the Mn or Fe ions produce dopant-acceptor hybridization with host defects in p-type Ge, but not Co ions. The magnetic moment of Mn2+ ions reaches a maximum for x = ∼ 0.1, which is much larger than that of the Fe2+ ions. The magnetization measurement also confirms the room-temperature ferromagnetism of Mn-doped Ge nanowires, which is maximized at x = ∼ 0.1. We conclude that the Mn ions are most efficiently doped into the Ge nanowires to form a ferromagnetic semiconductor.
Synthesis and Characterization of PMMA Coated Magnetite Nanocomposites by Emulsion Polymerization
Authors: Zhang Ming , O'Connor Charles J 
Published: April 2011

AbstractIn this paper, we report the synthesis and characterization of the PMMA-coated magnetite nanocomposite obtained from the emulsion polymerization method. In this approach, the magnetite particles were prepared separately with oleic acid as the capping ligands in nonaqueous solution and disperse in non-polar solvent. The micells structure consisting water, oil phase and surfactant will contain the oleic acid stabilized magnetite particles inside and the polymerization process will only occur on the surface of the emulsion system. This method allows the individual magnetic particles encapsulated in the polymer matrix. The resulting nanocomposites were characterized by TGA, XRD and SQUID
Cell Specific Targeting of Multifunctional γ-Fe2O3 Nanoparticles Through Surface Binding of dsDNA
Authors: Tremel Wolfgang , Shukoor Mohammed Ibrahim , Natalio Filipe , Tahir Muhammad Nawaz , Müller Werner E. G. , Schröder Heinz Christoph 
Published: April 2011

AbstractThe immobilization of polyinosinic-polycytidylic acid [poly(IC)] on ã-Fe2O3 maghemite nanoparticles via the phosphor-amidate route using a multifunctional polymer is reported. The dsRNA coupled nanoparticles were used to visualize the Toll-like (TLR3) receptors at the cell surface. The presence of TLR3 was demonstrated independently in the Caki-1 cell line by RT-PCR and immunostaining techniques
Study of Chromium Impurities in SrTiO3 by Photo-Electron Paramagnetic Resonance Spectroscopy
Authors: Dashdorj Jamiyanaa , Zvanut Mary Ellen 
Published: April 2011

AbstractChromium impurities in SrTiO3 grown by Verneuil and Float-zone methods were investigated using photo-electron paramagnetic resonance spectroscopy. The samples are the substrates typically used for deposition of multifunctional and ferromagnetic films. A maximum optical cross section for Cr3+ of 2.6×10−18 cm2 is obtained from the time-dependent data, and steady state measurements suggest the presence of a defect level 2 eV from one of the band edges. The cross section is similar to that obtained from optical absorption studies of Cr3+ in semiconductors. The results produced here should be useful for those trying to interpret photoluminescence or similar optical characterization data.
Time Resolved In-Situ Diffuse X-ray Scattering Measurements of the Surface Morphology of Homoepitaxial SrTiO3 Films During Pulsed Laser Deposition
Authors: Ferguson John David , Woll Arthur R. , Arikan Gokhan , Dale Darren S. , Amassian Aram , Tate Mark W. , Brock Joel D. 
Published: April 2011

AbstractHomoepitaxial SrTiO3 thin films were grown on SrTiO3 (001) using Pulsed Laser Deposition (PLD). The deposition process was monitored in-situ, via both x-ray reflectivity and surface diffuse x-ray scattering measurements in the G3 experimental station at the Cornell High Energy Synchrotron Source (CHESS). Using a CCD detector in 1D, or streak-camera, mode with approximately 0.3-second time resolution, data were collected during growths performed at two substrate temperatures: 695°C and 1000°C. While the specular reflectivity oscillations for the two growths are very similar, the diffuse scattering clearly shows a distinct change in the peak position. Using Atomic Force Microscopy (AFM), we illustrate how the peak position for the diffuse lobes of scattered intensity is directly related to the distribution of single unit cell high islands on the growing surface. Thus, the peak shift of the diffuse scattering indicates an order of magnitude change in the island density.
Effect of Growth Conditions on Structural and Electrical Properties of Pb(ZrxTi1−x)O3 layers grown by peroxide MBE
Authors: Izyumskaya Natalia , Avrutin V. , Gu X. , Xiao B. , Chevtchenko S. , Zhou Lin , Smith David J. , Yoon J.-G. , Morkoc H. 
Published: April 2011

AbstractPb(ZrxTi1−x)O3 (PZT) films were grown by molecular beam epitaxy using hydrogen peroxide as a source of reactive oxygen. Phase composition as well as structural and electrical properties of the films were studied by x-ray diffractometry, scanning and transmission electron microscopy, conductive atomic force microscopy, and electrical (I-V and polarization-field) measurements. The hydrogen peroxide pressure was found to control the phase composition of the films. Excess peroxide leads to PbO inclusions in PZT layers, whereas deficiency results in the TiO2 or the ZrO2 phase. The second-phase inclusions can be responsible for high leakage current in the films. Precise control over the peroxide pressure is imperative for single-phase PZT films with good ferroelectric properties.
Self-consistent Calculation of the Photocurrent in Polycrystalline Polarized Pb(ZrTi)O3 Films
Authors: Delimova Lyuba A. , Yuferev V. S. , Petrov A. A. , Afanasjev V. P. , Grekhov I. V. 
Published: April 2011

AbstractA polycrystalline Pb(ZrTi)O3 (PZT) film with Pb excess is considered as a heterophase medium that consists of PZT grains and semiconductor PbO phase. The latter is segregated on PZT grain boundaries during the PZT formation and forms conducting channels between the electrodes. In such medium, uncompensated polarization charge of PZT grains generates an electric field both inside PZT grains and PbO phase. This electric field affects on ferroelectric polarization itself and stimulates carrier transport through the PbO channels. A theory is developed, where the reciprocal effect of the electric field on the polarization is taken into account. The polarization is found due to this effect to be increased up to ∼30% near the interfaces, which differs from reduction of the polarization near the interfaces in homogeneous PZT films. Using the theory, the electric field, electrostatic potential and carriers transport in PbO channels are calculated. A comparison is made with the results calculated for the approach of the polarization constancy.
Radiation of X-rays Using Uniaxially Polarized LiNbO3 Single Crystal
Authors: Fukao Shinji , Nakanishi Yoshikazu , Mizoguchi Tadahiro , Ito Yoshiaki , Nakamura Toru , Yoshikado Shinzo 
Published: April 2011

AbstractIt is well known that by changing the temperature for the polarized hemimorphy single crystal, such as LiNbO3 or BaTiO3, the electric field with high intensity is generated and then atmospheric gas atoms or molecules around the crystal are ionized. Using these phenomena, X-rays could be radiated by the bremsstrahlung radiation of electrons in low pressure [1,2]. However, this method has some disadvantages. For example, it is difficult to maintain the intensity of X-rays for a long term. The gas pressure range, where the intensity of X-rays is high, is narrow. The purpose of this study is to increase the intensity of X-rays in a high vacuum. In a low vacuum, positive charges generated by the ionization of gas molecules near the crystal weaken the electric field strength. Consequently, the intensity of X-rays also becomes weak. On the other hand, in a high vacuum, the number of electrons decreases. Thus, thermally emitted electrons are supplied to the X-rays radiation system in high vacuum to increase and stabilize the intensity of X-rays.The -z plane of the congruent LiNbO3 single crystal polarized in the z-axis direction of a 5 mm thickness and a 10 mm diameter was opposed to the Cu target of a 10 μm thickness placed at a distance of 21 mm from the –z plane in the gas pressure of 10-2-10-4 Pa. The temperature of crystal was changed between from -5 to 75 °C using Peltiert device. The temperature history of the crystal consists of a repetition of a series of the increasing and decreasing processes with the same period. Filament of thorium-added-tungsten as a thermal electrons source was placed at a distance of approximately 20 mm from the crystal side edge. DC current flowing in the filament was adjusted from 0 to 4 A.In the increasing process of the temperature, the characteristic X-ray of Nb was radiated. This result indicates that the sign of net charge on -z plane of the crystal is positive. Because thermally emitted electrons are supplied to the positively charged –z plane, the electric field strength generated by the crystal is very low. Thus, the intensity of characteristic X-ray of Nb is low. On the other hand, in the decreasing process of the temperature, the characteristic X-ray of Cu was radiated. At the pressure of approximately 10-2 Pa and the filament current of 2.5 A, the intensity of X-rays showed the local maximum. If electrons are supplied more, synthetic electric field strength is weakened by the electric field made by the electron. The intensity of X-rays using thermal electron source was ten or more times higher at the maximum than that without the source and was almost comparable as the case of a low vacuum or more than it. Using thermal electron source, the intensity of X-rays increased with decreasing the pressure down to approximately 10-2 Pa and became constant at lower pressure.
Shape-Controlled Solution-Synthesis of Single Crystalline ZnTe 1D Nanocrystals
Authors: Fang Jiye , Kumbhar Amar , Sun Kai , Fang Jiye 
Published: April 2011

AbstractPrecursor-reduction method is employed to synthesize nanostructures of ZnTe. The shape of zinc blende ZnTe nanocrystals could be influenced by reaction temperature, concentration of the precursors as well as the use of stabilizing agent. By controlling the synthetic conditions, three types of nanoscaled ZnTe, quasi-spherical ZnTe nanocrystals, ZnTe nanobelts and ZnTe nanorods have been observed. Their crystalline structures are also discussed.
Electrochemical Fabrication of Zn1−xMgxO Films from an Aqueous Solution Containing Magnesium Nitrate and Zinc Sulfate
Authors: Ishizaki Hiroki , Maeda Hideaki 
Published: April 2011

AbstractZn1−xMgxO films with wurtzite structure were electrochemically grown on the conductive glass substrates from a 0.1mol/L magnesium nitrate aqueous solution containing 0.001mol/L zinc Sulfate kept at 323K. With a decrease in the cathodic potential, Mg/(Zn+Mg) atomic ratios of Zn1−xMgxO films decreased and the lattice parameter for c axes decreased. The band gap energy of Zn1−xMgxO films increased with an increase of Mg/(Zn+Mg) atomic ratio. Thus, Mg/(Mg+Zn) atomic ratio and the bandgap energy of these Zn1−xMgxO films will be controlled by the cathodic potential.
Electron carrier concentration dependent magnetization in ZnO:Co and ZnO:Mn thin films
Authors: Yang Zheng , Biasini Maurizio , Mandalapu Leelaprasanna J , Zuo Zheng , Beyermann Ward P , Liu Jianlin 
Published: April 2011

AbstractCo and Mn ions were implanted into n-type ZnO thin films with different electron carrier concentrations. X-ray diffraction measurements show that the ZnO:Co and ZnO:Mn thin films are of high crystallinity. From magnetization measurements, ferromagnetism was observed in both n-type ZnO:Co and n-type ZnO:Mn thin films with Curie temperatures well-above room temperature. Furthermore, the electron carrier concentration dependence of the saturated magnetization was measured in both types of thin films, and our results support an electron-mediated mechanism for ferromagnetism in ZnO:Co, as predicted by theory. However, our measurements seem to contradict theory for ZnO:Mn, which only predicts long-range ferromagnetism for p-type mediated material.
Mechanisms in the Formation of High Quality Schottky Contacts to n-type ZnO
Authors: Allen Martin Ward , von Wenckstern Holger , Grundmann Marius , Hatfield Stuart , Jefferson Paul , King Philip , Veal Timothy , McConville Chris , Durbin Steven 
Published: April 2011

AbstractPt, Ir, Ni, Pd, and silver oxide Schottky contacts were fabricated on the Zn-polar surface of hydrothermally grown bulk ZnO. A relationship was observed between the barrier height of the contact and the free energy of formation of the “metal” oxide. This is consistent with the dominating influence of oxygen vacancies (VO) which tend to pin the ZnO Fermi level close to the VO (+2,0) defect level at approximately EC - 0.7 eV, where EC is the conduction band minimum. Valence band x-ray photoemission spectroscopy and the current - voltage characteristics of planar Schottky diodes, measured on similar Zn-polar surfaces, showed the existence of a vacuum activated surface accumulation layer. This is possibly a consequence of the observed OH termination of the Zn-polar surface. The surface accumulation layer is compensated in atmospheric conditions by the presence of acceptor-like adsorbates, such as O2 and H2O. The formation of high quality Schottky contacts to ZnO should therefore involve the reduction of near surface oxygen vacancies and the removal of H or OH from the surface.
A Study of High Quality Al-doped ZnO Thin Films Grown at Low Temperature by Pulsed Laser Deposition
Authors: Gupta Ram , Ghosh K. , Mishra S. R. , Kahol P. K. 
Published: April 2011

AbstractHighly conducting and transparent Al-doped ZnO (AZO) thin films, which are oriented along c-axis and have wurtzite structure, were grown on quartz substrate at low temperature by pulsed laser deposition. The techniques of x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), optical transmission spectroscopy (OTS), electrical resistivity, and Hall Effect were used to study the effect of growth temperature and oxygen pressure on the structural, electrical transport, and optical properties of these films. The optical transparency in all the films is high and does not change much with oxygen pressure and growth temperature. However, electrical parameters such as resistivity, carrier concentration, and mobility strongly depend on both oxygen pressure and growth temperature. The temperature dependence resistivity measurement indicates semiconducting behavior of all the films. A detailed study indicates that the films which are highly conducting and transparent correspond to an optimum temperature of 200 °C and an oxygen pressure of 5 × 10−7 bar. Higher transmittance of the AZO films compared with pure ZnO and ITO and comparable mobility make us to suggest that Al-doped ZnO is an excellent material for optoelectronic applications.
Top-gate ZnO-based TFTs by RF Sputtering
Authors: Khan Shahrukh , jamshidi-Roudbari Abbas , Hatalis Miltiadis 
Published: April 2011

AbstractThis work emphasizes room temperature deposition and fabrication of top-gated staggered structure ZnO-TFTs and integration of ZnO-TFT based simple logic circuits. We synthesized ZnO thin films by RF sputtering in an Ar/Oxygen ambience with no intentional heating of the substrates. The electrical, optical and structural properties of the ZnO thin films can be well-controlled by altering process parameters such as RF power density and relative Oxygen partial pressure. Typical deposition was carried out at a chamber pressure of 15 mTorr, Ar/Oxygen flow rates of 15 sccm/1 sccm and RF power density of 3W/cm2. The resistivity of the as-deposited films was between 104-106 Ù-cm with high optical transparency (>80%) in the visible spectrum and minimal surface roughness as detected by high-resolution AFM imaging. Gated van der Pauw and Kelvin-bridge structures were lithographically patterned to asses ZnO channel resistance. In the completed devices, a dual-stack (Ta2O5/SiO2) dielectric layer was effective in suppressing gate-leakage current below 10 pA and enabled depletion-mode ZnO-TFT operation exhibiting hard saturation. A Ti/Au metallization scheme was adopted to provide good ohmic contact to ZnO. TFTs retained well-behaved transfer characteristics down to a channel length of 4 ìm with on/off drain current ratio exceeding 105, threshold voltage between -15 V to -5 V and inverse sub-threshold slope of around 1.75 V/decade.
Gas phase synthesis of zinc oxide nanocrystals and their surface modification using small and large acidic ligands
Authors: Chowdhury Sankhanilay Roy , Ali Moazzam , Sudfeld Daniela , Winterer Markus 
Published: April 2011

AbstractZinc oxide nanocrystals are synthesized using the chemical vapor synthesis (CVS) technique. Diethylzinc is used as zinc precursor. Synthesized zinc oxide nanocrystals are characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, transmission electron microscopy (TEM) and dynamic laser scattering. As-synthesized zinc oxide has a primary particle size of about 10 nm and an isoelectric point at pH 9.5. The surface of zinc oxide nanocrystals can be modified using short chain organic acids like formic acid and glycine as well as using low molecular weight polyacrylic acid (PAA). The isoelectric point shifts towards acidic pH when glycine is used as surface modifier whereas it shifts towards basic pH with formic acid. The use of PAA eliminates the isoelectric point with very high value of zeta potential over the range of pH studied in these experiments.
Polymer Composites for Radiation Detection: Diiodobenzene and light emitting polymer molecular solutions for gamma detection
Authors: Pei Qibing , Zhao Yongsheng , Zhong Haizheng 
Published: April 2011

AbstractConjugated polymers are largely intact by gamma exposure but can be energized in the presence of high-Z compounds. The resulting alteration of the polymer's high optical density and photoluminescence efficiency can be exploited for the detection of gamma radiation with high sensitivity. Diiodobenzene and conjugated polymers mix on the molecular level in solid thin films. Composite films of various thicknesses were conveniently cast from solution and exposed to gamma radiation. The responses of the films to gamma dosage were observed with dramatic changes in ultraviolet-visible absorption and photoluminescence.
Topographical Evolution of Nanocrystalline Diamond and Its Effect on Osteoblast Interactions
Authors: Yang Lei , Sheldon Brian W , Webster Thomas J 
Published: April 2011

AbstractThe potential of nanocrystalline diamond films (NDFs) for biological applications has been addressed by a variety of recent researchers. In the present work, we consider the topographical evolution of NDFs fabricated by microwave plasma assisted chemical-vapor-deposition (MPCVD) and its influence on osteoblast (bone forming cells) functions. One group of NDFs formed in this study were grown with 0.67% methane, 5%∼20% hydrogen and argon. The other group of NDFs composed of nano diamond and amorphous carbon was created with indirect exposure to plasma with 0.67% methane, 20% hydrogen and argon. Scanning electron microscope (SEM) images revealed that the nano diamond grains in the first group of NDFs evolved from round shapes into faceted and successively cubic shapes as hydrogen increased, whereas the second group of NDFs consisted of nano platelet grains. Atomic force microscopy (AFM) analysis confirmed this evolution as well as the variation of surface roughness. Cell results demonstrated that osteoblast adhesion and proliferation on NDFs varied dramatically depending on the different topographical features of the films. Specifically, results showed that NDFs with grain size less than 100 nm could be coated on the stem of a hip implant to promote cell adhesion. In contrast, NDFs with grain size greater than 200 nm or NDF with nano platelet grains may be optimal for the inside of acetabular articulation where cell adhesion is not preferred but wear-resistance is important. Further observation by contact angle measurement suggested that the differences in cellular adhesion and proliferation were related to the wettability associated to the topographical features of NDFs surfaces.
Microscopic Detection of DNA Hybridization using Miniaturized Diamond DNA-FETs
Authors: Nebel Christoph E. , Uetsuka Hiroshi , Yang Nianjun , Yamada Takatoshi , Watanabe Hideyuki 
Published: April 2011

AbstractMiniaturized DNA sensitive field-effect transistors (DNA-FET) have been realized using single crystalline diamond grown by plasma-enhanced chemical vapor deposition (CVD). To bond DNA to diamond, amine linker-molecules are covalently attached by photochemical means to H-terminated diamond surfaces. Using hetero-bifunctional cross-linker and thiol-modified single-strand (ss) cancer marker DNA (CK20), the gate of diamond FETs is modified to sense hybridization of DNA, forming double-strand (ds) DNA molecules on the gate. The density of DNA bonded to diamond has been adjusted to about 1012 cm−2 and the experiments have been performed in phosphate buffer with different ionicity to control the Debye length of the Helmholtz layer. By hybridization, a gate-potential shift of 64 mV is detected in case of the 100 Å Debye lengths, while 46 mV is detected for 10 Å. This is discussed with respect to DNA related variations of charge and pH by hybridization. Time resolved experiments reveal exponential hybridization dynamics with a time constant of 600 s. The sensitivity limit of our experiment is about 1 nM.
Nanocrystalline Diamond as a Dielectric for SOD Applications
Authors: Bevilacqua Mose , Tumilty Niall , Chaudhary Aysha , Ye Haitao , Butler James E , Jackman Richard B 
Published: April 2011

AbstractNanocrystalline diamond (NCD) has been grown on oxide coated silicon wafers by microwave plasma assisted chemical vapour deposition using a novel seeding technique followed by optimised growth conditions, and leads to a highly-dense form of this material with grain sizes around 100nm for films approximately 1.5 microns thick. The electrical properties of these films have been investigated using Impedance Spectroscopy, which enables the contributions from sources characterised by differing capacitances, such as grain boundaries and grain interiors, to be isolated. After an initial acid clean the electrical properties of the film are not stable, and both grain boundaries and grains themselves contribute to the frequency dependant impedance values recorded. However, following mild oxidation grain boundary conduction is completely removed and the films become highly resistive (>1013 ohm/sq). This is most unusual, as conduction through NCD material is more normally dominated by grain boundary effects. Interestingly, the AC properties of these films are also excellent with a dielectric loss value (tan δ) as low as 0.002 for frequencies up to 10MHz. The dielectric properties of these NCD films are therefore as good as high quality free-standing (large grain) polycrystalline diamond films, and not too dissimilar to single crystal diamond, and are therefore ideally suited to future ‘silicon-on-diamond’ applications.