bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hierarchical Assembly of 2D Nanostructures of Relevance for Organic Solar Cell Design
Authors: O'Donnell Sarah , Buettner Michael , Reinke Petra 
Published: April 2011

AbstractThe first step in synthesizing a model film morphology via a surface-driven hierarchical assembly process is presented. The goal of the hierarchical assembly is the control of the morphology of complex molecular layers for the investigation of fundamental processes in organic solar cells. Using a focused ion beam (FIB) with Ga+ ions at 30 keV, the surface of highly oriented pyrolitic graphite (HOPG) is patterned with an array of local amorphous carbon ellipsoid spots (ACES), which provide preferential nucleation lines at their perimeter, and thus are instrumental in the control of fullerene island growth. On the undamaged surface regions outside the ACES pattern the fullerene island growth is unperturbed, and presents the well-known combination of round and fractal island shapes. The fullerene deposition at the periphery of the ACES pattern, which is characterized by single ion impact defects, results in stunted, smaller and irregular islands. Inside the ACES array, the C60 island growth is controlled by the shape of the ACES and is constrained to lobes which form around each ACES spot. The array and C60 lobe morphology and geometry are characterized and a subsequent understanding of the C60 diffusion fields and nucleation lines within the array is discussed.
Doped Silicon Nanoparticles Synthesized by Nonthermal Plasma
Authors: Pi Xiaodong , Anthony Rebecca , Campbell Stephen , Kortshagen Uwe 
Published: April 2011

AbstractSilicon nanoparticles (Si-NPs) < 6 nm have been doped with B and P in nonthermal plasma. The doping efficiency of B is smaller than that of P, consistent with the theoretically predicted larger formation energy of B than P. The effect of doping on the oxidation-induced changes in light emission from Si-NPs is different between B and P. It appears that P is at or near the surface of Si-NPs, and that B is well incorporated inside Si-NPs. Inks based on doped Si-NPs are produced by attaching alkyl ligands to the surface of Si-NPs and dispersing them in organic solvents.
Concentrational restrictions for race track memories based on permalloy
Authors: Weinberger Peter 
Published: April 2011

AbstractIn using the fully relativistic versions of the Screened Korringa-Kohn-Rostoker method and of the Kubo-Greenwod equation domain wall resistivities at the equilibrium domain wall width are calculated for NicFe1-c. It is found that in comparison to the corresponding "bulk" case only between about 0.6¡Ü c<1 the anisotropic magnetoresistance is reduced in the presence of a domain wall sufficiently enough in order to be of practical use for potential race track memories. Around 80% Ni this reduction amount to remarkable 16%!
Magneto-transport Properties of Gd-doped In2O3 Thin Films
Authors: Gupta Ram , Brown D. , Ghosh K. , Mishra S. R. , Kahol P. K. 
Published: April 2011

AbstractDilute Magnetic Semiconductors (DMS) are a rare group of promising materials that utilize both the electronic charge - a characteristic of semiconductor materials - and the electronic spin - a characteristic of magnetic materials. Oxide based DMS show promise of ferromagnetism (FM) at room temperature. It has been found that doping metal oxides such as ZnO, TiO2, and In2O3 with magnetic ions such as Fe, Co, Mn, and Cr produces DMS, which exhibit FM above room temperature. In2O3, a transparent opto-electronic material, is an interesting prospect for spintronics due to a unique combination of magnetic, electrical, and optical properties. High quality thin films of rare earth magnetic gadolinium (Gd) doped oxide-based DMS materials have been grown by pulsed laser deposition (PLD) technique on various substrates such as single crystal of sapphire (001) and quartz under suitable growth conditions of substrate temperature and oxygen pressure in the PLD chamber. The effect of rare earth magnetic doping on the structural and electro - magnetic properties of these films has been studied using Raman Spectroscopy, X-Ray Diffraction, Scanning Electron Microscopy, and Magneto - Transport. An X- ray diffraction study reveals that these films are single phase and highly oriented. Characteristic Raman peaks typical of indium oxide are observed at 496 and 627 cm−1. We have observed high magnetoresistance (∼18 %) at a relatively small field of 1.3 Tesla for the films with 10 % gadolinium. A detailed study of temperature and magnetic field dependent resistivity, magnetoresistance, and Hall Effect will be presented.
Magnetic Properties of Nd-Fe-B-M (M=Si, C) Bulk Nanocomposite Magnets Prepared by the Spark Plasma Sintering Method
Authors: Fukuzaki Tomokazu , Tanaka Keisuke , Nishimoto Kazue , Muro Yuji , Nishio Keishi , Tamura Ryuji 
Published: April 2011

AbstractWe have prepared Nd2Fe14B/Fe3B bulk nanocomposite magnets at the compositions of Nd4Fe77.5B18.5-xMx (M=Si, C) by substitution of other elements M for B. For the sample substituted with 1 at.%Si and sintered at 600 oC, the coercivity exhibits the highest value of 227 kA/m. It has also been found that the grain sizes of the Nd2Fe14B and the Fe3B phases depend on the ramp-up time and the reduction of the grain size leads to an increase of the coercivity. On the other hand, the samples substituted with C exhibit soft magnetic behaviors, which is attributed to the suppression of the precipitation of the Nd2Fe14B hard magnetic phase.
Anomalous magnetic ordering transition and induced Raman scattering in BiFeO3 thin films
Authors: Singh Manoj K , Prellier W , Jang H M , Katiyar Ram S 
Published: April 2011

AbstractLow temperature magnetic properties and Raman spectrum of highly (111)-oriented rhombohedral BiFeO3 (BFO) thin films epitaxially grown on (111) SrTiO3 substrates by pulsed laser deposition have been studied. Zero field cooled (ZFC) and field cooled (FC) magnetization curves display divergence at characteristic temperature Tirr (H), which are magnetic field dependent, suggesting a spin-glass like behavior of the film. The change in magnetic ordering results in anomalous phonon behavior such as the extraordinary enhancement and appearance of new Raman modes due to Brillouin zone folding below ∼200 K.
Engineered Biferroic 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3/La0.6Sr0.4MnO3 Epitaxial Superlattices
Authors: Roy Chaudhuri Ayan , Krupanidhi S.B. 
Published: April 2011

AbstractSymmetric and asymmetric superlattices (SLs) composed of ferromagnetic La0.6Sr0.4MnO3 (LSMO) and ferroelectric 0.7Pb(Mg1/3Nb2/3)O3 – 0.3PbTiO3 (PMN-PT) with different periodicities have been fabricated on LaNiO3 (LNO) coated LaAlO3 (100) (LAO) substrates by pulsed laser ablation deposition. Structural, ferromagnetic and ferroelectric properties have been studied for all the SLs. All the heterostructures exhibited good ferromagnetic response over a wide range of temperatures (10K – 300K), whereas only the asymmetric SLs exhibited reasonably good ferroelectric behaviour. Ferromagnetic and ferroelectric hysteresis loops observed in the asymmetric SLs confirmed their biferroic nature. Studies were conducted towards understanding the influence of LSMO layers on the electrical responses of the heterostructures. Absence of ferroelectricity in the symmetric SL structures has been attributed to their high leakage characteristics. Strong influence of an applied magnetic field of 1.2T was observed on the ferroelectric properties of the asymmetric SLs. The effect of magnetic field on the ferroelectric properties of the SLs indicated possibility of strong interfacial effect.
PMN-PT Single Crystal Piezo-Electric Acoustic Sensor
Authors: Lee Sung Q , Kim Hye Jin , Lee Sang Kyun , Lee Jae Woo , Park Kang Ho 
Published: April 2011

AbstractThe MEMS (micro-electro-mechanical systems) microphone enables the manufacturing of small mechanical components on the surface of a silicon wafer. The MEMS microphones are less susceptible to vibration because of the smaller diaphragm mass and an excellent candidate for chip-scale packaging. In this paper, we present a piezoelectric MEMS microphone based on (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystal diaphragm. The PMN-PT materials exhibit extremely high piezoelectric coefficients and other desirable properties for an acoustic sensor. The piezoelectric-based microphone can offer the ability to passively sense without the power requirements. In particular, this paper introduces the design of a PMN-PT single crystal diaphragm with interdigitated electrode. We were able to fabricate miniaturized PMN-PT single crystal diaphragms. The fabricated sensor exhibits the sensitivity of 1.5mV/Pa. This implies that the PMN-PT thin film microphone has a potential of excellent acoustic characteristics.
Deposition Rate Effect on Critical Thickness of BaTiO3Epitaxial Thin Film Grown on SrTiO3(001)
Authors: Kawai Masanori , Kan Daisuke , Isojima Seiichi , Kurata Hiroki , Isoda Seiji , Kimura Shigeru , Sakata Osami , Shimakawa Yuichi 
Published: April 2011

AbstractBaTiO3/SrTiO3(001) epitaxial thin films were prepared at various growth rates by pulsed laser deposition, and their heterostructures were evaluated by synchrotron x-ray diffraction measurements and cross-sectional scanning transmission electron microscopy observations. In a film grown at a low deposition rate (0.01 nm/s), misfit dislocations are found near the interface and a fully relaxed BaTiO3thin film grows epitaxially on the substrate. On the other hand, a film grown at a high deposition rate (0.04 nm/s) consists of strained and relaxed BaTiO3lattices. Our results showed that the critical thickness of BaTiO3/SrTiO3(001) epitaxial thin films can be controlled by the deposition rate and that the critical thickness increases with increasing the deposition rate, and by adjusting the deposition rate we were able to prepare epitaxial thin films consisting of fully strained BaTiO3, partially strained BaTiO3or fully relaxed BaTiO3. We have also achieved the growth controlling of BaTiO3thin films on SrTiO3(001) substrates with SrRuO3bottom electrode layer.
Phase Transition and Dielectric Tunability of Chemical Solution Deposited (Pb0.35Sr0.65)(Zr0.5Ti0.5)O3 Thin Films on Pt/ZrO2/SiO2/Si Substrates
Authors: Karan Naba K , Perez Marilin , Saavedra Jose , Pradhan Dillip K , Thomas Reji , Katiyar Ram S 
Published: April 2011

Abstract(Pb0.35Sr0.65)(Zr0.5Ti0.5)O3 thin films were grown on Pt/ZrO2/SiO2/Si substrates by chemical solution deposition. As-deposited (pyrolysed at 500°C) films were amorphous and single phase films were obtained at temperature as low as 550°C with a 30 nm SrTiO3 seed layer. Dielectric constant and loss tangent at room temperature were 210 and 0.022, respectively at 100 kHz for the film annealed at 700°C. Frequency dispersion of the dielectric properties was low. The phase transition temperature (ferroelectric to paraelectric) was well below the room temperature and was around 220 K. The room temperature tunability and the k-factor at 500 kV/cm was around 45% and 16, respectively.
Synthesis and Characterization of Pb(Fe1/2Ta1/2)O3
Authors: Martinez Ricardo , Palai R. , Katiyar R.S. 
Published: April 2011

AbstractLead iron tantalate Pb(Fe1/2Ta1/2)O3 (PFT) is a compound derived of general formula Pb(BIxBII1-x)O3 wherein x=1/2. In this work synthesis, sintering processes, dielectric, electrical, magnetic measurement, and Raman spectroscopy properties of PFT ceramics are described. The dielectric properties of PFT showed typical relaxor behaviors. We saw that ferroelectric and magnetic orders coexist in PFT at room temperature.
Synthesis, characterization and growth mechanism of ZnO/TiO2 nanohybrid arrays
Authors: Chun Cheng , Ning Wang 
Published: April 2011

AbstractIn this paper, we demonstrate a simple method to synthesize ZnO/TiO2 nanohybrid structure arrays based on the site-specific deposition of titanium oxide on ZnO nanorods under the hydrothermal condition. We have found that the polarity of the ZnO (0001) surface plays an important role in the formation of the nanohybrid structures. Each ZnO nanorod is assembled with one TiO2 particle only at the (0001) end surface. High-resolution transmission electron microscopy study shows that the TiO2 particles that are connected to ZnO nanorods are amorphous. By annealing at different temperatures, these particles can be transformed to nanocrystals of the anatase and rutile phases, which have a particular relationship with the orientation of ZnO nanorods and good interface structures. This work provides a rational approach to the assembly of complex nanohybrids using the intrinsic properties of ZnO nanocrystals.
Visible Luminescence Related to Defects in ZnO
Authors: Reshchikov Michael A. , Nemeth B. , Nause J. , Xie J. , Hertog B. , Osinsky A. , Avrutin V. , Izyumskaya N. , Shimada R. , Morkoc H. 
Published: April 2011

AbstractWe studied several photoluminescence (PL) bands in undoped, Li-, Ga-, and N-doped high-quality ZnO bulk crystals and thin films grown by molecular beam epitaxy (MBE). By analyzing PL in a wide range of excitation power densities, sample temperature, and decay time after a laser pulse, we distinguished and analyzed more than 10 broad bands with unique luminescence properties. Among these bands, only the Cu-related green band with a characteristic fine structure and the Li-related orange band were well-studied and reliably identified in the past.
Hydrogen Migration in Single Crystalline ZnO
Authors: Johansen Klaus Magnus Håland , Christensen Jens Sherman , Monakhov Edouard V. , Kuznetsov Andrej Yu. , Svensson Bengt Gunnar 
Published: April 2011

AbstractHydrogen has been proposed as one of the contributors to the native n-type doping in as-grown Zinc Oxide and can also be used as an active (intentional) n-type dopant. In this work we have employed Secondary Ion Mass Spectrometry (SIMS) to study deuterium diffusion profiles in single crystalline ZnO. The samples used are hydrothermally grown, high-resistive (10 kΩ cm) monocrystalline ZnO implanted with deuterium to a dose of 1×1015 cm−2 yielding a peak concentration of approximately 5 × 1018 cm−3 at a depth of 2.2 µm. Diffusion profiles have been studied after 30 minutes isochronal heat treatments from 100ºC up to 400ºC in steps of 50ºC. The observed redistribution can be explained by employing a diffusion model which includes trapping of 2H by Li-impurities and an activation energy of 0.85 eV is extracted for the diffusion of 2H.
Hydrothermally Grown Single-Crystalline Zinc Oxide; Characterization and Modification
Authors: Svensson Bengt Gunnar , Børseth Thomas Moe , Johansen Klaus Magnus , Maqsood Tariq , Schifano Ramon , Grossner Ulrike , Christensen Jens S. , Vines Lasse , Klason Peter , Zhao Qing X. , Willander Magnus , Tuomisto Filip , Skorupa Wolfgang , Monakhov Edouard V. , Kuznetsov Andrej Yu. 
Published: April 2011

AbstractAn overview of our recent results on characterization and modification of high-resistivity n-type bulk zinc oxide samples, grown by hydrothermal techniques, is given. Three specific topics are addressed; (i) the role of lithium (Li) as an electrically compensating impurity, (ii) extrinsic n-type doping by hydrogen implantation, and (iii) influence of annealing conditions on deep band emission. In (i), furnace annealing of as-grown samples at temperatures above ∼800 °C is shown to cause out-diffusion of residual Li impurities and concurrently, the resistivity decreases. After annealing at 1400 °C, a resistivity close to 10−1 Ωcm is obtained and the Li content is reduced from above 1017 cm−3 to the mid 1015 cm−3 range, providing evidence for the crucial role of Li as an electrically compensating impurity. For ion-implanted samples, vacancy clusters evolve during post-implant flash lamp annealing (20 ms duration) and these clusters appear to trap and deactivate Li with a resulting improvement of the n-type conductivity. However, these clusters have a limited stability and start to dissociate already after 1h at 900 °C, accompanied by a decrease in the conductivity. For topic (ii), n-type doping by hydrogen implantation is shown to enhance the conductivity by about 5 orders of magnitude already in the as-implanted state. Despite substantial loss of hydrogen, the conductivity remains stable, or even increases, after annealing up to ≥600 °C, and necessary conditions for doping by hydrogen are discussed. In (iii), the origin of the commonly observed deep band emission from monocrystalline zinc oxide is investigated using a concept of annealing as-grown samples in different atmospheres. A strong influence by the atmosphere and temperature is observed and the results can be interpreted in terms of dominant effects on the emission by vacancy-related defects.
Application of ZnO to Passivate the GaN-based Device Structures
Authors: Kaminska Eliana , Piotrowska Anna , di Forte Poisson Marie-Antoinette , Delage Sylvain , Lahreche Hacene , Kwietniewski Norbert , Pasternak Iwona , Kruszka Renata , Guziewicz Marek , Boguslawski Piotr , Dynowska Elzbieta , Borysiewicz Michal 
Published: April 2011

AbstractThe fabrication of high-resistivity ZnO-based thin films lattice-matched to AlGaN/GaN structures has been developed. It relies on low-temperature reactive sputter deposition of ZnO:Sb from ZnSb target. Taking into account the hygroscopic nature of ZnO surface, an additional coating by Si3N4 films is applied to ensure the humidity protecition. The developped passivation suppresses leakage currents in Schottky diods, and substantially improves output characteristics of AlGaN/GaN HEMT.
Luminescence of Er-doped ZnO Films: Effects of Thermal Annealing and Doping Concentration
Authors: Pan Zhengda , Morgan S H , Ueda A , Aga R , Steigerwald A , Mu R 
Published: April 2011

AbstractPhotoluminescence (PL) of erbium-doped zinc oxide films with nano-sized grains was studied. The films were grown on silicon (100) and fused silica substrates using e-beam evaporation. The evaporating targets used were sintered pellets of ZnO and Er2O3 mixtures with two different Er concentrations. The films were subsequently annealed at 700 °C in air for an hour. PL was measured at two excitation wavelengths, 325 and 488 nm. The 325 nm is used for exciting the host semiconductor ZnO and 488 nm is used for directly exciting Er3+ ions in the ZnO host. Strong Er3+ luminescence of 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions was observed from annealed film with 4.0 % Er2O3 concentration using either 325 or 488 nm excitation. With 325 nm excitation, the Er3+ luminescence observed is attributed to energy transfer from the excitons in ZnO host to the Er3+ ions doped. The effective energy transfer from ZnO host to the doped Er3+ ions is an essential property for the realization of actual current-injection opto-electronic devices operating at wavelengths of Er3+ emission, for example, at 1.54 μm for the erbium-doped fiber amplifier (EDFA). Our PL results indicate that thermal annealing plays an important role for optically activating the doped Er3+ ions in ZnO nano-crystalline grains of the film.
Blue and Yellow Luminescence in ZnO Films Grown by Peroxide MBE
Authors: Avrutin Vitaliy , Reshchikov Mikhail A. , Izyumskaya Natalia , Shimada Ryoko , Morkoç Hadis 
Published: April 2011

AbstractWe observed strong shifts of the blue and yellow luminescence bands with variation of excitation intensity in ZnO films grown on sapphire by MBE using hydrogen peroxide as a source of reactive oxygen. The blue band, having a maximum in the range from 2.85 to 3.15 eV in different samples and different excitation intensities at 10 K, is attributed to diagonal transitions from the conduction band (or shallow donors) to the valence band in realm of potential fluctuations caused by random distribution of charged point defects in a compensated semiconductor. The yellow band is related to an unidentified deep acceptor.
Valence Band Structure of ZnO and MgxZn1−xO
Authors: Schmidt-Grund R. , Sturm C. , Schubert M. , Rheinländer B. , Faltermeier D. , Hochmuth H. , Rahm A. , Bläsing J. , Bundesmann C. , Zúñiga-Pérez J. , Chavdarov T. , Lorenz M. , Grundmann M. 
Published: April 2011

AbstractWe present an attempt to clarify the valence band order of ZnO and MgxZn1−xO films grown by pulsed laser deposition (PLD) on sapphire substrates. We derive the dependence of spin orbit interaction (Δso) and crystal field interaction (Δcf) on the temperature, strain and cation replacement (Zn with Mg) and compared this with theoretical predictions. The strain was varied by using different orientated sapphire substrates (c-, r-, and m-plane orientations) and by varying the film thicknesses. All these investigations support the conclusion that the symmetry order of the valence band is Γ7-Γ9-Γ7 for ZnO and MgxZn1−xO for x ≤ 0.55.
In-situ AFM study of the crystallization and pH-dependent stability of ZnO(0001)-Zn surfaces
Authors: Valtiner Markus , Grundmeier Guido 
Published: April 2011

AbstractPolar ZnO(0001)-Zn surfaces can be prepared as very well defined and single crystalline surfaces by hydroxide stabilization simply by introducing hydroxides via a wet chemical cleaning step. Within this proceeding we present an in-situ AFM imaging of the crystallization process. The pH dependent stability of the resulting hydroxide-stabilized surfaces was further investigated by means of an ex-situ LEED approach. These investigations show, that it is possible to obtain high quality single crystalline ZnO(0001)-Zn surfaces in a simple way. Moreover, these surfaces turned out to be very stable within a wide range of pH values between 11 and 3 of NaClO4 based 1mM electrolyte solutions.
Effects of Nanometer-Scale Surface Roughness and Applied Load on the Bond Strength and Contact Resistance of Cu-Cu Bonded 3D ICs
Authors: Leong Hoi Liong , Gan Chee Lip , Thompson Carl V. , Pey Kin Leong , Li Hongyu 
Published: April 2011

AbstractThe effects of total surface roughness of Cu bond layers and applied load during bonding on the bond strength and the contact resistance of the bonded interface were studied for three-dimensional (3D) devices. The 3D structures were fabricated by thermocompression bonding of two wafers, each fabricated with a Cu damascene process. The average bond strength of the samples was found to increase with increasing load, and with decreasing roughness. On the other hand, the average contact resistance increased as the total surface roughness of the bonded interface increased, as well as when the applied load decreased. The increase in bond strength (and also the dicing yield) is related to a smaller true contact area, which can be estimated using a model based on contact mechanics theory. The theory takes into account the roughness of the bonded surface, the applied load during bonding and the nominal bond area. A contact resistance model can also be used to estimate the contact resistance of bonded interfaces based on their true contact area. However, within each set of measurements, a significant spread about the average value of bond strength and contact resistance was observed, suggesting issues of contact and bonding non-uniformity of the wafers. Nonetheless, the contact resistance values given by the model were in good agreement with the minimum values observed in experiments, which may represent the ideal cases of bonding of rough surfaces. Our results show that the impact of surface roughness and applied load on the contact resistance of Cu-Cu thermocompression bonds can be quantified experimentally, and understood in the context of established theory for contact mechanics.
ALD of Lanthanum Aluminate Using Lanthanum Formamidinate Precursor
Authors: Li Huazhi , Shenai Deodatta Vinayak , Pugh Ralph , Kim Jiyoung 
Published: April 2011

AbstractThe physical and electrical characteristics of La2O3 and LaAlO3 films, deposited by atomic layer deposition (ALD) and using a new La formamidinate precursor (La-FAMD), were investigated. The La-FAMD precursor has superior thermal stability and is also the most volatile La source available today. The vapor pressure of La-FAMD, maintained at 100 ºC, is approximately 60 times higher than the commercial available source La-THD (THD = tetramethylheptanedionato).