bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Field Sensors based on Magnetoresistance Effect in Organic Semiconductor Sandwich Devices
Authors: Veeraraghavan Govindarajan , Mermer Ömer , Sheng Yugang , Nguyen Tho Duc , Francis Thomas Lee , Wohlgenannt Markus 
Published: April 2011

AbstractWe describe magnetic field sensors based on a recently discovered magnetoresistance (MR) effect in nonmagnetic organic semiconductor sandwich devices. The MR effect reaches up to 10% in a magnetic field of 10 mT at room temperature. We perform an extensive experimental characterization of this effect. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. We also measured the device response to alternating magnetic fields up to 100 kHz. To the best of our knowledge, the discovered MR effect is not adequately described by any of the MR mechanisms known to date.
Minimizing 1/f Noise in Magnetic Sensors using an AC MEMS Flux Concentrator
Authors: Edelstein Alan , Fischer Greg A. , Pedersen Michael , Nowak Edmund , Cheng Shu Fan , Nordman Cathy A 
Published: April 2011

AbstractWe are developing a device, the MEMS flux concentrator, that will greatly decrease the effect of 1/f noise in magnetic sensors. It does this by modulating the incoming signal and thus shifting the operating frequency of the sensor. This is accomplished by placing flux concentrators on MEMS structures that oscillate at kHz frequencies. Depending upon the sensor, shifting the operating frequency reduces the 1/f noise by one to three orders of magnitude at one Hz. We have succeeded in fabricating the necessary MEMS structures and observing the desired kHz normal mode resonant frequency. Only microwatts are required to drive the motion. We have used spin valves for our magnetic sensors. The measured field enhancement provided by the flux concentrators agrees to within 3% with the value estimated from finite element calculations. Noise measurements provide strong evidence that the device is likely to reduce the effect of 1/f noise. Flip chip bonding is likely to allow us to fabricate complete, fully functioning sensors.
In-situ Observations of Martensitic Transformation in Pure Ti Thin Films using the Dynamical Transmission Electron Microscope (DTEM)
Authors: LaGrange Thomas Bradley , Campbell Geoffrey H. , Colvin Jeffrey D. , King Wayne E. , Browning Nigel D. , Armstrong Michael R. , Reed Bryan W. , Kim Judy S. , Stuart Brent C. 
Published: April 2011

AbstractWe have measured the transient events of the α-β martensitic transformation in nanocrystalline Ti films via single shot electron diffraction patterns with 1.5 ns temporal resolution. This was accomplished with a newly constructed dynamic transmission electron microscope (DTEM), which combines pulsed laser systems and pump-probe techniques with a conventional TEM. The DTEM thereby enables studies of transformations that are (1) far too fast to be captured by conventional bulk techniques, and (2) difficult to study with current ultrafast electron diffraction (UED) instruments (which typically require an accumulation of multiple shots for each diffraction pattern). Martensitic transformations in nanocrystalline materials meet both criteria, with their rapid nucleation, characteristic interface velocities ∼1 km/s, and significant irreversible microstructural changes. Free-standing 40-nm-thick Ti films were laser-heated at a rate of ∼1010K/s to a temperature above the 1155 K transition point, then probed at various time intervals with a 1.5-ns-long intense electron pulse. Diffraction patterns show an almost complete transition to the β phase within 500 ns. Post-mortem analysis (after the sample is allowed to cool) shows a reversion to the α phase coupled with substantial grain growth, lath formation, and texture modification. The cooled material also shows a complete lack of apparent dislocations, suggesting the possible importance of a "massive" short-range diffusion mechanism.
In Situ Recrystallization Imaging of Polycrystalline Ni-S Alloy by SEM
Authors: Cornen Marilyne , Le Gall René 
Published: April 2011

AbstractImpurity segregation at alloy grain boundaries (GB) depends on many parameters such as GB character and prior thermomechanical history. In this paper we describe an experimental set-up designed to record the individual behaviour of GB during recrystallization of a Nickel-Sulphur alloy. The aim is to correlate segregation level with mobility and disorientation of GB. Therefore a method allowing direct observation of the GB motion as well as disorientation mapping is needed.Studying grain growth and recrystallization of this particular alloy by Scanning Electron Microscopy is possible thanks to real time in-situ imaging. This requires a sensitive crystal orientation contrast and the ability to image hot evolving samples. To heat the samples, a special device designed for the SEM analysis chamber is used. This device is used at 455°C but is able to reach higher temperatures. In order to get the orientation contrast images, as well as to protect the Secondary Electron (SE) detector from heat and light, a channel plate converter has been designed. This experimental set-up, combined with the heating system, allow the observation of the sample during recrystallization and recording small videos providing information such as grain boundary displacement rate. Then, associated with an EBSD analysis we can get the disorientation map of the area of interest and eventually an electrochemical technique is performed to create preferential dissolution at GB. Geometry of the grooves resulting from an electrochemical etching gives an evaluation of the segregation level in GB.
Pd/Ni(111) surface structure by impact-collision ion scattering spectroscopy
Authors: Umezawa Kenji , Yamauchi Kaname , Nakanishi Shigemitsu , Gibson Walter M 
Published: April 2011

AbstractPd deposits on Ni(111) have been studied by low energy ion scattering spectroscopy. We found that two different types of epitaxial growth exist: Pd[11 2]//Ni[11 2] and Pd[11 2]//Ni[11 2] at substrate temperature of 300 K. The Pd(111) planes grow as mixed domains of 50 % each. Surface alloying of the Pd-Ni system was confirmed for deposition at 300 K in which Pd atoms displace first-layer Ni atoms, with an outward displacement of 0.4 Å with respect to first layer Ni atoms.
Ion-Beam-Synthesised Ag-SiO2 Nanocomposite Layers for Electron Field Emission Devices
Authors: Tsang Wei-Mong , Stolojan V. , Adikaari A. A. D. T. , Wong S. P. , Silva S. R. P. 
Published: April 2011

AbstractAg-SiO2 nanocomposite layers were synthesised by Ag+ implantation into thermally oxidised SiO2 layers and demonstrated to have excellent field emission (FE) properties. These nanocomposite layers can give an emission current of 1 nA at electric fields less than 20 V/μm, compared to several thousand volts per micrometre of pure metal surfaces. Their fabrication processes are fully compatible with existing integrated circuit technology. By correlating the FE results with other characterisation techniques including atomic force microscopy, Rutherford backscattering spectroscopy and transmission electron microscopy, it is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the excellent FE properties of these cathodes. Firstly, the electrically conductive Ag nano-clusters embedded in the insulating SiO2 matrix give rise to a local electric field enhancement due to an electrical inhomogeneity effect and secondly, the dense surface protrusions provide a geometric local electric field enhancement. The FE properties of these layers are critically dependent on the size and distribution of the Ag clusters, which can be controlled by the Ag dose and modified by the post-implantation pulse annealing with a high power KrF Excimer laser operating at 248 nm.
Influence of Neutron Transmutation Doping on Optical Properties of Ge nanocrystals Prepared by Ion implantation
Authors: Dun Shaobo , Lu Tiecheng , Hu Qiang , Huang Ningkang , Zhang Songbao , Tang Bin , Dai Junlong , Resnick Lev , Shlimak Issai , Zhu Sha , Wei Qiangmin , Wang Lumin 
Published: April 2011

AbstractGe nanocrystals embedded in an amorphous SiO2film on Si matrix were prepared by ion implantation and subsequent annealing. Neutron transmutation doping (NTD) technique was used for doping Ge nanocrystals with As impurities. The microstructure, phase and photoluminescence of NTDed Ge nanocrystals were analyzed and compared with undoped Ge nanocrystals. A new photoluminescence peak related to As impurities was found. It is discovered that impurities are expelled from larger clusters resulted from Ge nanocrystal aggregation on the sample surface. To prevent nanocrystal aggregation and assure uniform doping of As, it is necessary to adopt appropriate implantation and annealing conditions.
Deposition energy dependence in cluster-assembled thin film densities
Authors: Meinander Kristoffer , Clauss Tina , Nordlund Kai 
Published: April 2011

AbstractMechanical properties of thin films grown by nanocluster deposition are highly dependent on the energy at which the clusters are deposited. Using molecular dynamics computer simulations we have quantitatively studied variations in the properties of copper thin films grown by deposition of Cu nanoclusters, at energies ranging from 5 meV to 10 eV per cluster atom, on a Cu (100) substrate.
Redistribution of Mn upon Annealing in Ferromagnetic Mn-implanted Si
Authors: Bolduc Martin , Awo-Affouda Chaffra , Ramos Frank , LaBella Vincent P 
Published: April 2011

AbstractThe redistribution of implanted Mn ions in Si after thermal annealing is studied. P-type Si wafers were implanted with 300-keV Mn+ ions at 350°C to a dose of 1×1015 cm-2, and then annealed at 800 °C for 5 min. Ferromagnetic hysteresis loops were obtained at 10 K using a SQUID magnetometer both before and after annealing. The saturation magnetization increases by ∼2 × after the post-implant annealing, while the Mn redistributes with sharp peaks in concentration. The calculated point-defect profile created during the implantation process peaks around the Mn-depleted region, suggesting that the residual implant damage may play a role in the ferromagnetic behavior of Mn-implanted Si.
An Exploration of Microscopy for Educational Applications in the High School Classroom
Authors: Fitzsimmons Ryan , Koekkoek Robert , Caragianis-Broadbridge Christine , Lehman Ann Hein , Cummings Karen 
Published: April 2011

AbstractThis project was initiated with an undergraduate student’s exploration of two advanced research tools: the scanning electron microscope (SEM) and the atomic force microscope(AFM). A research project was developed to study the application of microscopy to introductory physics instruction. Nine modules covering various aspects of introductory physics were created. Module components included discussions, laboratory experiments and assessments. Four of the nine modules were implemented in various high school classes. Assessments were used to compare student learning with the modules versus standard textbook/lecture techniques. Preliminary results of this study are presented along with recently developed methods created to facilitate implementation of these modules within the high school classroom.
Molecular Dynamic Computer Simulation of Thin Film's Heat Dissipation Rate
Authors: Cheng Ya-Yun , Hsieh Horng-Ming , Lee Cheng-Chung 
Published: April 2011

AbstractHeat dissipation rate of the thin film is theoretically related to the thickness of the film. As the film grows on a substrate of constant temperature, the heat dissipation rate would be lower when the film becomes thicker. It is difficult to observe rate change during the film growth through experiment. With MD simulation, this rate can be "observed". A system including Platinum substrate at constant temperature 300K is setup. The constant temperature is obtained by Phantom method.The average temperature of aluminum thin film is 600K. For various thickness of the film: 3.656nm, 5.302nm, and 7.567nm. The average temperature decays exponentially. Through the simple equation T=(T0-Ts)exp(-kt/d2PCp)+Ts, the dissipation rate should follow the parameter R=k/d2PCp and the parameter α=k/£Cp is the thermal diffusivity. It is observed that the thermal diffusivity increases with film thickness increases.
Thermal Conductivity and Natural Cooling Rate of Excimer-Laser Annealed SI: A Molecular Dynamics Study
Authors: Lee Byoung-Min , Seong Baek Seok , Baik Hong Koo , Munetoh Shinji , Motooka Teruaki 
Published: April 2011

AbstractTo investigate the relationship between the thermal conductivity and the cooling rate, we have performed molecular-dynamics (MD) simulations based on a combination of the Langevin and Newton equations to deal with a heat transfer from l-Si to c-Si. The thermal conductivity of c-Si was measured by the direct method. In order to deal with finite-size effects, different cell sizes perpendicular to the direction of the heat current were used. The values of the thermal conductivity of 58 W/mK and 35.7 W/mK in the Tersoff potential were obtained at 1000 K and 1500 K, respectively. A MD cell with a length of 488.75 ¡Ê in the direction of a heat flow was used for estimating the natural cooling rate. The initial c/l interface systems were obtained by setting the temperatures of the MD cell at 1000 K and 1500 K, respectively, for Z <= 35 ¡Ê and 3800 K for Z > 35 ¡Ê. During the natural cooling processes, the temperature of the bottom 10 ¡Ê of the MD cell was controlled. The cooling rates of 7.4 × 1011 K/sec for 1000 K and 5.9 × 1011 K/sec for 1500 K were obtained, respectively.
A Second Order Accurate Finite Difference Scheme for the Heat Equation on Irregular Domains and Adaptive Grids
Authors: Chen Han , Min Chohong , Gibou Frederic 
Published: April 2011

AbstractWe present a finite difference scheme for solving the variable coefficient heat equations with Dirichlet boundary conditions on irregular domains. A quadtree data structure is used to represent the non-graded adaptive Cartesian grids, and the interface is represented by the zero value points of the level set function. Numerical results in two spatial dimensions demonstrate second order accuracy for both the solution and its gradient.
Environment of Er Doped in a-Si:H and Its Relation with Photoluminescence Spectra
Authors: Kumeda Minoru , Sekizawa Yoshitaka , Morimoto Akiharu , Shimizu Tatsuo 
Published: April 2011

AbstractThe crystal-field potential at the Er3+ ion surrounded by six oxygen ions is expanded in terms of polynomials. After converting it into equivalent angular momentum operators, the Stark-splitting of the 4I15/2 ground state of the Er3+ ion is calculated. Influence of the change in the environment of the Er3+ ion on the shift of the energy levels is investigated and compared with the observed Er photoluminescence spectrum in a-Si:H. The scattering of the calculated energy levels by the structural fluctuation around the Er3+ ion is also compared with the linewidth of the component photoluminescence lines.
Role of Hydrogen in the Grain Growth in Microcrystalline Silicon Films
Authors: Lee Gye-Hyun , Yoon Jong-Hwan 
Published: April 2011

AbstractThick microcrystalline silicon (mc-Si:H) films were exposed to atomic hydrogen plasma at substrate temperature of 220°C after deposition. The microstructure of μc-Si:H films after exposure was characterized using Raman back scattering spectroscopy and transmission electron microscopy (TEM). Raman spectra reveal that the intensity near 520 cm−1 significantly increases after hydrogen exposure, indicating an increase of crystallinity in the films. TEM micrographs of μc-Si:H films exposed to atomic hydrogen also show an increase in the size of grains and a growth of crystalline grains ranging from surface to bulk. These results suggest that crystalline grain formation in μc-Si:H films is likely to be caused by chemical annealing.
Dielectric Functions of a-Si1-xGex:H versus Ge Content, Temperature, and Processing: Advances in Optical Function Parameterization
Authors: Podraza Nikolas J. , Wronski Christopher R. , Horn Mark W. , Collins Robert W. 
Published: April 2011

AbstractWe have applied an advanced model to analyze the dielectric functions e = e1 + ie2 of amorphous silicon-germanium alloys (a-Si1-xGex:H) (i) as a function of alloy content × by varying the flow ratio G = [GeH4]/{[SiH4]+[GeH4]} in plasma-enhanced chemical vapor deposition (PECVD), and (ii) for the first time as a function of the measurement temperature Tm by cooling the newly-deposited film. All e spectra (1.5 − 4.5 eV) have been measured by spectroscopic ellipsometry (SE) either in real time during deposition or in situ post-deposition in order to avoid surface contamination. From the resulting extensive database, the optical properties of the alloys can be predicted for any value × and Tm within the ranges of the database. Such a capability is expected to be useful, for example, in real time control of optical gap in the PECVD process and in predicting the quantum efficiency of multijunction a-Si:H-based solar cells versus operating temperature. The effect on the database of other deposition parameters such as the electrode configuration and the H2-dilution ratio R = [H2]/{[SiH4]+ [GeH4]} have also been explored. The latter two studies provide useful insights into materials properties that can be extracted from a single spectroscopic measurement performed in real time during PECVD. For example, the energy width of the resonance in e correlates closely with the precursor surface diffusion characteristics observed throughout growth -- both determined from real time SE. This result indicates that short-range ordering in the film is improved when surface diffusion is promoted.
High Efficiency Crystallization of Silicon Thin Films Using Continuous Wave Infrared Laser
Authors: Sano Naoki , Maki Masato , Andoh Nobuyuki , Sameshima Toshiyuki 
Published: April 2011

AbstractLaser crystallization of silicon thin films on inexpensive glass substrates with a photo-absorption layer of diamond like-carbon (DLC) film was investigated. Scanned near-infrared beam emitted from a continuous wave (CW) laser diode at speed of 30 cm/s with power density of 30 kW/cm2 and wavelength of 940nm was effectively absorbed by DLC films, and changed to thermal energy for heating underlying silicon films with thickness of 50 nm. As a result, crystallization of silicon films was achieved. Raman scattering spectra was measure for the structural analysis of silicon films, and the sharp TO phonon peak at wave number of 520 cm-1 was observed. It shows that silicon films were effectively crystallized using the near-infrared laser diode. On the other hand, no crystallization was observed when the laser diode was directly irradiated to 50-nm-Si/quartz, because silicon has no optical absorption coefficient at 940 nm.
Polysilicon Films Formed On Alumina By Aluminium Induced Crystallization Of Amorphous Silicon
Authors: Pihan Etienne , Slaoui Abdelilah , Maurice Claude 
Published: April 2011

AbstractWe investigated the structural quality of polysilicon films fabricated by the aluminium induced crystallization (AIC) of amorphous silicon on alumina substrates. We analyzed the overall crystallographic quality of the poly-Si films in terms of grain size distribution and grain orientation versus crystallization temperature. For these studies, we used extensively the orientation imaging micrograph (OIM) technique, a very powerful tool that allows elucidating the inner-grain structure, the grain boundaries, the grain orientation. From our analysis, we may conclude that the polysilicon films formed by AIC on alumina substrates have the following features: (i) for all investigated temperatures, most of the silicon grains have a deviation angle from (100) crystallographic orientation between 5 and 25°; (ii) increasing the annealing temperature tends to decrease the (100) preferred orientation; (iii) the angular boundary distribution revealed that the main defects are those that have been observed inside isolated dentrites, namely low angle boundaries (<2°) and coincident site lattice boundaries such as Σ3, Σ9 and Σ27.
Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon
Authors: Sharif Khalil , Abu-Safe Husam H. , Naseem Hameed A. , Brown William D. , Al-Jassim Mowafak , Kishore Ram 
Published: April 2011

AbstractEpitaxial silicon thin film growth has been achieved on crystalline silicon substrates using aluminum induced crystallization of amorphous silicon. The phenomenon of layer inversion has been utilized in this process. Silicon wafers <100> were used as the starting crystalline structure for the grown films. After the wafer is cleaned a thin layer of aluminum (300 nm) was deposited by sputtering. This deposition was followed by 300 nm film of amorphous silicon deposited using plasma enhanced chemical vapor deposition method. After annealing the samples for 40 minutes at 525 °C, a continuous film of silicon was formed on the silicon substrate. X-ray diffraction spectrum indicated that this film has the same orientation as that of the substrate. Scanning electron microscopy cross section images showed indistinguishable interface between the substrate and the crystallized film. Cross sectional transmission electron microscopy studies of the crystallized structure showed epitaxial nature of the films.
Fabrication of Poly-silicon Thin Films on Glass and Flexible Substrates using Laser Initiated Metal Induced Crystallization of Amorphous Silicon
Authors: Abu-Safe Husam , Naseem Hameed A. , Brown William D. 
Published: April 2011

AbstractPoly-silicon thin films on glass and Kapton® substrates are fabricated using laser initiated metal induced crystallization method. Amorphous silicon films of 200 nm thickness were deposited on the two substrates. The films were capped with 200 nm aluminum films. The annealing laser was a cw Argon-ion laser system. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. The samples were irradiated for various periods of time. X-ray diffraction patterns from the initial results indicated the crystallization of the films. Scanning electron microscopy showed dendritic growth in the annealed samples. The composition analysis of the samples indicated aluminum-silicon alloy regions in the films.
Preparation of Large, Location-Controlled SI Grains by Excimer Laser Crystallization of α-SI FILM SPUTTERED AT 100°C
Authors: He Ming , Neihof E.J.J. , Andel Y. Van , Schellevis H. , Ishihara R. , Metselaar J.W. , Beenakker C. I. M. 
Published: April 2011

AbstractLocation-controlled grains with a diameter of 4 μm are successfully prepared by excimer laser crystallization of sputtered α-Si with μ-Czochralski (grain filter) process at a maximum processing temperature of 100°C. By a pulsed DC magnetron sputtering, α-Si film is deposited firstly on non-structured oxidized wafers for a test. It is found that a-Si film is easily ablated even with a low laser fluence when it is deposited with a substrate bias. From a non-biased sputtered α-Si precursor, grains with 1.8 mm in diameter can be prepared with excimer laser crystallization at room temperature. α-Si is then sputtered on the SiO2 with narrow holes (grain filters) and crystallized at room temperature. The location-controlled grains can be successfully prepared in a large energy density window. These location-controlled grains with a low temperature process are promising for single-grain thin film transistors (TFTs) on plastic substrate for an application to system integration on flexible microelectronics.