bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Temperature Properties of Langasite
Authors: Fritze H. , Tuller H. L. , Borchardt G. , Fukuda T. 
Published: April 2011

AbstractMaterials such as langasite (La3Ga5SiO14) and related compounds are promising candidates for piezoelectric applications at high temperatures. In particular, langasite does not exhibit phase transformations up to the melting point of 1470 °C. Langasite was investigated with respect to potential applications in high temperature resonator devices. In contrast to current resonator materials, we have observed bulk oscillations at temperatures of up to 750 °C in langasite devices. At 700 °C the mass load response for 0.78 mm thick resonators is approximately 0.10 µg/Hz.At elevated temperatures, the bulk resistivity of the resonator devices cannot be neglected due to attenuation of the resonance signal. Therefore, the temperature dependence of the electrical properties of langasite resonator devices, including bulk resistivity, capacity and resonance frequency were measured and are presented. The electrical conductivity is characterized by an activation energy of 105 kJ/mol. In order to confirm langasites stability with respect to oxidation-reduction reactions, we examined the oxygen diffusivity by measuring 18O tracer profiles by SIMS. The diffusivity along the Y-axis is given by D = 5-10−5 exp(-140 kJ/mol / RT) cm2/s in the temperature range from 500 to 800 °C. Langasite shows low oxygen diffusion coefficients with respect to other materials which might be investigated using a langasite microbalance. This would, for example, enable oxygen diffusion kinetics to be examined in YBa2Cu3O6 at 600 °C by means of 18O/16O exchange.
Friction Measurement in MEMS Using a New Test Structure
Authors: Crozier B.T. , de Boer M.P. , Redmond J.M. , Bahr D.F. , Michalske T.A. 
Published: April 2011

AbstractA MEMS test structure capable of measuring friction between polysilicon surfaces under a variety of test conditions has been refined from previous designs. The device is applied here to measuring friction coefficients of polysilicon surfaces under different environmental, loading, and surface conditions. Two methods for qualitatively comparing friction coefficients (µ) using the device are presented. Samples that have been coated with a self-assembled monolayer of the lubricating film perfluorinated-decyltrichlorosilane (PFTS) have a coefficient of friction that is approximately one-half that of samples dried using super-critical CO2 (SCCO2) drying. Qualitative results indicate that µ is independent of normal pressure. Wear is shown to increase µ for both supercritically dried samples and PFTS coated samples, though the mechanisms appear to be different. Super critically dried surfaces appear to degrade continuously with increased wear cycles, while PFTS coated samples reach a steady state friction value after about 105 cycles.
Microinstrument for the Characterization of Submicron Silicon Fibers at High Strain
Authors: Chen J. M. , Reed B. W. , Chen J. M. , Reed B. W. , MacDonald N. C. 
Published: April 2011

AbstractWe present a MEMS microinstrument to interface submicron-scale structures and study their properties. Using this microinstrument integrated with a 150nm diameter silicon fiber that has high fracture strength and a high force micro-actuator, the non-linearity of n-type silicon's piezoresistive effect is measured up to the third order, using data from the high strain range of 0-1% for the first time.
Packaging MEM Sensor Arrays
Authors: Marinis T. F. , Fulginiti D. A. , Clausen H. G. 
Published: April 2011

AbstractMany applications of MEM sensors require hermetic or high vacuum packaging of sensor clusters. For example, multiple gyroscopes or accelerometers are fabricated on a single chip to improve alignment and stability of input axes or increase the dynamic range of instruments. Chemical sensors are fabricated as large arrays to both improve selectivity and increase the number of species that can be detected. Still larger arrays of sensors must be packaged for hydrophone and bolometer imaging devices. All of these applications place a demanding combination of requirements on the sensor package. The electrical outputs of the sensor array must be well isolated from each other as well as power and excitation signals, while parasitic capacitance is minimized. The package must also be capable of being evacuated and sealed to achieve a pressure of 5 millitorr with a leakage rate below 10−11 [Std cc sec−l]. Finally, the package must be compact and low cost to realize these same attributes of the MEM sensor. This paper describes a packaging approach that is based on low temperature cofired ceramic materials. This technology meets the packaging requirements of sensor arrays and is well suited to the research environment in which the sensor design is continually evolving.
Fatigue Properties for Micro-Sized Ni-P Amorphous Alloy Specimens
Authors: Maekawa S. , Takashima K. , Shimojo M. , Higo Y , Swain M. V 
Published: April 2011

AbstractFatigue crack propagation tests at different stress ratios of 0.1 and 0.5 have been performed on microsized Ni-P amorphous alloy specimens to investigate the influence of stress ratio in the crack growth properties of microsized materials. The specimens tested were cantileverbeam-type with dimensions of 10 × 12 × 50 νm3 prepared by focused ion beam machining. Notches with a depth of 3 [m were introduced in all specimens. The entire set of fatigue tests as performed using a newly developed fatigue testing machine in air at room temperature. Fine stripes deduced to be striations were observed on the fatigue fracture surface. Careful measurements of the striation spacings were made. Fatigue crack propagation rate, that is striation spacing, is plotted as a function stress intensity factor range. Fatigue crack propagation rate at stress-ratios of 0.1 and 0.5 in microsized Ni-P amorphous alloy specimens are given by da/dN ∼ 1.3 × 10−8 ΔK;1.16 and da/dN ∼ 3.7 × 10−8 ΔK0.5, respectively. At a given ΔK, crack propagation rate at a stress ratio of 0.5 was higher than that at 0.1. It is considered that a decrease in crack propagation rate at stress ratio of 0.1 is due to adecrease in effective stress intensity factor range ΔKeff, by the effect of crack closure.
Test Channels for Flow Characterization of Processed Plastic Microchannels
Authors: Chen Yandong , Chen Zhongping , Zhao Yonghua , Nelson J. Stuart , Bachman Mark , Chiang Yuh-Min , Chu Charles , Li G. P. 
Published: April 2011

AbstractCharacterization of the flow properties in microfluidic channels is important for designing and building biomedical microdevices, many of which depend on precise fluid flow for their operation. Similarly, in complex fluidic systems, it is important to identify flaws in processing which will potentially restrict, or short circuit the flow of the device. We explore the characterization of flow in plastic microfluidic systems through various test devices..
Inlayed “Atom-like Three-Dimensional Photonic Crystal Structures Created with Femtosecond Laser Microfabrication
Authors: Sun Hong-Bo , Xu Ying , Sun Kai , Juodkazis Saulius , Watanabe Mitsuru , Matsuo Shigeki , Misawa Hiroaki , Nishii Junji 
Published: April 2011

AbstractUltrashort laser pulses are utilized for fabrication of three-dimensional (3D) photonic crystals based on a multiphoton absorption process. The basic idea is, when a femtosecond laser pulse is tightly focused into some transparent media, a submicrometer hole will be generated due to microexplosion. By arraying these holes the same way as atoms in general solid crystals, 3D photonic lattices are achieved. Pronounced photonic bandgap effect shows that this technique is promising for tailoring arbitrary-lattice photonic crystals.
Methylamine Growth of SiCN Films Using ECR-CVD
Authors: Wen C.-Y. , Wu J.-J. , Lo H.J. , Chen L.C. , Chen K.H. , Lin S.T. , Yu Y.-C. , Wang C.-W. , Lin E.-K. 
Published: April 2011

AbstractContinuous polycrystalline SiCN films with high nucleation density have been successfully deposited by using CH3NH2, as carbon source gas in an ECR-CVD reactor. Fom the kinetic point of view, using CH3NH2, as carbon source could provide more abundant active carbon species in the gas phase to enhance the carbon incorporation in the SiCN films. The compositions of the SiCN films analyzed from Rutherford Backscattering Spectroscopy showed that higher [CH3NH2,]/[SiH4] ratio led to higher carbon content in the films. Moreover, a lower carbon content was measured when the film was deposited at higher substrate temperature. The direct band gap of the aforementioned SiCN films determined using PzR is around 4.4 eV, indicating a wide band gap material for blue-UV optoelectronics.
Effect of Precursor Sol Ageing on Sol-Gel Derived Ruthenium Oxide Thin Films
Authors: Bhaskar S. , Majumder S. B. , Dobal P. S. , Katiyar R. S. , Cruz A. L. M. , Fachini E. R. 
Published: April 2011

AbstractIn the present work we have optimized the process parameters to yield homogeneous, smooth ruthenium oxide (RuO2) thin films on silicon substrates by a solution deposition technique using RuCl3.×.H2O as the precursor material. Films were annealed in a temperature range of 300°C to 700°C, and it was found that RuO2 crystallizes at a temperature as low as 400°C. The crystallinity of the films improves with increased annealing temperature and the resistivity decreases from 4.86µΩ-m (films annealed at 400°C) to 2.94pµΩ (films annealed at 700°C). Ageing of the precursor solution has a pronounced effect on the measured resistivities of RuO2 thin films. It was found that the measured room temperature resistivities increases from 2.94µΩ-m to 45.7µΩ-m when the precursor sol is aged for aged 60 days. AFM analysis on the aged films shows that the grain size and the surface roughness of the annealed films increase with the ageing of the precursor solution. From XPS analysis we have detected the presence of non-transformed RuCl3 in case of films prepared from aged solution. We propose, that solution ageing inhibits the transformation of RuCl3 to RuO2 during the annealing of the films. The deterioration of the conductivity with solution ageing is thought to be related with the chloride contamination in the annealed films.
Analysis of a TEOS/Oxygen Plasma: Influence of Energy and Particle Flux on the Deposition Parameters
Authors: Silva M. L. Pereira da , Silva A. N. Rodrigues da , Santiago-Aviles J. J. 
Published: April 2011

AbstractIn this work we looked at deposition parameters such as rate and film microstructure during the plasma enhanced CVD processing of TEOS {Si (OCH2 CH3)4) + O2. This is a multi-component oxide due to the inevitable accidental inclusion of carbonatious contaminants. We decided to characterize the plasma parameters, namely the electron energy (from 50 to 600 eV), and the flux of the reactive species. The deposition chamber was modified by the introduction of a stainless steel tubular ring between the electrodes, such that when a positive bias is applied it is possible to inject electrons into the plasma. A dual role for the tubular ring is the transport of oxygen to different locations in the plasma, and to monitor the influence of the oxygen flux on deposition.
Mid-Infrared Photodetector Using Self-Assembled InAs Quantum Dots Embedded in Modulation-Doped GaAs Quantum Wells
Authors: Lee Seung-Woong , Hirakawa Kazuhiko , Shimada Yozo 
Published: April 2011

AbstractWe have designed and fabricated a quantum dot infrared photodetector which utilizes lateral transport of photoexcited carriers in the modulation-doped A1GaAs/GaAs two-dimensional (2D) channels. A broad photocurrent signal has been observed in the photon energy range of 100–300 meV due to bound-to-continuum intersubband absorption of normal incidence radiation in the self-assembled InAs quantum dots. A peak responsivity was as high as 2.3 A/W. The high responsivity is realized mainly by a high mobility and a long lifetime of photoexcited carriers in the modulation-doped 2D channels. Furthermore, we found that this device has high operation temperature and very high photoconductive gain.
IV-VI Compound Semiconductor Mid-Infrared Vertical Cavity Surface Emitting Lasers Grown by MBE
Authors: Shi Z. , Xu G. , McCann P.J. , Fang X. M. , Dai N. , Bewley W. W. , Felix C. L. , Vurgaftman I. , Meyer J. R 
Published: April 2011

AbstractMid-infrared vertical cavity surface emitting lasers (VCSELs) using PbSe as the active material and broadband high reflectivity Pb1−xSrxSe/BaF 2 distributed Bragg reflectors (DBR) as bottom and top mirrors were grown by molecular beam epitaxy. By pulsed optical pumping, this first IV-VI semiconductor VCSEL operated up to 290K at a wavelength of 4.5 µm. Further optimization of such VCSELs could lead to room temperature continuos wave operation.
Defects in CdTe-Based Photodetectors
Authors: Valdna V. 
Published: April 2011

AbstractThe photoluminescence spectra, defect composition and optoelectronic properties of chlorine doped CdTe monocrystals, thick layers and thin films are investigated. It is supposed that the complex defect (VCd-2ClTe) is a neutral defect that causes high resistivity of Cl doped CdTe. This complex can dissociate into two charged defects (VCd-ClTe) and ClTe at 300 K. Acentre (VCd-ClTe) is a stable defect that is responsible for p-type conductivity of Cl doped CdTe. Depending on the C1 concentration high resistivity, high photoconductivity or high p-type conductivity can be formed in CdTe that is only chlorine doped.
Electrical Characterization of InAs/(GaIn)Sb Infrared Superlattice Photodiodes for the 8 to 12νm Range
Authors: Bürkle L. , Fuchs F. , Kiefer R. , Pletschen W. , Sah R. E. , Schmitz J. 
Published: April 2011

AbstractInAs/(GaIn)Sb superlattice photodiodes with a cutoff wavelength of 8.711μm show adynamic impedance of R0A= 1.5 kωcm2at 77 K and a responsivity of 2 A/W, corresponding to a detectivity of D*= 1 x 1012 cmv√Hz/W. Diffusion limited performance is observed above 100 K. At lower temperatures the diodesare limited by generation-recombination currents. An analysis of the influence of different diode sidewall passivations on the surface contribution to the diode leakage current is presented. The out-of-plane electron mobility as well as the relative contributions of the electron and hole diffusion currents to the diode current were determined by a measurement of the magnetic field dependence of the reverse saturation current density of the diodes
UPS of a-Si:H<Er>: What is the energy of the Er 4f states?
Authors: Tessler Leandro R. , Piamonteze Cínthia , Iniguez Ana Carola , Siervo Abner de , Landers Richard , Morais Jonder 
Published: April 2011

ABSTRACTOne very important problem concerning erbium-doped silicon is the electronic structure of the Er3+ impurities. In particular, it is still not clear if the 4f levels can be treated as frozen core levels or their overlap with s and p states of their neighbors must be considered explicitly. For crystalline Si, the 4f levels have been supposed to be anywhere between 20 eV below the valence band and within the energy gap. In this paper we report on the first ultraviolet photoemission spectroscopy (UPS) measurements on Er-doped a-Si:H. Samples of a-Si:H<Er> with different Er contents (up to 1 at. % Er) were prepared by co-sputtering from a Si target partially covered with metallic Er platelets. In order to enhance the Er states relative to the Si and H states, the excitation energy was tuned between 40 and 140 eV with a synchrotron light source. At 140 eV excitation energy the cross-section of the Er 4f and 5p states is more than an order of magnitude higher than the cross section of the Si 3s or 3p states. As the Er concentration increases, a shoulder and then a peak appears at 10.0±0.5 eV binding energy. The intensity and width of this peak is well correlated with the Er concentration, and with the Er 5p and 5p½ levels at 26 and 32 eV binding energy, respectively. We attribute the peak at 10.0±0.5 eV binding energy to the Er 4f level. These are the only occupied states that can be related to the presence of Er, indicating that these levels are not valence states and consequently can be treated as frozen core levels.
The Emergence of an Amorphous-Silicon Based Photonic Technology; Optical Memories to 3-D Photonic Crystals
Authors: Hata N. , Fortmann C. M. 
Published: April 2011

ABSTRACTAmorphous silicon is an ideal system for optical engineering since its optical properties can drastically be changed through its ability to absorb such impurities as hydrogen whose contents range from zero to beyond twenty percent. In this work we report light-induced changes in its optical properties which may add potential in active optical engineering. Considerable changes in the phases in reflected polarized lights from transparent-substrate side of amorphous silicon films are observed both after prolonged illumination of intense light at the light-soaking temperature range from 40 to 250 °C. Most of the changes are localized to amorphous silicon region near substrate-film interfaces. Illumination time dependencies and annealing characteristics are examined, and physics behind these observed changes are discussed.
Recombination and Resistive Losses in Amorphous Silicon / Crystalline Silicon Heterojunction Solar Cells
Authors: Jensen Nils , Rau Uwe , Werner Jürgen H. 
Published: April 2011

ABSTRACTThis contribution investigates the electronic properties of a-Si:H/c-Si solar cells and explains their electrical output parameters open circuit voltage, short circuit current, and fill factor. Our device analysis is based on measurements of the internal quantum efficiency, of current/voltage and capacitance/voltage curves. We find carrier recombination within the crystalline silicon absorber material to be responsible for the limitation of the open circuit voltage. The short circuit current is restricted by collection losses in the absorber material and by absorption in the electrically inactive a-Si:H emitter. Resistive losses affecting the fill factor originate from the transport of minority carriers across the interface. The I/V curves measured at low temperatures reveal a characteristic S-shaped behavior. This effect increases with decrasing temperature and stems from the minority carrier transport, which is hindered by the band offset between a-Si:H and c-Si. We propose a new analytical model to describe this anomalous behavior.
Spin-Dependent Processes In Thin-Film Silicon Solar Cells
Authors: Lips K. , Müller R. , Kanschat P. , Finger F. , Fuhs W. 
Published: April 2011

ABSTRACTWe report on electrically detected magnetic resonance (EDMR) studies in three different types of thin-film silicon solar cells: (i) c-Si absorbers with epitaxially grown silicon thin-film emitters (ii) c-Si absorbers with hydrogenated amorphous silicon (a-Si:H) emitters, and (iii) microcrystalline silicon (µc-Si:H) pin diodes. Although cells of type (i) and (ii) are of a similar structure their EDMR spectra are completely different. We identify surface recombination via Pb0 centers in cells with c-Si emitters but hopping transport through conduction bandtail states in the 30 nm thin a-Si:H emitter layer. No signals related to interface recombination are detected in either cell. The EDMR signals of cell (iii) are identified as hopping among tail states of the conduction band with a subsequent nonradiative tunneling transition to neutral dangling bonds. At elevated temperature recombination is suggested to be dominated by direct capture. The EDMR signal of the dark current can be described with a simple diode model only involving diffusion and recombination currents.
Selective Area Cell Adhesion on Amorphous Silicon Using Patterned Self-Assembled Monolayers
Authors: Smith Laura L. , Wang Kai , Parsons Gregory N. , Hernandez Raquel , Brown Dennis T. 
Published: April 2011

ABSTRACTThe compatibility of inorganic materials with living tissues and biological compounds is crucial in many areas, including medical diagnostics, biosensors, drug delivery, etc. In this work, we are interested in the interaction of living mammalian cells with semiconductor surfaces for novel thin-film biosensor devices. Amorphous silicon may give advantages over crystalline silicon for some devices because of its large-area, low-temperature compatibility, and its large optical absorption coefficient in the visible spectrum. Amorphous silicon thin films (500Å) deposited on quartz glass were cleaned using ambient UV/O3 treatment, leaving the surface largely OH-terminated and hydrophilic. The hydrophilic surface was then exposed to a vapor of octyltrichlorosilane (CH3(CH2)7SiCl3, OTS). The resulting surface was strongly hydrophobic, with advancing contact angles with water <106°. This organic surface was masked to reserve areas of uncoated hydrophilic substrate, and placed in a cell culture (BHK-21 cells) to observe cell adhesion and proliferation. A high degree of cell attachment was observed on the UV/O3-treated surfaces (~400 cells/mm2) compared to ~450 cells/mm2 on the culture dish control surface, indicating cell proliferation and growth. Little cell adhesion occurred on the hydrophobic organiccoated surface (~40 cells/mm2), and the cells remained round and only minimally attached. On masked surfaces, the organic-free areas showed dense, well-adhered cell growth while the coated areas showed much fewer and rounded cells. On all samples as well as control surfaces, cell death was <1%. These results suggest a means for selectively controlling cell adhesion to thin film electronic device surfaces, through the patterning of hydrophobic surface coatings.
Multi-Band Electron Paramagnetic Resonance Study of Microcrystalline and Cluster Silicon Embedded in SiO2
Authors: Ehara Takashi , Ikoma Tadaaki , Tero-Kubota Shozo 
Published: April 2011

ABSTRACTDangling bond defects (DB) in silicon microcrystallines and clusters embedded in SiO2 have been studied by X- and Q-band electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra due to the DB were remarkably depending on the grain size, which was controlled by annealing temperature. The microcrystalline containing film shows a broad and unsymmetrical EPR signal at g = 2.006 with the line width of 13 G in X-band spectra. The signal can be simulated by using the anisotropic g-values of Pb center. The Si cluster samples obtained from the annealing at less than 800°C give an asymmetric EPR spectra at about g = 2.004 with the line width of about 9 G in X-band. The EPR signal due to the E' center was also observed.
Diffusion of Hydrogen and Deuterium in Stack Systems of SixNyHz/SixNyDz and Crystalline Si
Authors: Boehme Christoph , Lucovsky Gerald 
Published: April 2011

ABSTRACTH/D-, N-H/D- and Si-H/D-bond density changes were investigated in stacks consisting of a Cz-Si substrate, a thin layer of SiO2, amorphous deuterated silicon nitride as well as amorphous hydrogenated silicon nitride in order to see if the post deposition anneal of a-SixNyHz layers on crystalline silicon wafers can actually lead to a migration of H atoms into the Si-bulk, which is an important question in regard to emitter passivation of Si-solar cells.The stacks were grown with remote plasma enhanced chemical vapor deposition (RPECVD). A low temperature (≈200°C) process of down stream injected ammonia (NH3) and silane (SiH4) activated by an upstream injected He-plasma, produced through RF-radiation (13.65MHz) was used. Thermal treatment was executed by ex situ rapid thermal anneal in Ar ambient. For the measurements of H and D bond densities, FTIR was employed while SIMS determined atomic densities of H, D and O in the c-Si/nitride interface region. The experiments showed that H transport in silicon nitride is determined by several mechanisms including diffusion and dissociation processes and that silicon nitride deposited with high ammonia to silane ratios can produce molecular species like ammonia and H2. The study of the reaction dynamics showed that the production of molecular hydrogen is the most dominant process as long as Si-H-bonds are present in the system. After their exhaustion, an ammonia producing reaction prevails that leads with increasing temperatures to lower densities in the nitride films.