bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitride semiconductors as terahertz sources based on spontaneous and piezoelectric polarization
Authors: Metcalfe Grace D. , Shen Hongen , Wraback Michael , Hirai Asako , Koblmüller Gregor , Gallinat Chad S. , Speck James S. 
Published: June 2010

AbstractWe investigate the effects of internal polarization‐related drift and diffusion on the emitted THz radiation from m ‐plane (1$ \bar 1 $00), a ‐plane (11$ \bar 2 $0), and c ‐plane (0001) nitride semiconductors. Enhanced THz radiation is observed from c ‐plane InN/InGaN multiple quantum wells as compared to c ‐plane bulk InN at 800 nm excitation wavelength. THz generation in the quantum well structure is due to surface normal transport in electric fields due to the termination of spontaneous and piezoelectric polarization at the well/barrier interfaces. From high stacking fault density nonpolar GaN, we observe further enhanced THz emission as compared to stacking fault free m ‐plane GaN. THz generation from the high stacking fault density m ‐plane GaN is attributed to in‐plane transport in built‐in fields due to stacking fault‐terminated internal polarization. A similar effect is observed in m ‐plane as well as a ‐plane InN. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimizing performance to achieve multi‐terahertz operating frequencies in pseudomorphic HEMTs
Authors: Akis R. , Faralli N. , Goodnick S. M. , Ferry D. K. , Saraniti M. 
Published: June 2010

AbstractHigh‐electron mobility transistors (HEMTs) are important for high frequency applications, and they now operate in the range of several hundred GHz for the cut‐off frequency, fT and even higher for the maximum frequency of oscillation, fmax. To study the question of how much higher these frequencies can be pushed, we have used a full‐band, cellular Monte Carlo transport program to study scaled pseudomorphic HEMTs and their response at high frequency. Building on a previous study on fT, we have obtained the unilateral power gain for gate lengths ranging from 10 to 50 nm, extracted the corresponding fmax's and extrapolated the results to determine an ultimate frequency limit for the 300 nm long device shown here.. We find that fmax can exceed 4 THz, ∼25% higher than the limit for fT that was previously obtained. We also examine the effect of varying the gate to channel spacing has on the operation of these devices. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tunneling current of GaAs ultrashallow sidewall n+p+n+ and p+n+in+ structure prepared by area‐selective molecular layer epitaxy
Authors: Ohno Takeo , Oyama Yutaka 
Published: June 2010

AbstractSidewall n+p+n+ and p+n+in+ structures were fabricated by area‐selective molecular layer epitaxy of GaAs, and electrical evaluation was carried out on the structures by J ‐V measurement. In the n+p+n+ structure, tunneling current decreased as the thickness of the p+ layer increased. An Esaki peak was also observed when the p+ layer was thicker than the depletion layer. The J ‐V characteristic of the p+n+in+ structure depended on the thickness of the n+ layer, and its curve at the reverse bias shifted to the low voltage side when the n+ layer became thick. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent advances in Ge/Si PIN and APD photodetectors
Authors: Bowers John E. , Ramaswamy Anand , Dai Daoxin , Zaoui Wissem Sfar , Kang Yimin , Yin Tao , Morse Mike 
Published: June 2010

AbstractPhotodetectors on a Si platform are important because of the opportunity to manufacture literally millions of photodetectors per wafer and because the use of a mature CMOS (Complementary Metal‐Oxide‐Semiconductor) process results in low cost and high uniformity. In this paper, we review recent results on Ge‐Si‐based PIN‐type photodetectors and avalanche photodetectors (APD). We show several exciting advantages of SiGe photodetectors namely, the higher thermal conductivity of Si and Ge, resulting in higher power capability, and the lower k factor, resulting in higher gain bandwidth products in APDs (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equivalent circuit modeling of triple‐barrier resonant tunneling diodes taking nonlinear quantum inductance and capacitance into account
Authors: Asakawa Kiyoto , Naoi Mamoru , Iki Yuichi , Shinada Masaaki , Suhara Michihiko 
Published: June 2010

AbstractFocusing on compound semiconductor triple‐barrier (or coupled‐quantum well) resonant tunneling diodes (TBRTD), equivalent circuit topology and elements are expressed in terms of negative quantum inductance (LQ) and quantum capacitance (CQ) as well as negative differential conductance G. The circuit model is theoretically derived on the basis of rate equation approach and validity of the model was experimentally confirmed by impedance measurement up to 30 GHz and nonlinear bias‐voltage‐dependent. LQ and CQ were evaluated with electron quasi‐lifetime and escape time as tentative fitting parameters in the particular In0.52Al0.48As/In0.53Ga0.47As TBRTD grown by MBE. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Insertion loss and linearity of III‐nitride microwave switches
Authors: Deng Jianyu , Yang Jinwei , Hu Xuhong , Gaska Remis , Khan Bilal , Simin Grigory , Shur Michael 
Published: June 2010

AbstractWe report the insertion loss and linearity characteristics of novel microwave switches based on III‐Nitride heterostructure field‐effect transistors (HFETs) and Metal‐Oxide‐Semiconductor HFETs (MOSHFETs). The high mobility and large sheet carrier density make nitride‐based microwave switches ideal candidates for high power, low loss and high linearity microwave switching applications. The demonstrated SPDT switch achieved the third order intermodulation power of ‐68 dBm for 250 micron devices at 1 GHz and 10 dBM input power and the extrapolated IP3 of >80 dBm with <0.25 dB insertion loss and >35 dB isolation for 2GHz operation for 3mm devices. Further improvements of the insertion loss and linearity are expected from new material and contact development, which will achieve lower 2DEG sheet resistance and contact resistance. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nuclear spin polarization and relaxation probed by spin phase transition peak
Authors: Watanabe S. , Fauzi M. H. , Kumada N. , Hirayama Y. 
Published: June 2010

AbstractWe perform resistively‐detected nuclear‐spin relaxation measurements by using the spin phase transition (SPT) peak in the fractional quantum Hall system at the flling factor ν = 2/3. We investigate nuclear spin relaxation for several electronic systems under a spatially inhomogeneous nuclear spin polarization.When Skyrmions are introduced in the ground state, the position of the SPT peak shifts to higher magnetic feld. This result indicates that Skyrmions relax nuclear spins polarized anti‐parallel to the external magnetic feld more effectively than those parallel to the magnetic feld. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High efficiency violet to blue light emission in porous SiC produced by anodic method
Authors: Nishimura T. , Miyoshi K. , Teramae F. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I. 
Published: June 2010

AbstractPorous fluorescent (f‐) SiC containing N and B was produced by anodic oxidation. The average crystal size can be controlled by adding K2S2O8 as an oxidant to dilute HF solution during the anodic process. With the reduction of the average crystal size of the porous crystal, the PL peak wavelength becomes shorter, and its intensity increases. Such behavior can be explained by the quantum size effect of donor‐acceptor‐pair recombination. Finally, we confirmed the superior fluorescent property of blue light emission in porous f‐SiC crystal (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wurtzite InP nanowire arrays grown by selective area MOCVD
Authors: Chu Hyung‐Joon , Yeh Ting‐Wei , Stewart Lawrence , Dapkus P. Daniel 
Published: June 2010

AbstractInP nanowires are a unique material phase because this normally zincblende material forms in the wurtzite crystal structure below a critical diameter owing to the contribution of sidewalls to the total formation energy. This may allow control of the carrier transport and optical properties of InP nanowires for applications such as nano scale transistors, lasers and detectors. In this work, we describe the fabrication of InP nanowire arrays by selective area growth using MOCVD in the diameter range where the wurtzite structure is formed. The spatial growth rate in selective area growth is modeled by a diffusion model for the precursors. The proposed model achieves an average error of 9%. Electron microscopy shows that the grown InP nanowires are in the wurtzite crystal phase with many stacking faults. The threshold diameter of the crystal phase transition of InP nanowires is larger than the thermodynamic estimation. In order to explain this tendency, we propose a surface kinetics model based on a 2×2 reconstruction. This model can explain the increased tendency for wurtzite nanowire formation on InP (111)A substrates and the preferred growth direction of binary III‐V compound semiconductor nanowires. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigating the effect of aqueous extract of Chicorium intybus L. leaves on offspring sex ratio in rat
Authors: Behnam‐Rassouli Morteza , Aliakbarpour Ali , Hosseinzadeh Hossein , Behnam‐Rassouli Fatemeh , Chamsaz Mahmood 
Published: June 2010

AbstractA traditional belief in Iranian culture indicates that parental consumption of chicory leaves (Chicorium intybus L.) affects the gender of newborns. The aim of this study was to investigate the effect of aqueous extract of chicory on offspring sex ratio in rat. All rats in experimental groups 1 and 2 were i.p. injected with either 1.0 or 0.7 g/kg body weight (LD50 = 2.244 g/kg) of an aqueous extract of chicory leaves for 30 days at 72 h intervals. The control rats were injected with distilled water in the same manner. After the 8th injection, blood pH, and Na+, K+, Ca2+ and Mg2+ serum levels, were measured in all groups. On day 30, all the rats were mated within and between groups. The results revealed that in comparison with the control group, there were significant increases (p < 0.01) in Na+ and K+ levels, as well as the sex ratio of male to female offspring (10.23%) in experimental group 1. Therefore, it can be concluded that the administration of chicory leaf extract has a significant effect on the sex ratio of the rat offspring. Copyright © 2010 John Wiley & Sons, Ltd.
Molecular ions in cluster bombardment: what clues do the molecular dynamics simulations provide?
Authors: Garrison Barbara J. 
Published: June 2010

AbstractMolecular dynamics simulations of C60 bombardment of molecular solids suggest that there is a space–time divide between the fragmentation/ion creation process and the ejection of intact molecules via fluid flow physics. This space–time divide leads to the conclusion that molecular ions are preformed prior to ejection. Consequently, to increase the ion yield significantly, the sample must be altered to create more preformed ions. Copyright © 2010 John Wiley & Sons, Ltd.
RIMS analysis of Ca and Cr in Genesis solar wind collectors
Authors: Veryovkin I. V. , Tripa C. E. , Zinovev A. V. , King B. V. , Pellin M. J. , Burnett D. S. 
Published: June 2010

AbstractRIMS depth profiles have been measured for Cr and Ca in Genesis solar wind collector made from Si and compared to such measurements for ion‐implanted Si reference material. The presence of surface contamination has been shown to be a significant factor influencing the total Ca and Cr fluence measured in the Genesis collectors. A procedure to remove the contaminant signal from these depth profiles using the reference material implanted with a minor isotope demonstrated that 36% of the measured Ca fluence in our Genesis sample comes from terrestrial contamination. Copyright © 2010 John Wiley & Sons, Ltd.
Investigations of secondary ion yield‐enhancing methods in combination
Authors: Heile A. , Muhmann C. , Lipinsky D. , Arlinghaus H. F. 
Published: June 2010

AbstractToday, several methods are used for secondary ion yield enhancement in time‐of‐flight SIMS (ToF‐SIMS). Some deal with the modification of sample properties, e.g. with monolayer preparation of analytes on metal substrates instead of thick layers, or the metalization of thick‐layer samples with noble metals like gold or silver (MetA‐SIMS). Other methods deal with primary ion beam parameters, e.g. the use of heavier ions or the use of polyatomic instead of monoatomic primary ions.To investigate the yield‐enhancing effects of the combination of these techniques, (sub‐) monolayers of polyethylene imine, both pristine and metalized with different amounts of gold, were prepared on substrate materials with different stopping powers. For primary ion (PI) bombardment, monoatomic (Ne+, Ar+, Kr+, Xe+, Bi+) and polyatomic (Bin+, Bin++) primary ions were used.It was found that all techniques used in this contribution increase the secondary ion yield mainly by increasing the stopping power, thereby increasing the amount of PI energy that is deposited near the sample surface (upper 5 nm). Only a small additional yield enhancement was observed when to a yield‐enhancing technique such as polyatomic PI bombardment, which deposits nearly all the PI energy near the surface, another technique was added that is based on the same mechanism for yield enhancement. In other words, the yield enhancement achieved by two enhancement techniques used in combination was much smaller than the product of the yield enhancements obtainable with each technique taken by itself. Copyright © 2010 John Wiley & Sons, Ltd.
Examination of individual nanoparticles with cluster SIMS
Authors: Rajagopalachary S. , Verkhoturov S. V. , Schweikert E. A. 
Published: June 2010

AbstractWe report on nanoprojectile–nanoparticle (NP) interaction when the two collision partners are in the same size range. The experiments involved C60+ accelerated to 26 keV impacting isolated NPs of Ag and Au, both ∼5 nm in diameter, deposited as single layers on an organic substrate. A direct ‘bulls‐eye’ impact of one C60+ onto one NP can result in two processes: fragmentation of the NP and emission of metallic ions, or fragmentation of the NP with fragmentation of substrate molecule followed by recombination and emission of ions. The NPs were covered with self assembled monolayers (SAMs), grazing impacts were readily observed via emission of fragments of SAMs. A mix of Ag and Au NPs showed that emission can be affected by surrounding NPs. Mass spectrometric data from vanishingly small objects reflect size‐dependant processes and effects. Copyright © 2010 John Wiley & Sons, Ltd.
Present State of Development of Laser‐Assisted Wide Angle Three‐Dimensional Atom Probe
Authors: Mayama Norihito , Iwata Tatsuo , Yamashita Chikanori , Ito Satoko , Kaneko Tetsuya , Mikami Sunao , Hanaoka Yuya , Kajiwara Yasuko , Kaito Takashi , Adachi Tatsuya , Hoshino Hitoshi , Nikawa Kiyoshi , Nojima Masashi , Taniguchi Masahiro , Owari Masanori 
Published: June 2010

AbstractThree‐dimensional atom probe (3DAP) has been developed in our laboratory. In our instrument, the position‐sensitive detector with a diameter of 120 mm following a pair of microchannel plates (MCP) was set up at a distance of 110 mm in front of the apex of the sample. Our original preset‐type sample stage with a local microelectrode was adopted. The pulse laser, or voltage pulse, was used as a trigger for field evaporation. The pulse width of the laser was 180 fs at a wavelength of 1030 nm. The pulse width of the voltage pulse was less than 10 ns. The performance of our instrument was widely tested with the pure tungsten samples fabricated by the electropolishing and focused ion beam methods. The flight path compensation of detected ions, including the small inclination of MCP assembly, led to the good mass resolution approximately 220 (FWHM). By this compensation, we realized full 0.75 sr acceptable angle 3DAP. The detection efficiency of emitted ions was estimated to be about 50% from the three‐dimensional reconstruction images of samples. Copyright © 2010 John Wiley & Sons, Ltd.
Oxygen Influence on the Growth of Thin Hf Films on the 6H‐SiC(0001) Surfaces
Authors: Mazur Piotr , Markowski Leszek 
Published: June 2010

AbstractInitial stages of Hf growth on the SiC(0001) surface and the influence of annealing on the evolution of microstructure of the formed Hf films were investigated by XPS and scanning tunneling microscopy (STM). The character of XPS spectra and the shifts of the binding energies of Hf 4f, Si 2p, C 1s, O 1s levels, observed with increasing Hf depositions, indicate that even at room temperature a hafnium oxide in the form of HfO2 was created. The registered band bending created at the HfO2/SiC interface is about 0.4 eV. Hafnium tended to grow irregularly with a tendency to form nanocrystalline grains near terraces edges, and preferably on the surface regions not covered by additional graphite carbon layers which together with oxygen were present on the virgin SiC(0001) surface. The grain sizes were sensitive to annealing and efficiently increased during heating the sample at 1100 °C. These surface morphology changes proceeded through merging smaller nanoparticels into clusters. For longer Hf depositions, with average thickness over 10 monolayers, excess carbon segregated and migrated towards the surface, with simultaneous formation of Hf–C and O‐C‐O bonds. Copyright © 2010 John Wiley & Sons, Ltd.
Attenuation lengths in organic materials
Authors: Seah M. P. , Spencer S. J. 
Published: June 2010

AbstractMeasurements are reported for attenuation lengths in overlayers of guanine, poly(styrene), poly(methyl methacrylate) and poly(2‐vinylpyridine) in the energy range 700–1400 eV to evaluate the accuracy of theoretical computations and generic equations. The layers are deposited on gold, either by evaporation and condensation or by spin casting. Measurements are made by X‐ray photoelectron spectroscopy (XPS) for the substrate Au 4f, 4d and 4p peaks as well as the overlayer N 1s peak in guanine and poly(2‐vinylpyridine). These measurements all correlate with the theory of Tanuma, Powell and Penn, to an RMS deviation of 11%. Correlations with the predictions using the generic equation known as TPP‐2M exhibit a poorer RMS deviation of 20%. Use of an ‘average’ organic material for the inelastic mean free paths for the four materials also leads to a 20% RMS deviation. Additional data are also presented for Irganox 1010 that is used, increasingly, as a reference sample for secondary ion mass spectrometry. Comparisons for 5 materials with the Gries G1 formula gives an RMS deviation of 13%, but a small change to interpolate between Gries' classes of organic materials with H/C being around either 1 or 2, leads to a reduced RMS deviation of 10%. This final version, G1‐SS, requiring only the material density and chemical formula, is very simple to use for all organic materials where these data are known or can be estimated. © Crown copyright 2010. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
D‐SIMS analysis supporting SiOxNy film in‐line metrology
Authors: Budri Thanas , Getchell Donald 
Published: June 2010

AbstractD‐SIMS is used in conjunctions with in‐line metrology techniques to better monitor SiOxNy films. Different D‐SIMS analytical conditions are chosen in order to properly measure the nitrogen dose and profile since proper evaluation of both characteristics plays a major role on the performance of the device. Copyright © 2010 John Wiley & Sons, Ltd.
Sputtered and laser recrystalized phosphorus‐doped zinc oxide
Authors: Sämann Marc , Eisele Sebastian , Bilger Gerhard 
Published: June 2010

AbstractPhosphorus‐doped zinc oxide (ZnO:P) films with red phosphorus as dopant were grown in a radio‐frequency target‐to‐intermediate‐target sputtering process. As‐grown ZnO:P films were annealed at 500 °C for relaxing the mechanical strain in the films, and subsequently laser irradiated. X‐ray diffraction and SIMS reveal surface melting of the thin films due to laser irradiation and a subsequent strain relaxation during their recrystalization in (0002) direction. X‐ray photoelectron spectroscopy hints at the formation of stable complexes, such as PZn–2VZn, with phosphorus occupying a zinc site (PZn) and zinc vacancies (VZn). Copyright © 2010 John Wiley & Sons, Ltd.
Investigation of molecular surfaces with time‐of‐flight secondary ion mass spectrometry
Authors: Aoyagi Satoka , Namekawa Koki , Yamamoto Kenichiro , Sakai Kiyotaka , Kato Nobuhiko , Kudo Masahiro 
Published: June 2010

AbstractTOF‐SIMS is a promising technique for evaluating biodevices due to its ultrahigh surface sensitivity. Since a cluster ion source such as C60+ provides low collision energy per atom, time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) with the cluster ion is useful for detecting the uppermost surface of molecules immobilized on a substrate, and therefore, enables the evaluation of the orientation of these immobilized biomolecules. Effects of TOF‐SIMS with C60+ were investigated in this study. A relatively small protein, lysozyme, and polypeptides having five amino acid residues, Leu‐enkephalin and Met‐enkephalin, were employed as model samples. The protein and the polypeptides were immobilized on aminosilanized‐indium‐tin oxide (ITO) coated glass plates at their N‐terminal residues by covalent bonding. The aminosilanized‐ITO plate without protein or polypeptide was also prepared as a control sample. After freeze‐drying, the samples were measured with TOF‐SIMS using gallium and C60+ cluster ion sources, and then TOF‐SIMS spectra were analyzed to select peaks specific to each biomolecule by a comparison between the samples. As a result, the C60+ primary ion source showed advantages in evaluating biomolecules, because more peaks at a higher mass generated from the biomolecules can be obtained using C60+ than Ga+ or Au3+ as the primary ion source, although no difference was detected between the two polypeptide samples under the current measurement conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Zero‐energy SIMS depth profiling: the role of surface roughness development with XeF2‐based etching
Authors: Vanhove N. , Lievens P. , Vandervorst W. 
Published: June 2010

AbstractTo obtain monolayer depth resolution in the zero‐energy SIMS concept, an almost atomically flat surface during the electron beam‐induced etching (EBIE) is crucial. However, the surface roughness observed with Si EBIE and XeF2 shows the same characteristics as observed during spontaneous etching of Si with XeF2. The subsurface fluorine concentration in a Si EBIE process (even in a mass transport limited regime) can influence the unactivated formation of the SiFx reaction layer as well, and therefore, contribute to observed roughness development. SiO2 EBIE leads to extreme pit formation due to preferential etching of Si at the SiO2/Si interface. In general, preferential etching can deteriorate or enhance the depth resolution as shown on a SiGe epilayer structure. Finally, the capabilities of zero‐energy SIMS are shown on an ultra‐shallow SiGe structure demonstrating a narrow surface transient and a very good depth resolution in the surface region. Copyright © 2010 John Wiley & Sons, Ltd.