bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dislocation reduction in high Al‐content AlGaN films for deep ultraviolet light emitting diodes
Authors: Ahmad Iftikhar , Krishnan Balakrishnan , Zhang Bin , Fareed Qhalid , Lachab Mohamed , Dion Joseph , Khan Asif 
Published: June 2011

AbstractWe report a new approach for growing thicker (>2 µm) low‐defect AlGaN layers over sapphire using pulsed MOCVD procedure. These high content AlGaN layers serve as templates for subsequent n‐AlGaN growth for deep ultraviolet light emitting diodes (DUV LEDs). During the growth of the AlxGa1−xN layer, the pulsed‐growth conditions were cyclically adjusted to reduce the dislocations. This leads to AlGaN templates with an RMS roughness of 9.6 Å and (102) off‐axis X‐ray line‐width 550 arcsec. The transmission electron microscope (TEM) analysis shows 4 × 107 cm−2 edge type and 2 × 106 cm−2 screw type of threading dislocation densities at best regions. On the average dislocation density in these films is 4 × 108 cm−2. A light emitting diode (LED) structure emitting at 280 nm was deposited on these templates. A comparative study showed the EL emission for LEDs on the new low‐defect templates to be more than 1.6 times stronger than our conventional DUV LED structures. In this paper the details of our growth procedure, the epi‐structure X‐ray, atomic force microscopy (AFM), TEM, and other characterizations will be presented. A comparative study of DUV LED structures over conventional and improved templates of this work will be discussed.
Initiating polarity inversion in GaN growth using an AlN interlayer
Authors: Hite Jennifer K. , Twigg Mark E. , Mastro Michael A. , Eddy Charles R. , Kub Francis J. 
Published: June 2011

AbstractIn this work, we show that the polarity of GaN grown on N‐polar material can be controlled through a combination of surface conditioning and introduction of a non‐Mg inversion layer (IL). The IL we use is a thin, low‐temperature AlN layer deposited by metal organic chemical vapor deposition (MOCVD). The subsequent inverted films are Ga‐polar that do not contain inversion domain boundaries and with crystal quality similar to MOCVD films grown on sapphire. The polarity inversion technique is enhanced by the addition of an etching step prior to AlN deposition.
Metal‐face InAlN/AlN/GaN high electron mobility transistors with regrown ohmic contacts by molecular beam epitaxy
Authors: Guo Jia , Cao Yu , Lian Chuanxin , Zimmermann Tom , Li Guowang , Verma Jai , Gao Xiang , Guo Shiping , Saunier Paul , Wistey Mark , Jena Debdeep , Xing Huili (Grace) 
Published: June 2011

AbstractOhmic regrowth by molecular beam epitaxy (MBE) has been investigated for metal‐face InAlN/AlN/GaN high electron mobility transistors (HEMTs) for the first time. Using SiO2 mask n+‐GaN was regrown in the source/drain region while deposition on the mask was lifted off in buffered HF after regrowth. The lowest contact resistance measured was 0.40 ± 0.23 Ω mm by the transmission line method (TLM) in this initial study. The peak output current density of 1.25 A/mm at Vgs = 3 V and extrinsic transconductance of 264 mS/mm at Vds = 5 V were observed in 500‐nm gate length InAlN/Al/GaN HEMTs passivated by SiN with regrowth contacts.
Microstructure and frequency sensitive electrical conductivity in Fe3BO6:B2O3 of a hybrid vitroceramic nanocomposite
Authors: Kumari K. , Bhargav K. K. , Kumar N. , Ram S. , Kotnala R. K. 
Published: June 2011

AbstractIron oxyborate Fe3BO6, a mixed compound of iron oxide Fe2O3 and iron borate FeBO3, offers multifunctional properties for electrodes, gas sensors, drugs delivery, or biological probes. To accolade useful properties, in this paper we report frequency (f) dependence of ac electrical conductivity (σac) of Fe3BO6, which is crystallized in shapes of thin plates (40–50 nm thickness) and rectangular bars (50–100 nm thickness) from an iron borate glass 40Fe2O3–60B2O3. Residual B2O3 (10–15 wt%), which remains in a vitreous phase, forms a hybrid vitroceramic nanocomposite. This B2O3 is useful to surface modify Fe3BO6 so that it turns into a strongly correlated antiferromagnet with uncompensated surface Fe3+(3d5) spins, showing only very small magnetization of the order of a few 10−4 emu/g at room temperature. The σac‐values measured at selective frequencies 0.1–103 kHz over a temperature range 300–575 K follow an activation energy varied from 0.345 to 0.244 eV, if the plot is analyzed in nearly linear parts, in raising frequency from 10 to 103 kHz. Primarily oxygen vacancies preside over a thermal assisted condition process wherein the initial σac‐value increases effectively slowly against temperature. Otherwise, Fe3BO6 with an optical bandgap 3.1 eV is a typical insulator. At f ≥ 50 kHz, a characteristically weak peak arises in a spin‐reorientation transition near 433 K. The spin‐flops, which commence on a frequency assisted σac‐value, illustrate the effect of a coupled system of the spins and charge carriers.
Nearest‐neighbour antiferromagnetic interaction as a limiting factor for critical temperature in a model DMS system
Authors: Szałowski Karol 
Published: June 2011

AbstractIn numerous diluted magnetic semiconductor (DMS) systems, the competition takes place between the short‐range antiferromagnetic (AF) superexchange interactions and the long‐range Ruderman–Kittel–Kasuya–Yosida (RKKY) coupling mediated by the charge carriers. Such a situation strongly influences the critical temperature, the maximization of which constitutes a challenging task in DMS physics and technology. The aim of the paper is to discuss theoretically the limiting effect of AF interactions between nearest‐neighbour (NN) magnetic ions on the stability of inhomogeneous ferromagnetic state in a model diluted magnetic system reflecting some crucial features of DMS. The modified molecular field‐based model is constructed to account for the magnetic inhomogeneity. The behaviour of the system is studied as a function of the ratio of superexchange integral to effective ferromagnetic coupling integral, including the possibility of clustering/anticlustering tendency for the magnetic ions. The ground state of the system is analyzed. The critical temperature is found to change non‐monotonically with the concentration of magnetic ions and decrease severely for larger concentrations. The behaviour of the system significantly differs from the predictions of the usual homogeneous mean‐field model. Brief comparison with selected experimental results for (Zn,Mn)Te is provided.
LDA + slave‐boson approach to the correlated electronic structure of the metamagnetic bilayer ruthenate Sr3Ru2O7
Authors: Piefke Christoph , Lechermann Frank 
Published: June 2011

AbstractThe combination of the local‐density approximation (LDA) with the rotationally invariant slave‐boson theory (RISB) is used to investigate the realistic correlated electronic structure of Sr3Ru2O7. From Wannier‐downfolding the low‐energy band structure to a three‐band model for the Ru(t2g) states, the interacting problem is solved including intra‐ and inter‐orbital Hubbard terms as well as spin‐flip and pair‐hopping interactions. Therewith it is possible to obtain valuable insight into the orbital occupations, relevant local spin multiplets, and the fermiology with increasing correlation strength. Besides generic correlation‐induced band‐narrowing and ‐shifting, an intriguing quasiparticle structure close to the Fermi level is found in the neighborhood of the notorious γ2 pocket in the Brillouin zone. Along the Γ–X direction in k‐space, that structure appears very sensitive to electronic self‐energy effects. The subtle sensitivity, connected also to its manifest multi‐orbital character, may put this very low‐energy structure in context with the puzzling metamagnetic properties of the compound.
Structural defects and cathodoluminescence of InxGa1‐xN layers
Authors: Liliental‐Weber Z. , Ogletree D. F. , Yu K. M. , Hawkridge M. , Domagala J. Z. , Bak‐Misiuk J. , Berman A. E. , Emara A. , Bedair S. 
Published: June 2011

AbstractCorrelation between structural defects and appearance of multiple cathodoluminescence and photoluminescence peaks of InxGa1‐xN grown nominally with x = 0.1 and increasing layer thickness (100 nm to 1000 nm) is discussed. Cathodoluminescence studies were performed on the cross‐section samples earlier characterized by electron microscopy including Z‐contrast microscopy. Strained and relaxed layers with different In concentrations were observed for InGaN layers above the critical layer thickness. Stacking faults appear at high density in the relaxed layer which also roughens, created a saw‐tooth surface profile due to V‐shaped pits. Large domains of closely separated stacking faults (polytype‐like) were observed. In Z‐contrast microscopy stacking faults in upper/lower part of the layer appear with higher/lower brightness, suggesting different amount of In incorporation in agreement with x‐ray and RBS results. Only thin, strained InGaN layers showed single band‐edge CL peaks. Multiple CL peaks appear in the relaxed, defective portion of the InGaN layers. By comparison with GaN samples where structural defects are associated with CL peak shifts, we postulate that defects, their type and distribution are main contributors to the multiple peaks observed for InGaN samples (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stress analysis of a‐plane GaN grown on r‐plane sapphire substrates
Authors: Ma Bei , Hideto Miyake , Hiramatsu Kazumasa , Harima Hiroshi 
Published: June 2011

AbstractNon‐polarized and polarized Raman spectra were measured in a‐plane GaN films grown on r‐plane sapphire. Active phonon models were verified under different geometry configurations. Our results showes that all a‐plane GaN films are under	compressive strains both along and perpendicular the c‐axis. With increasing film thickness, compressive strains are gradually relaxed. Strain relaxation process relieves the tilt and twist of crystal grains to improve crystal quality. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
TEM investigation of anisotropic defect structure in cubic GaN/AlGaAs/GaAs(001) grown by MOVPE
Authors: Parinyataramas Jamreonta , Sanorpim Sakuntam , Thanachayanont Chanchana , Onabe Kentaro 
Published: June 2011

AbstractThe effects of AlxGa1‐xAs buffer layer insertion on the defect structures and their distribution in cubic (c‐) GaN films on GaAs (001) substrates grown by low‐pressure metalorganic vapor phase epitaxy have been investigated by means of bright‐ and dark‐field cross‐sectional transmission electron microscopy. It is demonstrated that a 300‐nm‐thick Al0.2Ga0.8As buffer layer can protect the GaAs (001) surface from thermal decomposition during the growth at 960 °C, remaining a growth of c‐GaN on GaAs substrate without any voids at the interface. Two different types of defect structures having an anisotropic distribution between the [110] and [1‐10] zone axes were observed. For the [110] zone‐axis, the pyramid‐shaped grains, which are proposed to construct from planar defects, such as SFs and twins, were observed. On the other hand, for the [1‐10] zone‐axis, a dense cubic phase structure with less contribution of planar defects was observed. However, threading dislocations, which were produced by a coalescence of pyramid‐shaped grains in the [110] direction, were observed at the top regions of c‐GaN layer. Both types of defect structures have an anisotropic distribution within a cubic symmetry that may be due to different atomic structures on the AlGaAs surface along the [110] and [1‐10] crystallographic directions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Detection of vitellogenin, an endocrine disrupter biomarker, using AlGaN/GaN high electron mobility transistors
Authors: Chu Byung Hwan , Chang C. Y. , Kroll Kevin , Denslow Nancy , Wang Yu‐Lin , Pearton S. J. , Lin Jenshan , Dabiran A. M. , Wowchak A. M. , Cui B. , Chow P. P. , Johnson J. W. , Rajagopal P. , Roberts J. C. , Piner E. L. , Linthicum K. J. , Ren Fan 
Published: June 2011

AbstractReal time detection of vitellogenin in largemouth bass serum was demonstrated using AlGaN/GaN HEMTs. Anti‐vitellogenin antibodies were chemically anchored to the gold‐coated gate area of the HEMT by thioglycolic acid. The potential difference that occurred from the vitellogenin antigen/antibody interaction induced a drain current change. The sensor was able to detect as low as 4 µg/mL Vtg. Successful detection in serum samples shows that HEMTs have the potential to be used as biological sensors in real‐world applications (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of silica antireflective films formed in sol‐gel processes
Authors: Jaglarz Janusz , Karasinski Pawel , Skoczek Edyta 
Published: June 2011

AbstractThe work presents optical properties of sol‐gel derived porous silica films of low refractive index, from 1.2 to 1.3. Due to low refractive index, the porous silica films can be applied to reduce the light reflection coefficient. This allows porous silica films as good candidates for the antireflective coatings (ARC) production. The spectroscopic ellipsometric measurements have been performed for the refractive indices and thickness of silica films determination. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscopic simulation of semiconductor laser devices
Authors: Bückers Christina , Hader Jörg , Moloney Jerome V. , Koch Stephan W. 
Published: June 2011

AbstractThis paper reviews the application of a systematic microscopic theory for the optical and electronic properties of semiconductors. The theory is applied to quantitatively model and analyze different semiconductor systems. Detailed theory‐experiment comparisons are shown for a variety of quantum well gain materials. It is demonstrated how the analysis can be used to aid in the design of modern semiconductor laser devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature sensitive near‐infrared luminescence of Er3+ ions in LiYF4
Authors: Tsuboi Taiju , Shimamura Kiyoshi 
Published: June 2011

AbstractThe photoluminescence spectra at 800‐1650 nm of Er3+ ions doped in LiYF4 crystal are investigated at temperatures between 296 and 12 K. Intense emissions were observed at 1460‐1540, 1205‐1235, 960‐1020, and 830‐860 nm. As temperature is increased from 12 K to room temperature, broadening and intensity increase were observed for the emissions at 1460‐1540 and 960‐1020 nm, but not observed for emissions at 1205‐1235 and 830‐860 nm. The broadening is explained by the transitions from upper Stark levels which are thermally excited at higher temperatures. Level assignment has been made for all the emissions including several weak emissions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of Eu2+‐doped A‐site and oxygen‐deficient perovskite related host for photoluminescent materials
Authors: Ishigaki Tadashi , Hatsumori Tomoki , Sakamoto Tatsuya , Uematsu Kazuyoshi , Toda Kenji , Sato Mineo 
Published: June 2011

AbstractPerovskite‐related compounds have been investigated in many fields, because they have various unique properties due to their compositions and structures which are characterized by various combinations of the A and B cations. In addition, defect perovskite‐type compounds have also been investigated in many areas, especially as ion conductors. In this study, we used the A‐site and oxygen‐deficient perovskite, Sr3Al2O6, as a photoluminescent host material. This means that the defect sites were able to substitute several ions. We investigated the A3Al2O6:Eu2+ phosphor material (A = Mg, Ca, Sr, Ba) produced by a solid state reaction in several kinds of atmospheres. Based on our results, the phosphor showed wide excitation and emission bands of 300–400 nm and 450–600 nm, respectively. The emission color control depended on the A‐site substitution ratio. It is a very useful phosphor for white LEDs. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Technology of mixed amorphous As2(Sx Se1‐x)3 from chemical solutions and their optical properties
Authors: Verlan V. , Buzurniuc S. , Malahov L. 
Published: June 2011

AbstractThin layers of amorphous chalcogenides semiconductors of mixed composition As2(SxSe1‐x)3 for x in the interval 0–1 were obtained from chemical solutions of amorphous compounds arsenic selenide (As2Se3) and arsenic sulfide (As2S2). Their optical properties (optical transmittance and recording of holographic information) were studied. The photodarkening of layers and shift of absorption edge in infrared (IR) area of spectra were found at ultra‐violet (UV) and actinic irradiations. Maximum efficiency of holographic writing of diffraction gratings (with Ar laser recording, λ = 488 nm) on thin layers is 2.5% and after additional processing in the negative etching is 36% (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoinduced bond breaking in a‐Se: Raman spectroscopic study
Authors: Lukacs R. , Veres M. , Shimakawa K. , Kugler S. 
Published: June 2011

AbstractIn flatly deposited a‐Se films photoexpansion has been found due to covalent bond breaking during the electron excitation process, and simultaneously photocontraction due to inter‐chain bond formation in the case of hole creation. Determination and explanation of the microscopic photoinduced changes in amorphous selenium structure was the purpose of this investigation. For this purpose Raman spectra measurements have been carried out on flatly amorphous selenium (a‐Se). Reversible covalent bond breaking process was found as a consequence of band gap light illumination in the experiments. Our bond breaking model obtained using Molecular Dynamics simulations has been confirmed experimentally by Raman spectroscopy (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependence of the threshold current density of a GaN based quantum dot laser
Authors: Asgari Asghar , Khorami A. A. 
Published: June 2011

AbstractWith considering a simple and almost exact models, a III‐nitride based spherical quantum dot cascade laser has been analyzed, where the generation of the terahertz waves are obtained. With self‐consistent solution of the Schrödinger, Poisson, and the laser rate equations, including all effects such as piezoelectric and spontaneous polarization in nitride‐based QDs and the effects of the temperature, the exact value of the lasing frequency and also the other parameters such as the energy levels, the wavefunctions, and the lifetimes of subbands are calculated. Also the laser parameters such as the optical gain, the output power and the threshold current density have been calculated at difference temperatures (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronics with and on paper
Authors: Martins R. , Ferreira I. , Fortunato E. 
Published: June 2011

AbstractToday there is a strong interest in the scientific and industrial community concerning the use of biopolymers for electronic applications, driven mainly by low‐cost and disposable applications. Adding to this interest, we must recognise the importance of the dream of wireless auto‐sustained and low‐energy‐consumption electronics. This dream can be fulfilled by cellulose paper, the lightest and the cheapest known substrate material, as well as the Earth's major biopolymer and of tremendous global economic importance. Most of the paper used up to now is optimised in terms of the required mechanical and physical properties to be used as the support of inks of different origins. In the future, specific electronic heterogeneous paper sheets should be fabricated aiming to get paper fibers with required bulk and surface functionalities, proper water/vapour barrier, size and diameter/thickness of the fibrils and full paper thickness. This will be the function of components/devices to be incorporated/integrated such as thin‐film transistors, complementary metal oxide semiconductor devices, passive electronic components (resistances, inductors and capacitors), memory transistors, electrochromics and thin‐film paper batteries. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust stability and performance analysis for uncertain linear systems—The distance measure approach
Authors: Lanzon Alexander , Engelken Sönke , Patra Sourav , Papageorgiou George 
Published: June 2011

SUMMARYThis paper presents readily applicable distance measures, robust stability margins and associated robust stability and robust performance theorems for three commonly used uncertainty structures (additive, input/output multiplicative, output/input inverse multiplicative). Besides providing robust stability results for a larger uncertainty class than previously reported (ℛℒ︁∞ instead of ℛℋ︁∞), this paper also states robust performance theorems for the above uncertainty structures. In contrast to previous methods for robust performance analysis, they only require the computation of two infinity norms for every uncertain plant considered. The theorems in this paper enable practising engineers to choose the most suitable uncertainty structure for a family of uncertain plants, as illustrated through a physically motivated numerical example. Copyright © 2011 John Wiley & Sons, Ltd.
Cisplatin‐Loaded Porous Si Microparticles Capped by Electroless Deposition of Platinum
Authors: Park Jennifer S. , Kinsella Joseph M. , Jandial Danielle D. , Howell Stephen B. , Sailor Michael J. 
Published: June 2011

AbstractThe loading and release of the anti‐cancer drug platinum cis‐dichlorodiamine (cisplatin) from mesoporous silicon (pSi) microparticles is studied. The pSi microparticles are modified with 1‐dodecene or with 1,12‐undecylenic acid by hydrosilylation, and each modified pSi material acts as a reducing agent, forming a deposit of Pt on its surface that nucleates further deposition, capping the mesoporous structure and trapping free (unreduced) cisplatin within. Slow oxidation and hydrolytic dissolution of the Si/SiO2 matrix in buffer solution or in culture medium leads to the release of drugs from the microparticles. The drug‐loaded particles show significantly greater toxicity toward human ovarian cancer cells (in vitro), relative to an equivalent quantity of free cisplatin. This result is consistent with the mechanism of drug release, which generates locally high concentrations of the drug in the vicinity of the degrading particles. Control assays with pSi particles loaded in a similar manner with the therapeutically inactive trans isomer of the platinum drug, and with pSi particles containing no drug, result in low cellular toxicity. A hydrophobic pro‐drug, cis,trans,cis‐[Pt(NH3)2(O2C(CH2)8CH3)2Cl2], is loaded into the pSi films from chloroform without concomitant reduction of the pSi carrier.
Structure and dynamics of microbial community in full-scale activated sludge reactors
Authors: Yi Taewoo , Lee Eun-Hee , Kang Shinyoung , Shin Jikyung , Cho Kyung-Suk 
Published: June 2011

Abstract
Phospholipid fatty acid (PLFA) profiles in four full-scale activated sludge reactors (ASR1 ~ 4) treating municipal wastewater, South Korea, were monitored to evaluate the influence of influent water quality on microbial community structure (MCS) and the effect of the MCS on effluent water quality. In ASR1 ~ 3, PLFA profiles were very similar, regardless of the influent water quality and seasonal differences, and 16:17c/15:0iso2OH and 16:0 were dominant. PLFA profiles in ASR4 during summer and autumn were very similar to those in ASR1 ~ 3, but increases in specific fatty acids, 16:1ω5c, 11methyl18:1ω7c and 15:0iso3OH, were found in ASR4 during winter and spring, with relatively high total suspended solid (TSS) concentrations in the effluent. 16:1ω5c and 15:0iso3OH, possibly related with Flexibacter sp., caused a bulking problem in the activated sludge. The community diversity indices such as Shannon diversity and equability decreased in summer but increased in autumn in all the ASRs. Canonical correspondence analysis results suggested that the influent BOD concentration played the most important role in changing MCS, followed by influent TSS concentration. In addition, the TSS and total phosphorus concentrations in the effluent were significantly affected by the change of the MCS.