bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhancement of Nonvolatile Floating Gate Memory Devices Containing AgInSbTe-SiO2 Nanocomposite by Inserting HfO2/SiO2 Blocking Oxide Layer
Authors: Chiang Kuo-Chang , Hsieh Tsung-Eong 
Published: September 2011

ABSTRACTThis work presents an enhancement of nonvolatile floating gate memory (NFGM) devices comprised of AgInSbTe (AIST) nanocomposite as the charge-storage trap layer and HfO2 or HfO2/SiO2 as the blocking oxide layer. A significantly large memory window (ΔVFB) shift = 30.7 V and storage charge density = 2.3×1013 cm−2 at ±23V gate voltage sweep were achieved in HfO2/SiO2/AIST sample. Retention time analysis observed a ΔVFB shift about 19.3 V and the charge loss about 13.4% in such a sample under the ±15V gate voltage stress after 104 sec retention time test. Regardless of applied bias direction, the sample containing HfO2/SiO2 layer exhibited the leakage current density as low as 150 nA/cm2 as revealed by the current-voltage (I-V) measurement. This effectively suppresses the electron injection between gate electrode and charge trapping layer and leads to a substantial enhancement of NFGM characteristics.
Origins of rapid aging of Ba-based proton conducting perovskites
Authors: Slodczyk Aneta , Dabrowski Bogdan , Malikova Natalie , Colomban Philippe 
Published: September 2011

ABSTRACTProton conducting ceramics are considered as promising membranes for medium temperature fuel cells, water stream electrolyzers and CO2/syngas converters. Materials for these applications have to be mechanically and chemically stable at corrosive conditions of temperature and water vapor pressure in order to ensure the long life-time operation. Our comprehensive Raman, infrared, thermogravimetric, thermal expansion and neutron diffraction studies have shown that the choice of A and B elements as well as the material processing (synthesis, geometry, density, etc.) are crucial to control aging of material. We will consider an example of BaZr0.25In0.75O3 perovskite to show that several factors such as the carbonation, the traces of secondary AO phases at the grain boundaries as well as the use of samples with highly active surface, i.e. powders or lightly densified ceramics can cause: i) preferential adsorption of surface protonic species such as hydroxides, (hydro)carbonates, water, ii) decreased incorporation of bulk protonic species responsible for the proton conduction, iii) significant modification of the host perovskite structure up to complete crumbling of the material. We will show how to improve potential application of perovskites by understanding and controlling these processes.
A Study of Phase Transition Behaviors of Chalcogenide Layers Using In-situ AC Impedance Spectroscopy
Authors: Huang Yin-Hsien , Huang Yu-Jen , Hsieh Tsung-Eong 
Published: September 2011

ABSTRACTThe electrical properties of chalcogenide thin films, both pristine Ge2Sb2Te5 (GST) and cerium-doped GST (Ce-GST), were investigated by in-situ AC impedance spectroscopy. In conjunction with the brick layer model, the contributions of both the grain and the grain boundary to the phase-transition behaviors of chalcogenide samples could be distinguished; the results illustrated the dominance of the grain boundary in the phase transition process. Moreover, impedance analysis applied to characterize the effects of doping on the phase-transition kinetics yielded results similar to those obtained by conventional methods. Therefore, in-situ AC impedance spectroscopy is a feasible tool for analyzing the phase transitions of chalcogenides.
Temperature Induced Evolution of Bond-Centered Hydrogen (BCH) Defects in Crystalline Silicon: Dynamical, Electronic, Vibrational and Optical Signatures
Authors: Ibrahim Zahraa A. , Shkrebtii Anatoli I. , Zimmer-De Iuliis Frederic , Gaspari Franco 
Published: September 2011

ABSTRACTThe thermal stability, evolution and structure of the bond-centered-hydrogen (BCH) defect in crystalline silicon, its temperature induced dissociation, and the new H complexes formed have been studied in the temperature range from 50 K to 650 K by first-principles molecular dynamics (MD). We demonstrate that BCH is stable at 60 K, but decays at and above 310 K in agreement with experimental results. The dissolved BCH forms new complexes: transitional interstitials, stable monohydride-like and monohydride/dihydride-like complexes. The calculated asymmetric vibrational frequency of H in the BCH complex is 2000 cm-1, very close to the experimental values. Calculated vibrational frequencies, electron charge densities, electron densities of states (DOS), and optical spectra demonstrate noticeable differences for the different geometries with the BCH, interstitial and monohydride-like complexes, especially in the vicinity of the energy gap. The BCH complex is found to induce characteristic donor states below the conduction band, and raises the Fermi level to above the donor state energies.
Properties of Phase Change Materials Modified by Ion Implantation
Authors: Raoux Simone , Cohen Guy M. , Hopstaken Marinus , Maurer Siegfried , Jordan Sweet Jean L. 
Published: September 2011

ABSTRACTIon implantation of germanium and carbon ions into thin films of Ge2Sb2Te5 (GST) and GeTe was applied to modify the properties of these phase change materials. It was found that it is possible to amorphize crystalline GST and GeTe using ion implantation for optimized ion doses and energies which depend on the film thickness, ion species and capping layer. A relatively low minimum dose is required for complete amorphization as judged by the absence of diffraction peaks in x-ray diffraction (XRD) scans. It is 4–5×1013 cm−2 for germanium implantation into GST, and slightly higher (1014 cm−2) for germanium implantation into GeTe. The properties of the re-amorphized films depend on ion species, dose and energy. The re-crystallization temperature of re-amorphized GST by ion implantation is comparable or higher than as-deposited amorphous GST. Carbon implantation in particular leads to a large increase in the crystallization temperature Tx. A carbon dose of 1016 cm−2 implanted into 20 nm amorphous GST yielded a crystallization temperature of 300 ºC, much higher than the crystallization temperature of 160 ºC we recorded for as-deposited, amorphous GST. Similarly, high dose carbon implantation into amorphous GeTe leads to large increase in Tx. We recorded a shift in Tx from 195 ºC for as-deposited GeTe to 400 ºC for C-implanted GeTe. Crystalline GeTe re-amorphized by a low dose germanium ion implantation exhibits a re-crystallization temperature below Tx of as-deposited amorphous GeTe and Tx increased with the implanted Ge dose to a crystallization temperature above that of unimplanted GeTe. Ion implantation can be regarded an additional tool to create phase change materials with different and improved switching properties that cannot be achieved by conventional sputter deposition.
Highly Efficient Dye-sensitized Solar Cells
Authors: Han Liyuan , Islam Ashraful 
Published: September 2011

ABSTRACTThe present paper discusses the principle of dye-sensitized solar cells (DSCs) in terms of equivalent circuit model and the key issues to improve the device efficiency. Equivalent circuit model is proposed following analysis by electrochemical impedance spectroscopy of the voltage dependence of the internal resistance elements of DSCs. The influence of these elements upon cell performance in areas such as short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF) was examined based on the equivalent circuit. Efficient sensitization of nanocrystalline TiO2 film was observed across the whole visible range and into the near-IR region as far as 1000 nm with a new panchromatic substituted β-diketonato Ru(II)-terpyridine dye (HIG1). Introduction of bulky alkyl substituent group in a β-diketonato Ru(II)-terpyridine dye (A3) suppress aggregate formation result in an improved performance of DSCs and the performance is independent of the additive added during the dye adsorption process. The haze factor of TiO2 electrodes is a useful index when fabricating light-confined TiO2 electrodes to improve Jsc. It was demonstrated that blocking of bare TiO2 surface with small molecules is an effective way of suppress interfacial charge recombination at the TiO2-dye/electrolyte interface and of improving shunt resistance and Voc. FF was also improved by reduction of the internal series resistance, which is composed of the following three elements: the redox reaction resistance at the platinum counter electrode, the resistance of carrier transport by ions in the electrolyte, and resistance due to the sheet resistance of the transparent conducting oxide. Finally, the highest efficiency scores of 10.4% and 11.1% (aperture illumination area 1.004cm2 and 0.219cm2, respectively) were confirmed by a public test center.
Low Temperature Transparent ITO-based Contacts for Mid-IR Applications
Authors: Genty F. , Margueron S. , Ould Saad Hamady S. , Petit J.C. , Srour H. , Karsaklian dal Bosco A. , Sadok J. , Huguenin J. , Bouirig M. , Jacquet J. 
Published: September 2011

ABSTRACTIn this work, thin films of Indium Tin Oxide (ITO)-based materials were tested as potential candidates for mid-IR transparent contacts on Te-doped GaSb and Si-doped InAs semiconductor wafers. Since these contacts are devoted to be inserted in Sb-based devices which are generally MBE-grown at ∼450°C, low-temperature fabrication processes were particularly tested with a maximum temperature of annealing of 400°C. 50 nm-thick ITO films were deposited on glass, Te-doped GaSb and Si-doped InAs wafers and resistivity of 8.10−4 Ω.cm combined with ∼80% of transmittance at 2 μm and ohmic contacts with a specific resistance of 3.10−4 Ω.cm2 were obtained. Then, in order to improve these properties in the mid-IR, other ITO-based materials were tested: In doped ZnO (IZO) and Zn doped ITO (ITZO). The first results obtained on these materials show that the insertion of 10% of Zn in classical ITO structure results in a degradation of the electrical properties of the layer without a real impact on its optical transmittance near 2 μm. Concerning IZO, a large improvement of the transmittance in the whole visible-mid-IR wavelength range was observed for annealed samples at a temperature as low as 350°C. However, the electrical resistivity appears very sensible to the temperature of annealing.
Photoactivity of Anatase–Rutile TiO2 Nanocrystalline Mixtures Obtained by Heat Treatment of Titanium Peroxide Gel
Authors: Bakardjieva Snejana , Subrt Jan , Pulisova Petra , Marikova Monika , Szatmary Lorant 
Published: September 2011

ABSTRACTNanosized titanium dioxide photocatalysts with anatase structure or mixture of anatase and rutile phases have been synthesized. Homogeneous precipitation of aqueous solutions containing TiOSO4 and ammonia and following treatment with H2O2 was used to prepare porous yellowish (Ti-Per) gel. The gel was lyophilized for 48h and (Ti-Per)LYO-powder was obtained. Single phase anatase TiO2 samples were prepared by heating of the (Ti-Per)LYO powder. The lamella-like particle morphology of TiO2 samples determined by SEM were stable in air up to 950°C.The structure evolution during heating of the starting (Ti-Per)LYO powder was studied by DTA and XRD analyses in overall temperature range of phase transformation. The morphology and microstucture characteristics were also obtained by HRTEM and BET methods. The photocatalytic activity of the sample titania TI-LYO/950 heated to 950ºC in air contained 78.4% anatase and 21.6% rutile was higher than standard Degussa P25. Titania sample TI-LYO/950 reveals the highest catalytic activity during the photocatalyzed degradation course of 4-chlorophenol in aqueous suspension under UV-irradiation.
Growth and Characterization of Thermoelectric Mg2Si Thin Films
Authors: Hasapis Thomas C. , Stefanaki Eleni C. , Siozios Anastasios , Hatzikraniotis Euripides , Vourlias George , Patsalas Panagiotis , Paraskevopoulos Konstantinos M. 
Published: September 2011

ABSTRACTIn this work, room temperature co-deposition of Mg and Si was used to successfully fabricate Mg2Si thin films on Si substrate by dual cathode magnetron sputtering (DCMS). Films were annealed at 380°C. Various Mg/Si sputtering power ratios have been examined. XRD, SEM and IR reflectivity measurements on grown and annealed films, reveal that annealing is enhancing the formation of crystalline Mg2Si.
Optical Properties of Carbon Nanoparticles
Authors: Melnik Nikolay N. 
Published: September 2011

ABSTRACTSamples of carbon nanoparticles obtained by different technologies (carbon plasma deposition, irradiation, anodic etching etc.). by Raman scattering and photoluminescence were studied. It was shown that there are carbon nanoparticles which consist of a core containing sp2 bonds and a shell containing sp3 bonds. These particles have a rather intense photoluminescence. We propose the following photoluminescence mechanism of such nanoparticles: first the nanoparticle core absorbs light; further excitation is transmitted to the external cover or environment where photorecombination occurs. This effect occurs when the size of the particles becomes smaller than the size of the wave function excited state of the nanoparticle. The aim of this research is to check this mechanism.
Photocatalytic reforming of formic acid with simultaneous hydrogen production under visible light over CdS sensitized Na2Ti2O4(OH)2
Authors: Tang Wendong , Jing Dengwei , Guo Liejin 
Published: September 2011

ABSTRACTThe present work reports the renewable hydrogen production by an anaerobic photocatalytic reforming of formic acid over CdS sensitized Na2Ti2O4(OH)2 nanotubes. the Na2Ti2O4(OH)2 nanotube was prepared and charactered by X-ray diffraction, UV-visible absorption, transmission electron microscopy, etc. The activity of the catalyst in formic acid was investigated. The greatest photocatalytic reforming activity of formic acid occurs as the formic acid initial concentration is 20 v.%. A probable mechanism for the photocatalytic reforming process was proposed and discussed.
Influence of Process Parameters on Resistive Switching in MOCVD NiO Films
Authors: Wang X.P. , Wouters D.J. , Toeller M. , Meersschaut J. , Goux L. , Chen Y.Y. , Govoreanu B. , Pantisano L. , Degraeve R. , Jurczak M. , Altimime L. , Kittl J. 
Published: September 2011

ABSTRACTThe unipolar resisitive switching properties of MOCVD deposited NiO in Ni/NiO/TiN stacks is reported. The switching quality is defined as function of RESET current and Roff/Ron ratio, and the importance of the Forming current and voltage on these parameters is discussed. The effect of structural stack variations as NiO thickness, Ti doping, and TiN thickness on the switching behavior of NiO is explained by the effect on the forming current and voltage conditions, and on Joule heating dissipation. Thinner NiO films, Ti doping, as well as thicker top electrode improve the switching quality by decreasing the RESET current and increasing the Roff/Ron ratio.
Ion irradiation effects in silicon nanowires
Authors: Nordlund K. , Hoilijoki S. , Holmstr¨om E. 
Published: September 2011

ABSTRACTIon irradiation effects in nanowires are of increasing interest due to potential applications of the wires as e.g. current-carrying elements in transistors or as efficient light emitters. Although several experiments have already demonstrated such functionalities, very few theoretical studies on the fundamental mechanisms of ion irradiation have been carried out. To shed light on the basic mechanisms of nanowire irradiation, we have simulated 0.03- 10 keV Ar ion irradiation of Si nanowires with a < 111 >-oriented axis and with all side facets being < 112 >. We compare the results with those for Si surfaces and bulk. The results show that the damage production in the nanowire is strongly influenced by surface effects.
Evaluation of Ultra-thin Layer Fabricated by Wet-process as a Pore-Seal for Porous Low-k Films
Authors: Ono Shoko Sugiyama , Kohmura Kazuo , Tanaka Hirofumi , Kayaba Yasuhisa , Kikkawa Takamaro 
Published: September 2011

ABSTRACTWe focused on detailed evaluations of properties of the ultra-thin pore-seal layer (< 3 nm-thick), such as Cu diffusion barrier property and thermal stability. Cu diffusion into dense thermal silica and porous silica low-k which are covered with the pore seal layer was evaluated using metal-insulator-semiconductor (MIS) capacitors under bias thermal stress (BTS). Triangular voltage sweep (TVS) measurement shows that the ultra-thin layer on dense thermal silica suppresses the drift of Cu ions. The Time-Dependent Dielectric Breakdown (TDDB) lifetime of porous silica low-k covered with the ultra-thin pore seal layer results in a drastic increase of the capacitor lifetime with respect to the no-pore-seal control system (stable at 125 °C at least for 10000 s). Thermal decomposition of bulk material of the pore sealant was measured by thermal gravity (TG) test in nitrogen. Bulk material did not decompose through around 350 °C. The amount of ultra-thin pore seal layer fabricated on silicon wafer after thermal cycle stress in vacuum was measured by x-ray photoelectron spectroscopy (XPS). Amount of pore sealant did not decrease even after 2 cycles of 20 min, at 250 °C. Those results show that the ultra-thin layer, which we propose here, has a potential as a pore seal layer for porous low-k films.
Synthesis and characterization of hybrid CdS/MEH-PPV nanocomposites for photovoltaic applications
Authors: Laera Anna M. , Resta Vincenzo , Piscopiello Emanuela , Schioppa Monica , Tapfer Leander 
Published: September 2011

ABSTRACTInorganic-organic nanocomposites, with II-VI or III-V semiconductor nanocrystals (NCs) embedded in semiconducting polymer matrix, are very promising materials for photovoltaic applications.Here, we present an effective and easy synthesis procedure to obtain a hybrid nanocomposite with CdS NCs dispersed in poly[2-methoxy-5-(2-(2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) conjugated polymer. CdS NCs are synthesized directly within the matrix through the decomposition of a suitable unimolecular precursor dispersed homogeneously in the polymer.We show that CdS NCs are formed at low annealing temperature avoiding structural damages and without affecting the functional properties of the MEH-PPV polymer. The NCs diameter ranges between 1.5nm and 4nm depending on the annealing temperature. In addition, no coalescence phenomena of CdS NCs were noticed in TEM observations even at very high particle density (40 wt %).
Photoluminescence X-ray Excitation Spectra in Eu-doped GaN Grown by Organometallic Vapor Phase Epitaxy
Authors: Emura S. , Higashi K. , Itadani A. , Torigoe H. , Kuroda Y. , Nishikawa A. , Fujiwara Y. , Asahi H. 
Published: September 2011

ABSTRACTX-ray-excited luminescence of GaN doped with Eu ions as a luminescent center was observed in the wavelength range from 350 nm to 650 nm. Three peaks at 375 nm, 550 nm and 622 nm were found. To survey the mechanism of the photoluminescence due to non-resonance excitation, photoluminescence X-ray excitation spectra are also measured. The mechanism of the luminescence occurrence was briefly discussed based on the model developed by Emura et al.
Zinc Oxide Nanorod Films for Electrochemical Urea Biosensor
Authors: Palomera Netzahualcóyotl , Balaguera Marcia , Arya Sunil K. , Hernández Samuel , Tomar Maharaj S. , Ramírez-Vick Jaime E. , Singh Surinder P. 
Published: September 2011

ABSTRACTMetal oxide nanostructures have shown significant promise for biosensors, gas sensors, photocatalyst and other biomedical applications. Among these, zinc oxide (ZnO) nanostructures, exhibiting interesting properties such as high catalytic activity, biocompatibility, high isoelectric point, large surface to volume ratio, make them a good candidate for biosensing applications. Here we report the synthesis of ZnO nanorods (ZnONR) on ITO films in aqueous phase and its application in Urea biosensor fabrication. ZnONR have been synthesized by a two-step method, first seed growth of ZnO by sputtering on ITO films followed by decomposition of zinc nitrate hexahydrate / hexamethylenetetramine (HMT) in aqueous phase. Exploiting the high isoelectric point of ZnO, a Urease/ZnONR/ITO bioelectrode has been fabricated by physical binding of Urease (Urs) onto ZnONRs. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and cyclic voltammetry (CV) have been used to characterize ZnONR and the Urs/ZnONR/ITO bioelectrode. The FE-SEM and XRD measurements confirm the formation of ZnONR. The electrochemical data from the Urs/ZnONR/ITO biolectrode reveal linearity between 1-11 mM with sensitivity of 0.9 μA/mM and a relatively low Michaelis-Menten constant (Km) of 5.01 mM for urea sensing. The results indicate the potential of ZnONR films for fabrication of commercial biosensors.
Tailoring the Crystallographic Texture and Electrical Properties of Inkjet-printed Interconnects for Use in Microelectronics
Authors: Cauchois Romain , Saadaoui Mohamed , Inal Karim , Dubois-Bonvalot Beatrice , Fidalgo Jean-Christophe 
Published: September 2011

ABSTRACTIn this paper, silver nanoparticles with a mean diameter of 40 nm are studied for future applications in microelectronic devices. The enhanced diffusivity of nanoparticles is exploited to fabricate electrical interconnects at low temperature. Sintering condition has been tuned to tailor the grain size so that electrical resistivity can be lowered down to 3.4 μOhm∙cm. In this study, a {111}-textured gold thin film has been used to increase diffusion routes. The combined effects of the substrate crystalline orientation and the sintering condition have been demonstrated to have a significant impact on microstructures. In particular, a {111} fiber texture is developed above 300°C in printed silver only if the underlying film exhibits a preferential orientation. This condition appeared as essential for the efficiency of the gold wire-bonding process step. Thus, inkjet-printed interconnects show a prospective potential compared to conventional subtractive technique and offers new opportunities for low cost metallization in electronics packaging.
Effects of Hydrogen Ion Implantation and Thermal Annealing on Structural and Optical Properties of Single-crystal Sapphire.
Authors: Spratt William T. , Huang Mengbing , Jia Chuanlei , Wang Lei , Kamineni Vimal K. , Diebold Alain C. , Matyi Richard , Xia Hua 
Published: September 2011

ABSTRACTDue to its outstanding thermal and chemical stability, single-crystal sapphire is a crucial material for high-temperature optical sensing applications. The potential for using hydrogen ion implantation to fabricate stable, high temperature optical waveguides in single crystal sapphire is investigated in this work. Hydrogen ions were implanted in c-plane sapphire with energies of 35 keV and 1 MeV and fluences 1016-1017/cm2. Subsequent annealing was carried out in air at temperatures ranging from 500˚C to 1200˚C. Complementary techniques were used to characterize the samples, including ellipsometry and prism coupling to examine optical properties, Rutherford backscattering/ion channeling for crystal defects, and nuclear reaction analysis for hydrogen profiling. Several guiding modes were observed in H-implanted (1 MeV) samples annealed above 800˚C through prism coupling, and a maximum index modification of 3% was observed in the 35 keV samples and 1% in the 1 MeV samples through ellipsometry, with the 1 MeV index variation being confirmed through prism coupling. The possible causes of the index modifications, such as H related defects, as well as implications for tailoring the refractive index of sapphire are discussed.