bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exciton and Defect Photoluminescence Signatures in Single Crystal Rubrene
Authors: Mitrofanov Oleg , Lang David V , Kloc Christian , Siegrist Theo , So Woo-Young , Sergent Michael A , Ramirez Arthur P 
Published: April 2011

ABSTRACTRadiative recombination processes provide valuable information about exciton dynamics and allow detection of defects in rubrene crystals. We demonstrate that the photoluminescence spectra of crystalline rubrene reflect exciton dissociation through oxygen-related defects in addition to the direct exciton recombination. The defect-assisted exciton dissociation results in a well-defined photoluminescence band. These defects play an important role in charge transport. Dark- and photo-conductivity is higher in rubrene crystals with a large density of the defects. The observations strongly suggest that the oxygen-related defect forms a bandgap state and acts as an acceptor center in crystalline rubrene.
Requirements and Constraints on Optimizing UV Processing of Low-k Dielectrics
Authors: Berry III Ivan L , Waldfried Carlo , Durr Kevin 
Published: April 2011

ABSTRACTUV curing of low-k dielectrics presents a unique challenge in that the cure process is expected to do the impossible – increase hardness, modulus, cohesive strength, adhesion and reliability, decrease water absorbtion and dielectric constant, remove porogens (for porogen containing films), improve dielectric breakdown and chemical stability, all while minimizing shrinkage and contributions to film stress. Achieving this, in general, requires optimization of all of the cure parameters, such as UV spectral intensity, temperature, time, pressure, background gas, and process sequence, as well as the formulation of the low-k material itself. The spectral dependence of many of these important parameters will be discussed. A good figure of merit for modulus and k-value is the ratio of modulus/k-value. If one plots the spectral response of this ratio, one finds it peaks at a specific wavelength range. In principle it is possible to measure the UV spectral response of all of the critical parameters (not just modulus and k-value) and by overlaying these responses together determine what the proper UV exposure wavelength ranges should be. An example of this will be shown for an idealized porogen containing low-k material, for modulus, k-value, porogen removal and porogen crosslinking. A real low-k dielectric system has many more wavelength parameters to consider and the problem of bulb spectral intensity optimization becomes complex. It is also found that the relative intensity of the important wavelength bands also plays a significant role, requiring a great deal of spectral optimization experiments.UV cure performance is also dependent on cure temperature, time, background gases and ironically, the deposition or post-deposition bake temperature. Most cure parameters such as modulus, hardness, leakage, adhesion, etc, have a strong and generally exponential dependence on cure temperature. As a result, most UV cures are performed at the highest temperature allowable as defined by thermal budget constraints and copper voiding thresholds. Background ambient can also play a critical role in the UV cure, especially for porous low-k materials and those containing porogens. Changes in composition of the background gases can alter interface. The ultimate in performance is obtained when the low-k material formulation itself is included as a key parameter in the cure optimization. By optimizing the material, UV spectrum, and cure parameters together, significant improvements can be made.In conclusion, UV curing cannot be implemented without serious consideration to the wavelength dependence on many critical process factors. The interdependence of all components that makeup the optical system such as the wavelengths employed, light source technology, chamber design and ironically, the dielectric film itself must be considered. Only with these factors in mind, can the full benefit of UV curing be realized.
Extendibility of the PECVD Porogen Approach for ULK Materials
Authors: Gourhant Olivier , Jousseaume Vincent , Favennec Laurent , Zenasni Aziz , Maury Patrick , Mage Lucile , Gonon Patrice , Vincent Gilbert 
Published: April 2011

ABSTRACTThe increase of integrated circuits performances requires ultra-low dielectric constant (ULK) materials to minimize the drawbacks of miniaturization. Amorphous SiOCH are promising candidates for ULK materials as porosity can be introduced via a two steps elaboration. In a first step, organo-silicon species and organic species are co-deposited by PECVD. Then, a thermal annealing, alone or assisted by UV radiation, removes the organic labile phase and creates pore inclusions into the final material. In this work, the extendibility of this porogen approach is investigated in order to lower the dielectric constant. An increase of the porogen loading in hybrid film is studied by tuning the precursors ratio injected in the plasma gas feed. The increase of organic species amount is operated in order to create more pores sites. However, the post-treatment does not lead automatically to higher porosity. Actually, an increase of the porosity is observed only until a porogen loading limit and decreases above this limit. The shrinkage of the film during the post-treatment can explain this limitation. For high ratios of porogen, the film shrinkage increases drastically and leads to a decrease of the porosity finally created. At last, the link between porosity and dielectric constant is enlightened and a minimum in term of K value is reached with both post-treatments: dielectric constant of 2.1 and 2.3 are obtained using respectively thermal treatment and UV curing.
Effect of CH4 Plasma Treatment on O2 Plasma Ashed Organosilicate Low-k Dielectrics
Authors: Shi Hualiang , Bao Junjing , liu Junjun , Huang Huai , Ho Paul S. , Goodner Michael D , Moinpour Mansour , Kloster Grant M 
Published: April 2011

ABSTRACTDuring an O2 plasma ashing process, carbon depletion and subsequent moisture uptake caused increase of keff and the leakage current in an organosilicate (OSG) low-k dielectric. For dielectric restoration, additional CH4 plasma treatment on the O2 plasma ashed OSG low-k dielectric was investigated using angle resolved x-ray photoelectron spectroscopy (ARXPS), XPS depth profiling, x-ray reflectivity (XRR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and contact angle goniometer. After CH4 plasma treatment on the O2 plasma ashed OSG, the surface carbon concentration and surface hydrophobicity were partially recovered. A dense surface layer containing C=C bonds was found to have formed on the top of the damaged OSG. The C-V hysteresis and the leakage current were reduced as a result of the CH4 plasma treatment. XPS depth profiling revealed that the recovery effect was limited to the surface region.
Organic-and Bio-Based Digital Memory Devices
Authors: Tseng Ricky J. , Ma Liping , Shao Yan , Yang Yang 
Published: April 2011

AbstractOrganic memory devices are considered as a viable approach for future information processing. We demonstrate this type of memory devices evolving from multiple layers structure to solution synthesis hybrid biomolecule structure. By forming a thin organic-nanoparticle layer or virus-nanoparticle layer in the crossbar junction, electronic memory effect based on electrical bistable states with a large on/off ratio, and long retention time is achieved. Temperature dependent data retention shows the nanoparticle formation determines the charge storage activation energy. Such organic, bio-inorganic nanostructures are promising for future memory technology.
Self-aligned TiSi2/Si Hetero-nanocrystal Nonvolatile Memory
Authors: Zhu Yan , Li Bei , Liu Jianlin 
Published: April 2011

AbstractThis work describes a novel nonvolatile memory device with self-aligned TiSi2/Si hetero-nanocrystal charge storage nodes. The TiSi2/Si hetero-nanocrystals can be readily fabricated using industrial standard self-aligned silicidation technique based on Si nanocrystals deposited on ultra-thin tunnel oxide with LPCVD. As compared with a Si nanocrystal memory device, a TiSi2/Si hetero-nanocrystal memory device exhibits faster programming and erasing, and longer retention time.
Memory window in ferroelectric PVDF copolymer gate integrated MOSFET devices for nondestructive readout memory application
Authors: Lim Sang-Hyun , Rastogi Alok C , Desu Seshu B 
Published: April 2011

AbstractMetal-Ferroelectric-Oxide-Si (MFEOS) field effect transistor (FET) with ferroelectric polyvinylidene fluoride trifluoroethylene copolymer (PVDF-TrFE) gate for nonvolatile memory application is demonstrated. Memory window ascribed to ferroelectric polarization switching has been quantified by shift of threshold voltage are ~ 4-5V. Non saturating IDS is due to free ionic polarization field. IDS-VDS characteristics of functional FET are realized after AC poling.
Nonvolatile Memory Device Based On Nanoparticle Functionalized Tobacco Mosaic Virus
Authors: Tsai Chunglin , Tseng Ricky J. , Yang Yang , Ozkan Cengiz S. 
Published: April 2011

AbstractHybrid virus/inorganic nanoscrystals are considered as important building blocks towards new types of functionality for electronic devices. We use tobacco mosaic viruses to assemble platinum nanoparticles and conjugate with quantum dots. By forming a thin hybrid nanocomposite layer in the crossbar junction, we show electronic memory effect based on electrical bistable states with a large on/off ratio, and long retention time. Such hybrid bio-inorganic nanostructures for the first time are promising for future bio-inspired nanoelectronics.
Oxygen Bonding in Bismuth Layered Compounds SrBi2Ta2O9
Authors: Su Dong , Jiang Nan , Wen Jianguo , Liu Jianshe 
Published: April 2011

AbstractWith the help of the high resolution Z-contrast scanning transmission electron microscopy (STEM), the near edge fine structures of the electron loss spectroscopy (EELS) arises from different layers are investigated in SBT. The EELS spectra are interpreted by comparing with the calculation using linearnized augment plane wave (LAPW) method within the local density approximation (LDA). The oxygen bonding nature in different layers are discussed. In Bi2O2 layer, oxygen 2p state interacted with the Bi 6p state leads to a high t2g state in density of state while in SrTa2O7 layer, oxygen 2p state hybridized with Ta 5d and Sr 5d, which leads a higher eg state than t2g state.
Study of the Effect of Metal/Semiconductor Interface Properties on a Resistance Switching Device
Authors: Villafuerte Manuel , Heluani Silvia P. , Juárez Gabriel , Comedi David , Braunstein Gabriel , Golmar Federico 
Published: April 2011

AbstractN-doped ZnO thin films were deposited by pulsed laser deposition on SiO2/Si substrates. X-ray diffraction analysis revealed that the films had the wurtzite structure, and were highly oriented along the c-axis direction. Au and Al electrical contacts were deposited by sputtering on the top surface of the samples, forming a two-terminal structure in each case. The current-voltage characteristics of the two terminal structure, and the temperature dependence of the resistance switching effect, were studied in the 125-300 K temperature range. The results of these measurements are presented and discussed in terms of the different Schottky barrier heights, as well as in terms of interfacial defect-induced gap states.
Reproducible Resistance Switching in Ni/NiO/Ni Trilayer
Authors: Shima Hisashi , Takano Fumiyoshi , Akinaga Hiro , Inoue Isao H , Takagi Hidenori 
Published: April 2011

AbstractThe resistance random access memory is attracting much attention as a high-density and high-speed non-volatile memory, having large resistance switching ration and good affinity with the conventional CMOS technologies. We demonstrate the resistance switching in the NiO thin film without using Pt electrode.
Adhesion of Crystalline GeSbTe/TiN Interface Characterized by Four Point Bend, Nanoindentation, and Nanoscratch
Authors: Wei guohua , Liu Jun , Fillmore David , Violette Mike , Lu Shifeng 
Published: April 2011

AbstractReversible structural phase change phenomenon of certain chalcogenide materials has been investigated extensively in the past decades. Among various phase change chalcogenide materials, Ge2Sb2Te5 (GST) is the most studied material due to its superior optical, electrical and mechanical properties. One of the challenges in using GST is the poor adhesion between crystalline GeSbTe (c-GST) and the substrate, such as TiN. In this work, the adhesion of the c-GST/TiN interface of two samples deposited by different techniques was characterized using four-point bend, nanoindentation and nanoscratch techniques. The nanoindentation and nanoscratch data agree well with the four point bend data. The paper also discusses the application potential of nanoindentation and nanoscratch techniques as qualitative methods for adhesion evaluation in semiconductor process development.
Energy Band States of an Oxygen-doped GeSbTe Phase-change Memory Cell; Mechanism of Low-voltage Operation
Authors: Fujisaki Yoshihisa , Matsuzaki Nozomu , Kurotsuchi Kenzo , Morikawa T , Kinoshita M , Kitai N , Hanzawa Satoru , Moriya H , Takaura Norikatsu , Terao M , Matsuoka M , Koga Tsuyoshi , Moniwa M 
Published: April 2011

AbstractPhase-change memory is promising because it has a simple structure and has scalability that originates from its unique operating mechanism. However, the programming current should be reduced in accordance with the scaling of cell size [1,2]. We previously reported PCM (Phase Change Memory) cells that operate under 1.5-V/100-μA writing pulses [3, 4]. This PCM had a cell structure composed of 180-nm-W (tungsten) bottom contact to an O-GST (Oxygen-doped GeSbTe) film. Its low-power characteristic is suitable for 0.13-μm generation embedded applications. In the present study, we introduced a new W/O-GST/TaO/W cell structure and found further decrease of programming current the improved stability in the fabrication process. We analyzed the mechanism by which oxygen in GST and the additional TaO layer reduce the power consumption during SET/RESET operations.
Effects of mass, energy and temperature on amorphization in ion implanted Ge2Sb2Te5 thin films
Authors: De Bastiani Riccardo , Piro Alberto Maria , Lombardo Salvatore , Grimaldi Maria Grazia , Rimini Emanuele 
Published: April 2011

AbstractThe paper reports on the amorphization kinetics of chalcogenides ternary alloy induced by Ar or Sb ion irradiation. The reflectivity data, obtained “in situ” during irradiation, allow a description of the amorphization process in terms of a threshold fluence. The results demonstrate that amorphization is caused by the elastic collisions of the projectiles with target nuclei. The influence of the ion mass and energy, of the target temperature in the amorphization is also reported.
In situ SEM Observation of Grain Formation and Growth Induced by Electrical Pulses in Lateral Ge2Sb2Te5 Phase-change Memory
Authors: Yin You , Niida Daisuke , Ohta Kazuhiro , Miyachi Akihira , Asai Masahiro , Higano Naoya , Sone Hayato , Hosaka Sumio 
Published: April 2011

AbstractA study of electric-pulse-induced crystallization of Ge2Sb2Te5 (GST) was conducted by in situ scanning electron microscopy observation and resistance measurement. A lateral phase-change memory with a top GST channel connected by two separate underlying electrodes was adopted in this study to easily observe the crystallization process. At a low voltage pulse, randomly distributed nuclei were initiated. At the first growth stage, these nuclei grew fast with the pulse amplitude at a rate of around 60 nm/V and then growth rate slowed down to around 14 nm/V when the grain diameter was closed to film thickness. Device resistance during crystallization dropped by around one order of magnitude, which should be due to amorphous to face-centered-cubic transition.
Growth and Characterization of Chalcopyrite Nanocrystals: Beyond Conventional Thin Films
Authors: Fuertes Marrón David , Lehmann Sebastian , Kosk Justyna , Sadewasser Sascha , Lux-Steiner Martha Ch. 
Published: April 2011

AbstractA dry method for the growth of highly-structured Cu-containing chalcopyrite material on solid substrates, based on the use of metallic precursors, is described. Nanocrystals, sub-micrometer polycrystalline dots, and macroscopic clusters have be grown, either as isolated units or alternatively as embedded structures in a matrix of a binary chalcogenide compound, by adjusting processing parameters. Vapor-liquid-solid (VLS) induced growth has been used for the growth of chalcopyrite nanowires. Examples of material characterization by scanning probe techniques are shown, demonstrating the suitability of the proposed growth method.
Study of CIGS Solar Cells Back Contact
Authors: Marsillac Sylvain , Khatri Himal 
Published: April 2011

AbstractMolybdenum thin films were deposited by r.f. magnetron sputtering. The strain in the films was mostly tensile and varied, with the Argon pressure and the r.f. power, along a bell curve, reaching a maximum at 8 mTorr (80 W) and 6 mTorr (100 W). The grain size deduced from the X-Ray diffraction measurements (FWHM) decreased with increasing Argon pressure and, to a lower extent, with decreasing r.f power. The change in grain size, as well as in morphology, was confirmed by AFM imaging. Finally, the resistivity of the films was found to increase with increasing Argon pressure, while the films maintained good adhesion to the soda-lime glass substrates for all Argon pressures and r.f. power.
Comparative Studies of the Structure and Microstructure of Zn2x(CuBIII)1-xX2 Semiconductors (BIII=Ga,In; X=S,Se,Te)
Authors: Schorr Susan , Wagner Gerald , Tovar Michael , Sheptyakov Denis 
Published: April 2011

AbstractPowder samples of (ZnX)2x(CuBX2)1-x mixed crystals (B=Ga,In; X=S,Se,Te) were prepared by solid state reaction of the elements and annealed with cooling rates between 2 - 42 K/h in the entire composition range. Structural parameters (e. g. lattice parameter, tetragonal deformation η) were investigated by X-ray and neutron diffraction studies. The microstructure was studied by transmission electron microscopy (TEM) and HRTEM. The chemical composition was determined by EDX analysis on the transmission electron microscope.The chemical disorder process in the 2(ZnX)x(CuBX2)1-x solid solution series leads to a phase separation, i. e. in a certain composition range (2-phase field) two phases, tetragonal domains and a cubic matrix, coexist. Its width depends on the three-valent cation only and is independent from the size of anion. The habit of the tetragonal domains is like a flat discus, its short extension lies always parallel to their tetragonal c-axis. They are simultaneously arranged on the (100),(010) and (001) planes within the cubic matrix. After nucleation of the domains, their growth obeys t1/2, i.e. it is controlled by diffusion. In the sulfides and selenides systems with In as three-valent cation the tetragonal domains are 'infected' by stannite type (or CuAuI type) cation ordering independently of their orientation, whereas in the tellurides system CuPt type cation ordering was obtained. The tetragonal (ZnX)2x(CuGaX2)1-x mixed crystals exhibit only chalcopyrite type structure and orientation domains without another type of cation ordering.In the single phase regions the lattice parameter follows Vegrads rule, whereas in the 2-phase field the both phases try to match in the a-b-plane (atetr∼acub), causing an increase of the tetragonal lattice parameter c and herewith a strong increase of the tetragonal deformation η.
Quantum Efficiency Measurements to Deduce Non-Ideal Solar-Cell Features
Authors: Nagle Timothy J. , Davies Alan R. , Sites James R. 
Published: April 2011

AbstractAppropriate interpretation of quantum-efficiency (QE) measurements made on non-ideal solar cells often reveal subtle features of the photodiodes. QE measurements on CIGS and CdTe thin-film solar cells with CdS buffer layers demonstrate some of these features, and in each case we identify the electrical processes responsible. One well-known complication in cells with CdS buffer layers is “photodoping”, where blue light exposure increases the n-type CdS carrier density. The resulting modification of the p-n junction alters the carrier collection for all wavelengths and can lead to misinterpretation of results. The use of a white, DC-bias light during QE measurements generally solves this problem, but it has not been clear what bias light level is sufficient for accurate results. Measurements with varying intensities of DC-bias light show that complications due to CdS photoconductivity are generally mitigated near 0.05 sun intensity. Other factors which can cause misinterpretation of QE measurements include the presence of secondary barriers, and photoconductivity in the absorber layer. Numerical simulations of band profiles under various light-bias conditions are consistent with the experimental data. The analysis is used to suggest a standard set of measurement conditions for reliable QE analysis.
Electron-Backscatter Diffraction of Photovoltaic Thin Films
Authors: Moutinho Helio , Dhere Ramesh , Jiang Chun-Sheng , To Bobby , Al-Jassim Mowafak 
Published: April 2011

AbstractIn electron-backscatter diffraction, crystalline orientation maps are formed while the electron beam of an SEM scans the sample surface. EBSD requires a flat sample to avoid shadowing of the electrons from the detector by surface features. In this work, we investigate the preparation of CdTe samples deposited by close-spaced sublimation for EBSD analysis. Untreated samples were rough, resulting in areas with no EBSD signal. We processed the samples by polishing and ion-beam milling. Polishing produced flat samples, but low-quality EBDS data, because the top surface of the samples had poor crystallinity. In contrast, ion-beam milling proved to be suitable for producing flat samples with minimal surface damage, yielding good EBSD data. We also analyzed the samples with atomic force microscopy, and correlated the quality of the EBSD data with sample roughness. The EBSD data showed that the CdTe films were randomly oriented and had columnar growth and a high density of <111> twin boundaries.
Kinetics of Charge Trapping and Emission in CIGS Solar Cells
Authors: Urbaniak Aleksander , Igalson Malgorzata , Siebentritt Susanne 
Published: April 2011

AbstractIn this work we investigate bias - induced metastability in CIGS solar cells. Long - term capacitance transients have been measured for two baseline CIGS devices with different efficiencies and a CGS cell in order to analyze carrier trapping processes. Based on the results we discuss hole emission process which leads to metastable increase of net acceptor density and also hole capture related to its relaxation. Time constants and activation energies for hole emission and capture have been obtained. Apart of carrier trapping processes we have also distinguished an interface-related change of capacitance. Our results indicate processes involving thermal lattice relaxation. We explain them in light of properties of (VSe+VCu) divacancy, defect with negative correlation energy, which can exist in both donor and acceptor configuration.