bluuebunny/crossref_metadata_2025_split huggingface dataset:
Luminescence Intermittency and Quantum Efficiency of Individual Porous Si Nanoparticles.
Authors: Mason Michael D. , Credo Grace M. , Carson Paul J. , Buratto Steven K. 
Published: April 2011

ABSTRACTWe have recently observed spectrally resolved vibronic structure and luminescence intermittency from nanometer-size porous silicon nanocrystals. In this study we examine the quantum efficiency of a single nanoparticle and show that emitting nanoparticles do so with near unity quantum efficiency. This result suggests that the emission from porous Si nanoparticles, and thus bulk porous Si, results from a small number of high quantum efficiency emitters. In our previous work we have shown that our nanoparticles contain more than one coupled chromophore. In order to examine these effects more closely we employ several spectroscopy and microscopy techniques including: 1) single-particle spectroscopy, 2) shear-force microscopy, and 3) time-resolved spectroscopy, on a colloidal suspension of size-selected, surface-oxidized nanoparticles. In addition we apply statistical techniques to provide a more complete picture of the coupling between chromophores in a given nanoparticle.
Electron Paramagnetic Resonance of Cr4+ in Yx2SiO5
Authors: Rakhimov Rakhim R. , Horton Holli D. , Loutts George B. 
Published: April 2011

ABSTRACTChromium-doped yttrium orthosilicate Cr:Y2SiO5 was studied by electron paramagnetic resonance (EPR) method at 9.5–9.7 GHz. EPR transitions were observed for Cr4+ substituting Si4+ in tetrahedral sites of Y2SiO5, and orientation dependence of the single crystal EPR spectrum was studied. The ground state of Cr4+ (electron configuration 3d2) in Y2SiO5 is a spin triplet (S = 1). Rhombic symmetry of the electron magnetic dipole-dipole interaction (zero field splitting) leads to three electron spin terms Tx, Ty and Tz in the absence of the external magnetic field. We have observed the magnetically induced anti-crossing of the terms Ty and Tz.We show that in the vicinity of energy level anti-crossing the linewidths and positions of the resonance lines depend on temperature.
Photoluminescence of Poly(P-Phenylene Vinylene) encapsulated In Mesoporous Silica
Authors: Pattantyus-Abraham Andras G. , Wolf Michael O. 
Published: April 2011

ABSTRACTThe preparation of poly(ρ-phenylene vinylene) (PPV) encapsulated in a mesoporous silica, MCM-41, is reported. In situ polymerization of xylylene bis(tetrahydrothiophenium chloride) yields a highly luminescent, yellow powder with a fluorescence spectrum matching that of unencapsulated PPV. Nitrogen adsorption isotherms show that the pore size of the PPVloaded MCM-41 is significantly smaller than that of empty MCM-41 and a polymer loading of ca. 8% by weight is obtained by thermogravimetric analysis. Photoluminescence data for the encapsulated PPV are presented.
Optimization of Cerium Doped Garnets Using Combinatorial Chemistry for Application as Luminescent Conversion Phosphors in White LEDs
Authors: Wu Jennifer L. , Devenney Martin , Danielson Earl , Poojary Damadora , Weinberg Henry 
Published: April 2011

ABSTRACTAn area of considerable research interest is the development of visible light, down- conversion phosphors for application in white light emitting diodes (LEDs). In such devices, a blue LED can act as the primary light source, exciting photoluminescence in a phosphor with subsequent broad band emission occurring at visible wavelengths of lower energy. A combinatorial approach to synthesize and screen potential inorganic phosphors for such an application has been developed. Using solution chemistry techniques, solid state thin film arrays of (Y1−xGdx)3-z(Al1−yGay)5O12:Ce3+Z, where x and y range from 0 to 1.0 and z is equal to 0.03 were synthesized. Subsequent characterization demonstrates that the combinatorial approach can be used to rapidly screen potential phosphors for use as luminescence down-converters in white LEDs. Emission and excitation trends match those reported in the literature for traditionally prepared powder samples. The optimal Ce3+ concentration in Y3Al5O12 (YAG) was identified as approximately 1.5 mol%, and within the YAG-substituted host specific compositions were identified as promising blue to yellow phosphor candidates.
Effect of Annealing on the Properties of thin Films of Free Base Phthalocyanine and Perylene-3,4,9,10-Tetracarboxylic Dianhydride Deposited by Organic Molecular Beam Deposition
Authors: Bayliss S.M. , Heutz S. , Rumbles G. , Jones T.S. 
Published: April 2011

ABSTRACTOrganic molecular beam deposition (OMBD) has been used to deposit thin films of free base phthalocyanine (H2Pc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). The structural, optical and morphological properties of the films have been measured as a function of annealing temperature using x-ray diffraction (XRD), electronic absorption spectroscopy and atomic force microscopy (AFM). A phase transition, (α-β), is observed for H2Pc films which is accompanied by changes in the bulk film properties and surface morphology. In the case of PTCDA increasing temperature does not affect the structural and optical properties of the film, but different surface morphologies are observed.
The Valence Electronic Structure of N-Doped P-Sexiphenyl
Authors: Theissl U. , List E.J.W. , Koch N. , Vollmer A. , Schrader S. , Pireaux J.-J. , Leising G. 
Published: April 2011

ABSTRACTThin films of p-sexiphenyl (6P) were doped with increasing amounts of potassium in situ, and the change in the valence electronic structure of 6P upon the alkali metal deposition was followed with ultraviolet photoelectron spectroscopy. We observe the evolution of new intragap emissions, which are attributed to the formation of bipolarons, even for very low doping concentrations. The low binding energy intra-gap emission exhibits a pronounced asymmetric lineshape, in contrast to the findings when cesium is used as dopant. In order to investigate whether this lineshape is due to different emissive electronic species in the bulk and on the surface of the 6P film the take-off angle for the photoelectrons was varied. As no change in the lineshape is found when going from normal to near-grazing emission we can exclude that charged 6P molecules in the bulk and on the surface yield different valence electronic spectra. Therefore, the characteristic lineshape of the low binding energy emission is proposed to be related to the interaction of the doped organic molecule with the different counterions.
Current-Voltage Characteristics of Single Layer Polymer Light Emitting Diodes Under High Intensity Electrical Excitation
Authors: Ruhstaller B. , Scott J.C. , Brock P.J. , Carter S.A. 
Published: April 2011

ABSTRACTWe study the current-voltage characteristics of both double and single carrier polymer light emitting devices in the high intensity electrical excitation regime. Single layer devices are investigated with the orange-emitting MEH-PPV as the active polymer. Performing very low duty (≈0.001 %) pulsed electroluminescence measurements with electric fields up to 1*109 V/m, we observe for the hole-dominated devices a space charge limited current with a saturating mobility and a saturating external quantum efficiency of 1%. For double carrier devices, the current starts to saturate in the high-field regime, appoaching Ohmic-like behavior. We report current densities of 100 A/cm2and brightnesses of 7*105 cd/m2. The spectral features are monitored below the onset of degradation.
Electromigration Testing of via Terminated Test Structures
Authors: Low Kia Seng , Poetzlberger Hans 
Published: April 2011

AbstractIn this paper we describe three phenomena that have been observed in via terminated test structures. The first is the effect of stress voiding on the electromigration current density exponent, n. We have tested stress-voided lines and the results show that the current density exponent is close to 1. This is consistent with the prediction that stress-voided lines have a lower lifetime. We propose that the current density exponent must be measured and not assumed for such lines. The second phenomenon is the reservoir effect in via-terminated lines. Void locations following electromigration stressing are shown for a via-terminated structure containing a reservoir, prepared by Focused Ion Beam (FIB), and a discussion of the reservoir effect is presented. Finally, we report on the correlation between void location and the bimodal distribution of failure mechanisms that have been observed.
Strain and Texture in Al-Interconnect Wires Weasured by X-Xay Microbeam Diffraction
Authors: Tamura Nobumichi , Chung J.-S. , Ice G. E. , Larson B. C. , Budai J. D. , Tischler J. Z. , Yoon M. 
Published: April 2011

AbstractThe local strain and texture in Al interconnect wires have been investigated using white and monochromatic x-ray microbeams on the MHATTCAT undulator beam line at the Advanced Photon Source. Intergrain and intragrain orientations were obtained with ∼0.01° sensitivity using white beam measurements on wide Al pads (∼100 μm) and thin (2 μm) Al wires. Orientation changes of up to 1°were found within individual grains of the (111) textured Al interconnects. Deviatoric strain measurements indicate small intragranular strain variations, but intergranular strain variations were found to be quite large.
Mechanical Stresses in Aluminum and Copper Interconnect Lines for 0.18µm Logic Technologies
Authors: Besser Paul R. , Joo Young-Chang , Winter Delrose , Ngo Minh Van , Ortega Richard 
Published: April 2011

AbstractThe mechanical stress state of conventional Al and damascene Cu lines of a 0.18 pm logic technology flow have been determined using a novel X-Ray diffraction method that permits measurement of stress on an array of critical-dimension lines on the product die. The effect of high density plasma oxide deposition and the influence of low-K dielectrics on the stress state of the Al lines is described. The effect of materials properties and fabrication methodology on the stress state of damascene Cu lines is shown with measurement of mechanical stress and strain in passivated lines at room temperature and during annealing. The effect of underlayer on the damascene Cu stress state is also quantified.
Diffusion Barrier Characteristics of Zirconium Diboride Films Grown by Remote Plasma CVD
Authors: Sung J. , Goedde D. M. , Girolami G. S. , Abelson J. R. 
Published: April 2011

AbstractLow resistivity and fully conformal ZrB2 thin films are deposited by remote plasma chemical vapor deposition using zirconium tetrahydroborate, Zr(BH4)4. The problems with thermal CVD using this precursor – excess B incorporation, oxygen contamination, and high resistivity – are eliminated by injecting atomic hydrogen from a remote microwave plasma source onto the substrate. Using this technique, the films are stoichiometric, have ∼ 40 μΩ-cm resistivity, < 4 at.% oxygen contamination, and are fully conformal in deep trenches and vias. We show that a 50 nm thick ZrB2 film on c-Si (100) prevents Cu in-diffusion after 1 hour annealing at 650°C.
Homogeneous Ultrathin Diffusion Barriers Deposited on Low Dielectric Constant Polymers
Authors: Kiene M. , Abramowitz P. P. , Ho P. S. 
Published: April 2011

AbstractTiN and TaN thin films are proposed as barrier layers between copper interconnects and low dielectric constant (low-k) polymers. As the barrier layer thickness is scaled down, the uniformity and morphology of these films will be severely affected by the nitride-polymer interface and become an important issue for the reliability of the whole interconnect structure. In order to evaluate nitride formation and the interfacial chemistry we deposited TiN and TaN on fully cured low-k polymers by two different techniques: reactive evaporation of the metal in nitrogen ambient and by ion assisted reactive deposition using a low energy (100 eV) nitrogen ion beam during evaporation. Photoelectron spectra were recorded in situ for metal coverages from 0.1 nm until bulk like metal or metal nitride spectra were obtained. Nitride concentrations, extracted from the photoelectron spectra, show that even though very similar nitride films are produced by both techniques for thicker films (>5 nm) we only find significant amounts of nitride at the interface in the ion assisted case. Thinner films formed in nitrogen ambient were very similar to those where the pure metal was deposited and were dominated by the formation of compounds with carbon and oxygen from the polymer. This shows that the composition of barrier layers can be drastically altered near the polymer interface. Low energy ions in contrast allow the growth of more homogeneous films which can significantly improve the reliability of copper based high density interconnects.
Epitaxial Growth and Thermal Stability of CoSi2 Layer on (100) Si from Co-C Films without Capping Layer
Authors: Rhee Hwa Sung , Sohn Dong Kyun , Ahn Byung Tae 
Published: April 2011

AbstractA uniform epitaxial CoSi2 layer was grown on (100) Si substrate by rapid thermal annealing at 800°C in N2 ambient without capping layers from an amorphous cobalt-carbon film. The amorphous cobalt-carbon film was deposited on Si substrate by the pyrolysis of cyclopentadienyl dicarbonyl cobalt. Co(η5-C5H5)(CO)2. at 350°C. The leakage current measured on the junction, fabricated with the epitaxial CoSi2 layer and annealed at 1000°C for 30 s. was as low as that of the as-fabricated junction without silicide. indicating that epitaxial (100) CoSi2 is thermally stable at temperatures even above 1000°C and has a potential applicability to the salicide process in sub-half micron devices.
Influence of SiGe Thickness on the Co/SiGe/Si Solid State Reaction
Authors: Donaton R. A. , Jin S. , Bender H. , Maex K. , Vantomme A. , Langouche G. 
Published: April 2011

AbstractThe effect of the thickness of the SiGe layers in the Co-SiGe/Si reaction is investigated. Formation of the disilicide phase is retarded when compared to the reaction of Co with pure Si substrates. This delay is dependent on the thickness of the SiGe layer, which determines the effective Ge concentration at the reaction front, changing the energetics of the reaction. Besides, Ge expelled from the Co(Si1-yGey) compound blocks the Co diffusion paths, slowing down the reaction. The thermal stability of the silicide layer is also affected by the Ge segregation, with the film agglomerating at lower temperatures when formed on thicker SiGe layers. The slow supply of Co atoms to the reaction front, due to the blocking of Co diffusion paths by the segregated Ge, is believed to be the reason for the presence of the preferential (h00) orientation of the disilicide phase observed in our samples.
Formation and Characterization of Spe Grown Ultra-Thin Cobalt Disilicide Film
Authors: Qu Xin-Ping , Ru Guo-Ping , Li Bing-Zong , Detavernier C. , Meirhaeghe R L. Van , Cardon F. 
Published: April 2011

AbstractUltra-thin epitaxial CoSi2 films formed by Co(3∼5nm)/Ti(1 nm)/Si(100) and Co(3∼5nm)/Si(lnm)/Ti(Inm)/Si are studied. The multilayers are deposited by ion-beam sputtering. Rapid thermal annealing (RTA) is used for silicidation. XRD, RBS, TEM, AFM, four-point probe, I-V and C-V measurements are carried out for characterization. The XRD spectra show the CoSi2 film formed by Co/Ti/Si or Co/Si/Ti/Si solid phase epitaxy has, epitaxial characteristic. XTEM shows that the film is continuous. RBS/Channeling shows that the formed CoSi2 has sharp interface with a minimum channeling yield of Co signal of 40%. AFM shows that the surface of ultra-thin CoSi2 film is smooth with a roughness of nearly 0.7 nm. The Rs∼T relationship shows that the CoSi2 films formed by Co/Si/Ti/Si reaction have the best thermal stability (stable up to 900°C). Those formed by Co/Ti/Si reaction are stable up to 850°C, while those formed by Co/Si reaction are only stable up to 750°C. By fitting the experimental I-V and C-V curves of the epitaxial CoSi2/Si Schottky diodes, barrier heights of around 0.6 eV and close to unity ideality factors are obtained.
Formation and Stability of NI(PT) Silicide on (100)SI and (111)SI
Authors: Mangelinck D. , Dai J. Y. , Lahiri S. K. , Ho C. S. , Osipowicz T. 
Published: April 2011

AbstractThe effect of a small amount of Pt (5 at.%) on the thermal stability of NiSi film on (100)Si and (111 )Si has been investigated. Rutherford back scattering, Scanning Electron Microscopy, and X-ray diffraction have been used to study the formation, microstructure and orientation of the silicide. The addition of platinum results in increasing the disilicide nucleation temperature to 900°C and thus leads to a better stability of NiSi at high IC processing temperatures. The presence of Pt also induced a texture of the NiSi film both on (11 1)Si and (100)Si. The increase in thermal stability is explained in terms of nucleation controlled reaction concept and should open new possibilities for the use of NiSi in self aligned silicidation. The redistribution of Pt in the silicide is examined and explained in terms of kinetics and thermodynamics considerations. The addition of Pt also increases the temperature of agglomeration of NiSi.
New Contact Etch Process for Embedded DRAM Applications
Authors: Yang Chan-Lon , Chen Tong-Yu , Huang Keh-Ching , Jung Le-Tien , Lin Tsu-An , Lur Water 
Published: April 2011

AbstractFor embedded DRAM (E-DRAM) devices with feature sizes of 0.25 µm and beyond, contact processes with low contact resistance and low junction leakage current are required. The contact etch process needs to etch through multi-layer structures with SiO2, SiON/SiN layers and stop on Ti-polycide gate and Ti-salicide active regions at the same time. The key issues include high selectivity to TiSix, vertical profile, complete removal of SiON/SiN cap layer and no polymer residues. In this paper, multi-layer contact etching without attacking TiSix is reported. Using new process chemistry, the new contact etch process has been demonstrated for the manufacturing of 0.25 µm E-DRAM and beyond.
Chemical Vapor Deposition of Ti-Si-N Films with Alternating Source Supply
Authors: Min Jae-Sik , Park Hyung-Sang , Koh Wonyong , Kang Sang-Won 
Published: April 2011

AbstractTitanium-silicon-nitride films were grown by atomic layer deposition using an alternating supply of tetrakis(dimethylamido)titanium (TDMAT), silane. and ammonia, at substrate temperature of 180°C. The supply of a reactant was followed by a purge with inert gas before introducing another reactant onto the substrate in order to prevent gas-phase reactions. In one set of experiments the reactants were supplied separately in the sequence of TDMAT. silane. and ammonia. The Si content of the films remained constant at 18 at.%. and the film growth rate varied little from 0.24 nm per reactant-supply-cycle, even though silane partial pressure varied from 0.002 to 0.1 torr. In the other set of experiments silane and ammonia were simultaneously supplied in the sequence of TDMAT and silane/ammonia. The Si content varied from 3 to 23 at.% as the silane-to-ammonia ratio varied from 0.01 to 10. Atomic layer deposition of Ti-Si-N films allows the precise control of Si content as well as film thickness.
Integration of PECVD Tungsten Nitride as a Barrier Layer for Copper Metallization
Authors: Ivanova A. R. , Galewski C. J. , Sans C. A. , Seidel T. E. , Grunow S. , Kumar K. , Kaloyeros A. E. 
Published: April 2011

AbstractAmorphous tungsten nitride (WNx) is a promising diffusion barrier for extending Cu metallization beyond 0.18 μm. This study evaluates the barrier performance, adhesion, and step coverage of PECVD WN 0.5 integrated with a CVD Cu seed layer. The WN0.5 films exhibit amorphous structure with 33% bottom and side-wall step coverage in 0.14 μm wide structures with 9:1 aspect ratio. The potential of 50 Å WN0.5 as an effective Cu barrier is shown by the absence of Secco etch-pits in the Si substrate after a 30 min anneal at 500°C. When deposited on PECVD WN0.5 the CVD Cu films exhibit uniform nucleation, and as deposited resistivity of 2.5 μΩ-cm. Step coverage of the CVD Cu is better than 95% in 0.14 μm structures. Adhesion exceeding epoxy strength of the CVD Cu seed layer even to air-exposed WN0.5 is demonstrated using stud-pull adhesion tests.
Highly Conformal Diffusion Barriers of Amorphous Niobium Nitride
Authors: Gordon R. G. , Liu X. , Broomhall-Dillard R. N. R. , Shi Y. 
Published: April 2011

AbstractElectrically conductive films of niobium nitride were formed by chemical vapor deposition from tetrakis(diethylamido)niobium and ammonia. The films were found to be highly conformal, with step coverage nearly 100% for substrate temperatures near 350°C. The structure of the films was amorphous by diffraction of X-rays and electrons. The reliability of the films as barriers to diffusion of copper was also tested.
Characterization of Plated Cu Thin Film Microstructures
Authors: Gignac L. M. , Rodbel K. P. , Cabral C. , Andricacos P. C. , Rice P. M. , Beyers R. B. , Locke P. S. , Klepeis S. J. 
Published: April 2011

AbstractElectroplated Cu was found to have a fine as-plated microstructure, 0.05 ± 0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.
Electroplated Damascene Copper: Process Influences on Recrystallization and Texture
Authors: Gross M. E. , Drese R. , Lingk C. , Brown W. L. , Evans-Lutterodt K. , Barr D. , Golovin D. , Ritzdorf T. , Turner J. , Graham L. 
Published: April 2011

AbstractElectroplated Cu films undergo a remarkable recrystallization at room temperature that has been associated with dislocations and defects arising from the influence of surface-active additives during plating. In the process of plating, the composition of the bath changes as the organic additives are depleted by incorporation into the Cu films or electrolytic decomposition and replenished by fresh additions. Given the sensitivity of the plating process to low concentrations of additives, the properties of the plated Cu might be expected to differ between a freshly prepared bath and an older bath that has processed thousands of wafers and achieved a steady state composition of additives and by-products.In this paper we compare the recrystallization rates of Cu films deposited from two such baths on wafers with damascene trenches of widths from 0.3 to 5 μm. Films deposited from the older bath consistently recrystallize at a faster rate for all trench widths and both barrier materials (Ta, TaN) studied. The concentration of impurities is comparable in the two films. Therefore, the difference in rates is likely due to a difference in defect densities in the film due to different adsorbate/surface interactions during plating. Although the recrystallization rates vary, X-ray diffraction pole figure analysis of films plated from the two baths show no differences in texture. Sidewall growth components are visible in both sets of samples. Data on the influence of the barrier material and trench width on recrystallization rates are also presented.