bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Organization of Steps and Domain Boundaries of 7×7 Reconstruction on Si(111)
Authors: Hibino H , Homma Y. , Ogino T.
Published: April 2011

We describe three different aspects of the self-organization of steps and domain boundaries of a 7×7 reconstruction on SI(111) surfaces. The first is the formation of a triangular-tiled pattern of “1×1’ and 7×7 domains during the phase transition. ‘1÷1’ and 7×7 domains have different surface stresses. The triangular-tiled pattern is stabilized through stress relaxation. The second is the step arrangement inside a hole, which was fabricated by a standard lithographic technique. The step arrangement in the hole depends on the temperature. Below the ‘1×1’-to-7×7 phase transition, the hole has a three-fold symmetry consisting of step-bunched and non-bunched regions. This is because the step arrangement on the vicinal Si(111) surfaces depends on the direction of the steps. The third aspect is the formation of a pattern of steps and domain boundaries induced by Si growth. During the step-flow growth on Si(111), steps preferentially protrude along the domain boundaries on the lower terrace. The resulting changes in step shape induce a unique rearrangement of the domain boundaries, the number of which decreases during growth. However, when a periodic pattern is formed in the initial stages, it remains stable during growth.
Triple Junction Engineering: the Distribution of Triple Junctions in Polycrystalline Gold Thin Films
Authors: Owusu-Boahen Kwame , King Alexander H.
Published: April 2011

We have investigated compliance with the σ-product rule at triple junctions with a common [111] axis using computer simulations and in real thin films, using electron microscopy. Large discrepancies exist between the simulations, which assume randomly distributed misorientations, and the experiments. Although for both cases the rule fails at most triple junctions, the real material shows a much higher than expected occurrences of compliance. This result can be explained in two distinct ways: first, there might be a preference for triple junctions that obey the rule (implying a distinct influence of the triple junction itself). Alternatively, the misorientations in the real crystal might not be randomly distributed: if there is a preference for boundaries that have only small deviations from coincidence, there will be an increase in the compliance with the rule.
Local Potential at Atomically Abrupt Oxide Interfaces by Scanning Probe Microscopy
Authors: Kalinin Sergei V. , Bonnell Dawn A.
Published: April 2011

Electrostatic force microscopy and scanning surface potential microscopy are combined to quantify nanometer scale field variations in the vicinity of grain boundaries in donor doped σ15 SrTiO3 bicrystals. An analytical electrostatic model is used to develop a procedure for determining interface potential from measurements made above the surface. Grain boundary potentials and depletion widths determined by both techniques are in excellent agreement despite the fundamental difference in imaging mechanisms. The comparison confirms the analytical approach and illustrates use of scanning probes to image interface properties.
Measurements of the Adhesion Strength of Cu/Epoxy Interfaces
Authors: Lee H. Y. , Yu Jin
Published: April 2011

Copper-based leadframe sheets were oxidized in a black-oxide forming solution, molded with epoxy molding compound (EMC), and the interfacial fracture toughness was measured using sandwiched double cantilever beam (SDCB) and sandwiched Brazil-nut (SBN) specimens.

Results showed that pebble-like Cu2O precipitates on the leadframe had almost no adhesion to EMC while the opposite was true of the acicular CuO precipitates. Thus, the fracture toughness of the leadframe/EMC interface was close to zero in the beginning but rapidly increased to ˜100 J/m2 as acicular CuO nucleated on the smooth-faceted Cu2O layer. Under the mixed Mode loading the fracture toughness increased parabolically with the phase angle (ψ) with minimum at ψ = 0°. For ψ < -340, interface crack kinked into EMC. Fractography analyses based on XRD, SEM and AES studies showed that the failure path along the leadframe/EMC interface varied significantly with the loading condition and the crack speed.
Observation of Localized Corrosion of Ni-Based Alloys Using Coupled Orientation Imaging Microscopy and Atomic Force Microscopy
Authors: Bedrossian Peter J. , Schwartz Adam J. , Kumar Mukul , King Wayne E.
Published: April 2011

We present a method for assessing the relative vulnerabilites of distinct classes of grain boundaries to localized corrosion. Orientation imaging microscopy provides a spatial map which identifies and classifies grain boundaries at a metal surface. Once the microstructure of a region of a sample surface has been characterized, a sample can be exposed to repeated cycles of exposure to a corrosive environment alternating with topographic measurement by an atomic force microscope in the same region in which the microstructure had been mapped. When this procedure is applied to Ni and Ni-based alloys, we observe enhanced attack at random grain boundaries relative to special boundaries and twins in a variety of environments.
Wet Etching Methods for Perovskite Substrates
Authors: Leca Victor , Rijnders Guus , Koster Gertjan , Blank Dave H. A. , Rogalla Horst
Published: April 2011

In oxide electronics substrates with atomically flat terraces are a request for growing high-quality epitaxial thin films. In this paper results on chemical etching of some substrates with perovskite, ABO3, structure (e.g., SrTiO3, LSAT - the (LaAlO3)0.3(Sr2AlTaO6)0.35 solid solution, and NdGaO3) are presented. In order to obtain high quality substrates, different etchants (NH4F + HF, HCl + NH4Cl, and HCl + HNO3) with various pH values have been studied. From Atomic Force Microscopy (AFM), in air, we conclude that, irrespective of the etchant that has been used, a substrate surface with a BOx terminated layer and atomically flat terraces without etch pits could be obtained. The pH-value and temperature of the etchant and the etching time, however, influence significantly the surface quality. Reflection high energy electron diffraction (RHEED) patterns confirmed the AFM results.
Authors: Norton D. P. , Budai J. D. , Chisholm M. F.
Published: April 2011

We describe the growth and properties of epitaxial (001) CeO2 on a (001) Ge surface using a hydrogen-assisted pulsed-laser deposition method. Hydrogen gas is introduced during film growth to eliminate the presence of the GeO2 from the semiconductor surface during the initial nucleation of the metal oxide film. The hydrogen partial pressure and substrate temperature are selected to be sufficiently high such that the germanium native oxides are thermodynamically unstable. The Gibbs free energy of CeO2 is larger in magnitude than that of the Ge native oxides, making it more favorable for the metal oxide to reside at the interface in comparison to the native Ge oxides. By satisfying these criteria, the metal oxide/semiconductor interface is shown to be atomically abrupt with no native oxide present. Preliminary structural and electrical properties are reported.
Mechanistic Studies of Wafer Bonding and Thin Silicon Film Exfoliation
Authors: Chabal Y.J. , Isaacs E. D. , Weldon M.K.
Published: April 2011

In this paper, we review and highlight the central role that infrared spectroscopy has played in elucidating the microscopic details of the bonding and exfoliation processes and we introduce a novel technique for imaging and measuring strain with submicron resolution. The mechanism for chemical bond formation between two interfaces is derived from monitoring the chemical evolution of interfacial species as a function of annealing. The mechanism for silicon shearing upon Himplantation/annealing is understood as an evolution of H-passivated point defects into H-stabilized internal surfaces, together with H2formation. The nucleation and propagation of microbubbles that form prior to exfoliation is imaged with x-rays and a detailed strain map in the vicinity of bubbles just prior to exfoliation can be made.
Growth of Large Diameter Silicon-Germanium Monocrystals
Authors: Deitch Richard H. , Jones Stephen H. , Digges Thomas G.
Published: April 2011

Si-Ge monocrystals up to 50 mm diameter and up to 17 at% germanium were grown using a modified Czochralski technique. Pre-grown large diameter silicon seeds with various crystallographic orientations were used as templates for the alloy solidification to reduce cap crystallization time and insure monocrystallinity at desired diameters. Discussed are the influences that seed preparation, crystal growing parameters, and post-growth processing have on the material that was produced using this new technique.
Effects of Sapphire Substrate Configurations on MBE Growth of ZnO
Authors: Sakurai Keiichiro , Nakahara Ken , Tanabe Tetsuhiro , Fujita Shizuo , Fujita Shigeo
Published: April 2011

MBE growth of ZnO films for optical semiconductor devices was investigated on off-angled c-plane sapphire substrates. Twin crystal RHEED patterns and surface facetting observed with c-plane just-oriented substrates were suppressed by enlarging the offset angles from near-zero to 2.87 degrees. Though no significant changes were seen in optical characteristics, FWHM of XRC narrowed and surface morphology improved with larger offset angles, indicating that the offset angle is also a sensitive factor for ZnO film growth.
Faceting of Single-Crystal SrTiO3 During Wet Chemical Etching
Authors: Spalding G. C. , Murphy W. L. , Davidsmeier T. M. , Elenewski J. E.
Published: April 2011

We use an Atomic Force Microscope (AFM) to study changes in the surface of single-crystal SrTiO3 etched in HF-based solutions. Attention in this work has been focused upon observations of pyramidal pitting – both because of an interest in avoiding etch pits during substrate preparation prior to heteroepitaxial growth, and because of an interest in micromachining this highly polarizable material. We note that (110) SrTiO3 is surprisingly robust against the formation of pits, while pitting is significant on {100} surfaces. Particular etch rates have been measured, and we discuss anisotropies in the rates of dissolution. These data are combined to extract a macroscopic model describing processes relevant to the most extreme pitting, which we show to be associated with surface defects.
Optical Emission Related to Holes Confined in p-Type δ-Doped Layers in GaAs
Authors: Zhao Q.X. , Willander M. , Holtz P.O. , Lu W. , Dou H. F. , Shen S. C. , Li G. , Jagadish C.
Published: April 2011

We present an optical investigation of thin Zn-doped GaAs layers embedded in bulk GaAs, by means of stationary optical spectroscopy. The samples were grown by metalorganic vapor phase epitaxy (MOVPE) The concentration of doped Zn acceptors were aimed at 2×1020/cm3 in 4 nm wide doping regions. We observed a novel optical radiative transition (denoted as F-emission) appearing in photoluminescence (PL) spectra below the energy position of the transition between the free electrons and holes bound to acceptors in bulk GaAs. The F emission shows a strong dependence on excitation intensity and temperature. The energy position varies from 1.46 eV to 1.49 eV when the excitation density increases from about 40 mW/cm2 to 23 W/cm2. Our results indicate that this emission is related to the transition between spatially separated electrons and holes. The holes are located in the p-type Zn δ-doped region, while the electrons are located in the undoped GaAs region.
Analysis of the Crystallization Kinetics and Microstructure of Polycrystalline Sige Films by Optical Techniques
Authors: Olivares J. , Martín P. , Rodríguez A. , Sangrador J. , Martínez O. , Jiménez J. , Rodríguez T.
Published: April 2011

In this work, two optical techniques, Raman spectroscopy and ultraviolet reflectance, have been used to characterize the solid phase crystallization kinetics and the microstructure of SiGe films deposited by LPCVD on oxidized Si wafers. The results have been compared to those obtained by X-ray diffractometry. The Ge fraction of the films (x) was in the 0−0.38 interval. The samples were crystallized at temperatures ranging from 525 to 600 °C. The crystallization kinetics follows Avrami's model. Two different behaviours have been observed depending on the Ge fraction of the films and the crystallization temperature: a) Either the three experimental techniques yield similar results, or b) the crystallization process, as monitored by UV reflectance and Raman spectroscopy, exhibits a greater incubation time than the one obtained if X-ray diffractometry is used. The results are discussed in terms of the identification of the nucleation sites, taking into account the probe depth of the different techniques and the preferred orientations of the grains. These techniques have also been used to characterize the presence of defects, the overall crystallinity and the surface roughness of the fully crystallized films. The results are correlated to the grain morphology and grain size, obtained by means of transmission electron microscopy.
Optical Characterization of Individual Nanostructures by STM Light Emission
Authors: Ushioda S.
Published: April 2011

Visible light is emitted when electrons (holes) are injected into a sample from the tip of the scanning tunneling microscope (STM). By analyzing the spectra of the emitted light, one can not only determine the surface geometry by usual STM imaging, but also learn the electronic and optical properties of specific individual nanostructures. This technique has been applied to investigate the electronic transitions of individual protrusions of porous Si and semiconductor quantum wells of AlGaAs/GaAs. The usefulness, limitations, and future expectations of this novel technique are discussed.
Quantum Confinement of Above-Band-Gap Transitions in Ge Quantum Dots
Authors: Teng C. W. , Muth J. F. , Kolbas R. M. , Hassan K. M. , Sharma A. K. , Kvit A. , Narayan J.
Published: April 2011

A number of research efforts have been focused on self-assembled germanium quantum dots in which indirect optical transitions take place across the band gap. However, many questions regarding the confined electronic state transitions of Ge quantum dots still remain unanswered. In the present report, we have deposited ten alternating layers of crystalline Ge quantum dots embedded in an Al2O3 or an AIN matrix on sapphire substrates by pulsed laser deposition. The average dot sizes (73 Å to 260 Å) were controlled by the laser energy density, deposition time and substrate temperature. The spectral positions of both the E1 and the E2 transitions in the absorption spectra at room temperature and 77 K shift toward higher energy (ΔE1=1.19 eV, ΔE2 =0.57 eV) as the Ge dot size decreases (73 Å). Structural analysis using transmission electron microscopy and atomic force microscopy and the interpretation of optical absorption measurements in terms of quantum confinement of carriers in both transitions are presented.
Effects of Rapid Thermal Annealing on the Intersubband Energy Spacing of Self-Assembled InAs/Gaas Quantum Dots
Authors: Wang X. C. , Chua S. J. , Xu S. J. , Zhang Z. H.
Published: April 2011

In this paper, we showed the significant reduction of the energy spacing between ground state and excited state emissions from InAs/GaAs quantum dots due to interface interdiffusion induced by thermal treatment. In addition, the strong narrowing of the luminescence linewidth of the ground state and excited state emissions from the InAs dot layers for the annealed samples indicates an improvement of the size-distribution of the QDs. Large blue-shift of the energy positions of both emissions was also observed. High resolution X-Ray diffraction experiments give strong evidence of the interface atom interdiffusion in the annealed samples. This work shows ability to tune the wavelength for applications like infrared detectors and lasers based on intrasubband transitions of self-assembled QDs.
Hybridization in Electronic States and Optical Properties of Covalent Amorphous Semiconductors
Authors: Shinozuka Yuzo
Published: April 2011

The electronic structure and optical properties of covalent amorphous semiconductors are theoretically studied with special attention to the s-p hybridization in electronic states and the spatial correlation in their mixing. One-dimensional tight binding model is used in which the interatomic transfer energy of an electron between nearest neighbor atoms depends linearly on their interatomic distance. All the electronic states are numerically calculated for a 150-atom system and the ensemble average is taken over 10 samples. Following results have been obtained. As the degree of randomness increases, the degree of hybridization decreases and rearrangements in the covalent bonds take place. The width of the band gap decreases but the gap remains rather long compared to a case where the spatial correlation is neglected. There appears a characteristic peak in the optical absorption spectrum, which reflects central peaks in the partial (s- or p-) density of states in the valence and conduction bands and is related to an electron localization caused by the spatial correlation.
Development of Low Energy Cathodoluminescence System and its Application to the Study of ZnO Powders
Authors: Sekiguchi Takashi
Published: April 2011

We have developed a cathodoluminescence (CL) system with high spatial resolution using a thermal-field emission gun operating with low electron beam energies. Since the electron range is proportional to the 1.7th power of the electron beam energy, operation with a low energy electron beam strongly reduces the probe size of CL. Luminescence property of ZnO tetrapods was studied with this system. High spatial resolution better than 100 nm was achieved when it was operated with a beam energy less than 3 keV. The variation of CL spectra along one leg of tetrapod was recorded. The ratio of the ultraviolet emission to the visible luminescence at the center of tetrapod was different from those of the points along the arm, suggesting that the center of tetrapod is much defective compared with the arms. We also observed a decrease of CL intensity during observation. Possible degradation mechanisms were discussed.
In Situ Studies of the Processing of Sol-Gel Produced Amorphous Materials Using Xanes, Saxs and Curved Image Plate XRD
Authors: Pickup DM , Mountjoy G , Newport RJ , Smith ME , Wallidge GW , Roberts MA
Published: April 2011

Sol-gel produced mixed oxide materials have been extensively studied using conventional, ex situ structural techniques. Because the structure of these materials is complex and dependent on preparation conditions, there is much to be gained from in situ techniques: the high brightness of synchrotron x-ray sources makes it possible to probe atomic structure on a short timescale, and hence in situ. Here we report recent results for mixed titania- (and some zirconia-) silica gels and xerogels. Titania contents were in the range 8–18 mol%, and heat treatments up to 500°C were applied. The results have been obtained from intrinsically rapid synchrotron x-ray experiments: i) time-resolved small angle scattering, using a quadrant detector, to follow the initial stages of aggregation between the sol and the gel; ii) the use of a curved image plate detector in diffraction, which allowed the simultaneous collection of data across a wide range of scattering at high count rate, to study heat treatments; and iii) x-ray absorption spectroscopy to explore the effects of ambient moisture on transition metal sites.
Maximum Entropy Method Charge Density Distributions of Novel Thermoelectric Clathrates
Authors: Iversen B. , Bentien A. , Palmqvist A. , Bryan D. , Latturner S. , Stucky G.D. , Blake N. , Metiu H. , Nolas G. S. , Cox D.
Published: April 2011

Recently materials with promising thermoelectric properties were discovered among the clathrates. Transport data has indicated that these materials have some of the characteristics of a good thermoelectric, namely a low thermal conductivity and a high electrical conductivity. Based on synchrotron powder and conventional single crystal x-ray diffraction data we have determined the charge density distribution in Sr8Ga16Ge3Ousing the Maximum Entropy Method. The MEM density shows clear evidence of guest atom rattling, and this contributes to the reduction of the thermal conductivity. Analysis of the charge distribution reveals that Sr8Ga16Ge30contains mixed valence alkaline earth guest atoms. The Sr atoms in the small cavities are, as expected, doubly positively charged, whereas the Sr atoms in the large cavities appear negatively charged. The MEM density furthermore suggests that the Ga and Ge atoms may not be randomly disordered on the framework sites as found in the conventional leastsquares refinements.
Structure of the Near-Surface Waveguide Layers Produced by Diffusion of Titanium in Lithium Niobate
Authors: Avrahami Y. , Zolotoyabko E. , Sauer W. , Metzger T. H. , Peisl J.
Published: April 2011

Titanium-induced structural modifications in thin waveguide layers of lithium niobate have been investigated by grazing incidence diffraction and complementary thin film techniques. The study was focused on the high-temperature phase transformation in this system and its influence on the lattice parameter changes, depending on the annealing time.
Nondestructive Determination of the Depth of Different Texture Components in Polycrystalline Samples
Authors: Patterson C.R. , Ignatiev K.I. , Guvenilir A. , Haase J.D. , Morano R. , Rek Z.U. , Stock S.R.
Published: April 2011

The surface and the center average textures (macrotexture) of plates of many alloys differ substantially, and nondestructive methods for determining the depth of different texture components would be very useful in various applications. This report evaluates one method based on recording microbeam transmission Laue patterns as a function of sample-detector separation and on tracing the diffracted rays back to their physical origin. Polychromatic synchrotron x-radiation and absorption edge filters are used. Results from sections of Al-Li 2090 T8E41 plates are reported, and limitations of the ray tracing technique are discussed
The Influence of Desulfovibrio Desulfuricans on Neptunium Chemistry
Authors: Soderholm L. , Williams C.W. , Antonio Mark R. , Tischler Monica Lee , Markos Michael
Published: April 2011

Biotic Np(V) reduction is studied in light of its potential role for the environmental immobilization of this hazardous radionuclide. The speciation of Np inDesulfovibrio desulfuricanscultures is compared with Np speciation in the spent medium and in the uninoculated medium. Precipitates formed in all three samples. Optical spectroscopy, x-ray diffraction, and x-ray absorption near edge structure (XANES) were used to determine the Np speciation. After 5 days of incubation, there was very little Np left in solution, which was present as Np(V). The precipitate that formed in all samples is an amorphous Np(IV) species, establishing that Np(V) is almost quantitatively reduced. These results demonstrate that the reduction of Np is independent ofDesulfovibrio desulfuricans.The underlying chemistry associated with these results is discussed.
Keys to the Enhanced Performance of Mercuric Iodide Radiation Detectors Provided by Diffraction Imaging
Authors: Steiner Bruce , van den Berg Lodewijk , Laor Uri
Published: April 2011

High resolution monochomatic diffraction imaging is playing a central role in the optimization of novel high energy radiation detectors for superior energy resolution at room temperature. In the early days of the space program, the electronic transport properties of mercuric iodide crystals grown in microgravity provided irrefutable evidence that substantial property improvement was possible. Through diffraction imaging, this superiority has been traced to the absence of inclusions. At the same time, other types of irregularity have been shown to be surprisingly less influential. As a result of the knowledge gained from these observations, the uniformity of terrestrial crystals has been modified, and their electronic properties have been enhanced. Progress toward property optimization through structural control is described.
x-ray Absorption Characterization of Diesel Exhaust Particulates
Authors: Nelson A. J. , Ferreira J. L. , Reynolds J. G. , Schwab S.D. , Roos J. W.
Published: April 2011

We have characterized particulates from a 1993 11.1 Detroit Diesel Series 60 engine with electronic unit injectors operated using fuels with and without methylcyclopentadienyl manganese tricarbonyl (MMT) and overbased calcium sulfonate added. x-ray photoabsorption (XAS) spectroscopy was used to characterize the diesel particulates. Results reveal a mixture of primarily Mn-phosphate with some Mn-oxide, and Ca-sulfate on the surface of the filtered particulates from the diesel engine.
XANES Analysis of BCC/FCC Two-Phase Binary Alloys
Authors: Schilling P.J. , Tittsworth R.C. , Ma E. , He J.-H.
Published: April 2011

A critical factor in the characterization of two-phase binary alloy systems is the determination of the phase fractions and compositions of the two coexisting solid solutions for any given overall composition of the two-phase mixture. In some systems, for example nanocrystalline alloys formed by high-energy ball-milling, these parameters are difficult to attain by traditional techniques like x-ray diffraction. A new technique has been developed to obtain these quantities indirectly from x-ray absorption near edge structure (XANES) data collected at the two relevant absorption edges, with the formulation of this technique presented here in detail. The technique has been tested using Fe-Ni fcc and bcc standards and the results indicate that the method is accurate to within 5%. This method has been applied to two-phase (f.c.c. and b.c.c.) binary alloys formed by ball-milling of Cu100-xFex(x = 50-80).
Spectroscopic Characterization of Mixed Titania-Silica Xerogel Catalysts
Authors: Holland MA , Pickup DM , Mountjoy G , Tsang SC , Wallidge GW , Newport RJ , Smith ME
Published: April 2011

The synthesis of high surface area (TiO2)0.18(SiO2)0.82xerogels has been achieved using the sol-gel route. Heptane washing was used before the drying stage to minimise capillary pressure and hence preserve pore structure and maximise the surface area. The as-prepared xerogels were tested for their catalytic activity using the epoxidation of cyclohexene with tert-butyl hydrogen peroxide (TBHP) as a test reaction. Surface areas up to 450 m2g-1 were achieved with excellent selectivities and reasonable percent conversions. SAXS data has identified that heptane washing during drying, in general, results in a preservation of the pore structure, and produces more effective catalysts with higher surface areas and larger pore diameters. Fr-IR spectroscopy has revealed that the catalytic activity is dependant upon the number of Si-O-Ti linkages, inferring intimate mixing of the precursors at the atomic level. XANES data reveals the presence of reversible 4/6-fold Ti sites that are thought to be ‘active’ catalytic sites. The most effective catalyst was produced with a calcination temperature of 500°C, and a heating rate of 5 °Cmin-l
An Inelastic Nuclear Resonant Scattering Study of Partial Entropies of Ordered and Disordered Fe3Al
Authors: Fultz B. , Sturhahn W. , Toellner T. S. , Alp E. E.
Published: April 2011

Inelastic nuclear resonant scattering spectra were measured on alloys of Fe3Al that were chemically disordered, partially-ordered, and DO3-ordered. The phonon partial DOS for 57Fe atoms were extracted from these data, and the change upon disordering in the partial vibrational entropy of Fe atoms was obtained. By comparison to previous calorimetry measurements, it is shown that the contribution of the Fe atoms to the vibrational entropy is a factor of 10 smaller than that of the Al atoms. With the assistance of Born – von Kárán model calculations on the ordered alloy, it is shown that differences in the vibrational entropy originate primarily with changes in the optical modes upon disordering. The phonon DOS of 57Fe was found to change systematically with chemical short range order in the alloy. It is argued that changes in the vibrational entropy originate primarily with changes in the chemical short-range order in the alloy, as opposed to long-range order.
Quantitative Contact Spectroscopy and Imaging by Atomic-Force Acoustic Microscopy
Authors: Arnold W. , Amelio S. , Hirsekorn S. , Rabe U.
Published: April 2011

Atomic Force Acoustic Microscopy is a near-field technique which combines the ability in using ultrasonics to image elastic properties with the high lateral resolution of scanning probe microscopes. We present a technique to measure the contact stiffness and the Young's modulus of sample surfaces quantitatively with a resolution of approximately 20 rum exploiting the contact resonance frequencies of standard cantilevers used in Atomic Force Microscopy. The Young's modulus of nanocrystalline ferrite films have been measured as a function of oxidation temperature. Furthermore images showing the domain structure of piezoelectric lead zirconate titanate ceramics have been taken.
Precise Determination of Thin Metal Film Thickness With Laser-Induced Acoustic Grating Technique
Authors: Maznev A.A. , Banet M.J. , Gostein M. , Hanselman R.B. , Joffe M.A. , Sacco R. , Nelson K.A.
Published: April 2011

An all-optical technique based on laser excitation and detection of surface acoustic waves is capable of precise, fast, noncontact and nondestructive measurements of metal film thickness. The technique is integrated into a compact and robust instrument. Applications to metal interconnect process control in integrated circuit technology are presented.
Characterization of nitrided silicon-silicon dioxide interfaces
Authors: Polignano M. L. , Alessandri M. , Brazzelli D. , Crivelli B. , Ghidini G. , Zonca R. , Caricato A. P. , Bersani M. , Sbetti M. , Vanzetti L. , Xing G. C. , Miner G.E. , Astici N. , Kuppurao S. , Lopes D.
Published: April 2011

A newly-developed technique for the simultaneos characterization of the oxide-silicon interface properties and of bulk impurities was used for a systematic study of the nitridation process of thin oxides. This technique is based upon surface recombination velocity measurements, and does not require the formation of a capacitor structure, so it is very suitable for the characterization of as-grown interfaces.

Oxides grown both in dry and in wet enviroments were considered, and nitridation processes in N2O and in NO were compared to N2 annealing processes. The effect of nitridation temperature and duration were also studied, and RTO/RTN processes were compared to conventional furnace nitridation processes.

Surface recombination velocity was correlated with nitrogen concentration at the oxide-silicon interface obtained by Secondary Ion Mass Spectroscopy (SIMS) measurements. Surface recombination velocity (hence surface state density) decreases with increasing nitrogen pile-up at the oxide-silicon interface, indicating that in nitrided interfaces surface state density is limited by nitridation. NO treatments are much more effective than N2O treatments in the formation of a nitrogen-rich interface layer and, as a consequence, in surface state reduction.

Surface state density was measured in fully processed wafers before and after constant current stress. After a complete device process surface states are annealed out by hydrogen passivation, however they are reactivated by the electrical stress, and surface state results after stress were compared with data of surface recombination velocity in as-processed wafers.
Experimental Simulation of Contamination Arising From Electro Rocket Engine-Jet on Surface of Spacecraft Units
Authors: Chirov A. , Nadiradze A. , Shaposhniko V. , Egorov V.
Published: April 2011

Under conditions of a vacuum simulation it was investigated how electric rocket thruster (ERT) SPT-70 contaminates space craft (SC) surfaces. The contamination content in the ERT jet was studied by using solid targets. The film composition was analysed by Rutherford backscattering spectroscopy (RBS) He+ ions and nuclear reaction analysis (NRA) with H+ ions methods. Using the results of this analysis a preliminary estimation of the composition and the angular distribution of contaminated components in the ERT jet were carried out.
Thermal Penetration Times as a Nondestructive Measure of Orientation in Polyimide Film
Authors: Chandler C. , Mathis N.E. , Samuels R.J.
Published: April 2011

Material properties depend on their fabricated structure and orientation. It is thus important to develop rapid nondestructive techniques that will both allow determination of the orientation fabricated, and identify any changes that occur over time as a result of subsequent in service environmental conditions.

The present study examines the relationship between the thermal penetration time and planarity in polyimide films. Polyimides are advanced materials that have good high temperature stability, excellent dimensional stability, and excellent mechanical, electrical, and chemical resistance properties. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation in the polyimide film was characterized by polarizing microscope techniques, while the thermal penetration time measurements utilized a new rapid nondestructive modified hot wire instrument.

This correlation will be the first time thermal penetration time has been measured by modified hot wire techniques and related to the internal structure of a polyimide. The work contributes to a deeper theoretical understanding of heat transfer mechanisms as they relate to orientation. Thermal penetration time evaluation could provide a new tool in the arsenal of structural characterization techniques.

This relationship between thermal penetration time and orientation is key for film manufacturers. Such a correlation has potential to speed the development cycles of new materials and assure properties during production and end-use applications.
IRS and ESR Characterizations of Nanocomposite Thin Films Derived From Alkanethiolates and Gold Nanoparticles
Authors: Zheng W. X. , Leibowitz F. L. , Maye M. M. , Gilbert D. C. , Doetschman D. C. , Zhong C. J.
Published: April 2011

A key to the ultimate technological applications of core-shell nanoparticle materials is the understanding of the structure-property correlation. This work focuses on the characterizations of the structural properties for composite thin films derived from gold nanoparticles and thiolates using infrared reflectance spectroscopic (IRS) and electron spin resonance (ESR) techniques. IRS provides information on molecular packing and ordering of the shell components in the films, which relates to the molecular interactions and interfacial reactivities. ESR probes the conduction electron spin resonance properties of the nanosized cores, which can be correlated with the network or environmental electronic effects on the crystal cores. Results are discussed in terms of their correlation with the nanoparticle core sizes and the organic shell functionality.
Characterization of Ni- and Ni(Pt)-Silicide Formation on Narrow Polycrystalline Si Lines by Raman Spectroscopy
Authors: Lee P. S. , Mangelinck D. , Pey K. L. , Ding J. , Osipowicz T. , Ho C. S. , Chen G. L. , Chan L.
Published: April 2011

The formation and thermal stability of Ni- and Ni(Pt) silicide on narrow polycrystalline Si (poly-Si) lines have been investigated using the non-destructive micro-Raman technique. The presence of Ni or Ni(Pt)Si on poly-Si lines with linewidths ranging from 0.5 gtm to 0.25 μm has been monitored by a distinct Raman peak at around 215 cm−1. Ni(Pt)Si was clearly identified to be present up to a RTA temperature of 900°C on narrow poly-Si lines as compared to pure NiSi which was found only up to 750°C. Raman scattering from the 100×100 μm2 poly-Si pads showed the formation of NiSi2 at 750°C for pure Ni-salicidation and 900°C for Ni(Pt)-salicidation respectively. The difference in the stability of NiSi on the poly-Si pads and lines is discussed in terms of agglomeration, inversion and/or nucleation of NiSi2that could be due to difference in nucleation sites and/or stress. In addition, a correlation between the line sheet resistance and the presence of Ni silicide was found using micro-Raman mapping along single poly-Si lines.
Characterization of Copper Surfaces Used in Electronic Circuit Boards by Reflectance FT-IR
Authors: Sloan James M. , Pergantis Charles G.
Published: April 2011

Organic and organo-metallic coatings are presently being applied over bare copper as an approach to improve the co-planarity of circuit boards. Conformal organic solderability preservative coatings (OSP) are environmentally and economically advantageous over the more commonly used lead based coatings [1-2]. Problems arise in assessing the solderability of the bare copper and the integrity of the organic coating.

Specular reflectance Fourier transform infrared spectroscopy (FT-IR) was utilized to monitor and evaluate the formation of Cu oxides occurring on copper substrates used in the manufacturing of electronic circuit boards. Previous studies reported the utility of this technique[3,4]. By measuring the oxide and protective coating characteristics of these surfaces, their solderability performance can rapidly be evaluated in a manufacturing environment. OSP coated test specimens were subjected to hot-dry and hot-wet environmental conditions using MIL-STD-202F [5] and MIL-STD-883E [6] as guides.

The resultant FT-IR spectra provided clear evidence for the formation of various Cu oxides at the Cu/OSP interface over exposure time, for the samples subjected to the hot-dry environment. IR spectral bands consistent with O-Cu-O and Cu202 formation appear, while very minimal deterioration to the OSP coating was observed. The appearance of the Cu oxide layers grew steadily with increased environmental exposure. Specimens subjected to the hot-wet conditions showed no significant signs of deterioration. The IR data can be directly correlated to solderability performance as evaluated by wet balance testing.
In Situ Monitoring of MOCVD of Aluminum Nitride by Optical Spectroscopies
Authors: Allen S.C. , Richardson H.H.
Published: April 2011

Trimethylaluminum and ammonia were used as precursors in the high temperature (900°C) deposition of AIN on silicon at vacuum pressure. The emitted radiation was collected in situ by a FTIR spectrometer. Film thickness was monitored in situ by interference oscillations in a red diode laser beam reflected off the sample. The thickness measurements were correlated with IR emission spectra from the emerging AIN film, and a principal component analysis (PCA) and principal component regression (PCR) were performed on the data.
High-Frequency Stroboscopic X-ray Topography Under Surface Acoustic Wave Excitation
Authors: Zolotoyabko E.
Published: April 2011

The pulse structure of synchrotron radiation was used in order to carry out timeresolved x-ray diffraction imaging of high-frequency (up to 0.6 GHz) surface acoustic waves propagating through a single crystal. In x-ray topographs, recorded in the stroboscopic mode, the short wavelength (down to 6 μm) individual wave fronts are clearly visible, providing information on the acoustic scattering processes with participation of lattice defects.
Chemical and Structural Characterization of Ultrathin Dielectric Films Using AEM
Authors: Scott J.H.J. , Windsor E.S.
Published: April 2011

The structure of ultrathin silicon oxynitride films, used as gate dielectrics in integrated circuits (ICs), is studied using analytical electron microscopy (AEM). Laterally homogeneous blanket films approximately 2 nm in thickness are characterized in cross section using a 300 keV field emission TEM/STEM. High resolution imaging (HRTEM) is used to investigate the accuracy and precision of film thickness measurements and their comparability to other techniques such as secondary ion mass spectrometry, spectroscopic ellipsometry, x-ray reflectivity, x-ray photoelectron spectroscopy, and medium energy ion scattering. A two dimensional magnification calibration scheme that fits a pair of basis vectors to experimental images is presented, and integrated intensity profiles are used to define film boundaries for measurement. These image processing tools simultaneously improve the repeatability of the measurements and remove subjective operator bias from the measurement process.
Analysis of MOS Device Capacitance-Voltage Characteristics Based on the Self-Consistent Solution of the Schrödinger and Poisson Equations
Authors: Raynaud C. , Autran J.L. , Masson P. , Bidaud M. , Poncet A.
Published: April 2011

The one-dimensional Schridinger and Poisson equations have been numerically solved in metal-oxide-semiconductor devices using a three-point finite difference scheme with a non-uniform mesh size. The capacitance-voltage characteristic of the structure has been calculated via this self-consistent approach and results have been compared with data obtained from the resolution of Poisson equation using different approximated methods based on the Boltzmann statistic with and without a first order quantum effect correction or the exact Fermi-Dirac statistic. The present work permits to evaluate and quantify the errors made by these approximations in determining the thickness of ultra-thin oxides.
An XPS Study of Silicon Oxynitride Rapid Thermally Grown in Nitric Oxide
Authors: Lai W. H. , Li M. F. , Pan J. S. , Liu R. , Chan L. , Chua T. C.
Published: April 2011

Earlier growth studies on the rapid thermal oxidation of silicon in NO (RTNO) were not sufficiently comprehensive and were limited by temperature measurement uncertainty and thermal non-uniformity across the wafer. Using a state-of-the-art rapid thermal processing (RTP) system, the RTNO growth characteristics at 100 and 760 Torr, from 900 to 1200°C and from 0 to 480 s were investigated. It was found that the initial growth rate anomalously decreasedwith temperature and pressure. These anomalies were correlated to the evolution of the XPS N 1s spectrum of the RTNO film with oxidation time, temperature and pressure.
Structure Analysis of CeO2/ZrO2/Si Multilayer Thin Films by HRTEM
Authors: Kiguchi Takanori , Wakiya Naoki , Shinozaki Kazuo , Mizutani Nobuyasu
Published: April 2011

The dependence of the structures of the CeO2/YSZ (Y2O3-ZrO2)/Si multilayer thin films on the YSZ thickness was investigated by HRTEM. The CeO2/YSZ interface is semicoherent with misfit dislocations for the films with 110 nm and 30 nm YSZ thickness. On the other hand, the structure of the films with 0.5 nun YSZ layer are very muzzy since the YSZ is very disordered. However, the CeO2 layer on the 0.5 nm of the YSZ has the lowest mosaicity (highest quality) near the surface, although once the epitaxy is weakened in the YSZ layer and the CeO2 layer just above the YSZ. The mosaicity of the YSZ layer is thought not to be taken over into the CeO2 layer since the columnar structure of the thinner YSZ layer becomes obscure. Moreover, a YSZ layer of only 0.5 nm could inhibit the reduction of CeO2 by Si. The ultra thin YSZ layer of 0.5 nm is necessary because it inhibits the growth of the columnar structure and protects the protection of CeO2 layer from reduction.
From Radiation Induced Leakage Current to Soft Breakdown in Irradiated MOS Devices With Ultrathin Gate Oxide
Authors: Ceschia M. , Paccagnella A. , Cester A. , Ghidini G. , Wyss J.
Published: April 2011

Metal Oxide Semiconductor (MOS) capacitors with ultra-thin oxides have been irradiated with ionising particles (8 MeV electrons or Si, Ni, and Ag high energy ions), featuring various Linear Energy Transfer (LET) ranging over 4 orders of magnitude. Different oxide fields (Fbias) were applied during irradiation, ranging between flat-band and 3 MV/cm. We measured the DC Radiation Induced Leakage Current (RILC) at low fields (3-6 MV/cm) after electron or Si ion irradiation. RILC was the highest in devices biased at flat band during irradiation. In devices irradiated with higher LET ions (Ni and Ag) we observed the onset of Soft-Breakdown phenomena. Soft-Breakdown current increases with the oxide field applied during the stress.
Modification of Si(001)/SiO2 Interfaces by Nitric Oxide Treatments: An Electron Paramagnetic Resonance Study
Authors: Cantin Jean-Louis , Bardeleben Hans Jurgen von
Published: April 2011

The modification of the Si(001)/SiO2 interface and the related interface defect reduction by thermal treatments in nitric oxide (NO) have been studied by Electron Paramagnetic Resonance spectroscopy for 630Å thick and ultrathin (28Å) oxides. The effects of annealing temperature, annealing time and rapid (RTN) or furnace annealing have been explored. Our results show that an appropriate NO treatment can drastically reduce the defect densities if, in addition to N incorporation in the transition layer near the interface, the thermal relaxation of the nitrided oxide is allowed. Our results indicate that NO treatment can lead to “defect free” Si/SiO2 interfaces.
Independent Tunneling Reductions Relative to Homogeneous Oxide Dielectrics From i) Nitrided Interfaces, and ii) Physically-Thicker Stacked Oxide/Nitride and Oxide/Oxynitride Gate Dielectrics
Authors: Lucovsky Gerry , Wu Yider , Lee Yi-Mu , Yang Hanyang , Niimi Hiro
Published: April 2011

Direct tunneling limits aggressive scaling of thermally-grown oxides to about 1.6 nm, a thickness at which the tunneling current. Jg, at one volt is ∼1 A/cm2. This paper presents results that demonstrate that stacked gate dielectrics prepared by remote plasma processing that include i) ultra-thin nitrided SiO2 interfacial layers, and ii) either silicon nitride or oxynitride bulk dielectrics can extend the equivalent oxide thickness, EOT, to 1.1-1.0 nm before Jg, > 1 A/cm2.
Measurement Technique, Oxide Thickness and Area Dependence of Soft-Breakdown
Authors: Nigam T. , Degraeve R. , Groeseneken G. , Heyns M. , Maes H.E.
Published: April 2011

For sub-5 nm oxides there are two different stages for breakdown; soft breakdown (SBD) and hard breakdown (HBD). It has been shown that both SBD and HBD exhibit the same statistics. Therefore, the physical mechanism governing them is the same. The major difference between them is the energy transferred from the capacitor to the localized conducting path. In this paper, a simple equivalent circuit is proposed to explain the effect of the measurement technique, oxide thickness, and test structure area on the detection of soft breakdown. Also an inelastic quantum tunneling model is proposed to discuss the current-voltage characteristics after SBD. The model is also successful in explaining the temperature dependence of SBD IV characteristics.
New Type of Superlattice: An Epitaxial Semiconductor-Atomic Superlattice, SAS
Authors: Tsu Raphael
Published: April 2011

Conventional superlattices are formed with repeating a basic period consisting of a heterojunction between two materials. A new type of superlattice are formed by replacing the heterojunction between adjacent semiconductors with semiconductor layers separated by adsorbed species such as oxygen atoms; and CO, molecules, etc. This new type of superlattice, SAS, semiconductor-atomic-superlattice, fabricated epitaxially, enriches the present class of heterojunction superlattices and quantum wells for quantum devices. The Si growth beyond the adsorbed monolayer of oxygen is epitaxial with fairly low defect density. At present, such a structure shows stable electroluminescence and insulating behavior, useful for optoelectronic and SOI (silicon-on-insulator) applications. SAS may form the basis of future all silicon ‘superchip’ with both electrons and photons.