bluuebunny/crossref_metadata_2025 huggingface dataset:
Ab Initio XAFS and XANES Standards
Authors: Rehr J. J. , Zabinsky S. I. , Albers R. C.
Published: March 2011

Ab initio x-ray-absorption fine structure (XAFS) and x-ray-absorption near edge structure (XANES) standards are developed for molecules and solids. These standard XAFS spectra are obtained from ab initio XAFS calculations, using an automated code, FEFF, which we have extended to include multiple-scattering (MS) and XANES calculations. Our treatment is based on state-of-the-art curved-wave MS theory. Sample results are presented and compared with experiment. We find that these theoretical standards are comparable with experimental measurements, yielding distance determinations better than 0.02 Å and coordination numbers better than 20%. Our approach also gives a new MS interpretation of the σ* shape-resonances in XANES.
New Techniques for Synchrotron Powder Diffraction Studies
Authors: Knapp G. S. , Beno M. A. , Jennings G. , Ramanathan M.
Published: March 2011

This manuscript discusses two different powder diffraction methods which possess high resolution, low background and very high counting rates. Both methods utilize analyzer crystals in combination with position sensitive detectors. The first method uses a curved perfect crystal analyzer diffracting in the scattering plane to diffract a range of angles into the position sensitive detector. The second method is somewhat simpler, it uses a graphite analyzer crystal diffracting out of the scattering plane. Applications of these methods to anomalous scattering from both powder and amorphous materials are also discussed. One of the techniques should also be very useful for small angle scattering.
The Local Atomic Structure in Hg0.80Cd0. 20Te
Authors: Quintana J. P.
Published: March 2011

Local atomic arrangements in Hg0.80Cd0. 20Te were investigated by measuring the diffuse x-ray scattering at two different energies near the HgLIII absorption edge to yield intensity due only to Hg-Hg, Hg-Te, and Hg-Cd pair interactions. The data were separated into short range order and displacement intensities. Simulation revealed ordered regions with 3:1 Hg-Cd near neighbor configurations. The Hg-Te length is contracted.
Anticlastic Curvature of Elastically Bent Crystals for Sagittal Focusing
Authors: Quintana J. P. , Kushnir V. I. , Georgopoulos P.
Published: March 2011

Finite element results are presented for the case of an elastically bent isotropic rectangular crystal with clamped boundary conditions. Results show that the anticlastic curvature can be eliminated in the center of the crystal provided the crystal length to width ratio fits a “golden aspect ratio” which is dependent on the Poisson coefficient ν. For ν=0.262 (appropriate for Si(111)), this ratio is approximately equal to 1.42.
EXAFS Studies on the Structure of Photoexcited Cyclopentadienylnickelnitrosyl(C5H5NiNO)
Authors: Chen Lin X. , Bowman Michael K. , Montano Pedro A. , Norris James R.
Published: March 2011

The structures of C5H5NiNO in a reversible photochemical reaction were studied via EXAFS, FTIR, and optical absorption spectroscopies. A photoexcited intermediate with distinctively different EXAFS, IR, and optical absorption spectra from those of the ground state molecules was generated upon irradiation using 365 nm light at 20K in a 3-methylpentane solution. The reverse reaction was induced by irradiation with 310 nm light. The EXAFS data analysis has shown a 0. 12 Å elongation of the Ni-N bond and the bending of Ni-N-O in the photoexcited intermediate. Several ZINDO calculations were conducted based on the structures obtained from the EXAFS spectroscopy. These calculations reproduced the changes in the optical spectra and the intramolecular electron transfer in C5H5NiNO.
X-Ray Absorption Analysis of Ge and Ga Environments in Ba-Gallogermante Glasses
Authors: Merzbacher Celia I. , McKeown David A.
Published: March 2011

X-ray absorption spectroscopy has been used to characterize the local structure surrounding Ga and Ge in BaO-Ga2O3-GeO2 glasses. Based on comparisons with results for crystalline standards of known structure, Ge and Ga in all of the glasses are primarily in tetrahedral coordination; no evidence for octahedral coordination is observed. Bond length and coordination values derived from fitting calculations are fairly uniform for all glasses, however disorder increases with increase in BaO and decrease in GeO2 content, especially in the second shell surrounding Ge and Ga. Ge absorption edges for all glasses resemble smoothed BGG-An or GeO2 [quartz] edges. Ga absorption edges of the glasses also resemble the BGG-An edge which has two edge maxima, but in the glasses the relative intensities of the two maxima vary with composition.
X-Ray Absorption Spectroscopy of the Rare Earth Orthophosphates
Authors: Shuh D. K. , Terminello L. J. , Boatner L. A. , Abraham M. M.
Published: March 2011

X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d104fn→3d94fn+1 transitions and these transitions exhibit a wealth of spectroscopic features. The XAS measurements of single crystal REPO4 (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Er) at the 3d edge were performed in the total yield mode at beam line 8–2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble the XAS of the corresponding RE metal. This is not unexpected and emphasizes the major contribution of the trivalent state to the electronic transitions at the RE 3d edges. These spectra unequivocally identify the transitions originating from well-characterized RE cores and correlate well with previous theoretical investigations.
Electron Microscopy at Atomic Resolution
Authors: Gronsky R.
Published: March 2011

The direct imaging of atomic structure in solids has become increasingly easier to accomplish with modern transmission electron microscopes, many of which have an information retrieval limit near 0.2nm point resolution. Achieving better resolution, particularly with any useful range of specimen tilting, requires a major design effort. This presentation describes the new Atomic Resolution Microscope (ARM), recently put into operation at the Lawrence Berkeley Laboratory. Capable of 0.18nm or better “interpretable” resolution over a voltage range of 400 kV to 1000kV with ± 40° biaxial specimen tilting, the ARM features a number of new electron-optical and microprocessor-control designs. These will be highlighted, and its atomic resolution performance demonstrated for a selection of inorganic crystals.
Crystallinity, Morphology, and Conductivity of Boron-Doped Microcrystalline Silicon
Authors: Rajeswaran G. , Tafto J. , Sabatini R. L. , Vanier P. E.
Published: March 2011

Boron-doped microcrystalline (μc) silicon films produced by rf glow discharge from dilute (1%) mixtures of SiH4 in H2 show a critical dependence of conductivity on deposition conditions. The dark conductivity was related to the microscopic features using electron microscopy. The μc−Si:H films contain clusters of crystallites embedded in an amorphous matrix. The size of the crystalline clusters is typically 0.2 μm in diameter, and the size of the individual crystallites is about 2.5 nm. Electron micrographs of samples prepared at substrate temperatures Ts=135°C, 150°C, 165°C, and 180°C show that the number of crystalline clusters increases with Tsup to 165°C. At Ts=180°C, the crystallites completely disappear. When the concentration of SiH4 in H2 is decreased to 0.25%, the microstructure shows a high density of crystallites with no apparent clustering.
Reflection Electron Microscopy and Diffraction from Crystal Surfaces
Authors: Cowley J.M.
Published: March 2011

The recent revival of techniques for the imaging of crystal surfaces, using electrons forward-scattered in the RHEED mode and employing modern electron microscopes, has lead to the introduction of valuable new methods for the study of surface structure. Either fixed beam or scanning transmission electron microscopy (STEM) instruments may be used and in each case a lateral resolution of 10Å or better is possible. Simple theoretical treatments suggest that the contrast from surface steps may be attributed to a combination of phase-contrast, diffraction contrast and geometric effects. With a STEM instrument the image information can be combined with information on the local composition and crystal structure by use of microanalysis and microdiffraction techniques. Examples of applications include studies of the surface structure of metals, semiconductors and oxides, and the surface reactions.
Interpretation of the Atomic Surface Structure of Ag2O on (111) Au thin films
Authors: Krakow William
Published: March 2011

A high resolution electron microscope investigation of the residual oxidized silver of a few monolayers thickness on the surface of (111) Au films has shown that a reconstructed (2×1) surface structure occurs for (110) oriented Ag2O and can be observed at atomic resolution levels. Image enhancement via a digital frame store processor has revealed improved images which have then been compared to computer simulated diffraction patterns and images of the Ag2O surface. Several iterations of surface structure models and image simulations reveal that the (2×1) reconstruction is consistent with a missing row model. The atomic arrangements of these rows often undergo a translation along the direction of the row to produce cusp like image features. It has also been possible to observe the effect of contraction of the underlying layer which can produce diagonal contrast lines in the images. These features often vary rapidly over lateral distances of a few tens of angstroms and give an indication of the surface topography and the degree ordering of the surface.
Dislocations, Steps and Interphase Boundary Migration
Authors: Smith D.A.
Published: March 2011

Interface migration is the fundamental process in numerous phase transformations. For those which are thermally activated the basic event is addition of atoms to a defect in an interface. Interfacial defects can have a range of topographic and elastic characteristics which complicates investigations by transmission electron microscopy, it is difficult to make quantitative in-situstudies of interface migration because of problems of resolution and control of driving forces in specimens where surface effects dominate.
High Resolution Study of the Relationship Between Misfit Accommodation and Growth of CU2-xS in Cds
Authors: Sands T. , Washburn J. , Gronsky R.
Published: March 2011

The growth of CU2-xS in the (0001) basal face of single crystal cadmium sulfide has been studied with high resolution transmission electron microscopy (HRTEM) and diffraction. Cross-sectional Cu2-xS/CdS specimens and plan-view Cu2-xS separated films were prepared from heterojunctions formed by the aqueous conversion of CdS to topotaxial Cu2-xS. Low chalcocite films were found to form in two principal stages; 1) coalescence of low chalcocite islands and 2) an accelerated reaction localized at pores in the Cu2-xS film. Several possible misfit accommodation mechanisms involving twinning, cracking, and a second copper sulfide phase were identified.
Fault Structures in CVD Silicon Nitride
Authors: Shaw T.M. , Steeds J.W. , Clarke D.R.
Published: March 2011

Fault structures occurring in crystalline CVD silicon nitride deposits have been examined using transmission electron microscopy. A variety of mixed rotation and displacement faults are observed. The faults have extensive basal plane facets but also extend onto other planes within the grains. Possible structures for the faults are discussed with reference fo the structures of the a and P silicon nitride polymorphs.
Image Processing for Electron Microscope Investigations of Materials
Authors: Krakow William
Published: March 2011

A time shared television digital image processing system has been developed for on-line electron microscopy and uses a large mainframe computer. The main component of the system is a digital television frame store which has many standard features for digital analysis such as: digitization, zoom and pan, arithmetic and Boolean processors, alphanumeric generators and so on. Images can be acquired at atomic resolution from a TEM, analyzed in real time and hard copy slides made under full computer control. A full range of computer software has been developed or modified from existing software and is generally compatible with IBM Fortran compilers. Some of the areas where extensive menu driven software has been developed are: particle size and feature analysis, algebraic and geometric image manipulations, Fourier analysis, digitization and process control, image contrast correction, text processing, etc. A number of applications areas have been explored which include: the structure of Si/SiO2interfaces; nucleation of Au on rocksalt; the formation of hexatic structures from amorphous phases under shear, tension and compression; analysis of atomic surface structure and image motion and the analysis of field ion micrographs of amorphous structures. Several of these areas will be discussed in the context of image processing and materials characterization.
Dopant Site Location by Electron Channeling in Ion Implanted Silicon
Authors: Pennycook S. J. , Narayan J. , Holland O.W.
Published: March 2011

A simple ratio technique using the phenomenon of electron channeling can be used to measure the substitutional concentrations of dopants in semiconductors on a submicron scale.A comparison was made between electron and ion channeling measurements on Si-Sb alloy samples having a range of nonsubstitutional fractions of Sb.Good agreement was obtained but both measurements indicated considerably more nonsubstitutional dopant than could be accounted for by precipitates observed in electron micrographs. The discrepancy can be explained if the precipitates are coherent in the early stages of growth and have their planes located interstitially with respect to the Si planes. The sensitivity of the electron channeling measurements to the implantation profile was investigated and found to be small.The determination of local dopant profiles in the electron microscope is described.
Bottom Electrodes for High Dielectric Oxide Compounds: Effects on Crystallization of Lead Containing Ferroelectrics
Authors: Grill A. , Beach D. , Smart C. , Kane W.
Published: March 2011

Several conductive structures, which appeared to be usable as base electrodes for integrated devices based on high dielectric materials, have been annealed for 30 minutes in oxygen at 650 °C. Similar structures coated with lead-based ferroelectrics deposited by the sol-gel method have been annealed for 1 min in oxygen at higher temperatures. The materials have been characterized by Rutherford backscattering (RBS) and scanning electron microscopy (SEM) and the crystallographic structure of the ferroelectrics films has been determined by X-ray diffractometry (XRD).

Only RuO2/Ru has been found to be suitable as an electrode, at temperatures not exceeding 650 °C. It has also been found that the electrode materials can strongly affect the crystallization behavior of the sol-gel ferroelectric films and the formation of single-phase perovskite layers.
MOCVD Growth and Structure of PbTiO3 Thin Films
Authors: Gao Y. , Bai G. , Merkle K. L. , Chang H. L. M. , Lam D. J.
Published: March 2011

PbTiO3 thin films grown on (001)MgO and (110)MgO by MOCVD have been characterized by x-ray diffraction and transmission electron microscopy. The PbTiO3 films deposited on (001)MgO under the optimum conditions always show a bi-layer structure. The top layer of the films near the free surface is c-axis oriented with the orientation relationship (001)[100]PbTiO3∥(001)[100]MgO. The bottom layer of the films near the substrate is a-axis oriented with (100)[001]PbTiO3∥(001)[100]MgO. 90° domains were observed, but only in the caxis oriented layers. The thickness of the a-axis oriented layers near the substrate decreases with decreasing the cooling rate. PbTiO3 films deposited on (110) MgO, however, are single-layer, epitaxial films with (101)[001]PbTiO3∥(110)[001]MgO.
Metallorganic Cheamcal Vapor Deposition (Mocvd) of Titanium-Based Ferroelectric Thin Films
Authors: Hendricks Warren C. , Desu Seshu B. , Si Jie , Peng Chien H.
Published: March 2011

Using hot-walled metallorganic chemical vapor deposition (MOCVD), thin fihns of lead zirconate titanate (PZT), lead titanate (PbTiO3 or PT) and bismuth titanate (Bi4Ti3O12 or BiT) were successfully prepared. For each material, titanium ethoxide (Ti(C2H5O)4) was used as the precursor for the titanium source, while lead bis-tetramethylheptadione (Pb(thd)2), zirconium tetrakistetramethylheptadione (Zr(thd)4) and triphenyl bismuth (Bi(C6H5)3) were used as sources for lead, zirconium and bismuth, respectively. Dense, specular and highly transparent films were obtained for all three materials. Deposition conditions are given for each of the materials as well as the properties of the resulting films as determined by XRD, SEM and UV-VIS-NIR spectrophotometry. Ferroelectric properties are also given for the PZT and BiT films; for PZT (%Zr = 41; %Ti = 9) annealed at 600 °C, the spontaneous polarization, Ps, was 23 μC/cm2 and the coercive field, Ec, was 65 kV/cm; for BiT annealed at 550 °C, the spontaneous polarization, Ps, was 27 μC/cm2 and the coercive field, Ec, was 240 kV/cm.
Growth and Characterization of Ferroelectric Pb(Zr,Ti)OM3 Thin Films by Mocvd Using A 6 Inch Single Wafer Cvd System
Authors: Shimizu Masaru , Fujimoto Masashi , Katayama Takuma , Shiosaki Tadashi , Nakaya Kenichi , Fukagawa Mitsuru , Tanikawa Eiki
Published: March 2011

Ferroelectric Pb(Zr,Ti)O3(PZT) films with a perovskite phase were successfully grown by MOCVD using a 6 inch wafer CVD system. A two step growth process was proposed to obtain perovskite PZT films at high gas supplying ratios of [Zr]/([Zr]+[Ti]). The electrical properties of the PZT films obtained were measured. Large area growths of PZT films were carried out and the uniform films could be grown on the entire area of a 6 inch Si wafer. It was also found that the step coverage characteristic of the films grown by MOCVD was good.
Crystallization Behavior and Electrical Properties of Wet-Chemically Deposited Lead Zirconate Titanate Thin Films
Authors: Merklein S. , Sporn D. , SchÖnecker A.
Published: March 2011

A wet chemical deposition process for smooth and crackfree films in the system Pb(Zr 1-x Tix)O3 (PZT) has been developed. Final film thicknesses, reached with one coating step, were in the region of 1 μm. Starting from lead acetate trihydrate, zirconium- and titanium-n-propoxide, high molarity (> 2M) coating sols have been prepared that could be handled in air and were stable for more than 170 days.

Films with compositions near the morphotropic phase boundary (x=47) and various lead contents were deposited on Pt-coated Si-wafers and Al2O3-substrates by a spin-on method. Wet films could be pyrolyzed and densified with a fast heat treatment without cracking. The crystallization of films into the desired perovskite structure started at comparatively low temperatures (ca. 530 °C) and proceeded rapidly at temperatures above 650 °C. A slight molar excess of lead and a proper heating rate were found to produce films with the best electrical properties. The films on platinized A12O3 substrates showed device-worthy dielectric and ferroelectric properties with typical values for Pn, EC, and ε, of 24 μC/cm2, 4.5 KV/mm and 650, respectively.
Substrate Influenced Nucleation and Crystallization of LiNbO3 Thin Films Made by Sol-Gel
Authors: Joshi Vikram , Roy Debasis , Mecartney Martha L.
Published: March 2011

Lithium niobate films were deposited on amorphous carbon, silicate glass, (0001) sapphire, and (100) silicon by spin or dip coating double metal ethoxide sols. The crystallinity and microstructure of the deposited films were examined by XRD and TEM. Crystallization behavior and resulting microstructure were strongly influenced by the type of substrate. The formation of crystalline LiNbO3 on amorphous carbon was detected at room temperature. Randomly oriented polycrystalline films were obtained on glass at 400°C. Choice of one mole of water per mole of ethoxide generated heteroepitaxial growth of LiNbO3 thin films on (0001) sapphire. Oriented but polycrystalline films were obtained on silicon. The electrical behavior of film on silicon was evaluated in metal-ferroelectric-semiconductor configuration. A dielectric constant of 35 and a dissipation factor of 0.004 was measured at 100 KHz.
Preparation and Characterization of Sol-Gel Derived Heteroepitaxial LiNbO3 and LiTaO3 Thin Films
Authors: Nashimoto Keiichi
Published: March 2011

Dense epitaxial LiNbO3 thin films without any misoriented plane on sapphire substrates were obtained with a sol-gel process utilizing 2-methoxyethanol based metal alkoxide precursors without pre-hydrolysis and rapid thermal annealing. Epitaxial LiNbO3 films annealed at 700°C were transparent and showed refractive indices close to bulk single crystal values. Epitaxial and transparent LiTaO3 films crystallized successfully on sapphire substrates with single orientations with the present process. X-ray rocking curve full widths at half maximum of epitaxial LiNbO3 and LiTaO3 films on sapphire (110) substrates and annealed at 700°C were less than 0.4 degree.
Microstructural Evolution of Pb(Zr,Ti)O3 Ceramics Using Electron Paramagnetic Resonance
Authors: Warren W. L. , Tuttle B. A. , Schwartz R. W. , Hammetter W. F. , Goodnow D. C. , Evans J. T. , Bullington J. A.
Published: March 2011

Using electron paramagnetic resonance (EPR) we have followed the microstructural evolution with temperature of lead zirconate titanate (PZT) ceramics from the amorphous to the perovskite phase. A number of paramagnetic point defects were identified (Carbon, Pb+3, and Ti+3) while traversing the evolution of these ceramics during various heat treatments both before and after optical illumination. Perhaps the most important finding is that the Pb+3 and Ti+3 centers can only be optically created in the perovskite materials, thereby, showing that they are not associated with the amorphous or the pyrochlore phases. It is also found that EPR signals attributed to carbon radicals are present in fairly high concentrations (4 × 1017/cm3) if the solution chemistry derived PZT materials are annealed in an oxygen deficient ambient (0.1% O2) at 650°C.
Low Temperature Preparation of BaTiO3 Films on Silicon
Authors: Pilleux M.E. , Fuenzalida V.M.
Published: March 2011

Insulating BaTiO3 thin films were obtained on titanium coated silicon wafers using a novel low temperature technique. They were produced hydrothermally by introducing the substrate in a 0.25M Ba(OH)2 solution inside an autoclave and heating in the 200- 250°C range for 8 hours. This treatment delivered smooth pinhole-free films on the Ti with thicknesses ranging from 35nm (200°C) to 45nm (250°C), with grains in the 100- 300nm diameter range in all films. The films exhibited a dielectric constant up to 227, a breakdown field of 70MV/m, and a dc resistivity of 4.106Ωm.
Deposition of Dielectric Thin Films by Atomic Layer Epitaxy and Their Application for Electroluminescence Displays
Authors: Lee Dong Heon , Cho Yong Soo , Lee Jeon Kook , Jung Hyung Jin
Published: March 2011

Various dielectric thin films have been studied for electroluminescence display (ELD) application to improve dielectric constant and breakdown voltage. In this work, amorphous BaTiO3 thin films were deposited on indium tin oxide (ITO) - coated glass substrates by atomic layer epitaxy (ALE) using metalorganic precursors. Influences of deposition conditions on microstructure, interface characteristics and dielectric properties are investigated. It was possible to obtain dielectric films with good dielectric properties and textured, flat surface microstructure without defects due to the improvement of qualities of the grown films. These results were examined by XRD, SEM and AES analysis.
Prism-Film Coupling in Anisotropic Planar Waveguides of Epitaxial (101) Rutile Thin Films
Authors: Foster C. M. , Chan S.-K. , Chang H.L.M. , Chiarello R. P. , Lam D. J.
Published: March 2011

We report optical waveguiding in single-crystal, epitaxial (101) oriented rutile (TiO2) thin films grown on (1120) sapphire (α-Al2O3) substrates using the MOCVD technique. The propagation constants for asymmetric planar waveguides composed of an anisotropic dielectric media applicable to these films are derived. Modifications to the prism-film coupling theory for this anisotropic case are also discussed. By application of this model to (101) oriented rutile thin films, we directly obtain values of the ordinary and extraordinary refractive indexes, no and ne, of the rutile thin films as well as film thicknesses. We obtain typical values of the refractive indexes (no=2.5701±0.0005; ne=2.934±0.001) near to those for bulk rutile single crystals indicating the exceptional quality of these films.
Electrical Properties of Amorphous Thin Films of Ferroelectric Oxides Prepared by Sol-Gel Technique
Authors: Xu Yuhuan , Xu Ren , Cheng Chih-Hsing , Mackenzie John D.
Published: March 2011

Amorphous thin films of ferroelectric oxides including lead zirconate titanate (PZT), barium titanate (BaTiO3) and lithium niobate (LiNbO3) on several kinds of substrates were prepared by a sol-gel technique. The heat-treatment temperatures for preparation of amorphous thin films were much lower than those for the corresponding crystalline ferroelectric thin films. Electrical properties of these amorphous thin films were measured and compared with those of corresponding crystalline films. These amorphous thin films exhibited ferroelectric-like behavior. A model of the microstructure of these films is proposed.
Pzt Thin Films on a Lead Titanate Interlayer Prepared by rf Magnetron Sputering
Authors: Ansari P. H. , Safari A.
Published: March 2011

Ferroelectric lead zirconate titanate (PZT) films with a composition near the morphotropic phase boundary have been deposited by if magnetron sputtering on a Si substrate coated with silicon oxide, titanium, and platinum (Si/SiO2/Ti/Pt). Substrate temperature and oxygen partial pressure were changed during deposition to prepare films with controlled stoichiometry and perovskite structure. The effects of lead titanate (PT) as a buffer layer were investigated. Thin films of PT/PZT have a dielectric constant of 800 with a dissipation factor of 0.04 at 1 kHz. The remnant polarization of 8μC/cm2 and the coercive field of 50 kV/cm were measured. The effect of processing on the formation of perovskite phase and the electrical properties will be discussed.
Effects of Process Parameters on the Ablated Flux Characteristics During Pulsed-Laser Ablation of Lead Zirconate Titanate (PZT)
Authors: Lichtenwalner D.J. , Auciello O. , Dat R. , Barnes R. , Schreiner A.F. , Hankins O.E. , Kingon A.I.
Published: March 2011

We have investigated the ablated flux characteristics of PbZrxTi1-xO3 as a function of deposition process parameters. The ablation-deposition rate, angular distribution, and type of ablated species axe all affected by the oxygen gas pressure. Visually, a change in the shape and color of the ablation plume are evident upon adding oxygen gas. The ablated flux distribution narrows as the oxygen pressure is increased, from a cos40θ distribution in a low gas pressure, up to a cos 260θ distribution at an oxygen pressure of 300 mTorr. This narrowing, or focusing, of the ablated plume also results in an increased deposition rate along the plume centerline for high laser power. However, at low laser power the deposition rate decreases as the pressure is increased, due to gas scattering effects. The energy of depositing species and the ratio of deposition flux to O2 flux will then be very different in each of these two regimes. The species in the plume have been examined using optical emission spectroscopy. We have found that mostly atomic species are present, but the ratio of ions to neutrals is very different for the Pb, Zr, and Ti atoms. Therefore, the application of electric fields near the substrate would affect the film composition to some degree.
The Application of Optical Interferometry to the Study of Field-Induced Effects in Bulk and thin Film Ferroelectrics
Authors: Lewis Keith L , Dexter Kathleen F
Published: March 2011

A study is reported of field-induced effects in ferroelectric materials using optical interferometry. One of the techniques used is based on the use of a WYKO TOPO3 system and provides a three dimensional representation of field-induced displacement. The information provided is supplemented by optical transmission measurements on thin sections of material fabricated to allow interference fringing to be seen. Initial work has centred on the characterisation of ceramic PLZT material. Both transverse and longitudinal electrode configurations have been studied and have highlighted the magnitude of the effects possible and the importance of electrostrictive processes in determining the direction of deformation. These can result in anomalously high strain gradients over distances of the order of 50-100µm. This behaviour is compared with that found for preliminary samples of thin film ferroelectric materials.
Cosio2 Formation on Strained GexSi1−x Layers BY Co/GexSi1−x Thermal Reaction
Authors: Ridgway M.M. , Elliman R.R. , Pascual R. , Whitton J.J. , Baribeau J.-M.
Published: March 2011

The formation of CoSi2 on Ge.17Si.83 layers by Co/Ge.17Si.83 thermal reaction nas been studied with a variety of analytical techniques. Co films deposited on strained Ge.17Si.83 layers were annealed at 600°C for 0–240 min. Following 240 rain annealing, the reacted surface layer was composed of CoSi, CoSi2 and GexSi1-x precipitates (the latter probably rich in Ge) as identified with transmission electron microscopy, x-ray diffraction and/or Raman spectroscopy. Lateral phase non-uniformity was evident with both transmission and scanning electron microscopy. For samples annealed with and without an evaporated Co film, enhanced relaxation of the underlying Ge.17Si.83 layer was apparent in the former.
Stability of Nanometer-Size Si Crystals in Amorphous Si Thin Films under Ion Irradiation
Authors: Yang Chih M. , Atwater Harry A.
Published: March 2011

In this paper we discuss the size-dependent shrinkage rate of nanometer-size Si crystals in amorphous Si thin films during ion irradiation. We obtain shrinkage rate of nanometersize crystals at low temperature under ion irradiation by studying the evolution of the crystal size distribution using transmission electron microscopy. Our results indicate that crystals less than 10 nm in diameter decrease in size faster than larger crystals under ion irradiation. In addition, we fit our data to a capillary model for growth of Si crystals in amorphous Si under ion irradiation.
Amorphization of Zr/Ni Bilayers by Ion-Beam-Mixing
Authors: Jagelski Jacek , Thome L. , Kopcewicz M.
Published: March 2011

The amorphization process induced by ion-beam-imxing was studied for the Zr/Ni bilayer system by means of the RBS/channelling and CEMS techniques. The number of atoms mixed per one incident atom was found to be the same for σ100 K and 300 K irradiations, whereas it was increased by the factor of 2.5 for 500 K irradiation what indicates, that the change in the mixing mechanism occurred above room temperature. The results show that amorphization of the Zr/Ni system is controlled by the number of mixed atoms and depends on the irradiation temperature. A change in CEMS spectra was observed at σ770 K what suggests that recrystallization of the amorphous phase occurs at this temperature.
Electron Irradiation Induced Crystallization of Amorphous Al2O3 Films on Silicon Substrates
Authors: Liu J. , Barbero C. J. , Corbett J. W. , Rajan K. , Leary H.
Published: March 2011

An in situ study of electron beam irradiation induced amorphous–to–crystalline transformation of Al2O3 films on silicon substrates has been carried out using transmission electron microscopy. Trigonal α–Al2O3 crystallites can be observed for electron beam dose rates larger than 10 mA/cm2. It is found that the nucleation and growth processes dominate near the Al2O3–Si interface. The possible effect of the silicon substrate on the growth of Al2O3 crystallites is considered.
Time Resolved X-Ray Diffraction Study of the Transformation Kinetics of TiSi2-C49 in Amorphous Si/Ti Multilayers
Authors: Sariel J. , Chen Haydn , Jongste J. F. , Radelaar S.
Published: March 2011

Amorphous Si/Ti multilayers transform at high temperatures (above 700°C) to TiSi2-C54. This phase is important for microelectronics applications because of its low resistivity, stability up to 900°C, and compatibility with silicon processing. However, an unfavorable metastable TiSi2-C49 phase is usually formed at lower temperatures. Thus, an understanding of the C49 phase formation kinetics is useful to the device processing strategy. The kinetics of the transformation of TiSi2-C49 phase can be characterized as a process of nucleation and growth, using the well known Johnson Mehl Avrami (JMA) equation. In the present work the formation kinetics of the C49 phase has been studied by an in situ x-ray diffraction technique. Isothermal annealing in vacuum was done at four temperatures, in the range of 275"C to 310°C. A position sensitive detector (PSD) was used to simultaneously collect the diffracted beams of (131) and (150) peaks of the C49 phase. From the data, the Avrami exponent, n, was determined to be 2.0±0.1. The reaction rate constant k follows a familiar Arrhenius-type equation with a measured activation energy of 2.5eV. Comparison of our x-ray results with kinetic data obtained by other means will be discussed.
Phase Transformation Kinetics of TiSi2
Authors: Mann R.R. , Clevenger L.L. , Hong Q.Q.
Published: March 2011

The microstructure and kinetics of the polymorphic C49 to C54-TiSi2phase transformation have been studied using samples prepared as in self-aligned silicide applications. For C49-TiSi2thin films formed at temperatures of 600°C and 625°C on (100) single-crystal silicon substrates, the effective activation energy was 5.6 ± 0.3 and 5.7 ± 0.08 eV, respectively, for this phase transformation carried out in the temperature range of 600°C to 700°C. The transformation process was observed to occur by nucleation and growth of the orthorhombic face-centered (C54) phase from the as-formed orthorhombic base-centered (C49) phase.
Equilibrium Shape of CoSi2in Silicon
Authors: Adams D.D. , Yalisove S.S. , Eaglesham D.D.
Published: March 2011

The energetics associated with the formation of CoSi2have been investigated by using the equilibrium shape of isolated precipitates. Two types of precipitates were studied: CoSi2equilibrated at the Si surface and CoSi2equilibrated within the Si lattice. CoSi2precipitates form by facetting along {111} and {1100} planes in Si. Using a reverse Wulff approach, a ratio of interfacial free energies of γ{100} / γ{111) has been measured to be 1.43 ± 0.07.
Reaction Rate Kinetics and Film Textures of Palladium Silicide Formed on Hydrogenated Amorphous Silicon
Authors: Manning N. R. , Chen Haydn , Abelson J. R. , Allen L. H.
Published: March 2011

The reaction rate kinetics of the thin film solid-state reaction between 120 nm of Pd and 100 or 300 nm of a-Si:H(18at%) to form Pd2Si were studied in situ using x-ray diffraction and four-point probe resistivity measurements during isothermal annealing. These two techniques yielded activation energies and prefactors of Ea=1. 36±:0.11 eV with ko=4.29 cm2/sec for the x-ray diffraction experiments; and Ea=0.97±0.22 eV with ko=3.42x10-4 cm2/sec for the resistivity measurements. The activation energy and prefactor obtained from the c-Si substrate of the resistivity measurements yielded Ea=l.41±0.31 eV and ko=10.6 cm2/sec. Comparisons showed that the silicide formed from the a-Si:H reacted approximately 1.4 times faster than the silicide formed from the c-Si in the same sample, but three times faster than silicide formed on pure c-Si(111). The crystalline texture and grain size of the metal and silicide films were examined.
Simultaneous Occurrence of Multiphases in the Interfacial Reactions of Ultrahigh Vacuum Deposited Ti, Hf and Cr Thin Films on (111)Si
Authors: Hsieh W.W. , Lin J.J. , Wang M.M. , Chen L.L.
Published: March 2011

Simultaneous occurrence of multiphases was observed in the interfacial reactions of ultrahigh vacuum deposited Ti, Hf and Cr thin films on (111)Si by high resolution transmission electron microscopy in conjunction with fast Fourier transform diffraction analysis and image simulation. For the three systems, an amorphous interlayer as well as a number of crystalline phase were found to form simultaneously in the early stages of interfacial reactions. The formation of multiphases appeared to be quite general in the initial stages of interfacial reactions of UHV deposited refractory thin films. The results called for a reexamination of generally accepted “difference” in reaction sequence between bulk and thin film couples.
Phase Transformation of Mo and W over Co OR Its Alloy in Contact with Si
Authors: Yang Fann-Mei , Chen Mao-Chieh
Published: March 2011

W or Mo directly deposited on Si cold substrate by electron-beam gun at a base pressure of 10-6 torr is not able to form silicide even annealed at 900 °C in either N2 or H2 ambient. We present an easy way that Mo and W silicides can be formed on the same depositing and annealing conditions with the help of an intervened layer of cobalt or its alloy. Investigation was made on various metallizations of Mo (or W)/Co/Si, W/Co-Mo/Si, and Co/Mo/Si in normal flowingnitrogen or in H2 ambient at various temperatures. In the systems of Mo (or W)/Co/Si and W/Co-Mo/Si, the overlying Mo (or W) can be transformed into silicide at 900 °C, while in the Co/Mo/Si system, where stable Co-Mo compounds are formed in advance, no silicide can be formed. Why silicide is formed in preference to metal oxide in N2 environment at higher temperature is based on Ellingham diagram.
Transmission Electron Microscopy Study of Thick Copper-304 Stainless Steel Multilayers
Authors: Wall M. A. , Barbee T. W. , Weihs T.
Published: March 2011

Thick (10 to 25 μm), free-standing, equal layer thickness, Copper(Cu)-304 Stainless Steel(SS) multilayer foils, having periods of lnm to 100 nm, synthesized by magnetron sputter deposition, have been examined by plan view and cross-sectional transmission electron microscopy. Multilayer growth morphology, individual layer structure and crystallographic phase orientation relationships were characterized in this study. Electron Energy Loss filtered imaging of a 20 nm period multilayer cross-section was also performed and showed that nickel had diffused into the Cu layers from the SS during synthesis. X-ray powder diffraction scans were performed and analyzed. A pure deposit of 304SS was synthesized and had a metastable BCC structure. Multilayer samples having periods of 20 nm were found to have a coherent layered Cu(FCC)- SS(FCC) structure. At larger periods (50 & 100 nm) a bimodal Cu(FCC)-SS(FCC & BCC) structure was formed. These observations show that the 304SS will grow with a metastable BCC structure when sputter deposited. When layered with Cu(FCC) the 304SS has its equilibrium FCC structure at layer thicknesses up to 10nm as a result of epitaxy with the copper. At larger SS layer thicknesses the SS appears to locally transform to the metastable BCC structure during synthesis, refining the grain structure of the depositing SS layer and the subsequent Cu layer. This transformation significantly increases the strength of the larger period multilayer.
Direct Deposition Reactions Between Nickel and Silicon Substrates
Authors: Zhang Lin , Ivey Douglas G.
Published: March 2011

Silicide formation through deposition of Ni onto hot Si substrates has been investigated. Ni was deposited onto <100> oriented Si wafers, which were heated up to 300°C, by e-beam evaporation under a vacuum of <2x10-6 Torr. The deposition rates were varied from 0.1 nm/s to 6 nm/s. The samples were then examined by both cross sectional and plan view transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy and electron diffraction. The experimental results are discussed in terms of a new kinetic model.
Hydrogen Evolution and Interface Reaction of Cu Thin Film on a-Si:H
Authors: Bemardino L. , Achete Carlos , Freire F. L.
Published: March 2011

The Cu/a-Si:H system has been studied by gas effusion method, elastic recoil detection analysis (ERDA), in situ sheet resistance measurements and scanning electron microscopy. Cu layers of 15 and 90 nm in thickness were deposited by e-beam evaporation onto 1 μm a-Si:H films produced by RF glow discharge on Si(100) substrates at 250 °C. The most important effects are observed in the effusion measurements, when pure a-Si:H samples and Cu/a-Si:H samples are compared. For the Cu/a-Si:H samples, three well-defined peaks are observed, one at very low temperature (T=200 °C), another at 380 °C and a high temperature peak at about. However, pure a-Si:H shows only one effusion maxima at 550 °C. The low temperature effusion peaks are directly correlated with steps increases in the sheet resistance measurements. The first one (T=200 °C) is due to the beginning of silicide formation. The H2 evolution at 380 °C is correlated to phase transition in the a-Si:H film. The hydrogen depth profiles obtained by ERDA and SEM observations are also used to describe the aspects of the Cu/a-Si:H interaction.
An Atomistic Study of Surface Vacancy Diffusion
Authors: Zhao L. , Najafabadi R. , Srolovtz D. J.
Published: March 2011

Diffusion of atoms and molecules on surfaces plays an important role in the growth of thin films. In the present study, the surface vacancy diffusion on Cu and Ni (100) and (111) planes is investigated via atomistic simulations. This investigation is performed using the Embedded Atom Method (EAM) interatomic potentials and the finite temperature properties are determined within the local harmonic and quasiharmonic frameworks. This study helps reveal fundamentals of surface vacancy diffusion in the thin film growth. Our results show that the vacancy diffusion is important on (100) surface but it is not the dominant diffusion mechanism on (111) plane.
The Influence of Deposition Pressure on the Incorporation of Target and Ambient Oxygen Into Laser Ablated Material
Authors: Tidrow M. Zhu , Tidrow S.S. , Wilber W.W. , Pfeffer R.R.
Published: March 2011

Oxygen plays an essential role in the growth of a variety of oxides such as high-Tc superconductors, ferroelectrics, ferrites and dielectrics. The oxygen available for film growth during laser ablation can come from two sources: the target material and the ambient deposition atmosphere. The amount of oxygen incorporated from these two sources at room temperature has been investigated over a range of deposition pressures. Thiswas accomplished using 18O as a tracer during pulsed laser deposition of amorphous filmsfrom Cu and CuO targets. It was found that the total amount of oxygen incorporated by the amorphous films increases with chamber pressure up to approximately 35 mTorr. For pulsed laser deposition from the oxide target, the major fraction of the oxygen within the deposited material comes from the target. For the oxide target, the amount of oxygen incorporated from the ambient atmosphere is strongly pressure dependent with a maximum near 35 mTorr. These results are compared to earlier work with YBa2Cu3O7.
Phase Formation in a Wedged Au-Ag-Cu Multilayered Structure
Authors: Goldfarb I. , Zolotoyabko E. , Shechtman D.
Published: March 2011

An advanced method for investigation of multicomponent systems is proposed. Thin wedged-shape films of pure components are subsequently deposited to form a multilayered structure with continuously-varying composition as a function of sample location, providing a large number of differently composed samples in one deposition run. Each sample is then subjected to various heat treatments, and phase content as well as the microstructure formed is under investigation.

In this study an Au-Ag-Cu multilayered structure was sputtered at a room temperature onto 55 Formvar-coated Mo grids. The satellite-like X-Ray Diffraction (XRD) patterns of these samples revealed the formation of an artificial composition-modulated ternary superlattice, complete destruction of which was observed during heat treatments, where phase formation according to the ternary Au-Ag-Cu phase diagram took place.

Several aspects of phase formation were analyzed using XRD, Electron Probe for Micro- Analysis (EPMA) in Scanning Electron Microscopy (SEM), and Scanning Transmission Electron Microscopy (STEM) combined with Selected Area Electron Diffraction (SAED), Digital X-Ray Mapping (DXM), Secondary Electron Mapping and EPMA methods.
Phase Selection During Interdiffusion in Ti-Fe Multilayered Films
Authors: Yan Z.Z. , Trudeau M.M. , Schulz R. , Bormann R. , Neste A.Van , Ström-Olsen J.J.
Published: March 2011

The formation of the metastable bcc solid solution and the amorphous phase during interfacial reaction of elemental multilayers has been studied using X-ray diffraction. Different kinds of interfaces have been synthesized in order to investigate the influence of the interfacial structure on phase evolution during annealing. The amorphization is found to be dependent on the structure of the interface and the results are discussed in terms of the kinetics and thermodynamics of the Ti-Fe system which has been calculated by the CALPHAD method.
Solid State Amorphization in the Interfacial Reactions of Yttrium Thin Films on (111)Si
Authors: Lee T.T. , Chen L.L.
Published: March 2011

Interfacial reactions of ultrahigh vacuum deposited yttrium thin films on atomically clean (111)Si at low temperatures have been studied by both conventional and high resolution transmission electron microscopy, Auger electron spectroscopy and x-ray diffraction. A 10–nm–thick yttrium thin film, deposited onto (lll)Si at room temperature, was found to completely intermix with Si to form an 11–nm–thick amorphous interlayer. Crystalline Y5Si3 and Si were observed to nucleate first within the amorphous interlayer in samples annealed at temperatures lower than 200 °C. Epitaxial YSi2−x was found to be the only phase formed at the interface of amorphous interlayer and crystalline Si in samples annealed at temperatures higher than 250 °C. In as deposited 20– to 60–nm thick Y thin films on silicon samples, crystalline Y5Si3, Si, and YSi and a 2.5–nm–thick amorphous layer were found to be present simultaneously.
Crystallization of Amorphous Germanium in a Silver Germanium Layered System
Authors: Konno Toyohiko J. , Sinclair Robert
Published: March 2011

We studied crystallization of amorphous germanium (a-Ge) induced in a Ag/a-Ge layered system, using in situ transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). Amorphous Ge was found to crystallize at about 270°C with the heat of reaction of 10±lkJ/mol. In situ TEM revealed that Ag grains migrate into the a-Ge phase leaving the crystalline Ge (c-Ge) phase behind. From this observation, we propose a model whereby the Ag provides the fastest path for the Ge atoms to diffuse from a-Ge to c-Ge phases.