bluuebunny/crossref_metadata_2025 huggingface dataset:
Indentation Creep Studies of Cross-linked Glassy Polymer Films
Authors: O'Connor Kevin M. , Cleveland Pamela A.
Published: March 2011

Indentation creep testing was done on cross-linked glassy polymers based on polystyrene, specifically poly(styrene-co-divinylbenzene) (PS-DVB) and poly(divinylbenzene) (PDVB). The continuous depth-sensing capabilities of the Nano-Indenter II were used to measure the time-dependent response to indentation at constant applied load. The raw creep data in terms of indentation depth vs time showed that PDVB was about 20% more resistant to penetration than PS-DVB. A data analysis program was developed that converted the raw data to stress σ and plastic strain rate ε and generated the plastic flow curve that was observed to follow the power law . The stress exponent a for PS-DVB increased with applied loads between 1 and 27 mN and was generally larger in magnitude than the exponent for PDVB. When compared at equivalent stress and indentation depth, the plastic strain rate for PDVB was observed to be about 100 times slower than for PS-DVB. This was attributed to the higher degree of cross-linking increasing the characteristic relaxation time governing creep flow in these polymers.
Elastic Properties of a Polyimide Film Determined by Brillouin Scattering and Mechanical Techniques
Authors: Sai Kumar R. , Schuller Ivan K. , Kumar Sudha S. , Fartash A. , Grimsditch M.
Published: March 2011

We discuss here the complete determination of the elastic properties of a polyimide film using two experimental techniques. One technique employs the polymer film as a vibrating membrane and allows a direct determination of the ’macroscopic’ biaxial modulus. Brillouin scattering, which measures the elastic properties on a ∼ 100 μ scale, allows for a complete characterization of the elastic behavior. The results obtained by the two techniques are in agreement within the reported error bars.
Continuous Microindentation of Passivated Surfaces in Surface Active Media
Authors: Venkataraman Shankar K. , Huang He , Kohlstedt David L. , Gerberich William .W.
Published: March 2011

Continuous microindentation tests on electropolished, single crystal Fe(3wt%Si) and Ni surfaces with thin passivation layers exhibit sharp discontinuities in the load-displacement behavior. At the discontinuity, which occurs at a load of 1.8 mN for Fe(3wt%Si) and 0.1 mN for Ni, stresses below the indenter were close to the theoretical strength of the corresponding metal. Microindentation tests performed to loads less than the discontinuity point showed an elastic load-unload behavior. On removing the passive film with a NaCl or HC1 solution, strengths are one to two orders of magnitude smaller in the presence of the chloride ions. On evaporation of the liquid, the load at the discontinuity returned to its initial value due to repassivation, indicative of a passivation oxide layer with varying thickness. This conclusion was verified by ellipsometry. Even though the elastic load-unload behavior on the passivated surface suggests elastic behavior, both elastic finite element and non-linear, elastic perfectly plastic finite element solutions strongly suggest that this might not be the case. Several suggestions as to the reasons for the deviation from continuum theory are presented.
Mechanical Property Characterisation of Crystalline, Ion Implantation Amorphised and Annealed Relaxed Silicon with Spherical Indenters
Authors: Williams J.S. , Field J.S. , Swain M.V.
Published: March 2011

Silicon single crystals have been ion implanted with Si ions at various energies and doses sufficient to achieve amorphisation to a depth of more than 1μm. This surface was subsequently annealed at 450°C for 30 minutes in vacuum to relax the implanted amorphous silicon. Mechanical properties of the different materials (crystalline, amorphous and annealed) were measured using a nominally 10 μm radius diamond tipped indenter and two indenting procedures; continuous loading and load partial-unloading. The crystalline material exhibited similar force-displacement behaviour to that observed by Weppelmann et al. [1] including a critical pressure to induce deformation on loading and a "pop-out" event during unloading. The amorphous and annealed materials showed a greater degree of plastic deformation but did not exhibit "pop-out" behaviour at lower loads (200 mN). The results are analysed to determine the difference of mean pressure with depth of penetration for all the materials. The onset of ductility was 5.5 to 6 GPa for the amorphous material and 10.9 GPa for the crystalline material. The depth dependence of hardness for the amorphous and annealed material showed substantial evidence of work hardening whereas the crystalline material did not.
Mechanical and Optical Properties of The Films of Tantalum Oxide Deposited by Ion-Assisted Deposition
Authors: Martin PJ. , Bendavid A. , Swain M.V. , Netterfield R.P. , Kinder T.J. , Sainty W.G. , Drage D.
Published: March 2011

Thin films of tantalum oxide 1 μm thick were deposited by oxygen ion-assisted electron-beam evaporation onto silicon and glass substrates. The packing density and optical properties of the films were controlled by the degree of ion assistance during growth. The films were characterized for hardness by ultra-micro indentation measurement and density by RBS. A strong correlation of hardness, and optical properties was found with the ion-to-vapor arrival ratio at the substrate during deposition. Evaporated films without ion assistance were found to be relatively soft with hardness values of 5.3 GPa and 6.5 GPa on glass and silicon respectively when measured with a Berkovich indenter. When the ion bombardment was increased the film hardness increased to a maximum hardness of 10 GPa for 1000 eV O2 ion bombardment. The measured microhardness of the films was found to be influenced by the nature of the substrate for all depositions with higher microhardness values being recorded for films deposited onto silicon. The films were found to be amorphous and homogeneous. Additional ultra-microhardness measurements with a spherical tipped indenter enabled the depth dependence of hardness and modulus to be determined.
Stress of Tio2 Thin Films Produced by Different Deposition Techniques
Authors: Ottermann C. , Otto J. , Jeschkowski U. , Anderson O. , Heming M. , Bange K.
Published: March 2011

Stress in thin films has been measured very precisely (< 10 MPa) by analysing the curvature of quartz glass substrates before and after film deposition by means of a ZYGO Mark IV interferometer system. TiO2 films of approximately 100 nm thickness were prepared by reactive evaporation (RE), reactive ion plating (IP), plasma impulse chemical vapor deposition (PICVD) and spin coating (SC). Large variations in stress are found for different coating techniques and deposition conditions. This can be correlated to differences in optical properties, film density and crystalline structure. Relaxation effects and the influence of thermal treatment are also studied. The crystallization of amorphous TiO2 during heat treatment is accompanied by significant changes in film stress. The crystal size and morphology of TiO2 films after heat treatment strongly depend on the deposition technique and process conditions.
Internal Strains and Relaxations in Lamellar TiAl
Authors: Hazzledine P.M. , Kad B.K. , Mendiratta M.G.
Published: March 2011

In the lamellar form of the ordered intermetallic TiAl, mismatches at the lamellar interfaces, of order 1%, give rise to internal stresses and lo interracial dislocations. The geometry of the microstructure ensures extreme plastic anisotropy. Three main trends are evident in the plastic tensile properties: Both the yield and fracture stresses are low when deformation occurs in the plane of the lamellae and they are high when deformation occurs across the lamellae, the ductility is high when the tensile axis lies close to the lamellar plane and low when the tensile axis is nearly normal to the lamellar plane. The variations of the yield stress and the fracture stress are explained principally by the effects of Schmid factors and anisotropies in the Hall-Petch (or Stroh) stresses resulting from the lamellar shapes. The variation in ductility may be understood in terms of a competition between the ductile propagation of dislocations across interfaces and the creation of Stroh cracks at the heads of dislocation pile-ups.
Formation and Transformation of Amorphous Silicide Alloys
Authors: Tu K.N. , Tien T. , Herd S.R.
Published: March 2011

Amorphous silicide films can be formed by rapid quenching using techniques of vapor deposition and ion beam mixing and also by slow heating using solid state interdiffusion and reaction. For example, amorphous TaSi2 films can be formed by sputtering or dual electron guns co-deposition. Amorphous Pt2Si3 films have been produced by mixing PtSi and Si at room temperature with an ion beam at about 100 to 300keV. Recently, an amorphous Rh-Si alloy phase has been made by slowly heating to 300°C a very thin crystalline Rh films (∼50Å) on amorphous Si. The formation and crystallization behavior of these amorphous silicide alloys has been studied by transmission electron microscopy and electrical conductivity measurement.
Microdiffraction Studies of Small Gold Metallic Particles
Authors: Jose-Yacaman Miguel , Gomez Alfredo , Truszkowska Krystyna
Published: March 2011

The crystalline structure of small gold particles in the size range between 50–200 Å is studied using STEM in microdiffraction.

It is found that some single-crystalline particles showed an anomalous diffraction pattern. In some cases these pattern be indexed as an hexagonal lattice with a ratio c/a= 2.46. A number of models to explain the hexagonal diffraction are discussed. In some other cases the patterns correspond to fcc structures but with a large splitting effect. The results reveal the strong dynamical character of the diffraction by small gold particles.
The Structure of Grain Boundaries and Phase Boundaries in Ceramics
Authors: Carter C. B.
Published: March 2011

The structure of different grain boundaries and phase boundaries are discussed by reference to a series of specific examples. The chosen examples of grain boundaries include the {l10} tilt boundary, the (001) twist boundary and the first-order twin boundary in spinel and the basal twin and the (1123) twin in Al2O3. The phase boundaries discussed are the β'''-alumina/spinel interface, the wustite/spinel interface and the spinel/alumina interface. It is shown that these interfaces do have properties which result specifically from the ionic nature of the material and the large unit cells involved in each case.
Tem of Dislocations in Sapphire (α−Al2O3)
Authors: Lagerlöf K.P.D. , Mitchell T.E. , Heuer A.H.
Published: March 2011

Dissociation of both basal and prism plane dislocations in sapphire,α−Al2O3,is common and the partial dislocations can be imaged using conventional transmission electron microscopy and weak beam dark field imaging techniques. At elevated temperatures the dissociation takes place by conservative self-climb, a process involving short range diffusion, whereas at low temperatures the dissociation can occur by glide. Dissociation of a dislocation can in some situations give rise to very strong contrast when using g vectors for which g→.b→=0 for the undissociated dislocation. Those contrast conditions can be used to obtain information about the dislocation morphology and the stacking fault energy of the fault plane through determination of the separation distance.
High Resolution Tem Studies of β-Alumina Type Structures
Authors: Morrissey K. J. , Elgat Z. , Kouh Y. , Carter C. B.
Published: March 2011

High resolution transmission electron microscopy (HRTEM) has been used to study structures found in secondphase particles in commercial alumina compacts. Analytical electron microscopy has been used to identify elements present in the particles. Computer image simulation has been used for both the structural interpretation of high resolution images and predicting the effect which the presence of other elements would have on the observed structures.
The γ→α Phase Transformation in Al2O3
Authors: Tucker D. S. , Hren J. J.
Published: March 2011

The primary objective of this research was to deduce the mechanisms of the γ to α transformation of Al2O3. The specimens studied were from spherical powder precipitated from sulfate solutions and thin films prepared by low temperature oxidation of Al. The primary experimental technique employed was the transmission electron microscope. Since alumina is so important commercially, there is a body of literature on both the mechanism and kinetics of the transformation. A brief review of the most relevant publications is thus essential.
Ordered Defect-Fluorite Compounds in ZrO2 Alloys
Authors: Farmer S. , Hangas J. , Lanteri V. , Mitchell T.E. , Heuer A.H.
Published: March 2011

Intermediate ordered-defect fluorite compounds are an important component of ZrO2 alloys containing the aliovalent solutes MgO, CaO, or Y2O3. These compounds also form in oxygen-deficient rare earth oxides and in other ternary oxides based on the fluorite structure, and can best be studied by TEM. Examples are given of such phases in the MgO-ZrO2, Y2O3-ZrO2, and CaO-ZrO2 systems.
Energy Release Due to Domain Formation in the Strained Epitaxy of Multivariant Films
Authors: Pompe W. , Gong X. , Suo Z. , Speck J.S.
Published: March 2011

Twin related domain formation is examined as a strain relaxation mechanism for a heteroepitaxial tetragonal film on a cubic substrate. Elastic relaxations are calculated for a single twin band in which the c-axis of the tetragonal domains is either related by a 90* rotation about an axis in the plane of the film or by a 90* rotation about the surface normal. In all cases, the strain energy change is evaluated for both the film and the substrate. A domain pattern map is developed that predicts single domain and multiple domain fields depending on the relative misfit strains and domain wall energy. The concept of a critical thickness, hc, for domain formation is developed. For cases in which the c-axis is rotated 90* about an axis in the plane of the film, the critical thickness depends only on the relative coherency strain between the substrate and film and the ratio of the domain wall energy to the stored elastic energy. For the case of a pattern consisting of energetically equivalent domains with the c-axis in plane, the equilibrium distance of multiple domains is derived. For such multiple domains, a minimum wall separation distance exists which depends non-linearly on the film thickness.
Physicochemical and Microstructural Characterization of Rf Sputtering Magnetron Pb(ZrTi)O3 Thin Films
Authors: Varniere F. , Caytan E. , Eakim B. , Achard H. , Agius B.
Published: March 2011

Lead zirconate titanate thin films were deposited on Pt/TiN/BPSG/Si structures by sputtering an oxide target of nominal composition (Pb(Zr0.55,Ti0.45)O3 or PZT) in argon plasma. The PZT films were deposited at different pressures and different substrate temperatures ranging from floating temperature to 400°; the thicknesses of the sputtered films were in the 15-720 nm range. The absolute and relative cation and oxygen compositions of the thin films were determined by a new method based on the simultaneous use of Rutherford Backscattering Spectroscopy (RBS) and Nuclear Reaction Analysis (NRA) induced by a deuteron beam. The total deposition rate and atomic ones are observed as a function of the substrate temperature and pressure. Therefore the dependence of fil composition on pressure and substrate temperature is discussed.

Post-deposition annealing studies and ferroelectric properties are presented. The values of the remanent polarization, Pr, were in the range 5-7 µC/cm2, the coercitive field, Ec, between 15 and 25 kV/cm and the dielectric constant, µr, evaluated from capacitance measurements around 1200, depending on the process parameters.
Imaging of Ferroelectric Domains in KTiOPO4 Single Crystals by Synchrotron X-RAY Topography
Authors: Wang S. , Dudley M. , Cheng L.K. , Bierlein J.D. , Bindloss W.
Published: March 2011

The application of synchrotron white beam X-ray topography to the study of ferroelectric domain structures in hydrothermally grown potassium titanyl phosphate (KTiOPO4: KTP) single crystals is reported. The domain walls can be exclusively imaged on topographs with selected diffraction vectors and X-ray wavelengths, while images of other defects, such as dislocations, inclusions and surface scratches, can be simultaneously made very diffuse. The topographic images correspond well with electrostatic toning images. X-ray topography readily reveals the three dimensional shapes of the domain walls. There are two contributions to domain wall contrast: one is fringe-like which can be interpreted in terms of the dynamical theory of X-ray diffraction, and the other is diffuse strain contrast arising from long range strain associated with the wall. These two contributions can be observed simultaneously or separately depending on the diffraction conditions. The long range strain is thought to be associated with the curvature of the domain walls. It appears that the main components of the displacement field associated with this strain are directed approximately perpendicular to the domain wall.
Study of Pbtio2 Formation Kinetics by an In-Situ Stress Measurement Technique
Authors: Li Chen C. , Desu Seshu B.
Published: March 2011

The primary objective of this study is to demonstrate an in–situ stress measurement technique for the study of formation kinetics of multicomponent thin films such as PbTiO3. Film stress–temperature and film stress–time plots have been successfully used to monitor the phase formation of PbTiO3 films in a in–situ way. It is believed that the mechanism of this reaction was dominated by grain boundary diffusion of the participating cations. The activation energy of the PbTiO3 phase formation from PbO/TiO2 double layers was estimated to be 108 kcal/mole.
Sputtering of Lead-Based Ferroelectrics
Authors: Iijima K. , Nagao N. , Takeuchi T. , Ueda I. , Tomita Y. , Takayama R.
Published: March 2011

PbTiO3(PT), Pb1-xLaxTi1-x/4O3(PLT) and PbZrxTi1-xO3(PZT) thin films were prepared by rf magnetron sputtering. It was found that the thin films have remarkably large pyroelectric effect and high figures of merit for infrared sensors without poling treatment. High performance pyroelectric infrared sensors (single element and linear array) were fabricated by using the PLT(x=0.1) thin films with the new structures and the device process. This type of sensor is carried on the air conditioner to detect a thermal environment. The PZT thin films with x=0.9 showed a large remanent polarization of 46μC/cm2 and small coercive force of 28kV/cm. In addition, good endurance behavior (no degradation of Pr after 1011 cycles) was observed. Recent activities of ferroelectric thin film research in Japan is also reported.
Fiber Optic Phase and Polarization Modulator Utilizing a Transparent Piezofilm with Indium Tin Oxide Coating
Authors: Sudarshanam V.S. , Desu S. B. , Claus R.O.
Published: March 2011

A fiber optic phase and polarization modulator is presented in which a thin transparent piezoelectric polyvinylidene fluoride film with indium tin oxide electrode metallization is placed directly in the path of the output of a single mode fiber. Experimental characterization is presented in terms of the linearity of response, phase shifting coefficient, and frequency response for two arrangements differing in the boundary clamping conditions. Many applications to fiber optic switches, intensity modulators and demultiplexers are indicated.
Ti-Ni Phase Diagram with Applied Stress
Authors: Jardine A.Peter
Published: March 2011

The role of stress on the phase evolution of thin-film TiNi has not been investigated and may play an important role in the phase evolution of thin film TiNi. In this paper, a preliminary set of phase diagrams for Ni-Ti at different pressures are presented relating the stability of the stoichiometric TiNi phase to the other well-documented intermetallics TiNi3 and NiTi2. It is found that for sufficient pressure of the order of a GPa, the region where NiTi (β) phase is single phase shifts towards the Ti-rich side of the diagram. The implications on the annealing of TiNi thin film is discussed.
Effect of Internal Stresses on Thermodynamics of Heterophase Structures in Epitaxial Layers
Authors: Roytburd Alexander L.
Published: March 2011

The effect of the elastic energy of internal stresses in a system of coherent phases within an epitaxial layer is considered. The equilibrium two-phase layer has a transversely modulated structure with a modulation period dependent on the layer thickness. The phase diagrams for the phases in an epitaxial layer can differ qualitatively from standard phase diagrams, and this difference also depends on the layer thickness.
Transmission Electron Microscopy Study of CoPt(001) and FePt(001) Films Formed from Epitaxial Co/Pt and Fe/Pt Multilayers
Authors: Visokay MR.M. , Lairson BM.B. , Clemens B.B. , Sinclair R.
Published: March 2011

Transmission electron microscopy was performed on epitaxial Fe/Pt and Co/Pt [001] oriented multilayers that were sputter deposited onto single crystal [001] MgO. Films were examined as-deposited and after annealing in vacuum. Before annealing, the films had a magnetic easy axis in the plane while after annealing the easy axis was out of the plane. Perpendicular anisotropies of 8× 106 erg/cm3 and 1.9x 107 erg/cm3 were measured for the Fe/Pt and Co/Pt post-annealed films. Large magneto-optic Kerr rotations were also measured, 0.6° and 0.4° for the Fe/Pt and Co/Pt annealed films, respectively. Changes in the magnetic properties were a direct result of the transformation of the multilayer into c axis oriented FePt and CoPt intermetallic compounds upon annealing.
Atomic Transport in Irradiated Solids
Authors: Averback R.R. , Ghaly Mai , Lee Y.Y. , Zhu H.
Published: March 2011

Atomic transport in irradiated solids has been investigated in both the prompt and delayed regimes. Prompt effects are revealed on an atomic level through molecular dynamics computer simulations. It is demonstrated that for metals like gold, which have high atomic numbers and low melting points, thermal spikes play a primary role in the cascade dynamics and that concepts like melting and rapid quenching are useful descriptions. Surface effects in these metals are also discussed. For metals with higher melting points and lower atomic numbers, the cascade dynamics are determined almost exclusively by energetic collisions far above thermal energies. This is illustrated by simulations of cascades in NiAl. The effect of the high ordering energy in this intermetallic compound on the radiation-induced defect structure has also been studied.

Atomic transport in the delayed regime is illustrated by two examples: an order-disorder alloy, Cu3Au, and an amorphous alloy, NiZr. The first example is used to illustrate various aspects of radiation enhanced diffusion (RED): ion beam mixing, diffusion kinetics, the effects of primary recoil spectrum, and the importance of chemical order. The second example illustrates that the basic theory of RED, which was developed to describe crystalline materials, appears to work adequately for amorphous metal alloys, suggesting that similar mechanisms may be operating. It is shown, however, that the kinetics of RED observed in amorphous alloys are not unique to point defect models.
Phase Transition and Formation of TiSi2 Codeposited on Atomically Clean Si(111).
Authors: Jeon Hyeongtag , Cho Y. S. , Kang E. Y. , Park J. W. , Nemanich R.R.
Published: March 2011

In this study, the phase transformation and the surface and interface morphologies of TiSi2 formed on atomically clean Si substrates are investigated. 200Å Ti and 400A Si films on Si(111) have been co-deposited at elevated temperatures (400°C - 800°C) in ultrahigh vacuum. The phase transition of TiSi2 is characterized with using XRD. The results distinguish the formation of the C49 and C54 crystalline titanium silicides. The surface and interface morphologies of titanium silicides have been examined with SEM and TEM. A relatively smooth surface is observed for the C49 phase while a rough surface and interface are observed for the C54 phase. The islanding of the C54 phase becomes severe at high temperature (800°C). Islands of TiSi2 have been observed at temperatures above 700°C but no islands are observed at temperatures below 600°C. For films deposited at 400TC and 500°C, weak XRD peaks corresponding to TiSi were observed and TEM micrographs exhibited small crystalline regions of titanium silicide at the interface.
Contact Reactions at Cu / a-Ge Thin Film Couples
Authors: KÖster Uwe , Blennemann Klaus P. , Schulte Axel
Published: March 2011

The aim of this paper is to investigate phase formation and growth kinetics in thin film Cu/a-Ge difflusion couples (150 nm Cu / 150 nm Ge) by means of cross-sectional transmission electron microscopy. During annealing in the temperature range between 100 and 180°C a highly supersaturated ζ-phase was formed first; the growth of this phase exhibits a parabolic dependence, thus indicating diffusion controlled growth; further annealing leads to a transformation into the orthorhombic ε1-phase. The first phase formed during the contact reaction probably depends on the texture and orientation of the copper layer with (111) Cu favouring the formation of the ζ-phase. When in contact with crystalline Ge the orthorhombic ε1-phase is formed directly, probably caused by a lack of driving force for the formation of the ζ-phase.

Crystallization of Cu-contaminated amorphous Ge is characterized by the formation of an extremely fine-grained microstructure; higher Cu contents lead to primary crystallization of the ε1-phase (orthorhombic Cu3Ge) followed by polymorphous crystallization of the amorphous matrix into crystalline Ge. These results indicate that the early formation of a crystalline interlayer is not due to the reduced crystallization temperature of an amorphous Ge(Cu) film as formed by Cu diffusion into the amorphous Ge.
Sputter Deposition and Thermally Induced Phase Transformation of Non-BCC Chromium Thin Films
Authors: O'Keefe M. J. , Horiuchi S. , Chu J.J. , Rigsbee J.J.
Published: March 2011

The crystal structure of sputter deposited chromium thin films on Coming 7059 glass, polytetrafluoroethylene, and cold rolled (110) oriented low carbon steel α-Fe substrates was investigated as a function of O and C incorporation into the growing Cr film. The as-deposited crystal structure of the films was found by X-ray diffraction to be either highly oriented (110) BCC α-Cr or (200) oriented A-15 δ-Cr. Chemical analysis of the films by Auger electron spectroscopy determined that the δ-Cr phaseformed when the combined O and C impurity concentration in the film was ∼15-30 at.%. At total impurity concentrations above ∼30 at.% or below ∼10 at.% standard BCC α-Cr formed. The crystal structure of the films was not influenced by the substrate material. X-ray photoelectron spectroscopy of the Cr 2pl/2-2p3/2 orbitals indicated that the dominate binding state of both the BCC α-Cr and A-15 δ-Cr films was characteristic of elemental Cr. Vacuum annealing of the A-15 δ-Cr films at 500º for one hour transformed the crystal structure into BCC α-Cr without a measurable change in chemical composition. The incorporation of O and C into the growing Cr film is believed to impurity stabilize the A-15 structure and favor its formation over the BCC structure.
Surface Modifications on Charge-Transfer Complexes Using Scanning Probe Microscopy
Authors: Yamaguchi Shoji , Valenzuela Carlos A. , Potember Richard S.
Published: March 2011

We are exploring high density information storage systems based on organometallic materials. Silver and copper salts of tetracyanoquinodimethane (TCNQ) and its derivatives exhibit an electrical and optical field induced reversible switching phenomenon. We have demonstrated a field-induced, charge-transfer reaction driven by the electric field at the STM tip when the field generated by the STM exceeds the switching threshold of the organic charge-transfer complex. The phase transition induced by the STM tip appears as nanometer-sized domains on the metal-TCNQ and derivatives surface. We also have shown this phase transition occur by means of optical laser irradiation. This paper discusses our plans to combine our research results in optical switching with the scanning near-field optical microscope (NSOM) to develop a very high density optical memory system. In order toassess the feasibility of this, we performed a series of experiments aimed at determining the limitations of information storage using this class of organic charge transfer complexes.
Anisotropic Surface Roughness in Strain Relaxed In0.40GA0.60As on Gaas with a Step-Graded InxGA1-xAs Buffer Layer
Authors: Chang J. C. P. , Kad B. K. , Nutt S. R. , Kavanagh K. L.
Published: March 2011

We report the structural characterization of the 3-D relaxation morphology of In0.4Ga0.6As grown on a step-graded InxGa1-xAs buffer layer on GaAs. Scanning electron microscopy showed “grooves” spaced on the order of microns running only in the [110] direction. Each groove was observed with cross-sectional transmission electron microscopy to mark the location of a vertical low-angle tilt and/or twist boundary. The veiy rough layer morphology may be the result of island coalescence or severe surface roughness that created the grain boudnaries as the layer grew. Strain relaxation in the In0.4Ga0.6As layer was much reduced in the [101] in-plane direction. The asymmetry in residual in-plane strains in the In0.3Ga0.7AS layer and/or the increased In composition may be responsible for the development of an anisotropic surface roughness. X-ray microanalysis revealed a periodic variation in layer composition which correlated with a fine contrast modulation presumably the result of phase segregation.
Segregation and Interdiffusion of in Atoms in GaAs/InAs/GaAs Heterostructures
Authors: Kawai T. , Yonezu H. , Ogasawara Y. , Saito D. , Pak K.
Published: March 2011

The segregation and interdiffusion of In atoms in the GaAs/InAs/GaAs heterostructures were investigated by secondary ion mass spectroscopy. When the 1 ML thick InAs layer was grown in a layer-by-layer growth mode with no dislocations, the segregation of In atoms became marked with the increase of the growth temperature. However, the segregation was observed even at relatively low growth temperature of 400°C in molecular beam epitaxy. It was found that the segregation was markedly enhanced by dislocations near the heterointerface when the thick InAs layers were grown in a three-dimensional island growth mode. The interdiffusion of In atoms toward the growth direction occurred after thermal annealing, which could be assisted by vacancies propagating from the film surface into epilayer. It became apparent that the interdiffusion was effectively suppressed by a thin AlAs layer inserted in the GaAs cap layer.
Measurement of the Lateral Periodicity of a Quantum Dot Array by Triple Crystal Diffractometry
Authors: Jenichen B. , Ploog K. , Brandt O.
Published: March 2011

The lateral periodicity of an InAs quantum dot array in a GaAs matrix is measured in the differential rocking curve by triple crystal diffractometry. The quantum dot array was grown by molecular beam epitaxy of submonolayer InAs films on a terraced (001) GaAs substrate. The x-ray diffraction of the array is described in the limits of the kinematical theory. Both the changes in the scattering factor and the tetragonal deformations due to the InAs quantum dots are taken into account. The lateral periodicity of the array along [100] is 8–11nm dependent on the position of the measured region compared with an average of 10nm obtained from the miscut of the sample. In addition the vertical periodicity of the array is measured by comparison of the double crystal rocking curve with the corresponding simulation in the dynamical approximation. The vertical period of the array along [001] is 26.5nm. The coverage of the submonolayer InAs films estimated from the same measurement is 0.4. The absence of plastic relaxation is confirmed by x-ray topography.
Change of Arsenic Coverage on GaAs(001)
Authors: Nörenberg Holger , Koguchi Nobuyuki
Published: March 2011

(2×4) and c(4×4) reconstructed GaAs(001) surfaces prepared by Molecular Beam Epitaxy (MBE) were studied by Reflection High Energy Electron Diffraction (RHEED). A method for accurate determination of the Arsenic coverage of reconstructed GaAs(001) surfaces is introduced. The time of Gallium supply to the reconstructed surface until a halo appears in the RHEED pattern is taken as measure for the Arsenic coverage. Structures between them were investigated at a substrate temperature of 200°C. The RHEED results were verified by High Resolution Scanning Electron Microscopy (HRSEM). Dependent on the surface reconstruction, Arsenic coverages between 0.76 and 1.22 monolayer (ML) were observed. Surface structures, observed during transformation between β(2×4) and c(4×4) will be discussed.
The Epitaxial Growth of Ge on Si(100) Using Te as a Surfactant
Authors: Yango X. , Cao R. , Li J. , Terry J. , Wu J. , Pianetta P.
Published: March 2011

The epitaxial growth of Ge on Si using Te as a surfactant has been studied with high resolution photoemission, low energy electron diffraction and cross-sectional transmission electron microscopy. The growth mode of Ge on Si changed from Stranski-Krastanov (S-K) to layer-by-layer mode when 1/4 ML Te atoms were on the surface. During the growth, Te atoms segregated to the top of the surface. If the growth temperature is too high (above ∼450°C), the Te coverage was less than that necessary to keep the layer-by-layer growth, and the growth mode of Ge on Si is still S-K.
Dynamics of Periodic Step-Bunching During Growth on Vicinal GaAs(110) Surfaces: Computer Simulations and Experiments
Authors: Krishnamurthy Mohan , Williams D. R. M. , Petroff P. M.
Published: March 2011

Molecular beam epitaxial growth on GaAs(110) vicinal surfaces results in the formation of periodic micro-facets. We compare experimental results with computer simulations of a simple one dimensional step-flow growth model. The simulations show that preferential adatom attachment to the down step in a step array results in the destruction of step uniformity. A kinetic limitation due to adatom diffusion length along the terraces leads to stabilization of a periodic array of step-bunches. We extend our simulations to show the effects of the attachment and diffusion parameters on the dynamics of facet evolution.
Compositional Ordering in Semiconductor Alloys
Authors: Stringfellow G. B.
Published: March 2011

Compositional ordering has been observed in a wide variety of III/V semiconductor alloys as well as in SiGe alloys. The thermodynamic driving force is now understood in terms of minimization of the microscopic strain energy of the bonds in the solid. However, the mechanism leading to the specific ordered structures formed is only now beginning to be understood. It appears to be intimately related to the physical processes occurring on the surface during epitaxial growth, specifically surface reconstruction and the attachment of atoms at steps and kinks. Thus, an improved understanding the ordering process may lead to a better understanding of the surface processes occurring during epitaxial growth from the vapor.

This paper will review the current understanding of the ordering process, including discussions of the arrangement of atoms on the surface and the nature of surface steps. The emphasis will be on the use of patterned surfaces to investigate and control the ordered structures formed during organometallic vapor phase epitaxial growth of GaInP. Using photolithography and chemical etching, [110]-oriented steps are formed on the (001) GaAs substrate. The direction of motion of these steps determines the specific variant of the Cu-Pt ordered structure (with ordering on (111) planes) formed. The step density at the edge of the groove apparently determines the degree of order. Highly stepped surfaces suppress ordering or lead to small domains of a single variant. When the steps are very shallow, the large domain of the predominant variant is filled with “inclusions” of the second variant. Step edges that are oriented at nearly 160 from (001) form a {511} variant during growth. This facet is observed to grow at the expense of adjacent (001) surfaces and to produce material that is completely disordered.

Growing on intentionally misoriented substrates leads to interesting structures consisting of both large, highly-ordered domains and disordered material. This allows, using cathodoluminescence(CL) imaging, a direct determination of the effect of ordering on the energy band gap. In the GaInP samples studied, the CL images show that the disordered material has a distinct emission pattern consisting of a single, sharp peak at an energy more than 100 meV higher than that observed in the adjacent ordered region.
Microanalysis of a Copper-to-Graphite Solder Bond
Authors: Intrater James B.
Published: March 2011

SEM, x-ray microprobe and EDS analysis was performed on a uniquely prepared joint of graphite soldered to copper with 60Sn-40Pb. The presented data shows a segregation of chromium out from the metallization paste to the graphite/solder interface. Dot maps of the other elemental species were also generated.
Low temperature photoluminescence from GaAs impinged by mass-separated low-energy C+ ion beams during molecular beam epitaxy
Authors: Iida Tsutomu , Makita Yunosuke , Winter Stefan , Kimura Shinji , Tsai Yushin , Kawasumi Yoko , Fons Paul , Yamada Akimasa , Shibata Hajime , Obara Akira , Niki Shigeru , Uekusa Shin-ichiro , Tsukamoto Takeyo
Published: March 2011

C-doped GaAs films were prepared by novely a developed, combined ion beam and molecular beam method (CIBMBE) as a function of hyperthermal (30–500 eV) energies (EC+) of carbon ion (C+) beam. Ion beams of a fixed beam current density were impinged during molecular beam epitaxy growth of GaAs at substrate temperature of 550 °C. Low temperature (2 K) photoluminescence (PL) has been used to characterize the samples together with Hall effects measurements at room temperature. Through the spectral evolution of an emission denoted by [g-g]β which is a specific emission relevant to acceptor-acceptor pairs, the activation rate was confirmed to increase with increasing EC+ for EC+ lower than 170 eV. It was explicitly demonstrated that the most effective Ec+ to establish highest activation rate is located at ~170 eV. This growing activation rate was suggested to be attributed to the enhanced migration of both impinged C and host constituent atoms with increasing EC+. This surmise was supported also by Hall effect measurements which revealed the maximum net hole concentration ( |NA-ND| ) for EC+=170 eV. For EC+ higher than ~170 eV, increasing EC+ was found to induce the reduction of activation rate. It was suggested that this observation is ascribed not to the formation of C donors but to the enhanced sputtering effect of impinged C+ ions with increasing EC+.
Ultrathin Low Energy Simox for Low Cost, High Density Applications
Authors: Namavar Fereydoon , Kalkhoran N.M. , Cremins A.
Published: March 2011

Silicon-on-insulator (SOI) materials made by standard energy (150 to 200 keV) separation by implantation of oxygen (SIMOX) processes have shown great promise for meeting the needs of radiation-hard microelectronics. Since much smaller doses are required, low energy SIMOX (LES) reduces cost, improves radiation hardness, and increases the throughput of any ion implanter. The process can also produce high quality thin SIMOX structures that are of particular interest for fully depleted and submicron device structures. In this paper, we address the formation as well as the material and electrical characterization of LES wafers and compare them with standard SIMOX wafers.
Application of Ion-Plasma-Electron Technological Source T A M E K for Modification of Materials
Authors: Tolopa Alexander M.
Published: March 2011

The same vacuum arc TAMEK source in pulse mode can generate a wide aperture S=300...2000 cm^2 ion flow of any hard electroconductive materials (metal or composites type -Tic, TiSiC, NiCrAlY, MoS, TiMoSi, WA1B, TІBNІ) both for ion implantation (Ei<200 keV, dDi=10^16 ion/cm^2/min) and for deposition dh=50...200 nm/min of the same ions. TAMEK design principle is to provide realization of ion implantation, deposition, mixing or ion beam assisted deposition of the same ions without switching off the source. TAMEK is able to create a mutual mixed (10×90 at.%) alloyed layer up to 3 μm for time in t=15 min, with structure improving (microhardness) of inner layer up to 50 μm in depth. This report presents a review of application of TAMEK source for improving the properties of surface layers of tools, construction materials, electrical contacts and electrodes, glass and other dielectric materials.
Slight Radiation Damage in Silicon for Si-Based Device Processing
Authors: Harnau A. , Schreiber H.-U.
Published: March 2011

Utilization of radiation damage by means of ion implantation to reduce parasitic capacitances in GaAs integrated circuits has become a well-established technique in the last years. Similar to GaAs, novel high-speed silicon-based devices, e.g. the Si/SiGe heterojunction bipolar transistor, are generally marked by additional short time annealing related to doping activation and a metallization annealing step in the range of 400 °C .

For reproducing the external base region of such devices, Si-p+nn+ diodes were realized and investigated using I-V and C-V measurements. Slight radiation damage was achieved by Ne-implantation. Apart from enhanced leakage currents due to space charge recombination, capacitance reduction for frequencies above 50 kHz was observed even for a n-layer doping concentration as high as 1 to 2x1017 cm-3 including a 12 min 400 °C annealing step. Preliminary tests with 250 keV-Ne-ions within a dose range between 1013 and 1014 cm-2 were carried out with Schottky diodes on moderately doped n-type Si-substrate (0.3 Ωcm). For a high temperature furnace anneal at 900 °C (2 min), no capacitance reduction could be observed.

Compared to previous results with Ar-implantation to obtain amorphized silicon layers, this technique allows a more easy technological handling concerning the metallization and the use of a simple photoresist pattern.
Point defect Production, Geometry and Stability in Silicon: a Molecular Dynamics Simulation Study
Authors: Caturla M.-J. , De La Rubia T. Diaz , Gilmer G.H.
Published: March 2011

We present results of molecular dynamics computer simulation studies of the threshold energy for point defect production in silicon. We employ computational cells with 8000 atoms at ambient temperature of 10 K that interact via the Stillinger-Weber potential. Our simulations address the orientation dependence of the defect production threshold as well as the structure and stability of the resulting vacancy-interstitial pairs. Near the <111> directions, a vacancy-tetrahedral-interstitial pair is produced for 25 eV recoils. However, at 30 eV recoil energy, the resulting interstitial is found to be the <110> split dumbbell configuration. This Frenkel pair configuration is lower in energy than the former by 1.2 eV. Moreover, upon warming of the sample from 10 K the tetrahedral interstitial converts to a <110> split before finally recombining with the vacancy. Along <100> directions, a vacancy-<110> split interstitial configuration is found at the threshold energy of 22 eV. Near <110> directions, a wide variety of closed replacement chains are found to occur for recoil energies up to 45 eV. At 45 eV, the low energy vacancy-<110> split configuration is found. At 300 K, the results are similar. We provide details on the atomic structure and relaxations near these defects as well as on their mobilities.
Ion Implantation Damage and Annealing in GaSb
Authors: Iyer S. , Parakkat R. , Patnaik B. , Parikh N. , Hegde S.
Published: March 2011

Ion implantation technique is being investigated as an alternate technique for doping GaSb. Hence an understanding of the production and removal of the damage is essential. In this paper, we report on the damages produced by implantation of Te, Er, Hg and Pb ions into undoped (100) GaSb single crystals and their recovery by Rutherford backscattering (RBS)/channeling. The implantations of 1013 to 1013 ions/cm2 in GaSb were done at liquid nitrogen temperature at energies corresponding to the same projected range of 447Å. A comparison of the damage produced by the different ions and their recovery was made by RBS/channeling along <100> axis of GaSb. Near surface damage equivalent to that of an amorphous layer was observed even at lower doses. Upon annealing at 600°C for 30 sec., the Te implanted samples showed best recovery compared to others (Xmin = 11%), the value of Xmin being better than those normally observed in unimplanted Te-doped substrates.
Suppression of Thermal Grain Growth in Nickel by Prior Electron Irradiation
Authors: Gao Yuzun , Allen Charles W. , Bitrtcher R. C.
Published: March 2011

An anomalous effect of electron irradiation on thermal grain growth in Ni has been observed using in situ TEM. Grain growth during thermal annealing was suppressed in areas irradiated with electrons. Grain growth suppression required a minimum electron energy between 100 and 200 keV. This alteration of thermal grain growth is attributed to electron beam injection of a surface contaminant such as carbon. This work points out that care must be exercised in the execution and evaluation of in situ TEM or ion beam experiments that deal with microstructural changes which are highly compositionally sensitive.
A Critical Regime for Amorphization of Ion Implanted Silicon
Authors: Goldberg R. D. , Williams J. S. , Elliman R. G.
Published: March 2011

A critical regime has been identified for ion implanted silicon where only slight changes in temperature can dramatically affect the levels of residual damage. In this regime decreases of only 5° C are sufficient to induce a crystalline-to-amorphous transformation in material which only exhibited the build-up of extended defects at higher temperatures. Traditional models of damage accumulation and amorphization have proven inapplicable to this regime which exists whenever dynamic defect annealing and damage production are closely balanced. Irradiating ion flux, mass and fluence have all been shown to influence the temperature— which varies over a range of 300° C for ion species ranging from C to Xe—at which the anomalous behaviour occurs. The influence of ion fluence suggests that complex defect accumulation plays an important role in amorphization. Results are presented which further suggest that the process is nucleation limited in this critical regime.
Modulation Wavelength Dependence of Ion Mdong in Metallic Superlattices
Authors: Alexander Dale E. , Fullerton Eric E. , Baldo P.M. , Sowers C.H. , Rehn L. E.
Published: March 2011

Ion mixing was studied in polycrystalline Nb/V and single-crystal Mo/V superlattices and in bilayers of the same materials. Systematic variation in the modulation wavelength, Λ, revealed a factor of three decrease in mixing efficiency at small Λ for Nb/V. The decrease appears to coincide with a structural transition in which the Nb/V superlattices become coherent. The results are consistent with a diffusion-induced grain boundary migration interpretation of mixing during irradiation.