bluuebunny/crossref_metadata_2025 huggingface dataset:
The Application of Laser Annealing to the Fabrication of Impatt
Diode Structures
Authors: Adams Anthony E , Hing L A
Published: March 2011

The conventional method for fabricating silicon IMPATT diode structures
involves the epitaxial growth of successive n- and p-type layers onto a
n+ substrate followed by a boron diffusion to form the final
p+ layer. The high temperature time cycles experienced by the
structure during these processes cause junction interfaces to become
degraded through dopant diffusion. In this paper we examine the application
of laser processing techniques to the epitaxial regrowth of low temperature
deposited layers and report on the nature of the recrystallised
material.
Disorder Production at Metal-Silicon Interfaces by MeV/amu Ion
Irradiation
Authors: Headrick F. L. , Seiberling L. E.
Published: March 2011

We have shown that irradiation of Ag-Si and Au-Si interfaces by 14 MeV 016
ions can produce non-registered silicon at the metal-silicon interface.
Evidence that this effect is due to electronic energy loss of the bombarding
ion is presented. The possible relationship of this effect to MeV-ion
enhanced adhesion is discussed.
Si-On-Insulator Formation Using a Line-Source Electron
Beam
Authors: Knapp J.A.
Published: March 2011

A line-source electron beam has been used to melt and recrystallize isolated
Si layers to form Si-on-Insulator structures, and the processis simulated by
heat flow calculations. Using sample sweep speeds of 100-600 cm/s and peak
power densities up to 75 kW/cm2 in the 1 × 20 mm beam, we have
obtained single-crystal areas as large as 50 × 350 μIm. Seed openings to the
substrate are used to control the orientation of the regrowth and the heat
flow in the recrystallizing film. A finite-element heat flow code has been
developed which correctly simulates the experimental results and which
allows the calculation of untried sample configurations.
Thermal Profiles in Silicon-On-Insulator (Sod Material
Recrystallized With Scanning Light Line Sources
Authors: Kubota Katsuhiko , Hunt Charles E. , Frey Jeffrey
Published: March 2011

A two dimensional solution of the classical heat equation is obtained and
used to predict thermal profiles during line source zone melting
recrystallization of silicon on insulators. A macroscopic solidification
model is used to find the extent of the molten zone in multilayered
structures. The problems of convergence associated with moving phase
boundaries are reduced by using transformed temperature and the enthalpy
model The resultant isotherms, obtained at varying zone scan speeds,
indicate optimum experimental conditions.
Two-Step Laser Recrystallization of Silicon Stripes in
Sio2 Grooves for Crystallographic Orientation
Control
Authors: Egami K. , Kimura M. , Hamaguchi T. , Endo N.
Published: March 2011

We demonstrate a new two step laser recrystallization for crystallographic
orientation control. In the cw Ar ion laser recrystallization of silicon
stripes in the structure consisting of SiO2
grooves/polycrystalline Si sublayer/backing substrates, first, one edge of
poly-Si stripes is intentionally recrystallized under relatively low laser
power and a long dwell time in order to form a strong <100> texture
with lamellar grains, second, poly-Si stripes are fully recrystallized using
the above <100> texture as seed crystals by scanning a laser beam
along the stripes. We discuss a strong <100> texture formation related
to partially molten state in the first process of secondary seed formation,
and use of a grooved structure with poly-Si sublayer suppressing edge
nucleation during lateral epitaxy.
X-Ray Studies of Strain in Laser-Crystallized SOI
Films
Authors: Rivier Michel , Reidinger F. , Goetz G. , Mckitterick J. , Cserhati A.
Published: March 2011

We have used x-ray diffraction to measure the strain perpendicular to the
substrate surface in laser crystallized silicon films on oxidized silicon
and fused quartz substrates. The dependence of the strain on
grainorientation was determined and the influence of the scan speed, the
insulating oxide thickness, and subsequent high temperature exposure was
examined. Maximum strain was obtained for grains oriented with the (100)
plane parallel to the substrate surface. The strain decreased with
increasing angle between the surface plane and the (100) plane of the
grains. The stress parallel to the surface in the variously oriented grains
was calculated from the stiffness tensor, assuming an isotropic, in-plane
stress, and a variation similar to the strain was found. The strain found on
oxidized wafers was about half that on fused quartz. Its dependence upon the
oxide thickness (0.2 μm to 1.0 μm) was not significant for scan speeds under
10 cm/sec. Similarly, the variation in strain with scan speed was very small
for speeds below 10 cm/sec. Scan speeds above 50 cm/sec caused significant
increases in the strain.

The measured strain was reduced by high temperature anneals. A 1100°C anneal
reduced the average strain by 60% and caused a clear reduction in grain
imperfections (as determined by diffracted beam width). However, a 900'C
anneal increased the diffracted beam widths even though the average strain
was reduced by about 30%.
Picosecond Photon-Solid Interaction Phase Transition in
Silicon
Authors: Malvezzi A.M. , Kurz H. , Bloembergen N.
Published: March 2011

Four different regimes of photoelectric emission are observed over a vide
fluence range of UV-laser pulses irradiating single-crystal silicon samples.
The role of the electron-hole plasma in the nonlinear photoemission is
demonstrated by temporal correlation measurements. A regime where ion
thermal evaporation processes take place is observed above the critical
fluence for melting. At higher laser fluences nonlinear ion acceleration is
demonstrated by direct time-of-flight measurements.
Pulse-Duration-Dependent-Free-Carrier-Absorption in
Semiconductors
Authors: Mukherjee P. , Sheik-Bahaei M. , Kwok H.S.
Published: March 2011

The free carrier absorption in InSb was found to depend on the pulse
duration of the picosecond CO2 laser pulse. This is interpreted as the
effect of incomplete carrier relaxation within the laser pulse duration. An
electron energy relaxation time of 5.6 ps was derived from the observation.
The present experiment presents a new method of measuring relaxation times
in semiconductors and metals.
The Diffusion of Phosphorus in Silicon from High Surface Concentrations
Authors: Schaake H. F.
Published: March 2011

An interstitial model is developed to quantitatively account for the anomalous effects which accompany the diffusion of phosphorus in silicon from high surface concentrations. Phosphorus is assumed to diffuse as both a positively charged (intrinsic diffusion) and an uncharged interstitial (high concentration case). Silicon is assumed to diffuse as both an uncharged (instrinsic) and a negatively charged interstitial (high phosphorus concentrations). The effect of internal fields on charged species is included. An excellent fit is found with published experimental data if a surface enhancement factor, analogous to that for the case of oxidation enhancement, is used. Flat-top diffusion is modelled by assuming the formation of a dislocation array, which alters the point defect equilibria.
Intrinsic Gettering in Oxygen-Free Silicon
Authors: Nauka K. , Lagowski J. , Gatos H. C.
Published: March 2011

We found that the intrinsic gettering can be effectively realized in oxygen-lean Czochralski silicon grown in a magnetic field as well as in oxygen-free float-zone silicon. The intrinsic gettering has been observed thus far only in oxygen-rich Czochralski silicon and it has been believed to be intimately related to oxygen. We present experimental characteristics of the new intrinsic gettering process, and we propose a model involving outdiffusion and precipitation of silicon interstitials rather than oxygen which is involved in the standard intrinsic gettering.
Palladium-Test: A Tool to Evaluate Gettering Efficiency
Authors: Graff K. , Hefner H.-A. , Pieper H.
Published: March 2011

A new method is presented which is suitable to check gettering processes and to evaluate gettering efficiencies. This method is based on an intentional contamination of the respective silicon wafer by means of palladium or any other haze forming metal. The palladium is diffused and haze is revealed by preferential etching. In order to determine gettering efficiency the sizes of the haze areas on gettered and non-gettered wafers are compared. The quantity of the gettered palladium can be deduced from lateral palladium profiles.

In contrast to procedures published in the literature this method is very simple and fast. Therefore it is suitable for routine application to check back side damaged wafers or internal gettering.
Characterization of Denuded Zones in Silicon Wafers
Authors: Rath H. J. , Reffle J. , Huber D. , Eichinger P. , Iberl F. , Bernt H.
Published: March 2011

Different techniques are presented for the characterization of the two-layered system consisting of a precipitate-free zone and a precipitated zone, generated in CZ-grown silicon wafers by thermal processing. The diffusion length profile can be determined by surface photovoltage characteristics; measurements of the collection efficiency for excess carriers generated by alpha particles gives relevant information about the soft error performance. Finally, oxygen depth profiling by SIMS is discussed. Results are shown and compared with damage patterns obtained from cleavage face etching.
Effects of Processing on Structural Defects in Silicon
Authors: Cheng L. J.
Published: March 2011

It is found that the recombination activities of dislocation complexes and structural defects decorating twin boundaries in as-grown, p-type cast polycrystalline silicon have no observable temperature dependence in the range of 100–300 K, but the activities of these defects in phosphorusdiffused samples decrease with the increase of temperature in the same range. The results suggest that the phosphorus diffusion can cause a significant shift of energy levels of these defects toward the valence band from the middle of the band gap.
Gettering & Precipitation Phenomena in Semiconductors
Authors: Sadana D. K.
Published: March 2011

Impurity gettering at defects/damage in Si is discussed. Details of intrinsic and extrinsic gettering in Si are presented. The utility of gettering is demonstrated by comparing the results from gettered and non-gettered test devices.
Gettering of Metallic Impurities in Silicon
Authors: Ourmazd A. , Schröter W.
Published: March 2011

We report the results of a study of the microstructural changes brought about by the gettering of metallic impurities in silicon. Phosphorus gettering proceeds by the formation of metal disilicides at the silicon/phosphosilicate glass interface. By showing that iron is strongly localized at the interface by phosphorus gettering, we present the first evidence that phosphorus gettering can proceed independently of Fermi level effects. Our first results on the intrinsic gettering of nickel lend support to the notion that the emission of silicon interstitials brought about by phosphorus diffusion (and SiP formation), or intrinsic gettering (SiOx, formation), plays an important role in the gettering process.
Gettering of Impurities during High Dose Implantation of Al or Cr into Si and the Resulting Effect on Structure and Composition
Authors: Namavar F. , Budnick J. I. , Otter F. A.
Published: March 2011

This paper presents strong evidence for carbon and oxygen gettering during high dose implantation of Cr and Al into Si by implanted ions or Si atoms. Rutherford Backscattering (RBS) and Auger Electron Spectroscopy (AES) experiments of Cr and Al implanted Si samples in a diffusion pumped vacuum (DPV) system (≃ 10−6 Torr) clearly indicate that the incorporation of carbon or oxygen occurs preferentially and depends on the surface composition which is controlled by the dose of implantation and by sputteripg.

The implantation of Cr and Al in a DPV system (≃ 10−6 Torr) results in a large increase in the concentration and retention of implanted atoms compared to implantation in a UHV system (≃ 10−8 Torr). For implantation in a DPV system, the Cr distribution broadens up to a factor of two. For Al a bimodal or broadened distribution could be observed by nuclear resonance profiling (NRP).
Silicon on Sapphire of Single Crystal Quality Obtained by Double Solid Phase Epitaxial Regrowth
Authors: Parker M. A. , Sinclair R. , Sigmon T. W.
Published: March 2011

A dual-implantation and annealing procedure has been refined which results in silicon films of single crystal perfection on sapphire substrates. This double solid phase epitaxy (DPSE) procedure consists of two self-implantation steps that serve to amorphize the defect structure of the parent silicon film with subsequent annealing steps employed to recrystallize the amorphized structure. High resolution cross-section transmission electron microscopy (HRXTEM) and ion channeling have been employed to study the microstructure of the silicon films, the sapphire substrates, and the interface. The resulting perfection of the silicon layer is shown to be a sensitive function of the first self-implant energy, dose, and silicon film thickness. Also, a correlation has been established between microtwin density and dechanneling profiles. HRXTEM of microtwins in silicon on sapphire (SOS) starting material demonstrates contrast features identified as rotational Moire' fringes between the microtwins and the matrix by means of optical diffractometry. Best results are achieved for the first implant energy of 170 keV 28Si+. Thus, the DSPE process is shown to give optimal results in defect reduction.
Tem Study of GaSb/InAs Strained Layer Supeplattices
Authors: De Cooman B. C. , Carter C. B. , Wicks G. W. , Tanoue T.
Published: March 2011

Cross-sectional TEM of GaSb/InAs superlattices grown by MBE on (100) GaAs and (100) GaSb substrates shows an unusual defect structure within the strained layers. Dislocations are present within the layers and at the interface. High-resolution TEM analysis of the structure of the InAs layers suggests that these layers grow by an island mechanism. A crystal structure different from the zinc blende, is found to be present within the GaSb layers.
Epitaxial Growth of SixGe1−x Films on Si by Solid Phase Epitaxy.
Authors: Pai C. S. , Lau S. S.
Published: March 2011

It has been demonstrated in the literature that amorphous Si (or Ge) can be transported across a metal layer and grown epitaxially on Si(Ge) single crystal substrates in the solid phase. The objective of this study is to investigate if amorphous SixGe1−x mixtures can be transported uniformly across a medium and grown epitaxially on single crystal substrates without phase separation. The samples were prepared by e-beam evaporation of thin Pd films onto Si<100> substrates, followed by co-evaporation of SixGe1−x alloyed films (0<x<1) without breaking vacuum. The samples were anneaie in vacuum at 300°C to form a Pd silicide-germanide layer at the interface, then at 500°C for transport of the alloyed layer across the Pd silicide-germanide layer and subsequent epitaxial growth on Si substrate. The samples were investigated by x-ray diffraction and by MeV ion backscattering and channeling. The results show the alloyed film transports uniformly with no phase separation detected. The channeling result shows the grown alloyed layer is epitaxial with some Pd trapped in the layer. This simple technique is potentially useful for forming lattice-matched non-alloyed ohmic contacts on III–V ternary and quaternary compounds.
Interdiffusion and Stability of Compositionally Modulated Films
Authors: Spaepen Frans
Published: March 2011

The thermodynamics and kinetics governing the stability of compositionally modulated materials are reviewed. Typical results of interdiffusion experiments on fcc and amorphous metals are discussed to demonstrate the sensitivity and special features of the technique. Two coarsening mechanisms, and the stability of orthogonal waves in phase separating systems are analyzed.
Strain and Damage Measurements in Ion Implanted AlxGa1−x As/GaAs Superlattices
Authors: Hamdi A. H. , Tandon J. L. , Vreeland T. , Nicolet M.-A.
Published: March 2011

Strain measurements in AlxGa1−x As/GaAs superlattices have been carried out before and after Si ion implantation. For doses up to 5 × 1015 cm−2, no atomic intermixing of the sublayers is observed by backscattering spectrometry. However, with x-ray rocking curve measurements, significant changes in the strain profiles are detected for implantations with doses as low as 7 × 1012 cm−2. Interpretation of the rocking curves suggests that low-dose implantations release strain in the AlxGa1−x As sublayers. The strain profile recovery of the implanted samples, upon annealing at ∼ 420°C, implies that the damage caused by implantation is largely reversible.
Low Temperature Reordering of Implanted Amorphous Si with Al Surface Layers
Authors: Hung L. S. , Chen S. H. , Mayer J. W.
Published: March 2011

Ion backscattering and channeling techniques, transmission and scanning electron microscopy, and secondary ion mass spectroscopy were used to investigate the reordering characteristics of implanted amorphous Si in the presence of an Al surface layer. It was found that reordering takes place at the temperature of about 400°C and is associated with an interfacial migration between Al and Si. The regrowth behavior appears to be a function of the initial annealing temperature and annealing sequence. High density of twin faults and substantial concentration of Al are observed in the regrown layers. We believe that the low temperature reordering is due to processes analogous to solid epitaxial growth with transport media.
Epitaxial Growth of Refractory Silicides on Silicon
Authors: Chen L. J. , Cheng H. C. , Lin W. T. , Chou L. J. , Fung M. S.
Published: March 2011

Epitaxial refractory silicides were grown on silicon by solid phase epitaxy method. Transmission electron microscopy has been performed to study the microstructures of epitaxial layers and their orientation relationships with respect to substrate Si.

Metal thin films, electron-gun deposited, or sputtered metal-silicon films were annealed in N2 ambient or in vacuum at 200°C-1100°C. Substrate heating, two step annealing and ion beam mixing were applied to induce the growth and improve the quality of epitaxial films. In this paper, formation and structures of epitaxial CrSi2, VSi2, ZrSi2, MoSi2 and WSi2 are presented. Preliminary results of the epitaxial growth of TiSi2, TaSi2 and NbSi2 are reported.
Transition From Single-Layer to Double-Layer Steps on GaAs(110) Prepared by Molecular Beam Epitaxy
Authors: Fuchs J. , Van Hove J. M. , Pukite P. R. , Whaley G. J. , Cohen P. I.
Published: March 2011

Even though GaAs (110) is the only semiconductor whose surface structure is known with confidence, little is known about its microscopic growth mechanisms. We have used RHEED to study the role of steps in the MBE growth of GaAs on vicinal GaAs(11O) surfaces which were misoriented by less than 2 mrad. After thermally desorbing the initial oxide, 20 layers of GaAs deposited at 700K produced a surface with single atomic-layer steps having an average terrace length of a few hundred Angstroms. Upon annealing to 8OOK, a slow mass migration occurred producing a surface with one thousand Angstrom average terrace lengths and predominantly double layer step heights. The RHEED pattern was nearly instrument limited at in-phase angles of incidence, with little background intensity and bright Kikuchi lines. Subsequent deposition showed only weak oscillations in the RHEED intensity, in contrast to growth on the (001) surface. The period of the observed oscillations indicates that the layer-by-layer growth involves single-layer steps. Growth of as little as 5 atomic layers on a surface with double steps could not be annealed to give a RHEED intensity as great as the first annealed surface. These measurements reconcile previous LEED results with the oxygen adsorption measurements of Ranke. The results clearly show the dominance of steps in the formation of RHEED streaks.
A Critical Comparison of the Techniques used to Characterize the Crystallography of an Interface: Pd on mbe “Rown GaAs(100)
Authors: Delrue I. P. , Wittmer M. , Kuan T. S. , Ludeke R.
Published: March 2011

In situ Reflection High Energy Electron Diffraction and ex-situ Transmission Electron Diffraction and Ion Channeling have been applied to a reacted Pd-GaAs interface and the results obtained are critically compared. The investigation has been done on the stabilized c(2×8) surface obtained by MBE on GaAs(100) substrates. Smooth surface epitaxial growth has been observed by RHEED as soon as a few monolayers of Pd are deposited at a substrate temperature of about 325°C. TEM diffraction studies indicate the presence of an intermetallic hexagonal structure similar to the orthorhombic Pd5Ga2 but with slightly different lattice parameters due to the possible incorporation of As. A less abundant phase was also identified as an hexagonal structure similar to Pd8As2. Ion Channeling indicates pronounced reduction in scattering yield when the [100] axis of the substrate was aligned with the impinging beam, thus supporting the RHEED analysis. The three techniques listed above were found to be useful for the determination of the epitaxial relationship between the identified phases and the substrate.
Morphological Studies of Polysilicon Emitter Contacts
Authors: Bravman John C. , Patton Gary L. , Sinclair Robert , Plummer James D.
Published: March 2011

Using high resolution lattice imaging techniques, the morphology of thepolycrystalline silicon - single crystal silicon interface has been correlated to (1) the surface treatment used prior to polysilicon deposition, (2) the polysilicon implant dose, and (3) high temperature annealing. Specimens which were chemically oxidized prior to deposition exhibited a continuous layer of amorphous oxide ≈1.5nm thick. High temperature annealing produces small discontinuities in this oxide which allow the polysilicon to make direct contact with, and become epitaxially aligned to, the substrate. Specimens which were etched in HF prior to deposition were characterized by nearly oxide-free interfaces, which, following implantation and annealing, exhibited regions of epitaxial realignment significantly larger than those found in the chemically oxidized films. Heavily implanted films annealed at high temperature displayed almost complete epitaxial realignment.
Amorphous Phase Formation in Solid State Reactions of Layered Nickel Zirconium Films
Authors: Clemens Bruce M. , Buchholz Jeffrey C.
Published: March 2011

Formation of an amorphous zirconium-nickel phase by solid state reaction of a layered crystalline structure has been studied by in-situ resistivity, x-ray diffraction, and Auger depth profiling. The reaction was studied as a function of layer thickness and reaction temperature.

Samples with a layer thickness of less than 4 atomic planes had x-ray diffraction spectra with one broad maximum characteristic of amorphous material. As the layer thickness increased, the maximum broadened and separated into two resolved peaks corresponding to crystalline nickel and zirconium. These structures were transformed to an amorphous nickel-zirconium alloy by an anneal at temperatures below the crystallization temperature of the amorphous phase. The reaction occured by a layer growth process, where the thickness of the layer evolved linearly with the square root of time.
Amorphous and Crystalline Phase Formation by Ion-Mixing of Ru-Zr and Ru-Ti
Authors: Cheng Y-T. , Johnson W. L. , Nicolet M-A.
Published: March 2011

Ion mixing of multilayered Ru-Zr and Ru-Ti at different compositions and substrate temperatures produced various metastable phases. The applicability of previously proposed rules regarding amorphous phase formation are examined. Effects of point defect in amorphous phase formation by ion mixing are discussed.
Metal Rich Silicide Formation Between Thin Films of Vanadium and Amorphous Silicon
Authors: Psaras P. A. , Eizenbergt M. , Tu K. N.
Published: March 2011

Extended Abstract

The formation of silicides via a solid state reaction of silicon and transition metal thin film is characterized by the sequential appearance of the various compounds rather than the simultaneous formation of all possible compounds [1]. Thin films of refractory metals will form disilicides on a single crystal silicon substrate (unlimited supply of silicon) and since they are stable with silicon, no other silicides will form. This situation is illustrated in Fig. la) by the formation of VSi2 in the case of vanadium on silicon. On the other hand, which silicide will form in the case where there is an excess amount of refractory metal is unknown. The objective of this work was to study this case utilizing the vanadium silicon binary system [2].
Phase Transitions in Gold Contacts to Gallium Arsenide
Authors: Beam Edward , Chung D. D. L.
Published: March 2011

X-ray diffraction was used in situ to study the phase transitions which occurred in 1500 Å Au/GaAs(100) upon heating and cooling. The reaction between Au and GaAs took the form Au + Ga → α Au-Ga. Upon heating, α Au-Ga completely dissolved in liquid Au-Ga. Upon subsequent cooling, β Au-Ga (or Au7Ga2) formed. In 1 atm of nitrogen, phase transitions were observed reversibly at 525 ± 25°C (due to the complete dissolution of α Au-Ga upon heating) and 415 ± 5°C (due to the peritectic transformation of β Au-Ga to α Au-Ga and liquid Au-Ga upon heating). In a vacuum of 425 μ (0.031 Kg/2m) similar phase transitions were observed at 425 ± 25°C and 387 ± 13°C, respectively.
Microstructures in Rapidly Solidified Ll2-TYPE Ni-Al-Cr Alloys
Authors: Huang S. C. , Chang K. M. , Hall E. L. , Laforce R. F.
Published: March 2011

A microstructural study of the melt spun alloys Ni75 Al25. Ni72.5 Al22.5Cr5. and Ni67.5A120Cr12.5 was carried out. Variations in grain morpfology; phase separation and ordering structure were observed. The results are discussed in terms of alloy stoichiometry, Cr effect on phase reaction, microsegregation of Al and the cooling rate.
Resistivity of Short-Range and Long-Range Order Changes in Ni4Mo
Authors: Lei T. S. , Vasudevan K. , Stansbury E. E.
Published: March 2011

Short-range order (SRO) and long-range order (LRO) reactions in Ni Mo as a function of room temperature deformation ahd thermal treatments betwean −269 and 1300°C are Reported. Resistivity results show that SRO is dispersed by heating near 1300°C and by cold working to 68% reduction of area (RA). The resistivity decreases to a minimum at 68% RA after which an increase is attributed to an increase in defect density.

The resistivity as a function of variations in the time-temperature history is reported. Cooling at 60°C/min; results in the maximum “frozen in” SRO with resistivity of 144 μohm cm at 25°C; th8 resistivity of the LRO state obtained on slow cooling is 48 μohm cm. At −269°C, the resistivities are 139 and 8 μohm cm for the SRO and LRO states respectively. Correlations relate kinetics and microstructures to resistivity changes during heating, cooling and isothermal SRO-LRO transformations. Preliminary results of reheating fully ordered samples to near 868°C and quenching are reported. Results are discussed with relevance to existing theories.
The Effects of Grain Size on the Flow and Fracture of Long-Range Ordered Alloys
Authors: Schulson Erland M.
Published: March 2011

Three points usually come to mind when considering the effects of grain size on the mechanical properties of polycrystals: strengthening at low temperatures through grain refinement, strengthening at high temperatures through grain coarsening, and lowering of the ductile to brittle transition temperature in materials such as ferritic steels and zinc through grain refinement. Ordered alloys, as we shall see, exhibit the same effects.
γ/γ′: The Key to Superalloy Behavior
Authors: Giamei A. F. , Pearson D. D. , Anton D. L.
Published: March 2011

Gamma prime (Ni3Al), with its unusual temperature dependence of yield strength, is the strengthening phase in Ni-base superalloys. Many facets of γ/γ′ coherent precipitation strengthening have been well studied: coarsening kinetics, volume fraction vs. strength, yield strength vs. temperature, dislocation dynamics, etc.

This contribution deals with several important aspects of two phase behavior in coherent systems (for high temperature application) which are either relatively new or have received inadequate attention. The most desirable γ/γ′ misfit, in sense and magnitude, is dependent on the temperature of application. It must be recognized that the sense and size of misfit are not only a function of alloying, but temperature as well. Sufficient data are presented for various alloying additions to γ and γ′ to allow one to roughly compute the misfit at room temperature or 1000C. The evolution and significance of the ′′ morphology are discussed. Stability of particle size and shape are related to misfit, temperature and stress. It is demonstrated that for high temperature creep resistance, a fine rafted structure is the most desirable. Finally, some data are presented which demonstrate the dependence of γ′ strength on stoichiometry as well-as temperature.

A portion of this work was sponsored by AFOSR, with A. Rosenstein as contract monitor.
The Effect of Surface Oxide Films on the Mechanical Behavior of NiAl
Authors: Noebe R. D. , Gibala R.
Published: March 2011

Thin surface films have been shown to enhance the ductility and decrease the flow stress of several body-centered cubic metals at temperatures T < 0.2 Tm. The origin of this effect lies in the large difference in the intrinsic mobilities of edge and screw dislocations in body-centered cubic crystals. B2 ordered intermetallic alloys, although simple cubic in structure, are based on the body-centered cubic structure and have dislocation core structures, dislocation mobilities and temperature and orientation dependent deformation qualitatively similar to that of bcc metals. This investigation was initiated to examine possible effects of surface films on the mechanical behavior of B2 ordered intermetallic alloys, using oxidized NiAl as the initial material for investigation. Experiments were performed on an impure non-stoichiometric (47.1 at.% Al) single crystal material with an axial orientation near [123]. Surface film softening was observed at room temperature in compression at a strain rate of 2 x 10-4 s-1. Flow stresses of the oxide coated crystals were as much as 20% lower than those of identically prepared uncoated crystals. The strains to fracture of coated specimens were larger than those of uncoated specimens and in a few instances the ductility enhancement was as much as four times. Of the several oxides examined, the largest softening effects were found for a thermally deposited delta-A1203 film formed at 1000 °C for 1 hour. The current results for NiAl are compared to results previously obtained for bcc metals. Experiments which could further enhance the film softening effects observed in B2 ordered intermetallic alloys are suggested.
creep Behaviour of the Ordered Intermetallic (FE, NI)Al Phase
Authors: Rudy M. , Sauthoff G.
Published: March 2011

The deformation behaviour of the ordered intermetallic (Fe, Ni)Al phase with B2 structure is studied as a function of composition and temperature with stress strain tests and creep tests.The alloy composition has been varied with respect to stoichiometry and the Fe/Ni ratio. The creep resistivity depends on the alloy composition in a complex manner: a deviation from the stoichiometric compositions leads to a reduction of the creep resistance, and there is a maximum of the creep resistance for the ternary alloys with about 10% Fe.
The B2 Aluminides As Alternative Materials
Authors: Stephens Joseph R.
Published: March 2011

As part of NASA's Conservation of Strategic Aerospace Materials (COSAM) Program, a research effort is underway to explore the potential of the B2 aluminides as structural material alternatives for the strategic element containing superalloys currently used in gas turbine engines. Emphasis is being place on the equiatomic Fe and Ni aluminides. Although Co is a strategic material, the equiatomic Co aluminide is also being studied to gain a more complete understanding of these fourth period intermetallics. The research effort is a cooperative program involving in-house research at NASA Lewis plus several university grant programs. Research focuses on initial processing techniques such as ingot melting, powder metallurgy, and rapid solidification with and without additional thermomechanical processing; high temperature deformation - primarily compressive creep; compositional effects within the binary B2 aluminides; third-element alloying addition effects on high temperature strength and oxidation resistance; and near room temperature ductility as influenced by processing, alloying, and grain size. This paper will review the various programs now underway and present some of the highlights of research results.
A review of Rapid Solidification Studies of Intermetallic Compounds
Authors: Koch C. C.
Published: March 2011

A review of rapid solidification studies of high temperature ordered intermetallic compounds is presented. Emphasis is on the nickel - and iron - aluminides which are of potential interest as structural materials. The nickel-base aluminides which have been rapidly solidified exhibit changes in grain size, compositional segregation, and degree of long range order (as reflected in APB size and distribution) which markedly affect mechanical properties. Some experiments indicate the formation of a metastable L12 phase in rapidly solidified Fe-(Ni, Mn)-Al-C alloys, while other work observes only a metastable fcc phase in the same composition range. The metastable phases and/or microstructures in both nickel and iron aluminides are destroyed by annealing at temperatures >750K, with subsequent degradation of mechanical properties. Rapid solidification studies of several other intermetallic compounds are briefly noted.
Ni-base Intermetallics for High Temperature Alloy Design
Authors: Nash P.
Published: March 2011

Further development of Ni-base superalloys based on γ–γ′ structures offers little hope of substantial improvements in properties for gas turbine applications. However because of the substantial technology base which exists for nickel base alloys there are considerable advantages, in research time and money, in developing new nickel base alloys. Interest in the 1970's in directionally solidified composites indicated some possible new systems to replace γ–γ′ alloys. More recently there has been renewed interest in aluminides such as FeAl, CoAl and NiAl. These materials exhibit melting points which are substantially greater than for current γ–γ′ alloys. Problems of lack of ductility for these alloys may be resolved by alloying and novel processing routes such as rapid solidification.

In addition to NiAl there are a number of other nickel intermetallics which from limited experimental data are worth considering at least as second phases. Some of these compounds are Ni7Hf2, Ni7Zr2, Ni5Zr, Ni6A1Ta and Heusler alloys of the type NiAlx where x is a transition element. The solubilities and phase relationships and where available the mechanical property data in a number of nickel ternary systems will be reviewed in terms of their potential for development of new high temperature alloys.
Silicon-Nickel Compounds by Ion Implantation
Authors: Mayer S. G. B. , Milillo F. F. , Potter D. I.
Published: March 2011

Compounds of silicon and nickel have been formed by implanting silicon ions into nickel at various fluences and temperatures. Temperature during implantation is a major factor controlling implanted ion concentrations and phase developments. The ordered phase Ni3Si, which forms during implantation at 600°C, is replaced by Ni5Si2 during implantation at 400°C or below. In contrast to aluminum implantation of nickel, crystalline phases form even at high fluences (>1 × 1018 ions/cm2) and at low temperatures (<200°C) in silicon implanted nickel.
Switchable Microcrystallization Near Threshold in Laser Annealing of GeSe2 Glass and Evaporated Films
Authors: Phillips J. C.
Published: March 2011

Just below threshold for irreversible macrocrystallization there may exist a narrow energy (or power) density region where microcrystallites are formed. In the case of Si and GaAs this region lies just above the threshold for melting and the microcrystallites are formed irreversibly. In the case of GeSe2 when Urbach tail laser energy is used just below the macrocrystallization threshold the photons selectively replace like-atom bonds with chemically ordered bonds, and microcrystallization can be thermally reversed in melt-quenched glass at temperatures as low as Tg/2.
The Crystallization and Amorphization of Si from the Melt at Interface Velocities Approaching 20 m/sec
Authors: Poate J. M.
Published: March 2011

Laser melting has been used to controllably vary the Si solidification velocity in the range 1–20 m/sec. The segregation of implanted impurities is found to be critically dependent on the liquid-solid interface velocity and substrate orientation for velocities <10 m/sec. This behavior can be understood in terms of different degrees of undercooling of the melt. While the (100) epitaxy is generally excellent up to velocities ∼10 m/sec, twins are observed for (111) epitaxy in the range ∼5–10 m/sec. Amorphous Si is produced from the melt for velocities in the vicinity of 20 m/sec. The amorphous phase forms at lower velocities on the (111) interface than on the (100) interface. These estimates of interface velocities come from heat flow calculations which do not include undercooling of the melt. Undercooling does not affect interface velocities ∼3 m/sec but significant lowering of the higher velocities could result from such effects.
Calculation of Carrier and Lattice Temperatures Induced in Si and GaAs By Picosecond Laser Pulses
Authors: Lietoila A. , Gibbons J. F.
Published: March 2011

A previously presented computer model was used to calculate melt thresholds and carrier temperatures in crystalline silicon and gallium arsenide subjected to picosecond laser pulses at 532 nm. The energy relaxation time of hot carriers was a variable parameter. For Si, a thermalization time of 1 ps yields results which are in very satisfactory agreement with published experimental data: the melt threshold is 0.19 J/cm2, and the maximum carrier temperature for the threshold pulse is 5500 K. The melt threshold in GaAs is substantially less, 0.03 J/cm2 for a thermalization time of 1 ps.
Amorphous Germanium Crystallization Processes in Multi-Pulse Low Power Laser Irradiation
Authors: Bertolotti M. , Vitali G. , Zammit U. , Marinelli M.
Published: March 2011

The regrowing features of disordered germanium under low power multi-pulse irradiation are discussed. It is shown that implanted amorphous germanium starts the regrowth from the specimen surface while glow-discharge amorphous material starts from the amorphous-single crystal interface. Evidence against a melting mechanism in the case of multi-pulse irradiation are also presented.
In Situ Laser Recrystallization of CVD Silicon Films
Authors: van der Leeden G. A. , Young R. T. , Appleton B. R. , Narayan J.
Published: March 2011

Polycrystalline silicon films were deposited on singlecrystal silicon substrates from a SiH4 –H2 mixture at 660°C and epitaxially recrystallized with ruby laser pulses during the deposition. The surface morphology was found to depend critically on the surface conditions of the substrate. Using appropriate cleaning procedures, 0.5 and 1.0 micron thick layers were deposited and laser recrystallized during the deposition. Ion scattering/channeling analysis showed that the layers were single crystalline with a high degree of perfection. Using TEM, dislocation densities of 103–104 cm−2 were found, but some areas were dislocation free.
Zone Refining Of Nonsubstitutional Impurities During Pulsed Laser Annealing
Authors: White C. W. , Naramoto H. , Williams J. M. , Narayan J. , Appleton B. R. , Wilson S. R.
Published: March 2011

A large number of impurities which do not form covalent bonds with silicon cannot be incorporated into the lattice at measurable (by RBS) concentrations by pulsed laser annealing. At low concentrations the impurities can be zone refined to the surface, while at high concentrations the interface becomes unstable during regrowth leading to a cell structure. For each impurity there is a critical concentration required for interfacial instability to develop. The results are in qualitative agreement with a simple model for solute trapping and zone refining which assumes that the impurity diffusivity in the interfacial region is intermediate between that of the liquid and the solid.
An Ion-Scattering Study of Oxygen Indiffusion During Pulsed Laser Annealing/Cleaning of Silicon
Authors: Westendorp J.F.M. , Wang Z.L. , Saris F.W.
Published: March 2011

Oxygen indiffusion during pulsed laser annealing of silicon has been studied using the 186 O(α,α) 186 O resonance at 3.045 MeV. Anneals were carried out with a Q–switched ruby laser, energy density of the pulses 1.5 J/cm2 , pulse width 20 ns. No evidence for oxygen indiffusion was found, neither for ion–implanted single pulse air–annealed silicon nor for a silicon wafer, cleaned with 8 laser shots in a UHV environment. In the latter case, the upper limit of the oxygen concentration was found to be 3.1 * 1018 at/cm3 , which is lower than the solid solubility limit of oxygen in silicon. The non–occurrence of indiffusion is consistent with the dissolution time of SiO2 in Si, which is orders of magnitude longer than the melt duration of the Si–substrate.
Photoemission Results for Laser-Annealed Si(111) and Ge(111) Surfaces
Authors: Himpsel F.J. , Eastman D.E. , Heimann P. , Reihl B. , White C.W. , Zehner D.M.
Published: March 2011

We have studied the valence band and surface-core-level states for laser-annealed, thermally-annealed, and cleaved Ge(111) and Si(l11) surfaces with high resolution photoelectronspectroscopy using synchrotron radiation. For the annealed surfaces we find two surface states near the top of the valence band as well as characteristic surface core level spectra. These indicate the existence of a common local bonding geometry for all these surfaces. We observe that the (1 × 1) and cleaved (2 × 1) surfaces are not related as recently reported for Si.
Emission of Charged Particles from Laser Irradiated Silicon
Authors: Liu J.M. , Yen R. , Kurz H. , Bloembergen N.
Published: March 2011

Emission of charged particles from (111) and (100) crystalline silicon surfaces during and following picosecond pulsed laser irradiation in vacuo has been investigated.

No thermionic electron emission is observable, setting an upper limit of 5000°K on the electron temperature during the laser pulses at 532 nm and at 266 nm. Equal number of positive and negative particles are emitted when the laser energy fluence is sufficient to cause vaporization of a few surface layers. Significantly larger amount of electrons than that of positive particles are emitted under irradiation with UV pulses at low energy fluences. This phenomenon can be tentatively explained by thermally enhanced photoelectric emission from a molten silicon surface.

The presence or absence of the emission of charged particles sets important lower or upper limits on the temperature of the electrons and of the lattice. Our data are fully consistent with a model of complete thermalization between carriers and lattice on a time scale of 10–11 sec.
The Characterisation of Laser and Electron Beam Annealed Silicon by Infrared Spectrophotometry
Authors: Pawlik Marek
Published: March 2011

An exact model of the IR reflectance and transmission spectra of inhomogeneously doped silicon has been developed. By comparing theoretically and experimentally generated spectra in the range 1.2 to 25 μm, information about the doping profile may be deduced. The technique has been applied to laser and electron beam annealed silicon (as well as furnace annealed) and comparisons made with theoretical profiles and SIMS analysis in the latter case. No values consistent with other published data have been found for the optical properties of silicon at high doping levels (>1020 cm−3).
Quenched-In Defects in CW Laser-Annealed Si
Authors: Sheng N.H. , Merz J.L.
Published: March 2011

DLTS has been used to investigate the nature of CW laser-induced defects in ion-implanted Si. A dominant hole trap (∼Ev + 0.45 eV), whose concentration depends on laser power, was observed immediately after sample preparation. This defect is not stable at room temperature; instead, it decays as a function of time, transmuting to a shallow level at Ev + 0.10 eV. The recovery of the Ev + 0.45 eV level can be stimulated by low temperature thermal annealing or by minority carrier injection. By comparing these defects in laser-annealed samples with defects produced by furnace annealing followed by rapid cooling, and with other published results, the laser-induced defects have beenidentified as interstitial Fe and Fe-B pairs. Experiments suggest that elevated substrate temperature during laser annealing may inhibit the formation of these deep hole traps.
Correlated Electrical and Microstructural Studies of Recrystallized Silicon Thin Films on Bulk Glass Substrates
Authors: Biegelsen D. K. , Johnson N. M. , Nemanich R. J. , Moyer M. D. , Fennell L. E.
Published: March 2011

To determine the nature and effect of defects which occur in the growth of crystalline semiconductor films on amorphous substrates, one must carry out microstructural and electrical studies on the same material regions. In previous publications we have demonstrated that by controlling optical absorption in and around delineated silicon areas, the nucleation and growth processes can be controlled. In this way we have been able to produce single crystal islands >20 μm on a side. Using a simple, novel parylene lift –off technique we can now routinely study the material crystallized on bulk glass using transmission electron microscopy. We report here preliminary results of correlated electrical and structural studies on pre – patterned silicon films crystallized under various conditions. Electrical characterization consists mainly of I – V measurements on diodes and MOSFETS fabricated in the crystallized material by conventional silicon IC processing techniques. For microstructural characterization of the same devices we rely on TEM, EBIC and spatially– resolved Raman scattering.
Defect Formation in CW CO2 Laser Annealed Silicon
Authors: Baumgart H. , Phillipp F. , Leamy H. J.
Published: March 2011

The EBIC mode of the SEM has been used to investigate the perfection of cw CO2 laser annealed Si. Even in material that contains no slip lines, non-uniform charge collection is found. A combined X-ray and electron microscopy (TEM, SEM) study identified the residual defects responsible for the EBIC contrast as interstitial submicron dislocation loops. Scanning cw laser annealing independent of the wavelength (10.6μm or 0.514μm) always introduces residual defects which act as recombination centers and reduce minority carrier lifetime.
Metallurgy and Microstructures of Pulse Melted Alloys
Authors: Follstaedt D. M.
Published: March 2011

The microstructures found in pulse melted metals are reviewed. Epitaxial resolidification and the defects found in pure metals are discussed. Pulse melted alloys are then examined in order of increasing complexity. First, single phase alloys which solidify into metastable solid solutions are discussed. For higher concentrations and liquid-insoluble species, phase separation can occur, and the requirements for such separation are identified. If precipitation does not reduce the impurity concentration of the liquid, the liquid may be quenched to an amorphous solid. Comparisons of ion-implantation and pulse-melt produced amorphous alloys are given.