bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Electrical Properties of Tin and Carbon Co-Implanted Silicon
Authors: Mei P. , Schmidt M. T. , Li P. W. , Yang E. S. , Wilkens B. J.
Published: March 2011

The alloy system Six(SnyC1-y)1-x was investigated. In this work, samples were prepared by co-implantation of tin and carbon ions into silicon wafers with dosage range 1015 − 1016cm−2, followed by rapid thermal annealing. Rutherford backscattering channeling, Auger sputter profiling, and secondary ion mass spectrometry were employed to study the crystallinity, chemical composition and depth profiles. A near perfect crystallinity for 0.5% at. of tin and carbon was achieved. To study the electrical properties in the implanted materials, diode I-V measurements were performed. The data show near ideal p-n junctions in the co-implanted region. This work demonstrates promising features of group IV semiconductor synthesis by ion implantation.
Incorporation of Ambient Oxygen During Silicon Deposition and the Effects of Argon Ion Bombardment
Authors: Brown David W. , Hubler Graham K.
Published: March 2011

The composition of SiOx films deposited by electron-beam evaporation of silicon in an oxygen atmosphere was measured as a function of silicon deposition rate and oxygen pressure. The compositions varied between X = 0.03 and 2.1 depending on the ratio of O2 molecules to Si atoms arriving at the substrate. Bombardment with 500 eV argon ions caused X to decrease at low arrival ratio and to increase at higher arrival ratio. The results are analyzed using an adsorption model in which chemisorption of O2 occurs after physisorption into one of two states: one on silicon and one on SiO2. A fit to the data for the unbombarded samples is achieved if physisorption occurs only on silicon. From this fit a sticking coefficient of 0.05 is obtained for O2 chemisorption on silicon. The effects of ion bombardment are consistent with the model if bombardment allows O2 to also physisorb on SiO2 and migrate to silicon where it chemisorbs.
Self Annealing Ion Implantation in thin Silicon Films
Authors: Rubio J. D. , Vijay R. P. , Hart R. R.
Published: March 2011

The self annealing phenomenon was studied utilizing 1 cm diameter, 1 μm thick, <100> oriented silicon films. Previous results established the viability of the self annealing process for medium energy argon beams incident on similar targets [1]. In the current work, doubly aligned backscatter spectra were obtained to improve the sensitivity of the residual lattice damage measurements. In addition, some implantations were performed at elevated temperatures to independently determine the effect of the flux and the sample temperature on the self annealing process. The results showed strong correlations between the implantation flux, sample temperature and the residual lattice damage. Two distinct temperature regions were observed above and below 330 °C with corresponding activation energies of 1.5 eV and 0.1 eV.
High Dose Rate Oxygen Implantation for Formation of Silicon-on-Insulator Structures
Authors: Cortesi E. , Namavar F. , Pinizzotto R. F. , Yang H.
Published: March 2011

We have studied Separation by IMplantation of OXygen (SIMOX) processes using very high dose rates (40–60 μA/cm2). For a dose of 4 × 1017 O+/cm2 at 160 keV, the structure formed by implantation at 50 μA/cm2 is very similar to that associated with lower dose rates. The same dose implanted at a dose rate of 60 μA/cm2, however, results in the formation of pits in the silicon surface as well as a somewhat different oxide structure. Implantation through a surface oxide layer appears to result in a structure similar to that associated with lower dose rate implantation. These and higher dose samples suggest that the threshold for pit formation is related to both dose rate and dose.
Superconducting YBaCuO thin Films by Cu-Ion Implantation
Authors: Hubbard Kevin M. , Bordes Nicole , Nastasi Michael , Tesmer Joseph R.
Published: March 2011

We have investigated the fabrication of thin-film superconductors by Cu-ion implantation into initially Cu-deficient Y(BaF2)Cu thin films. The precursor films were co-evaporated on SrTiO3 substrates, and subsequently implanted to various doses with 400 keV 63Cu2+. Implantations were preformed at both LN2 temperature and at 380°C. The films were post-annealed in oxygen, and characterized as a function of dose by four-point probe analysis, X-ray diffraction, ion-beam backscattering and channeling, and scanning electron microscopy. It was found that a significant improvement in film quality could be achieved by heating the films to 380°C during the implantation. The best films became fully superconducting at 60–70 K, and exhibited good metallic R vs. T. behavior in the normal state.
Ion Beam Synthesis of Buried Single Crystal Erbium Silicide
Authors: Golanski A. , Feenstra R. , Galloway M. D. , Park J. L. , Pennycook S. J. , Harmon H. E. , White C. W.
Published: March 2011

High doses (1016–1017/cm2) of 170 keV Er+ were implanted into single-crystal 〈111〉Si at implantation temperatures between 350°C and 520°C. Annealing at 800°C in vacuum following the implant, the growth and coalescence of ErSi2 precipitates leads to a buried single crystalline ErSi2 layer. This has been studied using Rutherford backscattering/channeling, X-ray diffraction, cross-sectional TEM and resistance versus temperature measurements. Samples implanted at 520°C using an Er dose of 7 × 1016/cm2 and thermally annealed were subsequently used as seeds for the mesocpitaxial growth of the buried layer during a second implantation and annealing process. Growth occurs meso-epitaxially along both interfaces through beam induced, defect mediated mobility of Er atoms. The crystalline quality of the ErSi2 layer strongly depends on the temperature during the second implantation.
Effect of Ion Implantation on YBCO Superconductor Thin Film
Authors: Zhang Zuhua , Liu Jiarui , Bui Ma Ki , Wu J. , Yu Ning , Zhao Yuan-Jun , Lam W. A. , Hsieh P. Y. , Chu Wei-Kan
Published: March 2011

The effects of the H+. C+. N+, F+, and Ne+ (25–200 keV)ion irradiations have been investigated by means of SEM, room temperature resistance measurement and aqueous degradation test. The room temperature resistance increases exponentially with irradiation doses. At lower dose, the annealing process is dominent, while at higher dose, the resistance increasing process is dominent. A reduction in the thickness induced by ion irradiation has been observed. The aqueous experiment shows that passing current will speed up the degredation and N+ implantations can increase the resistance of the YBCO thin film against attack by water.
Damage Accumulation and Annealing in Ion Irradiated Silicon
Authors: Priolo F. , Battaglia A. , Spinella C. , Rimini E.
Published: March 2011

The evolution of pre-existing damage structures in Si under high energy ion irradiation is discussed. Different initial morphologies are investigated: a sample partially pre-damaged with heavy ions and a sample partially pre-damaged with light ions are compared within them and with an undamaged single crystal. It is shown that ion irradiation can produce either damage accumulation, in the form of amorphous regions, or damage annealing depending on the pre-existing damage morphology, on the substrate temperature, and on the doping content in the irradiated layer. These data are discussed and interpreted on the basis of the existing models on ion induced amorphization and crystallization.
Ion-Surface Interactions During Epitaxy
Authors: Barnett S. A. , Choi C.-H. , Kaspi R.
Published: March 2011

Recent work on low-energy ion-assisted deposition of epitaxial films is reviewed. Much of the interest in this area has centered on the use of very low ion energies (∼ 25 eV) and high fluxes (> 1 ion per deposited atom) obtained using novel ion-assisted deposition techniques. These methods have been applied in ultra-high vacuum, allowing the preparation of high-purity semiconductor materials. The following ion-surface interaction effects during epitaxy are discussed: improvements in crystalline perfection during low temperature epitaxy, ion damage effects, improved homogeneity and properties in III-V alloys grown within miscibility gaps, and changes in nucleation mechanism from Stranski-Krastanov to layer-by-layer.
Dynamics Of MoS2 Photoablation
Authors: Murray P. T. , Dyhouse V. J. , Grazulis L. , Thomas D. R.
Published: March 2011

Speed distributions were determined for the ions ejected from MoS2 by excimer laser ablation. It was found that the majority of ionic species were atomic and were ablated with speeds in excess of 6 km/s. The speed distributions were found to be non-Maxwellian and were best described by a supersonic expansion model. The differences in ArF and KrF excimer laser ablation are discussed.
Channeling Study of Partially Ionized Beam Deposited Epitaxial Ag Films on Si(111) Substrates
Authors: Jin H.-S. , You L. , Lu T.-M.
Published: March 2011

Ag films deposited on Si(111) substrates by partially ionized beam (PIB) under conventional vacuum conditions were studied by MeV ion channeling techniques. In spite of their large lattice mismatch (24.8%), Ag films were still found to be epitaxial. With a deposition temperature of 350°C and without post-annealing, the Xmin value at the surface of a 2550 A° thick Ag film was found to be 10%. The azimuthal angular scan and the measured axial channeling dip showed that the Ag film was (111) oriented. The lattice quality of the films was comaparable to that deposited by MBE techniques. Dislocations were found in the PIB deposited Ag films. Lattice damage due to the bombardment of energetic ions was also observed. The thickness of the Ag film was found to have a pronounced effect on the crystalline quality at the surface. With the thickness increasing from 1240 A° to 2550 A°, the lattice quality at the Ag surface improved significantly, but not much change in the defect density in the Ag films was obseved.
Agglomeration of Cobalt Silicide Films
Authors: Xiao Z. G. , Rozgonyi G. A. , Canovai C. A. , Osburn C. M.
Published: March 2011

The agglomeration of Co silicide films formed on Si substrates processed with different Co film thickness was investigated by TEM, XRD, and four-point-probe measurements. It was found that thermal grooving always accompanies the film formation, while islanding can occur during high temperature thermal stability testing, or during formation of very thin films at moderate temperatures. In addition to whole film agglomeration, partial agglomeration on the top of the film has been observed, which is prominent and important for thin films. A theoretical model of agglomeration for silicide films is presented, which shows that when the ratio of grain size to film thickness is smaller than a critical value, the film will not lose its continuity. Also, grain boundary migration was found to have a suppressing effect on thermal grooving. Both a small grain size and a low grain boundary energy are shown to be favorable for improving the thermal stability.
Microstructural Evolution of Fe Grown on a (001) Cu Film and its Implication to the Elastic Anomaly in Metallic Superlattices
Authors: Koike J. , Nastasi M.
Published: March 2011

A large softening of the shear modulus has been reported in metallic superlattices composed of insoluble bcc/fcc metals. In an attempt to understand this elastic anomaly, we have studied the microstructure of Fe/Cu bilayers as a function of the Fe thickness with transmission electron microscopy (TEM). Analysis of the moire fringes observed in plan-view TEM images revealed that the fee Fe structure epitaxially grows on the (001) Cu up to a thickness of 2.0 nm. At 2.3 nm, the bec Fe structure nucleates, accompanying lattice rotation around the growth direction with respect to the underlying fee structure. As the Fe thickness further increases, submicron polycrystalline grains formed. Based on these results, the microstructure of the metallic superlattices and its relation to the softening of the shear modulus will be discussed.
Microstructural Development in Ion Beam Assisted Evaporation of Ni, Co and Fe Films
Authors: Trogolo J.A. , Roy R.A. , Petkie R. , Cuomo J.J. , Rajan K.
Published: March 2011

The development of microstructure in metal films deposited by ion-assisted evaporation has been studied by transmission electron microscopy (TEM). Films of Ni, Co, and Fe of about 350 to 500 nm thickness were deposited by electron beam evaporation with concurrent argon ion bombardment during growth. Films grown at high ion/atom ratios develop compressive stress as revealed by lattice dilatation. The trends in grain size, orientation, and shape as a function of ion bombardment are documented by TEM.
Vapor Deposited Thin Films and Their Densification During Ion Beam Assisted Deposition
Authors: Andreadis T.D. , Rosen Mervine , Haftel M.I. , Sprague J.A.
Published: March 2011

A computer simulation is presented of the reduction of void volume by incident energetic ions during Ion Beam Assisted Deposition (IBAD) of thin Ge films. The objective of the work is to understand the important mechanisms of thin film densification during IBAD. The density is affected by a number of mechanisms including: absorption of recoil atoms by voids and by diffusion of residual interstitials and vacancies. Simulations of Ge deposition under Ar ion bombardment were made using the collision cascade code MARLOWE with realistic void-sizes and for beam energies up to 500 eV. MARLOWE was used to obtain void volume loss as a function of void depth, void volume, and ion energy. The fate of residual interstitials and vacancies is taken into account.

In order to model IBAD it is important to be able to model the deposition process. We describe our three-dimensional Molecular Dynamics simulations of the vapor deposition of Ni on a Ni (100) surface under low atom mobility conditions. We found the deposited film to have a packing density of about 80% of the nominal value and to contain ribbon-like voids.
Atomic Structure of Heterophase Boundaries
Authors: Fecht Hans J.
Published: March 2011

Geometric models relating the energy of heterophase boundaries to their atomic structure can be based on the static distortion wave concept. This approach allows to separate the energetic contributions of commensurate and incommensurate boundary structures and provides the physical basis for models proposed previously to predict low energy configurations of such interfaces.
High Resolution Plan View Imaging of Clean and Au Deposited Si(111) Surfaces
Authors: Ozawa S. , Tanaka Y. , Kobayashi K. , Yamamoto N. , Yagi K.
Published: March 2011

High resolution plan view images of clean and Au deposited Si(111) surfaces are presented. Corner holes and small holes between dimers of the DAS model of the 7×7 structure were clearly resolved. In the case of the Si (111) 5×1-Au structure the 5 times period fringes did not show fine details.
Kinetics of Molecular Beam Epitaxy: Effect of Ion-Induced Sputtering
Authors: Richards Peter M.
Published: March 2011

Steady state roughness of surfaces growing by molecular beam epitaxy is investigated by Monte Carlo simulations under conditions where an ion beam is also present which sputters adatoms off the surface. If the sputtering is random, it only increases the roughness. But if the sputtering probability is strongly dependent on the binding energy of an adatom within a cluster or island, the ions can have a smoothening effect. Physical arguments are given in support of the results.
Improvement of Gaas Crystal Quality on Si Grown by Mocvd Through Two-Dimensional-Like Nucleation with Low Temperature in Situ Hydrogen/Arsine Plasma Cleaning
Authors: Yoon Euijoon , Reif Rafael
Published: March 2011

We report the significant improvement of GaAs crystal quality on Si grown by metal-organic chemical vapor deposition (MOCVD) with an in situ low temperature hydrogen/arsine plasma cleaning of the Si substrate at 450°C and a consequent controlled two-dimensional-like morphology of the low temperature buffer layer at its early stage. The most critical step that determines the interfacial cleanliness and the early stages of the nucleation and thin film formation of heteroepitaxial GaAs on Si in a non-ultrahigh vacuum MOCVD system is the substitution of hydrogen atoms passivating the Si surface after ex situ HF-dip with pas-sivating As atoms. Reduction of in situ cleaning temperature ensures the very slow kinetics of thermal desorption of the hydrogen atoms and re-oxidation of exposed Si surface from the reactor environment, and provides a fully As-passivated Si surface, leading to a 2D-like buffer layer.
Dynamics of Mbe Growth Surface Roughening of Ge (001) - A Stochastic Model Study
Authors: Khoie Venkatasubramanian R. , Khoie Rahim
Published: March 2011

A stochastic model for the MBE growth of Ge is developed based on the master equation approach with solid-on-solid restriction and quasi-chemical approximation. The surface kinetic processes included are: adsorption, evaporation and intralayer and interlayer migrations. The growth rate, the average surface roughness and the average intensity of reflection high energy electron diffraction (RHEED) (using kinematical theory of electron diffraction’ were obtained for the MBE growth of Ge with the temperature in the range 100-500°C and a typical flux of 1 Å/sec. The average surface roughness and the growth rate are found to be independent of substrate temperature below 150°C and above 400°C. In the intermediate temperature range, the growth rate increases and the surface roughness decreases with increasing temperature. The kinetic roughening temperature above which a smooth surface remains smooth, is identified from the temperature depen-dance of the average surface roughness and RHEED intensity, as 400°C. The temperature dependance of the average RHEED intensity and the kinetic roughening temperature obtained from this study compare favorably with the experimental results. At low substrate temperature, the surface migration rate is negligible irrespective of the temperature and therefore, the surface roughness and the growth rate become independent of the growth temperature. At high substrate temperatures, the surface roughness and the growth rate attain the limiting values for the flux chosen, owing to the saturation of the available sites for the interlayer migration process. Thus, these parameters become independent of the growth temperature.
Initial Stages of Gaas Growth on Scl-XErxas Surfaces
Authors: Finstad Terje G , Palmstrøm C. J. , Mounier S. , Keramidas V. G. , Zhu J. G. , Carter C. B.
Published: March 2011

Lattice matched ScxEr1-xAs (ScErAs) was grown on GaAs by MBE followed by a GaAs overlayer. The overgrowth of GaAs on ScErAs has been studied by Reflection High Energy Electron Diffraction (RHEED), Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), Nomarskii-interference microscopy and Transmission Electron Microscopy (TEM). In this study substrate temperature and crystal orientation have been varied. For GaAs growth on (100)ScErAs there is a strong tendency for island formation and three dimensional (3D) growth. For high substrate temperatures (>500 °C) and for moderate growth rates (10 ML/min) the growth can be described by the Volmer-Weber mode. For lower substrate temperatures we observe that one monolayer of GaAs on ScErAs is metastable. This monolayer shows a (3×1)/(1×3) surface reconstruction. The deposition of more than one monolayer, irrespective of substrate temperature, or the raising of the substrate temperature induces island growth. The metastable reconstructed surface layer of GaAs then partly dissolves into the islands. The strong tendency for 3D growth observed here is very similar to that seen in the growth on ErAs which is not lattice matched to GaAs. This observation demonstrates the significance of electronic bonding mismatch over lattice mismatch for heteroepitaxy between materials with ionic and covalent bonding character. Growth on {111}-polar surfaces yields smoother layers and a stronger tendency for 2D growth.
An Electron Microscopy Study of the effects of Deposition Conditions on the Growth of Glow Discharge Prepared a-Ge:H Films.
Authors: Jones Scott J. , Turner Warren A. , Pang Dawen , Paul William
Published: March 2011

Electron microscopy techniques have been used to study the effect of deposition conditions on island growth and coalescence in r.f. glow discharge prepared a-Ge:H. Planar views of 500 Å thick films were obtained using transmission electron microscopy (TEM) while scanning electron microscopy (SEM) was used to investigate the cross-sectional microstructure of thicker films. Films were prepared on both electrodes of a capacitively-coupled, diode deposition system. The substrate temperature, level of applied power, externally applied d.c. substrate bias, and the germane to diluent gas ratio were systematically varied. For films prepared on the unpowered electrode, island coalescence was dramatically enhanced with increasing substrate temperature while columnar structure, found for samples prepared at lower substrate temperatures, vanished. Both effects are attributed to the elimination of a coalescence barrier with increased temperature. Increasing negative substrate bias slightly increased island coalescence while increasing the level of applied power had no visible effect on film microstructure. The island size decreased with increasing dilution of the gas plasma by H2. The addition of GeF4 to the gas plasma leads to a low density, porous film. This observation is attributed to either a difference in the plasma chemistry or increased film etching due to the presence of F in the gas plasma. High quality films prepared on the powered electrode were found to be more structurally homogeneous and environmentally stable than films prepared on the unpowered electrode at the same substrate temperature. Enhanced bombardment and/or a different plasma chemistry near the powered electrode are two factors which may contribute to the observed difference in microstructure.
Approach Towards Heteroepitaxial Growth of Functional Molecular Crystals by Vapour Deposition
Authors: Inoue A. , Ishino M. , Akagi Y. , Koba M.
Published: March 2011

In order to realize a thin film of organic single crystals, we have been investigating fabrication process using vapour deposition technique. Up to now, highly oriented thin films of 2-methyl-4-nitroaniline(MNA) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene(DAN), both of which are promising organic materials for nonlinear optical devices, could be fabricated on a buffed polyimide and on a thermally oxidized silicon wafer, respectively. In the case of MNA films, a series of results by X-ray diffraction and by SEM observation showed weak two-dimensional characteristics suggesting the existence of topographic effects and/or of interaction between MNA molecules and molecular moieties of polyimide substrate. Small optical transmittance of both MNA and DAN thin films are explained in terms of light scattering by grain boundaries and surface roughness.
Characterization of Si/Si3N4 Layered Structures Grown By Physical Vapor Deposition/Ion Beam Assisted Deposition
Authors: Cotell C. M. , Donovan E.P.
Published: March 2011

Layered silicon/silicon nitride structures were fabricated on (100) Si with 0.1 mTorr of N2 background pressure. Evaporated Si (PVD) layers were alternated with layers grown by simultaneous nitrogen ion bombardment and Si evaporation (IBAD). The ion to vapor flux ratios were chosen to yield stoichiometric Si3N4 (XN=0.57) at 150, 500, 1000 and 1500 eV and varied at a constant energy of 500 eV to yield sub- and superstoichiometric Si1-xNx. The microstructures were examined by cross-sectional and plan-view TEM; composition of the layers was deteiTnined by RBS. Films grown at low substrate temperatures were amorphous. Stoichiometric and superstoichiometric compositions showed a cellular (5 nm) structure in the amorphous IBAD layers. In addition, the IBAD Si1-xNx layers showed variations in contrast parallel to the substrate interface, indicative of compositional fluctuations on a scale of <20 nm. The IBAD layers were dense, but the PVD-Si layers contained voids that were aligned with the direction of the impingement of the evaporant on the substrate surface. A high substrate temperature (750°C) yielded polycrystalline Si layers and phase-ordering in the Si1-xNx layers.
Interplay of Strain, Growth Kinetics and Surface Bonding in Growth Modes and Dislocation Generation in Strained Heteroepitaxy
Authors: Snyder C. , Pamulapati J. , Orr B. , Bhattacharya P. K. , Singh J.
Published: March 2011

In this paper we examine the role of strain and growth kinetics on the growth modes in pseudomorphic growth. Regimes below critical thickness and above critical thickness are examined. Based on atomistic modelling and in-situ RHEED and STM studies we show that a competition between surface chemical energy and strain energy is shown to lead to 3-dimensional blend mode for high strain pseudomorphy. Consequences for dislocation generation are discussed.
Initial Growth of Ag/Si(100) Studied with High Spatial Resolution Aes and Sem
Authors: Luo Frank C. H. , Hembree Gary G. , Venables John A.
Published: March 2011

The initial growth of Ag on reconstructed Si(100) has been studied with biassed secondary electron imaging (b-SEI) and Auger electron spectroscopy (AES) in an ultra-high vacuum (UHV) scanning transmission microscope (STEM) with nanometer resolution. Small Ag islands have been observed with strong contrast in b-SE images. Anisotropic growth, correlated with the (2×1) and (1×2) dimer reconstruction, is seen at room temperature and sub-monolayer (ML) coverage. Large Ag islands (∼1 μm) formed at 475 °C substrate temperature have even more dramatic forms with large aspect ratios. The Stranski-Krastanov (SK) mode is confirmed at both temperatures by AES and b-SEI between the islands, with the intermediate layer coverage equal to 0.5 ML or less.
Misfit Dislocations at the Critical Thickness for Ingaas/Gaas Strained Layers
Authors: Green G. S. , Tanner B. K. , Turnbull A. G. , Barnett S. J. , Emeny M. , Whitehouse C. R.
Published: March 2011

The contrast of misfit dislocations in an InGaAs layer, close to the critical thickness and capped with GaAs grown by MBE on a (001) oriented GaAs substrate has been investigated by double axis synchrotron X-radiation topography. The layer thickness variation as a function of position has been measured to a precision of 1A by matching interference fringes observed in the 004 symmetric reflection double crystal rocking curves with simulations. The misfit dislocation density is highly anisotropic, varying from zero to a high value with increasing thickness. The contrast of the dislocations in the 004, 224 and 044 reflections has been examined in detail. All of the long dislocation segments characterized were 60° in character with ½<110> Burgers vectors inclined to the specimen surface. No dislocations were found which did not appear to be of this type. A surprising difference in contrast of the background in the 224 and 224 reflections is discussed.
Epitaxial Layer Misorientation in CdTe on GaAs‡
Authors: Inglefield H. E. , Matyi R. J. , Korenstein R.
Published: March 2011

X-ray diffraction has been used to characterize the relative misorientation of [001] and [111] CdTe layers grown by hot-wall epitaxy on GaAs substrates. The magnitude of the misorientation of the CdTe epitaxial layer relative to the GaAs substrate depends on the magnitude of the miscut of the substrate; in addition, the [111] oriented CdTe exhibited significantly larger misorientations than did the [001] CdTe films. The azimuthal direction of the tilt of the epitaxial layer depends strongly on the nominal crystallographic orientation of the film. The [111] CdTe exhibited an azimuthal dependence of the tilt that is approximately coincident with the miscut of the substrate, while the azimuthal direction of tilt in the [001] CdTe layers differed from the substrate miscut direction by as much as 116°. These observations of epitaxial layer misorientation are discussed in terms of a dislocation model for layer tilt and azimuthal rotation in lattice-mismatched epitaxial systems.
Development of Pseudomorphic Structure in Ge Films Deposited on Si(100) at Low Temperatures
Authors: Lyman P. F. , Thevuthasan S. , Grant M. W. , Hoogenraad J. H. , Seiberling L. E.
Published: March 2011

We have studied the structure of 1 to 10 monolayer (ML) Ge films grown at room temperature on Si(100)–(2 × 1). Using transmission ion channeling spectroscopy, we have uncovered the first evidence for pseudomorphic structure in these films, contradicting the widely–held belief of amorphous growth at temperatures below 500 K. A model is proposed in which pseudomorphic domains constitute roughly half of the Ge films up to a critical thickness (∼4 ML), after which strain is relieved through defect introduction. Several of the films grown at room temperature were subsequently annealed for 20 min. at fixed temperatures ranging from 450 K to 790 K. A marked improvement in the epitaxial quality of the films is observed upon annealing that is consistent with growth proceeding from existing pseudomorphic domains.
Scanning Tunneling Microscope Study on Amorphous and Crystallized CoSi2 Films
Authors: Kuwabara M. , Smith D. A. , Welland M. E.
Published: March 2011

CoSi2 films were investigated using a scanning tunneling microscope (STM) to understand the film surface topology. The STM images showed that the as-deposited amorphous film had a nano-meter scale roughness which agrees with cross-sectional transmission electron microscope (TEM) observations and also had a uniform granular structure. Images of the crystallized film clearly show the crystal grain structure at the surface and the surface topography change associated with crystallization. In-situ crystallization was accomplished by operating the STM with a high bias; dome shape crystallites were produced at the surface of the amorphous films.
Interfacial Atomic Structures During Cobalt Silicidation
Authors: Catana A. , Schmid P.E.
Published: March 2011

High Resolution Electron Microscopy (HREM) and image calculations are combined to study microstructural changes related to the CoSi/Si-CoSi/CoSi2/Si-CoSi2/Si transformations. The samples are prepared by UHV e-beam evaporation of Co layers (2 nm) followed by annealing at 300°C or 400°C. Cross-sectional observations at an atomic scale show that the silicidation of Co at the lower temperature yields epitaxial CoSi/Si domains such that [111]Si // [111]CoSi and <110>Si // <112>CoSi. At about 400°C CoSi2 nucleates at the CoSi/Si interface. During the early stages of this chemical reaction, an epitaxial CoSi/CoSi2/Si system is observed. The predominant orientation is such that (021) CoSi planes are parallel to (220) CoSi2 planes, the CoSi2/Si interface being of type B. The growth of CoSi2 is shown to proceed at the expense of both CoSi and Si.
On The Nature of Multiple Orientation Relationships in Epitaxial Silicides
Authors: Felton L.E. , Dakshinamurthy S. , Rajan K.
Published: March 2011

The Invariant Line Criteria (ILC) has been used to explain experimentally observed precipitation and epitaxial orientation relationships in a number of metallurgical systems. We propose that ILC may explain the crystallography of misoriented silicide grains in epitaxially grown silicide films. We test our hypothesis on the case of misoriented grains in CoSi2 on Si (001). Our analysis shows that the experimentally observed orientation relationship is predicted by the ILC.
Evolution of Residual Stresses in Thin Films Deposited on Mechanically Strained Substrates
Authors: Sheikh G. , Berger A. , Noyan I. C.
Published: March 2011

A simple model for the formation of residual stresses in thin films deposited on elastically strained substrates was derived and experimentally tested. In the experiments, Cu thin films were deposited on elastically stretched nickel substrates. These Cu films were2 to 4.m thick and were deposited through vapor phase evaporation or electroplating. The loads applied during the deposition were then relaxed, and the total stress in both the film and the substrate were monitored (by x-ray diffraction) during this relaxation. It was seen that the final (residual) film stresses were significantly different for bothdeposition methods. The causes of such differences are discussed.
Studies on the Surface Modification of Benzocyclobutene(BCB) Film By Plasma Ions
Authors: Paik Kyung W. , Saia Richard J. , Chera John J.
Published: March 2011

The etch rates of BCB film in a reactive ion etcher(RIE) were measured using Ar, O2, O2+CF4, and O2+SF6 gas mixtures. Faster etch rates were obtained when CF4 and SF6 were added to oxygen, since the presence of atomic fluorine enhances the etch rate of organics, while also etching Si and SiO2 formed by exposure to oxygen gas. Surface compositional changes on the BCB film were observed by XPS after plasma modification. Pure O2 and O2+CF4 plasma oxidized the carbo-siloxane linkage (C-Si-O) of the BCB, resulting in the formation of SiO2 on the surface. The O2 +SF6 plasma, however, did not produce the surface SiO2, because of its faster Si and SiO2 etch rates. Ar ion sputtering following the plasma modification, restored the surface chemical composition to a state similar to the initial BCB surface.
Cavity Evolution in High Strength Electroless Copper
Authors: Pedraza A. J. , Godbole M. J. , Toth J. R.
Published: March 2011

Several industrial facilities produce electroless copper for use in printed circuit boards. One major class is the high- strength copper, so called because of its extremely high strength. During the deposition process, hydrogen is commonly incorporated into the film and it is thought to be the cause of poor ductility.

In this work, the hydrogen content was measured by the fusion technique in three sets of high strength electroless copper specimens, respectively annealed at 423, 520 and 573 K. The hydrogen content decreased very rapidly at the two higher temperatures, and tended to a saturation value of approximately 20 ppm by weight with increasing annealing time. The cavity evolution with annealing time at 520 and 573 K was studied by transmission electron microscopy (TEM). It was found that the number of cavities increased with annealing time and with increasing temperature.

The data indicate that hydrogen degassing is not controlled by bulk diffusion and, hence, that hydrogen must be trapped. A comparison with recrystallization results demonstrates that more than half of the hydrogen retained in the electroless copper is in saturable traps. The TEM observations indicate that cavity coarsening takes place during annealing at 520 and 573 K.
Mechanical Properties of CVD Tungsten Fibers
Authors: Lilienfeld David , Steinwall James , Borgesen Peter
Published: March 2011

Tungsten fibers were fabricated with dimensions relevant to microelectronics and microfabrication. The strength and modulus were 1.57±0.7GPa and 276±lO%GPa, respectively. The failure mode was most consistent with intergranular fracture.
Multi-Chip-Module Interconnections by Laser Direct Writing
Authors: Müller Heinrich G. , Paredes Alvaro , Buschick Klaus , Reichl Herbert
Published: March 2011

A very flexible maskless technique for thin film hybrid formation has been developed. Lay outs are transferred directly from work stations to laser controls. Openings in ceramic substrates are achieved through laser cutting, and chips are embedded to give a common chip-to-substrate surface, flat to within 2 μm. Dielectric layers of polyimide are formed by spin on techniques and are then laser structured for via hole formation.

Interconnections of the embedded chips are generated by laser direct writing of thin copper lines from copper formate, followed by chemical copper deposition. Chemical pretreatments of the aluminum contact pads allow for reasonable chip contacting with these methods. Electrical measurements on the dc line conductivity and the high frequency behaviour of these interconnections have also been performed.
The Formation and Morphology of Stress Induced Voids in Thin Narrow Aluminum Lines
Authors: Paszkiet C. A. , Korhonen M. A. , Li Che-Yu
Published: March 2011

Thin, narrow, lines were reactive ion etched from a highly textured aluminum film deposited on (100) silicon substrates; some arrays of lines were covered with a passivation layer of silicon nitride. Passivated and unpassivated lines were heat treated at 400°C.

Voids were present in nitride covered lines which were aged for over three months at room temperature as well as in nitride covered lines examined immediately after heat treatment. Voids were not visible in bare, heat treated lines. Void nucleation occurred at the points of intersection of grain boundaries with line edges and growth appeared to follow grain boundaries.
A Fracture Mechanics Approach to Thermal Fatigue Life Prediction of Solder Joints
Authors: Pao Yi-Hsin
Published: March 2011

The approach developed is based on the assumption that thermal fatigue crack propagation in solder joints is primarily controlled by C* and J integrals. The effect of microstructural coarsening on crack propagation is discussed. A fracture criterion, J≥Jc, is used to define the failure of the joints. A crack growth governing equation has been formulated and can be numerically integrated to obtain the crack growth history given stress history as an input. The approach was applied to model the experiment by Wong and Helling [15]. In their experiment, surface-mounted electronic devices using eutectic Pb/Sn solder were tested in thermal cycles of −20 to 100°C and −55 to 125°C. A unified constitutive equation was assumed for the eutectic Pb/Sn solder. An equation for solving the shear stress in the joint was formulated and is coupled with the crack growth equation. Both equations were solved simultaneously by the Runge-Kutta method for the stress-time and crack growth history. The results of the prediction are in a good agreement with the experimental data, which indicates that fracture mechanics may be applied to describe the failure process of solder joints under cyclic thermal loadings.
Integrated Matrix Creep: Application to Lifetime Prediction of Eutectic Tin-Lead Solder Joints
Authors: Knecht Sheera
Published: March 2011

The matrix creep failure indicator developed by Shine and Fox is extended to cases when strain is multiaxial and varies with position in the structure. Analysis of a thermal fatigue test of leaded surface mount devices found in the literature illustrates application of the method. A butt joint surface mount configuration is then tested in simple mechanical loading and also analyzed using the finite element method. It is found that the matrix creep “damage integral” method gives good correlation with observed solder fatigue failures for both cases.
Structural Investigation of the Silver—Polyimide Interface by Cross—Sectional Ten and Ion—Beam Sputtering
Authors: Foitzik A. , Faupel F.
Published: March 2011

When metals are deposited on polymers at low rates and elevated temperatures extended and non—uniform interfaces may form, the structural investigation of which requiresspecial techniques. In this paper the morphology of the silver—PMDA—ODA boundary formed during vapor deposition of the metal at 360 ºC has been investigated by means of cross—section TEM and a radiotracer technique in combination with ion—beam sputtering (IBS) for depth profiling. Ag was found to form clusters at the interface, but nearly spherical Ag particles up to diameters as large as 28 nm were also observed within the bulk of the polymer. The formation of Ag clusters is also reflected in the depth profiles, which, in addition, provide direct evidence for the diffusion o; singel Ag atoms deep into the polyimide. Diffusivities in the range of 10–21 – 10–18 m/s were determined for 300 ºC< T < 400 ºC. The Arrhenius plot is curved in accordance with a free—volume mechanism of diffusion. Cross—sectional TEM and low—energyIBS—depth profiling turned out to be an ideal combination for the investigation of extended metal—polymer interfaces.
Measurement of the Triaxial Stress State of Confined Line Structures During Thermal Cycling
Authors: Moske M.A. , Ho P.S. , Mikalsen D.J. , Cuomo J.J. , Rosenberg R.
Published: March 2011

A method based on the bending beam technique has been developed to measure the mechanical stresses of fine lines confined by a dielectric layer. This method has been employed to determine the thermal stress of AI(2at%Cu) lines passivated by a quartz overlayer between room temperature and 400ºC. The effect of quartz confinement was analyzed by matching the thermal strains at the metal/quartz interfaces and imposing a mechanical equilibrium condition on the structure. The analysis enables us to deduce the triaxial stress components of metal and quartz from measurements of the substrate bending parallel and perpendicular to the length direction of the lines. Results of the measurementshow a substantial stress enhancement as a result of the confinement, with the stress level significantly higher than that of a passivatecd blanket film. The magnitude of the stress depends on the line geometry, the layer deposition conditions and the extent of plastic deformation during thermal cycling. Results of this measurement are consistent with those determined using X-ray techniques.
Low Temperature Ceramic Coatings for Environmental Protection of Integrated Circuits
Authors: Chandra Grish
Published: March 2011

A novel concept for improved environmental protection of integrated circuits uses thin, in-situ formed ceramic layers on the circuit surface. Metastable ceramic precursors, hydrogen silsesquioxane and silacyclobutane, convert to pure silica and amorphous silicon carbide dielectric films respectively upon processing at temperatures from 175 to 250ºC. These twolayer ceramic films were shown to protect silicon CMOS circuits from industry-recognized autoclave and HAST exposure environments for more than 400 hours whereas unprotected circuits always failed within 200 hours.
Kinetics of Thermal Decomposition of Group-Hi Metal Alkyls on GaAs(100)
Authors: Donnelly V. M. , Mccaulley J. A. , Shul R. J.
Published: March 2011

We report studies of the kinetics of thermal decomposition of triethylgallium (TEGa), trimethylgallium (TMGa), and trimethylindium (TMIn) adsorbed on GaAs(100) in ultrahigh vacuum. The adsorbed layers were prepared by dosing GaAs(100) at room temperature, to either saturated coverage or coverages below saturation. Subsequent heating leads to loss of adsorbed hydrocarbons. The relative coverage of carbon was monitored by X-ray photoelectron spectroscopy (XPS), and products were detected with a differentially pumped quadrupole mass spectrometer. The kinetic analysis also includes measurements of laser-induced, rapid thermal decomposition (heating rates of ∼1011°C/s).

TEGa dissociatively chemisorbs on GaAs(100). Heating the substrate results in desorption of diethylgallium radicals at low temperature and C2H4 (and some C2H5) at higher temperatures, after most of the diethylgallium has desorbed. TMGa decomposes to yield a Ga-alkyl desorption product (either dimethylgallium, or a mixture of dimethylgallium and TMGa) at low temperature and CH3 at higher temperature. TMIn undergoes a methyl exchange reaction on GaAs(100) where a Ga-alkyl desorbs with the same cracking pattern as in TMGa decomposition. Decomposition mechanisms for these group-III metal alkyls are proposed, Arrhenius parameters are presented, and some implications are discussed for growth of Ga-containing III-V compound semiconductor films from these precursors by chemical vapor deposition and molecular beam techniques.
Carbon Incorporation in Metal Organic Vapor Phase Epitaxy Grown Gaas Using chyX1-y, TMG, and ASH3
Authors: Kuech T.F. , Buchan N.I. , Scilla G. , Cardone F. , Potemski R.
Published: March 2011

The unintentional and intentional incorporation of carbon has been investigated in order to understand both the growth kinetics as well as develop new and useful carbon doping sources. We present in this study a systematic investigation of the use of halomethanes during the MOVPE based growth of GaAs. We have used 13C tagged trimethyl gallium, AsH3, together with non-isotopically tagged halomethane sources, in order to determine the source and mechanism of the carbon incorporation. The carbon concentration was determined by secondary ion mass spectroscopy (SIMS). The carbon incorporation in the unintentionally doped material is compared to that obtained with the series of halomethanes, CHxI4-x (x=0,2-4), the chlorine analogs, CHC13 and CCI4, and the bromine containing compounds, CHBr3 and CBr4 which are used to intentionally introduce carbon in the epitaxial GaAs. The incorporation of carbon is studied here as a function of the halogen/H ratio in the source material and on the halogen ligand on the carbon nucleus. The standard growth parameters of susceptor temperature and gas phase composition were varied in order to discern the useful growth parameter regimes for these compounds.
Design and Characteristics of a Novel Close-Spaced Reactor for Organometallic Epitaxy
Authors: Chinoy P.B. , Ghandhi S.K.
Published: March 2011

A novel, close-spaced, inverted, stagnation flow, organometallic vapor phase epitaxy (OMVPE) reactor has been designed and fabricated for achieving high deposition efficiency and good large-area uniformity for solar cell applications. A computer model for this reactor, which is based on the conservation of mass, momentum, energy and species equations, has been used for predicting its operating characteristics. Due to the close spacing between the nozzle and susceptor, extensive measurements of the nozzle temperature were carried out for different reactor conditions and compared with simulation results. The maximum nozzle temperature was about 110°C showing the feasibility of GaAs growth from trimethylgallium and arsine. GaAs epitaxial layers were grown at different susceptor-nozzle distances, gas flow rates, reactor pressures and susceptor temperatures. The morphology, electrical properties and thickness uniformity of the layers were found to be of an acceptable quality. The measured and computed deposition efficiencies were found to be independent of reactor pressure and increasing with decreasing gas flow rates. The highest gallium deposition efficiency achieved was about 42%.
Surface Chemistry of Te-RICH CdTe
Authors: Zinck J.J. , Brewer P.D. , Olson G.L.
Published: March 2011

A study of the changes in surface structure and composition of CdTe(100) irradiated by 248 nm excimer laser radiation in the fluence range 18-75 mJ/cm2 is presented. Material is removed from the CdTe surface at all fluences, but above a threshold fluence of 40 mJ/cm2 the surface becomes Te-rich. Reflection high energy electron diffraction measurements indicate that the original 2×1 surface reconstruction is converted to a 1×1 pattern at fluences < 40 mJ/cm2. At exposures which generate a Te-rich surface a RHEED pattern is not observed. Temperature programmed desorption experiments show that weakly bound Tex exists on the surface after exposure at all fluences used in this study. A correlation of Auger data, desorption lineshapes, and model calculations suggest that the excess Te forms three dimensional islands on the surface.
Limitation of Selective Epitaxial Growth Conditions in Gas Source MBE Using Si2H6
Authors: Sakai Junro , Aketagawa Ken-Ichi , Tatsumi Toru
Published: March 2011

Low temperature and high growth rate selective epitaxial growth (SEG) on Si02 patterned Si (001) substrate in gas-source molecular-beam epitaxy (GS-MBE) using pure Si2H6 has been investigated by RHEED observation. In the temperature range of 550 to 850°C, SEG was completely obtained at an initial growth stage. Limiting conditions of SEG were closely related with critical volume of supply gas that was equal to the total amount molecules supplied on SiO2 surface during the incubation period of initial growth. The surface SiO2 was induced to evaporate with Si2H6 supplied above 800°C, so that thermal cleaning temperature for removing native oxide came down to 800°C. As a result, the maximum process temperature of Si SEG now became 800°C, and its growth rate reached as high as 645A/min at growth temperature of 700°C.