bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variations Of Fractal Dimension During the Phase Transformation To The Silucide Nucleation in Thin Film Systems
Authors: Cho Nam-Lhn , Nam H. Gin 
Published: March 2011

ABSTRACTDetailed relationship between the fractal dimension and the excess noise frequency exponent has been considered for metal-silicon interfacial structures during the phase transformation to the initial compound phase formation in thin film systems. In the estimation of the fractal dimension of the thin film structures, a technique has been used, which basically employs a digital image processing of highly magnified micrographs of the structures. Previously measured frequency exponent data of the excess noise power spectral density for the same thin film systems has been interpreted by introducing a multiplication process which combines the fractal dimension variations and cluster interactions of the interfaces. It has been assumed that the fractal dimension plays a role as a multiplication factor in the multiplication process.
Microstructure of Si Films Deposited on Si(100) Surfaces by Remote Plasma-Enhanced Chemicalvapor Deposition, Rpecvd: Dependence on Process Pressure and Substrate Temperature
Authors: Habermehl S. , He S. S. , Chen Y. L. , Lucovsky G. 
Published: March 2011

ABSTRACTThe microstructure of Si thin films, deposited on in-situ cleaned Si(100) surfaces by remote plasma-enhanced chemical-vapor deposition (RPECVD), is dependent on the process pressure, substrate temperature and H2 flow rate. Surface characterization by on-line low energy electron diffraction, LEED, has been used to detect changes in the character of the deposited films which can either be amorphous, microcrystalline or crystalline, hereafter designated as a-Si, Sμc-Si, and c-Si, respectively. We have used these results to generate phase diagrams for the Si microstructure as a function of the process pressure and substrate temperature, including the flow rate of H2 as an additional deposition parameter.
Laser Induced Phase Transformations in Thin Insb Films
Authors: Chou L.L. , Kuo M.M. 
Published: March 2011

ABSTRACTThin In46Sb54 films have been prepared on glass substrates by flash evaporation. Films of 1000 Å were deposited at room temperature. After 7 mins' thermal annealing at 450ºC, an average grain size increased from 20 nm to 200 nm. Under exposure to a Fraunhofer diffracted pulsed Nd-YAG laser beam, the films showed different microstructures for different applied laser power. In general, five regions are identified: ablation region, regions with grain sizes less than 20 nm, grain sizes ranging from 400 to 1000 nm, grain sizes ranging from 200 to 400 nm and unchanged region. The previous five regions are counted from the center of the exposed area outward. The pulse duration is 16 ns. In this paper, an atomic migration mechanism is proposed to explain the power dependent microstructures changes. Transmission electron microscopy was mainly used to characterize the films. The application of this type of phase transformations in the phase change optical storage is also discussed.
The Reactivity of Thin Titanium Films Towards Aluminum and the N-O-N Insulator Stack, and its Effects on the Composition and Properties of Voltage Programmable Links
Authors: Gleason Edward F. , Cohen Simon S. , Wyatit Peter W. 
Published: March 2011

ABSTRACTA metal-insulator-metal (MIM) voltage programmable link (VPL) has been fabricated that relies on the breakdown of a thin nitride - oxide - nitride (N-O-N) plasma deposited insulator stack. The metal electrodes were prepared by depositing a titanium layer (400 Å) on top (or bottom) of 7500 Å Al ( 1% Si). The resulting metallization resists hillock formation during thermal anneal steps and thus preserves the integrity of the thin link dielectric. The breakdown voltage is typically 10 volts for a 100 Å-150 A-100 Å NON stack. Sintering at temperatures up to 425°C results in a negligible increase in breakdown voltage. After sinter at 455°C, the breakdown voltage drops to 6 volts and continues to decrease with further sintering. Auger depth profiles of the as-deposited sample indicate the N-O-N stack is intact and the titanium has also not reacted with the aluminum film. After sinter at 455°C no distinct interfaces are observed in the auger depth profile. Angle-resolved x-ray photoelectron spectroscopy (ARXPS) of the nitride film after deposition and sinter indicate that the nitride film reacts with the titanium to form titanium nitride or titanium silicide. Angle resolved measurements indicate the titanium concentration has increased by a factor of 5 throughout the film as compared to the as-deposited sample. These results explain the observed drop in breakdown voltage since the insulator is being consumed and being converted into conducting titanium nitride or titanium silicide.
Grain Boundary Diffusion Controlled Precipitation as a Model For thin Film Reactions
Authors: Barmak K. , Coffey K.K. 
Published: March 2011

ABSTRACTIn order to arrive at a model for nucleation in the reaction of polycrystalline thin films, we have made use of a transport model that combines atom transport across interface reaction barriers with transport along grain boundaries. Through this transport model, the boundary chemical potential, μIi, and a characteristic length Li for each specie are defined. Li and the ratio of grain size to Li determine the spatial variation and the time evolution of the boundary chemical potential respectively. Nucleation of the product phase is modeled as a process whose driving force is determined by these position dependent (and time dependent) boundary chemical potentials. Thus thin film reactions become similar to precipitation from bulk homogeneous supersaturated solid solutions. Numerical calculations, however, show that boundary diffusion results in low “effective” driving forces for nucleation which can lead to heterogeneous nucleation of even the first phase. The model provides a new approach to phase selection by re-evaluation of the driving force and considers the effect of product and reactant grain structure to be fundamental to the reaction process.
Mechanisms of Transition Metal Diffusion into Semiconductor Film
Authors: Goldiner M. G. , Vaysleyb A. V. 
Published: March 2011

ABSTRACTDescriptions of metal (Me) diffusion into semiconductor (Se) film by diffusion-kinetic and purely kinetic methods were compared. To analyze thin film diffusion, thin film surfaces were considered as a substantial source/sink of point defects. Conditions of transition from one Me diffusion transport mechanism/regime to another, when Se sample thickness is changed, were found to be practically the same in both considerations. Critical Se film size, dislocation density, and temperature of diffusion mechanisms and regimes coincide, providing a correct interpretation of the experimental results in terms of the corresponding diffusion mechanism.
Evolution of Gd Thin Film Structure Due to Amorphization by Co Deposition
Authors: Hufnagel T.T. , Bertero G.G. , Sinclair R. , Clemens B.B. 
Published: March 2011

ABSTRACTMultilayers of Gd/Co produced by sputter deposition are observed to be amorphous for a wide range of bilayer periods. This structure is largely the result of an amorphization reaction during the deposition between crystalline Gd and newly arriving Co atoms. We explore this reaction by producing multilayers of Gd/Co/Cr, and examining the resulting microstructure. We observe both interfacial disordering due to a layer thickening mechanism and evidence for growth of the amorphous phase from Gd grain boundaries. The reaction is enhanced by the presence of a large number of crystalline defects in the Gd layers.
Interface Quality and Interdiffusion in Si-Ge Heterostructures
Authors: Baribeau J.-M. , Lockwood D. J. , Aers G. C. , Dharma-Wardana M. W. C. 
Published: March 2011

AbstractThe evolution of interfaces of short-period (SimGen)p superlattices upon annealing has been studied by x-ray reflectometry and Raman scattering spectroscopy. Isothermal annealing treatments at 700° C resulted in a significant material redistribution as evidenced by a strong decay of the superlattice x-ray satellites and by the decay of longitudinal acoustic modes and changes in the optical mode intensity ratios in Raman scattering. Interdiffusion was more pronounced in superlattices of short periodicity. This may possibly be explained by the strong composition dependence of the diffusivity of Ge atoms in Sil-xGex alloys and the degree of preexisting interfacial mixing. This composition dependence of the diffusion may favor atomic displacement parallel to the interfaces leading to an initial smoothing of the interfaces
The Dynamical Transition to Step-Flow Growth During Homoepitaxy of GaAs (001)
Authors: Orr B. G. , Sudijono J. , Johnson M. D. 
Published: March 2011

AbstractThe evolution of surface morphology of molecular-beam-epitaxy-grown GaAs (001) has been studied by scanning tunneling microscope. Images show that in the early stages of deposition the morphology oscillates between one -with twodimensional nucleation and coalescing islands, i.e. flat terraces. After the initial oscillatory regime, the system evolves to a dynamical steady state. This state is characterized by a constant step density. As such, the growth mode can be called a generalized step flow. Comparison with RHEED shows that there is a direct correspondence between the surface step density and the RHEED specular intensity. An increase in step density results in a decrease in specular intensity. Additionally, further deposition beyond 120 monolayers (up to 1450 monolayers) display a slowly increasing surface roughness.
Crystal Quality of III-V Substrate Wafers and Epitaxial Layers Studied by X-Ray Topography
Authors: Bassignana I. C. , Macquistan D. A. 
Published: March 2011

AbstractThe crystal quality of III-V substrates was studied by x-ray asymmetric crystal topography (ACT). An extensive study of device-quality GaAs (LEC SI, LEC n-type, VGF and VB) and InP (LEC n-type (S) and SI (Fe) ) wafers reveals that they can contain various defects: low angle grain boundaries, dislocation cell structure, slip, swirl and included mosaic structure.The high angular resolution of ACT was used to non-destructively study both the epitaxial layer and the substrate. Topographs of the substrate and the epitaxial layers of AlGaAs/GaAs layers grown by MBE and MOCVD are compared. The quality of the substrate has direct implications for the quality of the epitaxial growth. For coherent layers, both the large scale and small scale defects observed in the substrates were exactly reproduced in the epitaxial layers grown by both techniques.
Evolution of Roughness on InP Layers Observed by Scanning Force Microscopy
Authors: Cotta M. A , Hamm R. A , Chu S. N. G , Staley T. W , Harriott L. R , Panish M. B , Temkin H. 
Published: March 2011

AbstractThe evolution of surface roughness with increasing thickness of (100) InP layersgrown by metalorganic molecular beam epitaxy has been observed by scanningforce microscopy. The process of roughening gives rise to periodic elongatedfeatures on the surface aligned in the [011] direction, reflecting the surfaceanisotropy. The morphology eventually evolves to a grain-like surface. Theroughening is dependent on both the group III and V flux, and the growthtemperature, indicating that this phenomenon is kinetically controlled by surfacediffusion activation. For each set of parameters chosen for the growth, there is aminimum temperature where smooth, two-dimensional growth can be obtained.Below that temperature the roughening shows two distinct power law regimesdependent on the epitaxial layer thickness.
Low Temperature Growth Mechanisms for Rheed Oscillations
Authors: Biswas R. , Roos K. , Tringides M. C. 
Published: March 2011

AbstractLow temperature (T<150 K) RHEED oscillations during the growth of ultrathin films suggest the presence of substantial adatom mobility. In most systems thermal diffusion can not account for the observed oscillations, and the origin of the oscillations is an open question. Experiments on Ag/Si(111) at 150 K demonstrate the absence of thermal diffusion due to the observed scaling in the RHEED intensity for different flux rates. We have performed molecular dynamics simulations to understand the mechanisms of RHEED oscillations at low temperature. Classical two- and three-body Si potentials were used together with an adatom mass that is 3.84 times the Si mass to account for the Ag/Si mass ratio. Results indicate that the landing site for the adatom is very important to predict whether a particular adatom will display lateral motion or not. A fraction of the adatoms incident near a maximum of the potential energy surface display significant lateral motion. The substrate stiffness for Ag/Si results in an energy transfer process which is much slower than that in fcc/fcc systems.
Hopping Barriers at Step Edges
Authors: Šmilauer Pavel , Wilby Mark R. , Vvedensky Dimitri D. 
Published: March 2011

AbstractThe recent discovery of reentrant layer-by-layer growth in metal homoepitaxy has stimulated considerable interest in the role played by barriers to hopping down descending steps. However, the existence of step-edge barriers for semiconductors is far from being clearly established. We have investigated the effects of step-edge barriers for epitaxial growth and the “inverse” process of low-energy ion sputtering on metal surfaces using Monte Carlo simulations of a solid-on-solid model. Our results are in good agreement with available experimental data and provide new insights into the microscopic origins of the evolution of surface morphology during these processes. Our simulations also suggest that such step-edge barriers can explain the observed temperature and time dependence of the reflection high-energy electron diffraction intensity during post-growth recovery on GaAs(001), which sheds new light on this controversial subject.
Common Features of Epitaxial Growth on Vicinal GaAs(001), AlAs(001) and InAs(001) Surfaces
Authors: Shitara T. , Vvedensky D. D. , Neave J. H. , Joyce B. A. 
Published: March 2011

AbstractWe have carried out RHEED measurements and Monte Carlo simulations of the growth on GaAs(001), AlAs(001) grown on GaAs(001), and InAs(001) to address the common features of the growth near the transition to step flow. For a fixed V/IIl ratio, the cation flux and misorientation-angle dependencies of the transition temperature on AlAs(001) and InAs(001) follow the same pattern as on GaAs(001). The same anisotropic behavior was also obtained, in that the transition temperature on a surface misoriented toward [110] is higher than that on a surface misoriented toward [110]. Unlike the case of GaAs(001), however, the surface reconstruction could not be kept constant near the growth mode transition for AlAs(001) and InAs(001). Therefore, we cannot compare simulations with experiments in as much detail as we have done for GaAs(001). Nevertheless, we can still estimate the effective surface migration barrier for Al adatoms on AlAs(001) as approximately 1.74eV and for In adatoms on InAs(001) as at most 1.23eV. This value should be compared with the value of 1.58eV obtained for GaAs(001).
In-Situ Observation of The Initial Stages of Co (0001) Epitaxy on Pt (111) Using Grazing Incidence X-Ray Diffraction
Authors: Bain James A. , Clemens Bruce M. , Brennan Sean 
Published: March 2011

AbstractThe heteropitaxial growth of (111) Pt on (0001) sapphire and of (0001) Co on (111) Pt on (0001) sapphire has been observed in-situ using grazing incidence x-ray scattering (GIXS). The in-plane lattice parameters of the Pt and Co phases have been measured as a function of film thickness in the regime from two monolayers to 200 monolayers, Relaxation of elastic strain with thickness has been quantified. X-ray reflections consistent with stacking faults in the Co films have been observed and monitored as a function of thickness, giving a measure of the stacking fault density. A distinct Co phase was observed at two monolayers of Co on a thick Pt layer, indicating an incoherent interface between the Co and Pt, even at this very early stage of deposition.
Atomic Structure of The α-A12O3(0001)(√31×31)R±9° Reconstruction
Authors: Renaud G. , Villette B. 
Published: March 2011

AbstractThe atomic structure of the α-A12O3 (0001)(√31×√31)R±9° reconstruction has been solved by Grazing Incidence X-ray Diffraction. The surface structure is found to be perfectly commensurable with the underlying bulk lattice, with exponential correlation length ∼500 Å. It consists of hexagonal zones of two nearly perfect closed-packed Al(111) planes, separated by a defect of hexagonal periodicity with parameter 26.5 Å. This structure may explain why the reconstruction can be obtained at lower temperature by deposition of a few aluminum layers, and why Al/Al2O3 multilayers remain coherent, with aluminum of (111) orientation.
Natural Patterning of High-Index Gaas Surfaces
Authors: Nötzel Richard , Ploog Klaus H. 
Published: March 2011

AbstractWe present new methods to directly syntesize III-V semiconductor quantum-wire and dot structures based on the evolution of well ordered surface corrugations on non-(100)- oriented substrates and on the controlled step bunching during MBE growth. The distinct electronic properties of these novel structures highlight their potential for fundamental research and advanced device concepts.
Migration Enhanced Epitaxy of GaAs Studied by Reflection High Energy Electron Diffraction and Scanning Tunneling Microscopy
Authors: Fu Jianming , Miller D. L. , Kim J. , Gallagher M. C. , Willis R. F. 
Published: March 2011

AbstractMigration enhanced epitaxy (MEE) of GaAs on (001) GaAs substrates was studied by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). In MEE, Ga and As species are alternately deposited on the growing surface. Ga adatom migration can be enhanced by the low arsenic pressure environment. The STM study was performed ex-situ by the arsenic capping and decapping procedure. We have demonstrated the correlation between the peak RHEED specular intensity during MEE growth and the variation of the lateral step density on the surface, even though the surface stoichiometry changes repetitively during MEE. The peak RHEED intensity during MEE is inversely dependent on the surface step density. The MEE surface exhibited a lower step density than the MBE surface, as shown by both RHEED and STM. However, the MEE surface still exhibited a much higher step density than a well-annealed surface. Consequently we believe that to achieve an atomically flat interface, annealing at high temperature in an arsenic flux is still necessary even if MEE is employed.
A Comparison of Two Epitaxial Formation Mechanisms in the SiGe System
Authors: Prokes S. M. , Rai A. K. 
Published: March 2011

AbstractTwo epitaxial growth mechanisms and the resulting defect generation have been examined. The first involves standard growth by molecular beam epitaxy (MBE), while the second employs wet oxidation to form a Ge-rich epilayer from an initially amorphous film. The MBE-grown high Ge content layers evolve by island coalescence, while the oxidationproduced high Ge content layers form by a Ge exchange mechanism below a contamination layer, which results in a more uniform epitaxial layer. Thus, the resulting threading dislocation, stacking fault and twin densities, along with the surface roughness can be quite different. Results also indicate a high misfit dislocation density limited to the Si/SiGe interface and a strain redistribution into the Si substrate for the oxidation-produced epilayers.
Surface Ordering of MBE Grown 001 Ga0.5Al0.5As – a Theoretical Study
Authors: Trivedi Rita , Venkatasubramanian R. , Dorsey Donald L. 
Published: March 2011

AbstractThe surface kinetics of MBE growth of (100) Ga0.5 Al0.5As are studied theoretically using a stochastic model which is based on master equation with random distribution approximation. The kinetic processes considered are: adsorption and inter- and intra-layer migrations for Ga, Al and As. Both monoatomic and diatomic As molecular species are considered. The model parameters such as the atomic pair interaction energies, migrational requency and activation energy were obtained from available experimental and theoretical data. The surface ordering kinetics are studied as a function of the fluxes (2Å/sec. for cations), flux ratio (1 : 10, 1 : 20 and 1 : 30 for cation to anion) and substrate temperature (775° – 923°K). Degree of ordering was obtained in terms of a short range order (SRO) parameter. The order-disorder temperature defined as the temperature of maximum order (above and below which the order parameter decreases) was obtained for flux ratios of 1 : 10 and 1 : 20. Both As and As2 species were considered. The order-disorder temperature was found to increase as the flux ratio was changed from 1 : 10 to 1 : 30, while the maximum degree of ordering decreased slightly. The results are in good qualitative agreement with experiments. The surface ordering kinetics observed can be described in terms of effective surface migration rates of the cations as follows. Lower temperature and higher flux ratio yield smaller effective surface migration rates for cation, which results in lesser degree of ordering. Beyond the transition temperature, the thermal energy is large enough to thermally randomize the atom pair bonds, thereby decreasing the degree of ordering. The higher transition temperature for higher flux ratios is attributed to lower effective migration rate.
Defect Engineering and Characterization in Oxide Surfaces using Electron Beam Irradiation
Authors: Doering D. L. , Siek K. H. , Xiong-Skiba P. , Carroll D. L. 
Published: March 2011

ABSTRACTElectron beam irradiation at energies between 0.5 and 4 keV has been found to produce defects in oxide materials including SiO2, Al2O3 and ZrO2. These defects trap excess charge in the materials and affect their electronic and optical properties. Measurements of the thermally stimulated exoelectron emission following irradiation provides information on relative defect concentrations, defect creation mechanisms, electron trap binding energies, electron emission mechanisms and annealing properties of these materials. Electron emission during sample heating occurs via a variety of mechanisms including the thermionic emission of excess charge from defects at temperatures characteristic of each trap binding energy. By measuring relative trap concentrations as a function of beam parameters, we have identified electron beam energy thresholds for the creation of some types of defects which correlate with core level electronic transitions. Also, electron emission which occurs during defect annealing or diffusion to a surface shows the conditions for the elimination of defects. The ability to control and characterize defect formation and annihilation provides the possibility of engineering specific surface defect conditions. In addition, defect creation by electronic processes is very selective as compared with momentum transfer in ion beam damage of surfaces.