bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient Enhanced Diffusion of Dopants in Preamorphised Si Layers
Authors: Claverie A. , Bonafos C. , Omri M. , De Mauduit B. , Assayag G. Ben , Martinez A. , Alquier D. , Mathiot D. 
Published: April 2011

AbstractTransient Enhanced Diffusion (TED) of dopants in Si is the consequence of the evolution, upon annealing, of a large supersaturation of Si self-interstitial atoms left after ion bombardment. In the case of amorphizing implants, this supersaturation is located just beneath the c/a interface and evolves through the nucleation and growth of End-Of-Range (EOR) defects.For this reason, we discuss here the relation between TED and EOR defects. Modelling of the behavior of these defects upon annealing allows one to understand why and how they affect dopant diffusion. This is possible through the development of the Ostwald ripening theory applied to extrinsic dislocation loops. This theory is shown to be readily able to quantitatively describe the evolution of the defect population (density, size) upon annealing and gives access to the variations of the mean supersaturation of Si self-interstitial atoms between the loops and responsible for TED. This initial supersaturation is, before annealing, at least 5 decades larger than the equilibrium value and exponentially decays with time upon annealing with activation energies that are the same than the ones observed for TED. It is shown that this time decay is precisely at the origin of the transient enhancement of boron diffusivity through the interstitial component of boron diffusion. Side experiments shed light on the effect of the proximity of a free surface on the thermal behavior of EOR defects and allow us to quantitatively describe the space and time evolutions of boron diffusivity upon annealing of preamorphised Si layers.
Conductive Tungsten-Based Layers Synthesized by Ion Implantation Into 6H-Silicon Carbide
Authors: Weishart H. , schöneich J. , Voelskow M. , Skorupa W. 
Published: April 2011

AbstractWe studied high dose implantation of tungsten into 6H-silicon carbide in order to synthesize an electrically conductive layer. Implantation was performed at 200 keV with a dose of 1.2×1017 W+cm−2 at temperatures between 200°C and 400°C. The influence of implantation temperature on the distribution of W in SiC was investigated and compared to results obtained earlier from room temperature (RT) and 500°C implants. Rutherford backscattering spectrometry (RBS) was employed to study the structure and composition of the implanted layers. Implantation at temperatures between RT and 300°C did not influence the depth distribution of C, Si and W. The W depth profile shows a conventional Gaussian shape. Implanting at higher temperatures led to a more confined W rich layer in the SiC. This confinement is explained by Ostwald ripening which is enabled during implantation at temperatures above 300°C. The depth of the implantation induced damage decreases slightly with increasing implantation temperature, except for 400°C implantation. The amount of damage, however, is significantly reduced only for implantation at 500°C.
Electron Beam Enhanced Precipitation in Highly Carbon Doped GaAs Layers
Authors: Werner P. , Gösele U. , Kohda H. 
Published: April 2011

AbstractHighly carbon doped GaAs layers grown by metal organic vapor phase epitaxy (MOVPE) Has been investigated by transmission electron microscopy (TEM). Electron irradiation has been applied to generate point defects interacting with native defects, e.g., substitutional carbon. This irradiation induces periodically arranged striations perpendicular to the growth direction, which were observed in situ by TEM. Furthermore, precipitates (Ø= 10–15nm) were formed containing non-crystalline material, which most likely is gallium. To explain these phenomena a precipitation mechanism is proposed. It involvs small fluctuations of the incorporated C as well as the interaction of irradiation induced point defects, mainly As and C interstitials and As vacancies.
Ion Beam Modification of Cluster-Covered Silicon Surfaces
Authors: Gulko O. V. , Zinke-Allmang M. T. 
Published: April 2011

AbstractClusters of independently tailored areal density and size distribution were grown on semiconductor surfaces in ultra-high vacuum and used as masks for selective ion beam modification. First studies were undertaken to characterize the vertical interface between areas exposed to low energy ion beams and areas covered by clusters (crystalline silicon). Selective etching was employed to create a patterned surface as a substrate for heteroepitaxial growth of thick Ge layers to test defect density reduction due to finite size growth areas. The quality of the overlayers is discussed.
Monte Carlo Simulation of Cluster Growth and Defect Annealing
Authors: Fedorov A. V. , Veen A. Van , Hosson J. Th De 
Published: April 2011

AbstractA computer program MODEX has been developed to predict the evolution of the irradiation defects in materials during ion implantation and subsequent annealing. The evolution of the defect clusters is simulated through a number of trapping and dissociation events. Two examples of the program application are presented: (1) 1 keV helium ion implantation in molybdenum up to doses of 1013 cm-2 with the subsequent ramp annealing up to 1400 K; and (2) 2.5 keV helium ion implantation in silicon with 1016 cm-2 with ramp annealing up to 1600 K. The simulation results are compared to the experimental results obtained by gas desorption techniques. The threshold dose needed for micro-cavity formation in silicon is discussed.
Computer Simulation of Displacement Cascades in α-Zirconium
Authors: Gao F. , Wooding S. J. , Bacon D. J. , Calder A. F. , Howe L. M. 
Published: April 2011

AbstractThe damage produced in α-zirconium at 100 K by displacement cascades with energy up to 20 keV has been investigated by MD simulations. In agreement with modelling of fcc and bcc metals, the defect production efficiency in zirconium is well below the NRT estimate. The number and size of clusters, both vacancy and interstitial, are increased by increasing PKA energy, and clusters containing up to 25 interstitials and 30 vacancies were formed by 20 keV cascades. Most interstitial clusters have dislocation character with perfect Burgers vectors of the form 1/3<1120>, but a few metastable clusters are formed and are persistent over the timescale of MD simulations. Collapse of the 30-vacancy cluster to a faulted loop on the prism plane was found to occur over a period of more than 100 ps
The Dependence of Proton Irradiated Microstructure on Dose, Temperature and Composition of Austenitic Stainless Steels
Authors: Gan J. , Allen T. , Was G. S. 
Published: April 2011

AbstractThe radiation-induced microstructure of austenitic stainless steel was investigated using proton irradiation. Samples of Fe-20Cr-24Ni and Ni-18Cr-9Fe were irradiated using 3.2 MeV protons at a dose rate of 7×10−6 dpa/s between 300°C and 600°C. The irradiation produced a microstructure consisting of dislocation loops and voids in both alloys. The number density and size of dislocation loops and voids are strong functions of irradiation temperature with the number density decreasing and the size increasing with temperature for both defects. The dose dependence of dislocation loop density saturated around 1.0 dpa for Fe-20Cr-24Ni and 0.3 dpa for Ni-18Cr-9Fe. The microstructure evolution in the nickel base alloy is faster than that in Fe-20Cr-24Ni. The dose and temperature dependence of proton irradiated Fe-20Cr-24Ni closely follow that of neutron irradiated austenitic stainless steels. The changes in yield strength due to irradiation were estimated from nano indenter hardness measurements and compared to calculation using a dispersed barrier hardening model. Results were in close agreement with each other. Yield strength changes as a function of dose for proton irradiated Fe-20Cr-24Ni are similar to those resulting from neutron irradiation of austenitic stainless steels.
Modeling of Radiation-Induced Segregation in Austenitic Fe-Cr-Ni Alloys
Authors: Allen T. R. , Was G. S. 
Published: April 2011

AbstractTo improve the ability to predict radiation-induced segregation (RIS) in austenitic Fe-Cr-Ni alloys, a model for predicting RIS is developed which calculates diffusion parameters based on local atomic configuration. Comparisons of RIS measurements in austenitic iron-base and nickelbase Fe-Cr-Ni alloys with calculations using the Perks vacancy-driven RIS model have shown that to accurately predict segregation trends, composition specific diffusion parameters must be used. This requirement limits the ability of the Perks model to predict segregation in Fe-Cr-Ni alloys for which no prior segregation measurements exist. To overcome this limitation, the improved model calculates migration energies using pair interaction energies to account for composition dependent diffusivities. The advantages of this approach are that a single set of input parameters can be used to describe a wide range of bulk alloy compositions, and the effects of local order can be easily incorporated into the calculations. A description of the model is presented, and model calculations are compared to segregation data to show that significant trends in the measured segregation data can be modeled using a single set of input parameters.
Irradiation Spectrum and Ionization-Induced Diffusion Effects in Ceramics
Authors: Zinkle S. J. 
Published: April 2011

AbstractThere are two main components to the irradiation spectrum which need to be considered inradiation effects studies on nonmetals, namely the primary knock-on atom energy spectrum and ionizing radiation. The published low-temperature studies on A12O3 and MgO suggest that the defect production is nearly independent of the average primary knock-on atom energy, in sharp contrast to the situation for metals. On the other hand, ionizing radiation has been shown to exert a pronounced influence on the microstructural evolution of both semiconductors and insulators under certain conditions. Recent work on the microstructure of ion-irradiated ceramics is summarized, which provides evidence for significant ionization-induced diffusion. Polycrystalline samples of MgO, A12O3, and MgAl2O4 were irradiated with various ions ranging from 1 MeV H+ to 4 MeV Zr+ ions at temperatures between 25 and 650°C. Cross-section transmission electron microscopy was used to investigate the depth-dependent microstructure of the irradiated specimens. Dislocation loop nucleation was effectively suppressed in specimens irradiated with light ions, whereas the growth rate of dislocation loops was enhanced. The sensitivity to irradiation spectrum is attributed to ionization-induced diffusion. The interstitial migration energies in MgAl2O4 and A12O3 are estimated to be ≤0.4 eV and ≤0.8 eV, respectively for irradiation conditions where ionization-induced diffusion effects are expected to be negligible.
Growth Transients During the Nucleation of GaInAs on InP by Organometallic Vapor Phase Epitaxy
Authors: Emerson D.T. , Shealy J.R. 
Published: April 2011

AbstractBy using lattice matched short period (50 Å) GaInAs/InP superlattices, we are able to extensively characterize, ex-situ, nucleation of thin (20–30 Å) GaInAs layers on InP. Systematic variation of the interface formation technique allows us to understand how parameters such as growth temperature and growth rate can contribute to interfacial roughness, giving rise to growth transients near the interfaces that are unexpected from characterization of thick layers. Growth of multi-period structures such as those studied here enables the use of Raman scattering, photoluminescence, and double crystal x-ray diffraction to determine that Ga incorporation is favored over In incorporation near the InP to GaInAs interfaces. Furthermore, by examining the surfaces and structural properties of epitaxial layers (15 Å-1 μm) of both InP and GaInAs with atomic force microscopy and Raman scattering, respectively, we are able to correlate results on the superlattice structures with results from single layers. Finally, we show how understanding the nucleation of thin films through the process described here enables the growth of complicated, previously unrealizable, heterostructures for use in novel optoelectronic devices.
Mound Formation and Coarsening in Homoepitaxial Growth
Authors: Amar Jacques G. , Family Fereydoon 
Published: April 2011

AbstractThe effects of instabilities which lead to mound formation and coarsening in homoepitaxial growth on metal (100) surfaces are discussed. These include an instability due to the Ehrlich-Schwoebel step barrier to interlayer diffusion as well as an instability due to step-adatom attraction at ascending steps. A unified picture of the effects of attractive and repulsive interactions at ascending and descending steps on surface morphology and island nucleation is presented. An analytic calculation of the selected mound angle and critical temperature for mound formation as a function of both the Ehrlich-Schwoebel step barrier and the barrier to diffusion towards an ascending step is also presented. Depending on the sign of the step barrier and the magnitude of the prefactor for diffusion over a step various scenarios are possible, including the existence of a critical temperature for mound formation above which (for a positive step barrier) or below which (for a negative step barrier) quasi-layer-by-layer growth will be observed. A theoretical analysis also leads to an accurate prediction of the observed mound angle for Fe/Fe(100) deposition at room temperature. The general dependence of the mound angle, surface skewness, and mound coarsening exponent on temperature, deposition rate, and strength of the step barrier is also studied via kinetic Monte Carlo simulations of bcc(100) growth and compared with recent experiments.
The Role of Roughness in Texture Development
Authors: Whitacre J. F. , Bilello J. C. , Yalisove S. M. 
Published: April 2011

AbstractTo examine the dependence of in-plane texture development on substrate surface morphology, deposition was performed on an intentionally roughened surface. 2 μm thick sputter deposited Mo films were macroscopically roughened by ion bombardment. This process created aligned mounds on the surface which were ˜1 μm in length, ˜0.1 μm in width and ˜0.04 miimn height. To remove crystallographic orientation effects, this surface was coated with a thin layer of graphite. Using these roughened, coated surfaces as a new substrates, the role of well defined macroscopic roughness in subsequent thin film growth was probed. Mo films were deposited onto these prepared substrates which were placed on a rotating platen under a stationary ion sputter source. When the mounds are aligned with their elongated axes normal to the rotation direction, little to no in-plane texture is found. The same deposition on a flat surface, or on the roughened surface with the mounds oriented parallel to the platen rotation direction, gives films with a high degree of in-plane texture. Scanning electron microscopy, transmission electron microscopy, and transmission electron diffraction data will be presented to corroborate these findings.
A Study of Step Coverage Morphologies of SiH4-WSix, and SiH2Cl2-WSix for Ulsi Technologies
Authors: Ozkan Cengiz S. , Moinpour Mansour , Li Jian 
Published: April 2011

AbstractUltrathin refractory metal silicide films, such as tungsten silicide (WSix) offer a wide range of applications in VLSI and ULSI circuits such as local interconnects, bit lines and wordlines. One practical way of depositing WSix is by a CVD technique in which WF6, is reduced by either silane (SiH4) or dichlorosilane (SiH2 Cl2 ). In this investigation, step coverage characteristics of silane based and dichlorosilane based tungsten silicide films, deposited by low pressure chemical vapour deposition method will be compared. WSix films of various thicknesses (1200–2000 Å) were deposited on topographies created by patterning poly-Si layers. WSix, step coverage was evaluated as a function of deposition temperature, poly-Si layer thickness and poly-Si line spacing. Field emisssion scanning electron microscopy was used to characterize step coverage profiles. It is clearly shown that, silane based WSix films deposited on poly-Si lines with sub 0.5 micron spacings result in poor step coverage which could lead to higher localized stress, cracking and higher line resistance. Dichlorosilane based WSix, on the other hand showed more conformal step coverage, which results in better process marhin for subsequent patterning steps. Finally, it was also observed that, the final silicide profile is highly dependent on the thickness of the underlying poly-Si layer, as well as poly patterning process margin.
Initial Growth and Interface Structure of CdTe Thin Films Grown by MBE on 4° Miscut Si Substrates
Authors: Tsen S.-C. Y. , Smith David J. , Rujirawat S. , Sivananthan S. 
Published: April 2011

AbstractCdTe thin films with thicknesses in the range of 60˜100 nm have been grown on miscut (001) Si surfaces under different precursors, such as Te and As, with one cycle annealing. The thin-film microstructure was studied in cross section using high-resolution electron microscopy. Atomicresolution images revealed several interesting features of the initial growth of the heteroepitaxial CdTe thin films. With As as the precursor, the films initially grew in three different orientation variants (commonly referred to as domains): (A) CdTe (111)//Si (001) with CdTe (1–10)//Si(110); (B) CdTe (111)//Si (001) with CdTe (11–2)//Si(110), and (C) CdTe (001) // Si (001) with CdTe (110) // Si (110). Each variant has demonstrated its own characteristic defects such as twinning, interface Lomer dislocations and {111} stacking faults. With the [001] growth direction, the CdTe film became defect-free by having about 13° tilt relative to Si [001] such that CdTe (1–11) and Si(−111) planes aligned sideways at the interface. With Te as the precursor, A- and B-type variants were mainly observed. The interfaces were sharper, especially for the A-type interface, but the film adhesion was weaker than when As was the precursor.
Faceting of Stepped Silicon (113) Surfaces: Step Unbinding, Dynamic Scaling, and Nano-Scale Grooves
Authors: Mochrie S. G. J. , Song S. , Yoon Mirang 
Published: April 2011

AbstractX-ray scattering studies are reviewed of the faceting kinetics of stepped silicon (113) surfaces misoriented towards [001]. Following a quench from the one-phase region of the orientational phase diagram into the coexistence region, initially-uniformly-distributed steps rearrange to form a grooved superstructure. Our measurements reveal the behavior of the grooved surface morphology as a function of time. The surface is found to be self-similar in time, with a characteristic groove size (L) varying as a power-law versus time (t): L = L0tøwith a coarsening exponent of ø = 0.164 ± 0.021 ≃ 1/6, consistent with a theory for the kinetics of faceting which focuses on thermally fluctuating step bunches and their collisions. At later times, the groove size approaches a limiting value which depends on the stepped phase misorientation angle, as expected for faceted surfaces in the case that elastic effects are important.
Atomistic Study of Surface Polarization in Superconducting Perovskites
Authors: Fuks David , Dorfman Simon , Heifets Eugene , Kotomin Eugene , Gordon Alex 
Published: April 2011

AbstractWe simulated the surface relaxation of the cubic perovskite paraelectric SrTiO3 crystal. The atomic positions in ten near-surface layers placed into the electrostatic field of the remainder of the crystal were calculated. Two-dimensional, periodic slab model was combined with the pair potentials treated in terms of the shell-model. Our calculations show that Ti+4, Sr+2 and O−2 ions shift differently from their crystal sites. This leads to a creation of a dipole moment near the surface which might give the paraelectric crystal the ferroelectric properties.
Surface Morphology of Nb Films by Ion Beam Assisted Deposition
Authors: Ji Hong , Was Gary S. , Wayne J. , Moody Neville R. 
Published: April 2011

AbstractNiobium films of thickness 50 nm to 1000 nm were deposited by ion beam assisted deposition (IBAD) using ion energies of 0, 500 and 1000 eV, and R ratios (ion-to-atom arrival rate ratio) of 0, 0.1, and 0.4 on (100) silicon and (0001) sapphire substrates. The films have columnar structures and the column width increases with normalized energy (En = E × R). The surface morphology depends on both the normalized energy of the ion beam, En, and the film thickness. All films have dome-like surface features that are oriented along the ion beam incident direction. The dimension of these features increases with normalized energy and film thickness. Surface roughness also increases with normalized energy and film thickness, with the root mean square (rms) roughness increasing from 1.6 nm for the PVD sample (100 nm thick) to 36.7 nm for the IBAD film (1000 eV, R = 0.4, 800 nm thick). The surface morphology of IBAD films is the result of a combination of channeling and shadowing effects.
Dark Current Spectroscopy Of Metals In Silicon
Authors: Mccolgin William C. , Lavine James P. , Stancampiano Charles V. 
Published: April 2011

AbstractDark current spectroscopy (DCS) is used to identify the signature of metals that generate dark or leakage current in silicon image sensors. Individual metal atoms or defects are detected by DCS on a pixel-by-pixel basis. DCS is applied here to show how the number of electrically active iron atoms in a pixel changes with light and with low-temperature anneals. The measurements explore the dissociation and association of iron-boron pairs and the diffusion of iron near room temperature.
Influence of Si Substrate Crystallinity on Device Performance
Authors: Iwamoto T. , Takano J. , Makihara K. , Ohmi T. 
Published: April 2011

AbstractWe have demonstrated the influence of surface microroughness on the electrical characteristics of MOS devices and investigated the influence of wafer's manufacturing methods, such as Czochralski(Cz), floating-zone(FZ), and epitaxial(Epi) silicon wafers, on the susceptibility to the surface microroughness when some chemical treatment was performed. As a result, it was found that Cz and FZ wafers are very susceptible to the surface microroughness and the amount of the vacancy of Epi wafer is much smaller than that of another wafers. It was also demonstrated that the electrical characteristics of very thin gate oxide films are strongly influenced by the silicon substrate quality. Epi wafer is a strong candidate for fablication of highly-reliable devices on 300mm wafers.
Mechanism Of Defect Reactions In Semiconductors
Authors: Shinozuka Yuzo 
Published: April 2011

AbstractAn overview is presented on mechanisms of electronically induced (enhanced) defect reactions in semiconductors, which are classified into the local heating, the structural instability, and the recombination enhanced. A mechanism for the annihilation of a hydrogen-carbon complex in silicon is given as an example of the second one. The last two mechanisms can be treated in a unified scheme by using the correct configuration coordinate diagram, which enable us to treat correctly the correlation in successive captures of an electron and a hole. The energy conversion mechanism during the reaction is precisely discussed paying attention to the relation between the lattice relaxation mode and the symmetry breaking reaction coordinate.