bluuebunny/crossref_metadata_2025 huggingface dataset:
The Structure of Oxygen-Implanted (111) Silicon Before and After Heat-Pulse Annealing
Authors: Liliental-Weber Z. , Carpenter R. W. , Kelly J. C.
Published: March 2011

The structure of (111) oriented, unheated oxygen-implanted silicon (dose -7.3×1016cm-2) has been studied by transmission electron microscopy (TEM). The as-implanted material exhibited four structurally different layers: defect-free monocrystaline silicon, amorphous silicon, monocrystalline silicon with a high defect density, and the perfect crystalline substrate. After heat-pulse annealing for 20s at 800°C, 900°C, or 1000°C, the amorphous layer recrystallized resulting in polycrystalline silicon, rich in oxygen. The uniform insulator buried layer was not formed under these specific implantation and annealing conditions.
Rapid Thermal Annealing of Al and P Implanted Single Crystal Beta Silicon Carbide Thin Films
Authors: Edmond J. A. , Kim H. J. , Davis R. F.
Published: March 2011

Ion implantation of 27Al+ and 31p+ ions into monocrystalline s-SiC films was conducted in order to acquire p-type and n-type conducting layers, respectively. Implant energies ranging from 110 to 190 keV and fluences from 7 × 1013 to 9 × 1014 cm-2 were used. In order to activate each dopant specie, rapid thermal annealing (RTA) was employed. A decrease in sheet resistance with increasing annealing temperature for both type layers was observed up to 1800°C. After annealing at this highest temperature for 300 s in 1 atm. Ar, the percent of activated and ionized n-type and p-type dopant was ≅20% and ≅0.5%, respectively, as determined by room temperature capacitance-voltage measurements. Recrystallization of both heavily damaged and amorphized layers occurred as a result of the use of the aforementioned annealing process. Unlike SPE regrowth in other compound semiconductors, no microtwins were present in the regrown bulk as observed by XTEM. SIMS analyses also showed that there was essentially no redistribution of P and moderate redistribution of Al from the corresponding as-implanted profiles after annealing.
Deep Level Spectra of Ion-Implantation Defects and Slip Dislocations Introduced by CO2 Laser
Authors: Bao X. M. , Zhang X. Y. , Liu C. E. , Zheng X. Q.
Published: March 2011

The CW CO2 laser annealing is an effective method for removing deep level defects induced by ion-implantation. The available laser density range is 350˜600 W/cm2, which is consistent with that needed to fully activate implanted impurities. At high power density (>600W/cm2 ) slip dislocations can be induced. The energy spectra of dislocations were measured with DLTS technique. One peak at Ev + 0.33eV in p-Si and two at peaks at Ec −0.37eV and Ec −0.50eV in n-Si have been found. These peaks are stable during thermal annealing at high temperature. But they can be passivated with hydrogen plasma annealing and reactivated by subsequent thermal annealing in vacuum. The dislocation core is reconstructed.
Comparison of Short Time Annealing of Implanted Silicon Layers With Tungsten-Halogen Lamp and Mercury Arc Lamp Sources
Authors: Wouters D. , Avau D. , Mertens P. , Maes H. E.
Published: March 2011

Short time anneal (STA) experiments were performed in a specially designed system which uses either a bank of Tungsten-Halogen lamps or a moving Mercury arc lamp as the light source. Both STA results were compared with conventional furnace anneal. The Mercury arc lamp anneal is found to be a critical process but optimization for wafer damage free conditions can be achieved. The anneals result in general in a better profile control which is most outspoken for shallow Boron implants while the electrical activation is comparable for all elements to that obtained with Tungsten-Halogen or furnace anneal.
Rapid Thermal Annealing of Ion Implanted p-n Junction in Silicon
Authors: Ho C. , Kwor R. , Araujo C. , Gelpey J.
Published: March 2011

The rapid thermal annealing (RTA) of p+n and n+p diodes, fabricated by the LOCOS process, and its subsequent effects on junction leakage current, junction depth and dopant activation were investigated. The reverse bias diode leakage currents of implanted Si <100> samples (As+: 60 KeY, 5×1014 5×1015 cm−2, B+: 25 KeV, l×1014, l×1015 cm−2 and BF2+: 45 KeV, 1×1015cm−2 ) were measured as functions of annealing temperature, and dwell time. The annealing was performed using an Eaton RTA system (Nova ROA-400) at temperatures ranging from 950 °C to 1150 °C. Annealing times ranged from 0.2 sec. to 10 sec. The results from the diode leakage current analysis are correlated with those from Secondary Ion Mass Spectroscopy (SIMS) and differential Hall measurements. The reverse-biased leakage currents from the RTA-treated samples are compared with those from furnace-annealed samples.
Direct Silicidation of Co on Si by Rapid Thermal Annealing
Authors: Tabasky M. , Bulat E. S. , Ditchek B. M. , Sullivan M. A. , Shatas S.
Published: March 2011

Rapid thermal annealing is used to form cobalt silicide directly on unimplanted as well as B, As, and P implanted wafers. The films are characterized by sheet resistance, X-ray diffraction, SEM, SIMS, and contact resistance measurements. The direct silicidation of cobalt on Si by rapid thermal annealing yields smooth, low resistivity films with minimal dopant redistribution.
Formation of Titanium Nitride/Silicide Bilayers by Rapid Thermal Anneal in Nitrogen
Authors: Morgan A. E. , Broadbent E. K. , Reader A. H.
Published: March 2011

Sputter deposited Ti films on Si and SiO2 substrates have been rapid thermal annealed in N2 at temperatures of 400–1100°C, and the reaction followed using AES, TEM, electron diffraction and sheet resistance measurements. The Ti initially becomes contaminated with oxygen before being nitrided at the surface and silicided at the interface. The oxygen is expelled from the siuicide and a TiNxO1−x/TiSix bilayer eventually results. With Si substrates, TiNxO1−x is much the thinner layer whereas the reverse is true on SiO2. Extended annealing in N2 completely converts the TiSi2 layer on Si into TiN.
Stability of Heavily Doped Si Formed by As+ Implantation and Rapid Thermal Annealing
Authors: Numan Muhammad Z. , Lu Z. H. , Chu W. K. , Fathy D. , Wortman J. J.
Published: March 2011

Deactivation of ion implanted and rapid thermal annealed (RTA) metastable arsenic in silicon during subsequent furnace annealing has been studied by sheet resistance measurement, Rutherford backs cat t ering/ channeling (RBS), and transmission electron microscopy (TEM). Following RTA, thermal annealing induces deactivation of the dopant which increases the sheet resistivity monotonically with temperature for a very short time, Dislocation loops are formed near the peak of As concentration at post-anneal temperatures of 750°C or higher, where deactivation rate is fast. At lower temperatures deactivation is accompanied by displacement of As atoms, possibly forming clusters.
SiO2 Growth and Annealing by Lamp heating
Authors: Weinberg Z. A. , Nguyen T. N. , Cohen S. A. , Kalish R.
Published: March 2011

This paper reports the results of a study of thin SiO2 growth and annealing in a lamp heater (Heatpulse). Good quality 5–10 mn SiO2 films on silicon have been obtained. For good oxides the average destructive breakdown- field was 13 MV/cm and very few or no low-field breakdowns were found. The breakdown statistics were obtained with Al gate capacitors and by a current staircase-ramp technique which is described in the paper. Processing with a single oxidation step, oxidationannealing, and oxidation-annealing-oxidation are discussed.
Transient Thermal Processing of GaAs
Authors: Pearton S. J. , Gibson J. M. , Jacobson D. C. , Poate J. M. , Williams J. S. , Boerma D. O.
Published: March 2011

A comprehensive review is presented of the use of transient thermal processing for the activation of implanted dopants, the alloying of ohmic contacts, the pulse diffusion of Zn for p+ contacts, and other heat treatments of GaAs. In all cases, transient processing produces results at least as good as furnace heating, and in some instances, markedly better. The special needs of GaAs, such as encapsulation of the wafer surface, and prevention of slip and warpage are discussed, as well as recent results detailing implant damage removal processes during transient annealing.
The Role of Trapped Interstitials During Rapid Thermal Annealing
Authors: Pennycook S. J. , Culbertson R. J.
Published: March 2011

During the rapid thermal annealing of ion implanted layers, trapped interstitials are responsible for transient enhanced dopant diffusion and the formation of a band of defects at the mean projected ion range. We describe the detailed nature and extent of these effects and show how they can be predicted in practice. We present a model which explains why trapping only occurs with group V implantation and describe double implantation experiments which confirm the model and show how the formation of projected range defects can be suppressed.
A GaAs Sagfet Process Using TiSi2 and Rapid Thermal Annealing
Authors: Wood D. , Mun J.
Published: March 2011

For the first time a combination of titanium disilicide and rapid thermal processing has been used to produce a high temperature stable gate on gallium arsenide. A barrier height of 0.79 V with an ideality factor of 1.02 has been obtained after annealing up to 800°C, and useful results are found up to 900°C. Auger analysis shows little intermixing of the silicide with the underlying substrate, which is not the case for conventional annealing. The advantages of titanium disilicide over the more commonly used tungsten silicide with regard to film resistivity and stress will be discussed. A self-aligned gate MESFET (SAGFET) process has been developed using TiSi2 as the gate material.
Comparison of Isothermal Anneal Techniques for be or Si Implanted S.I. InP
Authors: Molnar B. , Dietrich H. B.
Published: March 2011

This paper presents a study of the annealing of Be and Si implants into InP. It compares rapid thermal anneal (RTA) and furnace anneal (FA) techniques over a temperature range of 600-;900° C. The results demonstrate that RTA results in activation and mobilities as good as those obtained by FA for both Si and Be implant. The background Fe concentration of S.I. InP substrates lead to substantial differences in activation. Arrhenius fit of optimal activation data of Si indicates an activation energy of 1.8 eV. The Si implants display no redistribution during either type of annealing, while the Be implants display more than one type of redistribution. Moreover, the complete description of the Be redistribution requires the knowledge of both the atomic and the electronic profiles. Capless annealing eliminates the additional processing steps of capping but it also sets a limit on the maximum temperature and time of the annealing.
A New Model of Tail Diffusion of Phosphorus and Boron in Silicon
Authors: Morehead Frederick F. , Lever R. F.
Published: March 2011

It is well known that high surface concentration phosphorus diffusion leads to deeply penetrating “tails” in its concentration profile. At 700 °C the tail diffusivity exceeds that of low concentration phosphorus by a factor of a thousand. Less spectacular, but very significant tailing also affects tioron, making the conventional models contained in commonly available process simulation programs quite inaccurate for boron diffusions with high surface concentrations. We show that the observed tailing can be accounted for by a model whose central assumption is the local equality of dopant and oppositely directed defect fluxes. As predicted by the model, the effect is greatest for normal processing at low temperatures for high surface concentrations. It is minimal for the high temperatures of rapid thermal annealing and unrelated to transient effects.
Dopant Redistribution During Pd2Si Formation Using Rapid Therm1al Annealing
Authors: Alvi Nadeem S. , Kwong Dim L. , Hopkins Craig G. , Baumane Scott G.
Published: March 2011

Rapid thermal annealing (RTA) has been used to form Pd2Si by reacting thin layers of Pd metal on As implanted Si. An enhanced growth rate for the Pd2Si has been measured which does not obey the diffusion limited growth kinetics as reported for the furnace reacted Pd2Si. The growing Pd2Si results in As redistribution which is sufficient to displace the shallow p-n junction as the silicide/silicon interface approaches the junction position. The As implanted profile changes little in the Pd2Si region, with As accumulating at the leading edge of the silicide/silicon interface.
MOLECULAR DYNAMICS STUDIES OF THE COHERENCY OF MONOLAYER FILMS
Authors: GRABOW MARCIA H. , GILMER GEORGE H.
Published: March 2011

The equilibrium configurations of monolayer films on crystalline substrates have been investigated using molecular dynamics techniques. Misfit dislocation densities are found to differ from those predicted by elasticity theory, because of the more realistic interatomic potential employed in the simulations (Lennard-Jones), and the absence of constraints on atomic positions. Two distinct dislocation core structures are observed, with a discontinuous transition between the two as the external conditions are changed. Shockley partial dislocations are found to be stable for a large range of misfits in the case of FCC (001) substrates, and recently an experimental observation of these dislocations was reported. The stability of monolayer films relative to the formation of three-dimensional clusters is also considered.
DIFFRACTION STUDIES OF METAL-SEMICONDUCTOR INTERFACES
Authors: CHERNS D. , KIELY C.J.
Published: March 2011

The use of convergent beam electron diffraction patterns (CBPs) for investigating metal—semiconductor interfaces in plan—view samples is considered. It is shown that a wide—angle diffraction technique provides a sensitive method of measuring tetragonal distortions in NiSi 2/(001)Si bicrystals. A study of CBP symmetry and the detailec branch structure in higher order Laue zone rings has enabled the interfacial rigid body displacement in NiSi 2/(001)Si and Al/(001)GaAs films to be determined.
STRAIN MEASUREMENT IN EPITAXIAL NiSi2/Si(lll) BY MeV ION CHANNELING
Authors: OKAMOTO MASAKO , HASHIMOTO SHIN , HUNT B.D. , SCHOWALTER L.J. , GIBSON W.M.
Published: March 2011

Strains in both type-A and type-B NiSi2 epitaxial films grown on Si(lll) substrates were measured by means of MeV 4He+ ion channeling. The results show the critical thickness to maintain pseudomorphic growth strongly depends on theepitaxial orientation of the NiSi2 film. The difference in critical thicknesses between type-A and type-B NiSi2 can be explained by considering the different type of misfit dislocations introduced at the interface. Namely, at the type-B interface, 1/<112> partial dislocations associated with interface steps are allowed while they are prohibited at the type-A interface. Dislocation densities measured by TEM also support these results.
Electron Beam Induced Current Studies of Nickel Silicide/Silicon Schottky Barrier Heights
Authors: Gibson J.M. , Joy D.C. , Tung R.T. , Ellison J.L. , Pimentel C. , Levi A.F.J.
Published: March 2011

We discuss the use of electron beam induced current measurements in a scanning electron microscope to deduce local Schottky barrier height with high spatial resolution. For theNiSi2/Si system, using UHV-prepared thin “templates”, wedemonstrate the uniformity of barrier heights for A or B single crystal films. In comparison, there is evidence for local variation of barrier height in mixed A+B films. Quantitative models for EBIC dependence on barrier height are discussed. Local variations in barrier height can be overlooked by other techniques and may be much more common than previously suspected.
EPITAXIAL GROWTH OF NICKEL SILICIDE LAYERS ON SILICON BY ELECTRON BEAM ANNEALING
Authors: Inada T. , Tohyama S. , Funaki Y. , Itoh K.
Published: March 2011

Epitaxial NiSi2layers have been grown onto (100) and (111) Si substrates by multiple scan electron beam annealing. The formation and the composition of the silicides have been analyzed by Rutherford backscattering techniques and by electron diffractionobservation. The phase and the composition of the silicides depend on the power density of the electron beam. Under the optimum conditions, epitaxial NiSi2layers with a high surface morphology can be grown. An attempt has been made to form crystalline Si—NiSi2—Si heterostructures and the preliminary data are also presented.
STLOY OF Nb/Si MULTILAYERS
Authors: Li C. , Cai X. , Ye Z. , Zhang H. , Zharng W. , Xiong G. , Wu K. , Wang S. , Yin D.
Published: March 2011

A systematic study of superconducting Te, Hc and also the behavior of resistivity of Nb/Si mfltiiayers is reported. Nb and Si layers with different thicknesses were deposited alternatively in an LUIV two electron—beam evaporating installation and controlled automatically by a microcomputerquartz—monitor system. Well reproduciole results were achieved. Structural analyses show very good modulated structure with (110)textured polycrystallino Nb and] amorphous Si layers. Superconducting Tc of Nb/Simultilayers are significantly higher than that of the sputtered Nb/Ge system. Thevariation of Hc(T) in parallel field manifests a 2D–3D crossover with transformation temperature of 0.7– 0.8 Tc. The possible mechanism and implication of these phenomena were discussed.
DEFECTS IN MBE SILICON
Authors: CHRENKO R.M. , SCHOWALTER L.J. , HALL E.L. , LEWIS N.
Published: March 2011

A study of defects that are observed in Si MBE layers under certain growth conditions is reported. Optical microscopy examinations of unetched and etched layers reveal particle-like defects of micron size, stacking faults, dislocations, and saucer pits. TEM shows interfacial defects of tens of Angstroms size at the substrate-epitaxial layer interface. Reproducible defect densities are given for various in-situ cleaning procedures.
STABILITY OF SI-DOPED AlGaAs/GaAs MODFET STRUCTURES DURING CONVENTIONAL FURNACE AND RAPID OPTICAL ANNEALING.
Authors: ABROKWAH J. K. , HIBBS H. , DANIELS R. R. , JOSLYN P.
Published: March 2011

The use of an AlGaAs/n-GaAs superlattice in place of the n-AlGaAs layer in MODFET devices reduces the light and temperature sensitivity of the threshold voltage. This paper considers the stability of Si doped superlattices under annealing conditions required for activation of the implant in the self-aligned gate MODFET fabrication process. Rapid optical annealing does not significantly degrade the superlattice structure. The DX center concentration in the superlattice structures is a factor of 30 less than measured in conventional MODFET structures. High performance MOOFET devices have been fabricated using the self-aligned gate process with rapid optical annealing.
THE INFLUENCE OF RECONSTRUCTION ON THE INITIAL STAGES OF SILICON MOLECULAR BEAM EPITAXY
Authors: Gossmann H.-J. , Feldman L.C.
Published: March 2011

High energy ion scattering/channeling and low energy electron diffraction are usedfor an investigation of the initial stages of interface formation during Si homoepitaxy. We find a strong dependence of the atomic. reordering – a necessary condition for pseudomorphic growth – on substrate surface, deposition temperature and Si coverage: (1) Si deposition at 300 K reorders the Si(100) substrate reconstruction in a layer by layer manner. In contrast Si( 111) is unaffected by Si deposition at that temperature. This difference between Si(100) and Si( 111) can be understood in terms of different structural models. (2) On both surfaces deposition at 300 K results in a disordered overlayer. (3) As a direct consequence of the dependence of the reordering on reconstruction we find a lower epitaxial temperature (≈570 K) for Si(100) than for Si(l 11) (≈790 K).
MEASUREMENT OF THE BANDGAP OF GexSi1−x/Si STRAINED-LAYER HETEROSTRUCTURES
Authors: LANG D. V. , PEOPLE R. , BEAN J. C. , SERGENT A. M.
Published: March 2011

We have used photocurrent spectroscopy to measure the optical absorption spectra of coherently strained layers of GexSi1−x grown on {001} Si by molecular beam epitaxy. A dramatic lowering of the indirect bandgap, relative to that of unstrained bulk Ge-Si alloys, is observed. Our results for 0 < × < 0.7 are in remarkably good agreement with recent calculations of the effects of misfit strain on the band edges of coherently strained Ge-Si heterostructures.
Optical Absorption Probability for the Zone-Folding Induced Quasi-Direct Gap in Ge(x)Si(1−x)/Si Strained Layer Superlattices
Authors: Jackson S. A. , People R.
Published: March 2011

Using a realistic zone-folding scheme for a Ge(x)Si(1−x)/Si strained layer superlattice having a Si-like conduction band structure (i.e ≲85% Ge) we calculate the transition probability for the zone-folding induced direct optical gap and compare it with the indirect band gap absorption probability. The results suggest that such zone-folding induced direct optical transitions are promising for optical devices made from Ge(x)Si(1−x)/Si strained layer superlattices and like structures, provided they are fabricated in such a way that the appropriate zone-folding occurs.
RAMAN SCATTERING AND X-RAY DIFFRACTION CHARACTERIZATION OF AMORPHOUS SEMICONDUCTOR MULTILAYER INTERFACES
Authors: GONZALEZ J. , ALLRED D.D. , NGUYEN O.V. , MARTIN D. , PAWLIK D.
Published: March 2011

In the present study, Raman spectroscopy (RS) and x-ray diffraction have been used to characterize semiconductor multilayer interfaces. A model for Raman spectra of multilayers is developed and applied to the specific case of the interfaces of a-Si/a-Ge multilayers. Quantification of the ‘blurring’ of interfaces is possible because RS is capable of directly ‘counting’ the total number of chemical bonds of a given type in the film. Multilayers, prepared by various deposition techniques, are compared. Several a-Si/a-Ge multilayers deposited by UHV evaporation (MBD) exhibit exceptionally sharp interfaces (intermixing width <l.0Å) and regular periodicities.
STRUCTURAL AND ELECTRONIC PROPERTIES OF POTASSIUM HYDROGEN INTERCALATED GRAPHITE
Authors: Yeh N. C. , Enoki T. , Salamanca–Riba L. , Dresselhaus G.
Published: March 2011

Because of the difference in charge transfer and superlattice formation of the various intercalant species, graphite intercalation compounds (GICs) exhibit a variety of interesting electronic properties and phonon properties. These compounds form monolayered metallic superlattices along the c—axis, in contrast to the multilayered metallic superlattices grown from MBE and sputtering synthesis methods. GICs are generally divided into donor—type and acceptor—type compounds, depending on whether the electrons are transferred to the graphite or from the graphite. The modification of the electronic energy bands of GICs by charge transfer is analogous to that of the nipi superlattices. Because of the strong electron affinity of hydrogen relative to that of graphite, the addition of hydrogen into donor—type GICs (e.g. K—GICs, KHg—GICs) modifies the charge transfer from the intercalates to the graphite л-bands. Therefore, studies of the donor—type KHx—GICs provide us with new understanding of the variation of the electronic properties of alkali—metal GICs as the as charge transfer is modified.
NUCLEATION KINETICS OF CdTe/CdTe (111) HOMOEPITAXY BY LASER MBE
Authors: Cheung J.T.
Published: March 2011

CdTe evaporates into Cd and Te atoms under high power, pulsed laser irradiation. The mechanism is different from thermal evaporation where only atomic Cd and molecular Te are formed. The presence of Te atoms is responsible for some unique nucleation processes, such as the epitaxial growth of CdTe on (111) CdTe substrates with either polarity and the enhancement in sticking coefficient in CdTe deposition.
EPITAXY OF CdTe ON (100) GaAs
Authors: KOLODZIEJSKI L. A. , GUNSHOR R. L. , OTSUKA N. , CHOI C.
Published: March 2011

Two epitaxial orientations [(111) and (100)] of CdTe are grown on (100) GaAs in the presence of a 14.6% lattice mismatch. Consistent nucleation of a selected orientation is achieved by employing specific growth techniques. The growth techniques for selection of both orientations are described. High resolution electron microscopy has been used to investigate the interface between the CdTe epilayer and the GaAs substrate. For the (111) orientation strong interaction exists between the epitaxial deposit and the substrate, whereas a weakened interaction between deposit and substrate induces the (100) orientation.
Formation of a Low Thermal Donor Concentration Layer in CZ Si Wafer During 450°C/64h Annealing
Authors: Hahn S.
Published: March 2011

For thermal donor and oxygen precipitation studies in Cz silicon wafers, extended 450°C thermal annealing (e.g., anneal at 450°C for 64 h) has frequently been used. But, our recent studies have shown that this kind of extended low temperature anealing leads to a low thermal donor (LTD) layer up to ∼ 8 um from the surface in the case of 450°C/64 h thermal annealing. In this study, effects of annealing ambients, protective layers, surface conditions, and bulk oxygen contents upon the LTD layer are discussed. Our data indicate that the LTD layer is a product of both surface- and bulk-related phenomena.
The Diffusivity and Solubility of Oxygen in Silicon
Authors: Mikkelsen J. C.
Published: March 2011

The diffusivity and solubility are two key parameters required for understanding and modeling the behavior of oxygen in silicon. This paper gives an up to date review of experimental determinations of these parameters, including some recent unpublished data. There is very good agreement within the long-range diffusivity results determined by secondary ion mass spectrometry (SIMS), charged particle analysis (CPA), and x-ray diffraction. The oxygen diffusivity is independent of [O], orientation, ambient, or crystal doping. The data also extrapolate well to the diffusivities obtained by the intrinsic oxygen atomic hop frequency at low temperature to give a combined expression of D = 0.13 exp(−2.53eV/kT) cm2s−1. There is somewhat poorer agreement on the solubility measurements, in part due to inconsistent calibration factors and the observation of a processing-dependent extrinsic oxygen solubility. The intrinsic solubility derived from SIMS, CPA, and infrared absorption is described by [O] = 9E22 exp (−1.52 eV/kT) cm−3. Finally, the above diffusivity and solubility parameters are compared to modeling of oxygen related phenomena in silicon, such as thermal donor and precipitate formation kinetics, and interaction with point defects during the relaxation of stress-aligned dichroism.
Microdiffraction Studies of Oxygen in Silicon - A New SiO2 Phase?
Authors: Spence J. C. H. , Long N. , Bergholz W. , Kim Y. , O'Keeffe M.
Published: March 2011

Evidence for a new microcrystalline precipitate in CZ Si annealed for 256 hrs at 635°C is presented by electron microdiffraction. This may be a precursor phase for the formation of amorphous platelets [9]. Multiple scattering microdiffraction calculations which distinguish the symmetries of two models for the thermal donor are also given.
Exigent-Accommodation-Volume of Precipitation and Formation of Oxygen Precipitates in Silicon
Authors: Tan T. Y.
Published: March 2011

In this paper we first describe, in some detail, the nature of an exigentaccommodation- volume factor associated with oxygen (Oi) precipitation in Czochralski (CZ) Si. This factor is regarded as a causal or characteristic factor which influences many aspects of the SiO2 precipitate nucleation and growth phenomena. Employing this factor, we then describe the possible explanations of two outstanding features of Oi precipitation in CZ Si: the precipitation retardation/recovery phenomena and the nucleation incubation phenomena.
Effects of Thermal Donor Generation and Annihilation Upon Oxygen Precipitation
Authors: Hahn S. , Shatas S. C. , Stein H. J.
Published: March 2011

Rapid thermal annealing and furnace annealing steps have been combined to investigate the effects of thermal donor generation and annihilation upon oxygen precipitation in low and high carbon content silicon wafers. Thermal donors were formed by furnace annealing at 450°C. Rapid thermal annealing was performed in 10 s periods at temperatures between 600° and 1000°C and was followed by two step furnace annealing at 700° and 950 °C. Rapid thermal annealing separates the annealing stage for thermal donor removal from that for removal of oxygen precipitate nuclei, and a marked dependence upon carbon is observed for nuclei stability under RTA. Implications of these observations for models of precipitate nuclei are considered.
Oxygen Precipitation in Silicon: Numerical Models
Authors: Lavine J. P. , Hawkins G. A. , Anagnostopoulos C. N. , Rivaud L.
Published: March 2011

We present a numerical model that simulates the evolution of precipitates and the diffusion of interstitial oxygen in Czochralski silicon. The growth and/or dissolution of each precipitate and the local concentration of interstitial oxygen with which the precipitates interact are followed as a function of time. We treat realistic densities of discrete, interacting precipitates and determine how the precipitate density influences the extent of the precipitation. The model also treats oxygen outdiffusion and the formation of precipitate-free or denuded zones. We apply the model to previous experimental data on the time dependence of precipitate growth and to the development of denuded zones during intrinsic gettering.
Trapping of Oxygen at Homoepitaxial Si-Si Interfaces Grown by Molecular Beam Epitaxy
Authors: Hull R. , Twigg M. E. , Bean J. C. , Gibson J. M. , Joy D. C.
Published: March 2011

Interfaces between Si substrates and epitaxial Si buffer layers grown by Molecular Beam Epitaxy (MBE) are shown to contain a high density of SiOx pockets for certain sustrate preparation conditions. It is also shown that post-deposition thermal annealing of these structures grown upon Czochralski wafers can lead to a greatly increased defect density at the interface. The primary model proposed for this increase is trapping of background oxygen diffusing from the bulk of the Czochralski substrate wafers.
Gettering of Impurities in Silicon
Authors: Ourmazd A.
Published: March 2011

Despite the apparent dissimilarities between different gettering methods, we show that many can be understood in terms of two basic mechanisms. The first involves the interaction of selfinterstitials (emitted, for example, by P in-diffusion and precipitation, 0 precipitation, or Ar implantation) with the impurities to be gettered. The second relies on a strain-field/point defect interaction (for example around a dislocation), which appears capable of enhancing the diffusivity of the impurities. In either case, gettering can be viewed as a particular and particularly useful instance of the wider class of defect/defect interactions.
Impurity Interactions with Dislocations in Silicon
Authors: Sumino Koji
Published: March 2011

A review is presented of some aspects on the interactions of light element impurities with dislocations in silicon crystals on the basis of the works done by the author's group. Topics taken up are gettering of impurities by dislocations, electrical and optical activities of impurity atoms accumulated at the dislocation core, immobilization of dislocations due to impurity gettering, and the mechanism of strengthening of silicon wafers due to doping of impurities such as oxygen and nitrogen.
Annealing Effects in Low- and High-Stress Silicon Ribbon
Authors: Dumas K. A. , Briglio A. , Cheng L. J.
Published: March 2011

X-ray topography and minority carrier lifetime measurements were used to study the structural and electrical properties in silicon dendritic web ribbon. The effects of annealing on the material quality of high- and lowstressribbon were investigated.
Hydrogen in Crystalline Silicon
Authors: Pearton S. J.
Published: March 2011

The ability of hydrogen to migrate in crystalline Si at low temperatures (<400°C) and bond to a variety of both shallow and deep level impurities, passivating their electrical activity, is of fundamental and technological interest. Recent results on the deactivation of the shallow acceptors in Si are compared with similar experiments in other semiconductors, microscopic models are proposed, and the implications for the states of hydrogen in the Si lattice at a variety of temperatures, and the diffusivity of some of these different states, is discussed. New results on the migration of atomic hydrogen under electronic stimulation are also detailed, along with a compendium of the deep levels in Si passivated by reaction with hydrogen. Surface damage by hydrogen-containing plasmas, and the infrared and electrical properties of H-related defect complexes are also reviewed.
Nitrogen in Crystalline Si
Authors: Stein Herman J.
Published: March 2011

Use of N doping, N gas ambients and N implantation in Si processing has stimulated study of the incorporation and behaviour of N in Si. Studies of N-implanted Si and comparisons with melt-doped Si have shown that N pairing is the dominant mode for bonding of N into crystalline Si for a wide range of processing conditions. Studies have also shown that laser annealing quenches a small percentage of implanted N into a substitutional site. Nitrogen diffusion and aggregation have been shown to occur in N-implanted Si upon furnace annealing at temperatures >700°C and there is a simultaneous formation of shallow donors. Interactions between N and other impurities occur in both as-grown and ion-implanted Si. Additional studies are needed to describe more fully the electrical and structural consequences of N-N, Nimpurity and N-defect interactions in Si.
Persistent Questions About The Oxygen Donor In Silicon
Authors: Stavola Michael
Published: March 2011

In spite of 30 years of study the most basic questions about the oxygen donor in silicon remain unanswered. There are not accepted models for the structure or formation kinetics. There is not even agreement on what the donor's constituents are. Nonetheless, substantial progress has been made in this field in recent years [1] that narrows model ideas and helps to focus continuing research.
The Electronic Structure and Atomic Symmetry of The Oxygen Donor in Silicon
Authors: Stavola Michael , Lee Keon M.
Published: March 2011

The infrared spectrum of oxygen donor complexes in silicon under uniaxial stress has been examined for the neutral and singly ionized charge states. Our results are consistent with an effective mass-like ground state wave function that is constructed from a single pair of conduction band valleys for both charge states. A thermal ionization experiment in which the stress split components of the ground state are monitored by the absorption of polarized light confirm this interpretation and provide correlation with DLTS and EPR results. Additional small splittings, due to deviations from effective mass theory, show that the electronic wave function of the oxygen donor is distorted by an extended “central cell” with C2v symmetry. Previously observed splittings of 1s → np± transitions for the singly ionized charge state at zero stress are interpreted in terms of the effect of the anisotropic oxygen donor structure upon excited state wave functions constructed from the single pair of conduction band valleys
Effect of Cerium Oxide Additions on the Densification Behaviour of Alumina Gels
Authors: Dwivedi Ratnesh , Adams Jane
Published: March 2011

Sintering behavior of gel-derived alumina containing 2.8 mol percent cerium oxide (Ce2 O3) was studied at 1400°C. The growth morphology of alpha alumina in cerium oxide-containing aluminas was found to be significantly different form that of pure gel-derived alumina. Alumina gel containing 2.8 mol % Ce2 O3 was found to densify to 81% of the theoretical density as compared to 65% for pure alumina gels. The powdered cerium oxide-containing gels, pressed into a pellet, could be sintered to 97% of the theoretical density at 1400°C as compared to 87% found for pure alumina gel powder processed in an identical manner.
Models for Electronic Conduction Across Ceramic Grain Boundaries
Authors: Burton L. C.
Published: March 2011

Electronic current flow over grain boundary potential barriers for low resistance grains is first reviewed. It is then shown that if the resistance of the grains increases and/or grain size is reduced, the grains may be totally depleted of mobile charge. The grain boundary barrier is thus reduced to (D/2W)2 of its original large grain value, D being grain width and W the full space charge width. For high resistivity grains satisfying the relation D ≪ 2W, the conduction band becomes essentially flat. Phenomena formerly caused by grain boundary potential barriers (varistor and PTC effects seen in semiconducting ceramic) will be greatly reduced, or eliminated.

Commercial COG and X7R MLC capacitors exhibit a transition from super-ohmic to ohmic behavior at high voltages, paralleling the behavior of the varistor. Two possible mechanisms that could account for this are varistor-like grain boundary behavior, or space charge limited diffusion current.
Defect Creation and Photoablation in Stoichiometric and Sub-Stoichiometric SiO2
Authors: Devine R. A. B. , Fiori C.
Published: March 2011

It is demonstrated that microscopic point defects can be created in amorphous silica using pulsed ultraviolet irradiation (λ = 248 nm) at energy densities ∼ 100 times less than those normally estimated to lead to damage creation. Identification of the physical character of the defects has been made using electron spin resonance spectroscopy and electrical measurement techniques. Continued irradiation of the SiO2 is found to lead to photoablation. Results obtained for bulk dry SiO2, thermal SiO2 and vacuum deposited SiOx are presented. The important role of non-stoichiometry (defect structure) in the process of photoablation is clearly manifested by comparison of the results obtained for the different types of SiO2. Possible physical mechanisms involved are discussed.
Ion Beam, Rapid Thermal, and Laser Mixing Phenomena in Insulators
Authors: Narayan J. , Appleton B.R.
Published: March 2011

We have studied mixing of metal overlayers (Ni, Cr, Ti, W, Ta, Zr, Cu) on insulators (SiC, Si3N4, Al2O3, SiO2) after ion beam irradiation, rapid thermal annealing, and pulsed laser irradiation. The nature and amount of mixing varies from stoichiometric to continuous, to ballistic, to no mixing at all. For a given system, the amount of mixing was found to increase with increasing substrate temperature. The enhanced mixing with increasing substrate temperature is correlated with concomitant free energy associated with the reactions. Certain systems such as Cu on Al2O3 do not exhibit mixing, but rearrangement within a few atomic layers at the interface results in enhanced adhesion and no aggregation upon annealing at moderate temperatures.
Ion Implantation and Annealing of Crystalline Oxides
Authors: White C. W. , Sklad P. S. , Boatner L. A. , Farlow G. C. , McHargue C. J. , Sales B. C. , Aziz M. J.
Published: March 2011

The crystallization of amorphous surface layers produced by ion implantation of single-crystal α-Al2O3 and CaTiO3 are discussed. During annealing, amorphous A12O3 converts first to the α-phase. The crystallized γ then transforms to the a-phase by the motion of a well-defined planar interface. The temperature dependence of the velocity of the γ/α interface has been measured and is characterized by an activation energy of ∼3.6 eV. In CaTiO3, crystallization of the amorphous phase takes place by solid-phase epitaxy. The velocity of the amorphous/crystal interface is characterized by an activation energy of 1.3 eV.
Photoluminescence, Raman Scattering and Rbs/Channeling of Epitaxial Fluorides
Authors: Choyke W.J. , Bradshaw J.L. , Mascarenhas A. , Feng Z.C. , Sinharoy S. , Hoffman R.A.
Published: March 2011

Growth conditions are described for producing high quality crystalline films of CaF2 on (100) and (111) GaAs and LaF3, CeF3 and NdF3 on (111) Si. Rutherford backscattering/channeling, low temperature (<2K) photolumin-escence and Raman scattering are used as diagnostic techniques to probe the crystalline quality of the films and the stress/disorder induced at the film-substrate interface due to lattice mismatch.
The Formation and Annealing of Amorphous Layers of Al2O3
Authors: Farlow G. C. , Sklad P. S. , White C. W. , McHargue C. J. , Appleton B. R.
Published: March 2011

The critical dose for formation of an amorphous layer of Al2O3 by ion irradiation at 77 K has been determined. It is found to lie between 2 and 3 × 1015/cm2 if the sample is irradiated near the <0001> axis of the substrate and is found to lie in the neighborhood of 2 × 1016/cm2 if the irradiation is near the <1210> axis. The amorphous layers are found to recrystallize epitaxially if annealed at 1190 degrees C and to form a metastable microstructure upon annealing at 800 degrees C.
Problems Associated with Active Ion Distributions in Solid State Laser Materials
Authors: Powell Richard C.
Published: March 2011

Problems associated with nonrandom distributions of active ions in solid state insulator laser materials are discussed. A12O3:Ti3+ and BeAl2O4:Cr3+ crystals are used to show typical examples of some of these problems. In addition some problems of this type observed in new materials with potential for solid state laser applications are discussed.
The Application of ß“-Alumina As A Solid State Laser Host
Authors: Barrie J. D. , Yang D. L. , Dunn B. , Stafsudd O. M.
Published: March 2011

Ion exchanged ß“-aluminas display a number of interesting optical properties which suggest that the material is well suited for application as a solid state laser host. Small platelets of Nd3+ Ion exchanged β“-alumina exhibit laser action with gain coefficients many times greater than YAG. The versatility of the ion exchange process enables one to form a wide variety of compounds with different active ions and concentrations, thereby allowing the study of many different effects within a single host crystal.
Ion Induced Alterations of LiNbO3
Authors: Buchal C. H. , Appleton B. R. , Christie W. H. , Ashley P. R.
Published: March 2011

An attempt is made to fabricate positive-index waveguides by ion implantation of metal ions into crystals of LiNb03. The observed structural, chemical, and optical damage is summarized and possible solutions are discussed.
Voltage Dependent Plasticity in Mercury Cadmium Telluride
Authors: Pellegrino Joseph , Galligan J. M.
Published: March 2011

The effect of an applied, time varying voltage on the plastic behavior of (Hg,Cd)Te has been investigated. We observe that both positive and negative voltages suppress plasticity, with the negative voltage being more effective. The influence of this voltage polarity is strain dependent and provides information on the charge of the mobile dislocations. From these results we present a model of the strain dependence of the voltage dependent plasticity.
Point Defects and High-Temperature Deformation of NiO
Authors: Goretta K. C. , Routbort J. L.
Published: March 2011

The steady-state flow stress τs in nonstoichiometric NiO single crystals has been measured in the temperature range of 1428 to 1653 K with oxygen partial pressures p(O2) between 6 and 1×105 Pa. Strain rates were varied from 1×10−5 to 2×10−3 s−1. Transmission electron microscopy indicates that dislocation climb is the primary mechanism of recovery. Because dislocation climb is diffusion controlled, the data may be described at fixed temperature by = Aτns (O2)1/m, where n is the stress exponent and m is a parameter that is determined by the dominant atomic defects on each sublattice. At high temperatures and p(O2) > 2×104 Pa, n was found to be in agreement with dislocation-climb models; however, n increased at low p(O2) owing to effects of impurities. The values of m are consistent with control of climb rate by diffusion of singly charged oxygen vacancies for low p(O2) and by diffusion of neutral oxygen interstitials for high p(O2). At lower temperatures, the values of n are strongly affected by dislocation/impurity interactions for all p(O2).
Effects Of Excess Al2O3 And TiO2 On Microstructure And Properties Of Al2TiO2 Ceramics Prepared from CVD Powders
Authors: Hori Saburo , Yoshimura Masahiro , Sōmiya Shigeyuki
Published: March 2011

The effects of excess AI2O3 and TiO2 on microstructure, bending strength and thermal expansion of Al2TiO5 ceramics were studied by sintering various compositions of CVD Al2O3-TiO2 powders at 1310°C for 4 h. Excess Al2O3 resulted in much higher bending strength with slightly higher thermal expansion, while excess Ti02 resulted in slightly higher strength with lower thermal expansion. The excess AI2O3 and TiO2 were uniformly dispersed as particles on the Al2TiO5 grain boundaries, creating interlocked grains and dispersed microcracks. Excess TiO2 enhanced the material diffusion while AI2O3 did not, and appeared to develop more anisotropy of Al2TiO5 grains, resulting in lower expansion. It was proved that the overall properties of Al2TiO5 ceramics could be improved by dispersing excess Al2O3 or TiO2 uniformly onto the grain boundaries.
Phase Separation in Reduced LiNbO3
Authors: Chan H.M. , Zhuang Z. , Smyth D. M.
Published: March 2011

LiNbO3 tolerates large amounts of disorder in the form of Li2O- deficiency, oxygen-deficiency, and substitutional impurities. These should all result in the formation of a self-consistent set of lattice defects, and there will thus be interactions between the different types of disorder. It is shown that reduction will result in an increase of the Li2O activity in LiNbO3 when it is kinetically hindered from exchanging Li2O with its surroundings. This is in fact the situation for exposure to reducing atmospheres for several hours near 1000°C. Available data on compositions and defect concentrations at 1050°C indicate that reduction should result in separation of a Li20-rich second phase for oxygen partial pressures below 10−17 about 10 atm. Evidence for such phase separation is described.
Crack Development in Cementitious Materials under Impact Loading
Authors: Mindess Sidney , Banthia Nemy P. , Ritter Andrew , Skalny Jan P.
Published: March 2011

Flexural specimens of hardened cement paste, fibre reinforced concrete, and conventionally reinforced concrete were tested in an instrumented dropweight impact machine, employing a 345 kg mass impact hammer dropped from a height of 500 mm. The crack development in the specimens was monitored using high speed motion picture photography, carried out at about 10,000 frames per second. It was found that, for all three specimens, some crack branching occurred. The cracks did not propagate in a continuous fashion; they appeared to arrest occasionally, and then began to grow again. However, it appeared as if the crack velocities reached a maximum value very soon after the impact occurred; they then decreased, and finally increased again just prior to failure. The average crack velocities were in the range of about 75 to 115 m/s.
Behaviour under Explosive Loading of Concrete Reinforced with Polymer Grids
Authors: Hobbs B. , Watson A. J. , Oldroyd P. N.
Published: March 2011

The characteristic of a new form of high strength polymer grid are outlined and its possible uses as reinforcement in concrete subjected to dynamic loading are discussed. Details are given of a test programme in which concrete slabs reinforced with a range of grid types in various configurations have been subjected to explosive loading from contact charges of plastic explosive. A range of both transient and post-test measurements were taken. Results are presented showing how the various damage parameters measured vary with the position and number of polymer grids used in the slabs. The results of the transient measurements are used to suggest mechanisms for damage formation. It is concluded that these polymer grids are effective in restraining explosively generated damage in concrete slabs and that in many circumstances their light weight and their inherent resistance to normal corrosion processes may give them significant advantages over conventional steel reinforcement.