bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Avoidance Is Regulated by Transient Receptor Potential (TRP) Channels and a Neuropeptide Signaling Pathway inCaenorhabditis elegans
Authors: Glauser Dominique A , Chen Will C , Agin Rebecca , MacInnis Bronwyn L , Hellman Andrew B , Garrity Paul A , Tan Man-Wah , Goodman Miriam B
Published: March 2011

The ability to avoid noxious extremes of hot and cold is critical for survival and depends on thermal nociception. The TRPV subset of transient receptor potential (TRP) channels is heat activated and proposed to be responsible for heat detection in vertebrates and fruit flies. To gain insight into the genetic and neural basis of thermal nociception, we developed assays that quantify noxious heat avoidance in the nematode Caenorhabditis elegans and used them to investigate the genetic basis of this behavior. First, we screened mutants for 18 TRP channel genes (including all TRPV orthologs) and found only minor defects in heat avoidance in single and selected double and triple mutants, indicating that other genes are involved. Next, we compared two wild isolates of C. elegans that diverge in their threshold for heat avoidance and linked this phenotypic variation to a polymorphism in the neuropeptide receptor gene npr-1. Further analysis revealed that loss of either the NPR-1 receptor or its ligand, FLP-21, increases the threshold for heat avoidance. Cell-specific rescue of npr-1 implicates the interneuron  RMG in the circuit regulating heat avoidance. This neuropeptide signaling pathway operates independently of the TRPV genes, osm-9 and ocr-2, since mutants lacking npr-1 and both TRPV channels had more severe defects in heat avoidance than mutants lacking only npr-1 or both osm-9 and ocr-2. Our results show that TRPV channels and the FLP-21/NPR-1 neuropeptide signaling pathway determine the threshold for heat avoidance in C. elegans.
Insect Population Control by Homing Endonuclease-Based Gene Drive: An Evaluation inDrosophila melanogaster
Authors: Chan Yuk-Sang , Naujoks Daniel A , Huen David S , Russell Steven
Published: March 2011

Insects play a major role as vectors of human disease as well as causing significant agricultural losses. Harnessing the activity of customized homing endonuclease genes (HEGs) has been proposed as a method for spreading deleterious mutations through populations with a view to controlling disease vectors. Here, we demonstrate the feasibility of this method in Drosophila melanogaster, utilizing the well-characterized HEG, I-SceI. In particular, we show that high rates of homing can be achieved within spermatogonia and in the female germline. We show that homed constructs continue to exhibit HEG activity in the subsequent generation and that the ectopic homing events required for initiating the strategy occur at an acceptable rate. We conclude that the requirements for successful deployment of a HEG-based gene drive strategy can be satisfied in a model dipteran and that there is a reasonable prospect of the method working in other dipterans. In characterizing the system we measured repair outcomes at the spermatogonial, spermatocyte, and spermatid stages of spermatogenesis. We show that homologous recombination is restricted to spermatogonia and that it immediately ceases when they become primary spermatocytes, indicating that the choice of DNA repair pathway in the Drosophila testis can switch abruptly during differentiation.
Maternal Smoking and Congenital Heart Defects in the Baltimore-Washington Infant Study
Authors: Alverson Clinton J. , Strickland Matthew J. , Gilboa Suzanne M. , Correa Adolfo
Published: March 2011

OBJECTIVE:

We investigated associations between maternal cigarette smoking during the first trimester and the risk of congenital heart defects (CHDs) among the infants.

METHODS:

The Baltimore-Washington Infant Study was the first population-based case-control study of CHDs conducted in the United States. Case and control infants were enrolled during the period 1981–1989. We excluded mothers with overt pregestational diabetes and case mothers whose infants had noncardiac anomalies (with the exception of atrioventricular septal defects with Down syndrome) from the analysis, which resulted in 2525 case and 3435 control infants. Self-reported first-trimester maternal cigarette consumption was ascertained via an in-person interview after delivery. Associations for 26 different groups of CHDs with maternal cigarette consumption were estimated by using logistic regression models. Odds ratios (ORs) corresponded to a 20-cigarette-per-day increase in consumption.

RESULTS:

We observed statistically significant positive associations between self-reported first-trimester maternal cigarette consumption and the risk of secundum-type atrial septal defects (OR: 1.36 [95% confidence interval (CI): 1.04–1.78]), right ventricular outflow tract defects (OR: 1.32 [95% CI: 1.06–1.65]), pulmonary valve stenosis (OR: 1.35 [95% CI: 1.05–1.74]), truncus arteriosus (OR: 1.90 [95% CI: 1.04–3.45]), and levo-transposition of the great arteries (OR: 1.79 [95% CI: 1.04–3.10]). A suggestive association was observed for atrioventricular septal defects among infants without Down syndrome (OR: 1.50 [95% CI: 0.99–2.29]).

CONCLUSIONS:

These findings add to the existing body of evidence that implicates first-trimester maternal cigarette smoking as a modest risk factor for select CHD phenotypes.
Ultraviolet Radiation: A Hazard to Children and Adolescents
Authors:   Council on Environmental Health and Section on Dermatology
Published: March 2011

Ultraviolet radiation (UVR) causes the 3 major forms of skin cancer: basal cell carcinoma; squamous cell carcinoma; and cutaneous malignant melanoma. Public awareness of the risk is not optimal, overall compliance with sun protection is inconsistent, and melanoma rates continue to rise. The risk of skin cancer increases when people overexpose themselves to sun and intentionally expose themselves to artificial sources of UVR. Yet, people continue to sunburn, and teenagers and adults alike remain frequent visitors to tanning parlors. Pediatricians should provide advice about UVR exposure during health-supervision visits and at other relevant times. Advice includes avoiding sunburning, wearing clothing and hats, timing activities (when possible) before or after periods of peak sun exposure, wearing protective sunglasses, and applying and reapplying sunscreen. Advice should be framed in the context of promoting outdoor physical activity. Adolescents should be strongly discouraged from visiting tanning parlors. Sun exposure and vitamin D status are intertwined. Cutaneous vitamin D production requires sunlight exposure, and many factors, such as skin pigmentation, season, and time of day, complicate efficiency of cutaneous vitamin D production that results from sun exposure. Adequate vitamin D is needed for bone health. Accumulating information suggests a beneficial influence of vitamin D on many health conditions. Although vitamin D is available through the diet, supplements, and incidental sun exposure, many children have low vitamin D concentrations. Ensuring vitamin D adequacy while promoting sun-protection strategies will require renewed attention to children's use of dietary and supplemental vitamin D.
Learning Disabilities, Dyslexia, and Vision
Authors: Handler Sheryl M. , Fierson Walter M. ,   the Section on Ophthalmology and Council on Children with Disabilities, American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, and American Association of Certified Orthoptists
Published: March 2011

Learning disabilities constitute a diverse group of disorders in which children who generally possess at least average intelligence have problems processing information or generating output. Their etiologies are multifactorial and reflect genetic influences and dysfunction of brain systems. Reading disability, or dyslexia, is the most common learning disability. It is a receptive language-based learning disability that is characterized by difficulties with decoding, fluent word recognition, rapid automatic naming, and/or reading-comprehension skills. These difficulties typically result from a deficit in the phonologic component of language that makes it difficult to use the alphabetic code to decode the written word. Early recognition and referral to qualified professionals for evidence-based evaluations and treatments are necessary to achieve the best possible outcome. Because dyslexia is a language-based disorder, treatment should be directed at this etiology. Remedial programs should include specific instruction in decoding, fluency training, vocabulary, and comprehension. Most programs include daily intensive individualized instruction that explicitly teaches phonemic awareness and the application of phonics. Vision problems can interfere with the process of reading, but children with dyslexia or related learning disabilities have the same visual function and ocular health as children without such conditions. Currently, there is inadequate scientific evidence to support the view that subtle eye or visual problems cause or increase the severity of learning disabilities. Because they are difficult for the public to understand and for educators to treat, learning disabilities have spawned a wide variety of scientifically unsupported vision-based diagnostic and treatment procedures. Scientific evidence does not support the claims that visual training, muscle exercises, ocular pursuit-and-tracking exercises, behavioral/perceptual vision therapy, “training” glasses, prisms, and colored lenses and filters are effective direct or indirect treatments for learning disabilities. There is no valid evidence that children who participate in vision therapy are more responsive to educational instruction than children who do not participate.
Fever and Antipyretic Use in Children
Authors: Sullivan Janice E. , Farrar Henry C. ,   the SECTION ON CLINICAL PHARMACOLOGY AND THERAPEUTICS,   COMMITTEE ON DRUGS
Published: March 2011

Fever in a child is one of the most common clinical symptoms managed by pediatricians and other health care providers and a frequent cause of parental concern. Many parents administer antipyretics even when there is minimal or no fever, because they are concerned that the child must maintain a “normal” temperature. Fever, however, is not the primary illness but is a physiologic mechanism that has beneficial effects in fighting infection. There is no evidence that fever itself worsens the course of an illness or that it causes long-term neurologic complications. Thus, the primary goal of treating the febrile child should be to improve the child’s overall comfort rather than focus on the normalization of body temperature. When counseling the parents or caregivers of a febrile child, the general well-being of the child, the importance of monitoring activity, observing for signs of serious illness, encouraging appropriate fluid intake, and the safe storage of antipyretics should be emphasized. Current evidence suggests that there is no substantial difference in the safety and effectiveness of acetaminophen and ibuprofen in the care of a generally healthy child with fever. There is evidence that combining these 2 products is more effective than the use of a single agent alone; however, there are concerns that combined treatment may be more complicated and contribute to the unsafe use of these drugs. Pediatricians should also promote patient safety by advocating for simplified formulations, dosing instructions, and dosing devices.
Beic Investigation of Defects Induced in Cw Beam-Annealed Si
Authors: Sheng N.H. , Mizuta M. , Merz J.L.
Published: March 2011

EBIC has been used to investigate the beam-induced damage in As+ -implanted Si subjected to scanned laser or electronbeam annealing. Comparison is made between these annealing techniques; in general, electron-beam annealing is found to give superior results. In addition, several different experiments combining these techniques are described. Samples were pre-annealed prior to laser annealing, using either thermal or electron-beam annealing. Other samples were given a thermal post-anneal after laser-annealing. The effect of these treatments on defect formation is discussed.
Defect-Induced Photoluminescence from Pulsed Laser Annealed Si
Authors: Skolnick M S , Cullis A G , Webber H C
Published: March 2011

Low temperature photoluminescence is used to study damage centers in ion implanted, pulsed laser annealed Si. A number of intense, damage related photoluminescence lines W, G and 13 are observed. It is shown that most of the W (and 13) centers are created by solid phase annealing of implant damage beyond the laser melted region. Peak G, on the other hand, is present in the tail of the implant damage before laser annealing.
Pulsed-Laser Annealing of Ion-Implanted GaAs: Theory and Exeriment
Authors: Wood R. F. , Lowndes Douglas H. , Christie W. H.
Published: March 2011

It is shown that, in the pulsed-laser irradiation of crystalline or lightly damaged GaAs, good agreement is obtained between measured and calculated thresholds for melting, for catastrophic damage due to vaporization, and for the duration of surface melting at various energy densities. Good agreement between theory and experiment is also obtained for dopant profile spreading during pulsed-laser annealing.
Optimization of Pulsed Annealing Techniques for GaAs Integrated Circuits
Authors: Martin G.M. , Mitonneau A , Cathelin M. , Makram-Ebeid S. , Venger C. , Barbier D. , Laugier A.
Published: March 2011

Ohmic contacts on GaAs were realized by pulse annealing AuGe and AuGe-Ni layers deposited on top of n-type GaAs conducting layers. We used focused and largediameter YAG laser beam pulses (λ =1.06 µm), a large diameter Ruby laser beam pulse (λ = 0.69 µm) and a largediameter electron beam pulse. We tested the electrical quality of the contacts obtained. We also examined the compatibility of the alloying techniques used with theself-alignment technology for IC fabrication. In particular, we tested the quality of Al Schottky diodes and of the boron implanted insulating regions which coexist on the same IC with the ohmic contacts and are subject to the same pulse annealing treatment. The relative merit of the different pulse treatments are discussed.
Cw Argon Ion Laser Annealed B and as Implanted Diodes in Oxide Defined Silicon Devices
Authors: Sedgwick T. O. , Solomon P. M. , Vollmer H. J.
Published: March 2011

In this paper, we present detailed reverse leakage data on laser annealed diodes which were formed by implanting 1 × 1013 and 1 × 1014 /cm2 B atoms at 20 keV and by implanting 1× 1014 and 1× 1015/cm2 As atoms at 50 keV into Si. The implant is made into bare Si through oxide windows where 1700Å thermal SiO2 is both the implant mask and the diode edge passivation. The thermal controls were annealed at 900°C for the B and 950°C for the As for 30 minutes. Diode reverse leakage curves versus voltage are reported for devices with variable perimeter to area ratios. The results indicate that B diodes can easily be made with characteristics similar to thermally annealed devices with leakage at 1V in the 10−9 A/cm2 range. For As implanted diodes, the results are mixed. For As implants of 1 × 1014 /cm2 the diodes had leakage currents at 3V in the high 10−9 A/cm2 range. At the 1 × 1015/cm 2 level devices with significantly higher leakage values at high reverse bias were obtained. The leakage and sheet resistance are determined in both cases and an optimum is shown as a function of laser power.
Scanned Electron Beam Annealing of Boron-Implanted Diodes
Authors: Yep T. O. , Fulks R. T. , Powell R. A.
Published: March 2011

Successful annealing of p+ n arrays fabricated by ion-implantation of 11B (50 keV, 1 × 1014 cm-2) into Si (100 has been performed using a broadly rastered, low-resolution (0.25-inch diameter) electron beam. A complete 2" wafer could be uniformly annealed in ≃20 sec with high electrical activation (>75%) and small dopant redistribution (≃450 Å). Annealing resulted In p+n junctions characterized by low reverse current (≃4 nAcm-2 at 5V reverse bias) and higher carrier lifetime (80 μsec) over the entire 2" wafer. Based on the electrical characteristics of the diodes, we estimate that the electron beam anneal was able to remove ion implantation damage and leave an ordered substrate to a depth of 5.5 m below the layer junction.
Characterization of Ion-Implanted SiO2 Properties Applicable to Laser Processing
Authors: Teng T. C. , Shiau Y. , Chen Y. S. , Skinner C. , Peng J. D. , Palkuti L. J.
Published: March 2011

The use of an antireflection oxide film applicable to laser annealing process has been investigated. The optical properties of the antireflection oxide film are changed by ion implantation although the antireflection characteristics are similar to calculations based on nominal optical constants. Implantation annealing can be achieved at powers lower than predicted by calculations. Using the antireflection(AR) technique, n+-p junction diodes were fabricated. Reverse bias junction leakage is around 10-9 A/cm2 , comparable to those annealed thermally. Short channel MOS devices were also fabricated and indicated much better resistance to the short channel effect than those thermally annealed.
Laser Epitaxy Over Buried Layers
Authors: Weeks S. P. , Celler G. K. , Leamy H. J.
Published: March 2011

The redistribution of antimony impurity atoms implanted in (111) and (100) substrates was studied as a function of the power density of Q-switched YAG laser radiation (λ = 0.53μm) used to recrystallize 4700Å films of amorphous silicon vapor deposited over blanket and patterned Sb buried layer structures. Results for fully crystallized layers show impurity profiles ranging from a sharp interface displaced outward slightly relative to the as-grown interface, to complete redistribution of antimony into the deposited layer. Studies of patterned buried layer structures indicate that epitaxial crystallization can be achieved on (111) and (100) substrates without serious damage to the surface topography necessary for subsequent mask alignment.
Pulsed Laser Recrystallization of Polysilicon: Analysis Via A Novel Sem Technique
Authors: Shah Rajiv R. , Crosthwait D. Lloyd
Published: March 2011

Large crystals of silicon were obtained via pulsed laser annealing of thinfilms of fine grain CVD polycrystalline silicon. These films were analyzed using a novel technique that provides rapid feedback of crystallographic and defect information. The technique uses very shallow angle metallurgical sections in conjunction with chemical decoration and scanning electron microscopy and results in excellent depth resolution (<10 nm) across large spatial distances (>100 μm). The technique was used to reveal conversion of very large areas (≈ 1 mm 2) of polysilicon films deposited on silicon into single crystal film, albeit with point defects, without requiring the melt depth to reach the polysilicon/silicon interface. A gradual transition from single crystal to increasingly polycrystalline material was observed going from top to bottom of the initially uniform polycrystalline film depending on the pulse energy used. Polysilicon on top of an oxide layer, on the other hand, transforms into large (≈ 10 μm) single crystals with grain boundaries penetrating the entire polysilicon film thickness. These experimental results shed new light on two very important questions: (1) Is laser annealing entirely an epitaxial process or is it strongly influenced by the thermal properties of the underlying substrate, and (2) Whether substantial regrowth of polysilicon requires equilibrium thermodynamics.
Silicide Formation using Laser and Electron Beams
Authors: Sigmon T. W.
Published: March 2011

The reaction of thin metal films with single crystal or amorphous silicon to form silicide compounds has been successfully undertaken using both scanned-cw and pulsed beam processing. Similar to the case for beam annealing of ion-implanted semiconductors, both the basic mechanisms and the experimental results are found to depend on whether pulsed or scanned beams are used to promote the reactions. For both cases the experimental results are often found to differ sharply from those obtained with standard furnace processing. For the pulsed beam reaction, melting and rapid resolidification occurs in the metal silicon films. The principal result is that the reacted film is frozen in a mixed phase compound which can consist of several silicide compounds including silicon and metal precipitation. Compositions inaccessible by conventional furnace annealing can also be formed by this process. In contrast to the pulsed beam results, scanned-cw beam processing of metal silicon films is found to result in the formation of large area uniform silicide phases with essentially no silicon or metal precipitation. These films are generally found to be homogeneous with well defined silicon/silicide interfaces.
Metastable Alloy Formation in Electron Beam Pulsed Al and Si
Authors: Picraux S. T. , Follstaedt D. M. , Knapp J. A. , Wampler W. R. , Rimini E.
Published: March 2011

The formation of metastable alloys by pulsed electron beam annealing of Al implanted with Sn or Ni and of Si implanted with Sn has been studied by TEM, ion backscattering and channeling. Surface segregation after pulsed melting is observed in Si but not in Al, even though all impurities have similar equilibrium distribution coefficients of∼10-2. This difference is attributed to the higher liquid-solid interface velocity and lower diffusivities in Al. Metastable substitutional solutions more than an order of magnitude above equilibrium solubilities are obtained for Ni and Sn in Al. At Ni concentrations ∼ 5 at.% a highly disordered transformation zone is formed in Al and a new phenomenon in which a polycrystalline layer forms on epitaxially regrown Al is observed.
Oxide Superconductors: A Chemist's View
Authors: Sleight A. W.
Published: March 2011

The brief history of oxide superconductors is presented and discussed in terms of structure, bonding and property interrelationships. The perovskite structure has been very prominent in the history of oxide superconductors, including the recently discovered copper oxide based superconductors. However, an alternate description of the high Tc superconductors in terms of sheets, chains and sticks may be more useful. Although chains and orthorhombic symmetry in RBa2Cu3O7 phases favor high Tc superconductivity, orthorhombic symmetry is not required to have well developed chains and reasonably high Tc (e.g ∼60 K). Furthermore, highly disordered LaBa2Cu3O7 and YBa2Cu3O6.7 phases are not superconducting even though they are weakly orthorhombic. Superconducting RBa2CueO6+x phases are prepared by oxygen intercalation of a semiconducting phase with a low x value; intercalation phases are not normally expected to be thermodynamically stable. A mechanism for superconductivity in oxides is presented based on disproportionation reactions such as 2CuII → CuI + CuIII and 2BiIV → BiIII + Biv.
Effect of GaAs Surface Stoichiometry on The Interface of As-Grown Epitaxial ZnSe/Epitaxial GaAs Heterostructures
Authors: Qiu J. , Gunshor R.L. , Kobayashi M. , Menke D.R. , Qian Q.-D. , Li D. , Otsuka N.
Published: March 2011

In the study reported here, the GaAs surface stoichiometry was systematically varied prior to the nucleation of ZnSe to form epitaxial ZnSe/epitaxial GaAs interfaces. The structures were grown by molecular beam epitaxy and evaluated by several techniques including capacitance-voltage (C-V) measurements. A dramatic reduction of interface state density occurred when the GaAs epilayer was made As deficient. The resulting interface state densities of as-grown structures are comparable to values obtained with (Al,Ga)As/GaAs interfaces.
The Effect of Surface Layers in Epitaxial N-Type Hg1−xCdxTe
Authors: Parat K.K. , Taskar N.R. , Bhat I.B. , Ghandhi S.K.
Published: March 2011

The presence of low mobility surface electrons on n-Hg1−1CdxTe is generally not apparent in the temperature dependence of the Hall Coefficient (RH) or the Hall mobility (µH) of the layer. However, its influence is clearly seen in the magnetic field (B-field) dependence of RH. The B-field dependence of RH can be analyzed to extract the bulk and surface carrier concentrations and their respective mobilities.

This diagnostic technique has been used for evaluating epitaxial Hg1−xCdxTe layers grown by organometallic vapor phase epitaxy (OMVPE), which have been converted to n-type by annealing in Hg overpressure. In addition, the effect of anodic sulfide passivation on the B-field dependence of Hall coefficient is also outlined.
Vapour Pressure Measurements on Organotellurium Precursors for Movpe
Authors: Hails J.E. , Irvine S.J.C. , Mullin J.B.
Published: March 2011

Before an organometallic compound can be used as an MOVPE precursor, certain basic properties need to be known and one of the most important of these is vapour pressure. A technique for the measurement of vapour pressures using an MOVPE system designed for precursor assessment is described. Results on the assessment of di-is-propyl-telluride, di-n-propyl-telluride, di-allyl-telluride, methyl-allyl-telluride and di-t-butyl-telluride are presented.
MBE Growth and Characterization of Small Band Gap HgTe-HgCdTe Superlattices.
Authors: Lansari Y. , Yang Z. , Hwang S. , Cook J.W. , Schetzina J.F.
Published: March 2011

A series of modulation-doped small-band-gap HgTe-Hg1−xCdxTe superlattices (SLs) have been grown by photoassisted MBE. N-type or p-type conductivity was obtained in the modulation-doped samples by incorporating either In or As dopant atoms in the barrier layers, respectively. The electrical and optical properties that these new multilayered quantum well structures display will be discussed.
On The Field Fmisiicn Fwom HgTe-CdTe Superlarrices with Graded Struijctures Under Magnetic Quantization
Authors: Ghatak Kamakhya P. , Biswas Sambjij N
Published: March 2011

In this paper, we studied the magneto-field emission from HgTe/Cdre superlattices with graded structure and compared the same with the bulk specimens of the constituent materials. It is found that the field emitted current density increases both with electron concentration and magnetic field in an oscillatory manner. The field emission in HgTe/CdTe SLi is greater than that of the same from constituent materials the theoretical results are in agreement with the experimental observation as reported elsewhere.
Tem Study of Defects In CdTe/CdMnTe Superlattices on (100) InSb
Authors: Diamond S.J. , Steeds J.W. , Ashenford D. , Lunn B.
Published: March 2011

CdTe/Cd1−xMnx Te superlattices with well/barrier thicknesses ranging from 20Å to 300Å were examined via plan and cross section TEM in analytical instruments capable of EDX and CL. Misfit dislocations, inclined dislocations and stacking faults were observed with a net density of around 109cm−2.

It was observed that the dislocations originated near the substrate/epilayer interface and that stacking faults appeared preferrentially on the pair of {111}B (tellurium terminated) planes in the growth direction rather than on the {111}A planes.

It is suggested that this is due to a difference in mobility between a and P dislocations originating at or near the substrate.
Ga and In Autodoping of Cdt, MnxTe Epitaxial Layers Grown on GaAs and InSb Substrates
Authors: Dubowski J.J. , Wrobel J.M. , Rolfe S. , Jackman J.A. , Mazur J.H. , Noadw J.
Published: March 2011

A study of Ga and In outdiffusion into Cd1−xMnxTe (0≥ x ≥ .70) epitaxial layers grown on (111)GaAs and (001)lnSb was carried out. The layers were grown by pulsed laser evaporation and epitaxy on substrates held at temperatures below 310 °C. The structural quality of the layers was examined using x-ray diffraction and transmission electron microscopy. A tendency toward precipitation of Ga at the near surface region of (11 1)CdMnTe grown on (11 1)GaAs, usually less than 300 nm wide, has been observed with secondary ion mass spectroscopy. Similar results were observed for the migration behaviour of In in (001)CdTe grown on (001)InSb. The ion imaging revealed that both In and Ga accumulate near the surface at localized spots, up to about 10 pm in diameter. The concentration of the spots is in the range of 104 - 106 cm−2. The Ga- and In-rich channels sometimes extend over the whole sample. Annealing at temperatures as low as 400 °C for 2 h significantly increases the concentration of the Ga spots and the average concentration of Ga in the films to above 1016 cm−3. Low-temperature photoluminescence data obtained for annealed samples do not indicate any structural deterioration typical for heavily doped Bridgman grown samples. A sharp neutral-donor bound-exciton transition (D°,X) is observed for samples with 0 < x < .10.
Ion-Implantation Getiering of Impurities in CdTe
Authors: Jin M. H. , James K. M. , Jones C. E. , Merz J. L.
Published: March 2011

This is the first reported use of ion-implantation damage gettering of impurities in CdTe to provide high-quality substrates for the epitaxial growth of appropriate binary or ternary compounds, or for related applications. We describe the results of photoluminescence (PL) measurements performed on samples of Bridgeman-grown CdTe to study both the annealing behavior and gettering effects in this material. From the PL results, it was found that impurity gettering occurs at temperatures at which liquid phase epitaxy take place (∼500°C) so that these two fabrication procedures are compatible. It was also found that the optimum anneal time at this temperature is four hours.
3d Transition Metals in II-VI Semiconductors
Authors: Heiman D. , Dahl M. , Wang X. , Wolff P.A. , Becla P. , Petrou A. , Mycielski A.
Published: March 2011

The magnetic and electronic properties of some I-VI semiconductors with 3d transition metals other than Mn are presented. For example, the nonzero orbital moment in Fe2+ leads to more complex electronic energy levels than for Mnt ions. In (CdFe)Se, inelastic light scattering experiments demonstrate that the ground state is nonmagnetic (Van Vleck ion), and directly measures the energy spacing between the three lowest levels. For Sc2+ ions the donor level lies above the bottom of the conduction band in the Cd-based materials.
Magnetization Study of Fe-Based II-VI Diluted Magnetic Semiconductors
Authors: De Jonge W.J.M. , Swagten H.J.M. , Twardowski A.
Published: March 2011

The high field magnetization for Fe based Diluted Magnetic Semiconductors has been calculated. It is shown that the low temperature magnetization displays characteristic steps, related to the nearest neighbour exchange interaction JNN, provided that JNN exceeds a critical value.
Characterization of Interfaces in SiC Particulate-Reinforced Al Alloys by AEM
Authors: Robertson Brian W. , Holm Chandra , Lin Yang-Pi , Corbin Stephen F. J. , Wilkinson David S.
Published: March 2011

As a preliminary step to detailed study of the interfaces in SiC particulatereinforced Al alloys, a number of methods of sample preparation have been explored; the resultant artefacts on the thinned foils observed in transmission electron microscopes are discussed and improvements to the preparation procedures are suggested. Initial observations of the microstructure of two alloys differing significantly in their matrix silicon content are presented.
The Influence of Annealing on the Behaviour of Epoxy-Glass Interphases
Authors: Schröder U. , Marzi T. , Heß M. , Kosfeld R.
Published: March 2011

Dynamic-mechanical measurements were used to study the properties of the interphase in glass fibre reinforced epoxy resins. The immobilisation of the polymer chains in the interphase is determined by the curing system, the annealing process, and the surface treatment of the glass fibres.
Interface Properties for Ceramic Composites from a Single-Fiber Pull-Out Test
Authors: Butler Elizabeth P. , Fuller Edwin R. , Chan Helen M.
Published: March 2011

An experimental approach has been developed using a single-fiber pullout test to measure intrinsic interface properties for ceramic composites. The properties are determined from a pull-out, force-displacement curve, which is directly related to reinforcement toughening via fiber/matrix debonding and frictional pull-out. They were evaluated for a model composite system of continuous SiC fibers with various surface treatments in a borosilicate glass matrix. For the processing conditions used, the interface fracture toughness and the interface frictional shear resistance were found to be 1.0 ± 0.5 J/m2 and 3.3 ± 0.6 MPa, respectively, for as-received fibers. Experiments conducted with long embedded fiber lengths allowed the shear resistance to be deconvolved into an interface friction coefficient of 0.05 ± 0.01 and an initial fiber-clamping pressure of 65 ± 6 MPa. Nitric acidwashed fibers gave an increased interface toughness of 3.6 ± 0.1 J/m2 and friction coefficient of 0.08 ± 0.02, but nearly the same initial clamping pressure, 72 ± 12 MPa. Calculations of the clamping pressure from the fiber/matrix thermal expansion mismatch and from stress birefringence measurements in the glass were in general agreement with this value.
The Role of Crystallization of an Intergranular Glassy Phase in Determining Grain Boundary Residual Stresses in Debased Aluminas
Authors: Padture Nitin P. , Chan Helen M. , Lawn Brian R. , Readey Michael J.
Published: March 2011

The influence of microstructure on the crack resistance (R-curve) behavior of a commercial debased alumina containing large amounts of glassy phase (28 vol %) has been studied using the Indentation-Strength test. The effect of two microstructural variables, viz. grain size and the nature of the intergranular second phase (glassy or crystalline) has been evaluated. Crystallization of the intergranular glass was carried out in order to generate residual stresses at the grain boundaries, which have been shown to enhance R-curve behavior in ceramic materials. Enhancement of the R-curve behavior was observed with the increase in grain size. However, no effect of the nature of the intergranular second phase on the R-curve behavior, in small and large grain materials, was observed. The results from characterization of these materials using various analytical techniques is presented, together with possible explanations for the observed effects.
The Production of Modulus Gradients at Interfaces
Authors: Garton Andrew , Haldankar Gautam , Shockey Edward
Published: March 2011

We have developed a range of “antiplasticizing” additives for epoxy and polyimide resins which can increase the modulus of the cured polymers by > 40%, increase their tensile and shear strengths, modify their fracture behavior, and decrease their water uptake. These additives may be used alone or in conjunction with rubber modifiers. The optimum additive formulations are complex mixtures, but we describe here two relatively pure model systems. The epoxy additive is the reaction product of 4-hydroxyacetanilide (HAA) and vinylcyclohexene dioxide (VCD), while the polyimide additive is the reaction product of epoxyphenoxypropane (EPP) and HAA. These additives are mixed with the epoxy resin and curing agent (or polyamic acid solution in the case of polyimides), before curing, and the mixture is then cured in the conventional fashion. We describe here some physical properties of the modified epoxies and polyimides and their use in adhesive formulations. These materials offer the potential for constructing modulus gradients at interfaces through their use as primers, so as to allow testing of the many hypotheses concerning desirable interphase properties. Some initial experiments in this area are described.
Correlation Between Fibre Surface Energetics and Fibre-Matrix Adhesion in Carbon Fibre Reinforced Peek Composite
Authors: Hodge D J , Middlemiss B A , Peacock J A
Published: March 2011

Surface energies of carbon fibres at different levels at surface treatment have been determined by a wetting force technique and related to fibre-matrix adhesion in carbon fibre reinforced PEEK composite. The effect of oxidative surface treatment on the surface free energy is detailed, along with the changes in surface oxygen and nitrogen content, as determined by X-ray photoelectron spectroscopy (XPS). The work of adhesion has been calculated for the carbon fibres and thermoplastic, which correlate well with experimental determination of interfacial strength. The technique can therefore be used to predict adhesion levels in fibre reinforced composites.
Effect of Surface Oxygen on Adhesion of Carbon Fiber Reinforced Composites
Authors: Yip P. W. , Lin S. S.
Published: March 2011

Five carbon fibers from different precursors were surface treated by various chemical reagents for the elucidation of the mechanism involved in interfacial adhesion. SEM, ESCA and SAM techniques were used to characterize morphology as well as surface constituents of the treated fibers. The transverse tensile strengths of the composites made from the treated fibers and epoxy resin were also obtained. The result indicated that the interlocking mechanism by surface roughness seemed to play a major role in the fiber-epoxy adhesion.
Interlaminar Fracture in Carbon Fiber/Thermoplastic Composites
Authors: Hinkley J. A. , Bascom W. D. , Allred R. E.
Published: March 2011

The surfaces of commercial carbon fibers are generally chemically cleaned or oxidized and then coated with an oligomeric sizing to optimize their adhesion to epoxy matrix resins. Evidence from fractography, from embedded fiber testing and from fracture energies suggests that these standard treatments are relatively ineffective for thermoplastic matrices. This evidence is reviewed and model thermoplastic composites (polyphenylene oxide/high strain carbon fibers) are used to demonstrate how differences in adhesion can lead to a two-fold change in interlaminar fracture toughness.

The potential for improved adhesion via plasma modification of fiber surfaces is discussed. Finally, a surprising case of fiber-catalyzed resin degradation is described.
A New Theory for the Debonding of Discontinuous Fibers in an Elastic Matrix
Authors: Leung Christopher K. Y. , Li Victor C.
Published: March 2011

The mechanical properties of fiber composites are strongly influenced by the debonding of fibers. When an embedded fiber is loaded from one end, debonding can occur at both the loaded end and the embedded end. Existing theories neglect the possibility of debonding from the embedded end and are thus limited in applications to cases with low fiber volume fraction, low fiber modulus, high interfacial strength/interfacial friction ratio or short fiber length. A new twoway fiber debonding theory, which can extend the validity of one-way debonding theories to all general cases, has recently been developed. In this paper, the physical reason for the occurrence of two-way debonding is discussed. The limit of validity for one-way debonding theories is considered. One-way and two-way debonding theories are then compared with respect to the prediction of composite behaviour. The determination of interfacial parameters from the fiber pull-out test will also be described.
Solid State Bonding of Si3N4 and Ni
Authors: Wang Jian-Yih , Hsu Shu-En , Suga Tadatomo , Ishida Yoichi
Published: March 2011

Solid state bonding of Si3N4 and Ni is considered to be a simple ceramic/metal diffusion bonding as the case of Al2O3/Nb. There are two kinds of bonding interfaces observed by transmission electron microscope(TEM). In addition to the directly bonded interface, an amorphous-like phase was found in some regions of the Si3N4/Ni interface. It is responsible for the degradation of bonding strength. In view of the experimental results, the existence of the amorphous-like phase in bonding interface results from the formation of SiO2 and accumulation of Al2O3 and Y2O3, which were used as sinterfng binders of Si3N4, via intergranular diffusion during the bonding process.
Integrated Titanium Silicide Processing
Authors: Nulman Jaim
Published: March 2011

The processing of titanium silicide in a multichamber processing system is described. Three processes are included: wafer cleaning, Ti deposition, and annealing. The results are compared to wafers processed in a conventional way with exposure to ambient air between Ti deposition and the annealing step. TEM, RBS and sheet resistance measurements indicate that the films processed without exposure to ambient air have thicker and purer TiN layers as compared to the films with air exposure. Furthermore, integration allows for a wider processing window for the first annealing step. The use of reactive cleaning chemistry prior to Ti deposition results in a smooth silicon surface and therefore uniform silicidation as compared to inert cleaning technology, where redeposit of etched material occurs.
Geometrical effects and disintegration of narrow TiSi2/poly-Si lines
Authors: Norström H. , Maex K. , Vandenabeele P.
Published: March 2011

The geometrical shape and the thermal stability of the TiSi2/poly-Si interface on narrow lines has been studied. The examined line-widths varied between 0.8 μm and 1.5 μm. The thermal stability was found to strongly correlate to the actual line-width of the structures. At the onset of degradation, at and above 900°C, narrow lines were observed to disintegrate at a much faster rate than wider ones. Cross-sectional microscopy (TEM and SEM) revealed the TiSi2/poly-Si interface to be curved inwards. The interface bowing was found to be more pronounced on narrow lines. It is suggested that the interface bowing results from a mechanical pinning of the TiSi2/poly-Si interface by the side-wall spacers.
Cobalt Silicide Formation on Polysilicon: Dopant Effects on Reaction Kinetics and Silicide Properties
Authors: Sitaram A. R. , Murarka S. P.
Published: March 2011

The concept of using cobalt disilicide as a self-aligned metallization scheme for gate/interconnection and contact formation is gaining wide acceptance. The silicide formation on the gate will require a Co-metal film interaction with the underlying polysilicon that may be doped heavily. We have investigated the silicide formation kinetics during this reaction. The effect of different dopants (B,P, and As) and their concentration on the Co-Si interaction and the dopant redistribution during such reactions were investigated. The results from these studies will be presented and discussed.
Reliable Metallization For InP-Based Devices and Oeic’s
Authors: Wada O. , Ueda O.
Published: March 2011

We describe techniques of reliable metallization in InP-based systems for application to discrete and opto-electronic integrated circuits (OEIC’s). Strong metallurgical interaction between Au and InP-based compounds can cause serious contact degradation in light emitting diodes (LED’s). By analyzing this interaction in detail, an improved thin Au/Zn/Au p-contact technique has been developed. The results are compared with Pt/Ti contacts, and it has shown that both provide sufficient reliability under temperature and current stresses in LED’s. We then describe a metallization technique for flip-chip bonding of opto-electronic devices on other semiconductor chips for OEIC applications. An acceptable reaction barrier effect of Pt in AuSn/Pt/Ti metallization structure has been demonstrated and this structure has been used for a high-reliability, flip-chip integrated GalnAs/InP PIN photodiode/GaAs amplifier receiver circuit. We also discuss requirements for metallization for future monolithic OEIC’s by taking up an example of metal-semiconductor-metal photodiodes in InP-based systems.
Reliability of Ohmic Contacts for AlGaAs/GaAs HBTs
Authors: Jackson G. S. , Tong E. , Saledas P. , Kazior T. E. , Sprague R. , Brooks R. C. , Hsieh K. C.
Published: March 2011

The reliability of ohmic contacts to thin, heavily doped layers of GaAs is investigated. Pd/Ge/Au contacts to n-type GaAs display excellent electrical stability over extended periods of thermal stress. The contact resistance stays below 0.5Ω-mm during a 2500h, 280°C bake. Reactive ion beam assisted evaporation of Ti with N forms TiN which is introduced as a barrier layer in Pt/TiN/Ti/Au contacts to a thin p+ layer. The TiN layer allows greater process latitude in the sintering process and improves long term stability of the ohmic contact. The microstructure of the p-type contacts is examined with TEM and Auger profiling at different instances of the 2500h, 280°C bake and compared to the contact resistance measurements.
Applications of Amorphous Ti-P-N Diffusion Barriers in Silicon Metallization
Authors: Kolawa E. , Halperin L. , Pokela P. , Vu Quat T , Nieh C. W.
Published: March 2011

Thin films of amorphous TiP and TiPN2 alloys were deposited by sputtering of a TiP target in an Ar and N2/Ar mixture, respectively. These alloy films were tested as diffusion barriers between Al and Si as well as between Cu and Si and also in metallizations which included TiSi2 as the contacting layer. Rutherford backscattering spectrometry, x-ray diffraction and electrical measurements were used to determine the barrier effectiveness. We find that TiP and TiPN2 films prevent the interdiffusion and reaction between Al and Si up to 500°C and 600°C for 30 minutes annealing, respectively, and between Cu and Si up to 600°C and 700°C, respectively.
Thermodynamic Stability of Ptal Thin Films on GaAs
Authors: Ko Dae-Hong , Sinclair Robert
Published: March 2011

The thermal stability of PtAl thin films on GaAs substrates has been studied using transmission electron microscopy and Auger electron spectroscopy. The PtAl thin films were formed by sequential deposition of discrete Pt and Al layers on GaAs by e-beam evaporation followed by subsequent annealing processes. Interfacial reactions in the Al/Pt/GaAs system proceed in two stages. Upon low temperature annealing Pt and GaAs react to form PtGa and PtAs2. Further high temperature annealing causes PtGa, PtAs2 and Al to react together producing the desired PtAl on GaAs. We observed solid-phase epitaxial regrowth of GaAs during the second stage of reaction. The PtAl/GaAs interface is determined to be thermally stable during an 800°C/30 min. anneal, while remaining morphologically uniform on GaAs.
A Two-Step Process for the Formation of Au-Ge Ohmic Contacts to n-GaAs
Authors: Dornath-Mohr M. A. , Cole M. W. , Lee H. S. , Wrenn C. S. , Eckart D. W. , Fox D. C. , Yerke L. , Chang W. H. , Lareau R. T. , Jones K. A. , Cosandy F.
Published: March 2011

The formation of low temperature Au-Ge contacts to n-GaAs is a two-step process. In the first step, the metals segregate into Au and Ge rich regions and the intermixing of the Au and Ge with the Ga and As causes a reduction in the barrier height. The second step occurs after extended annealing, during which time Au and Ge continue to diffuse into the substrate. An orthorhombic Au-Ga phase is formed and it is likely that other Au-Ga or Ge-As phases are formed. The length of the extended anneal is dependent upon the atomic percent of Ge in the film, with the 10 at. % Ge taking 6 hr., the 27 at. % Ge taking 3 hr. and the 50 at. % Ge taking 9 hr. to become ohmic. The 75 at. % Ge sample doesn’t show ohmic behavior even after 33 hr. of annealing. The metal-semiconductor interface configuration appears abrupt, showing no protrusions into the GaAs substrate.
Au Ohmic Contacts to P-Type Hg1-xCdxte Utilizing Thin Interfacial Layers
Authors: Krishnamurthy V. , Simmons A. , Helms C. R.
Published: March 2011

Ohmic behavior is observed in electroless Au contacts to p -type Hg1−xCdxTe. Our investigation of the interfacial chemistry of such contacts suggest that this ohmic behavior may be due to the presence of a Te,O, and CI layer. To verify this correlation with interfacial chemistry, thin plasma oxide layers were used in evaporated Au contacts. The annealed plasma oxidized contacts exhibited low contact resistances. This behavior was attributed to a low interface state density at the interfacial layer/Hg1−xCdxTe interface. In comparison, as-deposited and annealed Au contacts without a thin interfacial layer were rectifying with a large barrier height.