Very low surface recombination velocities on p-type silicon wafers passivated with a dielectric with fixed negative charge

Surface recombination velocities as low as 10 cm/s have been obtained by treated atomic layer deposition (ALD) of Al₂O₃ layers on p-type CZ silicon wafers. Low surface recombination is achieved by means of field induced surface passivation due to a high density of negative charges stored at the interface. In comparison to a diffused back surface field, an external field source allows for higher band bending, that is, a better performance. While this process yields state of the art results, it is not suited for large-scale production. Preliminary results on an industrially viable, alternative process based on a pseudo-binary system containing Al₂O₃ are presented, too. With this process, surface recombination velocities of 500–1000 cm/s have been attained on mc-Si wafers.     

The development of a glove-box/Vitrobot combination: air-water interface events visualized by cryo-TEM

Aqueous interfaces are of paramount importance in the study of biological systems as well as in the biomedical sciences. To study these interfaces at the nanometer level it is of interest to develop methods that allow their observation with cryogenic transmission electron microscopy (cryo-TEM). Prevention of dehydration to preserve the "native" state during sample preparation prior to vitrification is often one of the most important parameters to control in cryo-TEM experiments. For the preparation of these types of samples, we felt the need for an extended workspace with temperature and humidity control; a 'glove-box' that seamlessly connects to the vitrification instrument, the Vitrobot. In this paper we describe the use of the glove-box in the 2D and 3D cryo-TEM study of DNA adsorption and calcium carbonate mineralization to Langmuir films. The data presented illustrates the necessity of a humidity-controlled environment to preserve the original "native" state of the monolayer system.     

The effect of varying the polyethylene content and the co-polymer content on crazing in polystyrene—low-density polyethylene blends

The effect of varying the low-density polyethylene content and the polystyrenepolyethylene block co-polymer content on the rates of craze initiation and craze growth in polystyrene/low-density polyethylene blends has been studied. it was found that the parameters in the Eyring rate coefficients for craze initiation and craze growth are not dependent on the low-density polyethylene content. However, the rates of craze initiation increased with increasing low-density polyethylene content. This is explained tentatively by a new model for craze initiation. It is argued that effective crazes are only formed within clusters of low-density polyethylene particles that have overlapping stress-concentration fields. The dependence of the rate of craze initiation on the volume-fraction of dispersed phase that follows from this cluster model is qualitatively in agreement with experimental results. PS-PE co-polymer addition gives rise to changes in the Eyring parameters of the rate coefficients of craze initiation and craze growth. This may be a consequence of changes in morphology near the interface and of the different stress state at the interface.     

Morphology and properties of toughened poly(phenylene oxide)-polyamide blends

High impact strength poly(phenylene oxide)-polyamide blends can be prepared by chemically coupling the two components and incorporating a rubbery impact modifier in the resin. The resulting materials exhibit a distinctive morphology in which the rubber is selectively incorporated in the dispersed poly(phenylene oxide) phase. In this paper both the structure and toughening mechanisms in these blends are examined. An analysis of their deformation behaviour is presented in a companion paper.     

Effect of temperature on friction and wear behaviour of CuO–zirconia composites

Results of wear tests using an alumina ball sliding against 5 wt% copper oxide doped tetragonal zirconia polycrystalline (CuO-TZP) ceramics are reported as a function of temperature up to 700 °C. The specific wear rate and friction coefficient are strongly dependent on temperature. Below a critical temperature (T < 600 °C), CuO-TZP showed a high coefficient of friction as well as a high wear rate. This was ascribed to the formation of a rough surface, caused by brittle fracture and abrasive wear, based on observations by scanning electron microscopy (SEM), laser scanning microscopy (LSM) and X-ray photoelectron spectroscopy (XPS). However, above 600 °C a self-healing layer is formed at the interface and results in low friction and wear. The mechanism of layer formation and restoration is discussed and rationalized by onset of plastic deformation caused by a reduction reaction of CuO to Cu₂O at high temperatures.     

Isoxaben soil biodegradation in pear tree orchard after repeated high dose application

Dose uniformity within the treatment volume for tangent breast irradiation can be significantly improved through dynamic compensating collimation using all four independent jaws to define a superposition of sequentially reduced Enhanced dynamic wedge fields. The enhanced dynamic wedge angle is determined which optimizes dose uniformity in the central axis transverse plane, then the sequential reduction of the superior and inferior jaws is determined to optimize the sagittal dose uniformity. This technique could be applied under computer control through a record and verify system.     

Crystal growth in liquid steel during secondary metallurgy

Morphology of nonmetallic inclusions depends on their crystallographic structure, the growth conditions, and the presence of impurities. Inclusions were extracted from industrial aluminum-killed steel samples and investigated under high-resolution scanning electron microscopy. In this article, the morphology of these aluminum oxide inclusions, including their surface features, is approached from the viewpoint of crystal growth. Commonly, aluminum oxide inclusions are considered to be corundum, but some inclusion shapes prove that other aluminum oxide polymorphs are present as well.     

Effects of growth hormone, insulin-like growth factor-I, and cortisol on periparturient antibody response profiles of dairy cattle

The objectives of this study were to determine hormone and antibody response profiles from the prepartum period to peak lactation, and evaluate potential immunomodulatory effects of the classic endocrine hormones, growth hormone (GH), insulin-like growth factor-I (IGF-I) and cortisol. Specifically, 33 Holstein cows were immunized with ovalbumin (OVA) and Escherichia coli J5 at weeks -8 and -3 prior to parturition. At parturition (week 0), cows received an additional immunization of OVA. Blood was collected at weeks -8, -3, 0, 3 and 6 relative to parturition and various samples were used to determine plasma hormone concentration, serum immunoglobulin (Ig), and specific antibody response to OVA and E. coli. Colostrum and milk samples were also collected post-parturition to monitor local immunoglobulin and antibody responses. Results indicated that not all periparturient cows exhibited depressed immune response, and that antibody response to OVA could be used to partition cows into 3 groups recognizing animals with sustained measurable antibody response before and after parturition (Group 1), animals which responded poorly to immunization at parturition (Group 2), and animals which did not respond to immunizations at week -3 or parturition (Group 3). Cows with the highest antibody response to OVA (Group 1) also tended (P < or = 0.10) to have the highest response to E. coli J5 at parturition and had the lowest incidence of disease, particularly mastitis. Antibody response to OVA measured in milk tended to be higher in Group 1 cows, particularly at week 0 (P < or = 0.06) compared to cows of Group 3. IGF-I was higher (P < or = 0.05) in cows of Group 1 than Group 3 at peak lactation (week 6).     

Ductile tearing instability in some engineering thermoplastic blends

The stability of ductile crack growth in two engineering thermoplastic blends is examined. The blends are a poly(phenylene oxide)/nylon 6,6 blend and a poly(butylene terephthalate)/polycarbonate blend. Fracture tests were performed with single-edge notched specimens in tension and three-point bending over a wide range of test speeds. Both larger radius notches and longer specimens were found to promote ductile tearing instability. This behavior is attributed to the higher driving force for crack growth produced by increased elastic energy storage before crack initiation. Over a certain range of test speeds, these factors lead to a novel effect of notch sharpness on toughness; a sharp notch gives rise to a higher fracture energy than does a blunt notch. The results are discussed in terms of the tearing modulus concept developed by Paris and co-workers.     

The morphology and deformation behavior of poly(butylene terephthalate)/BPA polycarbonate blends

Summary In this communication the results of a series of recent studies of the morphology and deformation behavior of toughened poly(butylene terephthalate) (PBT)/BPA polycarbonate (PC) blends are briefly summarized. Several papers containing a more detailed account are currently in press (1–3). Among the unique morphological features of these blends are the consistent isolation of the core/shell impact modifier (IM) in the PC phase and the crystallization and phase separation of the PBT from the partially miscible PBT/PC melt on slow cooling. DSC studies provide corroborating evidence for melt miscibility of the two resins. The blends deform through a combination of cavitation and shear processes. In all cases cavitation occurs exclusively within the IM particles and is suppressed at higher PC concentrations and elevated temperatures.