Growth of conformal single-walled carbon nanotube films from Mo/Fe/Al2O3 deposited by electron beam evaporation

We discuss growth of high-quality carbon nanotube (CNT) films on bare and microstructured silicon substrates by atmospheric pressure thermal chemical vapor deposition (CVD), from a Mo/Fe/Al₂O₃ catalyst film deposited by entirely electron beam evaporation. High-density films having a tangled morphology and a Raman G/D ratio of at least 20 are grown over a temperature range of 750-900 °C. H₂ is necessary for CNT growth from this catalyst in a CH₄ environment, and at 875 °C the highest yield is obtained from a mixture of 10%/90% H₂/CH₄. We demonstrate for the first time that physical deposition of the catalyst film enables growth of uniform and conformal CNT films on a variety of silicon microstructures, including vertical sidewalls fabricated by reactive ion etching and angled surfaces fabricated by anisotropic wet etching. Our results confirm that adding Mo to Fe promotes high-yield SWNT growth in H₂/CH₄; however, Mo/Fe/Al₂O₃ gives poor-quality multi-walled CNTs (MWNTs) in H₂/C₂H₄. An exceptional yield of vertically-aligned MWNTs grows from only Fe/Al₂O₃ in H₂/C₂H₄. These results emphasize the synergy between the catalyst and gas activity in determining the morphology, yield, and quality of CNTs grown by CVD, and enable direct growth of CNT films in micromachined systems for a variety of applications.     

Nano-patterning photosensitive polymers using local field enhancement at the end of apertureless SNOM tips

We show experimentally that local optical field enhancement can occur at the end of an apertureless SNOM tip illuminated by an external light source. Our approach consists in the use of a photosensitive polymer, placed in the tip near‐field, to record intensity distribution in the vicinity of the tip end. The excited nanometre‐size light source permits us to produce nano‐patterns on the polymer surface which are then characterized by atomic force microscopy. Experimental images show the influence, on the field enhancement, of three important experimental parameters: the polarization state of the incident light, the geometry of the external illumination and the radius of curvature of the tip apex. These results are shown to be in good agreement with two‐dimensional numerical calculations based on the finite‐difference time‐domain method. We show preliminary nanometre‐size patterns created by this nano‐source excited at a metallic tip extremity and discuss the potential of this approach for near‐field optical lithography.     

Changes in pheromone titer of oblique-banded leafroller,Choristoneura rosaceana,virgin females as a function of time of day,age, and temperature

Under a 16:8 hr light-dark photoperiod and 20C constant temperature, the titers of (Z)-11-tetradecenyl acetate (Z11–14:Ac), (E)-11-tetradecenyl acetate (E11–14:Ac) and (Z)-11-tetradecenol (Z11–14:OH) produced by different-agedChoristoneura rosaceana virgin females varied significantly during the scotophase, with the maximum titer occurring before the onset of calling in day-0 and day-3 females, while in day-5 females the titer remained constant throughout the calling period. There was a significant decrease in the titer of all pheromone components with age, explaining the lesser attractiveness of day-5 females relative to day-0 and day-3 females observed in the field. Under a cold thermocycle simulating condition during the second flight period in the fall, the titers of all pheromone components did not vary with time of day. There was a significant decrease in the amount ofZ11–14:Ac with age but no changes occurred in the minor components. Furthermore, for any given age tested, the amount of each component produced during the period of maximal calling activity remained relatively similar at the two temperature regimes. However, as with the expression of calling behavior, pheromone production was initiated earlier at cooler than at warmer temperatures. At both temperature regimes, female age and time of day influenced the ratio of each pheromone component. These results are discussed in relation to the hypothesis that by calling earlier, less attractive older females may increase their probability of mating.     

In-line monitoring of advanced microelectronic processes using combined X-ray techniques

Accurate and reliable in-line monitoring of the different films thickness that occur throughout the integrated circuit manufacturing process is mandatory to develop and produce advanced microelectronic devices. X-ray reflectivity (XRR) is a fundamental and suitable metrology technique to precisely determine the thickness of both transparent and metallic thin films. Furthermore, XRR is very sensitive to surface and interface roughness, and also provides information about the film density. X-ray fluorescence (XRF) is currently used as a metrology technique to control the thickness and the elemental composition of relatively thick films. The performance of a new in-line metrology tool, which gathers XRR and XRF data to monitor film thickness, has been assessed. Results on the monitoring of high κ thin films, low κ materials, copper barrier and copper seed layers are presented.     

Accurate and rapid optical characterization of an anisotropic guided structure based on a neural method

Optimal performances of integrated optical devices are obtained by the use of an accurate and reliable characterization method. The parameters of interest, i.e., optical indices and thickness of the waveguide structure, are calculated from effective indices by means of an inversion procedure. We demonstrate how an artificial neural network can achieve such a process. The artificial neural network used is a multilayer perceptron. The first result concerns a simulated anisotropic waveguide. The accuracy in the determination of optical indices and waveguide thickness is 5 x 10(-5) and 4 nm, respectively. Then an experimental application on a silica-titania thin film is performed. In addition, effective indices are measured by m-lines spectroscopy. Finally, a comparison with a classical optimization algorithm demonstrates the robustness of the neural method.     

Influence of post-implantation physico-chemical changes in a macroporous ceramic on its mechanical strength

The aim of this study was to determine if the compressive strength of a macroporous biphasic calcium phosphate ceramic (MBCP) changed with post-implantation physicochemical transformations, in the absence of true bone deposition. MBCP cylinders were implanted in rabbit femurs and muscles. Compressive strength measurements and Fourier transform infrared (FTIR) spectroscopy measurements were performed after 1,2,3,6 and 12 weeks. MBCP blocks implanted in a human and removed after 1 week due to a clinical problem were also submitted to the same analyses. Results showed that compressive strength increased in both osseous and muscular sites. Mechanical improvement was also measured on MBCP implanted in a human. Physico-chemical changes, particularly biological apatite precipitations, were evident in MBCP implanted in muscle and in a human. This study has shown that the compressive strength of MBCP increased after implantation, even in the absence of true bone deposition. This suggests that in vivo physico-chemical processes could improve the mechanical properties of MBCP.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

Using entering reading comprehension performance as a predictor of performance in college classes.

In the reported study, we tested the hypothesis that the comprehension of reading material drawn from a college course could be used to predict learning performance in that course. Students enrolled in an educational psychology course or a business statistics course took at the beginning of the semester comprehension tests that were based on both psychology and statistics texts. The reading comprehension scores were related to examination performance in the courses and to overall college grade point average (GPA). For comparison purposes, Scholastic Aptitude Test scores were related to the same variables. The results revealed that course-relevant reading comprehension performance (i.e., psychology in the psychology course, statistics in the statistics course) was a significant predictor of course performance but not of GPA. The results are discussed in terms of a model of comprehension that contains general and specific factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validation de la version fran?aise du questionnaire: Coping with Children's Negative Emotions Scale--CCNES.

The purpose of this study was to measure the validity/reliability of a French version of the Coping with Children's Negative Emotions Scale--CCNES (R. A. Fabes et al., 1990). Parents (220 mothers, 154 fathers) of preschool-age children (mean age 54 mo; 111 girls, 109 boys) were presented with 12 situations in which children are likely to experience negative affects. For each situation, parents were asked to indicate how likely they would be to react in each of 6 alternative fashions (distress, punitive, encourage expression of emotion, comforting, problem-focused, and minimizing responses). Reliability (internal consistency, temporal stability) and validity findings indicate that CCNES-vf is a valid instrument to assess parental emotion-related reactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Directive gain and impedance of a ring array of antennas

Ring arrays can be made so that they concentrate the radiated power in the plane of the ring and are also omnidirectional (or nearly so) in this plane. This paper deals with ring arrays which exhibit these properties. For antenna lengths which are equal to and less thanlambda/4, graphs are included which show, or make it easy to calculate, antenna impedances the ratio of maximum to minimum directive gain in the plane of the ring, and the mean directive gain in the plane of the ring.