Effects of processing on the stability of molybdenum oxide ultra-thin films

The effects of wet chemical processing conventionally employed in device fabrication standards are systematically studied on molybdenum oxide (MoOx) ultra-thin films. We have combined x-ray photoelectron spectroscopy (XPS), angle resolved XPS and x-ray reflectivity techniques to provide deep insights into the changes in composition, structure and electronic states upon treatment of films with different initial stoichiometry prepared by reactive sputtering. Our results show significant reduction effects associated with the development of gap states in MoOx, as well as changes in the composition, density and structure of the films, systematically correlated with the initial oxidation state of Mo.Comment: 16 pages, 5 figures, Appendix include

Magnetostatic interactions in arrays of nanostructures

The physics of nanomagnetic elements has become one of the main areas of research in the last few decades. Their magnetic characterization is fundamental in order to understand the magnetic reversal mechanisms and to control the magnetic switching precisely in view of device applications. In such small elements, the magnetic behaviour is strongly determined by the interplay of magnetic anisotropy with the geometric shape. Moreover, in closed packed arrays, the effects of the inter-element interactions become important and reveal often unresolved issues regarding the strength of these couplings and their dipolar or exchange mediated origin. In this thesis three different cases have been discussed about the mechanisms of interactions among the magnetic elements of very densely packed systems. The experimental section opens with the study of the magnetization reversal process in magnetostatically interacting permalloy (an alloy of nickel and iron) nanowires, using the vectorial magneto-optical Kerr effect magnetometry. The measured in-plane magnetization components parallel and perpendicular to the applied field show a transition from coherent rotation to inhomogeneous reversal mode over and above a determined value of the wires thickness. A strong dependence on wires thickness is also observed in the analysis of effects of dipolar interactions. Successively, the motion and pinning of domain walls have been investigated in vertical and horizontal chains of permalloy triangular microrings and compared with the isolated rings case. Using longitudinal and diffracted magnetooptic Kerr effects, magnetic force microscopy and micromagnetic simulations, the field dependence of the spin structure into the ring has been determined. This investigation has allowed to observe how the dipolar inter-element interaction changes qualitatively the manner in which reversal occurs. Considering that the magnetic domain walls displacement can also be controlled by using magnetic fields, such structures could be viewed as a preliminary approach for the development of magnetic logic applications. Finally, static and dynamical properties have been studied in patterned arrays of pseudo spin-valves in which a layer of permalloy has been coupled with a layer of cobalt, through an interspacer of non-magnetic copper. Magnetic hysteresis loops have been measured by longitudinal magneto-optic Kerr effect and by X-ray resonant magnetic scattering, whereas the dynamical properties have been investigated using the Brillouin light scattering. The results show a complex magnetization reversal process determined by the interplay between the interlayer dipolar interaction and the different reversal nucleation fields in the two ferromagnetic layers. Reducing the thickness of the copper spacer, an interlayer magnetic exchange coupling between the permalloy and cobalt layers emerges, in addition to the dipolar interaction, introducing further possibilities for manipulating the magnetic behaviour of the system

In transition: examining students with learning disabilities\u27 transition from high school to college through Schlossberg\u27s transition theory

The goal of this study was to find out what selected freshmen students with learning disabilities reported about their experiences while transitioning from high school to college and the circumstances or situations that impact such experiences in relation to Schlossberg\u27s Transition Theory. The participants in this study were six freshmen students between 18 and 22 years old registered with Rowan University\u27s Office of Disability Resources who self-identified as having one or more learning disability during the spring 2015 semester. Data were collected using an adapted interview protocol with permission from Samantha DeVilbiss\u27 (2014) dissertation, The Transition Experience: Understanding the Transition from High School to College for Conditionally-Admitted Students Using the Lens of Schlossberg\u27s Transition Theory. The interview protocol consisted of two interview schedules with roughly 12 questions each, which totaled to about 24 questions. The questions asked about the feelings and experiences related to the participants\u27 transition from high school to college. Content analysis reported that multiple themes related to the four Ss of Schlossberg\u27s Transition Theory impacted participants\u27 transition experiences. The most significant themes were trigger, independence, assessment of the transition, awareness and acceptance of disability, institutional support, and community involvement

Optimization of an axial fan for air cooled condensers

We report on the low noise optimization of an axial fan specifically designed for the cooling of CSP power plants. The duty point presents an uncommon combination of a load coefficient of 0.11, a flow coefficient of 0.23 and a static efficiency ηstat > 0.6. Calculated fan Reynolds number is equal to Re = 2.85 x 107. Here we present a process used to optimize and numerically verify the fan performance. The optimization of the blade was carried out with a Python code through a brute-force-search algorithm. Using this approach the chord and pitch distributions of the original blade are varied under geometrical constraints, generating a population of over 24000 different possible individuals. Each individual was then tested using an axisymmetric Python code. The software is based on a blade element axisymmetric principle whereby the rotor blade is divided into a number of streamlines. For each of these streamlines, relationships for velocity and pressure are derived from conservation laws for mass, tangential momentum and energy of incompressible flows. The final geometry was eventually chosen among the individuals with the maximum efficiency. The final design performance was then validated through with a CFD simulation. The simulation was carried out using a RANS approach, with the cubic k -  low Reynolds turbulence closure of Lien et al. The numerical simulation was able to verify the air performance of the fan and was used to derive blade-to-blade distributions of design parameters such as flow deviation, velocity components, specific work and diffusion factor of the optimized blade. All the computations were performed in OpenFoam, an open source C++- based CFD library. This work was carried out under MinWaterCSP project, funded by EU H2020 programme