Abstract: In this contribution, we report a fundamental study of the factors that set the contact resistivity between metals and highly doped semiconductors. We investigate the case of n-type doped Si contacted with amorphous TiSi combining first-principles calculations with Non-Equilibrium Green functions transport simulations. The intrinsic contact resistivity is found to saturate at similar to 2x10(-10) Omega.cm(2) with the doping concentration and sets an intrinsic limit to the ultimate contact resistance achievable for n-doped Si vertical bar amorphous-TiSi. This limit arises from the intrinsic properties of the semiconductor and of the metal such as their electron effective masses and Fermi energies. We illustrate that, in this regime, contacting metals with a heavy electron effective mass helps reducing the interface intrinsic contact resistivity.

Abstract: We present a computational model to model the magnetic structure of two-dimensional (2D) dilute-magnetic-semiconductors (DMS) both the monolayers and multilayers using first-principles density functional theory (DFT), as well as their magnetic phase transition as a function of temperature using Monte-Carlo simulations. Using our method, we model the magnetic structure of bulk, bilayer, and monolayer MoS2 substitutionally doped with Fe atoms. We find that the out-of-plane interaction in bilayer MoS2 is weakly ferromagnetic, whereas in bulk MoS2 it is strongly anti-ferromagnetic. Finally, we show that the magnetic order is more robust in bilayer Fe-doped MoS2 compared to the monolayer and results in a room-temperature FM at an atomic substitution of 14-16%.

Abstract: Supershapes are used in Parametric Design to model, literally, thou-sands of natural and man-made shapes with a single 6 parameter formula. However, users are left to probe such a rich yet dense collection of supershapes using a set of independent 1-D sliders. Some of the formula’s parameters are non-linear in nature, making them particularly difficult to grasp with conventional 1-D sliders alone. VR appears as a promising setting for Parametric Design with supershapes since it empowers users with more natural visual inspection and shape browsing techniques, with multiple solutions being displayed at once and the possibility to design more interesting forms of slider interaction. In this work, we propose VR shape widgets that allow users to probe and select supershapes from a multitude of solutions. Our designs take leverage on thumbnails, mini-maps, haptic feedback and spatial interaction, while supporting 1-D, 2-D and 3-D supershape parameter spaces. We conducted a user study (N = 18) and found that VR shape widgets are effective, more efficient, and natural than conventional VR 1-D sliders while also usable for users without prior knowledge on supershapes. We also found that the proposed VR widgets provide a quick overview of the main supershapes, and users can easily reach the desired solution without having to perform fine-grain handle manipulations.

Abstract: For the first time, we demonstrate, using an atomistic description of a 30nm diameter spin-transfer-torque magnetic random access memories (STT-MRAM), that the difference in mechanical properties of its sub-nanometer layers induces a high compressive strain in the magnetic tunnel junction (MTJ) and leads to a detrimental magnetostrictive effect. Our model explains the issues met in engineering the electrical and magnetic performances in scaled STT-MRAM devices. The resulting high compressive strain built in the stack, particularly in the MgO tunnel barrier (t-MgO), and its associated non-uniform atomic displacements, impacts on the quality of the MTJ interface and leads to strain relieve mechanisms such as surface roughness and adhesion issues. We illustrate that the strain gradient induced by the different materials and their thicknesses in the stacks has a negative impact on the tunnel magneto-resistance (TMR), on the magnetic nucleation process and on the STT-MRAM performance.

Abstract: A new class of irregularly shaped dielectric lens antennas with a supershaped microstrip antenna feeder is presented and detailed in this work. The surface of the lens antenna and the feeder shape have been modelled by using the three and two-dimensional Gielis formula, respectively. The antenna design has been carried out by integrating an home-made software tool with the CST Microwave Studio®. The radiation properties of the whole antenna system have been evaluated using a dedicated high-frequency technique based on the tube tracing approximation. Moreover, the effects due to the multiple internal reflections have been properly modeled. The proposed model was applied to study unusual and complex lens antenna systems with the aim to design special radiation characteristics.

Abstract: In this work, a nonlinear dispersive multiphysic model based on Maxwell and asymptotic Smoluchowsky equations has been developed to analyze the electroporation phenomenon induced by pulsed electric field on biological cells. The irregular plasma membrane geometry has been modeled by incorporating in the numerical algorithm the Gielis superformula as well as the dielectric dispersion of the plasma membrane has been modeled using the multi-relaxation Debye-based relationship. The study has been carried out with the aim to compare our model implementing a thin plasma membrane with the simplified model in which the plasma membrane is modeled as a distributed impedance boundary condition. The numerical analysis has been performed exposing the cell to external electric pulses having rectangular shapes. By an inspection of the obtained results, significant differences can be highlighted between the two models confirming the need to incorporate the effective thin membrane into the numerical algorithm to well predict the cell response to the pulsed electric fields in terms of transmembrane voltages and pore densities, especially when the cell is exposed to external nanosecond pulses.

Abstract: The revolutionary development in digital theory and technology calls for non-trivial decisions in bridging between the virtual and real worlds. The field of conservation of cultural heritage thus provides various challenges, especially with regards to learning, study and investigation of tangible heritage through applications of intangible ICT technologies. This paper examines the interaction between e-learning, and the actual on-site learning and study of historic buildings and sites, with an emphasis on their visual characteristics. In this context, the paper presents some aspects of application of a methodology which allows basic documentation, monitoring and primary analysis of data on cultural (built) heritage sites by general public through educational process enabled by an e-learning platform.

Abstract: The available scenarios of pollutant trends in Europe indicate that the effect of industrial, domestic and transport emissions on corrosion and soiling will continue to constitute a serious threat to Cultural Heritage. Such effects require improved methods for a more accurate diagnosis, monitoring and assessment of the damage. Within this framework, the monitoring methodology applied within the European project TeACH (Technologies and tools to prioritize assessment and diagnosis of air pollution impact on immovable and movable cultural heritage) (2008-2012) allows to assess the impact of the main pollutants on historic buildings. As a part of this approach, a new kit able to monitor the environmental parameters critical for the conservation of architectural surfaces and to evaluate the related damage in terms of surface color change was developed. The monitoring methodology described in the present paper has valuable application potential in the definition of preventive conservation strategies for a wide range of heritage assets.

Abstract: Heterostructures of III-V materials under a mechanical strain are being actively researched to enhance the performance of the tunnel field-effect transistor (TFET). In scaled III-V device structures, however, the interplay between the effects of strain and quantum confinement on the semiconductor band structure and hence the performance is highly non-trivial. We have therefore developed a computationally efficient quantum mechanical simulator Pharos, which enables self-consistent full-zone k.p-based simulations of III-V TFETs under a general non-uniform strain. We present the self-consistent procedure and demonstrate it on confined staggered bandgap GaAs0.5Sb0.5/In0.53Ga0.47As TFETs. We find a large performance degradation due to size-induced quantum confinement compared to non-confined devices. We show that some performance can be regained either by applying a uniform biaxial tensile strain or through the non-uniform strain profile at a lattice-mismatched heterostructure.

Abstract: We calculate the contact resistance for an edge- and top-contacted 2D semiconductor. The contact region consists of a metal contacting a monolayer of MoS2 which is otherwise surrounded by SiO2. We use the quantum transmitting boundary method to compute the contact resistance as a function of the 2D semiconductor doping concentration. An effective mass Hamiltonian is used to describe the properties of the various materials. The electrostatic potentials are obtained by solving the Poisson equation numerically. We incorporate the effects of the image-force barrier lowering on the Schottky barrier and examine the impact on the contact resistance. At low doping concentrations, the contact resistance of the top contact is lower compared to edge contact, while at high doping concentrations, the edge contact exhibits lower resistance.

Abstract: In this paper the possibilities and limitations of a non-invasive prototype of macroscopic X-ray powder diffraction scanning device employed in transmission and reflection mode are demonstrated. Contrarily to e.g. macroscopic X-ray fluorescence scanners, which gather information on the elemental level, the prototype instrument allows to obtain information on the crystallographic structure of the components. When applied to cultural heritage artefacts, it becomes possible to identify and localize crystalline pigments. Furthermore, it became clear that different information can be available depending on the geometry of the scanner components. In transmission mode information over the entire stratigraphy of the painting is gathered, which is useful to e.g. identify background substrates and major pigments. On the other hand, reflection-XRPD is a surface-sensitive technique and allows the identification of pigments and degradation products located on the surface. The data acquired during both experiments can be presented as two-dimensional distribution maps which show the spatial distribution of every identified pigment. The complementary nature of transmission and reflectionmode makes it possible to gain more insight into the stratigraphy of the painting which is valuable information for conservation and restoration scientists.

Abstract: Many organic residue streams such as pig manure are not or inefficiently used, although they can be converted into valuable materials, as well as energy, using pyrolysis. The yield of the pyrolysis products (i.e. oil, gas and char) is dependent on the process conditions and the feedstock used. Char as a soil amendment or activated carbon are interesting options for valorization of biomass residues. Here, a review is presented of the techno-economic potential of both valorization options based on literature and own experiments with wood from phytoremediation, particle board and waste from beer production. The term “biochar” is specifically used to designate pyrolysis char that is intentionally applied to soil in order to enhance its structure and fertility. Biochar applications are often also motivated by the objective of climate change mitigation. Two main disadvantages for the economic feasibility of biochar applications have been discerned. Firstly, carbon sequestration in agricultural crops and soils is not yet eligible under the Clean Development Mechanism. Secondly, the impact of biochar on crop productivity is unclear. Activated carbon (AC) seems to have interesting adsorption characteristics resulting in potentially high sales prices. A preliminary techno-economic assessment showed that AC production is preferred above oil production for wood from phytoremediation as long as the market price of 2 kEUR.t(-1) for commercially available ACs can be attained. Whenever a feedstock with high nitrogen content is available (e.g. particle board with melamine urea formaldehyde resin), even higher market prices might be attained. This study shows that valorization of the pyrolysis char might be an answer to the slow adoption of pyrolysis in commercial applications. Focus in research and development, for instance in future research with regard to pig manure valorization, should therefore be on sustainable products with high economic value and direct utilization potential.