School of Architectural Technology Volume 4 [W2019 + S2019]

Welcome to Sheridan’s School of Architectural Technician/Technology printed portfolio volume 4. Student work has been amalgamated into a print and digital portfolio showing the academic excellence of our program. Student work in the book is largely from the course CADD 39788 Architectural Computer Visualisation with a few projects from other courses making guest appearances.https://source.sheridancollege.ca/fast_books/1010/thumbnail.jp

Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (C18H12) on a Gd2O3. Our study evidences a novel effect-oxidation of higher hydrocarbons at significantly lower temperatures (similar to 300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level

4 f occupancy and magnetism of rare-earth atoms adsorbed on metal substrates

We report x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements as well as multiplet calculations for Dy, Ho, Er, and Tm atoms adsorbed on Pt(111), Cu(111), Ag(100), and Ag(111). In the gas phase, all four elements are divalent and we label their 4f occupancy as 4f(n). Upon surface adsorption, and depending on the substrate, the atoms either remain in that state or become trivalent with 4f(n-1) configuration. The trivalent state is realized when the sum of the atomic correction energies (4f -> 5d promotion energy E-fd + intershell coupling energy delta E-c) is low and the surface binding energy is large. The latter correlates with a high substrate density of states at the Fermi level. The magnetocrystalline anisotropy of trivalent RE atoms is larger than the one of divalent RE atoms. We ascribe this to the significantly smaller covalent radius of the trivalent state compared to the divalent one for a given RE element. For a given valency of the RE atom, the anisotropy is determined by the overlap between the spd states of the RE and the d states of the surface. For all investigated systems, the magnetization curves recorded at 2.5 K show absence of hysteresis indicating that magnetic relaxation is faster than about 10 s

Sheridan School of Architectural Technology Volume 1 [W2017]

Welcome to Sheridan’s School of Architectural Technician/Technology inaugural printed portfolio. This volume is a celebration of the architectural achievements of Sheridan students. Much of the content presented here has been incubated in CADD39788, Architectural Computer Visualisation. Inside you will find an amalgamation of student and faculty work put together into a publication that reflects the rich theatre of creativity and complexity that is architectural education here at Sheridan. Student work within the magazine is from the last year of studies in the Architectural Technology program. Each student has selected their best work to represent some of the skills that they have learned over the years as part of Sheridan. Faculty work is a selection of research, teaching, and professional projects that represents that quality and diversity of educators that serve not only as teachers, but also as mentors to our students. They showcase the talent and skill of some of the individuals that make the Sheridan program a reality.https://source.sheridancollege.ca/fast_books/1001/thumbnail.jp

Fine-tuning the electrostatic properties of an alkali-linked organic adlayer on a metal substrate

The performance of modern organic electronic devices is often determined by the electronic level alignment at a metal–organic interface. This property can be controlled by introducing an interfacial electrostatic dipole via the insertion of a stable interlayer between the metallic and the organic phases. Here, we use density functional theory to investigate the electrostatic properties of an assembled structure formed by alkali metals coadsorbed with 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules on a Ag(100) substrate. We find that the interfacial dipole buildup is regulated by the interplay of adsorption energetics, steric constraints and charge transfer effects, so that choosing chemical substitutions within TCNQ and different alkali metals provides a rich playground to control the systems’ electrostatics and in particular fine-tune its work-function shift

Re-evaluating how charge transfer modifies the conformation of adsorbed molecules

The archetypal electron acceptor molecule, TCNQ, is generally believed to become bent into an inverted bowl shape upon adsorption on the coinage metal surfaces on which it becomes negatively charged. New quantitative experimental structural measurements show that this is not the case for TCNQ on Ag(111). DFT calculations show that the inclusion of dispersion force corrections reduces not only the molecule-substrate layer spacing but also the degree of predicted molecular bonding. However, complete agreement between experimentally-determined and theoretically-predicted structural parameters is only achieved with the inclusion of Ag adatoms into the molecular layer, which is also the energetically favoured configuration. The results highlight the need for both experimental and theoretical quantitative structural methods to reliably understand similar metal-organic interfaces and highlight the need to re-evaluate some previously-investigated systems

Magnetic Hysteresis in Er Trimers on Cu(111)

We report magnetic hysteresis in Er clusters on. Cu(111) starting from the size-of three atoms. combining Xray magnetic circular dichroism, scanning tunneling microscopy, and mean-field nucleation theory, we determine the size dependent magnetic properties of the Er clusters. Er atoms and dimers-are paramagnetic, and their easy magnetization axes are oriented in-plane. In contrast, timers and bigger dusters exhibit magnetic hysteresis at 2.5 K with a relaxation time of 2 min at 0.1 T and out-of-plane easy axis. This appearance of magnetic stability for trimers coincides with their enhanced structural stability

Phase Transitions in Confinements: Controlling Solid to Fluid Transitions of Xenon Atoms in an On-Surface Network

This study reports on "phase" transitions of Xe condensates in on-surface confinements induced by temperature changes and local probe excitation. The pores of a metal-organic network occupied with 1 up to 9 Xe atoms are investigated in their propensity to undergo "condensed solid" to "confined fluid" transitions. Different transition temperatures are identified, which depend on the number of Xe atoms in the condensate and relate to the stability of the Xe clustering in the condensed "phase." This work reveals the feature-rich behavior of transitions of confined planar condensates, which provide a showcase toward future "phase-transition" storage media patterned by self-assembly. This work is also of fundamental interest as it paves the way to real space investigations of reversible solid to fluid transitions of magic cluster condensates in an array of extremely well-defined quantum confinements

Watching nanostructure growth: kinetically controlled diffusion and condensation of Xe in a surface metal organic network

Diffusion, nucleation and growth provide the fundamental access to control nanostructure growth. In this study, the temperature activated diffusion of Xe at and between different compartments of an on-surface metal organic coordination network on Cu(111) has been visualized in real space. Xe atoms adsorbed at lower energy sites become mobile with increased temperature and gradually populate energetically more favourable binding sites or remain in a delocalized 'fluid' form confined to diffusion along a topological subset of the on-surface network. These diffusion pathways can be studied individually under kinetic control via the chosen thermal energy kT of the sample and are determined by the network and sample architecture. The spatial distribution of Xe in its different modes of mobility and the time scales of the motion is revealed by Scanning Tunneling Microscopy (STM) at variable temperatures up to 40 K and subsequent cooling to 4 K. The system provides insight into the diffusion of a van der Waals gas on a complex structured surface and its nucleation and coarsening/growth into larger condensates at elevated temperature under thermodynamic conditions

Large effect of metal substrate on magnetic anisotropy of Co on hexagonal boron nitride

We combine x-ray absorption spectroscopy (XAS), x-raymagnetic circular dichroism (XMCD) and x-ray magnetic linear dichroism (XMLD) data with first principles density functional theory (DFT) calculations and amultiorbital many-body Hamiltonian approach to understand the electronic and magnetic properties of Co atoms adsorbed on h-BN/Ru(0001) and h-BN/Ir(111). The XAS line shape reveals, for both substrates, an electronic configuration close to 3d(8), corresponding to a spin S = 1 Magnetic field dependent XMCD data show large (14 meV) out-of-plane anisotropy on h-BN/Ru(0001), while it is almost isotropic (tens of mu eV) on h-BN/Ir(111). XMLD data together with both DFT calculations and the results of the multiorbital Hubbard model suggest that the dissimilar magnetic anisotropy originates from different Co adsorption sites, namely atop Non h-BN/Ru(0001) and 6-fold hollow on h-BN/Ir(111)