Showing papers by "Amandine Bellec published in 2017"
TL;DR: In this article, the size-dependent bistability of a FeII[HB(3,5-(Me)2Pz)3]2 spin transition compound in the form of thin films, the thickness of which varies from 130 to 8500 nm, was investigated.
Abstract: We investigate the size-dependent bistability of a FeII[HB(3,5-(Me)2Pz)3]2 spin-transition compound in the form of thin films, the thickness of which varies from 130 to 8500 nm. From combined structural, magnetic and optical measurements, we demonstrate that the materials prepared by sublimation consist of crystalline grains of the triclinic phase exhibiting the first-order spin transition coexisting with those of a new high-spin metastable tetragonal polymorph in quite a large proportion (ca. 42%). Accordingly, we show that the as-sublimed thin-film of 130 nm thickness retains a remarkable 17 K width hysteresis (T1/2 = 152 K) while the spin transition becomes quantitative by the thermal annealing of the metastable phase at 373 K. The structural analysis based on single-crystal X-ray diffraction measurements provides evidence for a thermal hysteresis resulting from successive crystallographic phase transitions that is consistent with the calorimetric data. This accounts for the asymmetric shape of the hysteresis and the variation of cooperativity observed in the magnetic and optical data whatever the material dimension is.
42 citations
TL;DR: Control of the structure, electronic, and dynamical properties of a molecule achieved by trapping metallic atoms with a molecule on a surface is called "atom trapping chemistry" and it is shown that more complex structures can be envisaged.
Abstract: The ability to trap adatoms with an organic molecule on a surface has been used to obtain a range of molecular functionalities controlled by the choice of the molecular trapping site and local deprotonation The tetraphenylporphyrin molecule used in this study contains three types of trapping sites: two carbon rings (phenyl and pyrrole) and the center of a macrocycle Catching a gold adatom on the carbon rings leads to an electronic doping of the molecule, whereas trapping the adatom at the macrocycle center with single deprotonation leads to a molecular rotor and a second deprotonation leads to a molecular jumper We call “atom trapping chemistry” the control of the structure, electronic, and dynamical properties of a molecule achieved by trapping metallic atoms with a molecule on a surface In addition to the examples previously described, we show that more complex structures can be envisaged
13 citations
TL;DR: In this paper, the physical properties of carbon nanotubes functionalized with porphyrin derivatives were studied using scanning tunneling microscopy/spectroscopy (STM/STS) and classical molecular dynamics (MD) simulations.
Abstract: Noncovalent functionalization of carbon nanotubes (CNTs) allows the combination of the remarkable physical properties of these one-dimensional systems with the properties of the functional molecules and, at the same time, modifies the physicochemical properties of nanotubes for specific applications. The use of functionalized carbon nanotubes in electronics often requires the deposition of the nanotubes on a substrate, and eventually an annealing step, which can modify their properties due to molecule–surface interactions. Using scanning tunneling microscopy/spectroscopy (STM/STS) and classical molecular dynamics (MD) simulations we studied the physical properties of carbon nanotubes functionalized with porphyrin derivatives and discuss the effect of physisorption and sample annealing on the nanotube surface. The results reveal that the functionalized parts exhibit nonperiodic structure with a significant modification of the local density of states. The coverage degree can be estimated from STM images. Wh...
11 citations
TL;DR: In this paper, the growth of Ag on a carefully chosen Ni(11 9 9) substrate was studied and the specific orientation of the Ni substrate led to Ag(7 9 9 ) orientation for the Ag thin film and it prevented the formation of twin and stacking fault.
Abstract: Using vicinal surfaces as a template for heteroepitaxial growth offers a unique possibility to control the orientation and the crystallinity of the grown layer. The study presented here focuses on the growth of Ag on a carefully chosen Ni(11 9 9) substrate. Ag adopts a Stranski-Krastanov growth mode with a slightly constrained wetting layer limited to two monolayers on which well crystallized islands grow. The specific orientation of the Ni substrate leads to Ag(7 9 9) orientation for the Ag thin film and it prevents the formation of twin and stacking fault.
5 citations
TL;DR: In this article, the growth of two-dimensional superstructure and island morphologies of silver atoms evaporated on a nickel (100) surface are studied by scanning tunneling microscopy, and two distinct populations of islands coexist: rounded islands grown on the surface and spindle-shaped islands grown inside the Ni surface.