Search results for "Heterostructures"
showing 10 items of 20 documents
Fabrication of graphene ruthenium-complex heterostructures
2015
The aim of this study is to understand the photoresponse of a Ruthenium-complex/graphene heterostructure. Early work demonstrated that light detection by graphene field effect devices was enhanced by dropcasting Ruthenium Complex molecules. Here we proposed to fabricate a new class of devices where the Ruthenium-complex molecules are embedded between two layer of CVD monolayer graphene.
High-Mobility, Wet-Transferred Graphene Grown by Chemical Vapor Deposition
2019
We report high room-temperature mobility in single layer graphene grown by Chemical Vapor Deposition (CVD) after wet transfer on SiO$_2$ and hexagonal boron nitride (hBN) encapsulation. By removing contaminations trapped at the interfaces between single-crystal graphene and hBN, we achieve mobilities up to$\sim70000cm^2 V^{-1} s^{-1}$ at room temperature and$\sim120000cm^2 V^{-1} s^{-1}$ at 9K. These are over twice those of previous wet transferred graphene and comparable to samples prepared by dry transfer. We also investigate the combined approach of thermal annealing and encapsulation in polycrystalline graphene, achieving room temperature mobilities$\sim30000 cm^2 V^{-1} s^{-1}$. These …
Natural optical anisotropy of h-BN: Highest giant birefringence in a bulk crystal through the mid-infrared to ultraviolet range
2018
The giant birefringence of layered h-BN was demonstrated by analyzing the interference patterns in reflectance and transmittance measurements in the mid-infrared to the deep ultraviolet energy range. The refractive index for polarization perpendicular to the c axis is much higher than the refractive index for polarization parallel to the c axis, and it displays a strong increase in the ultraviolet range that is attributed to the huge excitonic effects arising from the unique electronic structure of h-BN. Thus, h-BN is shown to exhibit a giant negative birefringence that ranges from -0.7 in the visible to -2 in the deep ultraviolet close to the band gap. The electronic dielectric constants f…
Mapping an electron wave function by a local electron scattering probe
2015
A technique is developed which allows for the detailed mapping of the electronic wave function in two-dimensional electron gases with low-temperature mobilities up to $15\times {10}^{6}\;{\mathrm{cm}}^{2}\;{{\rm{V}}}^{-1}\;{{\rm{s}}}^{-1}$. Thin ('delta') layers of aluminium are placed into the regions where the electrons reside. This causes electron scattering which depends very locally on the amplitude of the electron wave function at the position of the Al δ-layer. By changing the distance of this layer from the interface we map the shape of the wave function perpendicular to the interface. Despite having a profound effect on the electron mobiliy, the δ-layers do not cause a widening of …
Phonons in MoSe2/WSe2 van der Waals heterobilayer
2021
We report first-principles calculations of the structural and vibrational properties of the synthesized two-dimensional van der Waals heterostructures formed by single-layers dichalcogenides MoSe2 and WSe2. We show that, when combining these systems in a periodic two-dimensional heterostructures, the intrinsic phonon characteristics of the free-standing constituents are to a large extent preserved but, furthermore, exhibit shear and breathing phonon modes that are not present in the individual building blocks. These peculiar modes depend strongly on the weak vdW forces and has a great contibution to the thermal properties of the layered materials. Besides these features, the departure of fl…
Enhanced NiO Dispersion on a High Surface Area Pillared Heterostructure Covered by Niobium Leads to Optimal Behaviour in the Oxidative Dehydrogenatio…
2020
[EN] A Nb-containing siliceous porous clay heterostructure (PCH) with Nb contents from 0 to 30 wt %) was prepared from a bentonite and used as support in the preparation of supported NiO catalysts with NiO loading from 15 to 80 wt %. Supports and NiO-containing catalysts were characterised by several physicochemical techniques and tested in the oxidative dehydrogenation (ODH) of ethane. The characterisation studies on Nb-containing supports showed the presence of well-anchored Nb(5+)species without the formation of Nb(2)O(5)crystals. High dispersion of nickel oxide with low crystallinity was observed for the Nb-containing PCH supports. In addition, when NiO is supported on these Nb-containi…
Two-Dimensional Crystals and van der Waals Heterostructures based on Inorganic and Molecular Strongly Correlated Layered Materials
2021
“En resumen, toda obra grande es el fruto de la paciencia y de la perseverancia, combinadas con una atención orientada tenazmente durante meses y aun años hacia un objeto particular”. “In summary, all great work is the fruit of patience and perseverance, combined with tenacious concentration on a subject over a period of months or years”. Santiago Ramón y Cajal (Reglas y consejos sobre investigación científica. Madrid: Academia de Ciencias Exactas, Físicas y Naturales, 1897). The present Thesis constitutes a journey –a romance of many dimensions, quoting Edwin Abbot Abbot– from 3D to 2D and, hopefully (we let the curious Reader judge), “Through Flatland to Thoughtland” (citing, again, Abbot…
Coordination chemistry on surfaces through vapor phase processing: smart molecular/graphene heterostructures based on spin-crossover complexes and 2D…
2023
Los compuestos de coordinación están últimamente focalizando la atención de los investigadores en el campo de la nanociencia. Particular interés están generando aquellos compuestos con propiedades magnéticas de cara a su integración a la nanoescala en ramas como la electrónica y/o la espintrónica moleculares. Sin embargo, para su uso real en dispositivos destinados a estas aplicaciones, su procesabilidad es un requisito indispensable. En el marco de esta necesidad, la presente tesis doctoral se ha destinado al estudio del procesado sobre superficies mediante técnicas de fase gas de dos tipos distintos de compuestos de coordinación. Por tanto, el trabajo se ha dividido en dos partes. La prim…
Effect of Confinement and Coulomb Interactions on the Electronic Structure of the (111) LaAlO3/SrTiO3 Interface
2023
A tight binding supercell approach is used for the calculation of the electronic structure of the (111) LaAlO3/SrTiO3 interface. The confinement potential at the interface is evaluated solving a discrete Poisson equation by means of an iterative method. In addition to the effect of the confinement, local Hubbard electron–electron terms are included at the mean-field level within a fully self-consistent procedure. The calculation carefully describes how the two-dimensional electron gas arises from the quantum confinement of electrons near the interface due to the band bending potential. The resulting electronic sub-bands and Fermi surfaces show full agreement with the electronic structure de…
Emergent ultrafast phenomena in correlated oxides and heterostructures
2017
The possibility of investigating the dynamics of solids on timescales faster than the thermalization of the internal degrees of freedom has disclosed novel non-equilibrium phenomena that have no counterpart at equilibrium. Transition metal oxides (TMOs) provide an interesting playground in which the correlations among the charges in the metal $d$-orbitals give rise to a wealth of intriguing electronic and thermodynamic properties involving the spin, charge, lattice and orbital orders. Furthermore, the physical properties of TMOs can be engineered at the atomic level, thus providing the platform to investigate the transport phenomena on timescales of the order of the intrinsic decoherence ti…