Controlled Carboxylic Acid-Functionalized Silicon Nitride Surfaces through Supersonic Molecular Beam Deposition.

The functionalization of inorganic surfaces by organic functional molecules is a viable and promising method towards the realization of novel classes of biosensing devices. The proper comprehension of the chemical properties of the interface, as well as of the number of active binding sites for bioreceptor molecules are characteristics that will determine the interaction of the sensor with the analyte, and thus its final efficiency. We present a new and reliable surface functionalization route based on supersonic molecular beam deposition (SuMBD) using 2,6-naphthalene dicarboxylic acid as a bi-functional molecular linker on the chemically inert silicon nitride surface to further allow for stable and homogeneous attachment of biomolecules.

Enhancement of X-ray-Excited Red Luminescence of Chromium-Doped Zinc Gallate via Ultrasmall Silicon Carbide Nanocrystals.

X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical probes due to being free of autofluorescence, while both their excitation and emission possess a high penetration efficacy . Herein, we report silicon carbide quantum dot sensitization of trivalent chromium-doped zinc gallate nanoparticles with enhanced near-infrared emission upon X-ray and UV-vis light excitation. We have found that a ZnGaO shell is formed around the SiC nanoparticles during seeded hydrothermal growth, and SiC increases the emission efficiency up to 1 order of magnitude due to band alignment that channels the excited electrons to the chromium ion.

Tailoring Superconductivity in Large-Area SingleLayer NbSe via Self-Assembled Molecular Adlayers.

Two-dimensional transition metal dichalcogenides (TMDs) represent an ideal testbench for the search of materials by design, because their optoelectronic properties can be manipulated through surface engineering and molecular functionalization. However, the impact of molecules on intrinsic physical properties of TMDs, such as superconductivity, remains largely unexplored. In this work, the critical temperature () of large-area NbSe monolayers is manipulated, employing ultrathin molecular adlayers.

Boosting and Balancing Electron and Hole Mobility in Single- and Bilayer WSe Devices Tailored Molecular Functionalization.

WSe is a layered ambipolar semiconductor enabling hole and electron transport, which renders it a suitable active component for logic circuitry. However, solid-state devices based on single- and bilayer WSe typically exhibit unipolar transport and poor electrical performance when conventional SiO dielectric and Au electrodes are used. Here, we show that silane-containing functional molecules form ordered monolayers on the top of the WSe surface, thereby boosting its electrical performance in single- and bilayer field-effect transistors.

Electronic properties of hybrid organic/inorganic semiconductor pn-junctions.

Hybrid inorganic/organic semiconductor heterojunctions are candidates to expand the scope of purely organic or inorganic junctions in electronic and optoelectronic devices. Comprehensive understanding of bulk and interface doping on the junction's electronic properties is therefore desirable. In this work, we elucidate the energy level alignment and its mechanisms at a prototypical hybrid pn-junction comprising ZnO (n-type) and p-doped N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (α-NPD) as semiconductors, using photoelectron spectroscopy.

Versatile and Scalable Strategy To Grow Sol-Gel Derived 2H-MoS Thin Films with Superior Electronic Properties: A Memristive Case.

Transition metal dichalcogenides, such as molybdenum disulfide (MoS), show peculiar chemical/physical properties that enable their use in applications ranging from micro- and nano-optoelectronics to surface catalysis, gas and light detection, and energy harvesting/production. One main limitation to fully harness the potential of MoS is given by the lack of scalable and low environmental impact synthesis of MoS films with high uniformity, hence setting a significant challenge for industrial applications. In this work, we develop a versatile and scalable sol-gel-derived MoS film fabrication by spin coating deposition of an aqueous sol on different technologically relevant, flexible substrates with annealing at low temperatures (300 °C) and without the need of sulfurization and/or supply of hydrogen as compared to cutting-edge techniques.

Publisher Correction: Collective molecular switching in hybrid superlattices for light-modulated two-dimensional electronics.

The original version of this article incorrectly listed an affiliation of Sara Bonacchi as 'Present address: Institut National de la Recherche Scientifique (INRS), EMT Center, Boulevard Lionel-Boulet, Varennes, QC, J3X 1S2, 1650, Canada', instead of the correct 'Present address: Department of Chemical Sciences - University of Padua - Via Francesco Marzolo 1 - 35131 Padova - Italy'. And an affiliation of Emanuele Orgiu was incorrectly listed as 'Present address: Department of Chemical Sciences, University of Padua, Via Francesco Marzolo 1, Padova, 35131, Italy', instead of the correct 'Present address: Institut National de la Recherche Scientifique (INRS), EMT Center, Boulevard Lionel-Boulet, Varennes, QC, J3X 1S2, 1650, Canada'. This has been corrected in both the PDF and HTML versions of the article.

Collective molecular switching in hybrid superlattices for light-modulated two-dimensional electronics.

Molecular switches enable the fabrication of multifunctional devices in which an electrical output can be modulated by external stimuli. The working mechanism of these devices is often hard to prove, since the molecular switching events are only indirectly confirmed through electrical characterization, without real-space visualization. Here, we show how photochromic molecules self-assembled on graphene and MoS generate atomically precise superlattices in which a light-induced structural reorganization enables precise control over local charge carrier density in high-performance devices.

A novel combined experimental and multiscale theoretical approach to unravel the structure of SiC/SiO core/shell nanowires for their optimal design.

In this work we propose a realistic model of nanometer-thick SiC/SiOx core/shell nanowires (NWs) using a combined first-principles and experimental approach. SiC/SiOx core/shell NWs were first synthesised by a low-cost carbothermal method and their chemical-physical experimental analysis was accomplished by recording X-ray absorption near-edge spectra. In particular, the K-edge absorption lineshapes of C, O, and Si are used to validate our computational model of the SiC/SiOx core/shell NW architectures, obtained by a multiscale approach, including molecular dynamics, tight-binding and density functional simulations.

Lithography-Free Miniaturization of Resistive Nonvolatile Memory Devices to the 100 nm Scale by Glancing Angle Deposition.

The scaling of nonvolatile memory (NVM) devices based on resistive filament switching to below a 100 nm footprint area without employing cumbersome lithography is demonstrated. Nanocolumns of the organic semiconductor 4,4-bis[N-(1-naphthyl)-N-phenyl-amino]diphenyl (α-NPD) were grown by glancing angle deposition on a silver electrode. Individual NVM devices were electrically characterized by conductive atomic force microscopy with the tip of a conductive cantilever serving as second electrode.

Electronic structure of CuTPP and CuTPP(F) complexes: a combined experimental and theoretical study II.

The unoccupied electronic structure of thick films of tetraphenylporphyrin and tetrakis(pentafluorophenyl)porphyrin Cu(ii) complexes (hereafter, CuTPP and CuTPP(F)) deposited on Au(111) has been studied by combining the outcomes of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy with those of spin-unrestricted time-dependent density functional (TD-DFT) calculations carried out either within the scalar relativistic zeroth order regular approximation (ZORA) framework (C, N and F K-edges) or by using the Tamm-Dancoff approximation coupled to ZORA and including spin-orbit effects (Cu L2,3-edges). Similarly to the modelling of NEXAFS outcomes pertaining to other Cu(ii) complexes, the agreement between theory and experiment is more than satisfactory, thus confirming the open-shell TD-DFT to be a useful tool to look into NEXAFS results pertinent to Cu(ii) compounds. The combined effect of metalation and phenyl (Ph) fluorine decoration is found to favour an extensive mixing between (Ph)σ* and pristine porphyrin macrocyle (pmc) (pmc)π* virtual levels.

Electronic structures of CuTPP and CuTPP(F) complexes. A combined experimental and theoretical study I.

Copper complexes of tetraphenylporphyrin (H2TPP) and tetrakis(pentafluorophenyl)porphyrin (H2TPP(F)) deposited as thin films on Au(111) have been studied experimentally and theoretically. Core level emissions from C 1s, N 1s, F 1s and Cu 2p as well as valence states of CuTPP and CuTPP(F) have been investigated using surface photoelectron spectroscopy. The interpretation of experimental results has been guided by theoretical calculations carried out on isolated species in the habit of the density functional theory.

Tuning the Electronic Structure of Graphene by Molecular Dopants: Impact of the Substrate.

A combination of ultraviolet and X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and first principle calculations was used to study the electronic structure at the interface between the strong molecular acceptor 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (F6TCNNQ) and a graphene layer supported on either a quartz or a copper substrate. We find evidence for fundamentally different charge redistribution mechanisms in the two ternary systems, as a consequence of the insulating versus metallic character of the substrates. While electron transfer occurs exclusively from graphene to F6TCNNQ on the quartz support (p-doping of graphene), the Cu substrate electron reservoir induces an additional electron density flow to graphene decorated with the acceptor monolayer.

Organic semiconductor/gold interface interactions: from physisorption on planar surfaces to chemical reactions with metal nanoparticles.

The interaction of gold nanoparticles (AuNPs) with prototypical organic semiconductors used in optoelectronics, namely, tris(8-hydroxyquinoline)aluminium (Alq3 ) and 4,4-bis[N-(1-naphthyl)-N-phenylamino]diphenyl (α-NPD), is investigated in situ by X-ray photoelectron spectroscopy (XPS). These AuNPs-on-molecule experiments are compared with the reversed molecule-on-Au cases. The molecules-on-Au systems show only weak interactions, and the evolution of the XP spectra is dominated by final-state effects.

Energy-Level Engineering at ZnO/Oligophenylene Interfaces with Phosphonate-Based Self-Assembled Monolayers.

We used aromatic phosphonates with substituted phenyl rings with different molecular dipole moments to form self-assembled monolayers (SAMs) on the Zn-terminated ZnO(0001) surface in order to engineer the energy-level alignment at hybrid inorganic/organic semiconductor interfaces, with an oligophenylene as organic component. The work function of ZnO was tuned over a wide range of more than 1.7 eV by different SAMs.

Tuning the Magnetic Properties of Carbon by Nitrogen Doping of Its Graphene Domains.

Here we present the formation of predominantly sp(2)-coordinate carbon with magnetic- and heteroatom-induced structural defects in a graphene lattice by a stoichiometric dehalogenation of perchlorinated (hetero)aromatic precursors [hexachlorobenzene, C6Cl6 (HCB), and pentachloropyridine, NC5Cl5 (PCP)] with transition metals such as copper in a combustion synthesis. This route allows the build-up of a carbon lattice by a chemistry free of hydrogen and oxygen compared to other pyrolytic approaches and yields either nitrogen-doped or -undoped graphene domains depending on the precursor. The resulting carbon was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, photoelectron spectroscopy (XPS), and SQUID magnetometry to gain information on its morphological, chemical, and electronic structure and on the location of the nitrogen atoms within the carbon lattice.

XAS of tetrakis(phenyl)- and tetrakis(pentafluorophenyl)-porphyrin: an experimental and theoretical study.

The unoccupied electronic structure of tetrakis(phenyl)- and tetrakis(pentafluorophenyl)-porphyrin thick films deposited on SiO2/Si(100) native oxide surfaces has been thoroughly studied by combining the outcomes of near-edge X-ray absorption fine structure spectroscopy at the C, N, and F K-edges with those of scalar relativistic zeroth order regular approximation time-dependent density functional theory calculations carried out on isolated molecules. Both experimental and theoretical results concur to stress the electronic inertness of pristine porphyrin macrocycle based 1s(C)→π* and 1s(N)→π* transitions whose excitation energies are substantially unaffected upon fluorination. The obtained results complement those published by the same group about the occupied states of both molecules, thus providing the missing tile to get a thorough description of the halide decoration effects on the electronic structure of the tetrakis(phenyl)-porphyrin.

Harnessing the liquid-phase exfoliation of graphene using aliphatic compounds: a supramolecular approach.

The technological exploitation of the extraordinary properties of graphene relies on the ability to achieve full control over the production of a high-quality material and its processing by up-scalable approaches in order to fabricate large-area films with single-layer or a few atomic-layer thickness, which might be integrated in working devices. A simple method is reported for producing homogenous dispersions of unfunctionalized and non-oxidized graphene nanosheets in N-methyl-2-pyrrolidone (NMP) by using simple molecular modules, which act as dispersion-stabilizing compounds during the liquid-phase exfoliation (LPE) process, leading to an increase in the concentration of graphene in dispersions. The LPE-processed graphene dispersion was shown to be a conductive ink.

Chemical vapor deposition of N-doped graphene and carbon films: the role of precursors and gas phase.

Thermally induced chemical vapor deposition (CVD) was used to study the formation of nitrogen-doped graphene and carbon films on copper from aliphatic nitrogen-containing precursors consisting of C1- and C2-units and (hetero)aromatic nitrogen-containing ring systems. The structure and quality of the resulting films were correlated to the influence of the functional groups of the precursor molecules and gas phase composition. They were analyzed with SEM, TEM, EDX, XPS, and Raman spectroscopy.

Synergic Exfoliation of Graphene with Organic Molecules and Inorganic Ions for the Electrochemical Production of Flexible Electrodes.

A facile and efficient method based on electrochemistry for the production of graphene-based materials for electronics is demonstrated. Uncharged acetonitrile molecules are intercalated in graphite by electrochemical treatment, owing to the synergic action of perchlorate ions dissolved in acetonitrile. Then, acetonitrile molecules are decomposed with microwave irradiation, which causes gas production and rapid graphite exfoliation, with an increase in the graphite volume of up to 600 %.

Electronic properties of CuPc and H2Pc: an experimental and theoretical study.

Phthalocyanine (H2Pc) and its open-shell copper complex (CuPc) deposited on amorphous gold films have been studied by combining the outcomes of several synchrotron based spectroscopic tools (X-ray photoelectron spectroscopy, UV photoelectron spectroscopy and near-edge X-ray absorption fine structure, NEXAFS, spectroscopy) with those of density functional theory (DFT) calculations. The assignment of experimental evidence has been guided by the results of DFT numerical experiments carried out on isolated molecules. With specific reference to CuPc NEXAFS data collected at the N K-edge, they have been assigned by using the open-shell time-dependent DFT (TDDFT) in the framework of the zeroth order regular approximation (ZORA) scalar relativistic approach.

Epitaxy of nanocrystalline silicon carbide on Si(111) at room temperature.

Silicon carbide (SiC) has unique chemical, physical, and mechanical properties. A factor strongly limiting SiC-based technologies is the high-temperature synthesis. In this work, we provide unprecedented experimental and theoretical evidence of 3C-SiC epitaxy on silicon at room temperature by using a buckminsterfullerene (C(60)) supersonic beam.

Excitonic recombination in superstoichiometric nanocrystalline TiO2 grown by cluster precursors at room temperature.

Unprecedented room temperature excitonic emissions are achieved from TiO(2) nanocrystals synthesized at 300 K by supersonic cluster beams. Transmission electron microscopy studies show the crystalline nature of the nanoparticles (NPs) with a diameter ranging from 5 to 30 nm. All the samples show mixed rutile and anatase phases as confirmed by Raman spectroscopy.