SF6 scattering from graphite surfaces: comparison of effects induced by thermal and laser controlled vibrational excitation.

We report scattering experiments of multiphoton vibrationally excited SF6 molecules from graphite surfaces demonstrating ro-vibrational excitation in the collision. The beam scattering experiments were carried out at different initial kinematic conditions and as a function of the surface temperature. The energy transfer depends both on the initial state of the molecule and on the momentum transferred as well as on the temperature of the surface. The role of surface atomic corrugation is evidenced

Polysaccarides-based gels and solid-state electronic devices with memresistive properties: Synergy between polyaniline electrochemistry and biology

A new architecture of organic memristive device is proposed with a double-layered polyelectrolyte, one of which is a biological system that alone drives the memristive behavior. In the device the Physarum polycephalum was used as living organism, the polyaniline as conducting polymer for the source-drain channel. The key choice for the device functioning was the interposition of a biocompatible solid layer between polyaniline and living organism, that must result both electrochemically inert and able to preserve a good electrical conductivity of the polyaniline, notwithstanding the alkaline pH environment required for the surviving of living being, by avoiding strong acids. Pectin with a high degree of methylation and chitosan were tested as interlayer, but only the first one satisfied the essential requirements. It was demonstrated that only when the living organism was integrated in the device, the current-voltage characteristics showed the hysteretic rectifying trends typical of the memristive devices, which however disappeared if the Physarum polycephalum switched to its sclerotic state. The mould resulted to survive a series of at least three cycles of voltage-current measurements carried out in sequence

Raman Identification of Polymorphs in Pentacene Films

We use Raman spectroscopy to characterize thin films of pentacene grown on Si/SiO x by Supersonic Molecular Beam Deposition (SuMBD). We find that films up to a thickness of about 781 A (∼ 52 monolayers) all belong to the so-called thin-film (TF) phase. The appearance with strong intensity of some lattice phonons suggests that the films are characterized by good intra-layer order. A comparison of the Raman spectra in the lattice and CH bending spectral regions of the TF polymorph with the corresponding ones of the high-temperature (HT) and low-temperature (LT) bulk pentacene polymorphs provides a quick and nondestructive method to identify the different phases

Hybrid nanostructures synthesized by supersonic molecular and cluster beams: The perspective of sensing devices exploiting their novel functional properties

A variety of approaches are aimed at developing functional nanocomposite hybrids with the basic idea of engineering the interfaces and interactions of the organic and inorganic counterparts at the nanoscale. The great versatility of such materials opens a wide range of applications including optoelectronics, gas sensing, biofunctionality, etc. We introduce a novel approach to the synthesis and growth of nanostructured organic-inorganic hybrids based on the co-deposition from Supersonic Molecular Beams seeded by molecules and clusters (SuMBE). We independently showed that SuMBE gives unprecedented control on reactivity and structure of: a) organic π-conjugated molecules (Pentacene, Porphyrines and to control the growth of hybrid organic-inorganic thin films; b) the synthesis of nanocrystalline films of oxides TiO2 (without any thermal process), c)the ability to activate chemical processes cinematically by tuning the kinetic energy of the precursors in the beam. The newly developed system allows the simultaneous deposition of metal oxides and organic molecules. In this new concept and experimental set up three supersonic beams can be used at the same time, together with a conventional Knudsen cell. The surface and interface electronic properties (UPS, XPS) show the successful ability to synthesize stable hybrid nanostructures such as nanocrystalline TiO2 decorated with organic pi-conjugated molecules (phtalocianines) and organolantanide structures formed by organic macrocycle (porphyrin) and erbium. The nanohybrids are formed by reactions activated by both the kinetic energy of the molecules and the strong reactivity of the inorganic clusters. Their novel functional properties have been demonstrated by gas sensing devices showing an enhanced specific response to, i.e. NOx, of 104 times due to the electron transfer occurring between the inorganic nanostructure and the molecule. The perspective is a new class of nano-hybrids with controlled novel functional properties for applications in sensing and opto-electronic devices

Controlling molecules\u27 momentum with SuMBD: the early stages of Pentacene growth on SiOx/Si

Organic semiconductors are suitable candidates for applications in fields ranging from photonics[1] to devices and sensors realization[2]. Good electrical properties, needed for these applications, can be achieved through molecular assembly in a crystalline structure. On the other hand, the feeble nature of the van der Waals forces between the molecules make this goal not easy to reach in organic thin films and the growth process often gives rise to different polymorphs and molecular orientations that strongly limit the final performances. Such limits need to be overcome by a higher control during the growth process. For this reason, the development of methods that permit to role the molecular assembly through the formation of a crystalline structure is of great interest. Between the vacuum deposition techniques, that up to now give the best results in term of order and purity of the materials, supersonic molecular beam deposition (SuMBD) has shown to improve the control on the growth, giving rise to better morphologies and enhanced electrical properties of the films[3,4]. Using SuMBD we can easily tune the kinetic energy, momentum and internal energy of the impinging molecules[5] influencing the molecules assembly, the island formation and coalescence[6]. The precursor state of the molecule is also important for the activation of new pathways for the adsorption of the molecules on the surface. The possibility to control the different energetic parameters of the impinging molecules and understand how they can influence the molecular assembling is of great importance for the realization of high performances devices. We report a systematic atomic force microscopy study of Pentacene sub-monolayer morphologies on SiOx/Si (60? contact angle), resulting from depositions at room temperature, in different growth conditions. During these early stages of growth, we found that the kinetic energy and the momentum of the impinging molecules play a key role in determining the monolayer morphology. In particular, we investigate the effects induced by changing the parallel and perpendicular momentum of the molecules arriving on the surface. Variations in the energy relaxation mechanisms involving the two component of the momentum activate different adsorption processes leading to modified island fractal dimension, island density and sticking coefficient. The parallel momentum favours a longer mean free path of the molecules adsorbed on the surface giving the possibility for a better assembly and surface energy minimization. Instead, the perpendicular momentum can be fundamental for the activation of deeper adsorption sites on the surface. Our measures show a progressive lowering of the island density when increasing the component of the molecules\u27 momentum parallel to the surface (k//) with the formation of more compact (less fractal) islands, better for the realization of ordered films (Figure1). Large single crystal domains are formed, which is a key aspect for increasing the devices performances

Transistor tridimensionale del tipo Organic ElectroChemical Transistor (OECT) e relativo metodo di fabbricazione.

La presente invenzione riguarda un metodo di fabbricazione di un transistor polimerico 3D

Vacuum ablation of CH3NH3SnCl3 Hybrid Perovskite: a tool for the sensitization of Metal Oxide Nanostructures

Metal oxide nanostructures (NS) are attracting great interest due to the large variety of physical properties they present. Control of size, shape, surface, and assembly properties of nanoscale oxides are prerequisites to their implementation in technological devices as well as to the development of nanostructures modelled and designed to match the physical requirements of their applications. The achievement of "purpose-built" nanomaterials has been often pursued by modifying the surface of inorganic nanostructures by organic molecules (organic sensitization), so that improved or even new functional properties have been obtained. To the best of our knowledge the sensitization of metal oxide NS by organic-inorganic hybrid perovskites has not been studied, yet. Hybrid perovskites are self-assembling compounds whose properties can be tailored by varying both organic and inorganic components, so that the sensitization of metal oxide NS by these hybrids may give a path to tune the composite functionalities. Here we investigate the sensitization of ZnO tetrapods and SnO2 nanowires by the CH3NH3SnCl3 hybrid perovskite via photoluminescence (PL) measurements. Hybrids were thermally ablated in vacuum on NS substrates. We show that hybrid deposition induces a different sensitization effect on the two nanostructures studied. In fact, while it affects to a negligible extent the PL of ZnO-tetrapods, hybrid deposition strongly influences the PL spectrum of SnO2 nanowires that otherwise show the usual broad featureless PL peak centred at about 490 nm. The mechanisms which may lead to the observed results are discussed, also considering the role of the interface due to the interaction between the nanostructure matrix and deposited hybrid since the PL efficiency of the hybrid perovskite itself is low and could not justify the observed PL modifications

Sensitization of Metal Oxide Nanostructures by CH3NH3SnCl3 Hybrid Perovskite

Metal oxide nanostructures (NS) are attracting great interest due to the large variety of physical properties they present. Control of size, shape, surface, and assembly properties of nanoscale oxides are prerequisites to their implementation in technological devices as well as to the development of nanostructures modelled and designed to match the physical requirements of their applications. The achievement o

Growth and performance of polycrystalline -Sexi-thiophene thin films deposited by Supersonic Molecular Beam Deposition

Conjugated small molecules are very interesting both as a model to study the growth model of crystalline organic films and as a very good performance organic material. Vacuum deposition is the most suitable technique to obtain high purity and order films. Nevertheless, the high anisotropy of organics makes easy the formation of different polymorphs or/and orientations that strongly limit the quality of the films. The innovative supersonic molecular beam deposition (SuMBD) technique, developed at the IFN-Lab, allows a wider control on the growth. The kinetic energy (EK) of the impinging molecules is the key factor that affects the growth modifying the assembling processes of molecules and their surface mobility. We report on the alfa-sexithiophene sub-monolayer growth, investigating the influence of energetic state of the impinging molecules, surface energy and substrate temperature. Each growth parameter affects the morphology of the molecular film in terms of coverage and fractality of the sub-monolayer islands. Optimizing the different parameters, we obtain larger and smoother islands and low density of grain-boundaries. The best conditions, including high kinetic energy of the beam, give rise to organic thin film transistors (OFETs) with a field effect mobility value of 1.5.10-1 V∙cm-1∙s-1, twice higher than the best values in literature. This work was financially supported by Provincia Autonoma di Trento Project Nanosmart and the Fondazione CARITRO Project ODINO