C. Ciceroni

A multifinger microtriode with carbon nanotubes field emission cathode operating at GHz frequency.

Vacuum microelectronic devices play an important role in the field of micro- and nano-electronics and they have been strongly developed in recent decades. Vacuum microelectronics are mainly based on the field emission effect and the employment of electrons in vacuum in a device with dimensions from tenths to hundredths of a micrometer. In this work, we present the development of a carbon-nanotube-based multifinger microtriode operating from 0.5 to 2 GHz. In this frequency range, a minimum RF signal gain of 5 dB is achieved. Such a device represents an optimized alternative to the standard Spindt-type microtriode. The advantage of such multifinger architecture consists in the possibility to reduce the cathode-grid capacitance by reducing the overlap between the two electrodes using a parallel patterning. This approach allows increasing the cut-off frequency of the devices with respect to the Spindt-type triode. We realized a prototype of the multifinger triode and the field emission properties have been characterized. The frequency behavior has been measured, demonstrating the possibility to amplify RF signal.

Electrostatic Beam Focusing of Carbon Nanotubes Electron Source

In this paper, we present the realization and characterization of a carbon nanotubes (CNTs) electron gun. The gun consists of a CNT cathode with an external extracting grid, that reached a maximum current density of 0, 6 A/cm2, assembled with an electrostatic focusing grid. The realized compact electron gun achieved a maximum output current density of 0, 11 A/cm2. This represents one of the first examples of a CNTs electron gun with an electrostatic focusing grid with high-output current density. The assembly process and the relative issues are described in detail together with the field emission characteristics of the cathodes and of the electron gun.

Graphene Oxide for DSSC, OPV and Perovskite Stability

In the broad context of photovoltaic technologies, first-generation silicon-based solar cells undoubtedly dominate the market, owing to the combination of their high power conversion efficiency (PCE) with consolidated production processes. However, their costs and consumption of base materials are still quite high. As an alternative, the second-generation photovoltaic based on thin-films technology is characterized by greatly reduced production costs, despite the toxicity of some materials (as cadmium remains an open issue to be addressed for a possible massive use). In this context, the new-generation photovoltaic aims at achieving PCEs comparable with those of existing technologies, but with low cost per meter square, tunability in color and shape, transparency, flexibility, and roll-to-roll production. In particular, organic and hybrid photovoltaic technologies are considered an “emerging PV” class, and their increasing efficiency trend during the last two decades underlines efforts to make the new solar cells competitive with other accomplished and well-known inorganic technologies. Graphene and graphene-related materials have been extensively investigated in this field of research as they can be used in several parts of the device (such as, for example, a substitute for the semitransparent electrode, in the transporting layers, or as a counter electrode). In this chapter, we will focus particularly on the use of graphene oxide (GO) as a material for the realization of dye-sensitized, organic, and perovskite solar cells. Several architectures will be considered for the three types of solar cells, showing in each of them the fundamental role of GO for increasing both their efficiency and stability.

Nanopatterning of P3HT:PCBM for organic solar cell realization

Organic solar cells (OSC) are becoming an important alternative to standard inorganic ones since they have many intrinsic advantage, such as light weight, flexibility, and low fabrication costs. The use of plasmonic backcontact grating with nanometric pitch can enhance the absorption in the active layer of organic solar cell and consequently increase the power conversion efficiency. We realized P3HT:PCBM films with a nanopatterned architecture. With transmission measurements and with the aid of simulations we demonstrate the increase of the absorption in the P3HT:PCBM film. This approach can be used to increase the efficiency in OSC. 20 working solar cells with flat and structured architecture were realized and the average efficiency of structured cells was 13.7 % higher than that of flat cells.

Field emission from tungsten oxide nanowires W5O14 film

Large area film of W5O14 nanowires was realized with synthesized by iodine transport method. The field emission characteristics of The W5O14 nanowires were then investigated. The measured samples showed up to 50 μA of emitting current at very low electric field of about 3 V/μm. Furthermore very good stability was achieved, the sample was allowed to emit for more than 70 hours without showing significant decays of the emitting current and without high current oscillations. This characteristics make these nanowires very promising for the realization of field emitting cathodes.

Anodized aluminum on transparent substrates as scaffold for perovskite growth

A proper growth of Iodine based perovskite nanocrystals is crucial for photovoltaic applications and this process is highly affected from the scaffold used for the crystallization. In this work, ordered nanoporous alumina, realized by controlled anodizing of two different thickness layer of Al, deposited on glass and Indium Tin Oxide (ITO), was used as the scaffold layer for the growth of perovskite nanocrystals. We present CH3NH3PbI3 crystals successfully converted on such substrates, using three different dipping techniques. Scanning Electron Microscopy (SEM) characterization, optical microscope analysis and absorbance measurements of the as grown perovskite layers are reported.

Patterned carbon nanotubes semitransparent electrodes

We report preliminary tests on the realization of a semitransparent contact based on carbon nanotubes (CNTs) realized on glass substrate. Using a “double-zone” chemical vapor deposition technique (CVD) to synthesize CNTs directly on glass substrates, conductive and partially transparent contacts have been realized. Then, through a laser etching process it was obtained a partial patterning of the metal catalyst that allowed achieving a transparency of the contacts above 75% in the visible spectrum with sheet resistances comparable to graphene growth with similar process. The reported technique is an initial step towards the realization of CVD based CNTs transparent contacts.

Study of the critical issues in the assembly of cold cathodes in electron gun for vacuum tube

In this work we present the realization of compact electron sources realized with carbon nanotubes (CNTs) cathodes. The main scope of this study is the description of the critical in the integration of CNTs cathodes in electron guns.

Field emission triode in a multifinger configuration with carbon nanotubes emitters

In this work we present the development of a Carbon Nanotubes based multifinger microtriodes. Such device represents a viable and optimized alternative to the standard Spindt-type microtriode. The main improvement of the multifinger geometry consists on the possibility to reduce the cathode-grid capacitance by reducing the overlap between the two electrodes using a parallel patterning of the metallic lines. This approach allows doubling the cut-off frequency of the devices with respect to the Spindt-type triode. The prototype multifinger triode has been realized and field emission properties have been measured.

Carbon nanotubes electron source

In this work we present a carbon nanotubes electron source assembled with a low cost technique. We used a carbon nanotube cathode that reached the remarkable current density of 0,6 A/cm2. The cathode has been assembled with an external grid in a compact electron source that achieved a maximum output current density of 45 mA/cm2. This represents one the first examples of a CNTs electron source realized with a low cost assembly.