Within the EC funded international project OPTHER (OPtically Driven TeraHertz AmplifiERs) a considerable
technological effort is being undertaken, in terms of technological development, THz device design and integration. The
ultimate goal is to develop a miniaturised THz amplifier based on vacuum-tube principles
The main target specifications of the OPTHER amplifier are the following:
- Operating frequency: in the band 0.3 to 2 THz
- Output power: > 10 mW ( 10 dBm )
- Gain: 10 to 20 dB.
The project is in the middle of its duration. Design and simulations have shown that these targets can be met with a
proper device configuration and careful optimization of the different parts of the amplifier. Two parallel schemes will be
employed for amplifier realisation: THz Drive Signal Amplifier and Optically Modulated Beam THz Amplifier.
The importance of nanocomposites materials such as carbon nanotubes-polymers composites for the efficient realization
of innovative solar cells based on organic as well hybrid organic-inorganic solar cells is more and more evident. We
present a study on the realization of dye sensitized solar cells (DSSC) and sublimation deposited solar cells, considering
the impact of using nanocomposite materials in the different sections composing the cells. We discuss the effect of using
poly-3,4-ethylene dioxythiophene/poly(styrene sulfonate) (PEDOT/PSS)-Carbon nanotube (CNT) blend as counterelectrode
in DSSC on the cell efficiency and fill factor, also considering DSSC structures where low cost, innovative
dyes are used. Nanocomposites can be used as solution processed or electropolimerized electrodes, where accurate
control of nanotube dispersion is obtained through specific chemical treatment of Carbon nanotubes solubility. The use
of Carbon based nanostructured material is also investigated in terms of their positive impact on the realization of
organic solar cells on flexible substrates.
We have performed studies on the correlation between mechanical deformations and electrical conductance on a new interesting hybrid material, a Single Wall Carbon Nanotubes (SWCNTs)/Poly(3,4-ethylenedioxythiophene) (PEDOT) composite. Two are the synthesis techniques utilized to prepare the composite material in form of few hundreds of nm thick films: a spin coating deposition starting from an aqueous dispersion of SWCNTs and PEDOT, and an electrochemical de*position starting from a dispersion of SWCNTs and EDOT monomer. The composite conductance changes induced by a modulated periodic elongation via a coherent technique have been monitored by measuring the voltage variations of a Wheatstone bridge connected with the films. The measurements were performed on SWCNTs/PEDOT composites layered on a rigid substrate. The piezoresistivity gauge factor (GF) of the various samples was evaluated by comparing their responses to mechanical deformations to those of a commercial strain gauge, sticked on a substrate of the same kind. We found no significant piezoresistive effect in the hybrid material films deposited by means of spin coating while the effect is remarkable for the composites prepared by means of the electrochemical technique. In this case the gauge factor is found to be up to 3-4 times higher than that of the commercial strain gauge.
We reported the design and realization of a carbon nanotube-based integrated multielectrode device. Patterned Si/SiO2/Nb/Nb2O5 multilayer was successfully realized by means of a few, common photolithographic processes with the minimum number of mask alignment steps. Such structure constitutes the patterned substrate of successive Hot Filament Chemical Vapour Deposition (HFCVD) process. Selective growth of highly oriented SWCNT arrays was obtained in the predefined locations while survival of the entire structure was achieved. Field emission measurements of such materials were carried out. Good and reproducible field emission behaviour has been observed in several realized structures.
Single Wall Carbon Nanotubes (SWCNTs) based nanotechnology appears to be promising for future nanoelectronics. The SWCNT may be either metallic or semiconducting and both metallic and semiconducting types of SWCNTs have been observed experimentally. This gives rise to intriguing possibilities to put together semiconductor-semiconductor and semiconductor-metal junctions for diodes and transistors. The potential for nanotubes in nanoelectronics devices, displays and nanosensors is enormous. However, in order to realize the potential of SWCNTs, it is critical to understand the properties of charge transport and to control phase purity, elicity and arrangement according to specific architectures. We have investigated the electrical properties of various SWCNTs samples whit different organization: bundles of SWCNTs, SWCNT fibres and different membranes and tablets obtained using SWCNTs purified and characterized.
Electrical characterizations were carried out by a 4155B Agilent Semiconductor Parameter Analyser. In order to give a mechanical stability to SWCNTs fibres and bundles we have used a nafion matrix coating, so an electrical characterization has been performed on samples with and without this layer. I-V measurements were performed in vacuum and in air using aluminium interdigitated coplanar-electrodes (width=20mm or 40mm) on glass substrates. The behaviour observed is generally supralinear with currents of the order of mA in vacuum and lower values in air with the exception of the tablet samples where the behaviour is ohmic, the currents are higher and similar values of current are detected in air and vacuum.