Luigi Mariucci

Bio: Luigi Mariucci is an academic researcher from National Research Council. The author has contributed to research in topics: Thin-film transistor & Polycrystalline silicon. The author has an hindex of 20, co-authored 151 publications receiving 1376 citations.

Carbon nanotube semitransparent electrodes for amorphous silicon based photovoltaic devices

Abstract: Different amounts of single wall carbon nanotubes (SWCNTs) have been sprayed on amorphous silicon substrates to form Schottky barrier solar cells. The measured external quantum efficiency showed a spectral behavior depending on the SWCNT network optical transparency, presenting a maximum up to 35% at a wavelength of about 460 nm. Ultrathin network of SWCNTs acts as semitransparent electrode and forms Schottky barrier with amorphous silicon, enabling new generation low cost amorphous silicon based solar cells. Numerical simulations show a poor efficiency of SWCNT contacts in collecting holes suggesting that improvement in contact quality is needed to further improve solar cell efficiency.

Two-dimensional delineation of ultrashallow junctions obtained by ion implantation and excimer laser annealing

Abstract: Junctions shallower than 100 nm, obtained by ion implantation and excimer laser annealing, have been characterized in two dimensions by transmission electron microscopy (TEM) on chemically treated samples. The chemical treatment selectively removes silicon as a function of the B concentration, making thinner the regions where B is present in the cross section of the sample, with respect to the n-type substrate. Both secondary ion mass spectrometry and spreading resistance profiling measurements have been performed, in order to quantify the contour line obtained by TEM in terms of B concentration. The results achieved by the two-dimensional technique show interesting features, related to the particular redistribution of B occurring when silicon is melted by excimer laser annealing irradiation. In particular, a rectangular shape of the doped region obtained by laser annealing could be evidenced, caused by the fast diffusion in the melted material, completely different from the typical half-moon-shaped, ther...

Bias‐stress‐induced stretched‐exponential time dependence of charge injection and trapping in amorphous thin‐film transistors

Abstract: The threshold voltage instabilities in nitride/oxide dual gate dielectric hydrogenated amorphous silicon (a‐Si:H) thin‐film transistors are investigated as a function of stress time, stress temperature, and stress bias. The obtained results are explained with a multiple trapping model rather than weak bond breaking model. In our model, the injected carriers from the a‐Si:H channel first thermalize in a broad distribution of localized band‐tail states located at the a‐Si:H/aSiNx:H interface and in the a‐SiNx:H transitional layer close to the interface, then move to deeper energies in amorphous silicon nitride at longer stress times, larger stress electric fields, or higher stress temperatures. The obtained bias‐stress‐temperature induced threshold voltage shifts are accurately modeled with a stretched‐exponential stress time dependence where the stretched‐exponent β cannot be related to the β=TST/T0 but rather to β≂TST/T0*−β0 for TST≤80 °C; for TST≥80 °C, the β is stress temperature independent. We have al...

Graphene Schottky diodes: an experimental review of the rectifying graphene/semiconductor heterojunction

Abstract: In the past decade graphene has been one of the most studied material for several unique and excellent properties. Due to its two dimensional nature, physical and chemical properties and ease of manipulation, graphene offers the possibility of integration with the exiting semiconductor technology for next-generation electronic and sensing devices. In this context, the understanding of the graphene/semiconductor interface is of great importance since it can constitute a versatile standalone device as well as the building-block of more advanced electronic systems. Since graphene was brought to the attention of the scientific community in 2004, the device research has been focused on the more complex graphene transistors, while the graphene/semiconductor junction, despite its importance, has started to be the subject of systematic investigation only recently. As a result, a thorough understanding of the physics and the potentialities of this device is still missing. The studies of the past few years have demonstrated that graphene can form junctions with 3D or 2D semiconducting materials which have rectifying characteristics and behave as excellent Schottky diodes. The main novelty of these devices is the tunable Schottky barrier height, a feature which makes the graphene/semiconductor junction a great platform for the study of interface transport mechanisms as well as for applications in photo-detection, high-speed communications, solar cells, chemical and biological sensing, etc. In this paper, we review the state-of-the art of the research on graphene/semiconductor junctions, the attempts towards a modeling and the most promising applications.

Calculating the trap density of states in organic field-effect transistors from experiment: A comparison of different methods

Abstract: The spectral density of localized states in the band gap of pentacene (trap DOS) was determined with a pentacene-based thin-film transistor from measurements of the temperature dependence and gate-voltage dependence of the contact-corrected field-effect conductivity. Several analytical methods to calculate the trap DOS from the measured data were used to clarify, if the different methods lead to comparable results. We also used computer simulations to further test the results from the analytical methods. Most methods predict a trap DOS close to the valence-band edge that can be very well approximated by a single exponential function with a slope in the range of 50--60 meV and a trap density at the valence-band edge of $\ensuremath{\approx}2\ifmmode\times\else\texttimes\fi{}{10}^{21}\text{ }{\text{eV}}^{\ensuremath{-}1}\text{ }{\text{cm}}^{\ensuremath{-}3}$. Interestingly, the trap DOS is always slightly steeper than exponential. An important finding is that the choice of the method to calculate the trap DOS from the measured data can have a considerable effect on the final result. We identify two specific simplifying assumptions that lead to significant errors in the trap DOS. The temperature dependence of the band mobility should generally not be neglected. Moreover, the assumption of a constant effective accumulation-layer thickness leads to a significant underestimation of the slope of the trap DOS.

液晶物質の有機トランジスタへの展開 ; Liquid Crystals for Organic Thin Film Transistors

Abstract: Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V−1 s−1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.