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Nanoporous metals are a class of nanostructured materials finding extensive applications in multiple fields thanks to their unique properties attributed to their high surface area and interconnected nanoscale ligaments. They can be prepared following different strategies, but the deposition of an arbitrary pure porous metal is still challenging. Recently, a dry synthesis of nanoporous films based on the plasma treatment of metal thin layers deposited by physical vapour deposition has been demonstrated, as a general route to form pure nanoporous films from a large set of metals. An interesting aspect related to this approach is the possibility to apply the same methodology to deposit the porous films as a multilayer. In this way, it is possible to explore the properties of different porous metals in close contact. As demonstrated in this paper, interesting plasmonic properties emerge in a nanoporous Au–Ag bi-layer. The versatility of the method coupled with the possibility to include many different metals, provides an opportunity to tailor their optical resonances and to exploit the chemical and mechanical properties of components, which is of great interest to applications ranging from sensing, to photochemistry and photocatalysis.

An experimental and theoretical study of the effect of excimer laser annealing (ELA) on B redistribution and electrical activation in Ge is reported. We performed detailed structural, chemical, and electrical characterizations of Ge samples implanted with B (20 keV, 1 × 1015, or 1 × 1016 B/cm2) and processed by ELA (λ = 308 nm) with multiple pulses (1, 3, or 10). We also developed a diffusion model, in order to simulate the B redistribution induced by the ELA process. We found an anomalous impurity redistribution in the molten phase, which causes a dopant incorporation during the melt-growth at the maximum melt depth. The investigated samples showed a partial electrical activation of the B dopant. The inactivation of B in the samples implanted with 1 × 1015 B/cm2 was correlated to an oxygen contamination, while the poor electrical activation of B in the samples implanted with 1 × 1016 B/cm2 was related to the precipitation of the dopant, in good agreement with the experimental and theoretical results. [ABSTRACT FROM AUTHOR]

Nickel enhanced amorphous Si crystallization and silicidation on polyimide were studied during multipulse excimer laser annealing (ELA) from submelting to melting conditions. A ∼8 nm thick Ni film was deposited on a 100 nm thick α-Si layer at ∼70 °C in order to promote partial nickel diffusion into silicon. In the submelting regime, Ni atoms distributed during deposition in α-Si and the thermal gradient due to the presence of the plastic substrate were crucial to induce low fluence (≥0.08 J/cm2) Si crystallization to a depth which is strictly related to the starting Ni profile. Αmorphous-Si crystallization is not expected on pure Si at those low fluences. Additional pulses at higher fluences do not modify the double poly-Si/α-Si structure until melting conditions are reached. At a threshold of ∼0.2 J/cm2, melting was induced simultaneously in the polycrystalline layer as well as in the residual α-Si due to a thermal gradient of ∼200 °C. Further increasing the laser fluence causes the poly-Si layer to be progressively melted to a depth which is proportional to the energy density used. As a consequence of the complete Si melting, columnar poly-Si grains are formed above 0.3 J/cm2. For all fluences, a continuous NiSi2 layer is formed at the surface which fills the large Si grain boundaries, with the beneficial effect of flattening the poly-Si surface. The results would open the perspective of integrating Ni-silicide layers as metallic contacts on Si during α-Si-crystallization by ELA on plastic substrate. [ABSTRACT FROM AUTHOR]

The threshold voltage (VT) variations induced by the drain bias (Vds) are investigated in polycrystalline silicon thin film transistors (TFTs), with channel length ranging from 20 to 0.4 μm, by combining experimental measurements and two-dimensional (2D) numerical simulations. A careful analysis of the electrical characteristics in both subthreshold and off regime is performed, by taking in account also the effects of the leakage current field enhanced mechanisms on the overall generation-recombination rate. We show that the main causes of VT variations are the drain induced barrier lowering (DIBL) and floating body effects (FBEs), induced by impact ionization. The relative influence of FBEs and DIBL is analyzed by performing numerical simulations with or without including the impact ionization model. A detailed analysis of the 2D Poisson equation has allowed to identify and evaluate the contributions of DIBL and FBEs to the threshold voltage variation when both are present. It is found that, in short channel TFTs at high drain bias, the VT variations can’t be attributed to DIBL effect alone and there is a noticeable contribution of the FBEs to the threshold voltage reduction. From the numerical simulations, the influence of FBEs and DIBL on the electrostatic barrier at source junction and its reduction for increasing Vds is analyzed for long and short channel TFTs. [ABSTRACT FROM AUTHOR]

The integration of excimer laser annealing (ELA) into the power MOS device technology has been studied and evaluated. The integration issues include patterning effect, extreme nonequilibrium kinetics of dopant and defects, material modification due to the melting-regrowth phenomena (in the melting regime), and residual implant damage. We demonstrated that ELA can be applied as a reliable, effective, and advantageous process in the context of semiconductor device fabrication. In particular, power MOS field-effect transistors were successfully fabricated with superior electrical characteristics than those fabricated according to the standard process. Optimization of the process was achieved through extensive characterization analyses, while an intense research effort was dedicated to the development of a technology computer-aided design tool for the simulation of the laser annealing process in Si-based devices. The electrical characterization of the transistor fabricated by ELA is presented, showing a device yield of 90% on wafer. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we studied the effects of different thermal annealing on the electrical characteristics of non-self-aligned low-temperature p-channel polycrystalline silicon (polysilicon) thin film transistors. Different thermal treatments were performed after Al-gate formation at different temperature (200°C, 250°C, 350°C and 450°C) and annealing times. We found that optimal conditions were obtained at 350°C, with transfer characteristics showing a subthreshold slope of 0.5V/dec, field effect mobility >100cm2/Vs and threshold voltage around −3.5V. Hot carrier induced degradation was also analyzed performing bias-stress measurements on devices annealed at 350°C and at different bias stress conditions. The experimental data show that a maximum transconductance degradation is obtained for V g(stress)− V t =−4V while bias-stress at V g = V t and ∣V g(stress)∣≫∣V ds(stress)∣ did not produce appreciable changes in both transfer and output characteristics. [Copyright &y& Elsevier]

Different drain field architectures have been recently investigated to reduce field-enhanced effects in conventional self-aligned polysilicon thin-film transistor (TFT) architecture, induced by the intense electric fields at the drain junction. Among these, gate overlapped lightly doped drain (GOLDD) architecture has been shown to be effective in reducing the drain field in both on and off states of the TFT, without introducing appreciable series resistance effects. In this paper, we investigate the electrical characteristics, both in the on- and in the off-regime, of GOLDD polysilicon TFTs, made with different LDD doses, by combining experimental data with two-dimensional (2-D) numerical analysis. We also demonstrate that both the on-state and off-state features of the GOLDD structure can be readily understood in terms of a simple, new model, based upon two TFTs series. This is consistent both with the experimental data and the results of full 2-D simulations. This paper not only clarifies the dependence of kink effect, leakage current, and series resistance upon the LDD-doping, but also provides the guidelines to optimize physical parameters of GOLDD TFTs. [ABSTRACT FROM AUTHOR]