Pier Francesco Fazzini

A Simple Chemical Route toward Monodisperse Iron Carbide Nanoparticles Displaying Tunable Magnetic and Unprecedented Hyperthermia Properties

We report a tunable organometallic synthesis of monodisperse iron carbide and core/shell iron/iron carbide nanoparticles displaying a high magnetization and good air-stability. This process based on the decomposition of Fe(CO)(5) on Fe(0) seeds allows the control of the amount of carbon diffused and therefore the tuning of nanoparticles magnetic anisotropy. This results in unprecedented hyperthermia properties at moderate magnetic fields, in the range of medical treatments.

Complex Nano-objects Displaying Both Magnetic and Catalytic Properties: A Proof of Concept for Magnetically Induced Heterogeneous Catalysis

Addition of Co2(Co)9 and Ru3(CO)12 on preformed monodisperse iron(0) nanoparticles (Fe(0) NPs) at 150 °C under H2 leads to monodisperse core-shell Fe@FeCo NPs and to a thin discontinuous Ru(0) layer supported on the initial Fe(0) NPs. The new complex NPs were studied by state-of-the-art transmission electron microscopy techniques as well as X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. These particles display large heating powers (SAR) when placed in an alternating magnetic field. The combination of magnetic and surface catalytic properties of these novel objects were used to demonstrate a new concept: the possibility of performing Fischer-Tropsch syntheses by heating the catalytic nanoparticles with an external alternating magnetic field.

Room-Temperature Tunnel Magnetoresistance in Self-Assembled Chemically Synthesized Metallic Iron Nanoparticles

We report on room temperature magnetoresistance in networks of chemically synthesized metallic Fe nanoparticles surrounded by two types of organic barriers. Electrical properties, featuring Coulomb blockade, and magnetotransport measurements show that this magnetoresistance arises from spin-dependent tunnelling, so the organic ligands stabilizing the nanoparticles are efficient spin-conservative tunnel barrier. These results demonstrate the feasibility of an all-chemistry approach for room temperature spintronics.

Monitoring the coordination of amine ligands on silver nanoparticles using NMR and SERS.

Low size dispersity silver nanoparticles (ca. 6 nm) have been synthesized by the hydrogenolysis of silver amidinate in the presence of hexadecylamine. Combining NMR techniques with SERS and DFT modeling, it is possible to observe an original stabilization mechanism. Amidine moiety is strongly coordinated to the Ag(0) nanoparticles surface whereas HDA ligand is necessary to prevent agglomeration, although it is only weakly interacting with the surface.

Detailed investigation of Ge–Si interdiffusion in the full range of Si1−xGex(0≤x≤1) composition

Based on the recently developed MCs2+ secondary ion mass spectrometry methodology, the Ge–Si interdiffusion has been investigated, using Ge(:B) solid sources, for Ge concentrations between 0 and 100 at. %. A strong dependence of the interdiffusion with the Ge content of SiGe alloys, formed during annealing, has been shown. The Boltzmann–Matano method was used to extract the interdiffusivity values for all the temperatures studied (750, 800, 850, and 900 °C) in the full range of SiGe compositions. Two regimes of interdiffusion have been identified, both exhibiting an exponential increase in the interdiffusion coefficient as a function of the Ge concentration. The high Ge content regime (>65 at. %) is in good agreement with the values known in the “extreme” cases of Ge diffusion in Si (0 at. %), Ge self-diffusion, and Si diffusion in Ge (100 at. %), while in the low Ge content regime (<50 at. %), the presence and evolution of misfit dislocation can explain the important values of interdiffusivity found in t...

Experimental and theoretical results of dopant activation by a combination of spike and flash annealing

The diffusion length of the flash anneal is lowest for all different implant conditions. For the arsenic implant similar diffusion length is seen for all the processes that include a spike anneal due to the fact that the overall thermal budget is mainly determined by the spike anneal. Boron implants into crystalline as well as pre-amorphized silicon show similarly low sheet resistance independent of whether they are annealed with spike + flash, flash or flash + spike. For the arsenic implant by far the lowest sheet resistance is seen with a combination of spike + flash anneal. For the boron and arsenic implants the defect density after the flash anneal and the spike + flash anneal is below the weak beam dark field detection limit of the transmission electron microscope therefore suggesting low leakage due to defects present. From the simulations of the arsenic and the boron concentration profiles it can be learned that the spike profile determines the position of the chemical profile and the activation is increased by the subsequent diffusion-less flash anneal. Thus junction depth can be easily adjusted by the spike anneal condition in a spike + flash scheme, while still maintaining a high degree of dopant activation. This offers great flexibility to next generation junction formation. Although in this study the spike and flash annealing were performed in different tools, a combination of spike + flash can be easily run in the Mattson fRTPtrade system. The combination of spike + flash anneals also has been shown to improve the transistor drive current significantly without undesirable shifts in the other transistor characteristics.

Advanced Activation and Deactivation of Arsenic-Implanted Ultra-Shallow Junctions using Flash and Spike + Flash Annealing

Millisecond annealing as an equipment technology provides ultra-sharp temperature peaks which favours dopant activation but nearly eliminates dopant diffusion to form extremely shallow highly electrically-activated junctions. On arsenic beamline implanted wafers the formation of ultra-shallow junctions at peak temperatures ranging from 1275degC to 1325degC was investigated. The thermal stability of these junctions was evaluated by subsequent thermal anneals ranging from 250 degC to 1050 degC with times ranging from seconds up to several hundred seconds. From these data the deactivation/reactivation mechanism for subsequent annealing can be quantified. Furthermore, the combination of spike and flash annealing is investigated to achieve a desired level of dopant diffusion and activation. For arsenic by far the lowest sheet resistance number is achieved by this annealing strategy. Finally, the arsenic profiles are compared to predictive simulation results which address the diffusion and activation at extrinsic concentrations.

Concerted Growth and Ordering of Cobalt Nanorod Arrays as Revealed by Tandem in Situ SAXS-XAS Studies

The molecular and ensemble dynamics for the growth of hierarchical supercrystals of cobalt nanorods have been studied by in situ tandem X-ray absorption spectroscopy-small-angle X-ray scattering (XAS-SAXS). The supercrystals were obtained by reducing a Co(II) precursor under H2 in the presence of a long-chain amine and a long-chain carboxylic acid. Complementary time-dependent ex situ TEM studies were also performed. The experimental data provide critical insights into the nanorod growth mechanism and unequivocal evidence for a concerted growth-organization process. Nanorod formation involves cobalt nucleation, a fast atom-by-atom anisotropic growth, and a slower oriented attachment process that continues well after cobalt reduction is complete. Smectic-like ordering of the nanorods appears very early in the process, as soon as nanoparticle elongation appears, and nanorod growth takes place inside organized superlattices, which can be regarded as mesocrystals.

Tuning Deposition of Magnetic Metallic Nanoparticles from Periodic Pattern to Thin Film Entrainment by Dip Coating Method

In this work, we report on the self-assembly of bimetallic CoFe carbide magnetic nanoparticles (MNPs) stabilized by a mixture of long chain surfactants. A dedicated setup, coupling dip coating and sputtering chamber, enables control of the self-assembly of MNPs from regular stripe to continuous thin films under inert atmosphere. The effects of experimental parameters, MNP concentration, withdrawal speed, amount, and nature of surfactants, as well as the surface state of the substrates are discussed. Magnetic measurements revealed that the assembled particles were not oxidized, confirming the high potentiality of our approach for the controlled deposition of highly sensitive MNPs.

Influence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions

Hole mobility degradation has been studied in high-dose boron-implanted ultrashallow junctions containing high concentrations of boron-interstitial clusters (BICs), combining an empirical method based on the self-consistent interpretation of secondary-ion-mass spectrometry (SIMS) and Hall measurements and liquid-nitrogen (LN2) to room temperature (RT) hole mobility measurements. It has been found that BICs act as independent scattering centers which have a strong impact on hole mobility in addition to the other scattering mechanisms such as lattice and impurities scattering. A mobility degradation coefficient α has been introduced, which gives information on the mobility degradation level in the analyzed junctions. In the case of very high concentrations of BICs (containing a boron density up to 8×1014 cm−2), measured hole mobilities were found to be ∼40% lower than corresponding theoretical values. BICs dissolution through multiple Flash anneals at high temperature (1300 °C) reduces the observe mobility ...