15 research outputs found
Optical Conductivity of Two-Dimensional Silicon: Evidence of Dirac Electrodynamics
No full textThe exotic electrodynamics properties of graphene come from the linearly dispersive electronic bands that host massless Dirac electrons. A similar behavior was predicted to manifest in freestanding silicene, the silicon counterpart of graphene, thereby envisaging a new route for silicon photonics. However, the access to silicene exploitation in photonics was hindered so far by the use of optically inappropriate substrates in experimentally realized silicene. Here we report on the optical conductivity of silicon nanosheets epitaxially grown on optically transparent Al2O3(0001) from a thickness of a few tens of nanometers down to the extreme two-dimensional (2D) limit. When a 2D regime is approached, a Dirac-like electrodynamics can be deduced from the observation of a low-energy optical conductivity feature owing to a silicene-based interfacing to the substrate
Highly sensitive detection of inorganic contamination
No full textAs the detection of inorganic contaminants is of steadily increasing importance for the improvement
of yields in microelectronic applications, the aim of one of the joint research activity within the
European Integrated Activity of Excellence and Networking for Nano- and Micro-Electronics
Analysis (ANNA, site: www.ANNA-i3.org) is the development and assessment of new methodologies
and metrologies for the detection of low concentration inorganic contaminants in silicon and in
novel materials. A main objective consist in the benchmarking of various analytical techniques
available in the laboratories of the participating ANNA partners, including the improvement of the
respective detection limits as well as the quantitation reliablity of selected analytical techniques
such as total-reflection x-ray fluorescence (TXRF) analysi
Terahertz and infrared plasmon polaritons in PtTe2 type‐II Dirac topological semimetal
No full textSurface plasmon polaritons (SPPs) are electromagnetic excitations existing at the interface between a metal and a dielectric. SPPs provide a promising path in nanophotonic devices for light manipulation at the micro and nanoscale with applications in optoelectronics, biomedicine, and energy harvesting. Recently, SPPs are extended to unconventional materials like graphene, transparent oxides, superconductors, and topological systems characterized by linearly dispersive electronic bands. In this respect, 3D Dirac and Weyl semimetals offer a promising frontier for infrared (IR) and terahertz (THz) radiation tuning by topologically-protected SPPs. In this work, the THz-IR optical response of platinum ditelluride (PtTe2) type-II Dirac topological semimetal films grown on Si substrates is investigated. SPPs generated on microscale ribbon arrays of PtTe2 are detected in the far-field limit, finding an excellent agreement among measurements, theoretical models, and electromagnetic simulation data. The far-field measurements are further supported by near-field IR data which indicate a strong electric field enhancement due to the SPP excitation near the ribbon edges. The present findings indicate that the PtTe2 ribbon array appears an ideal active layout for geometrically tunable SPPs thus inspiring a new fashion of optically tunable materials in the technologically demanding THz and IR spectrum
Plasma-Assisted Atomic Layer Deposition of IrO2 for Neuroelectronics
No full textIn vitro and in vivo stimulation and recording of neuron action potential is currently achieved with microelectrode arrays, either in planar or 3D geometries, adopting different materials and strategies. IrO2 is a conductive oxide known for its excellent biocompatibility, good adhesion on different substrates, and charge injection capabilities higher than noble metals. Atomic layer deposition (ALD) allows excellent conformal growth, which can be exploited on 3D nanoelectrode arrays. In this work, we disclose the growth of nanocrystalline rutile IrO2 at T = 150 °C adopting a new plasma-assisted ALD (PA-ALD) process. The morphological, structural, physical, chemical, and electrochemical properties of the IrO2 thin films are reported. To the best of our knowledge, the electrochemical characterization of the electrode/electrolyte interface in terms of charge injection capacity, charge storage capacity, and double-layer capacitance for IrO2 grown by PA-ALD was not reported yet. IrO2 grown on PtSi reveals a double-layer capacitance (Cdl) above 300 µF∙cm−2, and a charge injection capacity of 0.22 ± 0.01 mC∙cm−2 for an electrode of 1.0 cm2, confirming IrO2 grown by PA-ALD as an excellent material for neuroelectronic applications
Experimental electron band alignment of 1T’and 2H MoTe2/SiO2 interface using internal photoemission spectroscopy
No full textUnlike other two-dimensional (2D) transition metal dichalcogenides, molybdenum ditelluride (MoTe2) displays a stable biphasic character in artificially synthesizable 2H and 1T’ state. While these phases are inherently distinguished in their electronic band character (semiconducting and metallic, respectively), it is not clear how they electronically interface with technology relevant substrate where to engineer an electronic device layout. In this study, we experimentally determine the electron band alignment at interfaces between SiO2 and 1T'/2H of MoTe2 few-layers ultrathin films grown by chemical vapor deposition. We use internal photoemission spectroscopy to determine the energy barrier height between the 1T’/2H-MoTe2 Fermi level and the oxide conduction band (CB) bottom. This observation indicates the band gap opening in 2H-MoTe2 and provides an estimate of the barrier height for holes at the polytypic 1T’/2H-MoTe2 interface. In particular, by comparing the Fermi level energy in single-phase 1 T'-MoTe2 with the VB energy in 2H-MoTe2, we reveal a ≈ 0.4 eV difference, suggesting that the low Schottky barrier observed at the 1T'/2H interface results from Fermi level pinning, which is independent of interface defects and unaffected by the VdW gap. Our findings can be exploited for optimizing charge transport and device performance, facilitating the development of next-generation electronic and optoelectronic devices that harness the unique properties of both phases in MoTe2
Extreme Bendability of Atomically Thin MoS2 Grown by Chemical Vapor Deposition Assisted by Perylene-Based Promoter
No full textShaping two-dimensional (2D) materials in arbitrarily complex geometries is a key to designing their unique physical properties in a controlled fashion. This is an elegant solution, taking benefit from the extreme flexibility of the 2D layers but requiring the ability to force their spatial arrangement from flat to curved geometries in a delicate balance among free-energy contributions from strain, slip-and-shear mechanisms, and adhesion to the substrate. Here, we report on a chemical vapor deposition approach, which takes advantage of the surfactant effects of organic molecules, namely the tetrapotassium salt of perylene-3,4,9,10-tetracarboxylic acid (PTAS), to conformally grow atomically thin layers of molybdenum disulphide (MoS2) on arbitrarily nanopatterned substrates. Using atomically resolved transmission electron microscope images and density functional theory calculations, we show that the most energetically favorable condition for the MoS2 layers consists of its adaptation to the local curvature of the patterned substrate through a shear-and-slip mechanism rather than strain accumulation. This conclusion also reveals that the perylene-based molecules have a role in promoting the adhesion of the layers onto the substrate, no matter the local-scale geometry.sponsorship: This research was partially funded by the Italian Government, Ministero dell'Universita e della Ricerca (MUR), under the project PRIN "aSTAR", grant number 2017RKWTMY, and from the European Union's Horizon 2020 research and innovation programme under the project "CHALLENGES" grant agreement No 861857. (Italian Government, Ministero dell'Universita e della Ricerca (MUR), under the project PRIN "aSTAR"|2017RKWTMY, European Union|861857, H2020 - Industrial Leadership|861857)status: Published onlin
Defect generation by argon implantation: microscopy characterization and electrical properties
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