Epitaxial Growth of Crystalline CaF on Silicene.

Silicene is one of the most promising two-dimensional (2D) materials for the realization of next-generation electronic devices, owing to its high carrier mobility and band gap tunability. To fully control its electronic properties, an external electric field needs to be applied perpendicularly to the 2D lattice, thus requiring the deposition of an insulating layer that directly interfaces silicene, without perturbing its bidimensional nature. A promising material candidate is CaF, which is known to form a quasi van der Waals interface with 2D materials as well as to maintain its insulating properties even at ultrathin scales.

Optical Signatures of Dirac Electrodynamics for hBN-Passivated Silicene on Au(111).

The allotropic affinity for bulk silicon and unique electronic and optical properties make silicene a promising candidate for future high-performance devices compatible with mature complementary metal-oxide-semiconductor technology. However, silicene's outstanding properties are not preserved on its most prominent growth templates, due to strong substrate interactions and hybridization effects. In this letter, we report the optical properties of silicene epitaxially grown on Au(111).

Highly Biaxially Strained Silicene on Au(111).

Many of graphene's remarkable properties arise from its linear dispersion of the electronic states, forming a Dirac cone at the K points of the Brillouin zone. Silicene, the 2D allotrope of silicon, is also predicted to show a similar electronic band structure, with the addition of a tunable bandgap, induced by spin-orbit coupling. Because of these outstanding electronic properties, silicene is considered as a promising building block for next-generation electronic devices.

Silicene Passivation by Few-Layer Graphene.

The stabilization of silicene at ambient conditions is essential for its characterization, future processing, and device integration. Here, we demonstrate in situ encapsulation of silicene on Ag(111) by exfoliated few-layer graphene (FLG) flakes, allowing subsequent Raman analysis under ambient conditions. Raman spectroscopy measurements proved that FLG capping serves as an effective passivation, preventing degradation of silicene for up to 48 h.

Ultrascaled Germanium Nanowires for Highly Sensitive Photodetection at the Quantum Ballistic Limit.

We report an experimental study on quasi-one-dimensional Al-Ge-Al nanowire (NW) heterostructures featuring unmatched photoconductive gains exceeding 10 and responsivities as high as 10 A/μW in the visible wavelength regime. Our observations are attributed to the presence of GeO related hole-trapping states at the NW surface and can be described by a photogating effect in accordance with previous studies on low-dimensional nanostructures. Utilizing an ultrascaled photodetector device operating in the quantum ballistic transport regime at room temperature we demonstrate for the first time that individual current channels can be addressed directly by laser irradiation.

Direct writing of gold nanostructures with an electron beam: On the way to pure nanostructures by combining optimized deposition with oxygen-plasma treatment.

This work presents a highly effective approach for the chemical purification of directly written 2D and 3D gold nanostructures suitable for plasmonics, biomolecule immobilisation, and nanoelectronics. Gold nano- and microstructures can be fabricated by one-step direct-write lithography process using focused electron beam induced deposition (FEBID). Typically, as-deposited gold nanostructures suffer from a low Au content and unacceptably high carbon contamination.

Room-Temperature Quantum Ballistic Transport in Monolithic Ultrascaled Al-Ge-Al Nanowire Heterostructures.

Conductance quantization at room temperature is a key requirement for the utilizing of ballistic transport for, e.g., high-performance, low-power dissipating transistors operating at the upper limit of "on"-state conductance or multivalued logic gates.

Highly conductive and pure gold nanostructures grown by electron beam induced deposition.

This work introduces an additive direct-write nanofabrication technique for producing extremely conductive gold nanostructures from a commercial metalorganic precursor. Gold content of 91 atomic % (at. %) was achieved by using water as an oxidative enhancer during direct-write deposition.

Electrical transport properties of single-crystal Al nanowires.

Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10(-9) Ω m, i.e.

Synthesis, Morphological, and Electro-optical Characterizations of Metal/Semiconductor Nanowire Heterostructures.

In this letter, we demonstrate the formation of unique Ga/GaAs/Si nanowire heterostructures, which were successfully implemented in nanoscale light-emitting devices with visible room temperature electroluminescence. Based on our recent approach for the integration of InAs/Si heterostructures into Si nanowires by ion implantation and flash lamp annealing, we developed a routine that has proven to be suitable for the monolithic integration of GaAs nanocrystallite segments into the core of silicon nanowires. The formation of a Ga segment adjacent to longer GaAs nanocrystallites resulted in Schottky-diode-like I/V characteristics with distinct electroluminescence originating from the GaAs nanocrystallite for the nanowire device operated in the reverse breakdown regime.

Gate-Tunable Electron Transport Phenomena in Al-Ge⟨111⟩-Al Nanowire Heterostructures.

Electrostatically tunable negative differential resistance (NDR) is demonstrated in monolithic metal-semiconductor-metal (Al-Ge-Al) nanowire (NW) heterostructures integrated in back-gated field-effect transistors (FETs). Unambiguous signatures of NDR even at room temperature are attributed to intervalley electron transfer. At yet higher electric fields, impact ionization leads to an exponential increase of the current in the ⟨111⟩ oriented Ge NW segments.

Investigation of neurotrophic factor concentrations with a novel in vitro concept for peripheral nerve regeneration.

The regeneration of nerves of the peripheral nervous system after injuries is a complex process. This study presents a novel in vitro neurite regeneration concept to investigate the regeneration of neurons and their processes with different concentrations of neurotrophic factors. The core part of the concept is a transparent microfluidic neurite isolation (NI) device affixed on top of a microelectrode array (MEA), providing a fast and easy way to assess both the growth and the electrical activity of neurites.

Origin of anomalous piezoresistive effects in VLS grown Si nanowires.

Although the various effects of strain on silicon are subject of intensive research since the 1950s the physical background of anomalous piezoresistive effects in Si nanowires (NWs) is still under debate. Recent investigations concur in that due to the high surface-to-volume ratio extrinsic surface related effects superimpose the intrinsic piezoresistive properties of nanostructures. To clarify this interplay of piezoresistive effects and stress related surface potential modifications, we explored a particular tensile straining device (TSD) with a monolithic embedded vapor-liquid-solid (VLS) grown Si NW.

Direct-write deposition and focused-electron-beam-induced purification of gold nanostructures.

Three-dimensional gold (Au) nanostructures offer promise in nanoplasmonics, biomedical applications, electrochemical sensing and as contacts for carbon-based electronics. Direct-write techniques such as focused-electron-beam-induced deposition (FEBID) can provide such precisely patterned nanostructures. Unfortunately, FEBID Au traditionally suffers from a high nonmetallic content and cannot meet the purity requirements for these applications.

Electrostatic actuated strain engineering in monolithically integrated VLS grown silicon nanowires.

In this paper we demonstrate the fabrication and application of an electrostatic actuated tensile straining test (EATEST) device enabling strain engineering in individual suspended nanowires (NWs). Contrary to previously reported approaches, this special setup guarantees the application of pure uniaxial tensile strain with no shear component of the stress while e.g.

Multimode silicon nanowire transistors.

The combined capabilities of both a nonplanar design and nonconventional carrier injection mechanisms are subject to recent scientific investigations to overcome the limitations of silicon metal oxide semiconductor field effect transistors. In this Letter, we present a multimode field effect transistors device using silicon nanowires that feature an axial n-type/intrinsic doping junction. A heterostructural device design is achieved by employing a self-aligned nickel-silicide source contact.

Free-standing magnetic nanopillars for 3D nanomagnet logic.

Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape-controlled nanomagnets to enable digital processing. Currently, conventional resist-based lithographic processes limit the design of NML circuitry to planar nanostructures with homogeneous thicknesses. Here, we demonstrate the focused electron beam induced deposition of Fe-based nanomaterial for magnetic in-plane nanowires and out-of-plane nanopillars.

Generation of 3D nanopatterns with smooth surfaces.

Ga implantation into Si and reactive ion etching has been previously identified as candidate techniques for the generation of 3D nanopatterns. However, the structures manufactured using these techniques exhibited impedingly high surface roughness. In this work, we investigate the source of roughness and introduce a new patterning process to solve this issue.

Peculiarities of temperature dependent ion beam sputtering and channeling of crystalline bismuth.

In this paper, we report on the surface evolution of focused ion beam treated single crystalline Bi(001) with respect to different beam incidence angles and channeling effects. 'Erosive' sputtering appears to be the dominant mechanism at room temperature (RT) and diffusion processes during sputtering seem to play only a minor role for the surface evolution of Bi. The sputtering yield of Bi(001) shows anomalous behavior when increasing the beam incidence angle along particular azimuthal angles of the specimen.

Streptavidin binding as a model to characterize thiol-ene chemistry-based polyamine surfaces for reversible photonic protein biosensing.

Biotin- and iminobiotin-bonded surfaces obtained by thiol-ene chemistry and subsequent modification with polyamines were characterized with respect to streptavidin-binding capacity and reversibility for photonic biosensing using X-ray photoelectron spectroscopy and Mach-Zehnder-interferometric sensors. The streptavidin-iminobiotin system was exploited for reversible multilayer deposition and determination of affinity constants on each layer.

Impact of oxidation and reduction annealing on the electrical properties of Ge/LaO/ZrO gate stacks.

The paper addresses the passivation of Germanium surfaces by using layered LaO/ZrO high- dielectrics deposited by Atomic Layer Deposition to be applied in Ge-based MOSFET devices. Improved electrical properties of these multilayered gate stacks exposed to oxidizing and reducing ambient during thermal post treatment in presence of thin Pt cap layers are demonstrated. The results suggest the formation of thin intermixed La Ge O interfacial layers with thicknesses controllable by oxidation time.

Electrochemical current-sensing atomic force microscopy in conductive solutions.

Insulated atomic force microscopy probes carrying gold conductive tips were fabricated and employed as bifunctional force and current sensors in electrolyte solutions under electrochemical potential control. The application of the probes for current-sensing imaging, force and current-distance spectroscopy as well as scanning electrochemical microscopy experiments was demonstrated.

In situ monitoring of Joule heating effects in germanium nanowires by μ-Raman spectroscopy.

We explored a noninvasive optical method to determine the Joule heating of individual germanium nanowires. Using confocal μ-Raman spectroscopy, variations in the optical phonon frequency, in detail the downshifting of the first-order Stokes Raman band, are correlated to the temperature increase of vapor-liquid-solid grown germanium nanowires under an applied electrical bias. The germanium nanowires were found to handle high threshold current densities of more than 10(6) A cm(-2) before sustaining immediate deterioration.

Synthesis of individually tuned nanomagnets for Nanomagnet Logic by direct write focused electron beam induced deposition.

Nanomagnet Logic (NML) is a promising new technology for future logic which exploits interactions among magnetic nanoelements in order to encode and compute binary information. This approach overcomes the well-known limits of CMOS-based microelectronics by drastically reducing the power consumption of computational systems and by offering nonvolatility. An actual key challenge is the nanofabrication of such systems that, up to date, are prepared by complex multistep processes in planar technology.

Anisotropic lithiation behavior of crystalline silicon.

In this paper we demonstrate the anisotropic lithiation of silicon (Si). Therefore specimens with radiating Si beams were selectively covered with pure lithium (Li) and lithiation was investigated at different temperatures. Due to the radial arrangement, Si beams underwent a crystallographic orientation dependent lithiation.