E. Bertagnolli

Vienna University of Technology, Wien, Vienna, Austria

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Publications (229)558.12 Total impact

  • The 59th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIPBN), San Diego, US; 12/2015
  • Florian Maximilian Brunbauer · Emmerich Bertagnolli · Alois Lugstein ·
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    ABSTRACT: 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. Modulation of the transfer rates, manifested as a large tunability of the peak-to-valley ratio (PVR) and the onset of impact ionization is achieved by the combined influences of electrostatic gating, geometric confinement, and heterojunction shape on hot electron transfer and by electron-electron scattering rates that can be altered by varying the charge carrier concentration in the NW FETs.
    Nano Letters 10/2015; DOI:10.1021/acs.nanolett.5b03169 · 13.59 Impact Factor
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    ABSTRACT: Focused electron beam induced etching (FEBIE) with chlorine as etching agent has been used to geometrically shape and to electrically modify semiconductor nanodevices. Selected sections of monocrystalline nanowires were modified directly without the requirement for a photomask or a resist layer. FEBIE as a subtractive nanofabrication technology allows to locally etch active semiconductor devices made of Si or Ge. In this work, chlorine is used as the etchant gas to thin germanium channel structures fabricated by standard photolithography. For effective material removal a sufficiently high electron influence is essential to avoid the pitfalls of this method. Topography and conductivity of FEBIE-modified structures prior and after the etching process was studied by AFM and by electrical I–V characteristics. The presented work demonstrates the potential of Cl-based FEBIE for device prototyping and electrical trimming of future Ge-based nanodevices.
    Materials Science in Semiconductor Processing 09/2015; DOI:10.1016/j.mssp.2015.08.033 · 1.96 Impact Factor
  • Johann K Mika · Karin Schwarz · Heinz D Wanzenboeck · Petra Scholze · Emmerich Bertagnolli ·
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    ABSTRACT: 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. The NI-MEA isolates neurites from the culture with microchannels that serve as guidance tubes, equipped with microelectrodes. Thus, the NI-MEA allows neurite growth, as observed by microscopy, to be correlated with neurite electrical activity, as measured by electrophysiological recordings. To demonstrate proof of concept of neurite regeneration, we cultured cells from the superior cervical ganglion of postnatal mice under different concentrations of nerve growth factor (NGF). During the regeneration process, we observed an increase in the number of neurites entering the microchannels along with an increase in spike activity recorded by the microelectrodes in the microchannels. We also observed a concentration-dependent effect of neurotrophic factor on the excitability of the growing neurites, with neurites bathed in 20 ng/ml NGF exhibiting enhanced early growth. Thus, our neurite regeneration concept with the NI-MEA device allows further study of neurotrophic factors and reduces the requirement for in vivo experiments on the regeneration of peripheral nerves after injury. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    Journal of Neuroscience Research 07/2015; 93(11). DOI:10.1002/jnr.23598 · 2.59 Impact Factor

  • 20th Biennial European Conference on Chemical Vapor Deposition (EuroCVD), Sempach, Switzerland; 07/2015
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    ABSTRACT: In this letter we report on the exploration, of axial metal/semiconductor (Al/Ge) nanowire heterostructures with abrupt interfaces. The formation process is enabled by a thermal induced exchange reaction between the vapor-liquid-solid grown Ge nanowire and Al contact pads due to the substantially different diffusion behavior of Ge in Al and vice versa. Temperature dependent I-V measurements revealed the metallic properties of the crystalline Al nanowire segments with a maximum current carrying capacity of about 0.8MA/cm2. Transmission electron microscopy (TEM) characterization has confirmed both the composition and crystalline nature of the pure Al nanowire segments. A very sharp interface between the 111 oriented Ge nanowire and the reacted Al part was observed with a Schottky barrier height of 361meV. To demonstrate the potential of this approach, a monolithic Al/Ge/Al heterostructure was used to fabricate a novel impact ionization device.
    Nano Letters 06/2015; 15(7). DOI:10.1021/acs.nanolett.5b01748 · 13.59 Impact Factor

  • E-MRS Spring Meeting 2015, Lille ,France; 05/2015
  • Mostafa Moonir Shawrav · Zeynep Goekdeniz · Heinz Wanzenboeck · Emmerich Bertagnolli ·

    2nd Annual Meeting of the COST CM1301 Action, CELINA 2015, Bratislava, Slovakia; 05/2015
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    Karl Winkler · Emmerich Bertagnolli · Alois Lugstein ·
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    ABSTRACT: 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. Integrating the suspended NW in a gate all around (GAA) field effect transistor (FET) configuration with a transparent gate stack, enables optical and field modulated electrical characterization under high uniaxial tensile strain applied along the <111> Si NW growth direction. A model based on stress-induced carrier mobility change and surface charge modulation is proposed to interpret the actual piezoresistive behavior of Si NWs. By controlling the nature and density of surface states via passivation the "true" piezoresistance of the NWs is found to be comparable with that of bulk Si. This demonstrates the indispensability of application-specific NW surface conditioning and the modulation capability of Si NWs properties for sensor applications.
    Nano Letters 02/2015; 15(3). DOI:10.1021/nl5044743 · 13.59 Impact Factor
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    ABSTRACT: To advance existing in vitro cell impedance spectroscopy and improve reliability of impedimetric sensors for cell analysis, we have electrically insulated interdigitated microelectrodes using the high-k biomate-rial zirconium dioxide (ZrO 2). We report the smallest passivation thickness to electrode distance ratio of 10 −3 using atomic layer deposition resulting in electrically insulated metal oxide films of 15 nm thickness. For the first time the influence of the insulation on sensor performance is experimentally and theoretically analyzed using numerical simulations. In addition an equivalent electrical circuit model was established and validated using non-linear least square fitting. Results of the computational simulations revealed improved electrical current distribution across the electrically insulated interdigitated electrode structures in comparison to open (not passivated) electrodes. Furthermore, we found linear decrease of current density in z-direction within 5 ␮m distance from the sensor surface in the presence of ZrO 2 nanocoatings is ideally suited to assess confluent cell layers. Final practical application of the ZrO 2 nanolayer passivated impedimetric sensors is demonstrated for nanotoxicological investigations, where sensitivity and repeatability are crucial parameters for cell analysis. Results of our study show that the reproducible and standardizable deposition of a uniform metal oxide nanocoating improves current density distributions, has no performance drawbacks compared to open sensors and enables sensitive detection of protein-coating effects on cytotoxic silica nanoparticles. The presented novel sensor design allows for the integration of alternative electrode materials such as aluminum enabling cost-effective fabrication of large-volume sensor arrays.
    Sensors and Actuators 02/2015; 213:35-44. DOI:10.1016/j.snb.2015.02.018
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    ABSTRACT: A versatile synthetic protocol toward a series of various substituted triphenylamine derivatives serving as building blocks for organic electronic materials was developed. Key steps during synthesis were either Ullmann condensations or nucleophilic aromatic substitutions giving rise to structural modification of triphenylamines and their electronic nature. In turn, these scaffolds were exemplarily attached to a dendritic tris(2-thienyl)benzene core affording star shaped organic semiconducting materials which were characterized regarding their photo-physical, electro-chemical and thermal properties. A strong influence of the substituent's nature on both photo-physical and morphological thin film characteristic of star shaped target compounds was observed. The applicability of these materials in organic electronic devices was demonstrated in an organic field effect transistor configuration yielding a hole mobility of nearly 10−3 cm2 V−1 s−1. The performance of the materials can be correlated to the substituents applied.
    New Journal of Chemistry 01/2015; 39(3). DOI:10.1039/C4NJ01695E · 3.09 Impact Factor
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    ABSTRACT: Rhodium Schottky barrier contacts on germanium substrates are investigated in terms of electrical, physical, and chemical properties. The Rh, deposited by electron beam evaporation on a n-type (100)-Ge substrate, has been annealed in N2H2 at different temperatures ranging from 450°C up to 800°C. Rh/Ge Schottky diodes were fabricated to extract the Schottky barrier height, the ideality factor as well as the forward to backward current ratio. By using various analyzing techniques such as Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), and High-resolution Transmission Electron Microscopy (HR-TEM), the formation of polycrystalline Rh-germanide RhxGey phases has been proven. At 500°C germanidation temperature an effective SBH of 0.59 eV is extracted showing a high current ratio of 5 × 103 and a remarkable low ideality factor of 1.07.
    01/2015; 4(9):P387-P392. DOI:10.1149/2.0181509jss
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    ABSTRACT: We study electric field modulation of the thermovoltage in single-layer MoS2. The Seebeck coefficient generally increases for a diminishing free carrier concentration, and in the case of single-layer MoS2 reaches considerable large values of about S = -􏰀5160 μV/K at a resistivity of 490 Ωm. Further, we observe time dependent degradation of the conductivity in single layer MoS2, resulting in variations of the Seebeck coefficient. The degradation is attributable to adsorbates from ambient air, acting as p-dopants and additional Coulomb potentials, resulting in carrier scattering increase, and thus decrease of the electron mobility. The corresponding power factors remain at moderate levels, due to the low conductivity of single layer MoS2. However, as single-layer MoS2 has a short intrinsic phonon mean free path, resulting in low thermal conductivity, MoS2 holds great promise as high-performance 2D thermoelectric material.
    Applied Physics Letters 12/2014; 105(25):253103. DOI:10.1063/1.4905014 · 3.30 Impact Factor
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    ABSTRACT: The impact of thermal post deposition annealing in oxygen at different temperatures on the Ge/Y2O3 interface is investigated using metal oxide semiconductor capacitors, where the yttrium oxide was grown by atomic layer deposition from tris(methylcyclopentadienyl)yttrium and H2O precursors on n-type (100)-Ge substrates. By performing in-situ X-ray photoelectron spectroscopy, the growth of GeO during the first cycles of ALD was proven and interface trap densities just below 1 × 1011 eV−1 cm−2 were achieved by oxygen annealing at high temperatures (550 °C–600 °C). The good interface quality is most likely driven by the growth of interfacial GeO2 and thermally stabilizing yttrium germanate.
    Journal of Applied Physics 12/2014; 116(21):214111. DOI:10.1063/1.4903533 · 2.18 Impact Factor
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    S. Lindsey · S. Waid · G. Hobler · H. D. Wanzenboeck · E. Bertagnolli ·
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    ABSTRACT: FIB technologies possess a unique ability to form topographies that are difficult or impossible to generate with binary etching through typical photo-lithography. The ability to arbitrarily vary the spatial dose distribution and therefore the amount of milling opens possibilities for the production of a wide range of functional structures with applications in biology, chemistry, and optics. However in practice, the realization of these goals is made difficult by the angular dependence of the sputtering yield and redeposition effects that vary as the topography evolves. An inverse modeling algorithm that optimizes dose profiles, defined as the superposition of time invariant pixel dose profiles (determined from the beam parameters and pixel dwell times), is presented. The response of the target to a set of pixel dwell times in modeled by numerical continuum simulations utilizing 1st and 2nd order sputtering and redeposition, the resulting surfaces are evaluated with respect to a target topography in an error minimization routine. Two algorithms for the parameterization of pixel dwell times are presented, a direct pixel dwell time method, and an abstracted method that uses a refineable piecewise linear cage function to generate pixel dwell times from a minimal number of parameters. The cage function method demonstrates great flexibility and efficiency as compared to the direct fitting method with performance enhancements exceeding similar to 10x as compared to direct fitting for medium to large simulation sets. Furthermore, the refineable nature of the cage function enables solutions to adapt to the desired target function. The optimization algorithm, although working with stationary dose profiles, is demonstrated to be applicable also outside the quasi-static approximation. Experimental data confirms the viability of the solutions for 5 x 7 mu m deep lens like structures defined by 90 pixel dwell times.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 12/2014; 341:77-83. DOI:10.1016/j.nimb.2014.09.006 · 1.12 Impact Factor
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    ABSTRACT: Direct integration of high-mobility III-V compound semiconductors with existing Si-based complementary metal-oxide-semiconductor (CMOS) processing platforms presents the main challenge to increasing the CMOS performance and the scaling trend. Silicon hetero-nanowires with integrated III-V segments are one of the most promising candidates for advanced nano-optoelectronics, as first demonstrated using molecular beam epitaxy techniques. Here we demonstrate a novel route for InAs/Si hybrid nanowire fabrication via millisecond range liquid-phase epitaxy regrowth using sequential ion beam implantation and flash-lamp annealing. We show that such highly mismatched systems can be monolithically integrated within a single nanowire. Optical and microstructural investigations confirm the high quality hetero-nanowire fabrication coupled with the formation of atomically sharp interfaces between Si and InAs segments. Such hybrid systems open new routes for future high-speed and multifunctional nanoelectronic devices on a single chip.
    Nano Research 12/2014; 7(12):1769-1776. DOI:10.1007/s12274-014-0536-6 · 7.01 Impact Factor
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    ABSTRACT: During the last decades, focused electron beam induced deposition (FEBID) has become a successful approach for direct-write fabrication of nanodevices. Such a deposition technique relies on the precursor supply to the sample surface which is typically accomplished by a gas injection system using a tube-shaped injector nozzle. This precursor injection strategy implies a position-dependent concentration gradient on the surface, which affects the geometry and chemistry of the final nanodeposit. Although simulations already proposed the local distribution of nozzle-borne gas molecules impinging on the surface, this isolated step in the FEBID process has never been exper-imentally measured yet. This work experimentally inves-tigates the local distribution of impinging gas molecules on the sample plane, isolating the direct impingement com-ponent from surface diffusion or precursor depletion by deposition. The experimental setup used in this work maps and quantifies the local impinging rate of argon gas over the sample plane. This setup simulates the identical con-ditions for a precursor molecule during FEBID. Argon gas was locally collected with a sniffer tube, which is directly connected to a residual gas analyzer for quantification. The measured distribution of impinging gas molecules showed a strong position dependence. Indeed, a 300-lm shift of the deposition area to a position further away from the impingement center spot resulted in a 50 % decrease in the precursor impinging rate on the surface area. With the same parameters, the precursor distribution was also sim-ulated by a Monte Carlo software by Friedli and Utke and showed a good correlation between the empirical and the simulated precursor distribution. The results hereby pre-sented underline the importance of controlling the local precursor flux conditions in order to obtain reproducible and comparable deposition results in FEBID.
    Applied Physics A 11/2014; 117(4):1749-1756. DOI:10.1007/s00339-014-8755-y · 1.70 Impact Factor
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    Stefan Wagesreither · Emmerich Bertagnolli · Shinya Kawase · Yoshitada Isono · Alois Lugstein ·
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    ABSTRACT: 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. simultaneously measuring the resistance change of the NW. To demonstrate the potential of this approach we investigated the piezoresistivity of about 3 μm long and 100 nm thick SiNWs but in the same way one can think about the application of such a device on other geometries, other materials beyond Si as well as the use of other characterization techniques beyond electrical measurements. Therefore single-crystal SiNWs were monolithically integrated in a comb drive actuated MEMS device based on a silicon-on-insulator (SOI) wafer using the vapor–liquid–solid (VLS) growth technique. Strain values were verified by a precise measurement of the NW elongation with scanning electron microscopy (SEM). Further we employed confocal μ-Raman microscopy for in situ, high spatial resolution measurements of the strain in individual SiNWs during electrical characterization. A giant piezoresistive effect was observed, resulting in a fivefold increase in conductivity for 3% uniaxially strained SiNWs. As the EATEST approach can be easily integrated into an existing Si technology platform this architecture may pave the way toward a new generation of nonconventional devices by leveraging the strain degree of freedom.
    Nanotechnology 10/2014; 25(45):455705. DOI:10.1088/0957-4484/25/45/455705 · 3.82 Impact Factor
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    ABSTRACT: The combined capabilities of both a non-planar design and non-conventional carrier injection mechanisms are subject to recent scientific investigations to overcome the limitations of silicon MOSFETs. In this letter we present a multi-mode FET 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. The polymorph operation of the dual-gate device enabling the configuration of one p- and two n-type transistor modes is demonstrated. Not only the type but also the carrier injection mode can be altered by appropriate biasing of the two gate terminals or by inverting the drain bias. With a combined band-to-band and Schottky tunneling mechanism, in p-type mode a subthreshold swing as low as 143 mV/dec and an ON/OFF ratio of up to 10^4 is found. As the device operates in forward bias, a non-conventional tunneling transistor is realized, enabling an effective suppression of ambipolarity. Depending on the drain bias, two different n-type modes are distinguishable. The carrier injection is dominated by thermionic emission in forward bias with a maximum ON/OFF ratio of up to 10^7 whereas in reverse bias a Schottky tunneling mechanism dominates the carrier transport.
    Nano Letters 10/2014; 14(11). DOI:10.1021/nl503476t · 13.59 Impact Factor
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    ABSTRACT: Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape controlled nanomagnets, in order to allow 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. 3-dimensional (3D) NML was achieved based on the magnetic coupling between nanowires and nanopillars in a 3D array. Additionally, the same Fe-based nanomaterial was used to produce tilt-corrected high aspect ratio probes for the accurate magnetic force microscopy (MFM) analysis of the fabricated 3D NML gate arrays. The interpretation of the MFM measurements was supported by magnetic simulations using the Object Oriented MicroMagnetic Framework. Introducing vertical out of plane nanopillars not only increases the packing density of 3D NML but also introduces an extra magnetic degree of freedom, offering a new approach to input/output and processing functionalities in nanomagnetic computing.
    ACS Applied Materials & Interfaces 10/2014; 6(22):20254 − 20260. DOI:10.1021/am505785t · 6.72 Impact Factor

Publication Stats

2k Citations
558.12 Total Impact Points


  • 1999-2015
    • Vienna University of Technology
      • Institute of Solid State Electronics
      Wien, Vienna, Austria
  • 2008-2009
    • IST Austria
      Klosterneuberg, Lower Austria, Austria
  • 2005
    • Japan Advanced Institute of Science and Technology
      • School of Materials Science
      Ishikawa, Okinawa-ken, Japan
  • 2002
    • Infineon Technologies
      München, Bavaria, Germany
  • 2001
    • Atlanta University Center
      Atlanta, Georgia, United States
  • 1983-1986
    • University of Innsbruck
      • Institute for Experimental Physics
      Innsbruck, Tyrol, Austria
  • 1981
    • Karl-Franzens-Universität Graz
      Gratz, Styria, Austria