E. Bertagnolli

IST Austria, Klosterneuberg, Lower Austria, Austria

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Publications (261)

  • [Show abstract] [Hide abstract] ABSTRACT: All-oxide solar cells based on electrodeposited p-type Cu2O absorber and atomic layer deposited n-type ZnMgO are investigated. The introduced solar cell architecture is free of precious metals that are usually employed as electrodes in Cu2O solar cells and is composed almost exclusively of oxide layers. Firstly, a detailed investigation is made on the potentiostatic electrodeposition of the absorber layer on the sputtered, highly conductive and reflective Cr/ITO (ITO: tin-doped indium oxide) electrode. The focus is set on adjusting the deposition parameters to obtain Cu2O layers, which are void-free and with large grains. A multi-textured film is obtained with prominent (111), (200) and (220) reflections. The absorber has a bandgap of 1.93 eV and a rough, antireflective surface. Next, the n-type ZnMgO layer has been investigated and a linear relation of the optical bandgap (3.2–3.9 eV) versus Mg content was found. The valence band maximum levels have been extracted from X-Ray photoelectron spectroscopy and the band alignment of the Cu2O/ZnMgO was evaluated. Solar cells employing ZnMgO films with ~10 at% Mg show best photovoltaic performance, whereas for larger Mg contents a dramatic decrease of the performance takes place, presumably due to excessive, deep-level defects, leading to tunnel recombination. Best cells show short circuit current density of 6.8 mA/cm², open circuit voltage of 550 mV, fill factor of 45% and power conversion efficiency of 1.67%.
    Article · Mar 2017 · Solar Energy Materials and Solar Cells
  • Article · Nov 2016 · Physica Status Solidi (A) Applications and Materials
  • Source
    Mostafa M. Shawrav · Philipp Taus · Heinz D. Wanzenboeck · [...] · Emmerich Bertagnolli
    [Show abstract] [Hide abstract] ABSTRACT: 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. A model was developed based on the deposition rate and the chemical composition, and it explains the surface processes that lead to the increases in gold purity and deposition yield. Co-injection of an oxidative enhancer enabled Focused Electron Beam Induced Deposition (FEBID)-a maskless, resistless deposition method for three dimensional (3D) nanostructures-to directly yield pure gold in a single process step, without post-deposition purification. Gold nanowires displayed resistivity down to 8.8 μω cm. This is the highest conductivity achieved so far from FEBID and it opens the possibility of applications in nanoelectronics, such as direct-write contacts to nanomaterials. The increased gold deposition yield and the ultralow carbon level will facilitate future applications such as the fabrication of 3D nanostructures in nanoplasmonics and biomolecule immobilization.
    Full-text available · Article · Sep 2016 · Scientific Reports
  • Mostafa M. Shawrav · Philipp Taus · Heinz D. Wanzenboeck · [...] · Emmerich Bertagnolli
    File available · Data · Sep 2016
  • Source
    Florian M Brunbauer · Emmerich Bertagnolli · Johannes Majer · Alois Lugstein
    [Show abstract] [Hide abstract] ABSTRACT: 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. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 10¹² A m⁻² before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron–phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K.
    Full-text available · Article · Sep 2016 · Nanotechnology
  • [Show abstract] [Hide abstract] ABSTRACT: The realization of an efficient, silicon-based light source with nanoscale dimensions may be the missing link to overcome the physical limitations of electrical signaling. Therefore, the generation of hot-carriers to increase the transition possibilities within the band structure has shown promising results to cope with the inefficient light emission of indirect semiconductors. Here, we present the electroluminescent properties of NiSi2/silicon/NiSi2 nanowire heterostructures, operated at high electric fields. These hot carrier electroluminescent devices show highly reproducible, super- and sub-bandgap emission of light, covering the visible spectrum and extending toward the near infrared regime. A pronounced peak, centered in the blue visible region at 2.6 eV is assigned to phonon-assisted interband recombination of hot carriers. Spectral components at energies lower than 2.3 eV are linearly polarized along the nanowire axis and mainly attributed to intraband transitions.
    Article · Sep 2016 · Physica Status Solidi (A) Applications and Materials
  • C Zimmermann · O Bethge · B Lutzer · E Bertagnolli
    [Show abstract] [Hide abstract] ABSTRACT: The impact of annealing temperature and annealing duration on the interface properties of n-Ge/Y2O3/Pt MOS-capacitors is investigated employing an ultrathin catalytically acting Pt-layer. X-ray photoelectron spectroscopy analysis has been used to verify an enhanced growth of GeO2 and thermally stabilizing yttrium germanate at the n-Ge/Y2O3 interface induced by an oxygen post deposition annealing (PDA). Especially at 500 °C and 550 °C high quality Ge/Y2O3 interfaces have been achieved resulting in very low interface trap density of 7.41∗1010 eV-1 cm-2. It is shown that either a short oxygen annealing at higher temperatures (550 °C) or a long time annealing at lower temperatures (450 °C) are appropriate to realize low interface trap density (D it). It turns out that a Pt-assisted PDA in combination with a final PMA are needed to reduce hysteresis width significantly and to bring flat band voltages toward ideal values.
    Article · Jul 2016 · Semiconductor Science and Technology
  • Data · Jun 2016
  • Mostafa Moonir Shawrav · Heinz D Wanzenboeck · P. Taus · [...] · E. Bertagnolli
    Conference Paper · May 2016
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: 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. The observed electroluminescence was ascribed to radiative band-to-band recombinations resulting in distinct emission peaks and a low contribution due to intraband transition, which were also observed under forward bias. Simulations of the obtained nanowire heterostructure confirmed the proposed impact ionization process responsible for hot carrier luminescence. This approach may enable a new route for on-chip photonic devices used for light emission or detection purposes.
    Full-text available · Article · May 2016 · Nano Letters
  • B. Lutzer · S. Simsek · C. Zimmermann · [...] · E. Bertagnolli
    [Show abstract] [Hide abstract] ABSTRACT: In order to improve the electrical behaviour of metal-insulator-metal capacitors with ZrO2 insulator grown by Atomic Layer Deposition, the influence of the insertion of interfacial Cr layers between Pt electrodes and the zirconia is investigated. An improvement of the α-voltage coefficient of capacitance as low as 567 ppm/V2 is achieved for a single layer of Cr while maintaining a high capacitance density of 10.7 fF/μm2 and a leakage current of less than 1.2 × 10−8 A/cm2 at +1 V. The role of the interface is discussed by means of X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy showing the formation of Zr stabilized chromia oxide phase with a dielectric constant of 16.
    Article · Mar 2016 · Journal of Applied Physics
  • C. Zimmermann · O. Bethge · K. Winkler · [...] · E. Bertagnolli
    [Show abstract] [Hide abstract] ABSTRACT: Metal Oxide Semiconductor capacitors are investigated, employing ALD grown Y2O3 as gate dielectric, and n-type (1 0 0) germanium as channel substrate. The effect of post deposition annealing (PDA) in oxygen and forming gas atmosphere using a thin catalytically acting platinum (Pt)-layer on the Y2O3/Ge interface is electrically analyzed for buffered hydrofluoric (BHF) and thermally pre-treated Ge-surfaces. The Pt-assisted PDA ensures even for BHF pre-treated samples very low values for the interface trap density Dit of 1.55 × 1011 eV-1 cm-2 and low leakage current densities J of <7 × 10-9 A/cm2 outperforming conventional PDA treatments. The interfacial formation of GeO2 and yttrium germanate after PDA is proven by using X-ray Photoelectron Spectroscopy measurements.
    Article · Feb 2016 · Applied Surface Science
  • Florian Maximilian Brunbauer · Emmerich Bertagnolli · Alois Lugstein
    [Show abstract] [Hide abstract] 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.
    Article · Oct 2015 · Nano Letters
  • Mostafa Moonir Shawrav · P.Taus · Heinz D. Wanzenboeck · [...] · E.Bertagnolli
    Conference Paper · Sep 2015
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    M.M. Shawrav · Z.G. Gökdeniz · H.D. Wanzenboeck · [...] · E. Bertagnolli
    [Show abstract] [Hide abstract] 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.
    Full-text available · Article · Sep 2015 · Materials Science in Semiconductor Processing
  • Johann K Mika · Karin Schwarz · Heinz D Wanzenboeck · [...] · Emmerich Bertagnolli
    [Show abstract] [Hide abstract] 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.
    Article · Jul 2015 · Journal of Neuroscience Research
  • Mostafa Moonir Shawrav · J. Mika · H.D. Wanzenboeck · [...] · E. Bertagnolli
    Conference Paper · Jul 2015
  • Source
    [Show abstract] [Hide abstract] 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.
    Full-text available · Article · Jun 2015 · Nano Letters
  • Mostafa Moonir Shawrav · P.Taus · H.D. Wanzenboeck · [...] · E.Bertagnolli
    Conference Paper · May 2015
  • Mostafa Moonir Shawrav · J.Mika · H.D. Wanzenboeck · [...] · E. Bertagnolli
    Conference Paper · May 2015

Publication Stats

3k Citations

Institutions

  • 2008
    • IST Austria
      Klosterneuberg, Lower Austria, Austria
  • 2000-2004
    • Vienna University of Technology
      • Institute of Solid State Electronics
      Wien, Vienna, Austria
  • 2002
    • Infineon Technologies
      München, Bavaria, Germany