Role of the Si excess on the excitation of Er doped SiOx

The authors have investigated the role of the Si excess on the photoluminescence properties of Er doped substoichiometric SiOx layers. They demonstrate that the Si excess has two competing roles: when agglomerated to form Si nanoclusters Si-nc’s it enhances the Er excitation efficiency but it also introduces new nonradiative decay channels. When Er is excited through an energy transfer from Si-nc’s, the beneficial effect on the enhanced excitation efficiency prevails and the Er emission increases with increasing Si content. However, when pumped resonantly, the Er luminescence intensity always decreases with increasing Si content. These data are presented and their implications are discussed.

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Group IV semiconductor nanowires

What is the difference between the skin of the Statue of Liberty in New York, and an electric wire? Both are made of the same material (copper), but they have different properties because of the shape. Now, get your shrinking machine and make your electric wire smaller than one of your hair. Do you expect the wire to keep the same properties? Nope, of course!

You can do really amazing thing just changing the shape and the size of any material. This is what I did to enable new light sources made of silicon. All our electronics devices are made of silicon. Unfortunately, it cannot emit light by itself. But, if you fabricate a silicon wire smaller than a virus, things will change.

I investigated the growth of silicon and germanium nanowires by a self-assembled method, using electron beam evaporation. This is a relatively unexploited technique that offers a pathway towards high throughput production. By properly varying the experimental parameters of the evaporation it is possible to define the length, density and crystallographic orientation of the wires. The structural properties have been correlated to the atomistic growth mechanism. Moreover, we explored the possibility to bend and restore the wires. Ion beam irradiation amorphizes the nanowires, causing their bending in the direction opposite to the beam. A full recovery is possible after thermal annealing.

I explored a top-down approach as well. Metal-Assisted Chemical Etching is a full VLSI compatible process to grow very thin nanowires of arbitrary length and controlled doping. Room-temperature photoluminescence and electroluminescence has been demonstrated from silicon nanowires. Moreover, I introduced an innovative approach, based on the combination of standard Electron Beam Lithography and reactive ion etching, for nanopatterning nanowires in any arbitrary geometry. We demonstrate broadband photoluminescence enhancement up to approximately one order of magnitude after a reliable engineering of periodic and aperiodic array patterns.

These projects have been funded partly by University of Catania and CSFNSM (Growth and characterization of Si and Ge nanowires), and performed during my PhD course.

Publication output

Book / Book chapter

Conference participation

  • E-MRS Fall Meeting 2010 – Warsaw (PL) September 13-17, 2010 Oral presentation, Symposium E
  • International School on “Materials for Renewable Energies” – Erice (TP, Italy) May 28 – June 2, 2010 Poster session
  • E-MRS 2009 – Strasbourg (F) June 8-12, 2009 Oral presentation, Symposium I
  • NODE International Summer School – Cortona (AR, Italy) July 1-5, 2008 Poster session
  • XV International Winter School on “New Developments in Solid State Physics” – Bad HofGastein (Salzburg, AT) February 18-22, 2008
  • XIII National School of Materials Science – Bressanone (Bz, Italy) September 30 – October 9, 2007 Poster session
  • XV International conference on “Ion Beam Modification of Materials” – Taormina (ME, Italy) September 18-22, 2006 Poster session

Sub-250 nm optical gain

Room temperature deep-UV optical gain has been demonstrated in AlGaN/AlN multiple quantum wells structure with strong band-structure potential fluctuations grown by Molecular Beam Epitaxy. A maximum net modal gain of 118 cm-1 has been measured and the transparency threshold of 5 µJ/cm2 was experimentally determined. Amplified Spontaneous Emission results strongly TE-polarized.

This work has been funded by DARPA – Defense Advanced Research Projects Agency CMUVT Program under subcontract from Photon Systems Inc. (2011, March – 2012, March) and performed at Boston University.

Publication output

Conference proceedings

  • Sub-250nm room temperature optical gain from AlGaN materials with strong compositional fluctuations
    E. F. Pecora, W. Zhang, H. Sun, A. Yu. Nikiforov, J. Yin, R. Paiella, T. D. Moustakas, L. Dal Negro
    Bulletin of the American Physical Society, vol. 58, V1.00111
  • Sub-250nm room temperature optical gain from AlGaN/AlN multiple quantum wells structures
    E. F. Pecora, W. Zhang, L. Zhou, D. J. Smith, J. Yin, R. Paiella, L. Dal Negro, T. D. Moustakas
    CLEO: Science and Innovations, CTh3D, CTh3D.5
  • Sub-250nm room-temperature optical gain from AlGaN/AlN multiple quantum dot structures
    E. F. Pecora, W. Zhang, L. Zhou, D. J. Smith, J. Yin, R. Paiella, L. Dal Negro, T. D. Moustakas
    Bulletin of the American Physical Society, vol. 57
  • Room temperature low threshold stimulated emission of electron beam-pumped AlGaN-based deep UV laser structures emitting below 250 nm
    A. Nikiforov, W. Zhang, J. Woodward, J. Yin, E. Pecora, L. Zhou, L. Dal Negro, R. Paiella, D. Smith, T. Moustakas, A. Moldawer
    Bulletin of the American Physical Society, vol. 57

Conference participation

  • APS March Meeting 2013 – Baltimore, MD (USA) March 18 – 22, 2013 Poster presentation, Session V1
  • CLEO Conference 2012 – San Jose, CA (USA) May 6 – 11, 2012 Oral presentation, Session “Low-dimensional Photonic Structures”
  • APS March Meeting 2012 – Boston, MA (USA) February 27 – March 2, 2012 Oral presentation, Session L28

Stanford University

I joined Stanford University in September 2013 and I was a PostDoctoral Scholar in the group of Prof. Mark Brongersma till May 2016. This is one of the best environments I have been working in during my professional life. Located in the heart of California’s Silicon Valley, it is really one of the world’s leading teaching and research universities. I tried to take advantages of as many as possible opportunities offered by the Farm.

My research project focuses on improving the existing solar cells and make them cheaper and a real alternative to traditional energy sources. My project here is funded by 3Sun / Enel Green Power / ST Microelectronics and the US Department of Energy through the Bay Area PhotoVoltaic Consortium.

Publication output

Patent

  • Broadband, polarization-independent, omnidirectional, metamaterial-based antireflection coating for solar cells
    M. L. Brongersma, C. E. A. Cordaro, E. F. Pecora
    Provisional patent

Leadership experience

Leadership formation

  • Admitted at Adventures in Design Thinking: A d.school Experience class offered by the Stanford Office of the Vice Provost for Graduate Education (Summer 2015)
  • Admitted at The Improviser’s Mindset class offered by the Stanford Office of the Vice Provost for Graduate Education (Summer 2014)
  • Negotiation skills class, offered by the Stanford Office of Postdoctoral Affairs
  • Future Faculty Seminar INDE/CTL231 class, offered by the Stanford University
  • iRite/iSpeak course, offered by the Stanford Office of Postdoctoral Affairs
  • Stanford future leaders: Mentoring Workshop, offered by the Stanford Office of Postdoctoral Affairs

Invited talk

Conference participation

  • BAPVC meeting Spring 2013 – Stanford University
  • BAPVC meeting Fall 2013 – UC Berkeley
  • MRS Spring meeting 2014 – San Francisco, CA (USA) Poster presentation
  • BAPVC meeting Spring 2014 – Stanford University
  • BAPVC meeting Fall 2014 – UC Berkeley
  • BAPVC meeting Spring 2015 – Stanford University
  • MRS Fall meeting 2014 – Boston, MA (USA) Oral presentation
    Watch my presentation at MRS Fall meeting with MRS On Demand.
  • MRS Spring meeting 2015 – San Francisco, CA (USA) Oral presentation
  • MRS Fall meeting 2015 – Boston, MA (USA) Oral presentation
  • MRS Spring meeting 2016 – Phoenix, AZ (USA) Oral presentation

For download

Teaching activity

  • Guest lecturer for the CHEM26N class (The What, Why, How and wow’s of Nanotechnology) at Stanford University, Spring 2015 semester

Boston University

PostDoctoral Associate at the Photonics Center of Boston University from 2011, March to 2013, August.

Research projects

Publication output

Conference proceedings

  • Integration of metallic nanostructures on nanowires for modification of their optical properties
    A. Casadei, E. Alarcon-Llado, E. F. Pecora, J. Trevino, C. Forestiere, D. Ruffer, E. Russo-Averchi, F. Matteini, G. Tutuncuoglu, M. Heiss, L. Dal Negro, A. Fontcuberta i Morral
    Frontiers in Nanophotonics, CSF Conference 2015
  • Second harmonic excitation spectroscopy in studies of Fano-type coupling in plasmonic arrays
    G. F. Walsh, J. Tervino, E. F. Pecora, L. Dal Negro
    SPIE Optics + Photonics 2015
  • Engineering light coupling in single nanowire with metal nano-antennas
    A. Casadei, J. Trevino, E. F. Pecora, E. Alarcò- Lladò, D. Ruffer, E. Russo-Averchi, G. Tutuncuoglu, F. Matteini, C. Forestiere, L. Dal Negro, A. Fontcuberta i Morral
    International Conference on One dimensional Nanomaterials ICON 2013
  • Second-harmonic generation from plasmonic nanoantennas and arrays
    A. Capretti, C. Forestiere, E. F. Pecora, G. Walsh, J. Trevino, S. Minissale, L. Dal Negro, G. Miano
    The International Conference on Surface Plasmon Photonics SPP6
  • Sub-250nm room temperature optical gain from AlGaN materials with strong compositional fluctuations
    E. F. Pecora, W. Zhang, H. Sun, A. Yu. Nikiforov, J. Yin, R. Paiella, T. D. Moustakas, L. Dal Negro
    Bulletin of the American Physical Society, vol. 58, V1.00111
  • Second-harmonic generation in substoichiometric silicon nitride layers
    E. F. Pecora, A. Capretti, G. Miano, L. Dal Negro
    Bulletin of the American Physical Society, vol. 58, V1.00119
  • Rare-earth doped Si-rich ZnO for multiband near-infrared light emitting devices
    E. F. Pecora, T. I. Murphy, L. Dal Negro
    Bulletin of the American Physical Society, vol. 58, C23.00004
  • Nanopatterning of optically-active silicon nanowires
    E. F. Pecora, N. Lawrence, P. Gregg, J. Trevino, P. Artoni, A. Irrera, F. Priolo, L. Dal Negro
    Frontiers in Optics (FiO) – Novel Silicon Waveguides and Nanophotonics (FM4E)
  • Sub-250nm room temperature optical gain from AlGaN/AlN multiple quantum wells structures
    E. F. Pecora, W. Zhang, L. Zhou, D. J. Smith, J. Yin, R. Paiella, L. Dal Negro, T. D. Moustakas
    CLEO: Science and Innovations, CTh3D, CTh3D.5
  • Sub-250nm room-temperature optical gain from AlGaN/AlN multiple quantum dot structures
    E. F. Pecora, W. Zhang, L. Zhou, D. J. Smith, J. Yin, R. Paiella, L. Dal Negro, T. D. Moustakas
    Bulletin of the American Physical Society, vol. 57
  • Room temperature low threshold stimulated emission of electron beam-pumped AlGaN-based deep UV laser structures emitting below 250 nm
    A. Nikiforov, W. Zhang, J. Woodward, J. Yin, E. Pecora, L. Zhou, L. Dal Negro, R. Paiella, D. Smith, T. Moustakas, A. Moldawer
    Bulletin of the American Physical Society, vol. 57

Conference participation

  • APS March Meeting 2013 – Baltimore, MD (USA) March 18 – 22, 2013 Poster presentation, Session V1
  • APS March Meeting 2013 – Baltimore, MD (USA) March 18 – 22, 2013 Poster presentation, Session V1
  • APS March Meeting 2013 – Baltimore, MD (USA) March 18 – 22, 2013 Oral presentation, Session C23
  • MRS Fall Meeting 2012 – Boston, MA (USA) November 25 – 30, 2012 Oral presentation, Symposium DD
  • MRS Fall Meeting 2012 – Boston, MA (USA) November 25 – 30, 2012 Oral presentation, Symposium DD
  • MRS Fall Meeting 2012 – Boston, MA (USA) November 25 – 30, 2012 Poster presentation, Symposium Z
  • CLEO Conference 2012 – San Jose, CA (USA) May 6 – 11, 2012 Oral presentation, Session “Low-dimensional Photonic Structures”
  • APS March Meeting 2012 – Boston, MA (USA) February 27 – March 2, 2012 Oral presentation, Session L28

Leadership experience

  • Laboratory Safety Coordinator for the Boston University Research Compliance – Environmental Health & Safety (2011 – 2013)

Teaching activity

  • Substitute lecturer for the EC471 class (Physics of Semiconductor Devices) at Boston University, Spring 2012 semester

Centro Siciliano di Fisica Nucleare e Struttura della Materia

PostDoc Fellow at MATIS Labs. granted by Centro Siciliano di Fisica Nucelare e Struttura della Materia on Growth and Characterization of Si and Ge Nanowires from 2009, November through 2010, December.

Research projects

  • Growth and characterization of Si and Ge nanowires, funded by Centro Siciliano di Fisica Nucleare e Struttura della Materia (2009, November – 2010, December)

Publication output

Book / Book chapter

PhD in Physics

PhD in Physics, cum laude at University of Catania and MATIS Labs.
Thesis title: Growth, properties and processing of group IV semiconductor nanowires
Advisor: prof. Francesco Priolo
Date: 2010, February 15

Publication output

Book / Book chapter

Conference participation

  • E-MRS Fall Meeting 2010 – Warsaw (PL) September 13-17, 2010 Oral presentation, Symposium E
  • International School on “Materials for Renewable Energies” – Erice (TP, Italy) May 28 – June 2, 2010 Poster session
  • E-MRS 2009 – Strasbourg (F) June 8-12, 2009 Oral presentation, Symposium I
  • NODE International Summer School – Cortona (AR, Italy) July 1-5, 2008 Poster session
  • XV International Winter School on “New Developments in Solid State Physics” – Bad HofGastein (Salzburg, AT) February 18-22, 2008
  • XIII National School of Materials Science – Bressanone (Bz, Italy) September 30 – October 9, 2007 Poster session
  • XV International conference on “Ion Beam Modification of Materials” – Taormina (ME, Italy) September 18-22, 2006 Poster session

Leadership experience

  • Representative of Ph. D. Students in the Physics and Astronomy Department Council of the Catania University (2008 – 2009)
  • Webmaster of www.matis.imm.cnr.it (2006 – 2011)