Presentations

    Black silicon, at Physics Colloquium, University of Pretoria (Pretoria, South Africa), Thursday, May 31, 2012:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Femtosecond Laser Nanostructuring of Semiconductors and Metals, at 13th International Symposium on Laser Precision Microfabrication (LPM), The Catholic University of America (Washington, DC), Thursday, June 14, 2012:
    We have developed a unique technique to change the optoelectronic properties of many materials through hyperdoping and texturing [1]. By irradiating materials, such as silicon and titanium dioxide, with a train of amplified femtosecond (fs) laser pulses in the presence of a wide variety of dopant precursors, we can introduce dopants above the solubility limit while producing surface structures that have excellent anti-reflection and light-trapping properties.

    Femtosecond-laser texturing originates from the formation of laser induced period surface structures (LIPSS) and consists of semi...

    Read more about Femtosecond Laser Nanostructuring of Semiconductors and Metals
    Mid-infrared absorptance of silicon hyperdoped with chalcogens via fs-laser irradiation, at Black Silicon Symposium (Albany, NY), Thursday, August 9, 2012:
    Silicon hyperdoped with heavy chalcogen atoms via femtosecond-laser irradiation exhibits strong broadband absorption. Understanding this absorption could enable applications for infrared detection and the intermediate band photovoltaic effect. In this work, we extend absorption measurements to wavelengths >14 μm using Fourier transform infrared spectroscopy and study sulfur-, selenium- or tellurium-hyperdoped Si before and after annealing. We find that the surface morphology of the sample significantly influences the extent of absorption into the mid-infrared wavelength range.... Read more about Mid-infrared absorptance of silicon hyperdoped with chalcogens via fs-laser irradiation
    Towards increased efficiency in solar energy harvesting via intermediate states, at Gordon Research Conference on Defects in Semiconductors, University of New England (Biddeford, ME), Monday, August 13, 2012:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Towards increased efficiency in solar energy harvesting via intermediate states
    Femtosecond laser texturing and doping of metals and semiconductors for solar harvesting, at SPIE Optics and Photonics (San Diego, CA), Thursday, August 16, 2012:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Serendipity and the quest for new materials, at 9th Science and Technology in Society Forum (Kyoto, Japan), Monday, October 8, 2012:
    Throughout history, the development of new materials and serendipity have been tightly interwoven. I will illustrate the need for exploration and risk-taking with two anecdotes
    Black silicon, at Optoelectronics Research Centre Seminar, University of Southampton (Southampton, UK), Wednesday, November 7, 2012:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Black silicon, at Physics Seminar, Wright State University (Dayton, OH), Friday, November 30, 2012:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Black silicon and the quest for intermediate band semiconductors, at Zhejiang University (Hangzhou, China), Thursday, December 13, 2012:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Formation of mixed metal oxides by femtosecond laser irradiation for solar harvesting, at SPIE Photonics West (San Francisco, CA), Tuesday, February 5, 2013
    We present a novel method for producing mixed metal oxides using femtosecond laser doping of metallic foil in the presence of oxygen and another metallic dopant. We discuss doping titanium dioxide (TiO2) for above bandgap absorptance by irradiating titanium metal with an evaporated thin film of metal. As a wide bandgap, TiO2 most strongly absorbs in the UV range (?... Read more about Formation of mixed metal oxides by femtosecond laser irradiation for solar harvesting
    The photovoltaic potential of femtosecond laser textured amorphous silicon, at Photonics West (San Francisco, CA), Thursday, February 7, 2013:
    Femtosecond laser texturing of silicon yields nanometer scale surface roughness that reduces reflection and enhances light absorption. In this work, we study the potential of using this technique to improve efficiencies of amorphous silicon-based solar cells by laser texturing thin amorphous silicon films. We use Ti:Sapphire femtosecond laser systems to texture amorphous silicon in either hydrogen or sulfur hexafluoride ambient gases and we also study the effect of laser texturing the substrate before depositing amorphous silicon. We adjust the thin-film thickness and laser fabrication... Read more about The photovoltaic potential of femtosecond laser textured amorphous silicon
    Black silicon, at 2013 Swenton-Ouellette Lecture, Ohio State University (Columbus, OH), Thursday, February 14, 2013:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Black silicon and the quest for intermediate band semiconductors, at iCone Seminar, University of North Carolina Charlotte (Charlotte, NC), Friday, February 15, 2013:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Pushing a physics discovery towards commercial impact, at REU Seminar, Harvard University (Cambridge, MA), Wednesday, July 24, 2013:
    In 1997 my research group discovered that shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye, making this 'black silicon' useful for a wide range of commercial devices, from highly-sensitive detectors to improved photovoltaics. Over the following ten years we investigated this material and developed a prototype detector. The prototype gave us the confidence to commercialize black silicon. Together... Read more about Pushing a physics discovery towards commercial impact
    Towards increased efficiency in solar energy harvesting via intermediate states, at SPIE Laser Material Processing for Solar Energy Devices II (San Diego, CA), Wednesday, August 28, 2013:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Towards increased efficiency in solar energy harvesting via intermediate states
    Towards increased efficiency in solar energy harvesting via intermediate states, at SPIE Laser Material Processing for Solar Energy Devices II (San Diego, CA), Wednesday, August 28, 2013:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Towards increased efficiency in solar energy harvesting via intermediate states
    Black silicon, at Annual Meeting of the Stanford Photonics Research Center, Stanford University (Palo Alto, CA), Monday, September 16, 2013:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive photodetectors and imagers using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in imaging and energy harvesting.
    Laser-processing of semiconductors for solar energy harvesting applications, at Laser World of Photonics conference (Mumbai, India), Tuesday, November 12, 2013:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Laser-processing of semiconductors for solar energy harvesting applications
    Laser-processing of semiconductors and (some) applications , at HUCE Lunch Seminar, Harvard University (Cambridge, MA), Friday, January 31, 2014:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.

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