Presentations

    Black silicon: A new light absorber for solar cells and photodetectors, at OSA Annual Meeting (Baltimore, MD), Thursday, October 1, 1998
    We demonstrate a new light absorber for solar cells and optical detection devices. Micron-sized spikes generated by irradiating a silicon surface with femtosecond laser pulses in SF6 enhance light absorption in silicon to near 100%. We observe an increase of more than 60% in photocurrent compared to a flat silicon surface.
    Black silicon: A new light absorber for photovoltaic applications, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
    We demonstrate a new technique for texturing silicon surfaces using femtosecond laser pulses. Sharp micron-sized spikes are created by repeatedly irradiating a silicon surface with femtosecond laser pulses in the presence of SF6. The spikes are highly light-absorbing and enhance the light absorption in silicon close to 100 (increase in photocurrent of more than 60) over flat silicon. Spiked silicon is of potential use as a highly efficient light-absorber for solar cells and photodetectors.
    Black silicon, at Gordon Conference on Nonlinear Optics and Lasers, Colby Sawyer College (New London, NH), Monday, July 26, 1999:
    Black Silicon, at XI International Symposium Ultrafast Phenomena in Spectroscopy, Academia Sinica (Taipei, Taiwan), Monday, October 25, 1999:
    Below-band gap absorption in microstructured silicon, at Optical Society of America Annual Meeting (Providence, RI), Tuesday, October 24, 2000:
    We report two remarkable properties of silicon surfaces that are microstructured with laser-assisted etching: the absorptance for wavelengths between 0.25 and 2.5 micrometers is 97% or more, and photoelectrons are produced at 1.3 micrometers. We also report chemical and structural analysis of the microstructured material.
    Fabrication of Micrometer-Sized Conical Field Emitters Using Femtosecond Laser-Assisted Etching of Silicon, at MRS Spring Meeting (San Francisco, CA), Friday, April 20, 2001:
    We produce quasi-ordered arrays of sharp, conical microstructures by structuring the surface of a silicon wafer using femtosecond laser-assisted etching. Analysis of the arrays shows high, stable field emission without any further processing. The sharp, micrometer-sized conical structures result from irradiation of a silicon surface with hundreds of femtosecond-laser pulses in an atmosphere of SF6. These conical microstructures have sharp tips with a radius of curvature of about 250 nm and a subtended angle of less than 20°. They are 10–14 µm tall, have tip-to-tip separations of 6–10 µm, and... Read more about Fabrication of Micrometer-Sized Conical Field Emitters Using Femtosecond Laser-Assisted Etching of Silicon
    Black silicon: hot properties and many open questions, at Atomic and molecular physics at surfaces, ITAMP (Cambridge, MA), Thursday, June 14, 2001:
    A serendipitous discovery in our lab produced a novel form of microstructured silicon ("black silicon") that has many surprising properties: near unity absorption, even below the bandgap; production of photoelectrons in the visible and infrared; visible luminescence; and a strong field emission current. We are beginning to shed light on what might cause some of the material's remarkable properties. Much additional experimental and theoretical work is required to understand the surface physics and chemistry that leads to the formation of black silicon.
    Visible luminescence of silicon microstructures fabricated with femtosecond-laser irradiation, at International School of Atomic and Molecular Spectroscopy, Ettore Majorana Center for Scientific Culture (Erice, Sicily, Italy), Saturday, June 23, 2001:
    We report visible luminescence from SiOx formed by microstructuring silicon with femtosecond laser pulses in air. Incorporation of oxygen into the silicon lattice occurs only where the laser beam strikes the surface. Laser-structuring therefore offers the possibility to write luminescent submicron features without the use of masks. The amount of oxygen incorporated depends on the laser fluence used for microstructuring. The peak wavelength of the primary luminescence band varies between 540 and 630 nm and depends on the number of laser shots used for microstructuring. Upon annealing, the... Read more about Visible luminescence of silicon microstructures fabricated with femtosecond-laser irradiation
    Laser-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies, at Physics and Advanced Technologies Seminar, Lawrence Livermore National Laboratory (Livermore, CA), Tuesday, October 16, 2001:
    Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical, material and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. First, near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap... Read more about Laser-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies
    Black silicon: Microstructuring silicon with femtosecond lasers, at Physics Colloquium, University of Massachusetts-Lowell (Lowell, MA), Wednesday, November 14, 2001:
    Our research group has produced a novel form of microstructured silicon ("black silicon") with many surprising properties: near unity absorption, even below the band gap; production of photoelectrons in the visible and infrared; visible luminescence; and a strong field emission current. This talk will describe these properties and what is understood so far about their structural and chemical origin.
    Ultrafast laser microtexturing of silicon for optoelectronic devices, at Photonics West: Commercial and Biomedical Applications of Ultrafast Lasers (San Jose, CA), Thursday, January 24, 2002:
    Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. Near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap photocurrent... Read more about Ultrafast laser microtexturing of silicon for optoelectronic devices
    Femtosecond laser-structured silicon: properties and structure, at Gordon Conference on Laser Interactions With Materials (Andover, NH), Tuesday, July 23, 2002:
    Silicon surfaces that are microstructured with femtosecond laser pulses in a sulfur hexafluoride environment exhibit several remarkable properties, including near-unity below-band gap optical absorption (C. Wu et al., Appl. Phys. Lett. 78, 1850 (2001)). We report new structural and chemical characterization of this material, including cross-sectional TEM images of the microstructures. Our results indicate that the below-band gap absorption most likely comes from a surface layer of polycrystalline silicon roughly 1 micrometer thick, which includes nanopores, nanocrystals, and a high... Read more about Femtosecond laser-structured silicon: properties and structure
    Femtosecond laser-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies, at Department of Physics Seminar, Fudan University (Shanghai, China), Wednesday, October 16, 2002:
    Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. Near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap photocurrent... Read more about Femtosecond laser-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies
    Femtosecond laser-assisted microstructuring of silicon for novel detector, sensing, and display technologies, at State Key Laboratory for Silicon Material Lecture, Zhejiang University (Hangzhou, China), Thursday, October 17, 2002:
    Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. Near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap photocurrent... Read more about Femtosecond laser-assisted microstructuring of silicon for novel detector, sensing, and display technologies

Pages