Optical hyperdoping: black 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, at Physics Colloquium, Auburn University (Auburn, AL), Friday, September 19, 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.
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
Two-photon microfabrication of structures containing, at 2007 MRS Fall Meeting (Boston, MA, USA), Thursday, November 29, 2007:
We present the two-photon microfabrication of structures containing the bio-polymer Chitosan, using a guest/host scheme. The host resin we used consists of tris(2-hydroxyethyl)isocyanurate triacrylate and ethoxylated(6) trimethyl-lolpropane triacrylate. As guest material we used the Chitosan, which is a linear cationic polysaccharide obtained by deacetylation of chitin, a structural polysaccharide normally encountered in crustaceans. There are several potential applications for chitosan, mainly due to its biodegradability and biocompatibility. We induced the two-photon absorption... Read more about Two-photon microfabrication of structures containing
Black silicon: Engineering an intermediate band in silicon for sensing and energy harvesting, at First Annual Scialog Conference, Biosphere 2 (Oracle, AZ), Wednesday, October 13, 2010:
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.
Fabricating nanostructured TiO2 by femtosecond laser irradiating titanium, at PIERS 2012 (Kuala Lumpur, Malaysia), Wednesday, March 28, 2012:
many materials including titanium. Laser structuring of titanium surfaces has been investigated for a variety of applications, including biocompatibility and solar energy harvesting. We use femtosecond laser irradiation of titanium to create nanometer scale laser-induced periodic surface structures and study the influence of atmospheric composition on these surface structures. Altering the gas composition and pressure does not change the surface morphology, but it does impact the chemical composition of the surface. We demonstrate that irradiation of titanium in oxygen containing atmospheres... Read more about Fabricating nanostructured TiO<sub>2</sub> by femtosecond laser irradiating titanium
Black silicon and the quest for intermediate band semiconductors, at Laser-Based Micro and Nano Processing VIII, Photonics West 2014 (San Francisco, CA), Thursday, February 6, 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 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 Black silicon and the quest for intermediate band semiconductors
Laser doping and texturing of silicon for advanced optoelectronic devices, at Frontiers in Optics (FiO)/Laser Science (LS) Conference (Rochester, NY), Monday, October 17, 2016:
Irradiating a semiconductor sample with intense laser pulses in the presence of dopants drastically changes the optical, material, and electronic properties of the sample. The resulting material has applications for photodetectors and, potentially, intermediate-band solar cells.
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
Comparing properties of femtosecond and nanosecond laser-structured silicon, at Materials Research Society Fall Meeting (Boston, MA), Monday, December 2, 2002:
Sharp microcones form on crystalline silicon surfaces upon irradiation with either femtosecond or nanosecond laser pulses in a sulfur hexafluoride environment. While the general shape and aspect ratio of femtosecond and nanosecond laser cones are similar, several features (such as size and position relative to the original surface) suggest that different mechanisms may be involved in the formation of these structures. The microscopic structure and optoelectronic properties of surfaces covered with nanosecond or femtosecond laser cones could therefore differ as well. We compare the optical... Read more about Comparing properties of femtosecond and nanosecond laser-structured silicon
Femtosecond laser doping of silicon, at Photonics West 2007 (San Jose, CA), Wednesday, January 24, 2007:
Silicon is an abundant, stable, and efficient material for use in photovoltaic devices. However, it is costly to process, and is transparent at wavelengths longer than 1100nm, a spectral region containing 25% of solar energy. The limitations of silicon have spurred significant research into complex heterostructures that capture a greater fraction of sun’s energy. Engineering silicon to extend its effective spectral range, however, might offer a simpler way to increase the efficiency and decrease the cost of silicon-based photovoltaics. We report the creation of a thin, highly absorbing layer... Read more about Femtosecond laser doping of silicon
Optical hyperdoping: Extending silicon's reach, at Jones Seminar, Thayer School of Engineering, Dartmouth University (Hanover, NH), Friday, February 13, 2009:
Silicon is the world's most widely used semiconductor. As the building block of a photovoltaic cell, silicon offers a combination of stability, efficiency, and manufacturability currently unmatched by any other material. However, as an indirect absorber of light, thick layers of highly-pure, expensive material are required for efficient light absorption and charge collection. Furthermore, silicon does not absorb in the infrared, a spectral region that contains about a quarter of the sun's radiation. In this talk, I will discuss optical hyperdoping, a non-equilibrium laser-doping technique we... Read more about Optical hyperdoping: Extending silicon's reach
Optical Hyperdoping: Transforming Semiconductor Band Structure for Solar Energy Harvesting, at Third-Generation Solar Technologies Multidisciplinary Workshop: Synergistic Chemistry-Materials-Mathematical Sciences Approaches to Addressing Solar Energy Problems (San Francisco, CA), Monday, April 5, 2010:
Harvesting solar energy at the terawatt scale requires technologies that can be produced inexpensively using Earth-abundant materials. Although technologies built from Earth-abundant materials exist for converting solar energy to electrical energy or chemical energy, none are yet cost-competitive with fossil fuels. Meeting the challenge of harvesting solar energy with Earth-abundant materials such as Si and TiO2 will require transformative approaches to increase efficiency, lower manufacturing cost, and reduce material requirements. While these materials have been widely studied, we bring a... Read more about Optical Hyperdoping: Transforming Semiconductor Band Structure for Solar Energy Harvesting

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