Optical hyperdoping: black silicon

Serendipity, science, and engineering, at Faculty Seminar, REU Program, Harvard University (Cambridge, MA), Thursday, July 15, 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.
Femtosecond laser doped and nanostructured TiO2 for photocatalysis, at American Physical Society March Meeting (Boston, MA), Monday, February 27, 2012:
We present a novel method for femtosecond-laser doping of titanium dioxide (TiO2) for above bandgap absorptance by irradiating titanium metal in the presence of oxygen and dopants. With a bandgap of 3.2 eV for the anatase crystalline phase, TiO2 most strongly absorbs in the UV range (λ< 387 nm). However, doping with metals and nitrogen has been shown to create intermediate states in the bandgap. Using femtosecond laser doping techniques on titanium in a gaseous environment, we produce laser-induced periodic surface structures. Altering the gas composition and pressure does not change the... Read more about Femtosecond laser doped and nanostructured TiO2 for photocatalysis
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.
Ultrashort Lasers to Increase Efficiency in Solar Energy Harvesting via Intermediate States, at 2014 High Power Laser Ablation and Beamed Energy Propulsion Conference (Santa Fe, NM), Wednesday, April 23, 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 Ultrashort Lasers to Increase Efficiency in Solar Energy Harvesting via Intermediate States
Black silicon, at Institute for Atomic and Molecular Science, Academia Sinica (Taipei, Taiwan), Friday, January 29, 2016:
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 XI International Symposium Ultrafast Phenomena in Spectroscopy, Academia Sinica (Taipei, Taiwan), Monday, October 25, 1999:
Femtosecond-laser micromachining of silicon for novel optoelectronic devices, at 2005 SPIE Photonics West Conference (San Jose, CA), Tuesday, January 25, 2005:
Silicon is the most commonly used semiconductor in micro- and optoelectronics. However, silicon is not the best material for all applications: as an indirect band-gap material, it is a poor light emitter; silicon cannot be used to detect many important communications wavelengths; and silicon solar cells fail to convert nearly a third of the suns’ spectrum into electricity. The low cost and large manufacturing infrastructure drives research to alter the properties of silicon rather than rely on more exotic semiconductor materials. We present a novel technique that uses the intense conditions... Read more about Femtosecond-laser micromachining of silicon for novel optoelectronic devices
Extending silicon's reach: nonequlibrium doping using ultrafast lasers, at Physics Colloquium, University of Massachusetts, Lowell (Lowell, MA), Wednesday, October 22, 2008:
Silicon is the world's widely used semiconductor. As the building block of a photovoltaic cell, silicon offers the best combination of stability, efficiency, and manufacturability. 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 non-equilibrium laser-doping techniques we have been developing in the Mazur group that attempt to... Read more about Extending silicon's reach: nonequlibrium doping using ultrafast lasers
Black silicon, at SPIE Photonics West (San Francisco, CA), Monday, January 25, 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.
Femtosecond laser doped silicon for photovoltaic applications, at Photonics West 2011 (San Francisco, CA), Thursday, January 27, 2011:
Doping silicon to concentrations above the metal-insulator transition threshold yields a novel material that has potential for photovoltaic applications. By focusing femtosecond laser pulses on the surface of a silicon wafe in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. This material exhibits near-unity, broadband absorption from the visible to the near infrared (< 0.5 eV, deep below the silicon bandgap), and metallic-like conduction. These unusual optical and electronic properties suggest the formation of an intermediate band. We report on the... Read more about Femtosecond laser doped silicon for photovoltaic applications
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.
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
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
Nano-textured Surfaces, at DEAS Industrial Outreach Workshop, Harvard University (Cambridge, MA), Friday, April 11, 2003:
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. Second, chemical functionalization of the... Read more about Nano-textured Surfaces

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