Optical hyperdoping: black silicon

Infrared absorption of femtosecond laser doped silicon: effect of dopant types and thermal treatments, at 5th International Workshop on Crystalline Silicon Solar Cells (Boston, MA), Wednesday, November 2, 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 (fs-laser) pulses on the surface of a silicon wafer in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. Similar concentration of heavy chalcogen dopants (Se and Te) is achieved by fs-laser doping with solid-phase dopant precursors. Fs-laser doped Si:chalcogen systems exhibit near-unity, broadband absorption from the visible to the near infrared (< 0.5 eV, deep below the silicon... Read more about Infrared absorption of femtosecond laser doped silicon: effect of dopant types and thermal treatments
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.
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.
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-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies, at Physics Colloquium, University of Massachusetts Lowell (Lowell, MA), Wednesday, March 10, 2004:
Irridiating silicon surfaces with trains of ultrashort laser pulses in the presence of a sulfur containing gas drastically changes the structure and properties of silicon. The normally smooth and highly reflective surface develops a forest of sharp microscopic spikes. The microstructured surface is highly absorbing even at wavelengths beyond the bandgap of silicon and has many interesting novel applications.
High photoconductive gain and broad spectral sensitivity enabled by femtosecond laser doping of silicon, at SPIE Photonics West 2008 (San Jose, CA), Wednesday, January 23, 2008:
Femtosecond laser doping of silicon produces near-unity absorption from the ultraviolet to the short wave infrared. The resulting ‘black silicon’ has great potential for applications in photoactive devices. We have successfully incorporated black silicon into new silicon devices with unique characteristics including: high efficiency, room-temperature photoconductive gain, broad-spectral silicon photodetection, and enhanced near-infrared photovoltaic response. We present the current state of the research and discuss the potential for this processing technique to develop other new materials.
Optical Hyperdoping; Using lasers to tailor the optoelectronic properties of semiconductors, at 2009 Fall MRS Meeting: Ultrafast Materials Science Symposium (Boston, MA), Wednesday, December 2, 2009:
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: Engineering an intermediate band for optical sensing, at National Renewable Energy Laboratory (Golden, CO), Friday, October 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.
Applications of femtosecond lasers in materials processing, at Data Storage Institute, NUS (Singapore), Friday, March 30, 2012:
The intersection of materials research and ultrafast optical science is producing many valuable fundamental scientific results and applications, and the trend is expected to evolve as new and exciting discoveries are made. Femtosecond laser micromachining presents unique capabilities for three-dimensional, material-independent, sub-wavelength processing. At the same time the surface processing of materials permits the creation of novel materials that cannot (yet) be created under other conditions.

In this talk we will discuss how shining intense, ultrashort laser pulses on the surface of...

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Black silicon, at 2014 International High Power Laser Ablation Conference (Santa Fe, NM), Monday, April 21, 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.
Black silicon: Changing structure and properties with light, at Physics colloquium, Clark University (Worcester, MA), Thursday, December 12, 2002:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer changes its structure and properties dramatically: the formerly smooth, highly reflective surface becomes covered with a forest of sharp microspikes. This microstructured surface is highly absorbing even at wavelengths to which the original wafer is transparent. This talk will describe the properties of this microstructured surface and discuss why the microspikes form and what is responsible for the change in optical properties.
Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering, at Photonics West 2007 (San Jose, CA), Thursday, January 25, 2007:
We present a new substrate for efficient surface enhanced Raman scattering (SERS). Using a train of focused frequency-doubled femtosecond laser pulses from a regeneratively amplified Ti:Sapphire laser, we fabricate submicron surface structures on a silicon wafer. After irradiating the silicon wafer with 400nm, 100fs laser pulses in a cuvette of water, we observe the formation of an array of spikes, each approximately 500nm tall and 200nm wide. The wafer is scanned across the beam to form an arbitrarily-sized nanostructured area. When covered with a thin film of a noble metal, the structured... Read more about Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering

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