Optical hyperdoping: black silicon

C. H. Crouch, J. E. Carey, J. M. Warrender, M. J. Aziz, E. Mazur, and F. Y. Genin. 2004. “Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon.” Appl. Phys. Lett., 84, Pp. 1850–1852. Publisher's VersionAbstract
We compare the optical properties, chemical composition, and crystallinity of silicon microstructures formed in the presence of SF6 by femtosecond laser irradiation and by nanosecond laser irradiation. In spite of very different morphology and crystallinity, the optical properties and chemical composition of the two types of microstructures are very similar. The structures formed with femtosecond (fs) pulses are covered with a disordered nanocrystalline surface layer less than 1 m thick, while those formed with nanosecond (ns) pulses have very little disorder. Both ns-laser-formed and fs-laser-formed structures absorb near-infrared (1.12.5 m) radiation strongly and have roughly 0.5% sulfur impurities.
A. Serpengüzel, A. Kurt, I. Inanc, J. E. Carey, and E. Mazur. 2008. “Luminescence of black silicon.” J. Nanophoton., 2, Pp. 021770–9. Publisher's VersionAbstract
Room temperature visible and near-infrared photoluminescence from black silicon has been observed. The black silicon is manufactured by shining femtosecond laser pulses on silicon wafers in air, which were later annealed in vacuum. The photoluminescence is quenched above 120 K due to thermalization and competing nonradiative recombination of the carriers. The photoluminescence intensity at 10K depends sublinearly on the excitation laser intensity confirming band tail recombination at the defect sites.
B. R. Tull, J. E. Carey, E. Mazur, J. McDonald, and S. M. Yalisove. 2006. “Surface morphologies of silicon surfaces after femtosecond laser irradiation.” Mat. Res. Soc. Bull., 31, Pp. 626–633. Publisher's VersionAbstract
In this article, we present summaries of the evolution of surface morphology resulting from the irradiation of single-crystal silicon with femtosecond laser pulses. In the first section, we discuss the development of micrometer-sized cones on a silicon surface irradiated with hundreds of femtosecond laser pulses in the presence of sulfur hexafluoride and other gases. We propose a general formation mechanism for the surface spikes. In the second section, we discuss the formation of blisters or bubbles at the interface between a thermal silicon oxide and a silicon surface after irradiation with one or more femtosecond laser pulses. We discuss the physical mechanism for blister formation and its potential use as channels in microfluidic devices.

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