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Femtosecond Laser-Induced Formation Of Submicrometer Spikes On Silicon In Water, M. Y. Shen, Catherine Hirshfeld Crouch, J. E. Carey, E. Mazur
Femtosecond Laser-Induced Formation Of Submicrometer Spikes On Silicon In Water, M. Y. Shen, Catherine Hirshfeld Crouch, J. E. Carey, E. Mazur
Physics & Astronomy Faculty Works
We fabricate submicrometer silicon spikes by irradiating a siliconsurface that is submerged in water with 400 nm, 100 fs laser pulses. These spikes are less than a micrometer tall and about 200 nm wide—one to two orders of magnitude smaller than the microspikes formed by laser irradiation of silicon in gases or vacuum. Scanning electron micrographs of the surface show that the formation of the spikes involves a combination of capillary waves on the molten siliconsurface and laser-induced etching of silicon. Chemical analysis and scanning electron microscopy of the spikes show that they are composed of silicon with a 20-nm-thick …
Classroom Demonstrations: Learning Tools Or Entertainment?, Catherine Hirshfeld Crouch, A. P. Fagen, J. P. Callan, E. Mazur
Classroom Demonstrations: Learning Tools Or Entertainment?, Catherine Hirshfeld Crouch, A. P. Fagen, J. P. Callan, E. Mazur
Physics & Astronomy Faculty Works
We compared student learning from different modes of presenting classroom demonstrations to determine how much students learn from traditionally presented demonstrations, and whether learning can be enhanced by simply changing the mode of presentation to increase student engagement. We find that students who passively observe demonstrations understand the underlying concepts no better than students who do not see the demonstration at all, in agreement with previous studies. Learning is enhanced, however, by increasing student engagement; students who predict the demonstration outcome before seeing it, however, display significantly greater understanding.
Mini-Conference And Related Sessions On Laboratory Plasma Astrophysics, H. Ji, Michael R. Brown, S. C. Hsu, H. Li, R. P. Drake
Mini-Conference And Related Sessions On Laboratory Plasma Astrophysics, H. Ji, Michael R. Brown, S. C. Hsu, H. Li, R. P. Drake
Physics & Astronomy Faculty Works
This paper provides a summary of some major physics issues and future perspectives discussed in the Mini-Conference on Laboratory PlasmaAstrophysics. This mini-conference, sponsored by the Topical Group on PlasmaAstrophysics, was held as part of the American Physical Society’s Division of Plasma Physics 2003 Annual Meeting (October 27–31, 2003). Also included are brief summaries of selected talks on the same topic presented at two invited paper sessions (including a tutorial) and two contributed focus oral sessions, which were organized in coordination with the mini-conference by the same organizers.
Comparison Of Structure And Properties Of Femtosecond And Nanosecond Laser-Structured Silicon, Catherine Hirshfeld Crouch, J. E. Carey, J. M. Warrender, M. J. Aziz, E. Mazur, F. Y. Génin
Comparison Of Structure And Properties Of Femtosecond And Nanosecond Laser-Structured Silicon, Catherine Hirshfeld Crouch, J. E. Carey, J. M. Warrender, M. J. Aziz, E. Mazur, F. Y. Génin
Physics & Astronomy Faculty Works
We compare the optical properties,chemical composition, and crystallinity of siliconmicrostructures formed in the presence of SF6 by femtosecond laserirradiation 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 μm thick, while those formed with nanosecond (ns) pulses have very little disorder. Both ns-laser-formed and fs-laser-formed structures absorb near-infrared (1.1–2.5 μm) radiation strongly and have roughly 0.5% sulfur impurities.