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Investigation of the structure and optical absorption of silicon coated with a chromium film after femtosecond laser irradiation
摘要： Microstructured silicon (Si) doped with chromium (Cr) has been produced by femtosecond laser pulses. Microstructured surfaces were produced after laser irradiation at different fluence values. The dependence of its absorptance on laser fluence and thermal annealing were investigated. Microstructured Si that was fabricated at lower laser fluences exhibited perfect absorption below the Si bandgap as well as better thermal stability. The crystal structures of samples obtained before and after thermal annealing were characterized by Raman spectroscopy. The mechanism of absorption below the bandgap of Si is discussed in detail based on the results from Raman spectroscopy and optical absorption.
关键词： femtosecond laser,microstructured silicon,chromium doping,infrared absorption
更新于2025-09-11 14:15:04
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Photoelectron Spectroscopy and Theoretical Study of Cr <sub/><i>n</i> </sub> Si <sub/> 15– <i>n</i> </sub><sup>–</sup> ( <i>n</i> = 1–3): Effects of Doping Cr Atoms on the Structural and Magnetic Properties
摘要： CrnSi15?n? (n = 1?3) clusters were investigated by using size-selected anion photoelectron spectroscopy combined with density functional theory calculations. The results show that the most stable structure of CrSi14? is of C2v symmetry with the Cr atom encapsulated in a Si14 cage which can be viewed as a boat-shaped Si10 unit capped by four additional silicon atoms. A large HOMO?LUMO gap of neutral CrSi14 is confirmed based on the photoelectron spectrum of CrSi14?. Cr2Si13? has two isomers nearly degenerate in energy: one can be characterized as one Si atom interacting with a Cr2Si12 hexagonal prism while the other can be viewed as one Si atom capping a distorted Cr2Si12 hexagonal antiprism. Cr3Si12? has a D6d symmetric wheel structure in which three Cr atoms form an axle surrounded by 12 Si atoms. The magnetic moments of CrSi14?, Cr2Si13?, and Cr3Si12? increase from 1 to 3 μB and then to 7 μB with the increasing number of Cr atoms in the clusters. The magnetic moments of Cr2Si13? and Cr3Si12? are mainly contributed by the surface Cr atoms.
关键词： Photoelectron spectroscopy,Silicon clusters,Chromium doping,Density functional theory,Magnetic properties
更新于2025-09-04 15:30:14