Infrared absorption by conical silicon microstructures made in a variety of background gases using femtosecond-laser pulses

Younkin, R.; Carey, James E.; Mazur, Eric; Levinson, Joshua A.; Friend, Cynthia M.

doi:10.1063/1.1545159

Cited by 226 publications

(119 citation statements)

References 11 publications

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“…Mazur and co-workers found previously that fs structuring must take place in the presence of sulfur to produce featureless, near-unity below-band gap absorption; structures formed in air or in vacuum do not absorb strongly at wavelengths longer than 1.1 m. 7,8 Likewise, ns-formed structures formed in air do not absorb at below-band gap wavelengths. Sulfur impurities in the structures therefore appear to be critical to the below-band gap absorption.…”

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confidence: 99%

Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon

Crouch

Carey

Warrender

et al. 2004

Applied Physics Letters

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194

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confidence: 99%

Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon

Crouch

Carey

Warrender

et al. 2004

Applied Physics Letters

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355

194

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“…Silicon hyperdoped with chalcogens exhibits strong sub-band gap absorption down to photon energies as low as 0.5 eV 5-11 , sparking substantial recent interest in applications such as infrared detection and intermediate band photovoltaics [5][6][7][8][9][10][11] . The successful fabrication of rectifying junctions 10 and photodiodes 11-13 using S and Se hyperdoped silicon appears to justify such interest.…”

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Insulator-to-Metal Transition in Selenium-Hyperdoped Silicon: Observation and Origin

et al. 2012

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Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band gap absorption arises from direct defect-to-conduction band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.Of all the experimentally measurable physical properties of materials, the electronic conductivity exhibits the largest variation, spanning a factor of 10 31 from the best metals to the strongest insulators 1 . Over the last century, the puzzle of why some materials are conductors and others insulators, and the mechanisms underlying the transformation from one to the other, have been carefully scrutinized; yet even after such a vast body of research over such a long period, the subject remains the object of controversy. In 1956, Mott introduced a model for the insulator-to-metal transition (IMT) in doped semiconductors, in which long-ranged electron correlations are the driving force 2 . Hyperdoping (doping beyond the solubility limit) creates a new materials playground to explore defect-mediated IMTs in semiconductors. In this letter, we identify a defect-induced IMT in silicon hyperdoped with selenium concentrations exceeding 10 20 cm −3(compared to the equilibrium solubility limit 3 of about 10 16 cm −3 ) and we explore the detailed nature of the transition with both experiment and computation. We find that the IMT is largely driven by electron correlation and most resembles a classic impurity-driven Mott transition. Additionally, we find that the high density of Se present at the IMT yields direct optical transitions and an absorption coefficient in excellent agreement with the measured sub-band gap optical properties 4 .Hyperdoping is currently being used to engineer new materials with unique and exotic properties. Silicon hyperdoped with chalcogens exhibits strong sub-band gap absorption down to photon energies as low as 0.5 eV 5-11 , sparking substantial recent interest in applications such as infrared detection and intermediate band photovoltaics [5][6][7][8][9][10][11] . The successful fabrication of rectifying junctions 10 and photodiodes 11-13 using S and Se hyperdoped silicon appears to justify such interest. While isolated S and Se dopants are well-established deep double donors in silicon 3,14 , the enhanced optical properties of hyperdoped silicon (in which these chalcogenic impurities are present at much higher concentrations) are not y...

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“…In 1998, Eric Mazur developed a method to fabricate a new kind of material, black silicon, by using femtosecond laser to irradiate the single crystal silicon in the presence of SF 6 [2]. Black silicon owns lots of advantages, such as high absorptance ([90%) [3], wide absorption spectrum ranging from 250 to 2,500 nm [4][5][6], which broadens the detecting spectrum of optical sensor to a great extent. Nanostructure of the black silicon has been the focus of intense interest in recent years due to their extensive device application and possibility of investigation on 1/f noise [7,8].…”

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confidence: 99%

Optical properties of black silicon prepared by wet etching

Zhao

et al. 2012

J Mater Sci: Mater Electron

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In this paper, the optical properties of black silicon have been studied. The black silicon samples were fabricated by alkaline etching and metal assisted etching. The micro-columns and nanopores on the silicon surface were obtained in KOH and Au-induced HF/H 2 O 2 solution, respectively. The height and diameter of micro-columns prepared by KOH etching is about 470 nm and 2 lm. In the Au-induced HF/H 2 O 2 etching, the metallic nuclei behave as a cathode and their surrounding area acts as an anode, resulting in nanopores with diameters ranging from 80 to 120 nm. These microstructures formed in the etching process directly affect the optical properties of black silicon such as reflectance, transmittance and absorptance. According to the measurement of integrating sphere detector, the absorptance of the black silicon produced by wet etching remains roughly 90% from 250 to 1,000 nm wavelength, which is almost 150% of the absorptance of conventional silicon. However, the reflectance of black silicon is less than 13% and the transmittance is less than 4%.

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Infrared absorption by conical silicon microstructures made in a variety of background gases using femtosecond-laser pulses

Cited by 226 publications

References 11 publications

Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon

Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon

Insulator-to-Metal Transition in Selenium-Hyperdoped Silicon: Observation and Origin

Optical properties of black silicon prepared by wet etching

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