There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotube devices integrated into silicon technology.

https://science.sciencemag.org/content/sci/283/5401/512.full.pdf

Self-Oriented Regular Arrays of Carbon Nanotubes and Their Field Emission Properties

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

We demonstrate that a monolayer graphene membrane is impermeable to standard gases including helium. By applying a pressure difference across the membrane, we measure both the elastic constants and the mass of a single layer of graphene. This pressurized graphene membrane is the world's thinnest balloon and provides a unique separation barrier between 2 distinct regions that is only one atom thick.

/pdf/impermeable-atomic-membranes-from-graphene-sheets-xtis5huy2d.pdf

Impermeable atomic membranes from graphene sheets.

A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.

The structural and luminescence properties of porous silicon

Volume 84, Issue 21 Pages 8899-9654 Order Print Issue Editorial Analytical Chemistry: The Synergies between the Division and the Journal Jonathan V. Sweedler, David W. Koppenaal pp 8899–8899 Publication Date (Web): October 17, 2012 (Editorial) DOI: 10.1021/ac302945v Features 1-D and 2-D Photonic Crystals as Optical Methods for Amplifying Biomolecular Recognition Sudeshna Pal, Philippe M. Fauchet, and Benjamin L. Miller pp 8900–8908 Publication Date (Web): September 4, 2012 (Feature) DOI: 10.1021/ac3012945

/pdf/time-of-flight-secondary-ion-mass-spectrometry-based-4ay1qqv2ud.pdf

Time-of-Flight Secondary Ion Mass Spectrometry-Based Molecular Distribution Distinguishing Healthy and Osteoarthritic Human Cartilage

We have achieved 10.1% efficiency in a bulk porous polysilicon (PPS) solar cell in which the total thickness of the active layer was /spl sim/5 /spl mu/m. However, the removal of material from the active region of a solar cell during the etching process will limit its ultimate electrical efficiency. We have therefore started to investigate thin film PPS coatings that can be formed on the surface of a solar cell without disturbing the underlying junction characteristics. A systematic set of experiments specifically aimed at maximizing light trapping while maintaining the electrical properties of our devices is being conducted to improve our previous results. Substrates used in this investigation have included string ribbon grown polysilicon solar cells and thin film low-pressure chemical vapor deposited (LPCVD) polysilicon. The enhancement of light coupling into LPCVD polysilicon by incorporating a PPS layer has potential application in the development of thin film silicon solar cells on low cost substrates.

Porous silicon texturing of polysilicon substrates

Microcrystalline inclusions in hydrogenated and fluorinated amorphous silicongermanium alloys, α-Si, Ge:H, F, were studied. Microcrystals grown during RF or DC glow discharge deposition from SiF 4 , GeF 4 and H 2 consist of either pure Si or Ge. Microcrystals produced by thermal annealing of initially amorphous alloys are either microcrystalline Ge or microcrystalline Si-Ge alloys depending on the annealing temperature. Values for the grain size were calculated from X-ray diffraction (XRD) and Raman spectra. The grain size of the “grown” microcrystal ranges from 8 to 60 nm. These grown grains exhibit preferential orientation of the (220) planes parallel to the substrate surface. Microcrystals produced by high-temperature anneal are randomly oriented. Scanning electron micrographs of as-grown samples show protruding platelets several 100 nm long and several 10 nm wide. Fractured cross sections exhibit columnar structure.

Microcrystallinity in α-Si, Ge:H, F Alloys

In this work we study the role of fluorine for the selective suppression of porous silicon in localized SOI applications. The formation of porous silicon can be done selectively by controlling the Fermi level in areas to be etched or not etched, which is typically done by adjusting the level of doping. Implanted fluorine in silicon has demonstrated a donor effect upon annealing at low temperature (600 °C), which is reversible as the fluorine outdiffuses during higher temperature annealing (1100 °C). The investigated technique has been used to form crystalline silicon active regions with thickness less than 200 nm completely surrounded by oxidized porous silicon. The electronic integrity of the active area has also been established through nMOS transistor fabrication and characterization (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel technique for localized formation of SOI active regions

Devices made from silicon dominate the microelectronics industry, so silicon should be the material of choice for anyonc designing new electronic devices that will be integrated with microelectronic circuits. This also applies to the optoelectronic devices that act as gateways between the electronic realm and the worlds of photonics and optical communications. Most optoelectronic components such as waveguides and modulators can be made from silicon, but a completely silicon-based system has remained elusive because there is a crucial missing link: a silicon light source.

https://iopscience.iop.org/article/10.1088/2058-7058/14/2/24/pdf

Philippe M. Fauchet

Papers

Time-of-Flight Secondary Ion Mass Spectrometry-Based Molecular Distribution Distinguishing Healthy and Osteoarthritic Human Cartilage

Porous silicon texturing of polysilicon substrates

Microcrystallinity in α-Si, Ge:H, F Alloys

A novel technique for localized formation of SOI active regions

Silicon lasers start to take shape