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

Films consisting of nanometer-scale silicon crystals with narrow size distribution can be fabricated using a variety of techniques and are of technological interest for nonvolatile semiconductor memory applications One fabrication technique based on the crystallization of thin amorphous silicon films also shows potential for large-scale production of single isolated nanocrystals for future single-electron transistor and memory applications A review of the most promising nanocrystalline silicon fabrication techniques and a discussion of current research in the area of crystallized thin-film amorphous silicon are presented in this article

The development of nanocrystalline silicon for emerging microelectronic and nanoelectronic applications

Using a subpicosecond electro-optic sampling technique, we have characterized the photoresponse of current-biased YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) photodetectors, designed as 5-/spl mu/m-wide and 7-/spl mu/m-long microbridges patterned in 100-nm-thick, high-quality epitaxial films grown on LaAlO/sub 3/ substrates by pulsed laser deposition. The bridges were centered in a coplanar waveguide structure, allowing the photogenerated pulses to be measured 20 /spl mu/m from the detector. The experiments were conducted in the temperature range between 20 and 80 K; however, the bridges were biased in the switched (resistive) state, which corresponded to a hot-spot formation at the center of the microbridge. The photoresponse from 100-fs laser pulses (395-nm wavelength) was measured to be in the form of a single spike with the width as short as 1.3 ps. The physical origin of this ultrafast response is attributed to nonequilibrium electron heating, We extracted the intrinsic temporal parameters of the YBCO response-the electron thermalization time equal to 0.56 ps and electron-phonon energy relaxation time equal to 1.1 ps, Our measurements demonstrate that a simple YBCO microbridge can operate as a >100-GHz bandwidth photodetector, e.g., as an optical-to-electrical transducer for optoelectronic interface in YBCO digital electronics.

YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin-film picosecond photoresponse in the resistive state

We report temporal shaping of few-cycle terahertz pulses, using a slit in a conductive screen as a high-pass filter. The filter’s cutoff frequency was tuned by changing the width of the slit; the slope of the cutoff transition was altered by changing the thickness of the screen. We measured the transmission function of the filters, using large-aperture photoconducting antennas to create and detect the incident and transmitted electric field. Our experimental results were in excellent agreement with the performed finite-difference time-domain simulations of the propagation of the pulse through the slit. When the screen thickness was greater than the slit width, the filter was well modeled by a short, planar waveguide. Using a simple transfer function, we accurately describe the sharp cutoff and dispersion of such a filter. © 1997 Optical Society of America Recently terahertz (THz) pulses have proved useful for a wide variety of applications, including far-infrared 1 / time-domain spectroscopy, 2 study and control of Rydberg atoms, 3 T-ray imaging of optically opaque materials, 4 and impulse-ranging studies. 5 Applications exploit the features of THz pulses that distinguish them from optical pulses, namely their broad bandwidth and long center wavelength. The broad bandwidth allows for the exciting possibility for sculpting the pulses to meet a desired goal by modifying their spectra. Although shaped THz pulses have been made by modifying the optical pump intensity profile 6 or by manufacturing more complex emitters, 7 there are

Spatiotemporal Shaping of Terahertz Pulses

Ordering and self-organized growth of Si in the Si/SiO2 superlattice system

Porous silicon (PSi) multilayer structures are used in Si- based optoelectronic devices which exhibit interesting optical and electrical properties Integration of these structure can be achieved either passively or actively Passive elements include high reflectivity mirrors and optical filters with a maximum reflectivity peak approximately 100% The benefit of adding a multilayer mirror below a luminescent PSi film is to reduce the amount of light absorbed by the silicon substrate and increase the light output Placing two multilayer mirrors in between a highly luminescent PSi film creates an active microcavity resonator structure in which a significant photoluminescence and electroluminescence line narrowing (FWHM less than or equal to 20 nm) is observed A detailed study on the passive and active roles of PSi multilayer structures is presented in a device configuration

Philippe M. Fauchet

Papers

The development of nanocrystalline silicon for emerging microelectronic and nanoelectronic applications

YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin-film picosecond photoresponse in the resistive state

Spatiotemporal Shaping of Terahertz Pulses

Ordering and self-organized growth of Si in the Si/SiO2 superlattice system

Silicon interference filters and Bragg reflectors for active and passive integrated optoelectronic components