Current research into semiconductor clusters is focused on the properties of quantum dots-fragments of semiconductor consisting of hundreds to many thousands of atoms-with the bulk bonding geometry and with surface states eliminated by enclosure in a material that has a larger band gap. Quantum dots exhibit strongly size-dependent optical and electrical properties. The ability to join the dots into complex assemblies creates many opportunities for scientific discovery.

Semiconductor Clusters, Nanocrystals, and Quantum Dots

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

Novel physical phenomena can emerge in low-dimensional nanomaterials. Bulk MoS2, a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS2 crystal is thinned to monolayer, however, a strong photoluminescence emerges, indicating an indirect to direct bandgap transition in this d-electron system. This observation shows that quantum confinement in layered d-electron materials like MoS2 provides new opportunities for engineering the electronic structure of matter at the nanoscale.

Emerging Photoluminescence in Monolayer MoS2

Bulk nanostructured materials from severe plastic deformation

Nanotechnology is a multidisciplinary field, which covers a vast and diverse array of devices derived from engineering, biology, physics and chemistry. These devices include nanovectors for the targeted delivery of anticancer drugs and imaging contrast agents. Nanowires and nanocantilever arrays are among the leading approaches under development for the early detection of precancerous and malignant lesions from biological fluids. These and other nanodevices can provide essential breakthroughs in the fight against cancer.

Cancer nanotechnology: opportunities and challenges.

Fabrication.- Formation Survey.- Porosity.- Structures & Forms.- Properties.- Property Survey.- Thermal.- Mechanical.- Transport.- Optical.- Electrical.- Magnetic.- Luminescent.- Chemical & Biochemical.- Characterization.- Structural.- Porosity.- Thermal.- Magnetic.- Chemical.- Biochemical.- Theoretical Techniques.- Irradiation.- Processessing.- Patterning.- Drying.- Epitaxy.- Thermal.- Impregnation.- Encapsulation.- Derivitization.- Particles.- Electrical Contacts.- Macroporous Silicon.- Applications.- Application Survey.- Electronic.- Microsystems.- Optics.- Acoustic.- Diagnostic.- Medical.- Energy Conversion.- Food & consumer Care.

Handbook of porous silicon

Porous silicon multilayer optical waveguides

The systematic study of band‐edge luminescence in pseudomorphic Si/Si1−xGex/Si double‐heterostructure layers is reported for a wide composition range, 0.12<x<0.24, for the first time. An analytical expression for the exciton energy gap at 4.2 K valid for x<0.24 is derived from the no‐phonon line energies: ESX(x) = 1.155−0.874x+0.376x2 eV. Addition of an expression for the exciton binding energy provides an approximation for the energy difference between the alloy valence band and the lowest conduction‐band edge at low temperature. An exciton upshift of 16.9 meV due to quantum confinement is observed in a 6.3‐nm Si0.83Ge0.17 alloy well. This is consistent with either type‐I or type‐II band alignment for which the conduction‐band offset has a magnitude ‖ΔEc‖ ≤ 10 meV. The excitonic hole is closely confined in the alloy but the spectra suggest that the electron density in the silicon barriers is increased for the thin layer.

Near‐band‐gap photoluminescence from pseudomorphic Si1−xGex single layers on silicon

THE preparation of highly porous materials by sol–gel processing followed by supercritical drying was pioneered by Kistler in 19311. These materials, called aerogels and comprising a void fraction of more than 90%, are currently a focus of technological interest2. Here we show that supercritical drying can be used to prepare highly porous silicon, a material of particular interest because of its luminescent properties3. Porous silicon is prepared conventionally by electrochemical etching, but using supercritical fluid extraction allows us to obtain porosities that would otherwise lead to collapse of the network during drying. Electron microscopy reveals that our materials have a crystalline, columnar structure, and gravimetric and ellipsometric analysis indicates that the porosity exceeds 95%. Our silicon aerocrystals exhibit strong photo-luminescence. We predict that supercritical drying should greatly improve those properties of porous silicon films that are critical for optoelectronic applications.

Leigh T. Canham

Papers

Handbook of porous silicon

Porous silicon multilayer optical waveguides

Near‐band‐gap photoluminescence from pseudomorphic Si1−xGex single layers on silicon

Luminescent anodized silicon aerocrystal networks prepared by supercritical drying

Derivatized Mesoporous Silicon with Dramatically Improved Stability in Simulated Human Blood Plasma