Leigh T. Canham

Bio: Leigh T. Canham is an academic researcher from University of Birmingham. The author has contributed to research in topics: Porous silicon & Silicon. The author has an hindex of 42, co-authored 160 publications receiving 18268 citations. Previous affiliations of Leigh T. Canham include Defence Research Agency & Defence Science and Technology Laboratory.

Porous Silicon as an Educational Vehicle for Introducing Nanotechnology and Interdisciplinary Materials Science

Abstract: This paper describes why the authors view porous silicon (PSi) as an excellent vehicle for introducing university students to both basic and advanced materials science and engineering. Its ease of fabrication offers unique possibilities for university teachers to demonstrate nanoscale phenomena. Mechanical, physical, chemical and biological properties of PSi are amenable to laboratory tests employing a variety of modern but fairly standard characterization techniques. Its radically different behaviour from bulk silicon, but compatibility with VLSI technology, can be used to give students a taste of not only materials issues in electronics, but also optoelectronics, micro-optics, sensors, solar cells, micromachining, acoustics, medicine, biotechnology and even astrophysics! By way of an example, we analyze practical experience accumulated at the Technical University of Valencia during four years of teaching courses related with materials science. The introduction of PSi research into the curriculum has led to good synergy between theoretical aspects and practical studies, and has also improved personalization of studies where each student realizes their own nanostructure, and then has a choice of which material property and application area to delve into. Some prospects for future educational developments are then suggested.

Taste and mouthfeel assessment of porous and non-porous silicon microparticles

Abstract: Unlike the trace minerals iron, copper and zinc, the semiconductor silicon has not had its organoleptic properties assessed. Nanostructured silicon provides the nutrient orthosilicic acid through hydrolysis in the gastrointestinal tract and is a candidate for oral silicon supplements. Mesoporous silicon, a nanostructured material, is being assessed for both oral drug and nutrient delivery. Here we use taste panels to determine the taste threshold and taste descriptors of both solid and mesoporous silicon in water and chewing gum base. Comparisons are made with a metal salt (copper sulphate) and porous silica. We believe such data will provide useful benchmarks for likely consumer acceptability of silicon supplemented foodstuffs and beverages.

Determination of excitation profile and dielectric function spatial nonuniformity in porous silicon by using WKB approach

Abstract: We develop an analytical model based on the WKB approach to evaluate the experimental results of the femtosecond pump-probe measurements of the transmittance and reflectance obtained on thin membranes of porous silicon. The model allows us to retrieve a pump-induced nonuniform complex dielectric function change along the membrane depth. We show that the model fitting to the experimental data requires a minimal number of fitting parameters while still complying with the restriction imposed by the Kramers-Kronig relation. The developed model has a broad range of applications for experimental data analysis and practical implementation in the design of devices involving a spatially nonuniform dielectric function, such as in biosensing, wave-guiding, solar energy harvesting, photonics and electro-optical devices.

Gold nanoplasmonic particles in tunable porous silicon 3D scaffolds for ultra-low concentration detection by SERS.

Abstract: A composite material of plasmonic nanoparticles embedded in a scaffold of nano-porous silicon offers unmatched capabilities for use as a SERS substrate. The marriage of these components presents an exclusive combination of tightly focused amplification of Localised Surface Plasmon (LSP) fields inside the material with an extremely high surface-to-volume ratio. This provides favourable conditions for a single molecule or extremely low concentration detection by SERS. In this work the advantage of the composite is demonstrated by SERS detection of Methylene Blue at a concentration as low as a few picomolars. We systematically investigate the plasmonic properties of the material by imaging its morphology, establishing its composition and the effect on the LSP resonance optical spectra.

Exothermic phenomena and hazardous gas release during thermal oxidation of mesoporous silicon powders

Abstract: We report on the occurrence of exothermic phenomena during the thermal ramping of mesoporous silicon powders in ambient air. For furnace set temperatures of up to 800 °C, discrete exotherms occur during the initial ramp-up stage from room temperature. With an onset around 200 °C, the powder temperature rapidly self-elevates to significantly beyond the concurrent furnace baseline value and cools thereafter, in most cases over a period of a few minutes. A number of periodically spaced exotherms can occur, depending on both the weight and layout of the powder batch. A broadening and amalgamation of exotherms are observed for large batch sizes, indicating a longer-term retention of induced thermal energy, in one case with the powder temperature rising well beyond 1000 °C and being maintained for up to 80 min. We associate these exotherms with dehydrogenation processes, some of which may involve N–H as well as Si–H bonds. Oxidation is accompanied by the release of silanes and hydrogen, care therefore being required to avoid combustion of these pyrophoric gases.

Semiconductor Clusters, Nanocrystals, and Quantum Dots

Abstract: 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.

Dye-Sensitized Solar Cells

Abstract: 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 ...

Emerging Photoluminescence in Monolayer MoS2

Abstract: 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.

Cancer nanotechnology: opportunities and challenges.

Abstract: 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.