Investigating carbon materials for use as the electron emission source in a parallel electron-beam lithography system

A microelectronic parallel electron-beam lithography system using an array of field emitting microguns is currently being developed. This paper investigates the suitability of various carbon based materials for the electron source in this device, namely tetrahedrally bonded amorphous carbon (ta-C), nanoclustered carbon and carbon nanotubes. Ta-C was most easily integrated into a gated field emitter structure and various methods, such as plasma and heavy ion irradiation, were used to induce emission sites in the ta-C. However, the creation of such emission sites at desired locations appeared to be difficult/random in nature and thus the material was unsuitable for this application. In contrast, nanoclustered carbon material readily field emits with a high site density but the by-products from the deposition process create integration issues when using the material in a microelectronic gated structure. Carbon nanotubes are currently the most promising candidate for use as the emission source. We have developed a high yield and clean (amorphous carbon by-product free) PECVD process to deposit single free standing nanotubes at desired locations with exceptional uniformity in terms of nanotube height and diameter. Field emission from an array of nanotubes was also obtained. © 2001 Elsevier Science B.V.

1.36Tbit/s spectral slicing source based on a Cr4+:YAG femtosecond laser

We report a novel OTDM/WDM source based on spectral slicing of a passively mode-locked Cr4: YAG femtosecond pulse source. Total capacities up to 682Gbit/s and 1.36bit/s with spectral efficiencies of 0.2b/s/Hz and 0.4b/s/Hz have been achieved. © 2003 Optical Society of America.

A bone remodelling model coupling micro-damage growth and repair by 3D BMU-activity.

Bone as most of living tissues is able, during its entire lifetime, to adapt its internal microstructure and subsequently its associated mechanical properties to its specific mechanical and physiological environment in a process commonly known as bone remodelling. Bone is therefore continuously renewed and micro-damage, accumulated by fatigue or creep, is removed minimizing the risk of fracture. Nevertheless, bone is not always able to repair itself completely. Actually, if bone repairing function is slower than micro-damage accumulation, a type of bone fracture, usually known as "stress fracture", can finally evolve. In this paper, we propose a bone remodelling continuous model able to simulate micro-damage growth and repair in a coupled way and able therefore to predict the occurrence of "stress fractures". The biological bone remodelling process is modelled in terms of equations that describe the activity of basic multicellular units. The predicted results show a good correspondence with experimental and clinical data. For example, in disuse, bone porosity increases until an equilibrium situation is achieved. In overloading, bone porosity decreases unless the damage rate is so high that causes resorption or "stress fracture".