Ross Lockwood

Silicon Nanocrystals: Fundamental Theory and Implications for Stimulated Emission

Silicon nanocrystals (NCs) represent one of the most promising material systems for light emission applications in microphotonics. In recent years, several groups have reported on the observation of optical gain or stimulated emission in silicon NCs or in porous silicon (PSi). These results suggest that silicon-NC-based waveguide amplifiers or silicon lasers are achievable. However, in order to obtain clear and reproducible evidence of stimulated emission, it is necessary to understand the physical mechanisms at work in the light emission process. In this paper, we report on the detailed theoretical aspects of the energy levels and recombination rates in doped and undoped Si NCs, and we discuss the effects of energy transfer mechanisms. The theoretical calculations are extended toward computational simulations of ensembles of interacting nanocrystals. We will show that inhomogeneous broadening and energy transfer remain significant problems that must be overcome in order to improve the gain profile and to minimize nonradiative effects. Finally, we suggest means by which these objectives may be achieved.

Bridging the gap between the technological singularity and mainstream medicine : highlighting a course on technology and the future of medicine

The “technological singularity” is forecasted to occur in the mid-21st century and is defined as the point when machines will become smarter than humans and thus trigger the merging of humans and machines. It is hypothesized that this will have a profound influence on medicine and population health. This paper describes a new course entitled “Technology and the Future of Medicine” developed by a multi-disciplinary group of experts. The course began as a continuing medical education course and then transitioned to an accredited graduate-level course. We describe the philosophy of the course and the innovative solutions to the barriers that were encountered, with a focus on YouTube audience retention analytics. Our experience may provide a useful template for others.

A convenient method for electron tomography sample preparation using a focused ion beam

Here we report a new sample preparation method for three‐dimensional electron tomography. The method uses the standard film deposition and focused ion beam (FIB) methods to significantly reduce the problems arising from the projected sample thickness at high tilt angles. The method can be used to prepare tomography samples that can be imaged up to a ±75° tilt range which is sufficient for many practical applications. The method can minimize the problem of Ga+ contamination, as compared to the case of FIB preparation of rod‐shaped samples, and provides extended thin regions for standard 2D projection analyses. Microsc. Res. Tech. 75:1165–1169, 2012.

Electron tunneling in ensembles of silicon nanocrystals

Results from our calculations of the electron tunneling rates between silicon nanocrystals are presented. It is shown that tunnel transitions can be more efficient than radiative interband recombination and substantially influence emission in ensembles of silicon nanocrystals.