Volume 31, Issue 5, September 2013
Index of content:
31(2013); http://dx.doi.org/10.1116/1.4813687View Description Hide Description
The family of III-V nitride semiconductors has garnered significant research attention over the last 20–25 years, and these efforts have led to many highly successful technologies, especially in the area of light emitting devices such as light emitting diodes for solid state white lighting and lasers for high density optical read/write memories. These applications have taken advantage of a key material property of the III-N materials, namely a direct, tunable (0.7–6.2 eV, λ ∼ 200 nm to 1.7 μm) bandgap and have been accomplished despite a relatively poor level of material quality. But a direct, tunable bandgap is only one of many interesting properties of III-N materials of interest to potential future technologies. A considerable list of first and second order properties make this family of semiconductors even more attractive—namely, electric polarization, piezoelectricity, high breakdown field, pyroelectricity, electro-optic and photo-elastic effects, etc. The first few of these have found much utility in the development of high power transistors that promise significant commercial success in both communications and power switching applications. As these areas begin to flourish, it is reasonable to begin to explore what might be next for this versatile family of semiconductors. Here are highlighted three areas of significant potential for future III-N research—atomic layer epitaxy of complex heterostructures, variable polarity homo- and hetero-structures of arbitrary geometries, and nanowire heterostructures. Early results, key technical challenges, and the ultimate potential for future technologies are highlighted for each research path.
31(2013); http://dx.doi.org/10.1116/1.4809747View Description Hide Description
Since its initial development in the early 1970s, spectroscopic ellipsometry (SE) has become the primary technique for determining optical properties of materials. In addition to the other historic role of ellipsometry, determining film thicknesses, SE is now widely used to obtain intrinsic and structural properties of homogeneous and inhomogeneous materials in bulk and thin-film form, including properties of surfaces and interfaces. Its nondestructive capability for determining critical dimensions has made SE indispensible in integrated-circuits technology. The present work is aimed at those who are unfamiliar with SE but may feel that it could provide useful information in specific situations. Accordingly, the author gives some background and basic theory, and then illustrates capabilities with various applications. Coverage of the topic is necessarily limited, but references to more complete treatments are provided.
31(2013); http://dx.doi.org/10.1116/1.4816262View Description Hide Description
Electrical energy storage is a challenging and pivotal piece of the global energy challenge—the “currency” of the energy economy. The opportunity that nanostructures present for advances in storage, recognized two decades ago, has been substantially bolstered by profound advances in nanoscale science and technology, so that a next generation energy storage technology is in sight. The authors present a perspective on the science issues and technology challenges accompanying this vision, focused primarily on the issues as exemplified by lithium ion batteries and made amenable to science through precision heterogeneous nanostructures. The authors address the synthesis and characterization of heterogeneous nanostructures, architectural designs, and recent results, as well as the scientific and technological challenges of integrating dense arrays of nanostructures for a viable technology.