Because of their commercial availability in bulk single crystal form, the 6H- and 4H- polytypes of SiC are gaining importance for high-power, high-temperature, and high-frequency device applications. Selective area doping is a crucial processing step in integrated circuit manufacturing. In Si technology, selective area doping is accomplished by thermal diffusion or ion-implantation. Because of the low diffusion coefficients of most impurities in SiC, ion implantation is indispensable in SiC device manufacturing. In this paper the authors present their results on donor, acceptor, and compensation implants in 6H-SiC.

The latest ion-implantation results on SiC are presented. The authors have performed nitrogen and phosphorus (N/P) co-implantations to obtain very high n-type carrier concentrations, Si and C bombardments for compensating n-type SiC, and V-implantation for compensating p-type SiC. They have also performed N and Al implantations directly into V-doped semi-insulating 6H-SiC substrates. Vertical p-n junction diodes were made by selective area N, P, and N/P implantations into p-type epitaxial layers grown on 6H-SiC substrates.

To manage forests as ecosystems, the many values they hold for different users must be recognized, and they must be used so that those assets are not destroyed. Important ecosystem features of forests include nutrient cycling, habitat, succession, and water quality. Over time, the ways in which humans value forests have changed as forest uses have altered and as forests have declined in size and quality. Both ecosystem science and forest ecology have developed approaches that are useful to manage forests to retain their value. A historical perspective shows how changes in ecology, legislation, and technology have resulted in modern forest-management practices. However, current forest practices are still a decade or so behind current ecosystem science. Ecologists have done a good job of transferring their theories and approaches to the forest manager classroom but have done a poor job of translating these concepts into practice. Thus, the future for ecosystem management requires a closer linkage between ecologists and other disciplines. For example, the changing ways in which humans value forests are the primary determinant of forest-management policies. Therefore, if ecologists are to understand how ecosystem science can influence these policies, they must work closely with social scientists trained to assess …

Hydrocodes or more accurately, shock physics analysis packages, have been widely used in the US Department of Energy (DOE) laboratories and elsewhere around the world for over 30 years. Initial applications included weapons effects studies where the pressure levels were high enough to disregard the material strength, hence the term hydrocode. Over the last 30 years, Sandia has worked extensively to develop and apply advanced hydrocodes to armor/anti-armor interactions, warhead design, high explosive initiation, and nuclear weapon safety issues. The needs of the DOE have changed over the last 30 years, especially over the last decade. A much stronger emphasis is currently placed on the details of material deformation and high explosive initiation phenomena. The hydrocodes of 30 years ago have now evolved into sophisticated analysis tools that can replace testing in some situations and complement it in all situations. A brief history of the development of hydrocodes in the US will be given. The author also discusses and compares the four principal methods in use today for the solution of the conservation equations of mass, momentum, and energy for shock physics applications. The techniques discussed are the Eulerian methods currently employed by the Sandia multi-dimensional shock physics analysis package …