Low-temperature specific heat anomalies in the group V transition metals

Anomalies previously reported in the specific heat curve of normal-state niobium at 3 and 9.5 K prompted new measurements on single crystals of niobium, tantalum, and vanadium from their superconductingT _c 's up to 20 K. The upper anomaly was confirmed in Nb and found to occur at 10.3 K. At this temperature theC/T vs. T ² curve changed abruptly from a line with constants ₂ =7.67 mJ/K ² mole and ₂ =241 K to one with ₃ =9.16 mJ/K ² mole and ₃ =250 K. The NbT _c was 9.275 K. Anomalies similar to that occurring at 3 K in the niobium curve were discovered to exist in tantalum and vanadium as well, but at the higher temperatures of 7.19 and 7.47 K, respectively. The tantalum data yielded line constants of ₁ =5.42 mJ/K mole, ₁ =238 K, ₂ =4.36 mJ/K ² mole, and ₂ =228 K and aT _c of 4.475 K. For vanadium ₁ =397 K is higher than previous specific heat values of ₁ =382 K, and in agreement with that obtained from elastic constant measurements (399 K). The discontinuities in the slopes of the specific heat curves are analyzed in terms of anomalies in the electron and phonon spectra of the materials investigated.     

Theory and applications of near ballistic transport insemiconductors

A review of electronic transport in semiconductors in the near ballistic regime is presented. Recent experiments and theories are discussed in detail. It is shown that the basic physics of ballistic transport is qualitatively well understood. Quantitatively much work remains to be done, especially with respect to device applications. Some problems related to applications are discussed in context with hot-electron- and high-electron-mobility-transistors     

Approaching the quantum limit

The knowledge of the wavelike behavior of electrons that emerges as technology drives semiconductor geometries deeper into the nanometer domain is described. How the underlying size quantization effects restrict the scaling down of device dimensions is explained. Studies underway to explore and understand these phenomena are reviewed. Ways in which they can be exploited in new types of device are explored, alone with the fabrication problems attending such applications     

Application of quantum-based devices: trends and challenges

Revolutionary nanofabrication techniques and trends have opened the way to fabricating quantum wells, quantum wires and quantum dots that may provide the basic building blocks for future nanoelectronic and mesoscopic (quantum) device technologies. Furthermore, these trends lead to new opportunities for realizing quantum-based information processing devices but many challenges must be addressed and intensive international basic research is essential for the full exploitation of these revolutionary devices