Volume 97, Issue 1, 01 January 2005
Index of content:
97(2005); http://dx.doi.org/10.1063/1.1829395View Description Hide Description
We report on optical absorption,fluorescence, and time-resolved fluorescencemeasurements in Dominican ambers. The “blue” variety reveals an intense fluorescence emission in the visible wavelength region, between 430 and , with spectral features typical of aromatic hydrocarbons. On the contrary, the “red” and “yellow” varieties have a much weaker and featureless emission. The data for blue amber, including fluorescence lifetime, allow the identification of perylene as the compound responsible for its distinctive showy fluorescence.
97(2005); http://dx.doi.org/10.1063/1.1808473View Description Hide Description
We have grown composite epitaxial materials consisting of layers of semimetallic ErAs nanoparticles embedded in a semiconducting matrix. Although the addition of ErAs particles into the InGaAs matrix increases the free-electron concentration, compensation of these free electrons is possible by depleting electrons from the metal particles through Be acceptor doping of the semiconductor. The room-temperature electron concentration of an ErAs:InGaAs superlattice sample with 0.05 monolayer ErAs per layer can be reduced by by delta-doping the ErAs layers with of Be. The highest resistivity measured for a Be-doped ErAs:InGaAs superlattice was .
97(2005); http://dx.doi.org/10.1063/1.1826212View Description Hide Description
We have investigated the relationship between perpendicular magnetic anisotropy (PMA) and the magnetoelasticeffect of epitaxialsuperlattices as a large mismatch system and found the PMA for the thin Co layer to be less than . The magnitude of the PMA is comparable to those of typical PMA systems such as and . By taking account of the Co-thickness-dependent magnetoelasticanisotropy, arising from the lattice strain due to the 7% mismatch between Co and Rh, we found that the thickness-dependent PMA can be reproduced with no adjustable parameter.
97(2005); http://dx.doi.org/10.1063/1.1821632View Description Hide Description
The buildup process of an electron’s probability in a quantum dot coupled to two conducting leads is studied in the regime of strong electron–phonon interaction. Initially the electron occupies an eigenstate in one of the conducting leads. An analytical expression is obtained for the time dependence of the electron’s probability in the quantum dot using the Green’s-function technique. A significant enhancement in the buildup rate is found when there are phonons in the quantum dot at the beginning of the tunneling process. Strong enhancement is found when the electron energy equals the zero-phonon resonant tunneling peak. Speed enhancement in resonant tunneling devices can be achieved by using properly designed quantum dot structures.
Flexural strength of diamond: Comparison of nanocrystalline thin films, massive chemical vapor deposits, and natural single crystals97(2005); http://dx.doi.org/10.1063/1.1826211View Description Hide Description
The recently published fracture-strength data [H. Espinosa, B. Peng, B. Prorok, N. Moldovan, O. Auciello, J. Carlisle, D. Gruen, and D. Mancini, J. Appl. Phys.94, 6076 (2003)] for ultrananocrystalline diamond(UNCD)thin films throw valuable light on the strength performance of synthetic polycrystalline diamonds. On performing a Weibull statistical analysis that takes into account the impact of the stressed area on measured stresses at fracture, we find the following. (a) The characteristic strength—the effective strength of a uniformly stressed area—of microseeded UNCD membranes is and comparable to the strength of massive chemically vapor-deposited diamonds. (b) The characteristic strength of nanoseeded UNCD membranes is , which points to strength characteristics similar to those of single-crystaldiamond.