Volume 107, Issue 2, 15 January 2010
Index of content:
107(2010); http://dx.doi.org/10.1063/1.3294479View Description Hide Description
In many solids,diffusion of foreign atoms takes place primarily through highly mobile intermediate species that periodically exchange with atoms in the crystalline lattice. The governing reaction-diffusion equations include a diffusion coefficient as well as kinetic parameters describing the exchange of the intermediate species. Yet it is often convenient to model a diffusive process in terms of a single parameter, no matter what the time regime. This communication derives for a delta function initial profile an exact expression for the effective diffusivity that is valid in all time regimes. In the case of semiconductorsolids, such an expression can be helpful in the interpretation of dopantdiffusion measurements.
107(2010); http://dx.doi.org/10.1063/1.3291104View Description Hide Description
The efficiency of selective suppression of negative ions by photodetachment in a gas-filled radio frequency quadrupole ion cooler was investigated with a new detection method. A neodymiumdoped yttrium aluminum garnet laser beam at 1064 nm was used to remove ions in the radio frequency quadrupole cooler and the remaining ions were then probed by photodetachment and neutral particle detection. More than 99.99% suppression of the ions was observed. Under identical conditions, only 20% of a beam was suppressed. The results demonstrate that this isobar suppression technique can lead to nearly complete elimination of certain isobaric contaminants in negative ion beams, opening up new experimental possibilities in nuclear and atomic research and accelerator mass spectrometry.
107(2010); http://dx.doi.org/10.1063/1.3291115View Description Hide Description
An approach to control the interpore distances and nanopore diameters of 150-nm-thick thin aluminum films is reported here. The Al thin films were grown by sputtering on -type silicon substrate and anodized with a conventional anodization process in a phosphoric acid solution. It was found that interpore distance and pore diameter are related to the aluminum grain size and can be controlled by annealing. The grain contours limit the sizes of alumina cells. This mechanism is valid for grain sizes supporting only one alumina cell and consequently only one pore.
107(2010); http://dx.doi.org/10.1063/1.3294960View Description Hide Description
We report a technique to characterize adhesion of monolayered/multilayered graphene sheets on silicon wafer. Nanoparticles trapped at graphene-silicon interface act as point wedges to support axisymmetric blisters. Local adhesion strength is found by measuring the particle height and blister radius using a scanning electron microscope.Adhesion energy of the typical graphene-silicon interface is measured to be . The proposed method and our measurements provide insights in fabrication and reliability of microelectromechanical/nanoelectromechanical systems.