Volume 96, Issue 4, 15 August 2004
Index of content:
96(2004); http://dx.doi.org/10.1063/1.1774255View Description Hide Description
We investigate transport through thin epitaxial GaAs(001) barriers sandwiched between polycrystalline iron films. Apart from a pronounced tunnelingmagnetoresistance effect at low magnetic fields, we observe a distinct negative magnetoresistance(MR) at low and a positive MR at higher temperatures. We show that the negative MR contribution is only observed for the ferromagneticiron contacts but is absent if iron is replaced by copper or gold electrodes. Possible explanations of the negative MR involve suppression of spin-flip scattering or Zeeman splitting of the tunneling barrier, but neither of these explanations is fully consistent with the data.
96(2004); http://dx.doi.org/10.1063/1.1765853View Description Hide Description
We report Raman spectra of a single layer of silicon nanoparticles, spatially ordered in at a tunneling distance from a silicon substrate. This is achieved by exploiting effects which enhance the nanocrystal signal, while suppressing the substrate one. The method is applied to investigate the structure of ion-implantation-produced nanoparticles annealed under different conditions. The results, which are in good agreement with transmission electron microscopy data, are used to explain photoluminescence measurements.
96(2004); http://dx.doi.org/10.1063/1.1771472View Description Hide Description
Electron paramagnetic resonance(EPR) was used to study the annealing behavior of the positively charged carbonvacancy ( center) in electron-irradiated . At the EPR signal of the defect starts decreasing gradually. Clear ligand hyperfine structure is still observed after annealing at , while the central line can be detected after a anneal. A similar annealing behavior was also observed for the center suggesting that this defect may be also the positively charged carbonvacancy but at the hexagonal lattice site.
Comment on “Infrared spectra and second-harmonic generation in barium strontium titanate and lead zirconate titanate thin films: ‘Polaron’ artifacts” [J. Appl. Phys.94, 3333 (2003)]96(2004); http://dx.doi.org/10.1063/1.1773916View Description Hide Description
Scott et al. [Scott et al., J. Appl. Phys.94, 3333 (2003)] have questioned our measurements of the optical absorption of amorphous tungsten oxide, and have suggested that the polaronabsorption might be an artifact due to interference effects. In this comment we point out that we obtained the absorption coefficient from measurements of both the transmittance and the reflectance of thin filmsdeposited on transparent substrates. By this method the “true” absorption is easily obtained.
Response to “Comment on ‘Infrared and second harmonic generation in barium strontium titanate and lead zirconate titanate thin films: ‘Polaron' artifacts’ ” [J. Appl. Phys.96, 2409 (2004)]96(2004); http://dx.doi.org/10.1063/1.1773917View Description Hide Description
Several authors have recently interpreted infrared features in the region of the spectra of perovskite-family oxides as polarons or as plasmons; our view is that without measurements on different film thicknesses and∕or quantitative fits to linewidths and lineshapes, these features may be optical artifacts.