Armelles Reig, Gaspar; Ruiz, A.; Briones Fernández-Pola, Fernando; Recio Segoviano, Miguel
In this letter we report on Raman characterization of GaAs/GaP short period strained layer superlattices grown on GaAs (100) substrates by Atomic layer Molecular Beam Epitaxy (ALMBE). Confined optical phonons are observed in this highly strained system. The experimental results are compared with a calculation based on the equivalent wave-vector model. © 1989.
Martínez-Criado, G.; Martínez-Pastor, Juan; Cantarero, Andrés; Utzmeier, T.; Briones Fernández-Pola, Fernando
In this work we study the exciton recombination of InAs/InP self-organized quantum dots by means of photolumincscence (PL) as a function of temperature and excitation density. Well defined islands, spatially separated in most cases, and with different size distribution, make localized exciton recombination the dominant contribution to the PL spectrum. From our experimental results, we propose the co-existence of two types of islands, one with small height whose contribution to the PL spectra is important in samples with low InAs coverage (below two monolayers), and the properly 3D islands, whose dimensions and sheet concentration increase with the InAs coverage. Good...
Postigo, Pablo Aitor; García-Pérez, Fernando; Dotor, María Luisa; Golmayo, Dolores; Briones Fernández-Pola, Fernando
Undoped InP layers grown at low temperature by atomic layer molecular beam epitaxy have been studied by Hall measurements and deep level transient spectroscopy. The free carrier concentration at room temperature increases linearly with phosphorus pressure and it has been possible to obtain layers with a free carrier concentration of 1 × 1016 cm-3 and an electron mobility of about 3000 cm2 V-1 s-1, which are similar to values for samples grown at high temperatures. Deep level transient spectroscopy shows the presence, in all the samples, of five electron traps with emission energies of 0·60, 0·40, 0·25, 0·16, and 0·11...
Martin, J.; Campoy Quiles, Mariano; Nogales, Aurora; Garriga, M.; Alonso, M. I.; Goñi, Alejandro R.; Martín-González, Marisol S.
We study the structure of poly(3-hexylthiophene) (P3HT) subjected to nanoscale confinement in two dimensions (2D) as imposed by the rigid walls of nanopore anodic aluminum oxide (AAO) templates. P3HT nanowires with aspect ratios (length-to-diameter) above 1000 and diameters ranging between 15 nm and 350 nm are produced in the pores of the AAO templates via two processing routes. These are, namely, drying a solution or cooling from the melt. Our study focuses on the effects of nanoconfinement on the semicrystalline nature of the nanowires, the orientation of crystals, and the evolution of the structures that P3HT might develop under confinement,...
Ferrer, Juan Carlos; Peiró, F.; Cornet, A.; Morante, J. R.; Utzmeier, T.; Armelles Reig, Gaspar; Briones Fernández-Pola, Fernando
The growth evolution of capped InSb quantum dots grown on InP(001) substrates is reported for a range between 0.6 and 15 monolayers of InSb deposited by atomic layer molecular beam epitaxy. TEM studies have been performed in order to follow the progression in dot size and morphology. After the transition from an initial two-dimensional to a three-dimensional growth mode at 1.1 ML there is a range in which InSb nanometre scale islands are homogeneously distributed. Raman spectra have also been recorded to assess the effects of the introduction of the capping layer covering the islands, comparing the results with those...
Quintana Rodríguez, Carmen; Lancin, M.; Marhic, C.; Pérez, M.; Martin-Benito, J.; Avila, José; Carrascosa, José L.
Studies of crystallographic structure and composition of core nanocrystals of ferritin bound to aberrant tau filaments extracted from progressive supranuclear Palsy (PSP) and Alzheimer disease (AD) brain tissues were performed using high resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). The results were compared with those obtained from synthetic Fe3O4 crystal (magnetite) and horse spleen ferritin cores. Core dimensions of ferritin molecules from PSP and AD were similar to those found in normal brain. Ferritin cores nanocrystals in AD seems to have less ordered structure than in PSP. Some nanocrystals did not have the hexagonal ferrihydrite structure...
Gallego, J. M.; García Martínez, Jorge Manuel; Ortega, J. E.; Vázquez de Parga, A. L.; de la Figuera, Juan; Ocal, Carmen; Miranda, Rodolfo
6 páginas, 4 figuras.
Martínez, J. L.; Camarero, Julio; García Martínez, Jorge Manuel; Pastor, C. J.; Gallego, J. M.; Limones, C.; Prieto, J. E.; Vázquez de Parga, A. L.; de la Figuera, Juan; Ocal, Carmen; Miranda, Rodolfo
4 páginas, 3 figuras.