Carrier and Light Trapping in Graded Quantum Well Laser Structures

We investigated the carrier and light trapping in GaInAs/AlGaAs single quantum well laser structures by means of time resolved photoluminescence and Raman spectroscopy. The influence of the shape and depth of the confinement potential and of the cavity geometry was studied by using different AlGaAs/GaAs short-period superlattices as barriers. Our results show that grading the optical cavity improves considerably both carrier and light trapping in the quantum well, and that the trapping efficiency is enhanced by increasing the graded confining potential.Comment: PDF-format, 15 pages (including 4 figures), Applied Physics Letters (June 2000

Low-noise polymeric nanomechanical biosensors

A sensor device based on a single polymer cantilever and optical readout has been developed for detection of molecular recognition reactions without the need of a reference cantilever for subtraction of unspecific signals. Microcantilevers have been fabricated in the photoresist SU-8 with one surface passivated with a thin fluorocarbon layer. The SU-8 surface is sensitized with biological receptors by applying silanization methods, whereas the fluorocarbon surface remains inert to these processes. The thermal and mechanical properties of the chosen materials allow overcoming the main limitations of gold-coated silicon cantilevers: the temperature, pH, and ionic strength cross sensitivities. This is demonstrated by comparing the response of SU-8 cantilevers and that of gold-coated silicon nitride cantilevers to variations in temperature and pH. The sensitivity of the developed polymeric nanomechanical sensor is demonstrated by real-time detection of the human growth hormone with sensitivity in differential surface stress of about 1 mN/m.The authors acknowledge J. M. Rodríguez-Prado and M. Mellado for providing reagents for the molecular recognition experiments and J. Treviño, E. Mauriz, and D. Haefliger for fruitful discussion. J.T. and M.C. acknowledge financial support from the Spanish Ministry of Science (MERG-CT-2004- 510638) and the European Union (GEN2001-4856-C13-11).Peer reviewe

Valdeande, a dos leguas de camino de "Clunia". Novedades epigráficas

Abordamos el estudio de dos inscripciones ya conocidas, de las que damos nueva lectura e interpretación, y apuntamos su posible relación con Clunia. Asimismo, editamos otras tres piezas inéditas y tres grafitos hallados todos ellos en Valdeande (Burgos).In this paper, we present a new interpretation about the study of two known Latin inscriptions from Valdeande (Burgos), developing a new meaning of them and establishing a potential link with Clunia. In addition, we show three unpublished pieces and three graffities, all of them found in Valdeande (Burgos)

Periodically rippled graphene: growth and spatially resolved electronic structure

We studied the growth of an epitaxial graphene monolayer on Ru(0001). The graphene monolayer covers uniformly the Ru substrate over lateral distances larger than several microns reproducing the structural defects of the Ru substrate. The graphene is rippled with a periodicity dictated by the difference in lattice parameter between C and Ru. The theoretical model predict inhomogeneities in the electronic structure. This is confirmed by measurements in real space by means of scanning tunnelling spectroscopy. We observe electron pockets at the higher parts of the ripples.Comment: 5 page