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Random Electric Field Instabilities of Relaxor Ferroelectrics

Guzmán Verri, Gian Giacomo; Arce Gamboa, José Rafael (2017-06-13)

Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the ...

Los albores de la física y el desarrollo de la meteorología en Costa Rica

Amador Astúa, Jorge Alberto (2002)

El siguiente artículo describe algunos aspectos del desarrollo de la física en Costa Rica, con énfasis en el siglo XIX. El trabajo está basado en una investigación bibliográfica de fuentes históricas, donde se compilaron ...

Algunas ideas para lograr un mayor desarrollo científico y tecnológico en Costa Rica

Fernández Rojas, Walter (2000)

El propósito de este capítulo, el cual está basado en el trabajo de Fernández y Páez (2000), es describir las actividades en Ciencias Espaciales que se están llevando a cabo en Costa Rica, estas actividades están centradas ...

Electronic structure of silicon-based nanostructures

Guzmán Verri, Gian Giacomo; Lew Yan Voon, Lok Chong (2007-08-30)

We have developed a unifying tight-binding Hamiltonian that can account for the electronic properties of recently proposed Si-based nanostructures, namely, Si graphene-like sheets and Si nanotubes. We considered the sp3s∗ ...

The 2:3:6 quasi-periodic oscillation structure in GRS 1915+105 and cubic subharmonics in the context of relativistic discoseismology

Ortega Rodríguez, Manuel; Solís Sánchez, Hugo; López Barquero, Vanessa; Matamoros Alvarado, Bryan; Venegas Li, Ariadna (Monthly Notices of the Royal Astronomical Society 440:3011-3015, 2014-06-01)

We propose a simple toy model to explain the 2:3:6 quasi-periodic oscillation (QPO) structure in GRS 1915+105 and, more generally, the 2:3 QPO structure in XTE J1550−564, GRO J1655−40 and H1743−322. The model exploits the ...

Large isotropic negative thermal expansion above a structural quantum phase transition

Handunkanda, Sahan U.; Curry, Erin B.; Voronov, Vladimir; Said, Ayman H.; Guzmán Verri, Gian Giacomo; Brierley, Richard T.; Littlewood, Peter B.; Hancock, Jason N. (2015-10-01)

Perovskite structured materials contain myriad tunable ordered phases of electronic and magnetic origin with proven technological importance and strong promise for a variety of energy solutions. An always-contributing ...

Why is the electrocaloric effect so small in ferroelectrics?

Guzmán Verri, Gian Giacomo; Littlewood, Peter B. (2016-05-19)

Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity ...

Stochastic approach to the smart quantum confinement model in porous silicon

Ramírez Porras, Arturo; Weisz, S.Z. (Surface Science 515 (2002) L509-L513, 2002)

A model that encompasses two approaches to explain the photoluminescence in p-type porous silicon is proposed. The model considers a stochastic distribution of nanocrystallite sizes within the porous matrix and explain the ...

Design and Characterization of a High Vacuum Metals Deposition System based on Electron Beam Evaporation

Ramírez Porras, Arturo; Avendaño Soto, Esteban Damián; Araya Pochet, José (2010-08-03)

We describe a high vacuum metals deposition system based ona variation of a pendant-drop type electron beam evaporator.This system uses a Molybdenum crucible as an evaporantinstead of a rod or wire usually used in ultrathin ...

Estimation of Silicon Nanocrystalline Sizes from Photoluminescence Measurements of RF Co-Sputtered Si/SiO2 Films

Ramírez Porras, Arturo; Fonseca, L. F.; Resto, O. (Materials Research Society Symposium Proceedings 737 (2003), 2003)

A stochastic distribution of nanocrystalline sizes model is applied to fit photoluminescence (PL) spectra of luminescent Si nanocrystals in a Si/SiO2 matrix synthesized by RF co-sputtering on the top of quartz substrates. ...