Subnanosecond spectral diffusion of a single quantum dot in a nanowire

We have studied spectral diffusion of the photoluminescence of a single CdSe quantum dot inserted in a ZnSe nanowire. We have measured the characteristic diffusion time as a function of pumping power and temperature using a recently developed technique [G. Sallen et al, Nature Photon. \textbf{4}, 696 (2010)] that offers subnanosecond resolution. These data are consistent with a model where only a \emph{single} carrier wanders around in traps located in the vicinity of the quantum dot

Subnanosecond spectral diffusion measurement using photon correlation

Spectral diffusion is a result of random spectral jumps of a narrow line as a result of a fluctuating environment. It is an important issue in spectroscopy, because the observed spectral broadening prevents access to the intrinsic line properties. However, its characteristic parameters provide local information on the environment of a light emitter embedded in a solid matrix, or moving within a fluid, leading to numerous applications in physics and biology. We present a new experimental technique for measuring spectral diffusion based on photon correlations within a spectral line. Autocorrelation on half of the line and cross-correlation between the two halves give a quantitative value of the spectral diffusion time, with a resolution only limited by the correlation set-up. We have measured spectral diffusion of the photoluminescence of a single light emitter with a time resolution of 90 ps, exceeding by four orders of magnitude the best resolution reported to date

Defect-free ZnSe nanowire and nano-needle nanostructures

We report on the growth of ZnSe nanowires and nano-needles using molecular beam epitaxy (MBE). Different growth regimes were found, depending on growth temperature and the Zn--Se flux ratio. By employing a combined MBE growth of nanowires and nano-needles without any post-processing of the sample, we achieved an efficient suppression of stacking fault defects. This is confirmed by transmission electron microscopy and by photoluminescence studies.Comment: 4 pages, 4 figure

Photon correlation spectroscopy on a single quantum dot embedded in a nanowire

We have observed strong photoluminescence from a single CdSe quantum dot embedded in a ZnSe nanowire. Exciton, biexciton and charged exciton lines have been identified unambiguously using photon correlation spectroscopy. This technique has provided a detailed picture of the dynamics of this new system. This type of semi conducting quantum dot turns out to be a very efficient single photon source in the visible. Its particular growth technique opens new possibilities as compared to the usual self-asssembled quantum dots

Dark exciton optical spectroscopy of a semiconducting quantum dot embedded in a nanowire

Photoluminescence of a single CdSe quantum dot embedded in a ZnSe nanowire has been investigated. It has been found that the dark exciton has a strong influence on the optical properties. The most visible influence is the strongly reduced excitonic emission compared to the biexcitonic one. Temperature dependent lifetime measurements have allowed us to measure a large splitting of $\Delta E = 6$ meV between the dark and the bright exciton as well as the spin flip rates between these two states

Insertion of CdSe quantumdots in ZnSe nanowires : MBE growth and microstructure analysis

ZnSe nanowire growth has been successfully achieved on ZnSe (100) and (111)B buffer layers deposited on GaAs substrates. Cubic [100] oriented ZnSe nanowires or [0001] oriented hexagonal NWs are obtained on (100) substrates while [111] oriented cubic mixed with [0001] oriented hexagonal regions are obtained on (111)B substrates. Most of the NWs are perpendicular to the surface in the last case. CdSe quantum dots were successfully incorporated in the ZnSe NWs as demonstrated by transmission electron microscopy, energy filtered TEM and high angle annular dark field scanning TEM measurements

Eternamente joven

Eternamente jove

Aniversario: La Tribu, a los 20

Graffitis, periódicos, fanzines, televisoras, radio, páginas, blogs, son a veces medios, a veces espacios que andan esos caminos ya sea para hacer contra información, periodismo ciudadano activismo mediático, comunicación contra-hegemónica, popular, comunitaria, alternativa, libre. La TRIBU es una radio alternativa creada en Buenos Aires (1989),en ese momento era un refugio, un espacio donde afirmar una identidad (la de la resistencia al sistema triunfante, la de la heterogeneidad frente a la uniformización que genera el mercado). Remarca que lo comunitario es una organización distinta a la existente, pues tiene como centro a la gente, a la realidad, a su contexto social, así como geográfico. Lo comunitario es lo ciudadano, porque les interesa a todos. En América Latina la comunicación alternativa alimenta su utopía, de territorios múltiples liberándose de las leyes del beneficio y la acumulación de un mundo sin espectáculos

Programa Puente Uno. 7 de abril de 2013. Héctor Sejenovich charla en Puente Uno sobre la crisis ambiental. Parte II

Inundaciones en La Plata ¿era previsible? ¿Fue un fenómeno meteorológico o fue la consecuencia de un planeamiento urbano que respondió a las necesidad de un negocio? Héctor Sejenovich, economista, especialista en medio ambiente, profesor de Economía, Sociedad y Ambiente en la Universidad de Buenos Aires, Luján y de Montevideo, nos habla sobre las consecuencias del cambio climático, la relación que hay entre la economía y el cuidado del medio ambiente, y sobre el impacto ambiental que conlleva el actual modelo productivo

Programa Puente Uno. 8 de marzo de 2013. Cecilia Todd en Puente Uno

Cecilia Todd, cantante y militante de la cultura popular venezolana cuenta las transformaciones en materia de políticas culturales que se han producido bajo la presidencia de Cháve