ultrahigh-density-array-vertically-aligned-small-molecular-organic

Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

In  recent years &pi;-conjugated  organic semiconductors have emerged as the active material in a number of  diverse applications including large-area, ...

University of Alberta

We report experimental study of spin transport in all metal nanowire spin valve structures. The nanowires have a diameter of 50 nm and consist of three layers--cobalt, copper, and nickel. Based on the experimental observations, we determine that the primary spin relaxation mechanism in the paramagnet layer--copper--is the Elliott-Yafet mode associated with elastic scattering caused by charged states on the surface of the nanowires. This mode is overwhelmingly dominant over all other modes, so that we are able to study the pure Elliott-Yafet mechanism in isolation. We deduce that the spin diffusion length associated with this mechanism is about 16 nm in our nanowires and is fairly temperature independent in the range 1-100 K, which is consistent with the spin relaxation being associated with elastic scattering by surface states. The corresponding spin relaxation time is about 100 femtoseconds. We also find that the spin relaxation rate is fairly independent of the electric field driving the current in the field range 0.3-3 kV/cm.

Spin transport in self assembled all-metal nanowire spin valves: a study of the pure Elliott-Yafet mechanism.

Nous rapportons une &eacute;tude exp&eacute;rimentale du transport de spin dans toutes les structures de soupape spin de nanofils m&eacute;talliques. Les nanofils ont un diam&egrave;tre de 50 nm et se composent de trois couches : cobalt, cuivre et nickel. Bas&eacute; sur les observations exp&eacute;rimentales, nous d&eacute;terminons que le m&eacute;canisme de relaxation spin primaire dans la couche d&#39;existence--cuivre--est le mode de Elliott-Raphael associ&eacute; de diffusion &eacute;lastique caus&eacute;e par des &Eacute;tats charg&eacute;s sur la surface des nanofils. Ce mode est largement dominant sur tous les autres modes, afin que nous soyons en mesure d&#39;&eacute;tudier le m&eacute;canisme d&#39;Elliott-mohamed amine pur dans l&#39;isolement. On en d&eacute;duit que la longueur de diffusion de spin associ&eacute;e &agrave; ce m&eacute;canisme est environ de 16 nm dans notre nanofils et assez la temp&eacute;rature ind&eacute;pendante dans la gamme 1-100 K, qui est compatible avec la relaxation de spin &eacute;tant associ&eacute;e &agrave; une diffusion &eacute;lastique par les &Eacute;tats de surface. Le temps de relaxation spin correspondant est environ 100 femtosecondes. Nous constatons &eacute;galement que le taux de relaxation spin est relativement ind&eacute;pendant du champ &eacute;lectrique conduisant le courant dans le champ plage de 0,3 &agrave; 3 kV/cm.

Transport de spin dans soi assembl&eacute; tout m&eacute;tal NANOFIL vannes de spin : une &eacute;tude du m&eacute;canisme Elliott-mohamed amine pure.

Riportiamo studio sperimentale di trasporto di rotazione in tutte le strutture di metallo nanofilo spin valvola. I nanofili hanno un diametro di 50 nm e sono costituiti da tre strati - cobalto, rame e nichel. Basato su osservazioni sperimentali, determiniamo che il meccanismo di rilassamento di spin primario nello strato paramagnete - rame - &egrave; la modalit&agrave; di Elliott-Yafet associata scattering elastico causato dagli Stati di caricati sulla superficie dei nanofili. Questa modalit&agrave; &egrave; dominante sopra tutte le altre modalit&agrave;, in modo che siamo in grado di studiare il meccanismo di Elliott-Yafet puro in isolamento. Si deduce che la lunghezza di diffusione spin associata a questo meccanismo &egrave; di circa 16 nm nel nostro nanofili e temperatura &egrave; abbastanza indipendente nell&#39;intervallo 1-100 K, che &egrave; coerente con il rilassamento di rotazione di essere associato con scattering elastico di stati superficiali. Il tempo di rilassamento spin corrispondente &egrave; circa 100 femtosecondi. Troviamo anche che il tasso di rilassamento di spin &egrave; abbastanza indipendente del campo elettrico la corrente di guida nel campo intervallo 0,3-3 kV/cm.

Trasporto di spin in s&eacute; assemblati interamente in metallo nanofilo valvole a spin: uno studio del meccanismo di Elliott-Yafet puro.

We report on a hierarchical nanoarchitecture wherein distinct chromophores are deterministically placed at two different types of sites in a nanoporous metal oxide framework. One chromophore, namely Tris(8-hydroxyquinoline)aluminium(III) (Alq3), is embedded in the 1-2 nm sized nanovoids of anodic aluminum oxide (AAO) and another chromophore (carboxyfluorescein or pyrenebutyric acid) is anchored in the form of a monolayer to the surface of the walls of the cylindrical nanopores (- 20 nm in diameter) of AAO. We found the luminescence maximum to occur at 492 nm, blueshifted by at least 18 nm from the value in solutions and thin films. The excited state decay of Alq3 molecules in nanovoids was found to be biexponential with a fast component of 338 ps and a slower component of 2.26 ns, different from Alq3 thin films and solutions. Using a combination of steady state and time-resolved luminescence studies, we found that efficient Forster-type resonance energy transfer (FRET) from Alq3 in the nanovoids to the carboxyfluorescein monolayer could be used to pump the emission of surface-bound chromophores. Conversely, the emission of nanovoid-confined Alq3 could be pumped by energy transfer from a pyrenebutyric acid monolayer. Such intra-nanoarchitecture interactions between chromophores deterministically placed in different spatial locations are important in applications such as organic light emitting diodes, chemical sensors, energy transfer fluorescent labels, light harvesting antennas and organic spintronics.

Photophysics and energy transfer studies of Alq3 confined in the voids of nanoporous anodic alumina.

Nous rapportons un nanoarchitecture hi&eacute;rarchique dans lequel les chromophores distinctes sont plac&eacute;s de fa&ccedil;on d&eacute;terministe &agrave; deux diff&eacute;rents types de sites dans un cadre d&#39;oxyde m&eacute;tallique nanoporeux. Un chromophore, &agrave; savoir Tris(8-hydroxyquinoline)aluminium(III) (Alq3), est incorpor&eacute; dans les 1-2 nm de taille nanovoids de l&#39;oxyde d&#39;aluminium anodique (AAO) et un autre chromophore (acide carboxyfluoresc&eacute;ine ou pyrenebutyric) est ancr&eacute; dans la forme d&#39;une monocouche &agrave; la surface des murs de la nanopores cylindrique (- 20 nm de diam&egrave;tre) de l&#39;AAO. Nous avons trouv&eacute; la luminescence maximale se produit &agrave; 492 nm, blueshifted au moins 18 nm de la valeur des solutions et des couches minces. La d&eacute;sint&eacute;gration de l&#39;&eacute;tat excit&eacute; de mol&eacute;cules de Alq3 dans nanovoids s&#39;est av&eacute;r&eacute;e bi-exponentielle avec une composante rapide de 338 ps et une composante plus lente de 2.26 ns, diff&eacute;rents de Alq3 couches minces et des solutions. En utilisant une combinaison d&#39;&eacute;tat d&#39;&eacute;quilibre et d&#39;&eacute;tudes de luminescence r&eacute;solue dans le temps, nous avons constat&eacute; qu&#39;efficace Forster-type transfert d&#39;&eacute;nergie (FRET) de Alq3 dans la nanovoids de la monocouche carboxyfluoresc&eacute;ine pourrait servir &agrave; l&#39;&eacute;mission de surface-bondissent chromophores de la pompe. &Agrave; l&#39;inverse, l&#39;&eacute;mission de Alq3 nanovoid confin&eacute; pourrait &ecirc;tre pomp&eacute;e par transfert d&#39;&eacute;nergie d&#39;une monocouche d&#39;acide pyrenebutyric. Ces interactions intra-nanoarchitecture entre les chromophores d&eacute;terministe plac&eacute;s &agrave; diff&eacute;rents endroits spatiaux sont importantes dans les applications telles qu&#39;organic light emitting diodes, capteurs chimiques, &eacute;tiquettes fluorescentes &eacute;nergie transfert, lumi&egrave;re r&eacute;colte des antennes et spintronique organique.

Article	Year
Spin transport in self assembled all-metal nanowire spin valves: a study of the pure Elliott-Yafet mechanism. Journal of nanoscience and nanotechnology\| PubMed ID: 17025111	2006
Photophysics and energy transfer studies of Alq3 confined in the voids of nanoporous anodic alumina. Journal of nanoscience and nanotechnology\| PubMed ID: 23763140	2013

Sandipan Pramanik

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