InGaAs/GaAs/alkanethiolate radial superlattices: Experimental

A radial InGaAs/GaAs/1-hexadecanethiol superlattice is fabricated by the roll-up of a strained InGaAs/GaAs bilayer passivated with a molecular self-assembled monolayer. Our technique allows the formation of multi-period inorganic/organic hybrid heterostructures. This paper contains the detailed experimental description of how to fabricate these structures.Comment: 2 pages, no figures, Version 2; minor changes (fixed typos and update references

Fractal-Mound Growth of Pentacene Thin Films

The growth mechanism of pentacene film formation on SiO2 substrate was investigated with a combination of atomic force microscopy measurements and numerical modeling. In addition to the diffusion-limited aggregation (DLA) that has already been shown to govern the growth of the ordered pentacene thin films, it is shown here for the first time that the Schwoebel barrier effect steps in and disrupts the desired epitaxial growth for the subsequent layers, leading to mound growth. The terraces of the growing mounds have a fractal dimension of 1.6, indicating a lateral DLA shape. This novel growth morphology thus combines horizontal DLA-like growth with vertical mound growth.Comment: (5 Figures). Accepted to PR B (in print

Distribution of localized states from fine analysis of electron spin resonance spectra of organic semiconductors: Physical meaning and methodology

We develop an analytical method for the processing of electron spin resonance (ESR) spectra. The goal is to obtain the distributions of trapped carriers over both their degree of localization and their binding energy in semiconductor crystals or films composed of regularly aligned organic molecules [Phys. Rev. Lett. v. 104, 056602 (2010)]. Our method has two steps. We first carry out a fine analysis of the shape of the ESR spectra due to the trapped carriers; this reveals the distribution of the trap density of the states over the degree of localization. This analysis is based on the reasonable assumption that the linewidth of the trapped carriers is predetermined by their degree of localization because of the hyperfine mechanism. We then transform the distribution over the degree of localization into a distribution over the binding energies. The transformation uses the relationships between the binding energies and the localization parameters of the trapped carriers. The particular relation for the system under study is obtained by the Holstein model for trapped polarons using a diagrammatic Monte Carlo analysis. We illustrate the application of the method to pentacene organic thin-film transistors.Comment: 14 pages, 11 figure

La importancia de la personalidad del traductor en los itinerarios de especialidad y en la selección de personal

Treball Final de Grau en Traducció i Interpretació. Codi: TI0983. Curs acadèmic: 2016/2017A pesar de que a simple vista no lo pueda parecer, la personalidad de los traductores influye mucho más de lo que se cree en el proceso traductor y en la toma de decisiones, como han puesto de manifiesto estudios empíricos. Para analizar cuáles son las diferencias individuales en la personalidad de los traductores en la elección del itinerario de especialidad, se ha llevado a cabo un estudio con los estudiantes de los cuatro itinerarios de traducción de la Universidad Jaume I, a fin de ver si podemos identificar los rasgos típicos de los estudiantes de cada itinerario. Además, dada la gran importancia de la personalidad en las tareas de traducción, también se ha entrevistado a responsables de tres agencias de traducción para ver si la personalidad de los traductores es un factor relevante a la hora de reclutar personal. Se ha comprobado así que sí hay algunos rasgos comunes en la personalidad de los estudiantes de cada itinerario y que realmente esta cuestión no es un factor relevante en las agencias de traducción, sino que se valora, sobre todo, el trabajo diario y la calidad de las pruebas de traducción

Structural origin of gap states in semicrystalline polymers and the implications for charge transport

We quantify the degree of disorder in the {\pi}-{\pi} stacking direction of crystallites of a high performing semicrystalline semiconducting polymer with advanced X-ray lineshape analysis. Using first principles calculations, we obtain the density of states of a system of {\pi}-{\pi} stacked polymer chains with increasing amounts of paracrystalline disorder. We find that for an aligned film of PBTTT the paracrystalline disorder is 7.3%. This type of disorder induces a tail of trap states with a breadth of ~100 meV as determined through calculation. This finding agrees with previous device modeling and provides physical justification for the mobility edge model.Comment: Text and figures are unchanged in the new version of the file. The only modification is the addition of a funding source to the acknowledgment

Ambipolar charge transport in organic field-effect transistors

Published versio

Charge Delocalization in Self-Assembled Mixed-Valence Aromatic Cation Radicals

The spontaneous assembly of aromatic cation radicals (D+•) with their neutral counterpart (D) affords dimer cation radicals (D2+•). The intermolecular dimeric cation radicals are readily characterized by the appearance of an intervalence charge-resonance transition in the NIR region of their electronic spectra and by ESR spectroscopy. The X-ray crystal structure analysis and DFT calculations of a representative dimer cation radical (i.e., the octamethylbiphenylene dimer cation radical) have established that a hole (or single positive charge) is completely delocalized over both aromatic moieties. The energetics and the geometrical considerations for the formation of dimer cation radicals is deliberated with the aid of a series of cyclophane-like bichromophoric donors with drastically varied interplanar angles between the cofacially arranged aryl moieties. X-ray crystallography of a number of mixed-valence cation radicals derived from monochromophoric benzenoid donors established that they generally assemble in 1D stacks in the solid state. However, the use of polychromophoric intervalence cation radicals, where a single charge is effectively delocalized among all of the chromophores, can lead to higher-order assemblies with potential applications in long-range charge transport. As a proof of concept, we show that a single charge in the cation radical of a triptycene derivative is evenly distributed on all three benzenoid rings and this triptycene cation radical forms a 2D electronically coupled assembly, as established by X-ray crystallography