Improvement of electrical properties of ITO thin films by melt-free ultra-short laser crystallization

We describe a novel solid state crystallisation method for optimising a thin film transparent conductive oxide when deposited on flexible polymer substrates. The method is based on ultra-short non-thermal laser sintering of indium tin oxide (ITO) thin films. In this study, we used commercial ITO thin films deposited on a flexible polyethylene terephthalate substrate with a relatively low melting temperature compared with ITO on glass. We demonstrate the use of laser scanning with high pulse overlapping at fluences seven times less than the threshold required for melting/damage of ITO. The results confirm greater than four times enhancement in the mobility of charge carriers of ITO thin films after laser scanning and sheet resistance can be reduced up to 25%. There is no reduction in optical transparency observed in laser treated samples. Surface morphology and x-ray diffraction analyses confirm the improvement in crystallite sizes by laser sintering, resulting in a greater than 37% increase in grain size due to enhanced crystallization. Comparison of experimental and simulation based on a delayed two temperature model confirms that ITO thin film crystallization occurred at about one-third of the melting temperature of ITO

Galaxy Clusters Associated with Short GRBs. II. Predictions for the Rate of Short GRBs in Field and Cluster Early-Type Galaxies

We determine the relative rates of short GRBs in cluster and field early-type galaxies as a function of the age probability distribution of their progenitors, P(\tau) \propto \tau^n. This analysis takes advantage of the difference in the growth of stellar mass in clusters and in the field, which arises from the combined effects of the galaxy stellar mass function, the early-type fraction, and the dependence of star formation history on mass and environment. This approach complements the use of the early- to late-type host galaxy ratio, with the added benefit that the star formation histories of early-type galaxies are simpler than those of late-type galaxies, and any systematic differences between progenitors in early- and late-type galaxies are removed. We find that the ratio varies from R(cluster)/R(field) ~ 0.5 for n = -2 to ~ 3 for n = 2. Current observations indicate a ratio of about 2, corresponding to n ~ 0 - 1. This is similar to the value inferred from the ratio of short GRBs in early- and late-type hosts, but it differs from the value of n ~ -1 for NS binaries in the Milky Way. We stress that this general approach can be easily modified with improved knowledge of the effects of environment and mass on the build-up of stellar mass, as well as the effect of globular clusters on the short GRB rate. It can also be used to assess the age distribution of Type Ia supernova progenitors.Comment: ApJ accepted versio