Unravelling a simple method for the low temperature synthesis of silicon nanocrystals and monolithic nanocrystalline thin films

In this work, we present new results on the plasma processing and structure of hydrogenated polymorphous silicon (pm-Si:H) thin films. pm-Si:H thin films consist of a low volume fraction of silicon nanocrystals embedded in a silicon matrix with medium range order, and they possess this morphology as a significant contribution to their growth comes from the impact on the substrate of silicon clusters and nanocrystals synthesized in the plasma. Quadrupole mass spectrometry, ion flux measurements, and material characterization by transmission electron microscopy (TEM) and atomic force microscopy all provide insight on the contribution to the growth by silicon nanocrystals during PECVD deposition. In particular, cross-section TEM measurements show for the first time that the silicon nanocrystals are uniformly distributed across the thickness of the pm-Si:H film. Moreover, parametric studies indicate that the best pm-Si:H material is obtained at the conditions after the transition between a pristine plasma and one containing nanocrystals, namely a total gas pressure around 2 Torr and a silane to hydrogen ratio between 0.05 to 0.1. From a practical point of view these conditions also correspond to the highest deposition rate achievable for a given RF power and silane flow rate.ope

What are the Potential Economic Benefits of Enlarging the Gulf Cooperation Council?

This paper uses a variant of the IMF's Global Economy Model (GEM) to estimate the macroeconomic benefits of Yemen's accession into the Gulf Cooperation Council (GCC). After calibrating the model to Yemen and the GCC block, several simulations are carried out to estimate the potential impact of economic integration on both regions. The paper draws two fundamental conclusions. First, regional integration enhances competition which produces large economic benefits for both Yemen and the GCC. In particular, we show that in some cases economic integration can increase GDP in Yemen by up to 14% and in the GCC by up to 7% over the long run. Second, even if market structures do not improve substantially, GCC enlargement can still generate substantial spillover gains in each block. More specifically, one measure of economic prosperity measured by consumption can increase by up to 7% in Yemen and up to 8% in the GCC.Regional integration, competition, IMF's Global Economy Model (GEM),