Molecular fluorine chemistry in the early Universe

Some models of Big Bang nucleosynthesis suggest that very high baryon density regions were formed in the early Universe, and generated the production of heavy elements other than lithium such as fluorine F. We present a comprehensive chemistry of fluorine in the post-recombination epoch. Calculation of F, F- and HF abundances, as a function of redshift z, are carried out. The main result is that the chemical conditions in the early Universe can lead to the formation of HF. The final abundance of the diatomic molecule HF is predicted to be close to 3.75 10(-17) when the initial abundance of neutral fluorine F is 10(-15). These results indicate that molecules of fluorine HF were already present during the dark age. This could have implications on the evolution of proto-objects and on the anisotropies of cosmic microwave background radiation. Hydride of fluorine HF may affect enhancement of the emission line intensity from the proto-objects and could produce spectral-spatial fluctuations.Comment: Accepted in Astronomy and Astrophysics, 7 pages, 2 figure

Fabrication of 2D based pn junctions with improved performance by selective laser annealing

There is a growing body of research on transistors based on nanomaterials such as 2D transition metal dichalcogenides (TMDs) (WS2, MoS2, etc.) and carbon nanotubes (CNTs). Here we co-deposited MoS2 and WS2 as PN junctions. The deposition could be performed on a PCB (printed circuit board) with Cu electrodes. The current-voltage characteristics were obtained using an Arduino board. The effect of laser irradiation could be investigated by studying the IV curves and light sensitivity for the same kind of devices in which one of the Cu electrodes was modified by a laser. The IV curves from the devices with and without laser treatment could be compared to quantify the changes in performance