Browsing by Author "Ray, A.K."

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    Effect of plasma power on reduction of printable graphene oxide thin films on flexible substrates
    (Institute of Physics Publishing, 2018) Banerjee, I.; Mahapatra, S.K.; Pal, C.; Sharma, A.K.; Ray, A.K.
    Room temperature hydrogen plasma treatment on solution processed 300 nm graphene oxide (GO) films on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates has been performed by varying the plasma power between 20 W and 60 W at a constant exposure time of 30 min with a view to examining the effect of plasma power on reduction of GO. X-ray powder diffraction (XRD) and Raman spectroscopic studies show that high energy hydrogen species generated in the plasma assist fast exfoliation of the oxygenated functional groups present in the GO samples. Significant decrease in the optical band gap is observed from 4.1 eV for untreated samples to 0.5 eV for 60 W plasma treated samples. The conductivity of the films treated with 60 W plasma power is estimated to be six orders of magnitude greater than untreated GO films and this enhancement of conductivity on plasma reduction has been interpreted in terms of UV-visible absorption spectra and density functional based first principle computational calculations. Plasma reduction of GO/ITO/PET structures can be used for efficiently tuning the electrical and optical properties of reduced graphene oxide (rGO) for flexible electronics applications. ? 2018 IOP Publishing Ltd.
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    Synthesis and dielectric characterisation of triiodide perovskite methylammonium lead iodide for energy applications
    (Springer, 2018) Mahapatra,S.K.; Saykar, N.; Banerjee, Indrani; Hobson, P.R.; Sharma, A.K.; Ray, A.K.
    Impedance spectroscopic measurements on spin coated 550 nm thick perovskite films sandwiched between titanium oxide (TiO2) deposited on fluorine doped tin oxide (FTO) glass substrates and with a platinum (Pt) counter electrode have been performed to determine the influence of the percentage of PbI2 in methylammonium lead iodide (CH3NH3PbI3) compounds. These compounds with perovskite structure have been synthesized by weaving methylammonium iodide (CH3NH3I) and lead iodide (PbI2) in two different weight ratios of 1:4 and 3:7. The surface grains are found from the scanning electron microscoping images to have become relatively larger with increasing PbI2 content in spincoated perovskite film. Nearly 2% increase in optical band gap has been observed with increasing weight ratio of PbI2 content from 1:4 to 3:7.