Suman Shakya

Optical studies of Sm3+ ions doped Zinc Alumino Bismuth Borate glasses

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm(3+)) ions were prepared by using melt quenching technique and characterized for their lasing potentialities in visible region by using the techniques such as optical absorption, emission and emission decay measurements. Radiative properties for various fluorescent levels of Sm(3+) ions were estimated from absorption spectral information using Judd-Ofelt (JO) analysis. The emission spectra and con-focal photoluminescence images obtained by 410 nm laser excitation demonstrates very distinct and intense orange-red emission for all the doped glasses. The suitable concentration of Sm(3+) ions in these glasses to act as an efficient lasing material has been discussed by measuring the emission cross-section and branching ratios for the emission transitions. The quantum efficiencies were also been estimated from emission decay measurements recorded for the (4)G5/2 level of Sm(3+) ions. From the measured emission cross-sections, branching ratios, strong photoluminescence features and CIE chromaticity coordinates, it was found that 1 mol% of Sm(3+) ions doped ZnAlBiB glasses are most suitable for the development of visible orange-red lasers.

Formation of PbO hexagonal nanosheets and their conversion into luminescent inorganic–organic perovskite nanosheets: growth and mechanism

We report the formation of inorganic–organic (IO) hybrid perovskite (C6H9C2H4NH3)2 PbI4 hexagonal nanosheets, using anisotropically grown PbO hexagonal nanosheets as a parent material. In place of the conventional chemical synthesis route, the PbO hexagonal nanosheets have been synthesized by the bottom-up electrochemical deposition technique. Conversion of PbO into the desired hybrid material has been achieved by the intercalation of organic moieties into the alternate layers of inorganic networks. These hybrid structures have shown strong room-temperature excitonic emission at 518 nm. An extensive study has been performed to observe the deposition parameters responsible for the growth of a well-defined hexagonal nanosheet. High-resolution transmission electron microscope results confirmed the growth of single crystalline hexagonal nanosheets in (110) plane orientation. Investigation of the surface morphology, further verified the formation of nanosheets with a smooth surface having an average roughness of 2 nm. The study revealed that the anisotropic growth of nanosheets is a result of different growth rates of crystal faces associated with the crystal lattice.

Template assisted growth of microporous structures of CdSe x Te1 − x and thin film photocurrent studies

Ternary alloyed II?VI group semiconducting CdSe x Te1???x thin films (x?=?0.1 to 1) have been fabricated using electrodeposition technique for detailed photoelectrochemical study and to eventually grow their two-dimensional microporous photonic structures using self-assembled template for optoelectronic devices. Band gap tuning is achieved by controlling Se:Te ratio and the ratio of Se:Te has been controlled using appropriate precursors ratios and their respective concentrations, electrolyte pH etc. Extensive structural and photonic studies have been explored for alloyed CdSe x Te1???x thin films (x?=?0.1 to 1) to establish correlation between structural and optical properties for the series of x. The photoelectrochemical studies have shown a stable photocurrent response and confirmed the n-type semiconducting behaviour of CdSe x Te1???x thin films with photocurrent densities up to 0.6 mA cm?2.

Two-dimensional inorganic-organic perovskite hexagonal nanosheets: growth and mechanism

In this era of novel technological materials, inorganic-organic (IO) materials has emerged as new class of materials for their application in photonic materials, miniaturized sensors, optoelectronic devices, non-linear optical apparatus by exploiting the properties of both constituents in a single entity. Here we present the formation and growth mechanism of two dimensional Inorganic-organic (IO) perovskite structures from anisotropically grown PbO hexagonal nanosheets, in three steps: Fabrication of hexagonal PbO nanosheets by the versatile bottom-up electrochemical deposition technique, iodinization of PbO into PbI2, followed by conversion of PbI2 into IO hybrid by the intercalation of organic moiety. A systematic and detailed structural study reveals that PbO nanosheet formation is more likely to result from an oriented attachment mechanism, in which the sheets formed by the reduction in surface area that happens during aggregation of small nanoparticle that each has a net dipole moment, which tends to form a self-assembled structure. Intercalation of organic moiety into the PbI2 layers yielded a selfassembled quantum-wells system of one of the IO hybrid, i.e. (C6H9C2H4NH3)2PbI4 (CHPI), sustaining the hexagonal shape.