School Of Basic And Applied Sciences
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Item Electronic properties and STM images of vacancy clusters and chains in functionalized silicene and germanene(Elsevier B.V., 2017) Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.Electronic properties and STM topographical images of X (=F, H, O) functionalized silicene and germanene have been investigated by introducing various kind of vacancy clusters and chain patterns in monolayers within density functional theory (DFT) framework. The relative ease of formation of vacancy clusters and chain patterns is found to be energetically most favorable in hydrogenated silicene and germanene. F- and H-functionalized silicene and germanene are direct bandgap semiconducting with bandgap ranging between 0.1?1.9?eV, while O-functionalized monolayers are metallic in nature. By introducing various vacancy clusters and chain patterns in both silicene and germanene, the electronic and magnetic properties get modified in significant manner e.g. F- and H-functionalized silicene and germanene with hexagonal and rectangle vacancy clusters are non-magnetic semiconductors with modified bandgap values while pentagonal and triangle vacancy clusters induce metallicity and magnetic character in monolayers; hexagonal vacancy chain patterns induce direct-to-indirect gap transition while zigzag vacancy chain patterns retain direct bandgap nature of monolayers. Calculated STM topographical images show distinctly different characteristics for various type of vacancy clusters and chain patterns which may be used as electronic fingerprints to identify various vacancy patterns in silicene and germanene created during the process of functionalization. ? 2016 Elsevier B.V.Item Ultra-narrow blue phosphorene nanoribbons for tunable optoelectronics(Royal Society of Chemistry, 2017) Swaroop, Ram; Ahluwalia, P. K.; Tankeshwar, K.; Kumar, AshokWe report optoelectronic properties of ultra-narrow blue phosphorene nanoribbons (BPNRs) within the state-of-the-art density functional theory framework. The positive but small value of formation energy (?0.1 eV per atom) indicates the relative ease of the formation of BPNRs from their two-dimensional (2D) counterpart. The oscillatory behaviour of the electronic band gap of bare BPNRs with increasing width is attributed to the reconstruction of edge atoms. The static dielectric constant of BPNRs depends on the width and applied strain which in turn shows consistency with the Penn's model expression for semiconductors. Bare BPNRs exhibit both ? and ? + ? plasmonic structures while passivated ones possess only a ? + ? plasmonic structure that get blue-shifted (as large as ?3 eV) on increasing the width of the BPNRs which makes electron energy loss spectroscopy useful for identifying the width of BPNRs in real experimental situations. The mechanical strain induces a small red shift in, which is attributed to the modification in electronic band dispersion due to a different superposition of atomic orbitals on the application of applied strain. These tunable electronic and dielectric properties of BPNRs mean they may find applications in optoelectronic devices based on blue phosphorene. ? The Royal Society of Chemistry.