School Of Basic And Applied Sciences

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    First principles study of 2D ring-Te and its electrical contact with a topological Dirac semimetal
    (Royal Society of Chemistry, 2023-02-10T00:00:00) Singh, Jaspreet; Kumar, Ashok
    In recent years, researchers have manifested their interest in two-dimensional (2D) mono-elemental materials of group-VI elements because of their excellent optoelectronic, photovoltaic and thermoelectric properties. Despite the intensive recent research efforts, there is still a possibility of novel 2D allotropes of these elements due to their multivalency nature. Here, we have predicted a novel 2D allotrope of tellurium (ring-Te) using density functional theory. Its stability is confirmed by phonon and ab initio molecular dynamics simulations. Ring-Te has an indirect band gap of 0.69 eV (1.16 eV) at the PBE (HSE06) level of theories and undergoes an indirect-direct band gap transition under tensile strain. The higher carrier mobility of holes (?103 cm2 V?1 s?1), good UV-visible light absorption ability and low exciton binding (?0.35 eV) of ring-Te give rise to its potential applications in optoelectronic devices. Furthermore, the electrical contact of ring-Te with a topological Dirac semimetal (sq-Te) under the influence of an electric field shows that the Schottky barriers and contact types can undergo transition from p-type to n-type Schottky contact and then to ohmic contact at a higher electric field. Our study provides an insight into the physics of designing high-performance electrical coupled devices composed of 2D semiconductors and topological semimetals. � 2023 The Royal Society of Chemistry.
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    Design and development of a compact ion implanter and plasma diagnosis facility based on a 2.45 GHz microwave ion source
    (American Institute of Physics Inc., 2021-05-25T00:00:00) Swaroop, Ram; Kumar, Narender; Rodrigues, G.; Kanjilal, D.; Banerjee, I.; Mahapatra, S.K.
    A project on developing a 2.45 GHz microwave ion source based compact ion implanter and plasma diagnostic facility has been taken up by the Central University of Punjab, Bathinda. It consists of a double-wall ECR plasma cavity, a four-step ridge waveguide, an extraction system, and an experimental beam chamber. The mechanical design has been carried out in such a way that both types of experiments, plasma diagnosis and ion implantation, can be easily accommodated simultaneously and separately. To optimize microwave coupling to the ECR plasma cavity, a four-step ridge waveguide is designed. Microwave coupling simulation for the ECR plasma cavity has been performed at different power inputs using COMSOL Multiphysics. An enhanced electric field profile has been obtained at the center of the ECR plasma cavity with the help of a four-step ridge waveguide compared to the WR284 waveguide. The magnetic field distribution for two magnetic rings and the extraction system's focusing properties have been simulated using the computer simulation technique. A tunable axial magnetic field profile has been obtained with a two permanent magnetic ring arrangement. The dependency of the beam emittance and beam current on accelerating voltages up to 50 kV has been simulated with different ions. It shows that ion masses have a great impact on the beam emittance and output current. This facility has provision for in situ plasma diagnosis using a Langmuir probe and optical emission spectroscopy setups. This system will be used for ion implantation, surface patterning, and studies of basic plasma sciences. � 2021 Author(s).
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    Interfacial design of gold/silver core-shell nanostars for plasmon-enhanced photocatalytic coupling of 4-aminothiophenol
    (Royal Society of Chemistry, 2021-10-02T00:00:00) Kaur, Gagandeep; Tanwar, Swati; Kaur, Vishaldeep; Biswas, Rathindranath; Saini, Sangeeta; Haldar, Krishna Kanta; Sen, Tapasi
    Chemical reactions under mild conditions mediated by localized surface plasmon resonance (LSPR) of metals have emerged as a functional research field. In the present study, we report an interfacial designing procedure for the fabrication of a class of bimetallic hybrid nanomaterials as a profoundly active photocatalyst for the conversion of para-aminothiophenol (PATP) into 4,4?-dimercaptoazobenzene. For this purpose, core-shell nanostars composed of gold (core) and silver (shell) (Au/Ag NSs) were utilized as both surface-enhanced Raman scattering substrate and plasmon driven catalyst under 532 nm laser excitation. Au/Ag NSs with sharp tips display excellent surface-enhanced Raman scattering (SERS) efficiency of PATP. Employing the SERS study, it has been found that PATP rapidly converts into its dimerized product DMAB within few seconds by surface photochemical reaction in the Au-Ag heterojunction of core-shell nanostars. Au/Ag NSs with multiple sharp tips exhibit intense LSPR and highly strong electric fields are created at the tips, which enables the generation of hot electrons responsible for the rapid conversion reaction. Such well-designed interfacial bimetallic nanostars could have potential applications in surface enhanced spectroscopy, biosensing, and photoinduced surface catalysis. This journal is � The Royal Society of Chemistry.