Enhanced Raman and photoluminescence response in monolayer MoS2_2 due to laser healing of defects

Bound quasiparticles, negatively charged trions and neutral excitons, are associated with the direct optical transitions at the K-points of the Brillouin zone for monolayer MoS$_2$. The change in the carrier concentration, surrounding dielectric constant and defect concentration can modulate the photoluminescence and Raman spectra. Here we show that exposing the monolayer MoS$_2$ in air to a modest laser intensity for a brief period of time enhances simultaneously the photoluminescence (PL) intensity associated with both trions and excitons, together with $\sim$ 3 to 5 times increase of the Raman intensity of first and second order modes. The simultaneous increase of PL from trions and excitons cannot be understood based only on known-scenario of depletion of electron concentration in MoS$_2$ by adsorption of O$_2$ and H$_2$O molecules. This is explained by laser induced healing of defect states resulting in reduction of non-radiative Auger processes. This laser healing is corroborated by an observed increase of intensity of both the first order and second order 2LA(M) Raman modes by a factor of $\sim$ 3 to 5. The A$_{1g}$ mode hardens by $\sim$ 1.4 cm$^{-1}$ whereas the E$^1_{2g}$ mode softens by $\sim$ 1 cm$^{-1}$. The second order 2LA(M) Raman mode at $\sim$ 440 cm$^{-1}$ shows an increase in wavenumber by $\sim$ 8 cm$^{-1}$ with laser exposure. These changes are a combined effect of change in electron concentrations and oxygen-induced lattice displacements.Comment: 15 pages, 5 figures, Journal of Raman Spectroscopy, 201

Growing Dynamisms\u27 Of Business And Technology/ Global Perspective

Technology is the essence of change in business and society. In this paper we can learn about technology, its characteristics, its historical phases and how innovation is fuelled today. Technological advances in the modern world have created new business opportunities. Leverage advanced tools to rise above the competition. Technology has revolutionized the way companies conduct business by enabling small businesses to level the playing field with larger organizations. Businesses nowadays, whether it is big or small, also rely on the help of technology.Mostcompaniesdepends their daily operations on the use of technological innovation such as computers, internet connection, printers, applications, and file storages. That is why; every business can develop positively from small- scale to large-scale. Small businesses use an array of tech – everything from servers to mobile devices – to develop competitive advantages in the economic marketplace. Technology in business made it possible to have a wider reach in the global market. The basic example is the Internet, which is now a common marketing tool to attract more consumers in availing products and services offered by various businesses. The aim of the paper is to highlight the potential benefits of technology and advancement

Phonon Anomalies, Orbital-Ordering and Electronic Raman Scattering in iron-pnictide Ca(Fe0.97Co0.03)2As2: Temperature-dependent Raman Study

We report inelastic light scattering studies on Ca(Fe0.97Co0.03)2As2 in a wide spectral range of 120-5200 cm-1 from 5K to 300K, covering the tetragonal to orthorhombic structural transition as well as magnetic transition at Tsm ~ 160K. The mode frequencies of two first-order Raman modes B1g and Eg, both involving displacement of Fe atoms, show sharp increase below Tsm. Concomitantly, the linewidths of all the first-order Raman modes show anomalous broadening below Tsm, attributed to strong spin-phonon coupling. The high frequency modes observed between 400-1200 cm-1 are attributed to the electronic Raman scattering involving the crystal field levels of d-orbitals of Fe2+. The splitting between xz and yz d-orbital levels is shown to be ~ 25 meV which increases as temperature decreases below Tsm. A broad Raman band observed at ~ 3200 cm-1 is assigned to two-magnon excitation of the itinerant Fe 3d antiferromagnet.Comment: Accepted for Publication in JPC

Green and Sustainability in Software Development Lifecycle Process

This chapter gives an insight of GREENSOFT Model for sustainable software engineering. In today’s world, computing devices are extensively by all for many purposes. They consume lots of energy even though they reduce energy consumption. Computers are used extensively while developing software. Existing software engineering models do not pay much attention to green computing that focuses on the effective use of natural resources. Sustainability of resources is the key. The GREENSOFT model of software engineering proposes a methodology in which Green IT practices are used, which will reduce the energy consumption of computers while developing software

Metallic monoclinic phase in VO2_2 induced by electrochemical gating: in-situ Raman study

We report in-situ Raman scattering studies of electrochemically top gated VO$_2$ thin film to address metal-insulator transition (MIT) under gating. The room temperature monoclinic insulating phase goes to metallic state at a gate voltage of 2.6 V. However, the number of Raman modes do not change with electrolyte gating showing that the metallic phase is still monoclinic. The high frequency Raman mode A$_g$(7) near 616 cm$^{-1}$ ascribed to V-O vibration of bond length 2.06 \AA~ in VO$_6$ octahedra hardens with increasing gate voltage and the B$_g$(3) mode near 654 cm$^{-1}$ softens. This shows that the distortion of the VO$_6$ octahedra in the monoclinic phase decreases with gating. The time dependent Raman data at fixed gate voltages of 1 V (for 50 minute, showing enhancement of conductivity by a factor of 50) and 2 V (for 130 minute, showing further increase in conductivity by a factor of 5) show similar changes in high frequency Raman modes A$_g$(7) and B$_g$(3) as observed in gating. This slow change in conductance together with Raman frequency changes show that the governing mechanism for metalization is more likely to the diffusion controlled oxygen vacancy formation due to the applied electric field.Comment: 5 pages, 6 figure

Symmetry-dependent phonon renormalization in monolayer MoS2 transistor

Strong electron-phonon interaction which limits electronic mobility of semiconductors can also have significant effects on phonon frequencies. The latter is the key to the use of Raman spectroscopy for nondestructive characterization of doping in graphene-based devices. Using in-situ Raman scattering from single layer MoS$_2$ electrochemically top-gated field effect transistor (FET), we show softening and broadening of A$_{1g}$ phonon with electron doping whereas the other Raman active E$_{2g}^{1}$ mode remains essentially inert. Confirming these results with first-principles density functional theory based calculations, we use group theoretical arguments to explain why A$_{1g}$ mode specifically exhibits a strong sensitivity to electron doping. Our work opens up the use of Raman spectroscopy in probing the level of doping in single layer MoS$_2$-based FETs, which have a high on-off ratio and are of enormous technological significance.Comment: 5 pages, 3 figure

Effect of Concurrent Strength and Plyometric Training on Selected Biomotor Abilities

The underlying principle of this study was to assess the effect of eight weeks concurrent strength and plyometric training in enhancing the selected biomotor abilities. For the purpose of this study, thirty male volleyball specialization students from the department of physical education and sports sciences, Annamalai university, aged 20 to 22 years took part in the study. Subjects were randomly assigned to either concurrent training (n=15) or control (n=15) group. The training regimen lasted for eight weeks. The selected criterion variables were assessed using standard tests and procedures, prior to and immediately after the training programme. Analysis of covariance was employed to establish the degree of significant modification on chosen criterion variables. The findings of the study revealed that eight weeks of concurrent training had an effectiveness of 4.13% on leg strength, 11.81% on strength endurance, 0.40% on speed, and 7.53% on anaerobic power. These findings suggest that the concurrent strength and plyometric training programme have statistically significant influence in developing the selected criterion variables

Raman and high-pressure photoluminescence studies on porous silicon

We show that there is no correlation between the blue shift of the visible photoluminescence band and red shift of the Raman phonon line in porous silicon, in contrast to the recently reported results. We also report a drastic red shift of the photoluminescence peak position with pressure up to 6 GPa and show that this is much larger than that of the crystalline silicon. These observations cast doubt on the suggested mechanism of quantum size effects in porous silicon

Laboratory bred prawns from Narakkal cultured in salt pan reservoirs at Tuticorin—a success story.

Rapid developments and fast changes are taking place in the field of prawn culture in india and abroad. Domestication of the culturable species of marine prawns, their induced maturation and spawning in captivity and mass production of stockable size of prawn seeds have become a reality in india chiefly due to the researches conducted at the narakkal prawn culture laboratory (npcl) of the central marinefisheries research institute. Establishment of a land-based maturation facility and development ofMass cultures of locally available live feed organisms—diatoms, rotifers and cladocerans—were the major contributory factors in achieving this break-through. As a result of these developments over one million prawn seeds, chiefly belonging to the indian prawn penaeus indicus were produced at the npcl in the eariy half of 1980.the prawn seeds produced at the npcl were byproducts of the experiments conducted there and not products of a concerted production programme. Although most of these seeds were used in the lab to land programme of the institute at the vypeen island and quilon, some were supplied to the prawn culturists at goa and tuticorin and also to the calicut research. Centre of the cmfri for experiments in the polythene lined ponds on the sandy beach of calicut. The main objective of these supplies was to study the problems associated with long distance transport and to evaluate their growth and survival in different ecological conditions