822 research outputs found
Enhanced flexoelectricity at reduced dimensions revealed by mechanically tunable quantum tunnelling
No full textFlexoelectricity is a universal electromechanical coupling effect whereby all dielectric materials polarise in response to strain gradients. In particular, nanoscale flexoelectricity promises exotic phenomena and functions, but reliable characterisation methods are required to unlock its potential. Here, we report anomalous mechanical control of quantum tunnelling that allows for characterising nanoscale flexoelectricity. By applying strain gradients with an atomic force microscope tip, we systematically polarise an ultrathin film of otherwise nonpolar SrTiO3, and simultaneously measure tunnel current across it. The measured tunnel current exhibits critical behaviour as a function of strain gradients, which manifests large modification of tunnel barrier profiles via flexoelectricity. Further analysis of this critical behaviour reveals significantly enhanced flexocoupling strength in ultrathin SrTiO3, compared to that in bulk, rendering flexoelectricity more potent at the nanoscale. Our study not only suggests possible applications exploiting dynamic mechanical control of quantum effect, but also paves the way to characterise nanoscale flexoelectricity. © 2019, The Author(s
Determining the service quality of the city bus service based on users’ perceptions and expectations
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Colossal flexoresistance in dielectrics
No full text© 2020, The Author(s). Dielectrics have long been considered as unsuitable for pure electrical switches; under weak electric fields, they show extremely low conductivity, whereas under strong fields, they suffer from irreversible damage. Here, we show that flexoelectricity enables damage-free exposure of dielectrics to strong electric fields, leading to reversible switching between electrical states—insulating and conducting. Applying strain gradients with an atomic force microscope tip polarizes an ultrathin film of an archetypal dielectric SrTiO3 via flexoelectricity, which in turn generates non-destructive, strong electrostatic fields. When the applied strain gradient exceeds a certain value, SrTiO3 suddenly becomes highly conductive, yielding at least around a 108-fold decrease in room-temperature resistivity. We explain this phenomenon, which we call the colossal flexoresistance, based on the abrupt increase in the tunneling conductance of ultrathin SrTiO3 under strain gradients. Our work extends the scope of electrical control in solids, and inspires further exploration of dielectric responses to strong electromechanical fields11sci
Analysis of solid waste management strategies in Thimphu with reference to its detrimental effect and remission approach
No full textInformation content of IPO grading
No full textIn the year 2007, Indian capital market regulator-SEBI, introduced a unique certification mechanism for IPOs whereby all IPOs have to undergo mandatory quality grading by independent rating agencies. In this paper we argue that such objective, independent and exogenous certifying mechanism provides a better opportunity to test the well established certification hypothesis, especially in the context of emerging markets with institutional voids. Using a sample of 163 Indian IPOs we test the efficacy of IPO grading mechanism. We find, grading decreases IPO underpricing and positively influences demand of retail investors. Grading reduces secondary market risk and improves liquidity. However, grading does not affect long run performance of the IPOs. IPO grading successfully capture firm size, business group affiliation and firm's quality of corporate governance. Our findings imply that, in emerging markets, regulator's role to signal the quality of an IPO contributes towards the market welfare.Initial public offering (IPO) Underpricing IPO grading Certification hypothesis
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