Unipolar resistive switching in planar Pt/BiFeO3/Pt structure

This work was supported by the NASA EPSCoR Grant # NNX13AB22A. Financial support to various researchers from IFN-NSF grant # EPS 1002410 (RSK, DB, YS and BRW) is gratefully acknowledged. S. K. is thankful to UGC, India for a Raman fellowship under Indo-US 21st century knowledge initiatives (No:5-53/2013(I.C)).We report unipolar resistive switching suitable for nonvolatile memory applications in polycrystalline BiFeO3 thin films in planar electrode configuration with non-overlapping Set and Reset voltages, On/Off resistance ratio of similar to 10(4) and good data retention (verified for up to 3,000 s). We have also observed photovoltaic response in both high and low resistance states, where the photocurrent density was about three orders of magnitude higher in the low resistance state as compared to the high resistance state at an illumination power density of similar to 100 mW/cm(2). Resistive switching mechanisms in both resistance states of the planar device can be explained by using the conduction filament (thermo-chemical) model. (C) 2015 Author(s).Publisher PDFPeer reviewe

Holmium hafnate : an emerging electronic device material

Financial support from DOE Grant No. DE-FG02-08ER46526 is acknowledged. S.P.P. is grateful to NSF for financial assistance under Grant No. NSF-EFRI RESTOR #1038272. Y.S. is thankful to IFN-NSF for doctoral fellowship under NSF-RII-0701525 grant.We report structural, optical, charge transport, and temperature properties as well as the frequency dependence of the dielectric constant of Ho2Hf2O7 (HHO) which make this material desirable as an alternative high-k dielectric for future silicon technology devices. A high dielectric constant of similar to 20 and very low dielectric loss of similar to 0.1% are temperature and voltage independent at 100 kHz near ambient conditions. The Pt/HHO/Pt capacitor exhibits exceptionally low Schottky emission-based leakage currents. In combination with the large observed bandgap Eg of 5.6 eV, determined by diffuse reflectance spectroscopy, our results reveal fundamental physics and materials science of the HHO metal oxide and its potential application as a high-k dielectric for the next generation of complementary metal-oxide-semiconductor devices.Publisher PDFPeer reviewe

Potential antifungal plants for controlling building fungi

374-387The synthetic fungicides such as Pentachlorophenol, Tributyltin oxide, Zinc carboxylate, etc. have been removed from markets due to their harmful effects on the environment, residue problem and carcinogenic nature. However, the fungicides derived from plant products are safer alternatives for fungi control because they are richest source of bioactive phytochemicals such as alkaloids, terpenoides, polyacetylenes, unsaturated isobutylamides and phenolics. Plant products, traditionally used as biocides in indigenous culture are being re-evaluated for safer means of fungi control as compared to the synthetic. The present paper is an attempt to summarize antifungal potency of various plants along with their part (s) used, type of extracts and test fungi. In view of antifungal properties of some of these plants against some fungi found on buildings, it is hoped that detailed studies may yield many more effective natural fungicides for controlling various types of building fungi. Some fungi found commonly on buildings have also been discussed in this paper for ready reference and further studies on their possible control by plant extracts

BiFeO₃ Coupled Polysulfide Trapping in C/S Composite Cathode Material for Li-S Batteries as Large Efficiency and High Rate Performance

We demonstrated the efficient coupling of BiFeO3 (BFO) ferroelectric material within the carbon–sulfur (C-S) composite cathode, where polysulfides are trapped in BFO mesh, reducing the polysulfide shuttle impact, and thus resulting in an improved cyclic performance and an increase in capacity in Li-S batteries. Here, the built-in internal field due to BFO enhances polysulfide trapping. The observation of a difference in the diffusion behavior of polysulfides in BFO-coupled composites suggests more efficient trapping in BFO-modified C-S electrodes compared to pristine C-S composite cathodes. The X-ray diffraction results of BFO–C-S composite cathodes show an orthorhombic structure, while Raman spectra substantiate efficient coupling of BFO in C-S composites, in agreement with SEM images, showing the interconnected network of submicron-size sulfur composites. Two plateaus were observed at 1.75 V and 2.1 V in the charge/discharge characteristics of BFO–C-S composite cathodes. The observed capacity of ~1600 mAh g−1 in a 1.5–2.5 V operating window for BFO30-C10-S60 composite cathodes, and the high cyclic stability substantiate the superior performance of the designed cathode materials due to the efficient reduction in the polysulfide shuttle effect in these composite cathodes