Browsing by Author "Lou, J."

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    Universal ac conduction in large area atomic layers of CVD-grown MoS2
    (American Physical Society, 2014) Ghosh, S.; Najmaei, S.; Kar, S.; Vajtai, R.; Lou, J.; Pradhan, N.R.; Balicas, L.; Ajayan, P.M.; Talapatra, S.
    Here, we report on the ac conductivity [σ’(ω); 10 mHz < ω < 0.1 MHz] measurements performed on atomically thin, two-dimensional layers of MoS2 grown by chemical vapor deposition (CVD). Σ’(ω) is observed to display a “universal” power law, i.e., σ’(ω) ∼ ωs measured within a broad range of temperatures, 10 K< T <340 K. The temperature dependence of ‘‘s” indicates that the dominant ac transport conduction mechanism in CVD-grown MoS2 is due to electron hopping through a quantum mechanical tunneling process. The ac conductivity also displays scaling behavior, which leads to the collapse of the ac conductivity curves obtained at various temperatures into a single master curve. These findings establish a basis for our understanding of the transport mechanism in atomically thin, CVD-grown MoS2 layers.
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    Yield strength dependence on strain rate of molybdenum-alloy nanofibers
    (AIP Publishing LLC., 2014) Loya, P.E.; Xia, Y.Z.; Peng, C.; Bei, H.; Zhang, P.; Zhang, J.; George, E.P.; Gao, Y.F.; Lou, J.
    The yield strength dependence on strain rate was studied for molybdenum-alloy nanofibers with varying initialﾠdislocationﾠdensity at three different pre-strain levels.ﾠIn-situﾠtensile experiments at three displacement rates were carried out in aﾠscanning electron microscope.ﾠYield strength and its scatter decreased as a function of the pre-strain level for different displacement rates. Aﾠstatistical modelﾠwas used to analyze the results, and a negative strain rate dependence was inferred from the yield experiments. This finding suggests the need for theoretical investigations since classical models such as dynamic strain aging may have limitations at such nanoscales.