Browsing by Author "Terrones, M."

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    Hall and field-effect mobilities in few layeredﾠp-WSe2ﾠfield-effect transistors
    (Macmillan Publishers Limited, 2015) Pradhan, N.R.; Rhodes, D.; Memaran, S.; Poumirol, J.M.; Smirnov, D.; Talapatra, S.; Feng, S.; Perea-Lopez, N.; Elias, A.L.; Terrones, M.; Ajayan, P.M.; Balicas, L.
    Here, we present a temperature (T) dependent comparison between field-effect and Hall mobilities in field-effect transistors based on few-layered WSe2 exfoliated onto SiO2. Without dielectric engineering and beyond a T-dependent threshold gate-voltage, we observe maximum hole mobilities approaching 350 cm(2)/Vs at T = 300 K. The hole Hall mobility reaches a maximum value of 650 cm(2)/Vs as T is lowered below ~150 K, indicating that insofar WSe2-based field-effect transistors (FETs) display the largest Hall mobilities among the transition metal dichalcogenides. The gate capacitance, as extracted from the Hall-effect, reveals the presence of spurious charges in the channel, while the two-terminal sheet resistivity displays two-dimensional variable-range hopping behavior, indicating carrier localization induced by disorder at the interface between WSe2 and SiO2. We argue that improvements in the fabrication protocols as, for example, the use of a substrate free of dangling bonds are likely to produce WSe2-based FETs displaying higher room temperature mobilities, i.e. approaching those of p-doped Si, which would make it a suitable candidate for high performance opto-electronics.
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    Intrinsic carrier mobility of multi-layered MoS2 field-effect transistors on SiO2
    (American Institute of Physics, 2013) Pradhan, N.R.; Rhodes, D.; Zhang, Q.; Talapatra, S.; Terrones, M.; Ajayan, P.M.; Balicas, L.
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    Negative Differential Conductance & Hot-Carrier Avalanching in Monolayer WS2 FETs
    (Springer Nature, 2017) He, G.; Nathawat, J.; Kwan, C.-P.; Ramamoorthy, H.; Somphonsane, R.; Zhao, M.; Ghosh, K.; Singisetti, U.; Perea-López, N.; Zhou, C.; Elías, A.L.; Terrones, M.; Gong, Y.; Zhang, X.; Vajtai, R.; Ajayan, P.M.; Ferry, D.K.; Bird, J.P.
    The high field phenomena of inter-valley transfer and avalanching breakdown have long been exploited in devices based on conventional semiconductors. In this Article, we demonstrate the manifestation of these effects in atomically-thin WS2 field-effect transistors. The negative differential conductance exhibits all of the features familiar from discussions of this phenomenon in bulk semiconductors, including hysteresis in the transistor characteristics and increased noise that is indicative of travelling high-field domains. It is also found to be sensitive to thermal annealing, a result that we attribute to the influence of strain on the energy separation of the different valleys involved in hot-electron transfer. This idea is supported by the results of ensemble Monte Carlo simulations, which highlight the sensitivity of the negative differential conductance to the equilibrium populations of the different valleys. At high drain currents (>10 μA/μm) avalanching breakdown is also observed, and is attributed to trap-assisted inverse Auger scattering. This mechanism is not normally relevant in conventional semiconductors, but is possible in WS2 due to the narrow width of its energy bands. The various results presented here suggest that WS2 exhibits strong potential for use in hot-electron devices, including compact high-frequency sources and photonic detectors.