Browsing by Author "Feng, S."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item FAUST - V. Hot methanol in the [BHB2007] 11 protobinary system; hot corino versus shock origin(EDP Sciences, 2022) Vastel, C.; Alves, F.; Ceccarelli, C.; Bouvier, M.; Jiménez-Serra, I.; Sakai, T.; Caselli, P.; Evans, L.; Fontani, F.; Gal, R. Le; Chandler, C.J.; Svoboda, B.; Maud, L.; Codella, C.; Sakai, N.; Lόpez-Sepulcre, A.; Moellenbrock, G.; Aikawa, Y.; Balucani, N.; Bianchi, E.; Busquet, G.; Caux, E.; Charnley, S.; Cuello, N.; Simone, M. De; Dulieu, F.; Durân, A.; Fedele, D.; Feng, S.; Francis, L.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Imai, M.; Isella, A.; Johnstone, D.; Lefloch, B.; Loinard, L.; Maureira, M.; Murillo, N.M.; Mercimek, S.; Mori, S.; Menard, F.; Miotello, A.; Nakatani, R.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Ospina-Zamudio, J.; Oya, Y.; Pineda, J.E.; Podio, L.; Rimola, A.; Cox, D. Segura; Shirley, Y.; Testi, L.; Viti, S.; Watanabe, N.; Watanabe, Y.; Witzel, A.; Xue, C.; Zhang, Y.; Zhao, B.; Yamamoto, S.Aims.Methanol is a ubiquitous species commonly found in the molecular interstellar medium. It is also a crucial seed species for the build-up of chemical complexity in star forming regions. Thus, understanding how its abundance evolves during the star formation process and whether it enriches the emerging planetary system is of paramount importance.Methods. We used new data from the ALMA Large Program FAUST (Fifty AU STudy of the chemistry in the disc/envelope system of solar protostars) to study the methanol line emission towards the [BHB2007] 11 protobinary system (sources A and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disc has previously been detected.Results. Twelve methanol lines have been detected with upper energies in the [45–537] K range along with one 13CH3OH transition and one methyl formate (CH3OCHO) line blended with one of the methanol transitions. The methanol emission is compact (FWHM ~ 0.5″) and encompasses both protostars, which are separated by only 0.2″ (28 au). In addition, the overall methanol line emission presents three velocity components, which are not spatially resolved by our observations. Nonetheless, a detailed analysis of the spatial origin of these three components suggests that they are associated with three different spatial regions, with two of them close to 11B and the third one associated with 11A. A radiative transfer analysis of the methanol lines gives a kinetic temperature of [100–140] K, an H2 volume density of 106–107 cm−3 and column density of a few 1018 cm−2 in all three components with a source size of ~0.15″. Thus, this hot and dense gas is highly enriched in methanol with an abundance as high as 10−5. Using previous continuum data, we show that dust opacity can potentially completely absorb the methanol line emission from the two binary objects.Conclusions. Although we cannot firmly exclude other possibilities, we suggest that the detected hot methanol is resulting from the shocked gas from the incoming filaments streaming towards [BHB2007] 11A and B, respectively. Higher spatial resolution observations are necessary to confirm this hypothesis.Item 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.