Low-noise platform for in situ structural and electrical characterization by sub-Ångstrøm low-voltage transmission electron microscopy (SALVE IV)
Zusammenfassung der Projektergebnisse
During Phase II of the in situ SALVE project, we developed a TEM specimen holder and the requisite experimental expertise to perform in situ 4-probe electrical analysis of freestanding graphene sheets during transmission electron microscopy investigations. This enabled us to employ van der Pauw-type Hall measurements to characterize the changes in graphene electrical properties induced by electron beam irradiation. Moreover, by passing a fairly large electrical current through graphene membranes mounted on our TEM specimen holder, we found that we could raise the sample temperature above 2000 K by Joule heating - a procedure that was discovered to be effective in removing contamination from the surface. Electron irradiation of ‘contaminated’ graphene led to a systematic degradation of the carrier mobility along with an increase in carrier concentration, while no such effects were noted with ‘clean’ samples. When we applied the same heating protocol to graphene sheets covered with Au nanoparticles, we discovered the formation of a novel metastable AuC phase, the structure of which could be deduced from TEM imaging, EELS spectra and density functional theory calculations; the latter provided additional information regarding fundamental properties of this new material. Finally, we built up an in-house capacity for graphene synthesis by constructing a chemical vapor deposition (CVD) chamber. After optimizing the CVD parameters for growing large, single-layer graphene regions on Cu substrates and mastering the transfer of the resulting specimens to arbitrary substrates, we evaluated the potential application of CVD-grown graphene membranes as optically transparent resistive heaters.
Projektbezogene Publikationen (Auswahl)
-
“Graphene-based sample supports for in situ high-resolution TEM electrical investigations”, J. Phys. D: Appl. Phys., vol. 44, pp. 055502-1–7, 2011
B. Westenfelder, J.C. Meyer, J. Biskupek, G. Algara-Siller, L.G. Lechner, J. Kusterer, U. Kaiser, C.E. Krill III, E. Kohn, and F. Scholz
-
“Transformations of carbon adsorbates on graphene substrates under extreme heat”, Nano Lett., vol. 11, pp. 5123–5127, 2011
B. Westenfelder, J.C. Meyer, J. Biskupek, S. Kurasch, F. Scholz, C.E. Krill III, and U. Kaiser
-
“Atom-by-atom observation of grain boundary migration in graphene”, Nano Lett., vol. 12, pp. 3168–3173, 2012
S. Kurasch, J. Kotakoski, O. Lehtinen, V. Skakalova, J. Smet, C.E. Krill III, A.V. Krasheninnikov, and U. Kaiser
