Structure and bonding in amorphous iron carbide thin films
2015 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 4, 045002- p.Article in journal (Refereed) Published
We investigate the amorphous structure, chemical bonding, and electrical properties ofmagnetron sputtered Fe1−xCx (0.21 < x < 0.72) thin films. X-ray, electron diffraction andtransmission electron microscopy show that the Fe1−xCx films are amorphousnanocomposites, consisting of a two-phase domain structure with Fe-rich carbidic FeCy , and acarbon-rich matrix. Pair distribution function analysis indicates a close-range order similar tothose of crystalline Fe3C carbides in all films with additional graphene-like structures at highcarbon content (71.8 at% C). From x-ray photoelectron spectroscopy measurements, we findthat the amorphous carbidic phase has a composition of 15–25 at% carbon that slightlyincreases with total carbon content. X-ray absorption spectra exhibit an increasing number ofunoccupied 3d states and a decreasing number of C 2p states as a function of carbon content.These changes signify a systematic redistribution in orbital occupation due to charge-transfereffects at the domain-size-dependent carbide/matrix interfaces. The four-point proberesistivity of the Fe1−xCx films increases exponentially with carbon content from ∼200μcm(x = 0.21) to ∼1200μcm (x = 0.72), and is found to depend on the total carbon contentrather than the composition of the carbide. Our findings open new possibilities for modifyingthe resistivity of amorphous thin film coatings based on transition metal carbides through thecontrol of amorphous domain structures.
Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015. Vol. 27, no 4, 045002- p.
iron carbide, thin film coatings, sputtering, synchrotron radiation, amorphous nanocomposites, TEM, RDF
IdentifiersURN: urn:nbn:se:liu:diva-113089DOI: 10.1088/0953-8984/27/4/045002ISI: 000348493500002PubMedID: 25567721OAI: oai:DiVA.org:liu-113089DiVA: diva2:777337
We would like to thank the staff at the MAX IV Laboratory for experimental support, and Jill Sundberg, UU, for help with the Raman measurements. The work was supported by the Swedish Research Council (VR) by project, and Linnaeus grants (VR 2008-6582). MM, UJ and JL also acknowledge the Swedish Foundation for Strategic Research Synergy Project FUNCASE (RMA11-0029).2015-01-082015-01-082016-08-31