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De‐intercalation process from Stage ‐1 to Stage ‐2 graphite intercalation compounds revisited
Author(s) -
ChacónTorres J. C.,
Ganin A. Y.,
Rosseinsky M. J.,
Pichler T.
Publication year - 2012
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201200174
Subject(s) - intercalation (chemistry) , raman spectroscopy , graphite , materials science , stage (stratigraphy) , analytical chemistry (journal) , chemistry , optics , inorganic chemistry , physics , chromatography , paleontology , composite material , biology
The identification and contribution of the different phonons present in the G‐line Raman response in Stage ‐1 and Stage ‐2 graphite intercalation compounds (GIC) is crucial for a correct stage determination. Different factors like laser induced de‐intercalation play an important role in the precise stage assignment of these phases, and their intrinsic Raman response. In this contribution, an in situ micro‐Raman analysis was conducted under high‐vacuum conditions. Local heating of the samples was induced by using a high laser power (8.5 mW) in order to study the de‐intercalation process from Stage ‐1 to Stage ‐2 GICs. A detailed Raman line‐shape analysis was performed from the recorded spectra to determine the changes from the G‐line response of KC 8 , CaC 6 , and LiC 6 . We confirmed the assignment of the broad E 2 g Fano mode at ∼1510 cm −1 to the intrinsic Stage ‐1 Raman response in GICs. Additionally, the most evident change from Stage ‐1 to Stage ‐2 was observed in an asymmetric Fano mode in the range of 1565–1610 cm −1 . This mode is linked to the first‐order stretching Raman mode of Graphite, which tends to increase in frequency and decrease in width as function of de‐intercalation. Finally, the response of the Stage ‐2 phase after de‐intercalation was confirmed to be a useful benchmark for the identification of the intercalation stage in highly doped GICs.