Lattice dynamics of CaC 6 by Raman spectroscopy

Wirtz

Pichler

2014

Graphite intercalation compounds (GICs) are an interesting and highly studied field since 1970's. It has gained renewed interest since the discovery of superconductivity at high temperature for CaC 6 and the rise of graphene. Intercalation is a technique used to introduce atoms or molecules into the structure of a host material. Intercalation of alkali metals in graphite has shown to be a controllable procedure recently used as a scalable technique for bulk production of graphene, and nano-ribbons by induced exfoliation of graphite. It also creates supra-molecular interactions between the host and the intercalant, inducing changes in the electronic, mechanical, and physical properties of the host. GICs are the mother system of intercalation also employed in fullerenes, carbon nanotubes, graphene, and carbon-composites. We will show how a combination of Raman and ab-initio calculations of the density and the electronic band structure in GICs can serve as a tool to elucidate the electronic structure, electron-phonon coupling, charge transfer, and lattice parameters of GICs and the graphene layers within. This knowledge of GICs is of high importance to understand superconductivity and to set the basis for applications with GICs, graphene and other nano-carbon based materials like nanocomposites in batteries and nanoelectronic devices.

Section: Superconductivity In Stage I Gic and Implications For Intercsupporting

confidence: 55%

Section: Superconductivity In Stage I Gic and Implications For Intercmentioning

confidence: 56%

Section: Superconductivity In Stage I Gic and Implications For Intercmentioning

confidence: 99%

Section: Superconductivity In Stage I Gic and Implications For Intercmentioning

confidence: 99%

Section: Feature Articlementioning

confidence: 99%

See 3 more Smart Citations

Raman spectroscopy of graphite intercalation compounds: Charge transfer, strain, and electron–phonon coupling in graphene layers

Wirtz

Pichler

2014

Defect modulated Raman response of KC₈ single crystals

Pichler

2011

In situ experiments of graphite intercalation with potassium have been performed under high vacuum (HV) conditions. A detailed Raman lineshape analysis of the G‐line was applied to determine the intrinsic response of the stage one KC8 compound. Four defect‐modulated graphite single crystals were analyzed. We observe five vibrational modes (∼560, 1260, 1510, 1547, and 1563 cm−1). From a Breit–Wigner–Fano (BWF) lineshape analysis we elucidate the contribution of each vibrational mode observed. The intensity of the z‐axis mode (CZ) around ∼560 cm−1 varies depending on the defect modulated nominal KC8 crystal chosen. We prove that the intrinsic G‐line of KC8 is at 1510 cm−1, and it is strongly dependent on the actual defect content in the sample, which has important implications for the electron phonon coupling (EPC) responsible of superconductivity in this system.

De‐intercalation process from Stage‐1 to Stage‐2 graphite intercalation compounds revisited

Ganin

Rosseinsky

et al. 2012

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 deintercalation 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 2g Fano mode at $1510 cm À1 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 À1 . 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 deintercalation. 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.