Electronic properties and structure of stage-4 MoCl5 GICs prepared from highly crystallized graphite films

Films of stage-4 MoCl5 graphite intercalation compound (GIC) were synthesized from laboratory-prepared high-quality graphite films and their electronic properties such as electrical conductivity, Hall coefficient and transverse magnetoresistance were measured at 300, 77 and 1.3 K. The graphite films were prepared from polyimide films of Kapton (25 μm thick) and pyromellitic dianhydride-p-phenylenediamine-3,3′,4,4′-tetraaminobiphenyl (PMDA-PPD-TAB, molar ratio 100/92/4, hereafter called PPT) (45 μm thick) by heating them up to 3200 °C. The stage-4 MoCl5 GICs were made by heating the graphite films in a glass tube with a mixture of natural graphite flakes and MoCl5 powder at 450 °C for 7 days. Majority carriers in GICs were holes, the density of which was estimated to be about 5.2 × 1026 m−3 at 1.3 K. A Shubnikov-de Haas oscillation with a period of 7.84 × 10−3 T−1 and slight modulation of the amplitude was observed in the dependence of the transverse magnetoresistance on magnetic field at 1.3 K for both GIC films. The electronic and structural parameters suggested that the GIC film from a polyimide PPT has less perfect crystallinity than that from a polyimide Kapton, even though the pristine graphite film from PPT has better crystallinity.