In situx-ray study of an acceptor-donor heterostructure: Stage-1CoCl2-K-graphite intercalation compound

The sequential intercalation process of potassium atoms into a stage-2 ${\mathrm{CoCl}}_2$-graphite intercalation compound has been studied by in situ x-ray (00l) scans. The heterostructure was made in a two-zone furnace with pre-prepared stage-2 ${\mathrm{CoCl}}_2$-graphite intercalation compound and potassium metal sealed into an evacuated Pyrex glass tube. At temperatures $T_{\mathrm{K}}$=130 °C and $T_s$=230 °C for the potassium metal and stage-2 ${\mathrm{CoCl}}_2$-graphite intercalation compound, respectively, we observed a heterostructure with an interplanar spacing $d_H$=$d_1$+$d_2$=14.65 Å, where $d_1$=9.30 Å corresponds to a C-${\mathrm{CoCl}}_2$-C stacking, and $d_2$=5.35 Å to a C-K-C stacking. This is the first observation of a donor-acceptor heterostructure. The kinetics of the transformation from stage-2 CoCl-graphite intercalation compound to stage-1 heterostructure can be understood by the movement of potassium atoms through Daumas-Hérold domains.