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

The sequential intercalation process of potassium atoms into a stage-2 CoCl2-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 CoCl2-graphite intercalation compound and potassium metal sealed into an evacuated Pyrex glass tube. At temperatures TK=130°C and Ts=230°C for the potassium metal and stage-2 CoCl2-graphite intercalation compound, respectively, we observed a heterostructure with an interplanar spacing dH=d1+d2=14.65, where d1=9.30 corresponds to a C-CoCl2-C stacking, and d2=5.35 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.