In-situ intercalation of VSe2(0001) with K: direct observation of near-surface structure transformation by incoherent medium-energy electron diffraction

The intercalation of VSe2 with K is investigated in situ by a new technique for imaging the near-surface atomic structure, which is based on forward focusing of backscattered electrons. It is shown that room-temperature deposition of a few K monolayers on to the VSe2(0001) surface results in drastic changes of the crystal structure. Both a considerable expansion of the crystal lattice (the interlayer SeSe distance is increased by 75%) and a transition from 1T to 3R(I) structure are revealed.