THERMALLY-INDUCED DISORDER AND CONFORMATIONAL DEFECTS OF ALKANE MONOLAYERS ON GRAPHITE

The two-dimensional molecular lamellar arrangement of long chain alkan es adsorbed on the basal plane of graphite and its thermally induced d isordering has been studied by variable temperature scanning tunneling microscopy. Atomic scale resolution of the disordered phase is achiev ed by studying the quenched high temperature phase. Overall as well as conformational disorder, in particular molecular kink defects, have b een observed. High temperature snapshots show that the thermal evoluti on towards molecular disorder proceeds via small longitudinal fluctuat ions of molecules or blocks of molecules around their average position s. For increasing temperatures, molecular excursions along the long ax is of the molecules become larger until eventually the lamellae lose t heir individuality, accompanied by substantial loss of lateral order.