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

The two-dimensional molecular lamellar arrangement of long chain alkanes adsorbed on the basal plane of graphite and its thermally induced disordering has been studied by variable temperature scanning tunneling microscopy. Atomic scale resolution of the disordered phase is achieved by studying the quenched high temperature phase. Overall as well as conformational disorder, in particular molecular kink defects, have been observed. High temperature snapshots show that the thermal evolution towards molecular disorder proceeds via small longitudinal fluctuations of molecules or blocks of molecules around their average positions. For increasing temperatures, molecular excursions along the long axis of the molecules become larger until eventually the lamellae lose their individuality, accompanied by substantial loss of lateral order.