ORDERING OF ADSORBED ORGANIC MONOLAYERS CONFINED IN MOLECULE CORRALS DURING SCANNING-TUNNELING-MICROSCOPY OBSERVATION

Since the first report of the imaging of organic molecules by scanning tunneling microscopy (STM) (Foster, J. S.; Frommer, J. E. Nature 1988 , 333, 542-545) questions have arisen about the physical interaction b etween the scanning tip and the adsorbed monolayer. How much this inte raction affects the adsorbed monolayer, and whether the monolayer stru cture observed by STM is the same structure which is present in the ab sence of STM observation have been difficult questions to address, sin ce the monolayer typically cannot be seen at high resolution except by STM. Many reports of tip-induced substrate damage have appeared, but here we report nondestructive tip-induced orientation of an adsorbed m onolayer confined in molecule corrals and on graphite terraces. We bel ieve this is the first evidence that in some cases the scanning action of the STM tip can act to orient an adsorbed monolayer. For adsorbed monolayers of octadecanol and octatriacontane, the structures observed by STM are not the same structures which are present in the absence o f STM observation. The ordering action of the STM tip removes informat ion about the initial appearance of the monolayer but may lead to bett er understanding of the physical interactions between the tip and adso rbed monolayers and between the adsorbed monolayers and the substrate.