Highly Conducting Contacts for Single Molecule Transport Measured by STM-Break Junction*

We present a novel method to directly link single alkane chains to gold electrodes using trimethyl tin (SnMe$_{3})$ linkers. We characterize electron transport through single molecule junctions using the STM-based break-junction technique, where a gold point contact is repeatedly formed and broken in a solution of the SnMe$_{3}$-alkanes while conductance is measured.~Based on analysis of more than 10,000 individual junctions, we find that we create single molecule junctions which are $\sim $100 times more conducting than those with alkanes terminated with any other linker previously studied. The contact resistance, determined by extrapolating to zero carbons, is 4k$\Omega $, two orders of magnitude lower than analogous values found using amine linkers. Strong evidence supports the hypothesis that \textit{in situ} cleaving of the SnMe$_{3}$ end groups facilitates the formation of a direct bond between the carbon backbone and gold leads, thereby enhancing conductance.~We corroborate this result by comparing the conductance of junctions formed from SnMe3- and Ph$_{3}$PAu-terminated benzenes.