Maskless Arbitrary Writing of Molecular Tunnel Junctions

Since fabricating geometrically well-defined, noninvasive, and compliant electrical contacts over molecular
monolayers is difficult, creating molecular-scale electronic devices
that function in high yield with good reproducibility is challenging.
Moreover, none of the previously reported methods to form
organic−electrode contacts at the nanometer and micrometer scales
have resulted in directly addressable contacts in an untethered form
under ambient conditions without the use of cumbersome
equipment and nanolithography. Here we show that in situ
encapsulation of a liquid metal (eutectic Ga−In alloy) microelectrode, which is used for junction formation, with a convenient
photocurable polymeric scaffold enables untethering of the electrode
and direct writing of arbitrary arrays of high-yielding molecular
junctions under ambient conditions in a maskless fashion. The formed junctions function in quantitative yields and can afford
tunneling currents with high reproducibility; they also function at low temperatures and under bent. The results reported here
promise a massively parallel printing technology to construct integrated circuits based on molecular junctions with soft top
contacts