Nanometer scale metallic contacts which can be directly deposited on planar
substrates are of growing importance in view of future applications
involving the integration of molecular electronics with current silicon
technology. Here, a method which may provide well defined nanogap
electrodes of predetermined spacing in a reproducible manner, without the
need of sequential direct writing techniques, would be highly advantegous.
We present a novel technique using direct high-resolution metal
nanotransfer printing and demonstrate its capability to fabricate nanogap
electrodes of predetermined spacing on a solid substrate such as silicon. The
one-step transfer process is economical, simple and fast, and preserves the
mold for manifold transfer. Using molecular beam epitaxy (MBE) a
sandwich-like structure is grown with monolayer precision, comprising few nanometer thick GaAs layers embedded in AlGaAs. This structure is
cleaved atomically flat perpendicular to the <110> crystallographic
direction. Subsequently, the exposed GaAs layers are wet chemically etched
thereby generating a 3D grating structure with nanometer-resolution at their
edges. This structure serves as mold for nanotransfer printing: By coating
the grating surface with a metallic thin film of PdAu/Ti (7/5 nm) and
pressing the mold against a Si/SiO2 substrate the patterned PdAu/Ti
sandwich structure is directly transferred onto the surface. This one-step
process does not require any flexible buffer layer or additional organic
adhesion promoters. We report on a series of successful transfer
experiments using different multi-line molds with varying aspect ratios and
linewidths down to below 10 nm. In particular, we demonstrate electrically
functional PdAu metal electrode pairs with separations down to 25 nm,
featuring lead resistances of the order of kΩ and gap isolation in excess of
50 GΩ up to 2 Volts.