  Manipulating materials at the nanometer scale is challenging, particularly if
alignment with nanoscale electrodes is desired. Here we describe a
lithography-free, self-aligned nanotrench ablation (SANTA) technique to create
nanoscale trenches in a polymer like poly(methyl) methacrylate (PMMA). The
nanotrenches are self-aligned with carbon nanotube (CNT) and graphene ribbon
electrodes through a simple Joule heating process. Using simulations and
experiments we investigate how the Joule power, ambient temperature, PMMA
thickness, and substrate properties can improve the spatial resolution of this
technique. We achieve sub-20 nm nanotrenches for the first time, by lowering
the ambient temperature and reducing the PMMA thickness. We also demonstrate a
functioning nanoscale resistive memory (RRAM) bit self-aligned with a CNT
control device, achieved through the SANTA approach. This technique provides an
elegant and inexpensive method to probe nanoscale devices using self-aligned
electrodes, without the use of conventional alignment or lithography steps.
