  With shrinking dimensions in integrated circuits, sensors, and functional
devices, there is a pressing need to develop nanofabrication techniques with
simultaneous control of morphology, microstructure, and material composition
over wafer length scales. Current techniques are largely unable to meet all
these conditions, suffering from poor control of morphology and defect
structure or requiring extensive optimization or post-processing to achieve
desired nanostructures. Recently, thermomechanical nanomolding (TMNM) has been
shown to yield single-crystalline, high aspect ratio nanowires of metals,
alloys, and intermetallics over wafer-scale distances. Here, we extend TMNM for
wafer-scale fabrication of 2D nanostructures. Using Cu, we successfully
nanomold Cu nanoribbons with widths < 50 nm, depths ~ 0.5-1 microns and lengths
~ 7 mm into Si trenches at conditions compatible with back end of line
processing. Through SEM cross-section imaging and 4D-STEM grain orientation
maps, we show that the grain size of the bulk feedstock is transferred to the
nanomolded structures up to and including single crystal Cu. Based on the
retained microstructures of molded 2D Cu, we discuss the deformation mechanism
during molding for 2D TMNM.
