  Single-crystal carbon nanomaterials have led to great advances in
nanotechnology. The first single-crystal carbon nanomaterial, fullerene, was
fabricated in a zero-dimensional form. One-dimensional carbon nanotubes and
two-dimensional graphene have since followed and continue to provide further
impetus to this field. In this study, we fabricated designed three-dimensional
(3D) single-crystal carbon architectures by using silicon carbide templates.
For this method, a designed 3D SiC structure was transformed into a 3D
freestanding single-crystal carbon structure that retained the original SiC
structure by performing a simple single-step thermal process. The SiC structure
inside the 3D carbon structure is self-etched, which results in a 3D
freestanding carbon structure. The 3D carbon structure is a single crystal with
the same hexagonal close-packed structure as graphene. The size of the carbon
structures can be controlled from the nanoscale to the microscale, and arrays
of these structures can be scaled up to the wafer scale. The 3D freestanding
carbon structures were found to be mechanically stable even after repeated
loading. The relationship between the reversible mechanical deformation of a
carbon structure and its electrical conductance was also investigated. Our
method of fabricating designed 3D freestanding single-crystal graphene
architectures opens up prospects in the field of single-crystal carbon
nanomaterials, and paves the way for the development of 3D single-crystal
carbon devices.
