  We developed THz-resonant scanning probe tips, yielding strongly enhanced and
nanoscale confined THz near fields at their tip apex. The tips with length in
the order of the THz wavelength ({\lambda} = 96.5 {\mu}m) were fabricated by
focused ion beam (FIB) machining and attached to standard atomic force
microscopy (AFM) cantilevers. Measurements of the near-field intensity at the
very tip apex (25 nm radius) as a function of tip length, via graphene-based
(thermoelectric) near-field detection, indicate their first and second order
geometrical antenna resonances for tip length of 33 and 78 {\mu}m,
respectively. On resonance, we find that the near-field intensity is enhanced
by one order of magnitude compared to tips of 17 {\mu}m length (standard AFM
tip length), which is corroborated by numerical simulations that further
predict remarkable intensity enhancements of about 107 relative to the incident
field. Because of the strong field enhancement and standard AFM operation of
our tips, we envision manifold and straightforward future application in
scattering-type THz near-field nanoscopy and THz photocurrent nanoimaging,
nanoscale nonlinear THz imaging, or nanoscale control and manipulation of
matter employing ultrastrong and ultrashort THz pulses.
