  Refractory materials exhibit high damage tolerance, which is attractive for
the creation of nanoscale field-emission electronics and optoelectronics
applications that require operation at high peak current densities and optical
intensities. Recent results have demonstrated that the optical properties of
titanium nitride, a refractory and CMOS-compatible plasmonic material, can be
tuned by adding silicon and oxygen dopants. However, to fully leverage the
potential of titanium (silicon oxy)nitride, a reliable and scalable fabrication
process with few-nm precision is needed. In this work, we developed a
fabrication process for producing engineered nanostructures with gaps between
10 and 15 nm, aspect ratios larger than 5 with almost 90{\deg} steep sidewalls.
Using this process, we fabricated large-scale arrays of electrically-connected
bow-tie nanoantennas with few-nm free-space gaps. We measured a typical
variation of 4 nm in the average gap size. Using applied DC voltages and
optical illumination, we tested the electronic and optoelectronic response of
the devices, demonstrating sub-10-V tunneling operation across the free-space
gaps, and quantum efficiency of up to 1E-3 at 1.2 {\mu}m, which is comparable
to a bulk silicon photodiode at the same wavelength. Tests demonstrated that
the titanium silicon oxynitride nanostructures did not significantly degrade,
exhibiting less than 5 nm of shrinking of the average gap dimensions over
few-{\mu}m^2 areas after roughly 6 hours of operation. Our results will be
useful for developing the next generation of robust and CMOS-compatible
nanoscale devices for high-speed and low-power field-emission electronics and
optoelectronics applications.
