Fabrication of on-chip probes for double-tip scanning tunneling microscopy

A reduction of the interprobe distance in multiprobe and double-tip scanning tunneling microscopy to the nanometer scale has been a longstanding and technically difficult challenge. Recent multiprobe systems have allowed for significant progress by achieving distances of ~30 nm using two individually driven, traditional metal wire tips. For situations where simple alignment and fixed separation can be advantageous, we present the fabrication of on-chip double-tip devices that incorporate two mechanically fixed gold tips with a tip separation of only 35 nm. We utilize the excellent mechanical, insulating and dielectric properties of high-quality SiN as a base material to realize easy-to-implement, lithographically defined and mechanically stable tips. With their large contact pads and adjustable footprint, these novel tips can be easily integrated with most existing commercial combined STM/AFM systems.