Abstract
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.
Highlights
Scanning tunneling microscopy (STM) that uses two tips simultaneously, called double-tip STM, relies on two individually driven metal wire probes brought into close proximity to locally probe the resistivity[1,2,3] or access proposed electron correlations at the nanoscale[4,5,6,7,8,9,10,11]
High-magnification images provide a detailed view of the apices of the tips, where Fig. 1b was taken before the focused ion beam (FIB) step
The excellent mechanical and insulating properties of the silicon nitride (SiN) allow us to keep the tips attached via the SiN and utilize highresolution FIB milling of the metal layer to separate the two tips
Summary
Scanning tunneling microscopy (STM) that uses two tips simultaneously, called double-tip STM, relies on two individually driven metal wire probes brought into close proximity to locally probe the resistivity[1,2,3] or access proposed electron correlations at the nanoscale[4,5,6,7,8,9,10,11]. Achieving tip separation down to the nanometer scale, a long-standing goal in multiprobe STM, has proven challenging and is limited by the radius of curvature of the two tips[12] and requires sophisticated navigation routines[13,14]. Multiprobe systems able to achieve tip separation down to 30 nm have emerged[1,13] and have resulted in the first double-tip correlation measurements to date[15]. These experiments, must undergo complicated alignment procedures and are limited to specialized STM setups.
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