Nanofabricated tips as a platform for double-tip and device based scanning tunneling microscopy

We introduce a new kind of tip for scanning tunneling microscopy (STM) and report on its fabrication and performance [1]. By fully incorporating a metallic tip on a silicon chip using modern micromachining and nanofabrication techniques, we realize so-called smart tips and show the possibility of device-based STM tips. Contrary to traditional etched/grinded wire tips, these can be integrated in lithographically defined electrical circuits, photonic circuits and mechanical systems. We experimentally demonstrate the high performance of the smart tips, both in stability and resolution. In situ tip preparation methods are possible and we verify that they can resolve the herringbone reconstruction and Friedel oscillations on Au(111) surfaces. Smart tips can allow to considerably extend the range of STM, for example by enabling high-frequency tips to study noise on majorana zero modes and spin resonances, local gating using two tips or spin sensitive devices. As an example we present in detail two isolated tips with sub-50 nm apex-to-apex distance and calculations of how this can be used to measure electron correlations at the nanoscale.

[1] M. Leeuwenhoek et al., arXiv:1712.08620 (2017).