Fast and reliable pre-approach for scanning probe microscopes based on tip-sample capacitance

J M de Voogd; M A van Spronsen; F E Kalff; B Bryant; O Ostojić; A M J den Haan; I M N Groot; T H Oosterkamp; A F Otte; M J Rost

doi:10.1016/j.ultramic.2017.05.009

Fast and reliable pre-approach for scanning probe microscopes based on tip-sample capacitance

Ultramicroscopy. 2017 Oct:181:61-69. doi: 10.1016/j.ultramic.2017.05.009. Epub 2017 May 10.

Authors

J M de Voogd¹, M A van Spronsen², F E Kalff³, B Bryant⁴, O Ostojić², A M J den Haan², I M N Groot⁵, T H Oosterkamp², A F Otte³, M J Rost⁶

Affiliations

¹ Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands. Electronic address: voogd@physics.leidenuniv.nl.
² Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
³ Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
⁴ Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands; High Field Magnet Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
⁵ Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands; Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, the Netherlands.
⁶ Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands. Electronic address: rost@physics.leidenuniv.nl.

PMID: 28525802
DOI: 10.1016/j.ultramic.2017.05.009

Abstract

Within the last three decades Scanning Probe Microscopy has been developed to a powerful tool for measuring surfaces and their properties on an atomic scale such that users can be found nowadays not only in academia but also in industry. This development is still pushed further by researchers, who continuously exploit new possibilities of this technique, as well as companies that focus mainly on the usability. However, although imaging has become significantly easier, the time required for a safe approach (without unwanted tip-sample contact) can be very time consuming, especially if the microscope is not equipped or suited for the observation of the tip-sample distance with an additional optical microscope. Here we show that the measurement of the absolute tip-sample capacitance provides an ideal solution for a fast and reliable pre-approach. The absolute tip-sample capacitance shows a generic behavior as a function of the distance, even though we measured it on several completely different setups. Insight into this behavior is gained via an analytical and computational analysis, from which two additional advantages arise: the capacitance measurement can be applied for observing, analyzing, and fine-tuning of the approach motor, as well as for the determination of the (effective) tip radius. The latter provides important information about the sharpness of the measured tip and can be used not only to characterize new (freshly etched) tips but also for the determination of the degradation after a tip-sample contact/crash.

Keywords: Capacitance measurements; Coarse approach; Nano-positioning; Scanning probe microscope; Scanning tunneling microscope; Stepping motor.