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O: Fachverband Oberflächenphysik

O 45: Focus Session: Scanning Probe Microscopy with Quartz Sensors I

O 45.1: Talk

Wednesday, March 29, 2023, 10:30–10:45, CHE 89

The genesis of the qPlus sensor — •Franz Giessibl — Institute of Experimental and Applied Physics, University of Regensburg, Universitätsstraße 31, 93053 Regensburg

In 1985, Gerd Binnig found exile from the STM frenzy at IBM Rüschlikon by a one year move to Stanford, the heart of silicon valley, and built the first atomic force microscope (AFM) together with Christoph Gerber and Calvin Quate [1]. Therefore, it is not surprising that the core of all AFMs, the cantilever, was soon micromachined from Si. Even the first successful imaging of Si 7x7 relied on piezoresistive Si cantilevers in the frequency modulation mode, albeit at an insanely large oscillation amplitude of 34 nm [2]. Benchmarking, widely used in management consulting, led to the conviction that quartz tuning forks with their utmost frequency stability would be a promising alternative. The phantastic frequency stability of the quartz forks used in Swatch watches and the realization that their stiffness allows sub-Angstrom oscillation amplitudes led to the invention of the qPlus sensor. Its stability, small amplitudes and low noise soon enabled subatomic resolution by AFM [3]. While qPlus sensors are standard in vacuum today, it is open if widespread application in ambient or liquid environments will become attractive, although atomic resolution has been demonstrated [4]. [1] G. Binnig, C.F. Quate, C. Gerber, Phys. Rev. Lett. 56, 930 (1986). [2] F.J. Giessibl, Science 267, 68 (1995). [3] F.J. Giessibl, S. Hembacher, H. Bielefeldt, J. Mannhart, Science 289, 422 (2000). [4] D.S. Wastl, A.J. Weymouth, F.J. Giessibl, Phys. Rev. B 87, 245415 (2013).