MDSPM · Equipment and Methodology for Multi-Dimensional Scanning Probe Microscopy

The ability to perform scanning tunnelling spectroscopy simultaneously with a measurement of the vertical and lateral tip-sample interaction force and energy dissipation on selected atomic or molecular sites is the next revolution in scanning probe microscopy and will revolutionise entire areas of surface science. The aim is to develop, manufacture and commercialise a new UHV low temperature multi-dimensional scanning probe microscope (MDSPM). The two dimensional force and energy dissipation measurement is performed via micro-fabricated cantilevers with relatively high spring constants (200-2000N/m) which are simultaneously driven on their flexural and torsional oscillation modes with sub-Angstroem amplitudes. The deflection sensing is achieved by a focussing Fabry-Perot sensor with an up to 100 MHz bandwidth and an unprecedented sensitivity down to 1 fm/sqrt (Hz). The high bandwith allows the detection of higher oscillation modes and harmonics. While high resonance frequencies are favourable to measure local energy dissipation processes arising from stochastic force fluctuations the detection of higher harmonics may be used to directly reconstruct the force field from a site-specific measurement performed at a selected surfaces site at one fixed tip-sample distance. The operation of the cantilever with ultrasmall amplitudes not only allows the direct measurement of the local force gradient but is ideal for scanning tunnelling spectroscopy with excellent signal-to-noise ratio necessitated by ultra-stable tip-sample positioning. These advances in scanning probe microscopy instrumentation will not only allow to imaging of metallic, semiconducting and insulating surfaces with unprecedented resolution, but will revolutionize our understanding of entire areas of surface science such as: chemical reaction dynamics, local energy dissipation and excitations, nanoscale contacts and a rational approach catalyst design, to name a few.