(a) qPlus sensor with glued diamond tip on the front surface of the free tuning fork prong. In (b) the magnification of the tip, and (c) the top view of the tapered diamond tip are depicted.
(a) Topography of the graphene surface. (b) Same image rendered in 3D, with a ten time magnification in the z-direction to point out the graphene ridges on the lower terrace and on top of the steps. The ridges are marked with arrows in both pictures.
Schematic arrangement of sensor and sample. Only the tip of the qPlus sensor is immersed in liquid, therefore the damping is limited and the Q value stays relatively high.
Topographic image of calcite, showing steps in PEG. A profile line in the topography depicts steps with a height of 3.16 Å.
Progression of scans showing continuous dissolution process on calcite. The dissolution is caused by an increased setpoint of the frequency shift (from +10 Hz to +40 Hz). Picture (a) with a size of 105 nm depicts the center for the series. For (b) the size was increased to 200 nm. Clearly the dissolution of one monolayer of the calcite surface can been examined. In (c) the center was moved slightly to the right and upwards. Here, larger dissolved areas can be seen. The bar in picture (a) from the bottom right to the top left is now completely gone. Picture (d) has the center on the top of the scanframe. Horizontal lines are caused by scans of the baseline before starting a new scan.
Topography of a different kind of surface structure on calcite. Meandering step edges can be seen.
The values for the cantilever in liquid are taken from Fukuma et al. (Ref. 1) (except for the bandwidth B which was set to 1 kHz in Fukuma et al.’s atomically resolved data, where δ⟨k ts ⟩ min amounts to 25 mN/m). The qPlus sensor data are the ones used in the experimental part and the qPlus* data are calculated for a recently tested amplifier with a lower deflection noise density. The force gradient for the thermal- (δk ts th ), detector- (δk ts det ), and oscillator frequency noise (δk ts osc ) is listed and the minimum detectable average force gradient δ⟨k ts ⟩ min can be compared for the different sensors in liquid.
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