Scanning force microscopy ͑SFM͒ is employed to study nm-scale wear of single-crystal calcite in an aqueous solution. When the SFM tip is drawn back and forth in a linear fashion across the edge of a preexisting single atomic layer etch pit, dissolution is strongly enhanced at the point where the tip crosses the step. The wear rate as a function of contact force is consistent with a thermally activated wear process, where the activation energy is locally reduced in the strain field of the SFM tip. The activation volume for the strain dependence is on the order of the average volume per ion in the CaCO 3 lattice. This study provides further support for strain enhanced nucleation of double kinks along preexisting steps.

We report scanning force microscope (SFM) observations of enhanced calcite dissolution in aqueous solution due to mechanical stimulation induced by the SFM tip. Images and mechanical treatment were performed in saturated (≥60 μM) CaCO3 solution adjusted to pH ∼9. Small area scans of monolayer steps significantly increase the step velocity in the scanned area (in the direction corresponding to dissolution) when the applied contact force is above about 160 nN for the tips employed. The step velocity could be increased at least an order of magnitude by scanning at even higher contact forces (e.g., 270 nN). This enhancement is a function of step orientation relative to the calcite lattice. Indentations near preexisting steps also locally enhance the step velocity. We present evidence that the higher dissolution rates are caused by stress-induced increases in the rate of double-kink nucleation.

We report measurements of the neutral and ion emissions accompanying laser irradiation of cleaved and abraded NaNO3 and CaCO3. In both materials, abraded surfaces yield especially intense positive ion emissions during laser irradiation at low fluences (i.e., fluences well below those required for surface damage and/or the formation of a fluorescent plume). Abraded NaNO3 also yields extremely intense neutral emissions (NO, O2) derived from NO3− decomposition. Measurements of neutral molecules released during abrasion show significant anion-derived emissions from both materials (CO2 from CaCO3; NO from NaNO3). We attribute the effect of abrasion on the laser-induced emissions to the production of easily photoionized electron traps during abrasion. Such traps are expected to strongly enhance photoinduced ion emission from both materials. Because the NO3− ion undergoes dissociative electron attachment, photoionizable defects also enhance NO emission during laser irradiation. In contrast, the CO32−anion does not appear to undergo dissociative electron attachment and no enhancement of CO2 emission is observed during laser irradiation.

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We report observations of atomic, neutral Mg emitted from single crystal MgO during abrasion with a diamond stylus. These emissions take the form of bursts, where the onset of each burst coincides with a slip event often associated with the passage of the stylus over a cleavage step. After the onset, the emission intensity grows gradually to a peak, then drops sharply. Similar bursts of neutral Mg are observed when indented single crystal MgO is heated to temperatures above 1300°C. We attribute these bursts to the emission of neutral Mg during the relaxation of dislocation-related structures produced by mechanical deformation. Strain energy released as these structures annihilate at the surface drive Mg emission and heat the surrounding material. This heating accelerates subsequent relaxation, increasing the emission intensity until relaxation is complete and the emission rate drops sharply.