Small (1.0and 2.5 mm2) areas of the samples were then scanned with the AFM
operating in intermittent contact mode using tapping mode etched silicon probes (TESP). The spring constants for these probes were 20e100 N m1 and the nominal tip radius of curvature was 5e10 nm. The cantilever controls, namely drive frequency, amplitude, gains, and amplitude set point ratio (rsp) were adjusted to give height and phase-shift images with the clearest image details.