Since its very discovery, AFM has held the great promise as a technique of choice for non-destructive surface measurements. To achieve this goal, one need to decrease to a minimum the tip-sample interaction force. The strong interaction force can bring about deformation and/or destruction of the surface of soft, fragile, liquid and weakly adhering samples.

Soft and fragile samples can be imaged in Non-contact and Tapping modes only. Contact mode AFM is characterized by the presence of uncontrollable shear forces able to modify the morphological features.

To avoid sample deformation due to mechanical contact with an AFM tip in Tapping mode, one needs to decrease to a minimum the tip-sample interaction force by using sharp tips, soft cantilevers, smaller amplitudes, and higher set-point ratios. High resolution images of soft samples can be obtained by regular General Purpose tips; however, a better performance was achieved using Hi'RES probes.

Tapping mode

Hi'RES-C probes (Rtip<1nm) mounted on soft cantilever with a spring constant of 5 N/m and lower are recommended for scanning delicate samples in Tapping mode. "Light" tapping conditions including small free cantilever amplitudes (0.1..0.2V) and high setpoint ratios (0.8..0.95) provide stable imaging. Under light tapping conditions, Hi'RES-C probes do not break and remain clean during long-term measurements.

However, extra attention should be paid to engagement of Hi'RES probe. Scan rate should start at below 1 Hz. Scan size should start out at 50nm x 50nm.

Note that there can be additional smaller (satellite) spikes near the main one. Therefore, Hi'RES-C probes can be used on flat samples only with RMS surface roughness is below 1 nm. Corrugates surfaces may interact with satellite spikes on HI'RES-C probe resulting in double or multiple features.

Noncontact mode

Non-destructive surface imaging is also attainable in non-contact mode under ultra high vacuum conditions using regular GP probes. Cantilevers of DP15 series having high spring constant of 20..100 N/m and high resonant frequency over 300 kHz are usually used in this mode.