When it goes to red press engage (approach the surface) or just increase the force on the tip. Red typically means that piezo has extended or extracted out of its bounds. This helps at least Veeco Dimension 3100 AFM. 

When it goes to red press engage (approach the surface) or just increase the force on the tip. Red typically means that piezo has extended or extracted out of its bounds. This helps at least Veeco Dimension 3100 AFM. 

Hello Subhash!  f you have tried Jarkko's tips and the problem still occurs, than you should check that isn't your sample one-sided. This could also cause the piezo to be extended out of its range.

Dear Subhash,

As Jarkko and Bernadeth said, when tip  goes red is because to scanner is full extended or retracted during engage/approach  process or scanning the sample. It happens mainly beacuse surface plane is not parallel  to bottom surface of the sample or the sample was cement wrong,  in other words, the interest surface has a big slope wich does not allow to scanner adjust into its vertical scan range, you can resolve this issue polishing your substrate asuring both faces are parrellel or be careful when you glue the sample to disk/puck  triying that suface of interest  is as parallel as possible. Other is to approach using a bigger scan size (if the slope is not too big) to compensate where scan starts its vertical scan (typically in the mid of its range) and reduce scan size after engage it until scan size that you want.

Also, probabily the interaction force that you are using (setpoint) is not enough to engage in dynamic method, normally you will need increase a little the force after engage the tip to the surface. If  the engage force is not right,  Z scanner must travel to reach the tip extending  it out of its range, the other side is that force you are using is too high hince the scanner needs to move opposite rectracting it out of its range.

I think  you need to play a little with force/setpoint  in your experiment  to resolve the suturation problem whit the scanner.

I expect this information help you a little.

Best regards.

Óscar.