Standard vs. Rotated AFM Tips
The large majority of the silicon AFM probes we offer have pyramidal AFM tips which fall into two main categories: standard and rotated AFM tips. In both cases the AFM tip pyramid is roughly symmetric when viewed along the AFM cantilever axis. However, when viewed from the side, the pyramid edges have different slopes with respect to the normal to the cantilever plane.
The front edge of standard (non-rotated) AFM tips has a lower slope than the back edge.
The front edge of rotated AFM tips has a steeper slope than the back edge.
When a standard AFM probe is mounted in the AFM head at the industry-standard angle of 10-13⁰, the back edge of the AFM tip pyramid is roughly vertical and the front edge is at a 35-45⁰ angle to the vertical. With a rotated AFM probe mounted in the AFM head, the front and back edges of the AFM tip pyramid are both at 20-25⁰ angles to the vertical.
When a standard AFM tip is used for measuring structures with tall and steep sidewalls, the back sidewall is visualized accurately, however the front sidewall appears significantly less steep than it actually is. On the other hand, rotated AFM tips cause an equal and moderate image distortion of the sidewalls in all directions. The representation of the structure in this case is much more symmetric.
The choice of AFM tip depends on the AFM sample and the goal of the AFM measurement. If it is important to measure the sidewall angles at certain positions on the sample more precisely, then standard AFM tips are the right choice. In case a more balanced image is preferred with equal sidewall distortion in all directions, rotated AFM tips should be used.
On samples with relatively smooth topography both types of AFM tips can track the sample surface equally well.
For more information on tip-related AFM image artefacts please refer to our application note AFM Tip Shape Effects.
All NanoWorld Pointprobe® AFM probes have standard, non-rotated AFM tips. All MikroMasch® and BudgetSensors® silicon AFM probes have rotated AFM tips. NANOSENSORS™ PointProbe® Plus series offer both standard and rotated AFM tips. Visit our AFM Tips Guide to browse our large selection of standard AFM tips and rotated AFM tips.
Neither standard, nor rotated AFM tips are suitable for measurements on samples with high aspect ratio trenches. The specialized high aspect ratio (HAR) AFM probes are designed specifically for measurements on such samples.
