Large sample NanoScope AFMs, such as the Dimension 3000, 5000 or Vx series, or the BioScope, sometimes suffer from a problem we call “Z drift”. Upon engage, the Z position of the tip (as measured by the Z center voltage) is supposed to be near the center of the Z piezo range and, ideally, the average Z position should stay nearly constant while scanning, except as needed to track the surface topography. When an AFM suffers from Z drift, the Z position starts near the center of range at the moment the tip engages the surface, but then changes so that the Z position approaches or exceeds the retracted or extended limit. This can be annoying and costly. It is annoying when Z drift is accompanied by XY drift, resulting in distortion of high magnification images. It is more annoying when images of rough surfaces are partly out of range. It is costly when high forces are produced at the retracted limit, damaging the surface or breaking the tip.

Whether Z drift is a critical problem for you depends on how rapid the Z drift is, how long you want to scan at a single engage spot, and on other requirements. ASM has recently developed a service procedure for diagnosing and correcting the problem, achieving a great reduction in the Z drift rate without the need for expensive replacement or overhaul of your Z stage.

If your AFM has Z drift, contact ASM. We can help.