FIGURE 2-34 Software window used for measuring force/distance curves with an AFM.

2.5 LL-AFM Cantilevers and Probes

An LL-AFM force sensor requires a cantilever with a probe at its end for operation. Typically these are fabricated using MEMS technology and are considered a disposable component of the AFM. In principle, an AFM probe should last forever; however, in practice the probe tip is often blunted when it touches a surface. Changing the probe typically takes only a few minutes. Figure 2-35 illustrates the geometry of a typical probe/cantilever/substrate.

FIGURE 2-35 Illustration of an AFM cantilever/probe/substrate created by micromachining of Si or SiN. All commercially available probes have substrates with the same dimension.

The geometry of the probe is critical to the quality of images measured with an AFM. All AFM images are a convolution of probe geometry and surface. As an example, in Figure 2-36, if the probe cannot reach the bottom of the surface feature, the image will not indicate the correct geometry of the sample.