SAMPLE PREPARATION: Checking for sample flatness
You can check the sample flatness by either optical microscope or white-light profilometer. However, it is not always possible to judge relief by optical microscope and samples may require scanning by ZYGO white-light profilometer or a similar instrument with sub-micron resolution.
By optical microscope, use the hash marks on the focus knob to determine the difference in height between the focal plane at the sample vs. epoxy surface.
White-light profilometers are commonly housed in the Materials Science department of a university and can produce sub-micron-resolution maps of surface topography.