Standard free thickness determination of thin TEM samples via backscatter electron image correlation

Due to the ongoing progress in nanotechnology, high resolution TEM investigations become more and more important in structural and chemical material analyses. For such investigations the thickness of the TEM sample should be as thin as possible. The thickness of TEM samples prepared by focused ion beam (FIB) is about 50 to 100 nm. For light elements like silicon this might be sufficient for most of the analytical word. Due to the Z-dependence of the electron scattering it is also necessary to achieve even smaller thicknesses to perform TEM analyses at materials with high mass densities or high atomic numbers like Au or Pt. The difficulties to prepare plane-parallel lamellae with thicknesses of 10 to 50 nm by FIB are known. Common methods especially the FIB preparation do not have the abili ty to control the thickness precisely during the preparation process. Therefore, it is difficult or nearly impossible to stop the FIB sputtering process at the right target thickness.