Practical aspects of the use of the X2 holder for HRTEM-quality TEM sample preparation by FIB

The X2 holder enables the effective production of thin, electron transparent samples for high-resolution transmission electron microscopy (HRTEM). Improvements to the X2 holder for high-quality transmission electron microscopy (TEM) sample preparation are presented in this paper. We discuss the influence of backscattered electrons (BSE) from the sample holder in determining the lamella thickness in situ and demonstrate that a significant improvement in thickness determination can be achieved by comparatively simple means using the relative BSE intensity. We show (using Monte Carlo simulations) that by taking into account the finite collection angle of the electron backscatter detector, an approximately 20% underestimation of the lamella thickness in a silicon sample can be avoided. However, a correct thickness determination for light-element lamellas still remains a problem with the backscatter method; we introduce a more accurate method using the energy dispersive X-ray spectroscopy (EDX) signal for in situ thickness determination. Finally, we demonstrate how to produce a thin lamella with a nearly damage-free surface using the X2 holder in combination with sub-kV polishing in the Fischione Instruments׳ NanoMill® TEM specimen preparation system.