This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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Spherical-aberration (C_s) correction results in a reduced depth of focus (DoF) with the increase in the convergence angle θ, therefore, the three-dimensional (3-D) sectioning of the samples using STEM [1,2] can be improved. However, the achievable vertical information in real systems would also depend on many sample-related factors, for instance, channelling effect.

[1] Borisevich AY, Lupini AR, Pennycook SJ. Proc Natl Acad Sci USA 2006;103:3044–8.
[2] Xin HL, Muller DA. J Electron Microsc 2009;58:157–65.