Preparing TEM sections by FIB: stress relief to straighten warping membranes

摘要

Stresses in a TEM section can cause considerable problems, both in the preparation of the section and in the subsequent microscopy. As the FIB thins a stressed specimen, warping occurs as the section offers less resistance because of reduced rigidity. Compressive stress is relieved as the membrane finds its own length through excessive local bending. Cutting the membrane at one end allows the thinned region to expand into the cut without the necessity to bend out of the original plane. The membrane straightens for further thinning or TEM observation. Under exceptional circumstances, residual strain can prevent complete straightening of the membrane. In this case both sides of the membrane can be freed to allow complete relaxation. This has always been sufficient to allow completion of the thinning and a full TEM examination.