Preparation of a thin silicon membrane for transmission electron microscopy

A technique for preparing preselected local areas on a silicon wafer for transmission electron microscopy studies is described. The method yields mechanically strong specimens with membranes (foils) transparent for electrons. A crystal is thinned by the local formation of a porous silicon layer, which is subsequently removed by being dissolved in a solution of potassium hydroxide. The resultant recessed regions are brought to the required thickness with the chemicodynamic polishing technique.