[en] The inlet window of the detecting device with a semiconductor detector is made from a foil of an organic polymer. The window covers the entrance opening through which the ionizing radiation passes, and protects the detecting device against outer effects. Such an inlet window is superior to a beryllium window with respect to mechanical properties. Since the window is nontoxic, it is easier to handle, and its ionizing radiation absorption is lower, owing to which elements with atomic numbers Z < 11 can also be detected by electron microscopy. (Z.S.)