Abstract: An information storage device having an evacuated envelope containing writing means which is adapted to produce, in response to an input signal and by causing emission of secondary electrons, a charge pattern on a storage target disposed within the envelope. The storage target includes a semiconducting layer and a storage layer providing alternate semiconducting regions and storage regions. The semiconducting layer consists essentially of semiconductor material of substantially single conductivity type and the storage regions consist essentially of a secondary electron-emissive insulating compound of a semiconductor material. One of the two layers is interrupted and exposes portions of the other layer. A collector electrode disposed within the envelope intercepts the secondary electrons emitted by the target. The target is provided with means for applying electrical potential thereto and extracting signals therefrom.