A memory comprises a multilayer film (1) in which each layer (2) is capable of carrying a charge, built up by successive deposition of a plurality of monomolecular layers (2), at least one of which has been deposited by a process of chemisorption and a photo-injector layer(D) is located on one side of the film for introducing charges into the film in a time sequence which corresponds to the information to be carried. Means (6) are provided for applying a voltage between the faces of the film to cause the charge carried by any layer to be transferred to the adjacent layer. The sequence of charges carried by the film may be read out by a photon-emitting electron arrival detector (F) on the opposite side ofthefilm, or by a method of current differentiation. The film (1) is preferably formed of a polydiacetylene.