Multi-valued analogue information storage using self-assembled nanoparticle films

Digital computers use binary states, typically represented by 0 and 5 V, to store and process information at all stages of a calculation. If more states (ideally a continuum) were available in between, density of information could be dramatically increased. Here we show that self-assembled nanoparticle films can feature such continuous state or analogue information storage. Information provided by an arbitrary gate voltage is 'written' by trapping charges in local, gate-modified potentials when films are cooled below 175 K. The information is 'read' using the film's built-in ability to sense charge via Coulomb blockade. Application of a time-dependent, multi-step writing gate voltage generates conductance maps corresponding to multi-valued continuous information. As a proof of concept, we exploit this technique to store 'UT' in Morse code.