title: Unsupervised Learning by Spike Timing Dependent Plasticity in Phase Change Memory (PCM) Synapses.
abstract: We present a novel one-transistor/one-resistor (1T1R) synapse for neuromorphic networks, based on phase change memory (PCM) technology. The synapse is capable of spike-timing dependent plasticity (STDP), where gradual potentiation relies on set transition, namely crystallization, in the PCM, while depression is achieved via reset or amorphization of a chalcogenide active volume. STDP characteristics are demonstrated by experiments under variable initial conditions and number of pulses. Finally, we support the applicability of the 1T1R synapse for learning and recognition of visual patterns by simulations of fully connected neuromorphic networks with 2 or 3 layers with high recognition efficiency. The proposed scheme provides a feasible low-power solution for on-line unsupervised machine learning in smart reconfigurable sensors.
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano and IU.NET Milano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Ambrogio
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano and IU.NET Milano, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Ciocchini
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano and IU.NET Milano, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Laudato
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano and IU.NET Milano, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Milo
authors.affiliation: Research and Development Process, Micron Semiconductor Italia Vimercate, Italy.
authors.forename: Agostino
authors.initials: A
authors.lastname: Pirovano
authors.affiliation: Research and Development Process, Micron Semiconductor Italia Vimercate, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Fantini
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano and IU.NET Milano, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Ielmini
keywords: cognitive computing; memristor; neural network; neuromorphic circuits; pattern recognition; phase change memory; spike timing dependent plasticity