SYNAPse-like transisTOR (SYNAPTOR) and circuits for neuro-inspired computing architecture
The main objective of this project is to explore the behavior and functioning of circuits of synaptors for use in neuro-inspired computing architectures. To reach this global objective, the project will address three more focused objectives: <br />Objective 1: Functionalized NP with new molecular switches <br />Here the objective is the synthesis and the electrical characterization of new photo-isomerizable molecules. From a chemical point of view, the choice and design of the new molecules will be: (i) the red-shifting of the wavelength driven the isomerization, (ii) a short commutation time and (iii) a high ON/OFF conductance ratio between the two isomers. <br />Objective 2: A new synaptor the OG-NOMFET <br />Here we investigate a new type of synaptor: the OG NOMFET that will overcome some limitations of the NOMFET and add new functionalities. Here, we encapsulate in the previous NOMFET the NPs with an optically active SAM developed in the objective 1. This new device will be electrically characterized by controlling the conformation of molecule around the NPs by light. <br />Objective 3: Array of Synaptors <br />By using molecular-switch functionalized NPs in the OG-NOMFET, we pursue the objective to have two neuro-mechanisms in the same device. In term of circuit architectures, it means that it will be possible to envision some architecture with “blocks” of synaptors in the same circuits.
The project is divided in five work packages (WP).
WP0: Management (IEMN)
WP0 is transverse to all WPs. It implements the coordination and management activities of the project. The second task of WP0 is dedicated to results dissemination.
WP1: Chemical synthesis (MOLTECH-Anjou)
The synthesis and the characterization of the photo-switchable molecules will be done at MOLTECH-Anjou. The gold NPs will be then capped in solution with the synthesized molecules and characterized also at MOLTECH-Anjou. The formation of gold NPs capped with ligands that can change conductivity under light exposure is the starting point of the project.
WP2: NPs deposition and characterizations (IEMN & MOLTECH-Anjou)
The immobilization on solid surfaces of capped gold NPs developed in WP1 will be done at IEMN. The deposition will be optimized and validated by various techniques (AFM, STM, XPS, FTIR). Once the deposit mastered, single capped gold NPs will be electrically characterized by several Scanning Probe Microscopy (SPM).
WP3: Device fabrication and characterizations (IEMN)
By using capped gold NPs from WP1 and deposition techniques developed in WP2, we will form the OG-NOMFET structure. The condition of deposition for NPs developed in WP2 will be applied here to control the NPs film. Finally, we will carry out extensive measurements of the electric characteristics: curve current-voltage, retention and switching time, temperature and frequency response of these OG-NOMFETs.
WP4: Modelling and circuit architecture (CEA-LIST & IEMN)
Based on our previous experience on the NOMFET, we will develop a functional simulator model (SPICE-like) based on a physical model and a number of experimental parameters from WP3. Based on these simulator models, OG-NOMFET will be assembled to form a multi-terminal multi-gate array, which will be integrated into a neuromorphic circuit and applied to a simple problem such as associative memory.
Molecule-based devices are envisioned to complement silicon devices by providing new functions or already existing functions at a simpler process level and at a lower cost. Moreover, they are not bound to von Neuman architecture and this feature may open the way to other architectural paradigms. Neuro-inspired electronics is one of them. In the brain, memory and computation are mixed together and allow the processing of information both in time and in space via the time dependent properties of interconnected neurons, a property known as synapse plasticity. In a neuro-inspired device, this behavior can be obtained by virtue of the combination of two properties: the transconductance gain of the transistor and the memory effect due to charges stored in nanoparticles (NP). We will name such a type of device a synaptor (synapse-transistor).
In this project, we will investigate a new type of synaptor: the Optically-Gated Nanoparticle Organic Memory FET (OG-NOMFET). The device will be based on a classical organic FET structure (transconductance gain effect) with the presence, inside the channel, of gold NPs (memory effect). The originality of these new synaptor relies on the use of gold NPs functionalized by an optically active organic material. The property of this material is to change its conductivity reversibly under light exposure to improve the control of charge storage (and the time constant) of the synaptor and thus its plasticity (the response being dependent on past history and present solicitation). The presence of this material will allow us to change the synaptic behavior of the devices in situ during the functioning of the device. This will open new opportunities to use these synaptor in neuro-inspired circuits.
Before using the functionalized NPs in a new OG-NOMFET synaptor, our objective is to demonstrate and understand the change of the electronic properties of gold NPs capped by the optical switching molecules and materials. The demonstration of gold NPs capped with light-driven switchable ligands will contribute to a better understanding of the electronic properties of such systems. This will be done by studying the properties of these NPs with SPM (Scanning Probe Microscope) techniques.
The synaptic behaviors of the OG-NOMFET will be studied in details. We will mainly study various neuro-inspired plasticity behaviors. These results will permit to develop a functional simulator model (SPICE-like) to modelling the single OG-NOMFET behavior. With this simulator, we will be able to simulate the association of various synaptors to determine optimum parameters for new neuro-inspired circuits. These circuits will be first simulated before the technical realization and experimental validation will be done.
This project represents challenging research at the leading edge of field of nanosciences and information computing (ICT). This is, by definition, high-risk with a concomitant very high level of potential return. The development of molecular-scale ICT devices and systems is an issue that affects the future of global nanoelectronics and of industries related to it. Since there is no well-established experimental result in this domain, every research in the field will be advances and progresses.
Monsieur Stéphane Lenfant (Institut d'Electronique de Microélectronique et de Nanotechnologie) – firstname.lastname@example.org
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IEMN Institut d'Electronique de Microélectronique et de Nanotechnologie
CNRS MOLTECH-Anjou, Université d'Angers
CEA Commissariat à l'Energie Atomique et aux Energies Alternatives
Help of the ANR 434,481 euros
Beginning and duration of the scientific project: December 2012 - 36 Months