Tunnel current in self-assembled monolayers of 3-mercaptopropyltrimethoxysilane

The current density-voltage (J-V) characteristics of self assembled monolayers of 3-mercaptopropyltrimethoxysilane (MPTMS) chemisorbed on the native oxide surface of p+-doped Si demonstrate the excellent tunnel dielectric behavior of organic monolayers down to 3 carbon atoms. The J-V characteristics of MPTMS SAMs on Si are found to be asymmetric, and the direction of rectification has been found to depend upon the applied voltage range. At voltages < 2.45V, the reverse bias current was found to be higher than forward bias current; while at higher voltages this trend was reversed. This result is in agreement with Simmons theory. The tunnel barrier heights for this short chain (2.56 and 2.14 eV respectively at Au and Si interfaces) are in good agreement with the ones for longer chains (>10 carbon atoms) if the chain is chemisorbed at the electrodes. These results extend all previous experiments on such molecular tunnel dielectrics down to 3 carbon atoms. This suggests that these molecular monolayers, having good tunnel behavior (up to 2.5 eV) over a large bias range, can be used as gate dielectric well below the limits of Si-based dielectrics.Comment: Small, in pres

Substitutability and the Quest for Stability. : Some Reflections on the Methodology of General Equilibrium in Historical Perspective

Do not quote without permissionIn this paper, I propose to interpret the history of stability analysis of a Walrasian exchange economy through the lenses of the concept of substitutability. A purely mathematical approach of this story does not seem sufficient to account for the way economists have studied the question of stability and how thay have reacted to the results of this research program. My point is that mathematical constraints kept apart, the concept of substituability has shaped the path followed by stability analysis since the publication of Value and Capital (Hicks, 1939) up to the Sonnenschein-Mantel-Debreu theorems and beyond. Thus, I uphold that firstly, the concept of substitutability allows to catch the heuristic behind the work on stability, and secondly, it allows replacing the importance of SMD results in a broader context, giving a more subtle view of the ups and down of general equilibrium theory as a research program

Pavlov's dog associative learning demonstrated on synaptic-like organic transistors

In this letter, we present an original demonstration of an associative learning neural network inspired by the famous Pavlov's dogs experiment. A single nanoparticle organic memory field effect transistor (NOMFET) is used to implement each synapse. We show how the physical properties of this dynamic memristive device can be used to perform low power write operations for the learning and implement short-term association using temporal coding and spike timing dependent plasticity based learning. An electronic circuit was built to validate the proposed learning scheme with packaged devices, with good reproducibility despite the complex synaptic-like dynamic of the NOMFET in pulse regime