Nonvolatile Two-Terminal Molecular Memory
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0961-O03-07
Nonvolatile Two-Terminal Molecular Memory Jason Snodgrass1, Glen Kennedy1, Wai-Ning Mei1, and Renat Sabirianov1,2 1 University of Nebraska Omaha, Omaha, NE, 68182-0226 2 Nebraska Center for Materials and Nanotechnology, Lincoln, NE, 68588-0111
ABSTRACT We propose a nonvolatile two-terminal memory device with two resistance states based on the molecular tunnel junctions. This tunnel junction is composed of one or a few monolayers of polar molecules sandwiched between two electrodes made of materials with different screening length. As a prototype model system we study a rare earth endohedral metallofullerene molecule with reversible dipole moment sandwiched between metal and semiconducting electrodes, forming a double barrier junction. We use the Thomas-Fermi model to calculate the potential profile across the device. Calculated tunneling conductance through the proposed structure changes by order of magnitude upon the reversal of the dipole orientation (due to the applied voltage). This effect originates from the difference in potential profiles seen by tunneling electrons for two opposite dipole orientations. INTRODUCTION Resistive switching in metal-insulator heterostructures has recently attracted considerable attention because of their potential applications as two-terminal non-volatile memory where the resistance of a device can be switched and read by applying an external voltage [1,2]. Recently, similar switching has been observed in asymmetric metal/ferroelectric films [3] and theoretically predicted for ferroelectric tunnel junctions [4]. Advances in molecular electronics show possible resistive switching through conformational changes of the molecule, as well as by interface modifications.[5] In this work we propose a new method for the resistive switching in a variety of systems where abrupt modification of the surface properties is possible. This method is based on selecting interfaces with the possibility of changing their charge states. This can occur due to the conformational changes to the molecule or the charge trapping on the interface, and, as a result, a modification of the conducting properties. In this work, we show that the abrupt change of the state at the interface due to the applied voltage leads to a sizable change in the tunneling current. This provides a two-terminal electrical control of the resistance, including the possibility of controllable switching from a high resistance state (HRS) to a low resistance state (LRS). THEORY The particular system we will consider is a tunnel junction representing a molecule sandwiched between two asymmetric electrodes. The possibility of using molecules as tunnel barriers has been actively studied in recent years both experimentally and theoretically. These results suggest that the ratio of the resistance states (HRS) and (LRS) upon switching is quite
large. Recent experiments indicate that the electrical resistance switching in metal/molecule/metal junctions may not depend on the particular molecular specie but on the state of the in
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