Theoretical Analysis of Complementary Molecular Memory Devices

Abstract

The electrical behavior of π-conjugated oligo(phenyleneethynylene) systems functioning as memory devices is studied using quantum chemistry methods, including density functional and Green function formalisms combined in a fully self-consistent manner. Electron charge alters a molecule impedance characteristic providing in some cases distinguishable "impedance states" that can serve to determine experimentally the state of charge of the molecule. Conducting and nonconducting states can be strategically engineered by arranging substituents in a molecule. The NH 2 group localizes the highest energy occupied electronic states whereas the NO 2 group localizes the lowest energy unoccupied orbitals of the oligomer systems. These effects yield two complementary molecular memories, each occupying a volume smaller than 1 nm 3 .

Conductance switching in a molecular device: The role of side groups and intermolecular interactions

“…7 Theoretical studies of functionalized TW's, have so far been restricted to isolated molecules. Based on such studies, Seminario et al proposed that charging of the molecule and subsequent localization/delocalization of molecular orbitals is the microscopic mechanism behind NDR, 8,9 while Cornil et al have found that bias-induced alignment of molecular orbitals on the first and last phenyl rings of twisted TW's can lead to NDR. 10 In this paper we present the first studies of the electrical properties of functionalized TW's covalently bound to gold surfaces.…”

Charge Density Analysis and Transport Properties of TTF Based Molecular Nanowires: A DFT Approach

“…The charge transfer through a particular MO gradually decreases as we go away from the Fermi level of the electrode. Further, the MOs, which are fully delocalized, contribute more to conduction channel [58][59][60][61]. The frontier molecular orbitals are the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and the difference between them is known as HOMO-LUMO gap (HLG).…”

On Construction of Molecular Memory Based on Fullerene Adducts

“…Kwon et al [3] proposed a memory unit of molecular dimensions consisting of a carbon nanocapsule C 480 containing endohedral fullerene K@C 60 + that could be shifted between two ends of the capsule by external electric field. It was shown that self-assembled monolayers might be utilized to built molecular memory device [4] and Seminario et al [5] considered π-electrons conjugated systems with NH 2 and NO 2 substitutes whose electrical behavior would depend on transferred charge thus could be used for storing information. The investigations presented here are intended to find molecules whose structure may be changed externally therefore information might be stored using matrices of molecules that might adopt different stable conformations.…”