Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

http://chialvo.org/Curso/UBACurso/DIA7/Papers/Aono_NatMat_07_Ionic%20Switching%20Memory.pdf

Nanoionics-based resistive switching memories

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

2.2. Materials 929 2.3. Factors Influencing Charge Mobility 931 2.3.1. Molecular Packing 931 2.3.2. Disorder 932 2.3.3. Temperature 933 2.3.4. Electric Field 934 2.3.5. Impurities 934 2.3.6. Pressure 934 2.3.7. Charge-Carrier Density 934 2.3.8. Size/molecular Weight 935 3. The Charge-Transport Parameters 935 3.1. Electronic Coupling 936 3.1.1. The Energy-Splitting-in-Dimer Method 936 3.1.2. The Orthogonality Issue 937 3.1.3. Impact of the Site Energy 937 3.1.4. Electronic Coupling in Oligoacene Derivatives 938

Charge transport in organic semiconductors.

Resistive switching in transition metal oxides

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

Electron transfer in a new highly conducting donor-acceptor complex

Degree of charge transfer in organic conductors by infrared absorption spectroscopy

Stable and reproducible current‐controlled bistable electrical switching has been observed in polycrystalline organic semiconducting films. The effect has been observed in a lamellar structure with a film of microcrystalline Cu‐TCNQ between Cu and Al electrodes where the Cu‐TCNQ is grown on a Cu substrate via a spontaneous electrolysis technique. The switching effect is insensitive to moisture and is observed over a large temperature range. The current‐voltage characteristics reveal an abrupt decrease in impedance from 2 MΩ to less than 200 Ω at a field strength of 4×103 V/cm. The transition from a high‐ to low‐impedance state occurs with delay and switching times of approximately 15 and 10 nsec, respectively. Switching with high‐power dissipation yields a low‐impedance memory state which can be erased by application of a short current pulse. An interpretation of this behavior is based on the bulk properties of the mixed valence semiconductor Cu‐TCNQ.

Electrical switching and memory phenomena in Cu‐TCNQ thin films

Mechanisms of Photochemical Reactions in Solution. XXII.1 Photochemical cis-trans Isomerization

The effects of halogenated solvents such as n-butyl chloride, n-propyl bromide, and ethyl iodide, on the photochemistry of several aromatic compounds are reviewed. Dimerization of acenaphthylene is discussed in terms of spin -orbit coupling induced by the solvents. Appropriate wave functions are given for both the solvents and the compound. Cycloaddition reactions, electrocyclic rearrangements, and photochemical cis-trans isomerization are also considered.

Dwaine O. Cowan

Papers

Electron transfer in a new highly conducting donor-acceptor complex

Degree of charge transfer in organic conductors by infrared absorption spectroscopy

Electrical switching and memory phenomena in Cu‐TCNQ thin films

Mechanisms of Photochemical Reactions in Solution. XXII.1 Photochemical cis-trans Isomerization

Photochemical heavy-atom effects