Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

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Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

This review article attempts to provide a comprehensive review of the recent progress in the so-called resistive random access memories (RRAMs) First, a brief introduction is presented to describe the construction and development of RRAMs, their potential for broad applications in the fields of nonvolatile memory, unconventional computing and logic devices, and the focus of research concerning RRAMs over the past decade Second, both inorganic and organic materials used in RRAMs are summarized, and their respective advantages and shortcomings are discussed Third, the important switching mechanisms are discussed in depth and are classified into ion migration, charge trapping/de-trapping, thermochemical reaction, exclusive mechanisms in inorganics, and exclusive mechanisms in organics Fourth, attention is given to the application of RRAMs for data storage, including their current performance, methods for performance enhancement, sneak-path issue and possible solutions, and demonstrations of 2-D and 3-D crossbar arrays Fifth, prospective applications of RRAMs in unconventional computing, as well as logic devices and multi-functionalization of RRAMs, are comprehensively summarized and thoroughly discussed The present review article ends with a short discussion concerning the challenges and future prospects of the RRAMs

Recent progress in resistive random access memories: Materials, switching mechanisms, and performance

Polymer electronic memories: Materials, devices and mechanisms

Current issues in research on structure–property relationships in polymer nanocomposites

Graphene, a two-dimensional atomically thick carbon atom arranged in a honeycomb lattice, was recently isolated by repeatedly peeling highly oriented pyrolytic graphite (HOPG) using sticky tape. [ 1 ] Since then, outstanding physical properties predicted and measured for graphene have been explored for practical applications such as fi eld-effect transistors, [ 1–4 ] chemical sensors [ 5–7 ] and composite reinforcement. [ 8–10 ] Monolayer graphene possesses high crystallographic quality and ballistic electron transport on the micrometer scale with only 2.3% of light absorption. [ 11 , 12 ] Moreover, the combination of its high chemical and thermal stability, [ 13 , 14 ] high stretchability, [ 15–17 ]

Graphene as Transparent Electrode Material for Organic Electronics

The electrical properties of flexible nonvolatile organic bistable devices (OBDs) fabricated with graphene sandwiched between two insulating poly(methyl methacrylate) (PMMA) polymer layers were investigated. Current−voltage (I−V) measurements on the Al/PMMA/graphene/PMMA/indium−tin-oxide/poly(ethylene terephthalate) devices at 300 K showed a current bistability due to the existence of the graphene, indicative of charge storage in the graphene. The maximum ON/OFF ratio of the current bistability for the fabricated OBDs was as large as 1 × 107, and the endurance number of ON/OFF switchings was 1.5 × 105 cycles, and an ON/OFF ratio of 4.4 × 106 was maintained for retention times larger than 1 × 105 s. No interference effect was observed for the scaled-down OBDs containing a graphene layer. The memory characteristics of the OBDs maintained similar device efficiencies after bending and were stable during repetitive bendings of the OBDs. The mechanisms for these characteristics of the fabricated OBDs are descri...

Flexible Organic Bistable Devices Based on Graphene Embedded in an Insulating Poly(methyl methacrylate) Polymer Layer

Current-voltage measurements on the Al/[CdSe∕ZnS nanoparticles embedded in a hole-transporting poly(N-vinylcarbazole) (PVK) layer]/indium tin oxide (ITO)/glass structures at 300K showed a nonvolatile electrical bistability behavior. Capacitance-voltage (C-V) measurements on the Al/[CdSe∕ZnS nanoparticles embedded in a PVK layer]/ITO/glass structures at 300K showed a metal-insulator-semiconductor behavior with a flatband voltage shift due to the existence of the CdSe∕ZnS nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the CdSe nanoparticles. Operating mechanisms for the Al/[CdSe∕ZnS nanoparticles embedded in the PVK layer]/ITO/glass devices are described on the basis of the C-V results.

Organic bistable devices based on core/shell CdSe∕ZnS nanoparticles embedded in a conducting poly(N-vinylcarbazole) polymer layer

The current bistability and the carrier transport mechanisms of organic bistable devices (OBDs) using Ag nanoparticle-polymethyl methacrylate (PMMA) nanocomposites have been investigated. Current-voltage measurements at 300 K on the Al/Ag nanoparticles embedded in the PMMA layer/indium-tin-oxide devices exhibit a current bistability with an ON/OFF ratio of 103. Write-read-erase-read sequence results demonstrate the switching characteristics of the OBD. The cycling endurance number of the ON/OFF switching for the OBD is above 7×104. The current bistability and carrier transport mechanisms of the OBD fabricated utilizing hybrid Ag nanoparticle-PMMA polymer nanocomposites are described on the basis of the experimental data.

Current bistability and carrier transport mechanisms of organic bistable devices based on hybrid Ag nanoparticle-polymethyl methacrylate polymer nanocomposites

Transmission electron microscopy images showed that colloidal ZnO quantum dots (QDs) were distributed around the surface of a polymethylmethacrylate (PMMA) polymer. Current-voltage (I-V) measurements on the Al/colloidal ZnO QDs blended with PMMA polymer layer/indium-tin-oxide/glass devices at 300 K showed a current bistability. The maximum ON/OFF ratio of the current bistability for the organic bistable devices (OBDs) was as large as 5×104, and the cycling endurance time of the ON/OFF switching for the OBDs was above 105. The memory mechanisms of the fabricated OBDs are described on the basis of the I-V results.

Electrical bistabilities and memory mechanisms of organic bistable devices based on colloidal ZnO quantum dot-polymethylmethacrylate polymer nanocomposites

The bistable effects of cuprous oxide (Cu2O) nanoparticles embedded in a polyimide (PI) matrix were investigated. Transmission electron microscopy images and selected area electron diffraction patterns showed that Cu2O nanocrystals were formed inside the PI layer. Current-voltage (I-V) measurements on Al/PI/nanocrystalline Cu2O∕PI∕Al structures at 300K showed a nonvolatile electrical bistability behavior. A bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results. These results indicate that OBDs fabricated utilizing self-assembled inorganic Cu2O nanocrystals embedded in an organic PI layer hold promise for potential applications in nonvolatile flash memory devices.

Jae Hun Jung

Papers

Flexible Organic Bistable Devices Based on Graphene Embedded in an Insulating Poly(methyl methacrylate) Polymer Layer

Organic bistable devices based on core/shell CdSe∕ZnS nanoparticles embedded in a conducting poly(N-vinylcarbazole) polymer layer

Current bistability and carrier transport mechanisms of organic bistable devices based on hybrid Ag nanoparticle-polymethyl methacrylate polymer nanocomposites

Electrical bistabilities and memory mechanisms of organic bistable devices based on colloidal ZnO quantum dot-polymethylmethacrylate polymer nanocomposites

Nonvolatile organic bistable devices fabricated utilizing Cu2O nanocrystals embedded in a polyimide layer