Building on the success of organic electronic devices, such as light-emitting diodes and field-effect transistors, procedures for fabricating non-volatile organic memory devices are now being explored. Here, we demonstrate a novel organic memory device fabricated by solution processing. Programmable electrical bistability was observed in a device made from a polystyrene film containing gold nanoparticles and 8-hydroxyquinoline sandwiched between two metal electrodes. The as-prepared device, which is in a low-conductivity state, displays an abrupt transition to a high-conductivity state under an external bias of 2.8 V. These two states differ in conductivity by about four orders of magnitude. Applying a negative bias of 1.8 V causes the device to return to the low-conductivity state. The electronic transition is attributed to the electric-field-induced charge transfer between the gold nanoparticles and 8-hydroxyquinoline. The transition from the low- to the high-conductivity state takes place in nanoseconds, and is non-volatile, indicating that the device may be used for low-cost, high-density memory storage.

Recently, films created by incorporating metallic nanoparticles into organic or polymeric materials have demonstrated electrical bistability, as well as the memory effect, when subjected to an electrical bias. Organic and polymeric digital memory devices based on this bistable electronic behavior have emerged as a viable technology in the field of organic electronics. These devices exhibit fast response speeds and can form multiple‐layer stacking structures, demonstrating that organic memory devices possess a high potential to become flexible, ultrafast, and ultrahigh‐density memory devices. This behavior is believed to be related to charge storage in the organic or polymer film, where devices are able to exhibit two different states of conductivity often separated by several orders of magnitude. By defining the two states as “1” and “0”, it is now possible to create digital memory devices with this technology. This article reviews electrically bistable devices developed in our laboratory. Our research has stimulated strong interest in this area worldwide. The research by other laboratories is reviewed as well.

Nanostructured viruses are attractive for use as templates for ordering quantum dots to make self-assembled building blocks for next-generation electronic devices. So far, only a few types of electronic devices have been fabricated from biomolecules due to the lack of charge transport through biomolecular junctions. Here, we show a novel electronic memory effect by incorporating platinum nanoparticles into tobacco mosaic virus. The memory effect is based on conductance switching, which leads to the occurrence of bistable states with an on/off ratio larger than three orders of magnitude. The mechanism of this process is attributed to charge trapping in the nanoparticles for data storage and a tunnelling process in the high conductance state. Such hybrid bio-inorganic nanostructures show promise for applications in future nanoelectronics.

Two-terminal electrical bistable devices have been fabricated using a sandwich structure of organic/ metal/organic as the active medium, sandwiched between two external electrodes. The nonvolatile electrical bistability of these devices can be controlled using a positive and a negative electrical bias alternatively. A forward bias may switch the device to a high-conductance state, while a reverse bias is required to restore it to a low-conductance state. In this letter, a model to explain this electrical bistability is proposed. It is found that the bistability is very sensitive to the nanostructure of the middle metal layer. For obtaining the devices with well-controlled bistability, the middle metal layer is incorporated with metal nanoclusters separated by thin oxide layers. These nanoclusters behave as the charge storage elements, which enable the nonvolatile electrical bistability when biased to a sufficiently high voltage. This mechanism is supported by the experimental data obtained from UV-visible absorption spectra, atomic force microscopy, and impedance spectroscopy.

We report an organic transistor with a vertically stack structure, which consists of a layer-by-layer active cell (drain/organics/source) on top of a capacitor cell (source/dielectrics/gate); the middle source electrode is shared by the capacitor cell and active cell. Three unique characteristics of this transistor, (a) its very thin and rough middle source electrode; (b) its capacitor cell with high charge-storage capability, allow the active cell to be influenced when the gate is biased; and (c) the large cross-section area and small distance between the source and the drain allow current flowing between the source and drain electrodes. Devices have been fabricated by thermal evaporation with the source-drain current well modulated by the gate potential. We have achieved organic transistors with low working voltage (less than 5V) and high current output (up to 10mA or 4A∕cm2) and an ON/OFF ratio of 4×106. A model is proposed for the device operation mechanism. The demonstrated device with its enhanced operating characteristics may open directions for organic transistors and their applications.

The authors demonstrate a vertical organic light emitting transistor achieved by stacking a capacitor on top of an organic light emitting diode ͑OLED͒. This unique device has dual functions, emitting light as an OLED and switching current as a transistor. When the capacitor is under bias, the storage charges on the thin electrode shared by two cells modulate the charge injection of the OLED active cell, hence controlling the current flow and subsequently tuning the light emission. Due to the vertical integration, this device can be operated at low voltage, which provides a solution for OLED display applications.

Copper (Cu) migration into semiconductor materials like silicon is a well-known and troublesome phenomenon often causing adverse effect on devices. Generally a diffusion barrier layer is added to prevent Cu metallization. We demonstrate an organic nonvolatile memory device by controlling the Cu-ion (Cu+) concentration within the organic layer. When the Cu+ concentration is high enough, the device exhibits a high conductive state due to the metallization effect. When the Cu+ concentration is low, the device displays a low conductance state. These two states differ in their electrical conductivity by more than seven orders of magnitude and can be precisely switched by controlling the Cu+ concentration through the application of external biases. The retention time of both states can be more than several months, and the device is promising for flash memory application. Discussions about the device operation mechanism are provided.

Compared with the left thoracic approach, the right thoracic approach associated with increased DFS and OS in esophageal squamous cell carcinoma patients, particularly in those with lymph node involvement and/or R1-2 resection margins.