Three-terminal organic memory devices

Abstract

This device can be switched between a low-͑OFF͒ and a high-͑ON͒ conductivity state by external bias. In this article, we report a three-terminal organic memory device, which is realized by wiring out the metal-nanocluster layer of the OBD as the middle electrode. The ON and OFF states of the device can be read out by measuring the potential of the middle electrode. By controlling the interface formation of the device, a three-terminal OBD with a potential change on the middle electrode of more than three orders in magnitude between the OFF state and ON state ͑from 0.2 mV to 0.77 V͒ is achieved. By wiring out the middle electrode, the three-terminal OBD can also be considered as two 2-terminal devices stacked together. By proper interface engineering ͑to be discussed in detail in the text͒, we found that both the top and bottom devices show electrical bistability and memory effect. This can double the data storage density of the memory device. Details of the device mechanism are provided.

Overview of organic memory devices

“…Many layer thicknesses (Pyo et al 2005) and permutations of metals (Ma et al 2002a,b,c) were also studied with on/off ratios in the range from four to six orders of magnitude. Subsequent investigations by He et al (2005) used contacts to this middle nanocluster layer to show that switching mainly occurs in the bottom organic layer. It was postulated that this was due to organometallic complexes formed by contact evaporation, giving rise to an asymmetric device structure.…”

“…The next progression in devices came from structures first proposed by the Yang group at the University of California, Los Angeles (Ma et al 2002a(Ma et al ,b,c, 2003He et al 2005;Pyo et al 2005) and consisted of a layered structure of organic/metal-nanocluster/organic deposited between two aluminium electrodes. 2-Amino-4,5-imidazoledicarbonitrile (AIDCN), an organic semiconducting polymer, was used for the organic layers, whereas evaporation of a thin metal layer in the presence of oxygen or AIDCN formed discontinuous metal nanoclusters.…”

Gold nanoparticle charge trapping and relation to organic polymer memory devices

“…There is also a third type of device that simply shows hysteresis within the I -V characteristics, with no sudden switching or NDR. As mentioned previously, the first devices that can be classed as nanoparticle based were proposed by Ma et al (2002aMa et al ( ,b,c, 2003, He et al (2005) and Pyo et al (2005) and consisted of a trilayer structure of organic/metal-nanocluster/organic sandwiched between two aluminium electrodes (named three-layer organic bistable devices, 3L-OBDs). 2-Amino-4,5-imidazoledicarbonitrile (AIDCN), an organic semiconducting polymer, was used for the organic layers.…”

“…It is also shown in this paper that devices can be made symmetric by deliberately introducing an Al 2 O 3 layer under the top electrode. All of the devices based on nanocluster layers (Ma et al 2002a(Ma et al ,b,c, 2003Pyo et al 2005) were symmetric S-shaped devices, showing no NDR region, except for that of He et al (2005), which showed asymmetric S-shaped characteristics.…”

“…Many permutations of metals (Ma et al 2002a,b,c) and various layer thicknesses (Pyo et al 2005) were studied, with on/off ratios in the devices ranging from four to six orders of magnitude, depending on the structure studied. He et al (2005) showed that switching mainly occurs in the bottom organic layer, postulating that this was due to the organometallic complex formed by evaporating the top contact, giving rise to an asymmetric device structure. It is also shown in this paper that devices can be made symmetric by deliberately introducing an Al 2 O 3 layer under the top electrode.…”