Organic Non‐Volatile Memory Based on Pentacene Field‐Effect Transistors Using a Polymeric Gate Electret

Abstract

Many attempts have been made to realize a universal memory, [1] that is, an ideal memory device comprising new, fast, non-volatile, inexpensive methods for storing information. Compared to its inorganic counterparts, organic memory has attracted a great deal of interest because of its remarkable progress in organic electronics and its unique advantages: it is inexpensive, lightweight, and capable of printing ubiquitous components onto plastic substrates. [2][3][4] In an attempt to create a novel organic memory, several types of memory devices based on organic and polymeric materials have been evaluated, including organic electrical bistable devices, [5] organicinorganic hybrid memory using a polymeric fuse, [6] and organic field-effect transistors (OFETs) based on ferroelectric gate insulators and chargeable gate dielectrics. [7][8][9][10][11] Among these types of organic memory devices, a memory element based on FETs is especially attractive because of its non-destructive readout and single-transistor applications. [12] In this case, the functionality arises from the field-effect modulation by the spontaneous polarization that occurs in ferroelectrics or the trapped charges in chargeable dielectrics, which are referred to as electrets.While an OFET memory has many potential advantages, state-of-the-art results of OFET memory devices are in a less favorable position, compared to other types of organic memories. [7][8][9][10][11] With respect to the case of organic ferroelectrics, Naber et al. recently demonstrated an on/off ratio of 10 4 with a programming time of 0.3 ms and a memory effect stability of more than one week. [8] However, when compared to ferroelectrics, only a small amount of attention has been given to electret-charged OFET memory, in spite of the similar field-effect modulation. Moreover, the characteristics of OFET memory based on electrets are less well understood than those of ferroelectric-based OFET memory devices due to a lack of research. Katz et al. demonstrated an OFET memory with a polarizable gate insulator that induced a floating-gate-like behavior, [9] and Singh et al. also demonstrated an OFET memory using poly(vinyl alcohol) as a gate electret.[10] However, these devices still do not sufficiently satisfy the criteria demanded in order to compete with other types of memory devices. [13] Furthermore, details of the operating mechanisms of these devices are not well understood. Therefore, the mechanism should be further investigated to successfully develop a high-performance OFET memory based on electrets.In this Communication, we report on OFET memory devices built on silicon wafers and based on films of pentacene and an SiO 2 gate insulator that are separated by a thin layer of poly(a-methylstyrene) (PaMS), which acts as a polymeric gate dielectric. This OFET memory device displayed reversible shifts in the threshold voltage (V Th ) when an appropriate gate voltage (V g ) was applied above a certain threshold via a relatively short switching time. Based on these reversible shifts in...

Engineering of Amorphous Polymeric Insulators for Organic Field‐Effect Transistors

“…This memory device shows a fast writing and erasing speed of 1 µs. [37,79] Further, our group reported multibit storage OFETs based on light-assistant-voltage program with poly(methyl methacrylate) (PMMA) or polystyrene (PS) as charge storage layer (Figure 9). It showed long-time two-bit signal storage ability with a half-life time of 250 hours.…”

“…[30][31][32][33][34] In the past few years, the investigation of amorphous polymer insulators (APIs) has become more and more important not only due to their gate dielectric properties, but also their functional applications. For example, APIs have been used as high resolution masks in ultra-narrow-channel OFETs, [31,32] as charge-trapping layers in memory devices, [35][36][37][38][39][40] Organic field-effect transistors (OFETs) have received considerable attention across the world due to their potential applications in integrated circuits for large-area, flexible and low-cost electronics, and a series of breakthroughs in their research have been made in the past decade. Although numerous novel organic semiconductive materials with outstanding properties have been synthesized, the fabrication of OFETs and the investigation of amorphous polymer insulators (APIs) are attracting more and more research interest due to their significance in semiconductor growth, charge transport and device stability.…”

Phthalocyanine‐Cored Star‐Shaped Polystyrene for Nano Floating Gate in Nonvolatile Organic Transistor Memory Device

“…[ 2,3 ] Based on conventional transistors, OFET memory incorporates an additional distinct organic layer, such as a ferroelectric material, [4][5][6] a nano fl oating gate dielectric, [ 7,8 ] or a polymer-based electret, [9][10][11][12][13] between the semiconductor layer and the control gate, which enables the recognition of "0" or "1" digital states. Among them, nano fl oating gate memory devices have received much attention for organic fl ash memory due to their low cost and low power consumption as well as their high memory density.…”

Multilevel nonvolatile transistor memories using a star-shaped poly((4-diphenylamino)benzyl methacrylate) gate electret

“…[1][2][3][4][5]10 The storage of charge in a transistor dielectric can be achieved using chargeable polymer electrets, [13][14][15][16][17][18][19][20] organic ferroelectric oriented-dipole dielectric materials, [21][22][23] and nanoparticles embedded or nanostructured gate dielectrics. [24][25][26][27][28] An electret is a dielectric material that has a quasi-permanent electric charge.…”