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

electrets. In this Communication, we report on OFET memory devices built on silicon wafers and based on films of pentacene and an SiO2 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 (VTh) when an appropriate gate voltage (Vg) was applied above a certain threshold via a relatively short switching time. Based on these reversible shifts in VTh, a non-volatile organic memory was demonstrated that takes advantage of the simple configuration of a typical OFET. This device showed a large memory window (about 90 V), a high on/off ratio (IOn/IOff) (10 5 ), a short switching time (less than 1 ls), and a long retention time (more than 100 h). These memory characteristics were obtained only when an appropriate polymeric gate electret layer (e.g., PaMS) was inserted between the SiO2 gate insulator and the pentacene channel in the typical OFET structure. Therefore, it is possible that this behavior originates from the modulation of the gate field by stored charges in the polymeric gate electret. Detailed reasons for these results and a possible operating mechanism for our OFET memory device are discussed. A cross-sectional view of the fabricated device structure is shown in Figure 1a. Further details concerning the fabrication of this device are discussed in the Experimental section. Figure 1b and c shows the output and transfer characteristics of the devices, respectively. The results indicate reasonably good OFET behavior, suggesting the additional PaMS layer does not degrade the performance of the devices. [14] From the conventional characterization equation, [15] the measured values of the typical field-effect mobility (lFET), VTh, and IOn/IOff were 0.51 cm 2 V –1 s –1 (maximum value, 0.89 cm 2 V –1 s –1 ), – 19 V, and 10 5 , respectively. These transistor properties could