We demonstrate the modification of the memory effect in organic memory devices by adjusting the thickness of silver nanoparticles ͑NPs͒ layer embedded into the organic semiconductor. The memory window widens with increasing Ag NPs layer thickness, a maximum window of 90 V is achieved for 5 nm Ag NPs and the on/off current ratio decreases from 10 5 to 10 when the Ag NPs layer thickness increases from 1 to 10 nm. We also compare the charge retention properties of the devices with different Ag NPs thicknesses. Our investigation presents a direct approach to optimize the performance of organic memory with the current structure. © 2010 American Institute of Physics. ͓doi:10.1063/1.3462949͔The advent of the nonvolatile flash memory has provided remarkable benefits for data storage in computers and other portable electronic devices. Due to the advantages of organic electronic devices over their inorganic counterparts such as the low fabrication costs, suitable for large area fabrication, and compatible with flexible substrates, 1,2 organic memory devices fabricated on flexible substrates have great potential for the next generation of nonvolatile flash memory. They can be further integrated with other electronic devices and form a flexible circuit. Recently a 26ϫ 26 array of organic flash memory transistors based on floating gate structure was demonstrated on flexible plastic sheets, and the operating voltage was as low as 6 V. 3 Currently, different approaches have been adopted to fabricate organic nonvolatile memory devices, such as using ferroelectric polymer dielectric materials 4,5 and chargeable gate dielectric in the organic field-effect transistors ͑OFETs͒. 6 In these devices, the memory effect arises from the field effect modulation by either the spontaneous polarization that occurs in ferroelectric, or through the trapping of charges in a chargeable layer of the dielectric. 7 Usually, the charge-trapping elements in the chargeable gate dielectric are nanoparticles ͑NPs͒ of metals such as Cr, 8 Au, 6 and Ag. 9 Compared with ferroelectric polymer-based memory, devices using metal NPs as charge traps have an advantage that the trap density and distribution can be controlled by adjusting the density and location of the NPs during the NP formation process, by using ultrathin metallic films deposition or ion implantation techniques. 10,11 Recently, we reported a different structure of transistor memory device with remarkable memory window performance by placing silver NPs in between two pentacene layers. 12 A significant advantage of the structure is that it can eliminate the extra fabrication steps for the insulator layers as in the case of floating gate transistor memory structure, making it suitable for integrating with other electronic devices on the same substrate to form a circuit. In the current work, we focused on investigating the performance variation in the pentacene OFET-based memory with different silver NP layer thickness. We also compared the memory window, on/off current ratio, and charge retention ...

We investigate the annealing and thermal effects of organic non-volatile memory with floating silver nanoparticles by real-time transfer curve measurements. During annealing, the memory window shows shrinkage of 23% due to structural variation of the nanoparticles. However, by increasing the device operating temperature from 20 to 90 °C after annealing, the memory window demonstrates an enlargement up to 100%. The differences in the thermal responses are explained and confirmed by the co-existence of electron and hole traps. Our findings provide a better understanding of organic memory performances under various operating temperatures and validate their applications for temperature sensing or thermal memories.

This paper presents train-induced dynamic response and fatigue damage analyses for the hangers of a tied-arch railway bridge. A train–bridge interaction analysis is carried out using the vector form intrinsic finite element method, through which the inertial force effect of the moving train can be effectively analyzed. The responses of the bridge deck and its hangers are investigated at resonant train speeds. Significantly larger stresses are observed on the shorter hangers near the arch anchorages, which is primarily caused by the first two anti-symmetrical vibration modes. The fatigue damage to the hangers is estimated using the Palmgren-Miner model (PMM) for linear fatigue damage accumulation and the continuum damage mechanics (CDM) method for nonlinear accumulation. The mean stress effect is considered in the S–N curve primarily by Smith–Watson–Topper equation in terms of the effective stress range with a zero-mean stress. Two probability distributions for train speed are considered for the current and future operating conditions with mean speeds of 220 and 300[Formula: see text]km/h, respectively. This study found that the fatigue lives estimated by the nonlinear CDM are significantly shorter than those estimated by the linear PMM. It also found that the shortest hanger reflects the shortest fatigue life at the current operating speed, whereas the longer hanger near the third point of the bridge deck may have the shortest fatigue life at an increased speed in the future.