Abstract
Abstract Pentacene films deposited on a silica surface decorated with gold nanoparticles (Au-NPs) were characterizedand used as the active material in the fabrication of a transistor/memory device. The crystallinity and packing orientation of the deposited films are critically dependent on the surface characters of the nanoparticles, which can be tuned by a self-assembled monolayer (SAM) of organic thiolate on the nanoparticles. High performance field-effect transistors based on the Au-NPs-embedded pentacene films can be prepared if the nanoparticles are made “hydrophobic” as well as “oleophobic” by appropriate SAMs. Electrical bistability was observed in these devices. That is, different I-V traces are followed when the source/drain current was measured at a constant bias with the gate bias swept from positive bias toward negative direction or from negative bias toward positive direction. The threshold voltage shifts of the two traces (defined as the memory window) depend on the size and surface modification of the Au-NPs. The structural characterization and electronic characteristics of the devices are detailed. The charge trapping/storing (of both holes and electrons) property of the Au-NPs is suggested to be responsible for the electric bistability. Similar study with the incorporation of aluminum nanoparticles (Al-NPs) into the conduction channel of a pentacene-based field effect transistor was carried out. In this system, Al-NPs capped with SAMs of organic phosphonic acids serve as charge storage centers, with mainly hole carriers trapped. The memory window and retention characteristics of the device depend on the character and chain length of SAM-forming molecules. The results of detailed programming and erasing operations are discussed. In addition, embedding of organic molecules into pentacene film as the channel material was also studied. Polydiacetylenes, which can be prepared by topochemical polymerization of diacetylenic monomers, are studied as charge storage vehicles in pentacene film. Composite films of pentacene and poly(10,12-pentacosadiynoic acid) were prepared and used as the active channel material in a field-effect transistor. The transistors exhibited a high field-effect mobility as well as a large I-V hysteresis as a function of gate bias history. Detailed film structure analyses and correlation with the transistor/memory property are provided. Several organic metal complexes were also studied as charge traps at the semiconductor and dielectric interface. The crystallinity and packing orientation of pentacene film are strongly dependent on the presence of these metal complexes. The field-effect behavior and memory characteristics such as the memory window, device responses, and retention ability of the devices were further investigated.