| There is tremendous interest in leveraging conventional graphic printing infrastructure to produce low cost "printed" electronic components and devices on flexible substrates. Organic semiconductors and nano-materials are becoming viable material systems for these applications. Greater understanding of how to manipulate these material systems in the submicron and nanoscale regime is crucial for optimizing their performance in the intended end use application and is the focus of this work. The value of controlling the organization of both material modifications and geometrical changes are clearly illustrated in chapter one with two examples. We first demonstrate the interplay between chemistry and performance by controlling pentacene's growth and charge injection in a controlled manner with thin organic materials at the semiconductor/dielectric interface. The effects of surface modifiers that alter the growth morphology and charge injection at the pentacene interface and thus, control mobility at monolayer and sub-monolayer regime are described.; The second example in chapter one, exemplifies an alternative path towards manipulating electrical performance: incorporating a geometrical modification of the transistor channel length in the semiconducting layer. Transistors with increasing gain, transconductance, are fabricated by assembling a non-percolating random array of single walled carbon nanotubes (SWNT), which are linked via short switchable pentacene links. When non-percolating arrays of carbon nanotubes are linked via a semiconducting overlay, the majority of paths between source and drain follow the highly conducting nanotubes with short, switchable semiconducting links completing the circuit. This approach represents an effective, simple tool to substantially increase the transistor gain without large reductions in the current on/off ratio. Since field-induced percolating networks allow for high transconductance with relatively large source-drain distance, transistors can be manufactured inexpensively by commercially available printing techniques using a variety of available semiconductors.; Chapter 2 further illustrates the significance of engineered materials in the nanoscale regime by investigating electrospun fiber morphologies. These materials have potential applications as membranes with high surface area or as biomaterials in tissue engineering. Fiber shape, size and porosity can change depending on process and environmental conditions. Pore formation as a function of molecular weight and relative humidity is examined. |
