The discovery of (semi) conducting polymers opened a route to the fabrication of microelectronics by printing. We designed structural and electrical properties of printed polymeric thin films and multilayers to set up field-effect transistors. The polymeric transistors are fully logic capable as is proven by persistent operation of an integrated ring-oscillator circuit. Solution processing of the polymers in printing is completely done under ambient conditions resulting in stable operation of the printed transistors and microcircuits.
The combination of soluble polymers with printing and coating techniques enabled the fabrication of polymer field-effect transistors (PFETs) on flexible films. The devices were built in a top gate configuration, with four functional layers deposited. The electrodes were patterned by gravure offset printing, where source-drain were made from conducting polyanilin and carbon black filled conducting ink was used as gate material. The doctor blading technique was utilized for coating low viscosity solutions, where Poly(3-alkyllthiophene) served as active semiconductor material. Thus completely printed PFETs have been demonstrated. Further steps for printing integrated polymer circuits included the fabrication of inverters combined from two printed. Screen-printing could be used as an alternative to coating and has the potential to enable vertical electrical interconnects between top and bottom layer of circuits. To test the suitability insulating layers were screen-printed homogenously onto lithographically patterned electrodes made from gold. The PFETs' yield was sufficient enough to let a 7-stage ring oscillator work with a clock frequency of 4 Hz.
The electron beam induced conductivity (EBIC) of zinc oxide varistor ceramics is studied in the scanning electron microscope (SEM). It is found that only particular grain boundaries give rise to an EBIC signal and that the signal strength and its linescan profile show strong variation with bias voltage. The experimental results are discussed in terms of Schottky emission of majority carriers across the grain boundary potential barrier
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