Fabrication And Characterization Of Organic Field Effect Transistors

In recent years,organic field effect transistor(OFET) has attracted great interests and its performance has been improved drastically because of its low cost and structural flexibility.Based on the process optimization of the active layer materials,thermal evaporation and conventional silicon integrated circuit process were combined to fabricate OFET and the device's characteristics are studied in this paper.Optimization of the organic crystal fabrication process is important to obtain high performance of organic field-effect transistors (OFETs).In this paper, the thin-films of organic semiconductor pentacene were fabricated by thermal evaporation on silicon substrates coated with SiO2 layer by dry oxidation. X-ray diffraction (XRD) patterns and atomic force microscopic images were employed to analyze the surface morphologies and crystal structures of the samples. The influences of the deposition conditions on the crystallization were explored and the thin films with good crystal quality were obtained. The measurement of time-of-flight (TOF) demonstrated the negative differential mobility of the Pentacene film. The estimated value of the charge carrier drift mobility(μ) was about 10-3cm2V-1s-1.The charge carrier mobility was enhanced about 4 times when the tetracene was doped into pentacene thin film by considering of molecular's structure and energy band gap. This method might useful to improve the characteristics of organic field effect device.Based on the optimization of experimental conditions, OFET was fabricated, and field effect was observed from the output characteristics. Some special phenomena were observed under low gate voltage, and reasonable explanation was given out. Another full organic field effect transistor was also prepared, the results of measurement were analyzed.