The Present Micro-OFET Concept

High structural quality and minimisation of defects demand for an in situ UHV preparation of the substrate surface, deposition of the active organic layer, and application of the metal contacts without intermediate exposure to 

Organic films on sapphire were prepared in various UHV chambers with base pressures of less than 5 x 10 ° mbar. Chemical composition and cleanliness of all samples were determined with XPS using Mg-Ka radiation from a laboratory source and a hemispherical electron analyser. The preparation and characterisation of the sapphire substrates are discussed in Section 14.3.1.1. 

The Au films were evaporated from different resistively heated sources as well as from an electron beam evaporator. The Au frlm thicknesses and the growth rates were determined during growth by a quartz micro balance. 

The synchrotron experiments were performed at beamline UE52-PGM at BESSY, Berlin. Substrates and films were prepared at the end station in a UHV preparation chamber at a base pressure of 5 x 10mbar and transferred into the measurement chamber without exposure to air. The NEXAFS spectra on sapphire substrates were recorded by measuring the partial electron yield with a dedicated channeltron detector, the spectra on Au substrates were measured using the sample current. Energy calibration and intensity normalisation were carefully done according to [18]. 

The AFM experiments were performed under ambient conditions with a Topometrix Explorer AFM. The sapphire substrate samples were investigated in contact mode. The organic films were examined in tapping mode in order to decrease the interaction of the tip with the sample. The resolution of the AFM is 50 run in lateral and less than 1 nm in vertical direction. 

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