SKPM

The organic semiconductor was again regio-regular P3HT (Aldrich), spin-coated into thin films from chloroform, on printed source-drain structures, as described above. 

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A further spatially resolved method, also based on work function contrast, is scanning Kelvin probe microscopy (SKPM). As an extended version of atomic force microscopy (AFM), additional information on the local surface potential is revealed by a second feedback circuit. The method delivers information depending on the value (p (p(x) + A x). Here, A(zS(x) is the difference in work function between the sample and the AFM tip and cp(x) is the local electric potential [12]. (p x) itself gives information on additional surface charges due to... 

The information revealed by our SKPM measurements in air are split into three main scales or ranges with information on (i) the voltage drop at the elec-trode/polymer interface, (ii) linearity and (iii) fluctuations. 

Compared to the PEEM technique, the SKPM signal is directly proportional to the local work function of the organic device. Both methods, the spectromi-croscopic approach and the SKPM technique, offer lateral information in terms of homogeneity and interfaces. In the next section, we present a depth profiling of interfaces, performed using XPS. 

FIGURE 2.3.12 (a) Schematic diagram of experimental setup for scanning Kelvin probe microscopy (SKPM). (b) Profiles of an L = 5.5 J,m P3HT transistor with Cr electrodes taken at three different temperatures V = 0 V, = -8 V). The inset shows a profile obtained after switching the source and drain contacts on the same TFT with both Cr and Cr-Au contacts Vg = 0 V, = -8 V). (From Burgi, L. et ah, J. Appl. Phys., 94, 6129-6137, 2003. Reprinted with permission. Copyright 2003, American Institute of Physics.)... 

Franckum JP, Ramsay DP, Das NGPMR, Das SKPM. Pluronic lecithin organogel for local delivery of anti-inflammatory drugs. Int J Pharm Compd. 8(2) (2004) 101-105. 

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