Electrical Characterisation of MFIS Capacitors CV Measurements

In a next step, we study the flatband shift, the polarisation as a function of copolymer film thickness. For the measurements, a relatively thick Si02 buffer layer of 235 nm was used and we reveal a clear thickness dependence of the ferroelectric polarisation [32]. We calculated AiJpvDF s the voltage drop only over the P(VDF-TrFE) layer. For accumulation, negative voltages, the voltage is divided into two parts Ui = 17ipvdf + For depletion, we have to cal- 

We further recognise a significant reduction of polarisation for the P(VDF-TrFE) thickness below 100 nm, while between 200 nm and 950 nm the dependence is very similar. Generally it has been postulated that the coercive field increases with decreasing of its thickness [38]. For P(VDF-TrFE) a range of 70-100 nm has been proposed as a critical thickness due to reduced crystal- 

Unity [39] or due to interface interactions [14]. It must be pointed out here that a critical thickness is found for electrodes made of aluminium, not for PEDOT PSS [14], Our data are consistent in this context. In Section 21.3.3 we already showed reactive interactions between P(VDF-TrFE) and aluminium, not for the P(VDF-TrFE)/PEDOT PSS interface. This becomes even more important when the thickness of P(VDF-TrFE) film is further downscaled. 

Based on these results, we build up OFETs with a ferroelectric gate insulation, consisting of P(VDF-TrFE). 

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