ION MODULATED ORGANIC TRANSISTORS - Doria

Nikolai Kaihovirta3. RESULTS AND DISCUSSIONScompletely re-orient themselves at higher frequencies. Apparently, theionic mobility drops.-I D/ A4.02.00.0a)In airb)1d5d0.0 0.5 1.0 1.52 months0.0 0.5 1.0 1.5-V D/V-V D/VFigure 3.14. (a) Typical output-characteristics measured for a PTFE:PFSA-basedMemFET in ambient air and as a function of time in a dry atmosphere. Thearrow points at the gate leakage current caused by the hydrous electrolyte. Thegate leakage current diminishes upon drying the membrane. (b) Outputcharacteristicsfor a PTFE:PFSA-based MemFET measured after two months ofstoring in a dry atmosphere. The applied V G´s are 0 V (square), -0.4 V (circle)and -0.8 V (triangle).Based on the aforementioned observations on the bare PTFE:PFSA, achanging ambient humidity should also have a detrimental impact on thecharge transport in the MemFET. Indeed, as seen in Figure 3.14, theoutput-curves loose their transistor-characteristic features (i.e., the pinchoffand the modulation) by keeping the PTFE:PFSA-based MemFET in adry atmosphere for two months. If assuming that W, L and (V G - V T ) areconstant, throughout the measurements in Figure 3.14, then the observeddecrease of the channel conductance (g D) at V DS 10 %, the PTFE:PFSA-based MemFET suffers from anincreasing ionic conductivity [76]. Therefore, careful balancing of theambient humidity levels is essential on a longer time-scale.0.30.20.10.0-I D/ A37