Kelvin force gradient microscopy of pBTTT transistors in both the linear and saturation electrical regimes

Kelvin force gradient microscopy of pBTTT transistors biased in both the linear and saturation electrical regimes is presented. The linear regime potential profiles are dominated by the contacts and the true material mobility, 0.11±0.01 cm₂ V-1 s-1, is ten times higher than that derived from device electrical characteristics. In the saturation regime the potential profiles are well fitted by a simple model assuming a very weakly gate potential dependent mobility in the range 0.021-0.028 cm₂ V-1 s-1. These measurements indicate that contrary to the conclusion drawn from the device electrical characteristics, the linear mobility is larger than the saturation mobility.