TY  - JOUR
A1  - Kalbitz, Rene
A1  - Gerhard, Reimund
A1  - Taylor, D. M.
T1  - Fixed negative interface charges compromise organic ferroelectric field-effect transistors
JF  - Organic electronics : physics, materials and applications
N2  - Capacitance-voltage (C-V) and current-voltage measurements have been undertaken on metal-ferroelectric-semiconductor capacitors and ferroelectric field-effect transistors (FeFETs) using the ferroelectric polymer poly(vinylidenefluoride-trifluoroethylene) as the gate insulator and poly(3-hexylthiophene) as the active semiconductor. C-V measurements, voltage-dependence of gate currents and FeFET transfer characteristics all confirm that ferroelectric polarization is stable and only reverses when positive/negative coercive fields are exceeded for the first time. The apparent instability observed following the application of depletion voltages arises from the development of a negative interfacial charge which more than compensates the ferroelectric-induced shift, resulting in a permanent shift in threshold voltage to positive values. Application of successive bipolar voltage sweeps to a diode-connected FeFET show that significant remanent polarization is only induced in an unpoled device when the coercive field is exceeded during the first application of accumulation voltages. This initial polarization and its growth during subsequent bipolar voltage sweeps is accompanied by the accumulation of the fixed interfacial negative charges which cause the positive turn on voltages seen in C-V and transfer characteristics. The origin of the negative charge is ascribed either to layers of irreversible ferroelectric domains at the insulator surface or to the drift to the insulator-semiconductor interface of F-ions produced electrolytically during the application of accumulation voltages.
KW  - Organic TFT
KW  - Memory device
KW  - Ferroelectric polymer
KW  - Organic FeFET
KW  - Ferroelectric polarization
KW  - Trapped charges
Y1  - 2012
U6  - https://doi.org/10.1016/j.orgel.2012.01.034
SN  - 1566-1199
VL  - 13
IS  - 5
SP  - 875
EP  - 884
PB  - Elsevier
CY  - Amsterdam
ER  -