Regensburg 2004 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
SYOH: Organic and Hybrid Systems for Future Electronics
SYOH 5: Poster
SYOH 5.54: Poster
Donnerstag, 11. März 2004, 18:00–21:00, B
An impedance spectroscopy study of Ag/PTCDA/n-GaAs(100) heterostructures — •A. Bekkali, I. Thurzo, T. U. Kampen und D. R. T. Zahn — Insitut für Physik, TU Chemnitz, D-09107 Chemnitz
In this work impedance spectroscopy (IS) was applied to investigate Ag/PTCDA/n-GaAs(100) heterostructures. Describing the samples using an equivalent circuit consisting of resistors and capacitors, the potential drop across each relevant area of the sample, that is, the GaAs and PTCDA bulk as well as the Ag/PTCDA and PTCDA/GaAs interface, can be determined. The IS characteristics can be simulated by modeling the Ag/PTCDA interface using a parallel RoCo circuit connected in series with a bulk resistance Rb for the PTCDA layer. All the elements are found to be nonlinear with respect to the applied bias and frequency independent. The depletion layer in GaAs is correctly characterized by its parallel resistance Rd and capacitance Cd. The most important feature of the Ag/PTCDA interface is the capacitance Co, which consists of a geometric capacitance and an excess capacitance δ C, the latter originating from recharging a Gaussian density of states (DOS). This Gaussian DOS is attributed to surface states Nss(E), their respective capacitance δ Css(E) = q2Nss(E) peaking for an applied bias of 0.2 V. This value agrees with the thermal activation energy for carrier transport in the PTCDA layer.