Low Frequency Dielectric Loss of Metal/Insulator/Organic Semiconductor Junctions in Ambient Conditions

TL;DR

This study investigates the dielectric properties of metal/insulator/organic semiconductor junctions in ambient conditions, revealing low-frequency proton diffusion and distinct dipolar responses at higher frequencies related to defects at interfaces and within materials.

Contribution

It provides new insights into the dielectric loss mechanisms in organic semiconductor junctions, highlighting the roles of proton diffusion and defect-related dipolar contributions.

Findings

Proton diffusion in the oxide is anomalous and influences low-frequency admittance.

Two distinct dipolar responses are observed at higher frequencies, linked to different defect locations.

Different dynamic behaviors of defects are characterized by Debye and Cole-Cole models.

Abstract

The complex admittance of metal/oxide/pentacene thin film junctions is investigated under ambient conditions. At low frequencies, a contribution attributed to proton diffusion through the oxide is seen. This diffusion is shown to be anomalous and is believed to be also at the origin of the bias stress effect observed in organic field effect transistors. At higher frequencies, two dipolar contributions are evidenced, attributed to defects located one at the organic/oxide interface or within the organic, and the other in the bulk of the oxide. These two dipolar responses show different dynamic properties that manifest themselves in the admittance in the form of a Debye contribution for the defects located in the oxide, and of a Cole-Cole contribution for the defects related to the organic.