Effect of impurities on pentacene island nucleation

TL;DR

This study investigates how pentacenequinone impurities influence the nucleation and grain boundary structure of pentacene thin films, revealing that higher impurity levels reduce the critical nucleus size and promote complex formation.

Contribution

It provides a controlled analysis of impurity effects on pentacene film nucleation using AFM, highlighting the role of PnQ in defect formation and film morphology.

Findings

Higher PnQ content decreases critical nucleus size.

Formation of Pn-PnQ complexes is energetically favorable.

Impurities affect Pn mobility and film structure.

Abstract

Pentacenequinone (PnQ) impurities have been introduced into a pentacene source material in a controlled manner to quantify the relative effects of the impurity content on grain boundary structure and thin film nucleation. Atomic force microscopy (AFM) has been employed to directly characterize films grown using 0.0-7.5% PnQ by weight in the source material. Analysis of the distribution of capture zones areas of submonolayer islands as a function of impurity content shows that for large PnQ content the critical nucleus size for forming a Pn island is smaller than for low PnQ content. This result indicates a favorable energy for formation of Pn-PnQ complexes, which in turn suggests that the primary effect of PnQ on Pn mobility may arise from homogeneous distribution of PnQ defects.