Radiation induced electronic trap states and local structural disorder in van~der~Waals bonded semiconductor crystals

TL;DR

This study investigates how X-ray irradiation creates electronic trap states and induces structural disorder in van der Waals bonded organic semiconductors, revealing disorder as a key origin of trap states.

Contribution

It provides a quantitative analysis of trap state formation due to X-ray irradiation in Rubrene and links structural disorder to trap states in organic semiconductors.

Findings

Approximately 100 trap states form per absorbed photon.

Thermal annealing reduces trap states.

Structural disorder is a common origin of trap states.

Abstract

In controlled X-ray irradiation experiments, the formation of trap states in the prototypical van der Waals bonded semiconductor Rubrene is studied quantitatively for doses up to 82 Gy (Gy = J/kg). About 100 electronic trap states, located around 0.3 eV above the valence band, are created by each absorbed 8 keV photon which is 2-3 orders of magnitude more than 1 MeV protons produce. Thermal annealing is shown to reduce these traps. Local structural disorder, which has also been induced by other means in different studies, is thus identified as a common origin of trap states in van der Waals bonded molecular organic semiconductors.