Interface effects on an ultrathin Co film in multilayers based on the organic semiconductor Alq3

TL;DR

This study investigates how the thickness of an AlOx barrier influences the magnetic and morphological properties of ultrathin Co films in multilayer structures with organic semiconductor Alq3, revealing a critical 2 nm barrier thickness for optimal magnetic quality.

Contribution

It provides a systematic analysis of the impact of AlOx barrier thickness on magnetic and morphological properties of Co/Alq3 multilayers, highlighting the importance of a 2 nm barrier for good magnetic performance.

Findings

A 2 nm AlOx barrier is essential for high-quality magnetic cobalt layers.

NMR shows interface layer formation with defective cobalt.

Optimal magnetic properties are achieved at specific barrier thicknesses.

Abstract

The effect of the AlOx barrier thickness on magnetic and morphological properties of Ta/Co/(AlOx)/Alq3/Si hybrid structures was systematically studied by means of atomic force microscopy, SQUID magnetometry and nuclear magnetic resonance (NMR). All used techniques pointed out that the barrier thickness of 2 nm is required to obtain a magnetically good cobalt layer on top of Alq3. 59Co NMR measurements revealed that the AlOx barrier gives rise to the formation of an interface layer with "defective" cobalt favouring growth of "bulk" cobalt with good magnetic properties.