Ferromagnetic Mn doped InSb studied at the atomic scale by cross-sectional STM

TL;DR

This study uses atomic-scale cross-sectional STM to analyze Mn-doped InSb, confirming its ferromagnetism at room temperature, uniform Mn distribution without clustering, and the role of Mn as a shallow acceptor.

Contribution

It provides the first atomic-scale characterization of Mn-doped InSb grown by MBE, revealing disorder in Mn distribution and its implications for ferromagnetism.

Findings

Mn acts as a shallow acceptor in InSb

No Mn clustering or secondary phases observed

Disorder in Mn ion positions affects ferromagnetism

Abstract

We present an atomically resolved study of metal-organic vapor epitaxy grown Mn doped InSb that is ferromagnetic at room-temperature. Both topographic and spectroscopic measurements have been performed by cross-sectional scanning tunneling microscopy. The measurements show a perfect crystal structure without any precipitates and reveal that Mn acts as a shallow acceptor. The Mn concentration obtained from the cross-sectional STM data compares well with the intended doping concentration. No second phase material or (nano)clustering of the Mn was observed. While the pair correlation function of the Mn atoms showed that their local distribution is uncorrelated beyond the STM resolution for observing individual dopants, disorder in the Mn ion location is clearly noted. We discuss the implications of the observed disorder for a number of suggested explanations of the room-temperature ferromagnetism in Mn doped InSb grown by metal-organic vapor epitaxy.