All-wurtzite (In,Ga)As-(Ga,Mn)As core-shell nanowires grown by molecular beam epitaxy

TL;DR

This study investigates the structural and magnetic properties of all-wurtzite (In,Ga)As-(Ga,Mn)As core-shell nanowires grown by molecular beam epitaxy, revealing their crystalline structure, strain states, and ferromagnetic behavior at low temperatures.

Contribution

It provides detailed insights into the epitaxial growth, crystalline structure, and magnetic properties of (In,Ga)As-(Ga,Mn)As nanowires with wurtzite structure, a novel combination for such nanostructures.

Findings

Both core and shell have wurtzite structure.

Shell contains 5% Mn, core contains about 10% In.

Ferromagnetic coupling observed above 33 K, with superparamagnetic behavior below 17 K.

Abstract

Structural and magnetic properties of (In,Ga)As-(Ga,Mn)As core-shell nanowires grown by molecular beam epitaxy on GaAs(111)B substrate with gold catalyst have been investigated.(In,Ga)As core nanowires were grown at high temperature (500 {\deg}C) whereas (Ga,Mn)As shells were deposited on the {1-100} side facets of the cores at much lower temperature (220 {\deg}C). High resolution transmission electron microscopy images and high spectral resolution Raman scattering data show that both the cores and the shells of the nanowires have wurtzite crystalline structure. Scanning and transmission electron microscopy observations show smooth (Ga,Mn)As shells containing 5% of Mn epitaxially deposited on (In,Ga)As cores containing about 10% of In, without any misfit dislocations at the core-shell interface. With the In content in the (In,Ga)As cores larger than 5% the (In,Ga)As lattice parameter is higher than that of (Ga,Mn)As and the shell is in the tensile strain state. Elaborated magnetic studies indicate the presence of ferromagnetic coupling in (Ga,Mn)As shells at the temperatures in excess of 33 K. This coupling is maintained only in separated mesoscopic volumes resulting in an overall superparamagnetic behavior which gets blocked below ~17 K.