# Long-range order and thermal stability of thin Co$_{2}$FeSi films on GaAs(111)B

## TL;DR

This study investigates the growth, structural order, and thermal stability of Co$_{2}$FeSi thin films on GaAs(111)B, revealing stable interfaces and long-range order characteristics relevant for spintronic applications.

## Contribution

It provides detailed analysis of the growth modes, phase ordering, and stability of Co$_{2}$FeSi films on GaAs, highlighting the effects of substrate temperature on structure and order.

## Key findings

- Films grow in island mode between 100°C and 425°C.
- Stable interface maintained up to 275°C.
- Long-range order varies with local non-stoichiometry.

## Abstract

Co$_{2}$FeSi/GaAs(111)B hybrid structures are grown by molecular-beam epitaxy and characterized by transmission electron microscopy (TEM) and x-ray diffraction. The Co$_{2}$FeSi films grow in an island growth mode at substrate temperatures $T_{S}$ between $T_{S}$~=~100$\thinspace^{\circ}$C and 425$\thinspace^{\circ}$C. The structures have a stable interface up to $T_{S}=275~^{\circ}$C. The films contain fully ordered $L2_{1}$ and partially ordered $B2$ phases. The spatial distribution of long-range order in Co$_{2}$FeSi is characterized using a comparison of TEM images taken with superlattice reflections and the corresponding fundamental reflections. The spatial inhomogeneities of long-range order can be explained by local non-stoichiometry due to lateral segregation or stress relaxation without formation of extended defects.