# Epitaxy and Structural Properties of (V,Bi,Sb)$_2$Te$_3$ Layers Exhibiting the Quantum Anomalous Hall Effect

## TL;DR

This study investigates how Sb content, substrate type, and cap layers affect the quantum anomalous Hall effect in V-doped (Bi,Sb)$_2$Te$_3$ layers, demonstrating reproducible growth and robust quantization under various conditions.

## Contribution

It provides a detailed analysis of the growth conditions and parameters influencing the quantum anomalous Hall effect in V-doped (Bi,Sb)$_2$Te$_3$, highlighting the robustness of the effect.

## Key findings

- Optimal Sb content around 80% maximizes quantization.
- Quantization persists across different substrates and cap layers.
- Layer quality and interfaces do not significantly affect the quantum Hall effect.

## Abstract

The influence of Sb content, substrate type and cap layers on the quantum anomalous Hall effect observed in V-doped (Bi,Sb)$_2$Te$_3$ magnetic topological insulators is investigated. Thin layers showing excellent quantization are reproducibly deposited by molecular beam epitaxy at growth conditions effecting a compromise between controlled layer properties and high crystalline quality. The Sb content can be reliably determined from the in-plane lattice constant measured by X-ray diffraction, even in thin layers. This is the main layer parameter to be optimized in order to approach charge neutrality. Within a narrow range at about 80% Sb content, the Hall resistivity shows a maximum of about 10 k$\Omega$ at 4 K and quantizes at mK temperatures. Under these conditions, thin layers grown on Si(111) or InP(111) and with or without a Te cap exhibit quantization. The quantization persists independently of the interfaces between cap, layer and substrate, the limited crystalline quality, and the degradation of the layer proving the robustness of the quantum anomalous Hall effect.