Pulsed-laser epitaxy of topological insulator Bi2Te3 thin films

Zhaoliang Liao,Yogesh Sharma,Yanwen Zhang,Jong Mok Ok,Matthew Brahlek,Qiyang Lu,Lauren Nuckols,Ho Nyung Lee

doi:10.1063/1.5088190

Abstract

Determining optimized conditions necessary to achieve high-quality films by pulsed laser deposition (PLD) for materials with multiple volatile elements is challenging. In this work, we present the optimized growth of epitaxial films of the topological insulator Bi2Te3 on Al2O3 (0001) substrates using PLD. It is found that the key to maximize film quality requires balanced control of the Ar background pressure (PAr) and growth temperature (TG). Within a narrow window (200 ≤ PAr &lt; 350 mTorr and 300 ≤ TG &lt; 350 °C), we find that Bi2Te3 thin films are flat, stoichiometric, and of the highest crystalline quality. This is a result of balancing the kinetics of ablated species in the PLD plume and the bulk thermodynamics of Bi2Te3. This work demonstrates that a careful optimization of the growth parameters can enable PLD to successfully grow multielemental materials containing volatile constituents.

Highlights

Is advantageous for complex materials, in particular, multicomponent oxides, due to the ease of changing materials and combining multiple target materials for the creation of heterostructures
The key hypothesis in this work is can thermodynamic and kinetic growth parameters be balanced to enable the growth of highquality TIs using pulsed laser deposition (PLD) where one or multiple elements are volatile? This approach will both answer fundamental questions regarding the non-equilibrium nature of the growth mechanisms inherent to PLD and open new routes to develop novel hybrid materials beyond topological insulators by enabling the creation of heterostructures with other functional materials with TIs—examples include the FeSe/SrTiO3 interfacial superconductor,20 the multitude of novel 2-dimensional layered materials,21 and hybrid complex oxide/chalcogenide heterostructures
We demonstrate that it is possible to grow high-crystalline quality Bi2Te3 on Al2O3 (0001) substrates using PLD by mapping and finding optimum growth conditions

Summary

Introduction

Is advantageous for complex materials, in particular, multicomponent oxides, due to the ease of changing materials and combining multiple target materials for the creation of heterostructures.17,18. The high energies used often create complications, such as scitation.org/journal/apm non-stoichiometric transfer from the target to the films as well as impact damage; these challenges are amplified when the materials used are volatile, as with topological insulators9–14 and materials like iron based superconductors Ba(Fe1-xCox)As2.19 These effects, can be controlled by carefully tuning the growth conditions, in particular, the substrate temperature, background pressure, laser fluence, and laser spot geometry.16 the key hypothesis in this work is can thermodynamic and kinetic growth parameters be balanced to enable the growth of highquality TIs using PLD where one or multiple elements are volatile?

Results

Conclusion