Surface composition of BaTiO3/SrTiO3(001) films grown by atomic oxygen plasma assisted molecular beam epitaxy

TL;DR

This study investigates the growth, surface composition, and structural properties of BaTiO3 thin films on SrTiO3 substrates using atomic oxygen assisted molecular beam epitaxy, highlighting the importance of stoichiometry for device integration.

Contribution

It provides detailed insights into the epitaxial growth, surface composition, and lattice relaxation of BaTiO3 films grown by AO-MBE, emphasizing the role of surface layers and stoichiometry.

Findings

Epitaxial single crystalline BaTiO3 layers up to 10 nm were achieved.

A Ba oxide rich top layer was identified and can be removed by chemical etching.

Lattice parameter relaxation occurs within the first 10 nm of growth.

Abstract

We have investigated the growth of BaTiO3 thin films deposited on pure and 1% Nb-doped SrTiO3(001) single crystals using atomic oxygen assisted molecular beam epitaxy (AO-MBE) and dedicated Ba and Ti Knudsen cells. Thicknesses up to 30 nm were investigated for various layer compositions. We demonstrate 2D growth and epitaxial single crystalline BaTiO3 layers up to 10 nm before additional 3D features appear; lattice parameter relaxation occurs during the first few nanometers and is completed at {\guillemotright}10 nm. The presence of a Ba oxide rich top layer that probably favors 2D growth is evidenced for well crystallized layers. We show that the Ba oxide rich top layer can be removed by chemical etching. The present work stresses the importance of stoichiometry and surface composition of BaTiO3 layers, especially in view of their integration in devices.