Effects of epitaxial strain on the growth mechanism of YBa2Cu3O7-x thin films in [YBa2Cu3O7-x / PrBa2Cu3O7-x] superlattices

TL;DR

This study investigates how epitaxial strain influences the growth mechanism of ultrathin YBa2Cu3O7-x layers in superlattices, revealing a transition from 2D to 3D growth modes as strain relaxes.

Contribution

It provides new insights into the relationship between strain release and growth dimensionality in YBCO thin films within superlattices.

Findings

Ultrathin strained YBCO layers grow in a 2D mode.

Strain relaxation causes a transition to 3D growth.

Layer roughness increases with thickness and strain relaxation.

Abstract

We report on the growth mechanism of YBa2Cu3O7-x (YBCO). Our study is based on the analysis of ultrathin, YBa2Cu3O7-x layers in c-axis oriented YBa2Cu3O7-x / PrBa2Cu3O7-x superlattices. We have found that the release of epitaxial strain in very thin YBCO layers triggers a change in the dimensionality of the growth mode. Ultrathin, epitaxially strained, YBCO layers with thickness below 3 unit cells grow in a block by block two dimensional mode coherent over large lateral distances. Meanwhile, when thickness increases, and the strain relaxes, layer growth turns into three dimensional, resulting in rougher layers and interfaces.