Phase control of La2CuO4 in thin-film synthesis

TL;DR

This paper demonstrates that the phase of La2CuO4 in thin-film synthesis can be controlled by adjusting temperature and substrate, switching between K2NiF4 and Nd2CuO4 structures.

Contribution

It reveals how synthesis temperature and substrate choice influence the crystal structure of La2CuO4 in thin films, enabling phase control.

Findings

Low-temperature synthesis favors Nd2CuO4 structure.

Phase control achieved by temperature and substrate variation.

La2CuO4 can crystallize in different structures depending on synthesis conditions.

Abstract

The lanthanum copper oxide, La2CuO4, which is an end member of the prototype high-Tc superconductors (La,Sr)2CuO4 and (La,Ba)2CuO4, crystallizes in the "K2NiF4" structure in high-temperature bulk synthesis. The crystal chemistry, however, predicts that La2CuO4 is at the borderline of the K2NiF4 stability and that it can crystallize in the Nd2CuO4 structure at low synthesis temperatures. In this article we demonstrate that low-temperature thin-film synthesis actually crystallizes La2CuO4 in the Nd2CuO4 structure. We also show that the phase control of "K2NiF4"-type La2CuO4 versus "Nd2CuO4"-type La2CuO4 can be achieved by varying the synthesis temperature and using different substrates.