Buffer-layer-enhanced growth of a single-domain LaB 6 (1 0 0) epitaxial thin film on a MgO (1 0 0) substrate via pulsed laser deposition

Abstract

Epitaxial growth of LaB 6 (1 0 0) thin films was examined on MgO (1 0 0) and sapphire (α-Al 2O 3) (0 0 0 1) substrates with insertion of a 2–3 nm-thick epitaxial SrB 6 buffer layer by pulsed laser deposition in ultra-high vacuum. Reflection high-energy electron diffraction, X-ray diffraction, and the Raman scattering spectroscopy measurements proved that the heteroepitaxial structure of the LaB 6 (1 0 0)/SrB 6 (1 0 0)/MgO (1 0 0) substrate has a single-domain, while and that of the LaB 6 (1 0 0)/SrB 6 (1 0 0)/sapphire (0 0 0 1) substrate have three domains. LaB 6 thin films grown without the buffer layer were not epitaxial; instead, they developed as polycrystalline films with a random in-plane configuration. The buffer layer greatly affected the initial growth of the LaB 6 thin films. Epitaxial LaB 6 thin films exhibited metallic behavior with almost constant resistivities in the temperature range 12–300 K. At room temperature, the resistivities of single-domain LaB 6 (1 0 0) epitaxial thin films on MgO substrates were about 5 times smaller than those of the three-domain LaB 6 (1 0 0) epitaxial thin films on the sapphire substrates.