Buffer-layer enhanced crystal growth of BaB6 (1 0 0) thin films on MgO (1 0 0) substrates by laser molecular beam epitaxy

Crystalline BaB6 (1 0 0) thin films can be fabricated on MgO (1 0 0) substrates by inserting a 2–3 nm-thick epitaxial SrB6 (1 0 0) buffer layer by pulsed laser deposition (PLD) in ultra-high vacuum (i.e., laser molecular beam epitaxy). Reflection high-energy electron diffraction and X-ray diffraction measurements indicated the heteroepitaxial structure of BaB6 (1 0 0)/SrB6 (1 0 0)/MgO (1 0 0) with the single domain of the epitaxial relationship. Conversely, BaB6 thin films without the buffer layer were not epitaxial instead they developed as polycrystalline films with a random in-plane configuration and some impurity phases. As a result, the buffer layer is considered to greatly affect the initial growth of epitaxial BaB6 thin films; therefore, in this study, buffering effects have been discussed. From the conventional four-probe measurement, it was observed that BaB6 epitaxial thin films exhibit n-type semiconducting behavior with a resistivity of 2.90 × 10−1 Ω cm at room temperature.