Heteroepitaxial oxide structures grown by pulsed organometallic beam epitaxy (POMBE)

We describe the design, construction, and use of pulsed organometallic beam epitaxy (POMBE), a plasma-enhanced CVD technique to grow oxide heterostructures. Solid-state precursors are sampled in the gas line via quartz crystal monitors and injected into the O₂ microwave plasma with pulse time durations of a few seconds. The precursors are injected through pneumatic valves in a heated valve box. The valves and microwave power are under computer control. The microwave plasma is ramped between a forward power of 600 and 1500W to improve film epitaxy. We use POMBE to grow epitaxial BaYZrO₃/MgO, Y-ZrO₂/LAO, and YBa₂Cu₃O₇/Y-ZrO₂/LAO structures. The processing parameters leading to the heteroepitaxy are described. The best epitaxy results in X-ray FWHM of 0.12°, 0.38°, and 0.87° for BaYZrO₃, Y-ZrO₂, and YBa₂Cu₃O₇, respectively. We show the advantages of the POMBE technique over that of plasma-enhanced CVD. Selected TEM results of the heteroepitaxial oxide structures are shown, and the role that temperature plays in the oxide epitaxy. The epitaxy of BaYZrO₃ is the first described in the literature, and that of YSZ is among the best reported.