Hot Complex Oxides – Unlocking New Materials and New Physics via High Temperature Adsorption Controlled Molecular Beam Epitaxy

It has long been understood that molecular-beam epitaxy works best for materials that can be grown in an adsorption-controlled regime where thermodynamics automatically provides composition control. This approach has found greatest success for GaAs and other compound semiconductors, fundamentally underlying the capability of MBE to produce semiconductor films with the highest reported purity and mobilities. To date, however, adsorption control processes in complex oxide materials have been limited to specific systems, as the majority of binary oxide constituent compounds (such as SrO, BrO, TiO_x, etc) remain non-volatile up to ~1000 °C, the typical limit for conventional MBE substrate heater technologies. Here, we utilize a powerful CO₂ laser for MBE substrate heating, allowing access to growth temperatures up to and beyond 2000 °C on virtually all commercially available oxide substrates. Utilizing this approach, we have grown an increasing number of complex oxides in unconventional, ultra-high temperature adsorption-controlled regimes by MBE, some realized here for the first time in epitaxial thin film form. In each case we observe substantial improvements in structural and electronic properties as characterized by transport, XRD, and/or in situ angle-resolved photoemission spectroscopy measurements. In this talk, we outline the technical basis and future possibilities for CO₂ laser heating in epitaxial thin film synthesis, specifically discussing recent results for SrTiO₃, BaTiO₃, SrMoO₃, and Sr₂MoO₄ grown at substrate temperatures in the 1200-1500 °C range.