Thermal conductivity as a metric for the crystalline quality of SrTiO₃ epitaxial layers

Measurements of thermal conductivity by time-domain thermoreflectance in the temperature range 100<T<300 K are used to characterize the crystalline quality of epitaxial layers of a prototypical oxide, SrTiO₃. Twenty samples from five institutions using two growth techniques, molecular beam epitaxy and pulsed laser deposition (PLD), were analyzed. Optimized growth conditions produce layers with comparable to bulk single crystals. Many PLD layers, particularly those that use ceramics as the target material, show surprisingly low . For homoepitaxial layers, the decrease in created by point defects correlates well with the expansion of the lattice parameter in the direction normal to the surface.