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.
Bibliographical noteFunding Information:
This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Award Grant No. DE-FG02-07-ER-4645 and was carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the U.S. Department of Energy under Grant Nos. DE-FG02-07ER46453 and DE-FG02-07ER46471. The work at UCB (R.R.) was supported by the Division of Materials Sciences and Engineering of U.S. Department of Energy under Contract No. DE-AC02-05CH1123. J.R. acknowledges the Link Energy Fellowship and W.S. acknowledges support from the Dutch Organization for Scientic Research (NWO-Rubicon Grant).The work at UCSB (B.J. and S.S.) was supported as part of the Center for Energy Efficient Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DE-SC0001009.