RHEED controlled ultra-thin buffer layers of SrTiO3 have been deposited on (100) MgO by
pulsed laser deposition to growth YBaCuO films for microwave applications. A buffer layer with a
thickness between 2 and 15 nm, i.e. 5 to 40 unit cells of SrTiO3, is sufficient to expand to more than
60 °C the range of deposition temperatures leading to low microwave surface resistance. The Rs values
are as good as those obtained on LaAlO3 substrates with a slighly lower magnetic field dependency.
The SrTiO3 seed layer induces an oriented epitaxial growth with YBCO [100] // MgO [100] over this
range of deposition temperatures.