Film orientation, growth parameters and growth modes in epitaxy of YBa2Cu3Ox

With increasing radius of critical nuclei at low supersaturations the substrate parameters misfit and misorientation become crucial for the initial growth stage and the growth mode of thin films. The importance of substrate misfit and misorientation control in liquid phase epitaxy (LPE) and physical vapor deposition (PVD) of rare earth cuprates is discussed, and critical supersaturations to start growth on mismatched substrates are estimated. Good agreement with experiment was found for the a/c-transition of YBa2Cu3O7-delta (YBCO) on (1 1 0)NdGaO3 in LPE at a critical undercooling (supersaturation) Delta T approximate to 3 K. For tunnel device technology, atomically flat surfaces with interstep distances (monosteps) of about 10 mu m are needed. This requires a substrate misfit less than or equal to 0.08%, a relative supersaturation less than or equal to 0.18%, and a substrate misorientation less than or equal to 0.02 degrees to avoid step bunching. For c-oriented YBCO films on (1 1 0)NdGaO3. with a misfit of 0.28%, monospirals with a maximum interstep distance of y(0) = 2.5 mu m between monosteps can be grown. (C) 1999 Elsevier Science B.V. All rights reserved.