A model of structural disorder in (Ba-2-Cu-2-O4+X)/(Ca-Cu-O-2)(n) superlattices

The structural disorder in (Ba2Cu2O4+x)/(CaCuO2)(n) superlattices with ultr athin individual layers was investigated. Numerical simulations of x-ray sp ectra were carried out following a kinematical approach in a simplified mod el structure. The model assumes a two-dimensional layer by layer growth in which mixed composition layers can be corrugated to adjust the internal str esses due to the large mismatch between the constituent oxides. An addition al random disorder is added to take into account the experimental dispersio n in the amount of material deposited in each iteration. The model was succ essfully used to simulate x-ray spectra for samples with non integer n rang ing from 2 to 16, grown in optimal conditions to obtain a superconducting b ehavior. The same model was used to simulate spectra of samples grown at lo wer pressures monitored with in situ RHEED diagnostic. In this case, random disorder results more than one order of magnitude smaller.