We have studied the evolution of the structural modulation in epitaxial, $c$-axis-oriented, ${\mathrm{Bi}}_2{\mathrm{Sr}}_{2-x}{\mathrm{La}}_x\mathrm{Cu}{\mathrm{O}}_{6+\delta }$ thin films when varying the La content $x$ and for a given $x$ as a function of oxygen content. A series of thin films with $0⩽x⩽0.8$ has been prepared in situ by rf-magnetron sputtering and characterized by $R\left(T\right)$ measurements, Rutherford backscattering spectroscopy, transmission electron microscopy, and x-ray diffraction techniques. The oxygen content of each individual film was varied by thermal annealing across the phase diagram. The evolution of the structural modulation has been thoroughly studied by x-ray diffraction in determining the variation of the amplitude of satellite reflections in special two axes $2\theta ∕\theta \text{−}\theta$ scans (reciprocal space scans). It is shown that the amplitude of the modulation along the $c$ axis decreases strongly when $x$ increases from 0 to 0.2. It is demonstrated that this variation is essentially governed by La content $x$ and that changing the oxygen content by thermal treatments has a much lower influence, even becoming negligible for $x>0.2$. Such study is important to understand the electronical properties of ${\mathrm{Bi}}_2{\mathrm{Sr}}_{2-x}{\mathrm{La}}_x\mathrm{Cu}{\mathrm{O}}_{6+\delta }$ thin films.

• Received 6 April 2004

DOI:https://doi.org/10.1103/PhysRevB.71.174503