Radio Frequency Sputter Deposition of Epitaxial Nanocrystalline Nd_1-xSr_xCoO₃ Thin Films

In this paper we report the deposition of epitaxial thin films of Nd_1-xSr_xCoO₃ with x = 0, 0.2, and 0.5 on single-crystalline substrates (SrTiO₃ and LaAlO₃) carried out by means of rf-magnetron sputtering. The deposited films are all completely oriented and epitaxial and characterized by a nanocrystalline morphology. As-deposited films have an average roughness around 1 nm while after the thermal treatment this increases up to 20 nm while preserving the nanocrystalline morphology. All the films deposited on SrTiO₃ have shown to be under a certain degree of tensile strain while those on the LaAlO₃ experience a compressive strain, thus suggesting that at about 50 nm the films are not fully relaxed, even after the thermal treatment. For the x = 0.2 composition three different thicknesses have been investigated, revealing an increased strain for the thinner films.