Influence of the deposition parameters on the characteristics of CuxMo6S8 thin films in situ grown by pulsed laser deposition

CuxMo6S8 thin films have been grown in situ by pulsed laser deposition (PLD) on R-cut Al2O3 single-crystal substrates. Under selected deposition conditions, they are oriented and present epitaxial relationships with the in-plane substrate directions. The influence of deposition parameters on composition or epitaxial quality has been studied in detail. In most samples, an excess of metallic molybdenum has been detected by X-ray diffraction and quantified by Rutherford backscattering spectrometry (RBS). The deposition under argon (8.10−2 mbar) at 870°C with a target–substrate distance of 38 mm and an average laser fluence of 5 J cm−2, has entailed a significant reduction of this secondary phase. Moreover, using a small-sized, home made vacuum chamber, single-phased CuxMo6S8 films have been in situ grown for the first time. The epitaxial relations have been investigated by X-ray diffraction in various modes (namely θ-2θ, θ-scans and ϕ-scans) and by scanning electron microscopy. Under secondary vacuum, (100)Rh oriented thin films are obtained above 820°C and a progressive improvement of the epitaxial growth has been observed up to 890°C. The superconducting critical temperature Tc, measured by the a.c. susceptibility method, appears insensitive to the microstructural modifications. Such deposition conditions have been applied to other substrates like Al2O3C, (100) MgO or (100) Y: ZrO2 and have led to new complex epitaxial growth relations.