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2. EXPERIMENTAL METHODS geometry). For example with incident angle equal to 5◦, the effective film thick- ness is 12 times larger than in standard geometry (83). However, it is not always possible (or necessary) to employ grazing incidence set-up. A good example is the measurements presented here, which were made with the use of X-ray diffractome- ter XRD-7 from Seifert-FPM, Freiberg. Cobalt anode radiation was used (λKα1 = 1.788965 ̊A), which was filtered through the iron foil. The diffracted beam was detected by a scintillation counter. A standard Bragg-Brentano θ-2θ geometry was used. This caused the inevitable contribution of the silicon substrate, but the Bragg reflections of the substrate did not interfere with the reflections from the films. The analysis was made by comparison of the obtained intensities of diffraction peaks with reference patterns from the PDF-2 database from ICDD in Seifert software. Diffraction patterns were analyzed by Rietveld method with the use of FullProf software (86) and crystallographic information files (cif) from COD database (22, 37, 38, 39, 40, 79, 85). The crystalline structure of coatings or films, especially thin films is a result of complex interplay of the crystalline structure of substrate, deposition technique and conditions, subsequent post-treatment and film thickness. These factors de- cide what phases are being formed on the substrate, crystallinity, the type of crystal structure and its parameters as well as possible preferred orientation. Therefore care should be taken while analyzing the patterns. A standard powder pattern for a perovskite-type SmNiO3 compound is shown in the figure 2.2. The films were sputtered from a target that is composed of SmNi2O4 and NiO pellets. Therefore when grown as thin films, the Sm-Ni-O films may shown presence of other phases - unreacted NiO binary oxide or SmNi2O4, products of SmNi2O4 decomposition or Ruddlesden-Popper phases. Also phases that occur from interaction of the impinging species with the substrate may occur. Their formation is dependent on the availability of nucleation sites mainly due to crystal surface structure of a substrate and favourable thermodynamic conditions. Some conditions may also favour formation of Ruddlesden-Popper phases that share a general formula of An+1BnX3n+1, where A, B are cations and X is an anion, n∈ N. The n-th phase would consist of n layers of ABX3 and a AX layer on a stack. In case of an infinite n, the structure becomes the perovskite type ABX3. Regardless of the structural similarities between the Ruddlesden-Popper phases, their X-ray diffraction patterns may be quite different - as shown in figure 1.5. Another important factor is the crystalline orientation of the deposited film. It is known that the crystalline structure of thin film materials depend strongly on the substrate and manufacturing parameters. The difficulty lies in the proper 38PDF Image | Investigation of metal-insulator transition in magnetron sputtered samarium nickelate thin films
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