Synthesis of Bi2SiO5 thin films by confocal dual magnetron sputtering-annealing route

Abstract

Synthesis of nanocrystalline Bi2SiO5 thin films was achieved using confocal magnetron sputtering from independently driven alpha-Bi2O3 and Si targets. The correct composition was obtained by adjusting the power applied to each target, but crystallization was obtained after annealing the samples in air at 400 °C for 2 h. The films were systematically characterized by grazing angle X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared and Raman spectroscopy and UV-VIS transmittance and reflectance spectroscopies. The XPS analysis of the annealed samples, indicated that the correct Bi2SiO5 composition was obtained for the samples deposited using 80 W applied to the Si target, meanwhile the XRD results indicated the formation of randomly oriented nanocrystalline films, independently of the substrate used. Contrary to the commonly reported orthorhombic Bi2SiO5 phase, the detailed analysis of the Raman spectra suggested that the films presented the monoclinic structure, which is only slightly different to the orthorhombic phase due to the small titling of the beta angle. The optical analysis indicated a direct optical band gap of 3.8 eV, although the films were not transparent due to the light scattering produced by a rough-porous surface.