Structural, magnetic and electrical properties of calcium modified bismuth manganite thin films

The present investigation involves the growth of Bi1−xCaxMnO3 (BCMO) thin films with x = 0, 0.1, 0.2, 0.3 and 0.4 on platinized silicon substrates at two different substrate temperatures (400 °C and 800 °C) using RF magnetron sputtering. It also deals with their characterization by employing various techniques: X-ray diffraction analysis (XRD), Atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), Vibrating sample magnetometer (VSM), Leakage, dielectric and ferroelectric measurements. The XRD reveals that the single phasic monoclinic structure of pure BiMnO3 (BMO) is distorted to a small degree with the variation in growth temperatures and the addition of calcium at different concentrations. The composition and valence state of the elements analyzed with XPS confirms the formation of BiMnO3 phase and substitution of Ca ions on Bi site. The room temperature hysteresis loops of BCMO (x = 0.2) films grown at 400 and 800 °C show better magnetic moments of 754 and 858 emu/cc respectively than the values of the other prepared films. The leakage measurements indicate that the leakage current density decreases gradually with the increasing Ca concentration. For both the temperatures, a sharp minimum leakage current density of 5.7 × 10−3 A/cm2 has been observed for BCMO (x = 0.2) films. Moreover, the study evaluates the effects of calcium substitution and growth temperatures on morphology, elemental, dielectric and ferroelectric properties of BMO films.