Epitaxial growth of cobalt doped TiO2 thin films on LaAlO3(100) substrate by molecular beam epitaxy and their opto-magnetic based applications

Abstract

In this work, we report the growth process of pristine and cobalt (2%, 4%, 6% and 8%) doped TiO2 thin films on LaAlO3(100) substrate by molecular beam epitaxy (MBE) technique. The microstructural, magnetic, optical, photoconductivity and photocatalytic activity of the films were explored. Reflection high-energy electron diffraction (RHEED) confirms successful growth of single phase anatase TiO2 thin film and effects of cobalt (Co) doping on crystal phase depending on the growth conditions and correlating changes in their physical properties. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) establish highly pure crystalline nature and oxidation state of the elements. Magnetic measurements show room temperature ferromagnetism in all the thin films and suggest that growth conditions, oxygen vacancies and bound magnetic polaron (BMP) model account for the magnetic properties. The optical properties exhibit a red shift response associated with narrowing bandgap that influence photocatalytic activity. The 8% cobalt doped TiO2 film has shown 91% degradation with methylene blue and 88% degradation with Azo dye in 70 min under visible light irradiation exhibiting excellent photocatalytic performance. The photoconductivity measurements have confirmed photosensitive nature of TiO2 and 8% Co doped TiO2. Therefore, these opto-magnetic properties can be tuned for the applicability of future spintronic and optical devices.