Surface-disorder and cationic-site defect-induced ferromagnetism and correlated Raman vibrational modes in Sn0.9 In0.1O2 nanocrystalline thin-films

Abstract

Exploration of magnetism in otherwise nonmagnetic wide-band oxides through defect-engineering has been become a new challenge to achieve the goal of room-temperature ferromagnetic semiconductor for potential applications in spintronics. In this backdrop, we report surface-disorder and cationic-site defect-induced FM in series of Sn0.9In0.1O2 nanocrystalline thin films prepared using pulsed laser deposition different Argon (Ar) pressure. With the increase of deposition pressure, surface morphology of Sn0.9In0.1O2 nanocrystalline thin-films changes as nanoclusters, nanofibres, nanoflakes and nanowires respectively, crystallite size decreases and surface disorder increases gradually. Raman, X-ray photoelectron and Photoluminescence spectroscopic analysis confirm the formation tin-vacancy (VSn) and associated combinational defects that significantly increase the ferromagnetic signal in In-doped SnO2 thin-films. The substitution of trivalent In3+ in Sn site also cause serious lattice distortion which transform the Raman inactive modes A2g and Eu modes into Raman active modes and thus appeared at 574 cm−1 and 354 cm−1 respectively. The nanowires of Sn0.9In0.1O2 are found to possess highest concentration of VSn defects and therefore it exhibits strongest ferromagnetic moment (MS) ∼ 11.1 emu/cm3 and highest Curie temperature (TC) ∼ 572 K. The gradual decrease in carrier concentration with the increasing deposition pressure suggests stabilization of hole-mediated VSn-induced room temperature FM in series of In-doped SnO2 nanocrystalline thin-films.