Morphology-Dependent Magnetism and Raman Modes Induced by Surface-Disorder and Cation-Site Defects in Indium-Substituted SnO2 Thin Films

Defect-induced magnetism (DIM) in otherwise nonmagnetic wide-band oxides had recently been explored in order to prepare oxide dilute magnetic semiconductor (O-DMSs) as the next-generation spintronic materials. In this context, effect of morphology-dependent surface-disorder and cationic-site defects in tailoring ferromagnetic behaviour and Raman vibrational modes were investigated systematically in series of indium (In)-substituted SnO 2 thin films fabricated by pulsed laser deposition (PLD) in oxygen-deficient Argon (Ar) atmosphere. Surface morphology of the SnO 2 :In films had been changed as nanospheres (NSs), nanoflowers (NFs), nanoflakes (NFLs) and nanowires (NWs) with varying Ar pressure of 1, 10, 100 and 1000 Pa respectively. With increase of deposition pressure, crystallite size and thickness of the film decreased whereas surface disorder had enhanced considerably. Spectroscopic evidence revealed that both Sn vacancy ( V Sn ), oxygen vacancy ( V O ) defects were stabilized with enhanced surface disorder with the films. ESR spectroscopy indicated the presence of two major paramagnetic defect centres comprising Lande g -factor ~ 2.003, assigned to singly ionized V O + defect whereas other ‘ g ’ value about 1.89 were due to V Sn defects or its complex with Vo defects. Being enriched with substantial paramagnetic defects, In-doped SnO 2 films exhibited enhanced high- T C ferromagnetism. NWs of In:SnO 2 exhibited superior ferromagnetic signal with magnetic moment ~ 11.1 emu/cm 3 and Curie temperature ~ 570 K. We attribute RKKY type magnetic interaction between magnetic of isolated V Sn or associated defects complex like ( V Sn - Vo ) mediated through the holes introduced due to In Sn defects as the origin of FM in In:SnO 2 thin films. Therefore, the study depicts the promotion of cation vacancy defects by monitoring growth atmospheric conditions can be an effective way to achieve the oxide-based dilute magnetic semiconductors (O-DMSs) for spintronics applications.