Microstructural, magnetic and magneto-transport properties of NiO thin film deposited on Si (100) substrates

摘要

NiO thin film on p- and n-type Si (100) substrates were fabricated by electron beam evaporation technique and studied by structural, morphological, magnetic and magneto-electronic transport characterization techniques. The room temperature interfacial chemistry across the interfaces is found to affect the morphology, transport and magnetic behaviour of the structures. Structural study has shown the presence of magnetic nickel silicide phases along with some metallic phases as a result of interfacial intermixing. Isolated nano-granular features of magnetic grains along with the presence of clustered grains are observed. Strong magnetic signal strength is observed for NiOSi structure as compared to the interface on pSi substrate which suggests the formation of more magnetic silicide phases resulting in a higher magnetization value with increased coercivity. Magnetization characteristics of the NiO thin films on Si substrates have shown a nearly superparamagnetic behaviour with weak ferromagnetic contribution as compared to bulk antiferromagnetic nature of NiO. Electronic transport study measured across NiOSi interface have shown the enhancement in conductivity up to 2-3 orders of magnitude than for NiO film on pSi substrate with significant magnetic field sensitivity. Magnetic field induced enhanced current has been observed for NiOSi structure which is related to the magnetic field response of magnetic grains (of nickel silicide phases) or isolated magnetic clusters favouring the paths for spin alignment or spin-dependent scattering resulting in a negative magnetoresistance of ～50 %.