Magnetic and field emission studies of atom beam sputtered Ni:SiO(2) granular films
Abstract
Ni:SiO(2) granular films have been prepared by atom beam sputtering technique under ambient conditions. These films have been subsequently annealed at 200-600 degrees C temperature. GAXRD and TEM analyses show the growth of Ni particles and improvement in crystallinity with increase in annealing temperature. Selected area electron diffraction and XPS analyses show the presence of a small quantity of NiO phase in addition to metallic Ni. Room temperature magnetic measurements indicate that the films annealed at lower temperatures (<= 400 degrees C) are superparamagnetic and the film annealed at 600 degrees C is ferromagnetic. Magnetic results at 5 K are explained on the basis of exchange bias between Ni particles and surrounding nickel oxide. Systematic field emission studies on as-deposited and annealed films show a turn-on field similar to 6.2-13.5 V/mu m corresponding to an emission current density of similar to 1 A/m(2). Field emission results are explained on the basis of electrical inhomogeneity effects. (C) 2010 Elsevier Ltd. All rights reserved.