Amorphous silicon nitride films of different composition deposited at room temperature by pulsed glow discharge plasma immersion ion implantation and depositionIt is shown that bond contraction and nonbonding lone-pair interaction dominate at nitride surfaces. The maximum elastic recovery of a nitride surface was found to be 100% under a relatively lower nanoindentation load (Ͻ1.0 mN) and the hardness of the surface was found to be 100% higher than the bulk value. It is interpreted that the spontaneous bond contraction, estimated at 12%-14%, strengthens the binding energy and hence the hardness and Young's modulus at the surface. The lone-pair weak interaction claims the responsibility for ͑i͒ the high elastic recovery, ͑ii͒ the lower Raman frequencies of vibration, and ͑iii͒ the existence of critical loads for slide friction or lone-pair broken.
Polycrystalline Fe3O4 films have been prepared by reactive sputtering at room temperature. Transmission electron microscopy images show that the films consist of quite uniform Fe3O4 grains well separated by grain boundaries. It was found that the tunneling of spin-polarized electrons across the antiferromagnetic coupled grain boundaries dominates the transport properties of the films. Magnetoresistance (MR) {=[ρ(H)−ρ(0)]/ρ(0)} shows linear and quadratic magnetic-field dependence in the low-field range when the field is applied parallel and perpendicular to film plane, which is similar to the behaviors observed in the epitaxial Fe3O4 films consisting of a large fraction of antiferromagnetic antiphase domain boundaries. At 300 K, the size of the MR reaches −7.4% under a 50-kOe magnetic field, which is a very large MR for polycrystalline Fe3O4 films.
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