Bond contraction and lone pair interaction at nitride surfaces

Abstract

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.

From ice superlubricity to quantum friction: Electronic repulsivity and phononic elasticity

“…Therefore, the enhanced intra-layer strength makes a nitride usually harder (~20 GPa), and the weakened inter-layer bonding makes the nitride highly elastic and self-lubricate. This mechanism also Nanoindentation profiles from TiCrN surface and sliding friction measurements from CN and TiN surfaces have confirmed the predicted high elasticity and high hardness at lower pressing load and the existence of the critical scratching load [99]. As compared in Fig.…”

“…As compared in Fig. 19(a), under 0.7 mN load of indentation, the elastic recoverability and hardness for a GaAlN film are higher than that of an amorphous carbon film [99]. The GaAlN surface is also much harder than the amorphous-C film under the lower indentation load.…”

“…The mechanism of slipperiness of ice is analogous to the self-lubrication of metal nitride [99,100] and oxide [101] skins with electron lone pairs coming into play. TiCrN, GaAlN and -Al 2 O 3 skins exhibit a 100% elastic recovery at nanoindentation load under the critical friction load (e.g., <5 N for carbon nitride) at which the lone pair breaks.…”

Size dependence of nanostructures: Impact of bond order deficiency

“…An examination of the hardness (also stress) and the Young's modulus using nanoindentation revealed that the surface of the TiCrN thin film (2 mm thick) is 100% higher than its bulk value [136]. The same trend holds for amorphous carbon [209] and AlGaN surfaces [210].…”

“…It has been discovered [132], with VLEED that the OeCu bond contraction (from 4% to 12%) forms one of the four essential stages of the OeCu(001) bond forming kinetics and, about 10% OeCu bond contraction for the OeCu(110) surface is necessary [133e135]. A 12e14% contraction of TiCrN surface has been confirmed by measuring the enhanced surface stress and Young's modulus of TiCrN films [136]. Theoretical calculations [137] confirmed that the interatomic distance drops significantly associated with rise of cohesive energy per bond as the dimensionality decreases from three to one for Ag, Au and Cu nanosolids, as shown in Fig.…”