The Formation Conditions Of Ti-Si-N Interface Phase: First-principle Study

It is well known that Ti-Si-N nanocomposite thin films have good mechanical, optics,electrical and other performance. The researchers believe that the two phase of TiN and Si3N4are separated, and the nanocrystalline TiN wrapped by the interface phase of the SiN is the mainreason for the super-hard. In order to clarify the superhard mechanism of Ti-Si-Nnanocomposite thin film, we should understand the formation process and conditions ofinterface structure of Ti-Si-N composite film. In order to analyze formation process of theinterfacial structure accurately, it is necessary to insight into the details of the separation of TiNphase and SiN phase, and to calculate the required activation energy about the formation of theinterface phase. This research provides a theoretical basis for optimization manufacturing ofsuper-hard process about Ti-Si-N. In this paper, using first-principles method which is based ondensity functional theory (DFT) simulates both the process of forming and the requiredconditions of interface structure SiNx. This research discussed the increase of N, Ti particledeposition ratio effectting on the process of forming interface, as well as2D island growthshape on the surface of TiN (001). First, the paper calculated both the total energy and theadsorption energy of each island configuration which is on the surface of TiN (001) and themigration path of the particle and the size of the required activation energy during theconfiguration evolution. Second, the work analysizd difficulty of the the process of forminginterface, as well as Ti, N particles affect the separation of the SiN phase and the TiN phasedurning the process of forming interface. Finally, this paper analysized the migration behaviorin the direction of Ti, Si, N single-particle along the TiN (110) Island, the dynamical behaviorof particles around the2D island in TiN (001) direction, and the main growth ways of the2Dislands configuration on the surface of TiN (001).The following conclusions:First, seven evolutions of island configuration can lead to TiN phase and SiN phase areseparated to form interface structure. The evolution of4N4Ti1Si Island configuration requiredminimum activation energy (1.21eV). It is a relatively easy way for the formation of theinterface. The SiN island configuration around TiN Island boundary is a low-energy stablestructure, which the bond strength of Ti-N is strengther than the bond strength of Si-N. Second, with the proportion of N particles increasing, the activation energy required foreach configuration evolution is like "concave" curve. The evolution of3N2Ti1Si configurationrequires smaller activation energy. When the particles N: Ti=3:2, the separation of SiN phaseand a TiN phase is relatively easy. With the increase of the proportion of Ti particles, theactivation energy required for each configuration evolution is like "convex" curve. Theevolution of4N2Ti1Si configuration requires more activation energy. The evolution of4N4TiSiconfiguration requires smaller activation energy. When the particles N: Ti=2:1, the separationof SiN phase and a TiN phase is relatively difficult; but when the particles N: Ti=1:1, theseparation of SiN phase and a TiN phase is relatively easy, it can be carried out under the lowerdeposition conditions.Third, the main growth patterns of2D Island on the surface of TiN (001) are hexagon,octagon (diamond) and quadrilateral. The most stable and the final configuration is quadrilateralIsland configuration.In a word, the process of forming Ti-Si-N nanocomposite thin films which structure is thenanocrystalline TiN wrapped by the interface phase of the SiN, its foms may be one or more,but particle deposition ratio plays an important role in formation conditions of the interface.