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The Interface Structure, Properties and Formation of Ti-Si-N Nanocomposite Films: First Principle Study

Author: RenYuan
Tutor: LiuXueJie
School: Inner Mongolia University of Science and Technology
Course: Mechanical and Electronic Engineering
Keywords: Ti-Si-N Interfaces structure Elastic properties Formation Mechanism
CLC: TB383
Type: Master's thesis
Year: 2012
Downloads: 75
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Abstract

The interface structure, properties and formation of Ti-Si-N nanocomposite films werestudied with the first principle method which had introducted in this study. Inorder toinvestigate the microstructure and properties of interface, the interface structure, properties andformation of Ti-Si-N nanocomposite films (NCF) were studied with the first principle methodbased on density functional theory (DFT). The solid solution structures and elastic properties ofa single atom into transition metal nitrides were calculated by first principle. The structure andthe elastic properties of substitution and interstitial interfaces in nanocomposite films ofTi-Si-N were investigated by DFT. The total energies and absorption energies of the Ti-Si-Nisland configurations on the TiN(001) surface and the activation energy of the configurationevolution, and the pathways processes of atomistic (Ti, Si, N) on TiN(111) surface were studyby the method of Nudged Elastic Band based on the first principle.The investigation presents some results.(1) A silicon atom could not go into TiN, ZrN, HfN orTaN crystallites to form a solidsolution. It is the same case for a germanium atom into TiN crystallite. But as the distancebetween the crystallites becomes large, a silicon atom in TiN, ZrN, HfN orTaN and also agermanium atom in TiN may form interstitial or substitution interfaces. A silicon atom in NbNand a boron atom in TIN could form an interstitial interface or a substitution interface. Theinterface structure of a silicon atom in VN or a carbon atom in TiN is a substitution interface.The elastic modulus, bulk modulus, shear modulus and young’s modulus of lower energystructure substitution or interstitial solid solution less than that of transition metal nitridesgrain.(2) There is no silicon interstitial solid solution in the titanium nitride crystallite, and ifsome titanium atoms or nitrogen atoms are missing in the titanium nitride crystallite, it ispossible for silicon atoms to occupy the vacant sites and to form the substitution solid solution.The studies of the silicon addition as an interface sandwiched between the B1-TiN (001)oriented crystallites indicates that compared with the substitution interface structure, thestructure with the interstitial interface is a low energy structure. which means that the strengthof interfaces was lower than that of the transition metal nitride crystallites. The substitution andinterstitial interfaces of bulk modulus (B) and shear modulus (G), which were260.487Gpa and193.682Gpa,207.014Gpa and68.757Gpa, respectively. The elastic modulus, bulk modulus,shear modulus and young’s modulus of substitution or interstitial interfaces less than that oftransition metal nitrides grain. (3) The most stable island of the four configurations is Si-by-2Ti2N. It means that in theTi-Si-N film growth, Ti and N atoms tend to combine together to form island and Si atoms arelikely to stay outside of the island. In the growth process, a silicon atom does not tend to comeinto the TiN island, in which a N atom absents, to form N-by-2Ti1N1Si. The configurationtransition from Ti-2N1Ti1Si to Si-2Ti2N will lead to the island energy lower, the transitionactivation energy is about1.963eV. The pathways of atomistic diffusion were that atomsdiffused from fcc-site to hcp-site on TiN (111) surface. The results show that the diffusionenergy of Ti atom is greater than that of N atom; diffusion energy of Si on Ti layer is less thanthat of Si on N layer. Si and N atoms could easier formed stable structure with bonding on Nlayer. Si atoms could stabilize N atoms activity while promoting the spread of Ti atoms in thedeposition process.In conclusion, the substitution interface and interstitial interface in nanocomposite film ofTi-Si-N were formed by Si solid solution in TiN crystalline. The substitution interface waspreferential formed under the certain conditions. The formation condition of interstitialinterface was more rigorous.

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