Crystallization of Si3N4 layers and its influences on the microstructure and mechanical properties of ZrN∕Si3N4 nanomultilayers

Dong, Yao‐Rong; Zhao, Wei; Yue, Jianling; Li, Geyang

doi:10.1063/1.2348092

Cited by 57 publications

(31 citation statements)

References 16 publications

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“…Hardness maxima of 33 to 35 GPa have recently been reported also for fcc-TmN=SiN=TmN heterostructures when the pseudomorphic fcc-SiN, between roughly 4 nm thick TiN [5][6][7][8][9][10] or ZrN [11] slabs, was about 1 to 2 ML thick. Because the TiN-SiN x system is regarded as a ''prototype'' of all nitride-based superhard nanocomposites, we focus on it in this Letter.…”

mentioning

confidence: 99%

Friedel Oscillations are Limiting the Strength of Superhard Nanocomposites and Heterostructures

2009

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To obtain a deeper understanding of the mechanism of plastic deformation and failure in superhard nanocomposites and heterostructures we studied, by means of the ab initio density functional theory, the stress-strain response and the change of the electronic structure during tensile and shear deformation of a prototype interfacial systems consisting of 1 monolayer SiN sandwiched between a few nm thick TiN layers. This shows that peak Friedel oscillations of valence charge density weaken the Ti-N interplanar bonds next to that interface, where decohesion in tension and slip in shear occurs. These results provide ways to design new, stronger and harder materials. ZrN [11] slabs, was about 1 to 2 ML thick. Because the TiN-SiN x system is regarded as a ''prototype'' of all nitride-based superhard nanocomposites, we focus on it in this Letter.Hao et al. studied the stoichiometric TiN-Si 3 N 4 system by means of ab initio density functional theory (DFT). They found that the strongest configuration is a TiN= Si 3 N 4 =TiN sandwich containing 1 ML of -or -Si 3 N 4 -derived interfaces possessing decohesion strength larger than that of bulk Si 3 N 4 [12]. They also confirmed [13] the experimental finding [14] that oxygen impurities strongly degrade the strength of the Si 3 N 4 interface. Liu et al. studied several configurations of Si-atoms incorporated into TiN and found that the highest cohesive energy of 426.86 eV (bulk Ti-N 430.19 eV) have Si atoms tetrahedrally coordinated to 4N and 4Ti atoms with Si-N bonds being significantly shorter than the Si-Ti distance [15].We have shown that 1 ML of the interfacial, substoichiometric, pseudomorphic SiN is strengthened by a factor of 4 to 10 [16] as compared with bulk SiN [17]. Using the shear strength of the TiN=1 ML-SiN=TiN interfaces, calculated by ab initio DFT, Sachs averaging of these to obtain a tensile yield strength of the nanocrystalline assembly of grains, together with appropriately accounting for pressure enhancement of the shear resistances of the interfaces and using the Tabor relationship between hardness and the yield strength, the measured superhardness in excess of 100 GPa of nanocomposites has been fully explained [16]. However, in the papers quoted here, the electronic structure of the interface and its effect on the mechanism of decohesion and ideal shear under applied stress had not been studied. This is the subject of the present Letter which reveals for the first time that, although SiN is the weakest of all covalent materials under consideration, and unstable in bulk, the weakest link in the TiN=1 ML-SiN=TiN sandwich is the bond between Ti and N atoms within the interlayer next to the SiN x interface. This is a consequence of the ubiquitous Friedel oscillations that are found in electronically perturbed solids adjacent to their surfaces and interfaces [18].The ab initio DFT calculations were done using the ''Vienna ab initio simulation package'' (VASP) [19] with the projector augmented wave method employed to describe the electron-ion interaction [2...

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confidence: 99%

Friedel Oscillations are Limiting the Strength of Superhard Nanocomposites and Heterostructures

2009

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“…The results by Dong et al, 11 which suggest an epitaxial ZrN/SiN x film, may be explained from the interpretation of, e.g., Figure 5(b) and the differences in applied methods-uncorrected HRTEM and aberration corrected HAADF-(S)TEM. While uncorrected HRTEM does not produce strong elemental contrast and also delocalizes lattice fringes due to spherical aberration (C s ), SiN x inclusions like those visualized in Figure 5(b) may easily be overlooked and the structure appears epitaxially stabilized due to the bridging ZrN and by the homogeneously distributed lattice fringes.…”

Section: Discussionmentioning

confidence: 98%

“…Such multilayers were studied by Dong et al using TEM and they found epitaxy through several periods for 6 Å SiN x layers and a similar hardness to TiN/SiN x . 11 However, when comparing Zr-Si-N films with Ti-Si-N films it has been found not only that the hardest films have different texture (columnar structure 12,13 and nanocomposite, 14 respectively), different decomposition mechanisms, 15 but also different hardness dependence of silicon content (maximum hardness at $3 at. % Si (Refs.…”

Section: Introductionmentioning

confidence: 99%

Self-organization during growth of ZrN/SiNx multilayers by epitaxial lateral overgrowth

Fallqvist

Ghafoor

Fager

et al. 2013

Journal of Applied Physics

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ZrN/SiNx nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiNx thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiNx is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiNx—known to take place on TiN(001)—on ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiNx deposition, the material segregates to form surface precipitates in discontinuous layers for SiNx thicknesses ≤6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiNx precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiNx in samples deposited at 800 °C with up to 6 Å thick SiNx layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1–3 nm large SiNx precipitates along apparent column boundaries in the epitaxial ZrN.

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“…This can be expected to lead to different structure of the separated SiN x tissue phase compared to what has been demonstrated in TiN-SiN nanocomposites. It has been shown that while the SiN interfaces in TiNSiN prefer an orientation along the (111) direction, in ZrN they always align according to the (200) direction [157]. The stability of ZrN-SiN interfaces was studied in paper VIII where it was shown that this is due to a significant change in the dynamical stability of the superstructures compared to that of TiN-SiN, in particular the appearance of an extreme dynamic instability of 1ML of SiN between TiN(111) layers.…”

Section: Zrn-sinmentioning

confidence: 99%

Theoretical understanding of stability of alloys for hard-coating applications and design

Lind¹

2015

Linköping Studies in Science and Technology. Dissertations

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The performance of modern hard coating materials puts high demands on properties such as hardness, thermal stability and oxidation resistance. These properties not only depend on the chemical composition, but also on the structure of the material on a nanoscale. This kind of nanostructuring will change during use and can be both beneficial and detrimental as materials grown under non-equilibrium conditions transforms under heat treatment or pressure into other structures with significantly different properties. This thesis aims to reveal the physics behind the processes of phase stability and transformations and how this can be utilized to improve on the properties of this class of alloys. This has been achieved through the application of various methods of first-principles calculations and analysis of the results on the basis of thermodynamics and electronic structure theory.Within multicomponent transition metal aluminum nitride alloys (TMAlN) a number of studies have been carried out and presented here on ways of improving high temperature stability and hardness. Most (TMAl)N and TMN prefer a cubic B1 structure while AlN is stable in a hexagonal B4 phase, but for the purposes of hard coatings the metastable cubic B1 AlN phase, isostructural with the TMN phase is desired. It will be shown how the introduction of additional alloying components, such as Cr, into (TiAl)N changes the thermodynamic stability of phases so that new intermediary and metastable phases are formed during decomposition. In the case of such a (CrAl)N phase it is shown to have greater thermodynamic stability in the cubic phase than the pure AlN, resulting in improved high temperature hardness. Also, the importance of treating not just the binodal decomposition through the formation energy relative to end products but also the impact of spinodal decomposition from its second derivative due to the topology of formation energy surfaces is emphasized in the thesis. The impact of pressure on the AlN phase has also been studied through the calculation of a P-T diagram of AlN as part of a (TiAl)N alloy.During the study of chemical alloying of TM components into AlN the alloying of low concentrations of these TM were treated in great detail. What is generally referred to as the AlN phase in decomposition is not entirely pure and can be expected to contain traces of any alloying components, such as Ti and Cr or whatever other metals may be present. Low concentration alloying of Cr, on the order of 5-10% is also shown to be stable with regard to isostructural decomposition. Detailed analysis of the effect of Ti and Cr impurities in AlN has been carried out along with a systematic search of AlN alloyed with small amounts of other TM components. The impact of these impurities on the electronic structure and thermodynamic properties is analyzed and the general trends will be explained through the occupation of impurity states by d-like electrons.iv Theoretical treatment of such impurities is not straightforward however. AlN is an s-p semiconduct...

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Crystallization of Si3N4 layers and its influences on the microstructure and mechanical properties of ZrN∕Si3N4 nanomultilayers

Abstract: Microstructure, surface morphology, and mechanical properties of nanocrystalline TiN/amorphous Si 3 N 4 composite films synthesized by ion beam assisted deposition

Cited by 57 publications

References 16 publications

Friedel Oscillations are Limiting the Strength of Superhard Nanocomposites and Heterostructures

Friedel Oscillations are Limiting the Strength of Superhard Nanocomposites and Heterostructures

Self-organization during growth of ZrN/SiNx multilayers by epitaxial lateral overgrowth

Theoretical understanding of stability of alloys for hard-coating applications and design

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