Microstructure and properties of Ti–Si–N nanocomposite films

Abstract

Ti-Si-N nanocomposite films were deposited by multitarget reactive magnetron sputtering. Energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy were employed to characterize their microstructure and a microhardness tester was used to measure their hardness. The influence of substrate temperature on these films was investigated, too. The results reveal that the films consist of TiN and Si 3 N 4 . Si 3 N 4 exists as amorphous, which strongly prevents the growth of TiN grains and causes TiN to form a nanocrystalline or amorphous phase. The hardness of films deposited at room temperature reaches the peak value of 36 GPa at a Si content of 4.14 at. %, and then decreases gradually with the increase of Si content. The enhancement of the substrate temperature weakens the restraint effect of amorphous Si 3 N 4 on the growth of TiN grains, which results in coarse TiN grains and subsequently leads to a lower peak value and a slower decrease of the hardness of the films.

Electronic structure, stability, and mechanism of the decohesion and shear of interfaces in superhard nanocomposites and heterostructures

“…44 The values of V 0 , B 0 , and B 0 Ј obtained for the fcc͑NaCl͒-TiN and hcp͑ß͒-Si 3 N 4 are in good agreement with experimental results and calculated values reported in the literature. 26 The calculated values of the hypothetical fcc͑NaCl͒-SiN, which has been observed only as heteroepitaxially stabilized 1-2 ML thick interface in TiN/SiN/TiN heterostructures, [13][14][15][16] could not be compared with experimental data. Nevertheless, our calculated value of the first derivative of the bulk modulus, B 0 Ј, of this phase of about 4 is within the range predicted by the universal binding-energy relation.…”

“…It collapses and becomes amorphous at a greater thickness. [13][14][15] This is due to the inherent instability of this material as shown by ab initio DFT calculations 23 and by more recent calculations of the phonondispersion curves. 24 Furthermore, the thermodynamic studies [25][26][27] showed that the Gibbs free energy of the reaction 3SiN+ 0.5N 2 =Si 3 N 4 , which corresponds to a sufficiently large activity of nitrogen, is −168 kJ/ mol atom ͑see also remark Ref.…”

“…1 and 3͒ and selected area electron diffraction. 12 The fcc͑NaCl͒-SiN 1-3 ML thin interface, pseudomorphically stabilized between several nm thick TiN layers, has been recently reported in TiN/SiN/TiN heterostructures deposited by reactive sputtering, [13][14][15][16] and it has been suggested to be the prototype of the interface in the "Ti-Si-N nanocomposites." 17 However, a variety of different ͑hkl͒ interfaces, possibly also faceted, have to coexist in superhard nanocomposites deposited at sufficiently high pressure of nitrogen and temperature.…”

Structures, mechanical properties and thermal stability of TiN/SiNx multilayer coatings deposited by magnetron sputtering

“…Multilayers are useful as model systems since they allow the design and study of interfaces not readily accessible in three-dimensional nanocomposite. Recently, TiN/SiN x multilayer coatings have been synthesized, and hardness maxima of 33-40 GPa have been reported for fcc-TiN/SiN x /TiN heterostructures when SiN x was about 1-2 monolayer (ML) thick [3,4,[7][8][9][10]. The possible structure of SiN x layers in multilayer coatings is not completely understood.…”

“…The possible structure of SiN x layers in multilayer coatings is not completely understood. It was first considered as amorphous of effectively X-ray amorphous, but the possibility of crystalline structures was also shown [3,4,[7][8][9][10] when the thickness of SiN x layers was less than a critical value because of the "template effect" of TiN layers. The phase transformation for SiN x from amorphous to * Corresponding author.…”