Structural and mechanical properties of chromium nitride, molybdenum nitride, and tungsten nitride thin films

Abstract

Cr-N, Mo-N, and W-N thin films are deposited on silicon by rf reactive magnetron sputtering. The crystallographic phase and residual stress are determined by x-ray diffraction analysis. In each of the three material systems, a hexagonal and a face-centred cubic (fcc) phase are observed. Plasma diagnostics using energy-resolved mass spectroscopy reveal that a significant fraction of the Cr + ions exhibits a high flux and kinetic energy if the nitrogen partial pressure p N 2 is low. These high-energy ions effectively bombard the growing film and a densely packed morphology results. In contrast, in absence of a significant amount of high-energy ions at higher p N 2 , a columnar crystal morphology is observed by scanning electron microscopy. The grain size strongly depends on the presence of a second phase and on the nitrogen content. The hardness, measured by nanoindentation, increases in every material system if the content of the hexagonal phase increases. Under overstoichiometric conditions, the hardness of fcc compounds decreases. The observed hardness differences are explained by morphological changes and by differences in the electronic structure of the compounds.

Molybdenum Nitride Films: Crystal Structures, Synthesis, Mechanical, Electrical and Some Other Properties

“…The hardness of δ-MoN is similar to the one measured for γ-Mo2N [30], whereas the elastic modulus is somewhat higher (Table 3). In contrast with γ-Mo2N, compressive stresses are measured for the hexagonal phase.…”

“…Hones et al [30] used the same process as [29] to investigate the structural and mechanical properties of molybdenum nitride films about 1 μm thick in a wide range of nitrogen/metal ratios. The discharge power is kept constant at 120 W, the total pressure of (Ar-N2) gas mixture during the sputtering process is equal to 0.66 Pa and the substrate temperature is fixed at 500 ± 20 K in order to obtain films of structures in the zone T regime of Thornton's structure zone classification which allows optimizing the mechanical properties of films (Section 5).…”

“…The bulk modulus of γ-Mo2N has been determined by high pressure-high temperature method [24], it is equal to 304 GPa (Table 3). Hones et al [30] studied the mechanical properties of 1 μm thick molybdenum nitride films MoNy made by RF reactive magnetron sputtering (Section 4.1.2). The nitrogen stoichiometry y increases with increasing nitrogen partial pressure.…”

Nanostructured CrAlN Films Prepared at Different Pulse Widths by Pulsed DC Reactive Sputtering in Facing Target Type System

“…According to former research for CrN x deposition by reactive magnetron sputtering, different phases such as Cr, Cr þ N, Cr þ N þ Cr 2 N, Cr 2 N þ CrN, CrN can be obtained depending on nitrogen content. [18][19][20][21] In this study, an fcc-CrN phase has formed at lower pulse widths while a mixed structure of hcpAlN, hcp-Cr 2 N and a small amount of fcc-CrN phases exists in the films at higher pulse widths. Lin et al demonstrated that the maximum N þ ion energy increased with a decrease of pulse width (increasing the duty cycle) at lower frequencies below 300 kHz in the Pulsed Closed Field Unbalanced Magnetron Sputtering system.…”

Problem of FGM TBC coated cylinder

“…Other examples of transversely isotropic material with a pronounced columnar microstructure are CrN, Cr 2 N, MoN, and WN nitride thin films, deposited on silicon substrate, see Hones et al [25], or tool steel W300, to form protection coating against wear and oxidation. By use of scanning electron microscopy, various composition of nitrides have been examined, but in pure CrN films the pronounced columnar nanotexture was observed.…”