Structural and mechanical properties of NbN and Nb-Si-N films: Experiment and molecular dynamics simulations

Abstract

a b s t r a c tThe structural and mechanical properties of NbN and Nb-Si-N films have been investigated both experimentally and theoretically, in their as-deposited and annealed states. The films were deposited using magnetron sputtering at substrate bias (U B ) between 0 and À 70 V. While NbN films were found to crystallize in the cubic δ-NbN structure, Nb-Si-N films with Si content of 11-13 at% consisted of a twophases nanocomposite structure where δ-NbN nanocrystals were embedded in SiN x amorphous matrix.Films deposited at U B ¼0 V were highly (001)-textured. Application of substrate bias potential led to a depletion of light atoms, and caused a grain size refinement concomitantly with the increase of (111) preferred orientations in both films. The maximum hardness was 28 GPa and 32 GPa for NbN and Nb-Si-N films, respectively. NbN and Nb-Si-N films deposited at U B ¼ À70 V exhibited compressive stress of À 3 and À 4 GPa, respectively. After vacuum annealing, a decrease in the stress-free lattice parameter was observed for both films, and attributed to alteration of film composition. To obtain insights on interface properties and related mechanical and thermal stability of Nb-Si-N nanocomposite films, first principles molecular dynamics simulations of NbN/SiN x heterostructures with different structures (cubic and hexagonal) and atomic configurations were carried out. All the hexagonal heterostructures were found to be dynamically stable and weakly dependent on temperature. Calculation of the tensile strain-stress curves showed that the values of ideal tensile strength for the δ-NbN(111)-and ε-NbN(001)-based heterostructures with coherent interfaces and Si 3 N 4 -like Si 2 N 3 interfaces were the highest with values in the range 36-65 GPa, but lower than corresponding values of bulk NbN compound. This suggests that hardness enhancement is likely due to inhibition of dislocation glide at the grain boundary rather than interfacial strengthening due to Si-N chemical bonding.

The effects of Cr and Si additions and deposition conditions on the structure and properties of the (Zr-Ti-Nb)N coatings

“…The loads (L C5 ) for the (Zr-TiCr-Nb)N and (Zr-Ti-Cr-Nb-Si)N coatings increase with increasing substrate bias (from −100 to −200 V) their maxima of 62.06 and 45.57 N, respectively. In addition, it should be noted, that coatings, obtained under high bias, possessing the higher hardness are more resistant [53][54][55][56][57]. Nitride coatings (Zr-Ti-Cr-Nb)N and (Zr-Ti-Cr-NbSi)N with good adhesion strength demonstrate high values of hardness, 43.9 and 27.5 GPa, respectively.…”

Nanocomposite Nb-Al-N coatings: Experimental and theoretical principles of phase transformations

“…NbN based coatings are quite perspective for industrial application due to their high melting temperature, splendid physico-mechanical and superconducting properties [1][2][3][4][5][6][7][8][9]. Such coatings can be widely used for fabrication of Josephson's large integrated circuits [10][11][12][13], bolometers [10]- [15] and superconducting onephoton detectors [1,4,[14][15][16][17][18][19][20][21][22][23][24].…”

Multilayered vacuum-arc nanocomposite TiN/ZrN coatings before and after annealing: Structure, properties, first-principles calculations

“…Such computational conditions were proved to be quite justified [37]. In particular, the calculated lattice parameters for TiN and ZrN The tensile stress-strain relations were calculated by: 1) elongating the supercells along the c-axis (the (001)-direction in the hexagonal supercells, or the (111) direction in the B1-lattice) in an incremental step, 2) fixing of the c basis vector and 3) simultaneously relaxing the aand b-basis cell vectors and the positions of the atoms within the supercell [37,38].…”