Effects of post-deposition annealing on the mechanical and chemical properties of the Si3N4/NbN multilayer coatings

Abstract Multilayered thin films consisting of alternate layers of silicon nitride (Si3N4) and niobium nitride (NbN) have been prepared by a dc reactive sputtering technique in nitrogen and argon atmosphere using high purity Nb and Si targets for various flow ratios of N2/Ar. It has been found that the hardness of the multilayered system is higher than that of the constituent individual layers of equal thickness. Although a single layer of amorphous Si3N4 has higher hardness compared with a single layer of nanocrystalline NbN at all the deposition conditions used in this experiment, the hardness of the multilayer coatings consisting of consecutive Si3N4/NbN layers strongly follows the hardness variation of the polycrystalline NbN. When the multilayer coatings are subjected to post-deposition annealing at high temperatures, it has been found that both the hardness and the adhesion strength of the coating decrease with increasing annealing temperature. X-ray photoelectron spectroscopy (XPS) results reveal that oxidation of the coatings during annealing plays a crucial role behind such deterioration in mechanical properties. Further, it has been noted that NbN is a more oxidation resistant material than Si3N4. Therefore, it has been proposed that during preparation of multilayers with consecutive thin layers of NbN and Si3N4, the topmost layer should be made of NbN, instead of Si3N4, to prevent the oxygen diffusion from the top surface layer to the next layer underneath.

[1]  J. Halbritter,et al.  Angle-resolved XPS studies of oxides at NbN, NbC, and Nb surfaces , 1987 .

[2]  C. Sénémaud,et al.  Structural determination of sintered Si3N4/SiC nanocomposite using the XPS differential charge effect , 2000 .

[3]  W. Münz,et al.  Combined cathodic arc/unbalanced magnetron grown CrN/NbN superlattice coatings for applications in the cutlery industry , 2000 .

[4]  D. B. Lewis,et al.  Large-scale fabrication of hard superlattice thin films by combined steered arc evaporation and unbalanced magnetron sputtering , 1997 .

[5]  C. Severac,et al.  XPS study of NbN and (NbTi)N superconducting coatings , 1996 .

[6]  S. Barnett,et al.  Growth of single-crystal TiN/VN strained-layer superlattices with extremely high mechanical hardness , 1987 .

[7]  V. Gubanov,et al.  Influence of the deposition parameters on the composition, structure and X-ray photoelectron spectroscopy spectra of TiN films , 1992 .

[8]  W. Sproul,et al.  Deposition and properties of polycrystalline TiN/NbN superlattice coatings , 1992 .

[9]  Zafar Iqbal,et al.  A thermodynamic criterion of the crystalline-to-amorphous transition in silicon , 1982 .

[10]  M. Odén,et al.  Mechanical and thermal stability of TiN/NbN superlattice thin films , 2000 .

[11]  M. Grimsditch,et al.  Structural, elastic, and transport anomalies in molybdenum/nickel superlattices , 1983 .

[12]  Pasqualina M. Sarro,et al.  Optimization of a low-stress silicon nitride process for surface-micromachining applications , 1997 .

[13]  J. Zabinski,et al.  The chemistry, structure, and resulting wear properties of magnetron-sputtered NbN thin films , 1997 .

[14]  D. Gerstenberg,et al.  Physics of Thin Films , 1964 .

[15]  J. Halbritter,et al.  XPS and AES studies on oxide growth and oxide coatings on niobium , 1980 .

[16]  W. Stickle,et al.  Handbook of X-Ray Photoelectron Spectroscopy , 1992 .

[17]  S. Vepřek,et al.  A concept for the design of novel superhard coatings , 1995 .

[18]  An ultrahigh vacuum, magnetron sputtering system for the growth and analysis of nitride superlattices , 1992 .

[19]  John Wang,et al.  Nanocrystalline Si3N4 with Si-C-N shell structure , 2001 .

[20]  A. Toriumi,et al.  Initial oxidation features of Si(100) studied by Si2p core-level photoemission spectroscopy , 2001 .

[21]  P. Steiner,et al.  Photoemission study of the electronic structure of stoichiometric and substoichiometric TiN and ZrN , 1982 .

[22]  S. Barnett,et al.  Model of superlattice yield stress and hardness enhancements , 1995 .