Oxygen-penetration-induced large hardness enhancement in nanoscale Nb/Ti multilayers

doi:10.11890/1006-7191-122-141

Abstract

Abstract: Nb/Ti multilayers with different modulation periods were prepared by magnetron sputtering deposition. Microstructure and mechanical properties were investigated by XRD, SEM and Nanoindentation. It turns out that hardness of samples increases with decreasing modulation wavelength (Λ) and then dropped at small Λ Through scrutinizing other results in literature, we found that the coherent stress rather than modulus mismatch played more important role for hardness enhancement with decreasing Λ of the bcc-hcp multilayers. Annealing of samples in low (or high) vacuum at 400 ℃ for 30 min led to large (or medium) enhancement of hardness, while the modulated structure was still maintained. It was found that annealing in low vacuum resulted in oxygen penetration into the multilayers as revealed by auger electron spectroscopy, but hardly changed metallic sheet resistivity. XRD results suggested that some niobium oxides were formed in Nb layers and oxygen distributed interstitially in Ti layers. The large hardness enhancement after annealing is mainly due to the strengthening effect from dispersive distribution of nano-scale niobium oxides and interstitial oxygen in the multilayers. In addition, interfaces between adjacent layers were more distinct after annealing which indicated good thermal stability of laminated structure.

Key words: Nb/Ti multilayer, Hardness, Microstructure, Annealing, Nanoindentation

Yuxin ZHAO, Wensheng LAI. Oxygen-penetration-induced large hardness enhancement in nanoscale Nb/Ti multilayers[J]. Acta Metallurgica Sinica (English Letters), 2012, 25(2): 141-152.

References

[1] J.S. Koehler, Phys Rev B 2(2) (1970) 547

[2] S.L. Lehoczky, J Appl Phys 49(11) (1978) 5479

[3] J.H. Xu, M. Kamiko, Y.M. Zhou, G.H. Lu, R. Yamamoto, L.H.Yu and I. Kojima, Appl Phys Lett 81(7) (2002) 1189

[4] W.S. Lai and M.J. Yang, Appl Phys Lett 90(18) (2007) 181917

[5] S.P. Wen, R.L. Zong, F. Zeng, Y. Gao and F. Pan, Acta Mater 55(1) (2007) 345

[6] J.H. Xu, M. Kamiko, H. Sawada, Y.M. Zhou, R. Yamamoto, L.H. Yu and I. Kojima, J Vac Sci Technol B 21(6) (2003)2584

[7] X. Chu and S.A. Barnett, J Appl Phys 77(9) (1995) 4403

[8] S.L. Lehoczky, Bull APS 21(3) (1976) 361

[9] S.L. Lehoczky, Phys Rev Lett 41(26) (1978) 1814

[10] B.J. Daniels, W.D. Nix and B.M. Clemens, Appl Phys Lett 67(7) (1995) 1036

[11] M. Kato, T. Mori and L.H. Schwartz, Acta Metall 28(3) (1980) 285

[12] G.Y. Li, Z.H. Han, J.W. Tian, L.Q. Zhang and M.Y. Gu, Rare Met Mater Eng 32(1) (2003) 1

[13] R.C. Cammarata and K. Sieradzki, Phys Rev Lett 62(17) (1989) 2005

[14] C. Kim, S.B. Qadri, M.R. Scanlon and R.C. Cammarata, Thin Solid Films 240(1-2) (1994) 52

[15] A. Misra, J.P. Hirtha nd R.G. Hoagland, Acta Mater 53(18) (2005) 4817

[16] R.C. Cammarata, T.E. Schlesinger, C. Kim, S.B. Qadri and A.S. Edelstein, Appl Phys Lett 56(19) (1990) 1862

[17] L.H. Friedman and D.C. Chrzan, Phys Rev Lett 81(13) (1998) 2715

[18] M.J. Yang, W.S. Lai and F. Pan, Chin Phys Lett 24(9) (2007) 2635

[19] T. Sasaki and I. Itoh, Cryogenics 36(7) (1996)497

[20] S.P. Wen, R.L. Zong, F. Zeng, Y.L. Gu, Y. Gao and F. Pan, Surf Coat Technol 202(10) (2008) 2040

[21] K.W. Kwon, H.J. Lee and R. Sinclair, Appl Phys Lett 75(7) (1999) 935

[22] W.C. Oliver and G.M. Pharr, J Mater Res 7(6) (1992) 1564

[23] X.Y. Zhu, X.J. Liu, R.L. Zong, F. Zeng and F. Pan, Mater Sci Eng A 527(4-5) (2010) 1243

[24] B. Rodmacq, J Appl Phys 70(8) (1991) 4194

[25] R. Saha and W.D. Nix, Acta Mater 50(1) (2002)23

[26] G. Ning and W.S. Lai, Chin Phys Lett 23(11) (2006) 2913

[27] S. Yip, Nature 391(6667) (1998) 532

[28] Y. He, J.Z. Zhang, W.Q. Yao, D.X. Li and X. Teng, Appl Surf Sci 255(8) (2009) 4484

[29] F.M. Smits, Bell Syst Technol J 37 (1958) 711

[30] D.J. Bacon and Y.N. Osetsky, Math Mech Solid 14(1-2) (2009) 270

[31] R.L. Klueh, J.P. Shingledecker, R.W. Swindeman and D.T.Hoelzer, J Nucl Mater 341(2-3) (2005) 103

[32] X.W. Zhou, H. Wadley, R.A. Johnson, D.J. Larson, N. Tabat, A. Cerezo, A.K. Petford-Long, G. Smith, P.H. Clifton, R.L. Martens and T.F. Kelly, Acta Mater 49(19) (2001) 4005