Dynamic scaling phenomena and universality classes in growth of iron nitride thin films deposited by direct current magnetron sputtering X. Wang a,b , W.T. Zheng a, * , L.L. Wang a , H.W. Tian a , S.S. Yu a , F.L. Meng a , X.T. Li a , X.G. Kong b a Department of Materials Science and Key Laboratory of Automobile Materials of MOE, Jilin University, Changchun 130023, PR China b Key Lab of Physics on Excited States Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, Changchun 130033, PR China Received 17 September 2004; received in revised form 31 March 2005; accepted 22 June 2005 Available online 26 July 2005 Abstract In this paper, dynamic scaling approach has been used to investigate the growth of iron nitride films, which were deposited by direct current magnetron sputtering using an Ar/N 2 gas mixture (N 2 /(N 2 + Ar) = 30%) at room temperature and 250 -C substrate temperature. The structure of the deposited films was determined by using X-ray diffraction. The perpendicular fluctuations in the height h (x , t ) of the surface were analyzed by atomic force microscopy and grazing incidence X-ray scattering in the light of dynamical scaling approach, and the two dependent nontrivial exponents, roughness exponent a and growth exponent b, were determined. For the iron nitride films grown at room temperature and 250 -C, a = 0.39 T 0.01 and 0.30 T 0.02 and b = 0.29 T 0.03 and 0.28 T 0.07, respectively, which were in agreement with a type of universality that was suggested by Kardar, Parisi and Zhang. It might be concluded that it was desorption rather than the surface diffusion that dominated the relaxation process in both the case of room and higher substrate temperatures for the deposition of iron nitride thin films. D 2005 Elsevier B.V. All rights reserved. PACS: 81.15.Aa; 81.15.Cd Keywords: Dynamic scaling phenomena; Growth mechanism; Nitrides; Sputtering 1. Introduction The growth of variety of films under inhomogeneous deposition will lead to the formation of rough surface. The quantitative description of rough surfaces far from equili- brium has been an important aspect for years [1] because of its practical importance for the growth of solid films and the great scientific and practical interest [2,3]. Solid films growth under far from equilibrium conditions exhibit scale-invariance phenomenon and naturally evolve into self-affine fractal [4,5], which can be described by the dynamic scaling form: r L; t ð Þ¼ L a f t =L a=b   ð1Þ The exponent a in Eq. (1) is known as the ‘‘static scaling’’ exponent or ‘‘roughness exponent’’ which charac- terizes the L dependence of the saturated width r, for t H L a /b . L is the sample size perpendicular to the growth direction. The parameter b is the growth exponent, for t b L a /b . Much work [6–12] has been done to determine the values of the growth exponents analytically and numerically. It has been shown that models with locally very different growth rules can almost give similar values for the exponents of a and b, which suggests the existence of universality [5]. Some models [13] are representative of the Edwards–Wilkinson universality classes of linear growth; while much more of the others belong to the universality class of Kardar – Parisi – Zhang (KPZ) equation [14,15], which is given as follows: flh=flt ¼ ml 2 h þ k lh ð Þ 2 þ g r; t ð Þ ð2Þ 0040-6090/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2005.06.058 * Corresponding author. Tel./fax: +86 431 5168246. E-mail address: wtzheng@jlu.edu.cn (W.T. Zheng). Thin Solid Films 492 (2005) 75 – 78 www.elsevier.com/locate/tsf