Double in-plane alignment in biaxially textured thin films

Abstract

The scientific interest and technological relevance of biaxially textured polycrystalline thin films stem from their microstructure that resembles that of single crystals. To explain the origin and predict the type of biaxial texture in off-normally deposited films, Mahieu et al. have developed an analytical model [S. Mahieu et al., Thin Solid Films 515, 1229 (2006)]. For certain materials, this model predicts the occurrence of a double in-plane alignment, however, experimentally only a single in-plane alignment has been observed and the reason for this discrepancy is still unknown. The model calculates the resulting in-plane alignment by considering the growth of faceted grains with an out-of-plane orientation that corresponds to the predominant film out-of-plane texture. This approach overlooks the fact that in vapor condensation experiments where growth kinetics is limited and only surface diffusion is active, out-of-plane orientation selection is random during grain nucleation and happens only upon grain impingement. Here, we compile and implement an experiment that is consistent with the key assumptions set forth by the in-plane orientation selection model by Mahieu et al.; a Cr film is grown off-normally on a fiber textured Ti epilayer to pre-determine the out-of-plane orientation and only allow for competitive growth with respect to the in-plane alignment. Our results show unambiguously a biaxially textured Cr (110) film that possesses a double in-plane alignment, in agreement with predictions of the in-plane selection model. Thus, a long standing discrepancy in the literature is resolved, paving the way towards more accurate theoretical descriptions and hence knowledge-based control of microstructure evolution in biaxially textured thin films.<p>Funding Agencies|Linkoping University</p

Texture and Stress Evolution in HfN Films Sputter-Deposited at Oblique Angles

“…was observed (corresponding to 90° case), the present findings of a double in-plane alignment for HfN films deposited at α ≥ 35° provide experimental support to the 2D model proposed by Mahieu et al [26]. Examples of double in-plane alignments in off-normally sputter-deposited metal and oxide films have been reported by Elofsson et al for Cr films [49] and Saraiva and Depla [14] for Mg-M-O (M = Al, Cr, and Ti) films. If the in-plane orientation of the crystals can be explained by 2D calculations of the capture length, and reflects some azimuthal constraint of the crystallites along the projected flux direction at GLAD conditions, the origin of the texture tilt angle requires some 3D modelling.…”

“…While for TiN films, a single in-plane alignment was observed (corresponding to 90 • case), the present findings of a double in-plane alignment for HfN films deposited at α ≥ 35 • provide experimental support to the 2D model proposed by Mahieu et al [26]. Examples of double in-plane alignments in off-normally sputter-deposited metal and oxide films have been reported by Elofsson et al for Cr films [49] and Saraiva and Depla [14] for Mg-M-O (M = Al, Cr, and Ti) films.…”