AFM, SEM and<i>in situ</i>RHEED study of Cu texture evolution on amorphous carbon by oblique angle vapor deposition

Abstract

The evolution of the crystal orientation of a Cu film grown on an amorphous carbon substrate without intentional heating under $75\ifmmode\pm\else\textpm\fi{}6\ifmmode^\circ\else\textdegree\fi{}$ oblique angle vapor deposition was investigated ex-situ by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and in-situ by reflection high-energy electron diffraction (RHEED). At the initial stage of growth ($&lt;\ensuremath{\sim}12\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thick) the diffraction patterns showed uniform rings indicating random nucleations of crystals. With more Cu depositions ($&gt;\ensuremath{\sim}100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thick) the diffraction pattern started to break symmetrically from the middle of the (111) and (200) rings representing the absence of (111) and (200) planes parallel to the substrate. However, after this transition stage, at the thickness of $\ensuremath{\sim}410\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, the intensity distribution of diffraction patterns appeared asymmetric about the middle of the rings, which is interpreted as the appearance of a tilted (111) texture. Finally the diffraction patterns developed into separated short arcs and showed only a $⟨111⟩⟨\overline{1}10⟩$ II-O (two-orientation) texture. By comparing RHEED patterns with the SEM and AFM images of the final film, we argue that the tilted columns having tilted (111) top faces dominate in the later stage of growth. Furthermore, considering the geometry of crystals and shadowing effects, we argue that the vertices of columns having the highest growth velocity normal to the substrate and therefore receiving the maximum flux will dominate the film growth and determine the tilt angle of the texture and the preference of the azimuthal angle orientation.