We present a comparative study of the growth of the technologically highly
relevant gate dielectric and encapsulation material aluminum oxide in inorganic
and also organic heterostructures. Atomic force microscopy studies indicate
strong similarities in the surface morphology of aluminum oxide films grown on
these chemically different substrates. In addition, from X-ray reflectivity
measurements we extract the roughness exponent \beta of aluminum oxide growth
on both substrates. By renormalising the aluminum oxide roughness by the
roughness of the underlying organic film we find good agreement with \beta as
obtained from the aluminum oxide on silicon oxide (\beta = 0.38 \pm 0.02),
suggesting a remarkable similarity of the aluminum oxide growth on the two
substrates under the conditions employed
