SEARCH Articles Figures Tables Si substrates. The aluminum grain size is smaller in the sample deposited at ambient temperature. Root-mean-square roughness was measured at 5.23 and 7.45 nm, respectively, for the ambient and heated samples. The depth of the grain boundaries can be determined from a 3D image. The roughness of the aluminum on the unheated substrate is dominated by the different grains, but the heated substrate sample roughness is determined by grain boundaries. [Publishers Imprint] [Publishers Imprint]