The formation of nanocolumns of C clusters in thin films of a Si based inorganic polymer, allylhydridopolycarbosilane (HPCS), as a result of irradiation of the films with 100 MeV Au ions at fluences of 2 × 10(12) and 5 × 10(12) ions cm(-2) is demonstrated. The evolution and arrangement of the C clusters while subjected to the irradiation fluence is investigated by energy filtered cross-sectional transmission electron microscopy. Irradiation results in evolution of C clusters of sizes ≤5 nm, and their alignment along channels of ∼10 nm diameter, which are essentially the latent tracks created by the Au ions in the polymer. At the fluence of 5 × 10(12) ions cm(-2), these clusters become densely packed in the channels. The growth of such C cluster filled nanocolumns is shown to be a consequence of two simultaneous diffusion processes taking place during the transient molten phase of the latent tracks.