A new approach to solar cell design is the use of nanostructured heterojunctions of inorganic materials such as n-type TiO2 and p-type Cu1.8S. A major challenge is the deposition of the p-type material inside an n-type nanoporous matrix. In this paper the deposition of Cu1.8S with atomic layer deposition (ALD) inside nanocrystalline (nc)-TiO2 is presented. The growth of Cu1.8S inside nc-TiO2, is studied with Rutherford backscattering. Uniform films of Cu1.8S can be deposited inside nc-TiO2 consisting of 25 nm sized particles as deep as 3 mum, which is sufficient for solar cell applications. Long Cu(thd)(2) pulse times lead to a lower infiltration depth, because decomposion of Cu(thd)(2) clogs the pores. This indicates that the ALD process using these precursors is not ideal.