We have designed an improved pulsed-laser deposition-continuous composition-spread (PLD-CCS) system that overcomes the difficulties associated with earlier related techniques. Our new PLD-CCS system is based on a precisely controlled synchronization between the laser firing, target exchange, and substrate translation/rotation, and offers more flexibility and control than earlier PLD-based approaches. Most importantly, the deposition energetics and the film thickness are kept constant across the entire composition range, and the resulting samples are sufficiently large to allow characterization by conventional techniques. We fabricated binary alloy composition-spread films composed of SrRuO3 and CaRuO3. Alternating ablation from two different ceramic targets leads to in situ alloy formation, and the value of x in SrxCax-1RuO3 can be changed linearly from 0 to 1 (or over any arbitrarily smaller range) along one direction of the substrate. (C) 2003 Elsevier B.V. All rights reserved.