An ultrafast atomic layer deposition technique is presented, based on the spatial separation of the half-reactions, by which alumina layers can be deposited with deposition rates of more than 1 nm/s. The deposition rate is limited by the water half-reaction, for which a kinetic model has been developed. The alumina layers showed excellent passivation of silicon wafers for solar cell applications. Based on this concept, a high-throughput ALD deposition tool is being developed targeting throughput numbers of up to 3000 wafers/h. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610994] All rights reserved.