Method and apparatus for depositing thin films on a surface

A method and apparatus for depositing thin films onto a substrate is provided. The apparatus includes a gas injection structure that is positioned within a reaction chamber that has a platform. The gas injection structure may be positioned above or below the platform and comprises a first gas injector and a second gas injector. The first gas injector is in fluid communication with a first reactant source and a purge gas source. Similarly, the second gas injector is in fluid communication with a second reactant source and a purge gas source. The first and second injectors include hollow tubes with apertures opening to the reaction chamber. In one configuration, the tubes are in the form of interleaved branching tubes forming showerhead rakes. Methods are provided for deposition, in which multiple pulses of purge and reactant gases are provided for each purge and reactant step.