Method for growing thin films

A method of depositing a thin film on a substrate by atomic layer epitaxy, in which method a substrate placed in a reaction space including a reaction chamber is subject to alternately repeated surface reactions of at least first and second vapor-phase reactants for the purpose of forming a thin film by surface controlled growth, the reaction space defining a reaction space volume, the method comprising:

• feeding the first and second reactants in the form of vapor-phase pulses repeatedly and alternately, each reactant fed from a separate source, into the reaction space in a plurality of deposition cycles, wherein the first reactant is fed through a first inflow channel that opens directly into the reaction space and the second reactant is fed through a separate second inflow channel that opens directly into the reaction space, and wherein each deposition cycle comprises:
• providing the first reactant pulse through the first inflow channel while flowing only an inactive gas through the second inflow channel;
• stopping provision of the first reactant;
• removing first reactant from the reaction space;
• providing the second reactant pulse through the second inflow channel while flowing only the inactive gas through the first inflow channel;
• stopping provision of the second reactant;
• and
• removing second reactant from the reaction space;
• wherein the vapor-phase reactants react with a surface of the substrate for the purpose of forming a solid-state thin film compound on the substrate at a rate controlled by the surface chemistry properties of the reactants, wherein each pulse forms no more than a monolayer of reactant on the substrate, and
• wherein removing comprises moving sufficient gas through the reaction space to remove molecules of first and second reactant adsorbed on inner walls of the reaction space in an interval between each two successive vapor-phase reactant pulses.