Method of depositing an atomic layer on a substrate. The method comprises supplying a precursor gas from a precursor-gas supply of a deposition head that may be part of a rotatable drum. The precursor gas is provided from the precursor-gas supply towards the substrate. The method further comprises moving the precursor-gas supply by rotating the deposition head along the substrate which in its turn is moved along the rotating drum. The method further comprises switching between supplying the precursor gas from the precursor-gas supply towards the substrate over a first part of the rotation trajectory; and interrupting supplying the precursor gas from the precursor-gas supply over a second part of the rotation trajectory