A plasma processing method includes providing a substrate in a processing chamber, the substrate having a surface, and generating a plasma in the processing chamber. The plasma provides at least two regions that exhibit different plasma densities. The method includes exposing at least some of the surface to both of the at least two regions. Exposing the surface to both of the at least two regions may include rotating the plasma and may cyclically expose the surface to the plasma density differences. Exposing to both of the at least two regions may modify a composition and/or structure of the surface. The plasma may include a plasmoid characterized by a steady state plasma wave providing multiple plasma density lobes uniformly distributed about an axis of symmetry and providing plasma between the lobes exhibiting lower plasma densities. Depositing the layer can include ALD and exposure may remove an ALD precursor ligand.