For controlling a physical dimension of a solid state structural feature,
a solid state structure is provided, having a surface and having a
structural feature. The structure is exposed to a first periodic flux of
ions having a first exposure duty cycle characterized by a first ion
exposure duration and a first nonexposure duration for the first duty
cycle, and then at a second periodic flux of ions having a second
exposure duty cycle characterized by a second ion exposure duration and a
second nonexposure duration that is greater than the first nonexposure
duration, for the second duty cycle, to cause transport, within the
structure including the structure surface, of material of the structure
to the structural feature in response to the ion flux exposure to change
at least one physical dimension of the feature substantially by locally
adding material of the structure to the feature.