  The development of single charge resolving, macroscopic silicon detectors has
opened a window into rare processes at the O(eV) scale. In order to reconstruct
the energy of a given event, or model the charge signal obtained for a given
amount of energy absorbed by the electrons in a detector, an accurate charge
yield model is needed. In this paper we review existing measurements of charge
yield in Silicon, focusing in particular on the region below 1 keV. We
highlight a calibration gap between 12-50 eV (referred to as the "UV-gap") and
employ a phenomenological model of impact ionization to explore the likely
charge yield in this energy regime. Finally, we explore the impact of
variations in this model on a test case, that of dark matter scattering off
electrons, to illustrate the scientific impact of uncertainties in charge
yield.
