More generally, the aims in technological development of large-area field emitters are to enhance the uniformity of emission by increasing the value of the area efficiency of emission α r, and to reduce the "onset" voltage at which significant emission occurs, by increasing the value of β. Eq. (41) shows that this can be done in two ways: either by trying to develop "high- γ " nanostructures, or by changing the overall geometry of the system so that β M is increased. Various trade-offs and constraints exist.