Negative electron affinity group III-nitride photocathode demonstrated as a high performance electron source

The need for a high performance (low energy spread 3months per spot, emission stability <1%∕h) electron source continues as part of the development of new e-beam writing and inspection tools. We present measurements from a group III-nitride (indium gallium nitride) photocathode in a demountable vacuum system to measure energy spread, lifetime, and preliminary blanking effects. We show the results of cathodes operating in ultrahigh vacuum (UHV), high vacuum (HV), and oxygen-rich backpressures. Our results show InGaN has a longitudinal energy spread of <300meV in reflection mode, flat lifetimes of 60h per illuminated spot where the yield changes by <10%, and stable emission with typical recoveries within 99% of original photocurrent for all blanking periods and vacuum conditions tested (0.5to10min periods).