  R\&D activity on Cu photocathodes is under development at the SPARC\_LAB test
facility to fully characterize each stage of the photocathode "life" and to
have a complete overview of the photoemission properties in high brightness
photo-injectors. The nano(n)-machining process presented here consists in
diamond milling, and blowing with dry nitrogen. This procedure reduces the
roughness of the cathode surface and prevents surface contamination introduced
by other techniques, such as polishing with diamond paste or the machining with
oil. Both high roughness and surface contamination cause an increase of
intrinsic emittance and consequently a reduction of the overall electron beam
brightness. To quantify these effects, we have characterized the photocathode
surface in terms of roughness measurement, and morphology and chemical
composition analysis by means of Scanning Electron Microscopy (SEM), Energy
Dispersive Spectroscopy (EDS), and Atomic Force Microscopy (AFM) techniques.
The effects of n-machining on the electron beam quality have been also
investigated through emittance measurements before and after the surface
processing technique. Finally, we present preliminary emittance studies of
yttrium thin film on Cu photocathodes.
