This grant is for research examine the surface chemistry and electron emission physics of diamond and to determine key characteristics which enable Negative Electron Affinity (NEA) electron emission. The approach is to use surface electronic (UPS, XPS, AES) and structural (LEED, RHEED, ESDIAD) probes to fully characterize the surface, followed by near-bandgap UV photoemission studies. Controlled modification of the NEA surface will be explored to optimize emission efficiency and clarify the physics of electron emission from NEA diamond.