Angular-resolved study of secondary-electron emission from NEA diamond surfaces

We studied the angular distribution of secondary electrons emitted from different diamond surfaces using angular-resolved ultraviolet photoelectron spectroscopy (ARUPS). On a boron-doped lib type natural diamond, smooth and clean (111) surfaces were prepared by polishing and vacuum annealing. A negative electron affinity (NEA) was established by applying cesium at different coverages. The intensity of the secondary-electron emission, which originates from thermalized electrons collected in the conduction-band minimum, as well as the low-energy cutoff of the spectra were studied for different emission angles with respect to the sample surface and for different cesium coverages. While the intensity is peaked in the direction normal to the sample surface, we observed an upward dispersion of the low-energy cutoff of the spectra for off-normal detection angles. A theoretical model for this behavior is given. The same effects are evident to a lower extent for a polycrystalline, boron-doped, chemical vapor deposited (CVD) diamond film.