Secondary electron emission characteristics of single-crystal and polycrystalline diamond

Abstract

Secondary electron emission spectroscopy (SEES) is used to examine the transport and emission of low-energy electrons in diamond. In particular, SEES measurements from single-crystal (100) and (111) diamond and polycrystalline chemical vapor deposited (CVD) diamond are compared in order to examine the effect of crystallographic orientation on the emission characteristics. Crystal orientation is found to influence the surface properties of the samples but not the low-energy transport properties. Specifically, very high yields are obtained from negative-electron-affinity (NEA) surfaces of all three samples, indicating that low-energy electrons are transported and emitted very efficiently regardless of crystal orientation. However, the energy distributions measured from adsorbate-covered C(111) surfaces are broader and shifted lower in energy than those measured from corresponding C(100) surfaces. In fact, the energy distributions measured from polycrystalline CVD diamond surfaces appear to be a superposition of the energy distributions measured from the (100) and (111) crystal faces. For all three samples, a broader, lower-energy distribution is measured from cesiated NEA surfaces than from hydrogenated NEA surfaces. This indicates that the electron emission process differs at the two types of surfaces. The emission characteristics observed for the different crystal orientations and adsorbate coverages can be understood by considering the role of surface structure in the emission process.