Photoemission properties and surface structures of homoepitaxially grown CVD diamond(1 0 0) surfaces

In the present study, the surface properties of homoepitaxially grown chemical vapor deposition (CVD) diamond have been investigated using total photoyield measurements, scanning tunneling microscope (STM) observations and scanning tunneling spectroscopy (STS). The STM results show that as-grown CVD diamond(1 0 0) surfaces are characterized mainly by two types of regions with 2×1/1×2 structures and much less structures. These well-ordered surface structures can be significantly clearer after a low-temperature annealing at 150–200°C in ultra high vacuum. On the other hand, the STS results indicate the presence of band gap states, which agrees well with the fact that the observed photoemission threshold energy is located at 5 eV, well below the band gap energy of 5.5 eV, for the as-grown CVD diamond surface. The absolute value measurements of the photoemission total yields using a calibrated Si photodetector demonstrate substantially low photoemission efficiencies even for negative electron affinity (NEA) diamond surfaces, being consistent with the STM/STS data.