Recovery of negative electron affinity by annealing on (111) oxidized diamond surfaces

We discovered that oxidised (111) p-type boron-doped homoepitaxial diamond film surfaces grown by chemical vapor deposition (CVD) recover negative electron affinity (NEA) after annealing the samples in vacuum or under an Ar atmosphere. On the other hand, (001) p-type boron-doped homoepitaxial CVD diamond surfaces do not show NEA recovery. The oxidised (111) surface possesses positive electron affinity of + 0.6 eV, whereas the subsequently annealed surface has a negative electron affinity of − 0.8 eV, indicating a partial hydrogen termination condition that is supported by XPS results. These distinct behaviours should be taken into consideration for investigating the surface electronic properties of diamond.