Electronic structure tunability of diamonds by surface functionalization

Wide-bandgap semiconductors are exploited in several technological fields such as electron emission devices, energy conversion, high-power high-temperature electronics, and electrocatalysis. Their electronic properties vary significantly depending on the functionalization of the surface. Here, we investigated as a proof-of-concept the modulation of the electronic properties of one of the most common wide-bandgap semiconductors, that is, diamonds, to show the tunability of their properties by modifying the surface termination. Photoelectron spectroscopy was used to demonstrate the availability of a wide window of band bending, work function, and electron affinity. The band bending and work function were found to change by up to 360 meV and 2 eV, respectively, by varying the surface from hydrogen- to oxygen-terminated. Because of the negative electron affinity of diamonds, we were able to experimentally show the rigid shift of the whole band structure.