Atomic imaging for hydrogen and boron aggregates in boron-doped diamond by spectro-photoelectron holography

The electrical properties of diamond are modulated by impurity doping. Isolated substitutional boron atoms introduce holes; however, the fraction of electrically inactive boron atoms increases at higher doping concentrations. This has been attributed to boron aggregation and hydrogen passivation, although their structural identification based on atomic arrangement has yet to be experimentally verified. Here we show the origin of multiple chemical states in homoepitaxially grown boron-doped diamond thin films by analyzing the atomic environment of boron using spectro-photoelectron holography. Our analysis identifies boron dimers and boron-hydrogen complexes, with hydrogen occupying different atomic sites that give rise to distinct chemical shifts. These results suggest that hydrogen incorporation during growth leads to passivation of boron acceptors. We demonstrate that photoelectron holography serves as a promising tool for imaging hydrogen as well as determining the atomic sites of dopants. Using spectro-photoelectron holography, researchers visualized hydrogen trapping sites in boron-doped diamond. The results reveal the atomic-scale origin of acceptor passivation mechanisms in semiconductors.