Observation of nitrogen species at Al2O3/NO2/H-diamond interfaces by synchrotron radiation x-ray photoemission spectroscopy

Two nitrogen-related peaks were successfully detected by synchrotron radiation x-ray photoemission spectroscopy (XPS) at the interface of the Al2O3/NO2/H-diamond structure, which is used for metal-oxide-semiconductor field-effect transistors. The 399-eV peak was attributed to the CNH2 or CN bond, which was formed by electron transfer from the NO2 molecule to the H-diamond surface and subsequent decomposition of NO2 molecules at the H-diamond surface. The 407-eV peak was attributed to NO3- bond, which was formed by the decomposition of N2O4 molecules. We confirmed that N species are localized at the interface by changing the photoemission angle in XPS. The N interface density at the (111) interface was about twice that at the (001) interface. This difference is caused by C-H bond density on different surface orientations. The band alignments were determined to be type II (staggered type), and the valence band offset (Delta E-V) was determined to be 3.9 +/- 0.1eV for (001) and 4.3 +/- 0.1eV for (111) surface orientations. These results agree well with the higher hole sheet concentration on the (111) interface than on the (001) interface.