Nitrogen radical adsorption on InAs (001) surface studied by scanning tunneling microscopy and x-ray photoelectronic spectroscopy

The adsorption of nitrogen (N) radicals (nitridation) on InAs (001) surfaces has been studied by ultrahigh-vacuum scanning tunneling microscopy and x-ray photoelectronic spectroscopy. The nitridation proceeds as Langmuir adsorption. The N adsorption at 350 °C is faster than that at 100 °C, but N adsorption rates at 100 °C on InAs and GaAs are almost the same. These results are explained as follows: at 350 °C, N radicals bond mainly with the topmost In atoms on an In-stabilized surface, and at 100 °C, N radicals replace As atoms in the topmost layer on an As-stabilized surface, and subsequently bond with In atoms in the second layer. The amorphous 100 °C nitrided surface layer is found to have an insulating characteristic without surface states.