Photochemistry of N2O on Si(100): surface photo-oxidation

The oxidation of an Si(100) surface induced by photodissociation of adsorbed N2O has been studied by X-ray photoelectron spectroscopy, temperature-programmed desorption, and angle-resolved time-of-flight (TOF) measurements. N2O adsorbs in physisorption and chemisorption states on Si(100). The photochemical oxidation is induced by the irradiation of light in the wavelength range between 532 and 193 nm. The cross-sections of both adsorption states at 193 nm are larger than that of gaseous N2O by about two orders of magnitude. Substrate-mediated excitation is considered to be responsible for the photochemistry of N2O in the two adsorption states. Although the TOF distributions of N2 fragments from the physisorbed N2O are almost identical in the wavelength region studied, those from the chemisorbed N2O show a marked wavelength dependence. The interpretation is that there are multiple types of chemisorbed states whose photodissociation dynamics and the wavelength dependence of the cross-section are different to each other.