Atomic processes of NO oxynitridation on Si(100) surfaces

Atomic processes of NO oxynitridation on Si(100) surfaces were studied by the first-principles calculation technique. NO is molecularly chemisorbed at very low temperatures. A channel toward dissociative chemisorption opens at slightly elevated temperatures. The N atom is chemisorbed mostly in between dimer atoms and the O atom in a backbond. The energy barrier for the secondary NO chemisorption increases and further dissociative chemisorption is suppressed in accordance with the observed self-limiting process below room temperature. At high temperatures the N atom substitutes for an adjacent Si atom, forming threefold coordination. The ejected Si atoms may occupy interstitial sites. The calculated N $1s$ core level shifts at each stage of chemisorption correspond well with the observed variation of core-level shifts upon temperature.