Generation of atomic oxygen on Ag(111) and Ag(110) using NO2: a TPD, LEED, HREELS, XPS and NRA study

Clean atomic oxygen overlayers have been produced on Ag(111) and Ag(110) surfaces by dosing with NO2 between 500–520 K in UHV. These were studied using TPD, LEED, XPS, HREELS, AES and NRA. The high coverage atomic oxygen structures, Ag(111)-(4 × 4)O and Ag(110)-c(6 × 2)O are easily formed in UHV using moderate dosing pressures. The spectroscopic data indicate that these NO2-produced overlayers have the same structure as those produced using oxygen at high pressures. The absolute coverage of the Ag(111)-(4 × 4)O is determined to be 7.07(±0.55) × 1014 O atoms cm−2, or 0.51 ± 0.04 ML. This state is characterized by a single O 1s XPS peak at 528.2 eV. The NO2-produced Ag(111)-(4 × 4)O structure is suggested to be composed of two parts. The outer layer of this phase is composed of a coincidence mesh of a single layer of the (111) plane of Ag2O, which itself is comprised of a Ag plane sandwiched between two oxygen planes. Between this coincidence mesh and the Ag(111) surface is a partial monolayer of chemisorbed oxygen atoms. The c(6 × 2)O structure is characterized by two vibrational loss peaks at 298 and 339 cm−1, a single O 1s XPS peak at 528.5 eV, and a coverage of close to 1 ML.