AES investigation of annealing effects on the oxygen adsorbed Mn/Si(111) interface

Abstract

The present work reports the influence of in situ annealing of Mn promoted oxidation of silicon (111) surface by AES measurements. Clean Si(111)7×7, 0.7 monolayer (ML), 1.5 ML and thick Mn covered silicon (111) surfaces are exposed to 20 L oxygen at 10 −8 Torr oxygen partial pressure and at room temperature. Oxidation of silicon is observed in all cases except thick Mn covered surface where no substrate signal was detectable by AES. In all cases, Mn also gets oxidized at room temperature. In the case of clean silicon no further oxidation is observed on annealing and the oxide desorbed at 600°C, the desorption temperature of SiO. On Mn covered silicon, the room temperature silicon oxides present were enhanced by annealing. For thick Mn immediately after first annealing step oxidation of silicon was observed. Further annealing promoted the silicon oxides at the expense of MnO. AES observations as well as thermodynamic data support this reduction of metal oxide by silicon. Depending on the initial thickness of Mn, the low energy Mn(MVV) and Mn(LMM) transitions disappear at different annealing temperatures. These observations suggest that Mn is buried by the growing silicon oxide. Finally, at an annealing temperature of 800°C, silicon oxide desorbs from the silicon surface taking along with it the buried Mn.