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

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 x 7, 0.7 monolayer(ML), 1.5 ML and thick Mn covered silicon(lll) surfaces are e xposed to 20 L oxygen at 10(-8) Ton. oxygen partial pressure and at room te mperature. Oxidation of silicon is observed in ail cases except thick Mn co vered 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 n o further oxidation is observed on annealing and the oxide desorbed at 600 degrees C, the desorption temperature of SiO. On Mn covered silicon, the ro om temperature silicon oxides present were enhanced by annealing. For thick Mn immediately after first annealing step oxidation of silicon was observe d. 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(MW) and Mn(LMM) transitions disappear at different annealing temperatur es. These observations suggest that Mn is buried by the growing silicon oxi de. Finally, at an annealing temperature of 800 degrees C, silicon oxide de sorbs from the silicon surface taking along with it the buried Mn. (C) 1999 Elsevier Science B.V. All rights reserved.