Adsorption and reaction processes of physisorbed molecular oxygen on Si(111)-(7×7)

Abstract

The adsorption and reaction processes of physisorbed oxygen molecules on a Si͑111͒-͑7 ϫ 7͒ surface have been investigated using time-resolved O 1s core-level photoemission measurements at 45 K. Physisorbed oxygen molecules are only observed at 45 K and lower temperatures on a Si͑111͒-͑7 ϫ 7͒ surface. At the dosage when the dangling bonds are saturated by chemisorbed oxygen, the coverage of the physisorbed species increases drastically. This result indicates that oxygen species, which are chemisorbed on top of adatoms, modifies the potential energy curve for an oxygen molecule approaching the surface such that physisorbed oxygen molecules are stabilized. Further, the longer lifetime at a higher dosage indicates that an intermolecular force plays a role for the stabilization of this species. Taking these results into account, an oxidation stagedependent gas-surface interaction for an oxygen molecule approaching the Si͑111͒ surface is suggested.

Stabilization of silicon honeycomb chains by trivalent adsorbates

“…Similarly the Seiwatz chain requires two electrons per (2×1) cell, since it may be stabilized by 1/2 ML of divalent adsorbates. This is consistent with the number of surface states observed in ARPES [25]. The (5×2) unit cell can be thought of as being build from two (3×1) and two (2×1) cells, thus requires six electrons to be stabilized.…”

“…3 for the 5×"2" case). Similar series of reconstructions were also observed for the divalent rare earth metals (REM) Sm, Eu and Yb [15]. These REMs more commonly occur in the 3+ valence state, but depending on their chemical surrounding the 2+ configuration is occasionally preferred as in this case.…”

Real-Time Observation of Initial Thermal Oxidation on Si(110)-16x2 Surface by Photoemission Spectroscopy

“…This motivates us to compare the present O1s spectrum with that from the oxidized Si(111) surface. Sakamoto et al (8) have conducted detailed photoemission studies on the initial oxidation of Si(111) surface, and report several stable and metastable subpeaks in its O1s spectrum. Among them, metastable peaks at 533.1, 533.7 eV appear at similar positions as of the present subpeaks (532.6, 533.1 eV).…”

Unveiling new systematics in the self-assembly of atomic chains on Si(111)

“…Silicon honeycomb chains may also be stabilized by divalent adsorbates such as the alkaline earth metals (Mg, Ca, Sr, Ba) and rare earth metals (Sm, Eu, Yb) [9]. Although these rare earth metals commonly occur in a +3 valence state, a +2 configuration is occasionally preferred as in this case.…”