Molecularly Adsorbed Oxygen Species on Si(111)-(7×7): STM-Induced Dissociative Attachment Studies

Abstract

Scanning tunneling microscope (STM)-induced selective bond breaking in individual molecules and conventional STM imaging are combined to determine the nature of chemisorbed O 2 species formed during the initial stages of silicon (111)-(7×7) oxidation. A selective atomic-scale modification mechanism that involves dissociative electron attachment of tip-emitted electrons to empty adsorbate orbitals is introduced. Two molecular species were found: one involves O 2 bonded to an already oxidized silicon adatom, and the other involves an O 2 molecule that is bonded to a second-layer rest atom and interacting with two silicon adatoms.

Dissociative adsorption of pyrrole on Si(111)-(7×7)

“…Similar observations were reported for a number of molecules on Si (111) 34 and O 2 . 35 Careful examination of Fig. 4͑b͒ reveals that the profile for the reacted adatom seems to be asymmetric, showing a slight distortion of the (7ϫ7) unit cell.…”

Trapping and Characterization of a Single Hydrogen Molecule in a Continuously Tunable Nanocavity

“…3 The Scanning Tunneling Microscope (STM) is an ideal tool for the manipulation and characterization of chemical bonds in the nano-cavity that is formed by the STM tip and substrate and contains a single molecule. [4][5][6][7][8] The geometry and size of STM nanocavities can be precisely tuned by changing the substrate topography and the tip-substrate distance. Tunneling electrons can provide the driving force to induce atomic and molecular motions leading to the dissociation and formation of chemical bonds.…”

Tunneling Microscopy and Spectroscopy

“…As shown by the empty-state images in Fig. 13 (Martel et al, 1996), when a clean Si(lll) surface at room temperature is exposed to O 2 gas in UHV, the oxygen initially reacts almost exclusively with the atoms at the corners of the diamond-shaped unit cells (known as "corner hole adatoms"). The reaction results in two types of features at the corner holes, referred to as "bright" (B) and "dark" (D) sites.…”