Role of radicals in the reaction of oxygen difluoride with monohydrogenated silicon

• Published in: Physical chemistry chemical physics : PCCP 2025-01, Vol.27 (2), p.660
• Main Authors: Thake, Henry, Jenkins, Stephen J
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d4cp03375b

We present first-principles molecular dynamics simulations of oxygen difluoride impinging upon the monohydrogenated Si{001}(2 × 1) surface. Adsorption occurred in fewer than 10% of our computed trajectories, but in each reactive case the initial step involved partial dissociation to yield an adsorbed fluorine atom and a free oxygen monofluoride radical. In one trajectory, the adsorbed fluorine atom displaced a hydrogen atom into an unusual Si-H-Si bridge position, consistent with three-centre two-electron bonding. In another, a Si-Si-F motif was created, consistent with three-centre four-electron bonding. Depending upon its recoil direction, the ubiquitous monofluoride species either migrated across the surface before itself reacting to form a Si-O-Si bridge and a second adsorbed fluorine atom, or desorbed intact as a gas-phase radical.