Surface diffusion of phosphorus on Si(100) after PBr₃ adsorption

Area of Science:

• Surface Science
• Materials Science
• Physical Chemistry

Background:

• Understanding atom diffusion on semiconductor surfaces is crucial for microelectronics.
• Silicon (Si) surfaces are fundamental building blocks in semiconductor technology.
• Phosphorus (P) is a key dopant in silicon-based electronics.

Purpose of the Study:

• To investigate phosphorus diffusion mechanisms on a Si(100) surface.
• To determine the influence of temperature and surface adsorbates on phosphorus mobility.
• To elucidate the specific diffusion pathways and energetic barriers involved.

Main Methods:

• Scanning Tunneling Microscopy (STM) was employed to observe phosphorus diffusion at 77 K and 300 K.
• Density Functional Theory (DFT) calculations were used to determine activation energies for diffusion pathways.
• PBr3 molecules served as the phosphorus source, dissociating on the Si(100) surface.

Main Results:

• Phosphorus atoms diffused both along and across Si dimer rows.
• At 77 K, diffusion initiated and terminated primarily at bridge positions.
• At 300 K, diffusion occurred between end-bridge positions, influenced by co-diffusing bromine (Br).
• Bromine presence significantly hindered phosphorus mobility.
• Phosphorus was observed to diffuse towards oxygen atoms resulting from water adsorption, indicating a preference for oxidized sites.

Conclusions:

• The study elucidates distinct phosphorus diffusion pathways on Si(100) surfaces.
• Surface adsorbates like bromine and oxygen critically affect phosphorus diffusion dynamics.
• The findings enhance the understanding of phosphorus-silicon surface interactions, relevant for semiconductor fabrication.