Confinement effects in π-bonded chains at group IV semiconductor (111) surfaces.

Area of Science:

• Surface science
• Materials science
• Solid-state physics

Background:

• Group IV (111)-2 × 1 reconstructed surfaces feature quasi-one-dimensional (1D) π-bonded chains.
• The electronic properties of these surface chains are crucial for understanding surface behavior.

Purpose of the Study:

• To investigate the degree of 1D character in surface chains on group IV (111)-2 × 1 reconstructed surfaces.
• To compare the electronic behavior of reconstructed diamond, silicon, and germanium surfaces upon oxidation.

Main Methods:

• Surface-sensitive optical spectroscopy was employed.
• Optical experiments were conducted on clean and oxidized diamond C(111)-2 × 1, silicon Si(111)-2 × 1, and germanium Ge(111)-2 × 1 surfaces.

Main Results:

• Diamond and silicon surfaces showed a marked blueshift in absorption peaks related to dangling-bond transitions upon oxygen exposure, indicating quantum confinement.
• This blueshift was attributed to the decrease in the length of quasi-1D π-bonded chains with oxygen uptake.
• Germanium Ge(111)-2 × 1 exhibited only a very slight blueshift upon oxidation, suggesting a less pronounced 1D character.

Conclusions:

• The 1D character of surface chains on diamond and silicon is significant and sensitive to oxidation, consistent with quantum confinement effects.
• The reduced 1D character on germanium is attributed to stronger inter-chain coupling, leading to less pronounced quantum confinement effects upon oxidation.