Initial oxidation of gallium arsenide (001)-β2(2 x 4) surface using density functional theory

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• Gallium arsenide (GaAs) is a crucial semiconductor material.
• Understanding the initial oxidation of GaAs surfaces is vital for device fabrication and stability.
• The (001)-β2(2 x 4) reconstruction is a common and important surface termination.

Purpose of the Study:

• To investigate the initial adsorption and dissociation of an oxygen molecule on the gallium arsenide (001)-β2(2 x 4) surface.
• To determine the preferred dissociation pathways and the resulting bonding configurations of oxygen atoms.
• To provide theoretical insights complementing experimental observations.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Simulations focused on the interaction of an oxygen molecule with the GaAs (001)-β2(2 x 4) surface.
• Analysis of adsorption energies and dissociation barriers was performed.

Main Results:

• Oxygen molecule adsorption on the GaAs surface occurs spontaneously without an energy barrier.
• Two distinct dissociation pathways were identified on the first arsenic layer: inter-dimer and intra-dimer.
• The inter-dimer dissociation pathway was found to be energetically favored.
• Dissociated oxygen atoms preferentially break As-Ga back-bonds, forming As-O-Ga bonds.

Conclusions:

• The initial oxidation of the GaAs (001)-β2(2 x 4) surface by O2 is initiated by barrierless adsorption followed by preferred inter-dimer dissociation.
• The formation of As-O-Ga bonds is a key step in the oxidation process.
• Theoretical findings align well with experimental data from scanning tunneling microscopy studies.