Band gap modulation of SrTiO₃ upon CO₂ adsorption

Area of Science:

• Materials Science
• Surface Chemistry
• Computational Materials Science

Background:

• Strontium titanate (SrTiO3) is a promising material for chemical sensing applications.
• Understanding the interaction of gases like carbon dioxide (CO2) with SrTiO3 surfaces is crucial for developing effective sensors.

Purpose of the Study:

• To investigate the chemisorption of CO2 on SrTiO3(001) surfaces using ab initio calculations.
• To elucidate the underlying mechanisms of CO2 adsorption and its impact on the electronic properties of SrTiO3.
• To explore the potential of these mechanisms for novel chemical sensing applications.

Main Methods:

• Utilized ab initio calculations to simulate and study CO2 chemisorption on SrTiO3(001) surfaces.
• Analyzed the electronic band structure changes, specifically focusing on the valence band (VB) maximum and conduction band (CB) minimum.

Main Results:

• CO2 adsorption was found to open the band gap of SrTiO3.
• Distinct mechanisms were observed for TiO2-terminated and SrO-terminated surfaces: neutralization of VB states (TiO2) and suppression of CB minimum (SrO).
• The observed effects are dependent on CO2 coverage, influencing both adsorption energy and surface band gap.

Conclusions:

• The passivation of dangling bonds on TiO2-terminated surfaces and surface relaxation on SrO-terminated surfaces explain the observed band gap modulation.
• The TiO2 termination exhibits a more prominent band gap change due to direct modulation of VB states and charge distribution.
• The strong dependence of adsorption energy and band gap on CO2 coverage indicates potential for developing SrTiO3-based chemical sensors for various CO2 concentrations.