Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Thin oxide films are crucial in various electronic and catalytic applications.
• Understanding surface defects is key to controlling film properties.
• Advanced microscopy techniques are needed to probe nanoscale features.

Purpose of the Study:

• To investigate the surfaces of thin oxide films with atomic resolution.
• To characterize point and line defects in magnesium oxide and aluminum oxide films.
• To correlate defect types with electronic properties using advanced microscopy.

Main Methods:

• Utilized a dual-mode non-contact atomic force microscopy/scanning tunneling microscopy (NC-AFM/STM) system.
• Employed Kelvin probe force microscopy (KPFM) to measure contact potential.
• Applied scanning tunneling spectroscopy (STS) to determine electronic structure.

Main Results:

• Differentiated various color centers (F(0), F(+), F(2+), divacancies) in magnesium oxide based on contact potential using KPFM.
• Resolved atomic topography of line defects in aluminum oxide.
• Verified F(2+)-like centers at aluminum oxide domain boundaries using STS and KPFM, consistent with theoretical predictions.

Conclusions:

• NC-AFM/STM provides atomic resolution for thin oxide film topography and defect analysis.
• KPFM and STS enable nanometer-scale characterization of electronic properties and defect identification.
• This dual-mode microscopy approach is effective for comprehensive analysis of thin oxide films beyond surface imaging.