A density-functional theory study of tip electronic structures in scanning tunneling microscopy

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Scanning tunneling microscopy (STM) is a powerful surface science technique.
• Understanding the atomic and electronic structure of STM tips is crucial for high-resolution imaging.
• Transition metals (TMs) are commonly used as STM tip materials.

Purpose of the Study:

• To perform a detailed analysis of the atomic and electronic structures of various transition metal (TM) scanning tunneling microscopy tips.
• To investigate the behavior of d electrons near the Fermi level for different TM tips.
• To explore the electronic properties of TM atom tips supported on a tungsten (W) surface.

Main Methods:

• Utilizing ab initio density-functional theory (DFT) methods.
• Modeling pyramidal structures of Rh, Pd, W, Ir, and Pt as STM tips.
• Analyzing transition metal atom tips supported on a W surface.

Main Results:

• Observed distinct behaviors of d electrons near the Fermi level for Rh, Pd, W, Ir, and Pt apex atoms.
• Identified predominant dz(2) states near the Fermi level, particularly for the W tip.
• Reported and discussed the electronic structures and density of states for larger pyramidal TM tip models.

Conclusions:

• The electronic structure and d-electron occupation significantly influence the performance of TM STM tips.
• Specific d-electron states, like dz(2) for W tips, play a critical role near the Fermi level.
• This theoretical analysis provides insights into designing and optimizing TM-based STM tips.