Charge Carrier Injection Electroluminescence with CO-Functionalized Tips on Single Molecular Emitters

Area of Science:

• Surface Science
• Molecular Physics
• Scanning Probe Microscopy

Background:

• Investigating single-molecule electroluminescence is crucial for understanding molecular photophysics.
• Submolecular resolution imaging requires advanced microscopy techniques.

Purpose of the Study:

• To investigate the electroluminescence of single molecular emitters on metal surfaces.
• To understand the role of tip functionalization in scanning probe microscopy.
• To elucidate the mechanisms of charge carrier injection and excitation.

Main Methods:

• Low-temperature scanning probe microscopy with tunneling current, atomic force, and light detection.
• Utilizing metal and CO-functionalized tips for imaging zinc phthalocyanine (ZnPc) on Ag(111) and Au(111).
• Analyzing photon maps and atomic force microscopy data.

Main Results:

• Submolecular resolution electroluminescence imaging of ZnPc was achieved.
• CO-functionalized tips enhanced resolution and contrast by localizing tip-molecule orbital overlap.
• Distinct excitation mechanisms were observed on Ag(111) and Au(111) due to level alignment.

Conclusions:

• Tip state critically influences photon map quality and interpretation.
• CO-functionalization enables simultaneous high-resolution imaging and photon detection.
• Understanding orbital interactions is key to controlling molecular electroluminescence.