Four-probe measurements with a three-probe scanning tunneling microscope

Area of Science:

• Surface science
• Nanotechnology
• Materials science

Background:

• Scanning tunneling microscopy (STM) is crucial for atomic-scale surface analysis.
• Achieving stable, reproducible multi-tip STM measurements remains a challenge.
• Precise control over tip positioning and tip-surface interactions is essential for advanced characterization.

Purpose of the Study:

• To introduce an ultrahigh vacuum (UHV) three-probe STM system with atomic resolution capabilities for each probe.
• To demonstrate a method for precise inter-tip positioning using a single surface feature.
• To enable four-probe material characterization using a movable voltage probe.

Main Methods:

• Integration of a UHV JEOL scanning electron microscope for probe placement.
• Utilization of a field ion microscope for probe tip cleaning, imaging, and shaping.
• Implementation of automated feedback-controlled tip-surface contacts for stability and damage reduction.
• Development of a homebuilt pliers system for sample heating and loading.

Main Results:

• Demonstration of atomic resolution for each of the three STM probes.
• Successful registration of inter-tip positions by imaging a single surface feature with multiple tips.
• Achievement of four-probe material characterization by configuring two tips as current probes and one as a movable voltage probe.

Conclusions:

• The developed UHV three-probe STM system offers unprecedented control and precision for surface analysis.
• Automated contact control significantly enhances stability, reproducibility, and minimizes damage.
• The system facilitates advanced four-probe measurements for comprehensive material characterization.