QPlus: atomic force microscopy on single-crystal insulators with small oscillation amplitudes at 5 K

Area of Science:

• Surface Science
• Nanotechnology
• Materials Science

Background:

• Conventional atomic force microscopy (AFM) sensors face limitations in combined scanning tunneling microscopy (STM) operation.
• Quantitative force spectroscopy on insulators requires decoupling of tunneling current and AFM signals.
• Low-temperature amplification is crucial for detecting extremely weak signals in advanced microscopy.

Purpose of the Study:

• To integrate a QPlus sensor, utilizing a quartz tuning fork, into a low-temperature STM platform.
• To demonstrate the sensor's advantages for combined STM and non-contact AFM operations.
• To enable quantitative force spectroscopy on insulating thin films and semiconductors.

Main Methods:

• Utilized a proven low-temperature scanning tunneling microscope (STM) platform.
• Integrated a QPlus sensor with a quartz tuning fork for force detection.
• Employed constant frequency shift (df) imaging feedback for atomic resolution measurements.

Main Results:

• Achieved atomic resolution imaging on single-crystal NaCl(100) with oscillation amplitudes below 100 pm.
• Demonstrated successful atomic resolution measurements on MgO(100) and Au(111) surfaces.
• Performed initial evaluations of the QPlus sensor in Kelvin probe microscopy on Si(111) 7 x 7.

Conclusions:

• The integrated QPlus sensor offers significant advantages for combined STM and AFM.
• The system enables high-resolution imaging and quantitative force spectroscopy on diverse materials.
• This advancement facilitates detailed surface characterization at the atomic scale.