Study of high-low KPFM on a pn-patterned Si surface

Area of Science:

• Surface science
• Scanning probe microscopy
• Semiconductor characterization

Background:

• Kelvin probe force microscopy (KPFM) is crucial for surface potential analysis.
• Frequency modulation KPFM (FM-KPFM) offers high sensitivity.
• Understanding AC bias voltage effects is key for accurate measurements.

Purpose of the Study:

• To compare surface potential measurements using low-frequency bias FM-KPFM and high-frequency bias heterodyne FM-KPFM.
• To evaluate the accuracy and differences between these two FM-KPFM techniques.
• To investigate the influence of AC bias voltage on surface band bending measurements.

Main Methods:

• Comparative surface potential measurements were conducted using FM-KPFM and heterodyne FM-KPFM.
• A silicon substrate with p- and n-type impurities served as the quantitative sample.
• Multi-pass scanning was employed to mitigate tip-sample distance dependence.

Main Results:

• Both FM-KPFM techniques yielded surface potential measurements in good agreement with the work function order of the pn-patterned Si sample (p-type < n-type < n+-type).
• Observed differences in surface potentials between the two methods were linked to surface band bending.
• The discrepancies were attributed to the varying response of charge transfer to AC bias voltage.

Conclusions:

• FM-KPFM and heterodyne FM-KPFM are effective for quantitative surface potential mapping of semiconductors.
• Differences in measured potentials highlight the impact of AC bias voltage on surface band bending.
• Further investigation into charge transfer dynamics is warranted for precise KPFM analysis.