Systematic variations in apparent topographic height as measured by noncontact atomic force microscopy

Abstract

A flat Si(100) surface is prepared with neighboring n- and p-doped regions. The contact potential difference between the tip and the two well-defined regions of similar material is utilized to examine the effects and interplay of essential tip-sample forces in atomic force microscopy. Measurements with a frequency-modulated noncontact atomic force microscope (NCAFM) show large apparent topographic height variations across the differently doped regions. The height differences depend on the bias polarity, bias voltage, radius, and conducting state of the tip. The functional relationships are well explained by integrated model calculations. These findings provide a coherence scenario of NCAFM operation under these essential forces and facilitate quantitative understanding of the systematic errors in surface topographic height measurement commonly performed in nanoscience.