We present a comparative experimental and theoretical study of the frequency shift in ultrahigh vacuum dynamic force microscopy at 80 K on graphite(0001) measured as a function of the tip-sample distance for different resonance amplitudes A in the repulsive and attractive regime of the tip-sample forces. The resulting frequency shift versus distance curves scale with ${1/A}^{3/2}$ over the full range. We determined the tip-sample force from the frequency shift versus distance curves and found good agreement with specific force laws for long-range (van der Waals), short-range (Lennard-Jones), and contact (Hertz) forces.

• Received 19 January 2000

DOI:https://doi.org/10.1103/PhysRevB.61.12678