Extended Data Fig. 2: Parameter dependence of KPFM measurements.
From: Electrostatic moiré potential from twisted hexagonal boron nitride layers
a, Illustration of the tip scanning over the sample. Scan height h is the sum of the thickness of the top hBN, z = 7.8 nm, and tip-to-sample distance, zlift. b is the ___domain size as defined in the main text. b, Measured modulation potential depth ΔVs as a function of the scan height, h, for two ___domain sizes of 60 nm (blue sphere) and 370 nm (red sphere). The measured potential depth remains constant for large supercells while drops for small supercells with increasing scan height. It is important to note that the potential can be sensitive to scan height even for large supercells with a blunt tip and a reduced spatial resolution. The tip-to-sample distance is kept at zlift = 2 nm for all results presented in the main text. c, Potential modulation as a function of scan speed for a supercell of 60 nm period. The potential value does not change remarkably for the scan speed between 0.5 and 1.5 Hz. The images presented in the main text are taken at the scan speed of 1 Hz. All error bars represent the root mean square error from the sinusoidal fitting to KPFM measurements. d-f, KPFM images of the domains with supercell size of 60 nm (d, e) and 370 nm (f). The images (d) and (e) are identical images but represented on two different potential scales. The potential scale of (e) is chosen to be the same as that of (f) for comparison. Notice that several small features with higher potential are clearly resolved in (d) and (e), which is indicative of a high spatial resolution. The measurements were performed by a supersharp diamond-like carbon tip with a radius of 1 nm.
