Hallmarks of the Kardar-Parisi-Zhang universality class elicited by scanning probe microscopy

TL;DR

This study demonstrates that scanning probe microscopy can artificially produce KPZ universality class signatures due to probe tip limitations, affecting surface analysis interpretations.

Contribution

It reveals that the finite size of the probe tip induces KPZ-like features in scanned surfaces, providing a new understanding of surface analysis artifacts.

Findings

Height distributions match KPZ class in experiments and simulations.

Finite probe size causes apparent excess growth and KPZ signatures.

Strategies to distinguish true KPZ behavior from artifacts are discussed.

Abstract

Scanning probe microscopy (SPM) is a fundamental technique for the analysis of surfaces. In the present work, the interface statistics of surfaces scanned with a probe tip was analyzed for both \textit{in silico} and experimental systems that \textit{do not} belong to the prominent Kardar-Parisi-Zhang (KPZ) universality class. We show that height, local roughness and extremal height distributions of scanned surfaces quantitatively agree with the KPZ class in a range similar or better than recent experimental evidences of the KPZ class using SPM images. The underlying mechanism behind this artificial KPZ class is the finite size of the probe tip, which does not permit a full resolution of neither deep valleys or sloping borders of plateaus. The net result is a scanned profile laterally thicker and higher than the original one implying an excess growth, the major characteristic of the KPZ universality class. The actual universality class of self-affine scanned surfaces are expected at long times when the characteristic surface lengths become much larger than those of the probe tip but our finds can be of relevance to experiments where sufficiently long growth times cannot be easily achieved. We also propose that the KPZ signatures can be also elicited in mounded surfaces with high aspect ratio due to the interaction with the bulk of the probe tip. Strategies to prevent false positives of the KPZ class are discussed.