Quantitative mapping of smooth topographic landscapes produced by thermal scanning-probe lithography

TL;DR

This paper introduces FunFit, an open-source software for fitting analytical functions to SPM data, enhancing the analysis and reproducibility of nanoscale topographic landscapes created by thermal scanning-probe lithography.

Contribution

The paper presents a new protocol and software tool that improve analysis, reproducibility, and process development for tSPL and other SPM techniques.

Findings

Successful patterning of periodic and quasiperiodic landscapes in polymers

High-fidelity transfer of topographies to hBN flakes via reactive-ion etching

Efficient analysis within a day by inexperienced users

Abstract

Scanning probe microscopy (SPM) is a powerful technique for mapping nanoscale surface properties through tip-sample interactions. Thermal scanning-probe lithography (tSPL) is an advanced SPM variant that uses a silicon tip on a heated cantilever to sculpt and measure polymer films with nanometer precision. The surfaces produced by tSPL-smooth topographic landscapes-allow mathematically defined contours to be fabricated on the nanoscale, enabling sophisticated functionalities for photonic, electronic, chemical, and biological technologies. Evaluating the physical effects of a landscape requires fitting arbitrary mathematical functions to SPM datasets, however, this capability does not exist in standard analysis programs. Here, we provide an open-source software package (FunFit) to fit analytical functions to SPM data and develop a fabrication and characterization protocol based on this analysis. We demonstrate the benefit of this approach by patterning periodic and quasiperiodic landscapes in a polymer resist with tSPL, which we transfer to hexagonal boron nitride (hBN) flakes with high fidelity via reactive-ion etching. The topographic landscapes in polymers and hBN are measured with tSPL and atomic force microscopy (AFM), respectively. Within the FunFit program, the datasets are corrected for artefacts, fit with analytical functions, and compared, providing critical feedback on the fabrication procedure. Beyond application to tSPL, this protocol can improve analysis, reproducibility, and process development for a broad range of SPM experiments. The protocol can be performed within a working day by an inexperienced user, where fabrication and characterization take a few hours and software analysis takes a few minutes.