Recent advances in grayscale lithography have significantly expanded its capabilities for three-dimensional micro- and nanofabrication, offering distinct advantages over conventional binary lithography for the realization of complex integrated devices. This technology has enabled high-resolution 3D structuring in applications such as microlens arrays, blazed gratings, microfluidic systems, MEMS, and biomimetic interfaces. Nevertheless, existing methods remain fundamentally limited in vertical resolution—typically from the micrometer scale down to tens of nanometers—leaving grayscale patterning at the nanometric and even Ångström levels largely unexplored.

In this work, researchers report a probe-guided laser direct writing (PG-LDW) approach capable of fabricating multi-level step structures with step heights of ~2 Å. This resolution surpasses the current benchmark of 6 nm achieved by grayscale electron beam lithography, thereby breaking the long-standing resolution barrier. By employing probe-guided surface focusing in combination with laser power modulation, they achieve controlled material removal without photoresist masks or dry etching processes, thus eliminating contamination and etch-induced distortions. The process is performed under ambient conditions, allowing direct writing of complex patterns into 2D materials. The structural and chemical modifications were systematically characterized using in situ atomic force microscopy (AFM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Moreover, the integrated AFM capability of the probe further allows iterative multi-pass processing with real-time feedback and precise rewriting. This probe-guided laser lithography technique provides high-fidelity, sub-nanometer vertical-step resolution in a resist-free context, opening new opportunities for the down-scaling fabrication of next-generation nanophotonic, nanoelectronic, and biomimetic devices.