# Morphological evolution of silicon surfaces nanopatterned by focused ion beam irradiation

## TL;DR

This paper studies how silicon surfaces change when exposed to focused ion beams, revealing how nanopatterns like ripples and terraces form and how they affect surface adhesion.

## Contribution

The study systematically reveals the formation and transition of ripple and terrace patterns on silicon surfaces under focused ion beam irradiation and their impact on adhesion forces.

## Key findings

- Ripple patterns on silicon surfaces form most distinctly at a 30° ion incidence angle.
- Higher ion fluence leads to a morphological transition from ripples to terrace-like structures.
- Nanopatterns significantly influence adhesion forces measured using atomic force microscopy.

## Abstract

Nanopatterning on solid surface has emerged as an important tool in the field of nanotechnology, nano/micro-electromechanical systems (NEMS/MEMS), photonics, and biotechnology. Among the available techniques, focused ion beam (FIB) enables controlled and precise nanopatterning on solid surfaces. The formation and evolution of nanoripple patterns on silicon (Si) surfaces by 30 keV Ga⁺ focused ion beam (FIB) irradiation has been investigated in this study. We perform a systematic study to investigate the well-defined ripple pattern formation by conducting experiments at different ion incidence angles (0°-45°), ion energies (10–30 keV), and ion fluences. Well-defined ripple patterns are observed near 30° ion incidence angle, with ripple periodicity and amplitude strongly dependent on ion fluence. A distinct morphological transition at higher ion fluences from ripple patterns to terrace-like structures is observed. The force measurements are also carried out in terms of pull-off force test on ripple patterned Si surfaces to investigate the effect of nanopattern on adhesion force as employed by atomic force microscopy (AFM) in force mode with normal sharp probe and silica colloidal probe. The observed results reveal that one can fabricate well-defined nano ripple pattern along with terrace pattern at high fluence and adhesion force can also be tuned with nanoscale pattern. The mechanism of ripple pattern formation and its transition to terrace-like structure are discussed in the framework of well-established continuum models. Potential applications of such nanopatterned surfaces for nanoelectromechanical systems (NEMS) and other functional properties are also highlighted.

The online version contains supplementary material available at 10.1038/s41598-025-33947-y.