In-situ ion irradiation investigations on MBE grown Sb thin films on sapphire.

Two-dimensional antimony is a promising candidate for various emerging technological applications. The ability of antimony thin films to undergo crystalline–amorphous phase transitions under laser irradiation highlights its potential as a phase-change material (PCM) for integrated devices. In this work, we investigate the capability of ion beams to induce disorder or crystallization in antimony films. Antimony (Sb) thin films were grown on sapphire (c-Al2O3) substrate by molecular beam epitaxy (MBE) at room temperature (RT) and at 245 °C (HT), resulting in distinctly different morphologies. Films deposited at HT predominantly form well-faceted, discrete square-pyramidal and triangular Sb nanocrystals, whereas film deposited at RT produces a nearly continuous film with a worm-like morphology. The morphological evolution of these films under 2 MeV Al⁺ ion irradiation was studied using an in-situ ion irradiation and imaging with field emission scanning electron microscope facility. For the Sb films deposited at HT, at low ion fluences, irradiation induces disorder within the nanocrystals, effectively lower the melting point of antimony. At high ion fluences, evaporation of Sb occurs, leading to significant shape modifications in the nanocrystals. In contrast, Sb films deposited at RT exhibit a transition from a disordered structure to an ordered crystalline phase. Ion irradiation also drives dewetting of thin film at room temperature itself. This is driven by an in-plane compressive stress of ~ 0.34 GPa, which is generated during the thermal spike regime. These observed transitions (disordered to crystalline and crystalline to disordered) under ion irradiation demonstrate the potential of antimony for future phase-change material applications.